Three Common Problems in SMT Laser Steel Mesh Welding

Source: Linchuan Precision　 Article author：Linchuan Precision　 Time:2019-10-08 13:59　 Read: 4541

When the distance between the pads or the printed wires is 0.13 mm, the diameter of the solder balls may not exceed 0.13 mm, or more than five tin beads may not appear in the range of 600 mm square. The reasons are as follows:

1. The screen printing hole and the pad are not aligned, and the printing is not allowed to make the solder paste stain the PCB.

2. The solder paste is exposed too much in the oxidizing environment and the moisture in the air is too much.

3. The heating is too slow and uneven.

4. The heating rate is too fast and the preheating interval is too long.

5. The solder paste dries too fast.

6. Flux activity is not enough.

7. Too much small tin powder.

8. Flux volatility is not appropriate during the reflow process.

Open, the solution is to pre-solder the solder on the pad. The pin suction can be prevented by slowing down the heating rate and heating the bottom surface less and heating less. The cause of this problem:

1. The amount of solder paste is not enough.

2. The coplanarity of the component pins is not enough.

3, tin is not wet enough (not enough to melt, poor fluidity), tin paste is too thin to cause tin loss.

4, the pin is sucking tin (like the wick grass) or there is a connecting hole nearby.

SMT laser steel mesh

Solder Balls, the process standard for solder balls: When the distance between the pads or printed conductors is 0.13 mm, the diameter of the solder balls should not exceed 0.13 mm, or more than five tins should not appear in the 600 mm square range. Beads. The reasons are as follows:

1. The screen printing hole and the pad are not aligned, and the printing is not performed, so that the solder paste stains the PCB.