WO2018206119A1

WO2018206119A1 - Touch and force sensitive surface unit

Info

Publication number: WO2018206119A1
Application number: PCT/EP2017/061454
Authority: WO
Inventors: Ling Chih Daniel TENG; Chin Wooi ONG; Andreas BRÜNINGHAUS
Original assignee: Continental Automotive Gmbh; Continental Automotive Singapore Pte. Ltd.
Priority date: 2017-05-12
Filing date: 2017-05-12
Publication date: 2018-11-15

Abstract

There is provided a touch-sensitive surface unit (100) for receiving at least one input, each input defining a user command and comprising at least one input point, the unit comprising: a flexible circuit board (102) configured as a surface to receive the input point and determine the position of the input point on the surface, the surface being capable of flexing at the input point of contact such that each input is substantially isolated to the point of contact; at least one force-sensitive element (106) coupled to the flexible circuit board (102) and configured to measure the force of the input point; a processor (114) electrically connected to the flexible circuit board (102) and configured to receive the position and/or force measurement of the input point and process the user command directed by the position and/or force measurement of the input point, the unit (100) being capable of receiving more than one input and processing more than one user command.

Description

Touch and Force Sensitive Surface Unit FIELD OF INVENTION

This invention relates to interface devices permitting touch input to electrical systems and in particular, touch-sensitive interface devices for receiving one or more inputs. BACKGROUND OF INVENTION

A variety of known interface devices permit multi-touch input to electrical systems. These known interface devices, such as conventional resistive and capacitive touch panels, use ma- nipulation of electrical properties of electrically conducting elements to concurrently sense the locations of touch events. In particular, multi-touch sensors in the automotive industry are normally designed with capacitive sensing technology. Force sensors in the automotive industry are normally based on the measurement of a mechanical movement or deformation un^¬ derneath the interface, such as infrared, capacitive or inductive distance change measurements. Current technology typically provides for a resolution of the change in distance of 0.1 mm or more. However, it is desirable to reduce the physical movement of a pressed surface. It is desirable to increase the resolution of force-sensitive interfaces with cost-efficiency.

Furthermore, current technology does not provide for an interface permitting multiple press inputs or a combination of multiple press and touch inputs. Particularly, the combination of force sensing and touch sensing technologies requires additional mechanical and electronic components and a special mechanical feature that allows the sensor surface to move under an ap- plication of force.

There is therefore a need for an interface that overcomes or at least improves one or more of the disadvantages discussed above. DESCRIPTION

It is therefore an object of this invention to provide a touch-sensitive surface unit for receiving at least one input to address the problems discussed above. Particularly, it is an object of this invention to provide a touch-sensitive surface unit capable of sensing the physical movement of a pressed surface of less than 0.1 mm and processing the command directed by the pressed surface. That is, it is an object of this invention to provide a touch-sensitive surface unit with increased

force-sensing resolution yet with cost-efficiency. It is a further object of this invention to provide a touch-sensitive surface unit capable of receiving more than one press input and/or more than one touch input.

To accomplish these and other objects of the invention, there is provided, in a first aspect, a touch-sensitive surface unit for receiving at least one input, wherein each input defines a user command, each input comprising at least one input point, the unit comprising: a flexible circuit board configured as a surface to receive the input point and determine the position of the input point on the surface, wherein the surface is capable of flexing at the input point of contact such that each input is sub- stantially isolated to the point of contact; at least one force-sensitive element coupled to the flexible circuit board, the force-sensitive element configured to measure the force of the input point; a processor electrically connected to the flexible circuit board, the processor configured to receive the position and/or force measurement of the input point and process the user command directed by the position and/or force mea^¬ surement of the input point, wherein the unit is capable of receiving more than one input and processing more than one user command .

An input includes a touch contact, point or position, any type offorcedpress, e. g. zero force press (i.e. touch), light press , or heavy press, a movement, and combinations thereof. In some cases, an input may be configured to require a single input point contact such as a touch, a light press, and a forced press. In other cases, an input may be configured to require more than one input point, which includes a movement, zooming in or out of an area of a map, or highlighting of a text. Hence, an input is a set of one or more input points.

