A textured boron nitride ceramic with high thermal conductivity and high insulation, its preparation method and application

Abstract

This invention relates to the field of ceramic materials for heat dissipation substrates in integrated circuit packaging, and discloses a high thermal conductivity and high insulation textured boron nitride ceramic, its preparation method, and its application. By mass, the textured boron nitride ceramic is composed of highly oriented hexagonal boron nitride grains, with the (002) crystal planes of the hexagonal boron nitride grains oriented in a plane parallel to the casting surface, and the Lotgering orientation factor f of the (002) crystal plane ≥ 0.75. The raw materials for preparing the textured boron nitride ceramic are also specified by mass. This high thermal conductivity and high insulation textured boron nitride ceramic, its preparation method, and its application, through the use of a B2O3-Y2O3 composite sintering aid and a casting-hot pressing synergistic process, achieves a combination of highly oriented crystal planes and near-full density in the prepared textured boron nitride ceramic, with a room temperature thermal conductivity ≥ 100 W·m within the oriented plane. ‑1 ·K ‑1 Volume resistivity ≥ 1x10 14 Q·cm, which combines ultra-high thermal conductivity with excellent electrical insulation properties.

Description

Technical Field

[0001] This invention relates to the field of ceramic technology for heat dissipation substrates in integrated circuit packaging, specifically to a high thermal conductivity and high insulation textured boron nitride ceramic, its preparation method, and its application. Background Technology

[0002] Textured boron nitride ceramics are high-performance materials formed by oriented arrangement of numerous lamellar hexagonal boron nitride microcrystals through a special process. This oriented arrangement of microstructures allows boron nitride to exhibit extremely high in-plane thermal conductivity in the direction parallel to the grain arrangement, while maintaining excellent electrical insulation, high temperature resistance, and low dielectric loss. This makes it an ideal material for manufacturing key heat dissipation components in fifth-generation mobile communication technology, high-power integrated circuits, and third-generation semiconductor devices.

[0003] The current mainstream method for preparing textured boron nitride ceramics employs a combination of tape casting and hot pressing sintering, along with a single-type sintering aid system. However, there are shortcomings in the directional control of the forming and sintering process and in achieving a balance between densification and insulation. Firstly, the orientation driving force during the molding and sintering process is insufficient and difficult to sustain. The existing process only relies on the flow of slurry during tape casting to achieve the initial orientation of the sheet-like hexagonal boron nitride grains. In the subsequent hot pressing sintering stage, there is no precise directional pressure coordination control, and there is a lack of system support to stabilize the initial texture. As a result, the sheet-like grains are prone to rotation and displacement during the sintering process. The crystal planes of most grains cannot maintain a completely parallel arrangement. The Lotgering orientation factor of the final product is generally low, and the grain orientation degree is insufficient. This directly leads to a significant decrease in the in-plane thermal conductivity of the textured boron nitride ceramic, which cannot meet the high-efficiency heat dissipation requirements of the heat dissipation substrate for integrated circuit packaging. Secondly, existing technologies for achieving ceramic densification mainly use either a single B2O3 low-temperature sintering aid or a single Y2O3 high-temperature sintering aid. However, the liquid phase formed by a single B2O3 aid has too low a viscosity, which cannot provide stable support for grain orientation and is prone to leaving boron-based impurity ions at grain boundaries. A single Y2O3 aid, on the other hand, requires extremely high sintering temperatures, which can easily lead to abnormal grain growth and lattice defects. Furthermore, both single aid systems introduce conductive impurity ions at ceramic grain boundaries, and some aids may even undergo side reactions with the boron nitride matrix to generate conductive phases, directly resulting in a significant decrease in the volume resistivity of the ceramic and failing to meet the electrical insulation performance requirements for integrated circuit packaging applications. Summary of the Invention

[0004] (a) Technical problems to be solved: To address the shortcomings of existing technologies, this invention provides a high thermal conductivity and high insulation textured boron nitride ceramic, its preparation method, and its application, solving the problems mentioned in the background art where it is difficult to simultaneously achieve high levels of thermal conductivity and insulation properties, as well as high levels of crystal orientation and density.

