Ultra-high stiffness matt black stiffener and preparation method thereof

Abstract

A high-stiffness matte black reinforcing plate and its preparation method are disclosed. The reinforcing plate sequentially comprises a black polyimide varnish layer and a composite layer. The composite layer sequentially comprises a first epoxy adhesive layer, a first polyimide layer, another first epoxy adhesive layer, and a first metal layer. The black polyimide varnish layer has a thickness of 1 to 50 μm, each of the first epoxy adhesive layers has a thickness of 5 to 50 μm, each of the first polyimide layers has a thickness of 5 to 75 μm, and the first metal layer has a thickness of 9 to 100 μm. The disclosed high-stiffness matte black reinforcing plate exhibits excellent reinforcing effect, shielding properties, ultra-flatness, controllable surface gloss, and surface energy.

Description

Technical Field

[0001] The present disclosure relates to an ultra-high stiffness matte black reinforcing plate and its preparation method, and more particularly to a black reinforcing plate for printed circuit boards having ultra-high reinforcement effect and matte properties. Prior Art

[0002] With the rapid development of information technology, printed circuit boards (PCBs) have become an indispensable material in electronic products. As demand for consumer electronics grows, so too has the demand for PCBs. Due to their flexibility and ability to accommodate three-dimensional wiring, flexible printed circuits (FPCs) are now widely used in computers and their peripherals, communications products, and consumer electronics.

[0003] Polyimide (PI) is a type of polymer with imide repeating units. It has high thermal stability and excellent insulation, mechanical strength, and chemical resistance. This makes it suitable for use in electronic components. For example, it can be used as a reinforcement material in flexible printed circuit boards to prevent warping.

[0004] However, the polyimide reinforcement sheets currently used in printed circuit boards are limited by the cost and thickness of the polyimide film, as well as the inherent light transmittance of the polyimide itself. This makes them incapable of shielding circuit layout patterns, making them easily copied by competitors. Furthermore, polyimide reinforcement sheets are made from a polyimide film followed by a laminate, but the difference in thermal expansion coefficients between the two often leads to warping of the flexible printed circuit board even after the reinforcement sheet is applied to it. Furthermore, conventional commercially available FR4 fiberglass reinforcement sheets suffer from low stiffness at equivalent thickness. While they can provide stronger reinforcement than commercially available polyimide reinforcement sheets when total thickness is not considered, their high-temperature resistance, acid and alkali resistance, insulation, dimensional stability, and surface hardness are inferior to those of polyimide reinforcement sheets.

[0005] Furthermore, to address issues such as stress warping caused by material thermal expansion coefficient differences and insufficient reinforcement for flexible printed circuit boards, conventional methods have involved increasing the thickness of the reinforcing plate and selecting a material with a uniform composition and a thermal expansion coefficient close to that of the overall printed circuit board. To address the masking issue, conventional methods have replaced the polyimide film on the reinforcing plate surface with a black polyimide film to conceal the circuit layout. However, the glossiness of the black reinforcing plate surface obtained with this method is difficult to achieve the low gloss required by the industry, making it ineffective in applications requiring high gloss.

[0006] In view of this, there is an urgent need for an ultra-high stiffness matte black reinforcing plate and its preparation method, which has excellent reinforcing effect, shielding property, ultra-flatness, controllable surface gloss and surface energy. Summary of the Invention

[0007] To address the aforementioned issues, the present disclosure provides an ultra-high-stiffness matte black reinforced plate comprising: a black polyimide varnish layer; and a composite layer formed on the black polyimide varnish layer. The composite layer comprises: an odd-numbered layer structure consisting of alternating first epoxy adhesive layers and first polyimide layers, with the outermost layer of the odd-numbered layer being the first epoxy adhesive layer; and a first metal layer, with the odd-numbered layer structure formed between the black polyimide varnish layer and the first metal layer.

[0008] In a specific embodiment of the present disclosure, the reinforcement plate further includes a build-up layer structure, which can be an even-layer structure composed of at least one second epoxy layer and at least one second polyimide layer alternately stacked, and the second epoxy layer is adjacent to the first metal layer.

[0009] In a specific embodiment of the present disclosure, the reinforcement plate further includes a build-up layer structure, which can be an even-layer structure composed of at least one second epoxy layer and at least one second metal layer alternately stacked, with the second epoxy layer adjacent to the first metal layer.

