Louis,

Hull cells are great for touchy-feely type analysis of you brightner
concentration, but there are so many other factors which can drive your SPC
chart to madness or meaninglessness.  Air pressure, air temperature, anode
film, test panel preperation, lenght of time in etch, type of etch, no
etch, age of adhesive on the plastic cover sheet, how the panel got located
in the cell, consistant power source, drying technics, the light source
used to read the panel, where on the panel do you take the reading (top
bottom middle maximum), contamination interference (the age old photoresist
as copper brightner debate, iron will make it look shiney also), brightner
out of balance issues (high carrier, low carrier), the bath active or idle.
The list goes on.

Getting to the point:  The cost of getting meaningful SPC data on Hull
Cells would far out weight any benefit in the plating bath.  But if you
insist, double your amperage so you get a larger burn area, 0-3 millimeters
really is to small.  Try to move the feature you are measuring near the
center of the panel.  Reduce the plating time so that the total amp-minutes
remains the same.  Be sure you have enough anode area to support the higher
amperage.

The original message:

>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
>
>
>






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