Metal foil and metal-clad laminated plate

Abstract

The invention discloses a metal foil and a metal-clad laminated plate, which are characterized in that the change rate of the roughness Ra of any two selected test points is less than or equal to 10% in a first stripping surface, which is in contact with a stripping layer, on a carrier layer and / or a second stripping surface, which is in contact with the stripping layer, on a functional layer; the low profile of the first stripping surface and / or the second stripping surface can be ensured, and when the circuit board substrate is laminated, the situation that the stripping stability is influenced due to the fact that the profile fluctuation degree of the first stripping surface and / or the second stripping surface is too high and the stripping force is enhanced can be avoided. And meanwhile, the contour fluctuation degree of the first stripping surface and / or the second stripping surface is reduced, so that the relative distance between the carrier layer and the functional layer becomes far, the probability of permeation and adhesion of the carrier layer and the functional layer during hot pressing is effectively reduced, the stripping stability is further improved, and surface damage of the functional layer caused by poor stripping is avoided.

Description

Technical Field

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

[0002] Metal foil, such as electrolytic copper foil, is a key material in high-frequency and high-speed printed circuit boards for 5G communications. It plays a very important role, and ultra-thin metal foil is the current development direction of metal foil and a hot spot in market demand. As the market's demand for ultra-thin metal foil becomes higher and higher, the thickness of metal foil is gradually developing towards the ultra-thin direction of less than 5μm. However, the mechanical strength of ultra-thin metal foil is low, and it is difficult to completely peel it off from the cathode roller during preparation. In addition, it is prone to curling, wrinkling or tearing during transportation, which affects subsequent applications. At present, a preparation technology for ultra-thin carrier metal foil has been proposed. Since ultra-thin metal foil has the support of a carrier, its mechanical strength can be improved, solving the problems of transportation and storage.

[0003] Peelable metal foils with carriers are widely used to laminate with substrates through a hot press process. The carrier layer is then peeled off from the peelable foil, and the functional layer, such as a thin copper layer, is used as a metal-clad laminate. However, existing peelable metal foils are prone to peeling off the carrier layer improperly, resulting in surface damage to the functional layer, which affects its quality. Summary of the Invention

[0004] The present invention provides a metal foil and a metal-clad laminate to solve the technical problem that the existing metal foil is prone to poor peeling when the carrier layer is peeled off, resulting in surface damage of the functional layer, and aims to improve the reliability of the functional layer when making circuits.

[0005] In order to solve the above technical problems, a first aspect of an embodiment of the present invention provides a metal foil, comprising a carrier layer, a release layer, and a functional layer, wherein a surface of the carrier layer close to the release layer is a first release surface, a side of the release layer away from the first release surface is provided with the functional layer, and a surface of the functional layer close to the release layer is a second release surface;

[0006] In which, in the first peeling surface and / or the second peeling surface, the change rate of the roughness Ra of two arbitrarily selected test points is less than or equal to 10%; the change rate is the ratio of the difference between the roughness Ra of two arbitrarily selected test points to the average value.

[0007] As a preferred embodiment, N observation areas are pre-set in the first peeling surface and / or the second peeling surface, and the difference between the maximum and minimum values ​​of the average roughness Ra of the N observation areas is less than or equal to 0.02; wherein, the average roughness Ra of the observation area is the average value of the roughness Ra of the M test points randomly selected in the observation area; N and M are both positive integers greater than or equal to 5.

[0008] As a preferred solution, the roughness Ra of the first peeling surface and / or the second peeling surface is 0.05 μm to 0.2 μm.

[0009] As a preferred solution, the ratio of the actual surface area to the projected area of ​​the first peeling surface and / or the second peeling surface is less than or equal to 1.2.

[0010] As a preferred solution, in the sliced ​​state, within any length of 100 μm, the height difference between the highest point and the lowest point of the profile of the first peeling surface and / or the second peeling surface is less than or equal to 1 μm.

[0011] As a preferred solution, the roughness Rz of the surface of the functional layer on the side away from the release layer is 1.5 μm to 3 μm.

[0012] As a preferred solution, the peeling layer is made of an organic material, an inorganic material or a mixed material; wherein the mixed material includes the organic material and the inorganic material.

[0013] As a preferred solution, an anti-oxidation layer is further included, and the anti-oxidation layer is arranged on a surface of the functional layer away from the peeling layer.

[0014] As a preferred solution, it further comprises a heat-resistant layer, which is arranged on a surface of the carrier layer on a side away from the peeling layer.

[0015] A second aspect of the embodiments of the present invention provides a metal-clad laminate, wherein the metal-clad laminate is made of the functional layer in the metal foil as described in any one of the first aspects as one of the materials.

[0016] Compared with the prior art, the beneficial effect of the embodiments of the present invention is that by limiting the change rate of the roughness Ra of two arbitrarily selected test points in the first peeling surface in contact with the peeling layer on the carrier layer and / or the second peeling surface in contact with the peeling layer on the functional layer to be less than or equal to 10%, the low profile of the first peeling surface and / or the second peeling surface can be ensured, and when pressed with the circuit board substrate, the profile fluctuation of the first peeling surface and / or the second peeling surface can be avoided to be too high, thereby enhancing the peeling force and affecting the peeling stability.

