MIL-PRF-39009 Resistors, Fixed, Wire-Wound \(Power Type, Chassis Mounted\), Nonestablished Reliability, Established Reliability, General SpecificationThis specification covers the general requirements for nonestablished reliability \(non-ER\), and established reliability \(ER\), power type, wire wound, fixed resistors which utilize the principal of heat dissipation through a metal mounting surface. These resistors have initial resistance tolerances of ??1 percent. These resistors are suitable for continuous full load operation at an ambient temperature of +25 degrees C, and when derated up to +250 degrees C \(see figure 1\). These resistors should not be used in circuits where their ac performance is of critical importance in the operation of such circuits. However, provisions have been made in particular styles to minimize inductances \(see 3.1\). These resistors will have life failure rate levels \(FRL\) ranging from 1.0 percent to 0.001 percent per 1,000 hours \(see 1.2.1.4\). These FRL are established at a 60 percent confidence on the basis of the life tests. The FRL, identified by the appropriate symbol, is referred to operation at full rated wattage at +25 degrees C, with a permissible change in resistance of ??2 percent as the criteria for failure.

Pages 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12 - 13

MIL-PRF-39009E

4.5 Verification of qualification . Every 6 months, the manufacturer shall provide verification of

qualification to the qualifying activity. Continued qualification is based on meeting the following

requirements.

b. Design of resistor has not been modified.

c. Lot rejection for group A (subgroup 1 and subgroup 4) does not exceed 5 percent or one lot,

whichever is greater.

d. Lot rejection for group B inspection does not exceed 5 percent or one lot, whichever is greater.

e. Periodic group C inspection.

f. FR levels.

g. PPM assessment (NOTE: Grouping of style is permitted).

h. Continued qualification to non-ER level (C) shall be based on continued maintenance of

qualification for the ER part (minimum P FR level maintained).

4.6 Conformance inspection.

4.6.1 Inspection of product for delivery.

4.6.1.1 Non-ER resistors. The manufacturer's inspection system shall be used for preparation for

delivery.

4.6.1.2 ER resistors. Inspection of product for delivery shall consist of group A and group B

inspections. Group B inspection for delivery is not required when the qualifying activity has allowed group

B testing to be preformed annually (see table IX).

4.6.2 Inspection and production lot.

4.6.2.1 Inspection lot. An inspection lot, as far as practical, shall consist of all the resistors of the same

style, characteristic, protective enclosure or coating, and manufacturer under essentially the same process

and conditions during a manufacturing period of 1 month maximum. For purposes of lot formation all

terminal types may be included in the same lot; however, all lead types which are combined shall have the

same method of terminal attachment. All leads in the lot shall be represented in a similar proportion by

samples selected for inspection. Non-ER and ER lots shall be kept separate.

4.6.2.2 Production lot. A production lot shall consist of resistors of the same style, nominal resistance

value, resistance tolerance, resistance temperature characteristic, and terminal type. Manufacture of all

parts in the lot shall have been started, processed, assembled, and tested as a group. Lot identity shall be

maintained throughout the manufacturing cycle. Non-ER and ER lots shall be kept separate.