Andre,

The powder could simple just be oxides (tin oxides mostly).  The flux will
remove them from the bond area, and the loose oxides will float on the
solder and often end up at the top areas of the solder joint.  The area
untouched by the flux will also have some oxidation.
I was going to make a joke about powdered donut residue, but I realize that
the technet is pretty serious.  Happy Holidays everyone...he he..

Steve A

> -----Original Message-----
> From: Andre Leclair [SMTP:[log in to unmask]]
> Sent: Wednesday,December 19,2001 6:57 AM
> To:   [log in to unmask]
> Subject:      [TN] white powder on leads
>
> Hi All
>
> Here is another residue issue
>
> We have an assembly which has a white residue remaining after wash.
> The board is completely SMT (WS609) using a DI-Wash process,  the board is
> spotless except for one location.  The location is a QFP (from CRONTEL),
> the white powder is on the leads of the IC only.  There is not a spot on
> the PCB.
>
> The Powder dry brushes extremly easily. On a few of the leads ( usually
> about half way up the lead, nver near the joint)after brushing there is
> evidence of flux residue( yellow sort of like Crystal Flux residue) in
> spots.
> We have put a few boards through the Omega with readings lower then
> 2.3microgram/sq.inch.
>
> Could this be something the part manufacture has left/put on the leads? I
> have noticed that the plating is thin on the leads (exposed copper on the
> faces) the leads also look like sheared stock ( exposed copper on the
> sides)
>
> Thanks
> Andre
>
> --------------------------------------------------------------------------
> -------
> 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
> --------------------------------------------------------------------------
> -------

---------------------------------------------------------------------------------
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
---------------------------------------------------------------------------------