pcb assembly

Revolutionizing Electronic Design and Manufacturing: The Power of AI Technology

In recent years, the integration of Artificial Intelligence (AI) technology into various industries has revolutionized processes and improved efficiency. The electronic design and manufacturing sector is no exception. With its ability to analyze vast amounts of data, learn patterns, and make intelligent decisions, AI has become a game-changer in optimizing electronic design, enhancing manufacturing processes, and driving innovation. In this article, we will explore in detail the significant impact of AI technology on electronic design and manufacturing.

Design Optimization:

AI technology has transformed the electronic design process by enabling advanced optimization techniques. Designers can leverage AI algorithms to explore a vast design space, quickly evaluate numerous possibilities, and identify the most efficient and effective designs. AI algorithms can analyze design constraints, performance objectives, and historical data to generate optimized circuit layouts, improve power efficiency, reduce electromagnetic interference, and enhance overall design performance.

For example, AI-based optimization algorithms can analyze a wide range of circuit parameters and constraints to find the optimal trade-off between power consumption, performance, and cost. These algorithms can identify design solutions that human designers might overlook, leading to more efficient and innovative electronic designs.

Predictive Maintenance:

In the manufacturing phase, AI technology plays a crucial role in predictive maintenance. By continuously monitoring sensors and data points, AI algorithms can detect anomalies, predict equipment failures, and recommend preventive actions. This proactive approach minimizes unplanned downtime, reduces maintenance costs, and optimizes production efficiency.

AI-powered predictive maintenance algorithms can analyze real-time data, historical records, and equipment performance patterns to accurately forecast maintenance requirements and schedule interventions accordingly. For example, by monitoring equipment vibration, temperature, and power consumption data, AI algorithms can identify signs of impending equipment failure and alert maintenance teams to take preventive action. This ensures that equipment operates at peak performance, reduces costly downtime, and extends the lifespan of machinery.

Quality Control and Inspection:

AI technology enhances quality control and inspection processes in electronic manufacturing. Visual inspection, a critical aspect of quality control, benefits from AI-driven machine vision systems. These systems employ deep learning algorithms to analyze images and detect defects, such as soldering errors, component misalignment, or physical damage. By automating the inspection process, AI technology improves accuracy, reduces human error, and increases throughput, ultimately ensuring higher product quality.

AI-powered machine vision systems can quickly and accurately identify defects that may be difficult for human inspectors to detect. This technology not only improves the efficiency of quality control but also reduces the likelihood of defective products reaching the market, thereby enhancing customer satisfaction and brand reputation.

Supply Chain Optimization:

AI technology offers immense value in optimizing the electronic manufacturing supply chain. By analyzing historical data, market trends, and demand patterns, AI algorithms can accurately forecast material requirements, manage inventory levels, and optimize procurement processes. This helps to minimize supply chain disruptions, reduce excess inventory, lower costs, and enhance overall efficiency.

AI algorithms can analyze vast amounts of data to identify patterns and correlations, enabling more accurate demand forecasting. By leveraging this information, manufacturers can optimize their production schedules, avoid stockouts, and reduce inventory carrying costs. Additionally, AI-powered algorithms can continuously monitor market trends and supplier performance, allowing manufacturers to make informed decisions regarding sourcing strategies and supplier selection.

Process Automation:

AI technology enables process automation in electronic manufacturing, improving productivity and reducing manual labor. Robotic process automation (RPA) powered by AI algorithms can streamline repetitive and time-consuming tasks, such as data entry, documentation, and inventory management. This automation allows human workers to focus on higher-value tasks, leading to increased productivity, reduced errors, and improved overall workflow efficiency.

RPA can automate various tasks across the manufacturing process, such as generating production reports, updating inventory databases, or performing quality control checks.

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Exploring the Factors Affecting SMT Soldering Quality and Effective Solutions


Surface Mount Technology (SMT) soldering plays a crucial role in modern electronics manufacturing, enabling the assembly of compact and efficient electronic devices. However, achieving high-quality solder joints can be challenging due to various factors that can impact the soldering process. In this article, we will explore some key factors that affect SMT soldering quality and discuss potential solutions to address them effectively.

