Coplanar capacitive sensor and defect detection method

Abstract

The present application relates to a kind of coplanar capacitance sensor and defect detection method, belong to coplanar capacitance sensor technical field, solve the technical problem that same coplanar capacitance sensor cannot detect defect of different depth in prior art.The coplanar capacitance sensor of the present application includes: two sets of electrode assemblies arranged on the same plane, two sets of electrode assemblies are oppositely arranged along the first direction;Each electrode assembly includes at least two electrode plates, and the electrode plates of each electrode assembly are spaced apart along the second direction, and the second direction is perpendicular to the first direction, wherein each electrode plate can be independently connected to act as receiving electrode or excitation electrode.Realize the same coplanar capacitance sensor detects defect information of different depth, without replacing sensor, can reduce artificial measurement error, improve detection efficiency and precision accuracy, reduce equipment cost, while it is favorable to improve the stability and quality of signal transmission of coplanar capacitance sensor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coplanar capacitive sensor, and in particular to a coplanar capacitive sensor and a defect detection method. BACKGROUND

[0002] The coplanar capacitive sensor has low cost, fast response, no radiation, non-invasive, flexible electrode design and single-side detection capability. It has shown extensive research value and application potential in the field of non-destructive testing such as composite material (for example, aerospace composite material) detection, moisture detection, surface detection and concrete detection.

[0003] The coplanar capacitive sensor has an excitation electrode and a receiving electrode. When working, the excitation electrode excites electric charges, and the receiving electrode receives electric charges to form an arc-shaped electric field distribution dominated by edge effect above the electrode plate. The sensitive field distribution of the sensor can be calculated through the electric field data, and the quality of the sensitive field directly relates to the detection quality. When the measured object is placed in the electric field of the coplanar capacitive sensor, the electric field will be distorted, and the information of the measured object, such as the type and distribution of defects in the measured object, can be obtained through the change of the electric field.

[0004] The penetration depth of the coplanar capacitive sensor is directly related to the electrode area (the area of the excitation electrode and the receiving electrode). The larger the electrode area, the greater the capacitive signal strength and the penetration depth. The electrode area of the existing coplanar capacitive sensor cannot be changed, so the detection of defects is limited to the same depth. Therefore, in the prior art, when the defects are distributed at different depths in the material, the coplanar capacitive sensor needs to be replaced to detect the defect information at different depths. However, the process of frequently replacing the capacitive sensor is prone to human measurement errors, and the detection efficiency is low, and the detection result is not accurate enough. At the same time, different area coplanar capacitive sensors are needed, which is costly. SUMMARY

[0005] In view of the above analysis, the embodiments of the present application aim to provide a coplanar capacitive sensor and a defect detection method to solve the technical problem that the same coplanar capacitive sensor cannot detect defects at different depths in the prior art.

[0006] In one aspect, the embodiments of the present application provide a coplanar capacitive sensor, which comprises: two groups of electrode assemblies arranged on the same plane, the two groups of electrode assemblies being oppositely arranged along a first direction;

[0007] Each group of electrode assemblies comprises at least two electrode plates, and the electrode plates of each group of electrode assemblies are arranged in a spaced manner along a second direction, and the second direction is perpendicular to the first direction,

[0008] Each of the electrode plates is capable of being independently connected to serve as a receiving electrode or an exciting electrode.

[0009] In one embodiment, an inter-electrode shield is arranged between two adjacent electrode plates.

[0010] In one embodiment, the electrode plates are arranged in a triangular shape, wherein one corner of each of the electrode plates in each of the electrode assemblies is gathered together to form a tip of the electrode assembly, and the tips of the two electrode assemblies are opposite to each other.

[0011] In one embodiment, the distance between two adjacent electrode plates remains unchanged along the extension direction of their adjacent edges.

[0012] In one embodiment, the areas of the electrode plates in each of the electrode assemblies are equal or unequal.

[0013] In one embodiment, the electrode plates are arranged on the top surface of a circuit board,

[0014] The bottom surface of the circuit board is provided with pads corresponding to the electrode plates, the electrode plates are connected to the corresponding pads, and the electrode plates are connected to or led out of signals through the pads.

[0015] In one embodiment, the electrode plates are connected to the corresponding pads through conductive vias or conductive pillars.

[0016] In one embodiment, the circuit board is provided with an external shield and an internal shield, the external shield is arranged around the outer periphery of the two electrode assemblies, the internal shield is arranged between the two electrode assemblies, and the internal shield is connected to the external shield,

[0017] The bottom surface of the circuit board is provided with a bottom shield, and the bottom shield is connected to the external shield.