A user command is the action that results from the processing of the input, e.g. by means of the processor. For example, an input includes pressing lightly on a point on a user interface or the flexible circuit board surface, and this input is configured to correspond to a user command of opening a dropdown menu. Another input includes moving from the point where the dropdown menu is opened to another point where an option is displayed in the dropdown menu and pressing with more force on this other point. In this example, the input is configured to correspond to a user command of selecting the desired option in the dropdown menu and optionally executing the option. Examples of options include selection of a pre-set radio station, an increase in temperature of the climate control unit or selection of a navigation feature.

In some embodiments, the disclosed touch-sensitive surface unit may be configured to receive one input and process the cor^¬ responding one user command. In this example, a user interface may be configured to display a single screen communicating with one electronic control unit, e.g. a climate control unit. Thus, the touch-sensitive surface unit which is beneath the user interface may be configured to receive the single input and process the single user command.

In some embodiments, the disclosed touch-sensitive surface unit may be configured to receive more than one input and process the corresponding more than one user command. The user interface may therefore be configured to display more than one screen, each screen communicating with one or more than one electronic control unit. For example, the user interface may be divided into two halves individually operable by a front passenger and a driver. Thus, for example, the touch-sensitive surface unit which is beneath the user interface may be configured to receive and process the passenger's adjustment of the temperature of the climate control unit and the driver's manipulation of a map. In this case, the selection of the temperature may require only one input point, while the manipulation of the map may require two input points. Accordingly, the disclosed touch-sensitive surface unit advantageously provides such flexibility and freedom of use as described herein. Conventional touch-sensitive surfaces typically comprise a monolithic substrate whereby pressing on a part of the surface of the substrate depresses the whole substrate. Advantageously, because of the bendability of the disclosed flexible circuit board, depression of a part of the surface at the point of contact is substantially isolated to the part that is pressed. That is, depression or deformation of a part of the surface does not result in depression or deformation of other parts of the surface. Thus, the other parts of the surface retain their ability of receiving further inputs. The flexible circuit board may therefore be capable of bending such that one input does not affect another input when more than one input is received.

The substantial isolation of an input point of contact from another input point of contact may be configured or adjusted according to user or manufacturer requirements. Typically, parameters that may be used to adjust the minimum distance between two distinct points of contact include touch separation and touch merging threshold as known in the art. For example, the threshold for merging input points may include pixel intensity of each input point or total number of pixels of adjacent input points, whereby if the adjacent input points have a total number of pixels above a certain threshold, these two input points may be assumed to be caused by a single fingertip and may be merged. Further advantageously, less force is required to bend or depress the disclosed flexible circuit board due to its bendability as compared to conventional rigid touch-sensitive surfaces. Thus, the distance required to depress the surface from its original level to a depressed level capable of detecting the force measurement may advantageously be less than 0.1 mm. Accordingly, the force-sensitive element may be configured to measure the force from an input point that is depressed by less than 0.1 mm from the original surface level.

The term "circuit board" refers to any substrate, foundation or base layer on which an electrically conductive layer, track, or wiring can be or has been formed on its surface. Forming of the electrically conductive layer may be by printing or etching onto the surface of the substrate. Where the electrically conductive layer is printed onto the surface of the substrate, the substrate is termed a "printed circuit board". A circuit board which is capable of some degree of bending upon mechanical flexing is termed a "flexible circuit board" and a "flexible printed circuit board" is construed accordingly. As maybe appreciated, while the flexible circuit board possesses some degree of bending, it is mechanically stable to support the electrically conductive layer and/or other components coupled thereto.

The term "circuit board" as used herein covers any package, such as an integrated circuit package, that has multiple layers of signal wires or conductors and power reference planes. The flexible circuit board may be any suitable flexible circuit board that can be configured to receive the user input point and determine the position of the user input point. The flexible circuit board may be a flexible printed circuit board. The flexible circuit board may be transparent, substantially transparent, translucent, or opaque.

