Metal foil, metal-clad laminate, and wiring board

Abstract

The invention discloses a metal foil, a metal-clad laminated board and a circuit board, the metal foil comprises a functional layer and a plurality of agglomerated teeth formed on one side surface of the functional layer, each agglomerated tooth comprises a plurality of agglomerated bumps, and at least part of the agglomerated bumps are spine-shaped; the sharp agglomerates can be better inserted into gaps of microcosmic particles of the substrate in the pressing process, so that the bonding force is better; wherein the maximum width of the agglomerated teeth is 2-15 [mu] m, the agglomerated teeth are large in size, and the agglomerated teeth are stably combined with metal foil crystal grains, can be more easily inserted into gaps of a substrate after being pressed, and are further stably combined with the substrate. The low roughness can ensure the transmission efficiency and reduce the skin effect. According to the embodiment of the invention, the binding force between the metal foil and the substrate can be improved, relatively low transmission loss is ensured, and the stability of the circuit board is improved.

Description

Technical Field

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

[0002] High-frequency high-speed copper foil is a material with excellent conductivity in a special electromagnetic wave frequency band, and is usually used to make key components in fine circuits. When making fine circuits with current high-frequency high-speed copper foil, it is necessary to ensure stable bonding with the substrate, and one factor to ensure stable bonding is to increase the roughness of the pressed surface. However, too much roughness will lead to skin effect. As a printed circuit board for high-frequency circuits, in order to maintain and ensure the quality of the signal, it is necessary to strive to reduce transmission loss.

[0003] From the perspective of transmission loss of copper foil that constitutes the conductor circuit substrate, there are the following problems: first, the transmission loss increases in the conductor loss, and second, the low dielectric constant of the base material used to suppress dielectric loss and the low dielectric loss factor reduce the bonding strength of the resin. The shape of the copper foil surface has a great influence on the transmission loss. The copper foil with large roughness will have a longer signal propagation distance, which will cause problems of signal attenuation and delay. That is, the smoother the surface, the smaller the conductor loss. However, the surface roughness of the copper foil is related to the bonding strength of the resin substrate. If the surface roughness is too smooth, the bonding strength with the resin will be reduced, affecting the stability of the production circuit. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a metal foil, a metal-clad laminate and a circuit board, which can enhance the bonding strength between the metal foil and the substrate while ensuring low transmission loss and improving the stability of the circuit board.

[0005] In order to achieve the above-mentioned object, an embodiment of the present invention provides a metal foil, comprising a functional layer and a plurality of agglomeration teeth formed on one side of the functional layer, wherein each of the agglomeration teeth comprises a plurality of agglomeration bumps, and at least some of the agglomeration bumps are spike-shaped;

[0006] Wherein, the maximum width of the clustered teeth is 2 to 15 μm.

[0007] As an improvement of the above solution, within any unit area, the number of clustered teeth with a maximum width of 8 to 15 μm accounts for more than 40%.

[0008] As an improvement of the above solution, in the agglomerated teeth with a maximum width of 7 to 12 μm, the number of agglomerated nodules is greater than 20.

[0009] As an improvement of the above solution, there are gaps between the clustered teeth, and the shortest distance between any adjacent clustered teeth is 0.3-3 μm.

[0010] As an improvement of the above solution, in all the clustered teeth, each of the clustered tumors is in the shape of a spike.

[0011] As an improvement of the above solution, the top angle of any of the agglomerated nodules is 20° to 90°;

[0012] The tip angle is the angle between two tangent lines of the tip cross section of the agglomerate tumor in the sliced ​​state.

[0013] As an improvement of the above scheme, dendrites are formed between the agglomerates, and the axis angle between adjacent agglomerates is 40° to 110°;

[0014] The axis angle is the angle between the central axes of any two adjacent agglomerates in the sliced ​​state.

[0015] As an improvement of the above solution, the roughness Rz of the side of the metal foil provided with the agglomerated teeth is 3 to 6 μm.

[0016] As an improvement of the above solution, the bonding force between the side surface of the metal foil provided with the agglomerated teeth and the substrate is 1.5-2.2 N / mm.

[0017] As an improvement of the above solution, the metal foil further includes: a carrier layer; the carrier layer is arranged on a side of the functional layer facing away from the agglomerated teeth.

