WO1993010650A1

WO1993010650A1 - Controlled electrostatic discharge grounding system for a keyboard

Info

Publication number: WO1993010650A1
Application number: PCT/US1992/010241
Authority: WO
Inventors: Billy G. Gass; Kirk R. Holmes; Larry F. Norte; Thomas H. Kehoe
Original assignee: Key Tronic Corporation, Inc.
Priority date: 1991-11-19
Filing date: 1992-11-18
Publication date: 1993-05-27

Abstract

A controlled discharge grounding apparatus is provided for use with electronic devices. The apparatus is a part of the input device, such as a keyboard, for the electronic device of interest. The keyboard includes a conductive keycap which is adapted so that in addition to the key being able to perform its normal function, that keycap is electrically connected to a source of ground potential. The apparatus comprises a conductive keycap, a means for providing electrical resistance and an electrical conductor connected to a source of ground potential. The use of the means for providing electrical resistance prevents the operator from experiencing 'electrical shock' caused by rapid discharge of an accumulated charge to the source of ground potential.

Description

CONTROLLED ELECTROSTATIC DISCHARGE GROUNDING SYSTEM

FOR A KEYBOARD

FIELD OF THE INVENTION This invention is related generally to protection of electronic devices which ar susceptible to damage caused by uncontrolled electrostatic discharge (BSD) of a accumulated electrostatic charge, such as from an operator of a device. Mor specifically, this invention is directed toward providing ESD protection to the inpu portion of certain electronic devices such that the dissipation of an accumulate electrostatic charge from an operator is done in a controlled manner, through th ordinary use of the device, and in a way which prevents arcing between the electroni device and the operator, so as to minimize operator discomfort. In particular, th present invention is directed toward providing a controlled electrostatic discharg grounding system which can be incorporated into a typical computer keyboar through the use of at least one conductive keycap which is electrically connected to source of ground potential.

BACKGROUND OF THE INVENTION Some types of modern electronic equipment, particularly computer system such as personal computers, are sensitive to permanent damage or disruption of th overall system function due to ESD. One of the most common sources of ESD i human operators. Operators can accumulate an electrostatic charge in many ways including walking across a carpeted floor, movement where a synthetic garment rub against itself or another insulated object, and touching an object which has alread accumulated an electrostatic potential. It has been reported in numerous sources tha the electrostatic potentials of accumulated electrostatic charges obtained by operator of electronic equipment in an office environment can range from several hundre volts up to approximately thirty thousand volts.

Electronic devices such as personal computers contain many components tha are susceptible to damage by discharge of electrostatic potential, includin electrostatic potential which has been accumulated by an operator. These device include, to name a few, memory devices, logic devices, microprocessors and th miniature circuits and wiring used to interconnect these devices. Discharges in th range described above can result in temporary damage or disruption of thes components, resulting in undesirable device operating characteristics such a interruption of computer programs. Discharge of larger electrostatic potentials (e.g. 30,000 volts) can cause permanent damage to the sensitive electronic component mentioned above such as by destroying semiconductor junctions or causing conductor to melt, creating permanent open circuits.

One of the greatest opportunities for damage caused by ESD occurs when a operator makes his initial physical contact with the input portion of the device, suc as a keyboard, keypad or other touch-actuated entry mechanism. A great opportunit for damage exists because the input device such as a keyboard is frequently the first, and sometimes the only, part of an electronic device with which an operators come into contact after undergoing activity of the type which can produce an electrostati charge. If an operator who has accumulated an electrostatic charge comes into contact with a keyboard or other input device, the charge which comprises an electrostatic potential can often be discharged into the input device because it often offers a source of lower electrical potential through various conductors in the system which are often attached to a source of ground potential, which can be earth ground potential. If such a transfer occurs, the potential for damage exists on several levels. First, keyboards and other input devices often contain components which are sensitive to ESD. In addition, damage can be incurred by the electronic device to which the input device is connected, if a conductive path is available from the input device to the electronic device of interest. In both situations, the potential for serious damage is significant because both input devices, such as keyboards, as well as the electronic devices to which they are connected, such as computers, carry components which can be damaged by ESD. Consequently, it has been known for some time that it is highly desirable to remove any accumulated charge from an operator prior to contacting the keyboard, or any other part of the computer system.

