2 Shannon Court, 1 Tavistock Road, CR0 2AL, UK

GET A QUOTE

Archives

Home PCB
PCB assembly board

What are Optical Printed Circuit Boards?

Optical Integration on PCBs: A Look at the Advancements

As copper reaches its speed limit, engineers look at optics to replace copper for very high-speed signals. Engineers also envisage replacing copper links between servers, routers and switches with active optical cables. Already silicon chips are available with some optical components inside. The next phase is for optics inside printed circuit boards (PCBs).

Why Optical Systems in PCBs

Electro-optical printed circuit boards combine optical and copper paths on the same board. While the copper paths distribute power and low-speed data, the optical paths handle the high-speed signals. This segregation has several advantages. At high frequencies, signal integrity suffers due to skin effect, crosstalk, and skew when passing through copper systems. Optical systems do not have those issues, while also presenting greater channel density than copper does. Moreover, as optical signals do not need signal conditioning and equalization, optical systems consume lower power than do electrical signals. Additionally, optical systems can reduce the surface area of a PCB by 20% and the number of layers on the board by 50%.

Optical Technology for PCBs

Designers and manufacturers are migrating optical technology to the backplane and connectors. Although optical technology has been around in the form of SFP and QSFP interfaces for some time now, engineers are now developing optical backplane connectors and optical backplanes. These also include optical transceivers at their connecting edges. Now, it is increasingly possible to have optics appear within a board, rather than limit its presence at the edges. Therefore, optics is now moving closer to the electrical signal source. That means the processor, fiber optic patch cords, and waveguides can now be found on the PCB.

Manufacturers have been successful in developing optical backplane connectors and included a technique to align small waveguides to onboard transceivers. The future challenge is to develop onboard waveguides so that performance is guaranteed even if there are tight bends in the board.

Manufacturing Optical PCBs

Engineers use photolithography and film processing techniques to fabricate flexible optical waveguides that will be able to move light around components onboard. According to technical information available, waveguides in the build will need walls at least 100 µm thick, and a bend radius less than 5 mm. These dimensions would allow designers to place the waveguide within connectors. This will also let light travel between a line-card and a backplane, without the necessity to convert it to an electrical signal.

PCB Manufacturers usually follow two different techniques when constructing the waveguides—non-contact mask lithography and direct laser writing. In non-contact mask lithography, spin coating applies the material to the substrate. However, as this process is more applicable to semiconductor manufacturing, lithography is better suited for small areas, and cannot be scaled up to handle large areas. Engineers use a process of draw-down coating for large areas, along with a doctor blade.

pcb-01

However, engineers faced two problems with the above process. One, the waveguide material would curl up, requiring 170 g of force to flatten. Second, there was the difficulty of the waveguide adhering to the substrate. Adhesion to the substrate is important so the waveguide would not crack during mechanical processes such as cutting the wafer or the substrate board.

It is important to have waveguides that do not attenuate the light too much as it travels through. Optical power measurements made with laser diodes as a source and a photodetector as the receiver indicate onboard waveguides introduce optical losses ranging from 0.046-0.050 dB/cm, even when the waveguides were bent to form two or three loops. Some signal loss is customary from wall roughness within the waveguide as well.

Optical Interconnects on PCBs

Onboard optical interconnects on PCBs can handle very high data rates and offer larger numbers of data channels than other electrical interconnections do. Moreover, as optical signal transmission is impervious to electromagnetic interference or EMI, it is suitable for mixed-signal systems such as data acquisition and signal processing where sensor applications need high accuracy of analog electronics.

Optical waveguides on PCBs require not only low attenuation but also a reliable manufacturing process for the optical layer. In an optical PCB, the fabrication steps and material properties of the waveguides need to be compatible with the manufacturing and assembly techniques prevalent in the PCB industry.

Apart from the optical path in an optical interconnection system, there must be coupling elements that can couple optical signals into and out of the waveguides. Moreover, common pick-and-place machines must be capable of suitably and automatically mounting these coupling elements without any active alignment between the optical waveguide and the coupling element. The use of structured polymer foils helps in this integration.

