Multilayer metal foil and circuit board

Abstract

The invention discloses a multi-layer metal foil and a circuit board. The multi-layer metal foil comprises a carrier layer, a stripping layer and a functional layer which are sequentially stacked, wherein the stripping layer is used for enabling the carrier layer and the functional layer to be stripped from each other, the stripping layer comprises a nickel element, and the atomic fraction of the nickel element is 5%-40% in the total number of all atoms of the stripping layer. In the embodiment of the invention, the nickel element has higher thermal stability and lower diffusion coefficient, and during high-temperature lamination, nickel atoms are difficult to severely diffuse into the carrier layer and the functional layer, so that a firm alloying interface is prevented from being formed, and the interface atoms at high temperature are fundamentally inhibited from mutual diffusion; the stability and the consistency of the stripping force of the multi-layer metal foil at high temperature are remarkably improved, and damage or poor stripping of the functional layer caused by overlarge or fluctuating stripping force is avoided.

Description

Technical Field

[0001] This invention relates to the field of electronic products, and more particularly to a multilayer metal foil and circuit board. Background Technology

[0002] In today's booming electronics and information industry, the precision of the manufacturing process of printed circuit boards (PCBs), as the core carrier of electronic devices, is crucial. Peelable copper, a commonly used functional material in PCB fabrication, plays a key role in the multi-layer structure of PCBs due to its excellent peelability and conductivity. However, in actual production, peeling force is one of the key factors affecting the quality of peelable copper. In existing technologies, removing the carrier copper often employs mechanical or chemical peeling methods. During mechanical peeling, an automated robotic arm combined with vacuum adsorption / clamp positioning is commonly used. Simultaneously, a uniform peeling method is employed, with the robotic arm's servo motor precisely controlling the speed to avoid sudden acceleration or deceleration that could lead to localized stress concentration.

[0003] Coreless technology is an electronic manufacturing process that eliminates the need for traditional core boards. It uses copper foil with a carrier as a base, and through layering and lamination, the carrier is separated and the core material is removed to form an extremely thin or odd-layer structured substrate. In this process, the circuit board needs to be repeatedly laminated under high temperature and high pressure. Due to the nature of the peelable copper material, the peeling force can be unstable. For example, after one press, the peeling force is within a controllable range and can peel normally. However, after two or more presses, the peeling force becomes different in different places, with some places having a large peeling force and others having a small peeling force. This can lead to peeling damage, with the carrier layer remaining on the thin copper layer, or the peeling force being too large, causing the thin copper layer to be pulled off at the same time, affecting subsequent manufacturing processes. Summary of the Invention

[0004] The purpose of this invention is to provide a multilayer metal foil and circuit board that can effectively improve the stability of the peeling force of the multilayer metal foil at high temperatures, and ensure the peeling effect and circuit manufacturing quality.

[0005] To achieve the above objectives, embodiments of the present invention provide a multilayer metal foil, comprising a carrier layer, a release layer, and a functional layer stacked sequentially; wherein, the release layer is used for peeling the carrier layer and the functional layer from each other, the release layer comprises nickel, and the atomic fraction of nickel in the total number of atoms in the release layer is 5% to 40%.

[0006] As an improvement to the above scheme, the stripping layer further includes zinc, and the ratio of the atomic fractions of nickel to zinc in the total number of atoms in the stripping layer is 50:1 to 1:1.

[0007] As an improvement to the above scheme, the stripping layer further includes oxygen, and the ratio of the atomic fractions of nickel to oxygen in the total number of atoms in the stripping layer is 10:1 to 1:1.

[0008] As an improvement to the above scheme, the atomic fraction of oxygen element in the total number of atoms in the stripping layer is 1% to 20%.

[0009] As an improvement to the above scheme, when the multilayer metal foil is in a sliced ​​state, the coefficient of variation of the atomic fraction of nickel at any two points in the peeling layer is less than 20%.

[0010] As an improvement to the above scheme, when the multilayer metal foil is at a preset temperature and after n pressings, the coefficient of variation of the atomic fraction of oxygen at any two points in the peeling layer is less than 20%, where n≥2.

[0011] As an improvement to the above scheme, the ratio of the roughness Sku of the side of the functional layer away from the carrier layer to the thickness of the functional layer is in the range of 0.5 to 20.