One class of devices which has been used for this purpose includes static dissipative touch devices (SDTD) which can be placed adjacent to the input device.

These devices typically include a conductor means which can be contacted by the operator, and a means for dissipating static charge which has accumulated on an operator to a source of ground potential.

SDTD's sometimes also include a series resistance to reduce the rate of discharge from an operator to the device. By including a series resistance, it reduces the likelihood that a spark discharge will occur. This is desirable in order to πiinimize the discomfort experienced by the operator resulting from the transfer of the electrostatic charge to ground potential. SDTD's take several forms, including conductive pads, conductive touch bars, and conductive spheres. Such devices have common problems associated with them. A principal problem is that it is difficult to ensure that an operator will contact them prior to contacting the keyboard. Making contact typically requires extra movements beyond those required to make input into the electronic device of interest. Often, an operator may forget to touch an SDTD before touching the keyboard or other input device. In addition, it is also not alway possible to provide such SDTD's adjacent to the electronic device of interest due t space limitations and other considerations.

Another approach has been to provide a ground plane or a grounding mean near a keypad, such that the grounding plane is in closer physical proximity to an operator than are the components which are sensitive to ESD. It is not alway possible to use an approach of this type in all input devices due to space limitations and design constraints. For instance, while it might be used on a keypad for telephone handset, where a non-conductive key can be contacted by the operator and by operation of the key brought in close proximity to the ground plane, this is not necessarily the case for other configurations such as a computer keyboard, where it is difficult to bring the surface which the operator contacts in close proximity to a ground plane. Also, this type of approach may require the electrostatic charge to arc to the source of ground potential, rather than depending on direct contact. Consequently, an operator may experience discomfort resulting from the arc discharge when using this type of a system.

Yet another proposed solution to this problem has been to provide a conductive surface over the entirety of a keypad array, such as through the use of a wire mesh covering. Again, this approach may be conducive to some applications, but is not feasible for others, such as computer keyboards having key switches which require independent travel.

It has also been suggested that for individual switches which each have a separate housing for the switch, that the housing can be provided with a conductive path leading to ground potential. While this approach may be implemented successfully in some applications, not all devices have individual switch housings which lend themselves to being connected to ground potential. For instance, one popular approach to keyboard construction incorporates a plurality of keycaps 2, slidably engaged in a unitary housing sheet 4, as illustrated in Figure 1. In this instance, it is not feasible to provide the unitary housing with a conductive path to ground potential. Unitary housing sheet 4 is often made from nonconductive plastics. The typical arrangement of, and materials used for, the keycaps 2 and the unitary housing sheet 4 would not permit an electrostatic charge to be effectively transferred from the keycap to the housing sheet, as is possible when each key has an individual housing which comes up in close proximity to the key actuation surface. Finally, as is also illustrated in Figure 1, a related art approach has been to attach a wire 6 to keycap 2, such as a spacebar, for the purpose of removing an accumulated electrostatic charge from an operator. Such an approach presents several problems. Firstly, keycap 2 of the related art device was a nonconductive material. Therefore, effective removal of an accumulated charge on an operator is not ensured Depending on the arrangement of keycap 2 and wire 6, the manner in which a operator makes contact and the level of accumulated charge, the charge may b completely discharged, partially discharged, or not discharged at all. In addition, thi system does not incorporate a means for controlling the rate of discharge. Therefore if discharge does occur, it may occur by arc discharge through the air, resulting in a operator sensing an electrical shock. Secondly, since the rate of discharge is no controlled, large ESD related currents can result, leading to induction induce interference within the electronic device. Thirdly, large currents can also result i arcing to other devices, depending on the orientation and spacing of wire 6 relative t other parts of the electronic device. Finally, large currents also impose constraints o wire 6 and the subsequent conductors to which it may be connected, in order t prevent the current from causing a current density in some portion of the circui which will result in "fusing", or the creation of an open circuit. As pointed out by this discussion of the problems associated with ESD and the prior approaches to dissipating an electrostatic potential, with their inheren limitations, it is desirable to provide a structure which is compatible with an input device such as a computer keyboard, for the purpose of removing accumulated static charge on an operator.

SUMMARY OF THE INVENTION In accordance with the detailed description and drawings herein, the invention comprise a conductive keycap, a means for conducting an accumulated electrostatic charge away from the keycap to a source of lower potential, and a means for providing electrical resistance.