[0018] As an improvement of the above solution, the metal foil further includes: a peeling layer; the peeling layer is arranged between the carrier layer and the functional layer.

[0019] An embodiment of the present invention further provides a metal-clad laminate, wherein the metal-clad laminate comprises the metal foil as described in any one of the above items.

[0020] An embodiment of the present invention further provides a circuit board, the circuit board comprising the metal foil as described in any one of the above items, wherein the metal foil is arranged on the surface or inside of the circuit board.

[0021] Compared with the prior art, the beneficial effects of a metal foil, a metal-clad laminate and a circuit board provided by the embodiments of the present invention are: by forming a plurality of agglomeration teeth on one side of the metal foil functional layer, and each of the agglomeration teeth includes a plurality of agglomeration nodules, each of the agglomeration nodules is spike-shaped, and such a pointed agglomeration nodules can be better inserted into the gap of the substrate during the pressing process, so that the metal foil has better bonding force on the substrate; wherein, the maximum width of the agglomeration teeth is 2 to 15 μm, the size is large, the bonding with the metal foil grains is stable, and it is easier to insert into the gap of the substrate after pressing, and thus also has stable bonding with the substrate. And the larger agglomeration teeth width brings lower roughness, which is beneficial to reduce the skin effect, thereby ensuring the line transmission efficiency. The embodiments of the present invention can enhance the bonding force between the metal foil and the substrate, while ensuring lower transmission loss, and improving the stability of the circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of a preferred embodiment of a metal foil provided by the present invention;

[0023] Figure 2 This is an electron microscope image of the surface agglomerated teeth of a functional layer in a metal foil provided by the present invention;

[0024] Figure 3 This is a local electron microscope image of the surface agglomerated teeth of a functional layer in a metal foil provided by the present invention;

[0025] Figure 4 It is a partial electron microscope cross-sectional view of the surface agglomerated teeth of a functional layer in a metal foil provided by the present invention;

[0026] Figure 5 is a structural schematic diagram of another preferred embodiment of a metal foil provided by the present invention;

[0027] Figure 6 is a structural schematic diagram of another preferred embodiment of a metal foil provided by the present invention;

[0028] The reference numerals are as follows:

[0029] 1. Functional layer; 10. Agglomerated teeth; 11. Agglomerated tumors; 2. Carrier layer; 3. Peeling layer. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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 are within the scope of protection of the present invention.

[0031] In the description of the present application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0032] In the description of this application, the terms "first", "second", "third", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", "third", etc. may explicitly or implicitly include one or more of the feature. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0033] In the description of this application, it should be noted that, unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood by specific circumstances.

[0034] See also Figures 1 to 3 , Figure 1 is a schematic structural diagram of a preferred embodiment of a metal foil provided by the present invention, Figure 2 This is an electron microscope image of the surface agglomeration teeth of the functional layer in the metal foil provided by the present invention. Figure 3 This is a partial electron microscope image of agglomeration teeth on the surface of a functional layer in a metal foil provided by the present invention. An embodiment of the present invention provides a metal foil, comprising a functional layer 1 and a plurality of agglomeration teeth 10 formed on one side of the functional layer 1, and each of the agglomeration teeth 10 comprises a plurality of agglomeration nodules 11, at least some of the agglomeration nodules 11 are spike-shaped; wherein the maximum width of the agglomeration teeth 10 is 2 to 15 μm.

[0035] Specifically, the embodiment of the present invention forms a plurality of agglomerate teeth 10 on the surface of the raw foil by roughening the surface of the raw foil. It should be noted that the formation mechanism of the agglomerate teeth 10 is: in a specific electrolyte, by controlling parameters such as current, voltage, and temperature, an electrodeposition reaction occurs on the surface of the copper foil. In this process, the addition of additives has an important influence on the formation of the agglomerate teeth 10. For example, certain additives (such as a mixed solution of alkyne organic matter and chloride) can promote the uneven deposition of copper ions on the surface of the copper foil, thereby forming a rice-like or other shaped agglomerate tooth structure. In the embodiment of the present invention, each agglomerate tooth 10 is agglomerated by a plurality of agglomerate nodules 11, wherein at least a portion of the agglomerate nodules 11 in each agglomerate tooth 10 is in the shape of a spike, that is, a slender point, and the tip of the end away from the functional layer is acute. This spike-shaped agglomerate nodule 11 can be better inserted into the gap between the microscopic particles of the substrate during the pressing process, thereby having better bonding force. The maximum width L of the cluster teeth 10 is 2 to 15 μm, which is relatively large and can be stably combined with the copper foil grains. It is easier to insert into the gap of the substrate after pressing, and can also be stably combined with the substrate. Exemplarily, the maximum width L of the cluster teeth 10 is 2, 4, 6, 8, 10, 12, 14, 15 and / or an interval consisting of any two values.

