Investigation of Bonding Mechanism for Cu-Powder Contained Solderable Epoxy-Solder Composites

Abstract

A novel Cu-powder contained solderable epoxy-solder composite (Cu-SESC) was introduced, and its interconnection mechanism was proposed as a means to improve the interconnection properties of the SESC joints. To identify the possibility and strengthening effect for the SESC joints by added Cu powder, two types of wetting tests using planar and line type metallization formed test boards, and a microhardness evaluation were performed. The Cu-SESC showed appropriate wetting and spreading properties. The Cu powders in the wetted low melting-point alloy (LMA) exhibited a uniform dispersion state, and a Cu–Sn intermetallic compound created on the surface of the Cu powders. The SESC that had Cu powders showed a superior microhardness value to that of the SESC without Cu powders because of the strengthening effect from the added Cu powder. Additionally, the selective conduction joint establishment properties obtained through the flowage, integration, and selective wetting behaviors of the fused LMA were not interrupted by the incorporated Cu powders.

Fig. 5 Selective wetting morphology of fused fillers in Cu-SESCs. (a) Initial condition and that after reflow process and (b) cross-sectional inspection result.