The main issues of using polymers are their thermal and mechanical stability against the process conditions during PCB fabrication. Additionally, with close coupling tolerances and imperfect positioning of waveguides within the PCB, mounting coupling elements often require active alignment. Engineers circumvent such problems in an optical PCB by using standard multimode glass fibers integrated within the layer stack. As glass fibers are highly stable both thermally as well as mechanically, PCB manufacturers can easily follow their proven processing steps for embedding the fibers into multilayer PCBs.

Moreover, the geometrical accuracy of glass fibers, apart from offering very low optical attenuation, is also very important for coupling methods. Engineers can passively align active optoelectronic components at the stubs of the fiber—the PCB has cutouts to make them accessible. A specific micromechanical alignment structure makes this passive alignment possible when combined with the optoelectronic chips—making mirrors and lenses unnecessary for coupling to the waveguides.

rushpcb uk-01

Optical Coupling Elements

For using coupling elements on the PCB, they must be compatible with the assembly and soldering processes manufacturers use. Primarily, the alignment structure should be able to withstand the temperatures involved. Precision molding in silicon molds can achieve this. Manufacturers typically use a temperature of 180°C and a duration of 90 minutes under a pressure of up to 15 bar for the lamination process when manufacturing multilayer boards. Soldering processes expose the board to temperatures exceeding 250°C. Optical waveguide polymers often show discoloring or decomposition at such temperatures. Engineers find glass fibers to be a suitable substance.

Glass fibers remain optically stable without any damage at the above temperatures. Additionally, being mechanically strong, glass fibers offer very low attenuation and exhibit very tight tolerances for their diameter. Rather than fixing the fibers on top of a readily processed conventional PCB, engineers embed them completely into the layer stack of optical printed circuit boards, between the top and bottom layers of the PCB using standard material such as FR4.

Summary

As against waveguides made from polymer foils, embedded glass fibers allow engineers to automatically align the optoelectronic transmitter and receiver components due to the accuracy of their contours. That makes it easy to develop optoelectronic coupling elements onboard, as they can align positively on the fiber using an advanced microstructure and achieve low coupling losses without requiring active position optimization.

rush pcb

Flex pcb 2

How Stable are the Dimensions of Flexible Circuits

Compensating for Dimensional Changes in Flexible Circuit Fabrication

The difference between a rigid printed circuit board and a flexible circuit lies in the dielectric material sets manufacturers to use for fabricating them. Most rigid printed circuits are made from glass epoxy, whereas the material of choice for a majority of flexible circuits is Polyimide. The development of several versions of polyimide enables tailoring the material to meet specialty requirements such as in solar arrays, space applications, and other unusual environments.

Although it is possible to form glass epoxy in very thin constructions and even bend it for simple applications, polymer films are most suitable for continuous twisting, flexing, and multi-planar folding. Films of polyimide withstand numerous bending cycles without suffering any degradation of their mechanical and electrical properties. Therefore, polyimide films perform reliably in applications where bend cycles of over a million are common. The inherent flexibility of polyimide films offers the electronic packager a wealth of design options. However, a disadvantage of polyimide films is their material dimensional stability is inferior to that of glass epoxy materials.

Dimensional Stability

According to manufacturers, the dimensional stability of polyimide films depends on the residual stresses the manufacturing processes place in the film and its normal coefficient of thermal expansion.

However, the measure of stability represents only the effect of the film alone. The nature of stability grows more complex as the fabricator exposes the film to elevated temperatures and pressures for attaching the copper layers through processing to create an adhesive-less laminate, or through an adhesive lamination cycle. However, the process of creating a laminate and subsequently fabricating a circuit involves two different processing effects, and during each of these fabricating processes, the flexible substrate undergoes dimensional changes.

It is not easy to predict these changes. Raw material variation from batch to batch may cause dimensional changes to vary slightly. Changes also depend on the method of construction and processing conditions, as thin materials are likely to be less stable. Other contributing factors can be the percentage of copper etched, density of copper electroplating, ambient humidity, and material thickness.

Small dimensional changes in the circuitry panel are inevitable as it undergoes processing and exposure to a variety of etching, electroplating, pressures, temperatures, and chemistries. For instance, each shrink is the stress etching copper releases, but fabricators mistakenly use it as a catchphrase for representing all the dimensional changes that a flexible circuit undergoes during processing.

