Method for improving wettability of aluminum nitride copper clad substrate

Abstract

The application relates to the technical field of aluminum nitride copper-clad substrates, in particular to a method for improving the wettability of an aluminum nitride copper-clad substrate, which comprises the following steps: aluminum nitride ceramic pieces are laid on copper pieces which are cut and annealed, and are sent into a tunnel furnace to be evaporated together, the temperature of the tunnel furnace is controlled in 10 stages; the aluminum nitride ceramic pieces which are evaporated are put into a muffle furnace to be high-temperature oxidized, the aluminum nitride ceramic pieces which are treated by oxidation are cleaned, and then are subjected to copper-clad sintering, pattern transfer, etching, surface treatment, cutting and inspection in sequence. The method improves the copper-ceramic bonding force of the aluminum nitride copper-clad substrate, solves the interface air tightness defects caused by the oxide combination in the direct copper-clad method, and improves the yield of finished products.

Description

Technical Field

[0001] This invention relates to the field of aluminum nitride copper-clad substrate technology, specifically to a method for improving the wettability of aluminum nitride copper-clad substrates. Background Technology

[0002] Aluminum nitride (AlN) ceramics are ideal substrate materials for high-power electronic packaging due to their excellent thermal conductivity, low dielectric loss, and good insulation properties. However, in direct copper cladding (DBC) or active metal soldering (AMB) processes, the bonding strength and hermeticity between the copper layer and the aluminum nitride substrate are highly dependent on the interface wettability. Because of the strong chemical inertness of the aluminum nitride surface, the wetting angle of the molten copper (or solder) on its surface is large, leading to problems such as insufficient adhesion, micropores, and delamination after thermal cycling in traditional processes, which seriously affect the reliability and heat dissipation efficiency of power modules.

[0003] Currently, the mainstream methods for improving the wettability of aluminum nitride copper-clad substrates include:

[0004] Surface oxidation treatment: An Al2O3 transition layer is generated on the AlN surface by high-temperature oxidation (such as pre-oxidation in the DBC process), which improves the bonding by utilizing Cu-O-Al bonds. However, excessive oxidation will reduce thermal conductivity and introduce a brittle phase.

[0005] Active metal brazing (AMB): This method uses brazing filler metals containing active elements such as Ti and Zr (e.g., Ag-Cu-Ti) to generate a TiN / Al interface layer through reaction, which enhances the bonding. However, it is costly and has a narrow process window.

[0006] Surface metallization: Ni, Cr and other metal thin films are deposited on the AlN surface as a transition layer by magnetron sputtering or chemical plating, but there are problems such as uneven adhesion and increased process complexity.

[0007] The aforementioned methods all have significant limitations: oxidation and metallization may impair the intrinsic properties of the substrate, while the AMB process has stringent requirements for equipment and atmosphere control. Therefore, there is an urgent need to develop a low-cost, highly compatible method to significantly improve the wettability and bonding strength of the copper / AlN interface without sacrificing the thermal conductivity of aluminum nitride. Summary of the Invention

[0008] The purpose of this invention is to provide a method for improving the wettability of aluminum nitride copper-clad substrates, so as to solve the problems mentioned in the prior art.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] Step 1: Cut the copper sheet and then anneal it to obtain a pre-treated copper sheet;

[0011] Step 2: Lay the aluminum nitride ceramic sheet flat on the pretreated copper sheet and send them together into the tunnel furnace for vapor deposition. The temperature of the tunnel furnace is controlled in the following 10 stages: Stage 1 500~770℃, Stage 2 780~870℃, Stage 3 880~940℃, Stage 4 950~1050℃, Stage 5 950~1050℃, Stage 6 950~1050℃, Stage 7 850~950℃, Stage 8 740~950℃, Stage 9 740~950℃, Stage 10 740~950℃, to obtain the vapor-deposited aluminum nitride ceramic sheet;

[0012] Step 3: Place the vapor-deposited aluminum nitride ceramic sheet into a muffle furnace for high-temperature oxidation to obtain the oxidized aluminum nitride ceramic sheet;

[0013] Step 4: After cleaning the oxidized aluminum nitride ceramic sheet, perform the following processes in sequence: copper sintering, pattern transfer, etching, surface treatment, cutting, and inspection to obtain the finished product.