[0018] In another aspect, the embodiments of the present application provide a defect detection method, which uses the coplanar capacitive sensor as described above to detect defects of an object,

[0019] The defect detection method comprises the following steps:

[0020] The object is placed in the measurement domain of the coplanar capacitive sensor;

[0021] According to the selected excitation mode, the corresponding electrode plates are selected from the two electrode assemblies to be connected to detect defects of the object,

[0022] The excitation mode is that at least one electrode plate is selected from one electrode assembly as an exciting electrode, and at least one electrode plate is selected from the other electrode assembly as a receiving electrode.

[0023] Based on the further improvement of the above method, the defect detection method further comprises:

[0024] The excitation mode is changed, and the corresponding electrode plates in the two electrode assembly are connected according to the changed excitation mode to detect defects of the measured object.

[0025] Compared with the prior art, the present application can achieve at least one of the following beneficial effects:

[0026] 1、In the present application, a plurality of independent electrode plates are arranged in the two electrode assemblies of the coplanar capacitive sensor, and by selecting electrode plates at different positions or different numbers as receiving electrodes and excitation electrodes, the electrode area can be changed, thereby changing the penetration depth of the coplanar capacitive sensor, realizing the detection of defect information at different depths by the same coplanar capacitive sensor, without the need to replace the sensor, which can reduce human measurement error, improve detection efficiency and precision, reduce equipment cost, and at the same time, is conducive to improving the stability and quality of signal transmission of the coplanar capacitive sensor.

[0027] 2、The coplanar capacitive sensor of the present application is used to detect defects of the measured object by changing the electrode combination mode to set different electrode areas to detect defect information at different depths of the measured object, thereby realizing the chromatography effect.

[0028] In the present application, the above technical solutions can be combined with each other to realize more preferred combination schemes. Other features and advantages of the present application will be described in the subsequent specification, and some advantages will become apparent from the specification, or will be understood by implementing the present application. The purpose and other advantages of the present application can be achieved and obtained from the contents specifically pointed out in the specification and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0029] The accompanying drawings are only for the purpose of illustrating specific embodiments and are not considered as limiting the present application, and in the entire drawings, the same reference signs represent the same parts.

[0030] Figure 1 is a three-dimensional structure schematic view of the coplanar capacitive sensor of the embodiment of the present application;

[0031] Figure 2 is a top view of the coplanar capacitive sensor of the embodiment of the present application;

[0032] Figure 3 is a bottom view of the coplanar capacitive sensor of the embodiment of the present application;

[0033] Figure 4 is a flowchart of the defect detection method of the embodiment of the present application;

[0034] Figure 5 This is a schematic diagram of the sensitive field for a Type I excitation according to an embodiment of the present invention;

[0035] Figure 6 This is a schematic diagram of the sensitive field for Type II excitation according to an embodiment of the present invention;

[0036] Figure 7 This is a schematic diagram of the penetration depth of the sensor during Type I excitation according to an embodiment of the present invention;

[0037] Figure 8 This is a schematic diagram of the penetration depth of the sensor during Type II excitation according to an embodiment of the present invention;

[0038] Figure 9 This is a schematic diagram showing that the test object has different defects at different depths in the measurement direction, according to an embodiment of the present invention.

[0039] Figure 10 This is a schematic diagram showing the same defect of the object under test distributed at different depths along the measurement direction in an embodiment of the present invention.

[0040] Figure label:

[0041] 10. Circuit board; A01-A06. Electrode plate; B01-B15. Conductive via;

[0042] C01-C06, pads; E01-E04, inter-electrode shielding; E05, external shielding;

[0043] E06, Internal shielding; E07, Bottom shielding;

[0044] 100, Coplanar capacitance sensor; 200, Measured object; 20, Defect. Detailed Implementation

[0045] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0046] A specific embodiment of the present invention discloses a coplanar capacitance sensor 100, such as... Figures 1-2 As shown in the figure. The coplanar capacitance sensor 100 includes: two sets of electrode assemblies disposed on the same plane, the two sets of electrode assemblies being disposed opposite each other along a first direction; each set of electrode assemblies includes at least two electrode plates, the electrode plates of each set of electrode assemblies being spaced apart along a second direction, the second direction being perpendicular to the first direction, wherein each electrode plate can be independently connected to serve as a receiving electrode or an excitation electrode.

