Hi Dwight -
     
     I suggest you investigate your aqueous cleaning solution 
     concentration. I have seen several cases where Alpha 2110 
     saponifier/water solution was not correctly balanced per the product 
     use instructions. The Alpha 2110 saponifier is very basic (a pH of 
     10-11) and it will literally "etch" the solder joints if 
     saponifier/water solution is not balanced. I have seen several 
     instances of "blue" solder joints that are really oxidized due to the 
     cleaning solution etching action. Good Luck.
     
     Dave Hillman
     Rockwell Collins
     [log in to unmask] 


______________________________ Reply Separator _________________________________
Subject: PCB:  Solder Joint issue
Author:  [log in to unmask] at ccmgw1
Date:    3/20/97 7:08 AM


    =20
        TechNet:
    =20
          During our process of cleaning boards with our aqueous cleaner,=20
     the boards are coming out of the aqueous with a "light bluish" colored=
=20
     tint to the solder joint.  This bluish tint can be cleaned off of the=20 
     solder joint with alcohol and a brush but returns when aqueous=20 
     cleaned.  We tried to consider all of the items which might be causing=
=20
     this to occur such as water temperature breaking down the dyes in the=20 
     saponifier, varied conveyor speeds on the aqueous, RO water quality,=20 
     water pressure, redirection of aqueous nozzles, changing saponifier,=20 
     flux solids, etc. =20
    =20
          When this condition was noticed we took several actions to try to=
=20
     pinpoint what was causing this condition.  Following are those actions=
=20
     we have performed:
    =20
        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.
    =20
          The solder we use is Sn63Pb37, made by Alpha Metals.  It is=20
     tested for impurities every 30 operating days.  Solder temperature is=20 
     500 Deg F.  The flux we use is Alpha 615-15 for wave soldering and=20 
     615-25 for hand soldering and pretinning.  Saponifier is either Alpha=20 
     2110 or Vichem 600A by Interflux.  Solution concentrate is 5%.  Wash=20 
     temperature is 160 Deg. F.  Rinse temperature is 180 Deg. F.  Length=20 
     of wash is 12" and conveyor speeds are from 1 ft/min to almost 3.0=20 
     ft/min.  final rinse is Reverse Osmosis and de-ionized.
    =20
          The initial results of the actions above are that the solder=20
     joints look very shiny compared to using the Alpha 2110 saponifier,=20 
     but the light bluish tint still remains.  We are now considering that=20 
     the blue tint may simply be oxidation of the solder joint caused by=20 
     the saponifier and the heat since saponifiers are strong oxidizers.
    =20
          Does anyone have any ideas or previous experience with this=20
     condition?  Thanks for your time.
    =20
     Dwight Nolen
     Manufacturing Quality Engineer/QA Supervisor 
     Frontier Engineering
     405-624-5329  =20
     
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