CN115703683B - High-strength high-heat-conductivity large-size silicon nitride ceramic and preparation method thereof - Google Patents
High-strength high-heat-conductivity large-size silicon nitride ceramic and preparation method thereof Download PDFInfo
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Abstract
The invention provides a high-strength high-heat-conductivity large-size silicon nitride ceramic and a preparation method thereof, submicron-level low-oxygen silicon nitride powder is adopted as a raw material, and non-oxygen nitride and fluoride are added as a composite sintering aid, and the silicon nitride ceramic block blank is prepared through proportioning, powder mixing, cold isostatic pressing or vibration press forming, hot-pressing sintering and cooling annealing, wherein the bending strength is more than 800MPa, the oxygen content is low, the grain boundary glass phase is less, the heat conductivity is more than 80W/m.K, the thickness of each piece is 10-50 mm, the length is 190-385 mm, and the width is 230-350 mm; the silicon nitride ceramic substrate for packaging such as high-power semiconductor IGBT and the like with urgent industrial demands is manufactured by cutting, slicing and polishing through a diamond wire multi-wire cutting technology. Compared with the existing wet tape casting molding-degreasing-high-pressure atmosphere sintering process of the substrate manufacturing technology, the method can be used for preparing the high-performance large-size silicon nitride ceramic substrate with low cost, high efficiency, no pollution and short flow.
Description
Technical Field
The invention belongs to the technical field of semiconductor packaging substrate materials, and particularly relates to high-strength high-heat-conductivity large-size silicon nitride ceramic and a preparation method thereof, which are particularly suitable for preparing a silicon nitride ceramic substrate.
Background
The silicon nitride ceramic has excellent characteristics of high strength and high heat conduction, and the copper-clad ceramic substrate manufactured by combining an active metal welding process (AMB) has extremely high environmental reliability without failure after 5000 times of thermal cycles, so that the silicon nitride ceramic is the key material with the most development prospect in high-voltage high-power Insulated Gate Bipolar Transistor (IGBT) module packaging. Compared with the common aluminum oxide ceramic substrate material and aluminum nitride ceramic substrate material, the silicon nitride ceramic substrate material is known as a third-generation ceramic substrate material due to excellent comprehensive performance, is a preferred material for bearing a third-generation semiconductor high-temperature module represented by a SiC wafer in the future, and has strong competitiveness.
The silicon nitride ceramic substrate material is successfully used in new energy fields such as electric automobiles, rail transit fields, photovoltaics, wind power, smart grids and the like at present, and has the advantages of rapid increase of consumption and huge market. In addition, in the high concentration modeThe solar battery module, the semiconductor refrigerator, the high-power resistor, the AC-DC conversion module and the DC-DC conversion module for aerospace, the novel power electronic integrated module (PEBB) inverted by the chip for aerospace and other fields have very wide application requirements. Therefore, development of Si is highly demanded 3 N 4 And other packaging substrate materials with good heat conduction and high-temperature reliability, so that the thermal resistance of the power module is greatly reduced, and the performance is improved.
The silicon nitride ceramic substrate which is currently commercially applied is produced by the traditional process method of wet tape casting, degreasing and high-pressure nitrogen sintering, and the prior art has a plurality of defects. The technical threshold is high. The related technology of silicon nitride casting is mainly mastered by a few companies such as Japan, the United states and the like, the domestic start is late, no mature industrial production line exists at present, and key formulas, processes and equipment are difficult to break through in a short time. Second, the pollution is serious. The solvent of the casting molding slurry is toxic and harmful organic matters such as benzene, ketone and the like, the environmental pollution is serious, the harm to human bodies is great, and a water-based casting technology is also raised in recent years, but the polarity of water molecules is strong, the surface tension is high, the blank deformation and cracking are difficult to control, the qualification rate is low, and the mass production examples are few. Thirdly, the process flow is long. Besides the preparation of long-time complex system slurry and tape casting, the slurry needs to be sintered in a degreasing furnace at 500-600 ℃ for a long time to remove organic matters, and finally sintered and densified in a sintering furnace at 1850-2000 ℃ under high-pressure nitrogen atmosphere, which is equivalent to the requirement of two-step independent sintering, and has long time consumption, and continuous operations such as degreasing, sintering and the like cannot be performed except that the tape casting can continuously form a green body material. Fourth, the matching cost is high. The silicon nitride powder produced by the silicon imine decomposition method for the casting method high heat conduction substrate can be produced in batches by only one company in Japan, the selling price is very high, the high-pressure nitrogen sintering furnace controlled by a high-precision temperature field is mainly imported, the key consumable high-quality boron nitride burning plate and the crucible kiln furniture are basically all imported in Japan, the price is very high, and the distribution cost of the kiln furniture only far exceeds the investment of the sintering furnace. Fifth, the thermal conductivity is low. The thermal conductivity of the current casting method is 65-90W/m.K, and needs to be further improved. Sixthly, the product density is slightly low, the sintering qualification rate is low, a large amount of organic matters are required to be added in the casting process, the sintering shrinkage rate is high, the casting green body is a green body sheet with the thickness of 0.3-0.6 mm, the sheet is easy to warp and deform in the sintering process, and the strength and the mechanical property can be influenced.
