Good point, we have reworked boards made from exotic materials that did try to bulge locally under the BGA during rework. But our solution was to reflow the entire assembly. Even temperatures on accross the board eliminated the localized swelling. Guy Ramsey American Competitiveness Institute Senior Lab Technician / Instructor 610 362-1200 ext 107 -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of Trevor Goddard Sent: Wednesday, February 28, 2001 8:35 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 --------------------------------------------------------------------------------- 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 ---------------------------------------------------------------------------------