PCB

PCB Vias and Everything You Need to Know About Them

PCB Vias and Everything You Need to Know About Them

Looking at a complicated Printed Circuit Board (PCB) such as the motherboard of a computer, you are likely to find several tracks going nowhere, and terminated rather abruptly. However, a closer inspection, preferably with a magnifying glass, will reveal more details at the point of termination of the track. Most likely, you will see it ending in a small PCB pad, not much larger than the width of the track itself, with or without a hole in its center.

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Fig.1: Tracks on a PCB

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Fig.2: Close-Up of a Via

In reality, the track does not terminate, but rather continues to travel, albeit on a different layer, hidden under the outermost layer of the PCB. The pad at its end is actually a small pipe through the insulating material, electrically connecting the two parts of the track. In PCB terminology, such an arrangement that allows tracks to continue, but on a different layer, are known as a PCB vias.

Types of Via in PCB

Multilayer PCBs use different types of vias for various purposes. There might be through-hole vias, blind vias, and buried vias in the same PCB. Although the construction of all vias is same, their nomenclature depends on the layers of origin and termination.

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Fig.3: Type of Vias

For instance, a via originating from the outermost layer, traveling through the board, and terminating at the other outermost layer is a through-hole via. In its passage through the layers of the board, it may or may not connect to intermediate layers, depending on the necessity of the electrical circuit.

A blind via originates from one of the outermost layers, but terminates on an intermediate layer, and therefore, is visible only on the originating layer. It may or may not connect to other layers in between.

A buried via is not visible from either of the outermost layers, as it originates in one of the inner layers and terminates in another inner layer, possibly connecting other layers in between.

Construction of a Via

By design, a via consists of two outer pads and a copper tube electrically joining them. The two outer pads reside on the originating and the terminating layers of the PCB, while antipads on all intermediate layers allow electrical isolation of the copper tube from the electrical circuits on these layers as it passes through.

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Fig.4: Construction of a Via

While the two outer pads and antipads are part of the layout pattern a fabricator etches onto the PCB, an electrode position process forms the copper tube connecting the two. Although in regular multilayer PCBs, you may find through-hole vias, these are less likely in high density interconnect or HDI boards.

Difference Between Plated Through Hole and Via

The major difference between the two lies in their construction process. A fabricator can electroplate a through-hole only after assembling all the layers of a multilayer PCB, since a through-hole spans all the layers, while he can form a complete via, including electroplating it, when assembling each layer pair.

Another advantage with vias in multi layer PCBs is, the designer can either stack or stagger them to suit the requirements of the circuit layout, while he or she cannot do that with a through-hole. Therefore, vias help in increasing the layout density of a board, allowing the designer to reduce the size of and/or number of layers on a multilayer PCB.

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Filling a Via

The designer may decide to fill the vias in the PCB during manufacturing. While blind vias require filling to avoid surface dimpling, some designers may specify an additional epoxy filling after lamination to maintain better surface flatness.

You can ask your PCB fabricator to fill the vias with either epoxy or metal epoxy. The choice between epoxy and metal epoxy is that the latter is conductive. Therefore, if you have designed the via with a thermal application in mind, for instance, to disperse heat from one side to the other, filling the via with metal epoxy will be a better choice as opposed to epoxy filling of the non-conductive type. As its barrel always has a layer of copper, a via always retains electrical continuity, regardless of whether the filling is conductive or not.

In highly dense PCBs, especially those with fine-pitch components such as BGA, fabricators fill PCB vias with epoxy and planarize them to make them flat. Flash plating over them makes them perfectly flat and suitable for mounting BGAs.

Other applications may need a Faraday shield on one side of a chip, which could double as a heat sink as well. Stitching the underside of the chip with vias is a standard practice, while filling them up with a conductive epoxy fill, helps in the heat conduction.

When concerned with EMI, you may use multiple vias in the region of a ground strap, filling them up to provide a conductive wall. An impedance-controlled structure may also benefit from closely spaced and filled vias on either side.

Special Vias

Although you will find warnings about placing vias within pads as these can siphon off solder paste while soldering, leaving the joint devoid of solder, you may not have much choice when designing with very closely pitched BGA packages. The space available around the pads may not be adequate for a dog bone, and the only option may be a via in the SMT pad, or partially in it.

You can get over the solder siphoning by having the via epoxy filled, flattened, and plated to encapsulate it. The other side of the PCB via may not be important enough and you can wall it off with a mask.

