Reliability of flip chip die attach in multichip mechatronic power module

Motorola's Interconnect Systems Laboratory in Munich has developed the assembly technology for a mechatronic multichip power module, a new intelligent connector for automotive applications. Product's requirements for simultaneous high power dissipation, current carrying and device interconnecting capability lead to selection of insulated metal substrate (IMS) as a substrate technology and electroplated eutectic solder bump as an interconnection technology. To develop robust processes capable of meeting high reliability in the automotive product environment, fundamental knowledge was needed about the behavior of the materials and interfaces in a flip chip assembly. This paper presents results of the parametric analysis of flip chip attach on IMS substrate. Impact of main variables, including die size, substrate thickness, underfill material, soldermask material and die passivation on the stress distribution and reliability in IMS assemblies was studied. The detailed stress analyses, materials compatibility and interface studies has resulted in a high level of process control and an excellent reliability performance.