Printed Circuit Boards (PCBs) are essential components in many electrical devices today, connecting different components through complex arrays of circuitry. Global demand for PCBs is rapidly increasing—over the past eight years, total global PCB sales have grown by more than $3.7 billion annually on average, with a growing focus on reducing conflict mineral supply chain issues and improving technology. As of 2018, global PCB sales were approximately $82 billion.

　　Because of the significant investment in PCBs and their crucial role in numerous electrical devices and enclosure assembly components, PCB failures are a major concern for many companies. Below, you will learn more about common causes of PCB failures so your company can better prevent and effectively resolve PCB failures.

　 　What are PCB Failures?

　　PCB failures can stem from a variety of causes, ultimately resulting in the PCB no longer functioning correctly. Since PCBs are used in many electronic products, such as wearable devices, airplanes, satellites, and medical devices, it is imperative that any failures are quickly identified and addressed appropriately. Any company hoping to keep its electronics running smoothly can better resolve, and even prevent, PCB failures by learning more about the causes of PCB failures.

　　 Causes of PCB Failures – PCB Defects

　　The complexity of the PCB design and manufacturing process means that the potential for PCB failure issues is quite high. Some of these failures are due to design oversights, such as insufficient clearances or incorrect measurements, which can negatively impact the functionality of the finished product. Other failures may be due to issues in the manufacturing process, such as incorrect drilling or over-etching, which can similarly have disastrous consequences.

　　Fortunately, most of these errors can be avoided with an understanding and consideration of the manufacturing process and an awareness of more common PCB manufacturing problems. Following a set of standard design rules and considerations can help prevent component failures, connection issues, and other board problems. To help you and your company better understand and avoid potential errors in printed circuit board design, we have compiled a list of common problems in PCB manufacturing, including why they occur and how to prevent them:

　 　1. Plated Through-Hole Voids

　　Plated through-holes are plated copper holes in a printed circuit board. These holes allow current to travel from one side of the board to the other. To make these holes, PCB board manufacturers drill holes in the board, completely piercing the substrate. Then, a layer of copper foil or copper plating is added to the surface of the material and these hole walls through an electroplating process.

　　This process deposits a thin layer of electroless copper on the board, a process called deposition. After this step, additional copper layers are added and etched to create the circuit image.

　　While effective, the deposition process is not perfect and in some cases can lead to voids in the plating. Plated through-hole voids are essentially gaps or holes in the plating of the board, usually caused by problems during the deposition process. These plated through-hole voids are particularly problematic because defects in the through-hole plating will prevent current from passing through the hole, leading to product defects.

　　These plating voids occur because the material, for some reason, did not coat evenly during the deposition process. Causes for this include material contamination, trapped air bubbles in the material, insufficient hole cleaning, insufficient copper catalysis during the deposition process, or rough drilling. Any of these issues can lead to plating voids along the walls of the circuit holes.

　　Properly cleaning the material after drilling can avoid defects due to contamination, air bubbles, or insufficient cleaning. Furthermore, strictly following manufacturer instructions during use can avoid PCB defects due to incorrect drilling. Hiring a reputable and experienced PCB manufacturer can help avoid both of these issues.

　 　2. Insufficient Copper to Edge Clearance

　　Copper is a highly conductive metal that serves as the active component of a PCB. However, copper is also relatively soft and susceptible to corrosion. To prevent corrosion and protect the copper from interacting with the environment, the copper is covered with other materials. However, when trimming the PCB, if the copper is too close to the edge, this portion of the coating will also be trimmed, exposing the underlying copper layer. This can lead to numerous problems with the functionality of the board.

　　First, exposed copper planes may contact each other by simultaneously contacting conductive materials, leading to short circuits. This exposure also leaves the copper exposed to the environment, making it susceptible to corrosion. This exposure also increases the likelihood of someone touching the PCB and receiving an electric shock. Additionally, poorly insulated copper traces are more prone to plated through-hole voids.

　　This problem can be easily avoided by simply ensuring that the space between the copper edge and the board edge meets the acceptable standards for the type of board being manufactured. A thorough Design for Manufacturing (DFM) check performed by the manufacturer will typically catch any potential problems.

　　 3. Poor Solder Joints

　　Improper soldering during the printed circuit board assembly process can lead to serious problems. One common type of poor solder joint is insufficient heating of the solder by technicians, leading to cold solder joints, which in turn lead to PCB failures. Additionally, moisture during the soldering process can contaminate the PCB pads and other components. This contamination can cause PCB components to burn and create connection problems. Companies typically use visual or X-ray inspection to detect poor solder joints.

