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MIL-PRF-18546 Resistors, Fixed, Wire-Wound \(Power Type, Chassis Mounted\), General Specification ForThis specification covers the general requirements for power type, wire wound, fixed resistors which utilize the principal of heat dissipation through a metal mounting surface. The resistors have an initial resistance tolerance of ┬▒1 percent and a resistance temperature characteristic range from 30 ppm/Degrees C to 200 ppm/Degrees C depending upon the resistance value. They are not capable for application when the alternating current \(ac\) characteristics are of critical importance; however, provisions have been made to minimize the inductance.

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MIL-PRF-18546G
APPENDIX A
A.4 EXTENT OF QUALIFICATION
A.4.1 Resistance values. Qualification of a particular style and resistance value will qualify a range of
resistance values from the smallest value manufactured in that style to the resistance value qualified.
A.4.2 Characteristics N and G. Qualification of characteristic "N" resistors will also qualify
corresponding characteristic "G" resistors. Qualification of maximum resistance value in characteristic "N"
will also qualify highest value in characteristic "G".
A.5 SOLDER DIP (RETINNING) LEADS
A.5.1 Solder dip (retinning) leads. The manufacturer may solder dip/retin the leads of product supplied
to this specification provided the solder dip process of this appendix, or an equivalent process has been
approved by the qualifying activity.
A.5.2 Qualifying activity approval. Approval of the solder dip process will be based on one of the
following options:
a. When the original lead finish qualified was hot solder dip lead finish 52 of MIL-STD-1276 (Note:
The 200 microinch maximum thickness is not applicable). The manufacturer shall use the same
solder dip process for retinning as is used in the original manufacture of the product.
b. When the lead originally qualified was not hot solder dip lead finish 52 of MIL-STD-1276 as
prescribed in A.5.2a, approval for the process to be used for solder dip shall be based on the
following test procedure:
(1) Thirty samples of any resistance value for each style and lead finish are subjected to the
manufacturer's solder dip process. Following the solder dip process, the resistors are
subjected to the dc resistance test and other group A electricals. No defects are allowed.
(2) Ten of the 30 samples are then subjected to the solderability test. No defects are allowed.
(3) The remaining 20 samples are subjected to the resistance to solder heat test followed by the
moisture resistance test. No defects allowed.
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