Textured growth of Cu/Sn intermetallic compounds

The growth of Cu-Sn intermetallic compounds (IMCs) at the molten Pb-Sn solder/Cu interface was studied over a range of temperatures and for a range of solder compositions. Strong peaks of (10 (1) over bar2) and (10 (1) over bar1) planes of q-phase (Cu6Sn5) were detected by x-ray diffraction when the Sn content was high. In the low Sn solder (27Sn-73Pb), the eta-phase peaks were absent at the two high temperatures, but the (2 12 0) peak of the epsilon-phase (Cu3Sn) was prominent. A texture was detected in both layers in (10h) and (002) pole figures constructed for the eta phase and epsilon phase, respectively. The growth directions were identified to be <101> and <102> for the eta phase and <102> and <031> for the epsilon phase, normal to the Cu surface. The growth direction does not change with the morphology and the thickness of the IMC layer. The morphology of the 9 layer varied gradually from a cellular film with a rugged interface to a dense film with a scalloped interface as the Pb content, temperature, and reaction time increased. The epsilon layerwas always dense and nearly planar.