Ai-01

How Does Prototyping Help?

How Does Prototyping Help?

Rush PCB recommends that OEMs ensure a printed circuit board is functioning properly before starting a full production run. Although designers are careful when working on a project, invisible problems and small mistakes can pose a threat to the functioning of the PCB. If these problems are not sorted out before starting a full production run, the project as a whole may run into extra expenses, making it essential for designers to order prototype boards before giving the go-ahead for full-scale manufacturing.

At Rush PCB, we offer prototyping as an essential service. Designers refer to the prototype as an early sample of a product. They build the prototype with the purpose of testing the design idea to ensure if the idea works properly. Although designers make prototypes of their products to test its basis functionality, they make PCB prototypes with the aim it will be fully functional, as the PCB prototype allows testing the total functionality of the product.

SMT PCB

OEMs use different types of prototypes to test different stages of their design over the course of a project. The process may require multiple PCB prototypes at various stages. Usually the prototypes include:

Base Visual Models: These prototypes illustrate the physical aspects of the PCB related to the overall shape and component structure. As the first prototypes in the design process, designers use them to review the design to make it easy and affordable.

Proof-of-Concept: These prototypes demonstrate the primary functioning of the board and most often do not possess the complete capabilities of the final product. Designers use these prototypes to primarily demonstrate the viability of the design.

Working Prototypes: Designers use working prototypes to ensure the board functions as per plan with all features and functions of the final product. Testing these prototypes identifies weaknesses or problems in the design, allowing designers to rectify them before they build the functional prototype.

Functional Prototypes: These prototypes are meant to be as close to the final product as is possible. Designers use functional prototypes to demonstrate the working of the final product. The prototype PCB at this stage is usually fully functional.

Rush PCB recommends using prototype PCBs through the entire design cycle. Repeatedly testing prototypes along the design cycle helps designers confirm the viability and functionality of every new addition or change. Although making prototypes and testing them may seem to add time and expense to the design process, it offers several advantages to the OEMs and their clients, such as:

  • Reducing the Timeline
  • Review and Assistance during Manufacturing
  • Solving Design Issues before Production Starts
  • Testing Components Individually
  • Reducing Project Costs

Reducing the Timeline

Designers usually go through several iterations before deciding on a final product. In this process, prototypes help to consolidate the different steps that designers take—they can test the prototype and fix the problems before the final production run. Solving problems that crop up later in the design cycle usually takes longer.

Rush PCB specializes in quick PCB prototype turnarounds—visit our website today.

Review and Assistance during Manufacturing

OEMs using a third-party PCB prototyping service benefit from the assistance they provide. Third parties usually have experienced personnel helping in design rule checking (DRC), design for manufacturing (DFM), and design for assembly (DFA). Unless designers review and sort out these problems, they can lead to inefficiencies, design flaws, and other issues during production.

Working closely with the PCB contract manufacturer during the prototyping phase can help OEMs make the most of the expertise the contract manufacturer provides. This also helps to align the design to the capabilities of the contract manufacturer, ultimately allowing the production run to go through smoothly.

Rush PCB is a renowned contract manufacturer for PCBs—visit our website today.

Solving Design Issues before Production Start

A prototype PCB makes it much easier for designers to solve their design issues before production start. The more accurate the design and the prototype, the better they can identify the flaw. Accurate boards help designers assess whether the practical performance of the PCB matches its theoretical predictions, check for the differences, update them, and to reevaluate their potentiality.

Designers need to appropriately test their PCBs to make sure they can survive the environment conditions the product must endure. The best way to do this is to verify that the prototype can survive the conditions. Designers usually subject their prototypes to undergo power variation testing, temperature variation testing, shock resistance testing and more.

Use the expertise of Rush PCB to get accurate prototypes—visit our website today.

Testing Components Individually

For large systems, engineers use prototype PCBs for testing singular components and functions, before integrating them into the system. Such individual testing helps in proof-of-concept runs, and allows an engineer to test and verify a design idea. It also helps them to break down a complex idea into smaller basic parts, thereby ensuring each of these parts function on their own before the designer can integrate them.

Reducing Project Costs

Solving PCB problems during production runs can be expensive and cause unnecessary delays, leading to longer time to market. By periodically testing with prototypes and solving the issues early on, the OEM is actually reducing a cost buildup and saving money by reducing wastage.

Depending on the specific design, prototypes help a designer try out different combinations of material and components. This allows the design teams to work out the best and most economical combination to use for their project.

Rush PCB is a leader in PCB prototype services, and serves over 400 clients in the United Kingdom. Our commitment to quality and attention to details is what makes us stand out from the rest in the industry.

For all your prototype purposes, call us today or visit our website.

Ai PCB

Printed Circuit Boards and AI

Printed Circuit Boards and AI

With Printed Circuit Boards (PCBs) evolving from crude manual manufacturing processes to sophisticated high-density interconnect (HDI) and flexible boards, Rush PCB has matched the changeover by adapting to highly automated production processes for manufacturing and assembly. With further development of manufacturing technology, it is becoming increasingly more complex and sophisticated, and Rush PCB is now looking at capitalizing on Artificial Intelligence (AI) to optimize not only its production processes, but also its entire manufacturing facility.

Earlier, PCB manufacturing typically relied on experts with long experience, who had intimate knowledge and understanding of every aspect of the manufacturing process. By leveraging their knowledge, the experts would optimize production techniques and improve the yield. However, human limitations such as error and fatigue would often affect their accomplishments, leading to false alarms generated by operator errors, and or their mistaken identification of defects. Often, this led to over-handling, leading to reducing of yield.

Read about: Key Steps in Designing Printed Circuit Board Layouts

AI Integration

Rush PCB has successfully overcome the above by integrating AI into their manufacturing processes. By incorporating modern machines that add value by taking over the learned tasks, human experts are now free to take over more complex tasks that require intelligence, thought, and interaction, such as optimizing and training the AI system. This combination of human and artificial intelligence is significantly improving the overall efficiency of manufacturing operations.

Importance of Industry 4.0

Rush PCB recognizes that a fully integrated Industry 4.0 system is the future of any PCB manufacturing. We envisage the integration to work at both local manufacturing and at all levels across the company, rather than at individual manufacturing process levels alone. With the information exchange infrastructure and automation levels that Industry 4.0 provides, it is possible to ensure analysis of production at real-time, two-way communication and information sharing, on-demand information analysis, and traceability.

Industry 4.0 mechanisms such as two-way communication and traceability ensure collection of information from various manufacturing machines and systems. This not only helps improve all manufacturing processes, but Rush PCB benefits as a company. AI helps to analyze huge amounts of system-wide information for optimizing factory set up parameters, thereby achieving higher levels of productivity and yield. Artificial neural networks of the AI system help with ongoing self-learning, helping to create fully automated factories.

Implementation of Industry 4.0 and AI

Implementation of Industry 4.0 and AI requires complete connectivity of all factory systems, with AI acting as the monitoring and the decision-making mechanism. At present, Rush PCB must overcome several technical challenges limiting the complete automation of their factories, and therefore, we are adding AI to individual systems.

We have incorporated AI initially to our automated optical inspection stations, and this has resulted in more reliable detection of true defects in PCBs. By moving our production facilities completely towards AI integration, Rush PCB is looking at tremendous benefits of a feedback loop that will identify an issue, locate its source, and automatically revise the factory process for eliminating the related defect.

Moving Forward

In the future, Rush PCB intends to go further with machine learning and deep learning—our goal of moving PCB manufacturing to full automation levels. We plan to use computers with machine learning algorithms to improve task performance with data collection, past learning experiences, but without recourse to programming to do so.

