Metal slurry and preparation method and application thereof

Abstract

The invention discloses metal paste and a preparation method and application thereof, and relates to the technical field of the electronic industry. The metal slurry comprises metal powder and an organic carrier; the mass ratio of the metal powder to the organic carrier is (10-95): (1-90); the metal powder comprises first metal powder subjected to plasma treatment; the organic carrier comprises an organic solvent. By adopting the metal powder treated by the plasma, the sintering activity of the metal slurry is greatly improved, the metal slurry shows excellent conductivity and mechanical property after being sintered, a sintered joint formed by the metal slurry is high in shear strength and can tolerate relatively large thermal stress generated in a power cycle process, and a packaged device is endowed with good service reliability. The metal paste provided by the invention can resist large thermal stress by improving the binding force between the chip and the substrate layer, and is particularly suitable for the fields of electronic printed circuit manufacturing, sensor manufacturing, semiconductor manufacturing, packaging and the like.

Description

Technical Field

[0001] This invention relates to the field of electronic industry technology, and in particular to a metal paste, its preparation method and application. Background Technology

[0002] With the rapid development of cutting-edge fields such as electric vehicles, 5G communications, and artificial intelligence, third-generation wide-bandgap semiconductors, represented by silicon carbide (SiC) and gallium nitride (GaN), have become ideal choices for high-power power electronic devices and radio frequency devices due to their excellent physical properties. However, the operating junction temperature of these devices, exceeding 150°C, poses a severe challenge to the interconnect technology of chip packaging. Although the current mainstream metal sintering technology can achieve "low-temperature sintering and high-temperature service," there is a mismatch in the coefficients of thermal expansion between the chip, the sintered layer, and the substrate. During long-term power cycling, this mismatch will induce significant thermal stress. If the bonding force between the chip and the substrate is insufficient, it may eventually lead to delamination or cracking of the interconnect layer. This is the core problem currently facing high-power chip packaging.

[0003] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a metal paste, its preparation method and application. The metal paste provided by this invention exhibits excellent electrical conductivity and mechanical properties after sintering. The sintered joint formed by it has high shear strength and can withstand the large thermal stress generated during power cycling, thus giving the packaged device good service reliability.

[0005] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a metal slurry, wherein the metal slurry comprises metal powder and an organic carrier; The mass ratio of the metal powder to the organic carrier is (10~95):(1~90). The metal powder includes a first metal powder that has been treated with plasma; The organic carrier includes an organic solvent.

[0006] Optionally, the metal powder includes a first metal powder treated with plasma and a second metal powder that has not been treated with plasma. The plasma-treated first metal powder accounts for 5% to 100% of the total metal powder by mass.

[0007] Optionally, the composition of the plasma-treated first metal powder and the composition of the untreated second metal powder each independently include at least one of aluminum, titanium, vanadium, chromium, iron, cobalt, nickel, copper, zinc, gallium, zirconium, niobium, molybdenum, palladium, silver, cadmium, indium, tin, antimony, tungsten, platinum, gold, lead, and bismuth; And / or, the organic solvent includes at least one of alcohol organic solvents, alcohol ether organic solvents, and ester organic solvents; And / or, the organic carrier further includes at least one of a dispersant, a rheology modifier, an antifoaming agent, and a thickener.

[0008] Optionally, the plasma-treated first metal powder is obtained by one of the following processes (1) to (4): (1) Plasma treatment process; (2) A combined process of plasma treatment and mechanical processing; (3) A combined process of plasma treatment and heat treatment; (4) A combined process of plasma treatment and chemical treatment, wherein the chemical treatment includes chemical coating, oxidation treatment, reduction treatment, acid treatment, alkali treatment or chemical desorption.

[0009] Optionally, the combined plasma treatment process and machining process is a plasma ball milling process, and the process parameters used in the plasma ball milling process are as follows: The atmosphere is a vacuum, reducing atmosphere, oxidizing atmosphere, or inert atmosphere; Plasma discharge frequency ≥ 1 kHz; The ball-to-material ratio is 0.01:1 to 100:1; The ball milling speed is ≥100 rpm and the ball milling time is ≥1 min.

