Cover film and circuit board

Abstract

The invention discloses a cover film and a circuit board, the cover film comprises a color developing layer, the light transmittance of the color developing layer is less than or equal to 50%, and the heat conductivity coefficient of the color developing layer is greater than or equal to 20W / m.K. By adopting the technical means, the light transmittance and the heat conductivity coefficient of the color developing layer in the covering film are improved, so that the covering film can effectively shield the surface of the circuit board, meanwhile, the heat dissipation performance is excellent, and the reliability of the circuit board can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic information materials, and particularly to a cover film and a circuit board. Background Art

[0002] In existing circuit boards, a glue layer is usually provided on the surface of the circuit as a protective film. By covering the entire surface of the circuit board with the protective film, functions such as protection, moisture and dust prevention, and interlayer insulation are achieved. At the same time, it also has a certain identification and aesthetic function.

[0003] However, the protective film currently covering the circuit board is generally light yellow and transparent, with poor uniformity and serious light leakage. It is difficult to effectively block the surface of the circuit board in actual scenarios. At the same time, the existing cover film has poor heat dissipation effect, affecting the reliability of the circuit board. Summary of the Invention

[0004] The purpose of the embodiments of the present invention is to provide a cover film and a circuit board, which can effectively block the surface of the circuit board, and at the same time have excellent heat dissipation performance, and can effectively improve the reliability of the circuit board.

[0005] To achieve the above purpose, the embodiments of the present invention provide a cover film, including a color display layer, the light transmittance of the color display layer is less than or equal to 50%, and the thermal conductivity coefficient of the color display layer is greater than or equal to 20 W / m·K.

[0006] As an improvement of the above solution, the color display layer contains filler particles, and the filler particles include ceramic fillers; the ceramic fillers include alumina and zirconia.

[0007] As an improvement of the above solution, in the color display layer, the maximum diameter of 60% - 92% of the filler particles satisfies 0.1μm < W ≤ 5μm, and the maximum diameter of 8% - 40% of the filler particles satisfies 5μm < W ≤ 10μm, where the percentage sum of the filler particles within the above two maximum diameter ranges is 100%;

[0008] As an improvement of the above solution, in the color display layer, the mass fraction of the filler particles accounts for 5% - 30% of the total mass fraction of the color display layer.

[0009] As an improvement of the above solution, the morphology of the filler particles includes sheet-like and spherical.

[0010] As an improvement of the above solution, it further includes an adhesive layer, and the adhesive layer is disposed on one side of the color display layer.

[0011] As an improvement of the above solution, the roughness of the surface of the color display layer away from the adhesive layer is 2 - 10um.

[0012] As an improvement to the above solution, the thickness of the color display layer is 3 - 40 um.

[0013] As an improvement to the above solution, the cover film further includes a carrier layer, and the carrier layer is detachably disposed on the surface of the color display layer away from the adhesive layer.

[0014] An embodiment of the present invention also provides a circuit board, which includes a circuit board substrate and a cover film as described in any one of the above, and the cover film is laminated with the circuit board substrate.

[0015] Compared with the prior art, for the cover film and the circuit board disclosed in the present invention, by providing a color display layer with a light transmittance less than or equal to 50% above the adhesive layer, it can effectively block the complex circuits and components on the surface of the circuit board, reduce visual interference, make the appearance of the final product cleaner and more beautiful, enhance the concealment of the product, help protect the design details and intellectual property rights of the product, and prevent technology leakage. The low light transmittance of the color display layer ensures that light is difficult to penetrate the cover film, effectively avoiding the light leakage problem caused by light transmission and reducing light pollution. Moreover, by setting the color display layer to have a high thermal conductivity coefficient greater than or equal to 20 W / m·K, it can quickly conduct and radiate the heat generated from the circuit board outward, effectively reducing the working temperature of the circuit board and improving the reliability of the circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic structural diagram of the first cover film provided by an embodiment of the present invention;

[0017] Figure 2 is a schematic structural diagram of the second cover film provided by an embodiment of the present invention;

[0018] Figure 3 is a schematic structural diagram of the third cover film provided by an embodiment of the present invention;

[0019] Figure 4 is a schematic structural diagram of the fourth cover film provided by an embodiment of the present invention

[0020] Figure 5 is a schematic structural diagram of a circuit board provided by an embodiment of the present invention;

[0021] In the figure, 10, cover film; 11, color display layer; 12, filler particles; 13, adhesive layer; 14, carrier layer; 20, circuit board; 21, circuit board substrate. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0023] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the 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 thus should not be construed as a limitation to the present application.

