Electrostatic discharge ("ESD") is known to cause damage to electrical components and equipment. The prior art has developed certain ways to protect electrical equipment from human touch through specially designed user keypad panels. FIGS. 1 and 1A illustrate one such user keypad panel 10. Specifically, FIG. 1 shows a top view of keypad panel 10; and FIG. 1A shows a cross-sectional view of keypad panel 10. The upper-most layer of panel 10 is an embossed polycarbonate or polyester layer 11, which, for purpose of illustration, is shown transparent so as to view ESD screen layer 12. ESD screen layer 12 includes a silver-painted cross-hatch conductive pattern 12a that is connected to a conductive ESD tail 14. ESD tail 14 forms a mounting hole 16 used to electrically connect pattern 12a to equipment chassis.
FIG. 1A shows further detail of keypad panel 10, including button switch 18, button spacer layer 20, signal trace layer 22, and adhesive layer 23. Layer 11 includes an embossed button pattern 11a-illustratively shown as a dotted line in FIG. 1 and as an upward protrusion in FIG. 1A. Button pattern 11a is adjacent button switch 18 so that human pressure on embossed button pattern 11a activates button switch 18 through deformation of ESD screen layer 12. Button switch 18 is known in the art and operates with signal trace layer 22 to generate signals--via switch circuitry 22a--indicative of switch activation. These signals are detected in signal layer 22 by known techniques such as through signal cable 24. Spacer layer 20 is used to form a space between ESD layer 12 and signal trace layer 22. Adhesive layer 23 bonds panel 10 to a flat surface associated with electrical equipment.
Although keypad panel 10 is shown with only one button 11a, other buttons can be included. By way of example, button 11a can be a power on and power off button to the electrical equipment.
In operation, a user operates the electrical equipment through keypad panel 10. Screen layer 12a arguably attracts ESD pulses which are in turn shunted, through ESD tail 14, to chassis ground associated with the electrical equipment. ESD tail 14 is mounted to chassis ground with a screw and nut through mounting hole 16.
One problem with prior art panel 10 is that differential voltages can exist between lines of the cross-hatch pattern 12a, leaving residual voltage potential energy resident in ESD layer 12 even though other energy is drained off through ESD tail 14. Another problem is that panel 10 requires additional manufacturing cost and time due to ESD tail 14, and due to the nut and screw required to attach ESD tail 14 to chassis ground. Yet another problem is that ESD pulses are routed through a single location associated with panel 10, i.e., at ESD tail 14.
One object of the invention is to provide a new and improved ESD keypad panel that reduces or eliminates the above-described problems.
Another object of the invention is to provide an ESD protection panel with multiple ESD shunt contacts to improve grounding to equipment chassis.
Yet another object of the invention is to provide an ESD protection panel that has improved ESD protection capability, as compared to the prior art, and which requires less cost and manufacturing time.
Still another object of the invention is to provide an ESD-protected keyboard panel which has increased protection against ESD pulses coupling to associated electrical equipment.
These and other objects will become apparent in the description that follows.