Composite metal foil and circuit board

Abstract

A composite metal foil and a circuit board, the composite metal foil comprising a first electrically conductive layer and a first resistance layer; the ratio of a roughness Rz of the first electrically conductive layer to the maximum width D of crystal grains on the rough surface of the first electrically conductive layer is 0.06≤Rz / D≤30. The present application, by means of controlling the range of the ratio of roughness of an electrically conductive layer to the maximum value of crystal grains, increases sheet resistance uniformity of the film resistor, and further increases adhesion between the film resistor and a circuit board, thereby improving the yield of the finished product.

Description

Composite metal foil and circuit board

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on June 30, 2023, with application number 202310794927.6 and invention name “A composite metal foil and circuit board”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application belongs to the technical field of thin film devices, and specifically relates to a composite metal foil and a circuit board. Background Art

[0003] With the development of integrated electronic components, higher requirements are being placed on the performance and miniaturization of electronic components. Among them, the use of composite metal foil as an integrated passive resistor significantly reduces the surface parasitic effects and volume of semiconductor devices at high frequencies. It has the characteristics of high precision, increases packaging density, and improves device reliability. It is widely used in applications such as high-performance amplifiers, line drivers, consumer electronics, and power management. Among them, the resistor layer of the composite metal foil is stacked on the surface of the conductive layer. Therefore, the square resistance uniformity of the resistor layer is easily affected by the conductive layer. Poor resistance square resistance uniformity of the resistor layer will seriously affect the performance stability of electronic components. Therefore, how to improve the problem of poor square resistance uniformity in composite metal foil is an issue that needs to be urgently addressed in the field of thin film device technology.

[0004] Summary of the Invention

[0005] To solve the above technical problems, the present application provides a composite metal foil and circuit board, which improves the square resistance uniformity of the thin film resistor by controlling the ratio range of the roughness of the conductive layer and the maximum value of the grain size, and further improves the adhesion between the thin film resistor and the circuit board, thereby improving the yield of the finished product.

[0006] To achieve this goal, this application adopts the following technical solutions:

[0007] In a first aspect, the present application provides a composite metal foil, the composite metal foil comprising a first conductive layer and a first resistive layer, the first conductive layer having at least one rough surface; the first resistive layer being arranged on the rough surface of the first conductive layer; the roughness R of the rough surface of the first conductive layer z The ratio of the maximum width D of the grains on the rough surface of the first conductive layer is 0.06≤R z / D≤30, for example, can be 0.06, 0.08, 0.1, 0.5, 1, 2, 5, 10, 15, 20, 25 or 30, or a range between any two of the above values.

[0008] It should be noted that the rough surface of the conductive layer forms several irregular mountain-shaped protrusions on the rough surface; the bottom of the protrusion is connected to the surface of the conductive layer, and there is an obvious boundary between the bottom edges of different protrusions, which is the grain boundary between grains. The maximum width D of the grain is the maximum width of the measured bottom of the protrusion.

[0009] Optionally, the roughness R of the first conductive layer z The ratio of the maximum width D of the grains on the rough surface of the first conductive layer is 0.1≤R z / D≤25, for example, it can be 0.1, 0.2, 0.8, 3, 8, 12, 18, 22 or 25, or a range between any two of the above values.

[0010] Optionally, the roughness R of the first conductive layer z The thickness is 1 to 15 μm, for example, 1 μm, 5 μm, 10 μm, 12 μm or 15 μm, or a range between any two of the above values.

[0011] Optionally, the maximum width D of the grains on the rough surface of the first conductive layer is 0.5-15 μm, for example, 0.5 μm, 1 μm, 5 μm, 10 μm or 15 μm, or a range between any two of the above values.

[0012] Optionally, the composite metal foil is cut along the thickness direction of the composite metal foil, and a plurality of irregular protrusions are formed on the cut surface, the peak height of the protrusion is 0.3 to 10 μm, and the peak width of the protrusion is 0.8 to 15 μm; the peak height is the vertical distance between the highest point of the protrusion and the lower reference line, and the peak width is the length of the line segment formed by the two intersection points of the outline of the protrusion and the baseline; the baseline is the midline of the lower reference line and the upper reference line; the upper reference line is the horizontal line of the highest point of the outline of the rough surface, and the lower reference line is the horizontal line of the lowest point of the outline of the rough surface.

