A printed circuit board, a preparation method thereof, and a display device

Abstract

The present application discloses a printed circuit board, a preparation method and a display device, relating to the technical field of circuit boards. The printed circuit board includes a substrate layer, an insulating layer, a circuit layer and a pad layer which are sequentially stacked; wherein, the pad layer includes solder and a first inert heat-conducting medium, and the first inert heat-conducting medium is mixed in the solder. The printed circuit board provided by the present application can improve the oxidation resistance and heat-conducting performance of the pad layer and reduce the production cost of the printed circuit board.

Description

Technical Field

[0001] The present application relates to the technical field of circuit boards, and in particular to a printed circuit board, a preparation method, and a display device. Background Art

[0002] Micro-LEDs not only inherit the advantages of traditional LEDs, such as high efficiency, high brightness, high reliability and fast response time, but also have the characteristics of energy saving, simple structure, small size, thinness and no need for backlight source for light emission. As a result, Micro LED display devices are also widely used in different fields.

[0003] However, Micro LED display devices still have problems with poor heat dissipation of solder pads and prone to oxidation. Summary of the Invention

[0004] The present application provides a printed circuit board, a preparation method and a display device, so as to at least improve heat dissipation performance and reduce the oxidation rate of pads.

[0005] In a first aspect, the present application provides a printed circuit board, comprising a substrate layer, an insulating layer, a circuit layer, and a pad layer stacked in sequence;

[0006] The pad layer includes solder and a first inert thermally conductive medium, and the first inert thermally conductive medium is mixed in the solder.

[0007] The inert first thermally conductive medium in the pad layer increases the overall inertness of the pad layer, thereby enhancing the pad layer's oxidation resistance and ensuring reliability between the pad layer and the connected device (e.g., the MicroLED chip in a MicroLED display). Furthermore, the first inert thermally conductive medium provides thermal conductivity within the pad layer, accelerating heat transfer from the connected device (e.g., the MicroLED chip in a MicroLED display) to the printed circuit board (PCB), accelerating heat dissipation from the MicroLED chip in the MicroLED display, and thus extending the lifespan of the MicroLED display.

[0008] In some possible implementations, in the pad layer, the mass proportion of the first inert thermally conductive medium is 2% to 15%.

[0009] While ensuring that the pad layer can provide a stable and reliable connection function, the oxidation resistance and thermal conductivity of the pad layer are improved.

[0010] In some possible implementations, the solder is aluminum;

[0011] In the pad layer, the mass proportion of the first inert heat-conducting medium is 5% to 15%.

[0012] In some possible embodiments, the solder is gold;

[0013] In the pad layer, the mass proportion of the first inert heat-conducting medium is 2% to 10%.

[0014] In some possible embodiments, the first inert heat-conducting medium includes at least one of boron nitride powder, alumina powder, and aluminum nitride powder.

[0015] In some possible embodiments, the circuit layer includes a copper substrate and a second inert heat-conducting medium, and the second inert heat-conducting medium is mixed in the copper substrate.

[0016] It can be understood that the second inert heat-conducting medium can also be used for heat conduction in the circuit layer to accelerate heat dissipation.

[0017] In some possible embodiments, in the circuit layer, the mass proportion of the second inert heat-conducting medium is 2% to 8%.

[0018] In some possible embodiments, the insulating layer at least includes a resin material and a third inert heat-conducting medium mixed together.

[0019] Adding the third inert heat-conducting medium to the insulating layer can accelerate the heat transfer of the insulating layer through the third inert heat-conducting medium and improve the heat dissipation in the Micro LED display device.

[0020] In some possible embodiments, in the insulating layer, the mass proportion of the third inert heat-conducting medium is 20% to 50%.

[0021] In some possible embodiments, the substrate layer includes an aluminum substrate and a fourth inert heat-conducting medium, and the fourth inert heat-conducting medium is mixed in the aluminum substrate.

[0022] Among them, the fourth inert heat-conducting medium can be used for heat transfer in the substrate layer to accelerate heat dissipation.

