A nanocrystalline magnetic isolation sheet and its preparation method and application

Abstract

The present invention belongs to the technical field of electromagnetic shielding materials, and specifically relates to a nanocrystalline magnetic isolation sheet and its preparation method and application. The preparation method comprises the following steps: winding and annealing the nanocrystalline strip, and then coating it with a single layer of protective film or a multi-layer composite protective film, passing the coated strip through a magnetic crushing roller with transverse stripes for preliminary magnetic crushing, introducing transverse cracks, and then passing it through a magnetic crushing roller with grid patterns for secondary magnetic crushing to obtain a nanocrystalline strip with transverse cracks and flaky fragments, and finally die-cutting and then subjecting it to a single layer or multi-layer composite treatment to obtain a nanocrystalline magnetic isolation sheet. The nanocrystalline magnetic isolation sheet of the present invention can be applied to electromagnetic shielding of vertical coils. By introducing transverse cracks parallel to or appropriately deflected from the axis of the vertical coil, the magnetic line loss can be reduced, and the loss can be reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of electromagnetic shielding materials, and specifically relates to a nanocrystalline magnetic shielding sheet and a preparation method and application thereof. Background Art

[0002] Magnetic isolation sheets have important applications in the fields of wireless charging, radio frequency identification technology (RFID) and near-field wireless communication (NFC). In the field of wireless charging, magnetic isolation sheets can isolate metal objects from contact with electromagnetic signals, prevent electromagnetic signal attenuation, enhance the magnetic induction intensity passing through the coil, and improve charging efficiency. Magnetic sheets in radio frequency identification technology (RFID) and near-field wireless communication (NFC) can eliminate metal interference, increase communication sensitivity, and improve recognition accuracy and stability. Among them, nanocrystalline strips are widely used in the preparation of magnetic isolation sheets due to their high saturation magnetic induction intensity and magnetic permeability, low coercive force and loss. However, nanocrystalline has a large eddy current loss due to its low resistivity. Therefore, nanocrystalline magnetic isolation sheets usually need to be micro-crushed to reduce their eddy current losses.

[0003] The micro-fragmentation of nanocrystalline strips is usually achieved by rolling with two metal rollers. The degree of micro-fragmentation is controlled by the rolling pattern, pressure, and number of rolling times, and the real and imaginary magnetic permeabilities of the strips are then regulated. Finally, several micro-fragmented strip units are glued together with double-sided tape to form a composite magnetic sheet for wireless charging. Since the rolling patterns are mostly convex or polygonal, and the size of the rolling patterns is small, the size of the nanocrystalline fragments after multiple rolling is about 0.1-3mm, and the fragments are randomly distributed. When the wireless charging coil is energized and the magnetic flux enters the magnetic sheet vertically, the direction of the magnetic flux in the magnetic sheet is radiating (such as the attached Figure 1 As shown in the figure, the magnetic sheet of the planar coil does not need the magnetic lines of force to flow in a fixed direction. In a vertical coil (similar to a solenoid with power), when a magnetic sheet is wound around the inside or outside of the coil to achieve the effect of magnetic shielding, the direction of the magnetic flux is fixed on the outside or inside of the coil, and the magnetic lines of force enter the magnetic sheet along the height direction of the magnetic sheet. Since the magnetic lines of force will form a closed loop, they will eventually pass through the magnetic sheet. The magnetic flux in the height direction is required by the module. The conventional crushing method makes the nanocrystalline fragments distributed randomly. After the magnetic lines of force enter the magnetic sheet from the height direction, some of the magnetic lines of force will flow along the longitudinal direction of the material, causing magnetic line loss and causing the material to heat up. Summary of the invention

[0004] In view of the shortcomings and deficiencies of the above prior art, the primary purpose of the present invention is to provide a method for preparing a nanocrystalline magnetic isolation sheet.

[0005] Another object of the present invention is to provide a nanocrystalline magnetic isolation sheet prepared by the above method.