[0010] In one embodiment of the present disclosure, the thickness of the black polyimide varnish layer may be 1 to 50 μm, preferably 3 to 15 μm, for example but not limited to 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 25, 30, 35, 40, 45 or 50 μm, and the thickness of the first epoxy adhesive layer and the second epoxy adhesive layer may be independently 5 to 50 μm, preferably 15 to 30 μm, for example but not limited to 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 25, 30, 35, 40, 45 or 50 μm. The thickness of the first polyimide layer and the second polyimide layer may be 5 to 75 μm, preferably 12.5 to 50 μm, for example, but not limited to 5, 10, 11, 12, 12.5, 13, 13.5, 14, 14.5, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 35, 40, 45 or 50 μm, and the thickness of the first polyimide layer and the second polyimide layer may be 5 to 75 μm, preferably 12.5 to 50 μm, for example, but not limited to, 5, 10, 11, 12, 12.5, 13, 13.5, 14, 14.5, 15, 16 , 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 55, 60, 65, 70 or 75 μm, the thickness of the first metal layer and the second metal layer can be independently 9 to 100 μm, preferably 18 to 5 0 μm, for example, but not limited to, 9, 10, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 100 μm.

[0011] In a specific embodiment of the present disclosure, the first metal layer and the second metal layer are each: a metal foil selected from copper foil or aluminum foil, an alloy foil selected from copper-nickel alloy foil, copper-zinc alloy foil, copper-zinc-nickel alloy foil or copper-aluminum alloy foil, or a stainless steel sheet, and the first metal layer and the second metal layer have the same thickness.

[0012] In one embodiment of the present disclosure, the black polyimide varnish layer is a single layer or is composed of multiple black polyimide varnish sub-layers. The present disclosure can form a black polyimide varnish layer composed of multiple black polyimide varnish sub-layers through a multiple-coating process. This multiple-coating process is beneficial for reducing surface defects, and the multiple-layer structure facilitates adjusting the composition of each sub-layer, thereby balancing the mechanical and optical properties of the reinforcing plate.

[0013] In one embodiment of the present disclosure, the reinforcing plate further comprises: an adhesive layer, which may be formed on the first metal layer, the second polyimide layer, or the second metal layer; and a release layer, which may be formed on the adhesive layer. Specifically, the adhesive layer is formed on the first metal layer so that the first metal layer is positioned between the black polyimide varnish layer and the adhesive layer; the adhesive layer is formed on the second polyimide layer so that the second polyimide layer is positioned between the composite layer and the adhesive layer; and the adhesive layer is formed on the second metal layer so that the second metal layer is positioned between the composite layer and the adhesive layer.

[0014] In one embodiment of the present disclosure, the adhesive layer includes at least one resin selected from the group consisting of epoxy resin, acrylic resin, polyimide resin, polyester resin, silicone rubber resin, poly-p-xylylene (poly-p-xylylene or parylene) resin, bismaleimide resin and urethane resin.

[0015] In one embodiment of the present disclosure, the thickness of the adhesive layer may be 5 to 50 μm, preferably 15 to 30 μm, for example but not limited to 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 35, 40, 45 or 50 μm.

[0016] In a specific embodiment of the present disclosure, the release layer may be a release film or a release paper. The material of the release film may be at least one selected from the group consisting of polypropylene, biaxially oriented polypropylene, and polyethylene terephthalate, and the release film may be a release film with double-sided release capability.

[0017] The present disclosure also provides a method for preparing an ultra-high stiffness matte black reinforced plate, comprising: coating a first epoxy adhesive on one side of a first polyimide layer, and heating and drying to form a first epoxy adhesive layer; thermally pressing a first metal layer onto the first epoxy adhesive layer; coating a black polyimide varnish on a carrier film, and heating and drying to form a black polyimide varnish layer; coating the first epoxy adhesive on the black polyimide varnish layer, and heating and drying to form another first an epoxy adhesive layer; and hot pressing the other first epoxy adhesive layer on the black polyimide varnish layer on the other side opposite to the first polyimide layer, and peeling off the carrier film to obtain the black reinforced plate, wherein the black polyimide varnish layer has a thickness of 1 to 50 μm, the first epoxy adhesive layer has a thickness of 5 to 50 μm, the first polyimide layer has a thickness of 5 to 75 μm, and the first metal layer has a thickness of 9 to 100 μm.