[0005] (II) Technical Solution: To achieve the above objectives, the present invention provides the following technical solution: The textured boron nitride ceramic is composed of highly oriented hexagonal boron nitride grains, wherein the (002) crystal planes of the hexagonal boron nitride grains are oriented in a plane parallel to the casting surface, and the Lotgering orientation factor f of the (002) crystal plane is ≥0.75. The raw materials for preparing textured boron nitride ceramics, by mass parts, include: 50-250 parts of flake hexagonal boron nitride powder, 5-40 parts of B2O3-Y2O3 composite sintering aid, 3-12 parts of dibutyl phthalate, 10-25 parts of polyvinyl butyral, 5-10 parts of polyethylene glycol, 30-50 parts of methyl ethyl ketone, 1-5 parts of triethanolamine, and 100-150 parts of anhydrous ethanol. The hexagonal boron nitride powder has an average particle size of 10 μm, an aspect ratio of 100, and a mass purity of 99%. The amount of the B2O3-Y2O3 composite sintering aid added is 5-15 wt% of the lamellar hexagonal boron nitride powder; The amount of dibutyl phthalate added is 20-70 wt% of the polyvinyl butyral (PVB). The molar ratio of B2O3 to Y2O3 is 1:1-3.

[0006] Preferably, the hexagonal boron nitride grains are in the form of plates with an average aspect ratio of 50-200.

[0007] Preferably, the crystal faces of the hexagonal boron nitride grains are highly oriented along a fixed direction within a specific plane of the textured boron nitride ceramic, with a Lotgering orientation factor f ≥ 0.75.

[0008] Preferably, the textured boron nitride ceramic has a room temperature thermal conductivity ≥100 W·m in the orientation plane. -1 ·K -1 .

[0009] Preferably, the volume resistivity of the textured boron nitride ceramic is ≥1×10⁻⁶. 14 Ω·cm, relative density ≥96%.

[0010] A method for preparing textured boron nitride ceramics with high thermal conductivity and high insulation includes the following steps: Take the following components in parts by weight: 50-250 parts of flake-shaped hexagonal boron nitride powder, 5-40 parts of B2O3-Y2O3 composite sintering aid, 3-12 parts of dibutyl phthalate, 10-25 parts of polyvinyl butyral, 5-10 parts of polyethylene glycol, 30-50 parts of methyl ethyl ketone, 1-5 parts of triethanolamine, and 100-150 parts of anhydrous ethanol; add them to a ball mill jar and ball mill to obtain a cast slurry; The casting slurry is poured into the casting machine trough, and a boron nitride casting sheet with a thickness of 0.2 mm is obtained. The boron nitride casting sheets are stacked in multiple layers and pre-pressed at room temperature in a mold to obtain a green body of a predetermined thickness. The green body is placed in a degreasing furnace and protected by flowing nitrogen gas. The temperature is increased from room temperature to 600°C at a rate of 1-2°C / min and held for 3 hours to completely remove organic components. After degreasing, the green body is cooled in the furnace to form a degreased green body. After cooling, the green body is placed in a hot press furnace and sintered by hot pressing. After sintering, the green body is cooled to room temperature in the furnace to obtain a boron nitride ceramic sintered body. The boron nitride ceramic sintered body is cut, ground, and polished to obtain textured boron nitride ceramic sheets.

[0011] Preferably, the B2O3-Y2O3 composite sintering aid is synthesized by the sol-gel method.

[0012] Preferably, the casting molding parameters of the casting machine trough are as follows: under an environment of temperature 25±2°C and relative humidity 40±5%, the casting speed is set to 1.2m / min; the scraper height is 0.3mm; the temperature gradient of the drying zone is 50-70°C; and the total drying time is 20min.

[0013] Preferably, after the degreased preform enters the hot press furnace, it is protected by high-purity flowing nitrogen gas, heated to 1200°C at 5°C / min, pre-pressed at 10MPa, and then heated to 1800°C at 3°C / min, with a pressure of 35MPa applied. The heat and pressure are maintained for 2.5 hours, with the pressure direction always perpendicular to the plane of the cast sheet. After the heat maintenance is completed, the pressure is first released, and then the preform is cooled to room temperature with the furnace.

[0014] Application of textured boron nitride ceramics with high thermal conductivity and high insulation in integrated circuit packaging.

[0015] (III) Beneficial Effects: The present invention provides a high thermal conductivity and high insulation textured boron nitride ceramic, its preparation method, and its application, which have the following beneficial effects: 1. This invention relates to a high thermal conductivity and high insulation textured boron nitride ceramic, its preparation method, and its application. By employing a B2O3-Y2O3 composite sintering aid and a tape casting-hot pressing synergistic process, the textured boron nitride ceramic achieves a high degree of crystal orientation and near-full density, with a room temperature thermal conductivity ≥100 W·m within its orientation planes. -1 ·K -1Volume resistivity ≥ 1x10 14 Q·cm, which combines ultra-high thermal conductivity with excellent electrical insulation properties.