[0010] Optionally, the metal paste comprises the following components in weight percentage: Metal powder 10%~95%, organic carrier 1%~90%, and composite excipients 0.1%~30%; The composite excipient includes at least one of active excipients and inert excipients; The active excipients include metal precursors that can be thermally decomposed at low temperatures to form elemental metals or metal compounds, wherein the temperature of the low-temperature thermal decomposition is 80~300℃. The inert excipients include at least one of organic excipients and inorganic excipients; The organic additives include resins; The inorganic auxiliary material includes at least one of oxides, nitrides, carbides, elemental carbon, and a first derivative, wherein the first derivative is a derivative of one of oxides, nitrides, carbides, and elemental carbon, and the method for forming the first derivative includes at least one of elemental doping, surface modification, structural compositing, and functional group substitution.

[0011] Optionally, the active excipient includes at least one of a metal inorganic compound, a metal organometallic salt, a metal organometallic complex, and a second derivative, wherein the second derivative is a derivative of a metal inorganic compound, a derivative of a metal organometallic salt, or a derivative of a metal organometallic complex. The organic additives include at least one of epoxy resin, phenoxy resin, acrylic resin, polymethyl methacrylate resin, polyester, silicone resin, furan resin, polyimide resin, polyurethane resin, polyamide resin, polyvinyl alcohol resin, polybutadiene resin, acrylonitrile-butadiene-styrene copolymer, melamine-formaldehyde resin, polyethylene resin, polyvinyl alcohol butyral resin, acrylonitrile-ethylene-styrene copolymer, polystyrene resin, polyvinylidene chloride resin, polytetrafluoroethylene, and derivatives of these resins. The first derivative includes a complex formed by an oxide, nitride, carbide, or elemental carbon with a metallic material.

[0012] A second aspect of the present invention provides a method for preparing the metal paste as described above, comprising the following steps: The metal slurry is obtained by mixing the metal powder and the organic carrier in a certain proportion.

[0013] A third aspect of the present invention provides a method for preparing the metal paste of the present invention as described above, comprising the following steps: The metal slurry is obtained by mixing the metal powder, organic carrier and composite additives in a certain proportion.

[0014] A fourth aspect of the present invention provides an application of the metal paste of the present invention as described above or the metal paste prepared by the preparation method of the present invention as described above, wherein the application is conductive circuit manufacturing, sensor electrode manufacturing, via and blind via filling of interconnect boards, chip and substrate welding, module and heat sink welding, or chip electrode and copper foil welding.

[0015] Beneficial Effects: This invention utilizes plasma-treated metal powder, which significantly enhances the sintering activity of the metal paste. After sintering, it exhibits excellent electrical and mechanical properties, and the resulting sintered joints possess high shear strength, capable of withstanding significant thermal stress generated during power cycling, thus providing packaged devices with excellent service reliability. The metal paste provided by this invention can resist substantial thermal stress by improving the bonding force between the chip and substrate layers, making it particularly suitable for fields such as electronic printed circuit manufacturing, sensor manufacturing, semiconductor manufacturing, and packaging. Attached Figure Description

[0016] Figure 1 The figure shows the test results of the shear strength of the sintered joint in Application Example 2. Detailed Implementation

[0017] This invention provides a metal paste, its preparation method, and its application. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0018] Unless otherwise defined, all technical and scientific terms used herein 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 particular embodiments only and is not intended to be limiting of the invention.

[0019] If the embodiments of the present invention involve descriptions such as "first" or "second", such descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0020] This invention provides a metal slurry, wherein the metal slurry comprises metal powder and an organic carrier; The mass ratio of the metal powder to the organic carrier is (10~95):(1~90). The metal powder includes a first metal powder that has been treated with plasma; The organic carrier includes an organic solvent.

[0021] This invention utilizes plasma-treated metal powder, significantly enhancing the sintering activity of the metal paste. After sintering, it exhibits excellent electrical conductivity and mechanical properties, and the resulting sintered joints possess high shear strength, capable of withstanding significant thermal stress generated during power cycling, thus providing packaged devices with excellent service reliability. The metal paste provided by this invention can resist substantial thermal stress by improving the bonding force between the chip and substrate layers, making it particularly suitable for fields such as electronic printed circuit manufacturing, sensor manufacturing, semiconductor manufacturing, and packaging.