[0036] It should be noted that since the agglomerated tooth 10 is an irregularly shaped accumulation, its volume is difficult to measure and define. Generally, the agglomerated tooth 10 is observed by observing it under a metallographic microscope or a scanning electron microscope with an appropriate magnification. The maximum width L is the straight-line distance along the horizontal direction between the lowest points on both sides of the agglomerated tooth 10 in the cross-sectional state. The measurable maximum width L is used to characterize the size of the agglomerated tooth 10.

[0037] The embodiment of the present invention further limits the size of the reunion teeth 10. Since the size of the reunion teeth 10 will affect the bonding force and transmission loss, in order to avoid the reunion teeth 10 being too small, resulting in low bonding force, and also to avoid the reunion teeth 10 being too large, resulting in large transmission loss, the embodiment of the present invention sets the maximum width L in a moderate range of 2 to 15 μm, which can reduce transmission loss while ensuring bonding force.

[0038] In another preferred embodiment, within any unit area, the number of clustered teeth 10 with a maximum width of 8 to 15 μm accounts for more than 40%.

[0039] Specifically, in the embodiment of the present invention, the number ratio and the maximum width L of the clustered teeth 10 in the functional layer 1 are further limited. Within any unit area, for example, 100 μm 2The number of clustered teeth 10 with a maximum width L of 8 to 15 μm accounts for more than 40%. Since the maximum width L of the clustered teeth 10 and the number ratio are proportional to the bonding force, the larger the number of clustered teeth 10 with a maximum width L of 8 to 15 μm, the smaller the roughness Rz can be, and the skin effect can be avoided. Exemplarily, the number of clustered teeth 10 with a maximum width L of 8, 9, 10, 11, 12, 13, 14, 15 and / or any two of the values ​​is 40%, 50%, 60%, 70%, 80%, 90%.

[0040] In yet another preferred embodiment, in the agglomerated tooth 10 with a maximum width of 7-12 μm, the number of the agglomerated nodules 11 is greater than 20.

[0041] Specifically, in the embodiment of the present invention, the maximum width L of the agglomerated tooth 10 in the functional layer 1 and the number of agglomerated nodules 11 in the agglomerated tooth 10 are further limited. Within any unit area, for example, 100 μm 2 In the agglomeration teeth 10 with a maximum width L of 7 to 12 μm, the number of agglomeration nodules 11 is greater than 20. Because the number of agglomeration nodules 11 in the agglomeration teeth 10 will affect the bonding force between the metal foil and the substrate, the number of agglomeration nodules 11 in the agglomeration teeth 10 with a maximum width L of 7 to 12 μm is greater than 20, which can effectively improve the bonding force between the metal foil and the substrate. Exemplarily, in the agglomeration teeth 10 with a maximum width L of 7, 8, 9, 10, 11, 12 and / or an interval consisting of any two values, the number of agglomeration nodules 11 is 20, 30, 40, 50, 60, 70.

[0042] In another preferred embodiment, there are gaps between the clustered teeth 10, and the shortest distance between any adjacent clustered teeth 10 is 0.3-3 μm.

[0043] Specifically, in the embodiment of the present invention, there are gaps between the multiple clustered teeth 10 on the surface of the functional layer 1, and the shortest spacing between any adjacent clustered teeth 10 is 0.3-3 μm. There are gaps between the clustered teeth 10, and the gaps are small, which can increase the contact area, thereby reducing the roughness, improving the bonding force and ensuring the current transmission efficiency.

[0044] As a preferred solution, in all the clustered teeth 10, each of the clustered tumors 11 is in a spike shape.