[0017] At the same time, the contour undulation of the first peeling surface and / or the second peeling surface is reduced, so that the relative distance between the carrier layer and the functional layer becomes farther, effectively reducing the probability of penetration adhesion between the carrier layer and the functional layer during hot pressing, further improving the peeling stability, and avoiding surface damage of the functional layer caused by poor peeling. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 1 is a schematic structural diagram of a first metal foil according to an embodiment of the present invention;

[0019] Figure 2 Schematic diagram of the structure of the second metal foil in an embodiment of the present invention;

[0020] Figure 3 1 is a schematic structural diagram of a third metal foil in an embodiment of the present invention;

[0021] Among them, 1. carrier layer; 2. peeling layer; 3. functional layer; 4. first peeling surface; 5. second peeling surface; 6. anti-oxidation layer; 7. heat-resistant layer. DETAILED DESCRIPTION

[0022] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. The purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0023] In the description of this application, the terms "first," "second," "third," etc. are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first," "second," "third," etc. may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0024] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be a communication between the two components. The terms "vertical", "horizontal", "left", "right", "up", "down" and similar expressions used herein are for illustrative purposes only, and do not indicate or imply that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0025] In the description of this application, it should be noted that, unless otherwise defined, all technical and scientific terms used in this application have the same meanings 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 those skilled in the art in specific circumstances.

[0026] See Figure 1 In a first aspect of an embodiment of the present invention, a metal foil is provided, comprising a carrier layer 1, a release layer 2, and a functional layer 3. A surface of the carrier layer 1 close to the release layer 2 is a first release surface 4. A side of the release layer 2 away from the first release surface 4 is provided with the functional layer 3. A surface of the functional layer 3 close to the release layer 2 is a second release surface 5.

[0027] In which, in the first peeling surface 4 and / or the second peeling surface 5, the change rate of the roughness Ra of two arbitrarily selected test points is less than or equal to 10%; the change rate is the ratio of the difference between the roughness Ra of two arbitrarily selected test points to the average value.

[0028] It is worth noting that, in actual use, the carrier layer 1 is stacked with other material layers in the metal foil, such as the functional layer 3, to support and protect the functional layer 3, preventing it from being damaged by external contact or collision, or to meet the requirements of more sophisticated circuit manufacturing processes. After the functional layer 3 is laminated to the circuit board substrate at high temperature, the carrier layer 1 needs to be peeled off. In this embodiment, the material of the carrier layer 1 can include any one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver, and gold, and this embodiment is not specifically limited here.

[0029] The functional layer 3 plays a conductive role. The material of the functional layer 3 can include any one of aluminum, titanium, zinc, iron, nickel, chromium, cobalt, copper, silver and gold. This embodiment will not be described in detail here. In practical applications, for example, when the functional layer 3 is used in the field of circuit boards, the functional layer 3 is hot-pressed and bonded to the circuit board substrate. For example, when it is used in the field of electronic material production, the copper functional layer 3 is combined with other composite materials to make copper-clad laminates, flexible copper-clad laminates, or as raw materials for the production of adhesive-coated copper foil. For example, when it is used in the field of batteries, the copper functional layer 3 is used as the negative electrode material (negative current collector) of the battery, and it is hot-pressed and bonded to the negative active material in the negative electrode material. The aluminum functional layer 3 is used as the positive electrode material (positive current collector) of the battery.

[0030] The function of the peeling layer 2 is to separate the carrier layer 1 and the functional layer 3 by peeling. At the same time, due to the presence of the peeling layer 2, the metal migration between the functional layer 3 and the carrier layer 1 can be blocked. Moreover, the peeling layer 2 can cover or fill the uneven surface of the carrier layer 1, making the functional layer 3 formed on the other surface of the peeling layer 2 more flat, uniform and dense, reducing the occurrence of pinholes, and thus facilitating the subsequent circuit production.

[0031] In this embodiment, in order to prevent the metal foil from being improperly peeled off when peeling off the carrier layer 1, thereby causing surface damage to the functional layer 3, the rate of change of the roughness Ra of two randomly selected test points on the first peeling surface 4 on the carrier layer 1 that contacts the peeling layer 2 and / or the second peeling surface 5 on the functional layer 3 that contacts the peeling layer 2 is limited to be less than or equal to 10%. For example, the rate of change can be 0%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., which is not specifically limited in this embodiment. It is worth noting that the roughness Ra is the arithmetic average roughness, which represents the average value of the absolute value of the roughness within a reference length. The absolute value is relative to the reference line (average line) of the profile, that is, the arithmetic average roughness is the average value of the absolute value of the distance from the reference line (average line) of each point on the profile within the reference length. The roughness Ra of the first peeling surface 4 and the second peeling surface 5 can be directly measured by a roughness tester. The test point in this embodiment refers to a small reference length when the roughness tester performs a roughness Ra test, which is a setting value of the roughness tester.

