MIL-PRF-39018/7C
3. DC current. Unlike 2-terminal capacitors, the dc current flows through the capacitor and contributes to the
operating temperature. The temperature rise (TL) due to the dc current may be determined from figure 3.
The ability of the external leads to carry the desired current should be taken into consideration. Lead length
and heat sink qualities of the printed circuit board and capacitor will affect the current capability.
FIGURE 3. DC current vs. temperature rise.
4. Ripple current. The rms ripple current which will result in a 10°C internal temperature rise (TR), over the
frequency range of 10 kHz to 1 MHz, is tabulated in table I. For other temperature rises and frequencies, the
10 kHz - 1 MHz ripple currents may be multiplied by the factors shown in table II.
TABLE II. Factors for determining ripple currents at various frequencies.
Temperature rise
Frequency
5°C
10°C
15°C
20°C
25°C
30°C
(Hz)
60
0.35
0.50
0.65
0.75
0.85
1.00
120
0.45
0.65
0.80
0.95
1.10
1.30
400
0.50
0.75
0.95
1.10
1.30
1.50
1K
0.55
0.80
1.00
1.15
1.35
1.60
10K-1M
0.65
1.00
1.25
1.45
1.70
2.00
5. Operating temperature. The operating temperature (TC) is determined by obtaining the sum of the ambient
temperature (TA), the temperature rise due to the ripple current (TR) and the temperature rise due to the dc
current (TL). TC = TA + TR + TL. The sum should not exceed the maximum rated temperature (+105°C).
NOTES:
Reference document. MIL-PRF-39018.
Changes from previous issue. The margins of this specification are marked with asterisks to indicate where changes
from the previous issue were made. This was done as a convenience only and the Government assumes no liability
whatsoever for any inaccuracies in these notations. Bidders and contractors are cautioned to evaluate the
requirements of this document based on the entire content irrespective of the marginal notations and relationship to
the last previous issue.
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