[0014] Furthermore, in step 1, the copper sheet is cut to a width of 120–150 mm and a length of 180–220 mm.

[0015] Furthermore, the preparation steps for the aluminum nitride ceramic sheet in step 2 are as follows:

[0016] 1) The aluminum nitride powder was vacuum dried. The dried aluminum nitride powder was weighed and added to a three-necked flask along with succinic acid and γ-methacryloxypropyltrimethoxysilane. Toluene was added as a reaction solvent. Under the protective condition of continuous nitrogen gas, the system was heated to react. After the reaction was completed, the system was cooled, the product was filtered and separated, and the product was washed 3 to 5 times with anhydrous ethanol. Finally, the washed product was dried to obtain modified aluminum nitride.

[0017] 2) Weigh and mix modified aluminum nitride, carbon powder, yttrium oxide and calcium oxide, add ethanol, mix by ball milling, and dry the ball-milled slurry to obtain dry powder;

[0018] 3) Pass the dried powder through an 80-mesh sieve, weigh the sieved powder and put it into a mold, press it into shape, prepare a blank, place the blank in a graphite furnace, and sinter it at high temperature under the protection of flowing nitrogen to obtain aluminum nitride ceramic sheets.

[0019] Furthermore, the aluminum nitride powder, succinic acid, γ-methacryloyloxypropyltrimethoxysilane and toluene described in 1) are mixed in a mass ratio of 2:0.2:0.1:30.

[0020] Furthermore, the vacuum drying conditions described in 1) are a temperature of 130–135°C and a time of 12–14 h; the system heating reaction conditions are a temperature of 110–120°C and a time of 12–13 h.

[0021] Furthermore, the cooling temperature of the system described in 1) is 20–25°C; the drying temperature is 60–65°C.

[0022] Furthermore, the modified aluminum nitride, carbon powder, yttrium oxide, calcium oxide and 75% ethanol described in 2) are mixed in a mass ratio of 93.5:0.5:5:1:200.

[0023] Furthermore, the ball milling process described in 2) has a mixing time of 24–26 h and a drying condition of 100–105 °C.

[0024] Furthermore, the pressing pressure described in 3) is 190-200 MPa, the sintering temperature is 1500-1800℃, and the time is 100-110 min.

[0025] Furthermore, the conditions for high-temperature oxidation in step 3 are: temperature controlled at 800–1200°C, and holding time of 1–5 hours.

[0026] Furthermore, the surface treatment steps described in step 4 are as follows:

[0027] The etched aluminum nitride copper-clad substrate is mechanically ground to remove surface impurities, then placed in a 20% sodium hydroxide aqueous solution for alkali washing for 10-15 seconds, rinsed with pure water, and then placed in a 40% nitric acid aqueous solution for acid washing for 90-100 seconds. Finally, it is rinsed with pure water to obtain an aluminum nitride aluminum-clad ceramic substrate.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. This invention proposes a method to improve the wettability of aluminum nitride copper-clad substrates. First, the copper sheet undergoes an annealing and oxidation pretreatment to form a stable oxide layer, improving the adhesion of subsequent vapor deposition and reducing interface defects. Then, the copper sheet and aluminum nitride ceramic sheet are fed together into a tunnel furnace for vapor deposition. This process is controlled by multiple stages of temperature: segmented heating from 500 to 1050°C to prevent cracking of the aluminum nitride ceramic sheet due to thermal stress and ensure uniform deposition of vapor deposition vapor; a high-temperature isothermal zone (950–1050°C) to promote copper layer densification, improving conductivity and adhesion; and slow cooling (740–950°C) to reduce thermal stress during cooling and prevent warping or breakage of the ceramic sheet. After vapor deposition, high-temperature oxidation is performed to form a dense oxide layer on the aluminum nitride surface, improving insulation and high-temperature resistance. Finally, copper sintering is performed to enhance the metal-ceramic interface adhesion.