[0016] 2. This invention relates to a high thermal conductivity and high insulation textured boron nitride ceramic, its preparation method, and its application. By selecting a low-addition amount of B2O3-Y2O3 composite sintering aid instead of a single aid system, the synergistic effect of the two is utilized to form a high-viscosity borate liquid phase with a viscosity higher than that of existing borate liquid phases in the mid-temperature range. This effectively suppresses grain rotation, stabilizes the initial texture formed by tape casting, and simultaneously optimizes the ceramic densification kinetics and texturing thermodynamics. This avoids the grain disorder and texture collapse problems caused by excessively low viscosity of the liquid phase of a single low-temperature aid, as well as the high energy consumption and hexagonal boron nitride decomposition problems caused by the ultra-high sintering temperature required by a single high-temperature aid. In this way, production energy consumption and costs are effectively reduced.

[0017] 3. This high thermal conductivity and high insulation textured boron nitride ceramic, its preparation method and application, combines tape casting with directional hot pressing sintering process. First, tape casting is used to initially orient the hexagonal boron nitride powder into a sheet shape. Then, the hot pressing pressure perpendicular to the tape surface drives the grains to further orient, thereby solving the problems of low green density in traditional single tape casting method and disordered initial powder arrangement in single hot pressing method, and thus achieving simultaneous improvement of high orientation degree and high density.

[0018] 4. This high thermal conductivity and high insulation textured boron nitride ceramic, its preparation method and application, by using the textured boron nitride ceramic as a ceramic insulating layer for DPC and DBC substrates in integrated circuit packaging, its high thermal conductivity can quickly conduct the heat generated by the chip operation, its high insulation can effectively isolate conductive components, and its excellent high temperature resistance and chemical stability are suitable for the harsh working environment of integrated circuits, thereby improving the reliability and service life of the device. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the process for preparing textured boron nitride ceramics with high thermal conductivity and high insulation according to the present invention.

[0020] Figure 2 The image shows the XRD pattern of the textured boron nitride ceramic of this invention.

[0021] Figure 3 This is a SEM image of the surface morphology of the textured boron nitride ceramic obtained in Example 4 of the present invention. Figure 4 This is a SEM image of the surface morphology of the textured boron nitride ceramic obtained in Example 5 of the present invention. Figure 5 This is a SEM image of the surface morphology of the textured boron nitride ceramic obtained in Example 6 of the present invention. Figure 6This is a SEM image of the surface morphology of the textured boron nitride ceramic prepared in Example 7 of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0023] Example 1 The preferred embodiments of the present invention are described in detail below: refer to Figure 2 XRD diffraction tests were performed on the textured boron nitride ceramic. The tests were conducted on the plane parallel to the casting surface and the cross-section perpendicular to the casting surface. Only strong (002) crystal plane diffraction peaks were detected in the direction parallel to the casting surface, with no obvious diffraction signals from other crystal planes. However, diffraction peaks of non-basal planes such as (100) and (110) were detected in the cross-section perpendicular to the casting surface. This indicates that the hexagonal boron nitride grains inside the textured boron nitride ceramic are not randomly arranged, but rather their (002) crystal planes are highly parallel to the casting surface and arranged in a regular directional pattern, exhibiting a clear directional arrangement.

[0024] A textured boron nitride ceramic with high thermal conductivity and high insulation is provided. The textured boron nitride ceramic is composed of highly oriented lamellar hexagonal boron nitride grains. The (002) crystal planes of the hexagonal boron nitride grains are oriented in a plane parallel to the casting surface, and the Lotgering orientation factor f of the (002) crystal plane is ≥0.75 (preferably ≥0.8). The raw materials for preparing the textured boron nitride ceramic, by mass parts, include: 50-250 parts of lamellar hexagonal boron nitride powder, B2O3-Y2O3 composite sintering agent... The mixture contains 5-40 parts of binder, 3-12 parts of dibutyl phthalate, 10-25 parts of polyvinyl butyral, 5-10 parts of polyethylene glycol, 30-50 parts of methyl ethyl ketone, 1-5 parts of triethanolamine, and 100-150 parts of anhydrous ethanol. Dibutyl phthalate acts as a dispersant to effectively prevent the agglomeration of hexagonal boron nitride powder. Polyvinyl butyral and polyethylene glycol act as binders and plasticizers, respectively, which can improve the molding performance of the slurry and the flexibility of the cast sheet. The mixed solvent of methyl ethyl ketone and ethanol can ensure that all components are fully dissolved and dispersed.

