Copper measurement

CMI International says, there are five basic, non-destructive methods of determining coating thickness. Each method was devised to achieve cost-effective, accurate, and repeatable results. Those methods are: * X-Ray fluorescence * Eddy-current * Magnetic induction * Beta backscatter * Microresistance Each method is particularly suited to a specific coating(s)/substrate combination. For copper without a doubt, the best method for measuring surface copper thickness over epoxy is microresistance. It's faster and it can accommodate a greater thickness range than x-ray fluorescence, beta backscatter or eddy current. Microresistance does not penetrate the substrate to "see" copper on the other side of double-sided boards or inner layers on multi-layer boards as would the other methods.

Eddy current, magnetic induction and x-ray are all viable methods for measuring copper over steel. Eddy current, which is significantly less in cost than x-ray and slightly above magnetic induction, should be strongly considered before the other two methods.

To measure plated-through-hole copper, use eddy current prior to etch; micro-resistance after etch.

Eddy current and microresistance gage suppliers are: * Oxford Instruments [oicm.com 800-678-1117] * Fischer Technology [helmut-fischer.com 860-683-0781]

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