[0023] In some possible embodiments, in the substrate layer, the mass proportion of the fourth inert heat-conducting medium is 10% to 50%.

[0024] In addition, the present application also provides a printed circuit board, including a substrate layer, an insulating layer, a circuit layer, and a pad layer stacked in sequence;

[0025] Wherein, the pad layer includes a solder layer and an inert heat-conducting medium layer, the inert heat-conducting medium layer is located between the solder layer and the circuit layer, and the inert heat-conducting medium layer is made of a first inert heat-conducting medium.

[0026] In a second aspect, the present application further provides a method for manufacturing a printed circuit board for manufacturing the printed circuit board provided in each of the above embodiments. The method for manufacturing a printed circuit board includes:

[0027] Providing a substrate layer and a circuit layer respectively;

[0028] Laminating the circuit layer on one side of the substrate layer;

[0029] Preparing a pad layer mixed with a first inert heat-conducting medium on the side of the circuit layer away from the substrate layer.

[0030] In some possible implementation manners, the providing a substrate layer and a circuit layer respectively includes:

[0031] Heating and melting an aluminum substrate;

[0032] Adding a fourth inert heat-conducting medium to the molten aluminum substrate and stirring the fourth inert heat-conducting medium and the molten aluminum substrate;

[0033] Cooling and solidifying to form the substrate layer.

[0034] In some possible implementation manners, the providing a substrate layer and a circuit layer respectively includes:

[0035] Heating and melting a copper substrate;

[0036] Adding a second inert heat-conducting medium to the molten copper substrate and stirring the second inert heat-conducting medium and the molten copper substrate;

[0037] Cooling and solidifying to form the circuit layer.

[0038] In some possible implementation manners, the laminating the circuit layer on one side of the substrate layer includes:

[0039] Laying an insulating layer mixed with a third inert heat-conducting medium between the circuit layer and the substrate layer;

[0040] Laminating and bonding the circuit layer, the insulating layer and the substrate layer through a lamination process.

[0041] In a third aspect, the present application further provides a display device including the printed circuit board provided in each of the above embodiments. Description of the Drawings

[0042] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the accompanying drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present application and should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0043] Figure 1 Shows a schematic structural diagram of a printed circuit board in some embodiments;

[0044] Figure 2 Shows a schematic structural diagram of a printed circuit board in some other embodiments;

[0045] Figure 3 Shows a schematic flow diagram of a method for manufacturing a printed circuit board in some embodiments;

[0046] Figure 4 Shows a schematic flow diagram of providing a substrate layer in some embodiments;

[0047] Figure 5 Shows a schematic flow diagram of providing a circuit layer in some embodiments.

[0048] Main element symbol description:

[0049] 10 - Substrate layer; 11 - Fourth inert heat-conducting medium; 20 - Insulating layer; 21 - Third inert heat-conducting medium; 30 - Circuit layer; 31 - Second inert heat-conducting medium; 40 - Pad layer; 41 - First inert heat-conducting medium; 42 - Solder layer; 43 - Inert heat-conducting medium layer. Detailed description of specific embodiments

[0050] The following will describe the embodiments of the present application in detail. The examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and should not be construed as limiting the present application.

[0051] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present application.

[0052] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, "a plurality of" means two or more unless otherwise specifically defined.

[0053] In the present application, unless otherwise clearly specified and defined, terms such as "mounted", "connected", "coupled", "fixed", etc. shall be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0054] In the present application, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0055] An embodiment provides a printed circuit board, which can be used in a Micro LED display device. Among them, the printed circuit board can be a flexible printed circuit board.

[0056] In other embodiments, the printed circuit board can also be a rigid printed circuit board.

[0057] As Figure 1 shown, the printed circuit board may include a substrate layer 10, an insulating layer 20, a circuit layer 30, and a pad layer 40. The substrate layer 10, the insulating layer 20, the circuit layer 30, and the pad layer 40 may be stacked in sequence. When the printed circuit board is applied to a Micro LED display device, the Micro LED chip can be connected to the pad layer 40.