[0024] The terms "first" and "second" are only used for descriptive purposes, and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise specified, the meaning of "a plurality" is two or more.

[0025] In the description of the present application, it should be noted that unless otherwise clearly defined and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; 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 elements. 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.

[0026] See Figure 1 , which is a schematic structural diagram of the first covering film provided by the embodiments of the present invention. The embodiments of the present invention provide a covering film 10, including a color display layer 11, the light transmittance of the color display layer 11 is less than or equal to 50%, and the thermal conductivity coefficient of the color display layer 11 is greater than or equal to 20 W / m·K.

[0027] It should be noted that the covering film provided by the embodiments of the present invention is a protective film used to cover the surfaces of products such as circuit boards and semiconductor materials, so as to play roles such as protection, moisture-proof, dust-proof, and interlayer insulation, and at the same time, it also has the functions of identification and aesthetics.

[0028] In an embodiment of the present invention, the covering film 10 includes a color display layer 11, and the color display layer 11 mainly functions to block, protect, and beautify the circuit board. Optionally, the color display layer 11 can be any color such as red, orange, yellow, green, cyan, blue, purple, black, white, etc., and the color of the color display layer 11 can be different from the background color of the circuit board.

[0029] The light transmittance of the color display layer 11 is less than or equal to 50%, for example, it can be 50%, 48%, 45%, 43%, 40%, 35%, 30%, 25%, 21%, 17%, 14%, 12%, 10%, 8%, 6%, 3%, 0%, etc., which can make the color of the circuit board invisible, enhance the light-shielding performance, and effectively block the surface of products such as the circuit board.

[0030] Moreover, the thermal conductivity of the color display layer 11 is greater than or equal to 20 W / m·K, for example, it can be 20 W / m·K, 21 W / m·K, 22 W / m·K, 23 W / m·K, 24 W / m·K, 25 W / m·K, 28 W / m·K, 30 W / m·K, 33 W / m·K, 38 W / m·K, 40 W / m·K, 45 W / m·K, 50 W / m·K, 55 W / m·K, etc. Of course, it can also be set to other values that meet the conditions according to the actual situation, and no specific limitation is made here. The color display layer 11 can effectively dissipate the heat dissipated in the covering film from products such as the circuit board to the outside quickly while improving the blocking property, improve the heat dissipation efficiency, and ensure the reliability of the circuit board.

[0031] Of course, the above values of the light transmittance and thermal conductivity of the color display layer are only examples, and they can also be set to other values that meet the conditions according to the actual situation, and no specific limitation is made here.

[0032] By adopting the technical means of the embodiment of the present invention, the covering film has at least the following beneficial effects:

[0033] (1) Improve visual aesthetics and concealment: The covering film includes a color display layer with a light transmittance less than or equal to 50%, which can not only effectively block the complex circuits and components on the surface of the circuit board, reduce visual interference, make the appearance of the final product cleaner and more beautiful, but also enhance the concealment of the product, help protect the design details and intellectual property rights of the product, and prevent technology leakage.

[0034] (2) Enhance light-shielding performance and reduce optical interference: The low light transmittance of the color display layer ensures that light is difficult to penetrate the covering film, effectively avoiding the light leakage problem caused by light transmission. This is particularly important for electronic devices that require strict control of the light environment, such as display backlight modules, LED lighting systems, etc., which can reduce light pollution and improve display quality or lighting uniformity.

[0035] (3) High - efficient heat dissipation to enhance system stability: The color - showing layer has a thermal conductivity greater than or equal to 20 W / m·K, which can quickly conduct and radiate the heat generated from the circuit board outward, effectively reducing the operating temperature of the circuit board, and reducing the risks of performance degradation, component aging, and even failures caused by overheating, thus significantly improving the reliability of the circuit board.

[0036] (4) Simplify the manufacturing process and reduce costs: For the cover film with this structure, through an integrated design, additional light - shielding or heat - dissipation treatment steps are reduced, simplifying the production process and reducing the manufacturing cost. At the same time, the laminated arrangement of the color - showing layer and the adhesive layer facilitates automated mounting and improves production efficiency.

[0037] (5) Environmental protection and energy conservation: The high - efficient heat - dissipation ability helps reduce the need to rely on additional heat - dissipation devices (such as fans and radiators) due to overheating, thereby reducing energy consumption and carbon footprint, which is in line with the current green and energy - saving development trend.

