MIL-HDBK-773A
4.1.2 Static charge. A static charge is an excess or a deficiency of electrons on a surface. An excess of electrons produces a negatively charged surface and a deficiency of electrons produces a positively charged surface. Table I gives examples of common
materials that charge positively, or negatively when separated from each other. Materials that charge positively lose their loosely bound surface electrons and materials that charge negatively, attract and maintain those electrons. Table II shows typical electrostatic voltages that occur during normal workday activities, and table IV lists typical electrostatic charge sources.
4.2 ESD damage. As shown in table II, activities such as walking, working at a bench, and handling common materials can generate thousands of volts of static electricity. If a spark discharge occurs from an accumulation of electrostatic voltage, electronic components, PCB components, and other electronic assemblies can be destroyed or damaged. Spark discharges cannot be felt if the electrostatic voltage is less than the threshold level for that particular individual. This threshold level is usually within the range of 2,500 to 4,000 volts of electrostatic charge.
4.3 Description of an integrated circuit. Since the advent of the integrated circuit, electronic components have become smaller and their functional capabilities have become greater. A microprocessor, the core element in a microcomputer, is less than
one-half of a cubic inch in volume. Because of the micro-miniature size of the functional components in an integrated circuit, they are much more susceptible to ESD damage than their earlier, significantly larger counterparts. Table III provides the relative ranges for possible damage.
4.3.1 Damage by spark discharge. Considering the threshold levels at which most people can feel a spark discharge from electrostatic voltage, it is easy to understand how electronic parts can unknowingly be damaged during handling. If it is not immediately destroyed, the damaged part may not cause a functional system failure until after it reaches the user.
4.3.2 Microscope view. Figure 1 is a Scanning Electron Microscope view of a capacitor on a microchip of a high performance operational amplifier that has been damaged by ESD. Figure 1 shows the capacitor magnified at two different ranges with the damaged areas indicated by arrows. The ESD damage resulted in a 400-ohm path from the capacitor to ground, causing a malfunction in the amplifier.
4.4 Identification/acquisition. Items identified as ESDS will be protected from the very beginning of the acquisition process to final disposal. Specific control programs involved with item design, test, inspection, manufacture and maintenance are contained
in MIL-STD-1686 as implemented by MIL-HDBK-263.
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