[0013] Optionally, the composite metal foil includes a film layer located on a surface of the first resistance layer on a side away from the first conductive layer.

[0014] Optionally, a second conductive layer is provided on a side of the film layer away from the first resistance layer.

[0015] Optionally, a second resistance layer is provided between the film layer and the second conductive layer.

[0016] Optionally, the second conductive layer may or may not have a rough surface; if the rough surface is present, the rough surface is located on the side of the second conductive layer close to the second resistive layer, and the rough surface is provided with a plurality of irregular protrusions; the bottom of the protrusions is connected to the surface of the conductive layer, and there is a clear boundary between the bottom edges of different protrusions, which is the grain boundary between grains. When the second conductive layer has the rough surface, the roughness R of the rough surface of the second conductive layer is also satisfied. z The ratio of the maximum width D of the grains on the rough surface of the second conductive layer to the maximum width D of the grains on the rough surface of the second conductive layer is 0.06≤R z / D≤30.

[0017] Optionally, the first conductive layer, the second conductive layer, the first resistance layer and / or the second resistance layer may be independently a single-layer structure, or may be a stack of multiple layers.

[0018] In a second aspect, the present application provides a circuit board, wherein the circuit board includes the composite metal foil as described in the first aspect.

[0019] Compared with the prior art, this application has at least the following beneficial effects:

[0020] The present application improves the square resistance uniformity of the thin film resistor by controlling the ratio range of the roughness of the rough surface of the conductive layer and the maximum width of the bottom of the protrusion formed on the rough surface, further improves the adhesion between the thin film resistor and the circuit board, thereby improving the yield of the finished product. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG1 is a microscopic electron microscope image of the rough surface of the first conductive layer or the second conductive layer of the composite metal foil of the present application, wherein the circled positions are schematically represented as the crystal grains described in the present application.

[0022] FIG2 is a schematic diagram of one structure of the composite metal foil of the present application.

[0023] FIG3 is a schematic diagram of another structure of the composite metal foil of the present application.

[0024] FIG4 is a schematic diagram of another structure of the composite metal foil of the present application.

[0025] FIG5 is an enlarged schematic diagram of the protrusions on the rough surface of the first conductive layer or the second conductive layer of the composite metal foil of the present application.

[0026] Among them, 1: first conductive layer; 11: rough surface, 12: protrusion; 2: first resistance layer; 3: film layer; 4: second conductive layer; 5: second resistance layer. DETAILED DESCRIPTION

[0027] The technical solution of the present application is further described below through specific implementation methods. However, the following examples are merely simplified examples of the present application and do not represent or limit the scope of protection of the present application. The scope of protection of the present application shall be subject to the claims.

[0028] After extensive research, it was found that by limiting the ratio range of the roughness of the rough surface of the conductive layer and the maximum width of the grain, the square resistance uniformity of the thin film resistor was improved, and the adhesion between the thin film resistor and the circuit board was further improved, thereby improving the yield of the finished product.

[0029] The present application provides a composite metal foil, which includes a first conductive layer 1 and a first resistive layer 2. The first conductive layer 1 has at least one rough surface 11, on which a plurality of irregular protrusions 12 are formed. The first resistive layer 2 is arranged on the rough surface 11 of the first conductive layer 1; the roughness R of the first conductive layer 1 is z The ratio of the maximum width D of the grain 12 is 0.06≤R z / D≤30. The roughness R of the first conductive layer 1 is z By controlling the ratio of the maximum width D of the grains 12 on the rough surface 11 of the first conductive layer 1 within the above range, the square resistance uniformity of the composite metal foil can be greatly improved compared with the composite metal foil of the traditional structure. For example, it can be 0.06, 0.08, 0.1, 0.5, 1, 2, 5, 10, 15, 20, 25 or 30, or a range between any two of the above values.

