Enhancing moisture resistance of PBGA

One of the main package reliability limitations of PBGA is its moisture sensitivity performance, i.e. popcorn failure. The objective of this work is to enhance the moisture resistance of a 35/spl times/35 mm overmolded PBGA by matching its material combination. The approach taken is to correlate the package moisture sensitivity performance with the packaging material properties. JEDEC level 2 moisture sensitivity performance was achieved with two different combinations of materials. The best combination was close to achieving level 1 performance, thereby reinforcing the importance of material matching. Mold compound moisture absorption property has the strongest correlation with package moisture performance. A low value is favourable. For die attach material, the hot and wet adhesion shear strength showed the strongest correlation with package moisture performance. High adhesion shear strength is preferred. Unlike mold compound, the moisture absorption property of die attach material has a significantly weaker correlation.