[0025] The hexagonal boron nitride powder has an average particle size of 10 μm, an aspect ratio of 100, and a purity of 99% (range: average particle size of hexagonal boron nitride powder is 5–20 μm, average aspect ratio is 50–200, and purity is ≥99%). The plate-like hexagonal boron nitride powder exhibits good anisotropy at this particle size and aspect ratio, making it easier to orient and align along a specific direction during tape casting and hot pressing sintering. Furthermore, high purity reduces the negative impact of impurities on the thermal conductivity and insulation properties of ceramics.

[0026] The amount of B2O3-Y2O3 composite sintering aid added is 5%-15%wt of the flake hexagonal boron nitride powder. This allows the relatively small amount of B2O3-Y2O3 composite sintering aid to form an appropriate amount of liquid phase during medium-temperature sintering, promoting ceramic densification, while also avoiding the introduction of too many impurity ions due to excessive additives, thus ensuring the high insulation properties of the ceramic.

[0027] The molar ratio of B2O3 to Y2O3 is 1:1-3. This allows the B2O3-Y2O3 composite sintering aid to form a liquid phase with suitable viscosity in the intermediate temperature range (1750-1850℃). B2O3 lowers the sintering temperature, while Y2O3 stabilizes the texture. The synergistic effect of both promotes both densification and texturing of the ceramic. Different molar ratios can be adapted to h-BN powders with different particle sizes and aspect ratios to achieve optimal sintering results.

[0028] Hexagonal boron nitride grains are plate-shaped with an average aspect ratio of 50-200. This aspect ratio increases the contact area between grains, reduces phonon scattering, improves in-plane thermal conductivity, and also facilitates the formation of a highly oriented texture during molding and sintering.

[0029] The crystal planes of hexagonal boron nitride grains are highly oriented along a fixed direction within a specific plane of the textured boron nitride ceramic, with a Lotgering orientation factor f ≥ 0.75 (preferably ≥ 0.8). Within this range, it can be indicated that the (002) crystal planes of the hexagonal boron nitride grains are preferentially arranged along the direction parallel to the casting surface. This highly textured structure can fully utilize the high intrinsic thermal conductivity of hexagonal boron nitride in the ab plane, thereby significantly improving the in-plane thermal conductivity of the ceramic. At the same time, the regular grain arrangement can also reduce grain boundary defects and optimize the mechanical and insulating properties of the ceramic.

[0030] Textured boron nitride ceramics have a room temperature thermal conductivity ≥100 W·m within the orientation plane. -1 ·K -1 (Preferred ≥150W·m) -1 ・K -1(As shown in Examples 4 and 5), the thermal conductivity is higher than that of traditional boron nitride ceramics (Examples 6, 7, Comparative Examples 1, 2, and 3), thus meeting the stringent requirements of integrated circuit packaging heat dissipation substrates for efficient heat dissipation, thereby quickly conducting the heat generated by electronic devices during operation and preventing device failure due to overheating.

[0031] The volume resistivity of textured boron nitride ceramics is ≥1×10⁻⁶. 14 With a volume resistivity of Ω·cm and a relative density ≥96%, the ceramic possesses excellent electrical insulation properties, effectively isolating conductive components in integrated circuits and preventing leakage and short circuits. The ≥96% relative density indicates extremely low internal porosity, which not only improves thermal conductivity but also enhances the ceramic's mechanical strength and corrosion resistance, extending its service life.

[0032] Example 2 refer to Figure 1 A method for preparing textured boron nitride ceramics with high thermal conductivity and high insulation includes the following steps: Preparation of composite sintering aid: Using a B2O3-Y2O3 molar ratio of 1:1-3, analytical grade yttrium nitrate hexahydrate was selected as the yttrium source, and analytical grade boric acid as the boron source, with an excess of 10 mol% boric acid to compensate for high-temperature volatilization loss. The yttrium nitrate hexahydrate was dissolved in a mixed solvent of anhydrous ethanol and deionized water in a 2:1 volume ratio to obtain a yttrium source precursor solution. Boric acid was dissolved in anhydrous ethanol to obtain a boron source ethanol solution. The boron source solution was slowly sintered at room temperature. Add yttrium source solution dropwise, and adjust the pH to 2.5-3.5 with dilute nitric acid after addition; stir at 50℃ in a sealed, light-protected environment for 2 hours to form a transparent sol, let stand for 12 hours to gel, and age for 48 hours; perform gradient drying: dry at 60℃ under normal pressure for 18 hours, then increase the temperature to 110℃ at 1℃ / min and hold for 8 hours to obtain a dry gel; perform segmented heat treatment: increase the temperature to 400℃ at 3℃ / min and hold for 3 hours, then increase the temperature to 900℃ and hold for 4 hours, and cool with the furnace to obtain composite sintering aid powder.

