Thermal shock resistant ceramic circuit board and process for making same

Abstract

The application discloses a kind of heat shock resistant ceramic circuit board and its manufacturing process, to solve the problem of insufficient heat shock resistance of ceramic circuit board.The boron nitride coated silicon carbide whisker is used as the toughening phase of silicon nitride ceramic substrate, the grid-shaped micro-groove structure is etched on the surface of ceramic substrate by laser, the brazing paste with introduced rare earth elements is used, and the copper foil is vacuum brazed on the surface of etched silicon nitride ceramic substrate, so that the obtained ceramic silicon nitride ceramic circuit board has good interfacial bonding, good bending strength and heat shock resistance.

Description

Technical Field

[0001] This invention relates to the field of ceramic circuit boards, specifically to a thermal shock resistant ceramic circuit board and its manufacturing process. Background Technology

[0002] As semiconductor devices evolve towards higher power density and higher integration, the heat flux density generated within power modules also increases, placing more stringent demands on the heat dissipation capacity and thermal stability of circuit boards. Traditional circuit board materials are mostly organic resins, but due to their insufficient heat dissipation capacity and inherent defects such as aging and carbonization at high temperatures, they are no longer sufficient to meet the needs of next-generation semiconductor devices and are gradually being replaced by ceramic circuit boards. Compared to organic resin circuit boards, ceramic circuit boards, with their superior insulation properties, extremely high thermal conductivity, and excellent high-temperature stability, have gradually become the ideal carrier component for achieving high-density interconnection and efficient thermal management of electronic components.

[0003] Although ceramic circuit boards (PCBs) outperform organic resin substrates in thermal conductivity and heat dissipation, their thermal shock resistance and thermal stability still have some shortcomings in practical applications. Due to the difference in thermal expansion coefficients between the ceramic substrate and the copper layer, thermal stress concentration occurs at the ceramic-metal interface during repeated temperature cycles, easily inducing failure modes such as ceramic substrate cracking, metal circuit delamination, or interface delamination. Especially under thermal shock, pores on the surface of the ceramic PCB and internal glassy impurities become channels for rapid microcrack propagation, accelerating thermal aging and failure, leading to a sharp drop in thermal conductivity or even circuit breakage, seriously threatening the lifespan and safety of semiconductor components and equipment. Therefore, developing a ceramic PCB with excellent thermal shock resistance is of great significance for improving the integration and power density of semiconductor components and enhancing their thermal shock resistance and thermal stability. Summary of the Invention

[0004] To address the problem of insufficient thermal shock resistance in ceramic circuit boards, this invention provides a thermal shock resistant ceramic circuit board and its manufacturing process.

[0005] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows: A manufacturing process for a thermal shock resistant ceramic circuit board includes the following steps: S1: After activating silicon carbide whiskers in hydrochloric acid, they are embedded in a mixed system of boric acid and urea and sintered to obtain boron nitride coated silicon carbide whiskers. S2: Mix and ball-mill silicon nitride powder, boron nitride-coated silicon carbide whiskers, lanthanum oxide, aluminum oxide, polyvinyl butyral and dibutyl phthalate to obtain modified silicon nitride ceramic slurry; S3: Modified silicon nitride ceramic slurry is cast and then sintered to obtain a thermal shock resistant silicon nitride ceramic substrate; S4: Laser etching is used to process the surface of the heat-shock resistant silicon nitride ceramic substrate to form a grid-like micro-groove structure, resulting in a heat-resistant ceramic substrate with surface microgrooves. S5: Mix copper powder, tin powder, titanium dihydrogen powder, erbium powder, terpineol and ethyl cellulose to obtain a composite brazing paste, screen print it onto the surface of a heat-resistant ceramic substrate with microgrooves, cover it with copper foil and then vacuum braze it to obtain a heat-resistant copper-clad silicon nitride ceramic plate. S6: After laminating a film onto a heat-resistant copper-clad silicon nitride ceramic substrate, exposure, development, and etching are performed to obtain a heat-shock-resistant ceramic circuit board.

[0006] In a more optimized manner, the boron nitride-coated silicon carbide whiskers are prepared by the following process: Add silicon carbide whiskers to hydrochloric acid solution, stir evenly, ultrasonically disperse for 10-20 min, stir at 200-300 rpm for 1-2 h under water bath heating at 80-90℃, filter after stirring, wash with deionized water until the pH of the eluent is neutral, and vacuum dry at 80-90℃ for 6-8 h to obtain activated silicon carbide whiskers. Activated silicon carbide whiskers were spread evenly at the bottom of a crucible. Boric acid and urea were mixed, ground, and sieved. The sieved mixed powder was added to the crucible to completely cover the activated silicon carbide whiskers. The crucible was then transferred to a tube furnace and heated to 980-1000℃ under nitrogen protection and held for 1-2 hours. After holding, the temperature was further increased to 1780-1800℃ and held for 2-3 hours. After holding, the furnace was cooled to room temperature. The whiskers were removed from the crucible and added to an ethanol-deionized water solution with a volume ratio of 3:1. The mixture was ultrasonically cleaned for 10 minutes and then vacuum dried at 80℃ for 8 hours to obtain boron nitride-coated silicon carbide whiskers.

[0007] More preferably, the concentration of the hydrochloric acid solution is 2-2.5 mol / L; the mass ratio of activated silicon carbide whiskers, boric acid and urea is (1-2):(5-7):(15-20).

