Pre-glued composite silver foil and high-speed interconnection structure applied to 224g and 448g high-frequency communication

Abstract

The application relates to the technical field of high-speed data communication materials and high-speed interconnection structures, and discloses a composite silver foil applied to 224G and 448G high-frequency communication and a high-speed interconnection structure. The composite copper foil comprises a copper foil base strip, a first surface of the copper foil base strip is provided with a continuous and dense silver layer and constitutes a high-frequency signal transmission surface, and a second surface is provided with a bonding functional surface; the silver layer is formed through pulse electroplating or double-pulse electroplating, and is subjected to electrochemical leveling or electro-polishing treatment, so that the surface roughness Ra of the leveled silver layer is less than or equal to 0.05 mu m. The high-speed interconnection structure comprises a dielectric layer, a bonding layer and the composite copper foil, a side where the silver layer is located constitutes a high-frequency signal transmission side, and the second surface is combined with the dielectric layer through the bonding layer. The scheme can consider high-frequency low-loss transmission performance, bonding reliability with the dielectric layer and storage stability, and is suitable for 448G and above high-speed data communication.

Description

Technical Field

[0001] This invention relates to the field of high-speed data communication materials and high-speed interconnect structures, and in particular to a pre-coated composite silver foil and a high-speed interconnect structure for use in 224G and 448G high-frequency communication. Background Technology

[0002] As high-speed data communication develops towards 448G and higher transmission rates, conductor loss, interface loss, and signal integrity issues are becoming increasingly prominent. Under high-frequency transmission conditions, current tends to concentrate on the conductor surface. The conductivity, continuity, density, and surface roughness of the conductor surface have a significant impact on insertion loss, return loss, phase stability, and the difficulty of link equalization.

[0003] In the prior art, existing solutions improve high-frequency interconnect performance from various perspectives, including high-frequency circuit copper foil, low-roughness copper foil preparation, low-loss copper-clad laminate systems, and silver layer treatment on circuit surfaces. For example, CN1543292A discloses high-frequency circuit copper foil, its preparation method and equipment, and high-frequency circuits using the copper foil, focusing on the copper foil structure and its compatibility with the substrate; CN111235605A discloses a method for preparing ultra-low profile electrolytic copper foil, focusing on reducing the surface roughness of the copper foil; CN104228216B discloses low-loss high-performance copper-clad laminate and its preparation method, focusing on the copper-clad laminate system and dielectric layer compatibility; CN207802504U discloses a circuit board with low insertion loss, proposing to set a metallic silver layer on the surface of the outer circuit of the circuit board to reduce insertion loss.

[0004] While the aforementioned existing technologies improve high-frequency interconnect performance from different aspects, they have not yet provided a single-sided functionally separated composite conductor and its high-speed interconnect structure for 448G high-frequency data communication scenarios. In particular, existing technologies lack a scheme for the coordinated design of a single-sided continuous dense silver layer, a silver / copper interface bonding region, an ultra-low roughness surface obtained through post-leveling, and a bonding functional surface on the other side. Therefore, it is difficult to simultaneously meet the comprehensive requirements of high-frequency low-loss transmission, reliable bonding with the dielectric layer, and storage stability. Summary of the Invention

[0005] The purpose of this invention is to provide a composite silver foil and high-speed interconnect structure for 224G and 448G high-frequency communication, so as to solve the problem that it is difficult to balance high-frequency low-loss transmission performance, bonding performance with dielectric layer and storage stability in the prior art.