In general, the conductive keycap can comprise a plurality of structures such as homogeneous conductive material or other structures which result in keycap being conductive. In the embodiments shown, the conductive keycap includes either a conductive carbon-filled polymer insert located within a nonconductive polymer keycap which is adapted to receive the insert, or a completely conductive keycap made from a conductive material embedded in a nonconductive polymer matrix. Both embodiments result in a single keycap which has a conductive region on its upper contact surface, which extends through the keycap to its bottom surface.

A means for providing electrical resistance is electrically connected to the bottom surface of the keycap, and is also adapted to be electrically connected to a means for conducting an electrostatic charge to a source of ground potential.

Depending on the type of conductive keycap utilized, the means for providing electrical resistance may be a discrete carbon resistor or a screen printed ink resistor. A flexible circuit, including a polyester film substrate and a conductive ink, is used as the means for conducting. The flexible circuit is designed to be electrically connected to the means for providing electrical resistance and to a conductor path within the keyboard which is connected to a source of ground potential. An important feature is that an operator contacts a conductive keycap in the ordinary use of the keyboard. A key location or locations must be chosen so that the operator touches the conductive key as soon as possible relative to the nonconductive keys. Preferably, a conductive key would be touched first. A preferred embodiment is the spacebar because in the typical QWERTY keyboards, the operator usually begins by touching certain home row keys in the center of the keyboard, resulting in his thumbs contacting the spacebar key. The regular initial contact with this key makes it desirable for use in conjunction with the present invention.

As an operator makes contact, accumulated electrostatic charge is discharged into the grounding circuit. The resistor limits the rate of discharge and prevents arcing between the operator and the grounding circuit.

A principal object of the invention is to provide a grounding circuit for electronic devices, such as computers, which is an integral part of the device.

A second object is to control the discharge so as to avoid discomfort to an operator, by avoiding arcing between the device to be used and the operator. The integral nature of the device provides an important advantage because in contrast to related devices, it ensures that an operator will, in most cases, have an accumulated electrostatic charge removed in the ordinary use of the device, thereby avoiding damage caused by ESD. Additional objects, features and advantages of the invention may be apparent to one skilled in the art upon examination of the drawings and detailed description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an exploded perspective view of a related art keyboard showing a typical form of keyboard construction and having a spacebar which is connected to a wire, which in turn can be connected to a source of ground potential.

Figure 2 is an exploded perspective view of a keyboard illustrating the incorporation of a first embodiment of the invention into typical keyboard construction.

Figure 3 is an exploded perspective view of the embodiment of Figure 2, illustrating various of the components and their general spatial orientation with respect to one another. Figure 4 is a partial-cutaway exploded perspective view of the preferred embodiment of Figure 3, illustrating generally how the conductor is electrically connected to the keycap.

Figure 5a is a top view of the keycap of the embodiment of Figure 4. Figure 5b is a front view of the keycap of Figure 5a.

Figure 5c is a bottom view of the keycap of Figure 5a. Figure 5d is a representative section view of the keycap of Figure 5a, illustrating the attachment of the resistor to the conductive insert.

Figure 5e is a bottom view of the keycap of Figure 5a, illustrating a second means for attaching the resistor.

Figure 6 is an exploded perspective view of the keycap of Figure 5a. Figure 7 is an expanded top view of a portion of the structure of Figure 5c. Figure 8 is a section view of the structure shown in Figure 7 along section line AA. Figure 9 is a perspective view of the structure of Figure 7 shown with a flexible conductor inserted to illustrate how the flexible conductor makes electrical contact with the keycap.

Figure 10 is an exploded perspective view of a keyboard illustrating the incorporation of a second embodiment of the present invention into typical keyboard construction.

Figure 11 is an illustrative view of the conductor and screen printed resistor of Figure 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Figure 2 shows an exploded view of the construction of a typical keyboard 20, such as is commonly used as an input device for computers and other electronic devices and equipment. Keyboard 20 comprises base 22, cable 24, flexible circuit 26, elastomer bootsheets 28, housing plate 30 which is sometimes also known as a transfer plate or a transfer sheet, cover 32, and keycaps 34. Housing plate 30 houses keycaps 34, each having a downwardly extending flexible extension arm 36. Housing plate 30 has upwardly extending, hollow, cylindrical projections 38 which are adapted to engage and retain flexible extension arm 36 of keycaps 34.

