Fingerprint sensor compatible overlay materials

Abstract

Disclosed is a fingerprint sensor compatible cover layer material that uses anisotropic conductive materials to achieve accurate imaging of fingerprints through the cover layer. The anisotropic conductive material has an increased conductivity in a direction orthogonal to the fingerprint sensor, which increases the capacitive coupling of the fingerprint to the sensor surface, allowing the fingerprint sensor to accurately image the fingerprint through the cover layer. Also disclosed is a method for forming a fingerprint sensor compatible cover layer.

Description

[0001] Related Applications

[0002] This application is an international application of U.S. patent application No. 15 / 347,400 filed on 11 / 09 / 2016, which claims the benefit of U.S. Provisional Patent Application No. 62 / 255,027 filed on November 13, 2015 and claims the benefit of U.S. Provisional Patent Application No. 62 / 316,451 filed on March 31, 2016, all of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present disclosure relates generally to structures and methods of making anisotropic conductive materials, and more particularly to anisotropic conductive materials that are compatible with sensors that sense fingerprints through the material.

[0004] background

[0005] Various devices and systems, such as computing devices, mobile communication devices, automotive equipment, industrial equipment, household white goods, and entry systems, may require authentication methods to prevent unauthorized access. Fingerprint authentication using a fingerprint sensor can protect a device or system from unauthorized access.

[0006] The fingerprint sensor can use various capacitive sensing methods to image the fingerprint pattern, where imaging the fingerprint means detecting the fingerprint and generating a set of data values ​​(or "fingerprint data") representing the fingerprint in a digital format. The fingerprint data can be an image or other information specific to the fingerprint. The method requires that a portion of the finger or "finger pad" that includes the fingerprint is in direct contact with or close to the sensor surface. A very thin covering or overlay can be placed on the sensor surface. A thick overlay between the fingerprint and the fingerprint sensor may obscure fingerprint features.

[0007] There may be a variety of situations when a user may want to image a fingerprint through a thick material. A user may want to image a fingerprint using a sensor covered by a thick material to protect the sensor (or a device including the sensor) from harmful environmental factors (such as cold and water) and harmful physical factors (such as sharp objects and corrosive chemicals) or to improve the appearance of the fingerprint sensor (such as by providing a continuous surface with a touch screen). The protective cover or covering can be made of a rigid material (such as but not limited to glass or plastic) or a flexible material (such as but not limited to fabric or film). The protective cover can completely surround the device or can partially surround the device. Current fingerprint sensors cannot image fingerprints through thick materials. Using a cover or covering material that is thin enough to enable fingerprint sensing may limit the protective effect of the cover or film. If a thick cover or covering material is used, the user may have to remove the device from the cover or covering to enable fingerprint sensing. Removing the cover or cover may be inconvenient for the user and / or may risk damaging the device. It is desirable to create a material that can cover the sensor, wherein the material is thick enough to protect but can accurately image the fingerprint through the material.

[0008] Overview

[0009] In an embodiment, an anisotropic conductive material is disclosed that is thick enough to protect a fingerprint sensor but enables the fingerprint sensor to accurately image a fingerprint through the material. The anisotropic conductive material is substantially more conductive in one direction (such as a direction orthogonal to the surface of the fingerprint sensor) than in other directions, which increases the capacitive coupling of the fingerprint to the sensor surface, allowing the fingerprint sensor to accurately image the fingerprint through the material.

[0010] In an embodiment, a method for making anisotropic conductive materials is disclosed.Anisotropic conductive materials are substantially more conductive in one direction than in other directions.

[0011] In an embodiment, a method for imaging a fingerprint through a fingerprint sensor covered with an anisotropic conductive material is disclosed that is thick enough to provide protection but enables the fingerprint sensor to accurately image the fingerprint through the material. The anisotropic conductive material is substantially more conductive in one direction (such as, a direction orthogonal to the surface of the fingerprint sensor) than in other directions, which increases the capacitive coupling of the fingerprint to the sensor surface, allowing the fingerprint sensor to accurately image the fingerprint through the material.

[0012] In an embodiment, a fingerprint sensor device for imaging a fingerprint through a fingerprint sensor covered with an anisotropic conductive material is disclosed, the anisotropic conductive material being thick enough to provide protection but enabling the fingerprint sensor to accurately image the fingerprint through the material. The anisotropic conductive material is substantially more conductive in one direction (such as a direction orthogonal to the surface of the fingerprint sensor) than in other directions, which increases the capacitive coupling of the fingerprint to the sensor surface, allowing the fingerprint sensor to accurately image the fingerprint through the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A device with a fingerprint-enabled authentication system is shown.

[0014] Figure 2 A fingerprint sensing system is shown.

[0015] Figure 3 The fingerprint sensor structure is shown.

[0016] Figure 4 A capacitive sensor array suitable for detecting and imaging fingerprints is shown.

[0017] Figures 5A-5C A material is shown having pillars fabricated in one direction in the material according to various embodiments.

[0018] Figure 6A-6B A material is shown having pillars fabricated in a certain shape in the material according to various embodiments.

[0019] Figure 7A-7B Materials are shown in which conductive elements have been incorporated into the material according to various embodiments.

[0020] Figures 8A-8C Materials are shown in which conductive elements have been incorporated into the material according to various embodiments.

[0021] Figures 9A-9B The effect of anisotropic conductive materials on the electric field density of a capacitive fingerprint sensor according to various embodiments is shown.

[0022] Figures 10A-10B The effect of anisotropic conductive materials on imaging a fingerprint by a fingerprint sensor is shown according to various embodiments.

