MIL-PRF-27208F
6.2 Acquisition documents. Acquisition documents should specify the following:
a. Title, number, and date of the applicable association specification, and complete PIN (see 1.2.1 and 3.1).
If not otherwise specified (see 2.1), the versions of the individual documents referenced will be those in
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b.
effect on the date of release of the solicitation.
c. Packaging requirements (see 5.1)
6.3 Qualification. With respect to products requiring qualification, awards will be made only for products that are,
at the time of award of contract, qualified for inclusion in the applicable QPL whether or not such products have
actually been so listed by the 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 purchase orders for the products cover
by this specification. The activity responsible for the QPL and, information pertaining to qualification of products may
be obtained from the Defense Supply Center, Columbus, (DSCC-VQP) Post Office Box 3990, Columbus, OH 43218-
3990.
6.4 Sequence for examinations, measurements, and test. The sequence for examinations, measurements, and
tests should be in accordance with table XII.
6.5 High resistance and voltages. Where voltages higher than 250 volts rms are present between the resistor
circuit and grounded surfaces on which the resistor is mounted, or where the dc resistance is so high that the
insulation resistance to ground is an important factor, secondary insulation to withstand the conditions should be
provided between the resistor and mounting or between the mounting and ground.
6.6 Mounting resistors. Resistors should not be mounted by their lugs or flexible wire leads. Mounting hardware
should be used. Printed circuit types are frequently terminal mounted, although brackets may be necessary for a
high shock and vibration environment.
6.7 Resistance temperature characteristic. Consideration should be given to temperature rise and ambient
temperature of resistors under operation, in order to allow for the change in resistance due to resistance temperature
characteristic. Resistance tolerance may be exceeded easily, unless care is exercised.
6.8 Suppression of characteristic. The style in this specification supersedes the equivalent styles of
6.9 Reduction of power rating. When only a portion of the resistance element is engaged, the wattage rating is
reduced in approximately the same proportion as the resistance.
6.10 Stacking of resistors. When stacking resistors, care should be taken to compensate for the added rise in
temperature by derating the wattage rating accordingly.
6.11 Retinning leads. If retinning (hot solder dip) of the leads is required, see A.5.3.
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6.11.1 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).
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