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

3.3.2 PPM system. As part of the overall MIL-STD-790 QPL system, the manufacturer shall establish

a ppm system for assessing the average outgoing quality of lots in accordance with EIA-554-1 and 4.6.4.

Data exclusion, in accordance with EIA 554-1, may be used with approval of the qualifying activity. The

PPM system shall identify the PPM rate at the end of each month and shall be based on a six month

moving average. PPM and dc resistance shall be assessed for each style. Style reporting may include

both non-ER and ER style combinations.

3.4 Material. The material shall be as specified herein. However, when a definite material is not

specified, a material shall be used which will enable the resistors to meet the performance requirements

of this specification. Acceptance or approval of any constituent material shall not be construed as a

guaranty of the acceptance of the finished product.

3.5 Interface and physical dimension requirements. Resistors shall meet the interface and physical

dimensions as specified (see 3.1). The resistor assembly shall be protected by a coating or enclosure of

moisture resistant insulation material which shall withstand exposure to the humidity and temperature

conditions specified herein. In order to minimize inductance, resistors shall be wound by reverse

pi-winding, bifilar, or equivalent method.

3.5.1 Terminals. Terminals shall be made of a solid conductor of the length and diameter specified

(see 3.1). The terminals shall be solderable in accordance with method 208 of MIL-STD-202.

3.5.1.1 Solderable terminals. Solderable terminals shall be treated to meet the requirements of

solderability (see 3.10).

3.5.1.2 Weldable terminals. Weldable terminals shall be as specified in table I. The manufacturer shall

verify by certification that the weldable leads meet all the applicable requirements of MIL-STD-1276 (see

3.1). The solderability requirement of 3.10 is not applicable to weldable terminals.

3.5.2 Pure tin. The use of pure tin, as an underplate or final finish is prohibited both internally and

externally. Tin content of resistor components and solder shall not exceed 97 percent, by mass. Tin shall

be alloyed with a minimum of 3 percent lead, by mass (see 6.11).

3.5.3 Solder dip (retinning) leads. The manufacturer (or their authorized category B or category C

distributor) may solder dip/retin the leads of product supplied to this specification provided the solder dip

process (see appendix A) has been approved by the qualifying activity.

3.5.4 Protective coating or enclosure. Resistor assemblies shall be protected by a coating or

enclosure of moisture resistant insulating material which shall completely cover the exterior of the

resistance element, including connections or terminations. The coating shall not crack, craze, drip, run,

or form globules of any temperature up to and including 145�C, regardless of the mounting position of the

resistor. This material shall afford protection against the effects of prolonged exposure to high humidities.

The protective coating or enclosure shall be such as to minimize the establishment of leakage paths

between the terminals resulting from collection of moisture film on the external surface of the resistor.

3.5.5 Flux. The flux shall be of such a quality as to enable the resistors to meet the requirements of

this specification.

3.5.6 Weight. Resistors shall not exceed the weight specified (see 3.1).