[0038] As a preferred embodiment, referring to Figure 2 , it is a schematic structural diagram of the second cover film provided by the embodiment of the present invention. The color - showing layer 11 contains filler particles 12, and the composition of the filler particles 12 includes ceramic fillers. Filling the ceramic fillers in the color - showing layer can further improve the heat - dissipation function of the cover film.

[0039] Preferably, the ceramic fillers include alumina, zirconia, boron nitride, and / or silicon carbide.

[0040] Ceramic materials such as alumina (Al2O3), zirconia (ZrO2), boron nitride, and silicon carbide have high thermal conductivity. During the preparation process of the cover film, adding an appropriate amount of ceramic microparticles can effectively improve the thermal conductivity, enabling the entire coating system to dissipate heat more quickly when heated and avoiding local overheating. For example, by filling high - thermal - conductivity fillers such as zirconia, boron nitride, and silicon carbide, heat - flow paths can be formed within the entire color - showing layer, improving the heat - dissipation effect of the color - showing layer. In addition, ceramic fillers usually have high hardness and wear resistance, and can also enhance the physical properties of the color - showing layer, contributing to extending the service life of the color - showing layer.

[0041] As a preferred embodiment, in the color - showing layer, 60% - 92% of the filler particles have a maximum diameter satisfying 0.1μm < W ≤ 5μm, and 8% - 40% of the filler particles have a maximum diameter satisfying 5μm < W ≤ 10μm, where the sum of the percentages of the filler particles within the above two maximum - diameter ranges is 100%;

[0042] It should be noted that the maximum diameter refers to the straight - line distance between the two farthest points on the contour of the filler particles in the sliced state.

[0043] In an embodiment of the present invention, the structure of the color display layer is further optimized. By filling filler particles composed of ceramic fillers in the color display layer, the ceramic fillers have a heat dissipation function. Further, the maximum diameter of more filler particles is set to be between 0.1 μm and 5 μm, while the maximum diameter of fewer filler particles is set to be between 5 μm and 10 μm. By setting a mixed particle size of different sizes in the color display layer 11, large particles can effectively reduce costs, and small particles can fill the gaps. The combination of large particles and small particles can effectively increase the density of the heat conduction network, enhance the heat dissipation ability, and reduce the light transmittance. The filler particles in this particle size range are more evenly dispersed in the color display layer, and the gaps are more reasonable, which can ensure high heat dissipation efficiency. At the same time, it will not affect the bending resistance of the color display layer due to too large filler particles.

[0044] As a preferred embodiment, in the color display layer, the mass fraction of the filler particles accounts for 5% - 30% of the total mass fraction of the color display layer.

[0045] In an embodiment of the present invention, the mass ratio of the filler particles in the color display layer is further optimized. By setting the mass fraction of the filler particles to account for 5% - 30% of the total mass fraction of the entire color display layer, for example, it can be 5%, 5.5%, 6%, 7%, 8%, 9%, 10%, 12%, 15%, 18%, 20%, 23%, 25%, 26%, 27%, 28%, 29%, 30%, etc. Excessive fillers (such as a filling amount greater than 30%) may cause an increase in the brittleness of the covering film. Although the light transmittance can be reduced, the tensile strength decreases. While too few fillers (a filling amount less than 5%) will result in an insignificant heat dissipation performance, and the light transmittance may be too large and the shielding effect is poor. In the embodiment of the present invention, the mass ratio of the filler particles in the color display layer is controlled within the above range, and a continuous heat conduction network is formed between the particles, and the thermal conductivity is significantly improved (up to 5 - 10 times that of the substrate), effectively improving the heat dissipation efficiency of the color display layer, and achieving a smaller light transmittance, realizing a better shielding effect, while avoiding an excessive mass ratio of the filler particles that is likely to increase the hardness of the color display layer and not affecting the tensile performance and bending resistance of the covering film.

[0046] More preferably, the morphology of the filler particles includes sheet-like and spherical shapes.

[0047] In an embodiment of the present invention, by setting the filler particles as a heterogeneous structure, through the combination of structures such as BN (sheet-like) and AlN (spherical), the interfacial thermal resistance is reduced by using shape complementarity, thereby effectively improving the heat dissipation efficiency of the color display layer.

[0048] By adopting the technical means of the embodiments of the present invention and adding a ceramic material with high thermal conductivity to the color display layer, the heat dissipation function of the cover film can be effectively improved, and the filling of the ceramic filler can further improve the quality of the cover film.

