Hello, my name is Bob Willis. Welcome to Defect of the Month. Each month we try to provide examples of specific flaws and hopefully some solutions. I have created over 100 different defect videos over the years. Hopefully one will solve one of your production problems.
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Surface mount popcorn has been around for years now. I remember very early in my career at GEC when I introduced his SMT with a few small parts. As moisture builds up inside a plastic part, it can expand as a gas and try to escape. So cracks are often seen in the package around the edges of the plastic molding to his PCB interface of the plastic ball grid array (PBGA).
When using some BGA packages, cracks can occur in the top of the plastic package or the bottom of the plastic, and either of these situations can lead to intermittent or complete failure of the part. When reworking or repairing packages on a board, especially expensive boards containing expensive components, it is recommended to bakeout the board assembly before removing components. This is also true when performing failure analysis of specific parts. If you just take it off and throw it away, it doesn’t really matter. We also have to remember about adjacent components. This is because very high temperatures can actually occur during rework or repair.