WO2018145255A1 - Smart terminal, capacitive fingerprint sensor, and sensing module thereof - Google Patents

Abstract

A smart terminal, a capacitive fingerprint sensor, and a sensing module thereof, which relate to the field of fingerprint recognition. The sensing module (100) comprises a sensing array (1) and an insulation medium (2) covering the sensing array (1). Multiple first conductive elements (112) of a preset thickness are disposed on a conductive plate (110) of a sensing unit (11); because of a preset distance between any adjacent two first conductive elements (112), the area of side surfaces of the first conductive elements (112) can be effectively utilized, so that the effective sensing area of the conductive plate (110) is increased when the size of the conductive plate (110) is unchanged, which not only improves the penetration capability of a fingerprint sensor, and a higher medium thickness can be supported.

Description

 Intelligent terminal, capacitive fingerprint sensor and sensing module thereof

 [0001] The present invention belongs to the field of fingerprint identification, and in particular, to an intelligent terminal, a capacitive fingerprint sensor and a sensing module thereof.

 Background technique

 [0002] With the continuous development of fingerprint recognition technology, fingerprint sensors based on fingerprint recognition technology are widely used in various smart terminals (such as mobile phones, tablet computers, etc.). Capacitive fingerprint sensors have become the mainstream of fingerprint recognition applications due to their low device thickness, low cost and low power consumption.

 [0003] Existing capacitive fingerprint sensors include a sensing module, a reading module, a control module, and the like. As shown in FIG. la, the sensing module includes a sensing array ij1 arranged by a plurality of sensing units 11 and an insulating medium 2 overlying the sensing array ijl. During the measurement period, the control module controls the plurality of sensing units 11 to sense fingerprint information of a plurality of points contacting the finger on the insulating medium 2, respectively. Specifically, as shown in FIG. 1B, the sensing unit 11 includes a conductive electrode plate 110 and a measuring circuit 111. When the finger is in contact with the insulating medium 2, a capacitance CS is formed between the finger and the plurality of conductive electrode plates 110, due to the fingerprint. The distance between the crests and troughs and the conductive plate 110 is not equal. Therefore, the peaks and troughs of the fingerprint are different from the capacitance Cs of the capacitance CS formed by the conductive plate 110, and the measuring circuit 111 forms the conductive plate 110 and the fingers. The capacitance of the capacitor is converted to a voltage signal and a measured value Vo representing the peak or valley of the fingerprint is output. The reading module reads and processes the measured values output by the plurality of sensing units 11 to obtain complete fingerprint information.

The measured value of the measurement circuit 111 shown in FIG. 1 is Vo=Cs/Cf*Vb. Wherein, Vb is a preset voltage value raised by the power supply voltage during the measurement period, and Cf is a capacitance value of the feedback capacitor CF. In order to ensure the measurement accuracy of the fingerprint sensor, it is required that Vo cannot be too small. Considering the influence of noise, internal signal interference and parasitic resistance and capacitance, Cf should not be too small; and the preset voltage value Vb is limited by reliability and cost. Therefore, under the same conditions, it is a preferred solution to increase Cs. However, considering the small size characteristics of the fingerprint texture and the resolution requirements of the sensor, the size of the single sensing unit 11 cannot be made large, that is, the area of the conductive electrode plate 110 cannot be too large. The capacitance value of the capacitor is proportional to the plate area of the capacitor, and the distance between the plate and the plate is inversely proportional to the dielectric constant. The medium commonly used in the industry is tempered glass, that is, the dielectric constant is basically fixed. Therefore, the purpose of increasing Cs can be achieved only by shortening the distance between the electrode plate 110 and the finger, that is, reducing the thickness of the medium, thereby causing the fingerprint sensor not to support a higher medium thickness.

[0005] In summary, the existing capacitive fingerprint sensor has a problem that it does not support a higher dielectric thickness.

 technical problem

 [0006] An object of the present invention is to provide a smart terminal, a capacitive fingerprint sensor and a sensing module thereof, which aim to solve the problem that the existing capacitive fingerprint sensor does not support a higher medium thickness.