[0006] Another object of the present invention is to provide application of the above-mentioned nanocrystalline magnetic isolation sheet in electromagnetic shielding of vertical coils.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A method for preparing a nanocrystalline magnetic isolation sheet comprises the following steps:

[0009] (1) The nanocrystalline strip is wound and annealed, and then coated with a single layer of protective film or a multi-layer composite and then coated with a protective film;

[0010] (2) The nanocrystalline strip covered with the protective film is initially subjected to a magnetic crushing treatment by passing it through a magnetic crushing roller with transverse stripes to introduce transverse cracks;

[0011] (3) The nanocrystalline ribbon that has undergone the preliminary magnetic crushing treatment is subjected to a secondary magnetic crushing treatment through a magnetic crushing roller with a grid pattern to obtain a nanocrystalline ribbon with transverse cracks and flaky fragments;

[0012] (4) The nanocrystalline strip with transverse cracks and scaly fragments obtained in step (3) is die-cut and then subjected to single-layer or multi-layer composite treatment to obtain a nanocrystalline magnetic isolation sheet.

[0013] Furthermore, the thickness of the nanocrystalline ribbon in step (1) is 14-25 μm, preferably 18-20 μm.

[0014] Furthermore, the nanocrystalline ribbon in step (1) is a FeCuNbSiB nanocrystalline ribbon, and the annealing temperature is 500-650°C.

[0015] Furthermore, the multilayer composite in step (1) is bonded by double-sided adhesive with a thickness of 1 to 5 μm; the protective adhesive film is a PET film, PE film, PVC film or silicone protective film with a thickness of 20 to 100 μm.

[0016] Furthermore, the tooth spacing of the crushed magnetic roller with transverse stripes in step (2) is 0.5-5 mm; and the angle between the transverse crack direction and the transverse direction of the nanocrystalline strip is 0-30°.

[0017] Furthermore, the size of the scaly fragments in step (3) is 0.1-3 mm.

[0018] A nanocrystalline magnetic isolation sheet is prepared by the method.

[0019] Furthermore, the magnetic permeability of the nanocrystalline magnetic isolation sheet is 200-5000.

[0020] The above-mentioned nanocrystalline magnetic isolation sheet is used in electromagnetic shielding of vertical coils.

[0021] Furthermore, the application method is: winding the nanocrystalline magnetic isolation sheet on the vertical coil, so that the transverse cracks of the nanocrystalline magnetic isolation sheet are parallel to the axis of the vertical coil or deflected by 0-30 degrees.

[0022] The principle of the present invention is: first, a crushing roller with transverse stripes is used to introduce transverse cracks in the transverse direction of the nanocrystal, and then the nanocrystal material is further broken by rolling with an ordinary pattern roller (grid pattern) to adjust the magnetic permeability. In this way, most of the magnetic lines of force flow in the height direction (Y direction), and the longitudinal direction (X direction) of the material increases the insulation resistivity of the material in the X direction due to the presence of transverse cracks, greatly reducing the eddy current loss in its plane, reducing the magnetic permeability of the material, and thus reducing the flow of magnetic lines of force. When the nanocrystalline magnetic isolation sheet is wound on the vertical coil, the nanocrystalline fragments are discontinuous due to the presence of transverse cracks, and most of the magnetic lines of force flow in the height direction, thereby constraining most of the magnetic lines of force within the winding range of the magnetic sheet, and reducing the flow of magnetic lines of force in the transverse direction due to the presence of transverse cracks, thereby reducing eddy current losses and improving electromagnetic conversion efficiency.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The nanocrystalline magnetic isolation sheet of the present invention can improve the insulation resistance of the magnetic isolation sheet in the X direction, reduce the magnetic permeability in the X direction, hinder the flow of magnetic lines of force in the X direction, concentrate the magnetic lines of force in the Y direction, reduce the loss of magnetic lines of force, and reduce the loss by introducing transverse cracks parallel to or appropriately deflected from the axis (Y direction) of the vertical coil.

[0025] (2) Compared with ordinary pattern roller crushing, the introduction of transverse cracks can effectively reduce material loss, reduce eddy current loss, and reduce material heating. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the direction of the magnetic flux in the magnetic sheet when the wireless charging coil is energized and the magnetic flux enters the magnetic sheet vertically.

[0027] Figure 2 This is a structural diagram of a crushed magnetic roller with transverse stripes.

[0028] Figure 3 This is a structural diagram of a crushed magnetic roller with grid patterns.

[0029] Figure 4 and Figure 5 They are respectively a schematic diagram of the preparation process of the nanocrystalline magnetic isolation sheet obtained in Example 1 and a schematic diagram of the structure wound on a vertical coil.

