MIL-PRF-39035 Resistor, Variable, Nonwirewound \(Adjustment Type\), Nonestablished Reliability, And Established Reliability, General Specification ForThis specification covers the general requirements for nonestablished reliability \(non-ER\) and established reliability \(ER\), multiturn lead-screw actuated, and single-turn, nonwirewound, variable resistors with a contact bearing uniformly over the surface of the entire resistive element, when positioned by an actuator. These resistors are capable of full-load operation \(when the maximum resistance is engaged\), at a maximum temperature of 150 Degrees C, with a resistance tolerance of ??10 percent. The ER resistors will have life failure rate levels ranging from 1.0 to 0.001 percent per 1,000 hours \(see 1.2.1.5\). These failure rate levels are established at a 60 percent confidence level maintained at 10 percent producer\'s risk on the basis of the life tests.

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MIL-PRF-39035E

6.11 Contact corrosion. Contact corrosion may develop at the point where the wiper makes contact with the

element, if a current of 25 microamps or greater is not maintained.

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

6.12.1 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).

6.13 Subject term (key word) listings.

Ohmic

Potentiometer

Resistance

Trimmer

Multiturn

6.14 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.

Environmentally Protection Agency (EPA) is focusing efforts on reducing 31 priority chemicals. The list of chemicals

available at the following EPA site: https://www.epa.gov/epaoswer/hazwaste/minimize/. Included in the EPA list of 31

priority chemicals are cadmium, lead, and mercury. Use of the materials on the list should be minimized or eliminated

unless needed to meet the requirements specified herein (see section 3).

6.15 Changes from previous issue. The margins of this specification are marked with vertical lines to indicate

where changes from the previous issue were made. This was done as a convenience only and the Government

assumes no liability whatsoever for any inaccuracies in these notations. Bidders and contractors are cautioned to

evaluate the requirements of this document based on the entire content irrespective of the marginal notations and

relationship to the last previous issue.