[0006] Design Scheme: To achieve the above objectives, the present invention adopts the following technical solution: A continuous and dense silver layer is formed on the first surface of the copper foil substrate, which constitutes a high-frequency signal transmission surface; a bonding functional surface is formed on the second surface, which is used to bond with a dielectric layer, an adhesive layer, or other functional layers. The silver layer is formed by pulse electroplating or double pulse electroplating, and is subjected to electrochemical leveling or electropolishing treatment to achieve a surface roughness Ra ≤ 0.05 μm after leveling. In some embodiments, the surface roughness of the leveled silver layer can also meet the requirements of Rq ≤ 30 nm or Rz ≤ 0.30 μm. An interface bonding region can be formed between the silver layer and the copper foil substrate through surface activation, electrochemical transition deposition, or local diffusion. A temporary anti-gloss protection layer can also be provided on the surface of the silver layer, and it is placed in a sealed protective environment before use. The sealed protective environment includes one or more of the following: anti-gloss packaging film, inert gas environment, and sulfide adsorption unit. The above structure, process, and pre-protection measures are all applicable to 448G high-frequency data communication applications.

[0007] The design mechanism of this invention is as follows: (1) Conductive path optimization mechanism based on skin effect: Under high frequency conditions, the current mainly concentrates in the extremely thin area of ​​the conductor surface, and the surface state of the conductor directly determines the transmission loss. In this application, a continuous and dense silver layer (12) is constructed on the first surface (111) of the copper foil substrate (11). By utilizing the high conductivity of silver, the high frequency current is preferentially transmitted along the surface of the silver layer, thereby reducing the surface resistance loss. At the same time, by controlling the surface roughness of the silver layer to Ra≤0.05μm, and in some embodiments Rq≤30nm or Rz≤0.30μm, the current transmission path tends to be smooth and continuous, reducing the path extension effect and local current distortion caused by surface micro-undulations, thereby reducing high frequency transmission loss.

[0008] (2) Surface roughness and electromagnetic scattering suppression mechanism: The rough surface structure of traditional copper foil will cause electromagnetic wave scattering and additional impedance under high frequency conditions. This application achieves ultra-low roughness through the following synergistic means: 1) Selecting a copper foil substrate with an original surface roughness Rz≤1.5μm as the initial substrate; 2) Using pulse electroplating or double pulse electroplating to form a uniform fine-grained silver layer; 3) Further eliminating the microscopic peak-valley structure through electrochemical leveling or electropolishing. This forms a near-mirror-level conductive interface, reducing interface scattering loss and signal reflection, and improving signal integrity (SI) and transmission bandwidth.

[0009] (3) Mechanism of synergistic conductivity and low contact resistance at the silver / copper interface: An interfacial bonding region is formed between the silver layer and the copper foil substrate. The interfacial bonding region is a silver / copper transition region formed by surface activation, electrochemical transition deposition, or local diffusion, so that the interface presents a continuous transition state. This structure has the following functions: first, it reduces the interfacial contact resistance; second, it avoids the reflection or scattering of high-frequency current at the interface; and third, it improves the continuity of current carrying and conductivity stability, thereby realizing the synergistic conductivity mechanism of "silver layer-dominated conductivity + copper substrate-supported conductivity".

[0010] (4) Structural mechanism of single-sided functional separation: This application adopts a single-sided silver layer structure design: 1) The first surface (111) is constructed with an ultra-low roughness silver layer as a high-frequency signal transmission surface; 2) The second surface (112) forms a bonding functional surface (15), and the bonding strength with the dielectric layer (21) or the adhesive layer (22) is improved by roughening the structure or bonding reinforcement layer. This structure achieves decoupling of conductivity and interface bonding performance, avoids the adverse effects of double-sided roughening on high-frequency transmission performance, and simultaneously ensures mechanical reliability and electrical performance.

[0011] (5) Mechanism of crystal structure regulation by pulse electroplating: By using pulse or double pulse electroplating processes with a frequency of 20-100Hz, a duty cycle of 10%-50%, and a current density of 1.0-1.5A / dm², the silver layer deposition process is in a periodic nucleation and growth state. The mechanism is as follows: First, it increases the nucleus density and forms a fine-grained structure; second, it inhibits the growth of coarse grains and dendrites; and third, it improves the density and uniformity of the coating, providing a basis for subsequent leveling treatment.

