While I don't disagree with your choice to leave the vias open on one side or the other, it is a little misleading and shouldn't be used as a general rule. There are many things to consider, before you can safely implement that design strategy. Some of them are as follows: * you have complete knowledge and control of your processes and materials * You have a very benign end-use environment * your product is obsolete before it fails * free replacement is more cost effective than design change * you make Christmas toys and they only have to work once on Christmas morning( just make sure you pick them up before watering the tree and don't put the batteries in till just before opening them) If on the other hand you are making Hi-rel or Aerospace product that you have to rework and maintain and may not always be in control of your own destiny, there are only two ways to go. Permanently tent( SMOBC) the vias on both sides or completely plug and cap( or plate over )to protect the integrity of the via and provide the long term reliability that is required. Dewey -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Charles Caswell Sent: Wednesday, September 15, 2004 7:59 AM To: [log in to unmask] Subject: Re: [TN] Question about via masking on BGA pattern... I can agree to this. I suggested covering both sides just because most of our customers question uncovered via's. Not sure why, especially those with specific notes on drawing to leave via's unplugged and not masked. -----Original Message----- From: Jeffrey Bush [mailto:[log in to unmask]] Sent: Wednesday, September 15, 2004 7:56 AM To: [log in to unmask] Subject: Re: [TN] Question about via masking on BGA pattern... I would recommmend the opposite of this - plug from the BGA side and leave the bottom open for testing. Jeffrey Bush Director, Quality Assurance and Technical Support 76 Technology Drive - POB 1890 Brattleboro, Vermont 05302-1890 Tel. 802.257.4571.21 Fax. 802.257.0011 [log in to unmask] http://www.vtcircuits.com -----Original Message----- From: Steve Gregory [mailto:[log in to unmask]] Sent: Wednesday, September 15, 2004 8:44 AM To: [log in to unmask] Subject: [TN] Question about via masking on BGA pattern... Mornin' All! I have a question about solder masking via's in a BGA pattern, and want to see if I'm thinking correctly about this. I think it's a bad idea to leave the via's free from solder mask on the topside of the board beneath the BGA, and tent the bottomside via's. To me, you're just asking for trouble down the road because you'll trap flux residue and all kinds of stuff in the via's that won't be able to be cleaned out well. This is a 676 ball 1.0mm pitch BGA pattern. Am I wrong about this? Thanks! -Steve Gregory- --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------