The flexible circuit board may comprise a single substrate having an electrically insulating layer formed on one surface or both surfaces. Alternatively, the flexible circuit board may comprise two or more layers of substrates. For example, a single substrate having an electrically insulating layer formed on both surfaces may comprise a polyimide substrate (e.g. Kapton® polyimide film by DuPont, Delaware, USA) , a copper electrically conductive layer formed on a top surface of the polyimide substrate, a first polyimide electrically insulating layer formed on the copper electrically conductive layer, a second polyimide electrically insulating layer formed on a bottom surface of the polyimide substrate, and a stiffener layer formed on the second polyimide electrically insulating layer. In another example, a mul^¬ ti-substrate flexible circuit board may comprise a plurality of polyimide substrates (e.g. Kapton® polyimide film by DuPont, Delaware, USA) having copper electrically conductive layers formed therebetween, a first polyimide electrically insulating layer formed on an uppermost copper electrically conductive layer, a second polyimide electrically insulating layer formed on a bottommost copper electrically conductive layer, and a stiffener layer formed on the second polyimide electrically insulating layer. The electrically insulating layer may comprise solder pads formed on an outer surface facing away from the surface proximate the input point, and vias, e.g. via bridges. In yet another example, where the flexible circuit board comprises a capacitive touch sensor, a two-substrate flexible circuit board may comprise a first substrate having capacitive sensor nodes or lines formed on a surface and a second substrate having connecting bridges formed on a surface, the bridges connecting the nodes. In other examples, the flexible circuit board may comprise polyester or polyether ether ketone (PEEK) substrate (s) .

To be operable to determine the position of the input point, the flexible circuit board may comprise any suitable touch sensor, for example resistive, capacitive, surface acoustic wave, and/or infrared touch sensors. Hence, the part of the flexible circuit board comprising the touch sensor is termed as the

"touch-sensitive area". In an example, the touch sensor may be formed on the entire area of the flexible circuit board. In such example, the touch-sensitive area is maximized and comprises the entire surface area of the flexible circuit board. In other examples, the touch sensor may be formed on part of the flexible circuit board and thus, the touch-sensitive area comprises that part of the flexible circuit board. ^

In some examples, determination of the position of the input point is by capacitance measurement. That is, the flexible circuit board may comprise capacitive touch sensors. Although capacitive sensing technology is described herein, it is merely for simplicity of explanation and it should not be construed that the invention is limited to the embodiments described.

In some examples, the touch sensor is capable of determining multiple input points. In an example, the touch sensor may be a projected capacitive touch sensor which may advantageously be capable of determining multiple input points and determining an input point from a gloved finger.

Electrodes of a capacitive sensor may be formed on the surface of the flexible circuit board in an x-y grid matrix. The x electrodes may carry current (transmitter electrode or TX) , while the y electrodes may be capable of detecting the current at each x-y intersection (receiver electrode or RX) . In a single layer flexible circuit board, the x and y electrodes may be formed on a surface of the flexible circuit board in a grid matrix. Alternatively, in a two-layer flexible circuit board, the first layer may comprise the x electrodes formed on a surface of the first layer and the second layer may comprise the y electrodes formed on a surface of the second layer. When a user approaches or contacts part of the surface, the capacitance of that part of the x-y matrix is disturbed and the change in capacitance results in a voltage. The TX is excited with the voltage produced and the charges induced at the intersection on RX, which is grounded, are measured. Thus, the position of the contact point on the x-y grid can be determined.

The force-sensitive element may be configured to measure the force of the input point and determine whether the input point is depressed (i.e. when the force is not O ). In examples where the disclosed surface unit is configured to receive one input comprising one input point, the unit may comprise one

force-sensitive element. In such examples, the one force-sensitive element may be coupled to the middle of the touch-sensitive area of the flexible circuit board. If a force is applied on an area other than on the one force-sensitive element, an interpolation method may be used to measure the force of the one input point. In other examples where the disclosed surface unit is configured to receive more than one input point, whether as a single input or as multiple inputs, the unit may comprise more than one force-sensitive element. In an example, where the disclosed surface unit is configured to receive two input points, the unit may comprise two force-sensitive elements .

Where a force is applied on an area other than on the

force-sensitive element (s), e.g. at the edges of the

touch-sensitive area, it would be appreciated that the force measured may be less than the actual force applied. In such cases, the threshold of the force measurement near the edges of the touch-sensitive area may be adjusted to a higher threshold so that a lower force can be sensed. Thus, the sensitivity or flexibility or deformation of the surface may be adjusted by such posi- tion-specific thresholds of force-sensing algorithms known in the art. An example of a force-sensing algorithm may include a 3D table algorithm wherein the position of the input point in X, Y coordinates is entered into the table and the ratio of the actual force applied to the calculated force measurement is obtained.

The force-sensitive element may be coupled to the flexible circuit board such that depression of the input point on the surface depresses the force-sensitive element. The

force-sensitive element may be depressed at any angle between more than 0° (where 0° is parallel to the surface) and 90° (perpendicular to the surface) .

