Hi,



I finally received my little scale with .01g resolution. Not a lot but good
enough for government work! J



So I took a small board I make, 2 x 2 inches, weighted, rinsed, shook off
and air gunned. (26cm sq)

 See:  www.kondner.com/files/smallbrd.jpg



Initial Weight:                   17.81 gram

After Rinse and shake: 18.00

After blow off:                 17.83



After blow off I had .02g of water. Given my poor scale resolution let say
.03g or .03ml.



After the board dried some I noticed it was down to 17.80. I must have
removed some dust.



Assuming really poor rinse water at 100mg of NaCl equiv per L  we can expect
3 * 10**-6 g or 3 ug on the 26 cm sq PCB. Actually the surface area with the
second side and parts is probably several time that but let's use just the
two sides of the PCB or 52 cm sq.



Wow even without the water blow off the tap water is a non-issue. If I
simply rinse in distilled I am fine. Good, I can trash the blow off process
if rinse in distilled.



3ug / 52  = .058 ug / cm sq



Holy Cow, did I get all the conversions and math right?



Actually the final water related remaining contamination is probably 10% of
that as most tap water is cleaner and not all dissolved solids ate as ionic
as NaCl.



The normal NaCl found in epoxy laminates or uncured solder mask and silk
screen ink Ionics are probably more of a problem.





Summary:



Rinse water quality is only a TINY fraction of what goes into total board
cleanliness.



It is not the quality of the rinse water. The quality of the wash, getting
the wash material FLOWING under parts is the killer. And getting the
contaminated wash water removed is VERY important. As for the nature of the
rinse water it is a complete don't care.



Bob K.



OK: Tear into me. I saw the movie "The Grey" with my son over the weekend. I
am ready to be attacked by a pack of wolves. J









______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 16.0
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL)
To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest
Search the archives of previous posts at: http://listserv.ipc.org/archives
For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------