In a message dated 12/14/98 7:35:23 AM Pacific Standard Time, [log in to unmask] writes: << From: [log in to unmask] [SMTP:[log in to unmask]] Sent: Friday, December 11, 1998 6:23 PM To: [log in to unmask] Subject: [TN] Warped boards at PCI connector? To technet I have this board that is 18 by 14 though hole and SMT. After reflow the board looks good not warped. Once assembled and sent to wave the board warps, only around the PCI connectors. It warps so bad I don't have any lead protrusion. I have tried to run this board many ways fast slow and minimal preheat. I still have this problem. Has anyone ran into this problem before? Is this common around PCI connectors? I recall this happening once before many years ago, I resolved it by tacking down the edge and middle of the connectors then masking. Is this the only fix? Any other suggestions Thanks in advance Angie >> Hi Angie, Sounds like that there's something a lot different about the board in close around your PCI connectors as far as copper content in the inner layers compared to the rest of the board, are there heavy power or ground planes everywhere else except where the connectors are? Hold the board up to the light and look through it. Another thing that could be adding to things is possibly a very tight fit of the plastic guide pins that usually are on the bottom of the connector...at least on the connectors I've worked with before had them.(I have't had to wave any PCI connectors in a while). The reason I say it might be the hole diameter for the pins on the connector, is that I ran into something like this before at another place I worked at. We got one lot of boards from one of our customers that had the hole diameters swapped for the two plastic pins on the connector (usually one pin was larger than the other so you couldn't put them in backwards), how that happened I don't know. But what we wound-up doing was having to clip the pins off on the connector. We had been doing the same thing as what you talked about...tack-soldering a few pins on the ends and center before wave because of the warping. But found with the pins gone, the warping problem was eliminated, which caused me to realize what had been causing the problem. The CTE of the connector material was a lot less than the board, and the pins were constraining the board when it needed to move as it expanded. We asked our customer to increase the hole diameter a tad, and we didn't have to tack the connectors down from then on. The pins are there to take the force of insertion and removal of cards instead of the solder joints bearing the brunt of it, so be aware of that. We had to clip them so we could use the connectors, otherwise the customer would have had to scrap the fabs. But you might want to try an experiment on a solder sample fab of the ones you're running and some connectors by doing the same thing...clipping the pins and not tack-soldering the connector. Then you can ask for bigger holes on the fabs too. Hope this helps in some way... -Steve Gregory- ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################