[0012] As an improvement to the above scheme, the ratio of the roughness Sku of the side of the carrier layer near the functional layer to the thickness of the carrier layer is in the range of 0.01 to 5.

[0013] As an improvement to the above scheme, the stripping layer also includes carbon elements, and the atomic fraction of carbon elements in the total number of atoms in the stripping layer is 3% to 60%.

[0014] To achieve the above objectives, embodiments of the present invention also provide a circuit board, which is made of the multilayer metal foil described in any of the above embodiments.

[0015] Compared with existing technologies, the multilayer metal foil and circuit board disclosed in this invention include a carrier layer, a release layer, and a functional layer stacked sequentially. The release layer is used for peeling the carrier layer and the functional layer from each other. The release layer includes nickel, with the nickel atomic fraction ranging from 5% to 40% of the total atoms in the release layer. Due to nickel's high thermal stability and low diffusion coefficient, nickel atoms do not readily diffuse violently into the carrier layer and functional layer during high-temperature lamination, thus avoiding the formation of a strong alloying interface. This fundamentally inhibits inter-atomic diffusion at high temperatures, ensuring a clear and weakly bonded interface between the carrier layer and the functional layer after lamination. This significantly improves the stability and consistency of the multilayer metal foil under high-temperature peeling force, preventing damage or poor peeling of the functional layer due to excessive or fluctuating peeling force. Furthermore, nickel can enhance the chemical corrosion resistance of the release layer, better protecting the interface during subsequent PCB etching, electroplating, and other processes. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a multilayer metal foil provided in an embodiment of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] In the description of this application, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0019] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. The terms "vertical," "horizontal," "left," "right," "upper," "lower," 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, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0020] In the description of this application, it should be noted that, unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing specific embodiments only and is not intended to limit the invention. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0021] It should be noted that the detection equipment used in this invention is a focused ion beam scanning electron microscope (FIB-SEM) and a transmission electron microscope (TEM). The detection standards are JY / T 0583-2020 "Determination Method of Quantitative Analysis Parameters of Energy Dispersive Spectrometer" and GB / T 18907-2013 "Selected Area Electron Diffraction Analysis Method of Transmission Electron Microscopy". The detection conditions are FIB (Focused Ion Beam, a technique that uses a high-energy ion beam to precisely cut and deposit samples), with the voltage set at 30kV. This method allows for precise characterization and analysis of the microstructure and compositional distribution of the exfoliated layer in this invention.

[0022] See Figure 1 , Figure 1 This is a schematic diagram of a multilayer metal foil provided in an embodiment of the present invention. The multilayer metal foil includes a carrier layer 1, a release layer 2, and a functional layer 3 stacked sequentially. The release layer 2 is used for peeling the carrier layer 1 and the functional layer 3 from each other. The release layer 2 includes nickel, and the atomic fraction of nickel in the total number of atoms in the release layer 2 is 5% to 40%.

[0023] For example, Figure 1 This diagram illustrates the stacked structure of a multilayer metal foil and the peeling process. The carrier layer 1 primarily supports and carries the functional layer 3. The peeling layer 2, located between the carrier layer 1 and the functional layer 3, allows the carrier and functional layers to be peeled off. The functional layer 3 is a layer structure with specific functions, such as serving as conductive traces in PCB manufacturing. In coreless PCB manufacturing, after high-temperature, high-pressure lamination of the copper foil with a carrier, a peeling operation is required to separate the carrier to form an extremely thin or odd-layer substrate. For example, after two or more high-temperature, high-pressure laminations, the circuit board reaches specific structural requirements. To remove the carrier layer 1 and retain only the functional layer 3 and the subsequent circuitry, the properties of the peeling layer 2 are used to peel the carrier layer 1 off the functional layer 3, allowing it to proceed to subsequent manufacturing processes.

[0024] For example, atomic fraction refers to the proportion (expressed as a percentage) of the number of atoms of a certain element in the total number of atoms in a substance. Compared with traditional copper or chromium, nickel has higher thermal stability and a lower diffusion coefficient. During high-temperature pressing, nickel atoms are less likely to diffuse violently into the carrier layer 1 and functional layer 3, thereby avoiding the formation of a strong alloying interface. In this embodiment of the invention, the atomic fraction of nickel is controlled between 5% and 40%. If the content is too low, an effective diffusion barrier layer cannot be formed, and interdiffusion of atoms will occur; if the content is too high, the release layer itself may be too hard or too tightly bonded to both sides, which will increase the difficulty of release and make release difficult.

