Composite metal foil and metal-clad laminated plate

Abstract

The embodiment of the invention discloses a composite metal foil and a metal-clad laminate. The composite metal foil comprises a circuit layer and a resistive layer provided with a dielectric layer, the resistance layer is arranged on the circuit layer, and the dielectric layer is arranged on one side, away from the circuit layer, of the resistance layer; the tensile strength of the dielectric layer is greater than or equal to 100Mpa; one side, far away from the resistance layer, of the dielectric layer is pressed on a base material of the circuit board; after lamination, the sheet resistance uniformity of the resistive layer is less than or equal to 50%. According to the invention, the dielectric layer with the set tensile strength is arranged at one side, far away from the circuit layer, of the resistance layer, and the dielectric layer plays a role in buffering and fixing the resistance layer; the technical problems that in the prior art, the resistance characteristic fluctuation of the resistance layer is large, the resistance value uniformity deviation is large, and the sheet resistance uniformity is poor due to the fact that cracks and damage are prone to occurring when the resistance layer and the base material are in direct contact pressing are solved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of electronic devices, and in particular to a composite metal foil and a metal-clad laminate. Background Art

[0002] Currently, there are two main manufacturing processes for flexible copper-clad laminates: lamination and copper plating. Since the embedded resistor layer is plated on the copper foil surface through a vacuum sputtering process and then laminated, during the traditional lamination process, one side of the resistor layer is directly in contact with the substrate of the circuit board. At this time, the resistor layer may undergo a violent cross-linking reaction under the influence of high temperature and high pressure conditions, generating lateral tensile stress on the resistor layer, causing the resistor layer to be prone to cracks and damage after lamination. This results in large fluctuations in the resistance characteristics of the resistor layer, a resistance uniformity deviation of more than 150%, and poor square resistance uniformity. Summary of the Invention

[0003] The embodiments of the present invention provide a composite metal foil and a metal-clad laminate, which solve the technical problems in the prior art of large fluctuations in the resistance characteristics of the resistor layer, large deviations in resistance uniformity, and poor square resistance uniformity caused by cracks and damage easily occurring when the resistor layer is directly pressed into contact with the substrate.

[0004] An embodiment of the present invention provides a composite metal foil, comprising a circuit layer and a resistance layer provided with a dielectric layer;

[0005] The resistance layer is arranged on the circuit layer, and the dielectric layer is arranged on a side of the resistance layer away from the circuit layer;

[0006] The tensile strength of the dielectric layer is greater than or equal to 100 MPa;

[0007] The side of the dielectric layer away from the resistance layer is used for pressing onto the substrate of the circuit board;

[0008] After lamination, the square resistance uniformity of the resistance layer is less than or equal to 50%.

[0009] Furthermore, when the pressing temperature is between 200° C. and 400° C., after pressing, the change rate of the tensile strength of the dielectric layer is less than or equal to 5%.

[0010] Furthermore, the thickness of the dielectric layer is 20 μm to 50 μm.

[0011] Furthermore, the elastic modulus of the dielectric layer is greater than or equal to 3 GPa.

[0012] Furthermore, after lamination, the expansion and contraction rate of the dielectric layer is less than or equal to 0.05%.

[0013] Furthermore, the roughness of a side of the circuit layer close to the resistance layer is less than or equal to 3 μm.

[0014] Furthermore, an adhesive layer is provided on a side of the dielectric layer away from the resistance layer; the dielectric layer is bonded and pressed to the substrate via the adhesive layer;

[0015] The material of the adhesive layer is the same as that of the dielectric layer, or the material of the adhesive layer is the same as that of the substrate.

[0016] Furthermore, the resistance layer is a thermistor layer; the resistance layer has a positive temperature coefficient or a negative temperature coefficient.

[0017] Furthermore, the square resistance uniformity is calculated as follows: square resistance range / square resistance mean.

[0018] An embodiment of the present invention further provides a metal-clad laminate, which includes the composite metal foil described in any of the above embodiments.

