As the saying goes, details determine success or failure. In the same way, if the process control is not in place in PCBA processing, various undesirable problems are prone to occur, such as the most common "false soldering, wrong and missing" and so on. In addition, there are many factors that affect PCBA welding bubbles, such as: PCB design, chain speed, tin wave height angle, solder paste composition, etc. But having said that, why do bubbles occur? Next, we will analyze the causes and avoidance measures of pores in PCBA processing.

The bubble generation is actually easy to understand. For example, the PCB has not been baked, the components are damp (containing moisture), and then a layer of solder paste is covered on it. When high temperature reflow soldering or wave soldering, the PCB circuit board or components Moisture evaporates and expands when heated, and blows through the solder paste coverage to create pores. So how can we effectively avoid the generation of pores?

1. PCB baking. For products stored for 7 days without production, high-temperature baking is carried out before production.

2. Component storage. The storage of components must be considered in terms of packaging environment and storage environment. If it is a special device, it must be stored in a moisture-proof cabinet.

3. Solder paste. Solder paste is actually a mixture of tin and gold. In terms of its properties, since it is a paste, it contains a certain amount of water. However, as long as the solder paste is reasonably warmed and stirred, and the production process is optimized, the process from printing solder paste to reflow soldering is shortened to the shortest, so as to reduce the duration of solder paste exposure to the air.

4. Humidity control in SMT production workshop. According to the IPC-06 process control standard, the reasonable humidity of the SMT workshop is between 40-60%.

5. Furnace temperature curve. According to the different products of customers, optimize the furnace temperature curve in time, increase the temperature steadily, and set the preheating temperature reasonably to make the flux volatilize fully.

6. Flux. Do not spray too much flux during wave soldering.

Of course, in addition to the above-mentioned popular situations, there are many reasons that cause bubbles to be generated, which are not listed one by one. However, since there are so many links and each link may produce defects, we need to pay more attention to product technology and quality control, so as to effectively avoid defects.