What are Some Common PCB Problems and Circuit Board Issues?

Printed Circuit Boards defects are minor or major errors in PCBs that can hinder their electrical efficiency and mechanical strength. There are multiple factors that contribute to defects in PCBs and a manufacturer should be aware of them to protect the production of their PCBs from any manufacturing or assembly hazard.

In this article, we will go through an in-depth analysis of some of the most common PCB defects, which will hopefully help you gain insights into considerations to keep while designing Printed Circuit Boards.

Common Types of PCB Defects and Failures

Printed Circuit Boards (PCBs) are vital for electronic devices, providing interconnections that enable proper functionality. Ensuring high PCB quality is crucial as defects can disrupt electrical signals, leading to performance issues and system failures. Additionally, defects compromise mechanical stability, increasing vulnerability to damage. Poor soldering connections further diminish reliability and signal integrity, risking premature component failure. Defective PCBs can cause erratic behaviour, safety hazards, production delays, and costly repairs, damaging reputation and customer satisfaction. Therefore, prioritizing rigorous design, manufacturing, and testing processes is essential to deliver reliable and efficient electronic systems while meeting industry standards.

Following are some of the most common types of PCB defects, that a manufacturer must be aware of:
An open circuit as suggested by the red arrow

1. Open Circuits: Open circuits occur when there is a break in the electrical connection, causing a discontinuity in the circuit. This can happen due to loose or disconnected wires, damaged traces on the PCB, or faulty components. An open circuit disrupts the flow of current, leading to malfunction or non-functionality of affected components. Detecting and resolving open circuits is essential for maintaining proper electrical continuity and ensuring the reliable operation of electronic devices.
2. Short Circuits: Short circuits occur when conductive paths in a circuit come into unintended contact, causing current flow that can lead to overheating, component damage, and safety hazards. Common causes include exposed wires, soldering errors, or damaged insulation. Detecting and resolving short circuits promptly is crucial to prevent further damage and ensure safe device operation. This involves identifying the contact point, isolating the shorted paths, and repairing or replacing affected components to restore functionality.
3. Plating Voids: Plating Voids are defects that occur in Printed Circuit Boards (PCBs) during the plating process of PCB manufacturing. PCBs are made by designing and etching patterns of conductive traces on a non-conductive substrate. Furthermore, to ensure efficient electrical conductivity, these traces are plated with a thin layer of metal, such as copper, tin, nickel, or even silver.
   A cross-sectional image of a plating void
4. Solder Mask Inconsistency: In certain cases, the absence of a solder mask between pads on a circuit board can lead to issues. The solder mask acts as insulation and protection for the copper traces, preventing accidental contact and corrosion. However, when the solder mask is missing between pads, it exposes excess copper and increases the risk of unintended solder bridges during assembly. This can result in shorts and reduced corrosion protection, negatively impacting the functionality and lifespan of the PCB. To avoid this defect, it is important to thoroughly review the design and ensure appropriate solder mask coverage before manufacturing.
5. Soldering Defects: One of the most common PCB defects arises due to improper Soldering or not taking the measures necessary for the soldering process. Listed below are a few soldering defects:
   • Solder Dewetting: Solder Dewetting is a surface phenomenon that occurs due to the reduction of surface energy between the solder and the substrate. It is a process where the solder material loses its wetting ability and adhesion to the underlying substrate.
     A representation of a very basic solder dewetting
   • Cold Solder Joints: A cold solder joint is a type of soldering connection that is weak and has low reliability due to poor soldering technique or insufficient heat application during the soldering process. In a cold solder joint, the Solder may appear dull or grainy, indicating that it did not flow properly during the Soldering process, and may also have a weak mechanical bond to the component leads or circuit board.
     Left: A cold solder joint vs Right: A perfect alright solder
   • Solder Bridging: Solder bridging is an unintended connection or bridge formed by excess solder between adjacent points on a PCB. It can cause short circuits and improper electrical connections during the soldering process. Detecting and resolving solder bridging is important for circuit reliability.
     