Sometimes, to attain very high routing densities, it may be necessary for the designer to use landless vias. The trace directly enters the hole without a PCB pad. As the vias do not have PCB pads, the designer can pack in more traces in between adjacent vias.

Stacked Vias and Laser drilling

Even after using blind and buried vias, you may still not have enough room for proper routing. In such circumstances, you may consider using laser drilled micro vias and or stacked vias. The two major benefits of laser drilling are extremely fine holes (sub 0.004”), and excellent registration. Both are obvious benefits for very dense parts.

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Fig.5: Laser-Drilled Micro Via

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Fig.6: Staggered and Stacked Micro Vias

Laser drilling does not pass through the layers, unlike that in mechanical drilling. It vaporizes the top copper layer, burns through the substrate dielectric layer beneath it, and stops when it touches the bottom copper layer. This accounts for the v-shaped pit as against a straight hole a mechanical drill-bit creates.

For stacked vias, designers place laser drilled vias directly on top of each other. However, designers typically use stacked vias only when board real estate is at a premium.

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Vias and Signal Integrity

Just as people do, electrical signals too find it much easier to take a direct route when traveling from point A to point B. A via in the signal path forces the signal to take a detour, and the signal integrity suffers as a result.

For high-speed signals, there is also the challenge of via stubs. For instance, a via taking a trace from L1 to L3, may leave a stub down to L16. A high-speed signal will typically traverse all the way from L1 to L16 before reflecting to L3. This will attenuate the signal, as the effective electrical stub length will be almost double its mechanical length. Designers of thick boards take care of the problem by removing the unnecessary part of the barrel by back drilling. HDI boards do not face this problem, as they use laser drilled micro vias and stack them up to the desired layer.

Conclusion

The above types of via in PCB can increase density and bring down the cost in volume production. Laser drilled PCB vias can increase multilayer density and reduce layer count, without reducing the trace width or trace spacing.

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Integrity of the Signal in HDI Circuits

With rise-times of signals on the printed circuit boards (PCBs) continuing to drop, the age-old concerns related to signal integrity is always at the forefront of (PCB) Printed circuit board design. However, with the increasing quantities of printed circuits in high-density interconnect or HDI technology, there are some interesting new solutions.

Signal integrity analysis in PCBs has five major areas of concern:

  1. Reflection
  2. Cross-talk
  3. Simultaneous Switching
  4. Electromagnetic Interference (EMI)
  5. Interconnect Delays

Although HDI does offer improvements and alternatives for all the concerns above, it does not provide all the solutions. Signal integrity depends on the materials the PCB uses, and the materials the HDI technology uses, together with the PCB design rules and dimensional stack-up helps the electrical performance including signal integrity. Likewise, miniaturization of the PCB using the HDI technology is a major improvement for signal integrity.

HDI Benefits Signal Integrity

With new electronic components such as ball grid arrays and chip-scale packaging achieving widespread use, designers are creating PCBs with new fabrication technologies to accommodate parts with very fine pitches and small geometries. At the same time, clock speeds and signal bandwidths are becoming increasingly fast, and this is challenging system designers to reduce the effect of RFI and EMI on the performance of their products. Moreover, the constant demand for denser, smaller, faster, and lighter systems are compounding the problems with restrictions placed on cost targets.

With HDI incorporating microvia circuit interconnections, the products are able to utilize the smallest, newest, and fastest devices. With microvias, PCBs are able to cover decreasing cost targets, while meeting stringent RFI/EMI requirements, and maintaining HDI circuit signal integrity.

Advantages of Using Microvia Technology in HDI Circuits

Microvias are vias of diameter equal to or less than 150 microns or 6 mils. Designers and fabricators use them mostly as blind and buried vias to interconnect through one layer of dielectric within a multi-layer PCB. High-density PCB design benefits from the cost-effective fabrication of microvias.

Microvias offer several benefits from both a physical and an electrical standpoint. In comparison to their mechanically created counterparts, designers can create circuit systems with much better electrical performance and higher circuit densities, resulting in robust products that are lighter and smaller.

Along with reductions in board size, weight, thickness, and volume, come the benefits of lower costs and layer elimination. At the same time, microvias offer increased layout and wiring densities resulting in improved reliability.