[0023] Figures 11A-11B Measured capacitance according to various embodiments is shown.

[0024] Figures 12A-12I Arrangements of pillars according to various embodiments are shown.

[0025] Fig.13An arrangement of pillars according to an embodiment is shown.

[0026] Figures 14A-14B A fingerprint sensor structure according to various embodiments is shown.

[0027] Fig.15 A system fingerprint sensor structure according to an embodiment is shown.

[0028] Detailed Description

[0029] In the following description, for the purpose of explanation, numerous specific details are set forth in order to provide a comprehensive understanding of the embodiments of the invention discussed herein. However, it will be apparent to those skilled in the art that these and other embodiments may be practiced without these specific details. In other instances, well-known circuits, structures, and techniques are not specifically shown, but are shown in block diagrams to avoid unnecessary obscurity in the understanding of this specification.

[0030] References in the specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in relation to the embodiment is included in at least one embodiment of the present invention. The phrase "in one embodiment" in various places in this specification does not necessarily refer to the same embodiment.

[0031] For brevity and clarity of explanation, reference numerals may be repeated in various drawings to indicate corresponding or similar elements. Many details are set forth to provide an understanding of the embodiments described herein. Examples may be practiced without these details. In other instances, well-known methods, procedures, and components are not specifically described to avoid obscuring the described examples. This specification is not to be considered as being limited to the scope of the examples described herein.

[0032] Fingerprint sensing and imaging

[0033] Figure 1 An embodiment of a device 100 with a fingerprint-enabled authentication system is shown. Device 100 may be a mobile communication device including a fingerprint sensor 101 that may enable a user to access device applications. Surface 102 may be a display or a touch screen. Other embodiments of devices or systems with a fingerprint-enabled authentication system may include automotive consoles, industrial control panels, home security consoles, and entry mats.

[0034] In each such device or system, a fingerprint may be imaged using fingerprint sensor 101, wherein imaging the fingerprint may include detecting the fingerprint and generating a set of data values ​​or "fingerprint data" representing the fingerprint in a digital format. The fingerprint data may then be stored in a memory location. A second fingerprint may then be imaged. The first set and the second set of fingerprint data may be compared to determine whether they share fingerprint features. Upon determining that the two sets of fingerprint data share a substantial number of features, the device may enable the user to access the device or system.

[0035] Figure 2 A fingerprint sensor structure 200 is shown in accordance with various embodiments. Fingerprint sensor 201 includes a sensor surface 202. A portion of a finger 210 or "finger pad" 220 including a fingerprint may be disposed in direct contact with or in proximity to sensor surface 202. Fingerprint sensor 201 includes a capacitive sensor array 203 (not shown). Sensor surface 202 may be disposed above array 203, which experiences a change in capacitance in response to contact or proximity of fingerprint features of finger 210. Fingerprint sensor 201 may be coupled to a processor or controller 206. Processor / controller 206 may be configured to receive a voltage or current signal from capacitive sensing element 203 corresponding to a measured capacitance across and / or between capacitive sensing elements 203, and convert the voltage or current signal into fingerprint data represented by a visual representation of fingerprint 212.

[0036] Figure 3 A fingerprint sensor structure 300 is shown according to various embodiments. The fingerprint sensor structure 300 includes a fingerprint sensor 301 and a sensor surface 304, the fingerprint sensor 301 including a sensor array including Tx electrodes 302 and Rx electrodes 303. The fingerprint sensor structure 300 includes a cover layer 306 and an intermediate layer 305, which may be glass to provide a sensor surface, or an adhesive to attach the cover layer 306, or a paint for color matching. In other embodiments, there may be more than one intermediate layer between the sensor surface 304 and the cover layer 306 or between the cover layer 306 and the fingerprint pad.

[0037] Figure 4 An embodiment of a capacitive sensor array 400 suitable for detecting and imaging fingerprints is shown. The capacitive sensor array 400 may include a plurality of electrodes arranged in an array 402 having row electrodes 404 in a first axis and column electrodes 406 in a second axis. Figure 4Eight row electrodes 404 and eight column electrodes 406 are shown, but there may be many more electrodes arranged along both axes. Depending on the size of the array, there may be tens or hundreds of electrodes per row and column. The exact size and spacing of the electrodes may depend on the system design requirements.

[0038] A capacitive fingerprint sensor array includes capacitive sensing elements that can generate signals suitable for detecting, determining the location of, tracking, and / or imaging fingerprint features on or near a sensor surface. A capacitive sensing element can include an electrode, a discrete electrode unit, or an intersection of electrodes from which a measurement or signal can be obtained that is separate and distinct from measurements / signals obtained from other sensing elements in the capacitive sensor array. A unit cell refers to a discrete area of ​​a capacitive sensor array where each point within the unit cell is closer to one sensing element than to adjacent sensing elements.

[0039] Capacitive fingerprint sensors work by measuring the capacitance of a capacitive sensing element and detecting changes in capacitance that indicate the presence or absence of fingerprint features. Fingerprint features may include, but are not limited to, valleys and ridges that form bows, loops, and whorls. For example, when a fingerprint ridge comes into contact with or approaches a sensing element, a change in capacitance caused by the fingerprint ridge may be detected. The change in capacitance that can be measured in response to a fingerprint feature is approximately 0.05 fF. The change in capacitance of the sensing element may be measured by a circuit that converts the capacitance measured from the capacitive sensing element into a digital value from which fingerprint data can be derived. As used herein, "fingerprint data" refers to a collection of data values ​​that represent a fingerprint in a digital format. In some embodiments, the fingerprint data may be a data set that visually represents the valleys and ridges of a fingerprint using its loops, whorls, and whorls. In other embodiments, the fingerprint data may digitally represent a fingerprint in a non-visual form.