In an example, the force-sensitive element may be coupled to the surface of the flexible circuit board opposite the surface proximate the input point. Advantageously, the force-sensitive element may be arranged beneath an upper surface of the flexible circuit board that is presented for receiving the input point so that the force of an input point may be substantially concurrently measured with the position of the input point.

The one or more force-sensitive elements may be arranged on the flexible circuit board taking into account the arrangement of the touch sensor. For example, where the flexible circuit board is configured as a capacitive touch sensor, the force-sensitive element (s) may be arranged on the x-y grid mesh of electrodes. That is, the force-sensitive element (s) may be arranged to contact the electrodes. Alternatively, the force-sensitive element (s) may be arranged in between the x-y grid mesh of electrodes; that is, the force-sensitive element (s) may be arranged not to contact the electrodes. The force-sensitive element may be any suitable force or pressure sensor. In some examples, the force-sensitive element may be selected from the group consisting of: piezoresistive sensor, piezoelectric sensor, and capacitive sensor. In some examples, the force-sensitive element maybe a conductive polymer applied to the flexible circuit board as a polymer sheet or ink applied to the flexible circuit board by screen printing. In other examples, the force-sensitive element may be a standard component suitable for coupling to flexible circuit boards.

In a preferred example, the force-sensitive element may be a surface-mount device component that may be suitable for coupling to the flexible circuit board by a heat treatment, such as soldering, with the use of pick-and-place machines. Advan- tageously, as surface-mount device components are standard components for circuit boards, the disclosed force-sensitive element (s) may be relatively economical. The cost of the disclosed touch-sensitive surface unit may therefore be reduced. Further, the disclosed touch-sensitive surface unit may be relatively simple to produce. Accordingly in an example, the force-sensitive element is a piezoresistive surface-mount device commonly available on the market. The touch-sensitive surface unit may further comprise a rigid support to support the force-sensitive element. The support may provide a surface to enable depression of the force-sensitive element. The force-sensitive element may be arranged between the flexible circuit board and the support.

The force-sensitive element may be configured to measure the force of the input point by an interpolation method, wherein a force reading of the force-sensitive element is obtained and the force reading is interpolated based on the position of the input point to obtain the force measurement. In the embodiment where there is more than one force-sensitive element, the more than one force-sensitive elements may be configured to measure the force of the more than one input points by an interpolation method, wherein force readings of the force-sensitive elements are obtained and the force readings are interpolated based on the position of the input points to obtain the force measurement. Accordingly, the force measurement is obtained by interpolating the force readings of the surrounding one or more force-sensitive elements.

Advantageously, as the interpolation method may be used in this invention, force-sensitive elements need not be provided at every node of the x-y grid electrodes as is the case in certain prior art touch panels. In an example, each force-sensitive element may provide force measurements for every four nodes for sufficient force-sensing resolution.

Force-sensitive elements typically comprise a material which changes resistance or generates an electric charge in a pre^¬ dictable manner in response to applied mechanical stress. In an example, the disclosed force-sensitive element may be configured to convert the force of the input point, if more than O , to a voltage output. The voltage output may be transmitted to the flexible circuit board, then to the processor.

The processor may be configured to receive the position and/or force measurement of the input point and process the user command directed by the position and/or force measurement of the input point .

In some examples, the processor may additionally be configured to execute the user command. In such examples, the processor may be electrically connected to an electronic control unit, e.g. a climate control unit to adjust temperature.

In some examples, the processor may be comprised on a second circuit board electrically connected to the flexible circuit board. The second circuit board may comprise: the processor; circuitry operable to transmit the position and/or force measurement to the processor and away from the processor to, e.g., another electronic control unit such as a climate control unit; and a machine readable memory, wherein the user command to be executed is in the form of machine executable instructions stored in the machine readable memory. The second circuit board may itself be an electronic control unit. Where the processor is comprised on a second circuit board, the force-sensitive element may be arranged between the flexible circuit board and the second circuit board.

In other examples, the processor may be arranged on a portion of the flexible circuit board separate from the portion of the flexible circuit board receiving input, as long as the input portion of the flexible circuit board retains its flexibility.

