What method can prevent the generation of welding pores during PCBA processing?

Air holes generated by PCB welding, that is, we often say air bubbles. Generally, air holes will be generated during reflow welding and wave soldering in the process of PCB welding. What can be done to prevent air holes in PCB welding?

1. Baking: long term baking of PCB and components exposed to air can effectively prevent moisture loss.

2. Control of solder paste. Solder paste contains moisture, which is easy to produce pores and solder beads. First, select the solder paste with good quality. The mixing of solder paste shall be carried out strictly according to the operation. The exposure time of solder paste to the air shall be as short as possible. After printing, reflow welding shall be carried out in time.

3. Workshop humidity control: monitor the humidity status of the workshop in a planned way and control it between 40-60%.

4. Set reasonable furnace temperature curve, test the furnace temperature twice a day, optimize the furnace temperature curve, and the heating speed should not be too fast.

5. Flux spraying. During over wave soldering, the flux spraying amount should not be too large, and the spraying is reasonable.

6. Optimize furnace temperature curve. The temperature of the preheating zone shall meet the requirements and shall not be too low to make the flux volatilize fully, and the furnace passing speed shall not be too fast.

There are many factors that affect printed circuit board welding bubbles. It can be analyzed from the aspects of PCB design, PCB humidity, furnace temperature, flux (spray size), chain speed, Sn wave height, solder composition and so on. It needs many times of debugging to get a better process.