High-reliability AlN copper-clad ceramic substrate and preparation method thereof

Abstract

This invention discloses a high-reliability AlN copper-clad ceramic substrate and its preparation method, relating to the field of ceramic substrate technology. The process includes the following steps: Step 1: Solder paste is printed on an AlN ceramic sheet, allowed to stand and level, and then dried to obtain a solder paste print; Step 2: The solder paste print is sequentially subjected to vacuum brazing, pattern etching, step etching, electroplating, and microgroove fabrication to obtain the AlN copper-clad ceramic substrate; the AlN ceramic sheet is of the instant-fire type; the pattern etching parameters are: temperature 45~55℃, etching rate 8~15μm / min, etching factor 1.5~3.0; bottom insulation distance between copper islands 0.3~1.0mm. The AlN copper-clad ceramic substrate prepared by this application exhibits good thermal cycling stability and low porosity.

Description

Technical Field

[0001] This invention relates to the field of ceramic substrate technology, specifically a high-reliability AlN copper-clad ceramic substrate and its preparation method. Background Technology

[0002] AlN copper-clad ceramic substrates (AlN-AMB) are widely used in high-power, high-temperature, and high-reliability electronic devices. However, they often fail prematurely during thermal cycling (TC) testing due to structural or process issues, thus affecting device lifespan.

[0003] The existing technologies generally have the following problems: (1) Improper ceramic surface treatment: Conventional processes use non-fired ceramic sheets and perform alkaline washing, which leads to increased surface roughness and reduced chemical activity, resulting in a decrease in chemical bonding force during the brazing process; (2) Insufficient brazing layer thickness: The amount of solder paste and the printing process are not precisely controlled, resulting in a thin brazing layer and weak thermal stress buffering capacity; (3) Inadequate control of etching process: The etching factor fluctuates greatly, resulting in poor verticality of the copper pattern sidewalls, insufficient bottom spacing, and decreased insulation performance; (4) Inconsistent step size: The step height is not standardized, which affects the fit and heat conduction efficiency of the multilayer structure; (5) Stress concentration at edges and corners: The surface coating design does not consider the distribution of thermal stress, and cracks are easily generated at the edges and corners of the pattern, resulting in a decrease in TC reliability.

[0004] In summary, solving the above problems and providing a high-reliability AlN copper-clad ceramic substrate and its preparation method is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a high-reliability AlN copper-clad ceramic substrate and its preparation method, so as to solve the problems mentioned in the background art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A high-reliability AlN copper-clad ceramic substrate and its preparation method, comprising the following steps: Step 1: Print solder paste on an AlN ceramic sheet, allow it to stand, level, and dry to obtain the solder paste print. Step 2: The solder paste print is sequentially subjected to vacuum brazing, pattern etching, step etching, electroplating of metal layer, and fabrication of microgrooves to obtain AlN copper-clad ceramic substrate; The AlN ceramic sheet is of the immediate-fired type, wherein the AlN ceramic sheet is not subjected to alkaline washing treatment and directly enters the subsequent process, which can ensure the increase of surface chemical activity and avoid the decrease of chemical bonding force during the brazing process; the thickness of the AlN ceramic sheet is 0.6~1.0mm.

[0007] In a more optimized manner, the parameters for pattern etching are: temperature of 45~55℃, etching rate of 8~15μm / min, etching factor of 1.5~3.0; and bottom insulation distance between copper islands of 0.3~1.0mm.

[0008] The pattern etching liquid is a hydrochloric acid / sodium chlorate system, wherein the acid equivalent concentration is 1.7~2.1N, the copper ion specific gravity is 1.26~1.32, and the sodium chlorate potential is 15~60V.

[0009] The optimal process parameters for the step etching are: etching rate of 8~15μm / min and step height of 30~50μm.

[0010] The process flow of the step etching is as follows: chemical pretreatment - wet film printing - exposure - development - etching. Specifically, a photosensitive wet film is first printed on the copper foil of the product. The wet film in the area that does not need to be etched by the step is cured by exposure. The wet film in the area to be etched by the step is removed by development. Finally, etching is performed, and the etching rate is controlled to control the height of the step.