There is provided, in another aspect, a touch-sensitive panel comprising: the touch-sensitive surface unit as disclosed herein and a housing to house the touch-sensitive surface unit, the housing comprising a user interface arranged above the flexible circuit board, the user interface configured to receive and transmit the at least one input to the flexible circuit board. The input defines a user command which may comprise selection of an option displayed on the user interface. The disclosed touch-sensitive panel may find utility in any device or system requiring a user's input via contact. For example, the touch-sensitive panel may find utility as a graphical user interface of a head unit or telematics unit in the central stack of a vehicle. In such application, the flexible circuit board used may not require transparency. The

touch-sensitive panel may find utility as a touch screen for a mobile communication device (in which case it is preferable to choose a transparent or substantially transparent flexible circuit board) or a public display board (in which case the flexible circuit board may not require transparency) .

There is provided, in another aspect, a method of operating the touch-sensitive panel as disclosed herein, the method com- prising: receiving at least one input on the user interface, wherein each input defines a user command, each input comprising at least one input point; transmitting the at least one input to a surface of the flexible circuit board, wherein the surface is capable of flexing at the input point of contact such that each input is substantially isolated to the point of contact; de^¬ termining, by the flexible circuit board, the position of the at least one input point on the surface; determining, by the force-sensitive element, the force measurement of the at least one input point; processing, by the processor, the user command based on the position and/or force measurement of the at least one input point, wherein when more than one input is received, the processor processes the more than one user command inde^¬ pendently from each other. The method may further comprise executing the user command in cases where the processor is electrically connected to an electronic control unit, e.g. a climate control unit.

Advantageously, the disclosed method is able to process and/or execute more than one user command as directed by the user.

BRIEF DESCRIPTION OF DRAWINGS Objects and aspects of this invention will become apparent from the following description of embodiments with reference to the accompanying drawings in which: FIG. la shows a perspective view of a prior art touch-sensitive surface unit.

FIG. lb shows a top view of a touch-sensitive surface unit in accordance with a first embodiment of the present invention.

FIG. 2a shows an illustration of a cross-sectional view of the touch-sensitive surface unit of the first embodiment.

FIG. 2b shows an illustration of the cross-sectional view of the touch-sensitive surface unit of the first embodiment when a force is applied.

FIG. 3 shows an illustration of a cross-sectional view of a touch-sensitive surface unit in accordance with a second em- bodiment of the present invention.

FIG. 4 illustrates electrodes of a capacitive touch sensor formed in an x-y grid matrix in accordance with an embodiment of the present invention.

FIG. 5a shows a perspective view of a surface-mount device component comprising piezoresistive force-sensitive elements in accordance with an embodiment of the present invention. FIG. 5b shows a side view of a surface-mount device component comprising piezoresistive force-sensitive elements in ac^¬ cordance with an embodiment of the present invention.

FIG. 5c shows an illustration of a scenario where a force is applied to the surface-mount device component of FIGs. 5a and 5b. FIG. 5d shows the arrangement of the piezoresistive force-sensitive elements and circuitry in the surface-mount device component of FIGs. 5a and 5b. FIG. 5e shows an equivalent circuit of the arrangement of FIG. 5d.

FIG. 5f shows a graph of voltage output when a force is applied to the surface-mount device component of FIGs. 5a and 5b.

In the figures, like numerals denote like parts. DETAILED DESCRIPTION OF DRAWINGS Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description of this invention will be provided for the purpose of explaining the principles of the invention and its practical application, thereby enabling person skilled in the art to understand the invention for various exemplary embodiments and with various modifications as are suited to the particular use contemplated. The detailed description is not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Modifications and equivalents will be apparent to practitioners skilled in this art and are encompassed within the spirit and scope of the appended claims.

FIG. la shows a perspective view of a prior art touch-sensitive surface unit 100'. The touch-sensitive surface unit 100' comprises a flexible circuit board 102 configured as a surface to receive an input point and determine the position of the input point on the surface. An input comprises at least one input point and the input defines a user command. Flexible circuit board 102 comprises capacitive wiring or electrodes 104, which form a capacitive touch sensor. Therefore, determination of the po^¬ sition of the input point is by capacitance measurement.

Electrodes 104 are formed on the surface of the flexible circuit board 102 in a mesh of x-y lines. Electrodes 104 are then routed down to connector tail 110. The connector tail 110 may be electrically connected to a processor (not shown) , the processor configured to receive the position of the input point and process the user command directed by the position of the input point . Unit 100' is capable of receiving more than one input and processing more than one user command due to the bendability of the flexible circuit board 102. That is, the flexible circuit board 102 is capable of bending such that one input does not affect another input when more than one input is received. However, unit 100' does not comprise any force-sensitive elements coupled to the flexible circuit board 102. Thus, the input point (s) received by unit 100' may only be touch contact (s) as no force measurements are available.