[0032] Furthermore, regarding the aforementioned rate of change, assuming that the roughness Ra of two randomly selected test points on the first peeling surface 4 or the second peeling surface 5 is recorded as the first roughness Ra1 and the second roughness Ra2, respectively, then the rate of change of these two test points is the ratio of the difference between the first roughness Ra1 and the second roughness Ra2 to the average value of the first roughness Ra1 and the second roughness Ra2. By limiting the rate of change of the roughness Ra of two randomly selected test points on the first peeling surface 4 and / or the second peeling surface 5 to be less than or equal to 10%, this embodiment ensures a low profile of the first peeling surface 4 and / or the second peeling surface 5, i.e., a relatively flat first peeling surface 4 and / or the second peeling surface 5. This prevents excessive profile fluctuations of the first peeling surface 4 and / or the second peeling surface 5 during lamination with the circuit board substrate, thereby enhancing the peeling force. At the same time, since the undulation of the first peeling surface 4 and / or the second peeling surface 5 is reduced, the relative distance between the carrier layer 1 and the functional layer 3 becomes greater, effectively reducing the probability of penetration adhesion between the carrier layer 1 and the functional layer 3 during hot pressing. It is understandable that during the hot pressing process, the carrier layer 1 will move closer to the functional layer 3 due to pressure. If the undulation of the first peeling surface 4 and / or the second peeling surface 5 is high, that is, the relative distance between the carrier layer 1 and the functional layer 3 is close, the carrier layer 1 is likely to penetrate and adhere to the functional layer 3. When the carrier layer 1 is subsequently peeled off, it is easy to cause surface damage to the functional layer 3 or incomplete peeling of the carrier layer 1, thereby affecting the quality of the functional layer 3. Therefore, this embodiment can improve the peeling stability of the metal foil and avoid surface damage to the functional layer 3 caused by poor peeling.

[0033] It is worth noting that in this embodiment, the rate of change of the roughness Ra of two arbitrarily selected test points on the first peeling surface 4 may be less than or equal to 10%; the rate of change of the roughness Ra of two arbitrarily selected test points on the second peeling surface 5 may be less than or equal to 10%; or the rate of change of the roughness Ra of two arbitrarily selected test points on the first peeling surface 4 may be less than or equal to 10%, and at the same time, the rate of change of the roughness Ra of two arbitrarily selected test points on the second peeling surface 5 may be less than or equal to 10%. This embodiment does not make any specific limitations here.

[0034] As a preferred embodiment, N observation areas are pre-set in the first peeling surface 4 and / or the second peeling surface 5, and the difference between the maximum and minimum values ​​of the average roughness Ra of the N observation areas is less than or equal to 0.02; wherein, the average roughness Ra of the observation area is the average value of the roughness Ra of the M test points arbitrarily selected in the observation area; N and M are both positive integers greater than or equal to 5.

[0035] Specifically, in this embodiment, N observation areas are pre-set in the first peeling surface 4 and / or the second peeling surface 5, and the difference between the maximum value and the minimum value of the average roughness Ra of the N observation areas is less than or equal to 0.02. For example, the difference can be 0, 0.002, 0.005, 0.007, 0.01, 0.013, 0.015, 0.018, 0.02, etc. This embodiment is not specifically limited here, so as to ensure that the roughness Ra of each area in the first peeling surface 4 and / or the second peeling surface 5 is more uniform, avoiding the existence of locally protruding contours, making the overall first peeling surface 4 and / or the second peeling surface 5 more uniform and flat, further ensuring the peeling stability of the metal foil after hot pressing.

[0036] In this embodiment, the average roughness Ra of the observation area is the average of the roughness Ra of M test points randomly selected in the observation area, and both N and M are positive integers greater than or equal to 5. For example, the number N of observation areas can be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, etc., and the number of test points in each observation area can be 5, 7, 9, 11, 13, 15, 16, 18, 20, 22, 24, etc., which are not specifically limited in this embodiment. Preferably, N and M in this embodiment are both positive integers greater than 10, thereby further ensuring that the first peeling surface 4 and / or the second peeling surface 5 are more uniform and flat as a whole.

[0037] It is worth noting that in this embodiment, only the first peeling surface 4 may have N observation areas pre-set; or only the second peeling surface 5 may have N observation areas pre-set; or several observation areas may be set in both the first peeling surface 4 and the second peeling surface 5, and the number of observation areas in the first peeling surface 4 and the number of observation areas in the second peeling surface 5 both conform to the value range of the above-mentioned parameter N. The number of observation areas in the first peeling surface 4 may be equal to or unequal to the number of observation areas in the second peeling surface 5, and this is not specifically limited in this embodiment.

[0038] As for the number of test points in each observation area, the number of test points in each observation area may be the same or different, and this embodiment does not make any specific limitation here.

[0039] As a preferred solution, the roughness Ra of the first peeling surface 4 and / or the second peeling surface 5 is 0.05 μm to 0.2 μm.

[0040] Specifically, this embodiment further limits the roughness Ra of the first peeling surface 4 and / or the second peeling surface 5 to 0.05 μm to 0.2 μm. For example, the roughness Ra of the first peeling surface 4 and / or the second peeling surface 5 may be 0.05 μm, 0.07 μm, 0.09 μm, 0.11 μm, 0.13 μm, 0.15 μm, 0.17 μm, 0.19 μm, 0.2 μm, etc. This embodiment does not make specific limitations here. It can be understood that by limiting the roughness Ra of the first peeling surface 4 and / or the second peeling surface 5 to 0.05 μm to 0.2 μm, it is possible to Ensure that the roughness Ra of the first peeling surface 4 and / or the second peeling surface 5 is small, that is, the average value of the absolute value of the distance of each point on the surface profile of the first peeling surface 4 and / or the second peeling surface 5 from the baseline (average line) of the surface profile is small, thereby ensuring that the first peeling surface 4 and / or the second peeling surface 5 has a small degree of undulation, improving the peeling stability of the metal foil, and at the same time further ensuring that the relative distance between the carrier layer 1 and the functional layer 3 is relatively far, further reducing the probability of penetration adhesion between the carrier layer 1 and the functional layer 3 during hot pressing, thereby avoiding poor peeling and resulting in surface damage of the functional layer 3.

