Method for constructing electromagnetic shielding copper film on surface of chip

Abstract

A method for constructing an electromagnetic shielding copper film on the surface of a chip is characterized by comprising the following steps: S100, mixing copper salt and a reducing agent according to a certain mass ratio, and performing homogenization treatment to prepare copper precursor ink; s200, depositing the copper precursor ink on the surface of a chip to form an ink layer; and S300, sintering the ink layer to form a compact copper film. The invention aims to provide a method for constructing an electromagnetic shielding copper film on the surface of a chip, and the electromagnetic shielding copper film which can be stably deposited and rapidly sintered on the surface of the chip and has high conductivity and reliability can be realized.

Description

Technical Field

[0001] This invention relates to the field of electronic materials and microelectronics manufacturing, and in particular to a method for constructing an electromagnetically shielding copper thin film on the surface of a chip. Background Technology

[0002] With the continuous increase in chip integration and operating frequency, electromagnetic interference (EMI) has become a significant factor affecting chip performance and reliability. To suppress electromagnetic leakage and external interference, an electromagnetic shielding layer is typically constructed on the surface of the chip or package. Currently, common electromagnetic shielding materials include metal cover plates, electroplated metal films, and conductive polymer films. However, these solutions generally have the following shortcomings: First, metal cover plates require additional packaging processes, resulting in a larger volume, which is detrimental to chip miniaturization and high-density integration; second, the processes for preparing metal films by electroplating or sputtering are complex and costly, and are difficult to achieve at low temperatures, leading to insufficient compatibility with temperature-sensitive chips; third, conductive polymer films have limited conductivity and shielding performance, failing to meet the electromagnetic shielding requirements of high-speed devices.

[0003] In recent years, printing processes based on metal nanoparticles or metal precursor inks have emerged as a novel method for preparing shielding layers, offering advantages such as simplicity, patternability, and low cost. However, existing technologies still suffer from the following problems: ink film formation on chip surfaces is unstable; organic residues easily remain during sintering, leading to insufficient conductivity; and it is difficult to obtain copper films with high adhesion and high shielding effectiveness under low-temperature sintering conditions. Therefore, there is an urgent need for a method to prepare electromagnetic shielding copper thin films that can achieve stable deposition and rapid sintering on chip surfaces while maintaining both high conductivity and reliability. Summary of the Invention

[0004] To address the aforementioned shortcomings, the present invention aims to propose a method for constructing electromagnetic shielding copper thin films on chip surfaces, which can achieve stable deposition and rapid sintering of electromagnetic shielding copper thin films on chip surfaces while maintaining high conductivity and reliability.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] A method for constructing an electromagnetically shielding copper thin film on a chip surface includes the following steps:

[0007] S100. Copper salt and reducing agent are mixed in a certain mass ratio and homogenized to obtain copper precursor ink.

[0008] S200: Deposit the copper precursor ink onto the chip surface to form an ink layer;

[0009] S300: The ink layer is sintered to form a dense copper film.

[0010] Preferably, the copper salt is copper acetate, copper formate, copper citrate, copper oxalate, or a combination thereof;

[0011] The reducing agent is ethylene glycol, glycerol, formic acid, oxalic acid, or a combination thereof.

[0012] Preferably, the copper salt is mechanically ball-milled before mixing, using zirconia balls or ceramic balls as the grinding medium, with a ball-to-material ratio of 5:1 to 15:1, a grinding time of 30 to 180 minutes, and the particle size after grinding is controlled within the range of 100 to 1000 nm.

[0013] Preferably, the copper salt and reducing agent are mixed in a mass ratio of 1:0.5 to 1:4;

[0014] The homogenization process employs a high-speed shearing method with a rotation speed of 1000–1500 rpm, a processing time of 2–4 minutes, and a homogenization frequency of 1–3 times.

[0015] Furthermore, 0.1 to 10 wt% of additives are added to the precursor ink, the additives being selected from one or more complexing agents, dispersants, or surfactants, to improve ink stability and reduce sintering carbon residue.

[0016] Furthermore, the complexing agent is one of an amino acid, a citrate, or ethylenediamine;

[0017] The dispersant or surfactant is one of polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, or sodium dodecyl sulfate.

