Thermo-Mechanical Stability of Resin-Added Sintered Silver Joints Between Si Die and Ni-/Au-Electroplated Substrate

Abstract

Resin-added sintered silver is widely used in high-power electronic devices as a chip attaching material with low elastic modulus and superior thermal performance. The thermo-mechanical stability of joints, which join in resin-added sintered silver on nickel-/gold-electroplated substrate at 200 °C and 250 °C aging, is studied. At 200 °C aging, coarsening silver squeezes the resin into bonding interfaces, leading to a smooth fracture of the joint. The mechanical strength of the joint decreases with the increase in smooth fracture area proportion (SFP). The junction case thermal resistance of the sample increases from 0.97 to 1.12 K/W after 200 °C 500-h aging. At 250 °C aging, excessive silver–gold diffusion depletes the sintered silver and forms silver–gold solid solutions at the bonding interfaces. The mechanical strength of the joint sharply decreases with the increase in SFP. Fick’s second law is used to explain the formation of the solid solution. The diffusion coefficient and dimensionless parameter <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> of gold at 24, 72, and 150 h under 250 °C aging are calculated.