[0008] The silicon carbide whiskers were activated with hydrochloric acid to remove the silicon dioxide passivation layer on the surface of the silicon carbide whiskers and to increase the active sites on the silicon carbide whiskers for the deposition of the boron nitride coating layer. Subsequently, the activated whiskers were embedded in boric acid and urea. Under high temperature conditions, the boric acid and urea were thermally decomposed to form a three-dimensional ordered boron nitride coating layer structure. The coating layer and the silicon carbide whiskers were connected by chemical bonds. Silicon carbide whiskers play a toughening role in ceramic substrates. They dissipate fracture energy caused by thermal shock or mechanical impact through three energy dissipation mechanisms: crack bridging, crack deflection, and fiber pull-out, thus protecting the ceramic substrate and reducing the generation and propagation of cracks. After being coated with boron nitride, not only can the direct contact between silicon carbide whiskers and silicon nitride matrix be blocked, reducing high-temperature liquid phase corrosion, but also the stress relaxation effect can be used to reduce the shear stress caused by the mismatch of thermal expansion coefficients during thermal cycling and thermal shock through interlayer slip. This avoids the formation of microcracks and brittle fracture of silicon carbide whiskers due to stress concentration at the interface between the whiskers and the matrix, thereby enhancing the interface toughness, thermal shock resistance, and thermal cycling reliability of the ceramic substrate.

[0009] In a more optimized manner, the modified silicon nitride ceramic slurry is prepared by the following process: Polyvinyl butyral and dibutyl phthalate were added to anhydrous ethanol and stirred until homogeneous to obtain an additive mixture. Silicon nitride powder and boron nitride-coated silicon carbide whiskers were mixed evenly and added to a ball mill. The additive mixture was added, and the mixture was ball-milled at 200-300 rpm for 6-8 hours under nitrogen protection. After ball milling, lanthanum oxide and alumina were added, and ball milling continued for 3-5 hours. After ball milling, the material was discharged, and the liquid was ultrasonically dispersed for 10-20 minutes and then degassed under vacuum to obtain modified silicon nitride ceramic slurry.

[0010] In a more optimized manner, the modified silicon nitride ceramic slurry comprises, by weight, 80-90 parts silicon nitride powder, 4-8 parts boron nitride-coated silicon carbide whiskers, 4-6 parts lanthanum oxide, 2-4 parts alumina, 3-5 parts polyvinyl butyral and 2-4 parts dibutyl phthalate.

[0011] Lanthanum oxide, as the primary sintering aid, utilizes the large ionic radius of lanthanum ions. During sintering, these ions segregate at the grain boundaries of β-silicon nitride, inhibiting excessive grain growth and maintaining a suitable aspect ratio for the columnar β-silicon nitride structure, thus enhancing the toughness of the silicon nitride ceramic substrate. Alumina, as an auxiliary sintering aid, can partially replace ions in the β-silicon nitride lattice, lowering the energy barrier for β-phase precipitation. This allows for a more complete transformation of silicon nitride from the α-phase to the β-phase, enhancing the high-temperature strength, thermal shock resistance, and thermal cycling stability of the ceramic substrate.

[0012] The process parameters for tape casting include a doctor blade gap of 200-300μm, a drying temperature of 80-90℃, and a drying time of 10-12h.

[0013] In a more optimized manner, the sintering process in S3 adopts a gradient heating sintering method, wherein the vacuum is evacuated to 1-5 Pa, the sintering temperature is 300-320℃, the heating rate is 5-7℃ / min, and the holding time is 2-3h during the first sintering. The sintering temperature for the second sintering is 600-620℃, the heating rate is 2-4℃ / min, and the holding time is 3-4h. During the third sintering, nitrogen gas is introduced at a pressure of 2-4 MPa, the sintering temperature is 1580-1600℃, the heating rate is 8-10℃ / min, and the holding time is 2-3h. The sintering temperature for the fourth sintering is 1850-1870℃, the heating rate is 3-5℃ / min, and the holding time is 1-3h.

[0014] In a more optimized manner, the laser etching process parameters include a laser wavelength of 1064nm, a scanning speed of 80-100mm / s, a laser power of 10-15W, a single trench width of 20-30μm, a spacing between adjacent trenches of 50-90μm, and a trench depth of 5-10μm.

[0015] Before laser etching, the heat-shock resistant silicon nitride ceramic substrate was ultrasonically cleaned sequentially with acetone and anhydrous ethanol, with each cleaning session lasting 10-15 minutes. Laser etching was performed under argon protection.

[0016] Laser etching is used to create a grid-like microgroove on the surface of a silicon nitride ceramic substrate. This not only breaks the stress transmission path at the large-area continuous interface between the silicon nitride ceramic substrate and the metal, but also confines the shear stress generated during thermal shock and thermal cycling to a single or a few grid cells, preventing stress accumulation and crack propagation across different areas, thus enhancing the toughness, thermal shock resistance, and thermal cycling stability of the ceramic substrate. Simultaneously, the trench structure is filled with solder paste during subsequent brazing, forming a mechanical interlocking structure between the solder layer and the ceramic substrate, significantly improving the interfacial bonding strength and enhancing the thermal shock resistance and peel resistance of the ceramic circuit board.

[0017] In a more optimized manner, the composite solder paste comprises, by weight, 60-70 parts copper powder, 20-24 parts tin powder, 10-14 parts titanium dihydrogen phosphate powder, 0.5-0.7 parts erbium powder, 80-90 parts terpineol and 10-14 parts ethyl cellulose.