FIG. lb shows a top view of a touch-sensitive surface unit 100 in accordance with a first embodiment of the present invention. The touch-sensitive surface unit 100 of the first embodiment is capable of receiving at least one input, wherein each input defines a user command and each input comprises at least one input point. The user command may comprise selection of an option displayed on a user interface (not shown) . The unit 100 comprises a flexible circuit board 102 configured as a surface to receive the input point and determine the position of the input point on the surface, wherein the surface is capable of flexing at the input point of contact such that each input is substantially isolated to the point of contact. Flexible circuit board 102 comprises capacitive wiring or electrodes 104, which form a capacitive touch sensor. Electrodes 104 are formed on the surface of the flexible circuit board 102 in a mesh of x-y lines. In this first embodiment, unit 100 further comprises ten force-sensitive elements 106 coupled to the flexible circuit board 102, the force-sensitive elements 106 configured to measure the force of the input point. The force-sensitive elements 106 are coupled to the flexible circuit board 102 such that depression of the input point on the surface depresses the force-sensitive elements 106. The force-sensitive elements 106 are configured to convert the force of the input point, if more than O , to a voltage output. The force-sensitive elements 106 may be individually selected from the group consisting of: piezoresistive sensor, piezoe^¬ lectric sensor, and capacitive sensor. Force-sensitive elements 106 are electrically connected to the flexible circuit board 102 by wiring to transmit the voltage output to the flexible circuit board 102. The wiring of the force-sensitive elements 106 and the capacitive wiring 104 are routed down to the connector tail 110. The connector tail 110 may be electrically connected to a processor (not shown) , the processor configured to receive the position and/or force measurement of the input point and process the user command directed by the position and/or force mea^¬ surement of the input point. Unit 100 is capable of receiving more than one input and processing more than one user command due to the bendability of the flexible circuit board 102. That is, the flexible circuit board 102 is capable of bending such that one input does not affect another input when more than one input is received. Unlike the prior art touch-sensitive surface unit 100' , the input point (s) received by unit 100 may include a touch, a light press, a forced press, a movement, and combinations thereof, because unit 100 comprises force-sensitive elements 106.

Still referring to FIG. lb, the force-sensitive elements 106 are configured to measure the force of the input point by an in- terpolation method, wherein force readings of the

force-sensitive elements 106 are obtained and the force readings are interpolated based on the position of the input point to obtain the force measurement. That is, when a force x is applied on an area other than on force-sensitive elements 106, the force measurement is interpolated from the force readings of the surrounding force-sensitive elements 106 to obtain the force measurement of the force x.

