Shear of Sn-3.8Ag-0.7Cu solder balls on electrodeposited FeNi layer

The interfacial reaction between Sn-3.8Ag-0.7Cu solder and FeNi substrate was much slower, resulting in a thin FeSn 2 IMC layer at the interface. Interfacial bond between FeNi and Sn-3.8Ag-0.7Cu solder ball was examined by ball shear tests and the shear test results were compared to those on Cu and deposited Ni layers. Ball shear test showed that the Sn-Ag-Cu/FeNi-Cu interface had a comparable strength to that of Sn-Ag-Cu/Cu interface and the shear strength was relatively constant when reflow time increased from 2 minutes to over 15 minutes. The shear fracture occurred within the solder near the interface. Therefore, the electrodeposited FeNi layer may be used as a reliable under ball metallization (UBM).