The first reason：We should think about whether it is a customer design problem. It is necessary to check whether there is a connection mode between the pad and the copper sheet, which will lead to insufficient heating of the pad.
The second reason : Whether it is a customer operation problem. If the welding method is wrong, it will affect the insufficient heating power, temperature and contact time, which will make it difficult to tin.
The third reason : improper storage.
① Under normal circumstances, the tin spraying surface will be completely oxidized or even shorter in about a week.
② OSP surface treatment process can be stored for about 3 months.
③ Long term storage of gold plate.
The fourth reason：flux.
① The activity is not enough to completely remove the oxidizing substances of PCB pad or SMD welding position.
② The amount of solder paste at the solder joint is not enough, and the wetting property of the flux in the solder paste is not good.
③ The tin on some solder joints is not full, and the flux and tin powder may not be fully mixed before use.
The fifth reason : pcb factory.
There are oily substances on the pad that have not been removed, and the pad surface has not been oxidized before leaving the factory
The sixth reason: reflow soldering.
Too long preheating time or too high preheating temperature leads to the failure of flux activity. The temperature was too low, or the speed was too fast, and the tin did not melt.
There is a reason why the solder pad of the circuit board is not easy to tin. When it is found that it is not easy to tin, it is necessary to check the problem in time.
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Post time: Dec-20-2022