[0025] In addition, the release layer 2 contains 5% to 40% nickel. Since nickel easily forms a dense oxide film (such as NiO) in air or chemical environment, this oxide film has high chemical stability and can prevent etching solution, electroplating solution, etc. from contacting the interior of the release layer and the interface of the carrier layer / functional layer. This avoids the interface from being corroded and delamination, dissolution or abnormal bonding. This corrosion resistance ensures the structural integrity of the release layer 2 in the subsequent chemical process of PCB, maintains the stability of its release function, and leaves a reliable interface foundation for the final carrier layer 1 release process, reducing the problem of release failure caused by chemical corrosion.

[0026] In this embodiment of the invention, by setting the atomic fraction of nickel in the release layer 2 to 5%~40%, inter-atomic diffusion at high temperatures is fundamentally suppressed. This ensures that the interface between the carrier layer 1 and the functional layer 3 remains clear and weakly bonded after lamination, thereby significantly improving the stability and consistency of the high-temperature peel force and preventing damage or poor peeling of the functional layer 3 due to excessive or fluctuating peel force. Furthermore, nickel can also enhance the chemical corrosion resistance of the release layer, better protecting the interface during subsequent PCB etching, electroplating, and other processes.

[0027] In one embodiment, the stripping layer further includes zinc, and the ratio of the atomic fractions of nickel to zinc in the total number of atoms in the stripping layer is 50:1 to 1:1.

[0028] For example, the release layer 2 also includes zinc. The introduction of zinc is not a simple addition of components, but rather involves precisely controlling the atomic ratio of nickel to zinc to achieve a ratio of 50:1 to 1:1, allowing the two to form a stable composite oxide or alloy phase with a specific structure in the release layer 2. This composite structure is based on the difference in atomic radii and chemical affinity between zinc and nickel. When zinc is incorporated into the nickel-based release layer in a specific ratio, it alters the original crystal structure's stacking pattern. The embedding of zinc atoms can create appropriate defects in the crystal lattice. Simultaneously, due to the difference in electronegativity between zinc and nickel, localized charge distribution changes occur at the interface, providing a channel for stress release during subsequent release processes. Furthermore, zinc has a relatively low boiling point. During the preparation of the release layer 2 or subsequent high-temperature treatment, some zinc atoms undergo controllable volatilization or migration. This characteristic naturally forms a looser transition structure at the interface between the release layer 2 and the carrier layer or functional layer. This structure acts like a buffer zone, reducing the initial resistance during release.

[0029] In this embodiment of the invention, the synergistic effect of nickel and zinc further optimizes and reduces the peeling force, making it smoother and more stable. This solves the problem of sudden force changes caused by unstable interfacial bonding in traditional peeling layers, resulting in a smoother peeling operation and avoiding substrate damage or incomplete peeling caused by sudden force changes. Furthermore, the introduction of zinc can fine-tune the interfacial bonding strength, improving the peeling operation and eliminating sudden force changes. Moreover, the introduction of zinc broadens the deposition process window of the peeling layer 2, making the coating denser and more uniform, and reducing the risk of corrosion during subsequent use.

[0030] In one embodiment, the stripping layer further includes oxygen, and the ratio of the atomic fractions of nickel to oxygen in the total number of atoms in the stripping layer is 10:1 to 1:1.

[0031] For example, oxygen is introduced into the release layer in the form of a metal oxide or a non-stoichiometric oxide, and the ratio of nickel to oxygen is controlled to be 10:1 to 1:1. The introduction of oxygen is not a simple chemical doping, but rather a dual structure of reinforcement and barrier formed by the formation of an oxide phase. When oxygen is incorporated into the nickel-based release layer in a specific ratio, it forms uniformly dispersed fine oxide particles in the matrix. These oxide particles, dispersed in release layer 2, can very effectively pin grain boundaries and block atomic diffusion paths at high temperatures, acting as an excellent diffusion barrier. This effectively hinders the growth and migration of nickel grains, maintaining the stability of the release layer's microstructure. The oxide phase itself has a low atomic diffusion coefficient, serving as a natural diffusion barrier to suppress atomic interdiffusion between the release layer and the substrate material, avoiding abrupt changes in release force caused by the formation of brittle intermetallic compounds at the interface.

