MIL-PRF-28750F
APPENDIX B
B.3. REQUIREMENTS
B.3.1 General requirements.
B.3.1.1 Relay class. The manufacturer shall establish a component evaluation system based on the class of the
relay. There are two classes of relays defined in this specification: Class I which uses discrete device technology;
and class II which uses hybrid technology. Class II requires the manufacturer to meet the requirements as specified
herein.
B.3.1.2 Alternative systems requirements. The manufacturer has the option to use alternative methods for
achieving the general requirements of the component evaluation system specified herein. There are two methods for
approving alternative system requirements.
a.
Approval by the qualifying activity of proposals by the manufacturer.
b.
When the qualifying activity has approved the establishment of a Technology Review Board (TRB) in
accordance with MIL-STD-790, the TRB can approve alternative systems.
B.3.1.3 Pure tin. The use of pure tin, as an underplate or final finish, is prohibited both internally and externally.
Tin content of oscillator components and solder shall not exceed 97 percent, by mass. Tin shall be alloyed with a
minimum of 3 percent lead, by mass.
(NOTE) The use of alloys with tin content greater than 97 percent, by mass, may exhibit tin whisker growth problems
after manufacture. Tin whiskers may occur anytime from a day to years after manufacture and can develop under
typical operating conditions, on products that use such materials. Conformal coatings applied over top of a whisker-
prone surface will not prevent the formation of in whiskers. Alloys of 3 percent lead, by mass, have shown to inhibit
growth of tin whiskers. For additional information on this matter, refer to ASTM-B545 (Standard Specification for
Electrodeposited Coatings of Tin).
B.3.2 SSR element evaluation requirements. Herein, "SSR" refers to the hybrid or multichip microcircuit and
hybrid/integrated circuits. Four phases of SSR element evaluation are required (see table B-I).
TABLE B-I. SSR element evaluation summary.
Reference
Requirement
paragraph
Table
Microcircuit and semiconductor dice
Passive elements
Ceramic substrate printed wiring
Process control
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