Analysis and Solution of Defects in Ceramic Chip Capacitors

With the progress, development, and improvement of living standards of the times, intelligent electronic products are gradually appearing in society. Ceramic capacitors are made by using porcelain as the dielectric, coating silver layers on both sides of the ceramic substrate, and then using low-temperature fired silver films as electrode plates. Its appearance is mostly sheet-like, and there are also tubular, circular, and other shapes. Ceramic capacitors are usually circular blue in color. With the development of science and technology, the demand for ceramic capacitors in the electronic market is increasing day by day. Let's take a look at the root causes and solutions of the shortcomings of ceramic capacitors.

During the installation of reinforced frames and PCBA, as well as during the installation of PCBA with the chassis, the expansion and contraction PCBA is directly or forcibly installed or warped in the deformed chassis. Installation stress leads to damage and rupture of component wires (especially high-density ICs such as BGS, surface mount components), double layer PCB relay holes, and inner layer connecting wires and solder layers of the double layer PCB.

For PCBA or reinforced frames with warpage that does not meet the conditions, the designer should cooperate with the craftsman to take or design efficient "cushion" measures at the bow (torsion) position before construction.

The probability of defects in ceramic capacitors is the highest, mainly including the following:

1. The installation stress of the wire bundle causes the installation stress of the wire bundle to bend and deform PCBA.

2. The flatness of PCBA after welding exceeds 0.75%.

3. The welding layer design on both sides of the ceramic capacitor is different.

4. The welding time of the public welding layer exceeds 2 seconds, the welding temperature is too high at 245 ℃, and the overall welding frequency exceeds the standard value 6 times.

5. The coefficient of thermal expansion of ceramic chip capacitors and PCB materials are different.

6. During the PCB design process, the distance between the fixing hole and the ceramic capacitor is too close, which can cause stress when tightened.

7. Even if the specifications of the PCB solder layer are the same for porcelain chip capacitors, if the solder amount is too large, it will increase the tensile stress of the chip capacitor when the PCB is bent; The correct amount of solder should be 1/2 to 2/3 of the soldering end of extremely high chip capacitors

Solution: Strengthen the selection of ceramic chip capacitors, and use ceramic chip capacitors. C-SAM scanning laser acoustic microscope (SLAM) can select defective ceramic capacitors for classification.

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