[0032] In this embodiment of the invention, by setting the atomic fraction ratio of nickel to oxygen to 10:1 to 1:1, the diffusion resistance and thermal stability of the release layer 2 at high temperatures are greatly enhanced, which helps to ensure stable high-temperature peeling force. In addition, the presence of oxides can improve the hardness and smoothness of the release layer 2, which helps to obtain a smoother functional layer surface with low roughness, further improving the signal integrity of high-frequency and high-speed PCBs.

[0033] In one embodiment, the oxygen element has an atomic fraction of 1% to 20% in the total number of atoms in the stripping layer.

[0034] For example, an appropriate amount of oxygen can form uniformly distributed fine oxides, preventing the formation of large, non-uniform oxides, thereby ensuring the uniformity of interfacial strength. When the atomic fraction of oxygen is less than 1%, the oxygen content is too low, making it difficult to form a sufficient number of oxide particles. The grain boundary pinning and diffusion barrier effects are not significant, and it is unable to effectively suppress grain coarsening at high temperatures. When the atomic fraction of oxygen is higher than 20%, the excessive oxygen content will lead to the formation of a large number of large oxides. These non-uniform oxide phases are prone to becoming stress concentration points, which will increase the brittleness of the release layer and cause local fractures or fluctuations in release force during the release process.

[0035] In this embodiment of the invention, by setting the atomic fraction of oxygen to 1% to 20%, it is possible to ensure the formation of uniformly distributed fine oxides. This not only enhances the stability of the interface structure but also avoids fluctuations in interface strength caused by uneven oxide distribution, providing a stable and controllable force basis for the peeling process.

[0036] In one embodiment, when the multilayer metal foil is in a sliced ​​state, the coefficient of variation of the atomic fraction of nickel at any two points in the peeling layer is less than 20%.

[0037] It should be noted that the "slicing state" refers to the process of creating ultrathin slices from multilayer metal foil using techniques such as FIB (Focused Ion Beam) cutting, in order to observe the elemental distribution within the release layer, rather than simply detecting the surface. The coefficient of variation reflects the dispersion of data from multiple detection points, and is calculated as: standard deviation / mean × 100%. The smaller the coefficient of variation, the more uniform the distribution of nickel.

[0038] For example, limiting the coefficient of variation of nickel atomic fraction essentially lays the foundation for consistent peeling performance by controlling the spatial uniformity of the composition of the release layer in its initial preparation state. By limiting the coefficient of variation of nickel atomic fraction to less than 20%, it means that the atomic percentage of nickel is strictly controlled at any location in the release layer, including the central and edge regions and different slice cross-sections. As the matrix component of the release layer, the uniformity of nickel distribution directly determines the consistency of the microstructure of the release layer, preventing the formation of dense crystalline regions (leading to excessive peeling force) due to excessively high local nickel content or loose regions (leading to insufficient peeling force) due to excessively low content, thus ensuring the spatial uniformity of the physical properties of the release layer from the source.

[0039] Alternatively, achieving this uniformity relies on high-precision fabrication processes, such as magnetron sputtering, which controls the uniform sputtering rate of the target and the motion trajectory of the substrate, or precision electroplating, which ensures uniform ion deposition by optimizing the current distribution and electrolyte circulation.

[0040] In this embodiment of the invention, when the multilayer metal foil is in a sliced ​​state, the coefficient of variation of the atomic fraction of nickel at any two points in the peel layer is less than 20%. This ensures that the peel force reference value at any position on the surface of the multilayer metal foil remains consistent in the initial state, solving the problem of sudden increase or decrease in peel force caused by high-temperature pressing in traditional processes. This improves product reliability and effectively avoids damage to circuits or board drop caused by differences in peel force between the edge and the center. Simultaneously, it provides a stable performance foundation for subsequent pressing, heat treatment, and other processes, avoiding batch quality problems caused by the amplification of initial composition fluctuations in subsequent processes.

