The Effect of Reduction Capability of Resin Material on the Solder Wettability for Electrically Conductive Adhesives (ECAs) Assembly

Abstract

Electrically conductive adhesives (ECAs) have been developed as an alternative to traditional Sn-Pb solders for electronic and optoelectronic applications. However, there are critical limitations such as the low conductivity, and unstable contact resistance. These limitations have seriously hindered the broad applications of ECAs. In order to overcome these limitations, a new formulation using Pb-free conducting filler particles was proposed. Our previous study proved that the metallurgical interconnections among conducting filler particles and between particles and the conducting pads were established by process control. In particular, it was found that the wetting behavior of conducting fillers in ECAs is one of the main mechanisms for the establishment of conduction paths. In this study, we propose the fundamental concept of an assembly process using fusible Pb-free conducting filler particles. Also, the effect of the reduction capability of base resin material on the solder wetting property was investigated. As candidates for ECA compositions, two types of resin materials and two lead-free solders were investigated. The reflow temperature profiles for each ECA formulation were determined using a differential scanning calorimeter (DSC) dynamic scan. The wettabilities of the lead-free solders were investigated using an optical microscope with a CCD camera and a microfocus Xray television system. It was found that the developed resin material with an intrinsic reduction capability shows good wettabilities in both leadfree candidates.

Characteristics of Isotropically Conductive Adhesive (ICA) Filled with Carbon Nanotubes (CNTs) and Low-Melting-Point Alloy Fillers

“…Otherwise, the flow-coalescence-wetting behavior of LMPA fillers in the ICA during the adhesive bonding process is hindered by excessive curing of the ICA. 11,12) As shown in the results, the polymer matrix does not excessively. In addition, the polymer matrix was maintained at a sufficiently low viscosity for the molten LMPA fillers to flow, coalesce with each other, and wet the upper and lower electrodes.…”

Novel interconnection method using electrically conductive paste with fusible filler

“…After the upper test board was mounted and the assembly was reflowed, the fillers almost coalesced and wet on the copper patterns. In our previous work, 13 we demonstrated that one of the obstacles to this coalescence and wetting process was the oxide-film present on the surfaces of both the copper wiring and the fillers. As for the ECA formulation without reduction capability, the Sn-In solder alloy did not wet and the wetting angle on the copper surface was about 156.8°.…”

Self-Organized Interconnection Process Using Solderable ACA (Anisotropic Conductive Adhesive)

“…Previous studies [10][11][12] have shown that using fluxing capability to remove oxides of both LMPA fillers and conduction pads helps to promote wetting characteristics. The polymer should not be cured too much before it reaches the melting point of the LMPA filler in order to achieve a good electrical conduction path.…”