MIL-PRF-20M
4.7.2.1 Thermal shock. Capacitors shall be tested in accordance with method 107 of MIL-STD-202. The following
details and exception shall apply:
a. Test condition A, except that in step 3, sample units shall be tested at the applicable high test temperature
(see 3.1).
b. Measurements before and after cycling: Not applicable.
4.7.2.2 Voltage conditioning. One of the voltage conditioning tests in 4.7.2.2.1 or 4.7.2.2.2 shall be performed.
The lot traveler shall indicate which test is used. When the optional voltage conditioning test of 4.7.2.2.2 is used, the
traveler shall include the specific accelerated voltage used and the test time.
4.7.2.2.1 Standard voltage conditioning. Voltage conditioning shall follow the thermal shock test. The voltage
conditioning shall consist of applying twice the rated voltage to the unit at +125°C +4°C, -0°C for 96 hours minimum.
Voltage shall be applied and shall reach maximum value within one second, maximum.
After completion of the exposure period, the unit shall be allowed to stabilize at room temperature (+25°C). After
stabilization at room temperature, the DWV and IR shall be measured as specified in 4.7.5 and 4.7.7.1, respectively.
After measurement of DWV and IR at 25°C, the unit shall be stabilized at +125°C +4°C, -0°C and IR measured as
specified in 4.7.7.2. After allowing the unit to stabilize at room temperature, the capacitance and dissipation factor
shall be measured as specified in 4.7.3 and 4.7.4, respectively. NOTE: IR at +25°C may be skipped if +125°C IR is
performed with +25°C limits.
4.7.2.2.2 Optional voltage conditioning (ER only). The manufacturer, with approval from the qualifying activity,
may perform an optional voltage conditioning test instead of the standard voltage conditioning test of 4.7.2.2.1.
Optional voltage conditioning shall be limited to capacitors with a dc rated voltage of 200 volts or less. All conditions
of 4.7.2.2.1 apply, with the exception of the voltage applied and the test time. The minimum time duration, Ttest, shall
be calculated as follows:
2 x Erated < Etest < 4 x Erated
Where:
800
Ttest =
Ttest = Minimum test time in hours
(Etest/Erated)3
Etest = Applied voltage
Erated = Rated voltage of the capacitor
4.7.3 Capacitance (see 3.7). Capacitors shall be tested in accordance with method 305 of MIL-STD-202. The
following detail and exception shall apply:
a. Test frequency: 1 MHz ±100 kHz when the nominal capacitance is 1,000 pF or less, and 1 kHz ±100 Hz
when the nominal capacitance is greater than 1,000 pF. At the option of the manufacturer, capacitance
measurements may be made at any frequency from 1 kHz to 1 MHz and referred to measurements at 1 MHz
and 1kHz as applicable.
b. Limit of accuracy: The accuracy of measurement shall be .33 percent of the nominal capacitance tolerance or
2 percent, whichever is smaller; however, the accuracy need not be better than 0.1 pF.
c. Test jig for measuring capacitance values of less than 10 pF: Shall be a guarded three terminal type, or
equivalent.
4.7.4 Dissipation factor (see 3.8). The dissipation factor shall be measured with a capacitance bridge or other
suitable method at the frequency specified in 4.7.3a. The voltage shall be 1.0 ±0.2 volts rms. The inherent accuracy
of the measurement shall be ±2 percent of the reading plus 0.1 percent dissipation factor (absolute). Suitable
measurement techniques shall be used to minimize errors due to the connections between the measuring apparatus
and the capacitor.
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