[0030] It should be noted that, as shown in FIG1 , the rough surface 11 of the conductive layer 1 has a plurality of irregular peak-shaped protrusions 12 formed on the rough surface 11; the bottom of the protrusions 12 is connected to the surface of the conductive layer 1, and there is a clear boundary between the bottom edges of different protrusions 12, which is the grain boundary between grains (as shown in the circle in FIG1 ). In order to obtain better technical effects and further improve the uniformity of the square resistance of the composite metal foil resistor, the roughness R of the first conductive layer 1 is z The ratio of the maximum width D of the grain is 0.1≤R z / D≤25, for example, it can be 0.1, 0.2, 0.8, 3, 8, 12, 18, 22 or 25, or a range between any two of the above values.

[0031] The roughness R of the first conductive layer 1 is z The thickness of the first conductive layer 1 is 1-15 μm. Within the above range, the first conductive layer 1 has a uniform deposition surface, ensuring the uniformity of the square resistance of the first resistive layer 2 and reducing the roughness R z Too large will lead to the possibility of reduced continuity of the first resistance layer 1 and greater deviation of the square resistance uniformity; at the same time, it also reduces the possibility of large deviation due to the roughness R zIf the roughness R of the first conductive layer 1 is too small, the composite metal foil will not be able to meet the application requirements of the circuit board and may fall off or delaminate. z It may be outside the above range, for example, it may be 0.5 μm, 1 μm, 5 μm, 10 μm or 15 μm, or a range between any two of the above values.

[0032] It should be noted that the grain size D of the first conductive layer 1 is 0.5-15 μm. For example, the grain size D can be 0.5 μm, 1 μm, 5 μm, 10 μm or 15 μm, or a range between any two of the above values.

[0033] The composite metal foil is cut along its thickness, forming a plurality of irregular protrusions 12 on the cut surface. The protrusions 12 have a peak height of 0.3 to 10 μm and a peak width of 0.8 to 15 μm. The peak height is the vertical distance between the highest point of the protrusion 12 and the lower reference line, and the peak width is the length of the line segment formed by the two intersection points of the profile of the protrusion 12 and the reference line. The reference line is the midline between the lower and upper reference lines. The upper reference line is the horizontal line of the highest point of the rough surface profile, and the lower reference line is the horizontal line of the lowest point of the rough surface profile. As an optional implementation method, referring to FIG2 , the composite metal foil further includes a film layer 3 located on the surface of the first resistive layer 2 on the side away from the first conductive layer 1. On the one hand, film layer 3 protects the first resistor layer 2 from damage by external forces. On the other hand, when the composite metal foil is attached to a circuit board, film layer 3 adheres to the first resistor layer 2 and the circuit board, further improving the peel strength between the composite metal foil and the circuit board. This prevents the composite metal foil from being peeled off from the circuit board, facilitating the subsequent preparation of a resistor layer with a specific shape. Furthermore, the film layer 3 can be used to create a foil-clad laminate that can be directly applied to flexible printed circuit boards.

[0034] Optionally, the thickness of the film layer 3 is 0.5 μm to 100 μm. Exemplarily, the thickness of the film layer 3 can be 2 μm, 5 μm, 7 μm, 10 μm, 12 μm, 15 μm, 20 μm, 30 μm, 40 μm, 55 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm. The material of the film layer 3 is selected from at least one of polystyrene-based thermoplastic resins, vinyl acetate-based thermoplastic resins, polyester-based thermoplastic resins, polyethylene-based thermoplastic resins, polyamide-based thermoplastic resins, rubber-based thermoplastic resins, acrylic-based thermoplastic resins, phenolic-based thermosetting resins, epoxy-based thermosetting resins, thermoplastic polyimide thermosetting resins, urethane-based thermosetting resins, melamine-based thermosetting resins, alkyd-based thermosetting resins, and ABF resins. Illustratively, the film layer 3 is at least one selected from modified epoxy resin, modified acrylic resin, polyethylene terephthalate, polybutylene terephthalate, polyethylene, polyethylene naphthalate, polystyrene, polyvinyl chloride, polysulfone, polyphenylene sulfide, polyetheretherketone, polyphenylene oxide, polytetrafluoroethylene, liquid crystal polymer, polyoxaline, epoxy glass cloth, and BT resin. The specific thickness and material of the film layer 3 can be selected and set by those skilled in the art based on actual needs.

