Packaging and assembly

What is the phenomenon called in which, when a moisture-laden resin package is heated in solder reflow, the moisture inside suddenly vaporizes and expands, cracking the package?

  1. AWhisker
  2. BPopcorn effect
  3. CStiction
Show answer and explanation

Answer: B. Popcorn effect

Resin packages absorb moisture from the air during storage. If they are then exposed to high reflow temperatures, the moisture inside suddenly turns to steam and expands, causing resin delamination and cracks. Because the package cracks with a popping sound, it is called the popcorn effect; it is prevented by moisture-proof packing and baking before mounting.

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