Popcorning happens when moisture absorbed by a plastic component package vaporises during reflow and the pressure delaminates or cracks the package, sometimes with an audible pop. The damage may be internal and only show later as an intermittent failure. Moisture-sensitive parts carry an MSL rating that sets how long they may sit out of their dry pack, the floor life, before they must be baked.
Those QFNs sat out of the dry pack for three weeks, they'll popcorn in reflow, bake them first.
Also heard as
- popcorn effect
- popcorn cracking
Related terms
Bake
To heat bare boards or moisture-sensitive parts in an oven to drive out absorbed water before soldering.
Delamination
Separation between layers of a board's laminate or between laminate and copper, usually from heat or moisture.
Reflow
Soldering surface mount parts by melting printed solder paste in an oven that follows a set temperature profile.