[0022] In some embodiments, the metal powder is composed of a first metal powder that has been treated with plasma.

[0023] In some embodiments, the metal powder comprises a first metal powder treated with plasma and a second metal powder not treated with plasma. The plasma-treated first metal powder accounts for 5% to 100% of the total mass of the metal powder (for example, it can be 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%, etc.).

[0024] In some embodiments, the composition of the plasma-treated first metal powder and the composition of the untreated second metal powder each independently include at least one of aluminum, titanium, vanadium, chromium, iron, cobalt, nickel, copper, zinc, gallium, zirconium, niobium, molybdenum, palladium, silver, cadmium, indium, tin, antimony, tungsten, platinum, gold, lead, and bismuth.

[0025] For example, the first metal powder can be a single powder or several powders, such as a mixture of aluminum and titanium powder, a mixture of gold and copper powder, or a mixture of gold, copper, and silver powder. The first metal powder can also be an alloy powder composed of several metallic elements, such as copper-zinc alloy powder or gold-silver alloy powder. Furthermore, the first metal powder can be a powder with a special structure (such as the core-shell structure described below) composed of several metallic elements, such as silver-coated copper powder or gold-coated silver powder.

[0026] In some embodiments, the microstructure of the first metal powder and the second metal powder includes, but is not limited to, spherical, near-spherical, rod-shaped, linear, sheet-like, layered, dendritic, flower-like, hollow, porous, core-shell, loaded, coated, and other complex structures.

[0027] For example, when the first metal powder and the second metal powder have a core-shell structure, the core component can be copper and the shell component can be silver.

[0028] In some embodiments, the size distribution of the first metal powder and the second metal powder can be monodisperse or polydisperse; when the first metal powder and the second metal powder are nanoparticles, their size is <1000nm, preferably ≤500nm, more preferably 100~400nm, for example, 100nm, 200nm, 300nm or 400nm, etc.; when the first metal powder and the second metal powder are micron particles, their size is ≥1μm, preferably ≤50μm, more preferably 2~20μm, for example, 2μm, 5μm, 10μm, 15μm or 20μm, etc.

[0029] In some embodiments, the organic solvent includes at least one of alcohol organic solvents, alcohol ether organic solvents, and ester organic solvents.

[0030] In some embodiments, the alcohol organic solvents include, but are not limited to, at least one of ethylene glycol, glycerol, diethylene glycol, dodecyl alcohol, and terpineol; the alcohol ether organic solvents include, but are not limited to, ethylene glycol butyl ether and diethylene glycol butyl ether; and the ester organic solvents include, but are not limited to, diethylene glycol butyl ether acetate.

[0031] In some embodiments, the organic carrier further includes at least one of industrial-grade dispersants, rheology modifiers, defoamers, and thickeners commonly used in metal slurries, but is not limited thereto. The organic carrier can modulate the rheological properties of the metal slurry.

[0032] In some embodiments, the dispersant includes, but is not limited to, at least one of polycarboxylate dispersants and phosphate ester dispersants; the rheology modifier or thickener includes, but is not limited to, at least one of fumed silica thickening rheology modifiers and polyurethane associative thickening rheology modifiers; and the defoamer includes, but is not limited to, at least one of silicone defoamers and polyether defoamers.

[0033] In some embodiments, the plasma-treated first metal powder is obtained by using first metal powder as raw material and through a plasma treatment process or a combination of plasma treatment process and other material processing processes.

[0034] In some embodiments, the plasma processing technology includes thermal equilibrium plasma processing technology and non-thermal equilibrium plasma processing technology, such as glow discharge plasma technology, radio frequency plasma technology, atmospheric pressure plasma technology, plasma spheroidization technology, and plasma reduction technology, but is not limited thereto.

[0035] In some embodiments, the plasma treatment process is a composite process with other material processing processes, in which plasma and non-plasma processes such as machining, heat treatment, and chemical treatment work synergistically, such as plasma ball milling or plasma-chemical treatment composite processes, but not limited to these.

[0036] In some embodiments, the chemical treatment process includes surface modification, chemical coating (specifically surface chemical coating), oxidation treatment, reduction treatment, acid treatment, alkali treatment, chemical adsorption or chemical desorption, etc.