[0058] The pad layer 40 may include solder and a first inert thermal conductive medium 41. In some embodiments, the first inert thermal conductive medium 41 may be in powder form and may be uniformly mixed in the solder. In an embodiment, the particle size of the first inert thermal conductive medium 41 may be set to 5 μm to 10 μm. Exemplarily, the particle size of the first inert thermal conductive medium 41 may be 5 μm, 5.5 μm, 6.2 μm, 7 μm, 8.5 μm, 9 μm, 9.3 μm, 9.7 μm, or 10 μm, etc.

[0059] In some embodiments, the first inert thermal conductive medium 41 may be selected as boron nitride powder. Among them, boron nitride powder has good electrical insulation, thermal conductivity, and chemical corrosion resistance, stable chemical properties, is chemically inert to metals such as molten gold and aluminum, and can withstand high temperatures up to 2000 °C. In an embodiment, the boron nitride powder may be hexagonal boron nitride (h-BN), cubic boron nitride (c-BN), orthorhombic boron nitride (r-BN), wurtzite boron nitride (w-BN), etc.

[0060] In an embodiment, adding 2% to 15% of the first inert thermal conductive medium 41 to the pad layer 40 can improve the oxidation resistance of the pad layer 40 without affecting the bonding performance of the pad layer 40, that is, the oxidation rate during the use of the pad layer 40 can be reduced. Thus, the stability of the connection between the printed circuit board and the Micro LED chip can be ensured, the normal operation of the Micro LED display device can be ensured, and the service life of the Micro LED display device can be extended.

[0061] At the same time, the first inert thermal conductive medium 41 can also provide a heat conduction function in the pad layer 40, can quickly transfer the heat generated by the Micro LED chip, reduce the temperature of the Micro LED chip, and further improve the stability and brightness during the operation of the Micro LED chip, and further extend the service life of the Micro LED display device.

[0062] In some other embodiments, the first inert thermal conductive medium 41 may also be selected from other inert thermal conductive media, including but not limited to: alumina powder or aluminum nitride powder, etc. Or, the first inert thermal conductive medium 41 may also be a composition of at least two of boron nitride powder, alumina powder, and aluminum nitride powder. Among them, both alumina powder and aluminum nitride powder have high melting points, corrosion resistance, oxidation resistance, and good thermal conductivity, etc. It can be understood that when the pad layer 40 is mixed with alumina powder and / or aluminum nitride powder, the alumina powder and / or aluminum nitride powder can also provide good thermal conductivity and oxidation resistance, achieve rapid heat dissipation, and at the same time, can also delay the oxidation rate of the pad layer 40.

[0063] Such as Figure 2As shown, in some other embodiments, the first inert heat-conducting medium 41 may also be in the form of flakes. Correspondingly, the pad layer 40 may include a solder layer 42 and an inert heat-conducting medium layer 43, where the inert heat-conducting medium layer 43 may be located between the solder layer 42 and the circuit layer 30. In an embodiment, the inert heat-conducting medium layer 43 may be made of the flaky first inert heat-conducting medium 41.

[0064] As Figure 1 shown, in an embodiment, in the pad layer 40, the mass ratio of the solder may be set to 85% - 98%. The mass ratio of the first inert heat-conducting medium 41 may be set to 2% - 15%. Thus, while ensuring that the pad can be firmly connected to the Micro LED chip, the oxidation resistance and heat-conducting performance of the pad layer 40 can be increased.

[0065] In some embodiments, when the solder is aluminum, the mass ratio of the solder may be set to 85% - 95%, and the mass ratio of the first inert heat-conducting medium 41 is 5% - 15%. Exemplarily, when the solder is aluminum, the mass ratio of the solder may be set to 85%, 88.5%, 91.5%, 93%, 94.5%, 95%, etc. The mass ratio of the first inert heat-conducting medium 41 may be set to 5%, 5.5%, 7%, 8.5%, 11.5% or 15%, etc.