However, the major benefits of microvias and higher density go to improving the electrical performance and signal integrity. This is mainly because the HDI technology and microvias offer ten times lower parasitic influence of through-hole PCB design, along with less reflections, fewer stubs, better noise margins, and less ground bounce effects.

Along with higher reliability achieved from the thin and balanced aspect ratio of microvias, the board has ground planes placed closer to the other layers. This results in lowering the surface distribution of capacitance, leading to a significant reduction in RFI/EMI.

HDI PCBs use thin dielectrics of high Tg and this offers improved thermal efficiencies. Not only does this reduce PCB thermal issues, it also helps the designer in streamlining thermal design PCB.

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Improved Electrical Performance of HDI Circuits

The designer can place more ground plane around components, as they implement via-in-pad with microvias. The increase in routabilty offers better RFI/EMI performance due to the decrease in ground return loops.

As HDI circuits offer smaller PCB design along with more closely spaced traces, this contributes to signal integrity improvements. This helps in many ways—noise reduction, EMI reduction, signal propagation improvement, and lowers attenuation.

The improved reliability of HDI circuits with the use microvias also helps in PCB thermal issues. Heat travels better through the thin dielectrics. Streamlining thermal design PCB helps remove heat to the thermal layers. Several manufacturers make complex enhanced tape BGAs of thin, laser-drilled polyimide films to take advantage of PCB design with HDI.

The physical design of the microvia helps in reducing switching noise. The reason for this decrease is due to decrease in inductance and capacitance of the via, since it has a smaller diameter and length.

Signal termination may not be necessary in HDI circuits as devices are very close together. Since the thickness of the layers is also small, the designer can utilize the backside of the interconnection effectively as well.

Just as the signal path is important in PCB design, so is the return path. Moreover, the return path also influences the resistance, capacitance, and inductance experienced by the signal. As the signal return current takes the path of minimum energy, or the least impedance, the low frequencies follow the path minimizing the current loop.

Miniaturization from using HDI technology provides interconnections with shorter lengths, meaning signals have to traverse shorter distances from origin to destination. Simply by lowering the dielectric constant of the HDI material system, the designer can allow a size reduction of 28%, and still maintain the specified cross-talk. In fact, with proper design, the reduction in cross-talk may reach even 50%.

Conclusion

HDI PCB design not only helps in improving the integrity of signals, but the presence of thin dielectric helps with the PCB thermal issues as well. In fact, HDI technology helps with all the five major areas of concern related to signal integrity.

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Productive Approaches to Creating Prototype PCBs

So far, for printed circuit board or PCB prototype, designers limited their choice of PCB design tools to high-end, enterprise-level solutions, as these tools were expensive. The early design tools also added the cost of an extended setup time and learning curve, were limited in their capability, and most often, error-prone. Thankfully, modern tools are now affordable and come packed with all the features designers need for complex designs. Moreover, they are easy to use and focus more on ease of adoption.

Typically, a designer takes about two to three iterations for developing a custom PCB prototype for a working product with a high-speed computer-based design tool. However, with decreasing product life cycles, the time-to-market is steadily gaining in importance. Depending on overheads, board iterations can be expensive, because delaying the product’s market launch and the missed opportunity could cost the company several thousand dollars, or even the total loss of market share.

The above is prompting designers to employ simulation in the design cycle before they order PCB prototypes, as this dramatically reduces the cost of development. As the cost of change increases with development time, design changes occurring early in the design process cost substantially lower compared to those introduced during full-scale PCB fabrication. Using virtual prototyping has the advantage of identifying issues early on in the design process, and rectifying them is cheaper and simpler before they become a major problem.

Virtual Prototyping as a Productive Approach

Although entry-level tools did allow quick designs and prototype building, most designers relied on reference designs provided by chip vendors. Increasingly, designers are finding they cannot rely on reference designs to make their products work in operating environments—they need design for reliability and manufacturability for the real world.

Implementation of each new technology introduces multiple fast rise-time signals propagating at increasingly faster speeds. That does not allow the luxury of building prototypes, testing, reviewing, and revising the design approach with each build.

With virtual prototyping, designers can do with fewer PCB prototypes and improve their design efficiency. Virtual prototyping includes simulation of signal and power integrity, design for manufacturability, thermal analysis, and 3-D interference validation.