[0045] Specifically, in the embodiment of the present invention, each agglomeration tooth 10 is formed by agglomerating multiple agglomeration nodules 11, and each agglomeration nodules 11 in all agglomeration teeth 10 is spike-shaped, so that it can be better inserted into the gaps between microscopic particles of the substrate during the pressing process, thereby having better bonding force.

[0046] In another preferred embodiment, the top angle of any of the agglomerates 11 is 20° to 90°.

[0047] The tip angle is the angle between two tangent lines of the tip cross section of the agglomerate nodule 11 in the sliced ​​state.

[0048] For details, please refer to Figure 4 , Figure 4 It is a partial electron microscope cross-sectional view of agglomerate teeth on the surface of a functional layer in a metal foil provided by the present invention. In the embodiment of the present invention, each agglomerate tooth 10 is formed by the aggregation of multiple agglomerate nodules 11, and at least a part of the agglomerate nodules 11 is spike-shaped, that is, slender and pointed, with an acute tip. Since the shape of the agglomerate nodules 11 is irregular, the agglomerate nodules 11 are generally observed by magnifying them appropriately under a scanning electron microscope or a metallographic microscope. Therefore, in the embodiment of the present invention, the angle between the two tangents of the tip cross section of the agglomerate nodules 11 in the sliced ​​state is defined as its tip angle a, and the measurable tip angle a is used to characterize the shape of the agglomerate nodules 11. In the embodiment of the present invention, the tip angle a of any agglomerate nodules 11 is set to 20° to 90°, forming a pointed agglomerate nodules. On the one hand, it can increase the surface area of ​​the copper foil, and on the other hand, it can be more easily inserted into the substrate, thereby increasing the bonding force between the metal foil and the substrate. Exemplarily, the top angle a of the agglomerate 11 is 20°, 25°, 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, 85°, 90° and / or an interval consisting of any two values.

[0049] In another preferred embodiment, dendrites are formed between the agglomerates 11, and the axis angle between adjacent agglomerates 11 is 40° to 110°;

[0050] The axis angle is the angle between the central axes of any two adjacent agglomerates 11 in the sliced ​​state.

[0051] Specifically, each agglomerate nodule 11 in the agglomerate tooth 10 of the embodiment of the present invention is relatively divergent, forming a dendrite. Since the shape of the agglomerate nodule 11 is irregular, the agglomerate nodule 11 is generally observed by magnifying it appropriately under a scanning electron microscope or a metallographic microscope. Therefore, the embodiment of the present invention defines the angle between the central axes of any two adjacent agglomerates 11 in the sliced ​​state as the axis angle b, and uses the measurable axis angle b to characterize the morphology between the agglomerates 11. The angle between each particle is relatively large, that is, the axis angle b between adjacent agglomerates 11 is 40° to 110°, which can increase the contact area between the agglomerate nodule 11 and the substrate individually, and improve the bonding force. In this way, when pressed on the PTFE substrate, the bonding force can reach 1.5-2.2N / mm, while the bonding force of conventional copper foil is only 1.2-1.3N / mm. Exemplarily, the axial angle b between adjacent agglomerates 11 is 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75°, 80°, 85°, 90°, 95°, 100°, 105°, 110° and / or an interval consisting of any two values.

[0052] In another preferred embodiment, the roughness Rz of the side surface of the metal foil provided with the agglomerated teeth 10 is 3-6 μm.

[0053] In another preferred embodiment, the bonding force between the side surface of the metal foil provided with the agglomerating teeth 10 and the substrate is 1.5-2.2 N / mm.

[0054] Specifically, the roughness Rz of the side of the metal foil provided with the agglomeration teeth 10 in the embodiment of the present invention is 3-6 μm, which is lower than that of the conventional metal foil. The low roughness can ensure the transmission efficiency and reduce the skin effect. The bonding force between the side of the metal foil provided with the agglomeration teeth 10 and the substrate can reach 1.5-2.2 N / mm, while the bonding force of the conventional metal foil is only 1.2-1.3 N / mm.

[0055] Preferably, the metal foil further comprises: a carrier layer 2 ; the carrier layer 2 is arranged on a side of the functional layer 1 facing away from the agglomerated teeth 10 .

