PCBA failure characteristics
date：2021-08-19 16:51:51
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 board, double-sided board and multi-layer board.
PCBA Failure Characteristics
1. Mechanical damage
The components may be damaged due to stress such as bending and twisting. For SMD components, the solder joints of some components may be cracked or the components may be damaged. On PCBs with through holes, the package of the components may be cracked, or the pins may fall off the main body of the component.
2. Thermal damage
Excessive voltage applied to the circuit board causes excessive current. For smaller circuits or components, their power consumption capacity leads to electrical damage (EOS); damage caused by external heat sources of the device; thermal damage caused by component failure (The long-term high temperature causes the epoxy resin to become carbonized and black)
3. Pollution
Flux is not cleaned; fingerprints, dust or cleaning fluids are left during handling; metal fragments or solder bridges from assembly; contaminated atmosphere encountered during storage, equipment installation or operation; moisture or salt in the environment. Pollutants in the environment can cause corrosion of copper lines and reduce insulation. Pollutants can cause corrosion of copper circuits. After a long period of time, pollutants may cause metal migration. There are two forms: whisker growth and dendrite growth.
When identifying contaminants, the most commonly used microscope and SEM, EDX, or FTIR, SIMS, XPS and other technologies.
4. Thermal expansion mismatch
When materials with different thermal expansion coefficients are physically connected together, their size changes with temperature, especially when the temperature changes drastically, which can cause mechanical failure.
5. Component interconnection failure on PCB
Interconnection failures mostly occur on solder joints, the interface between 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 cause weak solder joints, which can cause solder joint cracks. Thermal stress, mechanical stress, and process problems can all cause interconnect failures. In addition, thermal expansion of volatile organic compounds (VOCs) can cause pores or cracks, which can cause connection failures.
Some circuits may need to be physically separated in order to be separated from the entire circuit system. This is to make individual circuit measurements more accurate. Complex components or circuit areas may need to be removed to investigate the fault location of interest. Check carefully under the microscope to confirm the actual source of leakage or contaminants, and use low-voltage techniques to measure to avoid damage to the device.
The above points are the characteristics of PCBA failure. Next time, FASTPCBA will analyze the PCB failure analysis steps for everyone.
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