Thermo- and hydro-mechanical modeling of an adhesive flip chip joint

This work presents the results of experimental work combined with numerical analysis, to explore the characteristics of anisotropic conductive adhesive (ACA) interconnects. The experimental program involved the assembly of 5×5mm die with 80 electro-plated Au bumps at 200μm pitch, attached by anisotropic conductive paste (ACP) onto a glass substrate with indium tin oxide (ITO) as conductor lines. Subsequent temperature cycling (TC -40°C/125°C) and temperature-humidity test (TH 85°C/85%RH) were carried out to assess the stability of the joint contact resistance. A bump-force vs joint-resistance (F-R) model based on Power Law was established experimentally. Numerical study using finite element analysis (FEA) was developed to determine the Au bump contact force after assembly, TC and TH simulations. After which, employing the F-R model, the joint resistances were predicted and validated with the experimental test results. The comparison between process modeling and the experimental results gave good agreement, while the TH modeling results showed better correlation compared to TC modeling results.