Development of low contact resistance interconnection for display applications

This paper focuses on development of a low contact resistance interconnection for low temperature bonding applications. Alternative to conventional display interconnection mechanisms using anisotropic conductive film (ACF), solder and underfill method using low melting point Bi58-Sn solder is suggested. Solder bumping is carried out using a maskless Solder-on-Pad technology. An average bump height of 16.4μm with 80μm bump pitch is achieved by optimizing the solder paste material called Solder-Bump-Maker. The test vehicle with bumps is flip chip bonded with a top die using Fluxing underfill. In order to analyze the quality of the bonded interconnection, contact resistance was measured using the 4-point probe method, and a moisture absorption test was conducted in a 85°C/85% relative humidity condition for 100 hours. The contact resistance values before and after the reliability test show no significant difference, which demonstrates that the suggested interconnection is a robust joint with increased electrical performance.