[0066] In some embodiments, when the solder is gold, the mass ratio of the first inert heat-conducting medium 41 is 2% - 10%, and the mass ratio of the solder may be set to 90% - 98%, or less than 90%. Exemplarily, when the solder is gold, the mass ratio of the first inert heat-conducting medium 41 may be set to 2%, 2.5%, 3%, 4.8%, 5%, 5.5%, 7%, 8.5% or 10%, etc., and the mass ratio of the solder may be set to 90%, 91.5%, 93%, 94.5%, 95%, 96.2%, 97%, 97.5% or 98%, etc.

[0067] Of course, in some other embodiments, other materials may be mixed in the pad layer 40 as needed. For example, materials such as graphene may also be mixed in the pad layer 40, which can provide a heat-conducting effect. Taking the case where the solder is gold as an example, the mass ratio of the first inert heat-conducting medium 41 is 10%, and materials such as graphene are mixed in the pad layer 40. At this time, the mass ratio of the solder is less than 90%.

[0068] As Figure 1As shown, further, in some embodiments, the circuit layer 30 may include a copper substrate and a second inert heat-conducting medium 31. The second inert heat-conducting medium 31 may also be in powder form and may be uniformly mixed in the copper substrate. Additionally, the particle size of the second inert heat-conducting medium 31 may be set to 5 μm to 10 μm. Exemplarily, the particle size of the second inert heat-conducting medium 31 may be 5 μm, 5.5 μm, 6.2 μm, 7 μm, 8.5 μm, 9 μm, 9.3 μm, 9.7 μm, or 10 μm, etc. It can be understood that the second inert heat-conducting medium 31 can also provide a heat-conducting function in the circuit layer 30 to achieve heat transfer.

[0069] In some embodiments, the second inert heat-conducting medium 31 may be selected as boron nitride powder.

[0070] In some other embodiments, the second inert heat-conducting medium 31 may also be selected from other inert heat-conducting media, including but not limited to: alumina powder or aluminum nitride powder, etc. Or, the second inert heat-conducting medium 31 may also be a composition of at least two of boron nitride powder, alumina powder, and aluminum nitride powder.

[0071] In some embodiments, in the circuit layer 30, the mass ratio of the second inert heat-conducting medium 31 may be set to 2% to 8%, and the mass ratio of the copper substrate may be set to 92% to 98%, or less than 92%. Exemplarily, the mass ratio of the second inert heat-conducting medium 31 may be set to 2%, 2.5%, 3%, 3.5%, 3.8%, 4.5%, 5%, 5.8%, 6%, 7%, 7.5%, or 8%, etc., and the mass ratio of the copper substrate may be set to 92%, 92.5%, 93%, 94%, 94.2%, 95%, 95.5%, 96.2%, 96.5%, 97%, 97.5%, or 98%, etc.

[0072] Of course, in some other embodiments, other materials may be mixed in the circuit layer 30 as needed. For example, materials such as graphene may also be mixed in the circuit layer 30, which can provide a heat-conducting effect. For example, the mass ratio of the second inert heat-conducting medium 31 is 8%, and materials such as graphene are mixed in the circuit layer 30. At this time, the mass ratio of the copper substrate is less than 92%.

[0073] As Figure 1 As shown, further, the insulating layer 20 may include a resin material, ceramic powder, silicon carbide, and a third inert heat-conducting medium 21 that are uniformly mixed. In the embodiment, the mass ratio of the resin material may be set to 20% to 40%, the mass ratio of the ceramic powder may be set to 15% to 20%, the mass ratio of the silicon carbide may be set to 15% to 20%, and the mass ratio of the third inert heat-conducting medium 21 may be set to 20% to 50%.

[0074] Exemplarily, in some embodiments, the mass ratio of the resin material can be set to 20%, 25%, 35%, 40%, etc. The mass ratio of the ceramic powder can be set to 15%, 16%, 18%, 20%, etc. The mass ratio of the silicon carbide can be set to 15%, 16%, 17%, 20%, etc. The mass ratio of the third inert heat-conducting medium 21 can be set to 20%, 30%, 43%, 50%, etc.

