Pat, I have to thank-you for sharing these photos, they are very
interesting!
I have a comment not related to the problem though, how much stuff built
nowadays is expected to be around 40-years from now?
Probably not much...
Steve
-----Original Message-----
From: David D. Hillman
Sent: Thursday, March 08, 2012 6:28 PM
To: [log in to unmask]
Subject: Re: [TN] Black substance
Hi Pat - if the soldering process consumed all of the silver but you had
pad edges that were exposed copper, you could have copper sulfide instead
of silver sulfide as a possible corrosion product. The crystal structures
looked very neat!
Dave
"Goodyear, Patrick" <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
03/08/2012 05:08 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
"Goodyear, Patrick" <[log in to unmask]>
To
<[log in to unmask]>
cc
Subject
Re: [TN] Black substance
The card has been stored in an enviromental room in the chassis, with
controlled humidity, very near the Pacific Ocean. The FUZZ is on the
edges of quite a few traces, as well as almost all of the land edges. I
just finshed going over the board with a microscope at 45X to see if I
could make any sense of it, where I removed the fuzz the copper edges of
he traces show copper. When I cleaned the turret it looks like a
tarnished silver spoon.
Suspect some form of silver dendrite.
Sorry no tires, I'm missing the winged shoe on my name. We sit on a bluff
90 feet above the Pacific, no one else within 5 miles as the seagull
flies.
Thanks for the ideas.
Dave, the plating is most likely silver. The solder is 40-60 I would
guess due to the age of it, these board were built around 1970 give or
take as they are OEM when the power plant was built.
Not sure exactly when 63-37 came around but I didn't run into it until
around 75 when we put together the Pace repair course for the Navy Nukes
in Idaho.
pat
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Woolley, Mark D.
(Mark)
Sent: Thursday, March 08, 2012 2:49 PM
To: [log in to unmask]
Subject: Re: [TN] Black substance
My first thought was silver sulfide.
Were the PWBs stored in a high sulfur gas area? Nearby a tire factory,
oil well or refinery, ot coal fired power plant?
mark
mark
Mark Woolley |PTRL Laboratory | Avaya | 1300 West 120th Ave | Westminster,
CO 80234 USA |
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Thursday, March 08, 2012 3:33 PM
To: [log in to unmask]
Subject: Re: [TN] Black substance
Hi Pat,
Got your pictures and have them posted. Sorry for the delay, but I'm still
running in low gear. Here they are, and all I can say is YIKES!
http://stevezeva.homestead.com/whisker1.JPG
http://stevezeva.homestead.com/whisker2.JPG
http://stevezeva.homestead.com/whisker3.JPG
http://stevezeva.homestead.com/whisker4.JPG
http://stevezeva.homestead.com/whisker5.JPG
These look like the classic silver/copper corrosion from being exposed to
reduced sulfur gasses such as hydrogen sulfide. Here's a good paper that
details it all:
http://chavant.net/new_site/files/pdf/HP_ImAg_Corrosion_Paper_ISTFA_2006
1.pdf
I would be very scared, very, very scared...
Steve
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Thursday, March 08, 2012 11:25 AM
To: [log in to unmask]
Subject: Re: [TN] Black substance
Hi Pat,
Reply to me with the pictures and I'll get them posted...
Steve
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Goodyear, Patrick
Sent: Thursday, March 08, 2012 1:39 PM
To: [log in to unmask]
Subject: [TN] Black substance
Ok got a new one. Found on the plated portion of a turret a black
fuzz,
also on the riveted backside and the plated portions of all of the lands
outside the soldered areas.
It cleans right off with alcohol leaves no residue, is crystalline in
structure and grows away from the metal has a coral like appearance.
I have attached pictures but Steve is off today so don't know who else can
post.
Again a 40 year old board.
Any ideas????
Pat
.
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