Formation of self assembled monolayer (SAM) on metal surfaces for high performance anisotropically conductive adhesives

To improve the electrical property of the anisotropically conductive adhesive (ACA) joints, self-assembled monolayer (SAM) compounds are introduced into the interface between the metal filler and the substrate bond pad. The formation of the SAM on various metal surfaces and their thermal stability are investigated by measuring the contact angles of SAM compounds with a hydrophilic or hydrophobic tail groups such as octadecanethiol (ODT) and mercpatoacetic acid (MAA) on Au, Cu, Sn and SnPb surfaces. Goniometer testing and grazing FTIR spectra demonstrate that SAM molecules are readily adhered to metal surfaces. The concentration of SAM solutions, immersing time, thermal treatment temperature and time were varied as experimental parameters. From the current-voltage (I-V) measurement, it was found that the SAM treated ACA joints showed a lower resistance at the same applied current than nontreated joints.