Peel Adhesion and Reworkability of Anisotropic Conductive Adhesive for Flex-to-Flex Assembly in Medical Devices

Reworkable anisotropic conductive adhesive film (ACA/ACF) is of interest when the material is used for the assembly of electronic modules with high value, such as in medical devices. This paper deals with the assembly of flexible printed circuits (flex-to-flex) using reworkable adhesive formulations comprising a blend of a thermosetting epoxy and a thermoplastic polysulfone (PSU). Effect of two silane adhesion promoters on the adhesion of epoxy-PSU based ACA to flexible substrates was evaluated. A commercially available ACF, specified as reworkable, was used as a reference. Peel-off adhesion strength and reworkability were the main focus in the characterization. Results from the work show that the peel-off strength of the epoxy-PSU based ACA is not as high as that obtained for the commercial ACF. The rework evaluation, however, show feasible reworkability for the epoxy-PSU based ACA whereas it was not possible for rework of the commercial ACF. The trade-off between adhesion strength and reworkability is realized as an important factor for the selection of proper reworkable ACA/ACF for flex-to-flex assembly.