[0041] It is worth noting that in this embodiment, the roughness Ra of only the first peeling surface 4 can be 0.05μm~0.2μm; the roughness Ra of only the second peeling surface 5 can be 0.05μm~0.2μm; or the roughness Ra of the first peeling surface 4 and the second peeling surface 5 can simultaneously meet the above-mentioned roughness Ra range: 0.05μm~0.2μm, which is not specifically limited in this embodiment.

[0042] As a preferred solution, the ratio of the actual surface area to the projected area of ​​the first peeling surface 4 and / or the second peeling surface 5 is less than or equal to 1.2.

[0043] Specifically, the projected area in this embodiment is the area of ​​the projection area in the projection direction perpendicular to the peeling surface. By limiting the ratio of the actual surface area of ​​the first peeling surface 4 and / or the second peeling surface 5 to the projected area to be less than or equal to 1.2, for example, the ratio can be 1.05, 1.07, 1.09, 1.11, 1.13, 1.15, 1.17, 1.19, 1.2, etc., which is not specifically limited in this embodiment, it is shown that the actual surface area of ​​the first peeling surface 4 and / or the second peeling surface 5 is relatively close to the projected area. Since the actual surface area is affected by Therefore, when the actual surface area is close to the projected area, it indicates that the roughness Ra of the first peeling surface 4 and / or the second peeling surface 5 is smaller and the degree of undulation is lower, which can avoid the contour undulation of the first peeling surface 4 and / or the second peeling surface 5 being too high to enhance the peeling force and affect the peeling stability. At the same time, it ensures that the relative distance between the carrier layer 1 and the functional layer 3 is relatively far, further reducing the probability of penetration adhesion between the carrier layer 1 and the functional layer 3 during hot pressing, further improving the peeling stability, and avoiding poor peeling and resulting in surface damage of the functional layer 3.

[0044] It is worth noting that in this embodiment, only the ratio of the actual surface area to the projected area of ​​the first peeling surface 4 may be less than or equal to 1.2; or only the ratio of the actual surface area to the projected area of ​​the second peeling surface 5 may be less than or equal to 1.2; or the ratio of the actual surface area to the projected area of ​​both the first peeling surface 4 and the second peeling surface 5 may be less than or equal to 1.2, wherein the ratio of the actual surface area to the projected area of ​​the first peeling surface 4 may be equal to or unequal to the ratio of the actual surface area to the projected area of ​​the second peeling surface 5, and this embodiment does not make any specific limitation here.

[0045] As a preferred solution, in the sliced ​​state, within any length of 100 μm, the height difference between the highest point and the lowest point of the contour of the first peeling surface 4 and / or the second peeling surface 5 is less than or equal to 1 μm.

[0046] Specifically, for further observation, in this embodiment, the carrier layer 1 or the functional layer 3 is sliced, and any area within a length of 100 μm is taken to observe the profile of the first peeling surface 4 or the second peeling surface 5. By limiting the height difference between the highest point and the lowest point of the profile of the first peeling surface 4 and / or the second peeling surface 5 to be less than or equal to 1 μm, for example, the height difference can be 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, etc. This embodiment is not specifically limited here, so as to ensure that the undulation of the first peeling surface 4 and / or the second peeling surface 5 is relatively low, so that the overall peeling surface is relatively flat and uniform, and the contour undulation of the first peeling surface 4 and / or the second peeling surface 5 is avoided to be too high, thereby enhancing the peeling force and affecting the peeling stability. At the same time, the relative distance between the carrier layer 1 and the functional layer 3 is ensured to be relatively far, thereby further reducing the probability of penetration adhesion between the carrier layer 1 and the functional layer 3 during hot pressing, further improving the peeling stability, and avoiding surface damage of the functional layer 3 caused by poor peeling.

[0047] As a preferred solution, the roughness Rz of the surface of the functional layer 3 away from the release layer 2 is 1.5 μm to 3 μm.

[0048] Specifically, the roughness Rz is the sum of the average of the five largest profile peak heights and the average of the five largest profile valley depths within a reference length. In this embodiment, the roughness Rz of the surface of the functional layer 3 facing away from the release layer 2 is limited to 1.5 μm to 3 μm. For example, the roughness Rz of this surface can be 1.5 μm, 1.7 μm, 1.9 μm, 2.1 μm, 2.3 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, etc. (this embodiment does not impose a specific limit here). This ensures that the roughness Rz of the surface of the functional layer 3 facing away from the release layer 2 is appropriate. The presence of certain micro-protrusions and depressions on this surface increases the contact area between the functional layer 3 and the circuit board substrate, ensuring sufficient bonding force. At the same time, the roughness Rz is not excessively large, resulting in a low profile for the functional layer 3, avoiding a significant skin effect on the bonding side, and improving the high-frequency and high-speed performance of the functional layer 3 after it is fabricated into a circuit.

[0049] As a preferred solution, the peeling layer 2 is made of an organic material, an inorganic material or a mixed material; wherein the mixed material includes the organic material and the inorganic material.