[0011] Ideally, the electroplating includes one of nickel plating, nickel-gold plating, or silver plating.

[0012] When the electroplating is nickel plating, the nickel plating operation steps are as follows: after washing and drying the copper-clad ceramic substrate, it is transferred to the nickel plating solution for nickel plating, and then washed and dried; micro-grooves are made; the nickel plating solution includes the following components in mass concentration: nickel chloride 100~200g / L, boric acid 35~50g / L, 3,5-dinitrosalicylic acid 30~50g / L, ethoxylated butynediol 20~120mg / L, 2-amino-4-methylbenzothiazole 30~90mg / L, sodium chloride 0.2~0.5g / L, sodium styrene sulfonate 15~45mg / L, sodium 2-ethylhexyl sulfate 40~80mg / L, and the balance is deionized water; When electroplating is nickel-gold plating, the nickel-gold plating operation steps are as follows: after washing and drying the copper-clad ceramic substrate, it is transferred to the nickel plating solution for nickel plating, then washed and dried again, and then transferred to the gold plating solution for gold plating, followed by washing and drying; microgrooves are then fabricated; the nickel plating solution is the same as the nickel plating process; the gold plating solution includes the following components in mass concentration: sodium gold sulfite 3~10g / L, 2,3-bis(2-pyridyl)pyrazine 30~90mg / L, 3,5-pyridinedicarboxylic acid 1~5g / L, 5-aminotetrazole 15~45mg / L, 5-fluorouracil 10~40mg / L, sodium polyacrylate 30~60mg / L, and the balance is deionized water; When the electroplating is silver plating, the silver plating operation steps are as follows: after washing and drying the copper-clad ceramic substrate, it is transferred to the silver plating solution for silver plating, and then washed and dried. The silver plating solution includes the following components in mass concentration: silver tetrafluoroborate 10~60g / L; methylpentynol 0.1~1.5g / L; 1,4-butynediol 0.1~1.2g / L; ammonium acetate 10~20g / L; anisaldehyde 7~20g / L; benzoic acid 10~25g / L.

[0013] More preferably, the location of the microgroove includes one or more of the following: the full-pattern edge of the AlN ceramic sheet, the back edge, or the corner of the pattern.

[0014] The diameter of the microgroove is 0.2~0.8mm, and the depth is 0~100% of the copper thickness.

[0015] In a more optimized manner, the process parameters for solder paste printing are: screen frame size of 100~200 mesh, single-sided wet weight of 3.65~3.95g, and weight after drying of 2.89~3.19g.

[0016] In a more optimized manner, the raw materials of the solder paste, by weight, are: 80-90 parts alloy nanoparticles, 3-5 parts acrylic modified rosin, 4-6 parts solvent, 0.2-0.4 parts dispersant, 0.5-1 part activator, 1-2 parts thickener, and 0.5-1 part thixotropic agent.

[0017] In a more optimized manner, the alloy nanoparticles are composed of the following components by mass percentage: 5~7% Sn, 0.5~1.5% Si, 0.5~0.7% Ti, 0.2~0.4% Zr, 0.1~0.2% Ga, 0.3~0.5% B, 4~6% P, with the balance being Cu and ≤0.02% impurities.

[0018] A more optimized method for preparing the acrylic acid-modified rosin is as follows: Rosin and 4,4'-thiobis(6-tert-butyl-3-methylphenol) are mixed under a nitrogen atmosphere, and the mixture is stirred at 160-170°C. The mixture is then heated to 200-210°C, and acrylic acid, 4-allyl catechol, and hydroquinone methyl ether are added. The mixture is stirred for 1-3 hours. Diethylene glycol monomethyl ether and glycerol are then added, and the mixture is further heated to 210-220°C and stirred for 30-60 minutes. The mixture is then cooled to 100-120°C and filtered to remove impurities. The mixture is then cooled to 60-70°C, and sodium vanadate-ethanol solution is added. The mixture is stirred for 1-2 hours and then dried to obtain the acrylic acid-modified rosin. The raw materials for the acrylic acid-modified rosin, by weight, are: 95-105 parts rosin, 0.1-0.3 parts 4,4'-thiobis(6-tert-butyl-3-methylphenol), 6-8 parts acrylic acid, 1-3 parts 4-allyl catechol, 0.04-0.06 parts hydroquinone methyl ether, 0.04-0.06 parts diethylene glycol monomethyl ether, 0.08-0.12 parts glycerol, and 10-20 parts sodium orthovanadate-ethanol solution.