[0035] As an optional implementation method, referring to FIG3 , a second conductive layer 4 is provided on the side of the film layer 3 away from the first resistor layer 2. In this case, the composite metal foil forms a foil-clad sheet comprising a first conductive layer 1, a first resistor layer 2, a film layer 3, and a second conductive layer 4 stacked in sequence.

[0036] As an optional implementation method, referring to FIG4 , a second resistor layer 5 is provided between the film layer 3 and the second conductive layer 4. In this case, the composite metal foil forms a foil-clad plate comprising a first conductive layer 1, a first resistor layer 2, a film layer 3, a second resistor layer 5, and a second conductive layer 4 stacked in sequence.

[0037] It should be noted that the second conductive layer 4 may or may not have a rough surface; if the rough surface 11 is present, the rough surface 11 is located on the side of the second conductive layer 4 close to the second resistance layer 5 , and a plurality of irregular protrusions 12 are provided on the rough surface 11 .

[0038] It should be noted that the roughness R of the rough surface 11 of the second conductive layer 4 is z The ratio of the maximum width D of the grains on the rough surface 11 of the second conductive layer 4 also satisfies 0.06≤R z / D≤30. For example, it can be 0.06, 0.08, 0.1, 0.5, 1, 2, 5, 10, 15, 20, 25 or 30, or a range between any two of the above values.

[0039] Optionally, the roughness R of the second conductive layer 4 is z The ratio of the maximum width D of the grains on the rough surface 11 of the second conductive layer 4 is 0.1≤R z / D≤25, for example, it can be 0.1, 0.2, 0.8, 3, 8, 12, 18, 22 or 25, or a range between any two of the above values.

[0040] Optionally, the roughness Rz of the second conductive layer 4 is 1 to 15 μm, for example, 1 μm, 5 μm, 10 μm, 12 μm, or 15 μm, or a range between any two of the above values. The grain size D on the rough surface 11 of the second conductive layer 4 is 0.5 to 15 μm, for example, 0.5 μm, 1 μm, 5 μm, 10 μm, or 15 μm, or a range between any two of the above values.

[0041] It should be further explained that the thickness of the first conductive layer 1 and / or the second conductive layer 4 is independently 2μm to 100μm. Exemplarily, the thickness of the first conductive layer 1 and / or the second conductive layer 4 can be 2μm, 4μm, 6μm, 8μm, 10μm, 20μm, 30μm, 35μm, 50μm, 60μm, 80μm or 100μm; or a range between any two of the above values.

[0042] It should be noted that the materials independently constituting the first conductive layer 1 and the second conductive layer 4 can be the same or different. The materials of the first conductive layer 1 and the second conductive layer 4 can be independently metals, and the metals are any one of Ni, Ti, Cu, Ag, Au, Pt, Fe, Co, Cr, W, Mo, Al, Mg, K, Na, Ca, Sr, Ba, Ge, Sb, Pb, In, or Zn, or alloys composed of at least two of the metals. The metal materials that independently constitute the first conductive layer 1 and the second conductive layer 4 can be independent single metals or alloys composed of any two or more of the above metals. In an optional embodiment, a second resistor layer 5 is provided between the film layer 3 and the second conductive layer 4, thereby forming a symmetrical structure.

[0043] It should be noted that the thickness of the first resistor layer 2 or / and the second resistor layer 5 is independently 5 nm to 3 μm, for example, 5 nm, 10 nm, 100 nm, 500 nm, 1 μm, 2 μm, or 3 μm, or a range between any two of the above values. Optionally, the thickness of the first resistor layer 2 or / and the second resistor layer 5 is independently 10 nm to 200 nm, for example, 10 nm, 25 nm, 50 nm, 75 nm, 100 nm, 125 nm, 150 nm, 175 nm, 200 nm, or a range between any two of the above values.

