HK1053548A - Flexible touchpad sensor grid for conforming to arcuate surfaces - Google Patents

Description

Flexible touchpad sensor grid conforming to an arcuate surface

Background

1. Field of the invention

The present invention relates generally to combining computer input devices such as keyboards and touch pads (touchpads). More particularly, the present invention relates to combining existing components of a keyboard with an integrated structural touchpad for an improved system for coupling a PC board with touchpad circuitry to the keyboard components, and to combining the flexible sensor portion of the touchpad with the rigid circuit component portion of the touchpad with other components.

2. Background of the invention

The prior art includes systems that provide computer input devices with integrated touch pads. For example, the related art includes information rooms (kiocks), computer keyboards, and information devices using a touch panel as an input interface. Perhaps the most common device is a computer keyboard. It is well known in the keyboard and touchpad arts that they can be included in the same keyboard housing or chassis. For example, fig. 1 shows a top view of a typical QWERTY keyboard 10 of the prior art, which has moved the 10-key numeric keyboard 12 closer to the alphabetic keys and has placed the touchpad 14 in its place.

Fig. 2 is another keyboard 18 constructed from a precursor technology that utilizes an ergonomic design. The keyboard 18 has a touchpad 20 placed in the area under the keyboard where the wrist is to be placed. This arrangement allows the 10-key keyboard 22 to remain in its most familiar position in the keyboard 18.

Unfortunately, placing a touchpad into a keyboard is not always a simple task for a number of important reasons. For example, it is clearly desirable to make the keyboard as inexpensive as possible. Touch pads also have component costs, and they also have certain structural requirements that are different from and often more costly than keyboards. These aspects will be discussed after explaining the internal structure of a typical prior art keyboard.

Fig. 3 illustrates a method of manufacturing the internal structure of the keyboard. In this figure, the internal layout of the keyboard is shown, which is constructed using several layers of sheet (sheet) made of a plastic-like material, such as mylar. These sheets are generally non-conductive in nature. The first sheet 30 has a plurality of conductive traces 32 disposed thereon and is drawn using a conductive material such as carbon ink or silver ink. The locations traversed by these conductive traces 32 are those on the first sheet 30 that are in contact with the keys of the keyboard when they are depressed. Simple screen printing processes can also be used to distribute ink traces on polyester film.

It is important to understand that this ink application process is not particularly precise and is therefore typically used for high tolerance (tolerance) processes, such as those used on conductive traces of a keyboard. The third polyester sheet 36 also has conductive traces 38 that intersect each location of the keyboard keys, the same as the conductive traces 32 of the first sheet 30, but along different axes.

The second or middle mylar sheet 40 is used to separate the first sheet 30 from the third sheet 36 when the keys are not depressed. A number of holes 42 are made in the second sheet 40, which also correspond to the positions of the keys of the keyboard. Thus, when a key is pressed, the conductive trace 32 on the first sheet 30 can be pressed into contact with the conductive trace 38 on the third sheet 36 due to the corresponding hole 42 in the middle or third sheet 36. This depression causes a set of conductive traces 32, 38 at a unique location to be pressed together, forming an electrical path that is sensed by the keyboard circuitry to determine which key was depressed. The keyboard circuitry is at least one integrated circuit that is located on a PC board separate from the plastic sheets 30, 36, 40.

The typical internal structure and operation of prior art keyboards has been explained, and the addition of a touch pad complicates the structure because the touch pad typically requires a rigid PC board (printed circuit board) as part of its sensing circuitry. For example, a capacitance sensitive touchpad typically requires a PC board to be used as a surface upon which to place the sensing electrodes. The reason for using a PC board is that the relative positions of these electrodes are often required to be very accurate because prior art touchpad sensing circuits do not have a large manufacturing tolerance. This tolerance to manufacturing irregularities is typically a function of the touch pad circuitry itself. Touchpad circuitry is inherently sensitive to electrical noise, electrode spacing, and other factors that limit the ability to accurately detect and determine the location of a pointing object on the surface of the touchpad.

