How to prevent bubbles from forming in SMT welding?

四川英特丽

How to prevent bubbles from forming in SMT welding? [Copy link]

How to prevent bubbles from forming in SMT welding?

After the SMT patch is completed, it is sometimes found that there are bubbles on the PCBA board after inspection. This type of defect is a headache. So what are the reasons for the bubbles and how to prevent these problems? Sichuan Yingteli editor will answer you next

1. Before preparing for formal processing, it is necessary to check whether there is moisture in the PCB board. Generally, the circuit board and components need to be baked to prevent moisture in the air from entering the welding equipment and reacting with the circuit board to produce bubbles.

2. Solder paste is also one of the important factors that determine whether bubbles are generated during welding. When selecting solder paste, try to choose high-quality solder paste. When using it, it must be reheated and stirred strictly in accordance with the requirements. At the same time, after printing the solder paste on the PCB board, reflow soldering must be performed in time. Try to avoid exposing the solder paste to the air for too long, as it will absorb moisture, affect the welding effect, and generate bubbles.

3. Require dedicated staff to record the temperature and humidity of the frame on time. Control the humidity in the production workshop and monitor the humidity in the workshop in a planned manner to control it between 40-60%. Unreasonable temperature and humidity are harmful to the PCB board and processing quality. The circuit board absorbs moisture in the air, which affects welding and produces bubbles.

4. Bubbles are mostly generated in the welding process. The temperature curve of the welding furnace needs to be set hellish. The furnace temperature should be tested twice a day to optimize the furnace temperature curve. The heating rate should not be too fast. The temperature of the preheating zone must meet the requirements and cannot be too low so that the flux can fully volatilize, and the speed of passing the furnace cannot be too fast.

5. Spray the flux reasonably. During wave soldering, the amount of flux sprayed should not be too much.

The above are the reasons summarized by the editor. In fact, there are many reasons that affect the welding effect. This requires employees to carefully check in their daily work, strive to eliminate defects and improve the quality of PCBA products.