Composite metal foil, metal-clad laminate and circuit board

Abstract

The present invention discloses a composite metal foil, a metal-clad laminate, and a circuit board. The composite metal foil comprises a resistor layer and a conductive layer. The resistor layer is disposed on a first surface of the conductive layer, and the first surface is provided with a plurality of raised structures, each of which includes at least one hollowed-out raised structure and at least one hollowed-out portion. The composite metal foil is sliced ​​along a first direction, and within a predetermined area, the ratio of the number of first hollowed-out raised structures to the number of raised structures is greater than 50%. The first direction is the direction from the conductive layer to the resistor layer, and the ratio of the total area of ​​the hollowed-out portions in the first hollowed-out raised structures to the slice area is less than 20%. The present invention improves the uniformity of the square resistance of the composite metal foil and enhances the quality of circuit manufacturing.

Description

Technical Field

[0001] The present invention relates to the technical field of composite metal foils, and in particular to a composite metal foil, a metal-clad laminate and a circuit board. Background Art

[0002] With the continuous advancement of the electronics industry and information technology, electronic components are moving towards higher performance and miniaturization. However, electronic components generate heat during operation. As operating temperatures rise, they can malfunction. Therefore, temperature control is necessary to maintain proper operation. Currently, some circuit boards incorporate embedded thin-film thermistor layers to reduce overall board size and thickness, while also enabling real-time thermal management and monitoring of components.

[0003] When conventional thermistor copper foil is used to make circuit boards, the resistor layer is connected to the circuit board. However, the resistor layer is extremely thin, and during the formation process, the resistance values ​​of different locations of the raw material are poorly uniform. This cannot meet the design requirements of the circuit board structure, resulting in poor circuit board production quality. Summary of the Invention

[0004] The present invention provides a composite metal foil, a metal-clad laminate and a circuit board, so as to improve the square resistance uniformity of the composite metal foil and enhance the circuit manufacturing quality.

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

[0006] A resistor layer and a conductive layer, the resistor layer is arranged on a first surface of the conductive layer, and the first surface is provided with a plurality of raised structures, the raised structures including at least one hollowed raised structure, and the hollowed raised structure including at least one hollow portion; the composite metal foil is sliced ​​along a first direction, and within a preset area, the ratio of the number of the first hollowed raised structures to the number of the raised structures is greater than 50%; wherein the first direction is the direction from the conductive layer to the resistor layer, and the ratio of the total area of ​​the hollow portions in the first hollowed raised structures to the slice area is less than 20%.

[0007] Furthermore, the hollow portion includes a first hollow portion and a second hollow portion;

[0008] The first hollow portion is communicated with the outside, and the second hollow portion is located inside the hollow protrusion structure.

[0009] Furthermore, the ratio of the number of the second hollow protrusion structures to the number of the protrusion structures is greater than 50%; wherein the number of the first hollow portions in the second hollow protrusion structures is less than the number of the second hollow portions.

[0010] Furthermore, in the first hollow protrusion structure, the maximum length of the hollow portion is less than 4.4 μm.

[0011] Furthermore, in the first hollow protrusion structure, the ratio of the number of the third hollow portions to the total number of the hollow portions is greater than 60%; wherein the aspect ratio of the minimum circumscribed rectangle of the third hollow portion is greater than 3.

[0012] Furthermore, in the first hollow protrusion structure, the ratio of the sum of the areas of the fourth hollow portions to the total area of ​​the hollow portions is greater than 30%; wherein the maximum length of the fourth hollow portion is in the range of 0.1 μm-0.5 μm.

[0013] Furthermore, the ratio of the number of the third hollow protrusion structures to the number of the hollow protrusion structures is less than 20%; wherein, the ratio of the total area of ​​the hollow portions in the third hollow protrusion structures to the area of ​​the slice is in the range of 20%-30%.

[0014] Furthermore, the thickness of the resistance layer ranges from 50 nm to 3 μm.

[0015] Furthermore, the roughness Rz of the conductive layer on the side close to the resistance layer is in the range of 1-7 μm.