[0012] (6) Surface energy minimization mechanism of electrochemical leveling: Electrochemical leveling or electropolishing is performed under the conditions of 3.0-4.0V voltage and 0.05-0.08A / cm² current density to preferentially dissolve the micro-protrusion areas on the surface, thereby minimizing the surface energy. This process reduces the surface peak-to-valley difference, eliminates the micro-rough structure, and forms a smooth conductive interface, thereby further reducing high-frequency transmission loss.

[0013] (7) System-level mechanism for 448G high-frequency communication: Through the synergistic effect of the above structure and process, this application achieves reduced conductor loss, suppressed signal attenuation, improved signal integrity, and supports high-speed data transmission of 448G and above. This structure can be applied to high-speed copper-clad laminates, printed circuit boards, packaging substrates, and high-speed connection modules.

[0014] In some embodiments, the specific implementation of the silver layer covering the first surface and forming a high-frequency signal transmission surface is as follows: first, a copper foil base band is provided, and the first surface is subjected to degreasing, micro-etching and activation treatment; then, a continuous and dense silver layer is formed on the first surface using pulse electroplating or dual-pulse electroplating process; after the silver layer is formed, electrochemical leveling or electropolishing treatment is performed to reduce the surface micro-peak-valley difference, so that the surface roughness of the silver layer reaches Ra≤0.05μm, thereby forming a high-frequency signal transmission surface suitable for high-frequency current transmission.

[0015] In some embodiments, the frequency of the pulse electroplating or dual-pulse electroplating is 20–100 Hz, the duty cycle is 10%–50%, and the average current density is 1.0–1.5 A / dm². Through the above deposition method, the nucleation density during the silver deposition process can be increased, the growth of coarse grains and dendrites can be suppressed, and the resulting silver layer can have better continuity, density, and uniformity.

[0016] In some embodiments, the voltage of the electrochemical leveling or electropolishing treatment is 3.0–4.0 V, and the current density is 0.05–0.08 A / cm². By performing post-leveling treatment on the silver layer, surface micro-protrusions can be preferentially removed, reducing surface roughness and minimizing path elongation effects, electromagnetic scattering, and local impedance disturbances during high-frequency transmission, thereby making the silver layer more suitable for use as a high-frequency signal transmission surface.

[0017] In some embodiments, an interface bonding region may be formed between the silver layer and the copper foil substrate. The interface bonding region may be formed by surface activation, electrochemical transition deposition or local diffusion to improve the bonding stability between the silver layer and the copper foil substrate and reduce the interface contact resistance.

[0018] The present invention adopts the following technical solution: a pre-coated composite silver foil for 224G and 448G high-frequency communication, comprising a copper foil base, wherein a continuous and dense silver layer is disposed on the first surface of the copper foil base and forms a high-frequency signal transmission surface, and a coating layer is coated on the second surface; the silver layer is formed by pulse electroplating or double pulse electroplating, and is subjected to electrochemical leveling or electropolishing treatment to make the surface roughness Ra of the leveled silver layer ≤ 0.05μm.

[0019] Furthermore, a high-speed interconnect structure is constructed based on the above-mentioned pre-coated composite silver foil. The high-speed interconnect structure includes a dielectric layer and the composite silver foil. The side where the silver layer is located constitutes a high-frequency signal transmission side, and the adhesive layer on the second surface is bonded to the dielectric layer.

[0020] In some embodiments, the pre-coated composite silver foil can be prepared by the following steps: S1, providing a copper foil substrate and performing degreasing, micro-etching, and activation treatment on the first surface; S2, forming a silver layer on the first surface by pulse electroplating or double pulse electroplating; S3, performing electrochemical leveling or electropolishing treatment on the silver layer to make the surface roughness Ra of the leveled silver layer ≤ 0.05 μm; S4, coating the second surface with an adhesive layer to form an adhesive coating layer; S5, forming a temporary anti-gloss protection layer on the surface of the silver layer, and storing the obtained pre-coated composite silver foil in a sealed protective environment.

