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March 2012

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Subject:
From:
Joyce Koo <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Joyce Koo <[log in to unmask]>
Date:
Thu, 8 Mar 2012 23:15:35 +0000
Content-Type:
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text/plain (137 lines)
If it is along the edge of a trace that adjacent to opposite bias, it might be conductive dust from the cooling.  Can you check the location if it is near the outlet of the air. Seen similar stuff before. Fuzzy dust balls with dark black colour.
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----- Original Message -----
From: Goodyear, Patrick [mailto:[log in to unmask]]
Sent: Thursday, March 08, 2012 06:08 PM
To: [log in to unmask] <[log in to unmask]>
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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