[0016] Furthermore, the composite metal foil further includes: an adjustment layer; the adjustment layer is arranged on a side of the resistance layer away from the conductive layer.

[0017] Furthermore, the resistance layer has a negative temperature coefficient, and within any 25° C. change range, the resistance value change rate of the resistance layer is greater than 5%.

[0018] Furthermore, the temperature is increased from 25° C. to 150° C. and then decreased to 25° C. as one temperature cycle, and after at least one temperature cycle, the resistance value recovery deviation of the resistor layer is less than 10%.

[0019] According to another aspect of the present invention, a metal-clad laminate is provided. The metal-clad laminate comprises the composite metal foil according to any one of the above embodiments.

[0020] According to another aspect of the present invention, a circuit board is provided. The circuit board includes the composite metal foil described in any one of the above embodiments.

[0021] The composite metal foil provided by the embodiments of the present invention limits the proportion of hollowed-out portions within the hollowed-out structures by ensuring that the ratio of the total area of ​​the hollowed-out portions to the area of ​​the slice is less than 20%, accounting for at least 50% of the total number of raised structures within a predetermined area. This improves the solidity and stability of the raised structures, reduces the probability of breakage and detachment of the raised structures during high-temperature and high-pressure lamination, effectively prevents holes and cracks in the resistor layer at the locations of the hollowed-out portions, and improves the continuity of the resistor layer. Furthermore, the relatively low proportion of hollowed-out portions is connected to the outside world, reducing the amount of chemical solution that penetrates the hollowed-out portions during etching of circuits. This prevents excessive etching of the conductive layer, which affects the quality of the line width and the bonding strength between the composite metal foil and the substrate, reduces or even prevents delamination and detachment of circuits, and improves the reliability of circuit fabrication.

[0022] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present invention, nor is it intended to limit the scope of the present invention. Other features of the present invention will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 This is a schematic structural diagram of a composite metal foil provided according to an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of a partial slice structure of a composite metal foil provided according to an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of a slice structure of a composite metal foil hollow protrusion structure provided according to an embodiment of the present invention;

[0027] Figure 4 Schematic diagram of the structure of another composite metal foil provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0029] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0030] The embodiment of the present invention provides a composite metal foil, Figure 1 1 is a schematic structural diagram of a composite metal foil provided according to an embodiment of the present invention. Figure 2 1 is a schematic diagram of a partial slice structure of a composite metal foil provided according to an embodiment of the present invention. Figure 3 This is a schematic diagram of a slice structure of a composite metal foil hollow convex structure provided by an embodiment of the present invention, with reference to Figure 1-Figure 3 The composite metal foil includes: a resistor layer 10 and a conductive layer 20. The resistor layer 10 is arranged on the first surface of the conductive layer 20, and the first surface is provided with a plurality of protrusion structures 201, and the resistor layer 10 covers the protrusion structure 201. The protrusion structure 201 includes at least one hollow protrusion structure 202, and the hollow protrusion structure 202 includes at least one hollow portion 2011. The composite metal foil is sliced ​​along a first direction. Within a preset area, the ratio of the number of first hollow protrusion structures to the number of protrusion structures 201 is greater than 50%. The first direction is the direction from the conductive layer 20 to the resistor layer 10. In the first hollow protrusion structure, the ratio of the total area of ​​all hollow portions 2011 to the slice area of ​​the first hollow protrusion structure is less than 20%.

[0031] Among them, the material of the conductive layer 20 can be metal materials such as copper, gold, silver, iron, aluminum, platinum, cobalt, nickel, manganese, or other non-metallic conductive materials. The embodiment of the present invention does not limit the material of the conductive layer 20, as long as it has good conductivity. The thickness of the conductive layer 20 can also be set according to actual conditions.

[0032] Specifically, the thickness of the conductive layer is 5-100 μm. For example, the thickness of the conductive layer 20 is 18 μm. For example, the conductive layer 20 is made of copper foil, and the conductive layer 20 can be made of electrolytic copper foil or rolled copper foil.