[0033] Take the following components in parts by mass: 100 parts of flake-shaped hexagonal boron nitride powder, 5-10 parts of B2O3-Y2O3 composite sintering aid, 5-10 parts of dibutyl phthalate, 17.5 parts of polyvinyl butyral, 10 parts of polyethylene glycol, 37.4 parts of methyl ethyl ketone, 3 parts of triethanolamine, and 125 parts of anhydrous ethanol. Add them to a ball mill jar, use high-purity zirconia balls as the grinding medium, with a ball-to-powder ratio of 3:1, and ball mill for 18 hours to ensure that the slurry is fully and uniformly mixed, so that the B2O3-Y2O3 composite sintering aid and organic additives are uniformly coated on the surface of the hexagonal boron nitride powder. At the same time, the mechanical force of the ball milling process can further refine the powder particles and improve the dispersibility of the powder. After standing in a vacuum environment above -0.09MPa to degas and remove micro bubbles, a uniform cast slurry with a viscosity of 1500-4000mPa·s is obtained. The casting slurry is poured into the casting machine's feed trough and cast onto a polyester (PET) carrier belt to produce a 0.2 mm thick boron nitride (BN) cast sheet, facilitating subsequent pre-pressing, degreasing, and hot-pressing sintering. The casting process allows the sheet-like hexagonal BN powder to initially align along the casting direction during slurry casting, providing a foundation for the high texturing required in subsequent hot-pressing sintering.

[0034] Multilayer boron nitride cast sheets are stacked and pre-pressed at room temperature in a mold to obtain a green body of a predetermined thickness. The green body is then placed in a debinding furnace, protected by flowing nitrogen gas, and heated from room temperature to 600°C at a rate of 1-2°C / min, held at that temperature for 3 hours to completely remove organic components. After debinding, the green body is cooled in the furnace to form a debinded green body. This process removes organic additives from the cast sheets, preventing defects such as porosity and cracking in the ceramic caused by the rapid decomposition of organic matter during sintering. After cooling, the debinded green body is placed in a hot press furnace and sintered by hot pressing, then cooled to room temperature in the furnace to obtain a sintered boron nitride ceramic body. The pressure and temperature during hot pressing drive the hexagonal boron nitride grains to further orient and align, forming a highly textured structure. Cooling in the furnace reduces the internal stress of the ceramic and improves the structural stability of the material.

[0035] Boron nitride ceramic sintered bodies are cut, ground, and polished to obtain textured boron nitride ceramic sheets, thereby obtaining textured boron nitride ceramic sheets with smooth and clean surfaces and precise dimensions, which meet the surface quality and dimensional requirements of ceramic insulating layers for integrated circuit packaging substrates.

[0036] The B2O3-Y2O3 composite sintering aid is synthesized by the sol-gel method, which enables atomic-level uniform mixing of B2O3 and Y2O3, enhances the activity and synergistic effect of the aid, and forms a liquid phase of suitable viscosity during medium-temperature sintering. This simultaneously promotes the densification and texturing of boron nitride ceramics, reduces the introduction of impurities, and lowers energy consumption.

[0037] The casting parameters for the casting machine's material tank are as follows: under an environment of temperature 25±2°C and relative humidity 40±5%, the casting speed is set to 1.2m / min; the scraper height is 0.3mm; the temperature gradient of the drying zone is 50-70°C; and the total drying time is 20min. This not only quickly removes the solvent from the slurry but also avoids problems such as warping and cracking of the cast sheet due to excessively rapid drying, thus ensuring the quality of the cast sheet.

[0038] After the degreased blank enters the hot press furnace, it is protected by high-purity flowing nitrogen gas. The temperature is increased to 1200℃ at 5℃ / min, and a pre-pressure of 10MPa is applied. Then, the temperature is increased to 1800℃ at 3℃ / min to enter the medium-temperature sintering zone. This reduces energy consumption and avoids the decomposition of hexagonal boron nitride caused by high temperature. The pressure of 35MPa is applied perpendicularly to the tape surface, which can force the hexagonal boron nitride grains to align in a direction parallel to the tape surface, thereby improving the texture. The pressure of 35MPa is applied and held at that temperature for 2.5 hours. The pressure direction is always perpendicular to the plane of the tape. After the holding period, the pressure is released first, and then the furnace is cooled to room temperature.

