Thermal shock effect of SMT capacitor

Chip capacitor is also called multilayer ceramic capacitor, the main body is mostly composed of ceramic, and ceramic characteristics are more fragile. Therefore, when the chip capacitor is subjected to temperature shock, it is easy to crack from the welding end. At this point, the small size capacitor is relatively better than the large size capacitor, mainly because the thermal conductivity of the large size patch capacitor does not reach the whole capacitor so quickly, so the temperature difference of the different points of the whole patch capacitor is large, so the expansion size is different, resulting in internal stress, resulting in cracks in the patch capacitor. This is the same reason that a thick glass is more likely to crack than a thin one when poured into boiling water.

In addition, during the cooling process after MLCC welding, external stress will be generated due to the difference in expansion coefficient between SMT capacitor and PCB, resulting in cracks in SMT capacitor. To avoid this problem, reflow soldering requires a good welding temperature curve. If wave soldering is used instead of reflow soldering, the failure rate of the SMD capacitor will be greatly increased.

In the chip capacitor welding process is to avoid using soldering iron manual welding process. However, things are not always so ideal. Hand soldering is sometimes unavoidable. For example, for electronic manufacturers of PCB outward processing, some of the products are very few, the chip manufacturers are not willing to accept this single, only manual welding; When the sample production, is also generally manual welding; Under special circumstances, rework or repair welding, must be manual welding; When repairmen repair capacitors, they also weld them by hand. It is inevitable that manual welding of MLCC should be attached great importance to the welding process.

We know whatever electronic components, as long as after electricity use will generate heat, especially in the large current in the circuit, SMD capacitors, SMD resistor production quantity of heat is very big, in the design, the size of the patch capacitance can also according to the withstand voltage, current and power lead to send out quantity of heat to consider heat dissipation rate, so the current and power, the greater the patch capacitor, the greater the surface area is also.