We have a good deal of bacteria that like to reproduce in our gold 
     plating rinses.  We have had them for years and they have not caused a 
     defect yet.  We have done some lab studies and consulted with some 
     microbiologist at the University of Texas to see what we could do to 
     get rid of them.  There are a number of algaecides and antibiotics 
     that will work but the "bugs" will become resistant over time.  You 
     have to rotate through a treatment reigme to keep their populations in 
     check.  They don't seem to favor the gold baths.  We surmise that the 
     temp and/or cyanide concentration is too high.  The 
     algaecides/antibiotics that we considered were to be used in such low 
     concentrations that we were not concerned with pass-through
     
     We simply use household bleach at 5% v/v on a maintenance schedules.  
     Since the bleach attacks their cell walls, they can not become 
     resistant.
     
     Michael Holan
     Radian International, LLC
     Elecronics Div.
     512/310-4209
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______________________________ Reply Separator _________________________________
Subject: Algaecides/Biocides
Author:  [log in to unmask] at INTERNET
Date:    6/5/96 7:03 PM


Hi everybody!
     
I am looking for some information about reducing algae and bacterial growth 
in process baths.  In the last few weeks, I've had several engineers 
propose some rather nasty chemicals they wanted to add to either gold 
baths, or photodeveloping baths to stop algae from growing.  Does anyone 
else have this problem?  What do you use?  Do you have any concerns about 
pass-through to your POTW?
     
I talked to some guys from DuPont at IPC Expo, and they weren't too 
concerned about pass-through.  However, they were selling photochemistry 
also!! (Sorry about that, John Lott.  I had to get that in.)
     
I would appreciate any information, abuse, snide comments, etc.
     
John Sharp
Merix Corporation
Forest Grove, OR Operations
503-359-9300 (ext. 5-4351)
503-359-1040 FAX
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