MIL-PRF-19978 Capacitors, Fixed, Plastic \(Or Paper-Plastic\) Dielectric \(Hermetically Sealed In Metal, Ceramic Or Glass Cases\), Established And Non-Established Reliability General Specification ForThis specification covers the general requirements for established reliability \(ER\) and non-established reliability \(non-ER\), direct current \(dc\), plastic or paper-plastic dielectric, fixed capacitors, hermetically sealed in metal or ceramic or glass cases. Capacitors meeting the established reliability requirements specified herein have failure rate \(FR\) levels ranging from 1.0 percent to 0.001 percent per 1,000 hours \(see 1.2.1.9\). These FRLs are established at a 90-percent confidence level and maintained at a 10-percent producer\'s risk and are based on life tests performed at maximum rated voltage and maximum rated temperature. An acceleration factor of 5:1 has been used to relate the life test data obtained at 140 percent of rated dc voltage at the applicable high test temperature to the rated voltage at the applicable high test temperature. This specification also covers removable mounting retainers for use with applicable capacitors \(see 3.1\). A parts per million \(ppm\) quality system is used for documenting and reporting the average outgoing quality of ER capacitors supplied to this specification. Statistical process control \(SPC\) techniques are required in the manufacturing process to minimize variation in production of ER capacitors supplied to the requirements of this specification.

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MIL-PRF-19978K

c. Duration of vibration: For tubular styles: 4 hours (2 hours in each of 2 mutually perpendicular planes). For

rectangular styles: 6 hours (2 hours in each of 3 mutually perpendicular planes).

d. Test and measurements during vibration: During the last 30 minutes of vibration in each direction, a signal

of 1 kilohertz (kHz) 0.2 kHz at a level of 1 volt 0.5 volt shall be placed across the capacitor and measured

with suitable ac detecting equipment to determine open-circuits or short-circuits, or intermittent contacts.

The accuracy of the detecting equipment shall be sufficient to detect any interruption with a duration of 0.5

ms or greater.

e. Examination after vibration: Capacitors shall be visually examined for evidence of mechanical damage.

4.7.11.2 High frequency. Capacitors and retainers shall be tested in accordance with method 204 of MIL-STD-

202. The following details and exceptions shall apply:

a. Mounting of specimens: Capacitors shall be rigidly mounted by the body to a vibration test apparatus.

Wire-lead capacitors shall be secured .5 inch .125 inch (12.7 mm 3.18 mm) from the case. The

extraneous leads beyond the .5 inch (12.7 mm) securing point may be removed or supplemental support

may be added.

b. Electrical-load conditions: During the test, a potential of 125 percent of the dc rated voltage shall be applied

between the terminals of the capacitor.

c. Test condition letter: B, with exception as specified (see 3.1).

d. Measurements: During the last cycle in each direction, a signal of 1 kHz 0.2 kHz at a level of 1 volt .05

volt shall be placed across the capacitor and measured with a suitable ac recording device (a permanent

record is not necessary for this test) to determine open- or short-circuits, or intermittent contacts. The

accuracy of the detecting equipment shall be sufficient to detect any interruption with a duration of 0.5 ms or

greater.

e. Measurements and examination after vibration: After the test, with capacitors still mounted on the vibration

jig, the insulating sleeve shall be tested for dielectric withstanding voltage, as specified in 4.7.6, with a

potential of 2,000 V dc between the case and bracket. Capacitors and retainers shall be visually examined

for evidence of mechanical damage.

4.7.12 Salt spray (corrosion) (see 3.16). Capacitors and retainers shall be tested in accordance with method 101,

MIL-STD-202. The following details and exceptions shall apply:

a. Applicable salt solution: The salt solution concentration shall be 5 percent.

b. Test condition letter: B (48 hours).

c. Examination after exposure: Capacitors and retainers shall be visually examined for evidence of harmful

corrosion, unwrapping of, or mechanical damage to insulating sleeves (when applicable), and obliteration of

marking.

4.7.13 Immersion (see 3.17). Capacitors and retainers shall be tested in accordance with method 104 of MlL-

STD-202. The following details shall apply:

a. Test condition letter B.

b. Measurements after final cycle: For capacitors with insulating sleeves, dielectric withstanding voltage, and

insulation resistance at +25�C shall be measured as specified in 4.7.6 and 4.7.8, respectively. The test

potential shall be applied between the case and a piece of metal foil placed around the insulating sleeve;

the metal foil shall be of such dimension as to allow at least .125 inch (3.18 mm) surface exposure of the

insulating sleeve on each end. In addition, dielectric withstanding voltage and insulation resistance at

+25�C of all capacitors shall be measured as specified in 4.7.6 and 4.7.8, respectively. Capacitors and

retainers shall then be examined for harmful or extensive corrosion and obliteration of marking.