Yesterday, I sent out a message about the message on TechNet about reducing
rinse water flowrates.  When I sent out a companion message on ComplianceNet
I failed to include my original TechNet message. So here it is, for those
who are not subscribed to TechNet (like me!).


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Several people have forwarded to me a message about reducing rinse water 
flowrates from the TechNet.  So here is what I know:
          
At the May 1995 IPC Expo in San Diego, Larry Lemke of Sheldahl (Longmont, CO) 
gave a talk on Environmentally Conscious Mfg of PWBs.  During his talk, he 
gave out some information about triple-cascade rinsing and some conductivity 
requirements.  The cleanest water is injected into the final rinse (cell #3), 
and overflows into cell #2, then into cell #1.  The DI water injected into 
cell #3 is 1-2 micromho (500,000 ohms to 1 Meg-Ohm).  This injection occurs 
when the conductivity of cell #3 reaches 10 micromhos (100,000 ohms).  Cell 
#2's conductivity is typically 14 micromhos, and cell #1's conductivity is
16 to 18 micromhos.
          
Our DI water is normally 16 to 18 Meg-Ohms, which is probably the typical 
conductivity (or actually resistivity) of everyone's DI water (that's just 
what you get with DI columns).  Larry's work at Sheldahl seems to say that you 
can get by with basically Reverse Osmosis-quality water.  Our RO system 
upstream of our DI beds puts out 500,000 ohm water.  However, it would be best 
to talk to Larry, and see how things are working out with those conductivity 
requirements.  At the time of his talk, the Longmont facility was in low 
production mode, and maybe the rampup has changed things somewhat. If you need 
a copy of the paper that Larry published in the Expo proceedings, e-mail me 
back your fax number.
          
John Sharp
Merix Corporation, Forest Grove, OR
503-359-9300 (ext. 5-4351)
503-359-1040 FAX
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