[0018] Further, in step S200, the deposition method is one of inkjet printing, electrohydraulic printing, screen printing, or spin coating;

[0019] During inkjet printing, the ink viscosity is 5–20 mPa·s, and the nozzle orifice diameter is 10–50 μm;

[0020] During electrohydraulic printing, the ink viscosity is 10–1000 mPa·s, and the voltage is 0.5–3.0 kV;

[0021] During screen printing, the ink viscosity is 500–5000 mPa·s, and the screen mesh count is 100–400.

[0022] During spin coating, the ink viscosity is less than 50 mPa·s, and the spin coating speed is 500 to 5000 rpm.

[0023] Furthermore, the chip surface is either the surface of a bare chip or the surface outside a chip package.

[0024] Furthermore, in step S300, the sintering method for sintering the ink layer is one of annealing, photonic sintering, and microwave sintering.

[0025] During annealing, the temperature is 150–300 °C, the time is 10–60 min, and the atmosphere is nitrogen, argon, or a reducing atmosphere containing 5–10% hydrogen.

[0026] Photonic sintering is performed using broadband pulsed light emitted by a xenon lamp at a wavelength of 200–1100 nm, with a pulse energy density of 1–10 J / cm² and a pulse width of 0.1–10 ms, under a nitrogen or argon protective atmosphere.

[0027] Microwave sintering is performed at a frequency of 0.9–2.6 GHz, a power of 100–1000 W, a processing temperature of 150–300 °C, and a time of 1–30 min, in a nitrogen, argon, or reducing atmosphere.

[0028] Furthermore, the thickness of the sintered copper film is 1–5 μm, and its conductivity is [missing information]. The electromagnetic shielding effectiveness is 20–80 dB in the range of 100 MHz to 10 GHz, the peel strength is 8–15 MPa, and the residual carbon content is less than 1 wt%.

[0029] One of the above technical solutions includes the following beneficial effects: Compared with existing electromagnetic shielding technologies, the present invention has the following beneficial effects: 1. Traditional EMI shielding methods such as metal electroplating, physical vapor deposition (PVD), or sputtering processes usually require a vacuum environment, complex equipment, and a thick metal layer, making them difficult to directly apply to molding compound packages or non-flat surfaces. The present invention uses solution-processable copper precursor inks to achieve dense film formation within a process temperature range of 150–300 °C, avoiding high-cost vacuum processes and additional metal cover plates. It can directly construct a shielding layer on the surface of the chip or its package, achieving compatibility with advanced packaging processes; 2. The copper thin film formed by the present invention has… The high conductivity provides 20–80 dB of electromagnetic shielding effectiveness in the 100 MHz–10 GHz frequency band, covering common interference frequency bands such as mobile communication, RF front-end, and high-speed computing. Simultaneously, the peel strength between the copper film and the substrate or package surface reaches 8–15 MPa, superior to most spray-coated shielding coatings, exhibiting higher long-term reliability. Furthermore, this invention is not only applicable to silicon chips but also to compound semiconductor chips such as GaN, SiC, and InP, as well as the surfaces of glass, ceramic, and molding compound packages. It can directly form electromagnetic shielding layers under different substrates and packaging forms, covering various application scenarios such as bare chips, molded packages, wafer-level packaging (WLP / FOWLP), and system-in-package (SiP). Attached Figure Description

[0030] Figure 1 This is a schematic diagram of a method flow according to an embodiment of the present invention; Detailed Implementation

[0031] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0032] like Figure 1 As shown, a method for constructing an electromagnetic shielding copper thin film on a chip surface includes the following steps:

[0033] S100. Copper salt and reducing agent are mixed in a certain mass ratio and homogenized to obtain copper precursor ink.

[0034] S200: Deposit the copper precursor ink onto the chip surface to form an ink layer;

[0035] S300: The ink layer is sintered to form a dense copper film.

[0036] Traditional EMI shielding methods, such as metal plating, physical vapor deposition (PVD), or sputtering, typically require a vacuum environment, complex equipment, and a thick metal cover layer. These processes are complex and costly, and the metal cover layer requires additional packaging processes, resulting in a large volume that hinders chip miniaturization and high-density integration. This invention utilizes solution-processable copper precursor inks combined with various sintering processes to achieve dense film formation, avoiding costly vacuum processes and additional metal cover layers. It enables the direct construction of a shielding layer on the surface of the chip or its package, achieving compatibility with advanced packaging processes.