Therefore, the current industrial manufacturing technology system of the silicon nitride ceramic substrate is single, has more defects, and needs to develop a new technology system.
Disclosure of Invention
The invention aims to provide high-strength high-heat-conductivity large-size silicon nitride ceramic and a preparation method thereof, solve the defect of the traditional casting method process for preparing the silicon nitride ceramic substrate, and realize substitution and progress.
In order to achieve the above purpose, the technical scheme adopted by the invention comprises the following steps:
a preparation method of high-strength high-heat-conductivity large-size silicon nitride ceramics comprises the following steps:
a step of batching and mixing powder, in which submicron-level low-oxygen silicon nitride powder is adopted as a raw material, and oxyfree nitride and fluoride are added as a composite sintering auxiliary agent to prepare batching, and then uniformly mixing is carried out to obtain formula powder;
pre-pressing, namely filling the formula powder into a die, vacuumizing, and performing cold isostatic pressing or vibration pressure forming to obtain a formed blank;
hot-pressing sintering, namely after trimming the molded blank, stacking at least one layer of the molded blank, placing the molded blank into a mold, and using graphite paper or a high-strength graphite plate as an interlayer between the stacked layers; then carrying out hot-pressing sintering treatment;
and cooling and annealing, namely cooling and annealing after the high-temperature heat preservation process of the hot-pressing sintering treatment is finished, and naturally cooling to obtain the high-strength high-heat-conductivity large-size silicon nitride ceramic.
In the above method for preparing a high-strength high-thermal conductivity large-size silicon nitride ceramic, as a preferred embodiment, after the step of cooling and annealing, the method further includes: and a post-treatment step, namely dividing, slicing and polishing by adopting an electroplated diamond wire slicing machine to obtain the silicon nitride ceramic substrate with the required size.
In the preparation method of the high-strength high-heat-conductivity large-size silicon nitride ceramic, as a preferred implementation manner, in the batching and mixing step, the oxygen content of the submicron low-oxygen silicon nitride powder is less than or equal to 1.2%; more preferably, the submicron low-oxygen silicon nitride powder is at least one of first silicon nitride powder prepared by adopting a high-temperature self-propagating combustion synthesis process and second silicon nitride powder prepared by adopting a silicon imine decomposition process; further preferably, in the submicron low-oxygen silicon nitride powder, the first silicon nitride powder accounts for 30-100 wt.%, the second silicon nitride powder accounts for 0-70 wt.%, still further, the first silicon nitride powder accounts for 55-90 wt.%, and the second silicon nitride powder accounts for 10-45 wt.%.
In the above method for preparing high-strength high-thermal conductivity large-size silicon nitride ceramic, as a preferred embodiment, in the step of mixing the ingredients and the powder, the nitride refers to SiMgN 2 、Mg 3 N 2 One or two of the fluoride is MgF 2 、YF 3 、YbF 3 、LaF 3 One or more of them.
More preferably, the composite sintering aid, i.e., the total amount of nitride and fluoride is added in a proportion of 8% or less (mass fraction such as 7%, 6%, 5%, 4%, etc.); in other words, the amount of the composite sintering aid added is 8% or less of the total mass of the silicon nitride powder and the composite sintering aid.
In the above method for preparing high-strength high-thermal conductivity large-size silicon nitride ceramic, as a preferred embodiment, in the step of batching and mixing powder, the uniform mixing treatment comprises sequentially performing ball milling, drying, granulating and sieving.
More preferably, the ball milling treatment is performed in an alcohol medium, and the grinding balls are silicon nitride ceramic balls.
More preferably, the drying treatment is spray drying under the protection of inert gas such as nitrogen or argon; or, drying in an oven at 60-110deg.C (such as 65deg.C, 70deg.C, 80deg.C, 90deg.C, 100deg.C, 105deg.C, etc.).