[0030] 2. This invention proposes a method for improving the wettability of aluminum nitride copper-clad substrates, which involves modifying aluminum nitride powder with succinic acid and γ-methacryloxypropyltrimethoxysilane. Succinic acid introduces carboxyl groups (-COOH) into the aluminum nitride, improving its dispersibility and adsorbing copper ions (Cu). 2+ It promotes electroless plating; γ-methacryloxypropyltrimethoxysilane provides double bonds (C=C) and siloxane (-Si-O-) to modify aluminum nitride powder, which enhances the chemical bonding with the copper plating layer. Through the synergistic modification of succinic acid and γ-methacryloxypropyltrimethoxysilane, the interfacial bonding strength of aluminum nitride copper-clad substrate is significantly improved.

[0031] 3. This invention proposes a method to improve the wettability of aluminum nitride copper-clad substrates. During the sintering of aluminum nitride, sintering aids such as calcium oxide-yttrium oxide-carbon powder are added, which enhances the surface energy of aluminum nitride and improves its wettability to copper. The CaYAlO4 or Y3Al5O4 formed at the grain boundaries... 12 Phase optimization can improve interfacial chemical activity. Through synergistic modification with succinic acid and γ-methacryloyloxypropyltrimethoxysilane, the aluminum nitride copper-clad substrate interface with added sintering aids calcium oxide-yttrium oxide-carbon powder can achieve atomic-level wetting, thereby improving the wettability of the aluminum nitride copper-clad substrate. Detailed Implementation

[0032] 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.

[0033] In the following specific implementation,

[0034] Copper sheet: sourced from Fuchen (Tianjin) Chemical Reagent Co., Ltd.;

[0035] Aluminum nitride powder: Product number S44988, sourced from Shanghai Yuanye Biotechnology Co., Ltd.;

[0036] Succinic acid: Product number S30140, sourced from Shanghai Yuanye Biotechnology Co., Ltd.;

[0037] γ-Methacryloxypropyltrimethoxysilane: Product No. S15030, sourced from Shanghai Yuanye Biotechnology Co., Ltd.;

[0038] Toluene: Product number T477370, sourced from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0039] Nitrogen: Product number NRD003, sourced from Wuhan Newride Specialty Gases Co., Ltd.

[0040] Anhydrous ethanol: Product number E111992, sourced from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0041] Toner: Part number PA93193, sourced from Guangdong Wengjiang Chemical Reagent Co., Ltd.;

[0042] Yttrium oxide: Product number S24438, sourced from Shanghai Yuanye Biotechnology Co., Ltd.;

[0043] Calcium oxide: Product number W21520, sourced from Shanghai Yuanye Biotechnology Co., Ltd.;

[0044] 75% ethanol: Product number 80176961, sourced from Sinopharm Chemical Reagent Co., Ltd.

[0045] Example 1: A method for improving the wettability of aluminum nitride copper-clad substrates, comprising the following steps:

[0046] Step 1: Cut the copper sheet into a shape of 150mm (width) × 220mm (length), and perform annealing treatment to form a uniform oxide layer on the surface of the copper sheet, thus obtaining a pretreated copper sheet;

[0047] Step 2: Lay the aluminum nitride ceramic sheet (model: JRFT, from Shenzhen Jia Ri Feng Tai Electronic Technology Co., Ltd.) flat on the pretreated copper sheet and send them into the tunnel furnace for vapor deposition. The temperature of the tunnel furnace is controlled in 10 stages: Stage 1 770℃, Stage 2 870℃, Stage 3 940℃, Stage 4 1050℃, Stage 5 1050℃, Stage 6 1050℃, Stage 7 950℃, Stage 8 950℃, Stage 9 950℃, and Stage 10 950℃ to obtain the vapor-deposited aluminum nitride ceramic sheet.

[0048] Step 3: Place the vapor-deposited aluminum nitride ceramic sheet into a muffle furnace for high-temperature oxidation. The oxidation temperature is controlled at 1200℃ and the holding time is 5h to obtain the oxidized aluminum nitride ceramic sheet.

[0049] Step 4: After cleaning the anodized aluminum nitride ceramic sheet, perform the following processes in sequence: copper sintering, pattern transfer, etching, surface treatment, cutting, and inspection to obtain the finished product;

[0050] The surface treatment steps are as follows:

[0051] The etched aluminum nitride copper-clad substrate was mechanically ground to remove surface impurities, then placed in a 20% sodium hydroxide aqueous solution for alkali washing for 10 seconds, rinsed with pure water, and then placed in a 40% nitric acid aqueous solution for acid washing for 90 seconds. Finally, it was rinsed with pure water to obtain an aluminum nitride aluminum-clad ceramic substrate.