[0041] In one embodiment, when the multilayer metal foil is at a preset temperature and after n pressing cycles, the coefficient of variation of the atomic fraction of oxygen at any two points in the peeling layer is less than 20%, where n≥2.

[0042] For example, the pressing process is typically accompanied by high temperatures and mechanical forces. Under these conditions, oxygen is prone to diffusion, aggregation, or reaction with other elements to form localized enrichment zones. By limiting the coefficient of variation of the oxygen atomic fraction to less than 20%, the release layer is required to maintain a uniform distribution of oxygen after undergoing complex processes. This means that oxygen has not undergone significant segregation, such as agglomerating at grain boundaries to form large oxide masses, nor has it resulted in localized oxygen depletion due to differences in diffusion rates. The interfacial properties of release layer 2 remain consistent. The uniformity of oxygen distribution is directly related to the stability of the interfacial bonding strength of release layer 2, as the oxide phase formed by oxygen is a key factor in controlling the release force.

[0043] In this embodiment of the invention, the peel force of any area on the multilayer metal foil remains highly consistent after multiple lamination processes. This solves the problem of sudden increases or decreases in peel force caused by high-temperature lamination in traditional processes, improving product reliability and effectively preventing damage to circuits or board detachment due to differences in peel force between the edges and the center. Simultaneously, it provides a stable performance foundation for subsequent lamination, heat treatment, and other processes, avoiding batch quality problems caused by the amplification of initial composition fluctuations in subsequent processes.

[0044] In one embodiment, the ratio of the roughness Sku of the side of the functional layer 3 away from the carrier layer 1 to the thickness of the functional layer 3 is in the range of 0.5 to 20.

[0045] For example, Sku is an indicator of the sharpness of surface peaks. A higher Sku value indicates that there are a large number of sharp peak structures on the surface; a lower Sku value indicates that the surface is relatively smoother. The ratio of the roughness Sku of the side of the functional layer 3 away from the carrier layer 1 to the thickness of the functional layer 3 is controlled within the range of 0.5 to 20. On the one hand, if the ratio is too high, that is, the surface is too sharp, the functional layer 3 will be bonded too firmly to the resin of the dielectric layer to be laminated later, making it difficult to separate the dielectric layer from the functional layer in subsequent processes. On the other hand, if the ratio is too low, that is, the surface is too flat, the adhesion between the functional layer and the dielectric layer will be insufficient, affecting the overall structural stability of the circuit board.

[0046] In this embodiment of the invention, by setting the ratio of the roughness Sku of the side of the functional layer 3 away from the carrier layer 1 to the thickness of the functional layer 3 to a range of 0.5 to 20, it is possible to ensure that the functional layer 3 and the dielectric layer have sufficient bonding force while avoiding the situation where the bonding force is too strong and difficult to separate. Furthermore, the relatively suitable surface state of the functional layer 3 helps to reduce signal loss during transmission, which is especially suitable for high-frequency and high-speed signal transmission scenarios, thereby improving the signal transmission performance of the printed circuit board in electronic devices.

[0047] In one embodiment, the ratio of the roughness Sku of the side of the carrier layer 2 near the functional layer 3 to the thickness of the carrier layer 1 is in the range of 0.01 to 5.

[0048] For example, the ratio of the roughness Sku of the side of the carrier layer 1 closest to the functional layer 3 to the thickness of the carrier layer 1 is controlled within the range of 0.01 to 5. If the ratio is too high, the surface is too sharp, and the carrier layer 1 and the release layer 2 will have excessively strong bonding force due to a large number of sharp peaks, making it extremely difficult to peel off the carrier layer 1 later, and even causing peeling damage. If the ratio is too low, the surface is too smooth, and the adhesion between the carrier layer 1 and the release layer 2 will be insufficient. During the high-temperature and high-pressure pressing process of the coreless process, structural failure problems such as premature separation and delamination of the release layer 2 and the carrier layer 1 are likely to occur, affecting the overall stability of the multilayer metal foil. When the ratio is between 0.01 and 5, the surface of the carrier layer 1 has a certain roughness, which can ensure that there is a suitable adhesion between the release layer 2 and the carrier layer 1, so that the multilayer metal foil structure remains stable during the pressing and other processes.