[0049] As a preferred embodiment, the embodiments of the present invention are further implemented on the basis of any of the above embodiments. Refer to Figure 3 , which is a schematic structural diagram of the third cover film provided by the embodiments of the present invention. The cover film further includes an adhesive layer 13, and the adhesive layer 13 is disposed on one side of the color display layer 11.

[0050] In the embodiments of the present invention, the cover film 10 includes an adhesive layer 13, and through the adhesive layer 13, the cover film can be thermally pressed and adhered to the surface of the circuit board. The color of the adhesive layer 13 can be different from the background color of the circuit board or different from the color of the color display layer 11.

[0051] Preferably, the roughness of the surface of the color display layer on the side away from the adhesive layer is 2 to 10 μm.

[0052] In the embodiments of the present invention, appropriately increasing the surface roughness of the cover film 10 can also improve the thermal emissivity. The rough surface can increase the surface area of thermal radiation, enabling the object to radiate heat outward in more directions and angles. Therefore, in the embodiments of the present invention, the roughness of the outer surface of the color display layer 11 is further optimized so that the roughness of this surface is between 2 and 10 μm, such as 2 μm, 2.3 μm, 2.5 μm, 2.8 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.2 μm, 8.5 μm, 8.7 μm, 9 μm, 9.4 μm, 9.5 μm, 10 μm, etc. Of course, it can also be set to other qualified values according to the actual situation, and no specific limitation is made here.

[0053] The way to increase the surface roughness of the cover film 10 can be to form a micro-nano structure on the surface of the cover film through a special spraying process, such as micro-pits, micro-protrusions, etc., which can improve the thermal emissivity. Of course, it can also be other ways to increase the surface roughness of the cover film, and no specific limitation is made here.

[0054] In the embodiments of the present invention, the color settings of the color display layer 11 and the adhesive layer 13 can be quite different, so as to achieve an effective shielding effect. Optionally, the color display layer can be a light color system, and the adhesive layer is set as a dark color system; or, the color display layer can be a dark color system, and the adhesive layer is set as a light color system.

[0055] As a preferred embodiment, the color display layer is a white ink layer or a film layer; the adhesive layer is a black film layer.

[0056] As a preferred embodiment, the embodiment of the present invention is further implemented on the basis of any of the above embodiments, and the thickness of the color display layer is 3 to 40 μm.

[0057] In the embodiment of the present invention, the color display layer 11 needs a certain thickness to well cover the surface of products such as circuit boards, so that only the color of the color display layer 11 is observed from the outside. However, the overall thickness of the covering film cannot be too thick to avoid occupying space and affecting the miniaturization of the circuit board.

[0058] Therefore, the embodiment of the present invention further optimizes the thickness of the color display layer 11, so that the thickness of the color display layer 11 is between 3 and 40 μm. For example, it can be 3 μm, 5 μm, 6 μm, 8 μm, 9 μm, 10 μm, 13 μm, 15 μm, 17 μm, 20 μm, 24 μm, 26 μm, 30 μm, 35 μm, 40 μm, etc. Of course, it can also be set to other qualified values according to the actual situation, and no specific limitation is made here.

[0059] By adopting the technical means of the embodiment of the present invention, by controlling the thickness of the color display layer within a reasonable thickness range, neither too large nor too small, it can effectively avoid the excessive thickness of the covering film from occupying space and affecting the quality of products such as circuit boards, and at the same time avoid the too small thickness of the covering film from being unable to play a good covering role for products such as circuit boards. The improvement of the embodiment of the present invention can effectively improve the shielding and protection functions of the covering film and improve the quality of the covered products such as circuit boards.

[0060] As a preferred embodiment, the embodiment of the present invention is further implemented on the basis of any of the above embodiments. Refer to Figure 4 , which is a schematic structural diagram of the fourth covering film provided by the embodiment of the present invention. The covering film 10 further includes a carrier layer 14, and the carrier layer 14 is detachably disposed on the surface of the color display layer 11 away from the adhesive layer 13.

[0061] In the embodiment of the present invention, generally when pressing the covering film, a carrier layer 14 is set as an intermediate medium. The carrier layer 14 is used to carry and protect the covering film, so that the covering film is not damaged by external contact or collision, etc. After the covering film and an application carrier such as a circuit substrate are hot-pressed through the carrier layer 14, the carrier layer 14 is peeled off.

[0062] The performance of the ordinary covering film and the covering film with the structure of the embodiment of the present invention are respectively tested with specific examples.

