Hi, Daan,
If you still have residues on the boards after cleaning the boards, it
rather sounds like your cleaning process isn't up to the job. I've also
long held the cynical opinion that Omegameters and Ionographs only measure
how good your cleaning system is and not how clean your board is. If the
cleanliness testing apparatus can remove any further contamination after
the cleaning operation in order to produce a reading, it only proves that
the tester is better at cleaning the board than the cleaning process is,
but there is still no guarantee that your board will be truly clean even
so, which is why you need SIR and other such tests as well.
You don't need as much as a few grams to test the chemistry of the
residues. If you can spare it, send a sample board to a good Chem lab who
will be able to tell you what you're dealing with. The last company I was
with had its own lab, so I can't recommend an independant one for you.
Sorry. I can give you the address of the in-house lab off-line, though, if
you're interested. It's in Edinburgh, Scotland (or it was).
Pete Duncan
"d. terstegge"
<[log in to unmask] To: [log in to unmask]
GROUP.COM> cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
Sent by: TechNet Subject: [TN] white residues after cleaning
<[log in to unmask]>
05/01/01 11:26 PM
Please respond to
"TechNet E-Mail Forum.";
Please respond to "d.
terstegge"
Hello Technet,
We've got some expensive boards here with white residues after cleaning.
Most of it is invisible for the naked eye (conforming IPC class 3
standards), but each board has a few small spots that are visible (if you
look really good).
Now the customer wants proof of what this residue is. Not because they can
see the residue, but because they know it's there.
These are double reflow boards, soldered with RMA solderpaste. After each
soldering step the boards are cleaned with Axarel 32 and rinsed with
deionised water.
Our ionograph shows that there is hardly any ionic contamination on these
products.
Some questions:
1) When there's so little residue present, will it be possible to do an
analyses ? To collect a few grams I'd have to scrape the residues of
hundreds of boards !
2) What kind of analyses should be done ?
3) Any recommendations on where to have the analyses done ? Locations in
Western Europe are prefered.
All answers are more than welcome.
Kind regards,
Daan Terstegge
Thales Communications
Unclassified mail
Personal Website: http://www.smtinfo.net
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