Composite metal foil, metal-clad laminate, and circuit board

Abstract

The invention discloses a composite metal foil, a metal-clad laminate and a circuit board. The composite metal foil comprises a substrate layer and a first resistance layer which are arranged in a stacked mode. Wherein under the conditions that the temperature is 85 DEG C and the humidity is 85% RH, after 100-500 hours, the resistance recovery deviation of the first resistance layer is smaller than or equal to 15%. According to the composite metal foil, the resistance recovery precision of the first resistance layer is high, the resistance value is stable, the composite metal foil can be used in a severe working environment, the size of the composite metal foil is small, the composite metal foil can be used for manufacturing a small-size circuit board temperature control circuit, and temperature monitoring of a tiny device is achieved.

Description

Technical Field

[0001] The invention relates to the field of electronic technology, 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 developing towards high performance and miniaturization. However, electronic components will generate heat during operation. As the operating temperature increases, the electronic components will not be able to operate normally. Therefore, it is necessary to control the temperature of the electronic components to keep them operating normally. To achieve this goal, temperature control elements are often set on the surface or side of the electronic components, or chip thermistors are attached to the surface of the electronic components to monitor the temperature of the electronic components.

[0003] At present, the volume of temperature control elements is relatively large. Setting temperature control elements or surface-mounted thermistors on the surface of electronic components to achieve temperature monitoring is not conducive to the integration of circuit boards and occupies space on the circuit boards. Due to the limited location of its use, it is not possible to set temperature monitoring elements on many small electronic components, and it is also difficult to monitor the heat generation of most electronic components. Inadequate heat monitoring may result in the unmonitored electronic components being burned or failing due to overheating, affecting the normal operation of the circuit board and the terminal. Summary of the invention

[0004] The present invention provides a composite metal foil, a metal-clad laminate and a circuit board. The resistance recovery accuracy of the first resistance layer in the composite metal foil of the present invention is high, the resistance value is stable, and it can be used in harsh working environments. In addition, the composite metal foil is small in size and can be used for the production of temperature control circuits of small-volume circuit boards to achieve temperature monitoring of tiny devices.

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

[0006] A base layer and a first resistor layer are stacked;

[0007] Wherein, under the conditions of temperature of 85° C. and humidity of 85% RH, after 100 h to 500 h, the resistance recovery deviation of the first resistance layer is less than or equal to 15%.

[0008] Optionally, the temperature changes from -55°C to 150°C and then to -55°C as a first temperature cycle, and after N first temperature cycles, the resistance recovery deviation of the first resistance layer is less than 20%; wherein N is an integer greater than or equal to 50 and less than or equal to 2000.

[0009] Optionally, the temperature changes from 25°C to 125°C and then to 25°C as a second temperature cycle;

[0010] After N first temperature cycles, and / or after 100h-500h at 85°C and 85%RH; and after 1 second temperature cycle, the resistance recovery deviation of the first resistance layer is less than 10% compared with the case without the second temperature cycle.

[0011] Optionally, the temperature changes from 25°C to 125°C and then to 25°C as a second temperature cycle;

[0012] After N first temperature cycles, and / or after 100h-500h at a temperature of 85°C and a humidity of 85%RH; after M second temperature cycles, the resistance recovery deviation of the first resistance layer is less than 15% relative to the case where the M second temperature cycles are not performed;

[0013] Wherein, M is an integer less than or equal to 10,000.

[0014] Optionally, in the second temperature cycle, during a temperature rise process, the resistance of the first resistance layer decreases, and during a temperature drop process, the resistance of the first resistance layer increases.

[0015] Optionally, the material used for the first resistance layer includes at least one element of Ni, Cr, Zn, Al, Fe, Si, P, Sn, O, N and Cu.

[0016] Optionally, the Cr content in the first resistance layer is less than 20%, the Fe content is less than 30%, the Ni content is greater than 30%, and the O content is less than 60%.

[0017] Optionally, the thickness of the first resistance layer is 5 nm-1 μm.

[0018] Optionally, the thickness of the base layer is 2 μm-70 μm.

[0019] Optionally, the roughness Rz of the surface of the base layer close to the first resistance layer is 0.5 μm-10 μm.

[0020] Optionally, the composite metal foil further comprises:

[0021] At least one of an absorbing layer, a second resistance layer and an adjustment layer is stacked with the base layer and the first resistance layer.

[0022] According to a second aspect of the present invention, there is provided a metal-clad laminate, the metal-clad laminate comprising the composite metal foil according to any embodiment of the present invention.

[0023] According to a third aspect of the present invention, a circuit board is provided, the circuit board comprising the composite metal foil according to any embodiment of the present invention, the composite metal foil being arranged on the surface or inside of the circuit board.

[0024] The composite metal foil of this embodiment is under the conditions of temperature 85°C and humidity 85% RH, and after 100h-500h, the resistance recovery deviation of the first resistor layer is less than or equal to 15%, that is, after a long time under the conditions of temperature 85°C and humidity 85% RH, the resistance value of the first resistor layer 10 is still close to the initial resistance value. The resistance recovery accuracy of the first resistor layer is high, the resistance value is stable, and it can be used in harsh working environments. In addition, the composite metal foil is small in size and can be used in the production of temperature control circuits of small-volume circuit boards to achieve temperature monitoring of tiny devices.

[0025] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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.

[0027] Figure 1 is a schematic diagram of a composite metal foil provided by an embodiment of the present invention;

[0028] Figure 2 is a schematic diagram of another composite metal foil provided by an embodiment of the present invention;

[0029] Figure 3 is a schematic diagram of another composite metal foil provided by an embodiment of the present invention;

[0030] Figure 4 is a schematic diagram of another composite metal foil provided by an embodiment of the present invention;

[0031] Figure 5 is a schematic diagram of a circuit board provided by an embodiment of the present invention;

[0032] Figure 6 This is a schematic diagram of another circuit board provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme 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 described embodiments 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 creative work should fall within the scope of protection of the present invention.

[0034] It should be noted that the terms "first", "second", etc. in the specification 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 data 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 that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0035] An embodiment of the present invention provides a composite metal foil. Figure 1 is a schematic diagram of a composite metal foil provided by an embodiment of the present invention, with reference to Figure 1 , composite metal foil includes:

[0036] A base layer 20 and a first resistor layer 10 are stacked;

[0037] Wherein, under the conditions of temperature 85° C. and humidity 85% RH, after 100 h to 500 h, the resistance recovery deviation of the first resistance layer is less than or equal to 15%.