 Problem solution

 Technical solution

 [0007] The present invention is implemented as a sensing module of a capacitive fingerprint sensor, including a sensing array that is arranged in two dimensions by a plurality of sensing units and overlying the sensing array. An insulating medium; the sensing unit includes a conductive electrode plate and a measuring circuit electrically connected to the conductive electrode plate; and the measuring circuit contacts the conductive electrode plate with the insulating medium during a sensing period The capacitance value of the capacitance formed between the fingers is converted into a voltage signal, and a measurement value corresponding to a peak or a trough of the fingerprint of the finger is output; the upper surface of the conductive electrode plate is provided with a plurality of first surfaces having a predetermined thickness a conductive element, and any two adjacent first conductive elements are spaced apart by a predetermined distance; a sensing area of the conductive plate is an area of an upper surface of the first conductive element, a side of the first conductive element The area of the conductive plate and the predetermined distance are determined together; wherein an upper surface of the conductive plate is a side of the conductive plate opposite to the insulating medium.

 The present invention also provides a capacitive fingerprint sensor, comprising a reading module and a control module, the capacitive fingerprint sensor further comprising the sensing module described above;

[0009] the sensing module is connected to the reading module and the control module;

 [0010] The control module controls the sensing module to sense the fingerprint information of the finger during the sensing period; the reading module reads the measured value output by the sensing module to obtain Fingerprint information of the finger.

 [0011] The present invention also provides an intelligent terminal, which includes the above capacitive fingerprint sensor.

 Advantageous effects of the invention

 Beneficial effect

[0012] The present invention provides a plurality of preset thicknesses on the conductive plates of the sensing unit of the capacitive fingerprint sensor. The first conductive element of the degree, since any two adjacent first conductive elements are spaced apart by a predetermined distance, the area of the side surface of the first conductive element can be effectively utilized, so that the size of the conductive plate is constant. The effective sensing area of the conductive plate not only improves the penetrating ability of the fingerprint sensor, but also enables it to support a higher dielectric thickness.

 Brief description of the drawing

 DRAWINGS

 1 is a top view of a capacitive fingerprint sensor provided by the prior art and the embodiment of the present invention; FIG. 1b is a cross-sectional view of a sensing module of the capacitive fingerprint sensor provided by the prior art;

2 is a cross-sectional view of a sensing module of a capacitive fingerprint sensor according to an embodiment of the present invention;

3 is a cross-sectional view of a sensing module of a capacitive fingerprint sensor according to another embodiment of the present invention; [0016] FIG. 4 is a sensing module of a capacitive fingerprint sensor according to an embodiment of the present invention; a top view of the conductive plate in the middle;

 5 is a top plan view of a conductive electrode plate in a sensing module of a capacitive fingerprint sensor according to another embodiment of the present invention;

 6 is a cross-sectional view of a capacitive fingerprint sensor according to an embodiment of the present invention.

Embodiments of the invention

 The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

 FIG. 2 is a top view of a capacitive fingerprint sensor according to an embodiment of the present invention; FIG. 2 is a schematic diagram of a circuit structure of a sensing module of a capacitive fingerprint sensor according to an embodiment of the present invention. For the convenience of description, only the parts related to the embodiment of the present invention are shown, which are described in detail as follows:

 [0021] As shown in FIG. 1a, a sensing module 100 of a capacitive fingerprint sensor includes a sensing array 1 that is arranged in two dimensions by a plurality of sensing units 11 and covers all of the sensing array 1 The insulating medium 2 above the sensing unit 11.

[0022] In practical applications, the sensing array 1 may be arranged by a plurality of sensing units 11 in a two-dimensional matrix. [0023] In practical applications, the insulating medium 2 may be an insulating medium such as tempered glass or plastic, and may also be other insulating media. It is determined according to actual needs, and there is no restriction here.

As shown in FIG. 2, the sensing unit 11 includes a conductive electrode plate 110 and a measuring circuit electrically connected to the conductive electrode plate 110.

11. During the sensing period, the measuring circuit 111 converts the capacitance value Cs of the capacitance CS formed between the conductive electrode plate 110 and the finger contacting the insulating medium 2 into a voltage signal, and outputs a peak or a valley corresponding to the fingerprint of the finger. The measured value is Vo.

 [0025] The upper surface of the electrode plate 110 is provided with a plurality of first conductive elements 112 having a predetermined thickness, and any two adjacent first conductive elements 112 are spaced apart by a predetermined distance; the sensing area of the conductive plate 110 is determined by The area of the upper surface of the first conductive element 112, the area of the side surface of the first conductive element 112, and the preset distance are determined together.

