MIL-PRF-19500/308D
4.5 Methods of inspection. Methods of inspection shall be as specified in the appropriate tables and as follows:
4.5.1 DC intermittent operation life. A cycle shall consist of an "on" period, when power is applied suddenly, not
gradually, to the device for the time necessary to achieve a delta case temperature of 85°C +15°C, -5°C followed by
an "off" period, when the power is suddenly removed, for cooling. Auxiliary (forced) cooling is permitted during the
"off" period only. The heating time is such that 30 s < theating < 60 s. P = VF x IF or P = VF(pk) x Iav if using sine wave
current. DC full wave current (or equivalent half sine wave current) shall be used for the power required during the
"on" period and equivalent half sine wave is permissible.
Within the time interval of 50 cycles before to 500 cycles after the termination of the test, the sample units shall be
removed from the specified test conditions and allowed to reach room ambient conditions. Specified end-point
measurements for qualification and quality conformance inspections shall be completed within 96 hours after removal
of sample units from the specified test conditions. Additional readings may be taken at the discretion of the
manufacturer.
4.5.2 Reverse recovery time. The reverse recovery time shall be measured in the circuit of figure 2 or equivalent.
Care should be exercised to minimize stray inductances in the test circuit and to ensure the total resistance of the
reverse current loop can be adjusted sufficiently low so that more than 2 amperes will flow if not blocked by the diode
being tested. Switch SW shall be activated and the regulated voltage source adjusted to achieve the following
characteristics of the waveform.
a.
The di/dt shall be the specified value between the forward 0.5 ampere point and the reverse 0.2 ampere
point.
The ir(rec) shall be the maximum value obtainable, except when it exceeds 2 amperes.
b.
The reverse-recovery time shall then be determined from the current waveform as shown on figure 3.
* 4.5.3 Pulse measurements. Conditions for pulse measurements shall be as specified in section 4 of MIL-STD-
750.
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