[0049] In this embodiment of the invention, by setting the ratio of the roughness Sku of the side of the carrier layer 1 near the functional layer 3 to the thickness of the carrier layer 1 to a range of 0.01 to 5, the bonding state between the carrier layer 1 and the release layer 2 can be effectively balanced. This avoids excessive bonding force between the carrier layer 1 and the release layer 2, which may affect the peeling process, while ensuring the stable adhesion of the release layer 2. When peeling off the carrier layer 1, the process can be cleaner and more efficient, reducing the number of metal particles from the carrier layer 1 remaining on the functional layer 3. This prevents short circuits or other defects caused by residual particles and ensures the smooth progress of subsequent manufacturing processes of the printed circuit board.

[0050] In one embodiment, the stripping layer further includes carbon, and the atomic fraction of carbon in the total number of atoms in the stripping layer is 3% to 60%.

[0051] For example, carbon in the release layer can exist in the form of amorphous carbon (such as graphitic carbon). Graphitic carbon itself has good lubricity, which can directly reduce the friction between the carrier layer 1 and the release layer 2 during the release process. At the same time, the introduction of carbon can refine the grains of the release layer, further suppress the interdiffusion of atoms between the carrier layer 1 and the functional layer 3 during high-temperature pressing, and increase the brittleness of the release layer 2, making it more prone to cohesive fracture during release. That is, the fracture occurs inside the release layer, rather than at the interface between the carrier layer 1 and the release layer 2, thereby avoiding the problem of interface residue. If the carbon content is less than 3%, the lubrication and grain refinement effects are insufficient; if it is more than 60%, it will lead to excessive embrittlement of the release layer, affecting the structural stability.

[0052] In this embodiment of the invention, by setting the atomic fraction of carbon in the release layer 2 to 3%~60%, the release force can be further reduced and stabilized, making the release process smoother and the force curve more stable, effectively avoiding functional layer damage or carrier residue caused by release force fluctuations. Simultaneously, the amorphous carbon structure possesses excellent diffusion barrier properties and chemical inertness, which can enhance the stability of the release layer under high temperature, high pressure, and chemical processes, adapting to the stringent requirements of coreless processes and improving the overall quality and process yield of peelable copper.

[0053] Furthermore, this embodiment of the invention also provides a circuit board, which is made of the multilayer metal foil described in the above embodiments.

[0054] In this embodiment of the invention, the circuit board manufactured using this high-performance metal foil naturally inherits all the advantages of multilayer metal foil: it avoids circuit damage caused by peeling problems, resulting in a high yield of finished boards; the functional layer has an ultra-low profile surface, making it suitable for high-frequency and high-speed designs; and it can maintain stable peeling performance even with slight fluctuations in the lamination process, improving the robustness of the production line.

[0055] To facilitate understanding of the above-described invention, the following specific embodiments are provided and tested: 1) Examples of comparative products: 1.1) Provide 50 peelable copper multilayer metal foil samples adapted to the coreless process, with the release layer containing no Ni. Press the samples onto a PCB substrate and simulate the high temperature and high pressure conditions of the coreless process (temperature 200°C, pressure 300psi, pressing time 1h) for 6 repeated pressing cycles. Then, use an automated robotic arm to peel off the carrier layer at an angle of 30°~60°, and record the peeling force fluctuations and the state of the functional layer after peeling.

[0056] Test results: After testing, 90% of the samples showed that the carrier layer remained on the functional layer, and 80% of the samples had their thin copper layer removed due to excessive peeling force, resulting in an interface corrosion defect rate of 70% in the subsequent PCB etching process.

[0057] 1.2) Provide 50 peelable copper multilayer metal foil samples adapted to the coreless process, with a Ni atomic fraction of <5% in the release layer. Press the samples onto a PCB substrate and simulate the high temperature and high pressure conditions of the coreless process (temperature 200°C, pressure 300psi, pressing time 1h) for 6 repeated pressing cycles. Then, use an automated robotic arm to perform carrier layer peeling operation at an angle of 30°~60°, and record the peeling force fluctuation and the state of the functional layer after peeling.

[0058] Test results: After testing, 70% of the samples showed that the carrier layer remained on the functional layer, and 60% of the samples had their thin copper layer removed due to excessive peeling force, resulting in an interface corrosion defect rate of 60% in subsequent PCB etching processes.

