PCBA circuit board welding disc black problem is a more common circuit board bad phenomenon, resulting in PCBA welding disc black for many reasons, but usually caused by the following reasons:
1, pad oxidation: If the PCBA pad is exposed to humidity for a long time, it will cause the surface of the pad to oxidize, forming an oxide film on the surface of the pad, resulting in black, therefore, when storing PCBA, attention should be paid to keeping the environment dry, and at the same time, PCBA should be vacuumed in time to avoid its long-term exposure to the air!
2, welding process problems: in reflow welding or wave soldering, if the welding temperature is too high or the welding time is too long, it will also lead to the oxidation of the welding pad black phenomenon, this reaction is usually due to the welding temperature exceeds the recommended temperature range of the solder, resulting in accelerated oxidation process, so in the welding process must be in accordance with the operating specifications for welding!
3, solder problem: solder generally refers to the solder paste, tin, solder quality is good or bad, if the use of poor quality solder, will also make the solder in the harmful substances and impurities released, resulting in black pad, so, in the choice of solder, we must avoid the use of low-quality solder!
4, cleaning problems: Generally speaking, in the case of the use of flux is needed to clean the board, in order to remove the flux residue on the pad, and if the flux residue is not fully removed, then these residual flux may degrade or carbonize at high temperatures, so that the pad appears black. Therefore, timely cleaning after welding is very necessary!
5, component problems: if the quality of the electronic components is not good, or the material of the component pin is improper, it may also lead to the phenomenon of black welding disc, so, when choosing electronic components, we must choose good quality components to ensure that the quality of the coating and the pin material of the components are qualified.
The above is the main reason for PCBA welding tray black, and according to different reasons, we can also choose the corresponding improvement measures, so as to effectively reduce the problem of PCBA welding tray black, improve the quality of products!