One coupon section I have always liked is for the last hit by a drill bit, before change out, be on the test coupon.  That is, even if the same size drill bit is used more than once on a panel, the last hit by each bit be on the coupon.  It is much easier to see if broken tips or poor resharpening is tearing holes in the board, instead of drilling holes.  Rough hole walls lead to all sorts of problems - voids/blowholes, incomplete electorless coverage, thin electroplate spots, etc.  Good luck mearuing aveage ENIG thickness inside poorly drilled holes. 

Denny Fritz


-----Original Message-----
From: Stadem, Richard D. <[log in to unmask]>
To: TechNet <[log in to unmask]>
Sent: Fri, Sep 17, 2010 10:06 am
Subject: Re: [TN] How to measure thickness of ENIG plating inside the via barrel


Fabien,
uality of via or through-hole plating is assessed by micro-sectioning a test 
oupon (solder coupon) that is representative of the PWB. The test coupon goes 
hrough the same fabrication steps as the PWBs, including the plating processes. 
t is a sacrificial panel that serves as a witness sample and is manufactured 
ust for facilitation of destructive testing.
-----Original Message-----
rom: TechNet [mailto:[log in to unmask]] On Behalf Of Fabien Guizelin
ent: Friday, September 17, 2010 2:14 AM
o: [log in to unmask]
ubject: [TN] How to measure thickness of ENIG plating inside the via barrel
Hi 
IPC-4552 calls for XRF to measure ENIG plating thickness. But, this method can 
nly be applied to surface pads.  How can we assess the quality of the plating 
n via barrel ?    (poor plating would compromise mechanical strength and 
esistance to corrosion)
Thanks for your insight
Fabien

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