A simple test chip to assess chip and package design in the case of plastic assembling

A simple large-area test chip with flat topography is used to investigate the thermomechanical sensitivity of a plastic package, namely, the extent of surface degradation after thermomechanical stress induced by temperature cycling. From the results obtained with a PLCC package one may conclude that the design of metal lines, adhesion of the molding compound to the chip surface, and type of molding compound are basic parameters for assessing the failure mechanism on the chip surface. Therefore, the thermomechanical stability of a plastic packaged chip can be represented as a function of these three parameters. In a second application the test chip is used to compare TSOP and SOJ packages under thermomechanical stress. We found for the TSOP an overall reduction in failures and-most important of all-an independence of the degradation of chip design and type of molding compound, provided there is sufficient adhesion between molding compound and chip