Machine learning offers several advantages for PCB manufacturing. Not only does machine learning increase the yield, it also improves fabrication processes and operations, while reducing manual operations to a minimum. Implemented on a factory level, Rush PCB expects machine learning to help with efficient handling of supply chain, inventory, and factory assets.

Rush PCB offers PCB manufacturing, automated assembly, and full turn-key services for various types of PCBs. For our full capabilities, please visit our website, or give us a call for a quote.

To further improve our global factory systems, Rush PCB has plans to implement deep learning to take AI to more complex levels. From the data collected from various equipment and systems, we plan to let software expert systems to effectively learn from informed representations of insights, patterns, and contexts for helping automated the process improvements for PCB manufacturing.

Advantages of Industry 4.0 and AI

Industry 4.0 uses various sensors to send data from equipment and systems. AI helps to process this data coming from PCB manufacturing processes, all the while tracking process parameters down to the lowest levels, such as etching, resist development, and concentration of different chemicals in the manufacturing process.

Ai, along with machine learning and deep learning, analyzes the data and decides on the optimization of the manufacturing methods and parameters. The algorithms identify patterns, and make informed decision on necessary changes in the processes, thereby helping Rush PCB eliminate human error.

PCB Assembly

PCB Layout and Assembly for EV Charging Stations

PCB Layout and Assembly for EV Charging Stations

With people all over the world endeavoring to give up use of fossil fuels, electric vehicles (EV) are beginning to take over the roads from vehicles using internal combustion engine. This is causing numerous charging stations to come up every day to help charge EVs. Rush PCB is driving innovations in such car charging stations by providing expert Printed Circuit Board (PCB) layouts, PCB manufacturing, and assembly solutions.

How EV Charging Stations Operate

Plug-in Electric Vehicles (PEVs) function with a battery in the vehicle driving an electric motor. As the battery charge depletes, periodically, it becomes necessary to recharge it from EV charging stations. This is possible to do by plugging in the vehicle to a wall outlet, which an EV charging station provides.

EV Charging Requirements

Although battery technology is still progressing, electric vehicle owners demand fast charging of the battery, as they must spend the minimum amount of time at the charging station. This is forcing the electronic industry to come up with innovative solutions for car charging stations to provide them with fast and high efficiency chargers. While the electronic industry is developing new and more efficient components for achieving better charging methods, Rush PCB offers their expertise in PCB manufacturing for improved layouts, manufacturing, and assembly techniques.

Contact Rush PCB for the latest types of PCBs for your EV charging station requirements.

Types of EV Charging Stations

Rush PCB offers high quality PCB prototypes using the latest technology. Manufacturers make EV charging stations for homes, commercial, or for public use, and Rush PCB caters to all types of PCB requirements with multi-functionality features. Depending on your requirement of a new type of customized solution for a pedestal charging structure, a wall mounted type of charging station, or a curve/ball type of charging platform, Rush PCB has the necessary solution to offer.

Commercial EV Charging Stations

Commercial EV charging stations usually demand a robust vandal resistant unit, typically providing one-way or two-way plug-in facility with customized fast-charging features. Rush PCB provides charging station manufacturers with innovative solutions for security including c/w hatch lock, overload protection, and fault current monitoring.

Challenges to PCB Manufacturing

Apart from automatic charging capabilities, commercial EV charging stations also require auto plug-in and payment facilities. These requirements are an additional challenge to the PCB manufacturer, as they require the presence of an embedded controller within the system offering Near Field Communication (NFC) and Internet capabilities for mobile payments. Rush PCB offers all the above at nominal cost of production, based on their highly efficient technology for manufacturing and assembling PCBs.

Commercial EV charging stations also require control centers with a dual facility—for optionally selecting pay-to-use or free-to-use car charging service. Additionally, one control center must manage multiple local EV charging points. Once a vehicle comes in and parks at a certain EV charging point, the control center automatically initiates the charging procedure. Rush PCB offers high quality PCBs for manufacturers of control centers, compatible with multiple charging stations.

Rush PCB Customized Design and Layout solutions

Rush PCB provides customized PCB design and layout solution for the EV charging station designer and manufacturer. We have a dedicated team of technical experts to provide an effective PCB layout for your project, and follow it up with unique assembly solutions. For realizing your market objectives, Rush PCB offers you the consigned and complete turnkey solution.

Rush PCB Customized Assembly Solutions

Rush PCB offers its customized PCB assembly using state-of-the-art techniques and machinery. We offer compact and multi-featured PCBs for the automobile industry using the latest Surface Mount Technology (SMT), but we also offer Through Hole Technology according to customer requirements. For the high-tech control systems that the EV charging stations use, we offer a complete PCB turnkey solution. If you require any type of consultation, we offer the services of our experienced technical personnel.

Contact Rush PCB Now

The main strength of Rush PCB lies in our extensive experience and our offer of quality PVB design and manufacturing solutions. Let us know of your requirements through email, or give us a call. We will solve all your queries, and we will give you a quote. Visit our website for more insight into our capabilities of PCB layout, manufacturing, assembly, and prototyping services.

Read About: Requirements for PCB Assembly Drawing

internet-of-things PCB

Influence of IoT on PCBs

Influence of IoT on PCBs

Rush PCB has deeply woven the effects of the fourth industrial revolution or the Internet of Things (IoT) into their daily life and within their framework of technology. IoT is growing at a tremendous pace in the  electronic industry. Globally, it is considered as one of the most significant movements of the century.

IOT PCB

Unobtrusively infiltrating into everyday life, IoT has been effectively changing the way consumers look at life and technology presently. At the same time, not many are aware that PCBs are keeping IOT at the forefront of technology. In fact, IoT and PCB technology are both advancing simultaneously. IoT is causing a paradigm shift in PCB design and manufacture. With the phenomenal increase in demand for IoT devices, PCB designers need to master the intricacies of Rigid, Flex, Rigid-Flex, and HDI PCBs. Pioneer PCB manufacturers such as Rush PCB are already at the forefront of technology that IoT demands.

Although people are more aware of consumer electronics as these devices are more visible, IoT devices dominate more in the manufacturing, transportation, and healthcare industries. IoT devices effectively span the physical and digital world as they can connect to IP networks without resorting to a personal computer. The most prominent example of an IoT device is the smartphone with its myriad apps. This app allows controlling home appliances and utilities. Other examples of IoT are the wearable devices and vehicles with data accessibility.

HDI PCBs for IoT

Earlier, the shape and size of the computer was dependent on the structure of its inner components—at present, that is no longer true. Thanks to the latest technologies used by eminent manufacturers such as Rush PCB, the industry can create optimal IoT products  easily. It is possible without  restricting their design or functioning.

In fact, Rush PCB is leading the way in making PCBs with sophisticated manufacturing processes. We make all types of flex, rigid-flex, and high density interconnect (HDI) PCBs.  that allow designers complete freedom to express their functionality and sustainability with the aspects of the new form they can create.

For instance, HDI PCBs allow the designer express their design freedom, while they cater to high-power demands in increasingly sparse spaces. Rush PCB makes HDI PCBs suitable for the harshest environments. It has high tensile strength of copper. Additionally, it is capable of withstanding constant device stress .That’s  why;  it is a suitable option to contemplate. At Rush PCB, we handle all the challenges you can present us with. You only need to give us a call, and we will do the rest.

Flex Printed Boards for IoT

Our customers can reduce their design limitations by using flex printed boards from Rush PCB. The structure of our flex boards allows designers use revolutionary forms and shapes. It is viable while reducing several types of errors and reducing costs. Major attributes of flex printed boards from Rush PCB are:

Lower Weight: Flex circuits from Rush PCB can save 95% of the weight of an equivalent regular rigid board. With lighter internal components, designers can make IoT devices much more versatile. With smaller hearing aids and more delicate surgical equipment, they are the best choice to consider.

