electromagnetic interference. Filters furnished to the requirements of this specification contain shunting ceramic discoidal capacitors and series inductors \(FSC 5915\). Capacitors furnished to the requirements of this specification contain shunting ceramic discoidal capacitors \(FSC 5910\). For the purposes of this specification, feed-through capacitor types \(C circuit configuration\) are referred to herein as a filter. Passband power may be alternating current \(ac\) or direct current \(dc\) and the filters used primarily in the reduction of broadband radio frequency interference. This specification provides for two levels of product assurance requirements. Filters covered by this specification are capable of operation over the temperature range of -55 degrees C to +125 degrees C.

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MIL-PRF-28861D

6.4.4 Solder coating. It is intended that solder coatings on terminals withstand extended storage without

deterioration of soldering qualities or appreciable increase in resistance.

6.5 Finishes.

6.5.1 Tin-plated finish. Pure tin plating is prohibited (see 3.5.3.1) since it may result in tin whisker growth (see

6.5.5). Based on past experience, tin plating in accordance with MIL-T-10727 or electro-tin fused (with a minimum

lead content of 3 percent) has been used successfully to meet the requirements of this specification.

6.5.2 Tin-lead plated. Based on past experience, tin-lead plating in accordance with MIL-P-81728 or hot-solder

dipped (40 percent to 60 percent tin in accordance with J-STD-006) has been used successfully to meet the

requirements of this specification.

6.5.3 Silver-plated. Based on past experience, silver-plating in accordance with QQ-S-365 has been used

successfully to meet the requirements of this specification.

6.5.4 Gold-plated. Based on past experience, gold plating in accordance with MIL-G-45204, (type II, grade C for

broadband and high frequency bolt-style or type III, grade A for solder-in styles) has been used successfully to meet

the requirements of this specification.

6.5.5 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 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 Coating of Tin).

6.6 Installation methods (recommended).

6.6.1 Mounting the filter to the chassis. The device should be treated as heat and mechanically sensitive. Heat

sink the filter when soldering on leads.

6.6.1.1 Threaded filters with flats. It is intended that these filters be mounted in a "D" hole using a washer, a nut

and a torque wrench. Caution: Do not grip the filter body more than finger tight. If there is an undercut on the filter

thread adjacent to the mounting surface, the bulkhead material must be thicker than the undercut. The

recommended mounting torque is specified in the appropriate specification sheet.

6.6.1.2 Threaded filters with a hex body or a hex top seal. If flats are provided, these filters may be assembled as

in 6.6.1.1. These filters may be mounted in a plain hole using a nut, a washer, a torque wrench, and a plain wrench.

Preferably the plain wrench should be used to steady the filter while the torque wrench should be used to tighten the

nut. If the hole in the chassis is threaded the filter should be mounted with a torque wrench.

6.6.1.3 Solder-in style.

6.6.1.3.1 Solder preform method. A fluxed solder preform of Sn 63 solder can be fitted into the subassembly.

The subassembly and filter can then be preheated to +125�C for 5 minutes to reduce thermal shock of the ceramic

material. To complete the soldering operation, heat may then be applied to the subassembly, in the immediate

vicinity of the filter, with sufficient magnitude to reflow the solder preform. This may be accomplished with a

controlled temperature source. Care should be taken to supply the heat via the subassembly, rather than heating the

filter directly and only for the time required to make a good solder connection. Cool the assembly slowly by gradually

returning it to room temperature.

6.6.1.3.2 Solder paste method. This second method is useful where there is a danger of damage to closely

packed components or very heat sensitive parts. A bismuth solder alloy paste composed of 43 percent tin, 43

percent lead, and 14 percent bismuth melts at around +152�C and effective soldering can be achieved with it. This

material, which is obtainable as a solder cream, can be applied by brush, or by hypodermic syringe and then heated