[0050] Specifically, the material of the peeling layer 2 in this embodiment can be an organic material, such as nitrogen-containing compounds, sulfur-containing compounds and carboxylic acids, among which nitrogen-containing organic compounds include the following types: ketoxime compounds, transition metal chelates, organic amine compounds and nitrogen heterocyclic compounds; ketoxime compounds include phenyl oxime, o-nitrobenzene oxime, etc.; transition metal chelates include nitrosopropanedione, etc.; organic amine compounds include aniline, diethylamine, etc.; nitrogen heterocyclic compounds include pyridine, imidazole, etc.; of course, in addition to the nitrogen-containing organic compounds mentioned above, other nitrogen-containing organic compounds can also be used, and this embodiment will not be described in detail here. Types of sulfur-containing organic compounds include disulfide compounds and thiosulfide compounds; disulfide compounds include ethylene disulfide, propylene disulfide, etc.; thiosulfide compounds include thiophenyl ether, thioethyl ether, etc.; of course, in addition to the sulfur-containing organic compounds mentioned above, other sulfur-containing organic compounds can also be used, and this embodiment will not be described in detail here.

[0051] In addition, the material of the peeling layer 2 in this embodiment can also be an inorganic material, including a metal base layer or alloy layer, such as an alloy made of any one or more materials of copper, nickel, silicon, molybdenum, titanium and niobium, which is not specifically limited in this embodiment.

[0052] In addition, the material of the peeling layer 2 in this embodiment can also be a mixed material including organic materials and inorganic materials, wherein the organic material can be the nitrogen-containing compounds, sulfur-containing compounds and carboxylic acids mentioned above, and the inorganic material can be an alloy made of any one or more of the copper, nickel, silicon, molybdenum, titanium and niobium mentioned above, and this embodiment is not specifically limited here.

[0053] In this embodiment, the release layer 2 is processed on the carrier layer 1 by any one of an electroplating process, a vacuum sputtering process, and a coating process.

[0054] As a preferred solution, an anti-oxidation layer 6 is further included, and the anti-oxidation layer 6 is arranged on a surface of the functional layer 3 away from the peeling layer 2 .

[0055] Specifically, see Figure 2 In order to enhance the anti-oxidation effect of the metal foil before use, an anti-oxidation layer 6 is provided on the surface of the functional layer 3 on the side away from the release layer 2 in this embodiment. This makes the surface of the functional layer 3 on the side away from the release layer 2 less susceptible to contamination by moisture, dust and other objects in the air, and can maintain a relatively dry and clean surface state. At the same time, it is not easily oxidized, which can ensure the normal storage and use of the metal foil and help extend the storage time.

[0056] As one optional embodiment, the anti-oxidation layer 6 includes a non-metallic layer and / or an inorganic metal layer, wherein the non-metallic layer includes an organic layer, and the material of the organic layer is a polymer organic material such as polyimide, PET, etc. Taking polyimide as an example, polyimide has excellent high temperature stability and chemical stability, and has good bonding with the functional layer 3 (such as copper foil). By coating a polyimide solution or suspension on the surface of the functional layer 3 (such as copper foil) and subjecting it to heat treatment, a uniform anti-oxidation layer 6 can be formed. Such an anti-oxidation layer 6 can effectively protect the functional layer 3 (such as copper foil) from the effects of oxidation, and has good bonding, and is suitable for use in the fields of electronics, communications, and aerospace. Polyimide as the material of the anti-oxidation layer 6 has excellent high temperature resistance. Polyimide materials can still maintain stable chemical and physical properties at high temperatures and can withstand temperatures of up to 400 degrees Celsius or more. Therefore, using polyimide as the material of the anti-oxidation layer 6 can not only protect the functional layer 3 (such as copper foil) from oxidation, but also maintain stable performance in a high temperature environment, and is suitable for application fields that require high temperature resistance.

[0057] In addition, the material of the organic layer can also be any one of nitrogen-containing organic compounds, sulfur-containing organic compounds and hydroxy acids. Nitrogen-containing organic compounds include the following types: ketoxime compounds, transition metal chelators, organic amine compounds and nitrogen heterocyclic compounds; ketoxime compounds, such as phenyloxime and o-nitrophenyloxime, can form complexes with the surface of metal oxides, thereby slowing down the oxidation rate of the metal; transition metal chelators, such as nitrosopropanedione, can form stable coordination complexes with metals, effectively preventing the oxidation reaction of the metal; organic amine compounds, such as aniline and diethylamine, can react with the surface of metal oxides to form amine copper complexes, thereby playing an antioxidant role; nitrogen heterocyclic compounds, such as pyridine and imidazole, have strong coordination ability and can form stable complexes with metals, thereby slowing down the oxidation rate of the metal. Of course, in addition to the nitrogen-containing organic compounds mentioned above, other nitrogen-containing organic compounds with antioxidant ability in the prior art can also be used, and this embodiment will not be described in detail here. Sulfur-containing organic compounds, such as mercaptoethanol and mercaptopropanol, can react with the surface of metal oxides to form relatively stable complexes, thereby slowing down the oxidation rate of the metal. Types of sulfur-containing organic compounds include disulfide compounds and thiosulfide compounds; disulfide compounds, such as ethylene disulfide and propylene disulfide, can form complexes with metal surfaces and have certain antioxidant properties; thiosulfide compounds, such as thiophenyl ether and thioethyl ether, can react chemically with metals to slow down the oxidation process of metals. Of course, in addition to the sulfur-containing organic compounds mentioned above, other sulfur-containing organic compounds with antioxidant properties in the prior art can also be used, and this embodiment will not be described in detail here. Hydroxylic acids can form stable complexes with metal ions by chelating metal ions, thereby slowing down the oxidation rate of metals and having certain antioxidant properties.

