Carrie

If you cross section the vias, remove the solder from the hole and look
at the copper barrels at very high magnification (use and SEM if
possible)you may see pin holes in the copper or glass bundles protruding
into the hole. This coupled with moisture in the dielectric which is
normal can create the mechanism. When the board is quickly heated in
assembly (reflow or wave solder) the moisture is pressurized and flows
out through the pin holes into the barrels blowing the molten solder in
the barrels out onto the board.

Best regards

Lee

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Morse, Carrie
Sent: Friday, September 10, 2004 2:33 PM
To: [log in to unmask]
Subject: [TN] Blow Holes -- Where the heck does the moisture come from
anyway?

Just wondering a few things here at 2:30 on Friday Afternoon:

1.  What else causes Blow Holes at wave on TH comps?  Is it primarily
moisture?
2.  Where does the moisture come from?
3.  Are certain board materials more likely to sponge up the moisture in
the air?
4.  Can hole wall quality play a part in contributing to blow holes?

-Carrie

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
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 847-509-9700
ext.5315
-----------------------------------------------------

---------------------------------------------------
Technet Mail List provided as a service by IPC using LISTSERV 1.8e
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 847-509-9700 ext.5315
-----------------------------------------------------