Moisture-Sensitive Components

The topic of moisture-sensitive components is rather boring but very important -- and frequently misunderstood. Increased moisture-sensitive component use, such as thin fine-pitch devices and ball grid arrays (BGA), has increased concern for this failure mechanism. When components are exposed to the elevated temperatures that occur during reflow soldering, moisture trapped inside plastic surface mount devices (SMD) produces enough vapor pressure to damage or destroy the device. Common failure modes include internal separation (delamination) of the plastic from the die or lead-frame; wire bond damage; die damage; and internal cracks that do not extend to the component surface. In extreme cases, cracks will extend to the component surface; in the most severe cases, the component will bulge and pop (referred to as the "popcorn" effect)....