[0075] In some embodiments, the resin material can be selected from one or a combination of materials such as epoxy resin, polyesterimide, polyimide, etc. The ceramic powder can be ceramic micro-powder.

[0076] In some embodiments, the third inert heat-conducting medium 21 can also be boron nitride powder, and the particle size of the third inert heat-conducting medium 21 can be set to 5 μm to 10 μm. Exemplarily, the particle size of the third inert heat-conducting medium 21 can be 5 μm, 5.5 μm, 6.2 μm, 7 μm, 8.5 μm, 9 μm, 9.3 μm, 9.7 μm, 10 μm, etc.

[0077] In some other embodiments, the third inert heat-conducting medium 21 can also be selected from other inert heat-conducting media, including but not limited to: alumina powder or aluminum nitride powder, etc. Or, the third inert heat-conducting medium 21 can also be a composition of at least two of boron nitride powder, alumina powder, and aluminum nitride powder.

[0078] It can be understood that the insulating layer 20 can have adhesiveness and can provide an adhesive function for the circuit layer 30 and the substrate layer 10. Accordingly, the circuit layer 30 and the substrate layer 10 can be bonded through the insulating layer 20. In the embodiment, the third inert heat-conducting medium 21 is added to the insulating layer 20, which can increase the heat conduction efficiency of the insulating layer 20 and increase the heat conduction rate between the circuit layer 30 and the substrate layer 10, that is, the heat transfer speed in the printed circuit board can be improved to quickly transfer and dissipate the heat generated by the Micro LED chip.

[0079] As Figure 1 shown, further, the substrate layer 10 can include an aluminum substrate and a fourth inert heat-conducting medium 11. Among them, the fourth inert heat-conducting medium 11 can also be in powder form, and the fourth inert heat-conducting medium 11 can be uniformly mixed in the aluminum substrate. In the embodiment, the particle size of the fourth inert heat-conducting medium 11 can be set to 5 μm to 10 μm. Exemplarily, the particle size of the fourth inert heat-conducting medium 11 can be 5 μm, 5.5 μm, 6.2 μm, 7 μm, 8.5 μm, 9 μm, 9.3 μm, 9.7 μm, 10 μm, etc.

[0080] In some embodiments, the fourth inert heat-conducting medium 11 can be selected from boron nitride powder.

[0081] In some other embodiments, the fourth inert heat-conducting medium 11 may also be selected from other inert heat-conducting media, including but not limited to: alumina powder, aluminum nitride powder, etc. Alternatively, the fourth inert heat-conducting medium 11 may also be a composition of at least two of boron nitride powder, alumina powder, and aluminum nitride powder.

[0082] In an embodiment, in the substrate layer 10, the mass ratio of the fourth inert heat-conducting medium 11 may be set to 10% - 50%, and the mass ratio of the aluminum substrate may be set to 50% - 90%, or less than 50%. Exemplarily, in some embodiments, the mass ratio of the fourth inert heat-conducting medium 11 may be set to 10%, 12.5%, 15%, 18%, 19.5%, 24%, 26.5%, 28%, 31.5%, 34%, 37%, 40%, 42.5%, 45%, 48%, or 50%, etc., and the mass ratio of the aluminum substrate may be set to 50%, 52%, 55%, 57.5%, 60%, 63%, 66%, 68.5%, 72%, 73.5%, 76%, 80.5%, 82%, 85%, 87.5%, or 90%, etc.

[0083] In an embodiment, the fourth inert heat-conducting medium 11 is mixed in the substrate layer 10. On the one hand, the fourth inert heat-conducting medium 11 can be used for heat conduction in the substrate layer 10, accelerating the heat dissipation in the Micro LED display device, improving the working stability of the Micro LED display device, and extending the service life of the Micro LED display device. On the other hand, it can also enhance the antioxidant property of the substrate layer 10, further extending the service life of the Micro LED display device.

[0084] Of course, in some other embodiments, other materials may be mixed in the pad layer 40 as needed. For example, materials such as graphene may also be mixed in the substrate layer 10 to provide heat-conducting effects.