　　 4. Slivers

　　Slivers are narrow, wedge-shaped pieces of copper or solder mask that are created during the PCB manufacturing process and can cause serious problems during board manufacturing. These slivers are typically created during the etching process and can occur in one of two ways.

　　First, slivers can be created when very long, very thin pieces of copper or solder mask are etched away. In some cases, these slivers will break off before they are completely dissolved. These broken-off slivers can float in the chemical bath and have the potential to land on another board, creating unwanted connections.

　　Another way slivers are created is by cutting a section of the PCB design that is too narrow or too deep. Even if they were intended to be attached to the board, if the etched section is narrow enough or the etching is deep enough, material slivers may break off completely or partially, creating floating slivers or lifted slivers. Both of these situations can have serious negative impacts on the functionality of the board.

　　These slivers may connect to other copper traces or expose plated copper that is normally covered by the solder mask. The former can lead to short circuits, resulting in a defective board, while the latter can lead to the copper corroding over time. Both of these problems will shorten the lifespan of the board.

　　Slivers can be avoided by designing smaller cross-sections, reducing the chance of slivers being created. Manufacturers typically catch potential slivers through DFM checks.

　　 5. Missing Solder Mask Between Pads

　　The solder resist is a layer above the copper layers of a circuit board. Located above the copper, it isolates the copper traces, preventing accidental contact with other metals, solder, or conductive debris. It also acts as a barrier between the copper and the environment, preventing corrosion and protecting circuit board operators from electric shock. Pads are the exposed metal portions of the board where components are soldered.

　　In some circuit boards, solder resist may be partially or completely absent between pads. This exposes more copper than necessary and can lead to accidental bridging between pins during assembly. This can cause short circuits and reduced corrosion protection, both of which negatively impact the functionality and lifespan of the circuit board.

　　This defect is often caused by design oversight, such as undefined solder resist or transferring settings from a larger board to a smaller one, resulting in pad holes that are too large for the smaller PCB. Careful design review before sending the design to the manufacturer avoids this.

　　 6. Acid Traps

　　"Acid traps" is a common term for sharp angles in a circuit. They are so called because these sharp angles trap acid during the PCB etching process, causing the acid to pool in the corners. Functionally, this angle allows the acid to remain in the corner longer than the design calls for, resulting in more etching than intended. Consequently, the acid undermines connections, leading to circuit failure and more serious problems later.

　　Most designers are aware that sharp angles on circuit boards cause problems and have been trained to avoid them. However, mistakes do happen. PCB acid traps are often caused by simple human error, although some design software programs may also set circuits at sharp angles if improperly configured.

　　Most designers will spot sharp angles when carefully reviewing their work, but oversights are possible. If this is the case, a good manufacturer will catch these errors through a DFM check. Get pricing and lead times

　　 7. Poor Component Manufacturing

　　Another cause of PCB failure is the engineering team using poorly manufactured components. Physical damage to the PCB during PCB production due to the use of improper components during electronic assembly can damage the PCB and lead to power failures. Common PCB assembly defects and failures caused by poorly manufactured components include connection problems and loose parts.

　　In addition, residual flux used during soldering can remain on the PCB board, causing significant damage and potentially requiring board repair. Successful companies ensure they work with manufacturers who use high-quality components in their PCBs.

　　 8. Thermal Vias

　　Thermal vias are small traces around a pad used to connect the pad to the plane. These vias allow the pad to dissipate heat more effectively and are an important part of the soldering process. However, sometimes gaps between the thermal vias and the rest of the plane or between the vias and the pad can result in incomplete connections, reducing the efficiency of the heat transfer system these vias create. This can lead to some functional problems.

　　Poor thermal vias require longer times to transfer heat from the pad to the rest of the plane, which can cause problems during soldering or when the circuit is under thermal stress. Poor thermal vias may solder abnormally and require unusually long times to reflow, slowing down the assembly process. After manufacturing, boards with poor thermal vias may suffer from inadequate heat transfer and are more susceptible to overheating and thermal damage.

　　The root cause of overheating and thermal damage usually appears during manufacturing. These thermal connections are usually correctly tied to the plane layer in the Computer-Aided Design (CAD) system, but somehow the connection to the rest of the plane is reduced during manufacturing. Manufacturing issues during the thermal forming or processing can both cause this problem. To fix this, it is usually good practice to replace the thermal connections.

　　Experienced and highly-rated manufacturing companies can easily identify these faulty thermal vias and replace them before they cause problems for the circuit board.