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A Comprehensive Guide to Manufacturing Printed Circuit Boards

Printed circuit boards (PCBs) are essential components of modern electronics, and they are used in everything from smartphones to medical devices. PCB fabrication is the process of manufacturing these boards, and it involves several steps, including design, material selection, and manufacturing. In this blog, we will explore the different stages of PCB fabrication and provide tips and best practices for each step.

Step 1: PCB Design

The first step in PCB fabrication is to design the board. This involves creating a schematic diagram and a layout using specialized software. It’s important to consider factors such as the size of the board, the number of layers, and the placement of components. Once the design is complete, it can be exported as a Gerber file, which is used in the manufacturing process.

Step 2: Material Selection

The next step is to select the materials for the PCB. The most common materials used in PCB fabrication are copper-clad laminate and solder mask. Copper-clad laminate is the base material for PCB, and it comes in different thicknesses and substrate materials. Solder mask is used to protect the PCB from environmental factors such as dust and moisture. Other materials used in PCB fabrication include ink, plating chemicals, and adhesives.

Step 3: Manufacturing

The manufacturing process for PCBs involves several stages, including drilling, plating, and etching. First, the PCB is drilled to create holes for components and traces. Then, a plating process is used to coat the holes with copper. Next, a layer of solder mask is applied to protect the PCB. Finally, the PCB is etched to remove any unwanted copper and create the desired traces and connections.

Step 4: Quality Control

Quality control is an essential part of PCB fabrication. It involves testing the PCB to ensure that it meets the required specifications and standards. This includes visual inspection for defects, electrical testing to check for shorts and opens, and other tests to ensure that the PCB is functioning correctly.

Step 5: Assembly

Once the PCB is manufactured and tested, it can be assembled with components to create a functional electronic device. This process involves placing the components on the PCB and soldering them in place. This can be done by hand or with automated equipment.

PCB fabrication is a complex process that requires specialized skills and equipment. It involves several stages, including design, material selection, manufacturing, quality control, and assembly. By following best practices and using high-quality materials and equipment, it’s possible to create high-quality PCBs that meet the required specifications and standards. Whether you’re a hobbyist or a professional, understanding the PCB fabrication process is essential for working with electronics and creating innovative new products.

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Optimized PCB Design for Functionality, Reliability, and Manufacturability

A Good PCB Design

A good PCB (Printed Circuit Board) design is one that is optimized for functionality, reliability, and manufacturability. Here are some key factors to consider when designing a good PCB:

Functionality: To ensure that the PCB meets the functional requirements, it is important to carefully select and place components, and route the traces in a way that minimizes interference between signals. This involves paying close attention to the electrical characteristics of the circuit, such as the signal frequency, voltage levels, and impedance matching. Simulation tools such as SPICE (Simulation Program with Integrated Circuit Emphasis) can be used to verify the circuit performance before the design is finalized.

Reliability: A reliable PCB design considers factors such as thermal management, EMI/EMC, and mechanical stresses that the board may be subjected to. Thermal management involves proper placement of components, heat sinks, and vias to dissipate heat generated by the components. EMI/EMC involves the careful routing of signals to minimize electromagnetic interference and ensure the PCB complies with relevant regulations. Mechanical stresses may include shock and vibration, which can be mitigated through the use of proper mounting techniques, support structures, and material selection.

Manufacturability: A PCB design that is optimized for manufacturability considers factors such as the use of standard components, design for ease of assembly, and minimizing the number of layers and vias. It is important to ensure that the design is compatible with the chosen manufacturing process, whether it is through-hole, surface-mount, or a combination of both. To minimize errors during manufacturing, it is important to follow industry best practices such as keeping traces and components within the recommended spacing and clearance guidelines.

Design for Testability (DFT): DFT is an important consideration in PCB design to ensure that the board can be tested accurately and efficiently. This involves adding test points, designing the circuit in a way that allows for easy access to components and signals, and using test software to automate testing. By designing the PCB for testability, defects can be detected early in the manufacturing process and fixed before the board is shipped.

Documentation: Clear and concise documentation is essential for a good PCB design. This includes detailed schematics, board layout files, and a complete BOM. The documentation should be organized and easy to navigate, with all necessary information included such as component specifications, reference designators, and manufacturing notes. By providing thorough documentation, the PCB can be manufactured and assembled accurately and efficiently.

By considering these factors and working closely with a manufacturer, a good PCB design can be achieved that is optimized for functionality, reliability, and manufacturability.

7 Steps to Improve Your PCB Design Skills

Introduction:

PCB design is an essential aspect of modern electronics. It involves designing and laying out printed circuit boards that serve as the foundation for electronic devices. Whether you are a beginner or an experienced PCB designer, there is always room for improvement. In this blog, we will explore 7 steps that you can take to improve your PCB design skills.

Step 1: Start with the basics of electronics

Before you start designing PCBs, it’s important to have a solid foundation in electronics. This includes understanding electronic components and circuits, as well as circuit analysis techniques. You can start by learning the basics of DC and AC circuits, Ohm’s law, Kirchhoff’s laws, and basic electronic components such as resistors, capacitors, inductors, and diodes.

