Thanks gang for the inputs it helped a lot.   Samples are being sent off for analysis.   Silver dendrites are my guess.

Inge, these are the boards for the instruments that monitor the power levels of a nuclear reactor they cannot be easily replaced, they are part of OEM, they were manufactured 1965 to around 1974 to the then state of the art soldered by hand.  They are single sided, single layer boards, without through plating, all of the runs appear to be plated with solder, there is no conformal coating.   I would expect the solder to be 60/40 and not 63/37 as I believe these were made before the time of 63/37 being widely used.    The boards were manufactured by Westinghouse, copper thickness is on the order of 5 thou. or thicker, all components are through hole.     Most of the "solid state" op amps are 1.5"x2" phenolic bricks made by Philbrick/Nexus (DL-21), all cards operate on +/- 25 vdc supplies.    Storage is in an environmental room with controlled humidity and temperature.     All of the hardware is either anodized, cad, or nickel plated, contacts are heavily gold plated Elco bifurcated contacts, most of the mounting posts are silver plated, most chassis components are aluminum with an anodized finish.

As a sidelight the nuclear program uses a lot of silver plating, this is good from an electronics standpoint but bad from a nuclear standpoint because if the silver is in an area of neutron bombardment it becomes VERY radioactive, contact readings can be on the order of several rem.

pat goodyear
control technician
Diablo Canyon Power Plant


________________________________
From: Inge Hernefjord [mailto:[log in to unmask]]
Sent: Thursday, March 08, 2012 11:15 PM
To: TechNet E-Mail Forum; Goodyear, Patrick
Subject: Re: [TN] Black substance

What is the purpose of your mixing with these antique boards?
My advice is that you perform a EDS or perhaps FTI R analysis of the fragments. Faster way than us guessing.
We know nothing about your products:
-manufacturer
-copper thickness
-number of layers
-finish
-size
-how were they stored?
-what environment?
etc.

Interesting forensic but little foggy

Inge




On 8 March 2012 19:39, Goodyear, Patrick <[log in to unmask]<mailto:[log in to unmask]>> wrote:
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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