A composite metal foil, metal-clad laminate, and circuit board

Abstract

This invention discloses a composite metal foil, a metal-clad laminate, and a circuit board. The composite metal foil includes a resistive layer and a conductive layer. The resistive layer is disposed on a first surface of the conductive layer, and the first surface has multiple protrusions. The composite metal foil is sliced ​​along a first direction, and within a preset area, the ratio of the number of standard protrusions to the total number of protrusions is greater than 60%. The maximum width W of each standard protrusion along a second direction is... 2 Maximum contact width W with standard protrusion structure and conductive layer 1 The difference is within a first preset range, where the first preset range is 0μm≤(W 2 -W 1 The diameter of the conductive layer is ≤30μm; the first direction is the direction from the conductive layer to the resistive layer, and the second direction is the direction perpendicular to the first direction. This invention avoids the formation of holes and cracks in the resistive layer, improves the continuity of the resistive layer, and thus improves the uniformity of resistance.

Description

A composite metal foil, a metal-clad laminate, and a circuit board Technical Field

[0001] This invention relates to the field of composite metal foil technology, and more particularly to a composite metal foil, a metal-clad laminate, and a circuit board. Background Technology

[0002] With the continuous advancement of the electronics industry and information technology, electronic components are developing towards high performance and miniaturization. However, electronic components generate heat during operation, and as the operating temperature increases, they may malfunction. Therefore, temperature control is necessary to ensure the normal operation of electronic components. Currently, some circuit boards use embedded thin-film thermistor layers to reduce the overall size and thickness of the circuit board and to perform real-time thermal management monitoring of the components.

[0003] In existing circuit board manufacturing using copper foil thermistors, the resistive layer is connected to the circuit board. However, the resistive layer is extremely thin, which leads to poor uniformity of resistance values ​​at different locations of the raw materials during the formation process. This fails to meet the design requirements of the circuit board structure, resulting in poor circuit board manufacturing quality. Summary of the Invention

[0004] This invention provides a composite metal foil, a metal-clad laminate, and a circuit board to avoid holes and cracks in the resistive layer, improve the continuity of the resistive layer, and thus improve the resistance uniformity.

[0005] According to one aspect of the present invention, a composite metal foil is provided, the composite metal foil comprising:

[0006] A resistive layer and a conductive layer are included. The resistive layer is disposed on the first surface of the conductive layer, and the first surface has multiple protrusions. The composite metal foil is sliced ​​along a first direction. Within a preset area, the ratio of the number of standard protrusions to the total number of protrusions is greater than 60%. The difference between the maximum width W2 of the standard protrusion along the second direction and the maximum contact width W1 between the standard protrusion and the conductive layer is within a first preset range, where the first preset range is 0μm≤(W2-W1)≤30μm. The first direction is the direction from the conductive layer to the resistive layer, and the second direction is the direction perpendicular to the first direction.

[0007] Furthermore, the difference between the maximum width W2 of the standard protrusion structure along the second direction and the maximum contact width W1 of the standard protrusion structure and the conductive layer satisfies the following condition: 10nm≤(W2-W1)≤2μm.

[0008] Furthermore, the maximum width W2 of the standard protrusion structure along the second direction and the maximum contact width W1 of the standard protrusion structure and the conductive layer satisfy the following condition: 0.7≤W2 / W1≤1.3.

[0009] Furthermore, the maximum height H of the standard protrusion structure and the maximum width W2 of the standard protrusion structure along the second direction satisfy the following condition: 2μm≤|H-W2|≤4μm.

[0010] Furthermore, the maximum height H of the standard protrusion structure and the maximum contact width W1 between the standard protrusion structure and the conductive layer satisfy the following condition: 50nm≤(H-W1)≤1.5μm.

