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From [log in to unmask] Wed May 15 16: |
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On Mon, 6 May 1996 01:00:26 -0700 [log in to unmask] wrote:
> From: [log in to unmask]> Date: Mon, 6 May 1996 01:00:26 -0700
> Subject: FAB: Hull cell measurements
> To: [log in to unmask]
>
> 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
>
>
> .
>
Louis:The first thing you need is a Hull Cell ruler.This allows you
to use a linear measurement to determine current density across the face of
the panel.From this you can then correlate the ASF to mm when the Hull Cell
is plated at a given input current.Most acid copper baths are run between 1
and 5 amps input curent on a 267ml Cell.Because the panel is angled in the
cell you can get a good indication of how the bath is plating over a wide
current density range.For example a 3 amp Hull Cell will correspond to a
0-120ASF current density across it's 100mm width.Varying the supply amperage
will allow you to look at different current density resolutions.
So how accurate is this whole thing----? Not very.
The question is what are you trying to control thru statistical
methods?Since you talk about using SPC to control the plating bath is it the
brightner/leveler concentrations?Unfortunately there are many things that can
affect the appearance of the Hull Cell besides the proprietary constituents;
metal content, acid concentration,chloride, temperature,
organics or lack of etc.etc.
Instead of hanging another chart on the wall I'd invest in a
brightner/leveler addition system that automatically doses the bath based on
amperage used.There is nothing wrong in using the Hull Cell as a diagnostic
tool but unless you understand what you're looking at it can lead you down a
false path.
Regards
Michael Barmuta
Staff Engineer
Fluke Corp.
Everett Wa.
(206)356-6076
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