TO 1-1-700 - Robins Air Force Base
TO 1-1-700 - Robins Air Force Base
TO 1-1-700 - Robins Air Force Base
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<strong>TO</strong> 1-1-<strong>700</strong><br />
vulnerable surfaces clean while the components are operating.<br />
In storage, however, the intrusion of contaminates can cause<br />
corrosion to continue unchecked until the component is<br />
ruined. Table 8-1 lists common effects of corrosion on electrical<br />
components and systems.<br />
8.5.1.3 Electronic. Electronic systems are particularly vulnerable<br />
to corrosion damage. In modern electronics, circuit<br />
areas are minimized to permit fast operation. Because of this,<br />
most circuit paths have a very small cross-sectional area, making<br />
them extremely vulnerable to corrosion damage. Often,<br />
corrosion that is barely visible to the naked eye is severe<br />
enough to impact the operation of a circuit and cause a system<br />
failure.<br />
Table 8-1. Effects of Corrosion on Electronic Equipment<br />
Component<br />
Failure Mode<br />
Antennas<br />
Relay and switching systems<br />
Plugs, connectors, jacks<br />
Power cables<br />
Display lamps<br />
Waveguides<br />
Printed circuit boards<br />
Batteries<br />
Bus bars<br />
Coaxial Lines<br />
Shorts, changes is circuit constants, structural deterioration<br />
Mechanical failure, shorts, intermittent operation, signal loss<br />
Shorts, increased resistance, intermittent operation, water seal deterioration<br />
Disintegration of insulation, wire and connector deterioration, shorts<br />
Intermittent operation, electrical failures<br />
Loss of integrity against moisture, pitting, reduction of efficiency, structural deterioration<br />
Shorts, increased resistance, component and system failures<br />
High terminal resistance, contact point failure, structural damage to mounting<br />
Structural and electrical failures<br />
Impedance fluctuations, signal loss, deterioration of connectors<br />
8.5.2 Recognizing Corrosion. The ability to recognize corrosion<br />
is essential to performing a comprehensive corrosion<br />
inspection. Metals tend to return to their natural forms (oxides,<br />
carbonates, and others) and are thus vulnerable to corrosion.<br />
Table 8-2 describes the application of common metals in communications<br />
electronics and the indicators of corrosion in<br />
those metals. Detailed instructions or guidelines for recognizing<br />
corrosion can be found in Chapter 9 of this manual. In<br />
most cases, deterioration of nonmetallic components allows<br />
moisture intrusion. This contributes to mechanical failure<br />
through swelling and cracking. In addition, it contributes to<br />
the alteration of the electronic characteristics of electronic<br />
components. Table 8-3 describes the type of attack and the<br />
appearance of the deterioration for common nonmetallic items<br />
in C-E-M equipment.<br />
8.5.3 Effects of Solder Flux. Solder flux residues are<br />
highly corrosive and may be conductive as well. In addition,<br />
they have adhesive properties, attracting and accumulating dirt<br />
or other contaminates. In turn, these contaminates may trap<br />
moisture, causing corrosion or circuit failure. Ultraviolet light<br />
may be used to detect solder flux residue.<br />
8.5.4 Effects of Microbial Presence. Bacteria and fungi<br />
can feed on organic material (encapsulants, conformal coatings,<br />
gaskets, thermoplastics, etc.). Some can release an acid<br />
which facilitates additional corrosion. The presence of these<br />
microbes can be identified by damp, slimy, and bad-smelling<br />
growths on the components in question.<br />
8.5.5 Effects of Insect and Animal Presence. Insects and<br />
small animals can also feed on some organic compounds. In<br />
addition, they can build nests which will trap moisture. The<br />
presence of insects or animals can be identified by the presence<br />
of nests, holes in packaging, and excrement.<br />
8.5.6 Inspection Procedures. This paragraph provides<br />
brief guidance with respect to corrosion inspections of communications<br />
electronics equipment. For more detailed information,<br />
see Chapter 9 of this manual.<br />
8.5.6.1 General. Frequent corrosion inspections are essential<br />
to minimizing and treating corrosion damage to electronic<br />
equipment. Early detection minimizes the cost of repairing<br />
corrosion damage.<br />
8-4