电子连接器表面锡层高温焊接变色原因分析

摘要

通过实验验证了不同环境及电镀条件对纯锡高温变色的影响.采用俄歇电子能谱仪(AES)分析变色试样的表面元素组成,以确认变色的可能原因和改进方向.排除了有机物析出以及底层金属扩散形成Sn-Ni合金这两种情况对锡层变色的影响,确定了表面氧化是锡层变色的主要原因,并且变色程度随氧化膜厚度增大而加深.提出了改善锡层抗高温变色性能的几项措施.在镀锡前,镀普通镍后电镀一层高温镍,可使变色率降至零.%The effects of different environments and electroplating conditions on discoloration of pure tin coating were verified by experiments.The elemental composition on the surface of discolored sample was analyzed using Auger electron spectrometer (AES) to determine the possible causes and improvement directions.The effects of two cases including precipitation of organic compound and formation of Sn-Ni alloy caused by diffusion of underneath metal coating on discoloration of tin coating were eliminated.The major cause for discoloration of tin coating was determined to be the surface oxidation.The discoloration gets deeper with the increasing of oxidation film thickness.Several methods for improving anti-discoloration at high temperature were suggested.The discoloration rate can be decreased to zero when the following process is carded out:normal nickel electroplating followed by high-temperature nickel electroplating before tin electroplating.