More preferably, the granulation/sieving process, such as spray drying process, may be accomplished directly in one step with spray granulation during the drying process, such as drying process in an oven at 60-110℃ (e.g., 65℃, 70℃, 80℃, 90℃, 100℃, 105℃, etc.), with the need for crushing followed by sieving, preferably through a 40-60 mesh screen (i.e., referring to undersize, the mesh size may be selected between 40-60 mesh).
In the above method for preparing a high-strength high-thermal-conductivity large-size silicon nitride ceramic, as a preferred embodiment, in the pre-pressing step, the pressure of the cold isostatic pressing is 150 to 300MPa (for example, 160MPa, 180MPa, 200MPa, 220MPa, 250MPa, 270MPa, 290MPa, etc.).
In the above method for preparing a high-strength high-thermal conductivity large-size silicon nitride ceramic, as a preferred embodiment, in the pre-pressing step, the vibration frequency of the vibration pressure forming treatment is 1000-3000 times/min (for example, 1200 times/min, 1500 times/min, 1800 times/min, 2000 times/min, 2300 times/min, 2500 times/min, 2800 times/min, etc.), and the exciting force is 20-60KN (for example, 25KN, 30KN, 40KN, 50KN, 55KN, etc.).
In the above method for preparing high-strength high-thermal conductivity large-size silicon nitride ceramic, as a preferred embodiment, in the hot press sintering step, the green body thickness after trimming the shaped blank is 15-80 mm, the length is 190-385 mm, and the width is 230-350 mm.
In the method for preparing the high-strength high-heat-conductivity large-size silicon nitride ceramic, as a preferred implementation manner, in the hot-press sintering step, the die is a high-strength carbon fiber reinforced carbon-carbon composite material die, and the volume density of the die is more than or equal to 1.7g/cm 3 The circumferential tensile strength is more than or equal to 100MPa. The traditional graphite mold can be adopted, but the effect is inferior to that of the carbon-carbon composite material mold reinforced by the high-strength carbon fiber.
In the above method for preparing a high-strength high-thermal conductivity large-size silicon nitride ceramic, as a preferred embodiment, in the hot press sintering step, the number of layers of the green mold-filling stack thickness is 1-5 (for example, 2, 3, 4).
In the above method for preparing high-strength high-thermal conductivity large-size silicon nitride ceramic, as a preferred embodiment, in the hot press sintering step, the hot press sintering treatment is to apply a pressure of 30-60 MPa (such as 35MPa, 40MPa, 45MPa, 50MPa, 55MPa, etc.) in a nitrogen atmosphere (such as 1620 ℃, 1650 ℃, 1700 ℃, 1750 ℃, 1800 ℃, 1850 ℃, 1880 ℃, etc.) in two directions for 2-10 h (such as 3h, 4h, 5h, 6h, 7h, 8h, 9h, etc.) under the condition of heat preservation.
In the above method for preparing high-strength high-thermal conductivity large-size silicon nitride ceramic, as a preferred embodiment, in the cooling annealing step, the cooling annealing treatment is to cool the silicon nitride ceramic to 1200-1500 ℃ (such as 1220 ℃, 1250 ℃, 1300 ℃, 1350 ℃, 1400 ℃, 1450 ℃, 1480 ℃) in the same furnace after the hot-press sintering high-temperature heat preservation process is finished, and keep the temperature for 2-6 hours (such as 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, etc.).
The high-strength high-heat-conductivity large-size silicon nitride ceramic is prepared by adopting the method.
Preferably, the density of the high-strength high-heat-conductivity large-size silicon nitride ceramic is more than 99.3%, the bending strength is 800-1180 MPa, and the heat conductivity is 80-136W/m.K.
Preferably, the thickness of the high-strength high-heat-conductivity large-size silicon nitride ceramic is 10-50 mm, the length is 190-385 mm, and the width is 230-350 mm.
Compared with the prior art, the invention has the beneficial effects that:
1. the preparation method provided by the invention can prepare the silicon nitride ceramic substrate with excellent performance, the density is more than 99.3%, the bending strength is 800-1180 MPa, the thermal conductivity is 80-136W/m.K, and the mechanical property and the thermal conductivity are excellent.
2. The preparation method provided by the invention can prepare 1-5 layers of large-size high-strength high-heat-conductivity silicon nitride ceramic blocks with the thickness of 10-50 mm, the length of 190-385 mm and the width of 230-350 mm at one time.