Step 2: Choose the right design software

There are many PCB design software options available, and it’s important to choose the one that best suits your needs. Some popular options include Altium Designer, Eagle PCB, KiCad, OrCAD, and PADS. Look for software that has a user-friendly interface, good customer support, and a wide range of features to help you design your PCB effectively.

Step 3: Learn the design rules

PCB design is subject to certain design rules that must be followed to ensure that the circuit works correctly and reliably. These rules include trace width, spacing, and clearance, as well as component placement and orientation. The design rules also cover aspects such as signal integrity, thermal management, and EMI/EMC compliance. It’s essential to learn and follow these design rules to produce a functional PCB.

Step 4: Use libraries

Most PCB design software includes libraries of pre-built components that can be easily placed on the board. Using libraries can save you time and ensure that your design is accurate. You can also create your own custom libraries for components that are not included in the software.

Step 5: Pay attention to placement and routing

The placement of components and routing of traces on the PCB is critical to the performance of the circuit. You should place components in a logical and organized way, paying attention to factors such as signal flow, power delivery, and heat dissipation. Routing the traces correctly is equally important, as it can affect signal integrity and EMI/EMC compliance. Be sure to use the design rules to guide your placement and routing decisions.

Step 6: Consider manufacturability

When designing a PCB, you should keep manufacturability in mind. This means designing the PCB so that it can be easily manufactured using standard processes and materials. Consider factors such as board size, component density, and assembly processes when designing your PCB. Also, make sure to generate the necessary manufacturing files such as Gerber files, drill files, and bill of materials (BOM) so that your PCB can be manufactured with ease.

Step 7: Keep learning

PCB design is a dynamic field that is constantly evolving. Keep up with the latest technologies and techniques by reading industry publications, attending conferences and workshops, and taking online courses. Learning new skills and techniques will help you become a better PCB designer and keep you competitive in the job market.

Conclusion:

By following these 7 steps, you can improve your PCB design skills and produce high-quality PCBs that meet the design requirements. Remember to start with the basics of electronics, choose the right design software, learn the design rules, use libraries, pay attention to placement and routing, consider manufacturability, and keep learning. With practice and dedication, you can become a skilled PCB designer who can create complex circuits and systems with ease

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Reliable PCB Fabrication & Assembly Services in Malaysia

What is Reliable and High-Quality PCB Fabrication and Assembly Services

Reliable and high-quality PCB fabrication and assembly services refer to a set of processes and techniques that ensure that a printed circuit board (PCB) is manufactured and assembled to meet the highest standards of quality, reliability, and functionality. This includes using high-quality materials, precise manufacturing processes, accurate component placement and soldering, thorough testing, and quality control measures.

Reliable and high-quality PCB fabrication and assembly services ensure that the final product is durable, long-lasting, and performs as intended. They are essential for a wide range of industries and applications, including aerospace, medical devices, telecommunications, and consumer electronics.

By choosing a reliable and high-quality PCB fabrication and assembly service, customers can expect to receive a product that meets their design requirements and performs as expected. This reduces the risk of product failure, improves the product’s overall reliability, and can save time and money in the long run.

A Good PCB Fabrication And Assembly

A good PCB fabrication and assembly process involves several key factors to ensure that the final product is of high quality, reliable, and meets the project’s requirements. Here are some key characteristics of a good PCB fabrication and assembly process:

High-Quality Materials: The quality of the materials used in the fabrication and assembly process is critical to the reliability and longevity of the PCB. The substrate material should be of high quality, such as FR4, and the copper foil should be of a suitable thickness and purity. The solder mask should be applied uniformly and accurately to provide a protective layer against environmental factors such as moisture, dust, and debris.

Precise Manufacturing Process: The PCB fabrication process involves several steps, including drilling, etching, plating, and applying the solder mask. Each step should be carried out with precision to ensure that the final product meets the design requirements. For example, the drilling process must be carried out accurately to ensure that the holes are in the correct location and that the plated through-holes have a good connection.

Accurate Assembly: The components should be assembled accurately and in accordance with the design requirements. This means that the correct components must be used, they must be placed in the correct orientation, and they must be soldered correctly. The soldering process should be carried out at the appropriate temperature and for the appropriate length of time to ensure a good connection.

Thorough Testing: The finished PCB should be tested thoroughly to ensure that it meets the design requirements. This includes checking for continuity, verifying the accuracy of the placement of components, and checking the functionality of the board. Various testing methods can be used, including visual inspection, electrical testing, functional testing, and environmental testing.

Quality Assurance: Quality assurance measures should be incorporated throughout the fabrication and assembly process to ensure that the final product is of high quality. Visual inspection and automated optical inspection (AOI) can be used to check for defects and errors in the board. X-ray inspection can be used to check the quality of the plate through holes and other hidden features of the board.

Overall, a good PCB fabrication and assembly process should result in a high-quality, reliable product that meets the project’s requirements and performs as intended.

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SMT 4.0 and CTF

AI Industry 4.0-aided manufacturing should incorporate CTF quality methodology.