[0018] In the solder paste, copper powder serves as the structural matrix, forming conductive and thermally conductive pathways during the brazing process. Tin powder, as a low-melting-point component, lowers the overall melting point of the solder paste while simultaneously enhancing the wettability of the active metal components on the ceramic substrate. During brazing, titanium atoms released from the decomposition of titanium dihydrogen nitride preferentially segregate towards the silicon nitride interface, reacting with the silicon nitride ceramic components to form a continuous TiN / Ti5Si3 reaction layer. This achieves a metallurgical bond between ceramic and metal, enhancing the interfacial bonding strength and the thermal cycling stability of the ceramic plate. The addition of trace amounts of erbium not only further removes residual oxides at the interface through a purification effect but also significantly refines the grain size of the TiN reaction layer through a solute dragging mechanism, inhibiting the coarse growth of brittle intermetallic compounds and enhancing the toughness and thermal cycling stability of the ceramic plate.

[0019] After covering with copper foil, apply a pre-tightening pressure of 0.5-1 MPa to the whole, heat to 25-270℃ and keep warm for 0.5-1.5 hours.

[0020] In a more optimized manner, during the vacuum brazing, ultrasonic-assisted brazing is employed. The brazing process parameters include a vacuum degree of 0.001-0.01 Pa, an ultrasonic-assisted brazing temperature of 410-430℃, an ultrasonic frequency of 20kHz, an ultrasonic power of 200-240W, and an ultrasonic time of 2-3 min. After the ultrasonic treatment, the temperature is further increased to 850-900℃, and the holding time is 60-90 min.

[0021] Before high-temperature brazing at 850-900℃, ultrasonic-assisted treatment at 410-430℃ is performed. Utilizing the ultrasonic cavitation effect, the oxide film on the copper foil and ceramic surface is physically broken down, while simultaneously enhancing the wettability of the brazing system. Furthermore, the mechanical vibration of ultrasound accelerates the decomposition of titanium dihydrogen hydride, resulting in a more complete and uniform release and distribution of active titanium atoms. This promotes the formation of a more uniform and dense reaction layer during the high-temperature brazing stage, significantly reducing interfacial thermal mismatch stress concentration, enhancing the shear strength at the interface, and improving the thermal shock resistance and thermal cycling stability of the ceramic plate.

[0022] A thermal shock resistant ceramic circuit board, manufactured using any of the above-described manufacturing processes.

[0023] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention employs boron nitride-coated silicon carbide whiskers as a toughening phase for silicon nitride ceramic substrates. The whiskers dissipate fracture energy induced during thermal shock or mechanical impact through three energy-dissipating mechanisms: crack bridging, crack deflection, and fiber pull-out, thus protecting the ceramic substrate and reducing the generation and propagation of cracks within it. The surface boron nitride also reduces shear stress caused by thermal expansion coefficient mismatch during thermal cycling and thermal shock through stress relaxation, utilizing interlayer slip. This prevents microcracks and brittle fracture of silicon carbide whiskers at the whisker-substrate interface due to stress concentration, thereby enhancing the interface toughness, thermal shock resistance, and thermal cycling reliability of the ceramic substrate.

[0024] 2. This invention employs laser etching to create a mesh-like microgroove structure on a ceramic substrate, breaking the stress transmission path of a large-area continuous interface and enhancing the toughness, thermal shock resistance, and thermal cycling stability of the ceramic substrate. Simultaneously, the trench structure also strengthens the interfacial bonding between the solder layer and the ceramic substrate, enhancing the thermal shock resistance and peel resistance of the ceramic circuit board.

[0025] 3. The present invention introduces the rare earth element erbium into the brazing paste, which can not only further remove residual oxides at the interface through the purification effect, but also significantly refine the grain size of the TiN reaction layer through the solute dragging mechanism, inhibit the coarse growth of brittle intermetallic compounds, and enhance the toughness and thermal cycling stability of the ceramic plate.

[0026] 4. This invention employs ultrasonic-assisted brazing, utilizing the ultrasonic cavitation effect to physically break down the oxide film on the copper foil and ceramic surface, while simultaneously enhancing the wettability of the brazing system. Furthermore, the mechanical vibration of ultrasound accelerates the decomposition of titanium dihydrogen hydride, resulting in a more complete and uniform release and distribution of active titanium atoms. This promotes the formation of a more uniform and dense reaction layer during the high-temperature brazing stage, significantly reducing interfacial thermal mismatch stress concentration, enhancing the shear strength at the interface, and improving the thermal shock resistance and thermal cycling stability of the ceramic plate. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention are described in detail below. It is understood that the described embodiments are only a part of the embodiments of the present invention, and not all of them. The dosages in the embodiments are all small-scale laboratory tests and can be scaled up proportionally. Based on the embodiments disclosed in this invention, all other equivalent embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0028] In the following examples and comparative examples, the silicon carbide whiskers are cubic β-SiC with a length of 20 μm, a diameter of 1 μm, and an aspect ratio of 20; the silicon nitride powder is hexagonal α-Si3N4 with a purity >99.9% and a particle size of 1 μm; the lanthanum oxide has a purity >99.99% and a particle size of 1 μm; the aluminum oxide has a purity >99.99% and a particle size of 1 μm; the copper powder has a purity >99.99% and a particle size of 5 μm; the tin powder has a purity >99.9% and a particle size of 5 μm; the titanium dihydrogen phosphate powder has a purity >99.5% and a particle size of 3 μm; the erbium powder has a purity >99.9% and a particle size of 1 μm; and the copper foil is oxygen-free copper C1020 with a purity >99.95% and a thickness of 0.3 mm.

