In a message dated 96-12-11 19:49:54 EST, you write:

<<   I haven't the foggiest idea what your brown residue is but you could 
      conduct a Fourier Transform Infrared (FTIR) analysis to pinpoint its 
      identity. FTIR analysis is the organic material analysis counterpart 
      to Scanning Electron Microscopy (SEM) analysis for elements. With the 
      FTIR analysis you can compare the residue scan with a phenolic scan, a 
      solder mask scan, and a lacquer scan to see if any match. Good Luck. >>

A good start Dave, but I don't think that FTIR will show much in this case.
 Since the residue is in the solder bath, I don't know of many organic
materials that would survive prolonged exposure to molten solder
temperatures.  The SEM would be a good choice.  He might also try inductively
coupled plasma (ICP), which is often used on plating bath residues.  Another
possibility would be mass spectroscopy, although somewhat expensive.

Doug Pauls
CSL

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