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

6.6 Military maintenance. For the purposes of supply standardization and item control of replacement

parts, terminal and ĆR performance requirement symbol "L" (solderable leads) is a substitute for symbol

"S" (solderable leads), and symbol "U" (weldable leads) is a substitute for symbol "W" (weldable leads).

NOTE: Symbol "S" and "W" specified in MIL-R-39005B.

6.6.1 Terminal. Symbol "L" and "U" are substitutable for items identified by symbols "S" and "W"

respectively, under MIL-R-39005B.

6.7 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 new equipment design.

All application and use information concerning these resistors is also provided in MIL-HDBK-199.

6.8 Power rating. The power rating of these resistors is conservative and are rated approximately 50

percent of the corresponding commercial ratings.

6.9 Retinning leads. If retinning (hot solder dip) of the leads is required, see 3.5.3.

6.10 PIN. PIN is a new term encompassing previous terms used in specifications such as part

number, type designator, and identification number, (see 1.2.1).

6.11 Tin whisker growth. The use of alloys with tin content greater than 97 percent, by mass, may

exhibit tin whisker growth problems after manufacture. Tin whiskers may occur anytime from a day to

years after manufacture and can develop under typical operating conditions, on products that use such

materials. Conformal coatings applied over top of a whisker-prone surface will not prevent the formation

of tin whiskers. Alloys of 3 percent lead, by mass, have shown to inhibit the growth of tin whiskers. For

additional information on this matter, refer to ASTM-B545 (Standard Specification for Electrodeposited

Coatings of Tin).

6.12 Low tolerance resistors. Low tolerance resistors (.005 and .01), exhibiting resistance shifts due to

high humidity are normal to precision, fixed resistors. Before being considered out of tolerance, resistors

should be conditioned in a dry oven. Users of said resistors should contact suppliers for temperature and

drying time. Resistors which continue to be out of tolerance after the above conditioning process should

be considered rejects.

6.13 Environmentally preferable material. Environmentally preferable materials should be used to the

maximum extent possible to meet the requirements of this specification. As of the dating of this

document, the U.S. Environmental Protection Agency (EPA) is focusing efforts on reducing 31 priority

chemicals. The list of chemicals and additional information is available on their website at

cadmium, lead, and mercury. Use of these materials should be minimized or eliminated unless needed to

meet the requirements specified herein (see Section 3).