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How to measure electrical resistivity of electroless nickel plating?

Is there a standard, accurate method for measuring the electrical resistivity of an electroless nickel deposit? For clarity, I am referring to the bulk dc electrical resistivity, rho, given by:

r = rho/A

where r is the resistance per unit length and A is the cross-sectional area (for example, see http://hyperphysics.phy-astr.gsu.edu/hbase/electric/resis.html).

I expect that a four-point probe technique is required with the deposit on an electrically insulating substrate (for example, see http://www.eeel.nist.gov/812/meas.htm#resi). Does the substrate need to be insulating, or can accurate results be obtained with a conducting one with an appropriate physical model? Are there techniques other than four-point probe that yield accurate values for the resistivity?

Grant Kiehne
manufacturing - Bloomfield, Connecticut, USA
2004

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Electrical resistivity of EN (or other coatings) is almost always determined by the "four point method". It is described by Riedel in his book, Electroless Nickel Plating ⇦[this on Amazon affil links]

While Riedel suggests using an EN foil (stripped from its substrate) for the test specimen, I believe most test have been done on coatings applied to non-conductors like ABS plastic.

The resistivity of Ni-P coatings as a function of their phosphorus content has been well documented.

Ron Duncan [deceased]
- LaVergne, Tennessee
It is our sad duty to note Ron's passing on Dec. 15, 2006. A brief obituary opens Episode 13 of our Podcast.
2004