[0056] Specifically, see Figure 5 , Figure 5 : is a structural schematic diagram of another preferred embodiment of a metal foil provided by the present invention. In the embodiment of the present invention, the metal foil further comprises a carrier layer 2, which is arranged on a side of the functional layer 1 facing away from the agglomerated teeth 10, that is, a side away from the agglomerated teeth 10. The material of the carrier layer 2 can be any one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver and gold. The material of the functional layer 1 can be any one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver and gold.

[0057] Preferably, the metal foil further includes: a peeling layer 3 ; the peeling layer 3 is arranged between the carrier layer 2 and the functional layer 1 .

[0058] Specifically, see Figure 6 , Figure 6 It is a structural schematic diagram of another preferred embodiment of a metal foil provided by the present invention. In the embodiment of the present invention, the metal foil also includes a peeling layer 3, and the peeling layer 3 is arranged between the carrier layer 2 and the functional layer 1. Before the metal foil product is manufactured and applied, the carrier layer 2, the peeling layer 3, and the functional layer 1 are stacked. As the product is applied, the functional layer 1 of the metal foil is pressed onto the applied carrier such as the circuit board substrate. After the pressing process is completed, the entire metal foil is bonded to the applied carrier through the bonding force between the roughened surface of the functional layer 1 and the applied carrier. Before the metal foil is further processed and the circuit is etched, the carrier layer 2 is peeled off through the peeling layer 3, and the circuit is subsequently formed on the circuit board substrate by copper plating, masking, etching and other means.

[0059] The processing method of the strippable metal foil is: first, a carrier layer 2 is formed by electrochemical deposition, vacuum sputtering + electroplating, vacuum sputtering, etc.; then a stripping layer 3 is formed on one side of the carrier layer 2, and the formation method can also be electroplating, vacuum sputtering, etc.; then a functional layer 1 is processed on the stripping layer 3, and the formation method can be vacuum sputtering, electroplating, etc.

[0060] The peeling layer 3 of the embodiment of the present invention is processed on the carrier layer 2 by physical vapor deposition. For example, magnetron sputtering is used. The material of the peeling layer 3 can be an organic peeling layer, a nitrogen-containing compound, a sulfur-containing compound, a carboxylic acid, etc., or an inorganic peeling layer, including a metal base layer or an alloy layer. The peeling layer 3 can also be an inorganic layer and an organic layer together, for example, a mixture of a metal oxide and an organic substance.

[0061] An embodiment of the present invention further provides a metal-clad laminate, wherein the metal-clad laminate comprises the metal foil as described in any one of the above embodiments.

[0062] An embodiment of the present invention further provides a circuit board, the circuit board comprising the metal foil as described in any of the above embodiments, the metal foil being arranged on the surface or inside of the circuit board.

[0063] In order to demonstrate the beneficial effects of the metal foil, metal-clad laminate and circuit board provided by the embodiments of the present invention, several embodiments and comparative examples are described below.

[0064] Example 1

[0065] In the present embodiment, the material of the functional layer is copper, and a plurality of copper teeth are formed on one side of the functional layer, and each of the copper teeth includes a plurality of copper nodules, and a single copper nodule is in the shape of a spike; wherein, within the observation range, the maximum width of all copper teeth is 5-10 μm; within any unit area, the number of copper teeth with a maximum width of 8-10 μm accounts for 42.7%; among the copper teeth with a maximum width of 8-11 μm, the number of copper nodules of each copper tooth is 21-36; the shortest distance between any adjacent copper teeth is 1.2-2.5 μm; the top angle of any copper nodule is 64°-82°; the axial angle between adjacent copper nodules is 65°-95°; the roughness Rz of the side of the metal foil provided with the copper teeth is 3.2-4.8 μm; the bonding force between the side of the metal foil provided with the copper teeth and the substrate is 1.6 N / mm.

[0066] Example 2

[0067] Different from Example 1, within any unit area, the number of clustered teeth with a maximum width of 8 to 13 μm accounts for 75%; the shortest spacing between any adjacent clustered teeth is 0.8 to 1.7 μm; the top angle of any of the clustered tumors is 33° to 75°; the axial angle between adjacent clustered tumors is 67° to 98°; the bonding force between the side of the metal foil having the clustered teeth and the substrate is 1.8 / N / mm.