A first embodiment of the present invention is shown in Figure 2, and in an expanded view in Figure 3.

Controlled discharge grounding system (CDGS) 40 comprises a keycap 34 which is conductive, and which in this instance is conductive spacebar 42, a means for providing electrical resistance 44, which is shown in one embodiment in Figure 5c, a conductor 46 which is capable of being connected to a source of groun electrical potential, and a means for connecting 48 conductor 46 to keycap 34.

Referring now to Figures 3, 5a, 5b, 5c and 6, CDGS 40 is capable of bein implemented in any keycap position. In this instance, it is implemented throug conductive spacebar 42. Conductive spacebar 42 can be made conductive by any on of a number of techniques, including, but not limited to, use of a conductive materia for the body of the spacebar, appropriate conductive coatings or in the embodimen shown through use of a conductive material for only a portion of the spacebar.

In the present embodiment, conductive spacebar 42 comprises non-conductiv body 50 and conductive insert 52. Non-conductive body 50 is made out of a typica keycap material, such as ABS plastic. Conductive insert 52 is made out of a carbo filled plastic such as ABS, with a 10% by weight carbon filler, however, conductiv insert 52 can also be made out of other types of conductive materials. As shown i Figure 6, conductive insert 52 is attached to non-conductive body 50. Thi attachment can be done using adhesives or other suitable methods for attachin conductive insert 52 to non-conductive body 50. It may also be possible to mol conductive insert 52 directly into non-conductive body 50 as part of the moldin process used to create non-conductive body 50.

As shown in Figures 5a, 5b and 5c, conductive insert 52 permits the transfe of an electrostatic charge from top surface 51 to bottom surface 53 of keycap 34.

This is an important feature because it permits the operator to discharge an electrostatic charge by touching the conductive portion of top surface 51, whil allowing the charge to be transferred to bottom surface 53 where the necessary electrical connections can be made to a source of ground potential without disturbing the normal function of conductive spacebar 42 as an input key, or otherwise effecting the esthetic appeal of keyboard 20 by requiring electrical connections to be made on top surface 51, which is in view of an operator.

The size and location of conductive insert 52 with respect to non-conductive body 50 is also an important feature, as further described below. Referring now to Figures 5c and 5d, means for providing electrical resistance

44 comprises resistor 54 having conductive leads 56, resistor insulating material 58, and means for connecting 60 resistor 54 to conductive insert 52. Resistor 54 is a carbon resistor with a value in the range on the order of 10 - 500 M Ω. In one embodiment, means for connecting 60 comprises copper foil 62 which is attached to conductive insert 52 through the use of conductive adhesive 64 which is conductive through its thickness or, as it is otherwise known, through the z-axis. One conductive lead 56 of resistor 54 is attached with solder 63 to copper foil 52 to establish electrical continuity from conductive insert 52 to resistor 54. In a second embodiment, as illustrated in Figure 5e, means for attaching 6 comprises a slotted post 65 which is molded into conductive insert 52. Conductiv lead 56 of resistor 54 can be placed into said slot and attached to slotted post 65 using head staking or other suitable attachment means. The other conductive lead 56, opposite conductive lead 56 which is attached t conductive insert 52, is inserted in opening 66 formed in non-conductive body 50 Conductive lead 45 is inserted in opening 66 such that it may be engaged wit conductor 46 as illustrated in Figures 4, 5c, 7, 8 and 9, in order to form an electrica contact between resistor 54 and conductor 46. Conductor 46 can be made from a number of conductive materials. In th present embodiment, conductor 46 comprises a flexible insulating substrate 68 such a a clear stabilized polyester film of thickness 0.002-0.007 inches, also know commercially as mylar, and a conductive circuit path 70 which is formed o insulating substrate 68. Conductive circuit path 70 can be formed through a numbe of methods including the screen printing of commercially available conductive ink to form conductive circuit path 70. This conductive ink can then be processed so as to adhere it to insulating substrate 68, thereby forming conductor 46. In the present embodiment, conductor 46 is formed using processes similar to those used to produce flexible circuit 26, which are widely known in the art. Conductive circuit path 70 is on only one side of insulating substrate 68. In order to establish an electrical connection between conductor 46 and resistor 54, means for connective 48 is utilized. Means for connecting 48 comprises an elastomeric spring 72 which is attached to the end of conductor 46, through the use of an adhesive 73, on the side opposite the side which has conductive circuit path 70 printed on it. Conductor 46, with elastomeric spring 72 attached, is inserted between retainer arm 74 and guides 76. Leveler rod 78, which is used principally to enhance the function of keycap 34 for its use as an input key, is inserted between elastomeric spring 72 and retainer arm 74, thereby compressing elastomeric spring 72 and forcing conductive circuit path 70 into conductive contact with lead 56. The action of retainer arm 74 against leveler rod 78 and elastomeric spring 72 creates electrical contact between resistor 54 and conductor 46, as illustrated in Figure 9.

