Solder Flux Residue
In Part 1, we mentioned that some of the constituents (e.g. Si, Ba, S) found in the EDS spectra of solder flux residue on a PCBA surface are likely due to the solder mask beneath the residue as the e-beam can penetrate through thin residue layers. Here we examine how to analyze EDS data to remove the contribution of the solder mask.
![BSE SEM image of solder flux residue between two PTH solder joints.](https://www.semlab.com/wp-content/uploads/2021/11/2970B_4-scaled.jpg)