Smaller Size: A rigid PCB not only limits the design freedom, but also requires much more space within the device. Replacing it with a flex circuit from Rush PCB allows the designer to reduce the size dramatically. The maintainiance or even enhancing the functionality is our core priority.

Improved Durability: Rush PCB makes flex PCBs with materials that are much more durable and can withstand stress from impacts or vibrations. This is an important requirement of industrial IoT devices.

Improved Reliability: Flex circuits from Rush PCB can replace wiring and interconnecting cables. It helps in reducing human assembly errors and improving assembly times.

Why Rush PCB for IoT

Rush PCB focuses on combining the best features of flex and HDI technology. The ultimate purpose is to create the most appealing and efficient designs for IoT. Apart from the individual advantages of either technology, typical benefits of this combination are:

  • Reduction of thermal stress
  • improvement in signal quality
  • Ability to withstand harsh environments
  • Use of Copper with high tensile strength

Our customers trust Rush PCB to provide industry-leading options. We surpass your expectations by not only meeting your budgets. We can make you stand outside the crowd.

Contact us today for your next IoT project.

PCB

Importance of Stiffeners for Flex PCBs

Importance of Stiffeners for Flex PCBs

As printed circuit boards (PCBs) evolve, they are gradually changing over from rigid boards to flexible types. Its demand is increasing in medical field. Additionally,  military, aerospace, and industrial markets, manufacturers are gearing up to produce flexible circuits board along with rigid ones. Rush PCB has the technology and expertise in place for producing various types of flexible boards to meet the market demands.

The major advantage flexible circuits offer designers is the capability to outfit products with a suitable circuit when the design of the product will not admit using a rigid circuit board. That makes flexible circuits invaluable to several applications in the electronics industry.

Although flexibility may be a desirable feature in most applications, some parts of the circuit may need to be stiff as well. For instance, if the area where a connector needs soldering on the PCB is not stiff, there is a potential risk of damage to the PCB with the insertion and removal of the connector. As the board is soft and flexible, the force of insertion and removal of the connector falls on the soldered pads. Also, it causes them to lift off the board, thereby damaging it. With a stiff board, the force distributes itself over the entire area. Furthermore, it does not damage the solder joints on the circuit.

The necessity for PCB Stiffeners

Rush PCB UK adds stiffeners in flexible circuits to reinforce areas containing components and where rigidity is necessary, but not in areas where the board will flex. There are various instances where a flexible circuit needs to have rigid areas. These include:

  • Presence of components near a flex zone
  • Increasing the abrasion resistance of the flex circuit
  • Specific areas of the board need mechanical strengthening
  • Maintaining the required thickness in the flex circuit
  • Supporting components and connectors on the PCB
  • Constraining flexibility to parts of the circuit that require it
  • Enabling better handling of the flexible board
  • Keeping specific areas of the flexible circuit stable and flat
  • Improving heat dissipation and providing strain relief
  • Meeting Zero Insertion Force (ZIF) connector specifications
  • Increasing and constraining the bend radius at the intersection of flex and rigid parts of the circuit — for avoiding stress on the flex part during repeated bending operations.

The basic reason for the use of stiffeners is when the flexible circuit requires a rigid area as protection against damage maybe from connectors or components attached to it. As the stiffener does not allow the circuit to bend, it protects the integrity of the solder joints in the area.

One may not need to use stiffeners if the flex circuit only has small SMD components that do not exert too much strain on the flexible part. Also, if there are no components mounted on the PCB in the flex region, the designer may decide not to use any stiffener.

Materials for Stiffeners

Although FR4 is the most common material Rush PCB uses for making stiffeners. Furthermore, they also use Polyimide, Aluminum, and Stainless Steel as the application demands. FR4 and Polyimide stiffeners may also have additional features such as pads, plated through holes, along with mounted components.

Although stiffener thickness may range from 8 mil to 59 mil (0.008”-0.059”), manufacturers prefer to use them in standard thicknesses. Generally, it is of 20 mil (0.020”), 31 mil (0.031”), 39 mil (0.039”), and 59 mil (0.059”). The requirement for a specific thickness of the stiffener depends on the application. In general, thicker the stiffener, better the support it offers the flexible PCB.

For instance, a ZIF connector requires the area of the flex circuit that plugs into it to be stiff. Manufacturers achieve this by using Polyimide stiffeners at the contact fingers. Typically, the PCB thickness requirement for ZIF connectors is between 0.2 and 0.3 mm. Allowing for the thickness of the actual flex PCB material, the stiffener thickness at the contact fingers can vary between 2 mil and 8 mil (0.002” and 0.008”).

Certain applications demand higher stiffness and manufacturers use Aluminum or Stainless-Steel stiffeners for the purpose. Metal stiffeners have the added advantage of acting as a heat sink if necessary. However, adding metal stiffeners increases the cost of the flexible circuit considerably.

Read Also:  New Configurations for Rigid-Flex PCBs

Application of Stiffeners

It is possible to use stiffeners for components requiring plated through holes (PTH). Rush PCB recommends using the stiffener on the side of the flex board on which the components will mount. This will allow access to solder pads on the flex circuit, making assembly easier. Designers should always enlarge holes on the FR4 stiffener to about 0.3 mm larger than those on the flex circuit. This will definitely ensure good alignment.

Rush PCB also recommends making flex circuits in the form of arrays, while including FR4 stiffeners all along the array border. This helps to make the array rigid enough to allow it to run through the automated assembly processes. It doesn’t require any additional tooling plates.

Manufacturers typically attach stiffeners to the circuit using heat and pressure. However,  Rush PCB recommends attaching stiffeners using pressure sensitive adhesives. Among the several varieties of such adhesives available to meet specific performance requirements. Two of the more popular types are thermally bonded adhesives and pressure sensitive adhesives.

Manufacturers select the type of adhesive to use depending on the location and configuration of the stiffener. For instance, if the stiffener size does not extend beyond the flexible board outline, pressure sensitive adhesive will be the best method for attaching it to the circuit. The manufacturer decides the specific pressure sensitive adhesive to use. It is mainly based on whether the flex PCB will undergo automated an automated reflow cycle, and or to what material it will finally adhere. Stiffeners often require their own prepreg lamination cycle, with certain stiffener materials requiring additional lamination cycles as well.

Bonding Between Rigid and Flex Circuits

Manufacturers prefer to use no-flow prepreg as the typical material for bonding flex and rigid material.It is most common in standard FR4 or Polyimide material. Depending on the application, a manufacturer may attach stiffeners to only one side or to both sides of the flex PCB. When attaching stiffeners to both sides, Rush PCB recommends a review by the designer to avoid complications at PCB assembly stages.

A single flex circuit design may require multiple stiffener thicknesses. This type of design has some limitations, and may need a thorough review of the PCB supplier for their capabilities.

Strain Relief for Stiffeners

Although designers add stiffeners to certain areas of a flex circuit to relieve the strain on the flexing part, the stiffener itself may need strain relieving. It’s needed more specifically where the circuit extends beyond the stiffener. Rush PCB recommends filleting the transient edge with a resilient adhesive or epoxy.  They can better relief such strains. Providing strain relief at the edge of a stiffener helps to prevent stress risers from occurring at transition areas such as from the flex to the rigid.

Conclusion

Stiffening some part of a highly flexible circuit may seem contrary to its functionality. However, the ability to do so helps the durability and reliability of the fragile circuit in many ways. Rush PCB recommends that designers use a stiffener. The suggestion is to relieve the strain on the flex circuit at a specific area. Mainly, it is the best way to extend its working life.

