Effect of Cu Cored Ball in Solder Ball on Microstructure and Strength of BGA Joint Using Electroless Plated Ni/Au Pad.
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概要
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Effect of Cu core in Sn-37Pb or Sn-36Pb-2Ag solder ball has been investigated on the shear strength and the microstructure of BGA joint with electroless Ni/Au plated pad joint after high temperature storage at 423K. For Sn-37Pb or Sn-36Pb-2Ag solder balls, stable Ni<SUB>3</SUB>Sn<SUB>4</SUB> reaction layer was formed at the joint after reflow soldering, and metastable (Au, Ni) Sn<SUB>3</SUB> reaction layer was formed on the interface between solder and Ni<SUB>3</SUB>Sn<SUB>4</SUB> after subsequent heat storage at 423K, while stable (Au, Cu, Ni) <SUB>6</SUB>Sn<SUB>5</SUB> reaction layer was formed for Cu cored solder ball. The growth rate was much slower for (Au, Cu, Ni) <SUB>6</SUB>Sn (η') reaction layer than that for (Au, Ni) -Sn reaction layer. The shear strength of BGA joint using Cu cored ball was higher than that using Sn-37Pb or Sn-36Pb-2Ag, because η' reaction layer plays a roll as a good barrier layer to suppress the Ni-Sn interaction.
- 社団法人 エレクトロニクス実装学会の論文