Could you be looking at some sort of sapponification result? Or perhaps it may be a pH delta fallout, this would manifest a calcium deposit. If your product is subjected to sudden change in pH, somewhere in the process, it may drop out a previously suspended contaminate.

Sorry to have wasted your time, if you have already thought of this.
Steve

-----Original Message-----
From: d. terstegge [mailto:[log in to unmask]]
Sent: Tuesday, May 01, 2001 11:27 AM
To: [log in to unmask]
Subject: [TN] white residues after cleaning

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

---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
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 delivery of Technet send the following message: SET Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------