[0052] Example 2: A method for improving the wettability of aluminum nitride copper-clad substrates, comprising the following steps:

[0053] Step 1: Cut the copper sheet into a shape of 120mm (width) × 180mm (length), and perform annealing treatment to form a uniform oxide layer on the surface of the copper sheet, thus obtaining a pretreated copper sheet;

[0054] Step 2: Lay the aluminum nitride ceramic sheet flat on the pretreated copper sheet and send them together into the tunnel furnace for vapor deposition. The temperature of the tunnel furnace is controlled in the following 10 stages: Stage 1 500℃, Stage 2 780℃, Stage 3 880℃, Stage 4 950℃, Stage 5 950℃, Stage 6 950℃, Stage 7 850℃, Stage 8 740℃, Stage 9 740℃, Stage 10 740℃, to obtain the vapor-deposited aluminum nitride ceramic sheet.

[0055] Step 3: Place the vapor-deposited aluminum nitride ceramic sheet into a muffle furnace for high-temperature oxidation. The oxidation temperature is controlled at 800℃ and the holding time is 1 hour to obtain the oxidized aluminum nitride ceramic sheet.

[0056] Step 4: After cleaning the anodized aluminum nitride ceramic sheet, perform the following processes in sequence: copper sintering, pattern transfer, etching, surface treatment, cutting, and inspection to obtain the finished product;

[0057] The preparation steps of the aluminum nitride ceramic sheet are as follows:

[0058] 1) Place aluminum nitride powder in a vacuum drying oven and dry it at 130℃ for 12 hours. Weigh 10g of the dried aluminum nitride powder and add it together with 1g of succinic acid and 0.5g of γ-methacryloyloxypropyltrimethoxysilane into a three-necked flask. Add 150mL of toluene as a reaction solvent. Under the protection of continuous nitrogen gas, heat the reaction system to 110℃ and maintain the temperature for 12 hours. After the reaction is complete, cool the system to 20℃, filter to separate the product, and wash the product three times with anhydrous ethanol. Finally, dry the washed product in a vacuum drying oven at 60℃ to obtain modified aluminum nitride.

[0059] 2) Weigh 93.5g of modified aluminum nitride, 0.5g of carbon powder, 5g of yttrium oxide and 1g of calcium oxide and mix them together. Add 200mL of 75% ethanol as a dispersion medium and mix by ball milling for 24h to ensure uniform dispersion of the components. Place the ball-milled slurry in a vacuum drying oven and dry it at 100℃ until the solvent is completely removed to obtain dry powder.

[0060] 3) Pass the dried powder through an 80-mesh sieve, weigh the sieved powder and put it into a mold. Press it into shape under a pressure of 190MPa to prepare a blank. Place the blank in a graphite furnace and sinter it at high temperature under the protection of flowing nitrogen. The sintering temperature is controlled at 1500℃ and the holding time is set to 100min. After sintering, aluminum nitride ceramic sheet is obtained.

[0061] The surface treatment steps are as follows:

[0062] The etched aluminum nitride copper-clad substrate was mechanically ground to remove surface impurities, then placed in a 20% sodium hydroxide aqueous solution for alkali washing for 12 seconds, rinsed with pure water, and then placed in a 40% nitric acid aqueous solution for acid washing for 95 seconds. After rinsing with pure water, the aluminum nitride aluminum-clad ceramic substrate was obtained.

[0063] Example 3: A method for improving the wettability of aluminum nitride copper-clad substrates, comprising the following steps:

[0064] Step 1: Cut the copper sheet into a shape of 145mm (width) × 200mm (length), and perform annealing treatment to form a uniform oxide layer on the surface of the copper sheet, thus obtaining a pretreated copper sheet;

[0065] Step 2: Lay the aluminum nitride ceramic sheet flat on the pretreated copper sheet and send them together into the tunnel furnace for vapor deposition. The temperature of the tunnel furnace is controlled in the following 10 stages: Stage 1 635℃, Stage 2 825℃, Stage 3 910℃, Stage 4 1000℃, Stage 5 1000℃, Stage 6 1000℃, Stage 7 900℃, Stage 8 845℃, Stage 9 845℃, Stage 10 845℃, to obtain the vapor-deposited aluminum nitride ceramic sheet.