[0047] For example, each group of electrode assemblies is provided with three electrode plates, for a total of 6 electrode plates A01-A06.

[0048] wherein the first direction and the second direction are two directions perpendicular to each other on the plane, for example, the length direction and the width direction of the coplanar capacitive sensor 100.

[0049] In the embodiment, the electrode plates A01-A06 of the two groups of electrode assemblies can be used as receiving electrodes or excitation electrodes. In practice, one or more electrode plates of one group of electrode assemblies are connected to be used as receiving electrodes, and one or more electrode plates of the other group of electrode assemblies are connected to be used as excitation electrodes.

[0050] Compared with the prior art, the embodiment provides the coplanar capacitive sensor 100, which is provided with a plurality of independent electrode plates in each of the two groups of electrode assemblies. By selecting different positions or different numbers of electrode plates to be connected as receiving electrodes and excitation electrodes, the electrode area can be changed, the penetration depth of the coplanar capacitive sensor 100 can be changed, the same coplanar capacitive sensor 100 can detect defect information at different depths, the sensor does not need to be replaced, human measurement errors can be reduced, the detection efficiency and precision can be improved, the equipment cost can be reduced, and meanwhile, the stability and quality of signal transmission of the coplanar capacitive sensor 100 can be improved.

[0051] It should be noted that the electrode area in the embodiment refers to the area of the electrode connected during detection, that is, the area of the excitation electrode and the receiving electrode.

[0052] The penetration depth of the coplanar capacitive sensor 100 refers to the farthest measurement distance of the coplanar capacitive sensor 100. Generally, if the measured object 200 moves from the infinite distance along the normal of the electrode plane of the sensor to a position, the capacitance change is equal to 3% of the capacitance change of the target moving from the infinite distance to the position with a distance of d e from the electrode plane, then the distance between the position and the normal of the electrode plane is the penetration depth of the coplanar capacitive sensor, which is denoted by γ 3％ , and the mathematical description is as follows:

[0053] wherein the adjacent electrode plates of each group of electrode assemblies have a spacing, so that each electrode plate can be independently connected. It should be noted that the spacing between the adjacent electrode plates cannot be too large, so as to avoid that the adjacent electrode plates are combined and connected as receiving electrodes or excitation electrodes, and the electric field generated by each electrode plate is far away.

[0054] Preferably, an inter-electrode shield is arranged between the two adjacent electrode plates. By arranging the inter-electrode shield, the electric field generated by the adjacent electrode plates can be divided. For example, the inter-electrode shields E01-E04 shown in Figures 1-2 .

[0055] For example, the coplanar capacitive sensor 100 shown in FIG. 1 is provided with two groups of electrode assemblies, and each group of electrode assemblies is provided with six electrode plates A01-A06.Figures 1-2 As shown in FIG. 1, the inter-electrode shields E01-E04 are in the shape of long strips, the length of which is consistent with the length of the adjacent edges of the electrode plates, and the two ends of the inter-electrode shields E01-E04 are not connected to the inner shield E06 and the outer shield E05, so that each inter-electrode shield E01-E06 can be independently grounded. Among them, if two adjacent electrode plates are selected to be connected as excitation electrodes or receiving electrodes at the same time, the inter-electrode shield between the two adjacent electrode plates is not grounded, that is, the electric field generated by the two electrode plates does not need to be divided at this time.

[0056] In a preferred embodiment, as shown in FIG. 1, Figures 1-2 As shown in FIG. 1, the electrode plates A01-A06 are arranged in a triangular shape. Among them, one corner of each of the electrode plates A01-A06 in each group of the electrode assembly is gathered together to form the tip of the electrode assembly, and the tips of the two groups of the electrode assembly are opposite to each other.

[0057] Specifically, the distance between the two adjacent electrode plates remains unchanged along the extension direction of the adjacent edges of the two adjacent electrode plates, that is, the adjacent edges of the two adjacent electrode plates are arranged in parallel. In this way, the electrode plates A01-A03 or A04-A06 in the electrode assembly are arranged closely.

[0058] Further, the bottom edges of the electrode plates A01-A03 or A04-A06 in each group of the electrode assembly are aligned in the second direction.

[0059] In this embodiment, the electrode plates A01-A06 are triangular, and each of the electrode plates A01-A03 or A04-A06 in each electrode assembly is combined to form a whole triangular shape. In other words, the electrodes of the coplanar capacitive sensor 100 in this embodiment adopt a triangular electrode plate design, and the tips are opposite to each other, so as to realize the most refinement of the sensitive field. In each electrode assembly, one triangular electrode plate is divided into a plurality of different small triangular electrode plates, and each small triangular electrode plate is an independent individual and can be individually received and excited. Different small triangular electrode plates can be combined to obtain different sensor areas, so as to realize the detection of defects 20 at different depths.

