The reliability of plastic ball grid array package

The reliability of Plastic Ball Grid Array(PBGA) package is studied from the point of the properties of materials. The reliability of the PBGA packages using conventional Bismaleimide-Triazine type PWB and our original high Tg epoxy type PWB is evaluated. The PBGA package using the original high Tg epoxy type PWB has a feature of lower warpage for the package, and has similar performance about the thermal cycling stability and the resistance during reflow soldering as compared with the PBGA using the conventional PWB. The resistance during reflow soldering for each PBGA is JEDEC level 3. In order to improve the resistance during renew soldering, not only PWB materials but also other factors are investigated. As a result, the molding compound with the property of low moisture absorption and the die attach material with the properties of high adhesion strength and fracture strength are effective to improve the resistance during reflow soldering. Additionally we report a new mechanism of package crack in this study. The delamination firstly occurs in gold-plated area for wire bonding by thermomechanical stress. And the water vapor pressure accelerates the propagation of delamination or a crack. The delamination propagates in the inner and outer directions along the interfaces of week adhesion strength or through materials of low fracture strength. It becomes clear that the key properties of materials are moisture absorption, adhesion strength and fracture strength.