[0044] It should be noted that the materials independently constituting the first resistor layer 2 and the second resistor layer 5 are the same or different, and the material used as the resistor includes at least one element selected from the group consisting of Ni, Cr, Si, P, N, Ti, Pt, Ta, Mo, Sn, and O. Alternatively, the material may be at least one selected from the group consisting of NiCrSi, NiCrAlSi, NiP, NiCr, AlN, TiN, Pt, Cr, Cr-SiO, Cr-Si, Ti-Si, Ti-W, TaN, Mo, and Ni-Sn.

[0045] It should be noted that the first conductive layer 1 , the second conductive layer 4 , the first resistance layer 2 and / or the second resistance layer 5 may be independently a single-layer structure or a stacked multi-layer structure.

[0046] It should be noted that when the first conductive layer 1 , the second conductive layer 4 , the first resistance layer 2 and / or the second resistance layer 5 are independently multi-layer structures, the materials used in different layers in the multi-layer structure may be the same or different.

[0047] It should be noted that the rough surface of the first conductive layer 1 is formed by post-processing, which mainly includes mechanical processing, chemical processing, electrolysis and laser processing. z The roughness of the rough surface 11 is defined as the sum of the average of the five largest profile peak heights and the average of the five largest profile valley depths within the sampling length. Grains are formed by the accumulation of subgrains. The first resistor layer 2 or the second resistor layer 5 is formed using at least one of electroplating, electroless plating, physical vapor deposition, and chemical vapor deposition processes. The sheet resistance of the first resistor layer 2 or the second resistor layer 5 is 1Ω to 2000Ω.

[0048] It should be noted that the square resistance of the first resistance layer 2 or the second resistance layer 5 is 1Ω-2000Ω, and the obtained numerical range is obtained by measuring the resistance materials listed above in this application.

[0049] It should be further explained that the thickness of each layer of the composite metal foil and the maximum width D of the grains and other related parameters in this embodiment are all measured using a scanning electron microscope with a magnification of 2000 to 70000 times. z The roughness tester is used for testing.

[0050] According to another aspect of the present application, a circuit board is provided, wherein the circuit board includes the composite metal foil.

[0051] To facilitate understanding of the present application, the present application lists the following examples. Those skilled in the art should understand that the examples are only provided to help understand the present application and should not be considered as specific limitations of the present application.

[0052] Example 1

[0053] This embodiment provides a composite metal foil, which includes a first conductive layer 1 and a first resistive layer 2 stacked from bottom to top.

[0054] The material of the first conductive layer 1 is copper foil with a thickness of 5 μm. The interface between the first conductive layer 1 and the first resistive layer 2 is a rough surface 11. The roughness R of the first conductive layer 1 is z The ratio of the maximum width D of the grain (R z / D) is 0.06, and the roughness R z The thickness of the first resistance layer 2 is 20 nm, and the material is NiCr.

[0055] Example 2

[0056] This embodiment provides a composite metal foil, which includes a first conductive layer 1 and a first resistive layer 2 stacked from bottom to top. The first conductive layer 1 is made of copper foil with a thickness of 5 μm. The interface between the first conductive layer 1 and the first resistive layer 2 is a rough surface 11. The roughness R of the first conductive layer 1 is 0.1%. z The ratio of the maximum width D of the grain is 30, and the roughness R z The thickness of the first resistance layer 2 is 20 nm, and the material is NiCr.

[0057] Example 3

[0058] This embodiment provides a composite metal foil, which includes a first conductive layer 1 and a first resistive layer 2 stacked from bottom to top. The first conductive layer 1 is made of copper foil with a thickness of 5 μm. The interface between the first conductive layer 1 and the first resistive layer 2 is a rough surface 11. The roughness R of the first conductive layer 1 is 0.1%. z The ratio of the maximum width D of the grain is 0.1, and the roughness R z The thickness of the first resistance layer 2 is 20 nm, and the material is NiCr.

