Since the printed circuit board is not a general end product, the definition of the name is a bit confusing. For example, the motherboard of a personal computer is called a motherboard, not a straight circuit board. While there is a circuit board on the motherboard, it's different, so you can't say the same thing when you rate the industry. For example, because the integrated circuit components are mounted on the circuit board, the news media refers to it as an IC test board, but in essence, it is not equivalent to a printed circuit board. We usually refer to a printed circuit board as a bare circuit board, that is, a circuit board without upper components. In the design of PCB circuit boards and the production process of circuit boards, engineers must not only prevent PCB circuit boards from being accidentally encountered during the manufacturing process, but also avoid design errors.
1. Short circuit of the circuit board: Due to this problem, one of the common faults in the work of the circuit board is directly caused. The biggest reason is that the short circuit of the PCB circuit board is caused by the incorrect design of the solder joints. At this point, the circular pad can be turned into an oval. shape to increase the distance between points to prevent short circuits. Improper design of the direction of the PCB proofing part will also cause the circuit board to be short-circuited and unable to work. If the feet of SOIC are parallel to the tin wave, it is easy to cause a short circuit accident. In this case, you can change the assembly direction perpendicular to the tin wave. The PCB circuit board may also be short-circuited, that is, automatic plug-in bending. Since the length of the welding wire specified by the industrial computer is less than 2mm, when the bending angle is too large, the part may drop, which is likely to cause a short circuit, and the offline requirement of the solder joint is greater than 2mm.
2. PCB solder joints become gold: The solder of the PCB circuit board is generally silver-gray, but occasionally gold solder joints appear. The main reason is that the temperature is too high, and it is only necessary to reduce the temperature of the tin furnace.
3. Black and granular contact on the circuit board: Black or small particle contact on the printed board is mainly caused by solder contamination and excess oxide in the tin, forming an overly fragile solder joint structure. Care must be taken not to confuse dark tin and low tin content due to the use of solder. Another reason for this problem is that the composition of the solder used in the manufacturing process has changed, with high levels of impurities, requiring the addition of pure tin or an alternative solder. Stained glass acts as a physical change in the fiber layers, such as separation between layers. However, this situation is not a bad solder joint. The reason is that the heating of the substrate is too high, and the preheating and welding temperature must be reduced, or the movement speed of the substrate must be increased.
4. Loose or misaligned PCB components: During the reflow process, small parts may float on the solder and eventually fall off the target solder joint. Possible causes of displacement or tilt include insufficient board support, remelting furnace settings, solder paste issues, human error, etc. resulting in vibration or springback of PCB soldered parts.
5. Open circuit board: An open circuit occurs when the trace is broken or the solder is only on the pad and not the component leads. In this case, there is no glue or connection between the components and the PCB board. Just like a short circuit, this can also happen in production or soldering and other operations. Shaking or stretching the board or other mechanical deformation factors can damage the board or solder joints. In addition, chemicals or moisture can cause wear on solder or metal parts, resulting in breakage of component conductors.
6. Soldering problems: The following are some of the problems caused by poor soldering: The solder joint is disturbed: the solder moves due to external interference before it solidifies. This is similar to cold solder joints, but for different reasons can be corrected by reheating, cooling the solder joint without outside interference. Cold Soldering: This occurs when the solder does not melt properly, resulting in a rough surface and an unreliable connection. Cold solder joints can also occur because too much solder prevents complete melting. The solution is to reheat the joint to remove the excess solder. Solder Bridging: This occurs when solder intersects and physically connects two leads together.
7. Bad PCB circuit boards are also affected by the environment: due to the structure of the PCB circuit board itself, it is easy to cause damage to the circuit board when it is in an unfavorable environment, extreme temperatures or temperature changes, other conditions such as high humidity, high-intensity vibration, etc. It is a factor that causes the performance of the circuit board to decline or even be scrapped. For example, changes in ambient temperature can cause circuit board deformation. This can break solder joints, bend the shape of the board, and can also cause the copper wires on the board to break. On the other hand, moisture in the air can cause oxidation, corrosion and rust on metal surfaces such as exposed copper traces, solder joints, pads and component leads. Dirt, debris or debris that accumulates on component and board surfaces also reduces air flow and component cooling, resulting in overheating and reduced performance of the PCB. The vibration, drop, impact or bending of the PCB can cause the PCB to deform and crack, while the high current or overvoltage can cause the PCB to be damaged or components, and the path can be rapidly aged.
8. Human error: Most defects in printed circuit board manufacturing are caused by human error. In most cases, faulty production processes, incorrect component placement and unprofessional manufacturing specifications lead to up to 64% avoidance. There is a defect in the product.
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