[0011] Furthermore, the standard protrusion structure includes at least one hollow protrusion structure, the hollow protrusion structure includes at least one hollow portion, and within a preset area, the ratio of the number of the first hollow protrusion structure to the total number of hollow protrusion structures is greater than 50%; wherein, the number of hollow portions included in the first hollow protrusion structure is less than 6.

[0012] Furthermore, the ratio of the number of the second hollow protrusion structure to the total number of hollow protrusion structures is greater than 80%; wherein, the number of hollow parts included in the second hollow protrusion structure is greater than or equal to 2 and less than or equal to 5.

[0013] Furthermore, the thickness of the resistive layer ranges from 50 nm to 3 μm.

[0014] Furthermore, the roughness Rz of the first surface of the conductive layer ranges from 1 to 7 μm; wherein, the first surface is the surface of the conductive layer close to the resistive layer.

[0015] Furthermore, the composite metal foil also includes an adjustment layer, which is disposed on the side of the resistive layer away from the conductive layer.

[0016] Furthermore, the resistive layer is a resistive layer with a negative temperature coefficient, and the resistance value of the resistive layer changes by more than 5% over any 25°C range.

[0017] Furthermore, a temperature cycle is defined as the temperature rising from 25°C to 150°C and then falling back to 25°C. After at least one temperature cycle, the resistance value of the resistive layer recovers to a deviation of less than 10%.

[0018] According to another aspect of the present invention, a metal-clad laminate is provided, the metal-clad laminate comprising the composite metal foil described in any of the above embodiments.

[0019] According to another aspect of the present invention, a circuit board is provided, the circuit board comprising the composite metal foil described in any of the above embodiments.

[0020] The composite metal foil provided in this embodiment of the invention has a ratio of the number of standard protrusions to the total number of protrusions on the first surface of the conductive layer within a preset area, which is greater than 60%. The difference between the maximum width W2 of the standard protrusion along the second direction and the maximum contact width W1 between the standard protrusion and the conductive layer is within a first preset range, which is 0μm≤(W2-W1)≤30μm. Within this range, during the fabrication of the resistive layer using the first surface of the conductive layer as a substrate, the area of ​​the first surface that cannot be covered by the resistive layer can be reduced, the continuity of the resistive layer can be improved, and the occurrence of holes and cracks in the resistive layer can be effectively avoided, thereby improving the sheet resistance uniformity of the resistive layer.

[0021] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 is a schematic diagram of a composite metal foil according to an embodiment of the present invention;

[0024] Figure 2 is a schematic diagram of a partial slice structure of a composite metal foil according to an embodiment of the present invention;

[0025] Figure 3 is a schematic diagram of a slice structure of a composite metal foil protrusion structure according to an embodiment of the present invention;

[0026] Figure 4 is a schematic diagram of another composite metal foil provided according to an embodiment of the present invention. Detailed Implementation

[0027] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0028] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0029] This invention provides a composite metal foil. Figure 1 is a structural schematic diagram of a composite metal foil according to an embodiment of the invention. Figure 2 is a partial slice structural schematic diagram of a composite metal foil according to an embodiment of the invention. Figure 3 is a slice structural schematic diagram of a raised structure of a composite metal foil according to an embodiment of the invention. Referring to Figures 1-3, the composite metal foil includes a resistive layer 10 and a conductive layer 20. The resistive layer 10 is disposed on a first surface of the conductive layer 20, and the first surface is provided with a plurality of raised structures 201. When the composite metal foil is sliced ​​along a first direction, the ratio of the number of standard raised structures to the total number of raised structures 201 within a preset area is greater than 60%. The difference between the maximum width W2 of the standard raised structure along a second direction and the maximum contact width W1 between the standard raised structure and the conductive layer is within a first preset range, where the first preset range is 0 μm ≤ (W2-W1) ≤ 30 μm. The first direction is the direction from the conductive layer 20 to the resistive layer 10, and the second direction is the direction perpendicular to the first direction.