[0066] Step 3: Place the vapor-deposited aluminum nitride ceramic sheet into a muffle furnace for high-temperature oxidation. The oxidation temperature is controlled at 1000℃ and the holding time is 3h to obtain the oxidized aluminum nitride ceramic sheet.

[0067] Step 4: After cleaning the anodized aluminum nitride ceramic sheet, perform the following processes in sequence: copper sintering, pattern transfer, etching, surface treatment, cutting, and inspection to obtain the finished product;

[0068] The preparation steps of the aluminum nitride ceramic sheet are as follows:

[0069] 1) Place aluminum nitride powder in a vacuum drying oven and dry it at 133℃ for 13 hours. Weigh 10g of the dried aluminum nitride powder and add it together with 1g of succinic acid and 0.5g of γ-methacryloyloxypropyltrimethoxysilane into a three-necked flask. Add 150mL of toluene as a reaction solvent. Under the protection of continuous nitrogen gas, heat the reaction system to 115℃ and maintain the temperature for 12.5 hours. After the reaction is complete, cool the system to 23℃, filter to separate the product, and wash the product four times with anhydrous ethanol. Finally, dry the washed product in a vacuum drying oven at 63℃ to obtain modified aluminum nitride.

[0070] 2) Weigh 93.5g of modified aluminum nitride, 0.5g of carbon powder, 5g of yttrium oxide and 1g of calcium oxide and mix them together. Add 200mL of 75% ethanol as a dispersion medium and mix by ball milling for 25h to ensure uniform dispersion of the components. Place the ball-milled slurry in a vacuum drying oven and dry it at 103℃ until the solvent is completely removed to obtain dry powder.

[0071] 3) Pass the dried powder through an 80-mesh sieve, weigh the sieved powder and put it into a mold. Press it into shape under a pressure of 195MPa to prepare a blank. Place the blank in a graphite furnace and sinter it at high temperature under the protection of flowing nitrogen. The sintering temperature is controlled at 1600℃ and the holding time is set to 105min. After sintering, aluminum nitride ceramic sheet is obtained.

[0072] The surface treatment steps are as follows:

[0073] The etched aluminum nitride copper-clad substrate was mechanically ground to remove surface impurities, then placed in a 20% sodium hydroxide aqueous solution for alkali washing for 14 seconds, rinsed with pure water, and then placed in a 40% nitric acid aqueous solution for acid washing for 97 seconds. Finally, it was rinsed with pure water to obtain an aluminum nitride aluminum-clad ceramic substrate.

[0074] Example 4: A method for improving the wettability of aluminum nitride copper-clad substrates, comprising the following steps:

[0075] Step 1: Cut the copper sheet into a shape of 150mm (width) × 220mm (length), and perform annealing treatment to form a uniform oxide layer on the surface of the copper sheet, thus obtaining a pretreated copper sheet;

[0076] Step 2: Lay the aluminum nitride ceramic sheet flat on the pretreated copper sheet and send them together into the tunnel furnace for vapor deposition. The temperature of the tunnel furnace is controlled in the following 10 stages: Stage 1 770℃, Stage 2 870℃, Stage 3 940℃, Stage 4 1050℃, Stage 5 1050℃, Stage 6 1050℃, Stage 7 950℃, Stage 8 950℃, Stage 9 950℃, and Stage 10 950℃, to obtain the vapor-deposited aluminum nitride ceramic sheet.

[0077] Step 3: Place the vapor-deposited aluminum nitride ceramic sheet into a muffle furnace for high-temperature oxidation. The oxidation temperature is controlled at 1200℃ and the holding time is 5h to obtain the oxidized aluminum nitride ceramic sheet.

[0078] Step 4: After cleaning the anodized aluminum nitride ceramic sheet, perform the following processes in sequence: copper sintering, pattern transfer, etching, surface treatment, cutting, and inspection to obtain the finished product;

[0079] The preparation steps of the aluminum nitride ceramic sheet are as follows:

[0080] 1) Place aluminum nitride powder in a vacuum drying oven and dry it at 135℃ for 14 hours. Weigh 10g of the dried aluminum nitride powder and add it together with 1g of succinic acid and 0.5g of γ-methacryloyloxypropyltrimethoxysilane into a three-necked flask. Add 150mL of toluene as a reaction solvent. Under the protection of continuous nitrogen gas, heat the reaction system to 120℃ and maintain the constant temperature for 13 hours. After the reaction is completed, cool the system to 25℃, filter to separate the product, and wash the product 5 times with anhydrous ethanol. Finally, dry the washed product in a vacuum drying oven at 65℃ to obtain modified aluminum nitride.

