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