[0019] In the sodium orthovanadate-ethanol solution, the concentration of sodium orthovanadate is 0.8-1.2%.

[0020] A method for preparing a high-reliability AlN copper-clad ceramic substrate.

[0021] Compared with the prior art, the beneficial effects achieved by the present invention are: This invention, by preserving the surface activity of the ceramic and employing an alkaline-free calcination process, enables the substrate to achieve higher surface energy and adhesion, thereby significantly enhancing the adhesion of the solder layer. Furthermore, the solder paste process optimizes the solder layer thickness through precise weight control, effectively enhancing its stress buffering capacity during thermal cycling. In addition, the etching process consistently achieves an etching factor of 1.5–3.0, ensuring pattern accuracy and insulation distance, and reducing the risk of short circuits. Simultaneously, standardized step height control ensures consistent interlayer contact, further optimizing thermal management performance and structural reliability. In particular, the introduction of innovative microgroove stress-relieving structures at edges and corners effectively disperses thermal stress, significantly extending the thermal cycle life of the substrate. This fabrication process also exhibits excellent compatibility, flexibly adapting to various plating systems and pattern designs, demonstrating outstanding industrial applicability.

[0022] Furthermore, this invention further optimizes the solder paste system by employing alloy nanoparticles with specific components in synergy with acrylic-modified rosin to enhance the interfacial properties of the ceramic substrate. The alloy nanoparticles are based on Sn-P and incorporate multiple active elements such as Ti, Zr, B, and Ga. During heat treatment, these active nanoparticles preferentially diffuse to the ceramic interface, reacting with the natural oxide layer on the AlN ceramic substrate surface to form a chemically bonded transition layer, significantly enhancing the bonding strength and thermal conductivity continuity of the ceramic-metal interface. Ga element reduces the overall melting range during alloying, improves the fluidity and wettability of the liquid alloy, and, due to its higher reactivity, preferentially reacts with trace amounts of oxygen on other metal surfaces in the early stages of sintering, thereby inhibiting excessive oxidation of the main metal components and providing a cleaner, more active metal surface for subsequent interfacial reactions.

[0023] Among them, acrylic acid-modified rosin is obtained by crosslinking acrylic acid with rosin, which effectively improves the rheological properties and thermal decomposition characteristics of rosin. In the solder paste printing stage, it can provide good processing adaptability and pattern retention ability, ensuring the molding accuracy of subsequent circuits and step structures, effectively preventing particle agglomeration and secondary oxidation, and ensuring the stability of the paste and the interfacial activity. In the brazing stage, the acrylic acid-modified rosin decomposes in an orderly manner with increasing temperature. During the decomposition process, it can consume trace oxygen, which can effectively improve the sintering density. In addition, the introduction of sodium orthovanadate can improve the interfacial wettability, effectively improve the brazing density, and reduce the void ratio, so that the ceramic substrate has good thermal cycling performance and low void ratio, achieving high reliability of the ceramic substrate. Attached Figure Description

[0024] Figure 1 This is an ultrasonic scanning image of the AlN copper-clad ceramic substrate prepared in Example 5 of the present invention. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] In the following embodiments, the parts are by weight; it should be noted that there are no special restrictions on the manufacturers of the raw materials involved in this invention. Exemplary examples include: AlN ceramic sheets (model ASD-1, provided by Zhuzhou Aisenda New Material Technology Co., Ltd.), rosin (CAS: 8050-09-7), 4,4'-thiobis(6-tert-butyl-3-methylphenol) (CAS: 96-69-5), acrylic acid (CAS: 79-10-7), hydroquinone methyl ether (CAS: 150-78-7), diethylene glycol monomethyl ether (CAS: 1 11-77-3), 4-allyl catechol (CAS: 1126-61-0), glycerol (CAS: 56-81-5), sodium orthovanadate (CAS: 13721-39-6), triethylhexyl phosphoric acid (CAS: 78-42-2), sebacic acid (CAS: 111-20-6), triethanolamine (CAS: 102-71-6), phenolic resin (model PF-2120), hydrogenated castor oil (CAS: 8001-78-3), dipropylene glycol methyl ether (CAS: 34590-94-8).

