NOTE
Some ESD control procedures involve conditions or operations that may produce corrosion. Special handling methods and materials must be used to prevent equipment damage. In case of conflict, refer to the applicable service directives and TO 00-25- 234 (Air Force only).
8-9.1. BASIC ESD PRECAUTIONS. ESD precautions are not limited to manufacturing or component repair personnel only. Anyone handling, processing, or using
ESD devices must take precautionary steps. It would be futile for component repair personnel to take full precautions, only to turn the repaired item over to technicians who ignore all precautions and inadertvently destroy the module. Maintenance personnel should refer to MIL-HDBK-773, MIL-HDBK- 263, and MIL-STD-1686 for more detailed descriptions of ESD control measures.
8-9.2. ESD PACKAGING PRACTICES. Packaging of ESD items must only be done at an ESD protective workstation. See Figure 8-6.
a. Packaging for electrostatic discharge protection requires the use of one or more of the following materials:
(1) MIL-PRF-81705, Type II barrier material, transparent, waterproof, electrostatic protective, static dissipative.
(2) Cushioning material, flexible, cellular, plastic film.
(3) Cushioning material, plastic open cell. (4) PPP-C-1797, cushioning material, resilient, low density, unicellular, polyproplene foam.
b. ESD items may be further protected in reusable
or shielded in a bag or pouch conforming to MIL-PRF-81705 Type I barrier material, water- vaporproof, grease-proof, electrostatic and electromagnetic protective (opaque).
c. Protection will be provided to prevent physical damage and to maintain leads and terminals in an as- manufactured condition during handling and transportation.
d. Packaging of ESD items shall be in accordance with MIL-E-17555 for electrostatic protection. Marking shall be in accordance with MIL-STD-129.
8-9.3. ESD WORKSTATION SHOP PRACTICES. a. Control humidity within 40% to 60% range. Humid air helps dissipate electrostatic charge.
b. Ionized air helps to bleed off static charges. c. Prohibit prime generators (Table 8-1) and carpeting from avionics shop areas.
d. Chairs and stools should have conductive surfaces and should be grounded through a 250 kilohm to 1 megohm resistor to ground.
e. Trays, carriers, cushioning materials, and bags should be made of conductive ESD protective material. f. Electrical equipment, tools, or soldering irons that come in contact with ESD devices should be grounded. Resistance to top of soldering irons should be less than 20 ohms. Only ESD safe tools should be used.
g. Test equipment with exposed metal surfaces should be grounded.
h. Personnel handling ESD devices should wear long sleeve ESD smocks or short sleeve shirts. Prohibit materials such as common plastic, rubber, or nylon.
i. Personnel grounding straps should have minimum resistance of 250 kilohms and maximum of 2 megohms.
8-9.4. ESD DEVICE HANDLING PRACTICES. Damage to ESD items may occur if untrained personnel are allowed to handle ESD items when the items are outside of an ESD protective package.
a. Protective apparel should be checked frequently, especially after cleaning, by scanning personnel with an electrostatic field meter to monitor for damaging ESD voltages.
b. Be sure to attach the wrist strap (mandatory) and heel straps (if used) before handling any ESD items. c. Avoid the presence of any nonantistatic or insulative material near work areas. For example, styrofoam cups, plastic or masking tape, wrapping or barrier materials, or synthetic materials.
d. Do not store or use magnetic material near work areas.
e. Do not perform stretch or shrink-wrapping operations within the ESD-controlled work area.
f. Do not use waxes, polishes, or similar materials on floormats or tabletops. They may deposit an insulating layer of residue. This reduces or eliminates the effectiveness of the floormat or tabletop. For the same reason, the use of topical antistatic spray is not recommended on packaging materials.
g. Sweep dust and dirt from the tabletop and floormats as often as needed to prevent any accumulation. Dirt will also insulate these surfaces and make them ineffective.
h. Antistatic pouches should be used for technical manuals, drawings, and work instructions rather than plain plastic pouches.
i. Ensure all containers, tools, test equipment, and fixtures are grounded before and/or during use by direct ground or by touching a grounded surface.
j. Avoid friction producing activities near ESD devices. For example, removing smocks, wiping feet, sliding objects over surfaces.
k. Wear cotton smock or other antistatic clothing. l. Prohibit prime generators (Table 8-1) from ESD areas.
m. Place ESD protective material on grounded surface to remove any charge before opening package. n. Remove ESD item from package only after grounding and place item on grounded surface.
o. Use noncorrosive ESD protective conductive foam or connect shorting clip, or bars to terminal of ESD device.
p. Perform periodic electrostatic checks to ensure work station meets specification.
8-9.5. TESTING AND/OR REPAIR PRACTICES. a. Ensure work area, equipment, and work strap assembly are grounded.
b. Attach wrist strap and place metal tools and accessories on grounded bench surfaces.
c. Place conductive container on bench. Remove component or assembly from package. Remove shorting device if present. Handle components by their body and place on conductive work surface/test fixture. d. Compressed gases shall not be used to cool fixtures.
e. Test through connectors or tabs only.
f. After testing, replace shorting packages and protective packaging.
g. Do not use Simpson 260 (or equivalent) multimeter to test parts. Instead use the Fluke 8000A or other high-impedance digital multimeter (DMM).
h. Dielectric strength tests are prohibited.
i. Only the use of anti-static type solvents is allowed. j. Heat guns for test or curing are prohibited. k. Drying lamps, photo spots, and thermal probes are allowed.
l. Do not remove components or assemblies from their sockets with power applied.
m. Apply dc voltages prior to applying signal inputs. n. The use of air to clean components/assemblies is prohibited unless a filtered ionizing air gun is used. o. Do not use solvent ultrasonic cleaning bath for component assemblies.
p. Device supply connections on the assembly should be made prior to making the ground connection. q. Cure conformal coatings by normal ambient curing or in an oven that contains grounding provisions to prevent static charge buildup.
8-10. PREVENTION, TREATMENT, AND CONTROL