Great! Looking forward to the article. -----Original Message----- From: Patrick Jabbaz [mailto:patrick@xxxxxxxxx] Sent: Thursday, November 11, 2004 10:44 AM To: Ken.Cantrell@xxxxxxxxxxxxxxxx; darshanmehta2k@xxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: RE: [SI-LIST] Re: BGA routing Ken Regarding the VIA in PAD, we just had an IPC meeting regarding the subject, The Speaker Donald A. Carron Director of Technology TTM Technologies, Inc. Santa Ana Division Gave an excellent presentation on the topic VIA-IN-PAD "a new approach" He explained in detail, the new process regarding via fill, to make a long story short, the problems you mentioned regarding VIA In Pad, are a thing of the past, quite a few PWB board fabricators now have the capabilities to have standard drill vias filled with epoxy, and are capped by conductive material to a very flat surface, I have used them, and have looked through a microscope and they are flat, I could not even tell that there was a via present just by looking at the board. Regarding Microvias, it does require a different process, and they are completely filled with conductive material, there is no air trapped inside. I will have the minutes from the meeting publish on IPC Route next week. Inkra Networks Patrick Jabbaz CID Sr Board Layout Eng. 40971 Encyclopedia Circle Fremont, CA 94538 Work (510) 249-4835 Mobile (408) 621-6533 patrick@xxxxxxxxx -----Original Message----- From: Ken Cantrell [mailto:Ken.Cantrell@xxxxxxxxxxxxxxxx] Sent: Thursday, November 11, 2004 8:25 AM To: darshanmehta2k@xxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: BGA routing Darshan, My understanding from the CAD guys is that you get a lot of cold solder joints from outgassing at the via site, even with micro-vias. The fill on a via is never flat, there is a small void. When you flow the BGA on top of that, the trapped gas expands and forms an even larger void in the ball-pad interface. Ken -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Darshan Mehta Sent: Thursday, November 11, 2004 4:41 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] BGA routing Hi All, I have one general question regarding BGA routing. I have seen many BGA boards and nobody puts via exactly below the BGA pad. Most of the times, we generate Fanout outside the BGA pad. Is there is a specific reason for that? I think we can save lot of space if we put via exactly below BGA pad. Is there will be any problem if we put via exactly below the pad of BGA? Thanks. Best Regards, Darshan Mehta --------------------------------- Do you Yahoo!? Check out the new Yahoo! 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