[0027] Pre-preparation: I. Preparation of acrylic acid-modified rosin: Under a nitrogen atmosphere, 100 parts of rosin and 0.2 parts of 4,4'-thiobis(6-tert-butyl-3-methylphenol) were mixed and the mixture was stirred at 165°C. The mixture was then heated to 200°C, and 7 parts of acrylic acid, 2 parts of 4-allyl catechol, and 0.05 parts of hydroquinone methyl ether were added. The mixture was stirred for 2 hours. Then, 0.05 parts of diethylene glycol monomethyl ether and 0.1 parts of glycerol were added. The mixture was heated to 210°C and stirred for 45 minutes. The mixture was then cooled to 110°C and filtered to remove impurities. The mixture was cooled to 65°C, and 15 parts of a 1% sodium orthovanadate-ethanol solution were added. The mixture was stirred for 1.5 hours and then dried to obtain acrylic acid-modified rosin. II. Preparation of solder paste: 85 parts of alloy nanoparticles (composed of 6% Sn, 1% Si, 0.6% Ti, 0.3% Zr, 0.15% Ga, 0.4% B, 5% P, with the balance being Cu and 0.01% impurities), 4 parts of acrylic acid-modified rosin, 0.3 parts of dispersant (triethylhexylphosphoric acid), 0.7 parts of activator (composed of 0.3 parts sebacic acid and 0.4 parts triethanolamine), 1.5 parts of thickener (phenolic resin), and 0.7 parts of thixotropic agent (hydrogenated castor oil) were sequentially added to 5 parts of solvent (dipropylene glycol methyl ether), stirred evenly, and filtered to obtain solder paste.

[0028] Example 1: A method for preparing a high-reliability AlN copper-clad ceramic substrate, comprising the following steps: Step 1: The 0.635mm thick ready-to-fire AlN ceramic sheet is not subjected to alkaline washing treatment. Then, solder paste is printed using a 150-mesh stainless steel mesh frame. The wet weight is controlled at 3.8g. After standing and leveling, the weight after drying is 3.04g, and the solder paste printed body is obtained. Step 2: (1) Place the solder paste print body under a vacuum of 5×10 -3In the furnace of Pa, the temperature was raised to 720℃ at 10℃ / min, a pressure of 0.15MPa was applied, and the temperature was held for 8min. After cooling, it was placed in the pattern etching solution (hydrochloric acid / sodium chlorate system: acid equivalent: 1.9N, copper ion concentration: 135g / L, specific gravity: 1.29, sodium chlorate potential: 40V) for pattern etching. The temperature was 50℃, the etching rate was 12μm / min, the etching factor was controlled at 2.0, the bottom insulation distance between copper islands was 0.35mm, and it was washed with water and dried. (2) After pattern etching, chemical pretreatment was performed on the copper foil, and then a photosensitive wet film was printed. The wet film in the area that does not need to be etched by step was cured by exposure, and the wet film in the area of ​​step etching was removed by development. Step etching was then performed. The etching rate is 12 μm / min, and the step height is set to 40 μm; (3) Then it is transferred to the nickel plating solution (composed of nickel chloride 150 g / L, boric acid 42 g / L, 3,5-dinitrosalicylic acid 40 g / L, ethoxylated butynediol 70 mg / L, 2-amino-4-methylbenzothiazole 60 mg / L, sodium chloride 0.35 g / L, sodium styrene sulfonate 30 mg / L, sodium 2-ethylhexyl sulfate 60 mg / L, and the remainder is deionized water) for nickel plating, washed with water, and dried; (4) A circular microgroove is set on the edge of the back side of the substrate. The diameter of the microgroove hole is 0.2 mm, the depth is 0.05 mm, and the copper thickness is 0.07 mm to obtain the AlN copper-clad ceramic substrate.