[0039] Example 3: Application of high thermal conductivity and high insulation textured boron nitride ceramics in integrated circuit packaging. Specifically, it can be applied to 5G mobile communication technology, high-power integrated circuits, and 3G semiconductor devices, serving as a ceramic insulating layer for direct plated copper substrates (DPC) and direct bonded copper substrates (DBC). It is ideally suited for 3G semiconductor power devices, 5G high-frequency communication devices, and high-power integrated circuit packaging scenarios. The textured boron nitride ceramic of this invention uses the formulation and preparation method of Example 4 to prepare textured boron nitride ceramics with parameters of aspect ratio 50, Lotgering orientation factor f=0.88, relative density 97.2%, in-plane room temperature thermal conductivity 105 W / (m·K), volume resistivity 1.8 x 10¹⁴ Q²·cm, flexural strength 62 MPa, and dielectric loss 3.0 x 10⁻⁴ (1 MHz). Using the formulation and preparation method of Example 5, a high-performance textured boron nitride ceramic with an aspect ratio of 150, f=0.94, relative density of 98.8%, thermal conductivity of 135 W / (m·K), and volume resistivity of 3.0 x 10¹⁴ Ω·cm can be prepared, which is far superior to the textured boron nitride ceramics prepared in Examples 6, 7, Comparative Examples 1, 2, and 3. The textured boron nitride ceramic prepared in Example 5 has an ultra-high in-plane thermal conductivity of ≥100W / (m·K), which can quickly conduct the heat of the chip with a power density of ≥50W / cm2, avoiding device overheating failure; the volume resistivity of 1×1014Q·cm and low dielectric loss can effectively isolate the conductive layer and reduce high-frequency signal transmission loss; the relative density of ≥96% and the bending strength of ≥54MPa ensure that the substrate does not crack, warp or delaminate during industrial processing such as cutting, grinding, copper bonding / electroplating and high and low temperature thermal cycling; and the 1750-1850℃ medium temperature sintering process is compatible with the existing DPC / DBC substrate production line, without the need for additional high-end equipment, and can be directly mass-produced to reduce costs.

[0040] In practical applications, the ceramic sintered body is first precision-cut, ground, and polished into a substrate with a thickness of 0.2–1.0 mm and a surface roughness Ra ≤ 0.05 μm. For the DBC substrate, a vacuum direct copper bonding process at 850–950℃ is used to achieve metallurgical bonding between the ceramic and oxygen-free copper foil. For the DPC substrate, plasma activation, magnetron sputtering of the seed layer, electrochemical copper plating, and photolithography etching are performed to form a high-precision circuit. Finally, the prepared DPC / DBC substrate is welded and assembled with the chip and heat dissipation components, and then encapsulated with adhesive. The finished product is tested and the insulation resistance is ≥ 1 × 10⁻⁶. 14 Q, Thermal resistance ≤ 0.5 C·cm 2 With a shear strength of ≥20MPa, it fully meets the stringent requirements for integrated circuit packaging.

[0041] Example 4 The process is essentially the same as in Example 2, except that the average particle size of the boron nitride powder is 5 μm, the aspect ratio is 50, the sintering aid is 10% B2O3-Y2O3 (boron nitride powder), the sintering temperature is 1750℃, the pressure is 30 MPa, and the holding time is 2 hours. All other parameters are the same as in Example 2. The resulting textured boron nitride ceramic, after performance testing, showed a Lotgering orientation factor f of 0.88, a relative density of 97.2%, a parallel thermal conductivity of 105 W / (m·K), a perpendicular thermal conductivity of 7.8 W / (m·K), a flexural strength of 62 MPa, and a volume resistivity of 1.8 × 10⁻⁶. 14 Ω·cm, dielectric loss 3.0×10 -4 (1MHz).

[0042] The performance parameters of the composite membrane obtained in Example 4 are shown in the table below: Example 5 The process was essentially the same as in Example 2, except that the average particle size of the boron nitride powder was 20 μm, the aspect ratio was 150, the sintering aid was 15% B2O3-Y2O3 (boron nitride powder), the sintering temperature was 1850℃, the pressure was 40 MPa, and the holding time was 3 hours. All other parameters were the same as in Example 2. The textured boron nitride ceramic produced was tested and found to have a lotgering orientation factor f of 0.94, a material density of 98.8%, a thermal conductivity parallel to the casting surface of 135 W / (m·K), a thermal conductivity perpendicular to the casting surface of 9.2 W / (m·K), a flexural strength of 54 MPa, and a volume resistivity of 3.0 × 10⁻⁶. 14 Ω·cm, dielectric loss 2.0×10 -4 (1MHz).

