We all know that the PCB pads are not easy to be tinned, which will affect the placement of components, which indirectly leads to the failure of subsequent tests. Here I will introduce to you the reasons why the PCB pads are not easy to be tinned. I hope that you can avoid these problems and minimize the loss when making and using them.
The first reason is: we have to consider whether it is a customer design problem, and we need to check whether there is insufficient heating of the pad due to the connection method between the pad and the copper skin.
The second reason is: whether there is a customer operation problem. If the welding method is wrong, it will lead to insufficient heating power, insufficient temperature, and insufficient contact time.
The third reason is: the problem of improper storage.
① Under normal circumstances, the tin surface will be completely oxidized in about a week, or even less than a week.
② The OSP surface treatment process can be maintained for about 3 months.
③ The immersion gold plate can be stored for a long time.
The fourth reason is: the flux problem.
① Insufficient activity, unable to completely remove the oxide substance on the PCB pad or SMD soldering position.
② The amount of solder paste in the solder joint is not enough, and the wetting performance of the flux in the solder paste is not good.
③ The tin on some solder joints is not full, and it may not be fully stirred before use, and the flux and tin powder are not fully fused.
The fifth reason is: the problem dealt with by the board factory.
The oily substance on the pad has not been removed, and the pad surface has not been oxidized before leaving the factory.
The sixth reason is: the problem of reflow soldering.
If the preheating time is too long or the preheating temperature is too high, the flux activity will be invalid; if the temperature is too low, or the speed is too fast, the tin will not melt.
The above is a summary of the reasons why the PCB pads are not easy to be tinned.