HDI

VeCS Competing with HDI

VeCS Competing with HDI

Consumers continue to demand electronic devices with increasing functionality, although quantum tunneling hinders further scaling. Smartphones and smartwatches already pack an amazing amount of functionality within these tiny devices. Rush PCB uses microvia technology, facilitating shrinking via structures and high-density interconnect to define routing in dense Printed Circuit Boards (PCBs).  Thereby, it is packing even more functionality within small footprints.

However, designers are under increasing pressure to decrease form factors further and pack even more functionality within single packages. For this purpose, they are exploring newer multi-layer routing architectures.

Microvia Technology

When designers work with only a few layers on a thin board, they usually employ through-hole vias to interconnect layers. As the number of connections increases within a small area, the designer must use unique ways for reaching the inner layers. It should be done while managing board space. It is not possible to route multiple signals through a specific interior layer area using through-hole vias. They are meant only for routing signals between two layers, even when the board has several layers.

Vias, even at microvia sizes, take up unnecessary internal board space. Buried vias do help to some extent, but still take up space when routing between layers not adjacent to one another. Microvias offer better flexibility.

Fabricators create boards with sequential buildup, where they use lasers to place microvia holes in layers instead of using drill bits. They use lasers to drill blind and buried microvias as well, and they plate all these vias using an electrolytic deposition process. Since microvias span only a single layer, connecting across multiple layers needs stacking the microvias or using skip vias for routing the desired connections.

Rush PCB estimates that in HDI PCBs microvias can reduce the total board space by 60-70%. However, microvias are a great help when routing components with high pin densities. In fact, designers can place microvias directly onto the mounting pads for increasing pin densities. Of course, these microvias need filling and plating to prevent them from wicking molten solder during assembly and creating weak electrical connections.

ELIC Technology

ELIC or Every Layer Interconnect routing is a recent innovative development. One big advantage of the ELIC technology is it does not require a core in the center of the board. It can facilitate connections throughout the interior of the board. ELIC is especially suitable for BGA packages for memories, CPUs, GPUs, and other extremely fine-pitch component routing. This technology essentially makes use of copper-filled, stacked microvias for connecting different layers on the board. However, with increasing layout and routing densities, designers are looking for newer technologies for routing between layers in a multi-layer PCB.

Vertical Conductive Structures (VeCS)

VeCS is a promising innovation that increases the routing density of a board tremendously. Designers can place a larger number of tracks between BGA pads using VeCS architecture than they can using microvias or ELIC alone. Therefore, VeCS allows designers to reduce their dependence on multiple interior signal layers when routing HDI boards.

Rather than using round or cylindrical vias, the VeCS architecture makes use of grooves plated with copper for routing into the board surface. The fabricator uses a slightly wider drill to drill holes along the groove. It helps in  leaving straight vertical conductors passing through the inner layers. As no other specialized manufacturing technique or tooling is necessary for VeCS.  It provides the same functionality as ELIC does. This new technique is very useful to designers looking for higher routing density in their HDI boards.

Significance of VeCS

This new technology, VeCS, is a shift from laser-drilled holes and conventionally drilled holes for increasing the densities in vertical connections. Apart from adding more traces in the routing channel, VeCS enhances power distribution to and from the grid array. This allows the reference planes to offer a constant and stable image to the signal layers. Resultantly, it reduces signal distortion and leads to higher data rates.

As the reference plane width under area array packages is much wider for VeCS compared to all other drill or laser processes, designers can lower the interlayer copper weight. Compared to traditional via processes, vertical connections of VeCS have much lower inductance and capacitance. Rush PCB recommends using VeCS architecture to improve signal integrity. It is one of the finest ways to achieve higher bandwidths.

VeCS and its Core Benefits

With VeCS capable of routing signal channels of greater width, designers can afford larger trace widths and higher thicknesses of the dielectric layer. Comparatively, it i better than to  any other innerconnect technology in the industry. For instance, for BGA with pitch 0.8 mm and below, the PCB manufacturing methods require HDI build-up with dual lamination. Additionally, it requires sequential lamination, and small hole drilling methods. All this tends to push up the cost compared to traditional PCBs.

However, the advantages of the VeCS technology becomes more prominent as the BGA pitch goes below 1 mm, and its size increases above 100 I/Os. Even when the BGA pitch goes below 0.5 mm, manufacturers can continue to use conventional manufacturing equipment and materials if they use the VeCS technology.

By increasing the routing channel width, VeCS technology helps designers lower the layer count of most large BGA PCBs. In addition, with VeCS, the designer can place all components in the same position on the topside of the PCB as earlier, use the same materials as with the previous PCBs. While lowering PCB costs and improving the signal integrity performance.

Also Read: Integrity of the Signal in HDI Circuits

Manufacturing Steps for VeCS

Rather than employ an entire hole to connect just two circuits on layers on either side of a PCB, the VeCS technology uses multiple vertical traces through a slot to connect multiple circuits.

The VeCS concept uses peck-drilling to route a cavity or slot into the board, then metallize and plate it to provide the connections. In the final step, the fabricator drills slightly larger holes to create vertical connections between the layers. The vertical connections take up less room than conventionally drilled through-holes do thereby allowing the designer more space for routing the traces.

The manufacturing process for VeCS does not require any change in the conventional multi-layer manufacturing process, apart from adding a few additional steps such as:

  • Drilling or routing a slot between lands for BGA
  • Metallizing the slot
  • Imaging with VeCS breakouts adjacent to the metallized slot
  • Plating the PCB and the slot
  • Etching as normal
  • Creating vertical traces by drilling the metallization

The VeCS process does not involve laser drilling, and the fabricator can use a panel plating process. This makes the VeCS fabrication process very conventional.

Manufacturing Processes for VeCS

VeCS technology can create multiple vertical connections within a slot in a dense area than is possible with the current HDI board technology.

It is possible to combine VeCS slots with microvias if necessary, and like microvias, the slots can form through, blind, or buried connections.

PCB manufacturers can use standard HDI PCB techniques, thereby avoiding capital investments and qualifying new processes.

Drilling Process

The separation between the vertical traces creates a direct barrier to prevent electron migration between adjacent traces. The fabricator can make separation between the adjacent traces to be as accurate as 0.1 mm or less. This is not possible using any other technology at present.

Milling Process

The drilling process creates slots with a minimum width of 0.3 mm. For still thinner slots, fabricators use the milling process, which extends to slots of 0.2 mm or less. Usually the length of the slot varies from a few mm to about 12 mm.  Manufacturers of semiconductor packages employing VeCS can make slots of 0.15 mm and below.

Plating Process

Fabricators use the conventional plating process to plate the slots for the VeCS technology. In fact, plating slots is easier than plating holes as fluid exchange is slots is better. Moreover, the high fluid exchange in slots prevents aspect ratio issues.

Materials and Stackups

Manufacturers can use the regular materials they use for circuit boards for VeCS as well. They can use the same dielectric and copper thicknesses typical to the industry.

Summary

Rush PCB suggests using VeCS technology for HDI PCBs, as it does not require any additional capital equipment. In addition, it doesn’t need any medium/high technology PCB manufacturer can start using it with some training. The VeCS technology offers a cost trade-off as the increase in the routing density. It results in a reduction of the number of signal and reference layers or a smaller board.

PCB

PCB Assembly Fabrication Methods

PCB Assembly Fabrication Methods

PCB or Printed Circuit Board assembly at Rush PCB UK Ltd involves combining the bare PCB, electronic components, and other accessories effectively to allow the assembly to function as the designer intended. Broadly, the fabrication methods involve a number of major steps:

  • Component placement
  • Soldering
  • Cleaning
  • Inspection
  • Testing

However, depending on the nature of the PCB undergoing the assembly, above steps may involve further activities.

