From: Paul M Fly Hi all, When we still did our own assembly "in-house" we did as Mike described. The via was tented on the side of the board the BGA was soldered on, and left untented on the bottom to allow test probes to make contact. Now we work with a contract assembler who does not want us to tent vias under a BGA. They claim to have seen this practice cause defects in the past. They will allow us to have soldermask extend onto the via pad, but it is not supposed to cover the drilled hole. As far as I know we never had problems with tented vias under BGA's when we did our own assembly, but working with a contract manufacturer has changed lots of things including this. ************************************ Paul Fly Eastman Kodak Company Engineering Technology Center - PEDT 2nd Fl. Bld. 205 K.P. 2400 Mt. Read Blvd. Rochester, New York 14650-3007 Phone: (716) 726-5670 Fax: (716) 726-0275 E-mail: [log in to unmask] ************************************ "Hiteshew, Michael" <[log in to unmask]> on 04/19/2001 01:08:31 PM Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond to "Hiteshew, Michael" <[log in to unmask]> To: [log in to unmask] cc: (bcc: Paul M Fly/243609/EKC) Subject: Re: [TN] Vias under BGA's - Tented or Not?? Rick, We've been using BGA's for about 3 years. When we started, we queried other divisions advanced packaging groups for guidelines. They suggested tenting vias on the top to prevent bridging. We left the vias untented on the bottom to allow test folks to probe them. Our boards are IR. reflowed. We've never experienced any problems as far as I know. Michael Hiteshew Lockheed Martin NE&SS Marine Systems 410-682-1259 > ---------- > From: Rick Thompson[SMTP:[log in to unmask]] > Reply To: TechNet E-Mail Forum.;Rick Thompson > Sent: Thursday, April 19, 2001 10:46 AM > To: [log in to unmask] > Subject: [TN] Vias under BGA's - Tented or Not?? > > Hi, > > We're running several designs from a new customer with multiple BGA's. The > boards are laid out such that the vias under the BGA's are not soldermask > tented on either side. Our experience with this type of layout is for a > greater tendency to bridge as well as requiring the bottom side to be > masked > prior to any wave solder operation. The customer is resistant to changing > this layout but I'd like to get some other opinions. > > My questions are: What are others doing in terms of PCB layout of BGA's? > Is > the above layout common? What if any trends are there in the industry for > these types of layout? > > Thanks in advance for any insights. > > > > Rick Thompson > Ventura Electronics Assembly > 2655 Park Center Dr. > Simi Valley, CA 93065 > > +1 (805) 584-9858 x-304 voice > +1 (805) 584-1529 fax > [log in to unmask] > > --------------------------------------------------------------------------- ------ 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 ---------------------------------------------------------------------------------