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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