Increased use and power of artificial intelligence-aided electronics manufacturing, such as Industry 4.0, creates the opportunity and need to revisit how one manages and improves quality and defect rates.

Traditionally, industry has relied on approaches such as acceptance sampling plans (ASP), Six Sigma (SS), and statistical process control (SPC). Although these approaches offer important data-driven tools to flag and correct the root causes of defects, they generally do so with equal emphasis attached to detecting any or all levels of defect criticality.

The problem with these methods is certain quality outcomes of primary significance to the customer can be missed, as the example below illustrates. This example
serves to illustrate how another strategic method can be cooperatively implemented that will help avoid catastrophic defects. We will label this approach as CTF (critical to function) testing.

In this article, we will address two different branches of CTF testing:

The first branch addresses appropriately linking customer criticality to the RQL (reject quality level) assigned and used in implementing acceptance sampling plans (ASP).
The second branch addresses satisfying customer CTF testing that appends to continuous process approaches. This includes AI failure detection methods installed in the new breed of assembly systems.

Using CTF Testing to Adjust Sampling Plan RQL

As an example, assume the very hypothetical case of a laptop density-type PCB with 500 components and 10,000 solder joints.

After the solder stencil step, the typical way to calculate the post-stencil current reject defect level (RDL) is to divide the number of missing, insufficient, open lead, and bridged solder deposits by the total number of solder deposits needed. Let’s say there’s solder missing or defective in 12 of the spots in the area where a large, expensive 1,000 I/O µBGA part is to reside. If we calculate the defect percentage as a function of the total number of solder deposits (10,000), the RDL is 0.12%.

If the standard RQL set for this kind of “critical” defect is RQL = 1% (with AQL set close to 0.1%), then generally the process running with RDL = 0.12% will pass the ASP testing about 95% of the time. This would probably be considered acceptable by the manufacturer and passed on to solder reflow steps. All would be considered as a smooth flow until after the PCB bearing the large BGA was electrically tested, three to four process steps later, and discovered to be nonfunctional.

By the time this is discovered, the manufacturer has two uncomfortable choices: one, very expensive surgical-level rework; the other, to scrap the assembled board, incurring significant financial loss.

Once the manufacturer becomes aware there are post-soldering failures under this critical area, it should react by raising the screening tests to a more critical RQL level, say RQL = 0.1%, requiring the production line to target test to a lower AQL (AQL = 0.01%).

This first-level reaction would be very costly to the manufacturer.

However, if the manufacturer at product production launch has the customer identify the CTF areas, and if those areas receive the extra level of inspection pre-reflow solder of say 100%, then the future disastrous post-stencil PCB could be caught before the disaster. This approach would be less costly.

Using AI within Industry 4.0 Systems to Improve Quality and Yields

When a company adds or replaces older assembly equipment with newer-AI capable equipment, the process engineer plays a bigger role than they did with their previous level of responsibility. Before taking advantage of the power of the AI-capable equipment, the engineer needs to know what’s right and wrong and the critical control variables with the key process steps, such as PCB planarity, stencil print control and solder paste variations.

In performing this CTF failure analysis, the process engineer must document the procedure that predicts process failure percentage, depending on all major failure modes. This is generally done by running designed experiments. With the help of a statistician, the ranking and variability of the key sources of defects can be predicted. These factors should be quantified mathematically by how they affect the overall defect rate (in this case, 0.12%). What this means is critical factors have a higher weighting (0.12% or 6/12+6/12+0), whereas minor factors have a negligible weighting (for example, 0.05%).

If one has a stable process, this weighting will remain the same indefinitely. However, there are generally changes of equipment, materials, temperature and a whole host of factors that impact the ranking of the causative defects on a continuous basis. Therefore, the control parameters need to be factored into an updatable system. As a result, the constant changes in defect rankings expand the job of the process engineer.

The greater the changes in each factory, the greater the need to reweight the CTF failure equation on an ongoing basis. The process engineer would then pass a first-level equation to the software engineer for implementation in AI. The process engineer then becomes responsible for updating the equation. For example, a major soldering equipment change or repair would certainly require an update to the equation. So might a change in humidity. Additionally, the process engineer would also be responsible for any CTF failure modes that are introduced into the process.

Another new task for the project engineer would be to incorporate the capability of troubleshooting ongoing process failures. For example, leading-edge post-stencil AOI systems are capable of detecting CTF problems if the system is taught where to look and what to do when defects are discovered. Hence, if CTF testing can immediately address solder defects when any, even one, occurs in that large CTF µBGA area, then continuous screening as monitored by AOI systems can produce RDL to desired levels.

If the customer successfully helps the manufacturer identify the CTF areas in advance and designates tests that isolate those areas, then future disastrous electrical test failures can be caught post-solder stencil. At this step in the process, affected PCBs can be washed and re-stenciled and reintroduced into the line before the placement and soldering of components.

Conclusions

Much of the PCB assembly community uses a reactive quality test method, measuring defects on a lot-by-lot basis. The negatives to this approach are larger numbers of rejected products and materials that cost excess money and the possibility of losing business.