[0085] In the traditional process, the FPC usually improves its heat dissipation function by adding one or more graphene heat-dissipating layers. However, the manufacturing cost of graphene is high, undoubtedly increasing the processing cost of the Micro LED display device. Additionally, by adding the heat-dissipating layer, it will also cause an increase in the thickness of the FPC, resulting in an increase in thermal resistance and making it inapplicable to ultra-thin Micro LED display devices.

[0086] In this application, by adding boron nitride powder to each structural layer in the printed circuit board, on the one hand, the overall thermal conductivity of the printed circuit board can be improved, and the service life of the Micro LED display device can be extended. On the other hand, compared with completely dissipating heat through the graphene layer, this application can reduce the production cost of the printed circuit board. In addition, by adding boron nitride powder to the pad layer, the oxidation resistance of the pad layer can also be increased, ensuring the stability of the connection between the printed circuit board and the Micro LED chip.

[0087] As Figure 1 and Figure 3 shown, in the embodiment, a method for preparing a printed circuit board is also provided, which may include the following steps:

[0088] S10, respectively provide a substrate layer 10 and a circuit layer 30.

[0089] Then, in combination with Figure 4 , in some embodiments, providing the substrate layer 10 may include:

[0090] S111, heat and melt the aluminum substrate.

[0091] Specifically, the solid aluminum substrate can be heated and melted to obtain a molten aluminum substrate.

[0092] S112, add a fourth inert thermal conductive medium 11 to the molten aluminum substrate, and stir the fourth inert thermal conductive medium 11 and the molten aluminum substrate.

[0093] In some embodiments, the fourth inert thermal conductive medium 11 can be selected as boron nitride powder. In the embodiment, a certain proportion of boron nitride powder can be mixed into the molten aluminum substrate and mixed evenly. In the substrate layer, the mass ratio of the fourth inert thermal conductive medium 11 can be set to 10% - 50%.

[0094] S113, cool and solidify to form the substrate layer 10.

[0095] That is, the molten aluminum substrate mixed with the fourth inert thermal conductive medium 11 is cooled and solidified to produce the substrate layer 10.

[0096] Then, in combination with Figure 5 , in some embodiments, providing the circuit layer 30 may include:

[0097] S121, heat and melt the copper substrate.

[0098] Specifically, the solid copper substrate can be heated and melted to obtain a molten copper substrate.

[0099] S122. Add a second inert heat-conducting medium 31 to the molten copper substrate, and stir the second inert heat-conducting medium 31 and the molten copper substrate.

[0100] In some embodiments, the second inert heat-conducting medium 31 can be selected as boron nitride powder. In the embodiments, a certain proportion of boron nitride powder can be added to the molten copper substrate and mixed evenly. In the embodiments, in the circuit layer 30, the mass proportion of the second inert heat-conducting medium 31 can be set to 2% - 8%.

[0101] S123. Cool and solidify to form the circuit layer 30.

[0102] That is, cool and solidify the molten copper substrate mixed with the second inert heat-conducting medium 31 to produce the circuit layer 30.

[0103] S20. Press the circuit layer 30 on one side of the substrate layer 10.

[0104] Specifically, in some embodiments, an insulating layer 20 can be arranged between the circuit layer 30 and the substrate layer 10, and they are press-bonded through a pressing process. Among them, 20% - 50% of a third inert heat-conducting medium 21 can be mixed in the insulating layer 20 to improve the heat conduction efficiency of the insulating layer 20.

[0105] S30. Prepare a pad layer 40 mixed with a first inert heat-conducting medium 41 on the side of the circuit layer 30 away from the substrate layer 10.

[0106] In some embodiments, the first inert heat-conducting medium 41 can be selected as boron nitride powder. In the embodiments, the solder can be melted by high-temperature heating, and a certain proportion of boron nitride powder can be added to the molten solder and stirred evenly. Then, the pad can be plated at specific positions on the circuit layer 30 through an electroplating process to obtain the pad layer 40.

