Formation and evolution of intermetallic compounds between the In-3Ag solder and Cu substrate during soldering

The formation and growth of intermetallic compounds (IMCs) have an important effect on the reliability of the solder. In this paper, formation and evolution of IMCs between the In-3Ag solder and Cu substrate were systematically explored for different soldering time ranged from 1 to 30 min. The interface soldered for 1 or 2 min was only composed of (Ag,Cu)In-2 IMCs. When the soldering time extended to 4 min, a new (Cu,Ag)(11)In-9 IMCs layer appeared under the (Ag,Cu)In-2 IMCs layer. When the soldering time exceeded 5 min, the (Ag,Cu)In-2 layer was completely decomposed and replaced by the (Cu,Ag)(11)In-9 layer. Meanwhile, the growth of (Ag,Cu)In-2 and (Cu,Ag)(11)In-9 intermetallic layers during jointing were all diffusion-controlled and the growth rates of them are 0.398 and 0.507 A mu m(2)/s, respectively. Furthermore, shear strength results showed that the shear strength of solder joints decreased with soldering time extending, and those decrease from 5.64 MPa after soldered for 1 min to 3.07 MPa when the soldering time extended to 30 min. The fracture mode also changed from typical ductile fracture mode to mixed ductile-brittle fracture mode with soldering time extending.