Seiji Oka

Reliability of plastic ball grid array package

The reliability of plastic ball grid array (PBGA) package is studied for different materials. The reliability of the PBGA packages using conventional Bismaleimide-Triazine type PWB and our original product PWB that is made of high Tg epoxy resin is evaluated. The PBGA package using our original PWB has a feature of lower warpage for the package, and has similar performance regarding the thermal cycling stability and the endurance during reflow soldering as compared with the PBGA using the conventional PWB. The endurance during reflow soldering for each PBGA is JEDEC STD Method A112 level 3. In order to improve the endurance during reflow 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 endurance property during reflow soldering. The package crack mechanism during reflow soldering is briefly described as follows.

Newly improved polymer alloy systems for printed wiring boards

A novel laminating resin system using polymer alloy technologies was investigated to see if it could meet demands of high density printed wiring boards. An experimental study was carried out on thermoplastic and thermosetting polymer alloy systems. Two combinations of linear phenoxy resin and thermosetting epoxy resin were characterized to investigate the synergetic qualities of the resin systems. For one system better mechanical properties were achieved when the content of phenoxy resin was not above 30%. No phase separation was observed in this region. Results on the gel fraction and crosslinking density of the systems support the speculation that the linear chains of phenoxy resin are interpenetrated into the network chains of the epoxy resin. The other combination of heat-resistant epoxy resin and phenoxy resin required smaller amounts of phenoxy resin to achieve homogeneous structure. The adequate phenoxy resin content for achieving better mechanical properties was determined.<<ETX>>