[0037] In some embodiments, the plasma-treated first metal powder is obtained by a plasma ball milling process.

[0038] In this embodiment, plasma ball milling technology is employed to achieve efficient activation of metal powders through the synergistic effect of plasma energy and mechanical grinding. This activation effect is not a simple superposition of single effects, but rather stems from the organic synergy of the plasma effect and the mechanical effect of ball milling. On one hand, high-energy particles (such as electrons and ions) in the plasma bombard the surface of the metal powder, effectively removing organic contaminants, recalcitrant surface ligands, oxide layers, and other inert substances, and forming microscopic etching pits on the surface, thereby increasing surface roughness. On the other hand, the impact and shearing action during mechanical grinding causes deformation and fragmentation of the metal powder, significantly increasing its specific surface area and exposing more fresh reaction sites. These newly formed surfaces can rapidly react with active species (such as hydroxyl, amino, and free radicals) in the plasma (such as surface oxidation, nitriding, and reduction reactions), maximizing the surface activation effect. Simultaneously, plasma has a certain softening effect on the metal surface, helping to reduce the agglomeration of metal particles and frictional resistance, creating favorable conditions for fine grinding of metal particles during ball milling and promoting grain refinement. Furthermore, mechanical forces can induce defects such as dislocations and vacancies in the metal lattice and accumulate stress within the material, thereby reducing the diffusion activation energy of metal atoms. In summary, the activation effect of plasma ball milling technology involves multiple aspects, including surface cleaning and modification, increased specific surface area, enhanced surface activity, and regulation of internal crystal stress. These changes are highly beneficial for the interdiffusion of metal atoms in metal powder under high-temperature conditions, thus improving the sintering performance of the metal powder and ultimately forming a sintering head with higher shear strength. This enhances the bonding force between the chip and the substrate and, to some extent, suppresses the problem of interconnect layer delamination or cracking caused by excessive thermal stress.

[0039] Specifically, the plasma ball milling process can be performed once or multiple times, and the process parameters can be the same or different each time, preferably once.

[0040] In some embodiments, the process parameters used in the plasma ball milling process are as follows: The atmosphere is a vacuum, a reducing atmosphere, an oxidizing atmosphere (such as an air atmosphere), or an inert atmosphere; Plasma discharge frequency ≥ 1 kHz; The ball-to-material ratio is 0.01:1 to 100:1 (for example, it can be 0.01:1, 0.1:1, 1:1, 2:1, 5:1, 8:1, 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1 or 100:1, etc.; preferably 10:1 to 30:1). The ball milling speed is ≥100 rpm and the ball milling time is ≥1 min.

[0041] The grinding media are zirconia grinding balls or cemented carbide grinding balls, etc.

[0042] In some embodiments, the process parameters used in the plasma ball milling process are as follows: The atmosphere is an inert atmosphere (such as argon atmosphere or nitrogen atmosphere); The plasma discharge frequency is 8~16kHz (e.g., it can be 8kHz, 9kHz, 10kHz, 11kHz, 12kHz, 13kHz, 14kHz, 15kHz or 16kHz, etc.). The ball-to-material ratio is 10:1 to 30:1; The ball milling speed is 1000~1500rpm (e.g., 1000rpm, 1100rpm, 1200rpm, 1300rpm, 1400rpm or 1500rpm, etc.), and the ball milling time is 2~4h (e.g., 2h, 2.5h, 3h, 3.5h or 4h, etc.).

[0043] In some embodiments, the metal paste comprises the following components in weight percentage: Metal powder 10%~95%, organic carrier 1%~90%, and composite excipients 0.1%~30%; The composite excipient includes at least one of active excipients and inert excipients; The active excipients include metal precursors that can be thermally decomposed at low temperatures to form elemental metals or metal compounds. The temperature of the low-temperature thermal decomposition is 80~300℃ (e.g., 80℃, 100℃, 150℃, 200℃, 250℃, or 300℃). For example, the metal elements in the metal precursors include, but are not limited to, at least one of magnesium, aluminum, titanium, vanadium, chromium, iron, cobalt, nickel, copper, zinc, gallium, zirconium, niobium, molybdenum, palladium, silver, cadmium, indium, tin, antimony, tungsten, platinum, gold, lead, and bismuth, but are not limited thereto.

