JP2007324088A

JP2007324088A - Capacitance detector device

Info

Publication number: JP2007324088A
Application number: JP2006156120A
Authority: JP
Inventors: Mikio Fujimura; 幹雄藤村
Original assignee: Tokai Rika Co Ltd; 株式会社東海理化電機製作所
Priority date: 2006-06-05
Filing date: 2006-06-05
Publication date: 2007-12-13

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitance detection device capable of reducing parasitic capacitance and of improving detection precision of the capacitance. <P>SOLUTION: The capacitance detection device has a sensor electrode 14 to form the capacitance between a ground electrode, an oscillator 22 mounted on a printing board 10, an inner wiring (wiring 24, electrode pad 26) to supply a high frequency signal generated in the oscillator 22 to the sensor electrode 14, and a substrate 21 in which the oscillator 22 and the inner wiring are installed, and detects the capacitance based on a detection signal a in which the high frequency signal is fluctuated according to the capacitance. The capacitance detection device is installed between the interior wiring and the substrate 21, and provided with shield layers 31, 32 to which a shield signal b of the same phase and the same amplitude as those of the detection signal a is supplied. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a capacitance detection device.

Conventionally, as a capacitance detection device, a high-frequency signal is supplied to a sensor electrode, and the capacitance is detected based on a detection signal that varies according to the capacitance that the sensor electrode forms with a ground electrode. What can be done is proposed (for example, patent document 1 etc.). In such a capacitance detection device, a detection integrated circuit for supplying a high-frequency signal to a sensor electrode is mounted on a printed circuit board, and the sensor electrode and the detection integrated circuit are connected by a wiring pattern on the printed circuit board. In general.

Further, in such a capacitance detection device, in order to reduce the parasitic capacitance of the wiring pattern, a shield layer is provided between the printed circuit board and the wiring pattern, and the shield layer has the same phase as the detection signal, and A device that supplies a shield signal having the same amplitude has been proposed. In this case, the capacitance detection accuracy is improved by reducing the parasitic capacitance of the wiring pattern.
JP 2001-264194 A

By the way, the parasitic capacitance that affects the detection accuracy of the electrostatic capacitance is generated not only in the wiring pattern but also in the electrode pad and the wiring inside the detection integrated circuit. Therefore, there is a possibility that the detection accuracy of the capacitance is lowered due to the parasitic capacitance of the electrode pad and the wiring inside the detection integrated circuit. In particular, when a very small capacitance of about several pF is detected, such an internal parasitic capacitance significantly affects the capacitance detection accuracy.

An object of the present invention is to provide a capacitance detection device capable of reducing parasitic capacitance and improving capacitance detection accuracy.

In order to solve the above-mentioned problems, the invention according to claim 1 is mounted on a printed circuit board with a sensor electrode for forming a capacitance between the ground electrode and a high-frequency signal source, and is generated by the high-frequency signal source. An internal wiring that supplies the high-frequency signal to the sensor electrode, and a substrate on which the high-frequency signal source and the internal wiring are provided, and the static signal is detected based on the detection signal in which the high-frequency signal is changed according to the capacitance. A capacitance detection device including a detection integrated circuit for detecting a capacitance, wherein the shield is provided between the internal wiring and the substrate and is supplied with a shield signal having the same phase and the same amplitude as the detection signal. The gist is that a layer is provided.

According to a second aspect of the present invention, in the capacitance detection device according to the first aspect, the internal wiring is at least one of an electrode pad for external connection and a wiring for connecting the electrode pad and the high-frequency signal source. It is a summary.

According to each of the above-described configurations, a shield signal having the same phase and the same amplitude as the detection signal is supplied to the shield layer provided between the internal wiring and the substrate, so that the parasitic capacitance of the internal wiring is obtained. And the detection accuracy of the capacitance can be improved.

According to a third aspect of the present invention, in the capacitance detection device according to the first or second aspect, at least a part of the shield layer is the internal wiring when viewed in a line of sight perpendicular to the surface of the substrate. The gist is to include

According to this configuration, at least a part of the shield layer has a sufficient area that can enclose the internal wiring, whereby the parasitic capacitance of the internal wiring can be more reliably reduced.

According to a fourth aspect of the present invention, in the capacitance detection device according to any one of the first to third aspects, the detection integrated circuit is a resistor that forms a low-pass filter with the capacitance. The detection signal is the high-frequency signal attenuated according to the capacitance.

According to this configuration, the configuration of the detection integrated circuit for detecting the capacitance can be made extremely simple.

According to the first to fourth aspects of the present invention, it is possible to provide a capacitance detection device that can reduce parasitic capacitance and improve capacitance detection accuracy.

Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS. FIG. 1 is a plan view showing an electrical configuration of a capacitance detection device used for detecting an operation of the touch panel, for example, and FIG. 2 is a cross section taken along line AA in FIG. FIG. FIG. 1 schematically shows a state viewed from a line of sight perpendicular to the surface, which is a mounting surface of a printed board 10 having a square plate shape. As shown in the drawing, a detection integrated circuit 11 having a square plate shape is mounted on the printed circuit board 10 so as to be included in the printed circuit board 10 in a plan view. A plurality of (in this embodiment, two in this embodiment) shield layers 12 having an elongated shape are extended outwardly on the outer side (the rectangular frame-like region in which hatching is drawn in FIG. 1), and each shield layer is further formed. The wiring pattern 13 is provided in such a manner that it is formed on the surface along the longitudinal direction of 12. The shield layer 12 and the wiring pattern 13 are formed of a conductor such as copper, for example, and the wiring pattern 13 on each shield layer 12 is electrically connected to the shield layer 12 via an insulating film (not shown). Insulated. The detection integrated circuit 11 is electrically connected to a plurality (two) of flat sensor electrodes 14 disposed outside the printed circuit board 10 via the wiring patterns 13. Each sensor electrode 14 forms an electrostatic capacitance with a ground electrode (for example, a ground conductor) having a predetermined potential, and electrostatically flows between the sensor electrode 14 and the human body as the human body (such as a finger) approaches or comes into contact. Form a capacity. That is, the capacitance formed between each sensor electrode 14 grounded to the ground electrode through the human body and the human body varies according to the distance from the human body.

The detection integrated circuit 11 includes a substrate 21 made of, for example, a semiconductor, and an oscillator 22 as a high-frequency signal source is installed on the substrate 21. One end of a resistor 23 is electrically connected to the oscillator 22, and one end of a wiring 24 formed of a conductor such as aluminum or polysilicon is electrically connected to the other end of the resistor 23. Has been. The other end of the wiring 24 forms an independent wiring portion 24a branched into the same number (two) as the sensor electrode 14 via the selector 25, and in each wiring portion 24a, for example, aluminum or poly It is electrically connected to one of a plurality (two) of electrode pads 26 for external connection formed of a conductor such as silicon. The wiring 24 and the electrode pad 26 constitute an internal wiring of the detection integrated circuit 11. The detection integrated circuit 11 is electrically connected to the corresponding wiring pattern 13, that is, the sensor electrode 14 in each electrode pad 26. As a result, the high-frequency signal generated by the oscillator 22 is supplied to the corresponding sensor electrode 14 via any one electrode pad 26 (wiring portion 24 a) selected by the selector 25 and the wiring pattern 13.

Each electrode pad 26 (wiring portion 24 a) is individually electrically connected to the input terminal of the amplifier 27 via the selector 25, and the output terminal of the amplifier 27 is electrically connected to the signal processing circuit 28. It is connected. The capacitance formed by each sensor electrode 14 forms a low-pass filter with the resistor 23, and a high-frequency signal from the oscillator 22 attenuated according to the capacitance is a detection signal a. Output to the amplifier 27. Then, the detection signal a amplified by the amplifier 27 is converted into a signal having an output level corresponding to the capacitance, for example, by performing processing such as rectification in the signal processing circuit 28. The capacitance formed by each sensor electrode 14 is detected.

As shown in FIG. 2, in the present embodiment, shield layers 31 and 32 formed of a conductor such as aluminum or polysilicon are provided between the wiring 24 and the substrate 21 and between each electrode pad 26 and the substrate 21. It is arranged. The shield layers 31 and 32 on the substrate 21 are electrically insulated from the substrate 21 by an insulating film 33 made of, for example, SiO ₂ interposed between the substrate 21 and the shield layers 31 and 32, and are shielded. The internal wiring (wiring 24, electrode pad 26) on the layers 31 and 32 is connected to the shield layers 31 and 32 by an insulating film 34 made of, for example, SiO ₂ interposed between the shield layers 31 and 32 and the internal wiring. It is electrically insulated. That is, the shield layers 31 and 32 and the internal wiring are sequentially laminated on the substrate 21 in a manner insulated by the insulating films 33 and 34. As shown by the dot pattern in FIG. 1, the shield layers 31 and 32 contain the wiring 24 and the electrode pads 26 when viewed in a line of sight perpendicular to the surface of the substrate 21 (printed substrate 10). To do.