[0030] The conductive layer 20 can be made of copper, gold, aluminum, silver, nickel, iron, manganese, platinum or other metallic or non-metallic conductive materials, and the thickness of the conductive layer 20 ranges from 10 to 50 μm.

[0031] The thickness of the conductive layer 20 can be set according to actual conditions; for example, the thickness of the conductive layer 20 is 18 μm. The conductive layer 20 can be fabricated using electrolytic copper foil or rolled copper foil.

[0032] Optionally, the resistive layer 10 can be formed by physical vapor deposition, chemical vapor deposition, evaporation deposition, electroplating, hybrid deposition, or other deposition methods. Specifically, the resistive layer is formed on the first surface of the conductive layer 20 by one or more magnetron sputtering operations. The thickness of the resistive layer 10 is 50 nm to 800 nm. This embodiment of the invention only provides a specific method for forming the resistive layer 10 and does not limit its application.

[0033] It should be noted that the preset area should be understood as the area of ​​any slice after slicing the composite metal foil. For example, the preset area can be 16μm. 2 20μm 2 32μm 2 50μm 2 100μm 2 200μm 2 Observation range, etc.

[0034] Specifically, when the difference between the maximum width W2 of the standard protrusion structure along the second direction and the maximum contact width W1 between the standard protrusion structure and the conductive layer is greater than or equal to zero and less than or equal to 30 μm, it indicates that the cross-section of the standard protrusion structure along the first direction is wider at the top and narrower at the bottom. During the fabrication of the resistive layer 10, this effectively reduces the occurrence of holes and cracks in the resistive layer 10, improves the continuity of the resistive layer 10, and enhances the uniformity of sheet resistance. Furthermore, by ensuring that the ratio of the number of standard protrusion structures to the total number of protrusion structures 201 is greater than 60% within any preset area, the probability of holes appearing in the resistive layer 10 can be effectively reduced, improving the continuity of the resistive layer 10 and enhancing the uniformity of sheet resistance.

[0035] The composite metal foil provided in this embodiment of the invention has a ratio of the number of standard protrusions to the total number of protrusions 201 on the first surface of the conductive layer 20 within a preset area, which is greater than 60%. The difference between the maximum width W2 of the standard protrusion along the second direction and the maximum contact width W1 between the standard protrusion and the conductive layer is within a first preset range, which is 0 μm ≤ (W2 - W1) ≤ 30 μm. Within this range, during the fabrication of the resistive layer 10 using the first surface of the conductive layer 20 as a substrate, the area of ​​the first surface not covered by the resistive layer 10 can be reduced, improving the continuity of the resistive layer 10, effectively preventing holes and cracks in the resistive layer 10, and thus improving the sheet resistance uniformity of the resistive layer 10.

[0036] Furthermore, referring to Figure 3, the difference between the maximum width W2 of the standard protrusion structure along the second direction and the maximum contact width W1 of the standard protrusion structure and the conductive layer satisfies the following condition: 10nm≤(W2-W1)≤2μm.

[0037] Specifically, the difference between the maximum width W2 of the standard protrusion structure along the second direction and the maximum contact width W1 between the standard protrusion structure and the conductive layer is set to satisfy the following condition: 10nm≤(W2-W1)≤2μm. This makes the formed standard protrusion structure more regular, further ensuring the continuity of the resistive layer, while also improving the bonding force between the composite metal foil and the substrate, thus enhancing the quality of circuit board manufacturing.

[0038] Furthermore, referring to Figure 3, the maximum width W2 of the standard protrusion structure along the second direction and the maximum contact width W1 of the standard protrusion structure and the conductive layer satisfy the following condition: 0.7≤W2 / W1≤1.3.