Component Placement

Methods of placing components on the PCB depend on several factors such as:

  • Single or double side component placement
  • SMD components only
  • Through-hole (TH) components only
  • Mix of SMD and through-hole components

A PCB may have components present only on one of its sides or on both, although assembling a PCB with through-hole components on both sides is a rare occurrence. Single side component placement with either all SMDs or all through-hole components is more common, while single sided PCBs with a mix of SMDs and through-hole components is also to be found.

For assemblies requiring SMDs on both sides of the PCB or a mix of SMD and through-hole components on the top and only SMDs on the bottom, the PCB assembly process must be broken up into several intermediate steps, and the assembler needs to take special precautions for each of them.

Single-Side Component Placement

This type of PCB may have only SMDs, only TH components, or a mix of both. If it is only SMDs, the necessary steps for assembly are:

  • Solder paste printing
  • SMD placement
  • Reflow soldering
  • Manual Inspection
  • Electrical and Functional Testing

When the PCB has only TH components, solder paste printing is not necessary, in place of SMD placement, there is either manual placement or machine placement of the TH components, and wave soldering replaces reflow soldering. For a mix of both components, the assembler places TH components after anchoring the SMDs to the underside using adhesive and follows it up by wave soldering. This is because SMD components at the bottom of the board require to be held in place, while component leads extending on the underside of the PCB are undergoing wave soldering.

Double-Side Component Placement

Similar to the single sided PCBs, double sided PCBs may have SMDs alone, TH components alone, or a mix of SMD and TH components. Although it is usual to mount SMD components on both sides, mounting TH components on both sides is not feasible. However, it is possible to have a mix of SMD and TH components on top, and only SMDs on the bottom side of the PCB.

With both sides of the PCB holding components, multiple steps are necessary for the placement and soldering of the individual sides. SMDs on the underside need anchoring to the bottom side of the PCB to prevent them from falling away. Assemblers use a glue dispenser or a glue stencil to deposit a small drop of glue at the coordinate where the pick-n-place machine will deposit the SMD on the bottom side of the PCB. Baking is necessary to allow the SMD to permanently stick to the board before the soldering process.

The top side of the board may have only SMDs, only TH components, or a mix of the two. If the board has only TH components on its top side, the assembler inserts them and sends the board for wave soldering. However, if there are only SMDs on the top or a mix of SMDs and TH components, the assembler mounts the SMDs first, solders them with reflow, mounts the TH components and then wave solders the bottom side of the PCB.

Soldering

Soldering is the process of joining two dissimilar metals using a molten filler metal alloy. The molten metal alloy enters the joint, and as it cools and solidifies, bonds with the adjoining metals. Primarily, there are three common ways of soldering:

  • Manual Soldering
  • Wave Soldering
  • Reflow Soldering

Manual Soldering

Manual soldering requires the use of a soldering iron whose tip is heated either by gas or electricity. The pcb assembler applies the hot tip to the component lead and pad to heat them up. Solder held on the heated junction melts and solidifies to form a joint. The assembler may apply flux to the surfaces to help the process of soldering.

Wave Soldering

Wave soldering is a bulk soldering method. The PCBs to be soldered pass over a bath of molten solder. The bath has a pump to create a wall of solder that washes the underside of the PCB as it passes over the wall, effectively soldering the components to the underside of the PCB.

Temperature of the molten solder in the bath and the time the PCB is exposed to the solder are the two important parameters governing the quality of the solder joints formed. It is also necessary to preheat the board mounted with components to allow proper wetting. Although wave soldering is primarily effective for TH components, it can solder SMD components anchored with adhesive on the underside of the PCB.

Reflow Soldering

Assemblers use reflow as the most common method for soldering SMD components to the top side of the PCB. However, before they can solder the components, they must deposit solder paste and mount the components in place. The sequence they follow are:

  • Solder Paste Printing
  • Mounting SMD Components in place
  • Passing the assembly through a Reflow Soldering Oven

The assembler first deposits solder paste using a prefabricated stencil onto the pads of the PCB. Instead of using solid solder, SMD assemblers use a paste of solder and flux, which they draw with a squeegee over a stencil placed on the PCB. Appropriate cutouts in the stencil allow the solder paste to deposit onto the pads. On removing the stencil, the pads that will hold the components only retain the solder paste.

A pick-n-place machine then places respective SMDs onto their locations on the PCB. A pre-assigned program on the machine allows it to pick a specific SMD component from reels or cassettes and position it on a predefined position on the solder paste.

This assembly of PCB, solder paste, and components then passes through an oven on a conveyor belt, where heat melts the solder paste, effectively soldering the SMDs to the board. The speed of the board through the oven and the oven temperature are very important settings for achieving a good quality of solder joints.

Cleaning

After soldering is over, some flux residue may remain on the printed circuit board. Over time, this can turn acidic, and corrosively damage solder joints. The flux residue can also attract fingerprints and make the PCB look unclean.

For cleaning and removing flux residue, Rush PCB UK Ltd prefers washing the PCB assembly with high-pressure deionized water. A quick drying cycle with compressed air removes all traces of water, and the PCBs are ready for inspection and testing.

Manual Inspection

Inspection is necessary at various stages of assembly. For instance, one stage of inspection is necessary when the operator has stuffed TH components into the board, and again once the assembly has undergone wave soldering.

Likewise, for reflow soldering, inspection is necessary once after solder paste printing is over, then again after mounting the SMD components, and once again after the boards have exited the reflow oven.

Also Read: PCB Assembly Compatibility with In-Circuit Testing

Inspectors in both cases above look for missing components, wrong components, wrong polarity, solder bridges, excess solder, inadequate solder, dry joints, and many more defects. For minor faults, a touch up station is enough to rectify them, but for more severe and persistent faults, a change in process parameters is the solution.

AOI & X-Ray Inspection

For large batches of PCB assembly, the manual inspection process may be too slow. A faster process is the Automatic Optical Inspection or AOI process. AOI machines have video cameras to capture images of the PCB, the components, and the solder quality, and they can compare the images with standard images in the machine’s memory. The AOI machines work at high speed processing a large number of PCBs within a relatively short time.

Fine pitch components such as BGA conceal the solder joints under the component body, preventing manual or automatic inspection. The only way to assess the quality of solder joints hidden under such components is by passing the board through an X-Ray machine, capturing the images on camera, and examining the results.

Electrical & Functional Testing

Electrical testing may be necessary after the assembly has passed through the above stages, to test whether the assembly functions as intended by the designer. This may involve programming the board, or calibrating certain components before the actual testing can begin.

Electrical and functional testing involves applying specific voltage/voltages to the circuit on the PCB and looking for normal/abnormal behavior at predefined outputs. Some tests may require a voltmeter and ammeter, while others may need more sophisticated instruments such as an oscilloscope or a waveform analyzer to complete the testing.

Conclusion

PCB assembly is a complicated process involving several technical processes with important setup parameters. Eminent assemblers such as Rush PCB UK Ltd are always careful with these setup parameters to allow the final product achieve the desired quality

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Toxic Materials and Safety Considerations During PCB Manufacturing

Rush PCB produces printed circuit boards (PCBs) as a platform for mounting electronic components such as semiconductor chips, resistors, and capacitors. Found virtually in all electronic products, PCBs have copper traces that provide the electrical interconnections between the components. With the proliferation of electronic gadgets and equipment, the once low-technology PCB has evolved into a high-technology product.

