Molding compounds for thin surface mount packages and large chipsemiconductor devices

摘要

It is noted that surface mounted devices have two majorrequirements: (1) resistance to the `popcorn' phenomenon during thesolder application process: and (2) minimization of stresses to the chipduring the thermal shock process. Generally, there is a tradeoffrelationship between these two properties. The range of importance ofthese two properties depends on the package types. Thicker surfacemounted devices such as the PLCC (plastic leaded chip carrier) showsvery little or no effect of the popcorn phenomenon. Cracks inpassivation glass easily occur during thermal shock cycling. On theother hand TSOP or VQFP packages crack easily when subjected to thesoldering process, while chip stresses are reduced during temperatureshock cycling when compared to thicker packages such as PQFP and PLCC.The authors present analytical and experimental results for these twophenomena and discuss required properties for molding compounds ordifferent types of surface mounted devices