[0039] Specifically, setting the ratio of the maximum width W2 of the standard protrusion structure along the second direction to the maximum contact width W1 between the standard protrusion structure and the conductive layer to be greater than or equal to 0.7 and less than or equal to 1.3 can avoid the formation of crown-shaped standard protrusion structures, thereby making the formed standard protrusion structures more uniform and regular. When processing the resistive layer, the resistive layer covers a larger area of ​​the first surface below the standard protrusion structure, which improves the bonding force between the composite metal foil and the substrate while ensuring the continuity of the resistive layer.

[0040] Furthermore, referring to Figure 3, the maximum height H of the standard protrusion structure and the maximum width W2 of the standard protrusion structure along the second direction satisfy the following condition: 2μm≤|H-W2|≤4μm.

[0041] Specifically, setting the maximum height H of the standard protrusion structure and the maximum width W2 of the standard protrusion structure along the second direction to satisfy the following condition: 2μm≤|H-W2|≤4μm, can make the difference between the maximum height H and the maximum width W2 of the standard protrusion structure along the second direction small. For example, the maximum height of the formed standard protrusion structure can be greater than or less than the maximum width along the second direction, which makes the types of formed standard protrusion structures more diverse, adjusts the roughness of the standard protrusion structure, increases the cross-sectional area of ​​the surface resistive layer of the standard protrusion structure, and thus increases the current carrying capacity of the resistive layer.

[0042] Furthermore, referring to Figure 3, the maximum height H of the standard protrusion structure and the maximum contact width W1 between the standard protrusion structure and the conductive layer satisfy the following condition: 50nm≤(H-W1)≤1.5μm.

[0043] Specifically, setting the maximum height H of the standard protrusion structure and the maximum contact width W1 between the standard protrusion structure and the conductive layer to satisfy the following condition: 50nm≤(H-W1)≤1.5μm, can make the difference between the maximum height H of the standard protrusion structure and the maximum contact width W1 between the standard protrusion structure and the conductive layer smaller. The roughness is adjusted, making the formed standard protrusion structure more regular. While ensuring the continuity of the resistive layer, the bonding force between the composite metal foil and the substrate is improved.

[0044] Furthermore, referring to Figures 2 and 3, the protruding structure 201 includes at least one hollow protruding structure 202, and the hollow protruding structure 202 includes at least one hollow portion 2011. Within a preset area, the ratio of the number of the first hollow protruding structures to the total number of hollow protruding structures is greater than 50%; wherein, the number of hollow portions 2011 included in the first hollow protruding structure is less than 6.

[0045] One can be understood as one or more. For example, the protrusion structure 201 may include one or more hollow protrusion structures 202.

[0046] Specifically, setting the number of hollow protrusions 202 containing fewer than 6 hollow portions 2011 to account for more than 50% of the total number of hollow protrusions 202 can effectively reduce the number of hollow portions 2011 within the protrusions 201. Consequently, during the fabrication of the resistor layer 10, by reducing the number of hollow portions 2011 within the protrusions 201, the probability of holes and cracks forming in the resistor layer 10 at the locations of the hollow portions 2011 is reduced, thus improving the continuity of the resistor layer 10.

[0047] Furthermore, continuing to refer to Figure 3, the ratio of the number of the second hollow protrusion structure to the total number of hollow protrusion structures 202 is greater than 80%; wherein, the number of hollow parts 2011 included in the second hollow protrusion structure is greater than or equal to 2 and less than or equal to 5.

[0048] Specifically, setting the number of hollow protrusions 202 containing two or more and five hollow parts 2011 to account for more than 80% of the total number of hollow protrusions 202 can further reduce the number of hollow parts 2011 in the protrusions 201. This can effectively prevent the formation of holes and cracks in the resistor layer 10 at the hollow parts 2011 positions due to a large number of hollow parts 2011 in the protrusions during the fabrication of the resistor layer 10, thereby further improving the continuity of the resistor layer 10.

[0049] Furthermore, the thickness of the resistive layer is 50nm-3μm.

[0050] Specifically, by setting the resistive layer to be relatively thin, after the composite metal foil is made into a circuit board, temperature monitoring of each component in the circuit board can be achieved without affecting the overall structure of the circuit board.