Solder Paste Quality:

Solder paste composition: Ensure that the solder paste is formulated to meet the specific requirements of the components and the soldering process. Consider factors such as lead-free vs. leaded solder, flux type, and activity level.

Viscosity: Monitor and control the viscosity of the solder paste to ensure consistent and uniform deposition. Use viscosity measurement tools and adjust the paste or the printing process parameters accordingly.

Particle size distribution: Solder paste with a well-controlled particle size distribution provides better stencil release and improves solder paste printing quality. Regularly check the particle size distribution using laser diffraction or similar methods.

Soldering Temperature Profile:

Preheat: Ensure that the preheating phase brings the PCB and components to the desired temperature gradually, avoiding thermal shock and potential component damage.

Soak: Maintain a stable temperature during the soak phase to allow the flux to activate fully and promote proper wetting.

Reflow: Optimize the reflow profile by adjusting the ramp rate, peak temperature, and cooling rate to achieve the right balance between solder joint formation and minimizing thermal stress on the components.

Component Placement Accuracy:

Vision systems: Utilize advanced pick-and-place machines equipped with vision systems to align and orient components accurately. These systems can detect variations in component position, rotation, or polarity, reducing the likelihood of misalignment.

Calibration and maintenance: Regularly calibrate the placement machines to ensure precision and accuracy. Maintain and clean the nozzles, feeders, and placement heads to prevent any debris or misalignment issues.

Automated Optical Inspection (AOI): Implement AOI systems to detect and flag any component placement errors. This allows for immediate corrective actions, reducing the chances of soldering defects.

PCB Design Considerations:

Pad design: Optimize the pad geometry, including pad size, shape, and solder mask relief, to ensure sufficient solder wetting and proper solder joint formation.

Stencil design: Collaborate with stencil manufacturers to design stencils that provide consistent and accurate solder paste deposition, taking into account the component footprint and recommended solder paste volume.

Solder mask clearance: Maintain appropriate solder mask clearance around pads to avoid solder bridging and ensure proper solder joint formation.

Operator Training and Skills:

Comprehensive training programs: Develop training programs that cover the fundamentals of soldering, equipment operation, process parameters, and quality standards. Provide hands-on training to enhance the operators’ skills in component handling, solder paste application, and reflow techniques.

Continuous improvement: Encourage operators to stay updated with the latest industry trends and advancements through workshops, seminars, and certifications. Foster a culture of continuous learning and improvement within the organization.


Attaining high-quality soldering in SMT assembly is a multi-faceted process that involves addressing various factors that can impact the final results. By focusing on solder paste quality, optimizing the soldering temperature profile, ensuring accurate component placement, considering PCB design factors, and investing in operator training, manufacturers can significantly enhance their SMT soldering quality. Implementing these solutions will lead to improved reliability, reduced rework, and enhanced overall product performance in the ever-evolving world of electronics manufacturing.

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Unveiling the Effects of High Temperature and Humidity on PCB Performance


Printed circuit boards (PCBs) are integral components in electronic devices, serving as the foundation for interconnecting and powering various electronic components. As electronic devices continue to advance, it becomes crucial to understand the environmental factors that can affect the performance and reliability of PCBs. In this article, we will explore the impact of high temperature and humidity on PCBs, shedding light on potential challenges and necessary precautions.

The Effects of High Temperature

  1. Thermal Stress: High temperatures can subject PCBs to thermal stress, which may lead to component failure or solder joint degradation. Excessive heat can cause expansion and contraction of the board and its components, potentially resulting in mechanical and electrical failures.
  2. Material Integrity: Elevated temperatures can adversely affect the material integrity of PCBs. The substrate material, typically made of fiberglass-reinforced epoxy, may experience thermal degradation, compromising the structural strength of the board.
  3. Signal Integrity: High temperatures can impact the electrical properties of the PCB, leading to signal integrity issues. Heat-induced expansion and contraction can alter the impedance characteristics of transmission lines, causing signal distortions or reflections.
  4. Component Performance: Electronic components on the PCB, such as integrated circuits (ICs), capacitors, and resistors, often have specified operating temperature ranges. Operating beyond these temperature limits can affect their performance, reliability, and even lifespan.