Earlier, skills of PCB designers and engineers were necessary for the entry-level tools to detect possible issues as they came up during the design process. High efficiency, complex designs, on the other hand, require a more constraint-driven approach, with correct-by-construction methodology. Once the engineers establish the rules, designers with downstream tools will follow them and use various design rule checks (DRCs) to conform their validation.

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Designing for Profitability

Modern PCB tools are able to handle several tasks other than simply laying traces. It is possible to use these design tools at every phase of the project from initial concept to the final assembly documentation. The addition of 3-D rendering engines in most of these design tools and the complete integration of 3-D component bodies in the footprint libraries makes this possible.

This capability allows designers to give shape to concepts very quickly. They can use virtual prototyping along with vendor-supplied 3-D step models to make a preliminary PCB layout. This allows a quick look at the finished product, such as the position of the I/O connectors, without the detailed board design.

This method helps designers handle request for change early in the design, as the visualization tools allows an upfront view of the design process, and everyone involved has a good idea of the direction the design is headed, and they can spot the misconception or conceptual errors early.

Virtual prototyping has an added side benefit. Every step of the process can confirm the mechanical fit of the product. Moreover, designers can now put together the fab drawing first and get quotes on any proposed design, material, and so on. They can pass the mocked-up fabrication drawing to the assembler for a review to uncover any issues. This not only saves time, but also the unnecessary expense of multiple prototypes. Silk-screeners, pick-and-place machines, and reflow ovens require tabs, holes, and other modifications that are not part of the original circuit design, but part of manufacturability. Assemblers reviewing the preliminary fab drawing often make recommendations based on their experience with materials and others.

Keeping a Dynamic Supply Chain Visibility

A major reason for design iterations is the supply chain information not being available to the designers in real time. Many a time designers have to manufacture printed circuit board prototypes only to have to change their design because of the non-availability or a certain component or components, which they have to replace with a suitable alternative and now requires a change in the PCB design. The cost of having to change the design at the prototype stage is much lower compared to that required once the product is in full production. Therefore, it is necessary to have a real-time view of the supply chain from the product management or procurement team.

Additive Manufacturing Rather than Subtractive

Regular PCB prototype making is a subtractive process. The fabricator starts with more material than needed, and removes the unnecessary parts. However, in an additive process, the fabricator starts with a thin substrate and adds the required copper traces with conductive ink.

Although still in its infancy, 3-D printing and additive manufacturing for electronics is a great way to generate less waste than traditional subtractive methods for PCB fabrication, especially for custom PCB prototypes. With additive manufacturing machinery deployed in-house, engineers can make necessary changes in a design without the traditional penalties in cost and time. The designer does not have to wait for the fab house to send the order PCB prototypes back, as he can create the prototype on his or her desktop.

Designers can select from 3-D printing and 2-D printing processes for additive manufacturing. The 3-D printing prints PCBs from scratch, using a variety of gels, inks, and substrates, layer by layer, manufacturing them at the nanoparticle level. This is a very new process and involves material complexity and extrusion requirements.

The 2-D inkjet-style printing matches more readily with the Gerber files designers generate to communicate designs to manufacturing. These machines only have print the conductive traces on a flat horizontal substrate. This is ideal for printing PCB prototypes for quick prototyping.

Conclusion

There are several ways to reduce the iterations involved with designing, PCB prototyping, and cutting down on the time to market factor. While virtual prototyping can actually save on the time required for ordering, testing, and reviewing prototypes, additive manufacturing can cut down the actual time for fabricating prototypes. Additionally, keeping a clear dynamic supply chain visibility precludes the necessity for redesigning the board at a later stage.

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How to Detect Circuit Board Faults?

How to Detect Circuit Board Faults?

Printed circuit boards (PCBs) are increasing in complexity and diversity. With a wide array of applications, the only requirement common to all types of PCBs is they must function in accordance with their design parameters, without errors and failures. In short, PCBs must perform flawlessly.

Complex PCBs can have hundreds of components with thousands of solder connections and that gives innumerable opportunities for failure. The Printed circuit boards manufacturing industry makes sure all their PCBs meet the above challenge of flawless working through a battery of inspection and testing procedures to ensure the quality of their products.

Assemblers detect circuit board faults before assembly through various inspection methods. After assembly is over, they employ another set of inspection and test methods to solve PCB errors.

