Composite shielding sheet for wireless charging and manufacturing method thereof

Abstract

The invention discloses a composite shielding sheet for wireless charging and a manufacturing method thereof, and the manufacturing method of the composite shielding sheet for wireless charging comprises the following steps: crushing treatment: crushing a nanocrystalline strip to obtain nanocrystalline powder; flattening treatment is carried out, the nanocrystalline powder is subjected to ball milling, and the nanocrystalline powder is subjected to ball milling until the thickness of the nanocrystalline powder is 3-6 microns; performing sieving treatment to obtain nanocrystalline powder with the sheet diameter ranging from 75 microns to 150 microns; surface activating treatment; mixing treatment: adding a resin material into a matched organic solvent, heating and stirring until the resin is completely dissolved, then adding the activated nanocrystalline powder, stirring until the powder is uniformly dispersed to form a mixture, and distilling part of the solvent to improve the viscosity of the mixture to a coating state; and coating treatment. The composite shielding sheet for wireless charging, which is prepared by adopting the manufacturing method of the composite shielding sheet for wireless charging, has the characteristics of high magnetic conductivity and high saturation magnetic induction of nanocrystalline, and can be applied to a high-power and high-frequency wireless charging system.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless charging, and in particular to a composite shielding sheet for wireless charging and a manufacturing method thereof. Background Art

[0002] In the wireless charging system, the main body includes an induction coil and a shielding sheet. The induction coil is responsible for realizing wireless energy transmission by electromagnetic induction. The main function of the shielding sheet is to gather energy, improve transmission efficiency, and prevent electromagnetic field overflow from affecting other electronic components.

[0003] At present, commonly used shielding sheets are made of soft magnetic materials such as nanocrystalline, amorphous, ferrite, and sheet Sendust. Among them, the processing methods of nanocrystalline and amorphous materials are the same. Micron-level thick direct-sprayed strips are selected as raw materials, and are made into shielding sheets that can be used for wireless charging through heat treatment, magnetic crushing, lamination, die-cutting and other processes; ferrite and sheet Sendust materials have similar processing methods, both of which use powdered precursors to form sheets through casting or coating, and then after die-cutting, they can obtain shielding sheets that can be used for wireless charging.

[0004] For the commonly used nanocrystalline and amorphous strip lamination solutions, the magnetic fragmentation process can fragment the material to suppress the eddy current loss under working conditions, but this process cannot completely block the contact between the fragments. When the material is used under high-frequency conditions (such as the 360kHz working state in the MMP2.0 protocol), the eddy current loss of the shielding sheet will increase significantly, affecting the transmission efficiency of the wireless charging system. For ferrite or sheet Sendust materials, due to the characteristics of the materials themselves, the saturation magnetic induction of ferrite materials is low, and the magnetic permeability of sheet Sendust is low, and they cannot be used in high-power wireless charging systems. Summary of the invention

[0005] The technical problem solved by the present invention is to provide a new method for manufacturing a composite shielding sheet for wireless charging. The composite shielding sheet for wireless charging manufactured by the method can effectively adapt to high-frequency and high-power wireless charging systems.

[0006] In order to solve the above technical problems, the present invention adopts a technical solution 1: a method for manufacturing a composite shielding sheet for wireless charging, comprising the following steps:

[0007] Crushing treatment, crushing the nanocrystalline strip to obtain nanocrystalline powder;

[0008] Flattening treatment, ball milling the nanocrystalline powder to reduce the thickness of the nanocrystalline powder to 3-6um;

[0009] Sieving: The flattened nanocrystalline powder is sieved multiple times to obtain nanocrystalline powder with a flake diameter in the range of 75um-150um;

[0010] Surface activation treatment, adding the sieved nanocrystalline powder into pure water, then adding sodium citrate, stirring and heating under reflux, filtering to remove the solvent, then washing with anhydrous ethanol and drying to obtain activated nanocrystalline powder;

[0011] Mixing treatment: adding the resin material to an appropriate organic solvent, heating and stirring until the resin is completely dissolved, then adding the activated nanocrystalline powder, stirring until it is evenly dispersed to form a mixture, and at the same time distilling part of the solvent to increase the viscosity of the mixture to a coatable state;

[0012] The mixture is coated, and during the coating process, the nanocrystalline powder in the mixture is oriented by using an external magnetic field, and then dried and solidified to obtain a sheet-like composite shielding sheet for wireless charging.

[0013] In one embodiment, after the coating process, a step of slicing is further included, in which the composite shielding sheet for wireless charging is die-cut.

[0014] In one embodiment, during the flattening treatment, an anti-oxidation medium is added during the ball milling process.

[0015] In one embodiment, during the mixing process, the resin material is an acrylic resin, and the organic solvent is a divalent acid ester.

[0016] In one embodiment, during the mixing process, the resin material is thermoplastic polyurethane and the organic solvent is N,N-dimethylformamide.

[0017] In one embodiment, the thickness of the nanocrystalline ribbon is 14-16 um.

[0018] In one embodiment, the external magnetic field is provided by a permanent magnet or an electromagnet.