[0060] At the same time, the electrode assembly is composed of triangular electrode plates, and when different electrode plates are selected as excitation electrodes or receiving electrodes, the electrode spacing of the coplanar capacitive sensor can be ensured not to change.

[0061] Specifically, the areas of the electrode plates A01-A03 or A04-A06 in each group of the electrode assembly are equal or unequal. Further, the number of electrode plates and the area of each electrode plate of the two groups of the electrode assembly can be arranged to be consistent or inconsistent.

[0062] If the areas of the electrode plates A01-A03 or A04-A06 in each electrode assembly are equal, the electrode area of the electrode assembly can be controlled by changing the number of the connected electrode plates. If the areas of the electrode plates A01-A03 or A04-A06 in each electrode assembly are different, the electrode area of the electrode assembly can be controlled by selecting different electrode plates A01-A06 and changing the number of the connected electrode plates A01-A06.

[0063] In addition, the electrode plates A01-A06 can also be set as trapezoids. If the electrode plates A01-A06 are trapezoids, the upper base of the electrode plates A01-A06 should be set shorter, so that the upper bases of the trapezoidal electrode plates A01-A06 are gathered together to form the tip of the electrode assembly. If the electrode plates A01-A06 are rectangles, when the excitation electrode and the receiving electrode are selected from the two electrode assemblies, the electrode spacing of the coplanar capacitive sensor should be changed as little as possible.

[0064] In one embodiment, the electrode plates A01-A06 are all arranged on the top surface of the circuit board 10, and the circuit board 10 is provided with pads C01-C06 corresponding to the electrode plates A01-A06 on the bottom surface, as shown in FIG. 3. The electrode plates A01-A06 are connected to the corresponding pads C01-C06, and the electrode plates A01-A06 are connected to or led out of the signal through the pads C01-C06.

[0065] Preferably, the circuit board 10 is a PCB circuit board 10.

[0066] Specifically, the electrode plates A01-A06 are connected to the corresponding pads C01-C06 through conductive vias B01-B06 or conductive columns.

[0067] In this embodiment, the electrode plates A01-A06 are arranged on the circuit board 10 and connected to or led out of the signal through the pads C01-C06, which is simple in structure and is conducive to reducing wiring.

[0068] Specifically, each pad C01-C06 can be connected to an electrical signal input device or an electrical signal output device through a signal line, so as to change the electrode area of the coplanar capacitive sensor 100.

[0069] Specifically, the circuit board 10 is provided with an external shield E05 surrounding the outer periphery of the two electrode assemblies and an internal shield E06 arranged between the two electrode assemblies, the internal shield E06 being connected to the external shield E05, and the bottom surface of the circuit board 10 is provided with a bottom shield E07 connected to the external shield E05. The external shield E05 and the internal shield E06 are used to confine the electric field generated by the electrode assemblies within a certain space, so that the electric field for detection is not too dispersed.

[0070] Further specifically, the internal shield E06 and the external shield E05 are connected to the bottom shield E07 through corresponding conductive vias B07-B11 or conductive columns, respectively.

[0071] In addition, the bottom surface of the circuit board 10 is provided with conductive vias B12-B15 or conductive columns corresponding to the inter-electrode shields E01-E04 for grounding the inter-electrode shields E01-E04.

[0072] The embodiment of the present application also provides a defect detection method, which uses the coplanar capacitive sensor 100 described above to detect defects of an object 200.

[0073] As shown in Figure 4 The defect detection method comprises the following steps:

[0074] Step 1: placing the object 200 in the measurement domain of the coplanar capacitive sensor 100;

[0075] Step 2: selecting corresponding electrode plates A01-A06 from the two electrode assemblies according to a selected excitation mode to connect, so as to detect defects of the object 200.

[0076] The excitation mode is: selecting at least one electrode plate from one group of electrode assemblies as an excitation electrode and selecting at least one electrode plate from another group of electrode assemblies as a receiving electrode.

[0077] Regarding the defects 20 in the object 200, mainly include different defects 20 existing at different depths of the object 200 as shown in Figure 9 and the same defect 20 of the object 200 distributed at different depths as shown in Figure 10 The existing coplanar capacitive sensor 100 with a fixed penetration depth can only detect defects 20 at the same depth, and therefore, cannot obtain whether the object 200 has defects 20 at other depths and the distribution of the same defect 20 at different depths.