[0018] The present disclosure further provides a method for preparing an ultra-high stiffness matte black reinforced plate, comprising: coating a first epoxy adhesive on one side of a first polyimide layer, and heating and drying to form a first epoxy adhesive layer; thermally pressing a first metal layer onto the first epoxy adhesive layer; coating a second epoxy adhesive on the first metal layer, and heating and drying to form a second epoxy adhesive layer; thermally pressing a second polyimide layer onto the second epoxy adhesive layer to form a build-up structure; coating a black polyimide varnish on a carrier film, and heating and drying to form a black polyimide varnish layer; and thermally pressing a second polyimide layer onto the second epoxy adhesive layer to form a build-up structure. A first epoxy adhesive is coated on the black polyimide varnish layer and heated and dried to form another first epoxy adhesive layer; and the other first epoxy adhesive layer is heat-pressed on the opposite side of the first polyimide layer, and the carrier film is peeled off to obtain the black reinforced plate. The black polyimide varnish layer has a thickness of 1 to 50 μm, the first epoxy adhesive layers each have a thickness of 5 to 50 μm, the first polyimide layer has a thickness of 5 to 75 μm, and the first metal layer has a thickness of 9 to 100 μm.

[0019] The present disclosure further provides a method for preparing an ultra-high stiffness matte black reinforced plate, comprising: coating a first epoxy adhesive on one side of a first polyimide layer, and heating and drying to form a first epoxy adhesive layer; thermally pressing a first metal layer onto the first epoxy adhesive layer; coating a second epoxy adhesive on the first metal layer, and heating and drying to form a second epoxy adhesive layer; thermally pressing a second metal layer onto the second epoxy adhesive layer to form a build-up structure; coating a black polyimide varnish on a carrier film, and heating and drying to form a black polyimide varnish layer; thermally pressing a second metal layer onto the second epoxy adhesive layer to form a build-up structure; A first epoxy adhesive is coated on the polyimide varnish layer and dried by heating to form another first epoxy adhesive layer. The other first epoxy adhesive layer is then heat-pressed onto the black polyimide varnish layer on the opposite side of the first polyimide layer, and the carrier film is removed to obtain the black reinforced plate. The black polyimide varnish layer has a thickness of 1 to 50 μm, the first epoxy adhesive layers each have a thickness of 5 to 50 μm, the first polyimide layer has a thickness of 5 to 75 μm, and the first metal layer has a thickness of 9 to 100 μm.

[0020] In a specific embodiment of the present disclosure, the method further includes: forming an adhesive layer by coating an adhesive on the first metal layer, the second polyimide layer or the second metal layer, and laminating a release layer on the adhesive layer.

[0021] In one embodiment of the present disclosure, the step of forming the black polyimide varnish layer in the above method includes: coating a black polyimide varnish on a carrier film, forming a black polyimide varnish sub-layer by heating and drying, and then repeating this step n times to form a black polyimide varnish layer consisting of n black polyimide varnish sub-layers, where n is 0 or a positive integer, such as but not limited to 1, 2, 3, or 4, so that the black polyimide varnish layer has a thickness of 1 to 50 μm.

[0022] In one embodiment of the present disclosure, the steps of forming the build-up structure in the above method include: applying a second epoxy adhesive, forming a second epoxy adhesive layer by heat drying, heat-pressing a second polyimide layer or a second metal layer on the second epoxy adhesive layer, and then repeating this step n times to form a build-up structure consisting of n layers of alternating second epoxy adhesive layers and second polyimide layers or second metal layers, where n is 0 or a positive integer, such as but not limited to 1, 2, 3, or 4. Simple diagram description

[0023] FIG1 is a schematic structural diagram of a specific embodiment of a reinforcing plate disclosed herein.

[0024] FIG. 2 is a schematic structural diagram of another embodiment of the reinforcing plate disclosed herein.

[0025] FIG3 is a schematic structural diagram of another embodiment of the reinforcing plate disclosed herein.