Specifically, the sensing area of the conductive electrode plate 110 is S=S1+S2+S3. Wherein S1 is the area of the upper surface of the first conductive member 112; S2 is the area of the side surface of the first conductive member 112; and S3 is the total area of the portion of the upper surface of the conductive electrode plate 110 that is not blocked by the first conductive member 110.

 In the embodiment of the present invention, the upper surface of the conductive electrode plate 110 is the opposite side of the conductive electrode plate 110 from the insulating medium 2.

 [0028] In the embodiment of the present invention, the preset distances of any two adjacent first conductive elements 112 may be equal.

, can also be unequal, specifically set according to actual needs, no restrictions here.

[0029] Of course, the preset thickness can also be set according to actual needs, and no specific limitation is made here.

[0030] As an embodiment of the present invention, as shown in FIG. 2, the first conductive member 112 may be integrally formed with the conductive electrode plate 110. In practical applications, it is also possible to achieve the same purpose by providing a groove having a predetermined depth on the conductive plate 110, and setting it according to actual needs, which is not limited herein.

 3 is a cross-sectional view of a sensing module of a capacitive fingerprint sensor according to another embodiment of the present invention.

 For the convenience of description, only the parts related to the embodiment of the present invention are shown, which are described in detail as follows:

As shown in FIG. 3, as another embodiment of the present invention, the first conductive element 112 may pass through the second conductive element.

113 is electrically connected to the electrode plate 110.

[0033] In practical applications, the conductive plate 110, the first conductive element 112, and the second conductive element 113 may all be made of metal. Of course, the conductive electrode plate 110, the first conductive element 112, and the second conductive element 113 may also be made of other conductive materials, which are not limited herein. [0034] In practical applications, the second conductive element 113 may be a conductive via.

 As an embodiment of the present invention, as shown in FIG. 2 and FIG. 3, the input end of the sensing circuit 111 is electrically connected to the conductive electrode plate 110, and the output end of the sensing circuit 111 outputs a measured value Vo. The sensing circuit 111 can use an existing sensing circuit including a switching SW, a feedback capacitor CF, and an amplifier AMP. Specifically, the first end of the SW, the first end of the feedback capacitor CF, and the inverting input of the amplifier AMP are commonly connected as an input end of the sensing circuit 111, and the second end of the SW and the feedback capacitor CF are The output terminals of the two terminals and the amplifier AMP are connected in common as the output end of the sensing circuit 111, and the non-inverting input terminal of the amplifier AMP is connected to the reference voltage Vref.

 4 is a top view of a conductive electrode plate in a sensing module of a capacitive fingerprint sensor according to an embodiment of the present invention; FIG. 5 is a schematic diagram of a capacitive fingerprint sensor according to another embodiment of the present invention. A top view of the conductive plates in the module. For the convenience of description, only the parts related to the embodiment of the present invention are shown, which are as follows:

 As shown in FIG. 4, as an embodiment of the present invention, the first conductive member 112 may be a rectangular parallelepiped. further

The first conductive element 112 can be a cube.

As shown in FIG. 5, as another embodiment of the present invention, the first conductive element 112 may also be a cylinder. specific

It can be a cylinder or a prism, etc., and there are no restrictions here.

[0039] In a practical application, the first conductive element 112 may also be a stage (not shown), such as a prism or a truncated cone, etc., and is specifically set according to actual needs, and is not limited herein.

[0040] In a practical application, the second conductive element 113 may be a rectangular parallelepiped or a cylinder, etc., and is specifically set according to actual needs, and is not limited herein.

[0041] As shown in FIG. 4 and FIG. 5, a plurality of first conductive elements 112 are arranged in a matrix of m rows x n columns; any two adjacent first conductive elements 112 of each row of first conductive elements 112 are spaced first. The preset distance dl is equal to any two adjacent first conductive elements 112 of each column of the first conductive elements 112 being separated by a second predetermined distance d2.

[0042] In the embodiment of the present invention, the first preset distance d1 and the second preset distance d2 may be equal or incompatible. It is determined according to actual needs, and there is no restriction here. For example, assuming that the length and width of the conductive plate 110 are both 50 μm (micrometers) and the first conductive member 112 is a rectangular parallelepiped, the first conductive member may be disposed.