[0078] The variable-area coplanar capacitance sensor 100 of this invention can control the penetration depth of the sensor by selecting an appropriate excitation method in order to detect defect information of the object under test 200 at that depth.

[0079] Furthermore, the defect detection method further includes:

[0080] Step 3: Change the excitation method and select the corresponding electrode plates A01-A06 from the two electrode assemblies according to the changed excitation method to perform defect detection on the test object 200 at different depths.

[0081] When the coplanar capacitance sensor 100 of the present invention is used to detect defects in the test object 200, different electrode areas are set by changing the excitation method, thereby detecting defect information at all depths in a single measurement direction. Each penetration depth obtains defect information on a plane. By combining the plane information obtained from each penetration depth, the three-dimensional distribution of defects 20 in the test object 200 is obtained, achieving the effect of "tomography". This allows for more efficient and accurate acquisition of defect information in the test object 200.

[0082] Before selecting the excitation electrode and the receiving electrode (step 2), the defect detection method further includes: obtaining the detection depth of the coplanar capacitance sensor 100 when selecting the excitation electrode and the receiving electrode from the two electrode assemblies in different combinations; during detection, selecting the excitation method according to the required detection depth.

[0083] Example 1

[0084] like Figures 1-2 As shown in the illustration, in this embodiment, the coplanar capacitance sensor 100 includes two sets of electrode assemblies disposed on the same plane. Each set of electrode assemblies includes three triangular electrode plates. The electrode plates of one set of electrode assemblies are numbered A01, A02, and A03, respectively; the electrode plates of the other set of electrode assemblies are numbered A04, A05, and A06, respectively.

[0085] The electrode area of ​​the sensor can be changed by connecting different electrode plates. For example, Type I excitation: electrode plates A01-A03 are used as excitation plates, and electrode plates A04-A06 are used as receiving plates, with a penetration depth denoted as 'a'. Type II excitation: electrode plates A01-A03 are used as excitation plates, and electrode plate A04 is used as the receiving plate, with a penetration depth denoted as 'b'.

[0086] The two different excitation methods generate different sensitive fields. The sensitive field is calculated based on the electric field and voltage of the electrodes, and is specifically represented as the spike-shaped space above electrode plates A01-A06, which is the "measurement domain" of the capacitive sensor. The sensitive fields of the two different excitation methods are as follows:Figure 5 and Figure 6 are shown in FIGS. Figure 5 and Figure 6 are respectively three-dimensional coordinate diagrams of the sensitive field of the sensor when the type I excitation and the type II excitation, wherein the Z axis represents the capacitance value, and the X axis and the Y axis represent two directions perpendicular to each other in a certain plane of the measurement field of the sensor.

[0087] The sensitive field geometries of the two different excitation modes are different, and the specific forms are different ranges of the bottom of the sensitive field and different peak values of the sensitive field. The height of the peak is the most important difference, which directly relates to the depth and range of the defect 20 that can be detected by the sensitive field, that is, the different penetration depths of the sensor. The two different penetration depth curves are shown in FIGS. Figure 7 and Figure 8 are respectively two-dimensional coordinate diagrams of the penetration depth curve of the sensor when the type I excitation and the type II excitation, wherein the X axis represents the depth value, and the Y axis represents the capacitance value. Figure 5 and Figure 6 are respectively two-dimensional coordinate diagrams of the penetration depth curve of the sensor when the type I excitation and the type II excitation, wherein the X axis represents the depth value, and the Y axis represents the capacitance value.

[0088] The penetration depths of the two different excitation modes are obviously different. The type I excitation adopts three electrode plates for excitation and three electrode plates for receiving, and the received capacitance signal is larger. The type II excitation only has one electrode plate for receiving, and thus the received signal is smaller. The signal strength determines the height of the peak of the sensitive field, and thus determines the penetration depth of the sensor. The penetration depth of the type I excitation is 27 mm, and the penetration depth of the type II excitation is 3 mm. The penetration depth of the type I excitation is 3 mm more than that of the type II excitation.

[0089] According to the above content, changing the electrode area on the same sensor can realize the measurement of defects 20 of different depths. If the number of electrode plates is increased and the excitation / receiving area of the electrode plates is changed, more changes in the penetration depth can be realized to detect all defects 20 of different depths in a single measurement direction.