[0029] Example 2: A method for preparing a high-reliability AlN copper-clad ceramic substrate, comprising the following steps: Step 1: The 0.635mm thick instant-fired AlN ceramic sheet is not subjected to alkaline washing treatment. Then, solder paste is printed using a 150-mesh stainless steel mesh frame. The wet weight is controlled at 3.9g. After standing and leveling, the weight after drying is 3.08g, and the solder paste print body is obtained. Step 2: (1) Place the solder paste print body under a vacuum of 5×10 -3In the furnace of Pa, the temperature is raised to 720℃ at 10℃ / min, a pressure of 0.15MPa is applied, and the temperature is held for 8min. After cooling, it is placed in the pattern etching solution (hydrochloric acid / sodium chlorate system: acid equivalent: 1.9N, copper ion concentration: 135g / L, specific gravity: 1.29, sodium chlorate potential: 40V) for pattern etching. The temperature is 50℃, the etching rate is 12μm / min, the etching factor is controlled at 2.5, and the bottom insulation distance between copper islands is 0.35mm; (2) After pattern etching, chemical pretreatment is performed on the copper foil, and then a photosensitive wet film is printed. The wet film in the area that does not need to be etched by step is cured by exposure, and the wet film in the area of ​​step etching is removed by development. Step etching is performed at an etching rate of 10μm / min and the step height is set to 35μm; (3) Then it is transferred to the electroplating nickel solution (composed of nickel chloride 150g / L, boric acid Nickel-gold plating was performed using a solution of sodium gold sulfite (6.5 g / L), 2,3-bis(2-pyridyl)pyrazine (60 mg / L), 3,5-pyridinedicarboxylic acid (3 g / L), 5-aminotetrazole (30 mg / L), 5-fluorouracil (25 mg / L), sodium polyacrylate (45 mg / L), and deionized water (the remainder was deionized water). The solution was then washed with water and dried. (4) A square microgroove was set on the back edge of the substrate. The microgroove hole diameter was 0.2 mm, the depth was 0.05 mm, and the copper thickness was 0.07 mm to obtain an AlN copper-clad ceramic substrate.

[0030] Example 3: A method for preparing a high-reliability AlN copper-clad ceramic substrate, comprising the following steps: Step 1: Without alkaline washing, a 1.0mm thick ready-to-fire AlN ceramic sheet is printed with solder paste using a 150-mesh stainless steel mesh frame. The wet weight is controlled at 4.0g. After standing and leveling, the weight after drying is 3.12g, resulting in the solder paste printed body. Step 2: (1) Place the solder paste print body under a vacuum of 5×10 -3In the furnace of Pa, the temperature was raised to 720℃ at 10℃ / min, a pressure of 0.15MPa was applied, and the temperature was held for 8min. After cooling, it was placed in the pattern etching solution (hydrochloric acid / sodium chlorate system: acid equivalent: 1.9N, copper ion concentration: 135g / L, specific gravity: 1.29, sodium chlorate potential: 40V) for pattern etching. The temperature was 50℃, the etching rate was 12μm / min, the etching factor was controlled at 1.8, and the bottom insulation distance between copper islands was 0.35mm; (2) After pattern etching, chemical pretreatment was performed on the copper foil, and then a photosensitive wet film was printed. The wet film in the area that does not need to be etched by step was cured by exposure and developed. Remove the wet film in the step etching area, perform step etching at a rate of 15 μm / min, and set the step height to 50 μm; (3) then transfer to an electroplating silver solution (composed of 35 g / L silver tetrafluoroborate, 0.3 g / L methylpentynol, 0.6 g / L 1,4-butynediol, 15 g / L ammonium acetate, 13 g / L anisaldehyde, 17 g / L benzoic acid, with the remainder being deionized water) for silver plating, wash with water, and dry; (4) set strip-shaped microgrooves on the back edge and corners of the substrate, with a microgroove hole diameter of 0.2 mm, a depth of 0.05 mm, and a copper thickness of 0.07 mm to obtain an AlN copper-clad ceramic substrate.

