Analyses of flip chip attach reliability

Computer based thermo-mechanical design and performance optimization are in widespread use. They are mainly based on finite element (FE-) analyses. Applications of the method in performing parametric studies on the thermomechanical behavior of different flip chip assemblies are given. Both die size and underfill material are varied. It is shown that for flip-chip on board (FCOB) assemblies the die size is no key reliability parameter. Fatigue failure limits are estimated for both not underfilled and underfilled assemblies with small dies. Underfill materials with different characteristics, ranging from stiff to soft, are treated. Polymer materials are of special importance for this packaging technology. The theoretical analysis of stresses within polymeric material compounds induced by environmental conditions, especially temperature changes, requires the characterization of material properties, especially for the underfill and solder mask materials. Measurement results on typical commercially available electronic polymers are reported, which have been investigated by DMA and TMA measurements as well as tensile tests. Isothermal relaxation tests were performed on tensile specimens to study the viscoelastic material behavior at different temperatures