Effects of Silver Dissolved in Eutectic Gold‐Silicon Solder on Silicon Devices

Abstract

In a die bond system using eutectic Au‐Si solder, stress in the die tends to increase when Au is replaced by Ag as a plating material on Cu alloy leadframes. The Ag dissolution into the solder is proved to be a major cause of fracture or thermal fatigue due to stress increase in bonded Si devices. The piezoresistance effect in a Si chip bonded to a Ag‐plated substrate is also shown to be larger. Thermal analysis indicates that the freezing point of the Au‐Si solder increases with the increase in the Ag content in the solder. Die bonding at a temperature below 380°C is also demonstrated to be effective in lowering the propensity of a die to fracture.

3D characterization of the eutectic Au–Si alloy by using a nuclear microprobe

“…Silicon alloyed with gold may form a eutectic alloy which can be used as a low melting point solder (Kato 1987). We have experimented with a new process of gold soldering involving two steps: (a) the formation of a microscopic gold-silicon eutectic alloy during silicon diffusion through polycrystalline gold foils along their Address for reprints: Guy Demonier L.A.R.N.…”

Au–Si eutectic alloy formation by Si implantation in polycrystalline Au

“…The foils were implanted with Si 2 ions using a 2 MV Tandetron Accelerator of LARN. The implanted area was around 0.04 cm 2 . The Au foils were kept tight in a frame made of brass and mounted on a target ladder which is connected to the current integrator.…”

“…At a temperature above the Au±Si eutectic temperature (363°C), the interaction between the Au ®lm and the Si substrate leads to the formation of an alloy rather than Au silicide. It has been established that silicon alloyed with gold may form an eutectic alloy which can be used as a low melting point solder for silicon devices [1,2]. High di usion rates of silicon in gold ®lm coatings on silicon crystals have been widely studied by various groups [3,4].…”