[0031] Example 4: A method for preparing a high-reliability AlN copper-clad ceramic substrate, comprising the following steps: Step 1: Without alkaline washing, 0.8mm thick ready-to-fire AlN ceramic sheets are printed with solder paste using a 150-mesh stainless steel mesh frame. The wet weight is controlled at 3.8g. After standing and leveling, the weight after drying is 3.04g, resulting in the solder paste printed body. Step 2: (1) Place the solder paste print body under a vacuum of 5×10 -3Inside the Pa furnace, the temperature was raised to 720℃ at 10℃ / min, a pressure of 0.15MPa was applied, and the temperature was held for 8min. After cooling, the sample was placed in a pattern etching solution (hydrochloric acid / sodium chlorate system: acid equivalent: 1.9N, copper ion concentration: 135g / L, specific gravity: 1.29, sodium chlorate potential: 40V) for pattern etching. The temperature was 50℃, the etching rate was 12μm / min, the etching factor was controlled at 2.2, and the bottom insulation distance between copper islands was 0.35mm. (2) After pattern etching, chemical pretreatment was performed on the copper foil, and then a photosensitive wet film was printed. The wet film in the area that does not need to be etched by step was cured by exposure, and the wet film in the area of ​​step etching was removed by development. Step etching was then performed. The etching rate is 13 μm / min, and the step height is set to 45 μm; (3) Then it is transferred to the nickel plating solution (composed of nickel chloride 150 g / L, boric acid 42 g / L, 3,5-dinitrosalicylic acid 40 g / L, ethoxylated butynediol 70 mg / L, 2-amino-4-methylbenzothiazole 60 mg / L, sodium chloride 0.35 g / L, sodium styrene sulfonate 30 mg / L, sodium 2-ethylhexyl sulfate 60 mg / L, with the remainder being deionized water) for nickel plating, washed with water, and dried; (4) a strip-shaped microgroove is set on the edge of the back side of the substrate, the microgroove hole diameter is 0.2 mm, the depth is 0.05 mm, and the copper thickness is 0.07 mm, to obtain the AlN copper-clad ceramic substrate.

[0032] Example 5: A method for preparing a high-reliability AlN copper-clad ceramic substrate, comprising the following steps: Step 1: The 0.635mm thick ready-to-fire AlN ceramic sheet is not subjected to alkaline washing treatment. Then, solder paste is printed using a 150-mesh stainless steel mesh frame. The wet weight is controlled at 3.8g. After standing and leveling, the weight after drying is 3.04g, and the solder paste printed body is obtained. Step 2: (1) Place the solder paste print body under a vacuum of 5×10 -3In the furnace of Pa, the temperature is raised to 720℃ at 10℃ / min, a pressure of 0.15MPa is applied, and the temperature is held for 8min. After cooling, it is placed in the pattern etching solution (hydrochloric acid / sodium chlorate system: acid equivalent: 1.9N, copper ion concentration: 135g / L, specific gravity: 1.29, sodium chlorate potential: 40V) for pattern etching. The temperature is 50℃, the etching rate is 12μm / min, the etching factor is controlled at 2.8, and the bottom insulation distance between copper islands is 0.35mm; (2) After pattern etching, chemical pretreatment is performed on the copper foil, and then a photosensitive wet film is printed. The wet film in the area that does not need to be etched by step is cured by exposure, and the wet film in the area of ​​step etching is removed by development. Step etching is performed at an etching rate of 8μm / min and the step height is set to 30μm; (3) Then it is transferred to the electroplating nickel solution (composed of nickel chloride 150g / L, boric acid 4 Nickel-gold plating was performed using a solution of sodium gold sulfite (6.5 g / L), 2,3-bis(2-pyridyl)pyrazine (60 mg / L), 3,5-pyridinedicarboxylic acid (3 g / L), 5-aminotetrazole (30 mg / L), 5-fluorouracil (25 mg / L), sodium polyacrylate (45 mg / L), and deionized water (the remainder was deionized water). The solution was then washed and dried. (4) A strip-shaped microgroove was set at the edge of the entire pattern. The microgroove hole diameter was 0.2 mm, the depth was 0.05 mm, and the copper thickness was 0.07 mm to obtain an AlN copper-clad ceramic substrate.