[0021] Compared with the prior art, this invention has the following advantages: First, by selecting a low-roughness copper foil substrate and constructing the silver layer on the high-frequency signal transmission surface, the high-frequency current preferentially propagates along the highly conductive, continuous, and dense silver layer surface, which helps reduce high-frequency conductor losses. Second, by controlling the silver layer thickness within the range of 0.5–2.0 μm, products with different silver plating processes are provided according to application scenarios and technical requirements, with 0.8–1.5 μm being particularly preferred, which improves the surface current-carrying stability. Third, by employing pulse electroplating or dual-pulse electroplating processes, combined with subsequent electrochemical leveling or electropolishing treatment, the grain structure of the silver layer can be improved, porosity and surface particle undulations can be reduced, and the surface roughness of the silver layer can be further reduced. Fourth, by forming an interface bonding region, the bonding between the silver layer and the copper foil substrate can be made more stable, reducing the risk of silver layer peeling, blistering, or local interface defects. Fifth, by constructing the second surface of the copper foil substrate as a bonding functional surface, both the adhesion performance with the dielectric layer and the reliability of lamination manufacturing can be considered. Sixth, by setting a temporary anti-gloss protection layer on the silver layer surface and cooperating with low-sulfur sealing packaging, the initial surface state of the silver layer can be maintained before use, reducing the adverse effects of gloss loss, discoloration, and surface film growth on high-frequency performance. Seventh, this invention can simultaneously achieve high-frequency low-loss transmission performance, lamination processing reliability, and storage stability before use. Eighth, this application, through a process path of pretreatment, pulse electroplating or dual-pulse electroplating, and electrochemical leveling or electropolishing, enables the silver layer to stably cover the first surface of the copper foil substrate, forming a continuous, dense, and extremely low-roughness high-frequency signal transmission surface. On the one hand, the high conductivity of the silver layer helps reduce high-frequency surface transmission loss; on the other hand, the ultra-low roughness surface obtained after post-leveling can reduce path extension effect and interface scattering loss, thereby improving signal integrity and high-speed transmission stability. At the same time, the setting of the interface bonding region can also improve the bonding reliability between the silver layer and the copper foil substrate. Attached Figure Description

[0022] Figure 1 This is a schematic diagram (cross-section) of the basic structure of pre-coated adhesive alloy silver foil used in 224G and 448G high-frequency communications.

[0023] Figure 2This is a schematic diagram of the three-dimensional structure of pre-coated adhesive alloy silver foil.

[0024] Figure 3 This is a schematic diagram (cross-section) of the laminated structure of pre-coated adhesive alloy silver foil and dielectric layer.

[0025] Figure 4 This is a three-dimensional structural diagram of a high-speed interconnect structure.

[0026] Among them, 1-single-sided silver layer ultra-low roughness composite copper foil; 2-high-speed interconnect structure; 11-Copper foil substrate; 111-First surface; 112-Second surface; 12-Silver layer; 13-Interface bonding area; 14-Temporary anti-gloss protection layer; 15 Adhesive layer 1 Pre-coated adhesive silver; 2-High interconnect structure; 21-Dielectric layer; 23-High frequency signal transmission side.

[0027] Description: The first surface 111 of the pre-coated composite silver foil of the present invention is a high-frequency signal transmission surface, and the second surface 112 is coated with an adhesive layer 15. The adhesive layer 15 is used to bond with the dielectric layer 21, which can achieve reliable bonding between the composite silver foil and the dielectric layer during the lamination process and meet the performance requirements of high-speed data communication of 224G, 448G and above. Detailed Implementation

[0028] like Figure 1 As shown, this embodiment provides a pre-coated composite silver foil 1, including a copper foil substrate 11. The copper foil substrate 11 has a first surface 111 and a second surface 112 disposed opposite to each other. A silver layer 12 is formed on the first surface 111, covering the first surface 111 and forming a high-frequency signal transmission surface. An adhesive layer 15 is coated on the second surface 112, the adhesive layer 15 being used for bonding with a dielectric layer.