[0026] 4A to 4C are schematic structural diagrams of a reinforcing plate having an adhesive layer and a release layer according to the present disclosure. Implementation Method

[0027] The following describes the implementation of the present disclosure through specific embodiments and / or combined with drawings. People skilled in the art can easily understand the advantages and effects of the present disclosure from the contents disclosed in this specification.

[0028] It should be noted that the structures, proportions, and sizes illustrated in the drawings and diagrams of this specification are intended solely to facilitate understanding and reading by those skilled in the art. They are not intended to limit the practical application of this disclosure and therefore have no substantive technical significance. Any structural modifications, changes in proportions, or adjustments in size, without affecting the efficacy and objectives of this disclosure, should still fall within the scope of the technical content disclosed herein. Furthermore, terms such as "first," "second," "upper," "lower," and "one" used in this specification are intended solely for clarity and are not intended to limit the practical application of this disclosure. Changes or adjustments in their relative relationships, without substantive changes to the technical content, should be considered within the practical application of this disclosure. Furthermore, all ranges and values ​​herein are inclusive and combinable. Any numerical value or point within a range, such as any integer or decimal, can be used as a minimum or maximum value to derive a lower range.

[0029] Please refer to Figure 1, which is a schematic diagram of the structure of the reinforcement plate disclosed in the present invention. The reinforcement plate includes, from top to bottom, a black polyimide varnish layer 1 and a composite layer 2 including a first epoxy adhesive layer 21, a first polyimide layer 22, a first epoxy adhesive layer 21 and a first metal layer 23.

[0030] Please refer to FIG. 2 , which is a schematic diagram illustrating another structure of the reinforcement plate disclosed herein. In addition to the stacked structure shown in FIG. 1 , the reinforcement plate further includes a build-up structure 3 under the composite layer 2 , which is composed of at least one second epoxy adhesive layer 31 and at least one second polyimide layer 32 alternately stacked.

[0031] Please refer to FIG3 , which is another schematic diagram illustrating the structure of the reinforcement plate disclosed herein. In addition to the stacked structure shown in FIG1 , the reinforcement plate further includes a build-up structure 3 under the composite layer 2 , which is composed of at least one second epoxy layer 31 and at least one second metal layer 33 alternately stacked.

[0032] Please refer to FIG. 4A to FIG. 4C , which are schematic diagrams illustrating other structures of the reinforcing plate disclosed herein. In addition to the stacked structure shown in FIG. 1 to FIG. 3 , these reinforcing plates further include an adhesive layer 4 and a release layer 5 under the build-up structure 3 .

[0033] Example 1

[0034] A first epoxy adhesive was applied to one side of the first polyimide layer and dried in an oven to form a first epoxy adhesive layer. A first metal layer was then heat-pressed onto the first epoxy adhesive layer using a hot roller. Next, a black polyimide varnish was applied to the carrier film and dried in an oven to form a black polyimide varnish layer. Subsequently, the first epoxy adhesive was applied to the black polyimide varnish layer and dried in an oven to form another first epoxy adhesive layer. This second first epoxy adhesive layer was heat-pressed onto the opposite side of the first polyimide layer using a hot roller, and the carrier film was removed. Finally, an adhesive was applied to the first metal layer to form an adhesive layer. A release layer was then attached to the adhesive layer to produce the reinforced plate of Example 1. The stacking structure is shown in Figure 4A. The heating and drying were performed in a coating oven at a continuous temperature range of 80 to 140°C for 4 minutes, and the heat pressing was performed at 70°C and 2.0 kgf.

[0035] Example 2

[0036] A first epoxy adhesive is applied to one side of a first polyimide layer and dried in an oven to form a first epoxy adhesive layer. A first metal layer is then heat-pressed onto the first epoxy adhesive layer using a hot roller. Next, a second epoxy adhesive is applied to the first metal layer and dried in an oven to form a second epoxy adhesive layer. A second polyimide layer is then heat-pressed onto the second epoxy adhesive layer using a hot roller to form a build-up structure. Additionally, a black polyimide varnish is applied to a carrier film and dried in an oven to form a black polyimide varnish layer. Subsequently, the first epoxy adhesive is applied to the black polyimide varnish layer and dried in an oven to form another first epoxy adhesive layer. This second first epoxy adhesive layer is then heat-pressed onto the opposite side of the first polyimide layer using a hot roller, and the carrier film is removed. Finally, an adhesive layer was formed by coating the second polyimide layer of the build-up structure with an adhesive. A release layer was then laminated onto the adhesive layer to obtain the reinforced plate of Example 2, the stacking structure of which is shown in Figure 4B . The heating and drying process was performed in a coating oven at a continuous temperature range of 80 to 140°C for 4 minutes, and the thermal pressing process was performed at 70°C and 2.0 kgf.

