There is a test called SERA (Sequential Electrochemical Reduction Analysis) 
which is non-destructive that can be used to predict solderability. The test 
produces a plot of cathode voltage vs. time. The plot reflects the type of 
oxide and the charged passed is a measure of the amount of oxide present. The 
test can be used for HASL and can be used as a presence tester for OSP. 

Contact
ECI
1 Madison St.
East Rutherford, N.J. 07073
201-773-8686



[log in to unmask] Wrote:
| 
|      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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