[0044] In some embodiments, the active excipient includes at least one of a metal-inorganic compound, a metal-organic salt, a metal-organic complex, and a second derivative; the second derivative is a derivative of a metal-inorganic compound, a derivative of a metal-organic salt, or a derivative of a metal-organic complex.

[0045] In some specific embodiments, the active excipient includes at least one of silver oxide, copper formate, silver acetate, copper amine complex, and silver amine complex.

[0046] In some embodiments, the inert excipients include at least one of organic excipients and inorganic excipients; The organic excipients include resins, which can be solid or liquid. Specifically, the organic excipients include at least one of epoxy resins, phenoxy resins, acrylic resins, polymethyl methacrylate resins, polyesters, silicone resins, furan resins, polyimide resins, polyurethane resins, polyamide resins, polyvinyl alcohol resins, polybutadiene resins, acrylonitrile-butadiene-styrene copolymers, melamine-formaldehyde resins, polyethylene resins, polyvinyl butyral resins, acrylonitrile-ethylene-styrene copolymers, polystyrene resins, polyvinylidene chloride resins, polytetrafluoroethylene, and derivatives of these resins. The organic excipients are preferably epoxy resins and acrylic resins.

[0047] The inorganic auxiliary material includes at least one of oxides (e.g., beryllium oxide, silicon oxide, bismuth oxide, aluminum oxide, etc.), nitrides (e.g., aluminum nitride), carbides (e.g., silicon carbide), elemental carbon (e.g., graphene), and a first derivative. The first derivative is a derivative of one of oxides, nitrides, carbides, and elemental carbon. The method for forming the first derivative includes at least one of elemental doping, surface modification, structural compositing, and functional group substitution (more preferably structural compositing, such as by loading, coating, or semi-coating).

[0048] The first derivative comprises a complex formed by an oxide, nitride, carbide, or elemental carbon with a metallic material. Preferably, the metallic material comprises, but is not limited to, at least one of magnesium, aluminum, titanium, vanadium, chromium, iron, cobalt, nickel, copper, zinc, gallium, zirconium, niobium, molybdenum, palladium, silver, cadmium, indium, tin, antimony, tungsten, platinum, gold, lead, and bismuth.

[0049] In some embodiments, the metal paste comprises the following components in weight percentage: Metal powder 70%~95%, organic carrier 1%~30% and composite auxiliary materials 0.5%~20%.

[0050] This invention also provides a method for preparing the metal paste as described above, comprising the following steps: The metal slurry is obtained by mixing the metal powder and the organic carrier in a certain proportion.

[0051] This invention also provides a method for preparing the metal paste as described above, comprising the following steps: The metal slurry is obtained by mixing the metal powder, organic carrier and composite additives in a certain proportion.

[0052] For solid materials used in the preparation of metal slurries, physical treatment, chemical treatment, and combined physical and chemical treatment may be selectively performed or not performed before use, as needed. Physical treatment includes, but is not limited to, at least one of the following: cleaning, sieving, magnetic separation, air separation, mechanical grinding, ultrasonic treatment, ball milling, heat treatment, and cold working. Chemical treatment includes, but is not limited to, at least one of the following: surface ligand exchange, surface coating, oxidation treatment, reduction treatment, acid treatment, alkali treatment, chemical adsorption, chemical desorption, and coupling agent modification. Combined physical and chemical treatment includes, but is not limited to, at least one of the following: mechanochemical method, plasma-assisted chemical treatment, and ultrasonic / microwave combined chemical treatment.

[0053] Specifically, the metal slurry is obtained by mixing plasma-treated first metal powder, untreated second metal powder, organic carrier, and composite additives in a certain proportion; or, the metal slurry is obtained by mixing plasma-treated first metal powder, untreated second metal powder, organic carrier, and composite additives and then vacuum stirring and degassing.

[0054] The plasma-treated first metal powder, the untreated second metal powder, the organic carrier, and the composite additives are placed in a high-speed mixer and mixed at a speed of 100-3000 rpm for 1-30 minutes.