[0033] Alternatively, the resistor layer 10 may be formed by physical vapor deposition, chemical vapor deposition, evaporation plating, electroplating, or mixed plating. Furthermore, the thickness of the resistor layer 10 is 50 nm to 800 nm. The resistor layer 10 may be formed on the first surface of the conductive layer 20 by one or more magnetron sputtering processes, which is not limited in this embodiment of the present invention.

[0034] The preset area can be understood as an area of ​​any size selected after slicing the composite metal foil. The plurality of protrusion structures 201 can be evenly arranged on the surface of the conductive layer 20 near the resistor layer 10, or unevenly arranged on the surface of the conductive layer 20 near the resistor layer 10.

[0035] Exemplarily, the raised structure 201 is a regular or irregular three-dimensional geometric structure formed during the roughening process of the conductive layer 20. The shape of the raised structure 201 can be one or more of a pointed corner, an inverted cone, a granular shape, a dendrite, a columnar shape, a block shape, an arc shape, etc., and the embodiment of the present invention is not limited to this.

[0036] Furthermore, at least one can be understood as one or more. For example, the protrusion structure 201 includes one or more hollow protrusion structures 202, and each hollow protrusion structure 202 includes one or more hollow portions 2011, wherein the hollow portion 2011 is a regular or irregular cavity structure formed in the process of forming the protrusion structure 201.

[0037] The composite metal foil provided in the embodiments of the present invention limits the proportion of hollowed-out portions 2011 in the hollowed-out raised structures 202 by setting the ratio of the total area of ​​the hollowed-out portions 2011 to the area of ​​the slice to less than 20%, accounting for at least 50% of the total number of raised structures 201 within a predetermined area. This improves the solidity of the raised structures 201, enhances the stability of the raised structures 201, and reduces the probability of breakage and detachment of the raised structures 201 during high-temperature and high-pressure lamination. This effectively prevents holes and cracks in the resistor layer 10 at the locations of the hollowed-out portions 2011, thereby improving the continuity of the resistor layer 10. Furthermore, the relatively low proportion of hollowed-out portions 2011 is connected to the outside world, reducing the amount of liquid that penetrates into the hollowed-out portions 2011 during etching of the circuits. This prevents excessive etching of the conductive layer 20, which affects the line width quality and the bonding strength between the composite metal foil and the substrate, and reduces or even prevents delamination and detachment of the circuits, thereby improving the reliability of circuit fabrication.

[0038] Optionally, in the slicing state, the hollow portion 2011 may be disposed in a closed manner in the hollow protruding structure 202 , or may be disposed at the edge of the hollow protruding structure 202 and communicate with the outside.

[0039] For further reference, Figure 1-Figure 3 The hollow portion 2011 includes a first hollow portion 01 and a second hollow portion 02. The first hollow portion 01 is connected to the outside, and the second hollow portion 02 is located inside the hollow protrusion structure 202.

[0040] Specifically, by reducing the number of first hollow portions 01, the formation of holes and cracks in the resistor layer 10 at the locations of the first hollow portions 01 can be effectively avoided during the fabrication of the resistor layer 10, thereby improving the continuity of the resistor layer 10. Furthermore, by reducing the number of first hollow portions 01, the infiltration of chemical solution can be reduced during the etching of the conductive layer 20, thereby preventing excessive etching of the conductive layer 20, which could affect the line width and bonding strength. This effectively prevents delamination of the conductive layer 20 from the substrate and the detachment of the lines on the conductive layer 20. By reducing the number of first hollow portions 01 and second hollow portions 02, the solidity of the raised structure 201 is increased, improving the stability of the raised structure 201 and reducing the probability of fracture and detachment of the raised structure 201 during the high-temperature and high-pressure lamination process.

[0041] For further reference, Figure 1-Figure 3 In one embodiment, the ratio of the number of the second hollow protrusion structures to the number of the protrusion structures is greater than 50%. In particular, the number of the first hollow portions 01 in the second hollow protrusion structure is less than the number of the second hollow portions 02.