[0043] The performance parameters of the composite membrane obtained in Example 5 are shown in the table below: Example 6 The process was basically the same as in Example 2, except that the average particle size of the boron nitride powder was 5 μm, the aspect ratio was 50, the sintering aid was B2O3 with 10% boron nitride powder, the sintering temperature was 1750℃, the pressure was 30 MPa, and the holding time was 2 hours. The rest was the same as in Example 2. XRD analysis of the textured boron nitride ceramic showed that it had a medium intensity diffraction peak on the (002) crystal plane parallel to the casting surface, and diffraction peaks such as (100) and (110) perpendicular to the casting surface. However, the peak intensity was weaker than that in Example 4, indicating that the degree of orientation was reduced. The Lotgering orientation factor f=0.65, relative density 92.5%, parallel thermal conductivity 75 W / (m·K), perpendicular thermal conductivity 6.2 W / (m·K), flexural strength 45 MPa, and volume resistivity 5.0 × 10⁻⁶. 14 Ω·cm, dielectric loss 6.0×10 -4 (1MHz).

[0044] The performance parameters of the composite membrane obtained in Example 6 are shown in the table below: Example 7 The process was basically the same as in Example 2, except that the average particle size of the boron nitride powder was 5 μm, the aspect ratio was 50, the sintering aid was Y2O3 with 10% boron nitride powder, the sintering temperature was 1750℃, the pressure was 30 MPa, and the holding time was 2 hours. The rest was the same as in Example 2. XRD analysis of the textured boron nitride ceramic showed that a medium intensity diffraction peak of the (002) crystal plane appeared in the direction parallel to the casting surface, and diffraction peaks of (100) and (110) appeared in the direction perpendicular to the casting surface. The degree of orientation was lower than that of Example 2 but slightly higher than that of Example 4. The lotgering orientation factor f=0.70, the relative density was 93.8%, the parallel thermal conductivity was 82 W / (m·K), the perpendicular thermal conductivity was 6.8 W / (m·K), the flexural strength was 48 MPa, and the volume resistivity was 4.2 × 10⁻⁶. 14 Ω·cm, dielectric loss 5.5×10 -4 (1MHz).

[0045] The performance parameters of the composite membrane obtained in Example 7 are shown in the table below: Comparative Example 1 The process was essentially the same as in Example 2, except that no sintering aids were added, the h-BN powder had an average particle size of 10 μm and an aspect ratio of 100, the sintering temperature was 1800℃, the pressure was 35 MPa, and the holding time was 2.5 hours. The remaining conditions were the same as in Example 2. The resulting textured boron nitride ceramic underwent performance testing and showed the following characteristics: Lotgering orientation factor f = 0.45, relative density 85.3%, parallel thermal conductivity 45 W / (m·K), perpendicular thermal conductivity 5.1 W / (m·K), flexural strength 32 MPa, and volume resistivity 8.0 × 10⁻⁶. 13 Ω·cm, dielectric loss 1.2×10 -3 (1MHz).

[0046] Comparative Example 2 The process is essentially the same as Example 2, except that hot pressing is not performed; only atmospheric pressure sintering is used at a sintering temperature of 1600℃ for 4 hours without external pressure. The resulting textured boron nitride ceramic, after performance testing, exhibits the following characteristics: Lotgering orientation factor f = 0.30, relative density 72.1%, parallel thermal conductivity 28 W / (m·K), perpendicular thermal conductivity 4.0 W / (m·K), flexural strength 20 MPa, and volume resistivity 6.5 × 10⁻⁶. 13 Ω·cm, dielectric loss 2.0×10 -3 (1MHz).

[0047] Comparative Example 3 The process is essentially the same as in Example 2, except that the h-BN powder is equiaxed (aspect ratio ≈ 5), and is directly dry-pressed and then hot-pressed for sintering without tape casting. The sintering aid is 10% B2O3-Y2O3 of boron nitride powder. The sintering temperature is 1950℃, the pressure is 30MPa, and the holding time is 2 hours. The resulting textured boron nitride ceramic, after performance testing, has the following characteristics: Lotgering orientation factor f = 0.25, relative density 88.5%, parallel thermal conductivity 38 W / (m·K), perpendicular thermal conductivity 6.0 W / (m·K), flexural strength 41MPa, and volume resistivity 3.5 × 10⁻⁶. 13 Ω·cm, dielectric loss 1.5×10 -3 (1MHz).

[0048] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A textured boron nitride ceramic with high thermal conductivity and high insulation, characterized in that: The textured boron nitride ceramic is composed of highly oriented hexagonal boron nitride grains, wherein the (002) crystal planes of the hexagonal boron nitride grains are oriented in a plane parallel to the casting surface, and the Lotgering orientation factor f of the (002) crystal plane is ≥0.