[0081] 2) Weigh 93.5g of modified aluminum nitride, 0.5g of carbon powder, 5g of yttrium oxide and 1g of calcium oxide and mix them together. Add 200mL of 75% ethanol as a dispersion medium and mix by ball milling for 26h to ensure uniform dispersion of the components. Place the ball-milled slurry in a vacuum drying oven and dry it at 105℃ until the solvent is completely removed to obtain dry powder.

[0082] 3) Pass the dried powder through an 80-mesh sieve, weigh the sieved powder and put it into a mold. Press it into shape under a pressure of 200MPa to prepare a blank. Place the blank in a graphite furnace and sinter it at high temperature under the protection of flowing nitrogen. The sintering temperature is controlled at 1800℃ and the holding time is set to 110min. After sintering, aluminum nitride ceramic sheet is obtained.

[0083] The surface treatment steps are as follows:

[0084] The etched aluminum nitride copper-clad substrate was mechanically ground to remove surface impurities, then placed in a 20% sodium hydroxide aqueous solution for alkali washing for 15 seconds, rinsed with pure water, and then placed in a 40% nitric acid aqueous solution for acid washing for 100 seconds. Finally, it was rinsed with pure water to obtain an aluminum nitride aluminum-clad ceramic substrate.

[0085] Comparative Example 1: Compared to Example 1, the aluminum nitride ceramic sheet was not vapor-deposited.

[0086] Step 1: Cut the copper sheet into a shape of 150mm (width) × 220mm (length), and perform annealing treatment to form a uniform oxide layer on the surface of the copper sheet, thus obtaining a pretreated copper sheet;

[0087] Step 2: Place the aluminum nitride ceramic sheet into a muffle furnace for high-temperature oxidation. The oxidation temperature is controlled at 1200℃ and the holding time is 5h to obtain the oxidized aluminum nitride ceramic sheet.

[0088] Step 3: After cleaning, the aluminum nitride ceramic sheet after oxidation treatment is stacked together with the pretreated copper sheet and the following processes are carried out in sequence: copper sintering, pattern transfer, etching, surface treatment, cutting, and inspection to obtain the finished product;

[0089] The surface treatment steps are as follows:

[0090] The etched aluminum nitride copper-clad substrate was mechanically ground to remove surface impurities, then placed in a 20% sodium hydroxide aqueous solution for alkali washing for 10 seconds, rinsed with pure water, and then placed in a 40% nitric acid aqueous solution for acid washing for 90 seconds. Finally, it was rinsed with pure water to obtain an aluminum nitride aluminum-clad ceramic substrate.

[0091] Comparative Example 2: Compared with Example 1, the temperature control conditions for the 10 stages of aluminum nitride ceramic vapor deposition are different:

[0092] Step 1: Cut the copper sheet into a shape of 150mm (width) × 220mm (length), and perform annealing treatment to form a uniform oxide layer on the surface of the copper sheet, thus obtaining a pretreated copper sheet;

[0093] Step 2: Lay the aluminum nitride ceramic sheet flat on the pretreated copper sheet and send them together into the tunnel furnace for vapor deposition. The temperature of the tunnel furnace is controlled in 10 stages: Stage 1 400℃, Stage 2 600℃, Stage 3 700℃, Stage 4 850℃, Stage 5 850℃, Stage 6 850℃, Stage 7 750℃, Stage 8 640℃, Stage 9 640℃, Stage 10 640℃, to obtain the vapor-deposited aluminum nitride ceramic sheet.

[0094] Step 3: Place the vapor-deposited aluminum nitride ceramic sheet into a muffle furnace for high-temperature oxidation. The oxidation temperature is controlled at 1200℃ and the holding time is 5h to obtain the oxidized aluminum nitride ceramic sheet.

