In the process of smt placement, there may be a phenomenon of gold finger dipping tin, that is to say, the yellow conductive contact of the pcb board is stained with solder paste during the printing/soldering process, which affects product performance. The editor of SMT processing factory _ Anhui Yingterite will take you to analyze the phenomenon of gold finger dipping tin, hoping to be helpful to everyone.

1. Why does tin sticking occur?

1. The pressure of the printing machine is too high, causing part of the solder paste to be squeezed out of the control range;

2. The pressure of the placement machine is too large;

3. The preheating time of reflow soldering is short and the heating speed is fast;

4. When the steel mesh is designed, the opening size is unreasonable;

5. The equipment is polluted;

2. How to avoid the phenomenon of tin sticking

1. In terms of technology:

1 Adjust the appropriate scraper pressure, wiping frequency and the distance between the printing plate and the stencil.

2) Appropriate chip pressure can reduce tin powder extrusion.

3) Strict machine cleaning and maintenance can reduce the pollution index.

4) Reduce the opening size of the steel mesh.

5) Slow heating rate/high soaking temperature curve.

2. In terms of materials:

1) Low-spatter solder paste helps reduce gold finger sticking to tin.

2) Use a solder paste with a slow wetting rate.

3) Low moisture parts and PCBs help reduce splashing.

4) Appropriate gold finger gold plating can reduce exposed nickel.

   If the phenomenon of tin sticking occurs, it is necessary to analyze according to the on-site environment, find out the cause in time, and solve it, so as to avoid affecting the quality of PCBA products and reduce the waste of production costs