[0107] In some embodiments, the mass ratio of the first inert heat-conducting medium 41 in the pad layer 40 can be set to 2% - 15%. In the embodiments, adding the first inert heat-conducting medium 41 to the pad layer 40 can improve the oxidation resistance of the pad layer 40, and further ensure a stable connection between the printed circuit board and the Micro LED chip, and extend the service life of the Micro LED display device.

[0108] It can be understood that in some embodiments, before step S10, it may further include the step of extracting boron nitride powder. Specifically, ultrasonic-assisted organic solvent isopropanol can be used to exfoliate bulk hexagonal boron nitride. Then, static centrifugation is carried out for transfer to obtain few-layer hexagonal boron nitride nanosheets. On this basis, a silane coupling agent can be added to the hexagonal boron nitride nanosheet suspension as needed, and the intermittent mode of ultrasonic waves is controlled for modification to obtain modified hexagonal boron nitride.

[0109] In some embodiments, operations such as developing, etching, and film coating of the circuit layer 30 may also be included between step S20 and step S30, which will not be elaborated herein.

[0110] The embodiment also provides a display device, which may include the printed circuit board provided in the embodiment.

[0111] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0112] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Claims

1. A printed circuit board, characterized in that, It includes a substrate layer, an insulating layer, a circuit layer, and a pad layer which are stacked in sequence; Among them, the pad layer includes solder and a first inert heat-conducting medium. The first inert heat-conducting medium is in powder form and is uniformly mixed in the solder. The first inert heat-conducting medium includes at least one of boron nitride powder, alumina powder, and aluminum nitride powder; the pad layer is used to connect with a device; In the pad layer, the mass ratio of the first inert heat-conducting medium is 2% - 15%; The circuit layer includes a copper substrate and a second inert heat-conducting medium. The second inert heat-conducting medium is mixed in the copper substrate. In the circuit layer, the mass ratio of the second inert heat-conducting medium is 2% - 8%; The insulating layer at least includes a resin material and a third inert heat-conducting medium mixed together. In the insulating layer, the mass ratio of the third inert heat-conducting medium is 20% - 50%; The substrate layer includes an aluminum substrate and a fourth inert heat-conducting medium. The fourth inert heat-conducting medium is mixed in the aluminum substrate. In the substrate layer, the mass ratio of the fourth inert heat-conducting medium is 10% - 50%.

2. The printed circuit board according to claim 1, wherein The solder is aluminum; In the pad layer, the mass ratio of the first inert heat-conducting medium is 5% - 15%.

3. The printed circuit board according to claim 1, characterized in that The solder is gold; In the pad layer, the mass ratio of the first inert heat-conducting medium is 2% - 10%.

4. A method for preparing a printed circuit board, characterized in that, For preparing the printed circuit board according to any one of claims  1 to 3, the method for preparing the printed circuit board includes: Providing a substrate layer and a circuit layer respectively; Pressing the circuit layer on one side of the substrate layer; Preparing a pad layer mixed with a first inert heat-conducting medium on the side of the circuit layer away from the substrate layer.

5. The method for preparing a printed circuit board according to claim 4, wherein The step of respectively providing a substrate layer and a circuit layer includes: Heating and melting an aluminum substrate; Adding a fourth inert heat-conducting medium to the molten aluminum substrate and stirring the fourth inert heat-conducting medium and the molten aluminum substrate; Cooling and solidifying to form the substrate layer.

6. The method for preparing a printed circuit board according to claim 4, wherein The step of respectively providing a substrate layer and a circuit layer includes: Heating and melting a copper substrate; Adding a second inert heat-conducting medium to the molten copper substrate and stirring the second inert heat-conducting medium and the molten copper substrate; Cooling and solidifying to form the circuit layer.

7. The method for preparing a printed circuit board according to any one of claims 4 to 6, characterized in that, The step of pressing the circuit layer on one side of the substrate layer includes: Laying an insulating layer mixed with a third inert heat-conducting medium between the circuit layer and the substrate layer; Pressing and bonding the circuit layer, the insulating layer, and the substrate layer through a pressing process.

8. A display device, characterized in that, It includes the printed circuit board according to any one of claims 1 to 3.

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