On Mon, 22 Apr 1996 22:38:52 -0700 [log in to unmask] wrote:

> From: [log in to unmask]> Date: Mon, 22 Apr 1996 22:38:52 -0700
> Subject: Reducing Rinse Water Flow Rates
> To: [log in to unmask]
> 
> Our printed circuit manufacturing facility is currently investigating ways 
to
> reduce the amount of water used in its rinsing operations.  I understand 
that
> conductivity meters could be used to ascertain the amount of contamination
> within the rinse water; however, is there a predefined limitation as to the
> amount of contamination that would be considered acceptable before product
> quality would be jeopardized.  In other words are there any established
> guidelines to follow when attempting to regulate rinse water flow rates 
using
> conductivity as the basis for water quality.  
> 
> Any assistance regarding water conservation would be greatly appreciated. 
> 
									
									
	TSmith:There is not just one answer to this question.It depends where 
in the process you are rinsing and what you are rinsing.For example you may 
want 2-3micromhos or less of conductivity for a final rinse after HAL.This 
would be overkill for a rinse after microetch prior to acid copper plate.	
									
	Some issues to consider in cojunction with some of the very good 
earlier posting are:							
		1. Are you using counterflow rinsing			
		2.What is the TDS and conductivity of your supply water	
		3.What is the temp. and GPM of the rinse water		
		4.Are work drain times established and repeatable	
		5.What is the production rate/loading/time between loads	
		6.What is the amount of drag-in contamination you can	
		  tolerate in subsequent process steps			
		7.What is the purpose of the rinse,is it to prevent dragging	
		  contamination chemistry down line or to leave the board	
		  surface in a clean state				
		8.Is metal the only concern or are organics an issue	
									
			ETC. ETC.ETC.Etc.etc.etc.			
									
	There was a very good article written by Marshall Gurian in PC Fab	
May 1982,a little old but still very applicable.If you can't locate it I can 
FAX you a copy.								
									
	Remember conductivity probes work well on metal bearing rinses but 
not very well with cleaners and weak acid chemistries and the like.	
									
	As a point of reference we are running conductivity probes from the 
Myron L Co. (619)438-2021.These have been in place 6+ yrs. and go by the name 
Controlstik.They are used on our electroplating and microetch rinses.These 
are 3GPM double counterflow immersion rinses.Conductivity settings range from 
500-2000 micromhos depending on the process chemistry.			
									
									
					Regards				
					Michael Barmuta			
					Staff Engineer			
					Fluke Corp.			
					Everett Wa.			
					206 356-6076