The Effects of High Humidity

  1. Corrosion: High humidity levels can create a conducive environment for the formation of moisture on the PCB surface. Moisture, in the presence of oxygen, can lead to corrosion of the conductive traces, solder joints, and component leads, compromising the electrical connectivity.
  2. Conductive Contamination: Humidity can contribute to the accumulation of conductive contaminants, such as dust, salts, or other pollutants, on the PCB surface. These contaminants can cause short circuits or interfere with signal transmission, leading to malfunction or reduced performance.
  3. Insulation Breakdown: Excessive humidity can deteriorate the insulation properties of PCB materials, such as solder mask or conformal coating. This breakdown may result in leakage currents, reduced insulation resistance, or even insulation failure.

Precautions and Mitigation Strategies

To mitigate the adverse effects of high temperature and humidity on PCBs, several precautions can be taken:

  1. Temperature Control: Ensure that electronic devices and PCBs operate within the recommended temperature range. Implement proper cooling mechanisms such as heat sinks, fans, or thermal management techniques to dissipate excess heat.
  2. Humidity Control: Use environmental controls such as dehumidifiers or humidity-controlled storage to maintain optimal humidity levels during storage, transportation, and operation of PCBs.
  3. Conformal Coating: Apply a conformal coating on the PCB surface to protect it from moisture, contaminants, and corrosion. This coating acts as a barrier, enhancing the PCB’s resistance to humidity-related issues.
  4. Enclosure Design: Employ effective enclosure design practices to prevent moisture ingress, ensuring that the PCB remains protected from high humidity environments.


High temperature and humidity can significantly impact the performance and reliability of PCBs. Thermal stress, material integrity concerns, signal integrity issues, corrosion, and conductive contamination are among the potential challenges. By implementing appropriate precautions such as temperature control, humidity control, conformal coating, and effective enclosure design, the detrimental effects of high temperature and humidity on PCBs can be mitigated. Understanding and addressing these environmental factors will contribute to the longevity and optimal functioning of electronic devices relying on printed circuit boards.

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An Introduction to Printed Circuit Boards, What You Should Know


In the realm of rapidly evolving technology, printed circuit boards (PCBs) serve as the backbone of electronic devices, powering and connecting them seamlessly. From smartphones to computers, PCBs play a crucial role in modern electronics. In this article, we will delve into the world of printed circuit boards, exploring their significance, construction, and various types.

What is a Printed Circuit Board?

A printed circuit board, or PCB, is a flat board made of non-conductive material that provides mechanical support and electrical connections for electronic components. It acts as a platform for assembling and interconnecting various electronic components using conductive pathways, or traces, etched onto its surface.

Construction of a PCB

PCBs are typically constructed in layers, consisting of a substrate layer, conductive layers, and a solder mask layer. The substrate layer is usually made of fiberglass-reinforced epoxy, while conductive layers, usually made of copper, are etched to form the desired circuitry. The solder mask layer provides insulation and protection to the copper traces, preventing accidental short circuits.

The PCB Design Process

The design process of a printed circuit board involves several crucial steps. It starts with schematic design, where the circuit is laid out using specialized software. The next step is the PCB layout, where components are positioned, and traces are routed to ensure proper connectivity. Once the layout is finalized, the PCB design is sent for fabrication, where the physical board is manufactured based on the design specifications.

Types of PCBs

PCBs come in various types, each serving different purposes:

  1. Single-sided PCB: Components and traces are present on one side of the board.
  2. Double-sided PCB: Components and traces are present on both sides of the board.
  3. Multilayer PCB: It consists of multiple layers of conductive material, allowing for complex circuitry and compact designs.
  4. Flexible PCB: It is made of flexible plastic material, enabling it to be bent or twisted to fit unconventional form factors.
  5. Rigid-Flex PCB: It combines rigid and flexible PCBs, offering both structural rigidity and flexibility.

