Some subcontractors have been asked to build stacked packages where customers do not have a dipping process for PoP assembly or are not confident with the process. They have felt more comfortable with the prestacking process being undertaken first. Solderability testing of stacked packages that have already been through a prestacking process can be fairly simple to perform. The test may also be applied to single parts prior to stacking or parts due to be stacked. The test method is subjective but can prove very effective, and with care, the tested components do not necessarily need to be scrapped.
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