[0030] Figure 6 and Figure 7 They are respectively a schematic diagram of the preparation process of the nanocrystalline magnetic isolation sheet obtained in Example 2 and a schematic diagram of the structure wound on a vertical coil.

[0031] Figure 8 This is a schematic diagram of the structure in which the nanocrystalline magnetic isolation sheet obtained in Comparative Example 1 is wound on a vertical coil. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto. Example 1

[0033] A method for preparing a nanocrystalline magnetic isolation sheet comprises the following steps:

[0034] (1) A FeCuNbSiB nanocrystalline ribbon with a thickness of 20 μm was wound and annealed at 560-580 °C for 2 h. The annealed nanocrystalline ribbon was bonded with two layers of double-sided tape with a thickness of 5 μm, and then covered with a PET protective film with a thickness of 50 μm to obtain a magnetic laminated structure containing two layers of nanocrystals.

[0035] (2) The magnetic laminated structure obtained in step (1) is passed through a crushed magnetic roller with transverse stripes (tooth spacing is 2 mm, and its structure is shown in the figure below). Figure 2 The nanocrystalline strip is subjected to preliminary magnetic crushing treatment (as shown in the figure) to introduce transverse cracks (the angle between the transverse crack direction and the transverse direction of the nanocrystalline strip is 0°).

[0036] (3) The nanocrystalline strips preliminarily crushed in step (2) are passed through a crushing roller with a grid pattern (its structure is shown in FIG. Figure 3 The magnetic lamination structure is subjected to secondary magnetic crushing treatment (as shown in the figure) to obtain nanocrystalline ribbons with transverse cracks and flaky fragments with a size of 0.1 to 3 mm. By adjusting the crushing pressure and the number of times, the initial magnetic permeability of the magnetic lamination structure after the crushing treatment is 500 at a test frequency of 100 kHz based on the total thickness of the nanocrystalline.

[0037] (4) The nanocrystalline strip with transverse cracks and scaly fragments obtained in step (3) is die-cut to obtain a nanocrystalline magnetic isolation sheet.

[0038] The schematic diagram of the preparation process of the nanocrystalline magnetic isolation sheet obtained in this embodiment is as follows: Figure 4 As shown; the schematic diagram of the structure of winding it on a vertical coil is shown in Figure 5 shown. Example 2

[0039] A method for preparing a nanocrystalline magnetic isolation sheet. Compared with Example 1, the angle between the transverse crack direction and the transverse direction of the nanocrystalline strip is 10°.

[0040] The schematic diagram of the preparation process of the nanocrystalline magnetic isolation sheet obtained in this embodiment is as follows: Figure 6 As shown; the schematic diagram of the structure of winding it on a vertical coil is shown in Figure 7 shown. Example 3

[0041] A method for preparing a nanocrystalline magnetic isolation sheet. Compared with Example 1, the angle between the transverse crack direction and the transverse direction of the nanocrystalline strip is 20°. Example 4

[0042] A method for preparing a nanocrystalline magnetic isolation sheet. Compared with Example 1, the angle between the transverse crack direction and the transverse direction of the nanocrystalline strip is 30°. Example 5

[0043] A method for preparing a nanocrystalline magnetic isolation sheet. Compared with Example 1, the angle between the transverse crack direction and the transverse direction of the nanocrystalline strip is 40°.

[0044] Comparative Example 1

[0045] A method for preparing a nanocrystalline magnetic isolation sheet, compared with Example 1, does not use a magnetic shredding roller with transverse stripes to perform preliminary magnetic shredding treatment to introduce transverse cracks, but directly uses a magnetic shredding roller with grid patterns to perform magnetic shredding treatment, thereby obtaining nanocrystalline strips with scaly fragments of 0.1 to 3 mm in size. By adjusting the crushing pressure and the number of passes, the initial magnetic permeability of the magnetic laminated structure after the shredding treatment is 500 at a test frequency of 100 kHz based on the total thickness of the nanocrystalline.

[0046] The schematic diagram of the structure of the obtained nanocrystalline magnetic isolation sheet wound on the vertical coil is shown in Figure 8 shown.