At Rush PCB, manufacturing printed circuit board is a highly complicated process, one requiring investments in several large equipment and involving over fifty process steps. We manufacture most of our high-speed miniature PCBs in clean-rooms, addressing the same concerns of health and safety as other microelectronic manufacturers do while manufacturing medical electronic equipment.

Apart from glycol-ethers, one of the major solvents the PCB industry commonly uses, large quantities of hazardous chemicals such as dimethyl formamide and formaldehyde are also in use. Lately, the PCB industry worldwide has made a serious effort to diminish the quantity of Lead it earlier used when manufacturing PCBs.

Waste Characteristics from PCB Manufacturing

There are typically three ways in which PCB manufacturing produces toxic materials waste:

  • Air Emissions
  • Effluents
  • Solid and Hazardous Waste

Air Emissions

Manufacturing PCBs produces potential air emissions from acids such as hydrochloric, sulfuric, nitric, phosphoric, and acetic; vapors from ammonia and chlorine; organic solvent vapors from acetone, isopropanol, trichloroethylene; petroleum distillates, xylene, acetate, and ozone depleting substances.

Assembling PCBs may produce air emissions such as from fumes of the soldering process, organic solvent vapors, including from organic acids, flux vapors, aldehydes and similar.

Although chlorofluorocarbons (CFCs) had been a preferred organic solvent for a variety of applications within the PCB manufacturing industry, most countries have now banned their use as these compounds exhibit a high potential for ozone depletion.

Effluents

Manufacturing PCBs produces a number of effluents rich in vinyl polymers, organic solvents, stannic oxide, and metals such as nickel, copper, iron, tin, chromium, palladium, lead, gold, cyanides, fluorides and fluoborates, sulfates, acids, and ammonia. Some metals may also form complex compounds with chelation agents.

Assembling PCBs may also produce effluents containing alkalis, acids, metals, fluxes, and organic solvents. Electroplating processes may produce effluents containing sulphates, cyanides, fluorides, and several metals.

Solid and Hazardous Waste

PCB manufacturing operations also produce solid waste that may occasionally be considered hazardous. Such solid waste may include inks, plating and hydroxide sludges, and scrap board material.

PCB assembly operations may also produce solid waste in the form of scrap boards, solder dross, rejected, broken, or discarded components, metals, and organic solvents. Assemblers may also treat some boards with brominated flame retardants, which may cause environmental risk when such boards are discarded in landfills.

As such, environmentalists consider all conventional electronics as hazardous in landfills, due to the presence of lead and other metal salts, specifically if a post-soldering operation has not cleaned them.

Apart from the above, PCB manufacturing may also produce sludges containing heavy metals. This is specifically the case where industries operate waste water treatment plants. Organic solvent waste residues may also be present requiring management and disposal.

Safely Considerations with Toxic Materials

PCB manufacturing and PCB assembly uses and produces many substances that are toxic enough to cause serious harm if they enter the body of individuals. Rush PCB recommends taking safety measures such as:

  • Working safely with toxic materials
  • Substituting with a less hazardous material where possible
  • Using good ventilation when working with toxic materials
  • Using warning signs and clear identification when storing toxic materials
  • Storing toxic material out of direct sunlight and in well ventilated spaces
  • Handling toxic materials safely
  • Disposing toxic material and waste safely
  • Wearing personal protective equipment

Good Housekeeping is Important

Preventing exposure to toxic material is very important during manufacture and assembly of PCBs. For this, Rush PCB suggests good housekeeping, as a clean and orderly workplace is safer for everyone. For instance, Rush PCB uses:

  • Appropriate spill control equipment and procedures to clean up any spills and build-up of toxic materials promptly and safely.
  • A pre-wetting technique and a vacuum cleaning equipped with a high-efficiency filter instead of dry sweeping of solid materials.
  • Proper disposal procedures for unlabeled and contaminated chemicals.
  • Waste containers compatible with the toxic material.
  • Properly labeled containers and storage for each toxic material.

Handling Toxic Materials Safely

All personnel who must handle the toxic materials need special training to do their jobs properly and safely. Rush PCB suggests the following:

  • Use only the smallest amount of chemical necessary for the job.
  • Never allow toxic vapor, dusts, mists, or gases to enter the workplace air—use proper exhaust techniques.
  • Avoid body exposure by wearing appropriate personal protective equipment for the eyes, respiration, and the skin.
  • Awareness of typical symptoms of poisoning and first aid procedures. Training should include immediate reporting to the supervisor any signs of illness or exposure.
  • Medical attention depending on the material, even when the exposure does not seem excessive.
  • Never allow returning unused or contaminated material to the original container.
  • Label containers legibly and inspect regularly for leakages or damage before handling.
  • Ensure container lids remain tightly closed when not in use.
  • Suitable emergency equipment for leaks, spills, and fires must readily be available.
  • Suitable emergency shower/eyewash stations must readily be available.
  • Open containers for transferring material using proper tools—prevent spillage.
  • Be careful when pouring toxic liquids—avoid spurting and splashing.
  • Never allow soldering, cutting, welding, or any other hot work on piping or containers unless they are free from all toxic vapors and liquid.
  • Maintain good housekeeping—do not allow accumulation of dust etc.

Disposal of Waste Toxic Materials

Safe disposal of waste toxic material is extremely important for the environment. Rush PCB suggests the following:

  • Always comply with local, provincial, and federal requirements when disposing toxic material. Requirements may vary depending on the jurisdiction.
  • Never allow flushing of toxic material down sewers or sanitary drains, as this method of disposal is illegal and unsafe practice.
  • Never allow mixing of hazardous waste material with regular garbage that is destined for a landfill.
  • Use only waste containers compatible with the waste material.
  • Properly and accurately label all waste containers.
  • Never allow mixing incompatible mixtures in a single waste container—avoid potential spills, fires, or explosions.
  • Never allow overfilling of liquid waste containers—allow filling only to about three-quarters capacity for vapors to expand. This reduces the potential for spills when moving overfilled containers.
  • Do not allow reusing empty containers as they may still be hazardous from the leftover toxic residue. Arrange for safe and proper decontamination before reusing the container.

Personal Cleanliness is Essential

Personal cleanliness is essential for those working with toxic materials. This provides protection not only for self but also for others (coworkers and family members). Rush PCB suggests the following:

  • Always wash hands before smoking, drinking, eating, or visiting the toilet.
  • Remove contaminated clothing and shoes, and wash them thoroughly in water before discarding or re-use.
  • Always store food and tobacco products in uncontaminated areas.
  • Make a conscious effort to not touch eyes or face with contaminated hands.
  • Never allow gum chewing when working with toxic materials.
  • Even when following all the above, it is necessary to wash thoroughly at the end of the workday.

Conclusion

At present, the world is facing a deluge from electronic waste or e-waste, comprising a multitude of components and materials, some toxic and hazardous, leading to an adverse impact on human health and the environment. Eminent electronic industries and PCB manufacturers such as Rush PCB are in the forefront of treating and disposing toxic and hazardous waste material they generate and using approved waste disposal and/or recycling operations.

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Key Steps in Designing Printed Circuit Board Layouts

Key Steps in Designing Printed Circuit Board Layouts

Recent advances introduced by Rush PCB UK Ltd have had sweeping effects across the Printed Circuit Board (PCB) design industry. PCBs form the core of any electronic product today. They serve to hold the innumerable minuscule electronic components together, while allowing them to interconnect and function as the designer intended. Design and layout of PCBs is therefore, and important stage in the development of any product—often deciding the success or failure of the product.