[0040] like Figure 4 The illustrated fingerprint sensor system may include certain features for enabling accurate imaging of a fingerprint. In an embodiment, the spacing of the row electrodes and the column electrodes may be small enough so that when a finger contacts or approaches the fingerprint sensor surface, multiple rows or columns may be arranged in the valley of the fingerprint feature or arranged to follow the ridge of the fingerprint feature. In some embodiments, the spacing may be selected so that each fingerprint feature can be detected by a minimum number of capacitive sensing elements (e.g., at least three capacitive sensing elements). In various embodiments, the spacing of the capacitive sensing elements may be less than 100 μm.

[0041] The thickness of the cover layer disposed over the sensor surface can affect the change in the measured capacitance of the capacitive sensing element in response to approaching fingerprint features. The thickness of the cover layer that enables accurate imaging of fingerprints can typically be less than 150 μm. A thicker cover layer can reduce the change in the measured capacitance of the capacitive sensing element in response to approaching fingerprint features, which may obscure fingerprint details.

[0042] Anisotropic Conductive Materials

[0043] The cover layer disposed on the sensor surface may generally be made of an isotropic conductive material. In other words, the conductivity of the material is substantially the same in all directions. In an embodiment, the cover layer may be made of an anisotropic conductive material. Anisotropic conductive materials may be substantially more conductive in one direction (such as a direction orthogonal to the fingerprint sensor surface) than in other directions. The impact of anisotropic conductive materials on fingerprint sensing will be discussed further below.

[0044] Figures 5A-5C A method of making anisotropic conductive materials by making conductive pathways or "pillars" in the material is shown. The pillars can be made by methods including, but not limited to, drilling, piercing, or perforating the material (including laser-assisted methods). The pillars can be areas within the material that lack material. The pillars can be filled completely or partially with air, dielectric materials, or conductive materials. The pillars can be filled with materials by methods including, but not limited to, sticking the material in the pillars, electroplating the pillars, or depositing particles. The pillars can be filled completely or partially. The pillars can be coated with conductive materials. The conductive materials can include copper or indium tin oxide.

[0045] Figure 5A A material 512 is shown having pillars 511 fabricated completely through the material 512 from one surface of the material in one direction. In some embodiments, pillars that penetrate the material may be preferred because the pillars that penetrate the material can provide uniform depth and conductivity because the pillars that penetrate the material perfectly match the thickness of the material they penetrate. As further described below, uniform depth and conductivity can improve fingerprint sensing through anisotropic conductive materials. The material fabricated with pillars that penetrate the material can be ground to reduce the material to a desired thickness. After fabricating the pillars, one or both of the surfaces of the material having the pillars that penetrate the material can be covered by a thin layer of a covering material to provide a surface to receive fingerprints. The covering material will have a controlled thickness across the surface of the anisotropic conductive material. Figure 5B Material 522 is shown having pillars 521 fabricated completely through material 522 and having a covering material 523 . Figure 5CMaterial 532 is shown having pillars 531 fabricated completely through material 532 and having a covering material.

[0046] Figure 5B A material 522 is shown with pillars 521 fabricated partially through the material 522. Pillars fabricated partially through the material may be referred to as "blind pillars." Blind pillars may eliminate the need to attach an intermediate material to provide a surface for receiving a fingerprint. The material fabricated with blind pillars may be ground to reduce the material to a desired thickness.

[0047] The columns can be manufactured in different shapes. Figures 5A-5C Pillars 511 , 521 , and 531 formed in a cylindrical shape are shown. Fig. 6A A material 610 is shown having pillars 611 formed in the shape of cones. Figure 6B A material 620 is shown with pillars 621 formed in the shape of a cylinder with flat plates 622 at each end. A cylinder with one or two flat plates 622 may have less capacitive coupling with adjacent pillars than a cylinder, while providing a large area at each surface to strongly couple to a fingerprint and fingerprint sensor. In other embodiments, the pillars may be formed in other shapes.

[0048] Fig. 7A and Figure 7B Another method of making anisotropic conductive materials by incorporating conductive elements in the material is shown. Fig. 7A A material 710 is shown in which conductive elements 711 have been randomly incorporated. In an embodiment, the diameter of the embedded conductive particles may be less than 20 μm. Figure 7BThe material 710 is shown after an electric or magnetic field force 720 has been applied throughout the material 710 during a manufacturing step. The electric or magnetic field 720 may be applied in a direction substantially orthogonal to the material surface 740 and the material surface 750. The direction of the applied electric or magnetic field 720 is indicated by an arrow. The electric or magnetic field force may align the conductive elements 711 in the direction of the applied electric or magnetic field 720, thereby forming the equivalent of a "pillar" 730 aligned in the direction of the applied electric or magnetic field 720. Thus, the material 710 will have an increased conductivity in the aligned direction of the pillars 730. In a specific embodiment, the conductive elements are ferroelectric conductive particles and a magnetic field has been applied. In other embodiments, other conductive elements 711 may be used, such as conductive filaments. In other embodiments, the conductive elements 711 may be aligned to form the equivalent of pillars 730 by applying an electric field throughout the material 710 in a direction substantially orthogonal to the material surface 740 and the material surface 750. In still other embodiments, conductive elements 711 may be aligned to form the equivalent of pillars 730 by applying pressure across material 710 in a direction substantially normal to material surfaces 740 and 750 .