[0033] Comparative Example 1: Based on Example 5: The composition of acrylic acid-modified rosin was adjusted, and sodium orthovanadate-ethanol solution was not added; the rest remained the same as in Example 5, except that: Under a nitrogen atmosphere, 100 parts of rosin and 0.2 parts of 4,4'-thiobis(6-tert-butyl-3-methylphenol) were mixed and the mixture was stirred at 165°C. The mixture was then heated to 200°C, and 7 parts of acrylic acid, 2 parts of 4-allyl catechol, and 0.05 parts of hydroquinone methyl ether were added. The mixture was stirred for 2 hours. Then, 0.05 parts of diethylene glycol monomethyl ether and 0.1 parts of glycerol were added, and the mixture was heated to 210°C and stirred for 45 minutes. The mixture was then cooled to 110°C, filtered to remove impurities, and dried to obtain acrylic acid-modified rosin.

[0034] Comparative Example 2: Based on Example 5, the composition of the solder paste was adjusted, with Cu replacing Ga; everything else remained the same as Example 5, except that: 85 parts of alloy nanoparticles (composed of 6% Sn, 1% Si, 0.6% Ti, 0.3% Zr, 0.4% B, 5% P, with the balance being Cu and 0.01% impurities), 4 parts of acrylic acid-modified rosin, 0.3 parts of dispersant (triethylhexylphosphoric acid), 0.7 parts of activator (composed of 0.3 parts sebacic acid and 0.4 parts triethanolamine), 1.5 parts of thickener (phenolic resin), and 0.7 parts of thixotropic agent (hydrogenated castor oil) were sequentially added to 5 parts of solvent (dipropylene glycol methyl ether), stirred evenly, filtered, and the solder paste was obtained.

[0035] Comparative Example 3: Based on Example 5, the composition of the solder paste was adjusted, and ordinary rosin was used instead of acrylic-modified rosin; the rest remained the same as in Example 5, except that: 85 parts of alloy nanoparticles (composed of 6% Sn, 1% Si, 0.6% Ti, 0.3% Zr, 0.15% Ga, 0.4% B, 5% P, with the balance being Cu and 0.01% impurities), 4 parts of ordinary rosin, 0.3 parts of dispersant (triethylhexylphosphoric acid), 0.7 parts of activator (composed of 0.3 parts of sebacic acid and 0.4 parts of triethanolamine), 1.5 parts of thickener (phenolic resin), and 0.7 parts of thixotropic agent (hydrogenated castor oil) were sequentially added to 5 parts of solvent (dipropylene glycol methyl ether), stirred evenly, filtered, and the solder paste was obtained.

[0036] Comparative Example 4: Based on Example 5, the AlN ceramic sheet was subjected to alkali washing treatment, and the rest remained the same as in Example 5.

[0037] Testing Experiments: The AlN copper-clad ceramic substrates prepared in the examples and comparative examples were subjected to thermal cycling tests. One cycle consisted of placing the sample at -40°C for 15 min and then at 150°C for 15 min. The temperature transition time was <30 s, the temperature deviation range was ±2°C, and the porosity was measured. The obtained data are shown in the table below.

[0038] Conclusion: The data in the table above show that the AlN copper-clad ceramic substrates prepared in Examples 1-5, using the solder in this scheme, exhibit good thermal cycle count and low void ratio, thus effectively improving their reliability. Comparing Example 5 with Comparative Examples 1-4, it can be found that Comparative Example 1 lacks sodium vanadate-ethanol solution, resulting in decreased interfacial wettability, thus decreasing sintering density, thermal cycle count, and increasing void ratio; Comparative Example 2 lacks Ga, leading to decreased melting point, wettability, and antioxidant properties, resulting in interfacial oxidation, decreased interfacial properties, reduced thermal cycle count, and increased void ratio; Comparative Example 3 uses ordinary rosin, resulting in a significant decrease in solder rheology, more residue during brazing, interfacial contamination leading to decreased bonding strength, reduced thermal cycle count, and significantly increased void ratio; In Comparative Example 4, the AlN ceramic sheet undergoes alkaline washing treatment, which increases roughness but may damage the surface strength of the ceramic sheet, introducing contamination risk, resulting in a decrease in thermal cycle count and an increase in void ratio. In summary, this application optimizes the solder paste system, synergistically and effectively increasing the thermal cycle life of AlN copper-clad ceramic substrates and reducing the void ratio.

