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