3. The large-size high-strength high-heat-conductivity silicon nitride ceramic block obtained by the invention can be flexibly adjusted according to the needs after being divided, sliced and polished by combining a diamond wire multi-wire cutting technology to obtain the large-size silicon nitride ceramic substrate with adjustable thickness of 0.2-0.6 mm and not limited to 114mm, 138 mm and 190mm which are common in current businesses, and the roughness is less than or equal to 0.5 mu m, so that the silicon nitride ceramic substrate for packaging of high-power semiconductor IGBT and the like is met.
4. Compared with the existing wet tape casting molding-degreasing-high-pressure atmosphere sintering process of the substrate manufacturing technology, the method for preparing the high-strength high-thermal conductivity large-size ceramic substrate by the hot-pressing sintering method develops a new process technology system, can solve the defects of the prior art, can prepare the high-strength high-thermal conductivity silicon nitride substrate material with low cost, high efficiency, no pollution, short flow and high performance, and can realize substitution and progress.
Drawings
FIG. 1 is a flow chart of a process for preparing a high-strength high-heat-conductivity large-size silicon nitride ceramic block and further preparing a silicon nitride ceramic substrate by hot-press sintering according to an embodiment of the invention;
fig. 2 is a process flow diagram of hot press sintering for preparing a high-strength high-thermal conductivity large-size silicon nitride ceramic substrate according to a preferred embodiment of the invention.
Detailed Description
The preparation method of the high-strength high-heat-conductivity large-size silicon nitride ceramic substrate according to a certain specific preferred embodiment of the invention, referring to a flow chart shown in fig. 1, comprises the following steps: batching, ball milling, drying, granulating/sieving, cold isostatic pressing, green body processing, single-layer or multi-layer die filling, hot pressing sintering, cooling annealing, cutting, slicing and polishing. Referring to fig. 2, the preparation method specifically comprises the following preparation steps:
step 100, mixing with low-oxygen silicon nitride powder serving as a raw material, and adding a nitride and a fluoride which do not contain oxygen serving as a composite sintering auxiliary agent;
step 101, ball milling, drying, granulating and sieving the materials prepared in the step 100 to obtain uniformly mixed formula powder;
102, filling the formula powder obtained in the step 101 into a die, vacuumizing, and prepressing by cold isostatic pressing to obtain a molded blank;
step 103, machining and trimming the molded blank obtained in the step 102 to obtain a green body;
104, stacking the processed green bodies obtained in the step 103 into a high-strength carbon fiber reinforced carbon-carbon composite material mold, and using graphite paper or a high-strength graphite plate as a separation layer between the stacked layers;
step 105, hot pressing sintering treatment under the condition of bidirectionally applying pressure in nitrogen atmosphere;
step 106, cooling and annealing treatment after the hot-pressing sintering high-temperature heat preservation is finished, and then naturally cooling;
and 107, cutting, slicing and polishing the high-strength, high-heat-conductivity and large-size silicon nitride block blank obtained in the step 106 by adopting an electroplated diamond wire slicing machine to obtain the silicon nitride ceramic substrate with the required size.
Preferably, the submicron silicon oxynitride powder described in step 100 has an oxygen content of 1.2wt.%; the composite powder formed by the silicon nitride powder prepared by the low-cost high-temperature self-propagating combustion synthesis process and the high-purity silicon nitride powder prepared by the silicon imine decomposition process is mainly silicon nitride powder prepared by the high-temperature self-propagating combustion synthesis process, for example, 55-90 wt.% of the silicon nitride powder prepared by the high-temperature self-propagating combustion synthesis process and 10-45 wt.% of the high-purity silicon nitride powder prepared by the silicon imine decomposition process.
Preferably, the composite sintering aid of step 100, wherein the nitride is SiMgN 2 、Mg 3 N 2 One or two of the fluoride is MgF 2 、YF 3 、YbF 3 、LaF 3 One or more of them.
Preferably, the composite sintering aid in step 100 includes the total amount of nitride and fluoride added in a proportion of 8wt.% (e.g., 7wt.%, 6wt.%, 5wt.%, 4wt.%, etc.), in other words, the composite sintering aid is added in an amount of 8% or less of the total mass of the silicon nitride powder and the composite sintering aid.
Preferably, the ball milling process in step 101 is performed in an ethanol medium, and the grinding balls are silicon nitride ceramic balls.
Preferably, the drying process in step 101 is a spray drying process under the protection of inert gas such as nitrogen or argon or a drying process in an oven of 60-110 ℃ (such as 65 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 105 ℃ and the like), and one of them is selected.