The length and width of 112 are both 0.5μηι, and the thickness is Ιμηι; the first preset distance dl and the second preset distance d2 are both 0.

5μηι.

An embodiment of the present invention further provides a capacitive fingerprint sensor, and FIG. 6 is a schematic diagram of an embodiment of the present invention. A cross-sectional view of a capacitive fingerprint sensor. For the convenience of description, only the parts related to the embodiment of the present invention are shown, which are described in detail as follows:

 [0044] A capacitive fingerprint sensor 1000 includes a reading module 200 and a control module 300. The capacitive fingerprint sensor 1000 further includes the sensing module 100 described above.

 [0045] wherein the sensing module 100 is connected to the reading module 200 and the control module 300.

 [0046] The control module 300 controls the sensing module 100 to sense the fingerprint information of the finger during the sensing period; the reading module 200 reads the measured value output by the sensing module 100 to acquire the fingerprint information of the finger.

 [0047] In the embodiment of the present invention, the control module 300 and its control logic may be the same as the control module and control logic in the existing capacitive fingerprint sensor. Specifically, the control module 300 can control the sensing module 100 to sense the fingerprint information of the finger by raising the power voltage and the ground voltage of the fingerprint sensor, and can also control the sensing module 100 by adding an excitation signal to the finger. The fingerprint information of the finger is sensed, and the sensing information of the finger can be sensed by the sensing module 100 by adding an excitation signal to the non-inverting input end of the amplifier AMP. It can be set according to actual needs, and there is no restriction here.

[0048] In practical applications, the read module 300 can employ an existing read circuit including a sample and hold circuit (S/H circuit) and an analog to digital converter (ADC). Set according to actual needs, no restrictions here.

The embodiment of the invention further provides an intelligent terminal, which comprises the above-mentioned capacitive fingerprint sensor.

 [0050] In the embodiment of the present invention, the smart terminal may be a terminal such as a mobile phone or a tablet computer, and may also be other terminals, and is not limited herein.

 [0051] The capacitive fingerprint sensor provided by the present invention is further described below in conjunction with the working principle:

 [0052] As shown in FIG. 6, during the sensing period, the control module 300 controls the plurality of sensing units 11 (for ease of observation)

Only one sensing unit is shown in the figure to sense the fingerprint information of a plurality of points contacting the finger on the insulating medium 2, respectively. The following describes the entire sensing process by taking the method in which the control module 300 senses the fingerprint by raising the power voltage and the ground voltage as an example:

[0053] During the sensing period, the control module 300 first controls the switching SW to be turned on. Thereafter, the sensing value output by the sensing module 100 is Vo=Vref (preset reference voltage); when the output signal is stable, the control module 300 control Shaoguan S W is broken, and the power supply voltage and the ground voltage of the sensor are raised to a preset preset voltage value Vb. After the signal is stabilized, the sensing value output by the sensing module 100 is Vo=

 Vref+Cs*Vb+Vb, and the sensed value Vo outputted by the previous engraving sensing module 100 becomes Vref+Vb, and the difference between the sensed values output by the two engraving sensing modules 100 is Vol=Cs/Cf *Vb (Formula 1), which is the fingerprint information of a single fingerprint detection point sensed by a single sensing unit 11.

 The embodiment of the invention improves the detection accuracy of the fingerprint sensor by increasing the capacitance Cs of the capacitor CS. Since C s = eS / (4 kd) (where ε is the dielectric constant of the insulating medium 2; S is the area of the conductive plate 110; π and k are constants; d is the sensing distance, that is, the conductive plate 110 The distance between the upper surface and the finger, in general, the distance between the conductive plate 110 and the insulating medium 2 is very small, negligible, that is, d can be approximated as the thickness of the insulating medium 2), therefore, The first conductive element 112 having a predetermined thickness is disposed on the upper surface of the conductive electrode plate 110 without sacrificing the thickness of the medium, and the overall size of the conductive electrode plate 110 is constant, and any adjacent two A conductive element 112 is spaced apart by a predetermined distance. Specifically, it is assumed that the length and width of the conductive plate 110 are both 50 μm, and the sensing area of the conductive electrode plate 110 in the prior art is S=250 (m 2 (square micrometer). In the embodiment of the present invention, A conductive element 112 is a rectangular parallelepiped, and the first conductive element 112 has a length and a width of 0.5 μm and a thickness of 1 μm. The first predetermined distance d1 and the second predetermined distance d2 are both 0.5 μm, and are common in the range of 50 μηιχ50 μιη. 2500 first conductive elements 112, then, in the range of 50μηιχ50μηη, the sensing area of the conductive plate 110 is S=(θ.5μηιχ0.5μιη

², 为现有技术的 3倍。 + 1μηιχ0.5μηιχ4) χ2500+1875μηι

² , 3 times the prior art.