[0063] The test data such as the light transmittance and thermal conductivity of the color display layer of the covering film S with the structure of the embodiment of the present invention and the control covering film R are shown in Table 1:

[0064] Table 1

[0065] Covering film Light transmittance of the color-developing layer (%) Thermal conductivity (W / m·K) Sample S1 50％ 20 W / m·K Sample S2 40％ 25 W / m·K Sample S3 30％ 28 W / m·K Sample S4 20％ 31 W / m·K Sample S5 10％ 35 W / m·K Control R1 60％ 5 W / m·K Control R2 70％ 3 W / m·K

[0066] The comparison results of the shielding effect and heat dissipation effect between the cover film S of the structure of the embodiment of the present invention and the control cover film R are shown in Table 2 as follows:

[0067] Table 2

[0068] Covering film Blocking effect Thermal conductivity Sample S1 Completely blocked, no light leakage 48％ Sample S2 Completely blocked, no light leakage 52％ Sample S3 Completely blocked, no light leakage 53％ Sample S4 Completely blocked, no light leakage 58％ Sample S5 Completely blocked, no light leakage 62％ Control R1 Partially blocked, with light leakage 15％ Control R2 Partially blocked, with light leakage 11％

[0069] It should be noted that the shielding effect is measured by the direct observation method, and the thermal conductivity refers to the change rate of the temperature between the substrate with the cover film of the present application and the substrate with the ordinary cover film under the same test conditions.

[0070] It can be seen from the experimental data in Table 2 that compared with the cover film samples in the comparative example, the cover film of the present invention has a better shielding effect and a higher thermal conductivity, indicating that the cover film of the present invention has more excellent performance.

[0071] See Figure 5 , which is a schematic structural diagram of a circuit board provided by an embodiment of the present invention. The embodiment of the present invention also provides a circuit board 20, which includes a circuit board substrate 21 and a cover film 10 as described in any of the above embodiments. The cover film 10 is laminated with the circuit board substrate 21.

[0072] It should be noted that the cover film includes a color display layer 11, and its specific structure can refer to the structure of the cover film described in any of the above embodiments, which will not be elaborated here.

[0073] By adopting the technical means of the embodiment of the present invention, the structure of the cover film covering the circuit board substrate is improved, the light transmittance of the cover film is controlled to be small, the light shielding performance is enhanced, so as to effectively shield and protect the surface of the circuit board, and it also has an aesthetic effect. At the same time, the cover film is controlled to have a high thermal conductivity coefficient, which can effectively dissipate the heat dissipated in the cover film in the circuit board quickly to the outside, improve the heat dissipation efficiency, and ensure the reliability of the circuit board. Through the structural improvement of the cover film, it is applicable to the production of high-frequency and high-density circuit boards, can effectively improve the quality of the cover film products, and then improve the quality and storage effect of the circuit board products, and reduce the defective rate of the circuit board products.

[0074] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A covering film, characterized in that, It includes a color display layer, the light transmittance of the color display layer is less than or equal to 50%, and the thermal conductivity of the color display layer is greater than or equal to 20 W / m·K.

2. The covering film according to claim 1, characterized in that, The color display layer contains filler particles, and the filler particles include ceramic fillers; the ceramic fillers include alumina and zirconia.

3. The cover film according to claim 2, wherein In the color display layer, the maximum diameters of 60% - 92% of the filler particles satisfy 0.1 μm < W ≤ 5 μm, and the maximum diameters of 8% - 40% of the filler particles satisfy 5 μm < W ≤ 10 μm, where the sum of the percentages of the filler particles within the above two maximum diameter ranges is 100%.

4. The cover film according to claim 2, wherein In the color display layer, the mass fraction of the filler particles accounts for 5% - 30% of the total mass fraction of the color display layer.

5. The cover film according to claim 2, wherein The morphology of the filler particles includes sheet-like and spherical.

6. The cover film according to claim 1, characterized in that, It further includes an adhesive layer, and the adhesive layer is placed on one side of the color display layer.

7. The cover film according to claim 6, wherein The surface roughness of the side of the color display layer away from the adhesive layer is 2 - 10 μm.

8. The cover film according to claim 1, wherein The thickness of the color display layer is 3 - 40 μm.

9. The cover film according to claim 6, characterized in that It further includes a carrier layer, and the carrier layer is detachably provided on the surface of the color display layer away from the adhesive layer.

10. A circuit board, characterized in that, The circuit board includes a circuit board substrate and a cover film as described in any one of claims 1 to 9, and the cover film is laminated with the circuit board substrate.

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