Popcorning: a failure mechanism in plastic-encapsulated microcircuits

Popcorning is a failure mechanism in plastic-encapsulated microcircuits. It occurs when the inherently hygroscopic encapsulant is rapidly exposed to high temperatures during reflow solder assembly of the component to a printed circuit card. At these temperatures the moisture absorbed by the molding compound vaporizes and rapidly expands leading to the development of high stresses. When these stresses exceed both the interfacial adhesion strength and the fracture toughness of the molding compound, delamination and cracking result. Cracking is accompanied by a characteristic pop sound (and thus the name popcorning). Popcorning can: lead to a long-term reliability problem, since the cracks can be a path for ionic contaminants, causing corrosion-induced failures; and result in sheared or cratered ball bonds, causing electrical failures