[0037] Example 3

[0038] The reinforcing plate of Example 3 was prepared in the same manner as Example 2. The difference between the two is that the second polyimide layer of Example 2 was replaced by the second metal layer of Example 3. The stacking structure of the reinforcing plate of Example 3 is shown in FIG4C .

[0039] In Examples 1 to 3, the thickness of the cured black polyimide varnish layer was 5 μm. The thickness of the first and second epoxy adhesive layers and the adhesive layer was 25 μm (epoxy adhesive HCLV2-N-004-14, purchased from Kunshan Yasen Electronic Materials Co., Ltd.). The thickness of the first and second polyimide layers was 25 μm (GF100, purchased from PIAM). The first and second metal layers were both made of 35 μm thick electrolytic copper foil (VF, purchased from Nan Ya).

[0040] Comparative Examples 1 to 4 respectively used commercially available AHBQX black reinforcing sheets of varying specifications (AHBQX 425 / 525 / 725 / A25, purchased from Kunshan Yasen Electronic Materials Co., Ltd.). These reinforcing sheets comprised, in order, a black polyimide layer (commercially available black polyimide film GD100, purchased from PIAM), a polyimide composite film of varying thicknesses (AHIPI, Kunshan Yasen Electronic Materials Co., Ltd.) composed of a polyimide film and an epoxy adhesive layer, an adhesive layer, and a release layer.

[0041] The thickness of each layer, total thickness, and various properties of Examples 1 to 3 and Comparative Examples 1 to 4 are shown in Table 1, and the various performance data are measured according to the following methods or standards: 1. Surface Gloss: According to ASTM D523, the reinforcing plates of the Examples and Comparative Examples were cut into samples larger than 3 cm x 8 cm. The gloss of the black polyimide varnish layer of the Example samples and the black polyimide film of the Comparative Example was measured in the machine direction (MD) using a gloss meter. The gloss meter readings were taken at a 60-degree angle. 2. Rebound Force (also known as Rigidity or Stiffness): According to the test method in TPCA-F-002, the reinforcing plates of the Examples and Comparative Examples were cut into samples measuring 1 cm x 3 cm. These samples were mounted on an electronic balance with a holder in the center of a tray, and bent horizontally into a U-shape. A 500g weight was placed above the holder. The holder was slowly lowered until the sample contacted the balance. At this point, the sample bending radius was 2.35mm. After the value stabilized, the reading on the balance was taken to determine the rebound force. 3. Flatness: The reinforcing plates of the Examples and Comparative Examples were cut into 25 cm × 25 cm samples and laminated at 180°C onto a 74.5 ± 1 μm adhesive-coated double-sided flexible copper foil substrate. The samples were then aged at 160°C and placed on a smooth surface. After standing for 20 minutes, the warpage height at the four corners of each sample was measured for flatness testing.

[0042] Table 1

[0043] The test results in Table 1 show that, compared to the commercially available reinforced sheet of the comparative example, the ultra-high-stiffness matte black reinforced sheet disclosed herein achieves superior optical properties by transfer-coating a coated black polyimide varnish through a matching carrier film. Furthermore, the addition of a metal layer provides enhanced stiffness, resulting in superior reinforcement compared to conventional PI reinforced sheets at equivalent or even thinner thicknesses.

