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