时效对无铅焊料Ni-P/Cu焊点的影响

研究了150℃等温时效为62Sn36Bp2Ag/Ni-P/Cu及共晶SnAg/Ni-P/Cu表面贴装焊点微结构及塑切强度的影响，结果表明，在钎料与Ni-P间的界面存在Ni3Sn4金属间化合物层，其厚度随时效时间增加，Ni-P层的厚度减小，时效后，SnPbAg,SnAg焊点的剪切强度下降，对于SnAg焊点，时效250h后其剪切强度剧烈下降，断裂发生在Ni-P/Cu界面上，在长时间时效后焊点一侧的Ni-P层中P的含量较主可能是Ni-P/Cu结合强度变差的主要原因，SnPbAg焊点保持着较高的剪切强度。

EFFECT OF AGING ON THE MICROSTRUCTURE AND SHEAR STRENGTH OF LEAD FREE/Ni-P/Cu SOLDER JOINTS

The effect of aging on the microstructure and shear strength of 62Sn36Pb2Ag/NiP/Cu and SnAg/Ni-P/Cu surface mount solder joints was investigated. Intermetallic (IMC) layer of Ni3Sn4 was found in the interface between both solders and Ni-P layer and it thickens with aging time, meanwhile accompanied with a decrease of the thickness of remaining Ni-P layer. A drastic drop of the shear strength of SnAg solder joint happens after 250h aging and fracture was found to occur at the interface between Ni-P layer and Cu substrate. This may possibly be caused by the rapid accumulation of P in the remaining Ni-P layer. which results in a poor adhesion between Ni-P and Cu substrate. On the other hand, SnPbAg solder joint keeps a relatively higher value of shear strength even though it decreases with aging time.