Preferably, the granulation/sieving process in step 101, such as selecting a spray drying process, may be accomplished directly in a drying process while spraying granulation in one step, such as selecting a drying process in an oven at 60-110 ℃ (e.g. 65 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 105 ℃, etc.), sieving after crushing is required, and the mesh size of the sieve may be 40-60 mesh.
Preferably, the cold isostatic pressing preform pressure in step 102 is 150-300 MPa (e.g. 160MPa, 180MPa, 200MPa, 220MPa, 250MPa, 270MPa, 290MPa, etc.).
Preferably, in step 103, the green body is obtained by machining and trimming the preform obtained by cold isostatic pressing, wherein the thickness of the green body is 15-80 mm, the length is 190-385 mm, and the width is 230-350 mm.
Preferably, the high-strength carbon fiber reinforced carbon-carbon composite material mold in step 104 has a bulk density of 1.7g/cm or more 3 The circumferential tensile strength is more than or equal to 100MPa.
Preferably, the green mold stack thickness in step 104 has 1 to 5 layers (e.g., 2, 3, 4 layers). If only 1 layer of green body is provided, obviously, graphite paper or high-strength graphite plates are not required to be used as a interlayer.
Preferably, the hot press sintering in step 105 is performed under a nitrogen atmosphere of 1600-1900 ℃ (such as 1620 ℃, 1650 ℃, 1700 ℃, 1750 ℃, 1800 ℃, 1850 ℃, 1880 ℃, etc.) under a pressure condition of 30-60 MPa (such as 35MPa, 40MPa, 45MPa, 50MPa, 55MPa, etc.) applied in two directions, and the heat is preserved for 2-10 h (such as 3h, 4h, 5h, 6h, 7h, 8h, 9h, etc.).
Preferably, the cooling annealing treatment in step 106 is to cool the furnace to 1200-1500 ℃ (such as 1220 ℃, 1250 ℃, 1300 ℃, 1350 ℃, 1400 ℃, 1450 ℃, 1480 ℃ and the like) after the hot-press sintering high-temperature heat preservation process is finished, heat-preserving for 2-6 hours (such as 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours and the like) for annealing, and then naturally cooling. And the annealing is carried out in the same furnace, so that the cost can be reduced, the thermal stress of the ceramic product can be reduced, and the Bao Zhibei silicon nitride ceramic substrate finished product can be cut further.
The high-strength high-heat-conductivity large-size silicon nitride ceramic prepared by the method has the compactness of more than 99.3%, the bending strength of 800-1180 MPa, the heat conductivity of 80-136W/m.K, and the dimension specification of 10-50 mm in thickness, 190-385 mm in length and 230-350 mm in width.
The core thought of the invention is as follows:
1) The hot pressing technology is adopted, which has short flow and is more suitable for densification sintering of simple-shaped products such as silicon nitride ceramic substrates and the like. Si-N bond in silicon nitride belongs to strong bonding effect, has low diffusion coefficient, and depends on low densification driving force generated by self, and hot-pressed sintering is to prepare compact Si 3 N 4 Is an effective method of (a). During sintering, mechanical pressure acts on the material to increase the sintering driving force, so that Si can be obtained 3 N 4 The grains of the ceramic are fully contacted in the sintering process, so that the atomic diffusion of the grains is promoted, the plastic deformation of the silicon nitride in the densification process is promoted, the rapid densification is facilitated, and the good mechanical property is obtained. Moreover, the shape of the substrate is simple, and the hot press sintering is easier to transmit sintering power and is beneficial to industrial realization. In addition, the hot pressing has the beneficial effects of reducing the consumption of sintering auxiliary agents, reducing the content of grain boundary phases, improving the purity of main phases and being beneficial to improving the heat conductivity.
2) In order to further break through the densification degree of hot pressing, the traditional method of directly adopting powder to load a die for hot pressing is improved, and a cold isostatic pressing preforming process is added before hot pressing. The cold isostatic pressing preforming can lead the blank to obtain more than 70% of density in advance, the compression amount is smaller in the later hot pressing process, the compression stroke of the pressure head is shorter, and the primary charging amount is larger.
