Sn-Cu、Sn-Ag-Cu系无铅钎料的钎焊特性研究

制备了Sn-0.7Cu、Sn-3.5Ag-0.6Cu钎料,用润湿平衡法测量了钎料对铜的润湿曲线,研究了温度、钎剂活性、钎焊时间对润湿行为的影响,并与Sn-37Pb钎料进行了比较。结果表明:升高温度能显著改善无铅钎料对铜的钎焊性。当温度<270℃时,Sn-0.7Cu的钎焊性明显低于Sn-3.5Ag-0.6Cu钎料;而当温度≥270℃时,两种钎料对铜都会显示较好的润湿性,而Sn-0.7Cu略优于Sn-3.5Ag-0.6Cu钎料。提高钎剂活性能显著增强钎料对铜的润湿性,其卤素离子的最佳质量分数均为0.4%左右。随着浸渍时间的延长,熔融钎料与铜的界面间产生失润现象。无铅钎料的熔点和表面张力较高,是钎焊性较差的根本原因。

Investigation for Solderability of Sn-Cu、Sn-Ag-Cu Lead-Free Solders

The Sn-0.7Cu and Sn-3.5Ag-0.6Cu lead-free solder were prepared. The wetting behavior curves of them on the face of copper were tested by wetting balance method, and compared with the results of Sn-37Pb. The results indicate that the increase of temperature can remarkably improve the solderability of Sn-0.7Cu and Sn-3.5Ag-0.6Cu alloy. The solderability of Sn-0.7Cu is lower than Sn-3.5Ag-0.6Cu when temperature <270℃, but it will be better than Sn-3.5Ag-0.6Cu when temperature >270℃. With an increase of halogen ion in flux, the solderability of Sn-0.7Cu and Sn-3.5Ag-0.6Cu alloy remarkably improves and the best halogen ion content is more than 0.4%. The wetting force of Sn-0.7Cu and Sn-3.5Ag-0.6Cu on the face of copper will decrease with the wetting time delay. Because the surface tension and melting point of lead-free solders are higher than that of Sn-Pb, the solderability of them are lower than Sn-Pb alloy.