[0049] Figures 8A-8B Another method of making anisotropic conductive materials by incorporating conductive elements in the material is shown. Fig. 8A A material 801 is shown in which conductive elements 802 have been fabricated into the material such that the conductive elements are aligned from one surface of the material to a second surface and extend through the material in one direction, forming "pillars". Figure 8B A material 811 is shown in which conductive elements 812 have been fabricated into the material such that the conductive elements are aligned in one direction from one surface of the material to a second surface of the material, but do not extend through the material, forming "pillars". Figure 8C A material 821 is shown in which conductive elements 822 have been fabricated in the material such that the conductive elements are aligned in a direction 833 from one surface of the material, and wherein the distance between the conductive elements in the direction 833 is smaller than the distance between the conductive elements in other directions, forming "pillars." Thus, materials 801, 811, and 821 will have increased conductivity in the alignment direction 833 of the pillars. Figures 8A-8C The conductive elements may include, but are not limited to, nanowires, flakes, particles, or rods. Figures 8A-8C The conductive elements shown in FIG. 1 may include Figures 5A-5C , Figure 6A-6B and Figure 7A-7B A conductive element that is the same as or similar to the conductive element disclosed in.

[0050] Anisotropic conductive materials can be made of rigid materials (including but not limited to glass, ceramics or plastics). Anisotropic conductive materials can be made of non-rigid materials (including but not limited to films or fabrics).

[0051] Anisotropic Conductive Materials and Fingerprint Sensing

[0052] Fig.9A and Fig. 9B Shown is the effect of pillars in anisotropic conductive material on the electric field density of a capacitive fingerprint sensor imaging a fingerprint. Fig.9A A mutual capacitance fingerprint sensor 900 is shown including a Tx electrode 911, Rx electrodes 901, 902, and 903, a sensor surface 904, and a cover material 905. In this example, the sensing element includes the intersection of the Tx electrode 911 and the Rx electrode 901, 902, or 903. The sensing element 912 includes the intersection of the Tx electrode 911 and the Rx electrode 902; the sensing element 913 includes the intersection of the Tx electrode 911 and the Rx electrode 901. In this example, the Rx electrodes 901, 902, and 903 correspond to Figure 4 The row electrode 404 in the embodiment, and the Tx electrode 911 corresponds to Figure 4 The mutual capacitance fingerprint sensor 900 measures the change in mutual capacitance of the sensing element 912 or 913 when a finger 909 is present on the surface 906 of the cover material 905. The magnitude of the decrease in mutual capacitance measured by the sensing elements 912 and 913 is represented by the number of field lines 907 that are coupled from the Tx electrode 911 to the finger 909 instead of being coupled to the Rx electrodes 901 and 902. In this example, the field lines are an abstraction of the strength of the capacitive coupling between the sensing elements 912 and 913 and the finger 909. Fig.9A Fingerprint ridge 910 is shown weakly coupled to sensing elements 912 and 913 through material 905 , resulting in a slight reduction in the measured mutual capacitance, as represented by a single field line 908 shunting away from sensing elements 912 and 913 to ridge 910 .

[0053] Fig. 9BA mutual capacitance fingerprint sensor 950 is shown that includes a Tx electrode 963, Rx electrodes 951, 952, and 953, a sensor surface 954, and a cover material 955. In this example, the sensing element includes the intersection of the Tx electrode 963 and the Rx electrode 951, 952, or 953. Sensing element 964 includes the intersection of the Tx electrode 963 and the Rx electrode 952; sensing element 965 includes the intersection of the Tx electrode 963 and the Rx electrode 951. Cover material 955 includes pillars 959 and 960. The magnitude of the reduction in mutual capacitance measured by sensing elements 964 and 965 when a finger 961 is present on the surface 956 of the cover material is represented by the number of field lines 958 that are coupled from the Tx electrode 963 to the finger 961 instead of to the Rx electrodes 951 and 952. Fig. 9B Fingerprint ridge 962 is shown to be strongly coupled to sensing elements 964 and 965 through pillar 959, resulting in a decrease in measured mutual capacitance, as represented by the four field lines 958 coupled to ridge 962 through pillar 959 away from sensing elements 964 and 965. In other words, pillar 959 acts as an electric field guide that increases the capacitive coupling of fingerprint ridge 962 to sensing elements 964 and 965 and increases the change in measured capacitance of sensing elements 964 and 965. The increase in the magnitude of the decrease in measured mutual capacitance using material 955 including pillars 959 and 960 as compared to material 905 without pillars is represented by the increase in the number of field lines 957 coupled to fingerprint ridge 962 away from sensing elements 964 and 965. Fig.9A and Fig. 9B In the example of FIG. 1 , the increase in using material 955 with pillars 959 and 960 is represented by four field lines 958 compared to one field line 908 for material 905 without pillars. It should be understood that conductive anisotropic materials can be similarly used with self-capacitive fingerprint sensors, where the increased capacitive coupling of the pillars results in an increase in the measured capacitance change of the sensing element. It should also be understood that the alignment of pillars 959 and 960 with fingerprint ridges 962 and 966 is merely exemplary; the pillars may or may not be aligned with fingerprint ridges and / or fingerprint valleys.