[0058] Furthermore, the material of the inorganic metal layer includes at least one of nickel, copper, chromium, zinc and the like and / or an alloy including at least one of them, which is not specifically limited in this embodiment.

[0059] As a preferred solution, a heat-resistant layer 7 is further included. The heat-resistant layer 7 is arranged on a surface of the carrier layer 1 that is away from the peeling layer 2 .

[0060] Specifically, see Figure 3In order to enhance the high-temperature resistance of the metal foil during hot pressing, a heat-resistant layer 7 is provided on the surface of the carrier layer 1 on the side away from the peeling layer 2 in this embodiment. It is understandable that during the high-temperature pressing process of the functional layer 3 and the circuit board substrate, the carrier layer 1 may come into contact with the high-temperature pressing plate of the press and cause melting or deformation, thereby affecting the structural stability of the metal foil. It may even cause the carrier layer 1 and the functional layer 3 to diffuse with each other at high temperatures and cause adhesion, making it difficult to peel the carrier layer 1 and the functional layer 3. The heat-resistant layer 7 can act as a heat insulator, reducing the heating temperature of the carrier layer 1 and the peeling layer 2, and ensuring the thermal stability of the carrier layer 1 and the peeling layer 2. The material of the heat-resistant layer 7 can be: tetrafluoroethylene film, polyimide film, heat-resistant adhesive, etc. The above materials all have certain heat resistance and can effectively protect the metal foil from heat damage during the pressing process.

[0061] A second aspect of the embodiments of the present invention provides a metal-clad laminate, wherein the metal-clad laminate is made of the functional layer in the metal foil described in any embodiment of the first aspect as one of the materials.

[0062] The metal foil and metal-clad laminate provided by the embodiments of the present invention have the following beneficial effects:

[0063] (1) By limiting the change rate of the roughness Ra of two arbitrarily selected test points on the first peeling surface in contact with the peeling layer on the carrier layer and / or the second peeling surface in contact with the peeling layer on the functional layer to be less than or equal to 10%, the low profile of the first peeling surface and / or the second peeling surface can be ensured. When pressing with the circuit board substrate, the profile fluctuation of the first peeling surface and / or the second peeling surface can be avoided to be too high, thereby increasing the peeling force and affecting the peeling stability.

[0064] At the same time, the contour undulation of the first peeling surface and / or the second peeling surface is reduced, so that the relative distance between the carrier layer and the functional layer becomes farther, effectively reducing the probability of penetration adhesion between the carrier layer and the functional layer during hot pressing, further improving the peeling stability, and avoiding surface damage of the functional layer caused by poor peeling.

[0065] (2) By limiting the difference between the maximum and minimum values ​​of the average roughness Ra of N pre-set observation areas on the first peeling surface and / or the second peeling surface to be less than or equal to 0.02, the roughness Ra of each area on the first peeling surface and / or the second peeling surface can be ensured to be more uniform, avoiding the existence of locally protruding contours, making the overall first peeling surface and / or the second peeling surface more uniform and smooth, and further ensuring the peeling stability of the metal foil after hot pressing.

[0066] (3) By limiting the roughness Ra of the first peeling surface and / or the second peeling surface to 0.05 μm to 0.2 μm, it is possible to ensure that the undulation of the first peeling surface and / or the second peeling surface is small, thereby improving the peeling stability of the metal foil. At the same time, it is possible to further ensure that the relative distance between the carrier layer and the functional layer is relatively far, thereby further reducing the probability of penetration adhesion between the carrier layer and the functional layer during hot pressing, thereby avoiding poor peeling and resulting in surface damage of the functional layer.

[0067] (4) By limiting the ratio of the actual surface area to the projected area of ​​the first peeling surface and / or the second peeling surface to be less than or equal to 1.2, it is possible to avoid excessive contour fluctuations of the first peeling surface and / or the second peeling surface, thereby increasing the peeling force and affecting the peeling stability.

[0068] (5) By limiting the height difference between the highest point and the lowest point of the contour of the first peeling surface and / or the second peeling surface to be less than or equal to 1 μm within any 100 μm length in the sliced ​​state, it is possible to ensure that the undulation of the first peeling surface and / or the second peeling surface is relatively low, making the overall peeling surface relatively flat and uniform, and avoiding the contour undulation of the first peeling surface and / or the second peeling surface being too high, thereby increasing the peeling force and affecting the peeling stability.

[0069] (6) By limiting the roughness Rz of the surface of the functional layer away from the peeling layer to 1.5μm to 3μm, it can be ensured that there is sufficient bonding force between the surface of the functional layer away from the peeling layer and the circuit board substrate. At the same time, the roughness Rz will not be too large, so that the functional layer presents a low profile, avoiding a large skin effect on the bonding side, and improving the high-frequency and high-speed performance of the functional layer after it is made into a circuit.

[0070] In order to fully demonstrate the beneficial effects of the metal foil and metal-clad laminate provided by the embodiments of the present invention, several embodiments and comparative examples are described below.

