Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Plating Thickness measurement by Eddy-Current
Q. Dear Reader,
I am looking for method of measuring the thickness of solder mask on a PCB(RF4 base, copper clad). The solder mask must be 0.02mm. I was wondering if an eddy current based machine would be effective and how it actually works. I would appreciate any and all suggestions. Thanks
Leah SpoonerKanata, Canada
1999
A. Dear Leah,
An eddy current machine will work nicely for your mask. Eddy current works something like this: there is a magnetic field at the end of the probe that changes shape when the tip of the probe touches an object. The amount of change is measured by the probe and is compared to the stored curve created with your standards. Eddy current can measure a non-conductor (solder mask) over a conductor pad or line (tin, tin-lead, or copper)of a certain size, shape, and thickness. You'll need to have or make standards for different thickness of solder mask and metals (one oz. copper may be different from 2 oz. copper).
Regards,
Fred Mueller, CEF- Royersford, Pennsylvania
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