[0029] Preferably, the copper foil substrate 11 is made of low-roughness copper foil with a thickness of 9–18 μm. The original surface roughness of the first surface 111 preferably satisfies Rz ≤ 1.5 μm. The silver layer 12 is preferably a continuous and dense silver layer with a purity of not less than 99.9% and a thickness of 0.5–2.0 μm. Products with different thicknesses of silver plating processes are provided according to application scenarios and technical requirements.

[0030] like Figure 2As shown, an interface bonding region 13 can be further formed between the silver layer 12 and the copper foil substrate 11. The interface bonding region 13 can be composed of a surface activation region, an electrochemical transition deposition region, a local diffusion bonding region, or a combination thereof, to enhance the bonding stability between the silver layer 12 and the copper foil substrate 11. After the silver layer 12 is formed by pulse electroplating or double pulse electroplating, it can be electrochemically leveled or electropolished to make its surface roughness Ra ≤ 0.05 μm. In some embodiments, a temporary anti-gloss protection layer 14 can also be provided on the surface of the silver layer 12. The temporary anti-gloss protection layer 14 is a removable protective layer covering the surface of the silver layer 12 to reduce the contact of the silver layer 12 with sulfur-containing media, chlorine-containing media, and moisture during storage.

[0031] like Figure 3 and Figure 4 As shown, in this embodiment, the pre-coated composite silver foil 1 is applied to the high-speed interconnect structure 2. The high-speed interconnect structure 2 includes a dielectric layer 21 and the pre-coated composite silver foil 1. The side where the silver layer 12 is located constitutes the high-frequency signal transmission side 23, and the adhesive layer 15 on the second surface 112 is bonded to the dielectric layer 21.

[0032] In this structure, high-frequency current is mainly transmitted near the surface of the silver layer 12. The continuous, dense, and ultra-low roughness surface of the silver layer 12 reduces surface-additional losses. The second surface 112 provides lamination bonding performance, thus balancing high-frequency transmission performance and manufacturing stability. The high-speed interconnect structure 2 can be specifically implemented as a high-speed copper-clad laminate, a printed circuit board, a packaging substrate, or a high-speed connection module, and is suitable for 448G high-frequency data communication.

[0033] In some embodiments, the silver layer 12 covering the first surface 111 and forming a high-frequency signal transmission surface is specifically implemented as follows: first, a copper foil substrate 11 is provided, and the first surface 111 is subjected to degreasing, micro-etching and activation treatment; then, a continuous and dense silver layer 12 is formed on the first surface 111 using pulse electroplating or dual-pulse electroplating process; after the silver layer 12 is formed, electrochemical leveling or electropolishing treatment is performed to reduce the surface micro-peak-valley difference, so that the surface roughness of the silver layer 12 reaches Ra≤0.05μm, thereby forming a high-frequency signal transmission surface suitable for high-frequency current transmission.

[0034] In some embodiments, the frequency of the pulse electroplating or double pulse electroplating is 20-100 Hz, the duty cycle is 10%-50%, and the average current density is 1.0-1.5 A / dm². Through the above deposition method, the nucleation density during the silver deposition process can be increased, the growth of coarse grains and dendrites can be suppressed, and the resulting silver layer (12) can have better continuity, density and uniformity.

[0035] In some embodiments, the voltage of the electrochemical leveling or electropolishing treatment is 3.0–4.0 V, and the current density is 0.05–0.08 A / cm². By performing post-leveling treatment on the silver layer 12, surface micro-protrusions can be preferentially removed, reducing surface roughness and minimizing path elongation effects, electromagnetic scattering, and local impedance disturbances during high-frequency transmission, thereby making the silver layer 12 more suitable for use as a high-frequency signal transmission surface.

[0036] In some embodiments, an interface bonding region 13 may be formed between the silver layer 12 and the copper foil substrate 11. The interface bonding region 13 may be formed by surface activation, electrochemical transition deposition or local diffusion to improve the bonding stability between the silver layer 12 and the copper foil substrate 11 and reduce the interface contact resistance.

