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Date: Mon, 6 May 1996 12:00:26 +0400 (EDT)
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Subject: FAB:  Hull cell measurements
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How does one make measurements of the dull region in the Hull cell?  Our 
chemist tells me that, after the copper electroplating bath is 
"adjusted", his Hull cell should read or measure 0 - 3 millimeters.  I 
asked how precisely that length could be measured.  He didn't know for 
sure, but felt the measurement was relatively coarse and might not be 
good to more than one significant figure.  

We are trying to put our processes under SPC, where possible.  We have a 
way to do it for the plating bath, but need a good way to measure Hull 
cell dull region.  Thanks for any suggestions or ideas.  Anyone who wants 
to discuss further is welcome to contact me.

Louis Hart
Quality Assurance Manager
Compunetics
412-858-6117


.
======== Fwd by: Tony King / N ========
Hi Louis,

The hull cell is not an exacting measurement, it is very difficult to impose
SPC quantitatively on a measurement that I consider qualitative.  If
absolutely necessary, are you familiar with the hull cell ruler which
defines burn in terms of current density ?  Perhaps a current density range
could be used to define the control limits.  A more exacting science to
measure plating bath additive levels is the CVS analysis although the scope
of this test is limited.


Tony King
Elexsys International
Nashua, NH
603-886-0066