Conductor 46 can then be electrically connected to a source of ground potential as illustrated in Figures 2 and 4. In the present embodiment, flexible conductor 46 is attached to a source of ground potential through ground layer 79 of flexible circuit 26. Flexible circuit 26 is in turn connected via electrical cable 24 to a source of ground potential in the electrical device of interest, such as a computer. Of course, flexible conductor 46 can be connected to any source of ground potential. So long as suitable connectors are provided, the source of ground potential could be provided in any of a number of configurations, including those which would connect to keyboard 20 directly without requiring connection to an external electronic device. Having described the various elements and their spatial relationship with respect to one another, the function of the device is now described. As an operator which may have accumulated an electrostatic charge prepares to utilize a particular electronic device, one of the first components which will be touched by the operator is the input device, in this case keyboard 20. When an operator contacts keyboard 20, it is common that the first keys contacted include the "home row" keys which are located in the center of the keycap 34 array, and conductive spacebar 42. Use of the spacebar as a conductive keycap is an important feature of the invention because it is desirable to remove any accumulated charge from an operator as quickly as possible, before it can be discharged in an uncontrolled manner and cause damage as described herein.

When an operator contacts conductive spacebar 42, charge which has accumulated on his body, particularly in the area of his hands, will flow toward the source of ground potential provided through conductive spacebar 42. The means for providing electrical resistance 44 is a very important feature at this point, because absent this means, if the accumulated electrostatic charge is large enough, the charge will be discharged rapidly to the source of ground potential. This can even include an arc discharge, which may result in an operator receiving an unpleasant "electrical shock" sensation. Means for providing an electrical resistance is included to limit the amount of current which can be discharged through this circuit. The net effect is to slow the rate of charge transfer such than an arc discharge does not occur. This ensures that the charge will be removed from an operator without the operator experiencing unpleasant side effects.

Also, it is desirable to avoid the uncontrolled discharge of an accumulated charge in an operator in order to prevent damage to various circuit components within keyboard 20 or the electronic device which it is connected to. If uncontrolled discharge is permitted, it is possible for the high currents involved to damage the circuit paths in areas where there may be high current density due to narrow conductor cross section, or defects in the conductor path over which the charge is being discharged. Also, depending on the proximity of components which may be adjacent to conductor 46 between the point at which the accumulated charge is discharged and the source of ground potential, it is possible for arcing to occur between conductor 46 and other circuit paths which offer less resistance to a source of ground potential. As an example, if resistor 54 is a discrete carbon resistor and is located on flexible circuit 26 rather than inside conductive spacebar 42, it has been noted that it is possible for the accumulated charge to short around resistor 54, or for shorting to occur between the conductor extending between conductive spacebar 4 and resistor 54, and other circuit paths on flexible circuit 26 which offer les resistance to the source of ground potential.

