1. No dehumidification treatment was carried out before PBGA assembly and welding, resulting in PBGA damage during welding.
SMD packaging forms: non-airtight packaging, including plastic potting packaging, epoxy resin, silicone resin and other packaging (exposed to ambient air, moisture permeable polymer material). All plastic packages absorb moisture and are not completely sealed
When MSD when exposed to elevated reflow soldering temperature environment, due to the infiltration of MSD internal moisture to evaporate to produce enough pressure, make packaging plastic box from the chip or pin on layered and lead to connect chips damage and internal crack, in extreme cases, crack extends to the surface of MSD, even cause MSD ballooning and burst, known as "popcorn" phenomenon.
2. When welding lead-free components, such as PBGA, the "popcorn" phenomenon of MSD in production will become more frequent and serious due to the increase of welding temperature, and even lead to the production can not be normal.