I read mail in wrong order, I should add that we had a big "flap" about
"blue solder" and found that ours was indeed (as Dave mentioned) an
etching effect.  We did extensive surface analysis (ESCA, SEM/EDX, FTIR
(extractive and reflective)) and showed (a) no residues (organic,
inorganic, etc) and b) that the "blue" areas were associated with etched
solder (one phase of the eutectic etching preferentially to the other)
where the eutectic structure spacing was ~that of blue light (ie. it
created a surface that would reflect white light as blue).

Cool stuff from analytical standpoint but we tossed a lot of cash
finding it out.  If you need more details of analysis please call.


===============================
Jim Maguire
Senior Principal Engineer
Boeing Defense & Space Group
(206)657-9063     fax 657-8903
Email:  [log in to unmask]
================================

>----------
>From: 	[log in to unmask][SMTP:[log in to unmask]]
>Sent: 	Thursday, March 20, 1997 4:46 AM
>To: 	[log in to unmask]
>Subject: 	PCB:  Solder Joint issue
>
>     
>        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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