In this regard, the overall design of the system is an important feature, particularly the arrangement of the conductive elements including conductive inser 52, conductive leads 56 and leveler rods 78, and resistor 54, with respect to th location of conductor 46. As noted above, if resistor 54 is not located near the poin at which the accumulated charge is to be discharged into the device, it is necessary t provide electrical isolation of the conductor extending from conductive insert 52 a least down to the point where resistor 54 is located, otherwise, the charge which is transferred to conductor 46 may be able to arc to other conductive paths located on keyboard 20 which offer less electrical resistance to a source of ground potential than does conductor 46. In the present embodiment, resistor 54 has been located within conductive spacebar 42 to minimize the amount of electrical isolation which must be provided. Even in this arrangement, however, it is necessary to ensure that no point of conductive insert 52 comes close enough to conductor 46 to permit arc discharge through the air or across bottom surface 53. In the first embodiment, conductive insert 52 is approximately three inches long and has a minimum separation between conductive insert 52 and conductor 46 on the order of 0.75 inches. In addition, electrical isolation is provided by the arrangement of elastomeric spring 72 and guides 76, because these elements are interposed between conductor 46 and conductive insert 52. Resistor insulating material 58 is also provided to prevent an electrical discharge directly to conductor 46. Resistor insulating material 58 consists of shrink wrap tubing of a type well known in the art which covers lead 56 and resistor 54 from the point at which lead 56 leaves copper foil 62 until the opposite lead 56 passes through guide 76. Resistor insulating material 58 ensures that an accumulated charge which is discharged into conductive insert 52 will not arc around resistor 54 or arc directly from conductive insert 52 to lead 56 which is between resistor 54 and guide 76.

A second embodiment of CDGS 40 is shown in Figures 10 and 11. This second embodiment retains the principal objects, features and advantages of the first embodiment, and comprises a conductive keycap 80, a means for providing electrical resistance 82, a conductor 84, and a means for connecting conductor 84 to keycap 80.

In this embodiment, conductive keycap 80 is a conductive spacebar 86.

Conductive spacebar 86 is conductive over the majority of its surface and does not rely on the use of a conductive insert. In this embodiment, conductive spacebar 86 is rendered conductive by the use of nickel-coated graphite fibers in a matrix of ABS plastic, wherein the fibers occupy approximately 6 volume percent of the keycap. Other conductive materials can be used, depending on the application requirement Conductive keycaps 80 are produced using typical plastic molding methods.

Means for providing electrical resistance 82 is a thick film screen resistor 8 screened on to conductor 84, which is a stabilized polyester film of a type describ previously above. The desired resistance value of resistor 88 is in the range of 10

500 MΩ. Resistor 88 is comprised of a mixture of carbon linear resistance polym 90 and clear resin 92, wherein the resin comprises a clear vinyl or clear polyest material. The volume percentage of these constituents ranges from approximately 4 55 volume percent polymer, to 55-45 volume percent resin. The constituents includ in one example Olin Hunt 435A carbon linear resistance polymer, Olin Hunt 6C-5 clear vinyl resin, or Olin Hunt 18DB9C polyester resin.

After the screen printed resistor 88, of the mixture described above, screened onto conductor 84, the resistor is cured at temperatures ranging fro approximately 95-120°C for times ranging up to 45 minutes. Conductor 84 is connected to, and may be an integral part of, ground layer 7

Conductor 84 is of the construction previously described for conductor 4 Conductor 84 has an open area 94 into which screen printed resistor 88 is locate The size of the open area 94 is determined by the electrical characteristics desired f screen printed resistor 88 and the electrical resistance properties of the screen printe material. For the resistor 85 materials utilized, the open area 94 is typically .7 inches or greater in length. It has been observed that for open area 94 of this siz that arcing around resistor 88 does not occur. Therefore, additional electric isolation of the types noted previously have not been necessary.

Conductor 84 is attached to conductive keycap 80 by means for attaching 9 In this embodiment, the means for attaching includes the combination of elastomeri spring 72 and leveler arm 78, described above and shown in Figures 4 and 9.

An additional feature of the second embodiment is that the materials used especially for screen printed resistor 88, are compatible with, and can become a integral part of the current construction materials and methods used to produc flexible circuit 26 and ground layer 79. This has the added advantage of lowering th material and labor costs required to implement the present invention.

The terms and expressions employed herein are intended as terms o description and not of limitation, and there is no intention in the use thereof o excluding any equivalents. On the contrary, it is anticipated that other embodiment of the invention are possible by the use of equivalents, adaptations and modification that may be deployed without departing from the spirit and scope of this invention.