[0055] The method for preparing the first metal powder after plasma treatment includes the following steps: The first metal powder is mixed with grinding beads and then subjected to plasma ball milling to obtain the plasma-treated first metal powder. The process parameters for the plasma ball milling are as follows: The atmosphere is any one of vacuum, reducing atmosphere, oxidizing atmosphere or inert atmosphere; Plasma discharge frequency ≥ 1 kHz; The ball-to-material ratio is 0.01:1 to 100:1; The ball milling speed is ≥100 rpm and the ball milling time is ≥1 min.

[0056] The present invention also provides an application of the metal paste of the present invention as described above or the metal paste prepared by the preparation method of the present invention as described above, wherein the application is conductive circuit manufacturing, sensor electrode manufacturing, via and blind via filling of interconnect boards, chip and substrate welding, module and heat sink welding, or chip electrode and copper foil welding.

[0057] The present invention will be further described below through specific embodiments.

[0058] Unless otherwise specified, the raw materials and equipment used in the following embodiments are all commercially available products.

[0059] Example 1 This embodiment provides a metal paste and its preparation method.

[0060] The metal paste is composed of the following components by mass percentage: The plasma ball milling process involves 80% copper powder, 15% organic carrier, and 5% composite additives (the composition of the organic carrier and composite additives is described in the preparation method below).

[0061] The preparation method of metal paste includes the following steps: (1) Preparation of copper powder treated by plasma ball milling: 5g of copper powder (with a spherical shape with a diameter of 2μm) and 50g of zirconia ball milling beads were sealed in the ball milling jar of a plasma ball mill and subjected to non-thermal equilibrium plasma ball milling under an argon atmosphere. The process parameters were as follows: the discharge mode was dielectric barrier discharge, the frequency was 10kHz, the rotation speed was 1000rpm, and the ball milling time was 2 hours to obtain plasma ball milled copper powder.

[0062] (2) Preparation of organic carrier: 5 mL of ethylene glycol butyl ether, 5 mL of terpineol and 0.05 g of polyvinylpyrrolidone (i.e. dispersant) were stirred and mixed evenly to obtain organic carrier.

[0063] (3) Preparation of composite excipients: 1.5g of copper formate and 2.7g of 2-amino-2-methyl-1-propanol were mixed at high speed to form a blue viscous liquid, and copper amine complex was obtained, which is the composite excipient.

[0064] (4) Preparation of metal paste: Weigh the plasma ball milled copper powder, organic carrier and composite auxiliary materials in a mass ratio of 80:15:5, place them in a high-speed mixer and mix at 800 rpm for 10 min to obtain the final metal paste (metal copper paste).

[0065] Example 2 This embodiment provides a metal paste and its preparation method.

[0066] The metal paste is composed of the following components by mass percentage: The plasma ball milling process is used to process 80% silver powder, 15% organic carrier, and 5% composite excipients (the composition of the organic carrier and composite excipients is shown in the preparation method below).

[0067] The preparation method of metal paste includes the following steps: (1) Preparation of silver powder by plasma ball milling: The only difference from step (1) in Example 1 is that 5g of copper powder (spherical with a diameter of 2μm) is replaced with 5g of silver powder (spherical with a diameter of 2μm).

[0068] (2) Preparation of organic carrier: Same as step (2) in Example 1.

[0069] (3) Preparation of composite excipients: Acrylic resin is directly used as composite excipient.

[0070] (4) Preparation of metal paste: Weigh the plasma ball milled silver powder, organic carrier and composite auxiliary materials in a mass ratio of 80:15:5, place them in a high-speed mixer and mix at 800 rpm for 10 min to obtain the final metal paste (silver paste).

[0071] Example 3 This embodiment provides a metal paste and its preparation method.

[0072] The metal paste is composed of the following components by mass percentage: The mixture consists of 40% silver-coated copper powder, 40% silver powder (i.e., untreated by plasma ball milling), 15% organic carrier, and 5% composite excipients (the composition of the organic carrier and composite excipients is described in the preparation method below).

[0073] The preparation method of metal paste includes the following steps: (1) Preparation of silver-coated copper powder by plasma ball milling: The only difference from step (1) in Example 1 is that 5g of copper powder (spherical with a diameter of 2μm) is replaced with 5g of silver-coated copper powder (spherical with a diameter of 2μm).

