TECHNET Archives

June 2012

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Phil Nutting <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Phil Nutting <[log in to unmask]>
Date:
Fri, 22 Jun 2012 09:12:59 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (73 lines)
Steve,

Air conditioners here died early yesterday morning.  I never realized I could create such a large pool of sweat on the floor.  Prognosis for repair is Monday.

I looked at your picture.  Stop zooming in on it and you won't notice the gunk.  Like turning up the car stereo so you don't hear the engine noise.

Chuckling,

Phil

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Friday, June 22, 2012 8:59 AM
To: [log in to unmask]
Subject: [TN] White Residues

Morning All,



Boy, I'm looking for it to cool off here this weekend, the last couple of days have been brutal! Heat indexes up around 100 F.!



Anyways, ran into a peculiar white residue issue with a few boards we just got through building. We've never had this problem before (that I've seen) with the solder paste we use here. Here's a photo of the residue on some 20-mil pitch TSSOP leads:



http://stevezeva.homestead.com/White_residue.jpg



The flux in the solder paste is a water soluble RELO, and we normally have no problem cleaning the residues. We use 130 F. DI water in a inline cleaner. Once the residue was noticed, we tried running them through the cleaner again, no luck. We tried a trick I remembered from a while back to remove white residues which was to take some of the same flux and apply it, then heat the board for a bit and run it through the cleaner again, no luck.



It seems the only way to remove it is to mechanically brush it away. Like I said, we've never had this problem before with this solder paste.



The two assemblies that we are seeing this problem with do have a different finish than we normally have on the boards we build. Most all of our boards are gold finished. But one of the boards that we saw the white residue with was finished with Immersion Tin (.ugh!), the other was HASL'ed with Sn/Pb.
Do you think that had anything to do with it? With one assembly the white residues weren't on all the boards, only some of them, which is strange. We hand solder all our through-hole here, and some of the boards may have sat around for a few days longer than others waiting on their through-hole before they were cleaned which may explain why some had white residues, and others didn't.



We only built 34 of these boards and they have already been brushed and cleaned, so I can't get anything analyzed now. But I'm wondering if any of you have an idea of what might have been going on here to cause these residues?



Thanks!



Steve





______________________________________________________________________
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] ______________________________________________________________________


Note: All the information contained in this e-mail and its attachments is proprietary to Kaiser Systems, Inc. and it may not be reproduced without the prior written permission of sender.  If you have received this email in error, please immediately return it to sender and delete the copy you received.



______________________________________________________________________
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] 
______________________________________________________________________

ATOM RSS1 RSS2