[0037] The copper salt is copper acetate, copper formate, copper citrate, copper oxalate, or a combination thereof;

[0038] The reducing agent is ethylene glycol, glycerol, formic acid, oxalic acid, or a combination thereof.

[0039] The functional groups of copper salts and reducing agents have simple structures, making them easy to decompose and volatilize during sintering. Combined with low-temperature processes, this reduces organic residues. In particular, reducing agents such as oxalic acid and formic acid have both reducing and decomposition-aiding effects, further reducing residual carbon content and ensuring high conductivity of the copper film.

[0040] The copper salt is mechanically ball-milled before mixing, using zirconia balls or ceramic balls as the grinding medium, with a ball-to-material ratio of 5:1 to 15:1, a grinding time of 30 to 180 minutes, and a particle size controlled within the range of 100 to 1000 nm after grinding.

[0041] Zirconia balls or ceramic balls are selected as the grinding media: This avoids the introduction of metallic impurities, ensures the purity of copper salts, and improves the conductivity and oxidation resistance of the final copper film. A ball-to-material ratio of 5:1 to 15:1 provides suitable grinding energy, ensuring sufficient particle refinement while avoiding over-grinding, resulting in precursor particles with a uniform particle size distribution. Grinding time is 30 to 180 minutes to ensure optimal particle size control, while preventing over-grinding that could lead to agglomeration or surface oxidation, thus improving ink stability. A particle size of 100 to 1000 nm balances deposition performance and sintering density, forming a smooth and dense copper film, improving conductivity and adhesion, and reducing porosity.

[0042] The copper salt and reducing agent are mixed in a mass ratio of 1:0.5 to 1:4.

[0043] The homogenization process employs a high-speed shearing method with a rotation speed of 1000–1500 rpm, a processing time of 2–4 minutes, and a homogenization frequency of 1–3 times.

[0044] Mixing copper salt and reducing agent at a mass ratio of 1:0.5 to 1:4 ensures a complete reduction reaction and avoids copper salt residue. This ratio also controls the amount of organic residue, resulting in a dense copper film with high conductivity and strong adhesion after sintering. A rotation speed of 1000–1500 rpm provides sufficient shear force to ensure thorough mixing and uniform dispersion of the copper salt and reducing agent, preventing particle agglomeration. A processing time of 2–4 minutes ensures uniform mixing and avoids excessive shearing that could lead to overheating or dispersant degradation. Homogenization cycles of 1–3 times further improve dispersion uniformity, ink stability, and the quality of subsequent film deposition.

[0045] In addition, 0.1 to 10 wt% of additives are further added to the precursor ink, the additives being selected from one or more complexing agents, dispersants or surfactants, to improve ink stability and reduce sintering carbon residue;

[0046] Additives can improve the dispersibility and storage stability of copper precursor inks, prevent copper salt particle agglomeration, and ensure that the ink is evenly spread on the chip surface during deposition. By optimizing the ratio of copper salt to reducing agent and introducing complexing agents, dispersants or surfactant systems, organic residues can be effectively suppressed during sintering, keeping the residual carbon content of the copper film below 1 wt%. Low residual carbon combined with stable ink film formation makes the copper film denser and has stronger adhesion, improving conductivity and electromagnetic shielding effectiveness, and solving the problem of electrical performance degradation of traditional conductive polymer shielding layers.

[0047] Furthermore, the complexing agent is one of an amino acid, a citrate, or ethylenediamine;

[0048] The dispersant or surfactant is one of polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, or sodium dodecyl sulfate.

[0049] In addition, in step S200, the deposition method is one of inkjet printing, electrohydraulic printing, screen printing or spin coating;

[0050] During inkjet printing, the ink viscosity is 5–20 mPa·s, and the nozzle orifice diameter is 10–50 μm;

[0051] During electrohydraulic printing, the ink viscosity is 10–1000 mPa·s, and the voltage is 0.5–3.0 kV;

[0052] During screen printing, the ink viscosity is 500–5000 mPa·s, and the screen mesh count is 100–400.