[0042] Specifically, the number of first hollow portions 01 in the hollowed-out raised structures 202 is smaller than the number of second hollow portions 02, and the proportion of the hollowed-out raised structures 202 in the total number of raised structures 201 is greater than 50%. This results in a smaller number of first hollow portions 01 in the hollowed-out raised structures 202. This effectively prevents holes and cracks in the resistive layer 10 at the locations of the first hollow portions 01 during the fabrication of the resistive layer 10, thereby improving the continuity of the resistive layer 10. Furthermore, when the composite metal foil is laminated to a substrate and the conductive layer 20 is dip-etched for circuitry, the reduced number of first hollow portions 01 reduces chemical penetration, thereby preventing over-etching of the conductive layer 20, which could affect line width and bonding strength. This effectively prevents delamination of the conductive layer 20 from the substrate and the detachment of circuitry on the conductive layer 20.

[0043] Furthermore, in the first hollow protrusion structure, the maximum length of the hollow portion is less than 4.4 μm.

[0044] Specifically, in the first hollowed-out protrusion structure, the maximum length of the hollowed-out portion is set to be less than 4.4 μm. This can prevent the first hollowed-out protrusion structure from breaking or falling off during the high-temperature and high-pressure pressing process due to the hollowed-out portion being too long, thereby improving the stability of the first hollowed-out protrusion structure. The maximum length of the hollowed-out portion in the first hollowed-out protrusion structure can be obtained by software scanning and calculation. For example, a focused ion beam electron microscope can be used to slice the composite metal foil, and the hollowed-out portions in the hollowed-out protrusion structure can be identified using visual statistical software. Based on the shape of the identified hollowed-out portions, the area, maximum length, minimum circumscribed rectangle, etc. of each hollowed-out portion can be determined.

[0045] Furthermore, in the first hollow protrusion structure, the ratio of the number of the third hollow portions to the total number of the hollow portions is greater than 60%; wherein the aspect ratio of the minimum circumscribed rectangle of the third hollow portion is greater than 3.

[0046] Specifically, if the third hollow portion is located within the hollowed-out protrusion structure, and the number of third hollow portions with a minimum external matrix aspect ratio greater than 3 accounts for more than 60% of the total number of hollow portions, the formation of a large hollow portion within the first hollowed-out protrusion structure can be avoided, thereby effectively preventing the first hollowed-out protrusion structure from breaking or falling off during high-temperature and high-pressure pressing, thereby improving the stability of the first hollowed-out protrusion structure. If the third hollow portion is connected to the outside world, the number of third hollow portions with a minimum external matrix aspect ratio greater than 3 accounts for more than 60% of the total number of hollow portions, thereby preventing the hollow portion from being excessively exposed to the outside world in the first hollowed-out protrusion structure. Furthermore, during the fabrication of the resistor layer, the formation of holes and cracks in the resistor layer at the locations of the third hollow portions is further avoided, thereby improving the continuity of the resistor layer. Furthermore, when etching the conductive layer through immersion, by reducing the exposure of the third hollow portions to the outside world, the infiltration of the chemical solution is effectively reduced, preventing the conductive layer from being over-etched, thereby affecting the line width and bonding strength, thereby effectively preventing delamination of the conductive layer from the substrate and the falling off of the lines on the conductive layer. For example, if the ratio of the number of third hollow parts to the total number of hollow parts in the first hollow protrusion structure is less than or equal to 60%, it means that the number of hollow parts with a larger internal range in the first hollow protrusion structure is large, and it is easy to break and fall off during the high-temperature and high-pressure pressing process. The hollow parts connected to the outside world are prone to excessive infiltration of chemicals when the conductive layer is immersed in the etching circuit, which causes the conductive layer to be over-etched and affects the line width and bonding strength.

[0047] Furthermore, in the first hollow protrusion structure, the ratio of the sum of the areas of the fourth hollow portions to the total area of ​​the hollow portions is greater than 30%; wherein the maximum length of the fourth hollow portion is in the range of 0.1 μm-0.5 μm.