For example, the X and Y conductive traces are arranged in a very precise pattern or grid. The error margins (dynamic ranges) of all touch pad circuits known to the inventors are such that without an accurate grid arrangement the touch pad will not function, and only with PC boards such an accurate grid arrangement can be consistently achieved. In other words, prior art touch pads are typically so sensitive that if the touch pad is to be included in a keyboard housing, it is necessary to include a PC board for the touch pad sensing electrode grid within the keyboard housing.

In examining the construction of prior art keyboards that include touch pads, it was found that plastic sheeting was typically removed or minimized in size to make room for the PC board for the touch pad sensing electrodes. This is the case with the touch pad shown in fig. 1. In fig. 2, the larger size of the ergonomic keyboard allows for the inclusion of a PC board therein without significant modification, but still requires the use of a large PC board for the touchpad. A hole must also be cut through the keyboard housing. Thereby exposing the touch pad surface to the pointing object.

In addition to including a PC board for the touchpad sensing electrode grid, some means must be included for connecting the conductive traces 32, 38 on the plastic sheets 30, 36, 40 to the control circuitry. The control circuitry is housed on those PC boards within the keyboard housing. This connector is relatively strong due to the nature of the materials used.

For example, the inks used in the conductive traces can oxidize. Thus, connectors are used that apply a greater amount of pressure to force the conductive traces against the corresponding conductive traces on the PC board, which pressure typically overcomes oxidation, but requires additional hardware to make the pressure connections.

It would be advantageous over the prior art to provide a means to reduce the number of PC boards required for a touchpad housed within a keyboard housing. It would be another advantage to improve the connection interface between the PC board and the plastic sheet of the keyboard. It would be another advantage to utilize a plastic sheet for the touchpad sensor electrodes of the touchpad, thereby reducing the cost and complexity of the keypad. Another advantage is to provide a new way to mount touchpad sensor electrodes to a keyboard housing, independent of the presence of the plastic foil of the keyboard itself. Finally, it is also an advantage to provide the touchpad sensor electrodes on a flexible material (such as a plastic or polyester sheet) so that the touchpad can conform to a curved surface, such as the interior of a keyboard housing.

Disclosure of Invention

It is an object of the present invention to provide a flexible surface upon which to place touchpad sensor electrodes so that the surface of the touchpad can be placed along an arcuate surface.

Another object is to integrate the touchpad and keypad into a keypad housing wherein the touchpad replaces the PC board material normally used for touchpad sensor electrodes with a plastic foil used in the construction of key sensing devices.

Another object is to improve the connection between the PC board and the plastic foil used for the touch pad sensor electrodes.

Another object is to eliminate the pressure connector and replace it with a more reliable and less costly connection device.

Another object is to reduce the cost of manufacturing the keyboard by using conductive ink for the keyboard circuit conductive traces to make the touchpad sensor electrodes.

Another object is to enable sensor electrodes to be manufactured in a relatively imprecise screen printing process by using a touchpad circuit with a high tolerance for manufacturing variations.

Another object is to place the sensor electrodes on a plastic sheet and then fix the plastic sheet directly to the underside of the keyboard cover, thereby eliminating the need to cut holes in the keyboard cover to allow the user to touch the touch pad.

In a preferred embodiment, the present invention is a touch pad comprised of a flexible non-conductive material for use as a touch sensitive surface and a PC board on which the touch pad circuitry is mounted, wherein the touch pad sensing electrodes are placed on the touch sensitive surface by creating conductive traces formed of conductive ink that can conform to various arcuate surfaces and can be sensed by a protective case so that the touch sensitive surface is protected from direct contact with a pointing object.

In a first aspect of the invention, a touchpad is placed within a keyboard having multiple layers of plastic sheets upon which conductive traces formed from conductive ink are placed, wherein touchpad sensor electrodes are placed on these same plastic sheets, but they extend to the touchpad area.

In a second aspect of the invention, a new connector couples conductive traces of a plastic sheet to at least one PC board that includes keyboard or touchpad circuitry to generate data regarding keystrokes and touchpad control.

In a third aspect of the invention, the touchpad sensing electrodes are placed on the plastic sheet using a low cost process that inherently has low manufacturing tolerances, such as screen printing.

In the fourth aspect of the present invention, the manufacturing tolerances for placing the touchpad sensing electrodes on a plastic sheet can be low because the circuitry that drives the touchpad sensing electrodes has a significantly higher dynamic range in its design.

