Simultaneous Measurements of Electrical Resistivity and Raman Scattering from Conductive Die Attach Adhesives

Abstract

ABSTRACTThe development of electrical conductivity in silver (Ag)-filled conductive polymer adhesives is dependent on the thermal profile of the curing process. Previous studies of polymer adhesive systems have shown that chemical reactions at the interface of the micronsized Ag filler are a key factor in determining the subsequent performance of the conductive system. In an attempt to correlate the behavior of electrical conductivity with the chemical nature of the Ag particle interface, we have simultaneously performed electrical resistivity and surface enhanced Raman scattering (SERS) measurements on a commercial conductive adhesive. At room temperature in the low conductance state (∼10−9 ohms−1), the SERS spectrum from the uncured adhesive exhibited peaks that were identified with a molecular species bound to Ag surface via the carboxylate functionality of the adsorbate. During the thermal cure processing, the SERS data showed a partial decomposition of the carboxylate species and the formation of an amorphous carbon layer at the Ag surface. A comparison of the simultaneously recorded electrical resistance and SERS data showed a strong correlation between the development of high conductance (∼ 1 ohm−1) in the adhesive and the formation of the amorphous carbon layer.