[0029] Example 1: A manufacturing process for a thermal shock resistant ceramic circuit board, specifically as follows: S1: Add 10g of silicon carbide whiskers to 200mL of 2.5mol / L hydrochloric acid solution, stir evenly, sonicate for 10min, stir at 200rpm for 1.5h under 90℃ water bath heating conditions, filter after stirring, wash with deionized water until the pH of the eluent is neutral, and vacuum dry at 80℃ for 8h to obtain activated silicon carbide whiskers. S2: Spread 10g of activated silicon carbide whiskers evenly at the bottom of the crucible. Mix and grind 50g of boric acid and 150g of urea, and pass through a 200-mesh sieve. Add the sieved mixed powder to the crucible to completely cover the activated silicon carbide whiskers. Then transfer the crucible to a tube furnace and heat it to 1000℃ under nitrogen protection and hold it for 1 hour. After holding, continue to heat it to 1800℃ and hold it for 2 hours. After holding, cool it to room temperature with the furnace. Take out the whiskers from the crucible and add them to an ethanol-water solution with a volume ratio of 3:1 of ethanol and deionized water. Clean them with ultrasonication for 10 minutes. After cleaning, dry them under vacuum at 80℃ for 8 hours to obtain boron nitride coated silicon carbide whiskers. S3: Add 3g of polyvinyl butyral and 2g of dibutyl phthalate to 100mL of anhydrous ethanol and stir evenly to obtain an additive mixture. Mix 93g of silicon nitride powder and 4g of boron nitride-coated silicon carbide whiskers evenly and add them to a ball mill. Add the additive mixture and ball mill at 250rpm for 6h under nitrogen protection. After ball milling, add 4g of lanthanum oxide and 2g of aluminum oxide and continue ball milling for 4h. After ball milling, discharge the material and ultrasonically disperse the liquid for 15min, then degas under vacuum to obtain modified silicon nitride ceramic slurry. S4: The modified silicon nitride ceramic slurry is added to the casting machine for casting. The doctor blade gap is set to 250 μm, the drying temperature is set to 80℃, and the drying time is set to 12 h to obtain a ceramic green body. The green body is placed in a vacuum sintering furnace, and the vacuum is evacuated to 5 Pa. The temperature is increased to 300℃ at a heating rate of 5℃ / min and held for 2 h. After the holding time, the temperature is increased to 600℃ at a heating rate of 2℃ / min and held for 4 h. After the holding time, nitrogen gas is introduced and the nitrogen pressure is set to 2 MPa. The temperature is increased to 1600℃ at a heating rate of 10℃ / min and held for 2 h. After the holding time, the temperature is increased to 1850℃ at a heating rate of 5℃ / min and held for 1 h. After the holding time, the temperature is cooled to room temperature with the furnace to obtain a heat-shock resistant silicon nitride ceramic substrate. S5: The heat-shock resistant silicon nitride ceramic substrate was sequentially placed in acetone and anhydrous ethanol for ultrasonic cleaning, with each cleaning time set to 15 min. After cleaning, it was vacuum dried at 80℃ for 6 h. Then, under argon protection, a grid-like microgroove structure was formed on the surface of the ceramic substrate by laser etching. The laser wavelength was set to 1064 nm, the scanning speed to 100 mm / s, the laser power to 10 W, the width of a single trench to 20 μm, the spacing between adjacent trenches to 50 μm, and the trench depth to 10 μm. After etching, the substrate was removed to obtain a heat-resistant ceramic substrate with surface microgrooves. S6: Mix 69.5g copper powder, 20g tin powder, 10g titanium dihydrogen powder and 0.5g erbium powder evenly, add to a ball mill, add 80g terpineol and 10g ethyl cellulose, ball mill at 250rpm for 3h to obtain composite brazing paste, screen print the composite brazing paste onto the surface of the microgroove heat-resistant ceramic substrate, then cover the composite brazing paste with copper foil and apply a pre-tightening pressure of 0.5MPa, heat to 200℃ and vacuum dry for 30min, after drying, transfer to a vacuum brazing device, set the vacuum degree to 0.01Pa, heat to 430℃, start the ultrasonic auxiliary device, set the frequency to 20kHz, the power to 240W, the ultrasonic time to 3min, after ultrasonication, continue to heat to 870℃ and hold for 70min, after brazing, cool to room temperature to obtain a heat-resistant copper-clad silicon nitride ceramic plate; S7: After laminating a film onto a heat-resistant copper-clad silicon nitride ceramic substrate, exposure, development, and etching are performed to obtain a heat-shock-resistant ceramic circuit board.

