Trelic’s picture of the week 09/2018

The quality of the surface finish in a microvia structure

 

In the last week’s picture we discussed about surface finishes of printed circuit boards (PCB) and their quality. This week’s picture is also about surface finishes and their deficiencies, but this time we are dealing with microvias (Check more about microvias from our earlier post).

While studying cross-sections using SEM (scanning electron microscope), we noticed some cracks on the surface of the microvias. We wanted to share this too with you to show that there can be all kinds of deficiencies with surfaces finishes.

A closer picture of the crack and an example of a crack seen in a cross-section is shown below. As mentioned last week, in worst case such defects can cause major reliability problems for example due to corrosion. In this week’s case we were dealing with thermal shock, so we did not have corrosion-related problems. However, sometimes such cracks act as stress concentration points and lead to further cracking and failures.