Implementation of artificially intelligent systems introduces the capability of continuous process monitoring and reporting. This opens the door for process engineers to implement more rigorous process improvements, since increased data creates increased knowledge of the sources of defects.

The process engineer plays an important role in new state AI. In the example presented, they must identify and categorize the 12 PCB spots by doing a rigorous defect analysis on those spots. This increased knowledge should also focus the engineer on determining whether they are CTF or not.

The CTF concept sounds simple to implement, but it requires closer involvement between the process team and the customer.

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AI Steps up to Solve Semiconductor Challenges

Companies turn to artificial intelligence to close the labor gap in semiconductor design.

The semiconductor industry is growing more competitive. Engineering talent shortages, shrinking time-to-market windows, and never-ending design complexity exacerbate the traditional design processes. These factors have increased the need for improved design results in semiconductor power, performance, and area (PPA). Those who can optimize these metrics faster and at a lower cost improve their competitive position.

One way to tackle these challenges without having dozens of engineers spend months, even years, designing chips is to use AI-enabled tools. We caught up with Arvind Narayanan, senior director of product line management at Synopsys EDA Group, to get his view on emerging solutions in chip design. Synopsys is a chip design company that deploys artificial intelligence to meet design challenges.

What are the current challenges in the semiconductor industry?

Moving to smaller geometry is one challenge for semiconductor design. Plus, there’s a new focus on power with the DoD mandate to reduce power. Talent shortages have become a challenge. By 2030 there will be a 30% worker shortage in the semiconductor industry. This brings about the need for greater productivity from existing personnel. How do you improve productivity? Artificial intelligence is one of the drivers.

AI can boost productivity while also improving the quality of the chips. Engineers can use AI in every stage of the chip design process to help discover the impossible – from system architecture, design, and manufacturing, to accessing AI-driven tools in the cloud. AI developers are on a mission to embed intelligence into the world’s leading industries to transform the way we live, work, learn and play.

What are some of the ways you can use AI in chip design?

You can use AI to understand the challenges and learn how to meet those challenges. You can apply AI tools, and they will get you to 80% of the design quickly. After that, developers can take it to the finish. You can immediately benefit from artificial intelligence.

AI is a proven solution that enhances engineering productivity and silicon quality, even making things possible that had previously been impossible. All of this comes from AI. We have AI as part of our implementation. We started by applying AI to the usable space. We have now expanded AI to the entire stack.

Explain some of the AI-based tools.

Engineering ingenuity has led to advancements like AI-powered chatbots, surgery-performing robotics, and self-driving cars. It has also produced solutions that offload repetitive chip design, verification, and testing tasks, allowing engineers to focus on what they do best: innovate.

We’re going to expand AI in all of the domains. There is a lot of work in manufacturing going from analog. The entire stack has to benefit from AI. In manufacturing, you can use the machines you already have and provide results that are significantly better. Each domain has different slices that need to be solved. You can slice and dice the AI and evolve as you move forward.

Where do you see AI going forward in the semiconductor industry?

Climate change, viral epidemics, and food insecurity present massive challenges. This has triggered the need for larger, more complex chips to process sophisticated algorithms, whether it’s in edge devices or in servers nestled inside hyper-scale data centers.

Optimizing such vast designs for PPA and ensuring that the chip will perform as intended is a huge undertaking, one that is no longer feasible for humans to take on without a boost in capacity. To get there you need AI.

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PCB In Malaysia

Printed Circuit Board

A Printed Circuit Board (PCB) is an electronic circuit board that is used as the foundation for electronic components to be connected and communicate with each other. PCBs are crucial components in a variety of electronic devices, including computers, mobile phones, televisions, and many others.

In Malaysia, the use of PCBs has grown significantly in recent years due to the country’s development as a major hub for electronics manufacturing. The benefits of using PCBs are numerous and include:

Increased Reliability: PCBs are designed to be reliable and long-lasting, making them ideal for use in electronic devices. They can withstand harsh conditions and ensure that the electronic components remain in good working order even after prolonged use.

Improved Performance: PCBs are designed to minimize interference and noise, which can cause electronic devices to malfunction. They are also optimized for speed and efficiency, which can improve the performance of electronic devices.

Cost Savings: The use of PCBs can help to reduce the cost of electronic devices by streamlining the reflow solder process, reducing the need for manual assembly and minimizing the number of components required to produce a device.

Improved Design: PCBs offer a great deal of design flexibility, allowing engineers to create complex circuits with a variety of components. They can also be used to create smaller and more compact devices, which can reduce the overall cost and size of electronic devices of different brands.

Increased Safety: PCBs are designed to meet strict safety standards, which helps to ensure that electronic devices are safe for use. They are also designed to be resistant to heat and electricity, which reduces the risk of fire and other safety hazards.

conclusion

the use of PCBs in Malaysia has brought a multitude of benefits to the electronics industry. With its advanced technology, high reliability, and cost-

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5G Network Infrastructure – Now and For the Future

With the Advent of 5G era, Teflon PTFE Market Will Re-enter the Growth Period

As the fifth-generation mobile communication technology, 5G has better performance than 4G and has the advantages of high speed, high stability, low latency, high spectrum utilization, and excellent scalability. High-frequency transmission technology is one of the critical technologies of 5G wireless communication. High-frequency transmission technology can effectively increase the availability of frequency band resources and enhance the technical requirements of 5G wireless communication technology for network development. To achieve high-frequency transmission, materials with low dielectric constant and low dielectric loss must be used.

