Common PCBA welding defects in circuit board welding processing
In the PCBA welding process, due to the influence of welding materials, technology, personnel and other factors, it will lead to the phenomenon of poor PCBA welding. Next, FASTPCBA mainly introduces the common poor welding of circuit boards.
1. Too much residue on PCBA board
Excessive residues on the PCB board may be caused by not preheating before soldering or the preheating temperature is too low, and the temperature of the tin furnace is not enough; the speed of the PCB board is too fast; the anti-oxidant and anti-oxidation oil are added to the tin liquid; the flux coating Too much; the component feet and the orifice plate are out of proportion (the holes are too large), which causes the flux to accumulate; in the flux application process, the thinner and other elements are not added for a long time.
2. Corrosion, green components, black pads
Mainly because of insufficient preheating, there are many flux residues and too many harmful residues; the flux that needs cleaning is used, but there is no cleaning after soldering.
3. Welding
Welding is a very common defect, and it is very harmful to PCB boards. Mainly related to the amount of flux coating is too small or uneven; some pads or solder feet are severely oxidized; PCB wiring is unreasonable; the foaming tube is blocked and the foaming is uneven, resulting in uneven flux coating; operation when hand dipping tin Improper method; unreasonable chain inclination; related to the inequality of crests.
4. Cold welding
The surface of the solder joints is like tofu. Mainly because the temperature of the electric soldering iron is not enough, or the vibration of the weldment before the solder is condensed, the bad solder joint is not strong, and the conductivity is weak, and the external force can easily cause the failure of the component.
5. White solder joints
Rugged, dull. Generally, it is formed because the temperature of the soldering 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 failure of the component to be disconnected by the external force.
6. Pad peeling
The main reason is that the pad is formed after being subjected to high temperature and peeled off from the printed circuit board, and this bad solder joint is very easy to cause the failure of the component.
7. tin beads
Process: low preheating temperature (the flux solvent is not completely evaporated); the speed of the PCB board is fast, and the preheating effect is not reached; the inclination of the chain is not good, there are bubbles between the tin liquid and the pcb, and tin beads are generated after the bubbles burst; Improper operation when tinning; humid working environment; PCB problems: the board surface is wet and moisture is generated; the layout of the holes for the PCB to run out is unreasonable, forming a gas trap between the PCB and the tin liquid; the PCB planning is unreasonable, and the parts are too densely formed Depressed.
There are many reasons for poor PCBA soldering, and each process needs to be strictly controlled to reduce the impact of the previous process on the follow-up.