Residues on PCBAs are unfortunately common place. SEM/EDS analysis helps to determine the nature of the residue.

residue on PCBA 1

The image above shows residue on the surface of the PCBA, but it is not clear what is the nature of the residue.

residue on PCBA 2

EDS analysis shows that the residue is likely tin bromide, suggesting corrosive bromide flux activator was left behind after assembly.

residue on PCBA 3

This is a BSE SEM image of some of the residue, which shows dendritic growth. The dendrites suggest that electrochemical migration (ECM) was a factor meaning ionic contamination, electric field, and moisture were likely at play. If the dendrites migrate between normally isolated signals (e.g. PWR & GND) then the circuit fails.

Check out SEM Lab, Inc.  to learn more.

Leave a Reply

Your email address will not be published.

You may use these HTML tags and attributes:

<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>