[0019] In order to solve the above technical problems, the second technical solution adopted by the present invention is: a composite shielding sheet for wireless charging, which is manufactured by adopting the above-mentioned composite shielding sheet manufacturing method for wireless charging.

[0020] In one embodiment, the saturation magnetic induction of the composite shielding sheet for wireless charging is greater than or equal to 800 mT.

[0021] In one embodiment, the relative magnetic permeability of the composite shielding sheet for wireless charging under a frequency condition of 100kHz-500kHz is greater than or equal to 1000H / m.

[0022] The beneficial effect of the present invention is that the composite shielding sheet for wireless charging obtained by the manufacturing method of the composite shielding sheet for wireless charging has the characteristics of high magnetic permeability and high saturation magnetic induction of nanocrystals, and can be applied to high-power wireless charging systems. In the composite shielding sheet for wireless charging, each flaky powder of the nanocrystal is completely isolated by the polymer material (resin), and the eddy current is suppressed in a single flaky powder, which effectively improves the eddy current loss under high-frequency conditions, especially under the 360kHz condition required by the MPP2.0 protocol. Compared with the traditional nanocrystal solution, the AC resistance of the composite shielding sheet for wireless charging is significantly reduced. Therefore, the composite shielding sheet for wireless charging obtained by the manufacturing method of the composite shielding sheet for wireless charging has better efficiency performance in high-frequency wireless charging systems, and is particularly suitable for high-power (above 20W) wireless charging systems under high-frequency (above 300kHz) conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0024] Figure 1 This is a flowchart of the method for manufacturing a composite shielding sheet for wireless charging according to the first embodiment of the present invention;

[0025] Figure 2 This is a schematic structural diagram of a composite shielding sheet for wireless charging according to Embodiment 1 of the present invention.

[0026] Description of Figure Numbers:

[0027] 1. Nanocrystalline powder;

[0028] 2. Resin material. DETAILED DESCRIPTION

[0029] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments.

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] It should be noted that if the embodiments of the present invention involve directional indications such as up, down, left, right, front, back, etc., then the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture as shown in the accompanying drawings. If the specific posture changes, the directional indication will also change accordingly.

[0032] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features.

[0033] In addition, if the meaning of "and / or" appears in the full text is to include three parallel solutions, taking "and / or" as an example, it includes solutions, or solutions, or and solutions that are satisfied at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0034] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0035] Embodiment 1

[0036] Please refer to Figure 1 and Figure 2 , Embodiment 1 of the present invention is: a method for manufacturing a composite shielding sheet for wireless charging, comprising the following steps:

[0037] S1: Crushing treatment: crushing the nanocrystalline strip with a thickness of 14-16um to obtain nanocrystalline powder with a micron-sized flake size.

[0038] S2: Flattening treatment, ball milling the nanocrystalline powder obtained in step S1 to further flatten the nanocrystalline powder. Specifically, the thickness of the nanocrystalline powder is ball milled to 3-6um. When implementing step S2, an anti-oxidation medium needs to be added during the ball milling process to ensure that the high temperature generated during the ball milling process will not oxidize the nanocrystalline powder.

[0039] S3: Screening treatment: the nanocrystalline powder after step S2 is screened multiple times to remove the nanocrystalline powder with a flake diameter less than 75um and the nanocrystalline powder with a flake diameter greater than 150um, and obtain the nanocrystalline powder with a flake diameter in the range of 75um-150um.

[0040] S4: surface activation treatment, adding the nanocrystalline powder after step S3 into pure water, then adding sodium citrate, stirring and heating under reflux, filtering to remove the solvent, then washing with anhydrous ethanol and drying to obtain activated nanocrystalline powder.

[0041] S5: Mixing treatment, adding the resin material to an appropriate organic solvent, heating and stirring until the resin is completely dissolved, then adding the activated nanocrystalline powder, stirring until it is evenly dispersed to form a mixture, and distilling part of the solvent to increase the viscosity of the mixture to a coatable state; due to the implementation of step S4, the nanocrystalline powder in the mixture will not agglomerate and affect the performance of the finished product. In the process of implementing step S5, when the resin material is acrylic resin, the organic solvent can be a divalent acid ester; when the resin material is thermoplastic polyurethane, the organic solvent can be N,N-dimethylformamide.

[0042] S6: coating treatment, coating the mixture obtained in step S5. During the coating process, the nanocrystalline powder in the mixture is oriented and arranged by using an external magnetic field, and then dried and solidified to obtain a sheet-like composite shielding sheet for wireless charging. During the coating process, the thickness of the composite shielding sheet for wireless charging can be controlled by adjusting the slit width and the coating speed; the external magnetic field is provided by a permanent magnet or an electromagnet.

[0043] S7: Slicing processing, die-cutting the composite shielding sheet for wireless charging to obtain a composite shielding sheet for wireless charging that meets the size specifications of the wireless charging module.

[0044] This embodiment also provides a composite shielding sheet for wireless charging, which is manufactured by the above-mentioned composite shielding sheet manufacturing method for wireless charging. Figure 2 As shown, the composite shielding sheet for wireless charging includes nanocrystalline powder 1 and resin material 2 , and each of the nanocrystalline powder 1 is wrapped by the resin material 2 .

