Radius of an asperity

[Timusop]

I am trying to determine the "Radius of curvature" of an asperity. I am using a Wyco NT-2000 surface optical profiler. I am not sure if I can determine the radius of curvature from the machine directly?

The machine can output, the "Mean Summit curvature" (as explained here

http://www.imagemet.com/WebHelp/spip.htm#roughness_parameters.htm

) but I am not sure this will be helpful in determining the the radius of curvature of an asperity or even the average radius of asperity curvature. I have attached an image of the test scan with the data available from the scan.

I would really appreciate some advice, thanks.

 

[Timusop]

Any ideas anyone? Thanks.

 

[TVP]

The radius of curvature of an asperity cannot be obtained from a surface parameter than is measured over the entire sampling length. I would take the individual peaks and estimate a radius of curvature for each one.

 

[IRstuff]

"trying to determine the "Radius of curvature" of [red]an[/red] asperity"

A SINGLE asperity? Are you actually looking for an individual asperity, or the class of asperities? For that matter, are these asperities actually round? How big is the sample whose data you are showing? Are your asperities reflected in the roughness value or the summit values, since they are both quite different?

The summit curvature works out to a radius of 305 um, which is awfully big for an "asperity" but small for some thing like wafer bow. The mean density of summits is shown as 1 per ~44 sq. um., but are your asperities really on the order of 6.6 um across?

Your rms roughness is 9 nm, drastically different than the summits.

TTFN

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