If your bare board pass ionograph test, the cause would be post pwb process. Sound like corrosion at high temp to me.
--------------------------
Sent using BlackBerry
----- Original Message -----
From: TechNet <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Thu May 07 09:12:49 2009
Subject: [TN] PB Surface Contamination
A cleaned bare PB is exposed to bake or reflow, and comes out with
measurable ionic contamination. The board is dirtier at the surface
after
a heat excursion.
The contamination isn't coming from the oven, handling, or anything
external.
Heat causes something to move from the inside of the board to the
outside.
We haven't done any ion chromatography or other testing yet to
run this down, but has anyone heard of or experienced anything similar?
In our normal process, we clean everything multiple times, but if the
contaminant builds up under solder mask, or in other areas that are
difficult to clean, we could have SIR or corrosion problems around fine
surface features or in high voltage areas.
And if this ionic contamination doesn't just move up to the surface,
but is somehow moving around inside the board, could it collect in
some places and lead to CAF or other problems?
Joe Kane
BAE Systems
Johnson City, NY
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
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
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
---------------------------------------------------------------------
This transmission (including any attachments) may contain confidential information, privileged material (including material protected by the solicitor-client or other applicable privileges), or constitute non-public information. Any use of this information by anyone other than the intended recipient is prohibited. If you have received this transmission in error, please immediately reply to the sender and delete this information from your system. Use, dissemination, distribution, or reproduction of this transmission by unintended recipients is not authorized and may be unlawful.
---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 15.0
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
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
-----------------------------------------------------
|