[0054] Fig. 10A and Fig. 10B Another example of the effect of anisotropic conductive materials on imaging a fingerprint by a fingerprint sensor is shown. Fig. 10AA self-capacitance fingerprint sensor 1000 is shown that includes an electrode 1001, a sensor surface 1004, and a cover material 1005. In this example, a sensing element 1012 includes the electrode 1001. The self-capacitance fingerprint sensor 1000 measures changes in the self-capacitance of the sensing element 1012 when fingerprint features 1006 corresponding to fingerprint valleys and fingerprint features 1007 corresponding to fingerprint ridges are present on a surface 1008 of the cover material 1005. When the fingerprint features 1006 and 1007 are capacitively coupled to the sensing element 1012 through the cover material 1005, the fingerprint features 1006 and 1007 spread. The spreading (or "blurring") of the fingerprint features 1006 and 1007 through the cover material 1005 is represented by lines 1010. In this example, the lines 1010 are an abstraction of the diffusion of the fingerprint features 1006 and 1007 through the cover material 1005 to the sensing element 1012. Fig. 10A The diffusion of fingerprint features 1006 and 1007 through cover material 1005 is shown to enable each fingerprint feature 1006 and 1007 to be capacitively coupled to multiple sensing elements 1012, and also to enable sensing element 1012 to be capacitively coupled to multiple fingerprint features 1006 and 1007. Increasing the number of fingerprint features 1006 and 1007 that are capacitively coupled to sensing elements 1012, or increasing the number of sensing elements 1012 that are capacitively coupled to each of fingerprint features 1006 and 1007, reduces the accuracy of imaging the fingerprint by sensing element 1012, and therefore by fingerprint sensor 1000.

[0055] Fig. 10B A self-capacitance fingerprint sensor 1050 is shown that includes electrodes 1051, a sensor surface 1054, and an anisotropic conductive material 1055. The direction of increased conductivity in the anisotropic conductive material 1055 is indicated by arrow 1059. In this example, a sensing element 1062 includes the electrodes 1051. The self-capacitance fingerprint sensor 1050 measures the change in self-capacitance of the sensing element 1062 when fingerprint features 1056 and 1057 are present on a surface 1058 of the anisotropic conductive material 1055. When the fingerprint features 1056 and 1057 are capacitively coupled to the sensing element 1062 through the anisotropic conductive material 1055, the fingerprint features 1056 and 1057 may diffuse. The diffusion of the fingerprint features 1056 and 1057 through the anisotropic conductive material 1055 is indicated by line 1060. Fig. 10B The diffusion of fingerprint features 1056 and 1057 through anisotropic conductive material 1055 is shown to be less than Fig. 10AThe diffusion of fingerprint features 1006 and 1007 through cover material 1005 is shown. Pillars (not shown) of anisotropic conductive material 1055 may act like electric field guides that reduce the diffusion of fingerprint features sensed by sensing element 1062. Reducing the diffusion of fingerprint features 1056 and 1057 may enable each fingerprint feature 1056 and 1057 to capacitively couple to fewer sensing elements 1062, and may enable each sensing element 1062 to capacitively couple to fewer fingerprint features 1056 and 1057, thereby increasing the accuracy with which fingerprint sensor 1050 images a fingerprint. It should be understood that conductive anisotropic materials may similarly be used with mutual capacitance fingerprint sensors, where the reduction in the diffusion of fingerprint features may also enable each fingerprint feature to capacitively couple to fewer sensing elements 1062, and may enable each sensing element to capacitively couple to fewer fingerprint features, thereby increasing the accuracy with which mutual fingerprint sensors image fingerprints.

[0056] Fig.11A and Fig. 11B An example of the effect of anisotropic conductive materials on imaging a finger through a fingerprint sensor using self-capacitance is also shown. Fig.11A and Fig. 11B In the graph of FIG. 1 , the y-axis represents the measured capacitance in units of femtofarads (fF). Position 0 on the x-axis represents the transition between the valleys and ridges of the imaged fingerprint. The graph shows the variation in capacitance measured between the fingerprint valleys and fingerprint ridges using different thicknesses (100 μm-550 μm) of cover material in contact with both the fingerprint and the fingerprint sensor surface. Fig.11A The change in measured capacitance using a cover material without pillars is shown. Line 1101 indicates the measured capacitance of an imaged fingerprint in which the cover material thickness is 100 μm. At an x-axis position of -2 corresponding to the valley, the measured capacitance on line 1101 is approximately 0.6 fF. At an x-axis position of 6 corresponding to the ridge, the measured capacitance of line 1101 is approximately 1.7 fF. Therefore, the measured capacitance change of line 1101 is approximately 1.1 fF. Line 1104 indicates the measured capacitance of an imaged fingerprint in which the cover material is 550 μm. At an x-axis position of -2 corresponding to the valley, the measured capacitance of line 1104 is approximately 0.35 fF. At an x-axis position of 6 corresponding to the ridge, the measured capacitance of line 1104 is approximately 0.40 fF. Therefore, the measured capacitance change of line 1104 is approximately 0.05 fF.

[0057] Fig. 11BAn example of a change in measured capacitance using a cover material with pillars is shown. Line 1152 indicates the measured capacitance of an imaged fingerprint in which the cover material with pillars is 100 μm. At an x-axis position of -2 corresponding to the valley, the measured capacitance of line 1152 is approximately 0.4 fF. At an x-axis position of 6 corresponding to the ridge, the measured capacitance of line 1152 is approximately 1.7 fF. Therefore, the measured capacitance change of line 1152 is approximately 1.3 fF. Line 1151 indicates the measured capacitance of an imaged fingerprint in which the cover material with pillars is 550 μm. At an x-axis position of -2 corresponding to the valley, the measured capacitance of line 1151 is approximately 0.6 fF. At an x-axis position of 6 corresponding to the ridge, the measured capacitance of line 1151 is approximately 1.7 fF. Therefore, the measured capacitance change is approximately 1.1 fF.

