MIL-PRF-83421 Capacitors, Fixed, Metallized, Plastic Film Dielectric, \(Dc, Ac, Or Dc And Ac\), Hermetically Sealed In Metal Cases Or Ceramic Cases, Established Reliability, General Specification ForThis specification covers the general requirements for established reliability \(ER\), metallized plastic film dielectric, fixed capacitors, hermetically sealed in metal or ceramic cases. Capacitors covered by this specification have failure rate levels \(FRL\) established in accordance with MIL-STD-690. The reliability for each level is identified by a symbol in accordance with table I. These FRLs are established at a 90 percent confidence level and maintained at a 10 percent producer\'s risk and, unless otherwise specified \(see 3.1\), are based on life tests performed at maximum rated voltage at maximum rated temperature. Unless otherwise specified \(see 3.1\), an acceleration factor of 5:1 has been used to relate life-test data obtained at 140 percent of rated voltage at maximum rated temperature, to rated voltage at maximum rated temperature \(see 6.1\). A part per million \(PPM\) quality system is used for documenting and reporting the average outgoing quality of capacitors supplied to this specification. Statistical process control \(SPC\) techniques are required in the manufacturing process to minimize variation in production of capacitors supplied to the requirements of this specification.

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MIL-PRF-83421E

3.4 Material. The material shall be as specified herein. However, when a definite material is not specified, a

material shall be used which will enable the capacitors to meet the performance requirements of this specification.

Acceptance or approval of any constituent material shall not be construed as a guaranty of the acceptance of the

finished product.

3.4.1 Impregnant. The impregnant shall be chemically inactive with respect to the capacitor element and the case.

The impregnant, either in the state of original application or as a result of having aged, shall have no adverse effect

on the performance of the capacitor. For liquid-impregnated capacitors, the same material shall be used for

impregnating as is used for filling.

3.4.2 Metals. Metals shall be of a corrosion-resistant type or shall be plated or treated to resist corrosion. Silver

plating shall not be used in any external portions of these capacitors.

3.4.2.1 Dissimilar metals. Where dissimilar metals are used in intimate contact with each other, provision shall be

made to provide protection against electrolysis and corrosion. The use of dissimilar metals in contact, which may

tend toward active electrolytic corrosion (particularly brass, copper, or steel used in contact with aluminum or

aluminum alloy), shall not be acceptable. However, metal plating or metal spraying of dissimilar metals to base

metals to provide similar or suitable abutting surfaces will be permitted (for example, the spraying of copper on

aluminum for soldering operations will be permitted). The use of dissimilar metals separated by insulating material

will also be permitted.

3.4.3 Pure tin. The use of pure tin, as an underplate or final finish, is prohibited both internally and externally. Tin

content of capacitor components and solder shall not exceed 97 percent, by mass. Tin shall be alloyed with a

minimum of 3 percent lead, by mass (see 6.7). Lead-free, tin alloy high temperature solders may be used where high

temperature solder is necessary with the approval of the qualifying activity. The tin content of lead-free high

temperature solders shall not exceed 97 percent, by mass.

3.5 Interface and physical dimension requirements. Capacitors and retainers shall meet the interface and physical

dimensions specified (see 3.1).

3.5.1 Case. Each capacitor shall be enclosed in a hermetically-sealed case (see 3.1) which will protect the

capacitor element from moisture, impregnant or filling compound leakage, and mechanical damage under all test

conditions specified herein.

3.5.2 Sleeving. The sleeving material shall not soften, creep, or shrink to a point where any part of the cylindrical

portion of the case is left uncovered at any test temperature specified herein. The sleeving shall not obscure the part

marking.

3.5.3 Leads. Leads shall be solderable and meet the requirements of 3.19.

3.5.3.1 Solder dip (retinning) leads. Only the manufacturer (or his authorized category B or C distributor) may

solder dip/retin the leads of product supplied to this specification provided the solder dip process (see appendix A)

has been approved by the qualifying activity.

3.6 Burn-in (when specified, see 3.1). When tested as specified in 4.7.2, capacitors shall withstand the exposure

to high temperature and voltage without visible damage.

3.7 Dielectric absorption (when specified, see 3.1). When measured as specified in 4.7.3, the dielectric absorption

shall not exceed the value specified.

3.8 Thermal shock. When tested as specified in 4.7.4, capacitors shall withstand the extremes of high and low

temperatures without visible damage.