[0053] During spin coating, the ink viscosity is less than 50 mPa·s, and the spin coating speed is 500 to 5000 rpm.

[0054] Inkjet printing enables fine patterning and is suitable for scenarios with high precision requirements; electrofluid printing is compatible with medium precision and thicker ink layers, and is suitable for uniform deposition on uneven chip surfaces; screen printing is adapted to the needs of large-area rapid deposition and has high process efficiency; spin coating can achieve the preparation of ultra-thin and uniform ink layers, avoiding local thickness unevenness.

[0055] As a supplement to the above technology, the chip surface is the surface of a bare chip or the surface outside the chip package.

[0056] The chip substrate is made of silicon, compound semiconductor, glass, or ceramic; the chip package substrate material can be selected from epoxy molding compound (EMC), polyimide (PI), silicone resin, or ceramic-based encapsulation material.

[0057] As a supplement to the above technology, in step S300, the sintering method for sintering the ink layer is one of annealing, photonic sintering, and microwave sintering:

[0058] During annealing, the temperature is 150–300 °C, the time is 10–60 min, and the atmosphere is nitrogen, argon, or a reducing atmosphere containing 5–10% hydrogen.

[0059] Photonic sintering is performed using broadband pulsed light emitted by a xenon lamp at a wavelength of 200–1100 nm, with a pulse energy density of 1–10 J / cm² and a pulse width of 0.1–10 ms, under a nitrogen or argon protective atmosphere.

[0060] Microwave sintering is performed at a frequency of 0.9–2.6 GHz, a power of 100–1000 W, a processing temperature of 150–300 °C, and a time of 1–30 min, in a nitrogen, argon, or reducing atmosphere.

[0061] Annealing sintering, through slow heating and holding, allows copper ions sufficient time to arrange themselves in an orderly manner, reducing porosity and forming a dense crystal structure; photonic sintering, through precise control of pulse energy, avoids cracking of the ink layer due to thermal shock while rapidly heating, ensuring the adhesion between the copper film and the substrate; microwave sintering, with its internal heating characteristics, avoids the problem of the surface solidifying first while the inside remains unreacted, reducing internal defects.

[0062] For thin, low-viscosity ink layers formed by inkjet printing and spin coating, the rapid energy input of photonic sintering can efficiently complete the reduction; for thick, high-viscosity ink layers formed by screen printing, the slightly longer treatment of annealing or microwave sintering can fully decompose organic matter, avoid internal residual carbon, and achieve efficient synergy between deposition and sintering.

[0063] This invention is compatible with deposition methods such as inkjet printing, electrohydraulic printing, screen printing, and spin coating, and can be combined with annealing, photonic sintering, or microwave sintering processes for curing. It can be used for high-resolution local patterning as well as large-area, low-cost deposition. Compared to traditional metal covers or overall shielding, this invention can achieve chip-level and module-level local shielding, improving design flexibility.

[0064] As a supplement to the above technology, the copper thin film formed by sintering has a thickness of 1-5 μm and a conductivity of The electromagnetic shielding effectiveness is 20-80 dB in the range of 100 MHz to 10 GHz, which can cover common interference frequency bands such as mobile communication, radio frequency front-end, and high-speed computing. The peel strength is 8-15 MPa, which has higher long-term reliability and the residual carbon content is less than 1 wt%.

[0065] Example 1

[0066] In this embodiment, the electromagnetic shielding copper film on the outer surface of the epoxy molding compound (EMC) encapsulation layer is constructed as follows:

[0067] 1) Ink preparation: Copper acetate was mechanically ball-milled using zirconia balls at a ball-to-material ratio of 10:1 for 60 min, resulting in an average particle size of 500 nm. Subsequently, copper acetate and ethylene glycol were mixed at a mass ratio of 1:2; 2 wt% polyvinylpyrrolidone was added, and the mixture was homogenized by high-speed shearing at 1200 rpm for 3 min, repeated twice to obtain the precursor ink with a viscosity of 10 mPa·s.

[0068] 2) Ink deposition: Ink is deposited on the outer surface of the epoxy molding compound (EMC) encapsulation layer using inkjet printing, with a nozzle orifice diameter of 20 μm;

[0069] 3) Sintering treatment: Under a nitrogen atmosphere, heat at 250 °C for 30 min to form a copper thin film with a thickness of 2.0 μm and a conductivity of The electromagnetic shielding effectiveness is 65 dB at 1 GHz, the peel strength is 12 MPa, and the residual carbon content is 0.8 wt%.

