The thickness and material optimization of flexible electronic packaging for functional electronic textile

In this paper a three dimensional model of the electronic package has been developed using Finite element analysis (FEA) technology to evaluate the shear load, tensile, bending and thermal stresses. Simulations of a flexible flip chip electronic packaging method are performed to minimize stresses on the packaged electronic device. Three under-fill adhesives (Loctite 4860, Loctite 480 and Loctite 4902) and three substrates (Kapton, Mylar and PEEK) are compared and the optimal thickness of each is found by shear load, tensile load, bending test and thermal expansion simulations. A fixed die size of 3.5 mm x 8 mm x 0.53 mm has been simulated and evaluated experimentally under shear load. The shear experimental results show good agreement with the simulation results and verify the simulated optimal thickness of the adhesive layer. The Kapton substrate together with the Loctite 4902 adhesive was identified as the optimum in the simulation. The simulation of under-fill adhesive and substrate thickness identified an optimum configuration of a 0.045 to 0.052 mm thick substrate layer and a 0.042 to 0.045 mm thickness of the Loctite 4902 adhesive.