In the process of PCBA welding, due to the influence of welding processing data, process, personnel and other factors, it will lead to poor welding processing of PCBA. Next, we mainly introduce the common bad PCB welding process.

1.PCB surface residue too much

Not preheated before welding or the preheating temperature is too low, and the temperature of the tin furnace is insufficient, which may cause too much board residue; walking speed is too fast; adding antioxidants and antioxidant oil to the tin liquid; too much flux coating; component feet and The orifice plate is not commensurate (the hole is too large), resulting in flow accumulation; during the use of flux, factors such as long-term no diluent are added.

2. Corrosion, green parts, black liner

The main reason is insufficient preheating, resulting in excessive flux residues and excessive harmful residues; the flux to be cleaned is used, but it is not cleaned after welding.

3. False welding

False soldering is a very common defect and is also very harmful to the circuit board. This is mainly related to too little or uneven flux coating; some foot pads or feet are severely oxidized; PCB wiring is unreasonable; Foaming pipe is blocked and foaming is uneven, resulting in uneven flux coating; Manual immersion tin operation method is improper; Chain inclination is unreasonable; wave crest is related to inequality.

4. Cold welding:

The surface of the welding spot is in the shape of bean curd residue. The main reason is that the temperature of the electric soldering iron is not enough, or the solder is vibrating before the solder is condensed, the strength of the bad solder joint is not high, the conductivity is weak, and it is easy to cause the problem of open circuit of the parts under the action of external force.

5. Whitening of solder joints:

Rugged and monotonous. Usually the temperature of the electric iron is too high or the heating time is too long. The strength of the bad solder joint is not enough, and it is easy to cause the problem of component open circuit under the action of external force.

6. Liner stripping:

This is mainly because the pads peel off from the printed circuit board after being subjected to high temperatures. Such poor solder joints are likely to cause the problem of component disconnection.

7. Tin beads

Process: Preheating temperature is low (flux solvent is not completely evaporated); The walking speed is fast, and the preheating effect is not achieved. The inclination angle of the chain is not good, there are bubbles between the liquid tin and PCB, and tin beads are generated after the bubbles burst. Improper manual tin immersion operation; Wet working environment; PCB problem: the surface of the circuit board is wet and moisture is generated; The planning of PCB gas escape holes is unreasonable, resulting in gas entrainment between PCB and molten tin; PCB planning is unreasonable, and the parts are too dense to form air.

There are many reasons for the formation of PCBA welding defects, and each process needs to be strictly controlled to reduce the impact of the previous process on the subsequent.

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