Adhesion improvement of thermoplastic conductive adhesives under humid environment

Abstract

The adhesion properties of poly (arylene ether) (PAE2 , thermoplastic) based isotropic conductive adhesive (ICA) material were investigated. PAEZ based ICAs as well as epoxy- based ICAs (thermoset) showed a dramatic reduction in adhesion onto a NiAu surface during 85 C/85% RH aging tests. It was found that a NiAu surface is more hydrophilic than a SnPb surface, which allows easier introduction into the interface between polymer and metal pads, as such hydrogen bonds between polymer and metal pads could be disrupted. To improve the adhesion strength of the PAE2 on a Ni/Au surface during aging tests, coupling agents and epoxy blends have been incorporated into the PAEZ formulations. Additionally, a self-assembled mono-layer (SAM) molecule is introduced to the interface between the polymer and the metal bond pad to increase the adhesion of PAEZ based ICA during aging. The combined usage of epoxy blending and coupling agents is considerably effective at increasing the adhesion strength of PAEZ before aging. With these additives, 50% of the adhesion strength is maintained after 85 C/85% RH aging. By depositing a self-assembled monolayer molecule on the top of the NiAu substrate, the adhesion strength after aging of epoxy blending/couplmg agent incorporated PAEZ as well as the pure PAE2 after aging is significantly improved.