[0071] Example 1

[0072] A metal foil comprising a carrier layer, a peeling layer and a functional layer, wherein a surface of the carrier layer close to the peeling layer is a first peeling surface, a functional layer is provided on a side of the peeling layer away from the first peeling surface, and a surface of the functional layer close to the peeling layer is a second peeling surface;

[0073] Among them, on the first peeling surface, the change rate of the roughness Ra of two randomly selected test points is 4.3% to 6.8%; on the second peeling surface, the change rate of the roughness Ra of two randomly selected test points is 5.5% to 7.5%.

[0074] Example 2

[0075] A metal foil comprising a carrier layer, a peeling layer and a functional layer, wherein a surface of the carrier layer close to the peeling layer is a first peeling surface, a functional layer is provided on a side of the peeling layer away from the first peeling surface, and a surface of the functional layer close to the peeling layer is a second peeling surface;

[0076] Among them, on the first peeling surface, the change rate of the roughness Ra of two randomly selected test points is 2.6% to 5.1%; on the second peeling surface, the change rate of the roughness Ra of two randomly selected test points is 3.6% to 8.1%.

[0077] In addition, the difference between the maximum and minimum values ​​of the average roughness Ra of the 12 observation areas pre-set in the first peeling surface is 0.005, and the difference between the maximum and minimum values ​​of the average roughness Ra of the 12 observation areas pre-set in the second peeling surface is 0.01. The average roughness Ra of each observation area is the average value of the roughness Ra of 15 test points randomly selected in the observation area.

[0078] The roughness Ra of the first peeling surface is 0.05 μm, and the roughness Ra of the second peeling surface is 0.08 μm; the ratio of the actual surface area to the projected area of ​​the first peeling surface is 1.08, and the ratio of the actual surface area to the projected area of ​​the second peeling surface is 1.1.

[0079] Example 3

[0080] A metal foil comprising a carrier layer, a peeling layer and a functional layer, wherein a surface of the carrier layer close to the peeling layer is a first peeling surface, a functional layer is provided on a side of the peeling layer away from the first peeling surface, and a surface of the functional layer close to the peeling layer is a second peeling surface;

[0081] Among them, on the first peeling surface, the change rate of the roughness Ra of two randomly selected test points is 6.7% to 8.9%; on the second peeling surface, the change rate of the roughness Ra of two randomly selected test points is 2.2% to 4.5%.

[0082] In addition, the difference between the maximum and minimum values ​​of the average roughness Ra of the 8 observation areas pre-set in the first peeling surface is 0.012, and the difference between the maximum and minimum values ​​of the average roughness Ra of the 5 observation areas pre-set in the second peeling surface is 0.015. The average roughness Ra of each observation area is the average value of the roughness Ra of 10 test points randomly selected in the observation area.

[0083] The roughness Ra of the first peeling surface is 0.07μm, and the roughness Ra of the second peeling surface is 0.11μm; the ratio of the actual surface area to the projected area of ​​the first peeling surface is 1.1, and the ratio of the actual surface area to the projected area of ​​the second peeling surface is 1.2; in the slicing state, within any 100μm length, the height difference between the highest point and the lowest point of the contour of the first peeling surface is 0.6μm, and the height difference between the highest point and the lowest point of the contour of the second peeling surface is 1μm.

[0084] Example 4

[0085] A metal foil comprises a carrier layer, a peeling layer, a functional layer, an anti-oxidation layer and a heat-resistant layer, wherein the surface of the carrier layer close to the peeling layer is a first peeling surface, the functional layer is provided on the side of the peeling layer away from the first peeling surface, and the surface of the functional layer close to the peeling layer is a second peeling surface; the anti-oxidation layer is provided on the surface of the functional layer away from the peeling layer, and the heat-resistant layer is provided on the surface of the carrier layer away from the peeling layer.

[0086] Among them, on the first peeling surface, the change rate of the roughness Ra of two randomly selected test points is 5.1% to 7.3%; on the second peeling surface, the change rate of the roughness Ra of two randomly selected test points is 8.4% to 10%.

[0087] In addition, the difference between the maximum and minimum values ​​of the average roughness Ra of the 15 observation areas pre-set in the first peeling surface is 0.02, and the difference between the maximum and minimum values ​​of the average roughness Ra of the 5 observation areas pre-set in the second peeling surface is 0.017. The average roughness Ra of each observation area is the average value of the roughness Ra of 14 test points randomly selected in the observation area.

[0088] The roughness Ra of the first peeling surface is 0.15μm, and the roughness Ra of the second peeling surface is 0.2μm; the ratio of the actual surface area to the projected area of ​​the first peeling surface is 1.04, and the ratio of the actual surface area to the projected area of ​​the second peeling surface is 1.16; in the sliced ​​state, within any 100μm length, the height difference between the highest point and the lowest point of the contour of the first peeling surface is 0.3μm, and the height difference between the highest point and the lowest point of the contour of the second peeling surface is 0.8μm; the roughness Rz of the surface on the side of the functional layer away from the peeling layer is 1.8μm.

[0089] Example 5

[0090] A metal foil comprises a carrier layer, a peeling layer, a functional layer, an anti-oxidation layer and a heat-resistant layer, wherein the surface of the carrier layer close to the peeling layer is a first peeling surface, the functional layer is provided on the side of the peeling layer away from the first peeling surface, and the surface of the functional layer close to the peeling layer is a second peeling surface; the anti-oxidation layer is provided on the surface of the functional layer away from the peeling layer, and the heat-resistant layer is provided on the surface of the carrier layer away from the peeling layer.