[0059] Example 4

[0060] This embodiment provides a composite metal foil, which includes a first conductive layer 1 and a first resistive layer 2 stacked from bottom to top. The first conductive layer 1 is made of copper foil with a thickness of 5 μm. The interface between the first conductive layer 1 and the first resistive layer 2 is a rough surface 11. The roughness R of the first conductive layer 1 is 0.1%.z The ratio of the maximum width D of the grain is 3, and the roughness R z The thickness of the first resistance layer 2 is 20 nm, and the material is NiCr.

[0061] Example 5

[0062] This embodiment provides a composite metal foil, which differs from the embodiment 1 in that the roughness R of the first conductive layer 1 is z The ratio of the maximum width D of the grain is 20.

[0063] Example 6

[0064] This embodiment provides a composite metal foil, which differs from the embodiment 1 in that the roughness R of the first conductive layer 1 is z The ratio of the maximum width D of the grain is 25.

[0065] Example 7

[0066] This embodiment provides a composite metal foil, which differs from the embodiment 1 in that the roughness R of the first conductive layer 1 is z 0.5μm.

[0067] Example 8

[0068] This embodiment provides a composite metal foil, which differs from the embodiment 1 in that the roughness R of the first conductive layer 1 is z It is 17μm.

[0069] Example 9

[0070] This embodiment provides a composite metal foil, which differs from the embodiment 1 in that the grain size D of the first conductive layer 1 is 0.3 μm.

[0071] Example 10

[0072] This embodiment provides a composite metal foil, which differs from the embodiment 1 in that the grain size D of the first conductive layer 1 is 17 μm.

[0073] Comparative Example 1

[0074] This comparative example provides a composite metal foil, which differs from Example 1 in that the roughness R of the first conductive layer 1 is z The ratio of the maximum width D of the grain is 35.

[0075] Comparative Example 2

[0076] This comparative example provides a composite metal foil, which differs from Example 1 in that the roughness R of the first conductive layer 1 is z The ratio of the maximum width D of the grain is 0.04.

[0077] Comparative Example 3

[0078] This comparative example provides a composite metal foil, which is different from Example 1 in that the surface of the first conductive layer 1 is smooth and not rough.

[0079] The composite metal foils of the above embodiments are prepared by the following method: the first conductive layer 1 of the composite metal foil is prepared by an electrolytic copper plating process, a roughened surface of the first conductive layer 1 is prepared by a copper foil post-treatment process, and the first resistive layer 2 is prepared on the roughened surface by a vacuum sputtering process.

[0080] The sheet resistance uniformity of the composite metal foil in each embodiment was tested using a four-probe square resistance tester. The test method was as follows: first, the sheet resistance M of the composite substrate at different positions was tested using a resistance tester. The sheet resistance test points were evenly distributed on the surface of the composite substrate, and the number of sheet resistance test points was 20. Then, the average sheet resistance M of the 20 positions of the composite substrate was calculated. ave , and select the maximum square resistance M of the location point max and the minimum square resistance M at the location point min , and then use the following method to calculate the upper and lower limits of the square resistance uniformity:

[0081] Upper limit of square resistance uniformity = (M max -M ave ) / M ave ×100%;

[0082] Lower limit of square resistance uniformity = (M min -M ave ) / M ave ×100%.

[0083] The test results are shown in Table 1.

[0084] Table 1

[0085] From Table 1 above, we can see that:

[0086] (1) From the comparison of Examples 1-2 and Comparative Examples 1-3, it can be seen that the present application improves the square resistance uniformity of the thin film resistor by controlling the ratio range of the roughness of the conductive layer and the maximum value D of the grain, further improves the adhesion between the thin film resistor and the circuit board, thereby improving the yield rate of the finished product.

[0087] (2) From the comparison between Examples 3-6 and Examples 1 and 2, it can be seen that when the roughness R of the first conductive layer 1 is z The ratio of the maximum width D of the grain is 0.1≤R z When the optional range of / D≤25 is selected, the square resistance uniformity of the thin film resistor can be improved to the greatest extent.