5G requires low dielectric materials with a dielectric constant between 2.8 and 3.2. Low dielectric constant materials are mainly used for antenna materials, circuit board materials, cover plate materials, and housing materials of 5G mobile phones. Currently, the primary low dielectric constant materials are PTFE, PPO, LCP, and PI (or MPI). Among them, PTFE, as one of the elements with the lowest dielectric constant among organic materials, will be widely used in the field of 5G communication, such as base station filters, high-frequency, high-speed PCB / FPC, 5G chip manufacturing process, and high-frequency connectors, cables and other areas.

The application of PTFE in high-frequency PCB in 5G field

In mobile communication base stations, the printed circuit board (PCB) copper-clad laminate is the core substrate of the printed circuit board. The copper-clad laminate (CCL) is made of petroleum wood pulp paper or glass fiber cloth as a reinforcement material, impregnated with resin, single-sided, or A plate-like material covered with copper foil on both sides and hot pressed. CCL material is the primary material for printed circuit board (PCB) production. It is mainly used to make PCBs, which play the role of interconnection, insulation, and support for PCBs. PCBs processed from high-frequency copper-clad substrates are widely used as the most fundamental connection devices in the 5G field. At present, epoxy resin glass cloth-based copper clad laminates are commonly used in PCBs in the 4G communication field, with Df values above 0.01, while the 5G field is mainly in the micrometer and millimeter-wave applications. For the dielectric constant and dielectric loss under high-frequency and high-speed conditions There are higher requirements, usually requiring low dielectric steady resin Df less than 0.005, and PTFE as the most inferior dielectric constant polymer material found so far, Df value is below 0.002, showing excellent dielectric in copper-clad laminate performance.

The application of PTFE in radio frequency transmission in the field of 5G

The coaxial cable in the communication field refers to a cable with two concentric conductors, and the conductor and the shield layer share the same axis. The most common coaxial cable consists of copper conductors separated by insulating material. On the outside of the inner layer of insulating material are another layer of the ring conductor and its insulator. Then the entire cable is covered by a sheath of PVC or PTFE material. PTFE has outstanding electrical insulation. It has a low dielectric constant and small loss factor in a wide range of operating temperature and frequency. Besides, expanded PTFE material (e-PTFE) can be produced by unidirectional stretching and bidirectional stretching. The dielectric constant can be further reduced; the volume resistivity and surface resistivity remain competent, in addition, the glass transition temperature is not affected by the external temperature. PTFE’s excellent properties of low moisture absorption, electrical performance stability, and chemical inertness are very suitable for data transmission cables that require low attenuation.

Application of PTFE in 5G base station antenna filter

The development of 5G communication will also bring about a continuous increase in the demand for filters. At present, the 5G filters used by significant communication equipment vendors are still mainly based on metal cavity filters. Many PTFE components are used in metal cavity filters to support The effect of insulation and heat insulation is generally processed by PTFE rod or directly molded. The metal cavity filter of 5G communication is more compact, the internal structure will be more, and the amount of PTEF is also higher than that of 4G.

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Flexible Printed Circuit Board FPCB manufacturing and PCB assembly service

What is a Flexible Printed Circuit Board (PCB)?

OPTIMIZATION OF POLYMERIC STRUCTURE OF ORGANIC PRINTED CIRCUIT BOARDS (PCB)

POLYMERIC STRUCTURE OF MULTILAYER FLEXIBLE PRINTED CIRCUIT BOARDS – ”Sulaiman Khalifeh, in Polymers in Organic Electronics, 2020“

The polymeric printed circuit boards (also called “organic printed circuit boards”) PCB are the simplest self-assembled structures of interconnected microelectronic/Nano-electronic components on a thin film substrate formed from polymer-based composites such as epoxy. As illustrated in Figure 5.1, such structure has several advantages, including very low cost, good electromechanical properties, easy to manufacture in any shape, and applicable for multilayer configurations. These printed circuit boards can be electrically connected to organic/polymeric circuits by either “through-hole technology” THT (older process) or “surface mount technology” SMT (newer process). A more recent solution includes “integrated circuits” IC (also called “microchip”) by which the polymeric printed circuit boards can be built with more circuits and components that are electro-chemically grown in place on the surface of a very small chip. The other method is called a “hybrid circuit” that contains some components, which can be grown onto the surface of the substrate without the need to be mounted on the surface and soldered.

Figure 5.1 Structure of organic/polymeric printed circuit boards.