[0058] like Fig.11A and Fig. 11B As shown, the measured capacitance change using conventional materials (without pillars) decreases significantly with increasing cover layer thickness. As the cover layer thickness increases, the measured capacitance change does not decrease as much when using materials with pillars. In other words, the pillars act like electric field guides that increase the capacitive coupling of fingerprint features to the sensing element, reducing the reduction in measured capacitance change due to the proximity of fingerprint features (such as ridges) through the thick cover layer. Therefore, using a cover layer with pillars significantly increases the thickness of the cover layer material, and the fingerprint sensor can accurately image the fingerprint through the cover layer material.

[0059] As the number of capacitive sensing elements that can detect each fingerprint feature increases, the accuracy of fingerprint imaging also increases. Increasing the density of pillars relative to the capacitive sensing elements increases the number of sensing elements that can couple to each fingerprint feature that are strong enough to detect the fingerprint feature. Increasing the density of pillars relative to the capacitive sensing elements also reduces the effect of the pillars aligning the sensing elements. Therefore, increasing the density of pillars increases the accuracy of imaging the fingerprint through the cover layer. Increasing the density of pillars also increases the thickness of the cover layer, which can achieve accurate imaging of the fingerprint.

[0060] Reducing the density of pillars relative to the capacitive sensing elements increases the effect of the alignment of the pillars to the sensing elements. In embodiments where each capacitive sensing element corresponds to one pillar, the alignment of each pillar to the sensing element increases the coupling of fingerprint features to each sensing element, thereby increasing the accuracy of fingerprint imaging. In specific embodiments where each capacitive sensing element corresponds to one pillar, concentrating the pillars in each unit cell provides the most efficient conductive coupling and the most accurate fingerprint imaging.

[0061] In embodiments where each capacitive sensing element corresponds to less than one pillar, the accuracy of fingerprint imaging through the cover layer is less than in embodiments where each capacitive sensing element corresponds to one or more pillars. However, the accuracy of fingerprint imaging through the cover layer when each capacitive sensing element corresponds to less than one pillar is greater than the accuracy of fingerprint imaging through the cover layer when there are no pillars.

[0062] In embodiments, the pillars may be in direct physical contact with the sensing element. In other embodiments, for ease of manufacturing, the pillars may not be in direct physical contact with the sensing element. In embodiments where the pillars are in direct physical contact with the sensing element, the accuracy of fingerprint imaging through the cover layer is greater than embodiments where the pillars are not in direct physical contact with the sensing element. However, the accuracy of fingerprint imaging through the cover layer where the pillars are not in direct physical contact with the sensing element is greater than the accuracy of fingerprint imaging through the cover layer without the pillars.

[0063] Fig. 12A -D shows an embodiment where the pillars are arranged symmetrically around the axis in the pillar direction with a uniform density of one pillar per mutual capacitance sensing element. Fig. 12A -D shows four symmetrical arrangements of pillars 1201 with a uniform density of one pillar per mutual capacitance sensing element 1203 , which comprises the intersection of an Rx electrode 1202 and a Tx electrode 1204 .

[0064] Fig.12E -F shows an embodiment where the pillars are arranged symmetrically around the axis with a uniform density of two pillars per mutual capacitance sensing element in the pillar direction. Fig.12E -F shows two symmetrical arrangements of pillars with a uniform density of two pillars 1201 per mutual capacitance sensing element 1203 , the sensing element 1203 comprising the intersection of an Rx electrode 1202 and a Tx electrode 1204 .

[0065] Figure 12G -H shows an embodiment where the pillars are arranged symmetrically around the axis with a uniform density of one pillar per self-capacitance sensing element in the pillar direction. Figure 12G -H shows two symmetrical arrangements of pillars 1201 with a uniform density of one pillar per self-capacitive sensing element 1205 , which includes an electrode 1206 .

[0066] Fig.12I An embodiment is shown in which the pillars are arranged symmetrically around the axis with a uniform density of two pillars per self-capacitance sensing element in the pillar direction. Fig.12IA symmetrical arrangement of pillars 1201 is shown with a uniform density of two pillars per self-capacitive sensing element 1205 , which includes an electrode 1206 .

[0067] It should be understood that the anisotropic material may include pillars where the relative density is more than two pillars per capacitive sensing element for both mutual capacitance and self capacitance.

[0068] Fig.13 An embodiment is shown in which the pillars 1301 are randomly and asymmetrically arranged around the axis with a uniform density of one pillar per mutual capacitance sensing element 1323 in the pillar direction. For ease of manufacturing, an asymmetric pillar arrangement may be desired. For ease of manufacturing, a random pillar arrangement may also be desired. An asymmetric pillar arrangement may be desired in a flexible material to allow the material to bend but still provide effective conductive coupling through the pillars. When the pillars have an asymmetric arrangement, the fingerprint sensor can more accurately image the fingerprint when the asymmetric pillars have a uniformly distributed density. When the pillars have an asymmetric arrangement, increasing the density of the pillars relative to the capacitive sensing elements increases the number of sensing elements that can be coupled to each fingerprint feature that is strong enough to detect the fingerprint feature. Therefore, increasing the density of the asymmetrically arranged pillars increases the accuracy of fingerprint imaging.

[0069] It should be understood that when the asymmetric pillars of each self-capacitance sensing element have a uniform distribution density, the self-capacitance fingerprint sensor can also image the fingerprint more accurately, and increasing the density of the asymmetrically arranged pillars increases the accuracy of fingerprint imaging using the self-capacitance sensing element.