[0038] Specifically, under the conditions of temperature 85°C and humidity 85%RH, after 100h-500h, the resistance recovery deviation of the first resistance layer = 100%*|resistance of the first resistance layer 10 after 100h-500h-initial resistance of the first resistance layer 10 before 100h-500h| / initial resistance of the first resistance layer 10 before 100h-500h. The base layer 20 carries and conducts electricity to the first resistance layer 10, so that the first resistance layer 10 can spread on its surface and can be used normally to make circuits.

[0039] The material of the base layer 20 is a conductive material or a dielectric material, and the base layer can be a single-layer structure or a multi-layer structure. The conductive material includes but is not limited to gold, silver, aluminum, iron, copper, titanium, zinc, nickel, chromium and cobalt. Specifically, the base layer 20 can be copper foil, aluminum foil, titanium foil, zinc foil, iron foil, nickel foil, chromium foil, cobalt foil, silver foil or gold foil, or an alloy foil containing at least two of copper, aluminum, titanium, zinc, iron, nickel, chromium, cobalt, silver and gold, or a composite foil composed of at least two of copper foil, aluminum foil, titanium foil, zinc foil, iron foil, nickel foil, chromium foil, cobalt foil, silver foil and gold foil. The dielectric material includes PET (Polyethylene Terephthalate), PP (Polypropylene), PS (Polystyrene), ABF (Acrylonitrile-Butadiene-Styrene Terpolymer, polyacrylamide / styrene / styrene sulfate terpolymer) film, BT resin, polyacrylic acid, polyurethane, polyimide, etc., which are not listed in detail here. Among them, BT resin is a thermosetting resin formed by adding bismaleimide (BMI) and triazine as the main resin components, and epoxy resin, polyphenylene ether resin (PPE) or allyl compounds as modified components. In the base layer 20 with a multi-layer structure, the materials of different layers can be the same or different.

[0040] The composite metal foil is a thin film resistor, which is also called buried copper foil, embedded copper foil, thin film resistor copper foil, etc. In this embodiment, the first resistor layer 10 has the properties of a thermistor. As the temperature rises, the resistance of the first resistor layer 10 changes. As the temperature returns to the initial position, the resistance of the first resistor layer 10 can return to the vicinity of the original resistance value. The operating temperature of the components to be tested can be monitored in real time by detecting the resistance change of the first resistor layer 10. When the preset temperature is exceeded, other temperature control circuits are used to protect the components to be tested in time, thereby protecting the components to be tested and preventing the electronic components from being burned out due to excessive temperature.

[0041] When conventional thermistors are used on circuit boards and terminal devices, they usually encounter harsh working environments, which will affect the resistance value of the thermistor and cause the thermistor to fail.

[0042] The composite metal foil of this embodiment has a resistance recovery deviation of the first resistance layer less than or equal to 15% after 100h-500h under the conditions of temperature 85°C and humidity 85% RH, that is, after a long time under the conditions of temperature 85°C and humidity 85% RH, the resistance value of the first resistance layer 10 is still close to the initial resistance value. The resistance recovery accuracy of the first resistance layer 10 is high and the resistance value is stable, so it can be used in harsh working environments.

[0043] Based on the above embodiment, optionally, the temperature changes from -55°C to 150°C and then to -55°C as a first temperature cycle. After N first temperature cycles, the resistance recovery deviation of the first resistance layer 10 is less than 20%; wherein N is an integer greater than or equal to 50 and less than or equal to 2000.

[0044] After N first temperature cycles, the resistance of the first resistor layer 10 recovers to the deviation

[0045] =100%*|resistance of the first resistor layer 10 at -55°C after N first temperature cycles−resistance of the first resistor layer 10 at -55°C before N first temperature cycles| / resistance of the first resistor layer 10 at -55°C before N first temperature cycles|.

[0046] For the composite metal foil of this embodiment, after 50-2000 first temperature cycles, the resistance recovery deviation of the first resistor layer 10 is less than 20%, and after multiple high and low temperature cycles, the resistance change of the first resistor layer 10 is small and remains near the initial resistance value, that is, the composite metal foil of this embodiment can withstand multiple hot and cold shocks, the resistance recovery accuracy of the first resistor layer 10 is high, the resistance value is stable, and it can be used in harsh working environments. In addition, the composite metal foil is small in size and can be used in the production of temperature control circuits of small-volume circuit boards to achieve temperature monitoring of tiny devices.

[0047] Based on the above embodiment, optionally, the temperature changes from 25° C. to 125° C. and then changes to 25° C. as a second temperature cycle;

[0048] After N first temperature cycles, and / or after 100h-500h at 85°C and 85%RH; and after 1 second temperature cycle, the resistance recovery deviation of the first resistance layer is less than 10% compared with the case without the second temperature cycle.

[0049] That is, after N first temperature cycles, after 1 second temperature cycle, the resistance recovery deviation of the first resistor layer is less than 10% relative to the case where the first temperature cycle has not been performed. After 100h-500h at a temperature of 85°C and a humidity of 85%RH, after 1 second temperature cycle, the resistance recovery deviation of the first resistor layer is less than 10% relative to the case where the first temperature cycle has not been performed. After N first temperature cycles, and after 100h-500h at a temperature of 85°C and a humidity of 85%RH, after 1 second temperature cycle, the resistance recovery deviation of the first resistor layer is less than 10% relative to the case where the first temperature cycle has not been performed.

[0050] Among them, the resistance recovery deviation of the first resistor layer after one second temperature cycle relative to not undergoing one second temperature cycle = 100%*|resistance of the first resistor layer 10 after one second temperature cycle - resistance of the first resistor layer 10 before one second temperature cycle| / resistance of the first resistor layer 10 before one second temperature cycle|.

[0051] The composite metal foil of this embodiment has little effect on the resistance characteristics of the first resistance layer 10 after N first temperature cycles and 100h-500h at a temperature of 85°C and a humidity of 85%RH. After N first temperature cycles and / or 100h-500h at a temperature of 85°C and a humidity of 85%RH, the temperature is raised and then restored to room temperature, and the resistance recovery deviation of the first resistance layer 10 is less than 10%, and the resistance can return to the vicinity of the initial resistance value, so that the composite metal foil can be reused to achieve the temperature detection function, ensuring that the composite metal foil has a long service life, ensuring its working accuracy, and improving its working reliability.