Three-dimensional polymeric printed circuit boards 3D-PCPs are the most developed solutions, where both single-sided or multilayered polymeric printed circuit boards can be fabricated in the form of 3D-prototypes depending on the “miniature technologies” such as “molded interconnect device” MID. With molded interconnect device technology, the copper traces act as an electrical circuit on the polymeric substrate that can be fabricated by “two-component injection molding,” “hot stamping, photolithography,” “in-mold circuit film,” or “laser direct structuring” LDS which can be considered as the most flexible technology. Such a process can be called “three-dimensional molding of interconnected devices” 3D-MID, while the resultant product can be called “three-dimensional printed circuit board” 3D-PCB as illustrated in Figure 5.2. The direct laser structuring can be achieved immediately after applying single-component injection molding of the carrier. Examples of polymers used for fabricating the polymeric substrates by injection molding process include: liquid crystal polymers LCP, poly(butylene terephthalate) PBT, Trogamid® (amorphous polyamide) (known as: PA 6-3-T), and poly(ethylene terephthalate)/poly(butylene terephthalate) blend PET/PBT.

Figure 5.2. Three-dimensional molded integrated device 3D-MID.

The concept of “optoelectronic printed circuit boards” has been developed to satisfy the increasing demand for high data rates along with progressive miniaturization of devices and components. Optoelectronic printed circuit board represents the integration of optics in a polymeric printed circuit board that is the need to utilize optical fibers, the generation of waveguides by UV lithography, embossing, or direct laser writing. An example of commercial polymers used for structuring optoelectronic printed circuit boards is Ormocer®, which is a type of inorganic/organic hybrid polymer.

POLYMERS FOR CONVENTIONAL PRINTED CIRCUIT BOARDS

The main function of printed wiring is to support circuit components and interconnect these components electrically. Several types of flexible and rigid printed wiring have been used, including traditionally printed circuit boards (single-sided, double-sided, and multilayered), ultra-multilayered printed circuit boards, and three-dimensional printed circuit boards. These types are based on variable dielectric materials (polymers and composites, conductors types, number of conductor planes, rigidity, flexibility, etc.) Rigid printed circuit boards of substrates formed from thermosetting polymers, such as epoxy composites, and flexible printed circuit boards of substrates formed from thermoplastic polymers (such as polyethylene terephthalate PET) are the main two types. Thermosetting composites can be used in the form of filled or glass fiber reinforced epoxy resin EP-GFR, while paper reinforced phenolic (phenol-formaldehyde PF) resin with a bonded copper foil or silicone Q substrates is used for fabricating very small chips (microchips) and stretchable circuits.

The first optimized type of glass fiber reinforced epoxy resin used for structuring conventional printed circuit boards is available in the form of epoxy glass, fire-retardant grade-4 (abbreviated as FR-4). It has very high thermal stability, good mechanical and electrical properties, flame retardance, excellent bonding to copper foil, electroless copper, and glass fibers. It is approved by National Electrical Manufacturers Association NEMA for synthetic resin bonded papers. FR-4 is a polymeric composite material made of woven glass impregnated with plasticized epoxy resin. The second optimized resin is phenolic glass, fire-retardant grade-2 (abbreviated as FR-2), which is a composite material made of paper impregnated with plasticized phenol-formaldehyde resin for the same application. The third optimized type is silicone, which has been used as a flexible substrate for fabricating hybrid stretchable circuits (Figure 5.3). It consists of a millimeter thick polydimethylsiloxane PDMS (IUPAC name: polydimethylsiloxane) having the formula ((C₂H₆OSi)_n) within which two concentric discs of polyimide PI foil (50 µm thick) are embedded. It is a derivative of polyorganosiloxane used as packaging polymer for electronic devices, as well. Polydimethylsiloxane is the first optimized derivative of silicone family used for structuring polymeric double-disk stretchable substrate due to its high strain property. Note: polymeric materials used for fabricating printed circuit board substrates are made of differential dielectrics. This means that they can be selected to provide different insulating values depending on the requirements of the circuit. For this reason, the two types of substrate that can be selected for traditional printed circuit boards are dielectric printed circuit boards and prepreg printed circuit boards.

Figure 5.3. A representation of the polymeric double-disk stretchable substrate.

DIELECTRIC SUBSTRATE-BASED POLYMERIC PRINTED CIRCUIT BOARDS

The dielectric materials (including most polymers) are insulators (non-conducting electricity) resisting the flow of an electrical current. Dielectric polymer represents the optimized class of dielectric materials used for dielectric substrate-based polymeric printed circuit boards, including polytetrafluoroethylene PTFE, epoxy glass, fire-retardant grade-4 (FR-4), epoxy glass, fire-retardant grade-1 (FR-1), composites of epoxy with cotton paper (CEM-1), and composed of nonwoven glass core combined with epoxy resins (CEM-3). The laminates of thermoplastic polymer polytetrafluoroethylene represent the first member of dielectric polymers used for antennas and base stations because of their high melt viscosity. The laminates are fabricated under the lamination pressure of 3.1-3.27 MPa.

An example of commercial polytetrafluoroethylene grade used as a polymer for structuring the substrate of double-sided printed circuits is Teflon®. Figure 5.4 is an example of multilayer laminate containing polytetrafluoroethylene used for printed circuit boards. Polytetrafluoroethylene is bonded with chloro-trifluoroethylene CTFE (IUPAC name: 1-chloro-1,2,2-trifluoroethene) having formula C₂ClF₃ or fluorinated ethylene-propylene copolymer FEP produced by free-radical polymerization of mixture of hexafluoropropylene and tetrafluoroethylene.

