Agilent metal work whisker growth (34420a)

[lowimpedance]

 Owners of Agilent and HP branded meters take note:
When servicing a 34420a at work I discovered extensive metallic crystal growth on the shield plate covering the display PCA.
See pictures, which is the best I could get and that still doesn't show the full extent of the length of the whiskers.
Having found that I opened another Agilent 34420 and an earlier HP one and both had the same issue although to a lesser extent on the HP !.
Out of interest I also checked the inside of a 34401a and the same growth could be seen on the mains transformer casing.
These meters have lived the greater part of their existence in 50% humidity and 21 deg C temps.

 A couple of years back I posted about an Agilent ARB that was killed by these metallic growths getting into the power supply, driven by the internal fan .
I would recommend checking your expensive hobby gear for any 'metallic' issues , if you haven't already !.
 

[Greybeard]

What type of metal plating is it? Zinc on steel?
I've seen such long whiskers (~2-3mm) on electroplated zinc or tin and on sintered silver tracks on ceramic substrate.

What can you do to avoid growing of new whiskers?

[MegaVolt]

What can you do to avoid growing of new whiskers?

Add lead to the alloy. Other methods do not save it. Not even a coat of varnish.

[bd139]

I’ve seen this in a tektronix 7L12 and HP 3478A before. Seems to be tin plated that does it. I brushed them off carefully and cleaned the device out.

[2N3055]

You can clean it and stick kapton film over it, where distance to danger is small....

[Ecogeek]

These whiskers are metal crystalline growth from stressed plating or manufacturing processes and are conductive and fragile, causing intermittent circuit havoc as they break off.
 One soluiton is to conformal coat the PCB to prevent any raining conductors from doing any damage.  It does seem it takes time for the crystals to grow so wiping down regularly is also a solution.
Cheers

[martinr33]

More than you ever wanted to know:

https://nepp.nasa.gov/whisker/

[Mickle T.]

Whisker hell inside a 0.1 ppm INL voltage source