[0030] Example 2: A manufacturing process for a thermal shock resistant ceramic circuit board, specifically as follows: S1: Add 15g of silicon carbide whiskers to 200mL of 2.5mol / L hydrochloric acid solution, stir evenly, sonicate for 10min, stir at 200rpm for 1.5h under 90℃ water bath heating conditions, filter after stirring, wash with deionized water until the pH of the eluent is neutral, and vacuum dry at 80℃ for 8h to obtain activated silicon carbide whiskers. S2: Spread 15g of activated silicon carbide whiskers evenly at the bottom of the crucible. Mix and grind 60g of boric acid and 160g of urea, and pass through a 200-mesh sieve. Add the sieved mixed powder to the crucible to completely cover the activated silicon carbide whiskers. Then transfer the crucible to a tube furnace and heat it to 1000℃ under nitrogen protection and hold it for 1 hour. After holding, continue to heat it to 1800℃ and hold it for 2 hours. After holding, cool it to room temperature with the furnace. Take out the whiskers from the crucible and add them to an ethanol-water solution with a volume ratio of 3:1 of ethanol and deionized water. Clean them with ultrasonication for 10 minutes. After cleaning, vacuum dry them at 80℃ for 8 hours to obtain boron nitride coated silicon carbide whiskers. S3: Add 4g of polyvinyl butyral and 3g of dibutyl phthalate to 100mL of anhydrous ethanol and stir evenly to obtain an additive mixture. Mix 91g of silicon nitride powder and 6g of boron nitride-coated silicon carbide whiskers evenly and add them to a ball mill. Add the additive mixture and ball mill at 250rpm for 6h under nitrogen protection. After ball milling, add 5g of lanthanum oxide and 3g of aluminum oxide and continue ball milling for 4h. After ball milling, discharge the material and ultrasonically disperse the liquid for 15min, then degas under vacuum to obtain modified silicon nitride ceramic slurry. S4: The modified silicon nitride ceramic slurry is added to the casting machine for casting. The doctor blade gap is set to 250 μm, the drying temperature is set to 80℃, and the drying time is set to 12 h to obtain a ceramic green body. The green body is placed in a vacuum sintering furnace, and the vacuum is evacuated to 5 Pa. The temperature is increased to 300℃ at a heating rate of 5℃ / min and held for 2 h. After the holding time, the temperature is increased to 600℃ at a heating rate of 2℃ / min and held for 4 h. After the holding time, nitrogen gas is introduced and the nitrogen pressure is set to 2 MPa. The temperature is increased to 1600℃ at a heating rate of 10℃ / min and held for 2 h. After the holding time, the temperature is increased to 1850℃ at a heating rate of 5℃ / min and held for 1 h. After the holding time, the temperature is cooled to room temperature with the furnace to obtain a heat-shock resistant silicon nitride ceramic substrate. S5: The heat-shock resistant silicon nitride ceramic substrate was sequentially placed in acetone and anhydrous ethanol for ultrasonic cleaning, with each cleaning time set to 15 min. After cleaning, it was vacuum dried at 80℃ for 6 h. Then, under argon protection, a grid-like microgroove structure was formed on the surface of the ceramic substrate by laser etching. The laser wavelength was set to 1064 nm, the scanning speed to 100 mm / s, the laser power to 10 W, the width of a single trench to 25 μm, the spacing between adjacent trenches to 75 μm, and the trench depth to 10 μm. After etching, the substrate was removed to obtain a heat-resistant ceramic substrate with surface microgrooves. S6: Mix 65.4g copper powder, 22g tin powder, 12g titanium dihydrogen powder and 0.6g erbium powder evenly, add to a ball mill, add 85g terpineol and 12g ethyl cellulose, ball mill at 250rpm for 3h to obtain composite brazing paste, screen print the composite brazing paste onto the surface of the microgroove heat-resistant ceramic substrate, then cover the composite brazing paste with copper foil and apply a pre-tightening pressure of 0.5MPa, heat to 200℃ and vacuum dry for 30min, after drying, transfer to a vacuum brazing device, set the vacuum degree to 0.01Pa, heat to 430℃, start the ultrasonic auxiliary device, set the frequency to 20kHz, the power to 240W, the ultrasonic time to 3min, after ultrasonication, continue to heat to 870℃ and hold for 70min, after brazing, cool to room temperature to obtain a heat-resistant copper-clad silicon nitride ceramic plate; S7: After laminating a film onto a heat-resistant copper-clad silicon nitride ceramic substrate, exposure, development, and etching are performed to obtain a heat-shock-resistant ceramic circuit board.