[0059] 1.3) Provide 50 peelable copper multilayer metal foil samples adapted to the coreless process, with a Ni atomic fraction >40% in the release layer. Press the samples onto a PCB substrate and simulate the high temperature and high pressure conditions of the coreless process (temperature 200°C, pressure 300psi, pressing time 1h) for 6 repeated pressing cycles. Then, use an automated robotic arm to perform carrier layer peeling operation at an angle of 30°~60°, and record the peeling force fluctuation and the state of the functional layer after peeling.

[0060] Test results: After testing, 70% of the samples showed that the carrier layer remained on the functional layer, and 20% of the samples had their thin copper layer removed due to excessive peeling force, resulting in an interface corrosion defect rate of 50% in the subsequent PCB etching process.

[0061] 2) Examples of the product structure of this application: 2.1) Fifty peelable copper multilayer metal foil samples adapted to the coreless process were provided, with the release layer containing Ni (atomic fraction 20%). Six pressing cycles were performed under the same high temperature and high pressure conditions as the control group, followed by peeling using the same robotic arm parameters, and relevant data were recorded.

[0062] Test results: After testing, all samples showed no carrier layer residue or functional layer damage, and the interface corrosion defect rate in subsequent PCB etching and electroplating processes was only 10%.

[0063] 2.2) Fifty peelable copper multilayer metal foil samples adapted to the coreless process were provided. The release layer contained Ni (atomic fraction 15%), and the atomic fraction ratio of Ni to Zn was 25:1. Under the same high temperature and high pressure conditions as the control group, six pressing cycles were performed, and the same robotic arm parameters were used for peeling. Relevant data were recorded.

[0064] Test results: After testing, all samples showed no carrier layer residue or functional layer damage, and the interface corrosion defect rate in subsequent PCB etching and electroplating processes was only 8%.

[0065] 2.3) Provide 50 peelable copper multilayer metal foil samples adapted to the coreless process. The release layer contains Ni (atomic fraction 25%), the atomic fraction ratio of Ni to Zn is 5:1, and the atomic fraction of oxygen is 5%. Under the same high temperature and high pressure conditions as the control group, xx pressing cycles were performed, and the same robotic arm parameters were used for peeling. Relevant data were recorded.

[0066] Test results: After testing, all samples showed no carrier layer residue or functional layer damage, and the interface corrosion defect rate in subsequent PCB etching and electroplating processes was only 6%.

[0067] 2.4) Fifty peelable copper multilayer metal foil samples adapted to the coreless process were provided. The release layer contained Ni (atomic fraction 18%), with a Ni to Zn atomic fraction ratio of 3:1 and an oxygen atomic fraction of 12%, with a Ni to oxygen atomic fraction ratio of 6:1. Six pressing cycles were performed under the same high temperature and high pressure conditions as the control group, and the same robotic arm parameters were used for peeling. Relevant data were recorded.

[0068] Test results: After testing, all samples showed no carrier layer residue or functional layer damage, and the interface corrosion defect rate in subsequent PCB etching and electroplating processes was only 6%.

[0069] 2.5) Provide 50 peelable copper multilayer metal foil samples adapted to the coreless process. The peeling layer contains Ni (atomic fraction 12%). Before high-temperature pressing, a corner of the multilayer metal foil is sliced ​​and observed. The coefficient of variation of the atomic fraction of nickel at any two points in the peeling layer is less than 15%. Under the same high-temperature and high-pressure conditions as the control group, six pressings are performed, and peeling is carried out using the same robotic arm parameters. Relevant data are recorded.

[0070] Test results: After testing, all samples showed no carrier layer residue or functional layer damage, and the interface corrosion defect rate in subsequent PCB etching and electroplating processes was only 8%.

[0071] 2.6) Fifty peelable copper multilayer metal foil samples adapted to the coreless process were provided, with the release layer containing Ni (atomic fraction 31%). Six pressing cycles were performed under the same high-temperature and high-pressure conditions as the control group. After high-temperature pressing, a corner of the multilayer metal foil was sliced ​​for observation. The coefficient of variation of the atomic fraction of nickel at any two points in the release layer was less than 18%. The same robotic arm parameters were used for peeling, and relevant data were recorded.

