Characterizing the formation and growth of intermetallic compound in the solder joint

A solder/intermetallic layers/copper joint assembly was prepared by the dip ping process and then aged thermally for an accelerating aging test. The ph ase transformation of the assembly was compared to the phase diagram of bin ary alloy, Cu-Sn, and it showed an agreement with the resultant intermetall ic phases formed between the pure tin and pure copper. Two theoretical mode ls proposed by Gosele and Shatynski were developed and then employed to cha racterize the assembly. The Gosele's model was used to predict whether the intermetallic layers grew or shrank during aging, while the Shatynski's mod el was employed to estimate the related reactive thicknesses and hence the ratios of the interdiffusivities in the joint assembly. After a series of c alculations, the Gosele's model predicted that Cu6Sn5 and Cu3Sn intermetall ic layers became thicker; the orders of the intermetallic interdiffusivitie s were also proven to approach theoretical values from the Shatynski's mode l. (C) 1998 Kluwer Academic Publishers.