Special Properties of Molding Compounds for Small-Outline Packaged Devices

Wave soldering techniques currently used in the surface mounting of plastic leaded chip carrier (PLCC) and small-outline integrated circuit (SOIC) devices may be contributing to significantly reduced moisture resistance performance levels after components are assembled on printed circuit boards. Research indicates that delamination of the plastic package from the silicon chip surface is associated with violent moisture evaporation that occurs during sudden immersion of the device package into molten solder. Experimental data to support this conclusion are presented, and an advancement in molding compound technology is introduced that greatly reduces the occurrence of the phenomenon.