Fabricators consider compensating for the above changes when setting up the part number for a new flexible circuit. However, accurate prediction of these feature movements requires empirical data from the parts they produce.

rushpcb uk 2

Effects of Material Instability

Lack of stability in the film material is manifest in violation of the minimal annular ring requirement, and in extreme cases, causes a full breakout of the hole-to-pad alignment. Another possibility is in the misalignment of the overlay. For a predictable material change, the operator can adjust either the conductor layout or the drill pattern to re-center the plated-through hole in the pad.

Dealing with Dimensional Changes

Fabricators deal with dimensional changes by limiting the panel size, and this works very well for cases where the tolerances are extremely tight. In small panel sizes, the effects of dimensional instability issues on registration and alignment are lower, and the handling damages are at a minimum. However, smaller panel sizes may be less efficient for processing as those for larger panels, since in a circuit factory several costs are based on panel size.

Compensating for Dimensional Changes

It is possible to achieve cost-effective production with suitable panel sizes while compensating for dimensional changes. Fabricators can adopt the following methods to adjust for dimensional changes occurring during circuit fabrication:

Applying Scaling Factors

Where the dimensional changes of the material are predictable, fabricators can apply scaling factors to tooling or secondary layers. The in-process measurements for a given lot can allow fabricators to use scaling factors based on dynamic calculations. For instance, the measured scaling factor of a panel may form the basis of the creation of its solder paste stencil. Another instance may be of a final drilling program compensated dimensionally for a multilayer circuit.

Applying Software Compensations

Alignment systems using software-controlled operations can use optical fiducials to detect dimensional shifts and compensate for them. Such fabrication machines measure these targets present on the outside corners of the panel and perform a dimensional analysis. Proper alignment is then a process of applying the necessary X, Y, and theta corrections.

rushpcb uk-01

Processing Sub-Panels

Fabricators often divide the panel into smaller arrays for handling dimensional changes. They do this usually after creating the circuit image. As the processing is on subsets of the panel, fabricators effectively gain some of the advantages of small panel alignment, but without compromising the cost advantages of processing a large panel.

Fabricators typically use optical targets on smaller subset panels to compensate for stencil registration commonly. They also use hard tool dies to cut smaller pieces at a time from a multi-piece panel.

Summary

Dimensional change is the primary difference between rigid and flexible circuitry, and this requires compensation. Even though the material change in flexible circuitry is typically less than one-tenth of one percent, it accumulates over a dimension of several units and can be significant. For a flexible circuit, this compensation for the expected change becomes a critical part related to penalization. This also serves to balance maximizing process efficiencies and maintaining dimensional tolerances and accuracy.

rush pcb

PCB Manufacture 2

How to Choose a Professional PCB Assembly Company

Transforming PCB Manufacturing: The Impact of Cloud Assembly Services

Hardware designers requiring PCB assembly in UK usually face tremendous obstacles to their need for prototyping and small batches. Large companies with huge inventory needs and long delivery horizons can wait for days or weeks for a proposal while accepting large minimum quantity requirements. For them, delays associated with overseas manufacturing are no big deal. However, these conditions are simply unacceptable for small industries, engineers, makers, and entrepreneurs.

A new approach to PCB assembly is gaining popularity. These PCB assembly services are also called kickstarter manufacturing or cloud manufacturing. For instance, RushPCB Inc., a PCB assembly company, now takes into the cloud activities such as quoting, sharing documents, ordering components, and other aspects of project management while working with PCB manufacturers. Customers can expect all interactions with the vendor streamlined and captured in real-time. Investors get the results they are looking for at reasonable prices. However, not all cloud PCB assembly companies are the same, and one has to look for the one that meets the specific requirements.

Best Practices of PCB Assembly Vendor

Selecting the professional PCB assembly company at the beginning determines the success of a project. Therefore, picking the right PCB assembly services provider becomes a highly important decision to be made. One must watch out for those offering very low prices, but subsequently are unable to provide the services, record of accomplishment, infrastructure, and technology to back up their promises. Rather, one must insist the PCB assembly services have the essential features, offer the services, and follow business practices such as:

rushpcb uk-01

Online Management and Reporting

The online administration portal of the PCB service provider is a window to the experiences as a customer. It should allow easy tracking and reporting on the progress of the project, make required changes, and upload design documents including the bill of materials. In short, it should allow the customer to check on the status of the product at any time, and from anywhere.