[0095] Step 4: After cleaning the anodized aluminum nitride ceramic sheet, perform the following processes in sequence: copper sintering, pattern transfer, etching, surface treatment, cutting, and inspection to obtain the finished product;

[0096] The surface treatment steps are as follows:

[0097] The etched aluminum nitride copper-clad substrate was mechanically ground to remove surface impurities, then placed in a 20% sodium hydroxide aqueous solution for alkali washing for 10 seconds, rinsed with pure water, and then placed in a 40% nitric acid aqueous solution for acid washing for 90 seconds. Finally, it was rinsed with pure water to obtain an aluminum nitride aluminum-clad ceramic substrate.

[0098] Comparative Example 3: The modified aluminum nitride powder in Example 4 was replaced with aluminum nitride powder:

[0099] Step 1: Cut the copper sheet into a shape of 150mm (width) × 220mm (length), and perform annealing treatment to form a uniform oxide layer on the surface of the copper sheet, thus obtaining a pretreated copper sheet;

[0100] Step 2: Lay the aluminum nitride ceramic sheet flat on the pretreated copper sheet and send them together into the tunnel furnace for vapor deposition. The temperature of the tunnel furnace is controlled in the following 10 stages: Stage 1 770℃, Stage 2 870℃, Stage 3 940℃, Stage 4 1050℃, Stage 5 1050℃, Stage 6 1050℃, Stage 7 950℃, Stage 8 950℃, Stage 9 950℃, and Stage 10 950℃, to obtain the vapor-deposited aluminum nitride ceramic sheet.

[0101] Step 3: Place the vapor-deposited aluminum nitride ceramic sheet into a muffle furnace for high-temperature oxidation. The oxidation temperature is controlled at 1200℃ and the holding time is 5h to obtain the oxidized aluminum nitride ceramic sheet.

[0102] Step 4: After cleaning the anodized aluminum nitride ceramic sheet, perform the following processes in sequence: copper sintering, pattern transfer, etching, surface treatment, cutting, and inspection to obtain the finished product;

[0103] The preparation steps of the aluminum nitride ceramic sheet are as follows:

[0104] 1) Weigh 93.5g of aluminum nitride powder, 0.5g of carbon powder, 5g of yttrium oxide and 1g of calcium oxide and mix them. Add 200mL of 75% ethanol as a dispersion medium and mix by ball milling for 26h to ensure uniform dispersion of the components. Place the ball-milled slurry in a vacuum drying oven and dry it at 105℃ until the solvent is completely removed to obtain dry powder.

[0105] 2) Pass the dried powder through an 80-mesh sieve, weigh the sieved powder and put it into a mold. Press it into shape under a pressure of 200MPa to prepare a blank. Place the blank in a graphite furnace and sinter it at high temperature under the protection of flowing nitrogen. The sintering temperature is controlled at 1800℃ and the holding time is set to 110min. After sintering, aluminum nitride ceramic sheet is obtained.

[0106] The surface treatment steps are as follows:

[0107] The etched aluminum nitride copper-clad substrate was mechanically ground to remove surface impurities, then placed in a 20% sodium hydroxide aqueous solution for alkali washing for 15 seconds, rinsed with pure water, and then placed in a 40% nitric acid aqueous solution for acid washing for 100 seconds. Finally, it was rinsed with pure water to obtain an aluminum nitride aluminum-clad ceramic substrate.

[0108] Experiment: Aluminum nitride copper-clad substrates obtained in Examples 1-4 and Comparative Examples 1-3 were used to prepare samples. The peel strength and yield were tested and the results were recorded.

[0109] Peel strength test: GB / T 13557-2017 was used as the reference standard, the sample size was 200mm×3.0mm, and the peel rate of the testing machine was 50mm / min;

[0110] Yield: 20 samples were taken from each example and comparative example. Products with no cracks and no visible pores were considered qualified.

[0111] All results are shown in Table 1.

[0112] Table 1

[0113] Test Project Peel strength N / mm Yield % Example 1 5.00 90％ Example 2 5.52 90％ Example 3 5.74 90％ Example 4 5.80 95％ Comparative Example 1 3.1 45％ Comparative Example 2 3.8 55％ Comparative Example 3 5.36 90％

[0114] According to the data in Table 1, the peel strength of the aluminum nitride copper-clad substrates prepared in Examples 1-4 is higher than that of the aluminum nitride copper-clad substrates prepared in Comparative Examples 1-2. This indicates that the method for improving the wettability of aluminum nitride copper-clad substrates proposed in this invention can improve the copper-ceramic bonding force and thus improve the peel strength of aluminum nitride copper-clad substrates. Moreover, the product yield under this method reaches 90%.

