MIL-PRF-28776F
6.7 Intermetallic contact. The finishing of metallic areas to be placed in intimate contact by assembly presents a
special problem, since intermetallic contact of dissimilar metals results in electrolytic couples which promote corrosion
through galvanic action. To provide the required corrosion protection, intermetallic couples are restricted to those
permitted by MIL-STD-889.
6.7.1 Tin plated finishes. Use of tin plating is prohibited (see 3.4.1a). Use of tin finishes can result in tin whisker
growth. Tin whisker growth can result in adverse effects on the operation of electronic equipment systems. For
additional information on this matter, refer to ASTM B545 (Electrodeposited Coating of Tin).
6.8 Fixturing losses. It is known that there is inherent resistance in sockets, wiring, etc.. The qualifying activity will
evaluate the manufacturer's system to determine conformance to specification requirements.
6.9 Environmentally preferable material. Environmentally preferable materials should be used to the maximum
extent possible to meet the requirements of this specification. As of the dating of this document, the U.S.
Environmentally Protection Agency (EPA) is focusing efforts on reducing 31 priority chemicals. The list of chemicals
and additional information is available on their website at https://www.epa.gov/osw/hazard/wastemin/priority.htm.
Included in the list of 31 priority chemicals are cadmium, lead, and mercury. Use of the materials on the list should
be minimized or eliminated unless needed to meet the requirements specified herein (see section 3).
6.10 Glossary. The definitions listed below are not a complete glossary of relay terminology, but rather are
intended as definitions of the technical terms as applied within the specification.
Adjunct sealant: Any hydrocarbon or silicone material used on the exterior of the unit to improve the hermeticity of a
hermetically sealed relay.
Bifilar winding: Two or more windings with the wire of each winding alongside the other, matching turn for turn; may
be either inductive or noninductive.
Bounce time: The interval between first make of the contact until the uncontrolled making and breaking of the contact
ceases.
Chatter, contact: The undesired opening of mating contacts resulting from uncompensated ac operation, or from
external shock and vibration.
Coil: One or more windings of a common form.
Contacts: The current-carrying parts of a relay that open or close electrical circuits.
Contact, bifurcated: A forked or branched, contacting member so formed or arranged, as to provide dual contacting.
Contact, closed: A normally-closed contact with the relay released is a closed contact. A normally-open contact with
the relay operated is a closed contact.
Contact, open: A normally-closed contact with the relay operated is an open contact. A normally-open contact with
the relay released is an open contact.
Contact arrangement: The combination of contact forms that make up the entire relay switching structure.
Contact bounce: Intermittent opening of contacts after initial closure due to contact impact.
Contact force: The force exerted by a movable contact against a mating contact when the contacts are closed.
Contact gap: The distance between a pair of mating relay contacts when the contacts are open.
Contact weld: A contact failure due to fusing of closed contacts, resulting in their failure to open.
Control signal: A voltage or current applied to the relay input and used to control (turn-on and turn-off) the hybrid
relay.
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