Abstract :
The trend to minaturized solid-state electronics has made appliance controls more vulnerable to human electrostatic discharge (ESD). Membrane switches may increase the likelihood of damage, since the inherently thin membranes provide less isolation than traditional full travel switches. In contrast to the manufacturing environment, relatively little attention has been given to ESD protection in service, where conditions of use cannot be controlled and where protection depends on the choice of keyboard materials and design. Electronic components can be damaged or destroyed and digital signals and data altered when ESD penetrates or circumvents keyboard dielectrics or electromagnetically induces transients in interface circuitry. Keyboard protection measures fall into three categories: grounded shielding, dielectric encapsulation, and transient suppression. Specific illustrations of these are cited. ESD simulators are discussed and practical suggestions given on objectives, preparation, and approach to ESD evaluation and testing of membrane keyboards.
