Pressure-less Ag-Sinter: Necking, Pores Structure and Its Properties

Abstract

Pressure-less Ag-sinter die-attach structure revealed good-networked silver interconnects along with discontinuous shrinkage porosities. A thin sheet test sample is processed to be evaluated with commercially available test equipment. In this study, test samples are stencil printed to a thickness from 70 to 100 µm and sintered at 200/250°C for 30/60 minutes. A test sample to a thickness of 13mm is processed by stacking a few layers of printed Ag-sinter and sintered at 200°C for 1h. Interestingly, good necking is observed in between the silver powder particles and measured properties for three different porosity levels of pressure-less Ag-sinter are as follows: • Discontinuous porosities of structure are about 15 to 20%, 25 to 35% and 45 to 55% depending on the paste chemistry and formulation (with or without binder) *Density of these pores structure is fro 4.5 to 7.7 g/cc • Electrical sheet resistivity is from 3.7 to 9.2 µΩ.cm • Thermal conductivity is from 80 to 190 W/m°K • Elastic modulus (ultrasonic testing method) is from 7.2 to 38 GPa 1. Lower the porostiy, hight the thermal conductivity and elastic modulus • Coefficient of thermal expansion (CTE) is about 19.2 to 21.5ppm • Specific heat capacity (Cp) is about 0.24-0.25 J/Kg°K *Both CTE and Cp properties of Ag-sinter are not influenced by porosity in the structure