[0044] 1: Black polyimide varnish layer 2: Composite layer 21: First epoxy layer 22: First polyimide layer 23: First metal layer 3: Layered structure 31: Second epoxy adhesive layer 32: Second polyimide layer 33: Second metal layer 4: Adhesive layer 5: Release layer

Claims

1. A high-stiffness matte black reinforcing panel, comprising: Black polyimide varnish layer; A composite layer is formed on the black polyimide varnish layer. The composite layer includes: an odd-numbered layer structure composed of alternating first epoxy layers and first polyimide layers, wherein the outermost layer of the odd-numbered layer structure is the first epoxy layer; a first metal layer, such that the odd-numbered layer structure is formed between the black polyimide varnish layer and the first metal layer; and an even-numbered layer structure composed of at least one second epoxy layer and at least one second polyimide layer alternately stacked, with the second epoxy layer adjacent to the first metal layer; wherein the black polyimide varnish layer has a thickness of 1 to 50 μm, each of the first epoxy layers has a thickness of 5 to 50 μm, each of the first polyimide layers has a thickness of 5 to 75 μm, the first metal layer has a thickness of 9 to 100 μm, and each of the second epoxy layers has a thickness of 5 to 50 μm. The second polyimide layer has a thickness of 5 to 75 μm.

2. A high-stiffness matte black reinforcing panel, comprising: Black polyimide varnish layer; A composite layer is formed on the black polyimide varnish layer. The composite layer includes: an odd-numbered layer structure composed of alternating first epoxy layers and first polyimide layers, wherein the outermost layer of the odd-numbered layer structure is the first epoxy layer; a first metal layer, such that the odd-numbered layer structure is formed between the black polyimide varnish layer and the first metal layer; and an even-numbered layer structure composed of at least one second epoxy layer and at least one second metal layer alternately stacked, with the second epoxy layer adjacent to the first metal layer; wherein the black polyimide varnish layer has a thickness of 1 to 50 μm, each of the first epoxy layers has a thickness of 5 to 50 μm, each of the first polyimide layers has a thickness of 5 to 75 μm, each of the first metal layers has a thickness of 9 to 100 μm, each of the second epoxy layers has a thickness of 5 to 50 μm, and each of the second metal layers has a thickness of 9 to 100 μm. A thickness of μm.

3. The ultra-high stiffness matte black reinforcing plate as described in claim 2, wherein, The first metal layer and the second metal layer are each: a metal foil selected from copper foil or aluminum foil, an alloy foil selected from copper-nickel alloy foil, copper-zinc alloy foil, copper-zinc-nickel alloy foil or copper-aluminum alloy foil, or stainless steel sheet, and wherein the first metal layer and the second metal layer have the same thickness.

4. The ultra-high stiffness matte black reinforcing plate as described in claim 1 or 2, wherein, The black polyimide varnish layer is a single layer or composed of multiple layers of black polyimide varnish sublayers.

5. The ultra-high stiffness matte black reinforcing plate as described in claim 1, further comprising: An adhesive layer is formed on the first metal layer, such that the first metal layer is located between the black polyimide varnish layer and the adhesive layer; And a release layer, which is formed on the adhesive layer.

6. The ultra-high stiffness matte black reinforcing plate as described in claim 1, further comprising: An adhesive layer is formed on the second polyimide layer, such that the second polyimide layer is located between the composite layer and the adhesive layer; And a release layer, which is formed on the adhesive layer.

7. The ultra-high stiffness matte black reinforcing plate as described in claim 2, further comprising: An adhesive layer is formed on the second metal layer, such that the second metal layer is located between the composite layer and the adhesive layer; And a release layer, which is formed on the adhesive layer.

8. The ultra-high stiffness matte black reinforcing panel as described in any one of claims 5 to 7, wherein, The adhesive layer comprises a resin selected from at least one of the group consisting of epoxy resin, acrylic resin, polyimide resin, polyester resin, silicone rubber resin, parylene resin, bismaleimide resin and urethane resin, wherein the adhesive layer has a thickness of 5 to 50 μm.

9. A method for preparing an ultra-high stiffness matte black reinforcing plate, comprising: A first epoxy adhesive is applied to one side of the first polyimide layer, and then the first epoxy adhesive layer is formed by heating and drying. A first metal layer is hot-pressed onto the first epoxy adhesive layer; a black polyimide varnish is coated onto the carrier film, and then a black polyimide varnish layer is formed by heating and drying. The process involves coating a first epoxy adhesive onto the black polyimide varnish layer, then heating and drying it to form another first epoxy adhesive layer; hot-pressing the other first epoxy adhesive layer onto the opposite side of the first polyimide layer onto the black polyimide varnish layer, and peeling off the carrier film to obtain the black reinforcing plate. The black polyimide varnish layer has a thickness of 1 to 50 μm, each of the first epoxy adhesive layers has a thickness of 5 to 50 μm, the first polyimide layer has a thickness of 5 to 75 μm, and the first metal layer has a thickness of 9 to 100 μm.