[0019] Embodiments of the present invention disclose a composite metal foil and a metal-clad laminate. The composite metal foil includes a circuit layer and a resistor layer provided with a dielectric layer. The resistor layer is provided on the circuit layer, and the dielectric layer is provided on a side of the resistor layer away from the circuit layer. The dielectric layer has a tensile strength greater than or equal to 100 MPa. The side of the dielectric layer away from the resistor layer is used for lamination onto a substrate of a circuit board. After lamination, the square resistance uniformity of the resistor layer is less than or equal to 50%. By providing a dielectric layer with a set tensile strength on the side of the resistor layer away from the circuit layer, the dielectric layer acts as a buffer and solidifier for the resistor layer. This solves the technical problems in the prior art of the resistor layer being prone to cracking and damage during direct contact lamination between the resistor layer and the substrate, resulting in large fluctuations in the resistance characteristics, large deviations in resistance uniformity, and poor square resistance uniformity. This reduces the lateral tensile stress on the resistor layer during lamination, prevents tearing and damage in the resistor layer, reduces resistance fluctuations in the resistor layer, and improves the square resistance uniformity of the resistor layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a structural diagram of a composite metal foil provided by an embodiment of the present invention;

[0021] Figure 2 This is an electron microscope image of the surface morphology of the resistor layer without a dielectric layer after lamination provided by an embodiment of the present invention;

[0022] Figure 3 This is an electron microscope image of the surface morphology of the resistor layer provided with a dielectric layer after lamination provided by an embodiment of the present invention.

[0023] Figure 4 This is a structural diagram of another composite metal foil provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0025] It should be noted that the terms "first," "second," and so on, in the specification, claims, and drawings of the present invention are used to distinguish different objects, and are not intended to limit a specific order. The following embodiments of the present invention can be implemented independently or in combination with each other, and the present invention does not impose specific limitations on this.

[0026] Figure 1 This is a structural diagram of a composite metal foil provided by an embodiment of the present invention.

[0027] like Figure 1 As shown, the composite metal foil includes a circuit layer 10 and a resistor layer 20 provided with a dielectric layer 30;

[0028] The resistor layer 20 is disposed on the circuit layer 10, and the dielectric layer 30 is disposed on a side of the resistor layer 20 away from the circuit layer 10; the tensile strength of the dielectric layer 30 is greater than or equal to 100 MPa; the side of the dielectric layer 30 away from the resistor layer 20 is used for lamination onto the substrate of the circuit board; after lamination, the square resistance uniformity of the resistor layer 20 is less than or equal to 50%.

[0029] Specifically, the circuit layer 10 is generally a copper foil layer, and the dielectric layer 30 is made of a flexible dielectric material that balances flexibility and high temperature resistance and is commonly used in flexible circuit boards. Tensile strength refers to the ability of a material to resist breaking under tension, and is measured in MPa or N / mm. 2 Generally, the higher the tensile strength, the lower the elongation. Therefore, in the embodiment of the present invention, the tensile strength of dielectric layer 30 is set to be greater than or equal to 100 MPa. Dielectric layer 30 is evenly formed on one side of resistor layer 20 by coating and then cured to provide buffering protection for resistor layer 20. During lamination, dielectric layer 30 can eliminate most of the lateral tensile stress, preventing the resistor layer 20 from tearing and damage due to expansion and contraction.

[0030] Alternatively, the dielectric layer 30 may be formed on one surface of the resistance layer 20 by a coating method.

[0031] In an embodiment of the present invention, the preparation process of the composite metal foil is as follows:

[0032] First, clean the circuit layer. Clean the circuit layer 10 to remove surface impurities to improve the adhesion of the resistor material during the sputtering process. For example, plasma treatment can be performed on the circuit layer 10 to further enhance surface activity.

[0033] Second, vacuum sputtering is used to form the resistor layer. The prepared copper foil circuit layer 10 is placed in a vacuum sputtering machine. A suitable target material is selected, and sputtering process parameters, including power, current, sputtering time, and gas flow rate, are adjusted to ensure uniform deposition of the resistor layer. Typically, the thickness of the resistor material deposited is 50-200nm, which can be adjusted based on the desired resistance characteristics.

[0034] Third, the dielectric layer coating process. Dissolve an appropriate dielectric material into a suitable solution or slurry, and evenly apply the solution to the surface of the resistor layer 20 using methods such as spin coating, blade coating, or spraying. During the coating process, the coating thickness is controlled to ensure that the dielectric layer 30 covers the entire resistor layer 20 without affecting the electrical properties of the resistor layer 20. The coated dielectric layer 30 is then dried or heat-treated to semi-cure and form a uniform dielectric layer 30. The semi-cured dielectric material also requires further dehydration and cyclization to ensure that the dielectric material has good electrical insulation properties, mechanical properties, and chemical stability.