Instant Quotations

Waiting for days or weeks and trading a bunch of emails only to find out the cost of a PCB assembly, is not only a waste of time, it is expensive. A vendor offering instant, online quotations is always preferable. In general, although all vendors will start by sending a quotation for the project, therefore, selecting one who gets the process off painlessly is advisable. Moreover, selecting the vendor who gives an estimate in terms of quantity offtake helps in determining capital needs and product prices.

Prototyping Requirements

Most customers, before placing their order, want to be sure their PCB works exactly as intended. This may require making a few iterations to perfect the design. So far, prototyping was a big challenge under the old manufacturing model. However, PCB assembly in UK has progressed technologically, and there are PCB manufacturers willing to handle even a single quantity. Usually, vendors keep their prices in check by combining orders of low volumes into large production runs.

Minimum Order Requirements

Earlier, PCB assembly services were unable to accept production runs of small quantities. Older technology did not allow profitability in smaller numbers, which turned out to be a major challenge for everyone. However, use of modern technologies allows easy combination of small orders into larger ones, while switching from one task to another is no longer a major hurdle. Therefore, professional PCB assembly providers accept all types of order, regardless of quantity, and execute them at reasonable prices.

Seamless Manufacturing

With advancement in PCB assembly technologies, it is no longer necessary to track multiple vendors and suffer long lead times. A modern PCB assembly solution such as the Rush PCB Inc., offers a platform to upload design files, review and mange bill of materials, and resolve any assembly problems, online and from anywhere. Once the customer is happy with the design, the professional PCB assembly company takes over the sourcing, purchasing, and assembly of the components. Take care that the vendor offers access to updates on the platform and sends email notifications reporting the project progress. With this approach, expect the product to be available in days.

rushpcb uk 1

On-Shore Manufacturing

Printed Circuit Board assembly in UK can now offer prices competitive with offshore options, thanks to modern PCB assembly techniques. Therefore, enterprises selecting a PCB assembly partner based in the UK can expect to eliminate the delays, risks, costs, and complexity of dealing with a provider from overseas.

Looking Beyond PCB Assembly

The PCB happens to be only the first step of the many for most inventions and products. Professional cloud PCB manufacturers, such as the RushPCB Inc., offer even more. For instance, they will allow shipping in of components and materials for building complex products. They also have a warehouse attached to their manufacturing line, which allows a reduction in delays and shipping fees.

Most products will ultimately be shipped to end-users. Therefore, look for a professional PCB assembly partner who can keep products in their inventory and transfer them directly to end-users upon order. Some, including RushPCB Inc., even provide an API for directly integrating with the enterprise ERP or other e-commerce system.

LED BOARD

Five Reasons Why RushPCB is the Leading LED Board Manufacturer in UK

Five Reasons Why RushPCB is the Leading LED Board Manufacturer in UK

LED PCBs and assemblies have unique requirements that only an eminent LED PCB board manufacturer understands. One of the leading LED PCB board manufacturers in the UK, RushPCB has the technical expertise to manufacture up to 32 layers of PCBs in small and bulk quantities for local and global supplies. With several hundreds of satisfied customers all over the UK and around the globe, there are several reasons why you can safely entrust your LED PCBs to RushPCB. Five of them are:

  1. RushPCB Understands LED PCB Principles

LED Manufacturing Companies in the UK face two major areas of concern related to LED PCBs—thermal management and spillover light. Thermal management means the heat generated from high-power LEDs mounted on PCBs must be effectively removed and vented to prevent damage to the LEDs. For better heat conduction, manufacturers use metal core printed circuit boards or MCPCBs. Although this allows the heat from the LEDs to pass through the prepreg to the metal core, the issue can be a big challenge. RushPCB uses excellent metal core substrates from Univaco, Arlon, Bergquist, and Thermagon to dissipate the excess heat from the LEDs very effectively.