Evolution of PCB Inspection and Test Methods

Simple circuit boards with a handful of components needed only manual visual inspection (MVI) methods to ensure solder problems and placement errors were weeded out. With increasing complexity and growing production volumes, MVI systems were found to be inadequate, as humans soon grew tired, and could not be relied upon to carry out the task of inspection repeatedly for long hours. As a consequence, inspectors missed defects and faulty boards reached later stages where it was more expensive to solve PCB errors.

This brought up the next step in inspection systems—Automated Optical Inspection (AOI) methods—now a widely accepted inline process. Assemblers effectively use AOI to inspect PCBs before and after reflow soldering to check for a variety of possible faults. Now, even pick-and-place machines incorporate AOI capabilities, allowing them to check for misalignment and faulty component placements.

With the advancement of surface mount technology, components became smaller, and this increased the board complexity along with PCBs becoming double sided and even multi-layered. Additionally, introduction of fine-pitch SMDs and BGA packages brought out the limitations of AOI, forcing assemblers to implement even better inspection methods such as the Automated X-ray Inspection (AXI) systems.

After the assembly, PCBs are often tested for in-circuit components (ICT) and for functional testing (FCT). While ICT ensures the functioning of individual components on the board, FCT offers a final go or no-go decision for the entire PCB.

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Expected Faults in PCBs

Statistical data on PCBs shows the most common types of faults related to placement, soldering, and functionality. Among placement faults, components may be missing, wrong, wrong orientation, or misaligned. Among soldering faults, there may be dry or incomplete soldering, excess amounts of solder, solder bridging, and whiskers. Assemblers vary their inspection and testing methods depending on the type of defects they encounter and the effectiveness of the inspection methods.

Automated Optical Inspection

AOI methods inspect PCBs visually. The system usually employs still or video cameras to scan a well-lit board. There can be several variations, with the board being illuminated by different sources of light at various angles, and there may be more than one camera. Images from the camera are fed to into a computer, which builds a picture of the board and its contents. The memory of the computer holds the reference image of a golden board that has no faults. The computer compares the image the cameras have captured with the reference image and highlights the faults it detects.

With AOI systems, it is easy to detect faults such as open circuits, shorts, and dry solders. Moreover, it can detect missing and misaligned components. The biggest advantage with AOI is they can help solve PCB errors much better than human inspectors can, with greater accuracy, in less time, and without tiring. Therefore, manufacturers employ AOI systems inline at several points in the PCB manufacturing process.

3-D AOI systems are capable of measuring the height of components, and able to detect faults in areas that are sensitive to heights. However, they use visible light, which limits the functionality of AOI systems to line-of-sight. AOI systems are incapable of inspecting hidden connections such as under IC packages, especially BGAs.

Automated X-Ray Inspection

Chip scale packages (CSP) and Ball Grid Arrays (BGA) are special IC packages that have their connections under them. When mounted, the connections are hidden between the circuit board and the body of the IC, preventing them from being inspected visibly. Assemblers resort to AXI methods to inspect such hidden solder joints.

Printed boards are made of substrates and copper traces, and SMD components are soldered onto them. Materials usually absorb X-rays in proportion to their atomic weights. While materials containing heavier elements absorb more X-rays, those containing lighter elements allow X-rays to pass through without absorption. The PCB substrate and components are mostly made up of lighter elements, and the X-rays pass through them without being absorbed.

On the other hand, solder contains heavy elements such as indium, silver, bismuth, and tin, and these do not allow X-rays to pass through. Therefore, when inspecting a PCB assembly with X-rays, the solder joints show up with great clarity, while the traces and SMD packages are barely visible.

Therefore, AXI systems make it easy to detect and solve PCB errors such as soldering defects normally invisible to AOI systems. However, AXI systems are more expensive, and assemblers install them only if necessary.

PCB Assembly                                 Prototype

In-Circuit Testing (ICT)

Assemblers perform testing only after completing all PCB inspections and soldering the components. For ICT, it is necessary the designer has placed testing pads at critical points in the circuit when designing the PCB layout. Usually, the designer will place the test pads on a grid so a testing jig with spring-loaded pins can connect to the pads on the PCB. This test fixture is usually called a bed-of-nails.

During ICT, the test pins can check various components for shorts, opens, resistance, capacitance, and more, for determining any errors. Usually, such bed-of-nails is specific to a circuit board, and therefore inflexible and expensive. Moreover, with circuit density increasing continuously, bed-of-nails soon reaches its limits. Assemblers use another approach instead. While a simple fixture holds the board, a single probe or a few of them move to make contact at different points as necessary. Usually, software controls the probe movements, and this makes it easy to adapt the system to different boards.