In a fifth aspect of the invention, the touchpad sensing electrodes are placed on plastic sheets that are in turn placed directly on the underside of the curved top cover of the keyboard housing.

In a sixth aspect of the invention, the touchpad circuitry and the sensing electrodes are sufficiently sensitive to enable detection and tracking of pointing objects on the keyboard housing directly above the touchpad sensing electrodes.

These and other objects, features and advantages of the present invention, as well as other aspects of the present invention, will become apparent to those skilled in the art upon a consideration of the following detailed description, taken in conjunction with the accompanying drawings.

Drawings

FIG. 1 is a top view of a prior art keyboard including a touchpad therein, which represents prior art in terms of the touchpad surface.

FIG. 2 is a perspective view of a prior art keyboard including a touchpad therein, which represents the prior art of a keyboard having an integrated touchpad surface from Cirgue corporation.

Fig. 3 is a perspective view of three plastic sheets used to form sensing electrodes used in prior art keypad designs.

Fig. 4 is a perspective view of plastic sheets used in a keypad constructed in accordance with a preferred embodiment of the present invention that leaves space on the sheets for placement of touch sensing electrodes of a touch pad thereon.

Fig. 5A is an elevational view of a prior art connector between a plastic sheet and a PC board, wherein a pressure connector is used to ensure electrical connection therebetween.

Fig. 5B is a cross-sectional view of fig. 5A.

FIG. 6 is an elevational cross-sectional view of a PC board with solder beads, to which a plastic sheet is attached using an adhesive material.

Fig. 7 is a top view of fig. 6.

FIG. 8 is a first embodiment illustrating how a solder ball can be used to increase the effectiveness of the electrical connection between the PC board and the touch-sensing electrodes on the plastic sheet.

Figure 9 is a preferred embodiment of an improvement to the design shown in figure 8.

Detailed Description

Reference is now made to the drawings, wherein the various elements of the present invention are designated by numerals, and wherein the invention is discussed with reference to the drawings, so as to enable one skilled in the art to make and use the invention. It is to be understood that the following description is only exemplary of the principles of the present invention, and should not be viewed as narrowing the claims which follow.

This preferred embodiment of the present invention is a touchpad comprised of a flexible non-conductive material that serves as a touch sensitive surface and a PC board on which the touchpad circuitry is mounted. The touch sensitive surface is connected to the touchpad circuitry mounted on the PC board using a new connection system that does not rely on prior art pressure connectors.

One of the most advantageous aspects of the present invention is a flexible touch sensitive surface. This aspect is advantageous because the touch sensitive surface can conform to an arc-type surface. For example, an ergonomic keyboard often has a wrist rest. The wrist rest is a curved plastic surface under the keys. The present invention can be advantageously placed under a curved wrist rest area without modification of the keyboard housing. This is because the touch panel of the present invention can also sense through a non-conductive material. In this way, the touchpad is protected under the hard plastic of the keyboard housing and conforms to the arcuate surface of the housing.

Another advantageous aspect of the invention results from the manner in which the touch sensing electrodes are placed on the touch sensitive surface. Specifically, the conductive traces are formed from conductive ink. This is the same conductive ink used to create the conductive traces in many prior art keyboard designs. Furthermore, although screen printing processes on plastic to form conductive traces can cause variations in the spacing between traces, these are tolerated by the touch panel circuitry of the present invention because of its large dynamic range.

Another embodiment of a keyboard including a built-in touchpad can share the manufacturing process used to build the keyboard key sensing grid. The exact location of the touchpad within the keypad is not particularly relevant in the present invention. It is important only that the plastic sheet on which the keyboard key conductive traces are placed extend in a particular direction so that the touchpad sensing electrodes can also be placed thereon. The touch pad can then be manufactured as an integral part of the plastic foil used for the keyboard.

Thus, FIG. 4 shows a perspective view of two plastic sheets assembled together in the same manner as the sheets shown in FIG. 3, but with a smaller space added at the right edge for the touchpad sensing electrodes. It should be appreciated that the space reserved for the touchpad sensing electrodes can be at any arbitrarily selected location, as long as this location can be conveniently used as space for a touch sensitive surface when the keypad cover is placed on a plastic sheet. Thus, it should be appreciated that the extension of the plastic sheet used for the touchpad sensing electrodes can be made in any orientation. It is also an aspect of the present invention that the plastic used for the touchpad sensing electrodes can also be manufactured as a separate item.