10. A method for preparing an ultra-high stiffness matte black reinforcing plate, comprising: A first epoxy adhesive is applied to one side of the first polyimide layer, and then the first epoxy adhesive layer is formed by heating and drying. A first metal layer is hot-pressed onto the first epoxy adhesive layer; a second epoxy adhesive is applied onto the first metal layer, and then dried by heating to form at least one second epoxy adhesive layer; at least one second polyimide layer is hot-pressed onto the second epoxy adhesive layer to form a layered structure; a black polyimide varnish is applied onto a carrier film, and then dried by heating to form a black polyimide varnish layer; a first epoxy adhesive is applied onto the black polyimide varnish layer, and then dried by heating to form another first epoxy adhesive layer; and the other first epoxy adhesive layer on the black polyimide varnish layer is hot-pressed onto the opposite side of the first polyimide layer, and the carrier film is peeled off to obtain the black reinforcing plate, wherein the black polyimide varnish layer has a thickness of 1 to 50 μm, each of the first epoxy adhesive layers has a thickness of 5 to 50 μm, and the first polyimide layer has a thickness of 5 to 75 μm. The thickness is μm, and the first metal layer has a thickness of 9 to 100 μm.

11. A method for preparing an ultra-high stiffness matte black reinforcing plate, comprising: A first epoxy adhesive is applied to one side of the first polyimide layer, and then the first epoxy adhesive layer is formed by heating and drying. A first metal layer is hot-pressed onto the first epoxy adhesive layer; a second epoxy adhesive is applied onto the first metal layer, and then at least one second epoxy adhesive layer is formed by heating and drying; at least one second metal layer is hot-pressed onto the second epoxy adhesive layer to form a laminate structure; a black polyimide varnish is applied onto a carrier film, and then a black polyimide varnish layer is formed by heating and drying; a first epoxy adhesive is applied onto the black polyimide varnish layer, and then another first epoxy adhesive layer is formed by heating and drying; and the other first epoxy adhesive layer on the black polyimide varnish layer is hot-pressed onto the opposite side of the first polyimide layer, and the carrier film is peeled off to obtain the black reinforcing plate, wherein the black polyimide varnish layer has a thickness of 1 to 50 μm, each of the first epoxy adhesive layers has a thickness of 5 to 50 μm, and the first polyimide layer has a thickness of 5 to 75 μm. The thickness is μm, and the first metal layer has a thickness of 9 to 100 μm.

12. The method as described in claim 9 further includes forming an adhesive layer on the first metal layer by coating an adhesive, and attaching a release layer on the adhesive layer.

13. The method as described in claim 10 further includes forming an adhesive layer on the second polyimide layer by coating an adhesive, and attaching a release layer on the adhesive layer.

14. The method as described in claim 11 further includes forming an adhesive layer on the second metal layer by coating an adhesive, and attaching a release layer on the adhesive layer.

15. The method as described in any one of claims 9 to 11, wherein, The steps for forming the black polyimide varnish layer include: coating a carrier film with black polyimide varnish, then drying it by heating to form a black polyimide varnish sublayer, and then repeating this step n times to form a black polyimide varnish layer composed of n black polyimide varnish sublayers, where n is 0 or a positive integer, so that the black polyimide varnish layer has a thickness of 1 to 50 μm.

16. The method as described in claim 10, wherein, The steps for forming the layered structure include: coating a second epoxy adhesive onto the first metal layer, forming a second epoxy adhesive layer by heating and drying, hot-pressing a second polyimide layer onto the second epoxy adhesive layer, and then repeating this step n times to form n layers of layered structure composed of alternating layers of the second epoxy adhesive layer and the second polyimide layer, where n is 0 or a positive integer.

17. The method as described in claim 11, wherein, The steps for forming the layered structure include: coating a second epoxy adhesive onto the first metal layer, forming a second epoxy adhesive layer by heating and drying, and then hot-pressing a second metal layer onto the second epoxy adhesive layer. This step is repeated n times to form n layers of layered structure composed of alternating layers of second epoxy adhesive layer and second metal layer, where n is 0 or a positive integer.

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