Functional Circuit Testing (FCT)

Under FCT, the circuit board assembly is powered up while test equipment is connected to simulate the actual environment the board is expected to undergo in normal use. The functional tester is unique to the board under test, and its software program sequences through various test scenarios while collecting operational data from the devices on-board.

Depending on the extent of testing, the type of inputs required, and the expected outputs from the device under test, the FCT can vary in its complexity. However, it identifies functional defects in the PCB assembly, and helps to solve PCB errors.

Conclusion

Assemblers use different inspection and testing methods to solve PCB errors during manufacturing and assembly. With high volumes of production and circuit complexity, the automatic visual methods have mostly replaced manual visual methods of inspection. For complex PCBs such as those using BGAs and CSPs assemblers have to use X-rays to inspect invisible solder joints.

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Best PCB Layout Practices for 2018

Best PCB Layout Practices for 2018

One of the first steps that PCB design experts recommend when taking up a PCB layout design is to start with a high quality PCB design software. Make sure the software package comes bundled with a good library of component parts, and allows you to add to it. It should allow you to manage your layer structure easily, and to place and route a complex multilayer board design. Among the necessary features, it should come with a strong but flexible built-in DRC and allow you to conduct a DFM check. Overall, the design of the software package must be intuitive to enable a short learning curve.

Set up the Library for Multilayer Designs

Designing multilayer boards requires a different library configuration than necessary for single or even double layer boards. It is important to set up the following three areas for handling multilayer board design:

Pad Shapes: Designers differentiate the first pin of a through-hole IC with a differently shaped pad for easy orientation. However, this is necessary only on the topmost layer while on the inner layers all pads can retain the same shape. For libraries not set up for multilayer configuration, the pad shapes may have a mismatch.

Drawing Marks: Designers place different marks on various layers to identify them during fabrication and assembly. Therefore, when setting up the software package for multilayer boards, the designer must save the corresponding logos, tables, and views to the library. Additionally, standardizing them for the organization will avoid confusion.

Negative Planes:  When creating power and ground planes, multilayer PCB layouts use negative image plane layers. These layers require additional clearances around pad and footprint shapes for drilled holes. Therefore, pads and footprint shapes for multilayer design must contain these additional clearances for the negative planes. If you are not careful with these clearances, they will ultimately create shorts.

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Understanding the Fabrication Shop Requirements

It is important for a PCB designer to work closely with a fabrication shop and understand their requirements, so that it is possible to fabricate the ultimate product without issues. Multilayer PCB designs offer several benefits over single and double-layer boards. Chief among them are space saving and increasing the design density. Multilayer boards also allow better control over signal integrity, but to achieve that it is necessary to make sure the fabrication shop is able to manufacture the multilayer design before you start.

Fabrications shops will have their own limitations based on their level of board technology. For instance, they may be set up to manufacture boards up to a certain layer count, or they may be able to make vias, traces, and spacing widths only to a certain dimension. Exceeding those limitations may mean looking for a better fabricator, thereby increasing fabrication costs, time, and effort, or not being able to get the board fabricated.

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Best Layout Practices for Basic Multilayer PCB Design

Reduce Crosstalk: It is important to guard against crosstalk from the beginning. Preferably, route the signals on adjacent layers so they are at 90° to each other—this helps to reduce broadside crosstalk problems.

Use Ground and Power Plane Layers: Distribute power and ground layers evenly throughout the stack. This will prevent ground loops, ground bounce, and help with creating microstrip structures for managing signal integrity.

Use Special Vias: Using special vias such as micro-vias, buried and blind vias opens up more routing channels for the designer. Check if the Printed Circuit Board CAD software allows using land-less vias and via-in-pad, as these are now becoming commonplace for packages such as BGA and other fine-pitch IC packages.

Use IPC-2223: Using a common point of reference makes it easier for both the designer and the fabricator. Communicating in a common language for documentation reduces errors and misunderstandings while avoiding expensive delays.

Use Modern File Formats: Rather than delivering files to your fabricator in Gerber format use a modern file format such as the ODB++ or one that meets IPC-2581 standards, as these formats identify specific layer types and the result is unambiguous documentation.

