When smt patching, you will encounter the phenomenon of tin beads hidden in the guide holes of the spray tin plate. What impact will this phenomenon cause?

Bad phenomenon:

For the tin spray board, as long as it is a through hole that is not a plug hole, there will usually be a phenomenon of tin beads hidden, mainly because the hole is opaque, as shown in the figure below.

The direct hazard of the tin beads hidden in the tin spray board is that they may come out and adhere to the pad, which will directly affect the printing quality of the solder paste. The further hazard is that after the tin beads fly out, they will pose a certain threat to reliability.

Bad case:

As shown in the picture below, the picture below shows the phenomenon of hidden tin beads.

Bad reason description:

1. The effect of hidden tin beads on the quality of products depends on the size of the PCB hole plate.

2. If the width of the pad ring is within 0.05mm, under normal circumstances, it will not affect the solder paste printing, but if the width of the pad ring is relatively large, it may form tin beads. Therefore, the solder mask with a small window is used on the spray tin plate. The phenomenon of hiding tin beads is acceptable within a certain range, but it is not feasible to open a large window for solder mask. It is best not to do this.

3. If the solder mask hole with a small window hides tin beads, the worst case is that the tin beads will run from the center of the hole to the hole, sealing the surface of the hole, but generally will not form a spherical shape obstructive. As shown below