The ground rules for selecting components are:
(1) Microcircuits are in accordance with MIL-M-38510 Class B Standard
Military Drawing (SMD) or are procured to Source Control Drawings,
Specification Control Drawings and Selected Item Drawings that provide the
same or a higher reliability level. Specification control drawings are
preferred over source control drawings.
(2) Diodes and transistors are JANTX (or JANTXV) or are procured to Source
Control Drawings, Specification Control Drawings and Selected Item Drawings
that provide the same or a higher reliability level. Specification control
drawings are preferred over source control drawings.
(3) Other discrete components are P-level or higher Established Reliability
(ER) components or equivalent.
(4) Magnetic components should be equivalent to MIL-T-27 insulation Class S
or better, with the addition of a 100% thermal-shock screen.
(5) Wet slug tantalum capacitors, except type CLR 79 per MIL-C-39006 /22
and /25, are not allowed in the design of militarized power supplies since
they are prone to leak, resulting in corrosion and power supply
There are special criteria for improving reliability for selected types of
components. These are as follows:
(1) Aluminum Electrolytic Capacitors
These devices are susceptible to external contaminants during the assembly
of the power supply, primarily by the cleaning agents. The failure mechanism
is an internal short from chloride contamination that is a long- term, time
and temperature process. Specifying epoxy end-seals minimizes or eliminates
these external contaminants inside the capacitors.
(2) Power Semiconductors
Avoid the use of packages with electronically hot cases and use isolated
cases where practical. Hot case devices require well thought out isolation
techniques and additional assembly steps that are susceptible to