Best Layout Practices for Rigid-Flex PCB Design

No Corner Bending: Always place copper traces at right angles to the flexible circuit bend to avoid bending them at the corners. If this is unavoidable, use conical radius bends.

Curved Traces are better: 45° hard corners and right angle traces increase stress on copper traces when bending—using curved traces is a better option.

No Abruptly Changing Trace Widths: Any abrupt change in the width of a trace can weaken it. As a trace approaches a pad or via, prefer to use teardrop patterns to change its width gradually.

Using Hatched Polygons: Planes using solid copper pour in flex boards offer heavy stresses when bent. Using hatched polygons such as hexagons makes the plane more flexible.

Stagger Flex Traces: For traces running over one another in the same direction on either side of a layer creates uneven tension between the layers. Staggering the traces eliminates the stress.

Best Layout Practices for Industrial PCB Design

Designing for Industrial environments requires PCB designers to demonstrate not only functionality of the PCB, but also its reliability to work under harsh conditions. This is especially true for applications with expensive downtimes.

Use Proper Grounding:PCB layout for industrial applications must carefully segregate power ground, analog ground, and digital ground. This is essential for reliable performance of the PCB in harsh electrical environment. Connecting these various grounds to a suitable single point is also important.

Maintain Signal Integrity: Harsh electrical environments affect communication, analog, and digital both. This can be detrimental to the performance producing erroneous data. Although a proper selection of cables and other installations can offset this largely, PCB designers and manufacturer must follow sound design practices to maintain signal integrity.

Heat Management: Industrial environments can be very hot, and PCBs generating their own heat may easily cross their safe operating temperatures. Use thermal vias and other heat management techniques such as heat sinks to remove heat from the PCB and its enclosure.

Group Components: Prevent interference by grouping components based on their function in the circuit. For instance, analog circuits separated from their digital counterparts, and power circuits in their own area prevents coupling of interference. PCB design experts advise arranging the schematics into modules to plan better components placement.

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Design for Moisture Control: Some industrial environments may be moist and humid. Moisture buildup on the PCB could damage circuits and components. PCB design experts suggest designing the PCB layout with a view to applying a layer of conformal coating on the assembly. The PCB designer needs to factor in the additional heat buildup and the necessity to remove it. It may be necessary for the PCB design to incorporate an intelligent circuitry to detect humidity and turn on a heater integrated into the system.

Conclusion

Using a good CAD software package for PCB layout does not guarantee an optimum output. Although CAD software packages incorporate auto-routers to help the designer, it is best to review the output after auto-routing and rectify the quirks the software may have introduced.

HDI

Benefits of HDI Flex Circuits

Benefits of HDI Flex Circuits

Flexible circuits built with High Density Interconnect (HDI) technology offer significant design, layout, and constructions benefits over regular flexible circuits. HDI technology involves incorporation of microvias and fine features for achieving highly dense flex circuitry, and offers increased functionality with smaller form factors.  Use of HDI technology offers improved electrical performance, allows use of advanced integrated circuit packages, along with better reliability using thinner materials and microvias. Some advantages of HDI flex circuits are:

Working in Harsh Environments

Fabricators cover HDI flex circuits with Polyimide. Although this is a standard practice, other cover and base materials are also available to suit a broad range of harsh ambient conditions. Compared to regular circuits covered with soldermask, the Polyimide dielectric layer is flexible, and protects the circuit far beyond the capabilities of the brittle soldermask.

Repeatable Installation with Flexibility

Compared to ribbon cables or discrete wiring, an HDI flex circuit offers a repeatable routing path, which you can customize within your assembly. Not only does this give dependability where necessary, but also the longer lifespan of the HDI flex circuitry drastically reduces service calls.

Capability to Withstand High Vibration

Along with flexibility, the ductility and low mass of HDI circuits allows it to withstand high amounts of vibration much better than conventional circuits can, reducing the impact upon itself and its solder joints. The higher mass of regular circuits imposes additional stress upon itself, the components soldered on it, and its solder joints.

Working with Longer Duty Cycles

The design of HDI flex circuits allows them to be very thin, but adequately robust to withstand a high number of flexing cycles. In fact, HDI flex circuits are capable of flexing thousands to millions of cycles while carrying power and signal without a break.