[0052] Based on the above embodiment, optionally, the temperature changes from 25° C. to 125° C. and then changes to 25° C. as a second temperature cycle;

[0053] After N first temperature cycles, and / or after 100h-500h at a temperature of 85°C and a humidity of 85%RH; after M second temperature cycles, the resistance recovery deviation of the first resistance layer is less than 15% relative to the case where the first resistance layer has not undergone the M second temperature cycles;

[0054] Wherein, M is an integer less than or equal to 10,000.

[0055] That is, after N first temperature cycles, after M second temperature cycles, the resistance recovery deviation of the first resistor layer is less than 15% relative to the case where the M second temperature cycles have not been performed. After 100h-500h at a temperature of 85°C and a humidity of 85%RH, after M second temperature cycles, the resistance recovery deviation of the first resistor layer is less than 15% relative to the case where the M second temperature cycles have not been performed. After N first temperature cycles, and after 100h-500h at a temperature of 85°C and a humidity of 85%RH, after M second temperature cycles, the resistance recovery deviation of the first resistor layer is less than 15% relative to the case where the M second temperature cycles have not been performed.

[0056] Among them, the resistance recovery deviation of the first resistor layer after M second temperature cycles relative to not undergoing M second temperature cycles = 100%*|resistance of the first resistor layer 10 after M second temperature cycles - resistance of the first resistor layer 10 before M second temperature cycles| / resistance of the first resistor layer 10 before M second temperature cycles|.

[0057] The composite metal foil of this embodiment has little effect on the resistance characteristics of the first resistor layer 10 after N first temperature cycles and 100h-500h at a temperature of 85°C and a humidity of 85%RH. After N first temperature cycles and / or 100h-500h at a temperature of 85°C and a humidity of 85%RH, and then multiple second temperature cycles, the resistance recovery deviation of the first resistor layer 10 is within 15%, and after multiple second temperature cycles, the resistance value of the first resistor layer 10 can still be restored to near the initial resistance value, so that the composite metal foil can be reused to achieve the temperature detection function, ensuring that the composite metal foil has a longer service life, ensuring its working accuracy, and improving its working reliability.

[0058] On the basis of the above embodiment, optionally, in the second temperature cycle, during the temperature rise process, the resistance of the first resistance layer 10 decreases, and during the temperature drop process, the resistance of the first resistance layer 10 increases.

[0059] Specifically, during the process of the temperature rising from 25°C to 125°C, the resistance of the first resistor layer 10 may decrease linearly or nonlinearly, and may decrease in a straight line or in a curve. During the process of the temperature falling from 125°C to 25°C, the resistance of the first resistor layer 10 may increase linearly or nonlinearly, and may increase in a straight line or in a curve. After the temperature changes to 25°C, the resistance of the first resistor layer 10 can return to the vicinity of the initial resistance. That is, the composite metal foil of this embodiment undergoes N first temperature cycles, and after 100h-500h at a temperature of 85°C and a humidity of 85%RH, the resistance characteristics of the first resistor layer 10 will not be affected. The first resistor layer 10 still has the properties of a thermistor, and accurate temperature monitoring can be achieved.

[0060] Based on the above embodiments, optionally, the material used for the first resistance layer 10 includes at least one element selected from the group consisting of Ni, Cr, Zn, Al, Fe, Si, P, Sn, O, N and Cu.

[0061] The first resistor layer may include one element, two or more elements selected from Ni, Cr, Zn, Al, Fe, Si, P, Sn, O, N and Cu. Exemplarily, the material of the first resistor layer 10 is an alloy such as nickel-chromium alloy or nickel-chromium-iron alloy. In addition, the first resistor layer 10 may also include oxides or nitrides. By adjusting the ratio of different elements, the resistance of the first resistor layer 10 can meet the performance of the above-mentioned embodiment.

[0062] Optionally, the first resistance layer 10 may be formed on the base layer 20 by bonding, electroplating, chemical plating, physical vapor deposition, chemical vapor deposition or other forming methods.

[0063] Specifically, the first resistor layer 10 is formed by vacuum magnetron sputtering process. The target material element is sputtered onto the base layer 20, and the common electroplating method is not used, and the water washing and drying operation after electroplating is not required. The first resistor layer 10 is formed by vacuum sputtering process, so that the resistance of the first resistor layer 10 is more stable and more uniform, and the uniformity of square resistance is improved.

[0064] On the basis of the above embodiments, optionally, the first resistance layer 10 includes Fe and O, or the first resistance layer 10 includes Fe and Cr, or the first resistance layer 10 includes Fe and Ni, or the first resistance layer 10 includes Fe and N, or the first resistance layer 10 includes Ni, Fe and O, or the first resistance layer 10 includes Ni, Cr, Fe and O, or the first resistance layer 10 includes Ni, Cr and N, or the first resistance layer 10 includes Ni, Cr and O, or the first resistance layer 10 includes Ni and O, or the first resistance layer 10 includes Fe, Cu and O, or the first resistance layer includes 10Fe, Sn and O, or the first resistance layer includes Fe, Mo and O, etc.

[0065] Based on the above embodiment, optionally, in the first resistor layer, the ratio of Fe content to Cr content is less than or equal to 2.5. Exemplarily, the ratio of Fe content to Cr content is 2 or 1.5.

[0066] Based on the above embodiment, optionally, in the first resistor layer, the ratio of Fe content to Ni content is less than 1. Exemplarily, the ratio of Fe content to Ni content is 0.7 or 0.8.

[0067] Based on the above embodiment, optionally, in the first resistor layer, the ratio of the O content to the Fe content is less than or equal to 3. Exemplarily, the ratio of the O content to the Fe content is 1.3, 1.5, 1.8 or 2, etc.

[0068] On the basis of the above embodiment, optionally, the ratio of the content of Ni to the content of Cr in the first resistor layer 10 is greater than 1.5, the ratio of the content of Ni to the content of Fe in the first resistor layer 10 is greater than 1, and the ratio of the content of Ni to the content of O in the first resistor layer 10 is greater than 0.5. In this way, after the first resistor layer 10 has undergone multiple first temperature cycles, the resistance recovery deviation is smaller, and after 100h-500h under the conditions of temperature 85°C and humidity 85%RH, the resistance recovery deviation of the first resistor layer 10 is smaller, and after multiple second temperature cycles, the resistance recovery deviation of the first resistor layer 10 is smaller and the service life is longer.

