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 MIL-HDBK-419A
CHAPTER 7
BONDING
7.1 DEFINITION OF BONDING. As used in these Volumes, bonding refers to the process by which a low
impedance path for the flow of an electric current is established between two metallic objects. Other types of
bonding which involve simply the physical attachment of one substance or object to another through various
mechanical or chemical means are not treated.
7.2 PURPOSES OF BONDING.
In any realistic electronic system, whether it be only one piece of equipment or an entire facility, numerous
interconnections between metallic objects must be made in order to provide electric power, minimize electric
shock hazards, provide lightning protection, establish references for electronic signals, etc. Ideally, each of
these interconnections should be made so that the mechanical and electrical properties of the path are
determined by the connected members and not by the interconnection junction. Further, the joint must
maintain its properties over an extended period of time in order to prevent progressive degradation of the
degree of performance initially established by the interconnection. Bonding is concerned with those techniques
and procedures necessary to achieve a mechanically strong, low impedance interconnection between metal
objects and to prevent the path thus established from subsequent deterioration through corrosion or mechanical
looseness.
In terms of the results to be achieved, bonding is necessary for the:
protection of equipment and personnel from the hazards of lightning discharges,
a.
establishment of fault current return paths,
b.
c.
establishment of homogeneous and stable paths for signal currents,
d.
minimization of rf potentials on enclosures and housings,
e.
protection of personnel from shock hazards arising from accidental power grounds, and
f.
prevention of static charge accumulation.
With proper design and implementation, bonds minimize differences in potential between points within the fault
protection, signal reference, shielding, and lightning protection networks of an electronic system. Poor bonds,
however, lead to a variety of hazardous and interference-producing situations. For example, loose connections
in ac power lines can produce unacceptable voltage drop at the load, and the heat generated by the load
current through the increased resistance of the poor joint can be sufficient to damage the insulation of the
wires which may produce a power line fault or develop a fire hazard or both. Loose or high impedance joints in
7-1
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