As shown in FIG. 1, the output terminal of the amplifier 27 is electrically connected to the input terminal of the amplifier 35, and the output terminal of the amplifier 35 is connected to the plurality of shield layers 12 and the electrode pad 36. All of the shield layers 32 are electrically connected. The detection signal a amplified by the amplifier 27 is passed through the amplifier 35 and the electrode pad 36 as the shield signal b having the same phase and the same amplitude as the detection signal a and the plurality of shield layers 12 and shield layers. 31 and 32. The amplifier 35 is used to supply the shield layers 12, 31, 32 as the shield signal b having the same phase and the same amplitude as the detection signal a without affecting the detection signal a amplified by the amplifier 27. Is. By supplying this shield signal b to the shield layer 12, the parasitic capacitance of the wiring pattern 13 is reduced, and by supplying the shield signal b to the shield layers 31 and 32, the parasitic of the internal wiring (wiring 24, electrode pad 26) is reduced. Capacity is reduced. Therefore, the signal processing circuit 28 detects the capacitance formed by each sensor electrode 14 with higher accuracy based on the detection signal a in which the parasitic capacitance of the internal wiring is reduced as well as the wiring pattern 13. The The detected capacitance is used to detect the proximity or contact of the human body to each sensor electrode 14, and is used to detect the operation of the touch panel, for example.

As described above in detail, according to the present embodiment, the following effects can be obtained.
(1) In the present embodiment, a shield signal b having the same phase and the same amplitude as the detection signal a is applied to the shield layers 31 and 32 provided between the internal wiring (wiring 24 and electrode pad 26) and the substrate 21. Is supplied, the parasitic capacitance of the internal wiring can be reduced, and the capacitance detection accuracy can be improved. In particular, when detecting a minute capacitance of about several pF, the minute parasitic capacitance of the internal wiring can be suitably reduced.

(2) In the present embodiment, the shield layers 31 and 32 have a sufficient area to contain the internal wiring when viewed with a line of sight perpendicular to the surface of the substrate 21. The parasitic capacitance of the internal wiring can be reduced more reliably.

(3) In the present embodiment, the detection integrated circuit 11 forms a low-pass filter between the capacitance formed by each sensor electrode 14 and the resistor 23, and the high frequency attenuated according to the capacitance. Since the signal is the detection signal a, the configuration of the detection integrated circuit 11 for detecting the capacitance can be made extremely simple.

In addition, you may change the said embodiment as follows.
In the embodiment, either one of the shield layers 31 and 32 may be omitted.
In the embodiment, a shield layer may be provided between the substrate 21 and the signal line L1 (see FIG. 1) that connects the selector 25 and the input terminal of the amplifier 27.

-In the said embodiment, the sensor electrode 14 and the corresponding wiring pattern 13 grade | etc., May be 1 or 3 or more.
In the embodiment, the circuit configuration of the detection integrated circuit 11 for detecting the capacitance is an example.

-You may apply this invention to the passenger | crew detection sensor mounted in vehicles, such as a suitable touch sensor and a motor vehicle, which detects the proximity | contact or contact of a human body.

The top view which shows the electrical constitution of one Embodiment of this invention. Sectional drawing along the AA line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Printed circuit board, 11 ... Detection integrated circuit, 14 ... Sensor electrode, 21 ... Board | substrate, 22 ... Oscillator as a high frequency signal source, 23 ... Resistance, 24 ... Wiring which comprises internal wiring, 26 ... Internal wiring Electrode pads, 28... Signal processing circuit, 31, 32... Shield layer.

Claims

A sensor electrode that forms a capacitance with the ground electrode;
A high-frequency signal source mounted on a printed circuit board; an internal wiring for supplying a high-frequency signal generated by the high-frequency signal source to the sensor electrode; and a substrate on which the high-frequency signal source and the internal wiring are provided. In response, a capacitance detection apparatus comprising an integrated circuit for detection that detects the capacitance based on a detection signal in which the high-frequency signal is changed,
An electrostatic capacity detection device comprising a shield layer provided between the internal wiring and the substrate, to which a shield signal having the same phase and the same amplitude as the detection signal is supplied.
The capacitance detection device according to claim 1,
The capacitance detection device according to claim 1, wherein the internal wiring is at least one of an electrode pad for external connection and a wiring for connecting the electrode pad and the high-frequency signal source.
In the capacitance detection device according to claim 1 or 2,
At least a part of the shield layer encloses the internal wiring when viewed with a line of sight perpendicular to the surface of the substrate.
The capacitance detection apparatus according to any one of claims 1 to 3,
The detection integrated circuit comprises:
Comprising a resistor constituting a low-pass filter with the capacitance;
The capacitance detection device, wherein the detection signal is the high-frequency signal attenuated according to the capacitance.