[0115] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process method article or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process method article or apparatus.

[0116] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for improving the wettability of aluminum nitride copper-clad substrates, characterized in that: Includes the following steps: Step 1: Cut the copper sheet and then anneal it to obtain a pre-treated copper sheet; Step 2: Lay the aluminum nitride ceramic sheet flat on the pretreated copper sheet and send them together into the tunnel furnace for vapor deposition. The temperature of the tunnel furnace is controlled in the following 10 stages: Stage 1 500~770℃, Stage 2 780~870℃, Stage 3 880~940℃, Stage 4 950~1050℃, Stage 5 950~1050℃, Stage 6 950~1050℃, Stage 7 850~950℃, Stage 8 740~950℃, Stage 9 740~950℃, Stage 10 740~950℃, to obtain the vapor-deposited aluminum nitride ceramic sheet; Step 3: Place the vapor-deposited aluminum nitride ceramic sheet into a muffle furnace for high-temperature oxidation to obtain the oxidized aluminum nitride ceramic sheet; Step 4: After cleaning the anodized aluminum nitride ceramic sheet, perform the following processes in sequence: copper sintering, pattern transfer, etching, surface treatment, cutting, and inspection to obtain the finished product; The preparation steps of the aluminum nitride ceramic sheet in step 2 are as follows: 1) The aluminum nitride powder was vacuum dried. The dried aluminum nitride powder was weighed and added to a three-necked flask along with succinic acid and γ-methacryloxypropyltrimethoxysilane. Toluene was added as a reaction solvent. Under the protective condition of continuous nitrogen gas, the system was heated to react. After the reaction was completed, the system was cooled, the product was filtered and separated, and the product was washed 3 to 5 times with anhydrous ethanol. Finally, the washed product was dried to obtain modified aluminum nitride. 2) Weigh and mix modified aluminum nitride, carbon powder, yttrium oxide and calcium oxide, add ethanol, mix by ball milling, and dry the ball-milled slurry to obtain dry powder; 3) Pass the dried powder through an 80-mesh sieve, weigh the sieved powder and put it into a mold, press it into shape, prepare a green blank, place the green blank in a graphite furnace, and sinter it at high temperature under the protection of flowing nitrogen to obtain aluminum nitride ceramic sheets. The aluminum nitride powder, succinic acid, γ-methacryloyloxypropyltrimethoxysilane, and toluene described in 1) are mixed in a mass ratio of 2:0.2:0.1:30; The modified aluminum nitride, carbon powder, yttrium oxide, calcium oxide and ethanol described in section 2) are mixed in a mass ratio of 93.5:0.5:5:1:

200.

2. The method for improving the wettability of aluminum nitride copper-clad substrate according to claim 1, characterized in that: In step 1, the copper sheet is cut to a width of 120~150mm and a length of 180~220mm.

3. The method for improving the wettability of aluminum nitride copper-clad substrates according to claim 1, characterized in that: The vacuum drying conditions described in 1) are a temperature of 130~135℃ and a time of 12~14h; the system heating reaction conditions are a temperature of 110~120℃ and a time of 12~13h.

4. The method for improving the wettability of aluminum nitride copper-clad substrate according to claim 1, characterized in that: The cooling temperature of the system described in 1) is 20~25℃; the drying temperature is 60~65℃.

5. The method for improving the wettability of aluminum nitride copper-clad substrate according to claim 1, characterized in that: The ball milling process described in section 2) involves a mixing time of 24-26 hours and a drying condition of 100-105°C.

6. The method for improving the wettability of aluminum nitride copper-clad substrate according to claim 1, characterized in that: The pressing pressure described in 3) is 190~200MPa, the sintering temperature is 1500~1800℃, and the time is 100~110min.

7. The method for improving the wettability of aluminum nitride copper-clad substrate according to claim 1, characterized in that: The conditions for high-temperature oxidation in step 3 are: temperature controlled at 800~1200℃, and holding time of 1~5h.