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Packaging Options with HDI Flex Circuits

Designers can shape HDI flex circuits to fit where no other circuit can. As HDI circuits are a hybrid combination of an ordinary flex circuit and a bunch of wires, they exhibit the benefits of each and more. In reality, you get unrestricted freedom of packaging ability with HDI flex circuits, all the time retaining the repeatability and precision necessary. HDI flex circuits replace a few major components in equipment—the hard board, usually called the printed circuit board (PCB), and the connectors and wiring harness that bridge multiple PCBs. This offers several packaging options such as:

  • Lower Mass
  • Versatile Shaping
  • Stiffeners for Component Mounting
  • Vibration Resistance
  • Robust Connections
  • Repeatable Wire Routing
  • Faster Assembly Times
  • Reduction in Weight and Space

As the HDI flex circuit is made of thin material, it can often save up to 75% of the weight and space required by conventional circuit boards and wires. Designers feel compelled to adopt HDI flex circuit technology because they can form it into three-dimensional configurations. However, the flexibility often makes it difficult to mount large surface mount components on HDI circuits and engineers surmount the problem by selectively bonding stiffeners where required.

Some equipment have multiple boards interconnected with wire harnesses. Shock and vibration plays a large part in failure of these harnesses resulting in recurring costs. In most cases, a single HDI flex circuit can replace all the boards including their wire harnesses. As the HDI flex circuit is lighter, it is more resistant to the effects of shock and vibration, resulting in huge reductions to the recurring costs, Elimination of wire harnesses leads to lower routing errors, ultimately reducing test times, rework, and rejections.

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Moreover, HDI flex circuits also replace the connectors at each end of the wire harness. Flat foil connectors may have to replace some connectors. This is an advantage over the use of round wires, as flat conductors with their larger surface area dissipate heat better, and thereby, carry more current. Conductor patterns in HDI flex circuits have more uniform characteristics, leading to a better prediction and control over impedance, crosstalk, and noise.

Use of HDI flex circuits reduces several assembly processes such as color-coding and wrapping bundles of wire. In volume production, this not only reduces the chances of assembly rejects and in-service failures, it saves assembly time, and lowers the total installation costs.

Benefits to the Designers

Designers build up HDI flex circuits with microvias as this offers them several advantages. Drilled by lasers, microvias are extremely small, and their effective use opens up more space for routing. Combined with the use of thinner traces, this leads to high routing densities, effectively resulting in fewer layers.

HDI flex circuits present the only practical way for designers to mount multiple large BGA packages with less than 0.8 mm pitch. They also offer the lowest cost for high-density boards with high control over power and signal integrity with appropriate stackup definitions.

Processes requiring Restriction of Hazardous Substances (RoHS) do well to use HDI flex circuits, as newer materials are available that offer higher performance with lower costs. This is an advantage over conventional boards, as these newer materials are not suitable for sequential or standard laminations.

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Summary

HDI flex circuits are the best alternatives to expensive, high layer count sequential or standard laminated boards. Smaller HDI features are the only way to effectively breakout and route multiple instances of high pin-count and finer pin-pitch component devices on a single board. With all the above features and advantages, handheld consumer electronics is currently committed to using HDI flex circuits.

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What are Optical Printed Circuit Boards?

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 on-board 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 the 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.

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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 process 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 photo detector 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 with 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. Use of structured polymer foils help in this integration.

Main issues of using polymers are their thermal and mechanical stability against the process conditions during PCB fabrication. Additionally, 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.

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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 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.

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How Stable are the Dimensions of Flexible Circuits

The difference between a rigid printed circuit board and a flexible circuit lies in the dielectric material sets manufacturers 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. Development of several versions of polyimide enables tailoring the material to meet specialty requirements such as in solar arrays, for space applications, and for 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 is inevitable as it undergoes processing and exposure to a variety of etching, electroplating, pressures, temperatures, and chemistries. For instance, etch shrink is the stress etching copper releases, but fabricators mistakenly use it as a catch phrase 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 parts they actually produce.

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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, cause full breakout of the hole-to-pad alignment. Another possibility is in the misalignment of the coverlay. For a predicable 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 against 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 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.

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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 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 of a significant nature. For a flexible circuit, this compensation for the expected change becomes a critical part related to panelization. This also serves to balance maximizing process efficiencies and maintaining dimensional tolerances and accuracy.

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How to Choose a Professional PCB Assembly Company

Hardware designers requiring PCB assembly in UK usually face tremendous obstacles for their need of 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 of 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:

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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.

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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.

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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.

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  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.

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  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.