TEM observation of interfaces in a solder joint in a semiconductor device

Author:

Matsuki, Hirohisa   Ibuka, Hiroshi   Saka, Hiroyasu   

Journal:

Science and Technology of Advanced Materials

Issue Date:

2002

Abstract(summary):

The microstructure of a joint between a Pb-Sn eutectic solder and electroless Ni-8 mass% P has been examined using transmission electron microscopy. Four layers, i.e. Ni 3Sn 4, Ni 48 Sn 52, Ni 2SnP and Ni-20 mass% P, are formed between the solder and the electroless Ni-8 mass% P. Among them, Ni 48Sn 52 and Ni 2SnP were found for the first time in a solder joint. Spherical voids are formed at the interface between Ni 48Sn 52 and Ni 2SnP, and columnar voids are formed at the interface between Ni 2SnP and Ni-20 mass% P. From the analysis of the migration of the respective interfaces observed during in situ heating experiments, it is concluded that these voids are Kirkendall voids formed due to the difference in diffusivity of Ni across the interfaces. Fracture takes place at either of those interfaces during a dropping test