[0035] For example, the material of the dielectric layer 30 can be realized by polymer blending and nanofiller compounding. By blending polyimide (PI) and polyethylene terephthalate (PET), adding nanofillers for compounding, and then forming the final composite dielectric material by coating.

[0036] Because PI has excellent thermal stability (> 400 DEG C) and mechanical strength (tensile strength > 100MPa), but cost is higher; And the mechanical strength of PET is moderate (tensile strength ≈ 55MPa), and processability is good and cost is low, but temperature resistance is poor (long-term use < 120 DEG C); Therefore the present embodiment is blended by a certain ratio by both, and improves interfacial compatibility by compatibilizer (such as epoxy resin), can collaboratively promote heat resistance and processability. In addition in the present embodiment, nanofiller is also added in blend to coordinately enhance material performance, nanofiller includes POSS (cage type silsesquioxane), POSS can effectively improve mechanical strength (tensile strength promotes 40%), reduce dielectric constant, enhance thermal stability, and improve PI / PET interface bonding force, can reduce the micro-crack of coating molding.

[0037] The dielectric material formed by the above-mentioned polymer blend and nanofiller composite can achieve the following effects: tensile strength: >100MPa (close to the level of pure PI), dielectric constant: 1.7~2.3 (1MHz), dielectric loss: <0.005, temperature resistance: long-term use >200℃.

[0038] In this embodiment, preferably, the dielectric layer material mixture comprises 70-80 wt% PI, 20-30 wt% PET, and 3-5 wt% POSS, with the total weight fraction of the three not exceeding 100%. The proportions can be adjusted according to actual conditions.

[0039] Figure 2 This is an electron microscope image of the surface morphology of the resistor layer without a dielectric layer after lamination provided by an embodiment of the present invention. Figure 3 This is an electron microscope image of the surface morphology of the resistor layer provided with a dielectric layer after lamination, provided by an embodiment of the present invention. Figure 2 The position framed by the square box is the fracture and damage part (only part of the fracture and damage part is framed for example). Figure 2 and Figure 3 By comparison, it can be seen that the resistance layer without the dielectric layer has more cracks and damages after lamination, while the resistance layer with the dielectric layer still maintains good integrity after lamination.

[0040] The present invention provides a dielectric layer with a set tensile strength on the side of the resistor layer away from the circuit layer. The dielectric layer acts as a buffer and solidifier for the resistor layer, thereby solving the technical problems in the prior art of the resistor layer being prone to cracking and damage when directly contacting and pressing the resistor layer with the substrate, resulting in large fluctuations in the resistance characteristics of the resistor layer, large deviations in resistance uniformity, and poor square resistance uniformity. The invention achieves the technical effect of reducing the lateral tensile stress on the resistor layer during pressing, avoiding tearing and damage of the resistor layer, reducing the resistance fluctuation of the resistor layer, and improving the square resistance uniformity of the resistor layer.

[0041] Optionally, when the pressing temperature is between 200° C. and 400° C., after pressing, the change rate of the tensile strength of the dielectric layer 30 is less than or equal to 5%.

[0042] Specifically, when the entire composite metal foil is pressed onto a substrate, the pressing temperature is generally greater than 200°C. By adding the dielectric layer 30, the present invention stabilizes the change in tensile strength of the dielectric layer 30 after high-temperature pressing, and does not exceed 5%. This also stabilizes the change in the resistance layer 20 after pressing, further preventing the resistance layer 20 from being torn or damaged.

[0043] Optionally, the dielectric layer 30 has a thickness of 20 μm to 50 μm.

[0044] Specifically, the dielectric layer 30 cannot be too thick. An overly thick dielectric layer 30 will result in poor flexibility of the entire composite metal foil, affecting its bending resistance. Experiments have shown that the optimal thickness of the dielectric layer 30 is 20 μm to 50 μm.

[0045] Optionally, the elastic modulus of the dielectric layer 30 is greater than or equal to 3 GPa.