[0074] (2) Preparation of organic carrier: Same as step (2) in Example 1.

[0075] (3) Preparation of composite excipients: The composite excipients are made of 1μm irregular silver-plated silicon carbide particles with a coating thickness of about 100nm (referred to as silver-plated silicon carbide).

[0076] (4) Preparation of metal paste: Weigh the plasma ball milled silver-coated copper powder, silver powder (microscopic morphology is spherical with a diameter of 500nm), organic carrier and composite auxiliary material in a mass ratio of 40:40:15:5, place them in a high-speed mixer and mix at 800rpm for 10min to obtain metal paste (i.e. silver-copper composite paste).

[0077] Comparative Example 1 This comparative example provides a metal slurry and its preparation method. The only difference from Example 1 is that copper powder without plasma ball milling is used directly, and the plasma ball milling step is omitted.

[0078] Comparative Example 2 This comparative example provides a metal slurry and its preparation method. The only difference from Example 2 is that silver powder without plasma ball milling is used directly, and the plasma ball milling step is omitted.

[0079] Comparative Example 3 This comparative example provides a metal slurry and its preparation method. The only difference from Example 3 is that it directly uses silver-coated copper powder without plasma ball milling, and skips the plasma ball milling step.

[0080] Application Example 1 (Conductive Circuit Manufacturing) The metal pastes from Examples 1-3 and Comparative Examples 1-3 were used to prepare conductive thin films. The specific process is as follows: each metal paste was printed onto a glass substrate using a stencil printing method (stencil aperture size: 4cm × 2cm × 100μm); after printing, the substrate was sintered at 200℃ under a nitrogen atmosphere for 60 minutes to form a conductive thin film. Then, resistivity tests were performed, and the results are shown in Table 1.

[0081] Table 1. Resistivity test results of conductive thin films

[0082] As shown in Table 1, the resistivity of the slurry containing metal powder treated with plasma ball milling is significantly reduced, indicating that plasma ball milling can effectively improve the sintering performance of metal powder.

[0083] Application Example 2 (Chip Packaging) The metal pastes from Examples 1-3 and Comparative Examples 1-3 were used for interconnecting the chip and the substrate. The specific process is as follows: (1) Paste printing: Each metal paste is printed onto a gold-plated ceramic copper-clad substrate by stencil printing (stencil opening size: 5mm×5mm×100μm), and a gold-plated silicon wafer is mounted on the surface of the printed paste.

[0084] (2) Sinter the product obtained in step (1): When using the metal paste in Example 1 and Comparative Example 1, the sintering process is as follows: under a nitrogen atmosphere, preheat at 130°C for 30 min, and then sinter at 240°C and 10MPa sintering pressure for 10 min to complete the interconnection. When using the metal pastes in Examples 2, 3, Comparative Examples 2 and 3, the sintering process is as follows: under an air atmosphere, preheat at 130°C for 30 minutes, and then sinter at 200°C under pressureless conditions for 60 minutes to complete the interconnection.

[0085] The shear strength test results of the sintered joint are as follows: Figure 1 As shown, by Figure 1 It is known that the shear strength of the slurry containing metal powder treated with plasma ball milling is significantly increased. This indicates that plasma ball milling can effectively improve the sintering performance of metal powder, thereby forming a sintered joint with superior mechanical properties after sintering. This can effectively improve the bonding force between the chip and the substrate layer and withstand the large thermal stress generated during power cycling.

[0086] This invention employs plasma ball milling technology to process metal powder, which significantly improves the sintering activity of the metal slurry. After sintering, the slurry exhibits excellent electrical conductivity and mechanical properties, and can withstand the large thermal stress generated during power cycling, thereby giving the packaged device good long-term service reliability.

[0087] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A metal paste, characterized in that, The metal slurry comprises metal powder and an organic carrier; The mass ratio of the metal powder to the organic carrier is (10~95):(1~90). The metal powder includes a first metal powder that has been treated with plasma; The organic carrier includes an organic solvent.

2. The metal paste according to claim 1, characterized in that, The metal powder includes a first metal powder treated with plasma and a second metal powder that has not been treated with plasma. The plasma-treated first metal powder accounts for 5% to 100% of the total metal powder by mass.

