PCBA is a system composed of PCB and various electronic components. The main material of PCB is a composite material of glass fiber and epoxy resin, which is divided into single-sided, double-sided and multi-layered boards. There are many types of boards, but no matter which type of board, if it is stored or used improperly, it is easy to have some failures, and we can't find the cause of some failures at once, but judge by observing some external characteristics . The following Sanjing will take you to understand the fault characteristics of PCBA:

1. Mechanical damage. If the PCBA board is subjected to stress such as bending or twisting, it may damage the components. For SMD components, it may cause cracks or damage to the solder joints of some components. On PCBs with through-holes, the component package may crack or cause the component pins to fall off the main body.

2. Thermal damage. If the voltage applied to the circuit board is too high to cause a larger current, the circuit or component with less power consumption is likely to cause over-electrical damage (EOS). If the damage is caused by the external heat source of the equipment, the component failure causes thermal damage, and the long-term high temperature will cause the epoxy resin to carbonize and turn black.

3. The thermal expansion coefficient does not match. When materials with different thermal expansion coefficients are physically connected together, their size will change with temperature, especially when the temperature changes drastically, it will cause mechanical failure.

Fourth, the interconnection of PCB components. The interconnection mostly occurs on the solder joints, the interface between the multilayer boards and the bonding pads. The pores between several layers and the through holes and the cracks in the circuit cause the connection to fail. Contaminants in the solder can also easily cause weak solder joints and may also cause solder joint cracks. In addition, thermal stress, mechanical stress, and process issues can all cause interconnect failures. If the volatile organic compound VOC is heated and expanded, it will also cause pores or cracks, which may cause connection failure.

5. Pollution. The flux is not cleaned, leaving fingerprints, dust or cleaning fluid during handling; residual metal fragments or solder bridging during assembly, and encountering contaminated atmosphere during storage, equipment installation or operation. Pollutants in the environment will corrode the copper circuit, resulting in a decrease in insulation. The longer the pollution time, it may also cause metal migration phenomena, such as whisker growth and dendrite growth.

The above is about the characteristics of PCBA faults, I hope it can be helpful to everyone!