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Date: | Thu, 10 Oct 1996 15:59:58 -0500 |
Content-Type: | text/plain |
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Address,
I have several boards types and part numbers that are older than 18
months. They are SMOBC with SnPb coated pads, SMT both sides. Based
on observation two types have been Horizontal HAL and One Vertical HAL
at an angle. Without an XRF, I going to assume 100 microin. on large
pads (>.025 pitch & caps) and 500~800 microin. on smaller pads (.020
pitch). From past experience and several Round Robin Studies these
boards should have a minimum solderability shelf life of 6 months (a
year in some cases). To validate this, I am going to apply solder
paste to the component side, via solder paste stencial, and run
through reflow as if a production panel. If solderability has been
degradated by copper migration or similar through the thin SnPb layer,
there should be signs of dewetting and/or no wetting.
My question: Is this still a valid test and are there other tests
used to verify bareboard solderability? Does the three, six or 12
months periods still apply if the boards are stored properly?
Should I find solderability problems, one corrective action is to
return the bareboards to the supplier for re-soldering and hope the
extra thermal cycle does not affect the board further.
Please advise. Thanks in advance.
p.s. Jack Crawford; I need your new email or will someone pass it
along.
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