[0031] Example 3: A manufacturing process for a thermal shock resistant ceramic circuit board, specifically as follows: S1: Add 20g of silicon carbide whiskers to 200mL of 2.5mol / L hydrochloric acid solution, stir evenly, sonicate for 10min, stir at 200rpm for 1.5h under 90℃ water bath heating conditions, filter after stirring, wash with deionized water until the pH of the eluent is neutral, and vacuum dry at 80℃ for 8h to obtain activated silicon carbide whiskers. S2: Spread 20g of activated silicon carbide whiskers evenly at the bottom of the crucible. Mix and grind 70g of boric acid and 170g of urea, and pass through a 200-mesh sieve. Add the sieved mixed powder to the crucible to completely cover the activated silicon carbide whiskers. Then transfer the crucible to a tube furnace and heat it to 1000℃ under nitrogen protection and hold it for 1 hour. After holding, continue to heat it to 1800℃ and hold it for 2 hours. After holding, cool it to room temperature with the furnace. Take out the whiskers from the crucible and add them to an ethanol-water solution with a volume ratio of 3:1 of ethanol and deionized water. Clean them with ultrasonication for 10 minutes. After cleaning, vacuum dry them at 80℃ for 8 hours to obtain boron nitride coated silicon carbide whiskers. S3: Add 5g of polyvinyl butyral and 4g of dibutyl phthalate to 100mL of anhydrous ethanol and stir evenly to obtain an additive mixture. Mix 89g of silicon nitride powder and 8g of boron nitride-coated silicon carbide whiskers evenly and add them to a ball mill. Add the additive mixture and ball mill at 250rpm for 6h under nitrogen protection. After ball milling, add 6g of lanthanum oxide and 4g of aluminum oxide and continue ball milling for 4h. After ball milling, discharge the material and ultrasonically disperse the liquid for 15min, then degas under vacuum to obtain modified silicon nitride ceramic slurry. S4: The modified silicon nitride ceramic slurry is added to the casting machine for casting. The doctor blade gap is set to 250 μm, the drying temperature is set to 80℃, and the drying time is set to 12 h to obtain a ceramic green body. The green body is placed in a vacuum sintering furnace, and the vacuum is evacuated to 5 Pa. The temperature is increased to 300℃ at a heating rate of 5℃ / min and held for 2 h. After the holding time, the temperature is increased to 600℃ at a heating rate of 2℃ / min and held for 4 h. After the holding time, nitrogen gas is introduced and the nitrogen pressure is set to 2 MPa. The temperature is increased to 1600℃ at a heating rate of 10℃ / min and held for 2 h. After the holding time, the temperature is increased to 1850℃ at a heating rate of 5℃ / min and held for 1 h. After the holding time, the temperature is cooled to room temperature with the furnace to obtain a heat-shock resistant silicon nitride ceramic substrate. S5: The heat-shock resistant silicon nitride ceramic substrate was sequentially placed in acetone and anhydrous ethanol for ultrasonic cleaning, with each cleaning time set to 15 min. After cleaning, it was vacuum dried at 80℃ for 6 h. Subsequently, under argon protection, a grid-like microgroove structure was formed on the surface of the ceramic substrate by laser etching. The laser wavelength was set to 1064 nm, the scanning speed to 100 mm / s, the laser power to 10 W, the width of a single trench to 30 μm, the spacing between adjacent trenches to 80 μm, and the trench depth to 10 μm. After etching, the substrate was removed to obtain a heat-resistant ceramic substrate with surface microgrooves. S6: Mix 61.3g copper powder, 24g tin powder, 14g titanium dihydrogen powder and 0.7g erbium powder evenly, add to a ball mill, add 90g terpineol and 14g ethyl cellulose, ball mill at 250rpm for 3h to obtain composite brazing paste, screen print the composite brazing paste onto the surface of the microgroove heat-resistant ceramic substrate, then cover the composite brazing paste with copper foil and apply a pre-tightening pressure of 0.5MPa, heat to 200℃ and vacuum dry for 30min, after drying, transfer to a vacuum brazing device, set the vacuum degree to 0.01Pa, heat to 430℃, start the ultrasonic auxiliary device, set the frequency to 20kHz, the power to 240W, the ultrasonic time to 3min, after ultrasonication, continue to heat to 870℃ and hold for 70min, after brazing, cool to room temperature to obtain a heat-resistant copper-coated silicon nitride ceramic plate; S7: After laminating a film onto a heat-resistant copper-clad silicon nitride ceramic substrate, exposure, development, and etching are performed to obtain a heat-shock-resistant ceramic circuit board.

[0032] Comparative Examples 1-3 are technical solutions based on Example 1, as detailed below: Comparative Example 1: This comparative example relates to a thermal shock resistant ceramic circuit board. The difference between this process and Example 1 is that boron nitride-coated silicon carbide whiskers are not added. Specifically: S1: Add 3g of polyvinyl butyral and 2g of dibutyl phthalate to 100mL of anhydrous ethanol and stir evenly to obtain an additive mixture. Add 94g of silicon nitride powder to a ball mill, add the additive mixture, and ball mill at 250rpm for 6h under nitrogen protection. After ball milling, add 4g of lanthanum oxide and 2g of aluminum oxide, and continue ball milling for 4h. After ball milling, discharge the material, ultrasonically disperse the liquid for 15min, and then degas under vacuum to obtain silicon nitride ceramic slurry. S2: Add silicon nitride ceramic slurry into a casting machine for casting. Set the doctor blade gap to 250μm, the drying temperature to 80℃, and the drying time to 12h to obtain a ceramic green body. Place it in a vacuum sintering furnace, evacuate to 5Pa, heat to 300℃ at a heating rate of 5℃ / min and hold for 2h. After holding, heat to 600℃ at a heating rate of 2℃ / min and hold for 4h. After holding, introduce nitrogen gas, set the nitrogen pressure to 2MPa, heat to 1600℃ at a heating rate of 10℃ / min and hold for 2h. After holding, heat to 1850℃ at a heating rate of 5℃ / min and hold for 1h. After holding, cool to room temperature with the furnace to obtain a heat-shock resistant silicon nitride ceramic substrate. The subsequent manufacturing process is the same as in Example 1, resulting in a ceramic circuit board resistant to thermal shock.