[0037] In this embodiment, the first surface 111 of the copper foil substrate 11 serves as the base surface for the formation of the silver layer 12. To ensure that the silver layer 12 stably covers the first surface 111 and forms a high-frequency signal transmission surface, the first surface 111 is first pretreated. The pretreatment includes degreasing, micro-etching, and activation treatment. Degreasing is used to remove residual oil and impurities from the surface, micro-etching is used to remove the surface oxide layer and renew the substrate surface, and activation treatment is used to improve the interfacial activity of the first surface 111, providing conditions for subsequent silver layer deposition.

[0038] After pretreatment, a silver layer 12 is formed on the first surface 111 using pulse electroplating or double pulse electroplating. In some embodiments, the frequency of the pulse electroplating or double pulse electroplating is 20–100 Hz, the duty cycle is 10%–50%, and the average current density is 1.0–1.5 A / dm². Under these conditions, the silver layer 12 can be deposited on the first surface 111 in a relatively uniform manner, thereby forming a continuous and dense silver layer structure. The formed silver layer 12 preferably has a purity of not less than 99.9% and a thickness of 0.5–2.0 μm, and products with different thicknesses of silver plating processes are provided according to application scenarios and technical requirements.

[0039] Furthermore, to improve the surface condition of the silver layer 12, it can be electrochemically leveled or electropolished after its formation. In some embodiments, the voltage for the electrochemical leveling or electropolishing treatment is 3.0–4.0 V, and the current density is 0.05–0.08 A / cm². Through this post-processing, the micro-protrusions on the surface of the silver layer 12 are preferentially removed, and the surface peak-valley difference is reduced, thereby achieving a surface roughness of Ra ≤ 0.05 μm for the leveled silver layer 12. In some embodiments, the surface of the leveled silver layer can also satisfy Rq ≤ 30 nm or Rz ≤ 0.30 μm.

[0040] In this embodiment, after the pretreatment, pulse electroplating or double pulse electroplating, and post-leveling treatment described above, the silver layer 12 not only covers the first surface 111, but also forms a continuous, dense, and ultra-low roughness conductive surface layer. Since high-frequency current tends to concentrate in the conductor surface area during transmission, the silver layer 12 can serve as the main transmission area of ​​high-frequency current, thereby constituting a high-frequency signal transmission surface.

[0041] In some embodiments, an interface bonding region 13 may be formed between the silver layer 12 and the copper foil substrate 11. The interface bonding region 13 may be composed of a surface activation region, an electrochemical transition deposition region, a local diffusion bonding region, or a combination thereof. By providing the interface bonding region 13, the bonding stability between the silver layer 12 and the copper foil substrate 11 can be enhanced, the risk of silver layer peeling, blistering, or local interface defects can be reduced, and the current carrying continuity and conductivity stability can be improved.

[0042] Compared to methods that only form a common metal capping layer on the conductor surface, this application utilizes a process path of pretreatment, pulse electroplating or dual-pulse electroplating, and electrochemical leveling or electropolishing to ensure that the silver layer 12 stably covers the first surface 111 of the copper foil substrate 11, forming a continuous, dense, and extremely low-roughness high-frequency signal transmission surface. On one hand, the high conductivity of the silver layer 12 helps reduce high-frequency surface transmission loss; on the other hand, the ultra-low roughness surface obtained after post-leveling reduces path elongation effects and interface scattering losses, thereby improving signal integrity and high-speed transmission stability. Simultaneously, the interface bonding region 13 further enhances the bonding reliability between the silver layer 12 and the copper foil substrate 11.

[0043] The term "super mirror surface" as used in this specification refers to a surface with a roughness Ra ≤ 0.05 μm after leveling the silver layer surface; in some embodiments, its Rq can be ≤ 30 nm or Rz can be ≤ 0.30 μm.

[0044] The implementation of the copper foil base strip 11 described in this invention has been described in detail in all previous applications of the applicant with the number "2026103350512", and will not be repeated here.