3) The multi-layer die-filling process can be used for sintering a plurality of blocks simultaneously, and the length and the width of the multi-layer die-filling process can be used for realizing large yield according to the multiple sizes of commercial substrates, so that the cost is reduced. To achieve this, a high strength mold made of carbon fiber reinforced carbon-carbon composite material is used. To achieve densification by simultaneous pressurization of large-size, multiple layers, the pressure of hot pressing must be increased, and a high-strength hot pressing die is critical. In addition, the pressurizing mode is bidirectional axial pressurizing in which the upper pressure head and the lower pressure head are simultaneously pressurized, so that the uniformity of the density among different layers is ensured. Moreover, the thick plate sintering is not easy to cause warping, deformation and the like in the casting method process.
4) To achieve high thermal conductivity, it is desirable to reduce the oxygen content in the silicon nitride ceramic to reduce phonon scattering. The adverse effect of oxygen can be reduced by compounding a low-oxygen silicon nitride raw material with a nitride or fluoride sintering aid that does not contain oxygen. The composite non-oxide sintering aid can reduce the content of M-Si-O-N glass phase at the grain boundary, and researches show that the heat conductivity of the glass phase is only about 1W/mK and is far lower than that of grains. Meanwhile, the method of vacuumizing during cold static pressure forming and the hot pressure sintering under the protection of nitrogen atmosphere can systematically reduce the oxygen content, and are beneficial to the improvement of heat conductivity.
5) In order to reduce the cost of raw materials, the silicon nitride powder synthesized by self-propagating combustion is mainly used. The hot press sintering process is favorable for densification, has lower requirement on sintering activity of raw materials than that of a casting method, reduces dependence on silicon nitride powder by a silicon imine decomposition method, and can greatly reduce production cost.
6) The obtained high-strength high-heat-conductivity large-size hot-pressed sintered block is divided, sliced and polished by adopting diamond wire multi-wire cutting, and the high-performance silicon nitride ceramic substrate with the quality meeting the requirement is obtained. The multi-line diamond wire processing technology has been successfully applied to the fields of high-hardness ceramic materials such as polycrystalline silicon wafer processing, sapphire processing, silicon carbide wafer processing and the like through development and iteration for many years, the processing efficiency is doubled, the processing loss is gradually reduced, the consumable price of equipment and electroplated diamond wires is reduced to a low point, multi-line slicing can be realized, and the cutting efficiency is higher. The hot-press sintering technology and the recent mature diamond wire multi-wire cutting technology are combined, so that the ceramic material is a historical intersection of material technology progress and processing technology progress, and can be distinguished from the traditional novel ceramic material preparation technology.
7) In order to ensure that the large-size hot-pressed sintered block has high processing qualification rate and few cracks, an annealing process is added at a low temperature section when the temperature is reduced after the hot-pressed sintering is finished at high temperature so as to reduce the internal stress of the sintered block and avoid crack expansion caused by the internal stress in the process of cutting into slices after cooling.
The following examples are given to illustrate the present invention in further detail, but the scope of the present invention is not limited to the following examples. The examples do not identify specific experimental procedures or conditions, which may be followed by procedures or conditions that are routine procedures described in the literature in this field. The reagents and starting materials used in the examples were all commercially available. Examples high strength carbon fiber reinforced carbon-carbon composite mold for hot-pressed sintering was produced from samekin electronic new materials, inc., carbon-carbon composite was a carbon fiber and its fabric reinforced carbon matrix composite with low density @, and<2.0g/cm 3 ) High strength, high specific modulus, high thermal conductivity, low expansion coefficient, good friction performance, good thermal shock resistance, high dimensional stability and the like.
Example 1
The embodiment provides a high-strength high-heat-conductivity large-size silicon nitride ceramic substrate, and the preparation method thereof sequentially comprises the following steps:
1) A certain amount of silicon nitride powder and a sintering aid are taken for proportioning, wherein d50=0.7 μm, the oxygen content is 1wt.% of self-propagating combustion synthetic powder silicon nitride powder 55.2%, d50=0.8 μm silicon imine decomposition method silicon nitride powder 36.8%, and the sintering aid SiMgN are calculated according to mass percent 2 4％、Mg 3 N 2 1％、YF 3 1％、YbF 3 2％；
2) Ball milling is carried out on silicon nitride balls in an alcohol medium for 6 hours, and slurry is dried and sprayed for granulation in a nitrogen protective atmosphere to obtain evenly mixed formula powder;
3) Filling powder into a rubber mold, vacuumizing, performing cold isostatic pressing molding under 200MPa, filling 1 layer of the green body into a carbon-carbon composite material mold reinforced by carbon fibers after machining, performing heat preservation for 4 hours under the condition of bidirectionally applying 35MPa pressure in a nitrogen protective atmosphere at 1800 ℃, performing hot pressing sintering, cooling to 1400 ℃ in the same furnace after high-temperature heat preservation is finished, performing heat preservation for 4 hours, performing annealing treatment, naturally cooling, and discharging to obtain 1 ceramic block with the thickness of 40mm and the length of 385mm and the width of 280 mm;
4) The silicon nitride ceramic substrate with 138 mm and 0.4 mu m roughness can be obtained by adopting a diamond wire saw to divide, cut and polish, and the bending strength 1180MPa and the thermal conductivity 136W/m.K of the material can be measured by block sampling.
