Hi Ioan, There a several things you can do to prevent the solder wicking down the hole with the current design, and that's where I would focus. 1) Via plug - From opposite of component side, 50~75% of via, nonconductive epoxy. 2) Via fill - From opposite of component side, +2 mils, -10 mils of conductor surface, nonconductive epoxy. 3) Via fill and plate over - Conductive or nonconductive epoxy. No hole in via for SMT. Cost goes up as you go down the list, but you don't need to respin the board, reduced to no solder starvation, and little to no rework. Glenn Disclaimer: Any ideas or opinions expressed here do not necessarily reflect the ideas or opinions of my employer. -----Original Message----- From: Tempea, Ioan [mailto:[log in to unmask]] Sent: Thursday, March 11, 2004 5:30 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 -----------------------------------------------------