 [0055] It should be noted that, in the above principle, the calculation method of the sensing area S of the conductive electrode plate 110 is based on the premise that the sensing distance d is much larger than the thickness of the first conductive element 112. Under this premise, the first conductive The thickness of element 112 is negligible.

 [0056] It can be seen that the capacitive fingerprint sensor provided by the embodiment of the present invention improves the fingerprint detection accuracy by increasing Cs, and ensures that the fingerprint sensor can support higher when the overall size of the conductive electrode plate 110 is kept unchanged. Medium thickness.

[0057] In the embodiment of the present invention, a plurality of first conductive elements having a predetermined thickness are disposed on a conductive plate of the sensing unit of the capacitive fingerprint sensor, because any two adjacent first conductive elements are separated by a predetermined distance. Therefore, the area of the side surface of the first conductive element can be effectively utilized, so that the effective sensing area of the conductive electrode plate is increased without changing the size of the conductive electrode plate, thereby improving the penetration capability of the fingerprint sensor. It also allows it to support higher media thicknesses.

 The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. Within the scope.

Claims

Claim  [Claim 1] A sensing module of a capacitive fingerprint sensor, comprising: a sensing array arranged in a two-dimensional manner by a plurality of sensing units; and an insulating medium overlying the sensing array; The sensing unit includes a conductive electrode plate and a measuring circuit electrically connected to the conductive electrode plate; the measuring circuit forms between the conductive electrode plate and a finger contacting the insulating medium during a sensing period Capacitance of the capacitor is converted into a voltage signal, and a measured value corresponding to a peak or a trough of the fingerprint of the finger is output; wherein the upper surface of the conductive plate is provided with a plurality of first conductive layers having a predetermined thickness An element, and any two adjacent first conductive elements are spaced apart by a predetermined distance; a sensing area of the conductive plate is an area of an upper surface of the first conductive element, and a side of the first conductive element The area and the predetermined distance are determined together; wherein an upper surface of the conductive plate is a side of the conductive plate opposite to the insulating medium.  [Claim 2] The sensing module of the capacitive fingerprint sensor according to claim 1, wherein the first conductive member is integrally formed with the conductive plate. [Claim 3] The sensing module of the capacitive fingerprint sensor of claim 1, wherein the first conductive element is electrically connected to the conductive plate through a second conductive element. [Claim 4] The sensing module of the capacitive fingerprint sensor according to claim 1, wherein the plurality of first conductive elements are arranged in a matrix of m rows x n columns; Any two adjacent first conductive elements in the element are spaced apart by a first predetermined distance, and any two adjacent first conductive elements of the first conductive element are spaced apart by a second predetermined distance. [Claim 5] The sensing module of the capacitive fingerprint sensor according to claim 4, wherein the first preset distance is equal to the second preset distance. [Claim 6] The sensing module of the capacitive fingerprint sensor according to claim 4, wherein the first preset distance is not equal to the second preset distance. [Claim 7] The sensing module of the capacitive fingerprint sensor according to claim 1, wherein the first conductive element is a rectangular parallelepiped. [Claim 8] The sensing module of the capacitive fingerprint sensor according to claim 1, wherein the first conductive element is a cylinder. [Claim 9] A capacitive fingerprint sensor, comprising: a reading module and a control module, wherein the capacitive fingerprint sensor further comprises the sensing module according to any one of claims 1 to 8; The sensing module is connected to the reading module and the control module;  The control module controls the sensing module to sense the fingerprint information of the finger during a sensing period; the reading module reads the measured value output by the sensing module to obtain the finger Fingerprint information.  [Claim 10] An intelligent terminal, comprising: the capacitive fingerprint sensor according to claim 9.