3. The metal paste according to claim 2, characterized in that, The composition of the plasma-treated first metal powder and the composition of the untreated second metal powder each independently include at least one of aluminum, titanium, vanadium, chromium, iron, cobalt, nickel, copper, zinc, gallium, zirconium, niobium, molybdenum, palladium, silver, cadmium, indium, tin, antimony, tungsten, platinum, gold, lead, and bismuth; And / or, the organic solvent includes at least one of alcohol organic solvents, alcohol ether organic solvents, and ester organic solvents; And / or, the organic carrier further includes at least one of a dispersant, a rheology modifier, an antifoaming agent, and a thickener.

4. The metal paste according to claim 1, characterized in that, The plasma-treated first metal powder is obtained through one of the following processes (1) to (4): (1) Plasma treatment process; (2) A combined process of plasma treatment and mechanical processing; (3) A combined process of plasma treatment and heat treatment; (4) A combined process of plasma treatment and chemical treatment, wherein the chemical treatment includes chemical coating, oxidation treatment, reduction treatment, acid treatment, alkali treatment or chemical desorption.

5. The metal paste according to claim 4, characterized in that, The combined process of plasma treatment and machining is plasma ball milling, and the process parameters used in the plasma ball milling process are as follows: The atmosphere is a vacuum, reducing atmosphere, oxidizing atmosphere, or inert atmosphere; Plasma discharge frequency ≥ 1 kHz; The ball-to-material ratio is 0.01:1 to 100:1; The ball milling speed is ≥100 rpm and the ball milling time is ≥1 min.

6. The metal paste according to claim 1, characterized in that, The metal paste comprises the following components in weight percentage: Metal powder 10%~95%, organic carrier 1%~90%, and composite excipients 0.1%~30%; The composite excipient includes at least one of active excipients and inert excipients; The active excipients include metal precursors that can be thermally decomposed at low temperatures to form elemental metals or metal compounds, wherein the temperature of the low-temperature thermal decomposition is 80~300℃. The inert excipients include at least one of organic excipients and inorganic excipients; The organic additives include resins; The inorganic auxiliary material includes at least one of oxides, nitrides, carbides, elemental carbon, and a first derivative, wherein the first derivative is a derivative of one of oxides, nitrides, carbides, and elemental carbon, and the method for forming the first derivative includes at least one of elemental doping, surface modification, structural compositing, and functional group substitution.

7. The metal paste according to claim 6, characterized in that, The active excipient includes at least one of a metal inorganic compound, a metal organometallic salt, a metal organometallic complex, and a second derivative; the second derivative is a derivative of a metal inorganic compound, a derivative of a metal organometallic salt, or a derivative of a metal organometallic complex. The organic additives include at least one of epoxy resin, phenoxy resin, acrylic resin, polymethyl methacrylate resin, polyester, silicone resin, furan resin, polyimide resin, polyurethane resin, polyamide resin, polyvinyl alcohol resin, polybutadiene resin, acrylonitrile-butadiene-styrene copolymer, melamine-formaldehyde resin, polyethylene resin, polyvinyl alcohol butyral resin, acrylonitrile-ethylene-styrene copolymer, polystyrene resin, polyvinylidene chloride resin, polytetrafluoroethylene, and derivatives of these resins. The first derivative includes a complex formed by an oxide, nitride, carbide, or elemental carbon with a metallic material.

8. A method for preparing a metal paste according to any one of claims 1-5, characterized in that, Includes the following steps: The metal slurry is obtained by mixing the metal powder and the organic carrier in a certain proportion.

9. A method for preparing a metal paste according to any one of claims 6-7, characterized in that, Includes the following steps: The metal slurry is obtained by mixing the metal powder, organic carrier and composite additives in a certain proportion.

10. The application of a metal paste according to any one of claims 1-7 or a metal paste prepared by the preparation method according to any one of claims 8-9, characterized in that, The applications include conductive line manufacturing, sensor electrode manufacturing, via and blind hole filling of interconnect boards, chip-to-substrate welding, module-to-heat sink welding, or chip electrode-to-copper foil welding.

Images