[0048] Specifically, in the first hollow protrusion structure, the ratio of the area of ​​the fourth hollow portion with a maximum length in the range of 0.1μm-0.5μm to the total area of ​​the hollow portion is greater than 30%, which increases the proportion of the smaller-sized fourth hollow portion, effectively improves the solidity of the protrusion structure, reduces the probability of the hollow protrusion structure breaking and falling off during the high-temperature and high-pressure pressing process, and improves the stability of the hollow protrusion structure.

[0049] Furthermore, the ratio of the number of the third hollow protrusion structures to the number of the hollow protrusion structures is less than 20%; wherein, the ratio of the total area of ​​the hollow parts in the third hollow protrusion structure to the slice area is within a second preset range, and the second preset range is 20%-30%.

[0050] Specifically, the ratio of the number of third hollow protrusion structures in which the ratio of the total area of ​​the hollow parts to the area of ​​the slice is 20%-30% to the number of hollow protrusion structures is less than 20%, which can effectively reduce the proportion of the third hollow protrusion structure in which the hollow parts account for a relatively large proportion in the hollow protrusion structure, improve the solidity of the protrusion structure, reduce the probability of the hollow protrusion structure breaking and falling off during the high-temperature and high-pressure pressing process, and improve the stability of the hollow protrusion structure.

[0051] Furthermore, the thickness of the resistance layer ranges from 50 nm to 3 μm.

[0052] Specifically, by setting the resistor layer to a relatively thin thickness, after the composite metal foil is fabricated into a circuit board, the temperature of individual components within the circuit board can be monitored without affecting the overall structure of the circuit board. Furthermore, compared to commonly used thermistors and chip resistors, the resistor layer is located directly in the circuit below the heat source, conducting heat through solder pads or copper wires. This is more efficient than air conduction, resulting in a faster response rate and improved thermal management accuracy.

[0053] Furthermore, the roughness Rz of the conductive layer on the side close to the resistance layer is in the range of 1-7 μm.

[0054] The roughness Rz is used to characterize the microscopic roughness of the surface of the conductive layer.

[0055] Specifically, the sum of the average value of the five largest profile peak heights and the average value of the five largest profile valley depths within the sampling length is usually taken as the roughness Rz. The roughness Rz of the first surface of the conductive layer is set in the range of 1-7μm, which can reduce the height difference of the protruding structure in the conductive layer, thereby effectively improving the bonding force between the composite metal foil and the substrate, thereby making the bonding between the composite metal foil and the substrate tighter.

[0056] Further, Figure 4 is a schematic structural diagram of another composite metal foil provided according to an embodiment of the present invention, Figure 4The composite metal foil further includes: an adjustment layer 30 ; the adjustment layer 30 is arranged on a side of the resistance layer 10 away from the conductive layer 20 .

[0057] Specifically, adding the adjustment layer 30 to the composite metal foil can effectively enhance the bonding strength between the composite metal foil pressed onto the substrate and the substrate, thereby preventing the composite metal foil from falling off.

[0058] Optionally, the adjustment layer 30 may be made of a silane coupling agent, a titanate coupling agent, an aluminate coupling agent, a phosphate coupling agent, a modified epoxy resin, an acrylic resin, a modified rubber, a modified thermoplastic polyimide, or other materials. Specifically, in this embodiment, the adjustment layer is made of a silane coupling agent, which helps ensure the bonding strength between the resistor layer 10 and the substrate and prevents the circuit from falling off.

[0059] Furthermore, the resistance layer has a negative temperature coefficient, and within any 25° C. change range, the resistance value change rate of the resistance layer is greater than 5%.

[0060] Specifically, the resistance layer's temperature change rate is set to be greater than 5% after a 25°C change from any temperature, thereby increasing the resistance layer's sensitivity to temperature changes. When the composite metal foil is fabricated into a circuit board, the monitoring of individual components within the circuit board becomes more precise.

