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

6. NOTES

(This section contains information of a general or explanatory nature which may be helpful, but is not

mandatory).

6.1 Intended use. Resistors described herein are intended to be used to utilize the principal of heat

dissipation through a metal mounting surface. Resistors should not be used in circuits where their ac

performance is of critical importance in the operation of such circuits.

6.2 Acquisition requirements. Acquisition documents must specify the following:

a. Title, number, and date of this specification, the applicable associated specification, and the

complete PIN (see 1.2.1).

b. If not otherwise specified (see 2.1), the versions of the individual documents referenced will be

those in effect on the date of release of the solicitation.

Packaging requirements (see 5.1).

d. Allowable substitution (see 3.23).

6.3 Qualification. With respect to products requiring qualification, awards will be made only for products

which are, at the time of award of contract, qualified for inclusion in Qualified Products List whether or not

such products have actually been so listed by that date. The attention of the contractors is called to these

requirements, and manufacturers are urged to arrange to have the products that they propose to offer to

the Federal Government tested for qualification in order that they may be eligible to be awarded contracts

or orders for the products covered by this specification. The activity responsible for the Qualified Products

List is the US Army Communications-Electronics Command, ATTN: AMSEL-LC-LEO-E-EP , Fort

Monmouth, NJ 07703-5023, however, information pertaining to qualification of products may be obtained

from the Defense Supply Center, Columbus (DSCC-VQP), Post Office Box 3990, Columbus, Ohio 43218-

3990.

6.4 Selection and use information. Equipment designers should refer to MIL-HDBK-199, "Resistors,

Selection and Use of", for a selection of standard resistor types and values for any new equipment design.

All applications and use information concerning these resistors are provided in MIL-HDBK-199.

6.5 MIL-PRF-18546 substitution data. Resistors of this specification, regardless of their FR designation,

are substitutes for resistors of the same resistance value as follows:

Inactivated specification and

Substitution specification

characteristic

MIL-R-18546/1 characteristic G

MIL-R-18546/1 characteristic N

6.6 Retinning leads. If retinning (hot solder dip) of the leads is required see 3.5.4.

6.7 Tin plated finishes. Tin plating is prohibited (see 3.5.3.1) since it may result in tin whisker growth.

Tin whisker growth could adversely affect the operation of electronic equipment systems. For additional

information on this matter refer to ASTM B545 (Standard Specification for Electrodeposited Coating of

Tin).