The rubber bands were outside. And you are right didn't matter much. We did a little experiment. The tarnish was visible within a week.
Charles Caswell
-----Original Message-----
From: Brian Ellis [mailto:[log in to unmask]]
Sent: Wednesday, June 05, 2002 1:17 AM
To: [log in to unmask]
Subject: Re: [TN] Oxidation problem in Silver plated components leads
I'll add a little grist to the mill.
Latex is vulcanised with sulfur to form rubber. Rubber bands, car tyres
and self-adhesive tapes have one thing in common: rubber (the last-named
is a mixture of rubber, unvulcanised latex, resin and low-volatility
organic solvents). Copper also sulfidises, albeit less readily than
silver. Many decades ago I directed a PCB manufacturing plant. Each
sheet of incoming laminate was enveloped in a thick polyethylene bag, to
which was stuck, on the outside, a small self-adhesive label, giving the
essential data of the contents (glass style, laminate thickness, Cu
thickness, date of manufacture and so on). Inevitably, the copper under
the label was blackened with sulfide, despite 0,1 mm of intervening
polyethylene. This just goes to show how poor polyethylene is as a
protection: it is a sieve!
It is not clear from Charles' post whether the rubber bands were inside
or outside the polyethylene but I suggest it would have made no
difference over the long term (say a month or two).
Silver chloride is less of a problem because it is easy to reduce it
back to elemental silver: just expose it to strong light, especially in
the UV! This can be accelerated in a reducing atmosphere (e.g., 2AgCl +
H2 > 2Ag + 2HCl). This was found out by Messrs Ničpce, Daguerre, Fox
Talbot, Lumičre and brother and Eastman about twice as many decades ago
as I am old (and that gives my age away!)!
Brian
"Karnwal, Pankaj" wrote:
>
> Dear all
>
> hello
>
> We are facing a problem that the leads of components getting
> tarnished(oxidized) in store only those which are the silver plated like BNC
> connectors , bridge rectifiers, LED's etc. all are through hole type. The
> humidity Laval varies 43 to 47 % .Is this is sufficient, Pls. suggest the
> special storage for these components .Is this problem comes by defaults ?
> and any method about the oxidized once re - using ?. Thanks in advance for
> your any response.
>
> With regards
> Pankaj Karnwal
> Quality Assurance
> BESL NOIDA
> PH .91-120-4420394-5 EXTN.211
> e mail : <mailto:[log in to unmask]>
> Barco, innovators in image processing
>
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