Causes of discoloration of metal terminal plating

The metal terminal plating has the functions of improving mechanical ability, corrosion resistance, and improving electrical performance. If the metal terminal plating changes color, these functions will be unstable and the appearance will be greatly faded. So what makes it discolored? Let's analyze the reasons for the discoloration of the metal terminal plating. 1. Related to the structure and shape: Compared with the strip, the structure of the hardware terminal is complicated, and the unevenness of the part changes greatly, which causes the current distribution problem on the surface of the part during the electroplating process. Therefore, the protruding part of the part distributes a lot of current and the coating is very thick; the recessed part distributes the current very little, and the coating is very thin. Then the plating layer is thin, the thickness is not enough, and the protection ability is reduced. This is the reason why the recess of the hardware terminal changes color first, and the other parts change color later. 2. Related to the performance of the plating solution: the performance of the plating solution is measured by two indicators, one is the leveling ability of the plating solution, that is, the plating solution makes the thickness of the plating layer evenly distributed on the parts; the other is the depth ability of the plating solution, namely The plating solution deposits a metal coating on the deep recess of the part. If these two capabilities are not good, the plating layer is thin, and the plating layer of the hardware terminal is easy to change color. 3. It is related to the speed of travel: the crystallization process of metal ions on the hardware terminal must involve a time factor. With the same machine, plating solution, and process, if the parts are electroplated for a long time, the coating will be thick, and the coating will be thin if the time is short. The electroplating time actually refers to the problem of the electroplating speed of the parts. If the walking time is short, the plating layer will be thin and the hardware terminals will easily change color, and vice versa.