75. The raw materials for preparing textured boron nitride ceramics, by mass parts, include: 50-250 parts of flake hexagonal boron nitride powder, 5-40 parts of B2O3-Y2O3 composite sintering aid, 3-12 parts of dibutyl phthalate, 10-25 parts of polyvinyl butyral, 5-10 parts of polyethylene glycol, 30-50 parts of methyl ethyl ketone, 1-5 parts of triethanolamine, and 100-150 parts of anhydrous ethanol. The hexagonal boron nitride powder has an average particle size of 10 μm, an aspect ratio of 100, and a mass purity of 99%. The amount of the B2O3-Y2O3 composite sintering aid added is 5%-15wt% of the lamellar hexagonal boron nitride powder; The amount of dibutyl phthalate added is 20-70 wt% of the polyvinyl butyral. The molar ratio of B2O3 to Y2O3 is 1:1-3.

2. The textured boron nitride ceramic with high thermal conductivity and high insulation according to claim 1, characterized in that: The hexagonal boron nitride grains are plate-shaped with an average aspect ratio of 50-200.

3. The high thermal conductivity and high insulation textured boron nitride ceramic according to claim 1, characterized in that: The crystal planes of the hexagonal boron nitride grains are highly oriented along a fixed direction within a specific plane of the textured boron nitride ceramic, with a Lotgering orientation factor f ≥ 0.

75.

4. A textured boron nitride ceramic with high thermal conductivity and high insulation according to claim 1, characterized in that: The textured boron nitride ceramic has a room temperature thermal conductivity ≥100 W·m in the orientation plane. -1 ·K -1 .

5. A textured boron nitride ceramic with high thermal conductivity and high insulation according to claim 1, characterized in that: The volume resistivity of the textured boron nitride ceramic is ≥1×10⁻⁶. 14 Ω·cm, relative density ≥96%.

6. A method for preparing textured boron nitride ceramics with high thermal conductivity and high insulation, characterized in that, Includes the following steps: Take the following components in parts by weight: 50-250 parts of flake-shaped hexagonal boron nitride powder, 5-40 parts of B2O3-Y2O3 composite sintering aid, 3-12 parts of dibutyl phthalate, 10-25 parts of polyvinyl butyral, 5-10 parts of polyethylene glycol, 30-50 parts of methyl ethyl ketone, 1-5 parts of triethanolamine, and 100-150 parts of anhydrous ethanol, add them to a ball mill jar and ball mill to obtain a cast slurry; The casting slurry is poured into the casting machine trough, and a boron nitride casting sheet with a thickness of 0.2 mm is obtained. The boron nitride casting sheets are stacked in multiple layers and pre-pressed at room temperature in a mold to obtain a green body of a predetermined thickness. The green body is placed in a degreasing furnace and protected by flowing nitrogen gas. The temperature is increased from room temperature to 600°C at a rate of 1-2°C / min and held for 3 hours to completely remove organic components. After degreasing, the green body is cooled in the furnace to form a degreased green body. After cooling, the green body is placed in a hot press furnace and sintered by hot pressing. After sintering, the green body is cooled to room temperature in the furnace to obtain a boron nitride ceramic sintered body. The boron nitride ceramic sintered body is cut, ground, and polished to obtain textured boron nitride ceramic sheets.

7. The method for preparing textured boron nitride ceramic with high thermal conductivity and high insulation according to claim 6, characterized in that, The B2O3-Y2O3 composite sintering aid is synthesized by the sol-gel method.

8. The method for preparing textured boron nitride ceramic with high thermal conductivity and high insulation according to claim 6, characterized in that, The casting parameters set for the casting machine's material tank are as follows: under an environment of temperature 25±2°C and relative humidity 40±5%, the casting speed is set to 1.2m / min; the scraper height is 0.3mm; the temperature gradient of the drying zone is 50-70°C; and the total drying time is 20min.

9. The method for preparing textured boron nitride ceramic with high thermal conductivity and high insulation according to claim 6, characterized in that, After the degreased preform enters the hot press furnace, it is protected by high-purity flowing nitrogen gas. The temperature is increased to 1200°C at 5°C / min, and a pre-pressure of 10MPa is applied. Then, the temperature is increased to 1800°C at 3°C / min, and a pressure of 35MPa is applied. The temperature and pressure are maintained for 2.5 hours, and the pressure direction is always perpendicular to the plane of the cast sheet. After the heat preservation is completed, the pressure is first released, and then the preform is cooled to room temperature with the furnace.

10. The application of the high thermal conductivity and high insulation textured boron nitride ceramic according to claims 1-5 in integrated circuit packaging.

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