| The effect of heat treatment on the residual stress, the sheet resistance, and the solderability of SnPb/Cu and SnPb/Ni/Cu system were studied. The sheet resistance in the Sn80-Pb20/Cu system increased steeply aged at 170℃. The residual stress and the texture of the SnPb layer were the prime factors to affect the sheet resistance change. Higher the heating temperature, thicker the SnPb layer, and higher the Sn content, the residual stress increased faster and changed more. The variation of residual stress was directly related to the intermetallic compound formation. Degradation of the solderabilities in SnPb/Cu system during the aging was affected by the intermetallic compound thickness, the residual stress changes, and the composition changes of the SnPb layer. In the SnPb/Ni/Cu system, the sheet resistances and the solderabilities did not change much in contrast to the SnPb/Cu system. The relative stability of the electrical and the solderability property of SnPb/Ni/Cu system might be due mainly to the coarse plate-like χ phase formation in the SnPb/Ni interface. |
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