[0072] Test results: After testing, all samples showed no carrier layer residue or functional layer damage, and the interface corrosion defect rate in subsequent PCB etching and electroplating processes was only 4%.

[0073] 2.7) Fifty peelable copper multilayer metal foil samples adapted to the coreless process were provided. The release layer contained Ni (atomic fraction 22%), and the ratio of the roughness Sku of the functional layer away from the carrier layer to the thickness of the functional layer was in the range of 5. Six pressing cycles were performed under the same high temperature and high pressure conditions as the control group. Peeling was carried out using the same robotic arm parameters, and relevant data were recorded.

[0074] Test results: After testing, all samples showed no carrier layer residue or functional layer damage, and the interface corrosion defect rate in subsequent PCB etching and electroplating processes was only 4%.

[0075] 2.8) Fifty peelable copper multilayer metal foil samples adapted for coreless processes were provided. The release layer contained Ni (atomic fraction 28%), and the ratio of the roughness Sku of the carrier layer near the functional layer to the thickness of the carrier layer ranged from 0.5. Six pressing cycles were performed under the same high-temperature and high-pressure conditions as the control group. Peeling was performed using the same robotic arm parameters, and relevant data were recorded.

[0076] Test results: After testing, all samples showed no carrier layer residue or functional layer damage, and the interface corrosion defect rate in subsequent PCB etching and electroplating processes was only 4%.

[0077] 2.9) Fifty peelable copper multilayer metal foil samples adapted to the coreless process were provided, with the release layer containing Ni (35% atomic fraction) and C (25% atomic fraction). Six pressing cycles were performed under the same high-temperature and high-pressure conditions as the control group. The same robotic arm parameters were used for peeling, and relevant data were recorded.

[0078] Test results: After testing, all samples showed no carrier layer residue or functional layer damage, and the interface corrosion defect rate in subsequent PCB etching and electroplating processes was only 2%.

[0079] Therefore, by applying the multilayer metal foil of this embodiment, the problem of unstable peeling force after multiple laminations in the coreless process can be effectively solved, the peeling defect rate and subsequent process risks can be greatly reduced, and the quality reliability of peelable copper and the PCB finished product qualification rate can be significantly improved.

[0080] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A multilayer metal foil, characterized in that, It includes a carrier layer, a release layer, and a functional layer stacked in sequence; wherein, the release layer is used for the carrier layer and the functional layer to be peeled off from each other, the release layer includes nickel, and the atomic fraction of nickel in the total number of atoms in the release layer is 5% to 40%.

2. The multilayer metal foil as described in claim 1, characterized in that, The stripping layer also includes zinc, and the ratio of the atomic fractions of nickel to zinc in the total number of atoms in the stripping layer is 50:1 to 1:

1.

3. The multilayer metal foil as described in claim 1, characterized in that, The stripping layer also includes oxygen, and the ratio of the atomic fractions of nickel to oxygen in the total number of atoms in the stripping layer is 10:1 to 1:

1.

4. The multilayer metal foil as described in claim 3, characterized in that, Of the total number of atoms in the stripping layer, the atomic fraction of oxygen is 1% to 20%.

5. The multilayer metal foil as described in claim 1, characterized in that, When the multilayer metal foil is in a sliced ​​state, the coefficient of variation of the atomic fraction of nickel at any two points in the peeling layer is less than 20%.

6. The multilayer metal foil as described in claim 1, characterized in that, When the multilayer metal foil is at a preset temperature and after n pressing cycles, the coefficient of variation of the atomic fraction of oxygen at any two points in the peeling layer is less than 20%, where n≥2.

7. The multilayer metal foil as described in claim 1, characterized in that, The ratio of the roughness Sku of the side of the functional layer away from the carrier layer to the thickness of the functional layer ranges from 0.5 to 20.

8. The multilayer metal foil as described in claim 1, characterized in that, The ratio of the roughness Sku of the side of the carrier layer near the functional layer to the thickness of the carrier layer ranges from 0.01 to 5.

9. The multilayer metal foil according to any one of claims 1 to 8, characterized in that, The stripping layer also includes carbon, and the atomic fraction of carbon in the total number of atoms in the stripping layer is 3% to 60%.

10. A circuit board, characterized in that, The circuit board is made of the multilayer metal foil as described in any one of claims 1 to 9.

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