LEDs do not have reflectors, and the light spilling over from its rear and sides is generally wasted. LED PCB board manufacturers use a reflective white mask on the PCB surface so that the spillover light emerges from the front. It is necessary that the white-reflective mask not change color when heated during reflow or in regular use. RushPCB uses special quality material for the white mask that retains its thickness and reflective property under all assembly and operative conditions.

rushpcb uk 1

  1. RushPCB Understands the PCB Bonding Process

MCPCBs require a different bonding process from conventional PCBs because the prepreg must bond to a metal core. There are two important aspects here—the thickness of the prepreg and the bonding process itself. As the prepreg is also the insulation between the metal core and the copper tracks, it must be of suitable thickness to withstand the voltages involved.

At the same time, the prepreg must also be thin enough to allow effective heat transfer from the LED to the metalcore. RushPCB uses prepregs of optimum thickness to allow very good transfer of heat, yet offer good electrical insulation. A special technique by RushPCB ensures the bonding between the prepreg and the metal core does not allow any air bubbles between them, as these air bubbles can impede heat transfer.

  1. RushPCB Offers Excellent Surface Finish

Although LED PCBs and assemblies have a metal core to enhance thermal management, there is a layer of etched copper tracks on top just as conventional PCBs do. The white mask covers most of the copper tracks leaving only the solderable pads exposed. Unless protected by surface finish, the exposed copper pads can oxidize and tarnish, making the PCB unsolderable.

RushPCB offers several types of surface finishes that protect the exposed copper surface. Depending on the customer’s requirement, these can be leaded solder, lead-free solder, Electroless nickel immersion gold, Immersion silver, Immersion tin, or Organic surface protectants.

  1. RushPCB Offer the Best Laminates

Although most LED PCBs and assemblies use single-layer MCPCBs, some applications call for double or multilayer MCPCBs as well. For such multilayer MCPCBs, RushPCB uses special laminate material that offers the best balance of cost and performance. They use different laminate materials from Japan, China, Korea, and Taiwan, which are not only efficient but also meet emerging trend requirements.

rushpcb uk 2

  1. RushPCB Offers the Best Balance of Quality, Value, and Cost

Eminent LED manufacturing companies in the UK source their LED PCBs and assemblies from RushPCB UK as they offer the best balance of quality, value, and cost in the market.

PCB BOARD 15

How to Choose Military and Aerospace PCB Assembly Company

RUSHPCB UK: Premier Military and Aerospace PCB Assembly Services

RushPCB UK is one of the few printed board manufacturers and a military and aerospace-approved supplier providing MOD contacts-ready PCB assembly services. With our commitment to innovation and excellence, we comply with the highest quality standards to provide our customers with the most advanced circuit board technologies the industry can offer for military and aerospace assemblies. As a premier PCB manufacturing and assembly company, we offer our vastly experienced PCB capabilities and extensive materials selection, along with innovative equipment.

For any PCB assembly company to meet the rigorous demands of the military and aerospace industry, they should meet the following criteria:

  • Must have mil/aero certification and quality assurance systems
  • Must be capable of supplying highly specialized defense and aerospace PCBs
  • Must be able to transition seamlessly from fabrication to PCB assembly
  • Must provide an extensive selection of materials

Mil/Aero Certification & Quality Assurance Systems

At RushPCB UK, we have the necessary quality assurance systems in place, and our team has the requisite technical expertise to provide our defense and aerospace customers with high-performing and reliable PCBs and PCB assemblies for critical applications. We have ITAR-registered state-of-the-art facilities, and we are certified to meet all major Aero/Mil requirements.

Image 1-01

Highly Specialized Defense and Aerospace PCBs

Military and aerospace have rigorous PCB design criteria with requirements of high precision and performance. We use advanced PCB technologies to meet these rigorous demands. Our capabilities include 40-layer boards, sequential laminations, vias-in-pads, laser-drilled micro vias, copper up to 20 oz., oversized boards, small boards for antenna/microwave, cavity boards, and laser direct imaging.

Seamless Transition from Fabrication and PCB Assembly

We are the stellar one-stop solution for PCBs in the UK, providing small quantities, quick turn military and aerospace assemblies all under one roof. We do not charge for set-ups and stencils, and neither do we charge for any Non-Recurring Expenses.

Extensive Selection of Materials

For military and aerospace PCBs, material selection is an important aspect of design and manufacturing. This ensures superior reliability and performance in the most extreme environments and critical applications. We offer a huge selection of advanced materials for meeting the demands of the military and aerospace industry.

