Package Failure
Internal delamination and cracking of plastic encapsulated microcircuits occur when trapped moisture expands rapidly during high-temperature reflow. Inside the SMT reflow oven, a popcorning defect occurs as accumulated moisture vaporization generates pressures exceeding the mechanical strength of the mold compound. This physical disruption can destroy the chip’s internal structure and sever critical wire bonds.
Moisture Behavior
Epoxies used in semiconductor packaging are naturally hygroscopic and absorb moisture from the surrounding air. When a component with high moisture content is subjected to reflow temperatures, this water vaporizes instantly and increases in volume. The expanding steam cannot escape through the dense plastic and creates high localized pressures that force the mold compound away from the die or lead frame.
This separation produces an audible popping sound, which gives the failure its common name, and leaves internal voids that can be detected through scanning acoustic microscopy.
Reflow Consequence
Internal damage from this failure is often invisible from the outside of the component, requiring advanced non-destructive test methods for detection. Left unchecked, the separation of the mold compound allows moisture and contaminants to enter the device, leading to corrosion and latent field failures. Assembly facilities prevent this issue by strictly managing the floor life and baking cycles of sensitive devices.
