Trevor, I too do not have to much experience with BGA's, but to answer your question, << When talking about component warpage. Are you able to determine, for sure that it is defiantly the component warping and not the PCB? Would it not be easier to warp the PCB, being that the PCB is usually much larger than the component and loaded with many different forces? Minimum deflection in a large plane would have a much greater effect on a smaller plane, would it not?>> The important thing to remember is that there is a aluminum heat sink on top of the BGA. I thing Bogdan was right on the mark where the problem lies. The heat sink is doing it's job by pulling the heat away from the BGA, unfortunately it is at a rate that is to rapid. If anyone out there is a car nut, then you know what I am talking about, aluminum heads and a cast iron engine block :). Bogdan's idea of slowing the cooling process will most likely solve your problem. hope this helps Ted -----Original Message----- From: Trevor Goddard [mailto:[log in to unmask]] Sent: Wednesday, February 28, 2001 7:35 AM To: [log in to unmask] Subject: Re: [TN] Heat-sinked BGA Bridging... Hi guys I don't have a whole lot of experience with trouble shooting BGA problems, but I have been following this conversation and would like to bounce a few things off you experts. First of all in Steve's case where the interior balls are bridging in both reflow and rework, the possibility of component warpage was mentioned. My question on this is, if the component had enough center warpage to bridge the interior balls, would it not pull up on the perimeter balls to create opens? Is there a possibility that the balls are collapsing at different rates? Like in this case more so in the center than the perimeter. If this is the case, could you put an adhesive dot in the center of the component to hold it up? When talking about component warpage. Are you able to determine, for sure that it is defiantly the component warping and not the PCB? Would it not be easier to warp the PCB, being that the PCB is usually much larger than the component and loaded with many different forces? Minimum deflection in a large plane would have a much greater effect on a smaller plane, would it not? Just a couple of thoughts Trevor -----Original Message----- From: Stephen R. Gregory [mailto:[log in to unmask]] Sent: Tuesday, February 27, 2001 4:34 PM To: [log in to unmask] Subject: [TN] Heat-sinked BGA Bridging... Hi all! This topic is a "moldy-oldie", but I've started to experience bridges again with this TI DSP (TMS320C6201GJC200). I've been doing okay up unil recently. We build these boards in work orders of around 25 pieces. Our last run we had 7 boards bridged out of 25!! Sent the boards out to be reworked. I asked that they be x-rayed before and after, and to my surprise after looking at the x-ray images, they were all bridging in the same general area. It's a 4-row periphery BGA, and the bridges are occuring on the inner two rows, around the center of the part, at the same side of the part. What's funny, is that the vendor we use to rework the boards for us is having difficulty as well. We've been asking him to remove, re-ball, and re-install the part, they said they've been having about a 50% success rate doing this...they've been getting the bridges too. They have a nice full-blown SRT BGA rework station and do this for a living. I print 6-mils of paste (square apertures for the BGA), have a Conceptronic HVN-70 which I run: 150 160 170 180 240 150 160 170 180 240 25-in. per min We never have had these problems before...it all started when TI put the heatsink into the top of the part. I've looked at our paste print and it's dead on, placement is dead on too, we verify that with a Ersascope. My question is could there be something wrong with the part? Warping causes bridges at the corners, right? Why would it bridge in the interior rows at the same general area? Thanks in advance! -Steve Gregory- ---------------------------------------------------------------------------- ----- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------- ----- ---------------------------------------------------------------------------- ----- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------