[0068] Example 3

[0069] The metal foil includes a functional layer, a peeling layer and a carrier layer which are stacked together. The carrier layer and the functional layer are both made of copper. A plurality of clustering teeth are formed on one side of the functional layer, and each of the clustering teeth includes a plurality of clustering nodules, each of which is in the shape of a spike. Unlike Example 1, the number of clustering nodules in the clustering teeth with a maximum width of 10 to 11 μm is 25 to 40, and the tip angle of any clustering nodule is 27°70°. The axial angle between adjacent clustering nodules is 3° to 104°. The bonding force between the side of the metal foil on which the clustering teeth are provided and the substrate is 1.7 N / mm.

[0070] Comparative Example 1

[0071] In this embodiment, the functional layer is copper, and a plurality of agglomeration teeth are formed on one side of the functional layer. The maximum width of the agglomeration teeth is 0.8-2.1 μm, and the end shape of a single agglomeration is an arc shape, similar to a sphere. The minimum distance between two adjacent agglomeration teeth is 2.1-4.5 μm.

[0072] Comparative Example 2

[0073] Different from Comparative Example 1, the number of agglomerates on each agglomerated tooth is 3 to 20.

[0074] Comparative Example 3

[0075] Different from Comparative Example 1, the roughness Rz of the side surface of the metal foil provided with the agglomerated teeth is 0.5-2 μm.

[0076] The 18 μm metal foil provided in Examples 1-3 and Comparative Examples 1-3 was laminated on a PTFE substrate to prepare fine circuits, and the bonding strength and transmission loss of the prepared fine circuits were observed. The transmission loss was measured using a vector network analyzer (VNA). The specific test environment was: using a 3-5 GHz operating frequency. The test results are shown in Table 1:

[0077] Table 1 Test results

[0078]

[0079]

[0080] It can be seen from Table 1 above that the metal foil prepared in the embodiment of the present invention can enhance the bonding force between the metal foil and the substrate, while ensuring low transmission loss, thereby improving the stability of the circuit board.

[0081] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A metal foil, characterized in that: It comprises a functional layer and a plurality of clustered teeth formed on a side of the functional layer, and each of the clustered teeth comprises a plurality of clustered bumps, and at least some of the clustered bumps are spike-shaped; Wherein, the maximum width of the clustered teeth is 2 to 15 μm.

2. The metal foil according to claim 1, characterized in that In any unit area, the number of agglomerated teeth with a maximum width of 8 to 15 μm accounts for more than 40%.

3. The metal foil according to claim 1, characterized in that In the agglomerated teeth with a maximum width of 7 to 12 μm, the number of agglomerates is greater than 20.

4. The metal foil according to claim 1, characterized in that There are gaps between the clustered teeth, and the shortest distance between any adjacent clustered teeth is 0.3-3 μm.

5. The metal foil according to claim 1, wherein In all the agglomerated teeth, each agglomeration tumor is in the shape of a spike.

6. The metal foil according to claim 1, characterized in that The top angle of any of the agglomerates is 20° to 90°; The tip angle is the angle between two tangent lines of the tip cross section of the agglomerate tumor in the sliced ​​state.

7. The metal foil according to claim 6, characterized in that Dendrites are formed between the agglomerates, and the axis angle between adjacent agglomerates is 40° to 110°; The axis angle is the angle between the central axes of any two adjacent agglomerates in the sliced ​​state.

8. The metal foil according to claim 1, wherein The roughness Rz of the side surface of the metal foil having the clustered teeth is 3 to 6 μm.

9. The metal foil according to claim 1, wherein The bonding force between the side surface of the metal foil provided with the agglomeration teeth and the substrate is 1.5-2.2 N / mm.

10. The metal foil according to any one of claims 1 to 9, characterized in that The metal foil further comprises: Carrier layer; The carrier layer is arranged on a side of the functional layer facing away from the agglomerated tooth.

11. The metal foil according to claim 10, characterized in that The metal foil further comprises: peeling layer; The release layer is arranged between the carrier layer and the functional layer.

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

13. A circuit board, characterized in that: The circuit board comprises the metal foil according to any one of claims 1 to 11, and the metal foil is arranged on the surface or inside of the circuit board.

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