[0069] Based on the above embodiment, optionally, the content of Cr in the first resistor layer is less than 20%, the content of Fe is less than 30%, the content of Ni is greater than 30%, and the content of O is less than 60%;

[0070] By such arrangement, after the first resistor layer 10 has undergone multiple first temperature cycles, the resistance recovery deviation is smaller, and after 100h-500h under the conditions of temperature 85°C and humidity 85% RH, the resistance recovery deviation of the first resistor layer 10 is smaller, and after multiple second temperature cycles, the resistance recovery deviation of the first resistor layer 10 is smaller, and the service life is longer.

[0071] Based on the above embodiment, optionally, the thickness of the first resistance layer is 5 nm-1 μm.

[0072] Specifically, if the thickness of the first resistor layer 10 is too large or too small, it will affect the resistance of the first resistor layer 10, thereby affecting the recovery accuracy of the resistance of the first resistor layer 10 and the accuracy of the monitoring circuit. Therefore, by setting the thickness of the first resistor layer 10 to be greater than or equal to 5 nanometers and less than or equal to 1 micron, the resistance of the first resistor layer 10 can be within a suitable range, so that the recovery accuracy of the resistance of the first resistor layer 10 and the accuracy of the monitoring circuit are both high, which can meet the requirements of monitoring the temperature of the component to be measured on the circuit board.

[0073] Based on the above embodiment, optionally, the material used for the base layer 20 includes at least one element selected from the group consisting of gold, silver, aluminum, iron and copper.

[0074] Specifically, the base layer 20 may be copper foil, aluminum foil, iron foil, silver foil or gold foil, or an alloy foil containing at least two of gold, silver, aluminum, iron and copper, or a composite foil composed of at least two of copper foil, aluminum foil, iron foil, silver foil and gold foil. When the material used for the base layer 20 includes at least one element of gold, silver, aluminum, iron and copper, the base layer 20 has better conductive properties when it has a better supporting effect.

[0075] Based on the above embodiment, optionally, the thickness of the base layer 20 is 2 μm-70 μm.

[0076] For example, the thickness of the base layer is 3 μm, 5 μm, 10 μm, 16 μm, 30 μm or 40 μm, etc. While the base layer 20 of such thickness ensures the supporting effect, when the base layer 20 is a copper layer, it can be used to directly etch the temperature measurement circuit to meet the circuit etching requirements.

[0077] On the basis of the above embodiment, optionally, the roughness Rz of the surface of the base layer 20 close to the first resistance layer 10 is 0.5 μm-10 μm.

[0078] Specifically, the roughness within the above range can improve the bonding force between the base layer 20 and the first resistor layer 10, and because the first resistor layer 10 is relatively thin, often at the nanometer level, the roughness of the first resistor layer 10 replicates the roughness of the base layer 20, so that after the composite metal foil is set on the surface of the device to be tested, the bonding force between the first resistor layer 10 and the circuit board is large, thereby improving the peeling resistance performance.

[0079] Figure 2 is a schematic diagram of another composite metal foil provided by an embodiment of the present invention, Figure 3 is a schematic diagram of another composite metal foil provided by an embodiment of the present invention, Figure 4 FIG. 1 is a schematic diagram of another composite metal foil provided by an embodiment of the present invention. Figure 2-Figure 4 , the composite metal foil also includes:

[0080] At least one of the absorption layer 40 , the second resistance layer 50 , and the adjustment layer 30 stacked with the base layer 20 and the first resistance layer 10 .

[0081] Specifically, refer to Figure 2 The absorption layer 40 can be disposed between the first resistance layer 10 and the base layer 20, or on the surface of the first resistance layer 10 away from the base layer 20, which is not limited in the embodiment of the present invention. The absorption layer 40 is used to absorb electromagnetic waves, and the material used in the absorption layer 40 includes polymer materials.

[0082] refer to Figure 3 The second resistance layer 50 can be located on the side of the first resistance layer 10 away from the base layer 20, or can be located between the first resistance layer 10 and the base layer 20. As the temperature changes, the resistance value of the second resistance layer 50 remains unchanged. The second resistance layer 50 is used to adjust the overall resistance of the composite metal foil, so that the basic resistance is larger, thereby improving the temperature measurement accuracy.

[0083] refer to Figure 4 The adjustment layer 30 can be arranged on the side of the first resistor layer 10 away from the base layer 20, and the side of the first resistor layer 10 away from the base layer 20 is pressed on the circuit board; the function of the adjustment layer 30 is to improve the bonding force between the composite metal foil and the circuit board to prevent the composite metal foil from falling off. The material of the adjustment layer 30 may include at least one of a silane coupling agent, an aluminate coupling agent, a metal composite coupling agent, a phosphate coupling agent, a borate coupling agent, polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC).

[0084] An embodiment of the present invention further provides a metal-clad laminate, which includes the composite metal foil described in any embodiment of the present invention.

[0085] The metal-clad laminate of the embodiment of the present invention has the same beneficial effects as the composite metal foil described in any embodiment of the present invention. The embodiment of the present invention also provides a circuit board, Figure 5 is a schematic diagram of a circuit board provided by an embodiment of the present invention, Figure 6 is a schematic diagram of another circuit board provided by an embodiment of the present invention, with reference to Figure 5 and Figure 6 The circuit board includes the composite metal foil 100 described in any embodiment of the present invention, and the composite metal foil 100 is arranged on the surface or inside of the circuit board.

[0086] refer to Figure 5 The composite metal foil 100 is pressed into the circuit board 300 through the prepreg 200 and is arranged on the surface of the circuit board 300. Figure 6 The composite metal foil 100 is pressed into the circuit board 300 through two prepreg sheets 200 and is arranged inside the circuit board 300 .

[0087] The circuit board according to the embodiment of the present invention has the same beneficial effects as the composite metal foil according to any embodiment of the present invention.

[0088] Example 1

[0089] This embodiment provides a composite metal foil, including a base layer and a first resistor layer. The base layer is a copper layer, and the thickness of the base layer is 10 μm. The materials used in the first resistor layer include Cr, Fe, Ni and O, the content of Cr is 15%, the content of Fe is 25%, the content of Ni is 35%, the content of O is 25%, and the thickness of the first resistor layer is 10 nm.

