Peter
It only seems like a "circus"....
> ----------
> From: [log in to unmask][SMTP:[log in to unmask]]
> Reply To: TechNet E-Mail Forum.;[log in to unmask]
> Sent: Wednesday, March 13, 2002 7:42 PM
> To: [log in to unmask]
> Subject: Re: [TN] Solder Joint Mechanical Stress
>
> 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?
>
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