[0033] Comparative Example 2: This comparative example relates to a thermal shock resistant ceramic circuit board. The difference between this process and Example 1 is that a microgroove structure was not laser-etched on the thermal shock resistant silicon nitride ceramic substrate. Specifically: S1: Mix 69.5g copper powder, 20g tin powder, 10g titanium dihydrogen powder and 0.5g erbium powder evenly, add to a ball mill, add 80g terpineol and 10g ethyl cellulose, ball mill at 250rpm for 3h to obtain composite brazing paste, screen print the composite brazing paste onto the surface of heat-shock resistant silicon nitride ceramic substrate, then cover the composite brazing paste with copper foil and apply a pre-tightening pressure of 0.5MPa, heat to 200℃ and vacuum dry for 30min, after drying, transfer to a vacuum brazing device, set the vacuum degree to 0.01Pa, heat to 430℃, start the ultrasonic auxiliary device, set the frequency to 20kHz, the power to 240W, the ultrasonic time to 3min, after ultrasonication, continue to heat to 870℃ and hold for 70min, after brazing, cool to room temperature to obtain heat-resistant copper-clad silicon nitride ceramic plate; S2: After laminating a film onto a heat-resistant copper-clad silicon nitride ceramic substrate, exposing and developing it, followed by etching, a heat-shock-resistant ceramic circuit board is obtained. The fabrication process of the heat-shock resistant silicon nitride ceramic substrate is the same as that in Example 1.

[0034] Comparative Example 3: This comparative example relates to a thermal shock resistant ceramic circuit board. The difference between this process and Example 1 is that erbium powder is not added to the composite solder paste. Specifically: S1: Mix 70g copper powder, 20g tin powder and 10g titanium dihydrogen powder evenly, add to a ball mill, add 80g terpineol and 10g ethyl cellulose, ball mill at 250rpm for 3h to obtain composite brazing paste, screen print the composite brazing paste onto the surface of the microgroove heat-resistant ceramic substrate, then cover the composite brazing paste with copper foil and apply a pre-tightening pressure of 0.5MPa, heat to 200℃ and vacuum dry for 30min, after drying, transfer to a vacuum brazing device, set the vacuum degree to 0.01Pa, heat to 430℃, start the ultrasonic auxiliary device, set the frequency to 20kHz, the power to 240W, the ultrasonic time to 3min, after ultrasonication, continue to heat to 870℃ and hold for 70min, after brazing, cool to room temperature to obtain a heat-resistant copper-clad silicon nitride ceramic plate; S2: After laminating a film onto a heat-resistant copper-clad silicon nitride ceramic substrate, exposing and developing it, followed by etching, a heat-shock-resistant ceramic circuit board is obtained. The fabrication process of the surface microgroove heat-resistant ceramic substrate is the same as that in Example 1.

[0035] Test method: Thermal shock resistant ceramic circuit boards were manufactured according to the manufacturing processes of each embodiment and comparative example, and the following tests were conducted.

[0036] Bending strength test: Refer to the "Test Method for Strength of Ceramic Materials" (GB / T 4740-2024) and use a universal testing machine to test the bending strength of the ceramic circuit board. The sample size is 36mm×4mm×3mm and the loading rate of the testing machine is 0.5mm / min.

[0037] Adhesion test: The peel strength of the ceramic circuit board was tested using a 90° peel strength tester with a sample size of 250mm×50mm×2mm, a peel angle of 90° and a peel speed of 0.5mm / min.

[0038] Thermal shock resistance test: The test was conducted using a high and low temperature cycling test chamber. The sample size was 250mm×50mm×2mm. First, the sample was cooled to -50℃ and held for 15 minutes. Then, it was heated to 150℃ within 5 minutes and held for 15 minutes. After that, it was cooled to -50℃ within 5 minutes. The total number of cycles was 2000. After every 50 cycles, the sample surface was observed with a metallographic microscope to see if cracks or peeling occurred at the edges. The number of times the first crack or peeling occurred was recorded.

[0039] Conclusion: The test results show that, compared with Example 1, the ceramic circuit board substrate in Comparative Example 1 did not contain boron nitride-coated silicon carbide whiskers, which affected the toughness and thermal shock resistance of the ceramic substrate, resulting in a decrease in the overall bending strength and thermal shock resistance of the circuit board. In Comparative Example 2, the lack of laser etching of microgrooves on the ceramic substrate resulted in the lowest overall peel strength of the circuit board. In Comparative Example 3, the absence of erbium powder in the composite brazing paste negatively impacted the peel strength and thermal shock resistance of the circuit board. The thermal shock resistant ceramic circuit board provided by this invention exhibits good interfacial bonding and excellent bending strength and thermal shock resistance.

[0040] Those skilled in the art should understand that the present invention is not limited to the details of the exemplary embodiments described above. Other specific embodiments may be adopted without departing from the spirit and essential characteristics of the invention. Therefore, the above embodiments should be considered exemplary only and not restrictive, and the scope of protection of the present invention is defined by the appended claims, not by the foregoing description. All changes within the meaning and scope of the claims and their equivalents should be covered within the scope of protection of the present invention.

Claims

1. A manufacturing process for a thermal shock resistant ceramic circuit board, characterized in that: Includes the following steps: S1: After activating silicon carbide whiskers with hydrochloric acid, they are embedded in a mixed system of boric acid and urea and sintered to obtain boron nitride coated silicon carbide whiskers. S2: Mix and ball-mill silicon nitride powder, boron nitride-coated silicon carbide whiskers, lanthanum oxide, aluminum oxide, polyvinyl butyral and dibutyl phthalate to obtain modified silicon nitride ceramic slurry; S3: Modified silicon nitride ceramic slurry is cast and then sintered to obtain a thermal shock resistant silicon nitride ceramic substrate; S4: Laser etching is used to process the surface of the heat-shock resistant silicon nitride ceramic substrate to form a grid-like micro-groove structure, resulting in a heat-resistant ceramic substrate with surface microgrooves. S5: Mix copper powder, tin powder, titanium dihydrogen powder, erbium powder, terpineol and ethyl cellulose to obtain a composite brazing paste, screen print it onto the surface of a heat-resistant ceramic substrate with microgrooves, cover it with copper foil and then vacuum braze it to obtain a heat-resistant copper-clad silicon nitride ceramic plate. S6: After laminating a film onto a heat-resistant copper-clad silicon nitride ceramic substrate, exposure, development, and etching are performed to obtain a heat-shock-resistant ceramic circuit board.