[0046] Specifically, the elastic modulus is the ratio of stress to strain in a material during its elastic deformation phase, measured in megapascals (MPa) or gigapascals (GPa). In the embodiment of the present invention, the elastic modulus of the limiting dielectric layer 30 is greater than or equal to 3 GPa. A high elastic modulus provides excellent deformation resistance, effectively solidifying the resistor layer 20 and further reducing the risk of tearing and damage to the resistor layer 20 after lamination.

[0047] Optionally, after lamination, the expansion / contraction rate of the dielectric layer 30 is less than or equal to 0.05%.

[0048] Specifically, the expansion / contraction ratio, also known as the coefficient of thermal expansion (CTE), characterizes the rate of dimensional change per unit temperature change of a material. It is a key parameter for measuring a material's dimensional stability under temperature fluctuations and directly impacts the reliability and performance of electronic devices. In the embodiments of the present invention, the expansion / contraction ratio of the dielectric layer 30 after lamination is limited to less than or equal to 0.05%. Within this expansion / contraction ratio range, the dielectric layer 30 exhibits excellent thermal stability and effectively strengthens the solidification effect on the resistor layer 20 even in high-temperature lamination environments, reducing the risk of tearing and damage to the resistor layer 20.

[0049] Optionally, the roughness of the circuit layer 10 on a side close to the resistance layer 20 is less than or equal to 3 μm.

[0050] Specifically, in order to make the resistance layer 20 formed by vacuum sputtering more uniform, the roughness Rz of one side of the circuit layer 10 is limited to no more than 3 μm, and the low profile of the sputtering surface is ensured while maintaining sufficient bonding force, so that the resistance characteristics of the formed resistance layer 20 are more stable.

[0051] Figure 4 This is a structural diagram of another composite metal foil provided by an embodiment of the present invention.

[0052] Alternatively, as Figure 4 As shown, a bonding layer 40 is provided on the side of the dielectric layer 30 away from the resistor layer 20; the dielectric layer 30 is bonded and pressed to the substrate through the bonding layer 40;

[0053] The material of the adhesive layer 40 is the same as that of the dielectric layer 30 , or the material of the adhesive layer 40 is the same as that of the substrate of the circuit board.

[0054] Specifically, an adhesive layer 40 may be applied over the dielectric layer 30 to act as a bonding agent, facilitating bonding and lamination with the substrate of the circuit board during multi-layer lamination. The adhesive layer 40 may be made of the same material as the dielectric layer 30 or the substrate of the circuit board.

[0055] Optionally, the resistance layer 20 is a thermistor layer; the resistance layer 20 has a positive temperature coefficient or a negative temperature coefficient.

[0056] Specifically, the resistor layer 20 may be a thermistor layer, including an NTC (Negative Temperature Coefficient) resistor layer, whose resistance decreases exponentially with increasing temperature; or a PTC (Positive Temperature Coefficient) resistor layer, whose resistance increases sharply above the Curie temperature.

[0057] Optionally, the material of the resistor layer 20 includes at least one metal element selected from the group consisting of nickel, iron, cobalt, chromium, titanium, and manganese, and / or an oxide selected from a combination of at least two of the group consisting of nickel, iron, cobalt, chromium, titanium, silicon, phosphorus, and aluminum. For example, the material of the resistor layer 20 may be at least one selected from the group consisting of iron oxide, manganese oxide, nickel oxide, cobalt oxide, copper oxide, nickel-iron oxide, nickel-zinc oxide, zinc oxide, aluminum oxide, and titanium oxide.

[0058] Optionally, the uniformity of the square resistance of the resistor layer 20 is calculated as follows: square resistance range / square resistance mean.

[0059] Specifically, the calculation process of the square resistance range and square resistance mean of the resistor layer is as follows:

[0060] After the side of the dielectric layer 30 of the composite metal foil away from the resistor layer 20 is pressed onto the substrate of the circuit board, the circuit layer 10 is etched away. Then, N test points are randomly selected on the surface of the resistor layer 20 for square resistance testing. The difference between the maximum value Max and the minimum value Min of the N square resistance values ​​is taken as the square resistance range, and the average value Ave of the N square resistance values ​​is taken as the mean square resistance. Where N is a positive integer, N ≥ 10, and the relationship between the maximum value Max and the minimum value Min of the N square resistance values ​​is as follows: 1 ≤ Max / Min ≤ 1.1.