[0088] (3) From the comparison between Examples 7 and 8 and Example 1, it can be seen that when the roughness R of the first conductive layer 1 is z The ratio of the maximum width D of the grain meets the range of this application, but the roughness R z When it is not within the optional range of the present application, the uniformity of the sheet resistance of the thin film resistor is affected.

[0089] (4) From the comparison between Examples 9 and 10 and Example 1, it can be seen that when the roughness R of the first conductive layer 1 is z When the ratio of the maximum width D of the grains meets the range of this application, but the grain size is not within the optional range of this application, the uniformity of the sheet resistance of the thin film resistor is affected.

[0090] In summary, the present application improves the square resistance uniformity of the thin film resistor by controlling the ratio range of the roughness of the conductive layer and the maximum value of the grain, further improves the adhesion between the thin film resistor and the circuit board, and thus improves the yield of the finished product.

[0091] This application uses the above-mentioned embodiments to illustrate the detailed process equipment and process flow of this application. However, this application is not limited to the above-mentioned detailed process equipment and process flow, that is, it does not mean that this application must rely on the above-mentioned detailed process equipment and process flow to be implemented. Those skilled in the art should understand that any improvements to this application, equivalent replacement of various raw materials of the product of this application, addition of auxiliary ingredients, selection of specific methods, etc., all fall within the scope of protection and disclosure of this application.

Claims

1. A composite metal foil, characterized in that: The composite metal foil comprises a first conductive layer and a first resistor layer, wherein the first conductive layer has at least one rough surface; the first resistor layer is arranged on the rough surface of the first conductive layer; the roughness R of the rough surface of the first conductive layer is z The ratio of the maximum width D of the grains on the rough surface of the first conductive layer is 0.06≤R z / D≤30.

2. The composite metal foil according to claim 1, characterized in that: The roughness R of the first conductive layer z The ratio of the maximum width D of the grains on the rough surface of the first conductive layer is 0.1≤R z / D≤25.

3. The composite metal foil according to claim 2, characterized in that: The roughness R of the first conductive layer z 1~15μm.

4. The composite metal foil according to claim 2, characterized in that: The maximum width D of the crystal grains on the rough surface of the first conductive layer is 0.5-15 μm.

5. The composite metal foil according to any one of claims 1 to 4, characterized in that: The composite metal foil is cut along the thickness direction of the composite metal foil, and a plurality of irregular protrusions are formed on the cut surface, and the peak height of the protrusions is 0.3 to 10 μm; The peak height is the vertical distance between the highest point of the protrusion and the lower reference line; The lower reference line is a horizontal line of the lowest point of the profile of the rough surface.

6. The composite metal foil according to any one of claims 1 to 4, characterized in that: The composite metal foil is cut along the thickness direction of the composite metal foil, and a plurality of irregular protrusions are formed on the cut surface, and the peak width of the protrusions is 0.8 to 15 μm; The peak width is the length of the line segment formed by the two intersection points of the protrusion profile and the reference line; The reference line is the midline between the lower reference line and the upper reference line; The upper reference line is a horizontal line of the highest point of the profile of the rough surface; The lower reference line is a horizontal line of the lowest point of the profile of the rough surface.

7. The composite metal foil according to any one of claims 1 to 4, characterized in that: The composite metal foil includes a film layer located on a surface of the first resistance layer on a side away from the first conductive layer.

8. The composite metal foil according to claim 7, characterized in that: A second conductive layer is disposed on a side of the film layer away from the first resistance layer.

9. The composite metal foil according to claim 8, characterized in that: A second resistance layer is provided between the film layer and the second conductive layer.

10. The composite metal foil according to claim 9, characterized in that: The second conductive layer may or may not have a rough surface; if the rough surface is present, the rough surface is disposed on a side of the second conductive layer close to the second resistance layer, and a plurality of irregular protrusions are disposed on the rough surface.

11. The composite metal foil according to claim 9, characterized in that: The first conductive layer, the second conductive layer, the first resistance layer and / or the second resistance layer are single-layer structures or are formed by stacking multiple layers.

12. A circuit board, characterized in that: The circuit board comprises the composite metal foil according to any one of claims 1-11.

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