[0051] Furthermore, the roughness Rz of the first surface of the conductive layer ranges from 1 to 7 μm; wherein, the first surface is the surface of the conductive layer close to the resistive layer.

[0052] Roughness Rz is used to characterize the microscopic unevenness of the conductive layer surface. Specifically, the average of the five largest profile peak heights and the average of the five largest profile valley depths within the sampling length is usually taken as the roughness Rz. Setting the roughness Rz of the first surface of the conductive layer in the range of 1-7 μm can effectively improve the adhesion between the composite metal foil and the substrate, thereby making the bonding between the composite metal foil and the substrate more compact.

[0053] Optionally, the resistive layer can be made of Ni (nickel), Cr (chromium), Zn (zinc), Al (aluminum), Sn (tin), O (oxygen), N (nitrogen), C (carbon), Cu (copper), Mn (manganese), Fe (iron) or other elements that can achieve good thermosensitive properties.

[0054] Specifically, the resistive layer is made of nickel-iron oxide alloy. Nickel-iron oxide is a ferrite material with good temperature sensitivity; its resistance exhibits a stable non-linear relationship with temperature changes, making it suitable for precise temperature measurement. It can operate over a wide temperature range, possesses chemical and thermal stability, and maintains stable performance even under long-term use or harsh environments (such as high temperature or high humidity). Its manufacturing cost is relatively low, making it suitable for mass production. By changing the ratio of nickel to iron or doping with other elements (such as manganese or zinc), its resistance temperature characteristics can be adjusted to meet specific application requirements.

[0055] Furthermore, in the resistive layer, the preferred composition ratio is: Fe (iron) content less than 30%, Ni content greater than 30%, and O content less than 60%. This composition ratio makes etching easier and further improves temperature sensitivity and thermal stability, thereby enhancing the quality of the composite metal foil.

[0056] When composite metal foil is placed on a circuit board for temperature monitoring, the changes in resistance, voltage, current or level of the circuit in the circuit board are monitored through the thermistor effect of the first resistive layer 10, thereby realizing the monitoring and even feedback regulation of the heat generation of electronic components.

[0057] Furthermore, Figure 4 is a schematic diagram of another composite metal foil provided according to an embodiment of the present invention. Referring to Figure 4, the composite metal foil further includes an adjustment layer 30, which is disposed on the side of the resistive layer 10 away from the conductive layer 20.

[0058] Specifically, adding an adjustment layer 30 to the composite metal foil can effectively improve the bonding force between the composite metal foil pressed onto the substrate and the substrate, preventing the composite metal foil from falling off.

[0059] Optionally, the adjusting layer can be made of silane coupling agents, titanate coupling agents, aluminate coupling agents, phosphate coupling agents, modified epoxy resins, acrylics, modified rubbers, modified thermoplastic polyimides, or other materials. Specifically, in this embodiment, the adjusting layer is a silane coupling agent, which helps to ensure the mechanical properties and corrosion resistance of the resistive layer 10.

[0060] Furthermore, the resistive layer is a resistive layer with a negative temperature coefficient, and the resistance value of the resistive layer changes by more than 5% over any 25°C range.

[0061] Specifically, by setting the resistance layer to have a resistance rate greater than 5% after a 25°C change from any temperature, the sensitivity of the resistance layer to temperature changes can be improved. After fabricating the composite metal foil into a circuit board, the monitoring of various components within the circuit board becomes more precise.

[0062] Furthermore, a temperature cycle consists of the temperature rising from 25°C to 150°C and then falling back to 25°C, and the resistance recovery deviation of the resistive layer is less than 10% within at least one temperature cycle.

[0063] "At least once" can be understood as "once or more than once". Resistance recovery deviation can be understood as the difference between the resistance of the resistive layer before heating and the resistance after one temperature cycle.