[0070] Example 2:

[0071] In this embodiment, the electromagnetic shielding copper thin film on the gallium nitride chip is constructed as follows:

[0072] 1) Ink preparation: Copper formate was mechanically ball-milled using zirconia balls at a ball-to-material ratio of 8:1 for 40 min, resulting in an average particle size of 600 nm. Subsequently, copper formate and formic acid were mixed at a mass ratio of 1:2; 5 wt% sodium citrate was added, and the mixture was homogenized by high-speed shearing at 1300 rpm for 2 min, repeated 3 times to obtain the precursor ink with a viscosity of 200 mPa·s.

[0073] 2) Ink deposition: Ink is deposited on the surface of the gallium nitride chip using electrohydrodynamic printing with a nozzle inner diameter of 25 μm and a voltage of 2.0 kV;

[0074] 3) Sintering treatment: Under an argon atmosphere, xenon lamp sintering was performed with a pulse width of 1 ms and an energy density of 5 J / cm², repeated 20 times to obtain a copper thin film with a thickness of 1.5 μm and a conductivity of [missing information]. The shielding effectiveness is 55 dB at 1 GHz, the peel strength is 10 MPa, and the residual carbon content is 0.85 wt%.

[0075] Example 3

[0076] In this embodiment, the electromagnetic shielding copper thin film on the silicon carbide chip is constructed as follows:

[0077] 1) Ink preparation: Copper oxalate was mechanically ball-milled using zirconia balls at a ball-to-material ratio of 12:1 for 30 min, resulting in an average particle size of 400 nm. Subsequently, copper oxalate and glycerol were mixed at a mass ratio of 1:1.5, and 5 wt% polyethylene glycol was added. The mixture was then homogenized by high-speed shearing at 1500 rpm for 2 min, repeated twice to obtain the precursor ink with a viscosity of 2000 mPa·s.

[0078] 2) Ink deposition: Ink layer is deposited on the surface of silicon carbide chip using screen printing;

[0079] 3) Sintering treatment: Under a nitrogen atmosphere, annealing at 300℃ for 30 minutes yields a copper thin film with a thickness of 3 μm and a conductivity of [missing information]. The shielding effectiveness is 60 dB at 1 GHz, the peel strength is 13 MPa, and the residual carbon content is 0.84 wt%.

[0080] Example 4:

[0081] In this embodiment, the electromagnetic shielding copper thin film on the indium phosphide chip is constructed as follows:

[0082] 1) Ink preparation: Copper citrate was mechanically ball-milled using zirconia balls at a ball-to-material ratio of 10:1 for 30 min, resulting in an average particle size of 450 nm. Subsequently, copper citrate and ethylene glycol were mixed at a mass ratio of 1:4, and 1 wt% polyvinyl alcohol was added. The mixture was then homogenized by high-speed shearing at 1200 rpm for 2 min, repeated three times to obtain the precursor ink with a viscosity of 15 mPa·s.

[0083] 2) Ink deposition: Ink is deposited on the surface of the InP chip by spin coating at a speed of 3000 rpm, an acceleration time of 3 s, and a holding time of 60 s;

[0084] 3) Sintering treatment: Under a mixed atmosphere of 5% H2 / 95% Ar, the copper film was heated at 200 °C for 20 min to obtain a copper film with a thickness of 1 μm and a conductivity of The shielding effectiveness is 40 dB at 1 GHz, the peel strength is 9 MPa, and the residual carbon content is 0.7 wt%.

[0085] Example 5

[0086] In this embodiment, the electromagnetic shielding copper film on the outer surface of the polyimide (PI) molding layer is constructed as follows:

[0087] 1) Ink preparation: Copper formate was mechanically ball-milled using zirconia balls at a ball-to-material ratio of 12:1 for 60 min, resulting in an average particle size of 350 nm. Subsequently, copper formate and oxalic acid were mixed at a mass ratio of 1:2, and 2 wt% glycine was added. The mixture was then homogenized by high-speed shearing at 1500 rpm for 4 min to obtain the precursor ink with a viscosity of 12 mPa·s.