Figure 5.4. Example of multilayer laminate containing polytetrafluoroethylene for printed circuit boards.

Epoxy glass, fire-retardant grade-4 FR-4 is the second optimized grade for structuring dielectric substrate-based polymeric printed circuit boards due to its very good mechanical and electrical properties, ability to resist flame, and excellent bonding to copper foil, electroless copper, and glass fibers. Epoxy is available as “difunctional-epoxy” DfEP blend formed by reacting epichlorohydrin and bisphenol-A with flame-retardant additive, “tetrafunctional epoxy” TfEP blend, and “multifunctional epoxy” MfEP blend, listed in Table 5.1. Importance of epoxy polymer is in acting as self-extinguishing binder (self-extinguishing term is used to describe the ability of a material/polymer to cease burning upon removal of the source of flame). Epoxy glass, fire-retardant grade-4 available in the form of laminate is resistant to high temperature and water absorption\, has good electrical insulation, and good machinability. To optimize both physical and electrical properties of the laminate, its glass fibers should be made perpendicular to one another. Some of these properties are listed in Table 5.2. An example of epoxy glass, fire-retardant grade-4 (FR-4) two-layer structure is illustrated in Figure 5.5. Such structure consists of a woven glass fiber mesh soaked in the organic polymer (epoxy as resin matrix) with copper layers laminated (sometimes filled with specific materials).

Properties	Units (condition)	Difunctional epoxy DfEP blend	Tetrafunctional epoxy TfEP blend	Multifunctional epoxy MfEP blend
Glass Transition Temperature	°C	130	130 – 140	160 – 190
Dielectric constant	at 1MHz	4.5	4.6	4.4
Dissipation factor	at 1 MHz	0.025	0.025	0.025
Moisture absorption	%	0.70	0.06 – 0.013	0.60 – 0.013

Table 5.1. Optimized epoxy types for dielectric substrate-based polymeric printed circuit boards.

Table 5.2. The general properties of epoxy glass, fire-retardant grade-4 (FR-4) and epoxy glass, fire-retardant grade-1 (FR-1).

Figure 5.5. Example of two-layer structure of epoxy glass, fire-retardant grade-4 (FR-4).

According to Figure 5.5, and Table 5.1, the polymeric matrix of epoxy glass, fire-retardant grade-4 FR-4 laminates consists of bi-, tetra- or multi-functional epoxy groups. Note: epoxy EP is chemically derived from the reaction of bisphenol-A epoxy BPAE with epichlorohydrin ECO which creates diglycidyl ether of bisphenol A (DGEBA) (also referred to as oxirane OXr). OXr (DGEBA) reacts in subsequent resin polymerization, curing the polymeric matrix. Higher crosslinking in the cured system can be achieved by the use of epoxy monomers with more than two epoxy functional groups per molecule.

Epoxy glass, fire-retardant grade-1 FR-1 is the second optimized epoxy glass, fire-retardant grade used in dielectric substrate-based polymeric printed circuit boards. It is a thermoset polymeric composite formed from the paper base with plasticized epoxy resin. Properties of this composite were listed in Table 5.2. Composite of epoxy with cotton paper (abbreviated as CEM) represents the third optimized class of polymeric composites used for structuring dielectric substrate-based polymeric printed circuit boards. These composites are commercially available in the form of five numbered grades, including CEM-1, CEM-2, CEM-3, CEM-4, and CEM-5. Where numbers from 1 to 5 are related to the type of the base. For example, number 1 means cotton (or cellulose) paper and epoxy.

CEM-1 is a polymeric composite consisting of woven glass fabric surfaces and paper core combined with epoxy resin. It is easy to punch, and has excellent mechanical and electrical properties, and higher flexural strength than paper-based grades. It is used in radio receivers, smoke detectors, and single-sided printed circuit boards. Its properties are listed in Table 5.3. CEM-3 is a composite of nonwoven glass core combined with epoxy resin. Similarly to CEM-1, it consists of epoxy resin with woven glass cloth surfaces, but its core is nonwoven matte fiberglass. The nonwoven mate fiberglass optimizes through-hole plating. It has better fine-line capability than FR-4. It has a very smooth surface and milky white color. It can be used as an alternative to FR-4, known as a flame retardant epoxy copper-clad plate glass material.

Table 5.3. The general properties of composites of epoxy with cotton paper CEM-1 and composites of non-woven glass core combined with epoxy resin CEM-3.

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Why do we need Multilayer PCB?

The Advantages of Multilayer PCB

Having more layers means the board is thicker and, therefore, more durable than single-sided PCBs. This is another reason adding functionality through additional layers is preferable to increase the dimensions of a single layer. Printed circuit boards have ubiquitous presence today, what with them being the core of most electronic items. With the growing complexity of devices, Printed circuit boards are therefore increasingly becoming more complex. From flexible to odd shaped ones, there is a range of PCBS out there. While electronic devices with limited functions can do with single layer PCBs, there is an exponential growth in multi layered PCBs. By definition, multilayered PCB are made up of layers of double-sided circuit boards with heat protective insulation between them. The electrical connections between the layers happen through various kinds of vias resulting in complex multilayered PCBs. With complexity in applications, PCBs today can range anywhere from four to twelve layers.