Rush PCB UK Ltd has been in the forefront of this innovation, constantly evolving this technology. As a result, these designs have reached new heights in complexity and expectation, with PCB design rules and production processes evolving to achieve new layouts and capabilities. For instance, mass-produced PCBs commonly have very thin tracks and multiple layers. Even a few years ago, no one would have believed the feasibility of such designs. The availability of advanced PCB design software has also helped this progression tremendously.

However, such improved capabilities alone are not sufficient to effectively design printed board layouts. Experienced electronic engineers routinely struggle with creating layouts on a PCB or when designing a PCB following the best practices in the industry. Often, it becomes really difficult creating a quality board that will fully meet the customer’s need. As each design is different, balancing the functionality of a PCB while following the best design practices is an ever-involving process. To make the process easier, Rush PCB UK Ltd has outlined the process of designing PCBs and included some essential PCB design rules.

RushPCB UK

RushPCB UK

Determining the Basic Needs

Although requirements are broadly spelled out by the customer, the design engineer must translate these requirements into mechanical, electrical, and electronic terms. For instance, the design engineer must decide if the equipment requires a single PCB or several, and the functionality of each of the PCBs. Depending on the functionality and the interconnection between the PCBs, the design engineer will apportion a certain part of the total circuitry to that PCB.

Determining the Material for the PCB

The basic needs of the project also help in determining several important aspects, one of them being the materials of which the PCB should be made. For instance, the project may require the PCB to handle high frequencies, and therefore, the designer will use materials with controlled impedance. On the other hand, applications involving medical or automotive devices often require components that will fit into tiny spaces, thereby requiring a flexible PCB. Additionally, the final size of the PCB and its functionality often determine whether it will be made of a single layer or with multiple layers.

Based on the above needs and the functionality of the PCB, the designer will decide the initial schematic of the PCB, and hence the Bill of Materials or BOM.

Determining the Schematics and BOM

While the schematic determines the functions of the PCB, the BOM lists the components that the PCB requires, their source, and their footprints. Essentially, the schematic forms the blueprint engineers and manufacturers use during the development, production, and the assembly processes. The schematic and the BOM together contain details of the hardware for the PCB, material, components, and details of other materials the manufacturer will need during the production process. The designer must ensure the schematic refers to each component with a unique identifier, and they all have the proper footprints associated with them. Additionally, the information in the schematic must also tally with the BOM. In fact, designers typically use PCB design software to generate the schematic and the BOM.

The design engineer must ensure the schematic and the BOM contain the manufacturer’s part number for the components, and where possible, alternatives for each component, as alternatives help in speeding up the procurement process.

Determining the Net List and the Layout

After finalizing the schematic and the BOM, the designer has to generate the Net List. This is a list of interconnections of the components on the PCB. Each PCB will have its own Net List.

The Net List serves two purposes. The first is to generate the layout, and second is to allow the PCB manufacturer verify the interconnections when fabricating the PCB. The designer imports the Net List into another part of the PCB design software, which recalls all the footprints from its library and connects the pins of the components according to the Net List using a series of straight lines also called the Rats Nest. In the next step, the design engineer must follow some best practices for achieving an effective layout:

  • Implement the Appropriate Panel Size for the PCB
  • Implement the Proper Grid
  • Implement Design Rule Checks or DRC
  • Implement Design for Manufacturing or DFM

Implementing the appropriate panel size of the pcb is a vitally important step for the design engineer to follow, as the PCB has to fit into the space allocated in the equipment. Moreover, it also marks the areas on the PCB allocated for mechanical attachments, and hence, the designer has to be careful of not placing any electronic component in these areas.

Implementing a proper grid is essential for maintaining proper spacing between components and tracks, and the distance components must maintain from the edge of the PCB.

DRC is another essential requirement that a design engineer should start implementing right from the start of the design rather than check at the end of the design process. This allows addressing problems identified by DRC quickly, thereby minimizing requirement of massive changes at the end of the design process and saving time.

From the beginning of the design process, the design engineer should also be concerned about the manufacturability of the PCB. A discussion with the Contract Manufacturer during the design process helps to address manufacturing and assembly constraints right at the beginning, thereby avoiding requirements of changes at the end of the design process.

Determining Placement of Components

Placing each component at its designated spot on the PCB is tricky and depends on numerous factors and considerations. These include the overall PCB functions, thermal considerations, EMI/EMC considerations, and many more. However, design engineers typically place components following best practices order such as:

  • Major Connectors and Mechanical Attachments
  • Power Components
  • Precision and Sensitive Circuits
  • Critical Components
  • Others

During placement of components, the design engineer must also keep Design for Assembly or DFA requirements in view. For instance, if a connector requires manual operation, it must have space around it for finger insertion.

A requirement the design engineer must address at this stage is the position of appropriate test points to ease fault detection. Another requirement is the silkscreen should show clean and unambiguous marking for the components. This is a very important requirement as the information on the silkscreen is useful not only to the designer, but also to the manufacturer, assemblers, and testers. If possible, the design engineer should mark the functionality of the circuit, put test markers, and add component and connection placement directions. Manual assembly gains from silkscreen markings on both sides of the board, while simplifying the production process.

Design Review

Once the design engineer has satisfactorily placed all components, it is a good idea to conduct a design review along with a round of DFM and DFA analysis. Although this step may look unnecessary, it helps to locate mistakes and anomalies for timely correction.

Printed Circuit Board Routing

Most PCB design software have capability to auto-route traces connecting the components based on the Net List. The program does this by using the number of layers available for the connection and taking advantage of the available space by calculating the position of vias.

It is always a good idea to cross-check the interconnections after the computer has finished auto-routing the board. Most design software can produce a second Net List after routing, and the design engineer can verify the connections by comparing with the original Net List. Some areas may be difficult for the auto-router, and the design engineer may have to alter the layout to some extent to generate more space to allow proper routing in a dense environment.

Sometimes, the computer may produce results the design engineer may not approve. This is especially true for high-speed traces, where the designer may have to control the impedance for maximizing energy transfer.

DRC is an important parameter the design engineer must use during the routing process. It should place restrictions on the minimum spacing between traces and pads not only on the outermost layers but also on the inner layers as well. Trace width determines current carrying capacity, and the design engineer must allow wider traces where higher current is flowing.

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Power and Ground Planes

One of the advantages of a stackup with multiple planes is to reduce the physical size of the PCB. Another advantage is to distribute power and ground lines as planes. PCB designers preferably dedicate one or more circuit layers for use as ground plane, and others as the power plane. Designers allocate the power and ground planes in pairs.

There are several advantages of using dedicated ground and power planes in multi-layered PCB. Planes have much lower inductance as compared to thinner traces, and act as low source resistance connection. They also act as shields on either side of the circuitry sandwiched in between the two. This helps to reduce EMI/EMC largely, while improving the operational efficiency. Being large tracts of copper, ground and power planes also act as efficient heat dissipators, especially as designers assign them to the top- and bottom-most layers of a PCB.

PCB Heat Management

Electronic components carrying current will generate heat. The extent of heat generated depends on several factors, which may include variation in copper thickness, the number of layers present, and absence of thermal paths. The design engineer must arrange to distribute this heat evenly, thereby preventing heat spots.

Design engineers follow several methods to manage heat in PCBs. One of them is to use the power and ground planes to the hot component to dissipate heat. As planes contain more copper, they dissipate heat better. Another method designers use for reducing heat generation is by using effective high-current routes and optimizing heat transfer. In some cases, designers also maximize the area they use for transferring heat. However, designers must do this early on in the design phase, and it can also affect the final size of the PCB.