[0061] Specifically, to calculate the square resistance uniformity of the resistor layer 20, after etching away the copper layer that serves as the circuit layer 10, at least ten or more sample areas, each two square centimeters, are sampled on the surface of the resistor layer 20. These sample areas are then tested using a square resistance meter to obtain multiple square resistance values. The square resistance uniformity of the resistor layer 20 can then be calculated. The greater the number of samples taken, the smaller the error in the obtained square resistance uniformity. When sampling, ensuring that the difference between the maximum square resistance value (Max) and the minimum square resistance value (Min) is not too large indicates greater uniformity and flatness of the resistor layer 20, and higher resistance accuracy.

[0062] In an embodiment of the present invention, a flexible dielectric material having a set tensile strength is coated on one surface of the resistor layer as a dielectric layer, which acts as a buffer and solidifier for the resistor layer. This effectively prevents the resistor layer from being damaged or broken during lamination or subsequent use, reduces the lateral tensile stress on the resistor layer during lamination, effectively avoids tearing and breakage of the resistor layer, and improves the uniformity of the square resistance of the resistor layer.

[0063] The performance of the composite metal foil provided by the present invention is introduced below with a specific embodiment.

[0064] For example, taking the circuit layer as copper foil, the copper foil used is electrolytic copper foil, and then a resistor layer is formed on the surface of the copper foil by vacuum sputtering, and a flexible dielectric material is coated on the side of the resistor layer away from the circuit layer as a dielectric layer.

[0065] The square resistance test method is to use a square resistance meter to test the resistive layer of the composite metal foil. The test conditions are as follows: After the dielectric layer of the composite metal foil is pressed onto the substrate of the circuit board on the side away from the resistive layer, the circuit layer is etched away. A four-probe test head is used to connect the square resistance meter to the test head and apply a 1V DC voltage to the test head. Then, N (N ≥ 10) test points are randomly selected on the surface of the resistive layer and tested using the four-probe test head. The probe surface curvature is Sr = 0.9mm, the probe pressure is 0.45±0.15N or 50±15gf, and the probe spacing is 3mm. The specific structural parameters are as follows:

[0066] Group 1: A resistance layer was magnetron sputtered on the surface of a conventional copper foil A1 to prepare a composite metal foil B1; wherein the thickness of the resistance layer was 20 nm.

[0067] The second group: A composite metal foil B2 was prepared by magnetron sputtering a resistive layer on the surface of conventional copper foil A1 and coating a dielectric layer on the surface of the resistive layer away from copper foil A1. The thickness of the resistive layer was 20nm, and the dielectric layer had a tensile strength of 80Mpa and a thickness of 30μm.

[0068] The third group: A composite metal foil B3 was prepared by magnetron sputtering a resistor layer on the surface of conventional copper foil A1 and coating a dielectric layer on the surface of the resistor layer away from copper foil A1. The thickness of the resistor layer was 20nm, and the dielectric layer had a tensile strength of 100Mpa and a thickness of 30μm.

[0069] Group 4: A composite metal foil B4 was prepared by magnetron sputtering a resistor layer on the surface of conventional copper foil A1 and coating a dielectric layer on the surface of the resistor layer away from copper foil A1. The thickness of the resistor layer was 20 nm, and the dielectric layer had a tensile strength of 150 MPa and a thickness of 30 μm.

[0070] Group 5: A composite metal foil B5 was prepared by magnetron sputtering a resistor layer on the surface of conventional copper foil A1 and coating a dielectric layer on the surface of the resistor layer away from copper foil A1. The thickness of the resistor layer was 20 nm, and the dielectric layer had a tensile strength of 200 MPa and a thickness of 30 μm.

[0071] Group 6: A composite metal foil B6 was prepared by magnetron sputtering a resistive layer on the surface of conventional copper foil A1 and coating a dielectric layer on the surface of the resistive layer away from the copper foil A1. The resistive layer had a thickness of 20 nm, and the dielectric layer had a tensile strength of 300 MPa and a thickness of 30 μm.

[0072] The tensile strength and thickness of each set of dielectric layers are set as shown in Table 1 below.

