脉冲电镀锡层可焊性的研究

Study on solderability of tin deposit by pulse plating

镀层与基体的润湿程度可用于检测镀锡层可焊性。通过正交实验，以镀锡层可焊性为评价指标，选择了紫铜毛细管表面脉冲电镀锡最佳工艺参数为：平均电流密度1．5A／dm^2，脉冲周期100ms，占空比10％，搅拌速率20次／min。研究了平均电流密度在1．0-2．5A／dm^2范围内，对镀锡层可焊性的影响。在相同的平均电流密度1．5A／dm^2下，比较了脉冲电镀与直流电镀2种方法所得镀层的可焊性，脉冲镀锡层的润湿程度明显优于直流镀层，这可能是由于脉冲电镀中阴极浓差极化降低，镀层中的杂质减少，因此镀层的可焊性得到了改善．

The solderability of tin deposit is determined by wettability between deposit and substrate. By orthogonal test and with deposit solderability as the evaluation index, the optimal process parameters for tin plating of copper capillary surface are chosen as follows： average current density of 1.5 A/dm^2, pulse period of 100 ms, duty ratio of 10%, and agitation rate of 20 times per minute. The effects of average current density on deposit solderability over a range of 1.0 - 2.5 A/dm^2 are investigated. At the same average current density of 1.5 A/dm^2, the solderability of deposits respectively obtained by pulse current plating and direct current plating is compared. The wettability of the former is much better than that of the latter. This may be due to the reduced concentration polarization of cathode in pulse plating and less impurities in deposit, and hence the deposit solderability is improved.