The use of an inexpensive screen printing process is considered a new aspect of the present invention. This process has inherent inaccuracies in the placement of the touchpad sensing electrodes compared to the use of a PC board.

Another novel aspect of the present invention is the ability to remove any support surface of the plastic sheet. This is achieved by gluing a plastic sheet up on the bottom surface of the fallboard. This design has several significant benefits, firstly the elimination of the support surface. Another benefit is that the keyboard manufacturer can choose to highlight the area under which the touchpad is placed if touchpad technology is included, or not highlight the area if no touchpad is included. It is a benefit to the seller that the same keymat cover can be used for both cases.

Typically, the use of a touchpad in a keyboard housing necessitates the cutting of a hole in the keyboard top cover to enable a user to contact the touchpad surface. However, the present invention can use touchpad technology, such as that incorporated into the CIRQVE CORPORATION (TM) capacitance sensitive touchpad, which will still operate using a keyboard top cover having an average thickness. Thus, the keyboard top cover is easier to manufacture because it is not necessary to cut holes or use a mold with holes to form the holes for the touch pad surface.

Another novel aspect of the present invention is the ability to eliminate the pressure connector used to apply pressure to the plastic sheet and the PC board on which the touch pad control circuitry is mounted. A typical pressure connector is shown in fig. 5A and 5B, wherein a rod 50 is screwed to at least one plastic sheet 52 and a PC board 54 to provide a secure connection therebetween. Pressure is applied in this manner so that there is good electrical contact where the plastic foil 52 and the surface 56 of the PC board 54 meet. Disadvantageously, screws 58 are required, as well as holes for securing the screws.

Removal of the pressure connector was first accomplished by introducing a solder bead (socket). It is preferred to create the solder balls 60 on the PC board 62 as shown in fig. 6. The weld bead advantageously creates an area that bends the plastic sheet 64 to be secured to the PC board 62 in area 66. The plastic sheet 64 is secured to the PC board 62 by applying an adhesive in an area 66 on the PC board, or on the portion of the plastic sheet 64 that contacts the PC board 62, or both. As should now be appreciated, the raised bead 60 causes the plastic sheet 62 to exert a greater force where it contacts the bead simply because the plastic sheet is bent. The plastic foil 62 is sufficiently flexible to allow good contact.

Fig. 7 shows another novel feature of the present invention, namely the staggered placement of the weld beads. The spacing in area 66 is visible in fig. 6, which creates the required tension for good connections, while the other purpose of the staggered placement is to thus bring those connections on the PC board closer together. FIG. 7 shows a plurality of solder balls disposed in a staggered pattern.

Figure 8 illustrates another method of connecting the touch pad sensing electrodes on the plastic sheet to conductive traces on the PC board. For example, assume a PC board is used as the surface upon which the touchpad sensing electrodes can rest. In one case, the touchpad sensing electrodes are placed on two different plastic sheets. In the second case, one set of touchpad sensing electrodes is on the PC board and the other set is on a plastic sheet. Either way, the touchpad sensing electrodes must be brought into contact with the control circuitry mounted on the PC board. This is achieved as shown in fig. 8. The PC board 70 is used as a substrate. Solder bumps (solder bumps) 72 are placed on the PC board 70. A first plastic sheet 74 is placed over the PC board and several holes are cut in the sheet to give access to the underlying solder bumps 72. A second plastic sheet 76 with touchpad sensing electrodes thereon is placed in contact with the solder bumps 72 of the PC board 70. A portion of the first plastic sheet 74 is raised and a portion of the second plastic sheet 76 is placed beneath it. However, insufficient contact may result between the touchpad sensing electrodes on the second plastic sheet 76 and the solder bumps 72. To ensure good electrical contact, the holes in the first plastic foil 74 are not made above the solder bumps 72, but instead in front of them. In this manner, the first plastic tab 74 remains above the solder bump 72, which forces the second plastic tab 76 against the solder bump 72.

