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We often encounter defects in soldering during reflow soldering. In response to this problem, Shenzhen SMT patch editor has sorted out and found that there are 13 reasons for this kind of thing to happen. Today, I will list it out in detail with you.

1. Poor wetting

2. Insufficient amount of solder and open circuit of virtual solder

3. Suspension bridge and displacement

4. Solder joint bridge or short circuit

5. Solder balls walking around the solder joints

6. Air holes and pinholes distributed on the surface or inside of solder joints

7. The solder joint is highly in contact with or exceeds the component body (material suction phenomenon)

8. Fine tin wires between component solder terminals, between pins, solder terminals or between pins and through holes

9. The electroplating layer of the element end is peeled off to varying degrees, exposing the material of the element body

10. The component surface is reversed

11. There are different degrees of cracks and defects in the component body or end

12. Cold welding, also known as solder joint disorder

13. There are also some invisible defects, such as grain size of solder joints, internal stress of solder joints, internal cracks of solder joints, etc., which can only be detected by means of X-ray and solder joint fatigue test. These defects are mainly related to the temperature profile. For example, if the cooling rate is too slow, large crystalline particles will be formed, resulting in poor fatigue resistance of the solder joints, but if the cooling rate is too fast, cracks in the component body and solder joints will easily occur; for example, if the peak temperature is too low or the reflow time is too short, solder will be produced. Insufficient melting and cold soldering phenomenon, but the peak temperature is too high or the reflow time is too long will increase the production of common metal compounds, make the solder joints brittle, and affect the strength of the solder joints. If it exceeds 235 degrees Celsius, it will also cause ring itching in the PCB. Resin carbonization affects PCB performance and life.