“In the process of reinforcement frame and PCBA installation, PCBA and chassis installation, direct or forced installation of warped PCBA or warped reinforcement frame and PCBA installation in deformed chassis. Mounting stress causes damage and breakage of component leads (especially high-density ICs such as BGS, surface mount components), relay holes of multilayer PCBs, and inner layer connecting wires and pads of multilayer PCBs.

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In the process of reinforcement frame and PCBA installation, PCBA and chassis installation, direct or forced installation of warped PCBA or warped reinforcement frame and PCBA installation in deformed chassis. Mounting stress causes damage and breakage of component leads (especially high-density ICs such as BGS, surface mount components), relay holes of multilayer PCBs, and inner layer connecting wires and pads of multilayer PCBs.

For the PCBA or reinforcement frame whose warpage does not meet the requirements, the designer should cooperate with the craftsman to take or design effective “pad” measures at the bow (twist) part before installation.

Among chip RC components, ceramic chip capacitors have the highest probability of defects, mainly including the following:

1. PCBA bow deformation caused by wire harness installation stress.

2. The flatness of PCBA after soldering is greater than 0.75%.

3. The design of the pads at both ends of the ceramic chip capacitor is asymmetrical.

4. For the common pad, the soldering time is greater than 2s, the soldering temperature is higher than 245℃, and the total number of soldering exceeds the specified value 6 times.

5. The thermal expansion coefficient between ceramic chip capacitors and PCB materials is different.

6. During PCB design, the fixing hole is too close to the ceramic chip capacitor, resulting in stress during fastening.

7. Even if the pad size of ceramic chip capacitors on the PCB is the same, if the amount of solder is too much, the tensile stress on the chip capacitor will be increased when the PCB is bent; the correct amount of solder should be the height of the chip capacitor solder terminals 1/2～2/3 of

solution:

Strengthen the screening of ceramic chip capacitors, and use C-type scanning acoustic microscope (C-SAM) and scanning laser acoustic microscope (SLAM) to screen ceramic chip capacitors to screen out defective ceramic capacitors.