Interfacial strength assessment of Cu-epoxy system by atomic force microscope

This paper presents a novel nano-scale interfacial covalent bond measurement method by atomic force microscopy (AFM) with reference to the adhesion of self-assembly monolayer on epoxy/copper systems. Covalent bond strength measurements were conducted using AFM for self assembly monolayer (SAM) coated copper (Cu) tips on epoxy after epoxy has been cured at its curing temperature. In-situ curing of Cu-epoxy force measurement simulates situation of epoxy molding compound (EMC) curing inside conventional transfer molding process. The Cu-SAM-epoxy system testing provides a good testing platform for evaluating the performance of various SAM materials as an adhesion promoter. Adhesion enhancement at the interface has been achieved by surface modification of Cu surface with thiol solution. Normalized adhesion strength was reported as measured adhesion force divided by tip epoxy contact area. It illustrated that with thiol treatment, Cu-epoxy interfacial adhesion strength has been enhanced from 2.83plusmn0.07times 10-5 nN/nm² and 5.38plusmn2.48times10-5 nN/nm²