化学镀镍磷工艺在印制电路板表面处理中的应用研究

Application of Electroless Nickel-Phosphorus Plating Technology to the Surface Treatment of Printed Circuit Boards

摘要: 本文采用改良的化学镀镍工艺，通过加入一种自研的复合添加剂以期获得更为致密的镀层，并应用于PCB板铜电路表面处理，可以达到目前ENIG和ENEPIG工艺的性能要求。采用单因素变量法，依次对镀液pH值、复合添加剂浓度和施镀温度进行优化。以镀层在3.5% NaCl溶液中的电化学测试结果为衡量指标，得到最优的镀液配方和工艺参数为：NiSO₄•6H2O 30 g/L，NaH₂PO₂•H₂O 20 g/L，复合添加剂30 g/L，pH = 4.0，温度65℃，结果表明镀层具有良好的耐腐蚀性。对最优条件下得到的镍磷镀层进行形貌与成分分析，结果表明所得镀层平整致密、元素分布均匀，呈非晶态结构。将上述工艺应用于PCB板铜电路制备镍磷镀层，经中性盐雾测试和浸焊测试均表现出良好的可靠性。

Abstract: An improved electroless nickel plating process uses a self-developed composite complexing agent result in a denser coating for PCB copper circuits, which meets the performance requirements of ENIG and ENEPIG. We used the single-factor variable method to optimize the pH value of the plating solution, the concentration of composite complexing agent, and the plating solution temperature. The electrochemical test results of the coating in a 3.5% NaCl solution were used to determine the optimal plating solution formula and process parameters, which were as follows: NiSO₄•6H2O 30 g/L, NaH₂PO₂•H₂O 20 g/L, composite complexing agent 30 g/L, pH = 4.0, temperature 65˚C. The corrosion resistance of the coating is excellent under these conditions. We examined the morphology and composition of the nickel-phosphorus coating obtained under optimal conditions. The results showed that the coating obtained was smooth and dense, with uniform element distribution and amorphous in structure. In this study, the above process was applied to the copper circuits on PCB boards to prepare nickel-phosphorus plating. A neutral salt spray test as well as a dip soldering test showed a high degree of reliability.