[0064] Specifically, after one temperature cycle, the resistance value of the resistive layer recovers to a deviation of less than 10%. This allows the resistance layer to return to near its original value after its temperature rises and then returns to room temperature, enabling the resistive layer to be reused for temperature control, ensuring working accuracy and improving reliability. Furthermore, the resistance of the resistive layer changes smoothly with temperature, ensuring stable circuit operation. After multiple temperature cycles, the resistance value of the resistive layer still recovers to near its initial value, and the resistance value remains stable, thus ensuring a longer service life for the composite metal foil.

[0065] Experimental group 1

[0066] A composite metal foil includes a conductive layer and a resistive layer. The conductive layer is made of Cu and has a base layer thickness of 18 μm. The resistive layer is made of nickel-iron oxide alloy and has a thickness of 530 nm. Under scanning electron microscopy, the ratio of the number of standard protrusions to the total number of protrusions is 78%. The difference between the maximum width W2 of the standard protrusion along the second direction and the maximum contact width W1 between the standard protrusion and the conductive layer is 0.5 μm ≤ (W2 - W1) ≤ 2 μm.

[0067] Experimental group 2

[0068] Based on experimental group 1, under the observation environment of scanning electron microscope, the difference between the maximum width W2 of the standard protrusion structure along the second direction and the maximum contact width W1 of the standard protrusion structure and the conductive layer satisfies the following condition: 200nm≤(W2-W1)≤1.5μm.

[0069] Experimental group 3

[0070] Unlike experimental group 1, under the observation environment of scanning electron microscope, the maximum width W2 of the statistical standard protrusion structure along the second direction and the maximum contact width W1 of the standard protrusion structure and the conductive layer satisfy the following condition: 0.9≤W2 / W1≤1.1.

[0071] Control group 1

[0072] The composite metal foil comprises a conductive layer and a resistive layer. The conductive layer is made of Cu, and the substrate layer has a thickness of 18 μm. The resistive layer is made of Ni-Al alloy, and the resistive layer has a thickness of 800 nm. Under scanning electron microscopy, the ratio of the number of standard protrusions to the total number of protrusions is 15%. The difference between the maximum width W2 of the standard protrusion along the second direction and the maximum contact width W1 between the standard protrusion and the conductive layer is 0 μm ≤ (W2 - W1) ≤ 6 μm.

[0073] Control group 2

[0074] Unlike control group 1, the resistive layer was made of Ni-Mn alloy and had a thickness of 3 μm. Under the observation conditions of a scanning electron microscope, the ratio of the number of standard protrusions to the total number of protrusions was 5%. The difference between the maximum width W2 of the standard protrusion along the second direction and the maximum contact width W1 between the standard protrusion and the conductive layer was 0 μm ≤ (W2-W1) ≤ 7 μm.

[0075] The composite metal foil samples from the above-mentioned experimental and control groups were used to prepare samples. These samples were then pressed onto a semi-cured core board layer at 185℃ for 10 minutes. The copper layer was removed using an alkaline etching solution, and after cleaning, the samples were baked in a 105℃ oven for 10 minutes to remove moisture. A 2cm × 2cm grid was marked on the surface of the samples after alkaline etching to remove copper. The sheet resistance of each grid was measured using a sheet resistance meter, and the sheet resistance uniformity was statistically measured. Table 1 shows a comparison of the sheet resistance uniformity between the different experimental and control groups.

[0076] Table 1. Comparison of sheet resistance uniformity between different experimental and control groups

[0077]

[0078] As shown in Table 1, the composite metal foils in test groups 1 to 3 have higher sheet resistance uniformity, which is beneficial to improving the quality of use.

[0079] This invention also provides a metal-clad laminate, which includes the composite metal foil described in any of the above embodiments. The metal-clad laminate of this invention has the same beneficial effects as the composite metal foil described in any embodiment of this invention.