[0073] Table 1. Dielectric layer tensile strength and thickness settings

[0074] serial number B1 B2 B3 B4 B5 B6 Tensile strength / Mpa - 80 100 150 200 300 Thickness / μm - 30 30 30 30 30

[0075] The sheet resistance of the composite metal foils B1-B6 in the first to sixth groups of the above experimental groups was tested according to the above test method and the sheet resistance uniformity was calculated. The test results are shown in Table 2 below. The upper limit value of the calculation of sheet resistance uniformity = (M max -M ave ) / M ave × 100%; lower limit = (M ave -M min ) / M ave ×100%; where M max is the maximum value, M min is the minimum value, M ave is the average value.

[0076] Table 2. Sheet resistance uniformity of composite metal foils in different experimental groups

[0077] serial number B1 B2 B3 B4 B5 B6 Upper limit of sheet resistance uniformity 123％ 46％ 38％ 27％ 21％ 15％ Lower limit of square resistance uniformity 133％ 43％ 35％ 31％ 23％ 17％

[0078] According to the test results of the above embodiments, it can be seen that the composite metal foil prepared according to the structure and structural parameters provided by this solution has better square resistance uniformity and can adapt to the current high-performance circuit boards.

[0079] In an embodiment of the present invention, to verify whether composite metal foils with dielectric layers exhibit superior tear resistance, the tear resistance of the six groups of composite metal foils with dielectric layers was observed after lamination. After etching away the copper foil layer, the resistor layer was directly observed under an electron microscope. The results showed that the composite metal foils with dielectric layers exhibited almost no cracks and good sheet resistance uniformity after lamination, while the composite metal foils without dielectric layers exhibited a high number of cracks and poor sheet resistance uniformity after lamination. Specifically, the dielectric layer with a predetermined tensile strength acts as a buffer and stabilizes the resistor layer, reducing the lateral tensile stress on the resistor layer during lamination, preventing tearing and damage in the resistor layer, and further improving the sheet resistance uniformity of the composite metal foils.

[0080] An embodiment of the present invention further provides a metal-clad laminate, which includes the composite metal foil in any of the above embodiments.

[0081] The metal-clad laminate provided in the embodiment of the present invention includes the composite metal foil in the above embodiment. Therefore, the metal-clad laminate provided in the embodiment of the present invention also has the beneficial effects described in the above embodiment, which will not be described in detail here.

[0082] In the description of the embodiments of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0083] Finally, it should be noted that the above are only preferred embodiments of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments and may include many other equivalent embodiments without departing from the scope of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. A composite metal foil, characterized in that: The composite metal foil includes a circuit layer and a resistance layer provided with a dielectric layer; The resistance layer is arranged on the circuit layer, and the dielectric layer is arranged on a side of the resistance layer away from the circuit layer; The tensile strength of the dielectric layer is greater than or equal to 100 MPa; The side of the dielectric layer away from the resistance layer is used for pressing onto the substrate of the circuit board; After lamination, the square resistance uniformity of the resistance layer is less than or equal to 50%.

2. The composite metal foil according to claim 1, characterized in that When the pressing temperature is between 200° C. and 400° C., after pressing, the change rate of the tensile strength of the dielectric layer is less than or equal to 5%.

3. The composite metal foil according to claim 1, characterized in that The thickness of the dielectric layer is 20 μm to 50 μm.

4. The composite metal foil according to claim 1, characterized in that The elastic modulus of the dielectric layer is greater than or equal to 3 GPa.

5. The composite metal foil according to claim 1, characterized in that After lamination, the expansion and contraction rate of the dielectric layer is less than or equal to 0.05%.

6. The composite metal foil according to claim 1, characterized in that The roughness of a side of the circuit layer close to the resistance layer is less than or equal to 3 μm.

7. The composite metal foil according to claim 1, characterized in that A bonding layer is provided on a side of the dielectric layer away from the resistance layer; the dielectric layer is bonded and pressed to the substrate via the bonding layer; The material of the adhesive layer is the same as that of the dielectric layer, or the material of the adhesive layer is the same as that of the substrate.

8. The composite metal foil according to claim 1, characterized in that The resistance layer is a thermistor layer; the resistance layer has a positive temperature coefficient or a negative temperature coefficient.

9. The composite metal foil according to claim 1, characterized in that The calculation method of the square resistance uniformity is: square resistance range / square resistance mean.

10. A metal-clad laminate, characterized in that: The metal-clad laminate comprises the composite metal foil according to any one of claims 1 to 9.

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