Claims

We claim:

1. A controlled electrostatic discharge grounding system (40), comprisin means for discharging (42) having at least limited electrical conductivity a adapted to be electrically connected to an electrical circuit leading to a source ground potential, wherein said means for discharging (42) is capable of being touch directly by a user of an electronic device for the purpose of discharging from the us an accumulated electrostatic charge to the source of ground potential; means for conducting (46) the accumulated electrostatic charge to the source ground potential, said means for conducting (46) electrically connected to said mea for discharging (34); and means for providing electrical resistance (44) which is electrically connected t said means for conducting (46) so as to provide control over the rate of discharge the accumulated electrostatic charge through said means for conducting (46) to th source of ground potential.

2. The apparatus of claim 1, wherein said means for discharging (42 comprises a keycap (34) having a top surface (51) capable of being touched by th user and a bottom surface (53) capable of being connected to the electrical circui leading to the source of ground potential.

3. The apparatus of' claim 2, wherein said keycap (34) comprises conductive insert (52) and a nonconductive (50) portion.

4. The apparatus of claim 3, wherein said conductive insert (52 comprises a conductive plastic.

5. The apparatus of claim 4, wherein said conductive plastic is a carbon filled ABS plastic.

6. The apparatus of claim 2, wherein said keycap (34) comprises plurality of nickel-coated carbon fibers in a matrix of ABS plastic.

7. The apparatus of claim 2, wherein said means for conducting (46) the accumulated electrostatic charge comprises: a flexible conductor (68,70) for conducting the accumulated electrostatic charge to the source of ground potential; and means for electrically connecting in series said keycap (34), said means for providing electrical resistance (44) and said flexible conductor (68,70).

8. The apparatus of claim 7, wherein said means for electrically connecting (48) comprises an elastomer (72) attached to said flexible conductor (68,70) and acting as a spring, said elastomer (72) inserted into a cavity on the bottom surface (53) of said keycap (34) such that the spring is compressed forming an electrical connection between said keycap (34), said means for providing electrical resistance (44) and said flexible conductor (68,70).

9. The apparatus of claim 8, wherein said flexible conductor (68,7 comprises a stabilized polyester substrate (68) and a screen printed ink conduct (70), wherein said screen printed ink conductor (70) is screen printed onto sa stabilized polyester substrate (68).

10. The apparatus of claim 9, wherein said means for providing electric resistance is a resistor (54) having a resistance in the range of 10-500 MΩ.

11. The apparatus of claim 10, wherein said resistor (54) is a discre carbon resistor.

12. The apparatus of claim 10, wherein said resistor is a screen printe resistor (88).

13. The apparatus of claim 12, wherein said screen printed resistor (8 comprises a mixture of carbon linear resistance polymer (90) and resin (92).

14. The apparatus of claim 13, wherein said resin (92) is a clear polyest resin.

15. The apparatus of claim 13, wherein said resin is a clear vinyl resin.

16. A controlled electrostatic discharge grounding system, comprising: a conductive keycap (34,80) adapted to be electrically connected to a electrical circuit leading to a source of ground potential, wherein said conductiv keycap (34,80) is capable of being touched directly by a user of an electronic devic for the purpose of discharging from the user an accumulated electrostatic charge to th source of ground potential; and a flexible conductor (46,84) to conduct the accumulated electrostatic charge t the source of ground potential, said flexible conductor electrically connected to sai conductive keycap (34,80); and an electrical resistor (54,88) connected in series between said keycap (34,80 and said flexible conductor (46,84) so as to provide control over the rate of discharg of the accumulated electrostatic charge to the source of ground potential.

17. The apparatus of claim 16, wherein said conductive keycap (34,80 comprises a plurality of nickel-coated carbon fibers in a matrix of ABS plastic.

18. The apparatus of claim 17, wherein said flexible conductor (46,84 comprises a stabilized polyester substrate and a screen printed ink conductor, wherei said screen printed ink conductor is screen printed onto said stabilized polyeste substrate.

19. The apparatus of claim 18, wherein said resistor (54,88) is a scree printed resistor.

20. The apparatus of claim 19, wherein said screen printed resisto comprises a screen printed resistor ink, including a mixture of a carbon linea resistance polymer and a resin, printed on a flexible substrate.

21. The apparatus of claim 20, wherein said resin is a clear polyester resi

22. The apparatus of claim 21, wherein said resin is a clear vinyl resin.

23. The apparatus of claim 20, wherein said screen printed resistor, sa stabilized polyester substrate and said screen printed ink conductor are all located on ground plane of a flexible circuit (26) used for key actuation in a keyboard (20).