For a reflow process without cleaning, low residues are often required for cosmetic or functional effects, examples of functional requirements include "probing test overlays with solder flux residues tested in circuits and Make electrical contact between the plug-in contact and the surfacing layer or between the plug-in contact and the through hole near the reflow solder joint”.

Excessive solder flux residue often results in excessive residue coverage on the metal surfaces where electrical contact is to be made, which hinders the establishment of electrical connections and is a growing concern as circuit densities increase.

Clearly, low-residue solder pastes that do not need to be cleaned are an ideal solution to this requirement. However, the associated reflow requirements further complicate the problem. In order to predict the soldering performance of low-residue solder pastes in different levels of inert reflow atmosphere, a semi-empirical model is proposed, which predicts that soldering performance improves rapidly with decreasing oxygen content and then gradually plateaus , the experimental results show that the solder strength and the wetting ability of the solder paste will increase with the decrease of the oxygen concentration. In addition, the solder strength also increases with the increase of the solid content in the solder flux.

The proposed model is comparable with experimental data and strongly demonstrates that the model is effective and can be used to predict the soldering properties of solder pastes and materials. Therefore, it can be asserted that in order to successfully use clean-up without cleaning in the soldering process. For low-residue solders, an inert reflow atmosphere should be used.