[0090] The first temperature cycle test and the second temperature cycle test were performed on some composite metal foils, and the following data were obtained: after 100 first temperature cycles, the resistance recovery deviation of the first resistor layer was 5%. After 100 first temperature cycles, the resistance recovery deviation of the first resistor layer after 1 second temperature cycle was 3% compared with the case where no second temperature cycle was performed. After 1200 second temperature cycles, the resistance recovery deviation of the first resistor layer was 8% compared with the case where no second temperature cycle was performed.

[0091] The following data were obtained by subjecting some composite metal foils to a temperature test of 85°C and a humidity test of 85%RH: after 200 hours, the resistance recovery deviation of the first resistor layer was 8%. After 200 hours, the resistance recovery deviation of the first resistor layer after one second temperature cycle was 4% compared with the case where the first resistor layer did not undergo one second temperature cycle; after 1200 second temperature cycles, the resistance recovery deviation of the first resistor layer was 7% compared with the case where the first resistor layer did not undergo the 1200 second temperature cycles.

[0092] A first temperature cycle test, a test at a temperature of 85°C and a humidity of 85% RH, and a second temperature cycle test were performed on some composite metal foils, and the following data were obtained: after 100 first temperature cycles, and under the conditions of a temperature of 85°C and a humidity of 85% RH, after 200 hours, and then after one second temperature cycle, the resistance recovery deviation of the first resistor layer was 5% relative to that before the one second temperature cycle, and after 1200 second temperature cycles, the resistance recovery deviation of the first resistor layer was 10% relative to that before the 1200 second temperature cycles.

[0093] For the composite metal foil of the present embodiment, the resistance change of the first resistor layer is small after 100 first temperature cycles, and the resistance recovery deviation of the first resistor layer is small after 200 hours under the conditions of temperature 85°C and humidity 85% RH. The resistance recovery accuracy of the first resistor layer is high and the resistance value is stable in a harsh working environment, and the resistance recovery deviation of the first resistor layer is small after 1200 second temperature cycles. The composite metal foil of the present embodiment can realize temperature monitoring of tiny devices in a harsh working environment and has a long working life.

[0094] Example 2

[0095] Different from the first embodiment, the content of Cr in the first resistor layer of this embodiment is 10%, the content of Fe is 25%, the content of Ni is 35%, and the content of O is 30%.

[0096] The first temperature cycle test and the second temperature cycle test were performed on some composite metal foils, and the following data were obtained: after 500 first temperature cycles, the resistance recovery deviation of the first resistor layer was 6%. After 500 first temperature cycles, the resistance recovery deviation of the first resistor layer after 1 second temperature cycle was 4% compared with the case where the first resistor layer did not undergo 1 second temperature cycle. After 1400 second temperature cycles, the resistance recovery deviation of the first resistor layer was 10% compared with the case where the first resistor layer did not undergo the 1400 second temperature cycles.

[0097] The following data were obtained by subjecting some composite metal foils to a temperature test of 85°C and a humidity test of 85%RH: after 300 hours, the resistance recovery deviation of the first resistor layer was 9%. After 300 hours, the resistance recovery deviation of the first resistor layer after one second temperature cycle was 5% compared with the case where the first resistor layer did not undergo one second temperature cycle; after 1400 second temperature cycles, the resistance recovery deviation of the first resistor layer was 9% compared with the case where the first resistor layer did not undergo the 1400 second temperature cycles.

[0098] The first temperature cycle test, the test at 85°C and 85% RH, and the second temperature cycle test were performed on some composite metal foils, and the following data were obtained: after 500 first temperature cycles, and under the conditions of temperature 85°C and humidity 85% RH, after 300 hours, and then after 1 second temperature cycle, the resistance recovery deviation of the first resistor layer was 7% relative to the case when the second temperature cycle was not passed through, and after 1400 second temperature cycles, the resistance recovery deviation of the first resistor layer was 11% relative to the case when the 1400 second temperature cycles were not passed through.

[0099] For the composite metal foil of the present embodiment, after 500 first temperature cycles, the resistance recovery deviation of the first resistor layer is small, and after 300 hours under the conditions of temperature 85°C and humidity 85% RH, the resistance recovery deviation of the first resistor layer is small. In a harsh working environment, the resistance recovery accuracy of the first resistor layer is high and the resistance value is stable. Moreover, after 1400 second temperature cycles, the resistance recovery deviation of the first resistor layer is small. The composite metal foil of the present embodiment can realize temperature monitoring of tiny devices in a harsh working environment and has a long working life.

[0100] Example 3

[0101] Different from the first embodiment, the content of Cr in the first resistor layer of this embodiment is 10%, the content of Fe is 15%, the content of Ni is 40%, and the content of O is 35%.

[0102] The first temperature cycle test and the second temperature cycle test were performed on some composite metal foils, and the following data were obtained: after 1000 first temperature cycles, the resistance recovery deviation of the first resistor layer was 10%. After 1000 first temperature cycles, the resistance recovery deviation of the first resistor layer after one second temperature cycle was 4% compared with the case where no second temperature cycle was performed. After 1700 second temperature cycles, the resistance recovery deviation of the first resistor layer was 12% compared with the case where no second temperature cycle was performed.

[0103] The following data were obtained by subjecting some composite metal foils to a temperature test of 85°C and a humidity test of 85%RH: after 300 hours, the resistance recovery deviation of the first resistor layer was 11%. After 300 hours, the resistance recovery deviation of the first resistor layer after one second temperature cycle was 4% compared with that before one second temperature cycle. After 1700 second temperature cycles, the resistance recovery deviation of the first resistor layer was 11% compared with that before 1700 second temperature cycles.

[0104] A first temperature cycle test, a test at a temperature of 85°C and a humidity of 85% RH, and a second temperature cycle test were performed on some composite metal foils, and the following data were obtained: after 1000 first temperature cycles, and under the conditions of a temperature of 85°C and a humidity of 85% RH, after 300 hours, and then after one second temperature cycle, the resistance recovery deviation of the first resistor layer was 6% relative to that before the one second temperature cycle; after 1700 second temperature cycles, the resistance recovery deviation of the first resistor layer was 13% relative to that before the 1700 second temperature cycles.

