A flexible circuit board based flush type eddy current probe

Abstract

The application discloses a flexible circuit board-based attached eddy current probe, which comprises a flexible base made of polyimide film material and having bendable deformation characteristics, an excitation coil etched on layer one of the flexible base through a printed circuit process, a detection coil etched on layer two of the flexible base through the printed circuit process and oppositely arranged with layer one, a lead wire electrically connected with the excitation coil and the detection coil to connect an external circuit, and a back pad layer fixedly bonded to the side of the flexible base away from a measured object, wherein the back pad layer is made of ferrite material and completely covers the projection area of the coil. The bendable characteristics of the flexible base enable the probe to be self-adaptively attached to measured surfaces with various curvatures like a sticker, and noise interference caused by uneven lift-off effect is completely eliminated. Meanwhile, the inductance is compensated by the ferrite back pad layer, the detection sensitivity is improved, and the application is very suitable for mass production.

Description

Technical Field

[0001] This invention belongs to the field of eddy current sensing, and more specifically, relates to a bonding eddy current probe based on a flexible circuit board. Background Technology

[0002] Eddy current sensors are widely used in displacement, vibration, and thickness measurement and non-destructive testing in fields such as machinery manufacturing, aerospace, and rail transportation due to their advantages of non-contact measurement, fast response speed, and high sensitivity. Traditional eddy current probes typically use a rigid frame with a coil wound around it, and the probe surface is flat or has a fixed curvature, making it difficult to achieve good contact with curved objects being measured (such as bearing outer rings, turbine blades, and pipe outer walls).

[0003] When using traditional rigid probes to inspect curved parts, the uneven lift-off gap (i.e., lift-off effect) between the probe and the workpiece often exists due to the curvature variation of the measured surface. This results in significant lift-off noise in the detection signal, severely affecting measurement accuracy and defect detection rate. Furthermore, traditional probes have poor consistency, making them unsuitable for mass production. Summary of the Invention

[0004] To address the above deficiencies, this invention provides a bonding-type eddy current probe based on a flexible circuit board, comprising, from top to bottom:

[0005] Metal shielding layer, backing layer, flexible substrate, and wear-resistant protective layer;

[0006] The flexible substrate includes an integrally formed layer one and a layer two. The upper surface of layer one and the upper surface of layer two are respectively etched with two symmetrical excitation coils and detection coils by printed circuit technology. The excitation coils and detection coils located on the same vertical line are electrically connected through lead wires and electrically connected to an external signal processing circuit.

[0007] The excitation coil and the detection coil, which are located on the same vertical line, are both planar spiral structures, and the excitation coil surrounds the periphery of the detection coil.

[0008] Furthermore, the excitation coil and the detection coil, positioned on the same vertical line, are arranged in concentric circles.

[0009] Furthermore, each of the detection coils consists of multiple coils, which are arranged in an array on layer two to form a detection coil array.

[0010] Furthermore, the flexible substrate is made of a polyimide film material with bendable and deformable properties.

[0011] Furthermore, the backing layer is made of ferrite material and completely covers the projection areas of the excitation coil and the detection coil on the flexible substrate.

[0012] Furthermore, the thickness of the flexible substrate is 0.1 mm.

[0013] Furthermore, there is an insulating layer between the first layer and the second layer for isolation, and the insulating layer is provided with a through hole for the lead wire to pass through.

[0014] Furthermore, the excitation coil is an external spiral, and the detection coil is an internal spiral. Both coils are made of copper foil with a line width of 0.1 mm and 20 turns.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. Good surface fit: Utilizing the bendable properties of the flexible substrate, the probe can adaptively fit the measured surface with different curvatures, significantly reducing the lift-off effect and improving measurement accuracy and defect detection rate.

[0017] 2. Good consistency: The coil is made using printed circuit technology, which avoids the individual differences caused by traditional hand-wound coils, making it easier for mass production and performance consistency control.

[0018] 3. High sensitivity: By adding a ferrite backing layer, the inductance of the coil is increased, thereby improving the sensitivity of the probe.

[0019] 4. Compact structure: The multi-layer structure design makes the probe thin and easy to integrate and install.

[0020] 5. Strong anti-interference capability: External electromagnetic interference can be effectively suppressed by selecting a metal shielding layer. Attached Figure Description

[0021] Figure 1 This is a cross-sectional schematic diagram of the present invention.

[0022] Figure 2 This is a top view of the coil arrangement in this invention.

[0023] In the diagram: 1. Metal shielding layer; 2. Backing layer; 3. Flexible substrate; 31. Layer 1; 32. Layer 2; 33. Insulation layer; 4. Protective layer; 51. Excitation coil; 52. Detection coil; 6. Lead wire. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example

[0026] like Figures 1 to 2 As shown, this embodiment provides a bonding eddy current probe based on a flexible circuit board, including a flexible substrate 3, an excitation coil 51, a detection coil 52, a lead wire 6, and a backing layer 2.

[0027] The flexible substrate 3 is made of polyimide (PI) film with a thickness of 0.1 mm. This material has excellent flexibility and high temperature resistance, allowing the probe to be bent in any direction, thereby adaptively fitting the test surface with different curvatures. In this embodiment, it is divided into layer 1 31 and layer 2 32, with an insulating layer 33 between them, and the three are integrally formed.

