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Why does tin connection occur during PCB assembly?

date:2022-01-14 16:48:10

PCBA factories will have wave soldering equipment. The quality of wave soldering has a great impact on the product. Today, FASTPCBA will analyze the problem of tin connection of PCB boards during wave soldering.

Reasons for connecting tin in wave soldering:

1. Insufficient flux activity.

2. The wettability of the flux is insufficient.

3. The amount of flux applied is too small.

4. Uneven flux coating.

5. The circuit board cannot be coated with flux regionally.

6. The circuit board is not tinned regionally.

7. Some pads or solder feet are seriously oxidized.

8. The wiring of the circuit board is unreasonable (the distribution of the components is unreasonable).

9. The direction of the board is not correct.

10. The tin content is not enough, or the copper exceeds the standard; [The melting point (liquidus) of the tin liquid is increased due to the excessive impurities.

11. The foaming tube is blocked and the foaming is uneven, resulting in uneven coating of the flux on the circuit board.

12. The setting of the air knife is unreasonable (the flux is not evenly blown).

13. The board speed and preheating are not well matched.

14. Improper operation method when dipping tin by hand.

15. The chain inclination is unreasonable.

16. Uneven crests.

Improvement measures:

1. Design according to the PCB design specification. The long axes of the two end chips are perpendicular to the welding direction, and the long axes of the SOT and SOP should be parallel to the welding direction. Widen the pad of the last pin after the SOP (design a tin stealing pad).

2. The pins of the plug-in components should be formed according to the hole spacing and assembly requirements of the printed board. If the short-insertion welding process is used, the component pins on the welding surface are exposed to the surface of the printed board by 0.8~3mm, and the component body is required to be inserted. correct.

3. Set the preheating temperature according to the size of the PCB, whether it is a multi-layer board, how many components there are, and whether there are mounted components.

4. The tin wave temperature is 250±5℃, and the soldering time is 3~5s. When the temperature is slightly lower, the speed of the conveyor belt should be adjusted slower.

5. Replace the flux.

The above is the analysis of PCBA processing wave soldering and tinning. For more PCBA processing technology articles, you can pay attention to FASTPCBA OEM PCB and PCBA manufacturer.



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