[0105] For the composite metal foil of the present embodiment, after 1000 first temperature cycles, the resistance recovery deviation of the first resistor layer is small, and after 300 hours under the conditions of temperature 85°C and humidity 85% RH, the resistance recovery deviation of the first resistor layer is small. In a harsh working environment, the resistance recovery accuracy of the first resistor layer is high and the resistance value is stable. Moreover, after 1700 second temperature cycles, the resistance recovery deviation of the first resistor layer is small. The composite metal foil of the present embodiment can realize temperature monitoring of tiny devices in a harsh working environment and has a long working life.

[0106] Example 4

[0107] Different from the first embodiment, the material used for the first resistance layer of the present embodiment includes Cr, Fe and Ni, the content of Cr is 18%, the content of Fe is 29% and the content of Ni is 53%.

[0108] The first temperature cycle test and the second temperature cycle test were performed on some composite metal foils, and the following data were obtained: after 1500 first temperature cycles, the resistance recovery deviation of the first resistor layer was 14%. After 1500 first temperature cycles, the resistance recovery deviation of the first resistor layer after one second temperature cycle was 7% compared with the case where no second temperature cycle was performed; after 2000 second temperature cycles, the resistance recovery deviation of the first resistor layer was 12% compared with the case where no second temperature cycle was performed.

[0109] The following data were obtained by subjecting some composite metal foils to a temperature test of 85°C and a humidity test of 85%RH: after 400 hours, the resistance recovery deviation of the first resistor layer was 12%. After 400 hours, the resistance recovery deviation of the first resistor layer after one second temperature cycle was 7% compared with that before one second temperature cycle. After 2000 second temperature cycles, the resistance recovery deviation of the first resistor layer was 12.5% ​​compared with that before 2000 second temperature cycles.

[0110] A first temperature cycle test, a test at a temperature of 85°C and a humidity of 85% RH, and a second temperature cycle test were performed on some composite metal foils, and the following data were obtained: after 1500 first temperature cycles, and under the conditions of a temperature of 85°C and a humidity of 85% RH, after 400 hours, and then after one second temperature cycle, the resistance recovery deviation of the first resistor layer was 5% relative to that before the one second temperature cycle, and after 2000 second temperature cycles, the resistance recovery deviation of the first resistor layer was 13% relative to that before the 2000 second temperature cycles.

[0111] For the composite metal foil of the present embodiment, after 1500 first temperature cycles, the resistance recovery deviation of the first resistor layer is small, and after 400 hours under the conditions of temperature 85°C and humidity 85% RH, the resistance recovery deviation of the first resistor layer is small. In a harsh working environment, the resistance recovery accuracy of the first resistor layer is high and the resistance value is stable. Moreover, after 2000 second temperature cycles, the resistance recovery deviation of the first resistor layer is small. The composite metal foil of the present embodiment can realize temperature monitoring of tiny devices in a harsh working environment and has a long working life.

[0112] Example 5

[0113] Different from the first embodiment, the thickness of the base layer in this embodiment is 20 μm, and the thickness of the first resistance layer is 50 nm.

[0114] The first temperature cycle test and the second temperature cycle test were performed on some composite metal foils, and the following data were obtained: after 1800 first temperature cycles, the resistance recovery deviation of the first resistor layer was 13%. After 1800 first temperature cycles, the resistance recovery deviation of the first resistor layer after one second temperature cycle was 8% compared with the case where no second temperature cycle was performed. After 2500 second temperature cycles, the resistance recovery deviation of the first resistor layer was 13% compared with the case where no second temperature cycle was performed.

[0115] The following data were obtained by conducting a temperature test of 85°C and a humidity test of 85%RH on some composite metal foils: at a temperature of 85°C and a humidity of 85%RH, after 500h, the resistance recovery deviation of the first resistor layer was 14%. At a temperature of 85°C and a humidity of 85%RH, after 500h, the resistance recovery deviation of the first resistor layer after one second temperature cycle was 8% compared with the case without one second temperature cycle, and after 2500 second temperature cycles, the resistance recovery deviation of the first resistor layer was 13.5% compared with the case without 2500 second temperature cycles.

[0116] The first temperature cycle test, the test at 85°C and 85% RH, and the second temperature cycle test were performed on some composite metal foils, and the following data were obtained: after 1800 first temperature cycles, and under the conditions of temperature 85°C and humidity 85% RH, after 500 hours, and then after 1 second temperature cycle, the resistance recovery deviation of the first resistor layer was 6% relative to the case when it did not undergo 1 second temperature cycle, and after 2500 second temperature cycles, the resistance recovery deviation of the first resistor layer was 14% relative to the case when it did not undergo 2500 second temperature cycles.

[0117] For the composite metal foil of the present embodiment, after 1800 first temperature cycles, the resistance recovery deviation of the first resistor layer is small, and after 500 hours under the conditions of temperature 85°C and humidity 85% RH, the resistance recovery deviation of the first resistor layer is small. In a harsh working environment, the resistance recovery accuracy of the first resistor layer is high and the resistance value is stable. Moreover, after 2500 second temperature cycles, the resistance recovery deviation of the first resistor layer is small. The composite metal foil of the present embodiment can realize temperature monitoring of tiny devices in a harsh working environment and has a long working life.

[0118] Example 6

[0119] Different from the first embodiment, the composite metal foil of the present embodiment further includes an adjustment layer. The material of the adjustment layer is an aluminate coupling agent. The thickness of the adjustment layer is 5 micrometers.

[0120] The first temperature cycle test and the second temperature cycle test were performed on some composite metal foils, and the following data were obtained: after 800 first temperature cycles, the resistance recovery deviation of the first resistor layer was 10%. After 800 first temperature cycles, the resistance recovery deviation of the first resistor layer after one second temperature cycle was 6% compared with the case where no second temperature cycle was performed. After 2100 second temperature cycles, the resistance recovery deviation of the first resistor layer was 13.5% compared with the case where no second temperature cycle was performed.

[0121] The following data were obtained by subjecting some composite metal foils to a temperature test of 85°C and a humidity test of 85%RH: after 350 hours, the resistance recovery deviation of the first resistor layer was 12%. After 350 hours, the resistance recovery deviation of the first resistor layer after one second temperature cycle was 9% compared with the case where the first resistor layer did not undergo one second temperature cycle. After 2100 second temperature cycles, the resistance recovery deviation of the first resistor layer was 13% compared with the case where the first resistor layer did not undergo the 2100 second temperature cycles.

