The reason for the bulge is often because the chip is damp
Our optical module is a moisture sensitive device, which is not stored according to the requirements, resulting in moisture. When SMT is passed, the instant high temperature will cause the water to vaporize, and the internal layer of the chip will appear, so that the bonding wire will be broken and the chip will fail. Laser packaging, there are airtight and non-airtight, according to different applications, semiconductor chip packaging is also divided into airtight and non-airtight, but we often see the black chip, non-airtight.