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Date: | Thu, 20 Mar 1997 08:34:10 -0800 |
Content-Type: | text/plain |
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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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