[0070] Fig.14A A fingerprint sensor structure 1400 is shown that includes a mutual capacitance fingerprint sensor 1401 having Tx electrodes 1402 and Rx electrodes 1403, an intermediate material 1404, and a cover layer 1405. The intermediate material 1404 can be an adhesive or a color-matched paint. The cover layer 1405 includes pillars 1406. In this embodiment, the pillars 1406 are arranged symmetrically around the axis in the pillar direction, with a density of one pillar per mutual capacitance sensing element, and the pillars 1406 are aligned with the sensing elements. It should be understood that the cover layer 1405 can be manufactured with pillars 1406 in other arrangements. In embodiments that include the intermediate material 1404, it should be understood that the intermediate material must allow sufficient coupling between the fingerprint and the sensing element through the intermediate material and the cover layer. In specific embodiments, the intermediate material 1404 can also include pillars; in various embodiments, the cover layer 1405 and the intermediate material 1404 can be manufactured with the same or different pillar arrangements.

[0071] Fig. 14B A fingerprint sensor structure 1450 is shown including a mutual capacitance fingerprint sensor 1451 having a Tx electrode 1452 and an Rx electrode 1453. A cover layer 1454 includes pillars 1455. In this embodiment, the pillars are randomly and asymmetrically arranged around the axis in the pillar direction, with a density of one pillar per mutual capacitance sensing element, and the pillars 1455 are not aligned with the sensing elements (Rx electrodes 1453). This embodiment does not include an intermediate material.

[0072] Re-reference Figure 5B , the fingerprint sensor structure can include a cover layer including material 522, pillars 521, and cover layer 523. In embodiments including cover layer 523, it should be understood that cover layer 523 must allow for sufficient coupling between the fingerprint and the sensing element through cover layer 523 and material 522. In specific embodiments, cover layer 523 can also include pillars; in various embodiments, material 522 and cover layer 523 can be manufactured using the same or different pillar arrangements.

[0073] refer to Figures 12A-14B The described fingerprint sensor cover layer including anisotropic conductive material can be made of rigid materials including but not limited to glass, ceramic or plastic, or can be made of flexible materials including but not limited to film or fabric. The fingerprint sensor cover layer including anisotropic conductive material as described above can be manufactured so that the surface can conform to the curvature of the finger; in specific embodiments, the surface does not deform due to the fingerprint ridge / valley structure. For ease of manufacturing or ease of use, it may be desirable for the fingerprint sensor cover layer to include anisotropic conductive material that is flexible and / or has a conformable surface. Fig.15 A fingerprint structure 1500 is shown including a mutual capacitance fingerprint sensor 1501 having a Tx electrode 1502 and an Rx electrode 1503. In this embodiment, a cover layer 1504 comprises a flexible material having pillars 1505 that are randomly and asymmetrically arranged around an axis in the direction of the pillars at a density of one pillar per mutual capacitance sensing element. In another embodiment, the cover layer may include a rigid layer and a cover layer that is flexible and / or has a conformable surface.

[0074] It should be understood that these embodiments are exemplary only.Other embodiments may include self-capacitive sensing elements, more than one intermediate layer, more than one layer of anisotropic conductive material including pillars, and a material having a conformable surface.

[0075] In the above description, many details are set forth. However, it will be apparent to those of ordinary skill in the art who have the benefit of this disclosure that embodiments of the present invention may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form rather than in detail to avoid obscuring this specification.

[0076] Some portions of the detailed description are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the means used by those skilled in the art of data processing to most effectively convey the substance of their work to others skilled in the art. An algorithm is here and generally conceived to be a self-consistent sequence of steps that produces a desired result. These steps are those that require physical manipulations of physical quantities. Typically, although not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. Mainly for reasons of common usage, it has proven convenient at times to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, and the like.

[0077] It should be remembered, however, that all of these and similar terms will be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically noted otherwise, it will be apparent from the above discussion that it should be appreciated that throughout the specification, discussions using terms such as "integrate," "compare," "balance," "measure," "perform," "accumulate," "control," "convert," "accumulate," "sample," "store," "couple," "change," "buffer," "apply," and the like refer to the actions and processes of a computing system or similar electronic computing device that manipulates and transforms data represented as physical (e.g., electronic) quantities within the computing system's registers and memories into other data similarly represented as physical quantities within the computing system's memories or registers or other such information storage, transmission, or display devices.

[0078] The word "example" or "exemplary" is used herein to refer to an example, instance or illustration. Any aspect or design described herein as an "example" or "exemplary" is not necessarily interpreted as being preferred or advantageous compared to other aspects or designs. On the contrary, the use of the word "example" or "exemplary" is intended to present concepts in a specific way. As used in this application, the term "or" is intended to represent an inclusive "or" rather than an exclusive "or". In other words, unless otherwise indicated or clear from the context, "X includes A or B" is intended to refer to any of the natural inclusive arrangements. In other words, if X includes A; X includes B; or X includes both A and B, then "X includes A or B" is satisfied in any of the aforementioned examples. In addition, the articles "a" and "an" as used in this application and the appended claims should generally be interpreted as meaning "one or more", unless otherwise indicated or clearly pointed to a single form from the context. Furthermore, unless otherwise described, use of the terms "an embodiment" or "one embodiment" or "an implementation" or "one implementation" are not entirely intended to mean the same embodiment or implementation.

[0079] The embodiments described herein may also be directed to a device for performing the operations herein. The device may be specially constructed for the desired purpose, or it may include a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a non-transitory computer-readable storage medium, such as, but not limited to, any type of disk including floppy disks, optical disks, CD-ROMs and magneto-optical disks, read-only memory (ROM), random access memory (RAM), EPROM, EEPROM, magnetic card or optical card, flash memory, or any type of medium suitable for storing electronic instructions. The term "computer-readable storage medium" should be considered to include a single medium or multiple media (e.g., a centralized or distributed database and / or associated cache and server) storing one or more instruction sets. The term "computer-readable medium" should also be considered to include any medium capable of storing, encoding or transmitting an instruction set that is executed by a machine and causes the machine to implement any one or more methods of the present embodiment. The term "computer-readable storage medium" should accordingly be considered to include, but not limited to, solid-state memory, optical medium, magnetic medium, any medium capable of storing an instruction set for a machine to execute and cause the machine to implement any one or more methods of the present embodiment.

