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March 1997

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Subject:
From:
"Maguire, James F" <[log in to unmask]>
Date:
Thu, 20 Mar 1997 08:34:10 -0800
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I would add that we've seen similar effects from even from just DI water
(that deionized not distilled).  High resistivity (>~7 Megohm) water is
actually pretty corrosive all by itself.  The addition of cleaning
solvents acts to further accelerate this problem.  We have some photos /
SEMs of this that we've presented at IPC and Nepcon.


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

>----------
>From: 	ddhillma[SMTP:[log in to unmask]]
>Sent: 	Thursday, March 20, 1997 5:34 AM
>To: 	[log in to unmask]
>Cc: 	[log in to unmask]
>Subject: 	Re: PCB:  Solder Joint issue
>
>     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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