Final Design Review

The final design review of the printed circuit board design must contain many other checks apart from the regular DRC check. At the very least, it should include among physical verification processes a layout-versus-schematic check, an electrical rule check, an XOR check, and an antenna check. Advanced PCB manufacturers such as Rush PCB UK Ltd use additional rules and checks for improving the yield, apart from basic checks manufacturers and designers typically employ.

For the design engineer, one of the good practices to follow is verifying the manufacturing parameters before submitting the PCB documents to the contract manufacturer. By personally generating and verifying the manufacturing parameters before submitting the final design of the PCB, the designer can save the OEM countless hours of confusion, misunderstanding, and losses. This is an important verifying step to expedite the manufacturing process, as it decreases the time necessary for correcting and rectifying the design before manufacturing can start.

Conclusion

According to Rush PCB UK Ltd, implementing the above key techniques and best practices leads to an effective and efficient method of designing Printed Circuit Board layouts. In fact, the process is further simplified by partnering with a contract manufacturer who works with the OEM to make the best and most cost-effective PCBs.

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The Future of Flexible Circuits

The Future of Flexible Circuits

As predicted by RUSH PCB UK Ltd, the market for flexible circuits is going to continue to expand steadily in the future, just as it has been doing for the past three decades. The reasons for this are not hard to find, as, on one hand, flexible circuits continue to support the existing technology so important to different industries, while on the other, advanced flexible circuits are able to comfortably meet the futuristic demands being made by up-coming industries, including the military, avionics, aerospace, telecommunication, consumer electronics, medical, and automotive. To interpret the future of flexible circuits appropriately, it is necessary to consider the subject from three angles:

  • Newer configurations of flexible circuits [1]
  • Newer applications where flexible circuits are useful [2]
  • Newer technology being used for manufacturing flexible circuits [3]

Newer Configurations of Flexible Circuits

Depending on the market demand, manufacturers are always willing to add higher flex layer counts along with prevalent blind and buried via structures, embedded components, integrated connectors, sculptured flex, and more.

Again, based on application, manufacturers can offer flex designs requiring shielding for EMI/EMC in specific areas, asymmetrical constructions, and varying thicknesses between different rigid areas.

Apart from the regular rigid-flex PCB methods of constructions, there have been recent advances in newer configurations of flexible circuits available from different manufacturers. The standard rigid-flex PCB is rather a symmetrical construction, acts as a baseline for building upon, and offers good control over impedance.

Fabrication of standard rigid-flex PCB usually has flex layers at the center of the construction and even layer counts in both, the flex and the rigid areas. Although four to sixteen layers are common in designs, there can be more. Placing the flex layers at the center offers the maximum level of flexibility. However, manufacturers such as RUSH PCB UK Ltd also offer variations in configurations such as:

  • Odd Layer Counts
  • Asymmetrical Construction
  • Varying Layer Count
  • Integrated ZIF Tail
  • Via-in-Pad Design
  • Air-Gap Construction
  • Multiple Rigid Area Thickness
  • Shielded Layers

Although most designs prefer an even layer construction, manufacturers do offer odd layer counts, and this has its own advantages. For instance, a rigid-flex PCB may have seven layers in its rigid portion, and three flexible circuit layers. Requirements of stripline impedance control mainly drive designs of this nature, where the flex area requires two-sided shielding. The construction in the flex area usually has ground layers on the two outer layers sandwiching a signal layer between them—offering large numbers of interconnects between the rigid sections.

The major factor in the odd layer count design is both rigid and flex areas may have odd layers, and the layers counts in the rigid and flex areas may be mutually independent. Manufacturers offer other variations too—even layer count on one side of the core, and odd layer count on the other. The advantage being higher flexibility and higher reliability of bending both in short-term and long-term. Leaving out unwanted layers also reduces the cost of the design.

Complex design requirements such as blind via construction and or widely different dielectric thicknesses within the same PCB calls for an asymmetrical construction. Manufacturers prefer to shift the flex layers towards the bottom of the stack rather than place them in the middle. Although this does raise some concerns of warp and twist during manufacturing, using hold-down fixtures handles them easily.

Manufacturers offer another variety of construction with varying flex layer counts between rigid sections. For instance, the first and second rigid sections may have four to six layers of flex between them, but have only one or two flex layers between rigid sections two and three. Leaving out unnecessary flex layers helps to improve the bend capabilities significantly for the portion with lower number of layers.

By integrating a ZIF tail into the rigid end of a rigid-flex design, the manufacturer eliminates the necessity of mounting a ZIF connector. This is a boon in high-density designs, as it saves both real estate and cost, while producing a thin design.

High-density designs often require blind and buried vias, whereas close-pitch BGA may require via-in-pad design along with via fill and capping. Although dimensional tolerances of materials and manufacturing methods limit the number of lamination cycles in multi-layer rigid-flex PCBs, manufacturing them with via-in-pad design is possible by placing them within the rigid parts of the board.

Manufacturers also offer flex layers in separately configured independent pairs with an air gap in between. This has the advantage of improving the flexibility of the flex part substantially. Of course, this design is only applicable where there are more than two layers of flex. The absence of adhesives within the rigid areas offers greater reliability of the vias therein, resulting in long-term operation of the board.

Although an expensive and complex stackup design, construction of flex circuits with different thicknesses in multiple rigid areas is possible, but presently limited to two rigid areas with different thicknesses.

Special flex circuits requiring shielded layers for reducing the effects of EMI and RF interference use specialized films rather than copper layers. Using copper layers as shield is an expensive proposition. Instead, the special films act as effective shielding material while keeping the thickness of the flex down, thereby improving the flexibility.

Also Read: Understanding the Basic Aspects of Electronic Components

Newer Applications Where Flexible Circuits Are Useful

One of the latest applications that flexible circuits have independently triggered as an explosion is the wearable electronics market. Wearing electronics on the body essentially calls for comfort, and flexible circuits guarantee this. Some examples of wearable electronic applications prevalent on the market are wrist-worn activity and body function monitors, foot-worn sensors, wearable baby monitors, medical sensors, pet monitors, and electronics on worn clothing. By bending and forming flexible circuits to suit the curve of the human body, the applications provide comfort for long wear and use.

Newer Technology Being Used for Manufacturing Flexible Circuits

Manufacturing flexible PCBs still follows the traditional methods of photo-lithography and etching to get rid of the excess copper. To make even thinner flex circuits, researchers at the McCormick School of Engineering at the Northwestern University are dispensing with the copper layer altogether. Rather, they are using a graphene-based ink sprayed onto the substrate in the required pattern to provide the electrical connections.

The advantages of using graphene are twofold. One, graphene can exist as only one atom thick, and its two-dimensional characteristics makes it both flexible as well as transparent. However, the researchers are spraying it on as 14-nanometer thick layers for creating the tracks and patterns. The second advantage is graphene being 250 times more conductive than copper is, only very thin layers are necessary. This improves the flexibility significantly, reduces the weight, and allows for even thinner flex circuits. The next attempt is to allow doping of graphene so that apart from its use as a conductor, it can be used as a semiconductor to make embedded transistors.

Conclusion

The combination of configuration, technology, and application is making rigid-flex circuits a formidable force in the electronics field. It has already overtaken the applications of traditional rigid printed circuit boards, and is threatening the more sophisticated uses of special PCBs in military, aerospace, medical, and consumer electronics industry.

For further information, refer to RUSH PCB UK Ltd.

References:

  1. https://www.epectec.com/articles/how-rigid-flex-pcb-design-configurations-are-advancing.html
  2. http://circuitcellar.com/cc-blog/the-future-of-flexible-circuitry-2/
  3. https://spectrum.ieee.org/nanoclast/semiconductors/nanotechnology/graphenebased-ink-promises-future-flexible-electronics-