[0080] The algorithms and circuits presented herein do not inherently relate to any particular computer or other device. Various general purpose systems may be used with the program according to the teachings herein, or it may prove convenient to construct more specialized devices to perform the required method steps. The structures required for the various systems used in these systems will emerge from the following description. In addition, the present embodiment is not described with reference to any particular programming language. It will be appreciated that various programming languages ​​may be used to implement the teachings of the embodiments as described herein.

[0081] The above description sets forth many specific details of examples such as specific systems, components, methods, etc., in order to provide a good understanding of several embodiments of the present invention. However, it will be apparent to those skilled in the art that at least some embodiments of the present invention may be put into practice without these specific details. In other examples, well-known components or methods are not specifically described or are presented in the form of simple block diagrams to avoid unnecessarily obscuring the present invention. Therefore, the specific details set forth above are merely exemplary. Specific implementations may differ from these exemplary details and are still considered to be within the scope of the present invention.

[0082] It will be understood that the above description is intended to be illustrative rather than restrictive. After reading and understanding the above description, many other embodiments will be apparent to those skilled in the art. Therefore, the scope of the present invention should be determined with reference to the appended claims together with the entire scope of equivalents to which these claims are entitled.

Claims

1. A device comprising: a fingerprint sensor comprising a plurality of capacitive sensing elements disposed adjacent to a sensor surface, wherein the plurality of capacitive sensing elements are configured to measure changes in capacitance corresponding to fingerprint features; and A covering layer, the covering layer comprising: a first cover layer surface disposed adjacent to the sensor surface; and a first electrical conductivity in a first direction between the first cover layer surface and the second cover layer surface, wherein the first electrical conductivity is greater than a second electrical conductivity in at least one other direction; Wherein, the covering layer is configured as: receiving a fingerprint in direct contact with or in proximity to the second cover layer surface; and increasing the capacitive coupling of the fingerprint feature with the plurality of capacitive sensing elements so that the plurality of capacitive sensing elements measure a capacitance change corresponding to the fingerprint feature, The covering layer includes a plurality of conductive pillars, and the plurality of conductive pillars also include conductive elements arranged in the covering layer material, the plurality of conductive pillars are aligned along the first direction in the covering layer material and the longitudinal axis of each conductive pillar is parallel to the first direction, wherein the plurality of conductive pillars are formed without applying any electric field, partially or completely penetrate the covering layer material at the same depth and remove the hole area of ​​the covering layer material therein, and the hole area is completely or partially filled with air, dielectric material or conductive material.

2. The device according to claim 1, wherein: The cover layer is flexible.

3. The device according to claim 1, wherein: The second cover surface is configured to conform to the curvature of a finger.

4. The device according to claim 1, wherein: The first conductivity is constant.

5. The device according to claim 1, wherein: The plurality of conductive pillars are symmetrically arranged in the cover material around an axis in the first direction.

6. The device according to claim 1, wherein: The plurality of conductive pillars are asymmetrically disposed in the cover material about an axis in the first direction.

7. The device according to claim 6, wherein: The plurality of conductive pillars are also randomly disposed in the cover material.

8. The apparatus of claim 1 , further comprising a processor configured to receive measurements of changes in capacitance corresponding to fingerprint features and, based on the measurements of changes in capacitance, generate a set of data values ​​representing the fingerprint in a digital format.

9. A method comprising: The cover material is positioned over the sensor, wherein: The sensor includes a plurality of capacitive sensing elements disposed adjacent to a sensor surface, wherein the plurality of capacitive sensing elements are configured to detect a change in capacitance corresponding to the presence of an object; The cover material has a first conductivity in a first direction between a first cover surface and a second cover surface, wherein the first conductivity is greater than a second conductivity in at least one other direction, and The first cover layer surface is adjacent to the sensor surface, and the second cover layer surface is configured to receive an object in direct contact with or in proximity to the second cover layer surface such that the first conductivity increases capacitive coupling of the object to the plurality of capacitive sensing elements; and detecting, by the plurality of capacitive sensing elements, a change in capacitance through the cover material corresponding to the presence of an object in direct contact with or proximate to the second cover surface; coupling the plurality of capacitive sensing elements to a capacitance measurement circuit; receiving, by the capacitance measurement circuit, a plurality of voltage or current signals corresponding to capacitance changes from the plurality of capacitive sensing elements; and generating a set of data values ​​representing the object in a digital format based on the plurality of voltage or current signals, The covering layer material includes a plurality of conductive pillars, the plurality of conductive pillars also include conductive elements arranged in the covering layer material, the plurality of conductive pillars are aligned along the first direction in the covering layer material and the longitudinal axis of each conductive pillar is parallel to the first direction, the plurality of conductive pillars are formed without applying any electric field, partially or completely penetrate the covering layer material at the same depth and remove the hole area of ​​the covering layer material therein, and the hole area is completely or partially filled with air, dielectric material or conductive material.

10. The method according to claim 9, wherein: The cover material is flexible.

11. The method according to claim 9, wherein: The second cover surface is configured to conform to the curvature of the object.

12. The method according to claim 9, wherein: The first conductivity is constant.

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