In the electronic soldering industry of integrated circuits, a layer of solderable tin plating is usually plated on the component pins to improve the soldering performance of electronic devices, and the current application of solderable tin plating layer is necessary and irreplaceable. However, in practice, the solderability of the plating is prone to failure.
Failure of plating solderability
Although the chemical stability of tin is good, the tin plating layer is exposed for a long time, and the surface is easy to turn gray and yellow, resulting in decreased welding performance of the product, resulting in quality defects such as virtual welding, underwelding, and air welding. When powered on, the components will be abnormally hot, resulting in safety accidents.
Discoloration of the tin layer can cause solderability failure
Many of the failures of solderable tin plating begin with the observation of the color change of the tin layer, and the practice results show that there are many links affecting the tin-layer discoloration. Some people believe that the inclusion of organic additives in the plating solution causes the coating to contain organic substances of different degrees, and the organic substances will migrate from the pore space in the plating layer to the surface through the capillary effect of oxidation aggregation of the film, resulting in the yellowing and discoloration of the tin layer.
However, there is more evidence that the oxidation of the tin layer by a combination of humidity and temperature is the main driver of the accelerated discoloration.
In the air environment, if the tin layer is exposed for a long period of time, acidic gases and oxidizing gases in the air (e.g. O2, CO2, NO2, SO2), these will interact with the moisture in the air to generate electrolytes with corrosive properties.
This kind of electrolyte can accelerate the oxidation of the tin plating layer at high temperatures, oxidize Sn into Sn2+, generate SnO, SnS and other products (the appearance is yellow), resulting in discoloration of the coating surface, if the situation is serious, it will further become SnO2 oxides.
These substances, on the one hand, will change the color of the tin layer, on the other hand, will affect the solderability of the coating.
Conclusion
In order to improve the solderability and other properties of the coating, we need to choose a suitable matte tin additive Sn-808, which is an additive made by the engineer team after years of research and development. The tin layer made can be stored in the air environment for a long time and can maintain good solderability. At the same time, it is necessary to control the storage and use environment of the product.
If you are interested in matte tin additives, please feel free to contact us.
