Development of fluxless bonding using deposited Gold-indium multi-layer composite for heterogeneous silicon micro-cooler stacking

Abstract

In this paper, Gold-indium fluxless eutectic bonding at short process time has been successfully developed for stacking multi-layers and heterogeneous structure of silicon micro-cooler. This paper introduces gold-indium eutectic bonding process which uses deposited thin and multilayer composites directly onto the silicon surfaces which to be bonded. The parameters DOE (design of experiment) study was carried out to develop thermal compression bonding process conditions as tabulated in Table 1. These eutectic bonds are examined using shear test, Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDX). This shear test results is compared with eutectic AuSn which is best known as hard solders, good fatigue-resistance and mechanical properties. Nearly void-free bonds are achieved and confirmed by cross-sectional SEM and X-ray scanning. A pre-clean process steps is required to ensure sufficient wetting and good adhesion for this fluxless process. Furthermore, a thermal cycling test and Scanning Acoustic Microscope (SAM) analysis will be carried out to evaluate the failure mode, reliability of solder joint and the bonded structure.