   • Sunken Joints: Sunken joints refer to solder joints on a PCB that has insufficient solder, resulting in a concave or depressed appearance. This defect can occur due to factors such as inadequate solder volume, improper heating, or component misalignment during the soldering process. Sunken joints can lead to poor electrical connections.
   • Tombstoning: Tombstoning is a defect that occurs during surface mount technology (SMT) assembly when a component becomes partially or completely upright, resembling a tombstone. This defect typically arises due to imbalanced solder paste deposition, differing component and pad sizes, or uneven heating during reflow soldering.
   • Shadowing: Shadowing refers to the phenomenon where adjacent components or structures obstruct the flow of solder paste during the soldering process. This can result in insufficient solder deposition on the affected pads or pins, leading to poor solder joints and potential connectivity problems.
6. Dendrite Growth: Dendrite Growth on PCBs refers to the formation of tiny, conductive filaments that can branch out and grow on the surface of a PCB board. Eventually, these branches of conductive material start bridging two or more adjacent conductive elements. These filaments, also called Dendrites, can form due to an electrochemical process called electrolysis, which can occur when there is an applied voltage and an electrolyte present between two conductive elements on the board.
7. Acid Traps in PCBs: Acid traps are acute angles in a circuit that can cause problems during the PCB etching process. These angles can trap acid, leading to excessive corrosion and compromising connections. While designers are trained to avoid acute angles, mistakes can occur due to human error or improper software settings. Checking for and addressing these traps is crucial to prevent circuit defects and potential issues down the line. Manufacturers with the proper design for manufacturability (DFM) checks can help identify and rectify these mistakes.
8. Slivers: Slivers are thin, elongated pieces of material that can be conductive or non-conductive and remain attached to the PCB during manufacturing or assembly. They can cause issues such as short circuits, electrical leakage, and interference with nearby components. Slivers can also compromise the structural integrity of the board. Detecting and removing slivers during manufacturing and assembly is essential to maintain PCB quality. Inspection methods like visual inspection, AOI, or X-ray inspection help identify and address sliver defects.
9. Inefficient PCB Components: PCB failure can also result from the use of poorly manufactured components during assembly. Physical damage and connection issues can arise when subpar components are incorporated into the PCB. Additionally, residual flux left on the board from soldering can cause significant damage and necessitate repairs. To mitigate these risks, it is important to collaborate with manufacturers who prioritize the use of high-quality components in PCB production.
10. Delamination: Delamination is a common PCB defect where layers of the board separate due to factors like moisture absorption and thermal stress. Moisture can infiltrate the PCB, creating internal pressure when exposed to high temperatures, leading to the separation of layers. Thermal stress, caused by temperature fluctuations and different material expansion coefficients, weakens adhesive bonds, resulting in delamination. This defect reduces mechanical strength, making the PCB prone to damage, and disrupts signal integrity, causing impedance and connection issues. Preventive measures include selecting low moisture absorption materials, implementing moisture barriers, using reliable adhesives, and considering thermal compatibility to minimize delamination risks. Understanding and addressing these factors are crucial for producing robust and reliable PCBs.
    Delamination in PCBs

By being aware of these common PCB defects and taking preventive measures, manufacturers can enhance the reliability and performance of their PCBs, ensuring customer satisfaction and meeting industry standards.

Conclusion

Printed Circuit Board (PCB) defects can have significant consequences for the functionality, reliability, and safety of electronic devices. In this article, we have explored some of the most common PCB defects, including open circuits, short circuits, plating voids, solder mask inconsistency, soldering defects, sunken joints, tombstoning, shadowing, dendrite growth, acid traps, slivers, and inefficient PCB components.

Understanding these defects is essential for manufacturers to improve their manufacturing and assembly processes, minimize risks, and deliver high-quality PCBs. In the upcoming articles, we will delve into the causes and consequences of PCB defects in more detail. We will also discuss strategies and best practices for preventing these defects, including rigorous design considerations, manufacturing techniques, quality control measures, and testing methodologies.

By addressing and preventing PCB defects, manufacturers can ensure the production of reliable and efficient electronic systems that meet industry standards and exceed customer expectations. Stay tuned for our next articles, where we will provide valuable insights and practical recommendations to help you optimize your PCB manufacturing process and deliver superior products.