[0090] It should be noted that in the embodiment, only two different area change conditions are shown: the electrode plates A01-A03 are excited, and the electrode plates A04-A06 are received; and the electrode plates A01-A03 are excited, and the electrode A05 is received. In the embodiment of the present application, more area combination conditions can be artificially designed, such as the electrode plates A01 and A02 for excitation and the electrode plate A05 for receiving, and the penetration depths of each asymmetric combination are different, so that different penetration depth changes of the same coplanar capacitive sensor 100 are realized to detect defects 20 of different depths.

[0091] Those skilled in the art can understand that all or part of the processes of the above-mentioned embodiment methods can be completed by instructing the relevant hardware by a computer program, and the program can be stored in a computer readable storage medium. The computer readable storage medium is a disk, an optical disk, a read-only memory, a random access memory, etc.

[0092] The above description is merely preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A co-planar capacitive sensor, characterized by, The coplanar capacitive sensor comprises two sets of electrode assemblies arranged on the same plane, and the two sets of electrode assemblies are oppositely arranged along a first direction; Each set of electrode assemblies comprises at least two electrode plates, and the electrode plates of each set of electrode assemblies are arranged at intervals along a second direction perpendicular to the first direction, and the areas of the electrode plates in each set of electrode assemblies are equal or unequal; Each electrode plate can be independently connected as a receiving electrode or as an excitation electrode, and corresponding electrode plates are selected from the two sets of electrode assemblies according to a selected excitation mode to detect defects of the measured object, The excitation mode is that at least one electrode plate is selected as an excitation electrode from one set of electrode assemblies, and at least one electrode plate is selected as a receiving electrode from the other set of electrode assemblies; The excitation mode is changed, and corresponding electrode plates are selected from the two sets of electrode assemblies according to the changed excitation mode to detect defects of the measured object at different depths; When the coplanar capacitive sensor detects defects of the measured object, different electrode areas are set by changing the excitation mode, so that defect information at all depths in a single measurement direction is detected, and defect information on a plane is obtained at each penetration depth. The plane information obtained at each penetration depth is combined to obtain the three-dimensional distribution of defects in the measured object.

2. The co-planar capacitive sensor of claim 1, wherein, An inter-electrode shield is arranged between adjacent two electrode plates.

3. The coplanar capacitive sensor according to claim 1 or 2, characterized in that, The electrode plates are arranged in a triangular shape, One corner of each electrode plate in each set of electrode assemblies is gathered together to form a tip of the electrode assembly, and the tips of the two sets of electrode assemblies are opposite to each other.

4. The co-planar capacitive sensor of claim 3, wherein, The distance between adjacent two electrode plates remains unchanged along the extension direction of the adjacent sides.

5. The co-planar capacitive sensor according to claim 1 or 2, characterized in that, The electrode plates are arranged on the top surface of a circuit board, Corresponding pads are arranged on the bottom surface of the circuit board, the electrode plates are connected to the corresponding pads, and the electrode plates are connected to or led out of signals through the pads.

6. The co-planar capacitive sensor of claim 5, wherein, The electrode plates are connected to the corresponding pads through conductive vias or conductive columns.

7. The co-planar capacitive sensor of claim 5, wherein, External shields and internal shields are arranged on the circuit board, the external shields are arranged around the outer periphery of the two sets of electrode assemblies, the internal shields are arranged between the two sets of electrode assemblies, and the internal shields are connected to the external shields, A bottom shield is arranged on the bottom surface of the circuit board, and the bottom shield is connected to the external shield.

8. A defect detection method characterized by, The coplanar capacitive sensor according to any one of claims 1-7 is used to detect defects of a measured object, The defect detection method comprises the following steps: Placing the measured object in the measurement domain of the coplanar capacitive sensor; According to a selected excitation mode, corresponding electrode plates are selected from the two sets of electrode assemblies to detect defects of the measured object, The excitation mode is that at least one electrode plate is selected as an excitation electrode from one set of electrode assemblies, and at least one electrode plate is selected as a receiving electrode from the other set of electrode assemblies; The excitation mode is changed, and corresponding electrode plates are selected from the two sets of electrode assemblies according to the changed excitation mode to detect defects of the measured object at different depths; The coplanar capacitive sensor detects defects of the measured object by changing the excitation mode to set different electrode areas, thereby detecting defect information of all depths in a single measurement direction, obtaining defect information on a plane for each penetration depth, combining the plane information obtained for each penetration depth, and obtaining three-dimensional distribution of defects in the measured object.

Images