Defect of the Month
Microsections Can Show Much
Getting a close-up look at board quality.
A PRINTED BOARD microsection is one of the best ways to examine the quality of boards and any faults or failures.

The microsection (FIGURE 1) shows a plated through-hole that has been soldered with the nickel layer and through-hole copper visible. Normally, customers would accept the plating standards offered by the fabricator, or define their own, which may or may not impact the price. The nickel layer is part of the nickel/gold surface finish with the very thin gold of less than 1µm consumed during soldering and not visible. The remaining nickel is 5µm, and the copper is around 32µm. This is generous on many circuits board produced today and soldered very easily in production.

In this case, the board is fine and will continue to operate reliably in the field. No defects are present, just a little copper wicking into the glass bundle.

We have presented live process defect clinics at exhibitions all over the world. Many of our Defect of the Month videos are available online at youtube.com/user/mrbobwillis. Find out how you can share our new series of Defect of the Month videos to explain some of the dos and don’ts with your customers via CIRCUITS ASSEMBLY: https://bit.ly/3mfunlF.

Microsection of a PTH with a visible nickel layer
Figure 1. Microsection of a PTH with a visible nickel layer.
Bob Willis Caricature
Bob Willis
is a process engineering consultant; bob@bobwillis.co.uk. His column appears monthly.