2. The manufacturing process of a thermal shock resistant ceramic circuit board according to claim 1, characterized in that: The boron nitride-coated silicon carbide whiskers are prepared by the following process: Add silicon carbide whiskers to hydrochloric acid solution, stir evenly, ultrasonically disperse for 10-20 min, stir at 200-300 rpm for 1-2 h under water bath heating at 80-90℃, filter after stirring, wash with deionized water until the pH of the eluent is neutral, and vacuum dry at 80-90℃ for 6-8 h to obtain activated silicon carbide whiskers. Activated silicon carbide whiskers were spread evenly at the bottom of a crucible. Boric acid and urea were mixed, ground, and sieved. The sieved mixed powder was added to the crucible to completely cover the activated silicon carbide whiskers. The crucible was then transferred to a tube furnace and heated to 980-1000℃ under nitrogen protection and held for 1-2 hours. After holding, the temperature was further increased to 1780-1800℃ and held for 2-3 hours. After holding, the furnace was cooled to room temperature. The whiskers were removed from the crucible and added to an ethanol-deionized water solution with a volume ratio of 3:

1. The mixture was ultrasonically cleaned for 10 minutes and then vacuum dried at 80℃ for 8 hours to obtain boron nitride-coated silicon carbide whiskers.

3. The manufacturing process of a thermal shock resistant ceramic circuit board according to claim 2, characterized in that: The concentration of the hydrochloric acid solution is 2-2.5 mol / L; the mass ratio of activated silicon carbide whiskers, boric acid and urea is (1-2):(5-7):(15-20).

4. The manufacturing process of a thermal shock resistant ceramic circuit board according to claim 1, characterized in that: The modified silicon nitride ceramic slurry is prepared by the following process: Polyvinyl butyral and dibutyl phthalate were added to anhydrous ethanol and stirred until homogeneous to obtain an additive mixture. Silicon nitride powder and boron nitride-coated silicon carbide whiskers were mixed evenly and added to a ball mill. The additive mixture was added, and the mixture was ball-milled at 200-300 rpm for 6-8 hours under nitrogen protection. After ball milling, lanthanum oxide and alumina were added, and ball milling continued for 3-5 hours. After ball milling, the material was discharged, and the liquid was ultrasonically dispersed for 10-20 minutes and then degassed under vacuum to obtain modified silicon nitride ceramic slurry.

5. The manufacturing process of a thermal shock resistant ceramic circuit board according to claim 4, characterized in that: By weight, the modified silicon nitride ceramic slurry includes 80-90 parts of silicon nitride powder, 4-8 parts of boron nitride-coated silicon carbide whiskers, 4-6 parts of lanthanum oxide, 2-4 parts of alumina, 3-5 parts of polyvinyl butyral and 2-4 parts of dibutyl phthalate.

6. The manufacturing process of a thermal shock resistant ceramic circuit board according to claim 1, characterized in that: S3 is sintered using a gradient heating method. During the first sintering, the vacuum is reduced to 1-5 Pa, the sintering temperature is 300-320℃, the heating rate is 5-7℃ / min, and the holding time is 2-3h. The sintering temperature for the second sintering is 600-620℃, the heating rate is 2-4℃ / min, and the holding time is 3-4h. During the third sintering, nitrogen gas is introduced at a pressure of 2-4 MPa, the sintering temperature is 1580-1600℃, the heating rate is 8-10℃ / min, and the holding time is 2-3h. The sintering temperature for the fourth sintering is 1850-1870℃, the heating rate is 3-5℃ / min, and the holding time is 1-3h.

7. The manufacturing process of a thermal shock resistant ceramic circuit board according to claim 1, characterized in that: The laser etching process parameters include a laser wavelength of 1064nm, a scanning speed of 80-100mm / s, a laser power of 10-15W, a single trench width of 20-30μm, a spacing between adjacent trenches of 50-90μm, and a trench depth of 5-10μm.

8. The manufacturing process of a thermal shock resistant ceramic circuit board according to claim 1, characterized in that: By weight, the composite solder paste contains 60-70 parts copper powder, 20-24 parts tin powder, 10-14 parts titanium dihydrogen phosphate powder, 0.5-0.7 parts erbium powder, 80-90 parts terpineol and 10-14 parts ethyl cellulose.

9. The manufacturing process of a thermal shock resistant ceramic circuit board according to claim 1, characterized in that: During vacuum brazing, ultrasonic-assisted brazing is used. The process parameters for brazing include a vacuum degree of 0.001-0.01 Pa, an ultrasonic-assisted brazing temperature of 410-430℃, an ultrasonic frequency of 20kHz, an ultrasonic power of 200-240W, and an ultrasonic time of 2-3 min. After ultrasonic treatment, the temperature is increased to 850-900℃ and the holding time is 60-90 min.

10. A thermal shock resistant ceramic circuit board, characterized in that: It is manufactured using the manufacturing process described in any one of claims 1-9.

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