Could you please elaborate further on your statement "Given what's coming out about voids now....." Is there new research showing better/worse reliability for larger voids? Looking forward to more information. Pete Barton ===== Original Message from [log in to unmask] (TechNet E-Mail Forum.) at 11/03/04 19:03 >Joe > >I was on the AT&T group that did some VIP for BGAs. We produced what we >called "lead balloons." Mostly just BIG single voids. (Bob's point about >height is also well taken.) > >They were so dramatic looking we didn't reliability test them. > >Given what's coming out about voids now I wish we would have! I think it was >a great (and lost) opportunity to look a extreme voids and telecom >reliability. > >Greg > > >-----Original Message----- >From: Furrow, Robert Gordon (Bob) [mailto:[log in to unmask]] >Sent: Thursday, March 11, 2004 10:42 AM >To: [log in to unmask] >Subject: Re: [TN] Reliability of via in pad > > >Joe, > >Fortunately we have no experience with VIP on BGA or CSP pads. Due to >concerns about solder joint height we never allowed VIPs in those pads. > >Thanks, >Robert Furrow >Printed Circuit Board Engineer >Supply Chain Networks >Lucent Technologies >978-682-2260 [log in to unmask] > > >-----Original Message----- >From: Macko, Joe @ IEC [mailto:[log in to unmask]] >Sent: Thursday, March 11, 2004 1:33 PM >To: 'TechNet E-Mail Forum.'; 'Furrow, Robert Gordon (Bob)' >Subject: RE: [TN] Reliability of via in pad > > >Robert, > >What has been your experience with VIP for BGA pads? I have seen them >contribute significantly to voiding. Look forward to your response. > >joe > >-----Original Message----- >From: Furrow, Robert Gordon (Bob) [mailto:[log in to unmask]] >Sent: Thursday, March 11, 2004 10:15 AM >To: [log in to unmask] >Subject: Re: [TN] Reliability of via in pad > > >Hi Ioan, > >We have designed boards with via in pad (VIP) for well over a decade and >assuming you have a good solder joint, reliability in Telecom product has >not been a problem. We did not evaluate for automotive applications. Having >said that, let me also say that VIP is great for the designer but a royal >pain for the assembler. It was only intended for designs where absolutely >necessary, but it quickly got out of hand when designers realized that by >checking off "yes" to VIP, the computer time required to route a board was >significantly reduced. It essentially became a defacto standard on many of >our designs. Some lessons learned were that you need to carefully control >the finished holes size. If you specify a 10 mil nominal finished hole there >is a world of difference between a 13 mil received and one that is truly 10 >mils. Also, as discrete sizes get to 0603 you need to require a smaller >finished hole. We used enlarged stencil openings as well as step stencils in >order to get the n! > eeded solder paste applied. Another issue is to make sure that the via is >not shared on both sides of the board with discretes or other surface mount >pads. I would be glad to discuss further offline if you have additional >questions or comments. We also did some work with plugging the vias, but >found it not to be necessary if the surface mount process was optimized, so >the cost wasn't justified. It is a slippery slope, as once you get >proficient at one set of pad sizes, the designers are going to want to >expand the use of VIP to other sizes and feature types. > >Thanks, >Robert Furrow >Printed Circuit Board Engineer >Supply Chain Networks >Lucent Technologies >978-682-2260 [log in to unmask] > > >-----Original Message----- >From: Tempea, Ioan [mailto:[log in to unmask]] >Sent: Thursday, March 11, 2004 8:30 AM >To: [log in to unmask] >Subject: [TN] Reliability of via in pad > > >Hi Technos, > >I've got an annoying one. I am looking at an assembly for automotive, which >has 100+ SMT resistor and capacitor pads with vias in them, on both sides of >the 9 layer PCB. Now, I know that I will expect solder starvation, since the >solder will flow into the via. I could eventually patch this by plugging the >vias on the opposite sides of the concerned pads and make slightly bigger >apertures in the stencil. Or even charge more and touch-up all the opens. > >But what does via in pad mean in terms of reliability? > >1. There will be voids, which are going to become even more important on >lead-free (the customer is after the european market). Any reliability >concerns related to that? Once again, I'm talking automotive. > >2. PTH reliability. 100+ vias will have totally random quantities of solder >in them. I remember one of Werner's contributions (Entschuldigung Herr >Engelmeier, aber... I lost the e-mail) saying that less than 50% fill >degrades the reliability. Am I right? > >A good fix would be, in case they refuse to re-spin the board and move the >vias, to fill the holes. What kind of specification should I issue for >filling, in terms of material and fill percentage? > >Any other concerns? > >Thanks, >Ioan > >--------------------------------------------------- >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 >----------------------------------------------------- ----------------------------------------------------------------------- Peter Barton Senior Process Eng ACW Technology Ltd Dinas Isaf West Tonypandy Mid Glamorgan. CF40 1XX Wales Tel: 01443 425200 Fax: 023 8048 4882 International Tel : +44 1443 425200 International Fax : +44 23 8048 4882 Website/URL: www.acw.co.uk --------------------------------------------------- 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 -----------------------------------------------------