[0061] Furthermore, the temperature is increased from 25° C. to 150° C. and then decreased to 25° C. as one temperature cycle, and after at least one temperature cycle, the resistance value recovery deviation of the resistor layer is less than 10%.

[0062] The term "at least once" may be understood as one or more than one time. The resistance recovery deviation may be understood as the ratio of the difference between the resistance value of the resistor layer before temperature increase and the resistance value after one temperature cycle to the resistance value of the resistor layer before temperature increase.

[0063] Specifically, after a single temperature cycle, the resistance value of the resistor layer recovers with a deviation of less than 10%. This allows the resistance layer to return to near its original value after a temperature increase and then to room temperature, making it reusable. This achieves temperature control, ensures operational accuracy, and improves operational reliability. Furthermore, the resistance of the resistor layer changes smoothly with temperature, ensuring stable circuit operation. After multiple temperature cycles, the resistance value of the resistor layer can still return to near its initial value, and the resistance value continues to change smoothly, thereby ensuring a longer service life for the composite metal foil.

[0064] Experimental group 1

[0065] A composite metal foil includes a conductive layer and a resistive layer. The conductive layer is made of Cu, the base layer is 18 μm thick, and the resistive layer is made of a nickel-iron oxide alloy, with a thickness of 610 nm. Under electron microscopic observation, the ratio of the number of first hollowed-out raised structures to the number of raised structures is 65%, and the ratio of the total area of ​​the hollowed portions of all first hollowed-out raised structures to the area of ​​a section of the first hollowed-out raised structures is less than 20%.

[0066] Experimental Group 2

[0067] Based on experimental group 1, under the observation of a scanning electron microscope, the ratio of the number of second hollow protrusion structures to the number of protrusion structures was set to 60%, wherein the number of first hollow portions in all second hollow protrusion structures was less than the number of second hollow portions.

[0068] Experimental Group 3

[0069] Different from the experimental group 1, under the observation of a scanning electron microscope, the maximum length of the hollow portion in the first hollow protrusion structure is less than 4.4 μm.

[0070] Control group 1

[0071] The composite metal foil includes a conductive layer and a resistive layer. The conductive layer is made of Cu, and the base layer has a thickness of 18 μm. The resistive layer is made of ferrite and has a thickness of 1.5 μm. Scanning electron microscopy revealed that the ratio of the number of first hollowed-out raised structures to the number of raised structures was 46%, and the ratio of the total area of ​​all hollowed portions of all first hollowed-out raised structures to the area of ​​a section of the first hollowed-out raised structures was less than 20%.

[0072] Control group 2

[0073] A composite metal foil comprises a conductive layer and a resistive layer, wherein the conductive layer is made of Cu, the base layer has a thickness of 18 μm, and the resistive layer is made of Ni-P alloy, with a thickness of 2.5 nm. Under a scanning electron microscope, the ratio of the number of first hollowed-out protruding structures to the number of protruding structures is 13%, wherein the ratio of the total area of ​​all hollowed-out portions in all first hollowed-out protruding structures to the slice area of ​​the first hollowed-out protruding structures is less than 20%. Samples were prepared using the composite metal foils of the experimental group and the control group, and were pressed onto a semi-cured core layer at 185°C for 10 minutes. The copper layer was removed with an alkaline etchant, and after cleaning, the sample was baked in a 105°C oven for 10 minutes to remove moisture. A small 2 cm × 2 cm grid was marked on the surface of the sample after alkaline etching to remove the copper. The square resistance of each grid was tested using a square resistance meter, and the square resistance uniformity was statistically measured to form a square resistance uniformity comparison table of different experimental groups and control groups as shown in Table 1.

[0074] Table 1. Comparison of square resistance uniformity of different test groups and control groups

[0075]

[0076] It can be seen from the data in Table 1 that the composite metal foils of test groups 1-3 have higher square resistance uniformity, which is beneficial to improving the quality of use.

