MIL-DTL-3950J
3.4.1 Metals. All metal parts, other than current-carrying parts, shall be of corrosion-resistant material,
or shall be suitably protected to resist corrosion. Paint is not acceptable for corrosion protection. Ferrous
material shall not be used for current-carrying parts.
3.4.1.1 Dissimilar metals. When dissimilar metals are used in intimate contact with each other,
protection against electrolysis and corrosion shall be provided. The use of dissimilar metals which, in
contact, tend toward active electrolytic corrosion (particularly brass, copper, or steel used in contact with
aluminum or aluminum alloy) is not acceptable. However, metal plating or metal spraying of dissimilar
base metals to provide similar or suitable abutting surfaces is permitted. The use of dissimilar metals
separated by a suitable insulating material is also permitted. For additional information and guidance on
dissimilar metals see 6.7.
3.4.1.2 Pure tin. The use of pure tin, as an underplate or final finish, is prohibited both internally and
externally. Tin content of switch components and solder shall not exceed 97 percent, by mass. Tin shall
be alloyed with a minimum of 3 percent lead, by mass (see 6.9). The only exception allowed is if the pure
tin is used on non-current carrying parts and said component is completely isolated from all current
carrying parts by materials that are not electrically conductive.
3.4.2 Plastic materials. Unless otherwise specified (see 3.1), molded plastic material shall conform to
ASTM D 5948-96. Stacked laminations shall not be used for the switch body. Other types of plastic
materials may be used provided the manufacturer submits acceptable evidence of performance to the
qualifying activity during the qualification test program on the submitted product. The plastic material
used shall be inert or fungus resistant in accordance with ASTM G-21 plastic material used in all external
switch parts and enclosures shall be tested in accordance with UL94 and classified as 94V-0; this
requirement applies to all materials for external parts and enclosures regardless of whether the material
used is acquired to a specification or not.
3.4.3 Elastomer seals. The material for elastomer seals shall be silicone rubber in accordance with
A-A-59588. Other types of silicone rubber may be used provided the manufacturer submits acceptable
evidence of performance to the preparing activity during the qualification test program on the submitted
product.
3.5 Interface and physical dimension requirements. Switches shall be of the interface and physical
3.5.1 Toggle lever. The toggle lever shall be metal, shall have a lusterless finish, and shall be
insulated from all current-carrying parts.
3.5.2 Attitude. Switches shall be constructed to assure proper operation when mounted in any
position.
3.5.3 Terminals. Terminals shall be as specified (see 3.1). Only the number of terminals required to
accomplish the circuit characteristic shall be furnished.
3.5.3.1 Solderable terminals. Solderable terminals shall be treated to facilitate soldering. Silver plating
shall not be used as the external coating. When gold plating is used because the terminals are integral
with the gold contacts, its thickness shall be a minimum of 30 millionths of an inch and a maximum of
100 millionths of an inch. Terminals shall be designed so that wires can be mechanically secured prior to
soldering. Terminals may be tapped or drilled after coating.
3.5.3.2 Screw terminals. Screw terminals shall be provided with the hardware specified (see 3.1 and
the appendix herein).
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