Another aspect of the present invention is that in these applications where the touchpad sensing electrodes are not placed on the PC board, a less expensive PC board material can be used. The quality of the PC board can significantly affect the cost of the final product. In this case, there is no need to use high quality materials for the PC board because when using the touch pad control circuit of CIRQUE CRPORATION (TM), the touch pad sensing electrodes no longer need such high precision, thereby enabling the touch pad sensing electrodes to be screen printed onto a plastic sheet.

Another aspect of the invention is the ability to bend the plastic so that both the touch sensitive surface and the PC board with control circuitry can fit into a smaller space. For example, consider a touch panel as shown in fig. 10A.

Fig. 10A is a perspective view of a plastic sheet 80 on which touch pad sensing electrodes are placed. The touchpad sensing electrodes are placed on a curved plastic sheet 84 that is bent toward the PC board 82, and the PC board 82 is aligned to be placed under the touch sensitive surface plastic sheet 80. The plastic sheet 80 can be fixed to the underside of the keyboard housing or a separate touch pad housing with the PC board directly underneath. One of the advantages of this structural arrangement is that the overall space required to accommodate the touchpad is reduced because the PC board is not placed on one side, but is placed directly beneath the surface of the touchpad. It is only necessary to properly insulate the touch sensitive surface from the touchpad circuitry so that they can be placed in relatively close proximity. Thus, the separate touch pad can be smaller when the PC board is placed directly under the touch sensitive surface.

FIG. 10B is an elevational cross-sectional view of FIG. 10A showing the touch sensitive surface plastic sheet 80, the PC board 82 underneath, and the curved plastic sheet 84 that leads the touch sensing electrodes to the PC board.

FIG. 10C is a top view of FIG. 10A showing the outlines of the touch sensitive surface plastic sheet 80, the curved plastic sheet 84, and the PC board 82 placed underneath the plastic sheet.

It is to be understood that the above-described arrangements are only illustrative of the application of the principles of the present invention. Numerous modifications and other arrangements may be devised by those skilled in the art without departing from the spirit and scope of the present invention. It is intended that the appended claims cover such modifications and arrangements.

Claims (17)

1. A touch pad for providing data input to a computer system, the touch pad including a flexible touch sensitive surface conformable to an arcuate surface, the touch pad comprising:

at least two flexible non-conductive sheets upon which the touchpad sensing electrodes are disposed, wherein the at least two flexible non-conductive sheets overlap such that the touchpad sensing electrodes form at least one grid that defines a touch sensitive area of the touchpad, and wherein the at least two flexible non-conductive sheets are capable of flexing to conform to an arcuate surface;

a printed circuit board; and

a touchpad control circuit mounted on the printed circuit board, wherein the touchpad control circuit is electrically coupled to the touchpad sensing electrodes to receive sensing information from the touchpad sensing electrodes, and wherein the touchpad control circuit generates a plurality of signals corresponding to data inputs from the touchpad.

2. The touch panel of claim 1, wherein the at least two flexible nonconductive sheets are selected from the group of flexible nonconductive sheets consisting of plastic and mylar.

3. The touch panel of claim 2, wherein the touch panel sensing electrodes are formed from conductive ink.

4. The touch panel of claim 3, wherein the touch panel further comprises a connection system between the at least two flexible electrically non-conductive sheets and touch panel circuitry on the printed circuit board, said connection system comprising:

at least two rows of solder bumps disposed on the printed circuit board, wherein the at least two rows of solder bumps are separated from each other to form a gap therebetween; and

a portion of the at least two flexible nonconductive sheets are positioned to cover the at least two rows of solder bumps, wherein the portion of the at least two flexible nonconductive sheets positioned over the gap is secured to the printed circuit board to fill the gap, wherein the gap between the at least two rows of solder bumps is sufficient to create a tensile force on the portion of the at least two flexible nonconductive sheets secured thereto.

5. The touch panel of claim 4, wherein the touch panel further comprises an adhesive for securing the portions of the at least two flexible non-conductive sheets to the printed circuit board.