Example 2
The embodiment provides a high-strength high-heat-conductivity large-size silicon nitride ceramic substrate, and the preparation method thereof sequentially comprises the following steps:
1) A certain amount of silicon nitride powder and a sintering aid are taken for proportioning, wherein d50=0.7 μm, the oxygen content is 1wt.% of self-propagating combustion synthetic powder silicon nitride powder 55.2%, d50=0.8 μm silicon imine decomposition method silicon nitride powder 36.8%, and the sintering aid SiMgN are calculated according to mass percent 2 4％、YF 3 4, batching;
2) Ball milling is carried out on silicon nitride balls in an alcohol medium for 6 hours, and slurry is dried and sprayed for granulation in a nitrogen protective atmosphere to obtain evenly mixed formula powder;
3) Filling powder into a rubber mold, carrying out cold isostatic pressing molding under 200MPa after vacuumizing, stacking 2 layers of carbon fiber reinforced carbon-carbon composite material molds after machining, separating the stacked layers by using high-strength graphite plates, carrying out heat preservation for 4 hours under the condition of bidirectionally applying 35MPa pressure in a nitrogen protective atmosphere at 1820 ℃, carrying out hot pressing sintering, cooling to 1400 ℃ with a furnace after the high-temperature heat preservation is finished, carrying out heat preservation for 4 hours, carrying out annealing treatment, then naturally cooling, and discharging to obtain 2 ceramic blocks with the thickness of 30mm and the length of 190mm and the width of 280 mm;
the silicon nitride ceramic substrate with 138 mm, 0.4 mu m roughness can be obtained by adopting a diamond wire saw to divide, cut and polish, and the bending strength 970MPa and the thermal conductivity 118W/m.K of the material can be measured by block sampling.
Example 3
The embodiment provides a high-strength high-heat-conductivity large-size silicon nitride ceramic substrate, and the preparation method thereof sequentially comprises the following steps:
1) Taking a certain amount of silicon nitride powder and sintering aid, and preparing the silicon nitride powder and the sintering aid according to mass percentage, wherein d50=0.7 mu m, the self-propagating combustion synthetic powder silicon nitride powder with the oxygen content of 1% is 55.2%, d50=0.8 mu m silicon imine decomposition method silicon nitride powder is 36.8%, and the sintering aid SiMgN is prepared by the following steps of 2 4％、YbF 3 4, batching;
2) Ball milling is carried out on silicon nitride balls in an alcohol medium for 6 hours, and the material paste is dried and sprayed for granulation in a nitrogen protective atmosphere to obtain evenly mixed formula powder;
3) Filling powder into a rubber mold, carrying out cold isostatic pressing molding under 250MPa after vacuumizing, stacking 3 layers of powder into a carbon-carbon composite material mold reinforced by carbon fibers after machining, separating the stacked layers by using high-strength graphite plates, carrying out heat preservation for 5 hours under the condition of bidirectionally applying 40MPa pressure in a nitrogen protective atmosphere at 1850 ℃, carrying out hot pressing sintering, cooling to 1400 ℃ with a furnace after the high-temperature heat preservation is finished, carrying out heat preservation for 5 hours, carrying out annealing treatment, then naturally cooling, and discharging to obtain 3 ceramic blocks with the thickness of 25mm and the length of 240mm and the width of 240 mm;
4) The silicon nitride ceramic substrate with 114mm and 0.4 mu m roughness can be obtained by adopting a diamond wire saw for segmentation, dicing and polishing, and the bending strength 870MPa and the thermal conductivity 93W/m.K of the material can be measured by block sampling.