[0091] Among them, on the first peeling surface, the change rate of the roughness Ra of two randomly selected test points is 3.3% to 5.2%; on the second peeling surface, the change rate of the roughness Ra of two randomly selected test points is 4.9% to 6.5%.

[0092] In addition, the difference between the maximum and minimum values ​​of the average roughness Ra of the 20 observation areas pre-set in the first peeling surface is 0.01, and the difference between the maximum and minimum values ​​of the average roughness Ra of the 20 observation areas pre-set in the second peeling surface is 0.016. The average roughness Ra of each observation area is the average value of the roughness Ra of 20 test points randomly selected in the observation area.

[0093] The roughness Ra of the first peeling surface is 0.09μm, and the roughness Ra of the second peeling surface is 0.18μm; the ratio of the actual surface area to the projected area of ​​the first peeling surface is 1.1, and the ratio of the actual surface area to the projected area of ​​the second peeling surface is 1.13; in the sliced ​​state, within any length of 100μm, the height difference between the highest point and the lowest point of the contour of the first peeling surface is 0.5μm, and the height difference between the highest point and the lowest point of the contour of the second peeling surface is 0.9μm; the roughness Rz of the surface on the side of the functional layer away from the peeling layer is 2.6μm.

[0094] Comparative Example 1

[0095] A metal foil comprising a carrier layer, a peeling layer and a functional layer, wherein a surface of the carrier layer close to the peeling layer is a first peeling surface, a functional layer is provided on a side of the peeling layer away from the first peeling surface, and a surface of the functional layer close to the peeling layer is a second peeling surface;

[0096] Among them, on the first peeling surface, the change rate of the roughness Ra of two randomly selected test points is greater than 10%; on the second peeling surface, the change rate of the roughness Ra of two randomly selected test points is greater than 10%.

[0097] After hot pressing the metal foils in the above-mentioned embodiments and comparative examples with the same circuit board substrate under the same hot pressing conditions, the carrier layer was peeled off and the surface damage of the functional layer was observed. The results are shown in Table 1 below:

[0098] Table 1 Surface damage of functional layer

[0099] Detection object Surface damage of the functional layer Example 1 The surface of the functional layer is not damaged Example 2 The surface of the functional layer is not damaged Example 3 The surface of the functional layer is not damaged Example 4 The surface of the functional layer is not damaged Example 5 The surface of the functional layer is not damaged Comparative Example 1 The surface of the functional layer is damaged

[0100] It can be seen that the metal foils of Examples 1 to 5 can ensure a low profile of the first and second peeling surfaces because the rate of change of the roughness Ra of any two test points selected on the first and second peeling surfaces is less than or equal to 10%. When pressed with the circuit board substrate, the profile fluctuations of the first and second peeling surfaces can be avoided to be too high, thereby increasing the peeling force and affecting the peeling stability, and effectively avoiding poor peeling and resulting in surface damage of the functional layer.

[0101] In contrast, in the metal foil of Comparative Example 1, the rate of change of the roughness Ra at any two test points selected on its first peeling surface and second peeling surface is greater than 10%, resulting in excessive contour fluctuations on the first peeling surface and the second peeling surface, and excessive peeling force, causing damage to the surface of the functional layer when the carrier layer is peeled off.

[0102] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles 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 The invention comprises a carrier layer, a peeling layer and a functional layer, wherein a surface of the carrier layer close to the peeling layer is a first peeling surface, a side of the peeling layer away from the first peeling surface is provided with the functional layer, and a surface of the functional layer close to the peeling layer is a second peeling surface; In which, in the first peeling surface and / or the second peeling surface, the change rate of the roughness Ra of two arbitrarily selected test points is less than or equal to 10%; the change rate is the ratio of the difference between the roughness Ra of two arbitrarily selected test points to the average value.

2. The metal foil according to claim 1, wherein N observation areas are pre-set in the first peeling surface and / or the second peeling surface, and the difference between the maximum and minimum values ​​of the average roughness Ra of the N observation areas is less than or equal to 0.02; wherein, the average roughness Ra of the observation area is the average value of the roughness Ra of M test points randomly selected in the observation area; N and M are both positive integers greater than or equal to 5.

3. The metal foil according to claim 1, wherein The roughness Ra of the first release surface and / or the second release surface is 0.05 μm to 0.2 μm.

4. The metal foil according to claim 1, wherein A ratio of an actual surface area to a projected area of ​​the first peeling surface and / or the second peeling surface is less than or equal to 1.

2.

5. The metal foil according to claim 1, wherein In the sliced ​​state, within any length of 100 μm, the height difference between the highest point and the lowest point of the profile of the first peeling surface and / or the second peeling surface is less than or equal to 1 μm.

6. The metal foil according to claim 1, wherein The roughness Rz of the surface of the functional layer on a side away from the release layer is 1.5 μm to 3 μm.

7. The metal foil according to claim 1, wherein The peeling layer is made of an organic material, an inorganic material or a mixed material; wherein the mixed material includes the organic material and the inorganic material.

8. The metal foil according to claim 1, wherein The invention also includes an anti-oxidation layer, which is arranged on a surface of the functional layer on a side away from the peeling layer.

9. The metal foil according to claim 1, wherein It also includes a heat-resistant layer, which is arranged on a surface of the carrier layer on a side away from the peeling layer.

10. A metal-clad laminate, characterized in that: The metal-clad laminate is produced by using the functional layer in the metal foil according to any one of claims 1 to 9 as one of its materials.

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