6. The touch panel of claim 5, wherein the touch panel further comprises providing the at least two flexible electrically non-conductive sheets with a toughness sufficient to generate a pressure to maintain electrical contact between the touch panel sensing electrodes on the at least two flexible electrically non-conductive sheets and the at least two rows of solder bumps.

7. The touch panel of claim 6, wherein the touch panel further comprises staggered solder bumps within the at least two rows of solder bumps such that a first row of solder bumps is offset from a second row of solder bumps relative to the portion of the at least two flexible electrically non-conductive sheets.

8. The touch panel of claim 3, wherein the touch panel further comprises a connection system between the at least two flexible electrically non-conductive sheets and touch panel circuitry on the printed circuit board, said connection system comprising:

a first nonconductive sheet fixed to the printed circuit board;

a second nonconductive sheet partially secured to the printed circuit board parallel to and spaced apart from the first nonconductive sheet to form a gap therebetween, wherein the second nonconductive sheet is unsecured along the gap; and

a row of solder bumps is positioned beneath the second non-conductive sheet at a location on the printed circuit board not to be secured, parallel to and proximate to the edge of the gap, wherein the portion of the at least two flexible non-conductive sheets is positioned between the second non-conductive sheet and the row of solder bumps, and wherein the touchpad sensing electrodes are in contact with the row of solder bumps.

9. A method of providing a touch pad having a flexible touch sensitive surface conformable to an arcuate surface, said method comprising the steps of:

(1) providing a flexible non-conductive surface conforming to the arcuate surface and formed by coupling together at least two flexible non-conductive sheets having touch pad sensing electrodes disposed thereon, a printed circuit board and touch pad control circuitry mounted on the printed circuit board, wherein the touch pad control circuitry is electrically coupled to the touch pad sensing electrodes to receive sensed information from the touch pad sensing electrodes, and wherein the touch pad control circuitry generates a plurality of signals corresponding to data inputs from the touch pad;

(2) placing the flexible touch sensitive surface against a mounting surface, wherein the mounting surface is sufficiently thin to enable the flexible touch sensitive surface to detect a pointing object on the other side of the mounting surface; and

(3) an indicating object that is in contact with and moving along the other side of the mounting surface is detected and tracked.

10. The method of claim 9, wherein the method further comprises the step of securing the flexible touch sensitive surface to a mounting surface using a non-conductive adhesive.

11. The method of claim 10, wherein the method further comprises the step of selecting the at least two flexible non-conductive sheets from a group of flexible non-conductive sheets, the group comprising plastic and polyester films.

12. The method of claim 11, wherein the method further comprises the step of forming the touchpad sensing electrodes from conductive ink.

13. The method of claim 12, wherein the method further comprises a step of providing a pressure connector independent connection system between the at least two flexible non-conductive sheets and the touch pad circuitry on the printed circuit board.

14. The method of claim 13, wherein the method further comprises the steps of:

(1) providing at least two rows of solder bumps on the printed circuit board, wherein the at least two rows of solder bumps are separated from each other to form a gap therebetween; and

(2) fixing a portion of the at least two flexible nonconductive sheets to cover the at least two rows of solder bumps, wherein the portion of the at least two flexible nonconductive sheets placed on the gap is fixed on the printed circuit board to fill the gap.

15. The method of claim 13, wherein the method further comprises a step of securing the portion of the at least two flexible non-conductive sheets to the printed circuit board with a non-conductive adhesive.

16. The method of claim 15, wherein the method further comprises a step of staggering the solder bumps within the at least two rows of solder bumps such that a first row of solder bumps is offset from a second row of solder bumps relative to the portion of the at least two flexible electrically non-conductive sheets.

17. The method of claim 12, wherein the method further comprises the steps of:

(1) securing the first nonconductive sheet to the printed circuit board;

(2) partially securing a second nonconductive sheet to the printed circuit board parallel to and spaced from the first nonconductive sheet to form a gap therebetween, wherein the second nonconductive sheet is secured along the gap; and

(3) providing a row of solder bumps positioned beneath the second non-conductive sheet and not secured to the printed circuit board, parallel to and proximate to the edge of the gap, wherein the portion of the at least two flexible non-conductive sheets is positioned between the second non-conductive sheet and the row of solder bumps, and wherein the touchpad sensing electrodes are in contact with the row of solder bumps.