FIG. 2a shows an illustration of a cross-sectional view of the touch-sensitive surface unit 100 of the second embodiment. Unit 100 comprises flexible circuit board 102, two force-sensitive elements 106 coupled to the flexible circuit board 102, and the processor comprised on a second circuit board 114 electrically connected to the flexible circuit board by connector tail 110. As can be seen, the force-sensitive elements 106 are coupled to the surface of the flexible circuit board 102 opposite the surface proximate the input point. The force-sensitive elements 106 are arranged between the flexible circuit board 102 and a support 112 to enable the force-sensitive elements 106 to be depressed. Support 112 is configured as a fixed support plate to hold the force-sensitive elements 106 in place. Unit 100 may be coupled, e.g. glued, to a user interface 108 comprised in a touch-sensitive panel (not shown) . The user interface 108 may be a plastic or glass covering supported by a plastic support to achieve stiffness of the surface exposed to the user. The touch-sensitive panel further comprises a housing (not shown) to house the unit 100. The housing comprises the user interface 108 configured as the touch surface to receive and transmit at least one input from the user to the flexible circuit board 102. The user interface 108 is arranged above the flexible circuit board 102. In an em^¬ bodiment, the area of the user interface 108 exposed to the user may be larger than the area of the flexible circuit board 102 available for receiving the input point. In this embodiment, the part of the user interface 108 not configured to contact the touch area of the flexible circuit board 102 form a bezel or frame of the touch-sensitive panel. In other embodiments, the area of the user interface 108 exposed to the user may be about the same size as the area of the flexible circuit board 102 available for receiving the input point. Thus, the user may utilize the whole user interface area for providing inputs, if configured as such. It is not preferable that the area of the user interface 108 exposed to the user is smaller than the area of the flexible circuit board 102 available for receiving the input point because such arrangement wastes the resources afforded by the flexible circuit board 102 as well as results in a larger housing required to house the flexible circuit board 102. FIG. 2b shows an illustration of the cross-sectional view of the touch-sensitive surface unit 100 of the second embodiment when a force is applied. In operation, a user applies a force (indicated by the arrow x) on the user interface 108, thereby depressing or deforming the flexible circuit board 102. As the distance between the user interface 108 and the fixed support plate 112 decreases due to the force applied, the force-sensitive elements 106 beneath the flexible circuit board 102 also become depressed. The force applied on the force-sensitive elements 106 is converted to a voltage output which is transmitted from the force-sensitive elements 106 to the flexible circuit board 102 and routed down by connector tail 110 to second circuit board 114 to process and execute the user command directed by the position and/or force measurement of the input point. Accordingly, in an embodiment, the method of operating a touch-sensitive panel as disclosed herein comprises: receiving at least one input on the user interface 108, wherein each input defines a user command, each input comprising at least one input point; transmitting the at least one input to a surface of the flexible circuit board 102, wherein the surface is capable of flexing at the input point of contact such that each input is substantially isolated to the point of contact; determining, by the flexible circuit board 102, the position of the at least one input point on the surface; determining, by the force-sensitive elements 106, the force measurement of the at least one input point; processing, by the processor on second circuit board 114, the user command based on the position and/or force measurement of the at least one input point. Advantageously, although not shown, when more than one input is received, the processor is able to process the more than one user command independently from each other. Advantageously, because less force is required to bend the flexible circuit board 102, the force-sensitive elements 106 are configured to measure the force from an input point that is depressed by less than 0.1 mm from the original level of the surface.

FIG. 3 shows an illustration of a cross-sectional view of a touch-sensitive surface unit in accordance with a third em^¬ bodiment of the present invention. The third embodiment of unit 100 is similar to the second embodiment of unit 100 in FIG. 2, except that in the third embodiment, additional coupling of the force-sensitive elements 106 and the support 112 is provided to ensure secure coupling and to ensure that the flexible circuit , _

board 102 is not unnecessarily bent. The additional coupling may be any coupling suitable to secure the flexible circuit board 102 to the support 112. For example, the additional coupling may be in the form of double-sided adhesive elastomer 116. The ad- ditional coupling may advantageously provide the flexible circuit board 102 with sufficient mechanical stability to support the capacitive wiring 104, force-sensitive elements 106 and/or other components coupled to the flexible circuit board 102.

FIG. 4 illustrates electrodes 104 of a capacitive touch sensor formed in an x-y grid matrix in accordance with an embodiment of the present invention. The electrodes 104 are formed on the surface of the flexible circuit board 102 in an x-y grid matrix. The electrodes 104 may have shapes or designs as in typical x-y capacitive touch sensors known in the art. The x electrodes may carry current (transmitter electrode or 104TX) , while the y electrodes may be capable of detecting the current at each x-y intersection (receiver electrode or 104RX) . In operation, when a force x is applied on an intersection or node of the x-y grid electrodes, the capacitance of that part of the x-y matrix is disturbed and the change in capacitance results in a voltage. Electrode 104TX is excited with the voltage produced and the charges induced at the intersection on 104RX, which is grounded, are measured. Thus, the position of the contact point on the x-y grid can be determined. Alternatively, when a force x is applied on an area other than a node, the capacitance measurement is interpolated from the surrounding nodes to obtain the position of the force x. FIG. 5a shows a perspective view of a surface-mount device component 600 comprising piezoresistive force-sensitive ele^¬ ments 602 in accordance with an embodiment of the present invention. FIG. 5b shows a side view of the surface-mount device component 600 comprising piezoresistive force-sensitive ele- ments 602 in accordance with an embodiment of the present invention. FIG. 5c shows an illustration of a scenario where a force is applied to the surface-mount device component 600 of FIGs. 5a and 5b. In this embodiment, the embodiment of FIGs. 5a and 5b, the force-sensitive element 106 is the surface-mount device (SMD) component 600. Referring to FIGs. 5a to 5c, component 600 is a standard SMD component for circuit boards, which are typically coupled to circuit boards by a heat treatment, such as soldering. Standard components are known in the art. Thus, a brief description of standard component 600 is provided. Component 600 comprises a raised portion 604 on which a force is applied (arrow x) . Component 600 also comprises a diaphragm 606 which bends according to the force applied. Piezoresistive force-sensitive elements 602 are attached or affixed to the bottom of the diaphragm 606 and flexes or bends according to the bending of the diaphragm 606. The force applied on the elements 602 is converted to a voltage output. FIG. 5d shows the arrangement of the piezoresistive