Best Space and Military Electronic Manufacturing Company

For electronics specifically, space is an unforgiving environment, as the conditions up there are vastly different from those on the surface of the earth. Electronic assemblies must function flawlessly not only after leaving the assembly line, but must also complete their life span without faltering—there is no concept of maintenance or servicing in space.

With electronic manufacturing companies developing and manufacturing complex electronic assemblies for missiles, satellites, and spacecraft, each electronic device must be customized for the specific requirements of the purchaser to ensure superior quality, affordability, and prompt deliveries.

rush pcb

When dealing with military and aerospace requirements, it is insufficient to produce decent quality products. Military and aerospace assemblies must be of only the finest quality capable of enduring the stringent conditions.

Therefore, NADCAP certified electronic manufacturing services with exclusive qualities are required to produce devices that can weather the challenges from space programs with the help of radiation toughened electronic assembly services. Manufacturers gain this certification to make sure the PCB assemblies they product conform to the military and aerospace specifications.

PCB Assembly Services Offered

Electronic manufacturing services with ISO-9000 and NASA certifications have in-house knowledge ensuring the following:

  • Fast PCB assembly services
  • Flying probe tests
  • Conformal coatings
  • 5σ – 6σ processing (less than 200 faults per million opportunities)
  • Experienced design and layout personnel
  • NASA trained soldering experts

Electronic PCB assembly and manufacturing services incorporate the above advanced manufacturing technologies in operation-critical services such as quality management systems to achieve competitive production within a short span of time. This is because high-reliability MOD and aerospace electronics demand the highest standards for quality, reliability, and conformance.

Rush PCB UK manufacture these assemblies with zero defects, and they function error-free for their entire lifetime, under the most severe environmental conditions including the most intense cold, high moisture content, and high temperatures.

Image 2-01

PCB BOARD COMP

Why PCB Manufacturing Companies Should Train Their PCB Technicians

Training the Technicians: A Necessity for Professional PCB Manufacturers

PCB manufacturing companies such as Rush PCB Inc. have come a long way from their earlier counterparts who conducted most of their operations manually. These professional PCB manufacturers now use sophisticated automatic machines for most of their operations. Therefore, there is no way a nonprofessional can simply walk in and start working in a modern facility manufacturing PCBs.

Components of printed circuit boards go through several complicated processes involving physical, chemical, and mechanical operations before the PCB can be certified as ready for dispatch to customers. As most professional PCB manufacturers are ISO 9001:2015 certified, regular training is part of their Quality Management System.

Professional PCB manufacturers offer all or part of a range of services that may include:

  • Design of multilayer PCB layout
  • Multilayer flex, rigid-flex, rigid, and HDI PCB manufacturing
  • Surface-mounted and through-hole assembly
  • Electromechanical and cable harness assembly
  • Final product assembly and automated testing services
  • Components purchasing services
  • Complete turnkey from design to finished product

Each of the above services requires trained personnel to execute their activities.

Design of Multilayer PCB Layout

Multilayer printed circuit board layout and design require powerful computer-aided design packages to take care of the intricacies of different layers of the design. Technicians working at this level require in-depth knowledge of design rules, routing traces, grounding planes, the difference between analog and digital grounding, and more. They must also be well-versed in working with the specific CAD software package the company uses. Additionally, they must understand the use and importance of different types of vias such as micro-vias, blind, and buried vias.

Multilayer Flex, Rigid Flex, Rigid, and HDI PCB Manufacturing

PCB manufacturing is a complicated activity involving a large number of operations. Technicians involved in these operations need sophisticated hands-on training in identifying materials, handling them, working with them on different sophisticated machines, and learning to identify faults.

For instance, only a trained technician can know the method of programming a baking chamber for the right temperature and duration or program a computer-driven drilling machine using data from the Gerber files sent over by the customer.

PCB manufacturing involves several chemical processes. Technicians need to be trained in operational safety and the proper use of these chemicals. They would also need to be trained in the proper use of personal protective equipment these activities require wearing.

pcb-01

Surface Mounted and Through Hole Assembly

Professional PCB manufacturing companies such as Rush PCB Inc. also offer assembly services, for which they employ highly trained technicians. These technicians are thoroughly trained in different fields of surface mounting activities such as in operating pick-and-place machines, reflow machines, and automated testing machines.

