I don't believe the Cadmium Oxide is a finish.  I believe it is within the
mass of the contact material.

Gregg

-----Original Message-----
From: Pratap Singh [mailto:[log in to unmask]]
Sent: Monday, January 31, 2005 1:03 PM
To: [log in to unmask]
Subject: Re: [LF] Cadmium in relay & switch contacts - Used to be [LF]
RoHS, Lead-Free and North American regulatory agencies?


Camille,
There are lots of electrical connectors that have no Cadmium. Most
electronic connector contacts are manufactured with beryllium copper as
the spring material over plated with nickel and gold. Only when high
current/voltages are to be used as in power switches and relays, the
cadmium oxide is used to provide a erosion resistant finish. see below
for more details.

> Applications and use of Banned Materials (RoHS)
>
>
>           Cadmium Oxide
>
> Although cadmium has only limited use as a pure metal it forms many
> binary and more complex alloys which have useful properties for many
> commercial applications. The presence of cadmium improves some feature
> of the alloy. Small amounts of cadmium can improve the hardness and
> wear resistance, mechanical strength, fatigue strength, castability
> and electrochemical properties of a number of alloys. Cadmium is added
> principally to alloys based on copper, tin, lead and zinc although
> several others benefit from its presence. Silver electric contacts
> incorporating 10 to 15 per cent cadmium or cadmium oxide are useful in
> many heavy duty electrical applications such as relays, switches and
> thermostats. The presence of cadmium gives some degree of arc
> quenching and improves resistance to material transfer and electric
> erosion.
>
> Cadmium Oxide (CdO) is a chemical compound of cadmium, which is a
> plentiful chemical found on earth. It is fairly evenly distributed in
> the earth's crust and in the oceans. Cadmium has been found to have
> many commercial and industrial uses, such as in dyes for food and
> plastics. Cadmium is a key ingredient in the production of
> rechargeable nickel cadmium batteries and, when alloyed with precious
> metals, Cadmium Oxide improves the performance and life of electrical
> contacts.
>
> Cadmium is a cumulative toxicant. Cadmium levels in the body build
> with each exposure since the human body does not effectively eliminate
> cadmium. Long term exposure to low levels of cadmium poses health
> risks that include kidney and lung disease, and also causes bones to
> become brittle. Cadmium enters the body through ingestion of foods and
> water. It may also enter the body by breathing in airborne particles.
> Water and soil can become contaminated with cadmium by leaching from
> landfills or unregulated disposal sites.
>
> The EPA, FDA, and OSHA have set limits for the presence of and
> exposure to cadmium. The national occupational exposure standard for
> cadmium, cadmium compounds and cadmium oxide fumes set by National
> Occupational Health and Safety Commission (NOHSC) is a time weighted
> average (TWA) of 0.01 mg/m3. The U.S. Department of Health and Human
> Services also believes cadmium and cadmium compounds are carcinogens.
> Cadmium is classified as human carcinogen of Category 2 and as such
> all exposure should be minimized to the lowest levels.
>

_____________________
pratap singh
Tel./Fax: (512) 255-6820
email: [log in to unmask]
www.rampinc.com


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