force-sensitive elements 602 and circuitry 608 in the

surface-mount device component 600 of FIGs. 5a and 5b. FIG. 5e shows an equivalent circuit of the arrangement of FIG. 5d. The force applied on the elements 602 is converted to a voltage output which is transmitted through circuitry 608. Circuitry 608 comprises Vdd, which is the supply voltage to drive the elements 602; Voutl, Vout2 and Vout, which are the voltage outputs (- and + ) ; and GND, which is to ground. This arrangement is akin to having four resistors on each wire as shown in FIG. 5e. The voltage output of piezoresistive force-sensitive elements 602 preferably linearly increases with the amount of force applied, as shown in FIG. 5f.

Claims

Patent claims

1. A touch-sensitive surface unit (100) for receiving at least one input, wherein each input defines a user command, each input comprising at least one input point, the unit comprising: a flexible circuit board (102) configured as a surface to receive the input point and determine the position of the input point on the surface, wherein the surface is capable of flexing at the input point of contact such that each input is substantially isolated to the point of contact;

at least one force-sensitive element (106) coupled to the flexible circuit board (102), the force-sensitive elements (106) configured to measure the force of the input point;

a processor (114) electrically connected to the flexible circuit board (102), the processor (114) configured to receive the position and/or force measurement of the input point and process the user command directed by the position and/or force mea^¬ surement of the input point,

wherein the unit (100) is capable of receiving more than one input and processing more than one user command.

2. The unit (100) of claim 1, wherein the force-sensitive element (106) is selected from the group consisting of: pie- zoresistive sensor, piezoelectric sensor, and capacitive sensor.

3. The unit (100) of any preceding claim, wherein the force-sensitive element (106) is coupled to the flexible circuit board (102) such that depression of the input point on the surface depresses the force-sensitive elements (106).

4. The unit (100) of any preceding claim, wherein the force-sensitive element (106) is coupled to the surface of the flexible circuit board (102) opposite the surface proximate the input point.

5. The unit (100) of any preceding claim, wherein the force-sensitive element (106) is coupled to the flexible circuit board (102) by a heat treatment.

6. The unit (100) of claim 5, wherein the force-sensitive element (106) is a surface-mount device component.

7. The unit (100) of any preceding claim, wherein the force-sensitive element (106) is configured to measure the force of the input point by an interpolation method, wherein a force reading of the force-sensitive element (106) is obtained and the force reading is interpolated based on the position of the input point to obtain the force measurement.

8. The unit (100) of any preceding claim, wherein the force-sensitive element (106) is arranged between the flexible circuit board (102) and a rigid support (112) .

9. The unit (100) of any preceding claim, wherein determination of the position of the input point is by capacitance measurement.

10. A touch-sensitive panel comprising:

the touch-sensitive surface unit (100) of any preceding claim; and

a housing to house the touch-sensitive surface unit (100), the housing comprising a user interface (108) arranged above the flexible circuit board (102), the user interface (108) configured to receive and transmit the at least one input to the flexible circuit board (102).

11. The panel of claim 10, wherein the user command comprises selection of an option displayed on the user interface (108) .

12. A method of operating the touch-sensitive panel of claim 10 or 11, the method comprising:

receiving at least one input on the user interface (108) , wherein each input defines a user command, each input comprising at least one input point;

transmitting the at least one input to a surface of the flexible circuit board (102), wherein the surface is capable of flexing at the input point of contact such that each input is sub^¬ stantially isolated to the point of contact;

determining, by the flexible circuit board (102), the position of the at least one input point on the surface;

determining, by the force-sensitive element (106), the force measurement of the at least one input point;

processing, by the processor (114) , the user command based on the position and/or force measurement of the at least one input point, wherein when more than one input is received, the processor (114) processes the more than one user command independently from each other .