| Solder bump interconnection of integrated circuits using flip chip technology has been practiced for over 30 years. Flip chip is currently being pursued because it is extendible to meet the requirements of future high performance chips. In contrast, other assembly methods are not. This technology has some very attractive advantages. Flip chip connections are arranged over the entire area of the die, consequently the I/O can be arranged over the entire area of the substrate, which creates much higher densities and new design possibilities.; Currently flip chip is not being widely utilized, primarily because the infrastructure is not yet in place, and availability of die with flip-chip bumps is not always accessible. Another dilemma is inspection of the assembled joints. Flux removal is difficult, and there is a need for underfill to maintain package reliability.; Cost considerations just add to the problem. In particular, the cost of the substrate is an important factor. One of the key substrate items is the surface finish. Some offer more resistance to heat stress, while some offer high resistance to moisture.; It is important to determine the feasibility of OSP's (Organic Surface Protectants) as antioxidant protectant or surface finish. The use of alternative surface finishes has over the past several years received a great deal of attention as a replacement for conventional Ni/Au. Organic Surface Protectants, OSP's, provide flat, planar pads, and deliver sufficient protection to pad surfaces at a significantly reduced cost. |