[0039] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A high-reliability AlN copper-clad ceramic substrate and its preparation method, characterized in that: Includes the following steps: Step 1: Print solder paste on an AlN ceramic sheet, allow it to stand, level, and dry to obtain the solder paste print. Step 2: The solder paste print is sequentially subjected to vacuum brazing, pattern etching, step etching, electroplating of metal layer, and fabrication of microgrooves to obtain AlN copper-clad ceramic substrate; The AlN ceramic sheet is of the instant-fire type.

2. The method for preparing a high-reliability AlN copper-clad ceramic substrate according to claim 1, characterized in that: The parameters for pattern etching are: temperature 45~55℃, etching rate 8~15μm / min, etching factor 1.5~3.0; bottom insulation distance between copper islands 0.3~1.0mm.

3. The method for preparing a high-reliability AlN copper-clad ceramic substrate according to claim 1, characterized in that: The process parameters for the step etching are: etching rate of 8~15μm / min, and step height of 30~50μm.

4. The method for preparing a high-reliability AlN copper-clad ceramic substrate according to claim 1, characterized in that: The electroplating includes one of nickel plating, nickel-gold plating, and silver plating.

5. The method for preparing a high-reliability AlN copper-clad ceramic substrate according to claim 1, characterized in that: The location of the microgroove includes one or more of the following: the full edge of the AlN ceramic sheet, the back edge, or the corner of the pattern.

6. The method for preparing a high-reliability AlN copper-clad ceramic substrate according to claim 1, characterized in that: The process parameters for solder paste printing are as follows: the screen frame size is 100~200 mesh, the wet weight on one side is 3.65~3.95g, and the weight after drying is 2.89~3.19g.

7. The method for preparing a high-reliability AlN copper-clad ceramic substrate according to claim 1, characterized in that: The raw materials of the solder paste, by weight, are: 80-90 parts alloy nanoparticles, 3-5 parts acrylic modified rosin, 4-6 parts solvent, 0.2-0.4 parts dispersant, 0.5-1 part activator, 1-2 parts thickener, and 0.5-1 part thixotropic agent.

8. The method for preparing a high-reliability AlN copper-clad ceramic substrate according to claim 7, characterized in that: The alloy nanoparticles are composed of the following components by mass percentage: 5~7% Sn, 0.5~1.5% Si, 0.5~0.7% Ti, 0.2~0.4% Zr, 0.1~0.2% Ga, 0.3~0.5% B, 4~6% P, with the balance being Cu and ≤0.02% impurities.

9. The method for preparing a high-reliability AlN copper-clad ceramic substrate according to claim 7, characterized in that: The preparation method of the acrylic acid modified rosin is as follows: Under a nitrogen atmosphere, rosin and 4,4'-thiobis(6-tert-butyl-3-methylphenol) are mixed and the temperature is set at 160~170℃. The mixture is stirred and reacted, then the temperature is raised to 200~210℃, acrylic acid, 4-allyl catechol, and hydroquinone methyl ether are added, and the mixture is stirred for 1~3 hours. Then diethylene glycol monomethyl ether and glycerol are added, and the temperature is raised to 210~220℃. The mixture is stirred for 30~60 minutes, cooled to 100~120℃, and filtered to remove impurities. The temperature is then lowered to 60~70℃, sodium orthovanadate-ethanol solution is added, and the mixture is stirred for 1~2 hours. The mixture is then dried to obtain acrylic acid modified rosin. The raw materials for the acrylic acid-modified rosin, by weight, are: 95-105 parts rosin, 0.1-0.3 parts 4,4'-thiobis(6-tert-butyl-3-methylphenol), 6-8 parts acrylic acid, 1-3 parts 4-allyl catechol, 0.04-0.06 parts hydroquinone methyl ether, 0.04-0.06 parts diethylene glycol monomethyl ether, 0.08-0.12 parts glycerol, and 10-20 parts sodium orthovanadate-ethanol solution.

10. An AlN copper-clad ceramic substrate prepared by a method for preparing a high-reliability AlN copper-clad ceramic substrate according to any one of claims 1 to 9.

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