Was this strength test written into the requirements when the job was taken on? 20 in pounds is quite a torque to apply to an electronic component. Does your customer have any first-hand experience of circus board manufacture? - it's sounds like "no", or he'ld understand for himself why it's a bad idea to perform a test like this. Is it intended to be 100% inspection? The process to stick the heatsinks to the BGA's should have been confirmed as part of a product qualification test, as should the means and method of testing the adhesion. Properly specified, this process can then be passed onto CM's or whoever assembles the boards to repeat. For process monitoring purposes, to ensure adequate adhesion is being maintained, batch sampling can be done, but I wouldn't do it on expensive "live" product - I would load the occasional board with appropriate dummy components, mount the heatsink and test those. If there's a problem, stop and review the processes. Otherwise, what is the test going to prove? Either the heatsink comes off, or the BGA does (especially if it's one of Earl's illigitimate TI things), or they both stay on the board but the solder joints (ball to board or balls to device or both) have been unnecessarily stressed, which is bound to reduce working life by anyone's reasoning - by how much, should have been one of the HALT test results, using a non-torqued set of pieces for comparison. How to change the customer's mind? Ask what qual tests were done and what results were obtained along the lines I suggested above, and judge for yourself if they were adequate. If not explain why you think so, and if he's still adamant about carrying out the test on live product, get him to sign a disclaimer removing your liability for failures now or later for any boards on which this test has been carried out. Can't suggest anything else, but good luck. Peter Carl Ray <carlr.ray@SANMIN To: [log in to unmask] A-SCI.COM> cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Sent by: TechNet Aero/ST Group) <[log in to unmask]> Subject: [TN] Solder Joint Mechanical Stress 03/14/02 12:17 AM Please respond to "TechNet E-Mail Forum."; Please respond to Carl Ray I have a customer who is requiring that I verify the bond strength of a heat sink that is glued to the top of PBGA. The customer has supplied me with a torque tool to verify the strength of the bond between the heat sink and the BGA. I have concerns that testing the strength of the glue bond may affect the solder joint reliability of the BGA. The tool supplied by the customer is set at 20 in pound torque. Any ideas how I can "change" my customer mind? --------------------------------------------------------------------------------- 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 e-mail to [log in to unmask]: SET Technet NOMAIL To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest 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 --------------------------------------------------------------------------------- [This e-mail is confidential and may also be privileged. If you are not the intended recipient, please delete it and notify us immediately; you should not copy or use it for any purpose, nor disclose its contents to any other person. Thank you.] --------------------------------------------------------------------------------- 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 e-mail to [log in to unmask]: SET Technet NOMAIL To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest 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 ---------------------------------------------------------------------------------