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March 2012

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Subject:
From:
Bev Christian <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Bev Christian <[log in to unmask]>
Date:
Thu, 8 Mar 2012 20:20:15 -0500
Content-Type:
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text/plain (227 lines)
Man those are some nice pictures, Pat.  I would LOVE to be able to look at
them with SEM/EDX or maybe even better X-ray diffraction.  
In decreasing order of likelihood my guesses would be:
CuS or Cu2S
Ag2S

And WAY down the list:
Environmental contamination
lead whiskers (not likely, really looks like dendrites)
Tin pest (Just KIDDING!)
Bev

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wenger, George M.
Sent: Thursday, March 08, 2012 7:29 PM
To: [log in to unmask]
Subject: Re: [TN] Black substance

Dave,

I was thinking the same thing.  If you look at Chen's creep corrosion paper
at APEX last year and the year before he should showed similar corrosion and
while he originally thought it was due to the ImAg as he continued his
evaluations he realized it happens also on OSP boards.

Regards,
George
George M. Wenger
Senior Principal Reliability / FMA Engineer
Andrew Corporation - Wireless Network Solutions
40 Technology Drive, Warren, NJ 07059
(908) 546-4531 Office (732) 309-8964 Mobile
E-mail: [log in to unmask]


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of David D. Hillman
Sent: Thursday, March 08, 2012 6:29 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]>


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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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