The reliability of plastic ball grid array package

Abstract

The reliability of plastic ball grid array (PBGA) packages is studied from the viewpoint of materials properties. The reliability of PBGA packages using conventional bismaleimide-triazine type PWB and the authors' original high T/sub g/ epoxy type PWB is evaluated. The PBGA package using the original high T/sub g/ epoxy type PWB has the feature of lower package warpage, and has similar performance in terms of thermal cycling stability and package crack resistance during reflow soldering as compared with the PBGA using the conventional PWB. The crack resistance during reflow soldering for each PBGA is JEDEC level 3. In order to improve crack resistance during reflow soldering, both PWB materials and other factors are investigated. As a result, the low moisture absorption molding compound and the high adhesion strength and fracture strength die attach material are effective for improved crack resistance during reflow soldering. Additionally, we report a new package crack mechanism in this study. The delamination firstly occurs in the gold-plated wire bonding area due to thermomechanical stress. Water vapor pressure accelerates the propagation of delamination or cracking. The delamination propagates in the inner and outer directions along weak adhesion strength interfaces or through low fracture strength materials. It becomes clear that the key properties of materials are moisture absorption, adhesion strength and fracture strength.