[0080] This invention also provides a circuit board comprising the composite metal foil described in any of the above embodiments. The composite metal foil can be disposed on the circuitry and component surfaces of the circuit board for temperature measurement of the circuitry or components. The circuit board of this invention, comprising the composite metal foil, exhibits better uniformity of the resistive layer formed in the composite metal foil, enabling precise monitoring of every location on the circuit board, improving temperature detection accuracy, and preventing damage to the circuit board due to excessive temperature.

[0081] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution of this invention can be achieved, and this is not limited herein.

[0082] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A composite metal foil, characterized in that, include: The composite metal foil comprises a resistive layer and a conductive layer. The resistive layer is disposed on a first surface of the conductive layer, and the first surface has multiple protrusions. The composite metal foil is sliced ​​along a first direction. Within a preset area, the ratio of the number of standard protrusions to the total number of protrusions is greater than 60%. The difference between the maximum width W2 of the standard protrusion along a second direction and the maximum contact width W1 between the standard protrusion and the conductive layer is within a first preset range, where the first preset range is 0μm ≤ (W2-W1) ≤ 30μm. The first direction is the direction from the conductive layer to the resistive layer, and the second direction is a direction perpendicular to the first direction. Each standard protrusion includes at least one hollow protrusion, and each hollow protrusion includes at least one hollow portion. Within a preset area, the ratio of the number of first hollow protrusions to the total number of hollow protrusions is greater than 50%. The number of hollow portions included in the first hollow protrusion is less than 6 to reduce the number of hollow portions within the protrusion.

2. The composite metal foil according to claim 1, characterized in that, The difference between the maximum width W2 of the standard protrusion structure along the second direction and the maximum contact width W1 of the standard protrusion structure and the conductive layer satisfies the following condition: 10nm≤(W2-W1)≤2μm.

3. The composite metal foil according to claim 1, characterized in that, The maximum width W2 of the standard protrusion structure along the second direction and the maximum contact width W1 of the standard protrusion structure and the conductive layer satisfy the following condition: 0.7≤W2 / W1≤1.

3.

4. The composite metal foil according to claim 1, characterized in that, The maximum height H of the standard protrusion structure and the maximum width W2 of the standard protrusion structure along the second direction satisfy the following condition: 2μm≤|H-W2|≤4μm.

5. The composite metal foil according to claim 1, characterized in that, The maximum height H of the standard protrusion structure and the maximum contact width W1 of the standard protrusion structure and the conductive layer satisfy the following condition: 50nm≤(H-W1)≤1.5μm.

6. The composite metal foil according to claim 1, characterized in that, The ratio of the number of the second hollow protrusion structure to the total number of the hollow protrusion structures is greater than 80%; wherein, the number of hollow portions included in the second hollow protrusion structure is greater than or equal to 2 and less than or equal to 5.

7. The composite metal foil according to claim 1, characterized in that, The thickness of the resistive layer ranges from 50 nm to 3 μm.

8. The composite metal foil according to claim 6, characterized in that, The roughness Rz of the first surface of the conductive layer is in the range of 1-7 μm; wherein, the first surface is the surface of the conductive layer close to the resistive layer.

9. The composite metal foil according to claim 1, characterized in that, It also includes an adjustment layer disposed on the side of the resistive layer away from the conductive layer.

10. The composite metal foil according to claim 1, characterized in that, The resistive layer is a resistive layer with a negative temperature coefficient, and the resistance value of the resistive layer changes by more than 5% over any 25°C range.

11. The composite metal foil according to claim 1, characterized in that, A temperature cycle consists of the temperature rising from 25°C to 150°C and then falling back to 25°C. Within at least one temperature cycle, the resistance value of the resistive layer recovers a deviation of less than 10%.

12. A metal-clad laminate, characterized in that, Includes the composite metal foil according to any one of claims 1-11.

13. A circuit board, characterized in that, Includes the composite metal foil according to any one of claims 1-11.

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