[0122] A first temperature cycle test, a test at 85°C and 85% RH, and a second temperature cycle test were performed on some composite metal foils, and the following data were obtained: after 800 first temperature cycles, and under the conditions of temperature 85°C and humidity 85% RH, after 350 hours, and then after 1 second temperature cycle, the resistance recovery deviation of the first resistor layer was 5% relative to the case when the second temperature cycle was not passed through, and after 2100 second temperature cycles, the resistance recovery deviation of the first resistor layer was 12% relative to the case when the 2100 second temperature cycles were not passed through.

[0123] For the composite metal foil of the present embodiment, after 800 first temperature cycles, the resistance recovery deviation of the first resistor layer is small, and after 350 hours at a temperature of 85°C and a humidity of 85% RH, the resistance recovery deviation of the first resistor layer is small. In a harsh working environment, the resistance recovery accuracy of the first resistor layer is high and the resistance value is stable. Moreover, after 2100 second temperature cycles, the resistance recovery deviation of the first resistor layer is small. The composite metal foil of the present embodiment can realize temperature monitoring of tiny devices in a harsh working environment and has a long working life.

[0124] Comparative Example 1

[0125] The metal foil comprises a base layer and a resistor layer, wherein the base layer is a copper layer and the resistor layer is a nickel-phosphorus alloy. The base layer has a thickness of 10 micrometers and the resistor layer has a thickness of 100 nanometers.

[0126] The first temperature cycle test and the second temperature cycle test were carried out on some metal foils, and the following data were obtained: after 100 first temperature cycles, the resistance recovery deviation of the resistor layer was 100%. After 100 first temperature cycles, the resistance recovery deviation of the resistor layer after 1 second temperature cycle was 50% compared with the case where no second temperature cycle was carried out; after 1000 second temperature cycles, the resistance recovery deviation of the resistor layer was 200% compared with the case where no second temperature cycle was carried out.

[0127] Part of the metal foil was subjected to a temperature test of 85°C and a humidity test of 85%RH and a second temperature cycle test, and the following data were obtained: at a temperature of 85°C and a humidity of 85%RH, after 100 hours, the resistance of the resistance layer recovered by 150%. At a temperature of 85°C and a humidity of 85%RH, after 100 hours, the resistance of the resistance layer recovered by 60% after one second temperature cycle relative to the case where one second temperature cycle was not passed, and after 1000 second temperature cycles, the resistance of the resistance layer recovered by 250% relative to the case where the 1000 second temperature cycles were not passed.

[0128] A first temperature cycle test, a test at a temperature of 85°C and a humidity of 85% RH, and a second temperature cycle test were performed on some metal foils, and the following data were obtained: after 100 first temperature cycles, and under the conditions of a temperature of 85°C and a humidity of 85% RH, after 100 hours, and then after one second temperature cycle, the resistance recovery deviation of the resistor layer was 80% relative to that before the one second temperature cycle, and after 1000 second temperature cycles, the resistance recovery deviation of the resistor layer was 300% relative to that before the 1000 second temperature cycles.

[0129] For the metal foil of Comparative Example 1, after 100 first temperature cycles, the resistance recovery deviation of the resistance layer is large. After 100 hours under the conditions of temperature 85°C and humidity 85% RH, the resistance recovery deviation of the resistance layer is large. Moreover, after 1000 second temperature cycles, the resistance recovery deviation of the resistance layer is large, the thermal sensitive characteristics of the resistance layer are destroyed, the resistance recovery accuracy is low, and temperature monitoring cannot be performed.

[0130] Comparative Example 2

[0131] Different from Comparative Example 1, the thickness of the resistance layer is 2.5 micrometers.

[0132] The first temperature cycle test and the second temperature cycle test were performed on some metal foils, and the following data were obtained: after 50 first temperature cycles, the resistance recovery deviation of the resistor layer was 100%. After 50 first temperature cycles, the resistance recovery deviation of the resistor layer after one second temperature cycle was 50% compared with the case where no second temperature cycle was performed; after 500 second temperature cycles, the resistance recovery deviation of the resistor layer was 200% compared with the case where no second temperature cycle was performed.

[0133] Part of the metal foil was subjected to a temperature test of 85°C and a humidity test of 85%RH and a second temperature cycle test, and the following data were obtained: at a temperature of 85°C and a humidity of 85%RH, after 50 hours, the resistance of the resistor layer recovered by 90%. At a temperature of 85°C and a humidity of 85%RH, after 50 hours, after one second temperature cycle, the resistance of the resistor layer recovered by 50% relative to the case where no second temperature cycle was performed, and after 500 second temperature cycles, the resistance of the resistor layer recovered by 210% relative to the case where no second temperature cycle was performed.

[0134] A first temperature cycle test, a test at a temperature of 85°C and a humidity of 85% RH, and a second temperature cycle test were performed on some metal foils, and the following data were obtained: after 50 first temperature cycles, and under the conditions of a temperature of 85°C and a humidity of 85% RH, after 50 hours, and then after one second temperature cycle, the resistance recovery deviation of the resistor layer was 50% relative to the case when the second temperature cycle was not passed through, and after 500 second temperature cycles, the resistance recovery deviation of the resistor layer was 270% relative to the case when the 500 second temperature cycles were not passed through.

[0135] For the metal foil in Comparative Example 1, after 50 first temperature cycles, the resistance recovery deviation of the resistance layer is large. After 50 hours at a temperature of 85°C and a humidity of 85% RH, the resistance recovery deviation of the resistance layer is large. Moreover, after 500 second temperature cycles, the resistance recovery deviation of the resistance layer is large, the thermal sensitive characteristics of the resistance layer are destroyed, the resistance recovery accuracy is low, and temperature monitoring cannot be performed.

[0136] Combining Examples 1 to 6 and Comparative Examples 1 and 2, it can be seen that:

[0137] In the composite metal foil of this embodiment, the first resistor layer uses Cr, Fe, Ni and O or uses elements such as Cr, Fe and Ni, and the Cr content in the first resistor layer is less than 20%, the Fe content is less than 30%, the Ni content is greater than 30%, and the O content is less than 60%. When the thickness of the first resistor layer is greater than or equal to 5 nanometers and less than or equal to 1 micrometer:

[0138] After 100-1800 first temperature cycles, the resistance recovery deviation of the first resistor layer is less than or equal to 14%. After 100-1800 first temperature cycles, after one second temperature cycle, relative to not having undergone one second temperature cycle, the resistance recovery deviation of the first resistor layer is less than or equal to 8%, and after 1200-2500 second temperature cycles, relative to not having undergone the 1200-2500 second temperature cycles, the resistance recovery deviation of the first resistor layer is less than or equal to 13.5%.

