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 MIL-HDBK-419A
(6) Jumpers should be made of tinned copper, cadmium-plated phosphor bronze, aluminum, or
cadmium- plated steel.
(7)
Mating metals should be selected to offer maximum gaIvanic compatibility (see Section 1.7.3).
i.
Where electrical continuity across the shock mounts is necessary, bonding jumpers should be
installed across each shock mount. Jumpers for this application should have a maximum thickness of 0.06 cm
(0.025 in.) so that the damping efficiency of the mount is not impaired. In severe shock and vibration
environments, solid straps may be corrugated or flexible coarse wire braid may be used.
Where rf tightness is required and welded joints can not be used, the bond surfaces must be
j.
machined smooth to establish a high degree of surface contact throughout the joint area. Fasteners must be
positioned to maintain uniform pressure throughout the bond area.
k.
Chassis-mounted subassemblies should utilize the full mounting area for the bond as illustrated in
Figures 3-13 and 3-14. Separate jumpers should not be used for this purpose.
l.
Equipments attached to frames or racks by means of flange-mounted quick disconnect fasteners
must be bonded about the entire flange periphery as shown in Figure 3-15. Both the flange surface and the
mating rack surface must be cleaned over the entire contact area.
m. Rack-mounted packages employing one or more dagger pins should be bonded as shown in
Figure 3-16.
The recommended practices
for effective bonding of equipment racks are shown in Figure 3-17.
n.
Bonding between the equipment chassis
and the rack is achieved through contact between the equipment front
panel and the rack front brackets. These
brackets are bonded to the horizontal slide which is in turn arc welded
to the rack frame. The ground stud at
the top of the rack is used to interconnect the rack structure to the
facility ground system.
Where hinges are used, establish an alternate electrical path through the use of thin, flexible straps
o.
across the hinges as shown in Figure 3-18.
p.
Standard MS-type connectors and coaxial connectors must be bonded to their respective panels over
the entire mating surfaces as illustrated in Figure 3-19. Panel surfaces must be cleaned to the base metal for
no less than 0.32 cm (1/8 in.) beyond the periphery of the mating connector.
In ideal situations cable shields should be bonded to the connector shell completely around the
q.
periphery of the shield with either compression or, preferably, soldered bonds.
When an rf tight joint is required at seams, access covers, removable partitions, and other shield
r.
discontinuities, conductive gaskets should be used. They may also be used to improve the bond between
irregular or rough bonding surfaces. Gaskets should be sufficiently resilient to allow for frequent opening and
closing of the joint and yet be stiff enough to penetrate any nonconductive films on surfaces.
3-20
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