Advantages of PCBs

Printed circuit boards offer numerous advantages over other wiring methods:

  1. Compactness: PCBs allow for compact and space-efficient designs.
  2. Reliability: They offer stable connections and reduced risk of loose connections or short circuits.
  3. Easy Repairs and Modifications: PCBs facilitate easier troubleshooting, repairs, and modifications compared to point-to-point wiring.
  4. Cost-Effectiveness: Once the initial setup cost is covered, PCBs can be mass-produced at a relatively low cost.
  5. Signal Integrity: PCBs are designed to minimize signal loss and interference, ensuring better overall performance.


Printed circuit boards form the foundation of modern electronics, providing the necessary connectivity and support for electronic components. Their construction, design process, and various types highlight their versatility and importance. As technology continues to advance, PCBs will undoubtedly evolve to meet the ever-increasing demands of the electronics industry.

Next time you hold a smartphone or power up a computer, remember the intricate world of printed circuit boards working silently behind the scenes, enabling our digital lives.

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Expert Tips for PCB Assembly

PCB Assembly

Printed circuit boards (PCBs) are essential components of modern electronics, and the process of assembling PCBs is a critical step in the manufacturing process. PCB assembly involves several stages, including preparation, component placement, soldering, and inspection. In this blog, we will explore the different stages of PCB assembly and provide tips and best practices for each step.

Step 1: Preparation

The first step in PCB assembly is to prepare the PCB and components for assembly. This involves inspecting the PCB for any defects, such as scratches or damage to the solder mask. The components should also be checked for any defects or damage. Once the PCB and components are inspected, they can be prepared for assembly by cleaning and organizing them.

Step 2: Component Placement

The next step is to place the components on the PCB. This can be done by hand or with automated equipment, depending on the complexity of the PCB and the number of components. It’s important to place the components accurately and securely to ensure that they are in the correct position for soldering.

Step 3: Soldering

Soldering is the process of attaching the components to the PCB using solder. There are two main methods of soldering: through-hole and surface mount. Through-hole soldering involves inserting components into pre-drilled holes in the PCB and soldering them in place. Surface mount soldering involves attaching components to the surface of the PCB using solder paste and a reflow oven. Both methods require a high degree of precision and accuracy to ensure that the components are securely attached, and the solder joints are of high quality.

Step 4: Inspection

Inspection is a critical part of PCB assembly, and it involves checking the quality of the solder joints and the overall integrity of the PCB. This can be done using visual inspection or automated inspection equipment. Any defects or issues should be addressed and corrected before moving on to the next step.

Step 5: Testing

Once the PCB is assembled, it should be tested to ensure that it is functioning correctly. This involves electrical testing to check for shorts and opens and other tests to ensure that the PCB is functioning as intended. Testing can be done manually or using automated equipment.

PCB assembly is a complex process that requires specialized skills and equipment. It involves several stages, including preparation, component placement, soldering, inspection, and testing. By following best practices and using high-quality materials and equipment, it’s possible to create high-quality PCB assemblies that meet the required specifications and standards. Whether you’re a hobbyist or a professional, understanding the PCB assembly process is essential for working with electronics and creating innovative new products.

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A Comprehensive Guide to Manufacturing Printed Circuit Boards

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: 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 the 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

PCB Design

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


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.


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 and High-Quality PCB Fabrication and Assembly Services

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 plated 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

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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:

  1. The first branch addresses appropriately linking customer criticality to the RQL (reject quality level) assigned and used in implementing acceptance sampling plans (ASP).
  2. 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 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 the 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.


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 product 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 create 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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What is Flexible Printed Circuit Board (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 coast, good electromechanical properties, easy to be manufactured 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). 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.

[Data from Laser Micronics GmbH, 3-Dimensional Circuitry, Laser Direct Structuring Technology (LPKF-LDSTM) for Molded Interconnect Devices, 2012.]Copyright © 2012.

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.


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.


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 blendTetrafunctional epoxy TfEP blendMultifunctional epoxy MfEP blend
Glass Transition Temperature°C130130 – 140160 – 190
Dielectric constantat 1MHz4.54.64.4
Dissipation factorat 1 MHz0.0250.0250.025
Moisture absorption%0.700.06 – 0.0130.60 – 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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