[0077] An embodiment of the present invention further provides a metal-clad laminate, comprising the composite metal foil described in any one of the above embodiments. The metal-clad laminate of the present invention has the same beneficial effects as the composite metal foil described in any one of the embodiments of the present invention.

[0078] An embodiment of the present invention further provides a circuit board comprising the composite metal foil described in any of the above embodiments. The composite metal foil can be applied to the circuitry and component surfaces of the circuit board to measure the temperature of the circuitry or components. The circuit board of this embodiment of the present invention comprises the composite metal foil, and the resistive layer formed within the composite metal foil has improved uniformity, enabling precise monitoring of every location on the circuit board, improving temperature detection accuracy, and preventing damage to the circuit board due to excessive temperatures.

[0079] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in the present invention can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved. This is not limited herein.

[0080] The above specific embodiments do not limit the scope of protection of the present invention. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention.

Claims

1. A composite metal foil, characterized in that: include: A resistor layer and a conductive layer, wherein the resistor layer is disposed on a first surface of the conductive layer, and the first surface is provided with a plurality of raised structures, wherein the raised structures include at least one hollowed-out raised structure, and the hollowed-out raised structure includes at least one hollowed-out portion; the composite metal foil is sliced ​​along a first direction, and within a preset area, the ratio of the number of the first hollowed-out raised structures to the number of the raised structures is greater than 50%; wherein the first direction is the direction from the conductive layer to the resistor layer, and the ratio of the total area of ​​the hollowed-out portions in the first hollowed-out raised structure to the slice area is less than 20%.

2. The composite metal foil according to claim 1, characterized in that The hollow portion includes a first hollow portion and a second hollow portion; The first hollow portion is in communication with the outside, and the second hollow portion is located inside the hollow protrusion structure.

3. The composite metal foil according to claim 2, characterized in that The ratio of the number of the second hollow protrusion structures to the number of the protrusion structures is greater than 50%; wherein the number of the first hollow portions in the second hollow protrusion structure is less than the number of the second hollow portions.

4. The composite metal foil according to claim 1, characterized in that In the first hollow protrusion structure, the maximum length of the hollow portion is less than 4.4 μm.

5. The composite metal foil according to claim 1, characterized in that In the first hollow protrusion structure, the ratio of the number of the third hollow portions to the total number of the hollow portions is greater than 60%; wherein the aspect ratio of the minimum circumscribed rectangle of the third hollow portion is greater than 3.

6. The composite metal foil according to claim 1, characterized in that In the first hollow protrusion structure, the ratio of the sum of the areas of the fourth hollow portion to the total area of ​​the hollow portions is greater than 30%; wherein the maximum length of the fourth hollow portion is in the range of 0.1 μm to 0.5 μm.

7. The composite metal foil according to claim 1, characterized in that The ratio of the number of the third hollow protrusion structures to the number of the hollow protrusion structures is less than 20%; wherein the ratio of the total area of ​​the hollow parts in the third hollow protrusion structure to the slice area is in the range of 20%-30%.

8. The composite metal foil according to claim 1, characterized in that The thickness of the resistance layer is in the range of 50 nm to 3 μm.

9. The composite metal foil according to claim 7, characterized in that The roughness Rz of the conductive layer on a side close to the resistance layer is in a range of 1-7 μm.

10. The composite metal foil according to claim 7, characterized in that Also includes: Adjustment layer; The adjustment layer is arranged on a side of the resistance layer away from the conductive layer.

11. The composite metal foil according to claim 1, characterized in that The resistance layer has a negative temperature coefficient, and within any 25° C. change range, the resistance change rate of the resistance layer is greater than 5%.

12. The composite metal foil according to claim 1, characterized in that The temperature rises from 25° C. to 150° C. and then drops back to 25° C. as one temperature cycle. After at least one temperature cycle, the resistance value recovery deviation of the resistor layer is less than 10%.

13. A metal-clad laminate, characterized in that: The composite metal foil comprises the composite metal foil according to any one of claims 1 to 12.

14. A circuit board, characterized in that: The composite metal foil comprises the composite metal foil according to any one of claims 1 to 12.

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