Common problems and solutions for PCB surface SMT placement

2019-08-19 08:01:06 436

1. The PCB board is not preheated during reflow soldering;

2. The reflow soldering temperature curve is set to be unfair, and the board surface temperature before entering the soldering zone is relatively spaced from the soldering zone temperature;

3. The solder paste failed to completely return to room temperature when it was taken out of the cold storage;

4. The solder paste is exposed to the air for a long time after being opened;

5. When the patch is placed, tin powder splashes on the PCB surface;

6. During the printing or transfer process, oil or moisture adheres to the PCB;

7. In the solder paste, the flux itself is unfairly distributed and it is difficult to evaporate the solvent or liquid additive or activator;

The first and second reasons above can also clarify why the new replacement solder paste is prone to such problems. The main reason is that the current temperature profile does not match the solder paste used.

The third, fourth and sixth reasons are not able to be manipulated by the operator;

The fifth reason is that the solder paste is not sticky or the adhesiveness is too low due to the improper storage of the solder paste or the failure of the solder paste to form the solder paste, and the solder powder is splashed when the patch is formed;

The seventh reason is formed by the production technology of the solder paste supplier itself.

(3) There are more residues on the surface after welding:

There is a lot of residue on the PCB surface after soldering. It is also a question often reflected by customers. The presence of more residues on the board surface not only affects the brightness of the board surface, but also has an inevitable effect on the electrical properties of the PCB itself. The main reasons for multi-residue are as follows:

1. When implementing solder paste, it is not known about the customer's board condition and customer's needs, or other reasons for the selection of faults;

2. The content of rosin resin in solder paste is too high or its quality is not good.