Warren, some board shops are able to fill the vias with a conductive paste and then plate over the top. This avoids the problem of a partially plugged via while giving you a surface to probe. The BGA side could use soldermask to cover the plugged via. Good luck, Terri > ---------- > From: [log in to unmask][SMTP:[log in to unmask]] > Reply To: TechNet E-Mail Forum. > Sent: Friday, November 09, 2001 3:23 PM > To: [log in to unmask] > Subject: [TN] BGA Via's to tent or cover or not? > > I have seen different ways to address masking small vias (<13mils) under > BGA. > cover them with mask prior to HASL top an bottom ( can't we need to ict > probe > bottom) > cover top with mask prior to HASL (could cause trapped chemistry in via > and > will not allow solder thru, we like the effect on thermal reliability > for > environmental extremes) > leave the mask opening only slightly larger than via (tent) > do a post hasl mask to cover over via ( causes 2x the thickness of mask > at > overlap, could be a problem with uBGA ball only 14mils dia to start > with may > not touch pads) > > > We use #3 but have problems with rework leaving solder plugged vias that > look > like shorts in xray. > > If there are some other ideas or thoughts on how to design the via masking > under > the BGAs I would like input. Thanks! > > -------------------------------------------------------------------------- > ------- > 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 ---------------------------------------------------------------------------------