TechNet:
     
          During our process of cleaning boards with our aqueous cleaner, 
     the boards are coming out of the aqueous with a "light bluish" colored 
     tint to the solder joint.  This bluish tint can be cleaned off of the 
     solder joint with alcohol and a brush but returns when aqueous 
     cleaned.  We tried to consider all of the items which might be causing 
     this to occur such as water temperature breaking down the dyes in the 
     saponifier, varied conveyor speeds on the aqueous, RO water quality, 
     water pressure, redirection of aqueous nozzles, changing saponifier, 
     flux solids, etc.  
     
          When this condition was noticed we took several actions to try to 
     pinpoint what was causing this condition.  Following are those actions 
     we have performed:
     
        1.  Draining of the Aqueous machine.
        2.  Thorough cleaning of the machine.
        3.  Refill of machine with Alpha 2110 saponifier.
        4.  New membranes for the RO water system.
        5.  Varied conveyor speeds.
        6.  Varied water pressure.
        7.  Lowered water temperature from 180 to 160.
        8.  Redirection of water nozzles.
        9.  Changing of solids in our flux from 25% to 15%
       10.  Changing to a dyless saponifier by Interflux (Vichem 600A).
       11.  Added de-ionizer.
     
          The solder we use is Sn63Pb37, made by Alpha Metals.  It is 
     tested for impurities every 30 operating days.  Solder temperature is 
     500 Deg F.  The flux we use is Alpha 615-15 for wave soldering and 
     615-25 for hand soldering and pretinning.  Saponifier is either Alpha 
     2110 or Vichem 600A by Interflux.  Solution concentrate is 5%.  Wash 
     temperature is 160 Deg. F.  Rinse temperature is 180 Deg. F.  Length 
     of wash is 12" and conveyor speeds are from 1 ft/min to almost 3.0 
     ft/min.  final rinse is Reverse Osmosis and de-ionized.
     
          The initial results of the actions above are that the solder 
     joints look very shiny compared to using the Alpha 2110 saponifier, 
     but the light bluish tint still remains.  We are now considering that 
     the blue tint may simply be oxidation of the solder joint caused by 
     the saponifier and the heat since saponifiers are strong oxidizers.
     
          Does anyone have any ideas or previous experience with this 
     condition?  Thanks for your time.
     
     Dwight Nolen
     Manufacturing Quality Engineer/QA Supervisor
     Frontier Engineering
     405-624-5329   

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