As they handle both passive and active components, the technicians need to be aware of Electro Static Discharge (ESD), its devastating effects on electronic components, and the methods of avoiding this menace.

They also need to be trained in the identification of different packaging the industry uses for SMD components, and their proper handling by the pick-and-place machines. The PCB industry mostly uses lead-free solder paste, which requires training for storage and handling.

The reflow process is another area where special training is required for technicians operating the machine. Apart from learning how to program the computer-operated reflow oven, the technician should also be trained in profiling the reflow oven to allow perfect soldering for different boards.

Through-hole soldering using manual methods also requires proper training, especially with lead-free solder, as it has a much higher melting point. Without adequate training, a novice can very quickly ruin a flex PCB when manually soldering a component.

Electromechanical and Cable Harness Assembly

The ability to read diagrams and follow assembly instructions is very critical to the successful completion of an electromechanical and cable assembly. Technicians in this area need to be trained to understand the different symbols electrical diagrams use. Cable harness assembly uses colors and numbers for proper identification and orientation, and technicians need training to work efficiently and quickly using the codes on their assembly drawings.

Final Product Assembly and Automated Testing Services

Professional PCB manufacturing companies usually maintain a state-of-the-art manufacturing facility along with a team of technicians, experienced in product assembly and testing. However, this team also requires training since each product is unique, and they must understand the manner in which the different parts come together to make the product function coherently.

Likewise, testing is unique to each product, and the technicians must be capable of being trained in the unique testing process to be followed for each product.

rushpcb uk-01

Component Purchasing Services

Being completely flexible towards the requirements of the customer, printed circuit board manufacturers also offer turnkey projects that involve component purchasing. There is an inherent danger in an untrained person purchasing components from the open market, as there is always a chance of counterfeit parts coming through. Therefore, technicians involved in purchasing components need training to know reliable sources for electronic components, and the means of identifying counterfeit ones.

Complete Turnkey from Design to Finished Product

Professional PCB manufacturing companies such as Rush PCB Inc. guarantee world-class results in the electronic industry. They make this possible by ensuring their factory floor technicians obtain consistent, regular training. Regular training has the advantage that technicians use standardized methods, follow best practices, generate efficiencies, and improve on the specific process on which they are working.

Both printed circuit board assembly companies as well as PCB manufacturing companies need to implement training schedules that are highly standardized for guaranteeing the top-quality service their clients demand. Consistent training schedules ensure professional PCB manufacturers prioritize manufacturability from the very beginning of the design process.

rush pcb

Rush PCB UK

Best Practices for Assembly and Fabrication of PCBs

Best Practices for Assembly and Fabrication of PCBs

As an expert manufacturer and PCB assembly company, Rush PCB Inc. uses several best practices when working with industries including aerospace, consumer electronics, automotive, and many more. The best practices involve PCB design, technical aspects, and assembly issues.

Best Practices Start Early

Efficient fabrication of PCBs that high-speed circuitry utilizes is essential to ensuring results for the end user. Often, the design of the PCB layout is not thought of as a proactive step in the process. However, it requires advanced thinking and adherence to important factors to provide designs where the results lead to successful fabrication of PCBs to achieve the desired functionality. Designers need to address the practice of DFM or designing for manufacturing and including extra considerations for demands of high speed circuits early in the design stages of board layout rather than taking them on as an afterthought.

The results of poor layout show up during fabrication, assembly, and later on, as issues related to performance when putting fabricated PCBs to testing or production use. However, at that point of time, redesign or rework can be exponentially more expensive and time-consuming, requiring evaluation of circuit failures and reconfiguration of layouts of prototypes.

Material Handling

Best practices in the assembly process of any PCB assembly company start with material handling of PCBs, solder paste, and SMD components.

PCB Handling

Resin coated foils, prepreg, and core materials are susceptible to damage while handling. They need handling by their edges by operators using clean latex or nitrite gloves. Prepreg needs storing on a flat surface in a cool dry environment, preferably at less than 23°C and lower than 50% relative humidity.