Size: Multilayer PCB have an added advantage on account of their small size as they lend themselves well.
Lightweight: Small PCBs also come with reduced weight. This is particularly true also because single and double layered PCBs need a number of connectors that add to the weight and hence restrict mobility.
Reliability: Typically multilayered PCBs are high on reliability as well as of high quality.
Durability: Multilayer PCBs also come with high durability as they are able to withstand the heat and pressure that is applied on them.
Flexibility: For assemblies that use flexible construction techniques, a flexible multilayered PCB can be helpful particularly in applications that require some amount of bending.
Powerful: Multilayer PCBs typically are high density and have greater capacity as well as speed.
Single Connection Point: With single connection points, multilayered PCBs are beneficial for gadgets where size and weight are constraints.

On account of all these advantages, multilayer PCBs are the preferred option especially as greater functionality and reduced size increasingly become the norm.

All of this is not to say that multilayered PCB Fabrication does not have any disadvantages. Largely, compared to single layered PCBs, multilayered ones come with added cost as well as increased design time. Multi layered PCBs also necessitate that there be skilled designers who have a wide experience and hence can overcome issues related to crosstalk and impedance. In efficient design it can directly impact board functioning. Also, multilayer boards require increased production time and hence a lower turnover rate.

However, it is their improved functionality that more than covers for the many disadvantages associated with multi layered boards. As far as their increased costs go, with the advancement of technology, the costs are only slated to decrease.

However, even while using multi layered PCBs it is important to ensure that as far as possible you go with an even number of layers as opposed to PCBs with odd number of layers. This is on account of many factors including but not limited to the cost efficiency:

Single layer PCBs are cost ineffective

The cost ineffectiveness of odd number of layers stems from the fact that the process of creating an odd layered PCB begins with creating an even layered PCB and then etching away the unwanted layer. As the process suggests, this leads to a lot of wastage which in turn lead to cost inefficiencies.

Warping

Other than the cost aspect, etching also results in warping of the layer. With one side having copper and the other side not having it, there are different cooling rates, thereby creating stress on the PCB.

Risk of over & under plating

What the etching also does is that it leaves the two sides (one with copper and one without), with different weights, thereby adding to the risk of under or over plating.

On account of all the above reasons, it isn’t advisable to have single layers unless there is a specific, compelling reason to do so.

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Multilayer PCB stack-up design showing copper layers signal layer power plane and ground plane arrangement

How to Design a Good PCB Stack-Up

The rules and standard for designing a good PCB stack-up

The rules and standards for designing a good stack-up are hundreds. Let’s just see a few:

Ground plane boards are better because they allow signal routing in a microstrip or strip-line configuration. It also significantly reduces the ground impedance and, therefore, the ground noise;
High speed signals should be “routed” on intermediate layers located between the various levels. In this way, ground planes can act as a shield and contain the radiation coming from the tracks at high speed;
The signal layers should be very close to each other, even in adjacent planes.
A signal layer must always be adjacent to a plane;
Multiple ground planes are very advantageous, since they lower the board’s ground impedance and reduce radiation in a common way;
The power and mass planes must be rigorously coupled together;

To achieve all these objectives, it is necessary to operate with a minimum of eight layers. Moreover:

From a mechanical point of view, it is advisable to implement a cross section to avoid deformations;
Configurations should be symmetric. For example, on an eight-layer PCB, if level 2 is a plane, level 7 should also be a plane;
If the signal levels are next to the levels of the plane (ground or power) the return current can flow on an adjacent plane reducing the inductance of the return path to a minimum;
To further improve noise and EMI performance, insulation between a signal layer and its adjacent plane can be made even thinner;
An important consideration to be made is the thickness of each signal layer. There are standard thicknesses together with the properties of different types of printed circuit material. When selecting the materials, it is advisable to consider their electrical, mechanical and thermal properties;
Use excellent software to help you design your stack-up. All this should be done in order to choose the correct materials from the library and perform impedance calculations based on the materials and their dimensions.

Careful PCB design is necessary

At the high operating speeds of today’s circuits, careful PCB design is necessary, and it is becoming, in all respects, an art. A poorly designed printed circuit board can degrade the electrical performance of signal transmission, power delivery, producibility and long-term reliability of the finished product.

The sending of Gerber files to companies determines the production costs, which, as with any other goods, are lowered according to the required quantities. The global growth of the PCBs market is driven by the increased use of multilayer, flexible PCBs. The board density and design complexity keep increasing as electronic companies try to add more features to the devices. Price, quality, delivery time and service are the most common criteria for choosing a PCB manufacturer, and most people should be concerned about the price first.

Proto-Electronics’ mission is to help you in this crucial prototyping phase by cutting your lead times. Online quotes in 10 minutes and delivery lead times starting from 5 working days will give you more peace of mind to work.

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