[0028] The excitation coil 51 and the detection coil 52 are etched and formed using flexible printed circuit board (FPC) technology, such as... Figure 2 As shown, the excitation coil 51 has an outer planar spiral structure, and the detection coil 52 has an inner planar spiral structure. Both are formed on the flexible substrate 3 by etching process.

[0029] Specifically, the excitation coil 51 is located on the upper surface of the flexible substrate 3 (i.e., layer 31), and the detection coil 52 is located on the lower surface of the flexible substrate 3 (i.e., layer 32). The two layers are electrically isolated by an insulating layer 33, and a through hole is provided on the flexible substrate 3 for the lead wire 6 to pass through.

[0030] In addition, the excitation coil 51 and the detection coil 52 are made of copper foil with a line width of 0.1 mm and a number of 20 turns. They are manufactured by micro-nano PCB etching, which greatly ensures the precise control of the coil geometry (line width, line spacing, number of turns, etc.) and eliminates the individual performance differences of traditional hand-wound coils.

[0031] A lead wire pad is provided on the flexible substrate 3. The lead wire 6 is electrically connected to the excitation coil 51 and the detection coil 52 by soldering. It is used to input a high-frequency excitation signal to the excitation coil 51 and at the same time to lead out the induced signal generated by the detection coil 52 and transmit it to an external signal processing circuit (such as a preamplifier, filter, etc.).

[0032] The backing layer 2 is disposed above the flexible substrate 3 (i.e., on the side opposite to the surface being measured), and is made of high-performance ferrite material. It is fixed to the flexible substrate 3 by adhesive bonding. The size and shape of the backing layer 2 are designed to completely cover the orthogonal projection area of ​​the excitation coil 51 and the detection coil 52 on the flexible substrate 3. Its main function is that, since the flexible FPC coil is very thin, its inherent inductance will decrease. By setting the ferrite backing layer 2, the magnetic flux can be effectively increased, the inductance of the coil can be compensated and improved, and the detection sensitivity of the probe can be significantly improved.

[0033] like Figure 1 As shown, in this embodiment, a thin and wear-resistant protective layer 4 is covered on the outermost surface of the flexible substrate 3 facing the surface to be tested. This protective layer 4 is used to protect the fragile etched coil from physical wear during direct contact testing.

[0034] In addition, a metal shielding layer 1 is laid on the outer side (i.e. the top surface) of the backing layer 2. This metal shielding layer 1 is used to isolate and suppress environmental electromagnetic interference from the external space.

[0035] This embodiment describes a bonding-type eddy current probe based on a flexible circuit board. During testing, the probe is directly laid out and gently pressed onto the irregular or curved surface to be tested. Thanks to the excellent adaptive bending characteristics of the 0.1mm polyimide flexible substrate 3, the entire probe adheres tightly to the surface to be tested like a "sticker". This complete bonding physically eliminates uneven lift-off gaps and eliminates lift-off noise interference at the source, ensuring extremely high accuracy in the testing of complex curved components (such as bearing outer rings, turbine blades, etc.).

[0036] It should be noted that the structure of the present invention can be implemented in many different forms and is not limited to the embodiments. Any equivalent transformations made by those skilled in the art based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, such as the loading and unloading of other items, are included within the protection scope of the present invention.

Claims

1. A bonding-type eddy current probe based on a flexible circuit board, characterized in that, From top to bottom, they include: Metal shielding layer (1), backing layer (2), flexible substrate (3) and protective layer (4); The flexible substrate (3) includes an integrally formed layer one (31) and layer two (32). The upper surface of layer one (31) and the upper surface of layer two (32) are respectively etched with two symmetrical excitation coils (51) and detection coils (52) by printed circuit technology. The excitation coils (51) and detection coils (52) located on the same vertical line are electrically connected through lead wires (6) and electrically connected to an external signal processing circuit. The excitation coil (51) and the detection coil (52) located on the same vertical line are both planar spiral structures, and the excitation coil (51) surrounds the periphery of the detection coil (52).

2. The eddy current probe based on a flexible circuit board as described in claim 1, characterized in that: The excitation coil (51) and the detection coil (52) located on the same vertical line are arranged in concentric circles.

3. A bonding-type eddy current probe based on a flexible circuit board as described in any one of claims 1 or 2, characterized in that: Each of the detection coils (52) consists of multiple coils, which are arranged in an array on layer two (32) to form a detection coil array.

4. The eddy current probe based on a flexible circuit board as described in claim 1, characterized in that: The flexible substrate (3) is made of a polyimide film material with bendable and deformable properties.

5. The eddy current probe based on a flexible circuit board as described in claim 1, characterized in that: The backing layer (2) is made of ferrite material and completely covers the projection area of ​​the excitation coil (51) and the detection coil (52) on the flexible substrate (3).

6. The eddy current probe based on a flexible circuit board as described in claim 1, characterized in that: The thickness of the flexible substrate (3) is 0.1 mm.

7. The eddy current probe based on a flexible circuit board as described in claim 1, characterized in that: There is an insulating layer (33) between the first layer (31) and the second layer (32) for isolation, and a wire hole is provided at the insulating layer (33) for the lead wire (6) to pass through.

8. The eddy current probe based on a flexible circuit board as described in claim 1, characterized in that: The excitation coil (51) is an external spiral and the detection coil (52) is an internal spiral. Both coils are made of copper foil with a line width of 0.1 mm and 20 turns.

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