[0045] It should be understood that the above embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. All equivalent substitutions, improvements, and modifications made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A pre-coated composite silver foil for use in 224G and 448G high-frequency communication, characterized in that: The device includes a copper foil substrate (11), on which a silver layer (12) is disposed on the first surface (111), the silver layer (12) covering the first surface (111) and forming a high-frequency signal transmission surface; the second surface (112) of the copper foil substrate (11) is coated with an adhesive layer (15), the adhesive layer (15) being used to bond with a dielectric layer; the silver layer (12) is a continuous and dense silver layer, and its surface roughness Ra≤0.05μm after leveling.

2. The pre-coated composite silver foil for 224G and 448G high-frequency communication according to claim 1, characterized in that: The thickness of the copper foil substrate (11) is 9–18 μm.

3. The pre-coated composite silver foil for 224G and 448G high-frequency communication according to claim 1, characterized in that: The original surface roughness Rz of the first surface (111) is ≤1.5μm.

4. The pre-coated composite silver foil for 224G and 448G high-frequency communication according to claim 1, characterized in that: The purity of the silver layer (12) is not less than 99.9%, and the thickness is 0.5 to 2.0 μm.

5. The pre-coated composite silver foil for 224G and 448G high-frequency communication according to claim 1, characterized in that: An interface bonding region (13) is formed between the silver layer (12) and the copper foil substrate (11). The interface bonding region (13) is a silver / copper transition region formed by surface activation, electrochemical transition deposition or local diffusion.

6. The pre-coated composite silver foil for 224G and 448G high-frequency communication according to claim 1, characterized in that: The coating layer (15) is one or more of the following: hot melt adhesive layer, modified resin adhesive layer, low dielectric adhesive layer, or adhesive layer for high frequency communication cable sheathing.

7. The pre-coated composite silver foil for 224G and 448G high-frequency communication according to claim 1, characterized in that: The silver layer (12) is formed on the first surface (111) by pulse electroplating or double pulse electroplating.

8. The pre-coated composite silver foil for 224G and 448G high-frequency communication according to claim 7, characterized in that: The frequency of the pulse electroplating or dual-pulse electroplating is 20-100Hz, the duty cycle is 10%-50%, and the average current density is 1.0-1.5A / dm².

9. The pre-coated composite silver foil for 224G and 448G high-frequency communication according to claim 1, characterized in that: The silver layer (12) is electrochemically leveled or electropolished after it is formed.

10. The pre-coated composite silver foil for 224G and 448G high-frequency communication according to claim 9, characterized in that: The voltage for the electrochemical leveling or electropolishing treatment is 3.0–4.0V, and the current density is 0.05–0.08A / cm².

11. The pre-coated composite silver foil for 224G and 448G high-frequency communication according to claim 1, characterized in that: The surface of the silver layer (12) is provided with a temporary anti-gloss protection layer (14), which is a removable protective layer covering the surface of the silver layer (12) to reduce the contact between the silver layer (12) and sulfur-containing media, chlorine-containing media and moisture during storage.

12. The pre-coated composite silver foil for 224G and 448G high-frequency communication according to claim 11, characterized in that: The temporary anti-light loss protective layer (14) is one or more of a nanoscale organic protective layer, a transparent barrier layer, or a low-residue protective layer.

13. A high-speed interconnect structure, characterized in that: The device includes a dielectric layer (21) and a pre-coated composite silver foil as described in any one of claims 1 to 12, wherein the side where the silver layer (12) is located constitutes a high-frequency signal transmission side (23), and the adhesive layer (15) on the second surface (112) is bonded to the dielectric layer (21).

14. The high-speed interconnect structure according to claim 13, characterized in that: The high-speed interconnect structure is a high-speed copper-clad laminate, a printed circuit board, a packaging substrate, or a high-speed connection module.

15. The high-speed interconnect structure according to claim 13, characterized in that: The high-speed interconnect structure is used for 448G high-frequency data communication.

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