If the room temperature of the PCB assembly services is significantly higher than the storage temperature, the prepreg needs to be acclimatized to the ambient temperature, prior to starting assembly. During acclimatization, the prepreg must remain in its sealed package for the stabilization period to prevent any moisture condensing on it. Any unused prepreg must be returned to their package bags and resealed. Therefore, it is best to package PCBs in brick counts that closely emulate run quantities. Prepregs must not be folded.

Some moisture is inevitably absorbed into the PCB material during the time the fabrication process is completed and start of exposure to the assembly soldering. Removal of this absorbed residual moisture may need baking the PCBs at 105-125°C for 4-6 hours.

Also read:  History of Circuit Boards

Solder Paste Handling

As solder paste is a shelf-life dependent item, it should be put directly into a storage refrigerator of the PCB assembly services on delivery, and stored as FIFO or first in first out manner, preferably with refrigerator temperature below 10°C. Preferably store solder past in lots, and ensure older lots are used first for optimal material management.

Manufacturers usually print the manufacturing date on each label and include a use by date for best performance of PCB assembly in UK. This must be strictly followed. Prior to use, equilibrate the solder paste to the environmental conditions where it will be used. For a jar or cartridge of solder paste, it is best to remove from refrigeration one day prior to use. This allows the solder paste plenty of time to equilibrate in the environment. However, this is not recommended for syringes.

Never expose solder paste to heat greater than 25°C for bringing it up to temperature fast. However, temperature-controlled water bath at around 25°C may be used. Whenever removing a container from refrigeration, label it with the date of removal for monitoring exposure.

Although homogenizing solder paste prior to use may not always be required, if necessary, stirring with a plastic spatula is recommended. Solder paste removed from the stencil must always be stored in a separate jar, rather than reintroducing it into fresh paste, as this can result in process inconsistency. Do not return solder paste to the refrigerator after opening the container, as this can cause condensation and compromise performance.

SMD Components Handling

While storing SMD components, it is essential to ensure they are kept in conditions that prevent moisture ingress and avoid electrostatic charge build up to prevent any damage.

While storing incoming SMD material, PCB assembly in UK such as Rush PCB Inc., use an ERP system help to keep track of information such as delivery date, order number, and material data. If unused material is returned to the stores, the ERP system can keep track of the used components, rejections, and damaged SMDs.

pcb

Best Practices for Screen Printing

Consistent stencil printing requires proper board support, typically provided bch as y vacuum tooling. Adequate paste must be used to enable a generous bead to roll freely when the squeegee moves. The squeegee pressure must be adequate to ensure a clean sweep without leaving paste on the stencil after a pass.

Enable proper gasketing to align the apertures with the pads properly. Ensure levelness of the board surface, and solder mask definition must not detract from contact between the stencil and the surface of the board.

Occasionally wipe the underside of the stencil to remove any excess paste. Although wipe frequency is recommended with the product data sheet, it also depends on the process optimization and proper gasketing.

Read Also;   Assembling Wearable Electronics

Best Practices for Reflow Soldering

For best results, the reflow soldering profile should be broken down into four phases—preheat, pre-reflow, reflow, and cooling.

The preheat phase allows preconditioning the PCB assembly prior to the actual reflow. It removes flux volatiles while reducing thermal shock to the assembly.

The pre-reflow phase uses the flux activator to remove any existing surface oxide from the PCB pad finishes, component leads, and any oxides on the powder particles within the solder paste. Basically, it prepares the surfaces to be joined during reflow. This phase also involves a temperature soak, allowing the thermal gradient across the PCB assembly to equilibrate prior to reflow.

The actual reflow of the solder alloy allows the creation of a suitable electrical and mechanical bond. Formation of an optimum bond involves two critical parameters—the peak temperature, generally 20-30°C above the liquidus temperature of the alloy, and the time-above-liquidus, typically 30-90 seconds to form the effective intermetallics.

To form a reliable mechanical bond, the grain structure should be fine, which can be formed via the cooling phase. A rapid cooling rate while transitioning from liquidus to solidus can stress the joint; therefore, a cooling rate of 4°C/second is preferable.

Best Practices for Handling PCB Assemblies

ESD is one of the major causes of failure of assembled PCBs. Therefor proper electrical grounding of worktables and operators is necessary. Worktables must have electrically conducting mats and workers must wear anti-static clothing, while being grounded with discharge straps on the wrists or ankles.

rush pcb