Solder paste selection, the quality of solder paste itself is an important problem to be solved in PCB manufacturing and assembly, PCB quality will also be affected by the solder paste, therefore, the basis of quality is to choose a good solder paste.Clean and low residue solder paste is also suitable for environmentally friendly applications and development of solder paste, as the name implies, after welding no need to clean.In fact, it still has a certain amount of residue after PCB welding, mainly concentrated in the solder joint area of the circuit board, sometimes it still affects the test needle bed inspection.
What are the two features required to clean the low residue solder paste?
The first is that the active agents no longer use halogens. The second is to reduce the amount of rosin and increase the amount of other organic compounds.
The practice shows that the amount of rosin is very important to reduce, when welding circuit board, if the rosin dose is low enough, it will lead to the reduction of flux activity, and welding area to prevent secondary oxidation effect will be reduced.
Therefore, in order to achieve the purpose of no cleaning, nitrogen shielded reflow welding is often required when using low-residue solder paste that does not need cleaning.Nitrogen welding can effectively improve the wetting effect of solder paste and prevent secondary oxidation.In addition, under the protection of nitrogen, the residue volatilization rate of solder paste was significantly faster than that under normal conditions, and the amount of residue decreased.
When using non-cleaning low-residue solder paste, the performance of the solder paste should be thoroughly and rigorously tested to ensure that there is no negative impact on the electrical performance of printed circuit board components after welding.Grade e electronic products, even when using non-clean solder paste, should usually be cleaned to ensure true product reliability.
These are the characteristics of no residual and low residual solder paste