[0088] 2) Ink deposition: Ink is deposited on the outer surface of the polyimide (PI) molding layer using inkjet printing, with a nozzle orifice diameter of 30 μm;

[0089] 3) Sintering treatment: Under a nitrogen atmosphere, xenon lamp sintering was performed with a pulse width of 2 ms and an energy density of 8 J / cm², repeated 15 times to obtain a copper thin film with a thickness of 2.5 μm and a conductivity of [missing information]. The shielding effectiveness is 70 dB at 1 GHz, the peel strength is 11 MPa, and the residual carbon content is 0.9 wt%.

[0090] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A method for constructing an electromagnetically shielding copper thin film on a chip surface, characterized in that, Includes the following steps: S100. Copper salt and reducing agent are mixed in a certain mass ratio and homogenized to obtain copper precursor ink. S200: Deposit the copper precursor ink onto the chip surface to form an ink layer; S300: The ink layer is sintered to form a dense copper film.

2. The method according to claim 1, characterized in that, The copper salt is copper acetate, copper formate, copper citrate, copper oxalate, or a combination thereof; The reducing agent is ethylene glycol, glycerol, formic acid, oxalic acid, or a combination thereof.

3. The method according to claim 1, characterized in that, The copper salt is mechanically ball-milled before mixing, using zirconia balls or ceramic balls as the grinding medium, with a ball-to-material ratio of 5:1 to 15:1, a grinding time of 30 to 180 minutes, and a particle size controlled within the range of 100 to 1000 nm after grinding.

4. The method according to claim 1, characterized in that, The copper salt and reducing agent are mixed at a mass ratio of 1:0.5 to 1:4; The homogenization process employs a high-speed shearing method with a rotation speed of 1000–1500 rpm, a processing time of 2–4 minutes, and a homogenization frequency of 1–3 times.

5. The method according to claim 1, characterized in that, The precursor ink is further supplemented with 0.1 to 10 wt% of additives, which are selected from one or more complexing agents, dispersants, or surfactants, to improve ink stability and reduce sintering carbon residue.

6. The method according to claim 5, characterized in that, The complexing agent is one of an amino acid, citrate, or ethylenediamine; The dispersant or surfactant is one of polyvinylpyrrolidone, polyethylene glycol, polyvinyl alcohol, or sodium dodecyl sulfate.

7. The method according to claim 1, characterized in that, In step S200, the deposition method is one of inkjet printing, electrohydraulic printing, screen printing, or spin coating; During inkjet printing, the ink viscosity is 5–20 mPa·s, and the nozzle orifice diameter is 10–50 μm; During electrohydraulic printing, the ink viscosity is 10–1000 mPa·s, and the voltage is 0.5–3.0 kV; During screen printing, the ink viscosity is 500–5000 mPa·s, and the screen mesh count is 100–400. During spin coating, the ink viscosity is less than 50 mPa·s, and the spin coating speed is 500 to 5000 rpm.

8. The method according to claim 1, characterized in that, The chip surface is either the surface of a bare chip or the outer surface of a chip package.

9. The method according to any one of claims 1 and 7, characterized in that, In step S300, the sintering method for sintering the ink layer is one of annealing, photonic sintering, and microwave sintering. During annealing, the temperature is 150–300 °C, the time is 10–60 min, and the atmosphere is nitrogen, argon, or a reducing atmosphere containing 5–10% hydrogen. Photonic sintering is performed using broadband pulsed light emitted by a xenon lamp at a wavelength of 200–1100 nm, with a pulse energy density of 1–10 J / cm² and a pulse width of 0.1–10 ms, under a nitrogen or argon protective atmosphere. Microwave sintering is performed at a frequency of 0.9–2.6 GHz, a power of 100–1000 W, a processing temperature of 150–300 ℃, and a time of 1–30 min, in a nitrogen, argon, or reducing atmosphere.

10. The method according to claim 1, characterized in that, The copper thin film formed by sintering has a thickness of 1–5 μm and a conductivity of The electromagnetic shielding effectiveness is 20-80 dB in the range of 100 MHz to 10 GHz, the peel strength is 8-15 MPa, and the residual carbon content is less than 1 wt%.

Images