Bonding Practices

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Figure 3-11. Typical Equipment Cabinet Grounding Detail

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Grounding, Bonding, and Shielding for Electronic Equipments and Facilities

Figure 3-12. Acceptable and Unacceptable Uses of Bonding Jumpers

MIL-HDBK-419A

3.3 BONDING PRACTICES. Equipment emission and susceptibility requirements for proper system operation

should be accomplished with the most cost-effective combination of interference reduction techniques.

This section presents design and

Bonding is an essential element of the interference control effort.

construction guidelines to aid in the implementation of effective bonding of equipment circuits, equipment

enclosures, and cabling. These guidelines are not intended as step-by-step procedures for meeting EMC

specifications. Rather they are aimed at focusing attention on those principles and techniques which lead to

increased compatibility between circuits, assemblies, and equipments.

Welded seams should be used wherever possible because they are permanent, offer a low impedance

bond, and achieve the highest degree of rf tightness.

Spot welds may be used where rf tightness is not necessary. Spot welding is less desirable than

continuous welding because of the tendency for buckling and the possibility of corrosion occurring between

welds.

Soldering should not be used where high mechanical strength is required. If mechanical strength is

required, the solder should be supplemented with fasteners such as screws or bolts.

Solder must not be used to form bonds which may be reasonably expected to carry large currents,

such as those produced by power line faults or lightning currents.

Fasteners such as bolts, rivets, or screws should not be relied upon to provide the primary current

path through a joint.

Rivets should be used primarily to provide mechanical strength to soldered bonds.

Sheet metal screws should be used only for the fastening of dust covers on equipment or for the

attachment of covers to discourage unauthorized access by untrained personnel.

Bonds that can not be made through direct metal-to-metal contact must use auxiliary straps or

jumpers. The following precautions should be observed when employing bonding straps or jumpers (see Figure

3-12):

(1)

Jumpers should be bonded directly to the basic structure rather than through an adjacent part.

(2)

Jumpers should not be installed two or more in series.

(3)

Jumpers should be as short as possible.

(4)

Jumpers should not be fastened with self-tapping screws.

(5)

Jumpers should be installed so that vibration or motion will not affect the impedance of the

bonding path.

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