[0139] Under the conditions of temperature 85°C and humidity 85% RH, after 100-500 hours, the resistance recovery deviation of the first resistor layer is less than or equal to 14%. Under the conditions of temperature 85°C and humidity 85% RH, after 100-500 hours, after one second temperature cycle, the resistance recovery deviation of the first resistor layer is less than or equal to 9% relative to the case where no second temperature cycle has been passed, and after 1200-2500 second temperature cycles, the resistance recovery deviation of the first resistor layer is less than or equal to 13.5% relative to the case where no second temperature cycle has been passed.

[0140] After 100-1800 first temperature cycles, and under the conditions of temperature 85°C and humidity 85% RH, after 200-500 hours, and then after one second temperature cycle, the resistance recovery deviation of the first resistor layer is less than or equal to 7% compared with not undergoing one second temperature cycle, and after 1200-2500 second temperature cycles, the resistance recovery deviation of the first resistor layer is less than or equal to 14% compared with not undergoing the 1200-2500 second temperature cycles.

[0141] The material of the resistance layer in the comparative example is Ni-P alloy, and the thickness of the resistance layer is 100 nanometers to 2.5 micrometers. After the metal foil in the comparative example has undergone 50-100 first temperature cycles, the resistance recovery deviation of the resistance layer reaches 50%-100%. After 50-100 first temperature cycles, after one second temperature cycle, the resistance recovery deviation of the resistance layer reaches 50% relative to the case where no second temperature cycle has been undergone. After 500-1000 second temperature cycles, the resistance recovery deviation of the resistance layer reaches 200% relative to the case where no second temperature cycle has been undergone.

[0142] Under the conditions of temperature 85°C and humidity 85% RH, after 50-100 hours, the resistance recovery deviation of the resistor layer reaches 90%-150%. Under the conditions of temperature 85°C and humidity 85% RH, after 50-100 hours, after one second temperature cycle, the resistance recovery deviation of the resistor layer reaches 50%-60% relative to that without one second temperature cycle, and after 500-1000 second temperature cycles, the resistance recovery deviation of the resistor layer reaches 210%-250% relative to that without 500-1000 second temperature cycles.

[0143] After 50-100 first temperature cycles, and under the conditions of temperature 85°C and humidity 85% RH, after 50-100 hours, and then after one second temperature cycle, the resistance recovery deviation of the resistor layer reaches 50%-80% relative to the case where it has not undergone one second temperature cycle. After 500-1000 second temperature cycles, the resistance recovery deviation of the resistor layer reaches 270%-300% relative to the case where it has not undergone 500-1000 second temperature cycles.

[0144] It can be seen that after the metal foil of the comparative example has undergone multiple first temperature cycles and after a period of time at a temperature of 85°C and a humidity of 85%RH, the resistance recovery deviation of the resistor layer is large, and after multiple second temperature cycles, the resistance recovery deviation of the first resistor layer is large, the thermal sensitive characteristics of the resistor layer are destroyed, the resistance recovery accuracy is low, and temperature monitoring cannot be performed. The composite metal foil of the present application has a small resistance recovery deviation of the first resistor layer after multiple first temperature cycles and after multiple hours at a temperature of 85°C and a humidity of 85%RH. The resistance recovery accuracy of the first resistor layer is high in a harsh working environment, and the resistance value is stable. After multiple second temperature cycles, the resistance recovery deviation of the first resistor layer is small. The composite metal foil of this embodiment can realize temperature monitoring of tiny devices in a harsh working environment and has a long working life.

[0145] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0146] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A composite metal foil, characterized in that: include: A base layer and a first resistor layer are stacked; Wherein, under the conditions of temperature of 85° C. and humidity of 85% RH, after 100 h to 500 h, the resistance recovery deviation of the first resistance layer is less than or equal to 15%.

2. The composite metal foil according to claim 1, characterized in that: The temperature changes from -55°C to 150°C and then to -55°C as a first temperature cycle. After N first temperature cycles, the resistance recovery deviation of the first resistance layer is less than 20%; wherein N is an integer greater than or equal to 50 and less than or equal to 2000.

3. The composite metal foil according to claim 1 or 2, characterized in that: The temperature changes from 25°C to 125°C and then back to 25°C as a second temperature cycle; After N first temperature cycles, and / or after 100h-500h at 85°C and 85%RH; and after 1 second temperature cycle, the resistance recovery deviation of the first resistance layer is less than 10% compared with the case without the second temperature cycle.

4. The composite metal foil according to claim 1 or 2, characterized in that: The temperature changes from 25°C to 125°C and then back to 25°C as a second temperature cycle; After N first temperature cycles, and / or after 100h-500h at a temperature of 85°C and a humidity of 85%RH; after M second temperature cycles, the resistance recovery deviation of the first resistance layer is less than 15% relative to the case where the M second temperature cycles are not performed; Wherein, M is an integer less than or equal to 10,000.

5. The composite metal foil according to claim 3, characterized in that: In the second temperature cycle, the resistance of the first resistance layer decreases during a temperature rise process, and the resistance of the first resistance layer increases during a temperature drop process.

6. The composite metal foil according to claim 1, characterized in that: The material used for the first resistance layer includes at least one element selected from the group consisting of Ni, Cr, Zn, Al, Fe, Si, P, Sn, O, N and Cu; Preferably, the Cr content in the first resistance layer is less than 20%, the Fe content is less than 30%, the Ni content is greater than 30%, and the O content is less than 60%; Preferably, the thickness of the first resistance layer is 5 nm-1 μm.

7. The composite metal foil according to claim 1, characterized in that: The thickness of the base layer is 2 μm-70 μm; Preferably, the roughness Rz of the surface of the base layer close to the first resistance layer is 0.5 μm-10 μm.

8. The composite metal foil according to claim 1, characterized in that: Also includes: At least one of an absorbing layer, a second resistance layer and an adjustment layer is stacked with the base layer and the first resistance layer.

9. A metal-clad laminate, characterized in that: The metal-clad laminate comprises the composite metal foil according to any one of claims 1 to 8.

10. A circuit board, characterized in that: The circuit board comprises the composite metal foil according to any one of claims 1 to 8, and the composite metal foil is arranged on the surface or inside of the circuit board.

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