[0045] In high-power wireless charging systems, shielding materials are required to have higher saturation magnetic induction and higher magnetic permeability to cope with the strong magnetic field environment generated during working conditions. The saturation magnetic induction of the composite shielding sheet for wireless charging can reach above 800mT (i.e., greater than or equal to 800mT), which is better than the 500mT of ferrite materials. At the same time, the relative magnetic permeability of the composite shielding sheet for wireless charging under the frequency condition of 100kHz-500kHz can reach above 1000H / m (i.e., greater than or equal to 1000H / m), which is much better than the 200-300H / m of sheet-like sendust material. In other words, the composite shielding sheet for wireless charging can be adapted to higher-power wireless charging systems.

[0046] In addition, in the wireless charging system, the proportion of eddy current loss increases exponentially with the increase of frequency. In the high-frequency wireless charging system, it is necessary to suppress the eddy current loss in the shielding material to improve the transmission efficiency of the system. In this composite shielding sheet for wireless charging, the nanocrystalline powders are completely blocked by the resin, and the eddy currents are suppressed in the single nanocrystalline powder. The loss is significantly improved, especially under the 360kHz working condition required by the MPP2.0 protocol. Compared with the traditional nanocrystalline solution, the AC resistance is significantly reduced.

[0047] Here, the inventors compared the performance of ferrite shielding sheets, nanocrystalline shielding sheets and the composite shielding sheets for wireless charging in a high-frequency wireless charging system. As shown in Table 1 below, the magnetic permeability, thickness and appearance of the three sets of shielding sheets remain consistent. They are installed in the same wireless charging module to conduct basic performance and charging efficiency tests.

[0048] Table 1 Performance and charging efficiency test results of ferrite shielding sheet, nanocrystalline shielding sheet and composite shielding sheet for wireless charging

[0049]

[0050] It can be seen from Table 1 that although the ferrite shielding sheet has the lowest AC resistance Rs in static state, the charging efficiency is significantly attenuated under the 20W charging condition, proving that its saturation magnetic induction is not sufficient to support high-power conditions; while the nanocrystalline shielding sheet has a higher AC resistance Rs in static state and a lower charging efficiency; the Rs and charging efficiency of the composite shielding sheet for wireless charging are the best.

[0051] The above are only optional embodiments of the present invention, and do not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for manufacturing a composite shielding sheet for wireless charging, characterized in that: The following steps are included Crushing treatment, crushing the nanocrystalline strip to obtain nanocrystalline powder; Flattening treatment, ball milling the nanocrystalline powder to reduce the thickness of the nanocrystalline powder to 3-6um; Sieving: The flattened nanocrystalline powder is sieved multiple times to obtain nanocrystalline powder with a flake diameter in the range of 75um-150um; Surface activation treatment, adding the sieved nanocrystalline powder into pure water, then adding sodium citrate, stirring and heating under reflux, filtering to remove the solvent, then washing with anhydrous ethanol and drying to obtain activated nanocrystalline powder; Mixing treatment: adding the resin material to an appropriate organic solvent, heating and stirring until the resin is completely dissolved, then adding the activated nanocrystalline powder, stirring until it is evenly dispersed to form a mixture, and at the same time distilling part of the solvent to increase the viscosity of the mixture to a coatable state; The mixture is coated, and during the coating process, the nanocrystalline powder in the mixture is oriented by using an external magnetic field, and then dried and solidified to obtain a sheet-like composite shielding sheet for wireless charging.

2. The method for manufacturing a composite shielding sheet for wireless charging according to claim 1, characterized in that: The coating process also includes the steps of slicing and die-cutting the composite shielding sheet for wireless charging.

3. The method for manufacturing a composite shielding sheet for wireless charging according to claim 1, characterized in that: During the flattening process, an anti-oxidation medium is added during the ball milling process.

4. The method for manufacturing a composite shielding sheet for wireless charging according to claim 1, characterized in that: During the mixing process, the resin material is acrylic resin and the organic solvent is divalent acid ester.

5. The method for manufacturing a composite shielding sheet for wireless charging according to claim 1, characterized in that: During the mixing process, the resin material is thermoplastic polyurethane and the organic solvent is N,N-dimethylformamide.

6. The method for manufacturing a composite shielding sheet for wireless charging according to claim 1, characterized in that: The thickness of the nanocrystalline ribbon is 14-16 um.

7. The method for manufacturing a composite shielding sheet for wireless charging according to claim 1, characterized in that: The external magnetic field is provided by a permanent magnet or an electromagnet.

8. A composite shielding sheet for wireless charging, characterized in that: The composite shielding sheet for wireless charging is manufactured by the manufacturing method of any one of claims 1 to 7.

9. The composite shielding sheet for wireless charging according to claim 8, characterized in that: The saturation magnetic induction of the composite shielding sheet for wireless charging is greater than or equal to 800mT.

10. The composite shielding sheet for wireless charging according to claim 8, characterized in that: The relative magnetic permeability of the composite shielding sheet for wireless charging under the frequency condition of 100kHz-500kHz is greater than or equal to 1000H / m.

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