The main cause of solder cracks
The solder cracks of MLCC will not only occur in the manufacturing process such as the soldering process, but also will occur under severe use conditions after being launched on the market. The main reasons are as follows.
(1) Thermal shock and temperature cycling cause thermal fatigue
In an environment with repeated temperature changes of high and low temperatures, thermal stress is applied to the solder joints due to the difference in thermal expansion coefficient between MLCC and PCB. In addition, in the welding process, this situation can also occur due to imperfect temperature management.
(2) Lead-free solder
The lead-free solder used for environmental protection purposes is hard and fragile. Compared with the conventional eutectic solder, solder cracks are more likely to occur, so special attention is required.
Applications and substrates that require special attention in solder crack countermeasures
The main causes of solder cracks are thermal shock, thermal fatigue caused by temperature cycling, and the use of hard and brittle lead-free solder.
Therefore, special attention should be paid to the packaging around high-temperature heat-generating parts such as automobile engine compartments in environments where rapid heating (rapid) or rapid cooling (rapid cooling) may occur, such as rapid changes in peripheral temperature (thermal shock).
In addition, products installed in environments where the temperature changes repeatedly, such as outdoors, such as solar power generation, wind power generation, base stations, and other infrastructures, require attention to countermeasures against solder cracks due to their long maintenance cycles.
Summary of MLCC solder crack countermeasures
When stress is applied to the junction between the capacitor and the substrate, "solder cracks" may occur, which may cause components to fall off and open circuit failures.
Equipment exposed to thermal shocks and temperature cycles such as automobile engine compartments or equipment with other heat sources; implementation of maintenance-free infrastructure; hard and brittle lead-free solder joints require special attention.