Effect of copper-tin intermetallic compound on reliability of fine bump joint structures

Mechanical and electrical reliability of fine bumps with diameter and height of tens of μm was studied considering the growth of the intermetallic compound (IMC) at the interface between a bump and a copper thin-film interconnection. It was found that the increase of the thickness of the IMC change the stress and strain field around the interface significantly, and thus, the fracture mode from the fatigue crack of solder to fatigue crack of the copper interconnection or delamination between the IMC and the copper interconnection. This is because that the mechanical properties of the grown IMC differ from those of copper and tin and that a large amount of Kirkendall voids appeared around the interface. In addition, the resistance of the bumps increased drastically with the increment of the thickness of the IMC layer because of the growth of Kirkendall voids. Therefore, it is very important to minimize the growth of the IMC to assure the reliability of the bump joint structures. ©2009 The Society of Materials Science.