[0047] Performance Evaluation

[0048] The nanocrystalline materials of the above embodiments and comparative examples were die-cut into strips with a width of 23 mm, which were wound on a sleeve with an outer diameter of 10 mm and a three-turn coil, with a winding length of 165 mm, for testing the inductance Ls and inductive resistance Rs of the sleeve after winding the magnetic sheet. The test equipment was a Wenke 6500B impedance analyzer, and the test frequencies were 100 kHz, 360 kHz, 1 MHz, and 10 MHz. The test results are shown in Table 1 below.

[0049] Table 1

[0050]

[0051] It can be seen from the comparison results of Example 1 and Comparative Example 1 in Table 1 that the nanocrystalline magnetic isolation sheet of the present invention can reduce the induction resistance by introducing transverse cracks parallel to the axis of the vertical coil, which is beneficial to reduce material loss, and the higher the frequency, the more obvious the loss reduction. It can be seen from the comparison results of Examples 1 to 5 that with the increase of the deflection angle between the transverse crack and the axis of the vertical coil, the induction resistance shows an increasing trend. When the deflection angle reaches 40° (Example 5), its induction resistance exceeds that of Comparative Example 1 in which the transverse crack is not introduced, indicating that a deflection angle that is too large will lead to increased losses. In summary, the nanocrystalline magnetic isolation sheet of the present invention can be applied to electromagnetic shielding of vertical coils. By introducing transverse cracks parallel to the axis of the vertical coil or appropriately deflected (0~30°), the magnetic line loss can be reduced and the loss can be reduced.

[0052] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. Application of a nanocrystalline magnetic isolation sheet in vertical coil electromagnetic shielding, characterized in that: The application method is as follows: winding the nanocrystalline magnetic isolation sheet on a vertical coil, so that the transverse crack of the nanocrystalline magnetic isolation sheet is deflected by 10-30 degrees from the axis of the vertical coil; The nanocrystalline magnetic isolation sheet is prepared by the following method: (1) The nanocrystalline strip is wound and annealed, and then coated with a single layer of protective film or a multi-layer composite and then coated with a protective film; (2) The nanocrystalline strip covered with the protective film is initially subjected to a magnetic crushing treatment by passing it through a magnetic crushing roller with transverse stripes to introduce transverse cracks; (3) The nanocrystalline ribbon that has undergone the preliminary magnetic crushing treatment is subjected to a secondary magnetic crushing treatment through a magnetic crushing roller with a grid pattern to obtain a nanocrystalline ribbon with transverse cracks and flaky fragments; (4) The nanocrystalline strip with transverse cracks and scaly fragments obtained in step (3) is die-cut and then subjected to single-layer or multi-layer composite treatment to obtain a nanocrystalline magnetic isolation sheet.

2. The use of a nanocrystalline magnetic isolation sheet in vertical coil electromagnetic shielding according to claim 1, characterized in that: The thickness of the nanocrystalline ribbon in step (1) is 14-25 μm.

3. The use of a nanocrystalline magnetic isolation sheet in vertical coil electromagnetic shielding according to claim 1, characterized in that: The nanocrystalline ribbon in step (1) is a FeCuNbSiB nanocrystalline ribbon, and the annealing temperature is 500-650°C.

4. The use of a nanocrystalline magnetic isolation sheet in vertical coil electromagnetic shielding according to claim 1, characterized in that: The multilayer composite in step (1) is bonded by double-sided adhesive with a thickness of 1 to 5 μm; the protective adhesive film is a PET film, PE film, PVC film or silicone protective film with a thickness of 20 to 100 μm.

5. The use of a nanocrystalline magnetic isolation sheet in vertical coil electromagnetic shielding according to claim 1, characterized in that: The tooth spacing of the crushed magnetic roller with transverse stripes in step (2) is 0.5-5 mm; the angle between the transverse crack direction and the transverse direction of the nanocrystalline strip is 10-30°.

6. The use of a nanocrystalline magnetic isolation sheet in vertical coil electromagnetic shielding according to claim 1, characterized in that: The size of the scaly fragments in step (3) is 0.1-3 mm.

7. The use of a nanocrystalline magnetic isolation sheet in vertical coil electromagnetic shielding according to claim 1, characterized in that: The magnetic permeability of the nanocrystalline magnetic isolation sheet is 200-5000.

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