Dynamic mechanical analysis of silver/glass die attach material

Abstract

Dynamic mechanical analysis (DMA) was employed to characterize the modulus behavior of a silver filled glass material. The method employed a simulated die attach process to understand the behavior of the storage modulus and the complex viscosity. Of specific interest are the various physical states of the silver glass material during the temperature excursions. Thermogravimetric analysis (TGA) and differential scanning carolimetry (DSC) were also employed to describe the transition stages of the material. A marked decrease in probe position during heating, which indicated the decrease in thickness of the silver glass paste, described the initiation of glass wetting the Ag flake and coalescing to form a glass-Ag composite. The analysis showed that the material remained in a low viscosity throughout this process. Solidification of the composite material occurred during the cooling cycle as the temperature went through the glass transition temperature, unlike thermoset polymers, in which gelation and curing occur during the heating process. The storage modulus of the solidified material was also verified by the three-point bending technique.the organic system comprises of a fugitive vehicle system made up of a resin, surfactant and solvent. The paste is dispensed into the package cavity, the die is placed on the paste during the die attach process, and the whole system is fired in air at an elevated temperature. The key events that occur during processing are depicted in Figure 1. The processing involves volatilizing the solvent and burning out the organic components. The glass melts and densification of the structure occurs during the firing. The successful adhesion of the die to substrate is when the glass wets the Ag flake and the interfaces before solidified into a glass-Ag composite. The elastic modulus of the solidified silver/glass ranges at 10" Pascals.Volatilization burnout I Heating . )