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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