MIL-PRF-39005 Resistors, Fixed, Wirewound \(Accurate\), Nonestablished Reliability, Established Reliability, General Specification ForThis specification covers the general requirements for nonestablished reliability \(non-ER\), established reliability \(ER\), accurate, wire-wound, fixed resistors that have a maximum resistance tolerance of 1 percent and a high degree of stability with respect to time under specified environmental conditions. The resistors are capable for continuous full-load \(or voltage\) operation at any ambient temperature up to 125??C, and when derated, up to 145??C \(see 6.5\). They are not capable for application where the alternating current \(ac\) characteristics are of critical importance. ER resistors have life failure rates \(FR\) ranging from 1.0 percent to 0.001 percent per 1,000 hours \(see 1.2.1.5\). These FR are established at 60-percent confidence level on the basis of the life tests. The FR, identified by the appropriate symbol, is referred to operation at full rated voltage and temperature.

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MIL-PRF-39005G

d. Final measurements: Upon completion of step 6 of the final cycle, the resistors shall be

conditioned at a temperature of 25�C �2�C, and at a relative humidity of 90 percent to 95 percent

for a period of 1 hour 30 minutes to 3 hours 30 minutes. After conditioning, the resistors shall be

removed from the chamber and within 8 hours, the dc resistance shall be measured as specified in

4.8.5. Wiping and forced air drying prior to measurement is not allowed. The subsequent 4-hour

to 24-hour conditioning period and measurements do not apply.

e. Examinations after test: Resistors shall be examined for evidence of breaking, cracking, spalling,

and loosening of terminals and mounting hardware.

4.8.11 Resistance to soldering heat (see 3.15). Resistors shall be tested in accordance with

method 210 of MIL-STD-202. The following details and exceptions shall apply:

a. Measurement before test: DC resistance shall be measured as specified in 4.8.5.

b. Sample units shall not have been soldered during any of the previous tests.

c. Test condition: C.

d. Measurement after test: After completion of terminal immersion and the parts have returned to

room temperature, the dc resistance shall be measured as specified in 4.8.5.

e. Examination after test: Resistor shall be examined for evidence of mechanical damage.

4.8.12 Shock, specified pulse (see 3.16). Resistors shall be tested in accordance with method 213 of

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

a. Special mounting means: Resistors shall be mounted in relation to the test equipment in such a

manner that the stress applied is in the direction which would be considered most detrimental.

Resistors shall be rigidly mounted on appropriate jig fixtures with their bodies restrained from

movement and their leads supported at a distance of .375 inch �.0625 inch (9.53 mm �1.588 mm)

from the resistor body. These fixtures shall be constructed in a manner to insure that the points of

the resistor mounting supports will remain in a static condition with reference to the shock table.

b. Test leads: Test leads used during this test shall be no larger than AWG size 22 stranded wire, so

that the influence of the test lead on the resistor will be held to a minimum. The test lead length

shall be no longer than necessary.

c. Measurement before shock: DC resistance shall be measured as specified in 4.8.5.

d. Test condition: I.

e. Number and direction of applied shocks motion: The resistors shall be subjected to five shocks

(total of 15 shocks) in each of three mutually perpendicular planes. The initial plane shall pass

through the resistor axis and terminals, and the other two planes shall be mutually perpendicular.