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6.5 Sealing. The following procedure is suggested as a guide; however, every effort should be made
to utilize the most effective procedure consistent with the state of the art.
a. Evacuate to less than 200 microns.
b. Heat to maximum rated ambient temperature with continued evacuation (see 3.1).
c. Maintain heat and vacuum for 12 hours or longer, continuing the treatment until a maximum
pressure of 80 microns is reached.
d. Turn off heaters and maintain pressure for 4 hours.
e. Close evacuation valve and fill chamber with the desired pressurizing gas.
f. Seal relay before removing from chamber.
6.6 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-HBK-889.
6.6.1 Tin plated finishes. Use of tin plating is prohibited (see 3.3.1.1a). 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 B545-83 (Standard
Specification for Electrodeposited Coating of Tin)."
6.7 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.
6.8 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 silicon 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 time interval between first make of the contact until the uncontrolled making and
breaking of the contact ceases.
Chatter, contact: Externally caused, undesired vibration of mating contacts during which there may or
may not be actual physical contact opening. If there is no actual opening but only a change
in resistance, it is referred to as dynamic resistance.
Coil: One or more windings on 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.
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