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.

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MIL-PRF-39009E

3.25 Soldering. Where soldering is employed, only noncorrosive fluxes shall be used, unless it can be

shown that corrosive elements have been satisfactorily removed after soldering. Solder shall not be used

for obtaining mechanical strength. Electrical connections shall be mechanically secure before soldering

and electrically continuous after soldering. Except for solder used to coat the terminals, the solder used

shall in no case start to melt at a temperature less than +300�C.

3.26 Recycling, recovered, or environmentally preferable materials. Recycled, recovered, or

environmentally preferable materials should be used to the maximum extent possible provided that the

material meets or exceeds the operational and maintenance requirements, and promotes economically

advantageous life cycle costs.

3.27 Workmanship. Resistors shall be processed in such a manner as to be uniform in quality and shall

be free from other defects that will affect life, serviceability, or appearance.

4. VERIFICATION

4.1 Classification of inspection. The inspection requirements specified herein are classified as follows:

a. Qualification inspection (see 4.4).

b. Verification of qualification (see 4.5).

c. Conformance inspection (see 4.6).

d. Periodic group C inspection (see 4.7).

4.2 Reliability and quality.

4.2.1 QPL system. The manufacturer shall established and maintain a QPL system (see 3.3).

Evidence of such compliance is a prerequisite for qualification and verification of qualification.

4.2.2 SPC. A SPC program shall be maintained in accordance with EIA-557. Evidence of such

compliance is a prerequisite for qualification and verification of qualification.

4.3 Inspection conditions and precautions.

4.3.1 Inspection conditions. Unless otherwise specified herein, all inspections shall be performed in

accordance with the test conditions specified in the "GENERAL REQUIREMENTS" of MIL-STD-202.

4.3.2 Precautions. Adequate precautions shall be taken during inspection to prevent condensation of

moisture on resistors, except during moisture-resistance test. Precautions shall be also taken to prevent

damage by heat when soldering resistor leads to terminals.

4.4 Qualification inspection. Qualification inspection shall be performed at a laboratory acceptable to

the Government (see 6.3).