An investigation of conductive polymer flip chip attachment in multichip module applications

Conventional flip chip solder bump technology is being confronted by the need to remove lead content and eliminate CFC containing solvents by the year 2000, as mandated by the Montreal Protocol. In addition, this process can be expensive, involves complex manufacturing sequences, and is susceptible to failure due to fatigue. Electrically conductive polymers have the potential for solder replacement in chip-to-substrate level interconnection. The scope of the project involves selection, evaluation, and comparison of candidate materials for low cost multichip module(MCM) applications. This paper discusses the design, processing, and assembly of an MCM test vehicle, developed at the University of Arkansas, which can incorporate various flip chip interconnection materials. An evaluation of two commercially-available, silver-based epoxies is being performed. The test vehicle is used to investigate possible reliability problems, as well as for comparison of the various interconnection materials. Interconnect failure identification is accomplished through continuously monitoring daisy chains which provide paths from substrate to chip. Environmental stresses can be effectively used to accelerate failure mechanisms and prove device reliability under real operating conditions. Mechanical tests including die pull-off and die shear can be performed to determine bond strength. This paper describes testing procedures used, in conjunction with the developed test vehicle, to compare and evaluate interconnection material performance and reliability. Preliminary testing results are also presented