Example 4
The embodiment provides a high-strength high-heat-conductivity large-size silicon nitride ceramic substrate, and the preparation method thereof sequentially comprises the following steps:
1) A certain amount of silicon nitride powder and a sintering aid are taken for proportioning, wherein d50=0.7 μm, 50.6% of self-propagating combustion synthetic powder silicon nitride powder with the oxygen content of 1wt.% and 41.4% of d50=0.8 μm silicon imine decomposition method silicon nitride powder are prepared according to mass percentage, and the sintering aid SiMgN is prepared by the following steps of 2 4％、Mg 3 N 2 1％、YbF 3 2％、LaF 3 1, batching;
2) Ball milling is carried out on silicon nitride balls in an alcohol medium for 6 hours, and the material paste is dried and sprayed for granulation in a nitrogen protective atmosphere to obtain evenly mixed formula powder;
3) Filling powder into a rubber mold, vacuumizing, performing cold isostatic pressing molding under 250MPa, stacking 5 layers of powder into a carbon-carbon composite material mold reinforced by carbon fibers after machining, separating the stacked layers by graphite paper, performing hot pressing sintering under the condition of bidirectionally applying 45MPa pressure in a nitrogen protective atmosphere at 1880 ℃, cooling to 1400 ℃ with a furnace after high-temperature heat preservation is finished, performing heat preservation for 5 hours, performing annealing treatment, naturally cooling, and discharging to obtain 5 ceramic blocks with the thickness of 20mm and the length of 240mm and the width of 240 mm;
4) The silicon nitride ceramic substrate with 114mm and 0.4 mu m roughness can be obtained by adopting diamond wire saw cutting, dicing and polishing, and the bending strength of the material is 830MPa and the thermal conductivity is 89W/m.K by block sampling.
According to the embodiment, the invention discloses a preparation method for preparing a high-strength high-heat-conductivity large-size silicon nitride ceramic substrate material by hot-press sintering, which adopts low-oxygen silicon nitride powder as a raw material, adds non-oxygen nitride and fluoride as a composite sintering auxiliary agent, prepares a large-size silicon nitride ceramic block blank with high mechanical property and high heat conductivity by proportioning, ball milling, drying, granulating/sieving, cold isostatic pressing preforming, green body machining, multilayer die filling, hot-press sintering and annealing, and has the advantages of high compactness, high bending strength of more than 800MPa, low oxygen content, less grain boundary glass phase, high heat conductivity of more than 80W/m.K, thickness of 10-50 mm, length of 190-385 mm and width of 230-350 mm; and then the silicon nitride ceramic substrate for packaging such as high-power semiconductor IGBT and the like with urgent industrial requirements can be prepared by cutting, slicing and polishing through a diamond wire multi-wire cutting technology. Compared with the existing wet tape casting molding-degreasing-high-pressure atmosphere sintering process of the substrate manufacturing technology, the hot pressing sintering method provided by the invention can be combined with the new process method of multi-wire cutting of the diamond wire which is raised in recent years, so that the high-strength high-heat-conductivity silicon nitride substrate material can be prepared with low cost, high efficiency, no pollution, short flow and high performance.
Finally, it is further noted that relational terms such as left and right, first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
While the disclosure has been disclosed by the foregoing description of specific embodiments thereof, it will be understood that various modifications, improvements, or equivalents may be devised by those skilled in the art that will fall within the spirit and scope of the appended claims. Such modifications, improvements, or equivalents are intended to be included within the scope of this disclosure.
Claims (2)
1. The preparation method of the high-strength high-heat-conductivity large-size silicon nitride ceramic is characterized by comprising the following steps in sequence:
1) Taking a certain amount of silicon nitride powder and a sintering aid, and preparing the silicon nitride powder and the sintering aid according to mass percentage, wherein d50=0.7 μm and oxygen content 1wt.% are 55.2% of self-propagating combustion synthetic powder silicon nitride powder, d50=0.8 μm silicon imine decomposition method silicon nitride powder 36.8%, and the sintering aid MgSiN 2 4%、Mg 3 N 2 1%、YF 3 1%、YbF 3 2%；
2) Ball milling is carried out on silicon nitride balls in an alcohol medium for 6 hours, and slurry is dried and sprayed for granulation in a nitrogen protective atmosphere to obtain evenly mixed formula powder;
3) Filling powder into a rubber mold, vacuumizing, performing cold isostatic pressing molding under 200MPa, filling 1 layer of the green body into a carbon-carbon composite material mold reinforced by carbon fibers after machining, performing heat preservation for 4 hours under the condition of bidirectionally applying 35MPa pressure in a nitrogen protective atmosphere at 1800 ℃, performing hot pressing sintering, cooling to 1400 ℃ in the same furnace after high-temperature heat preservation is finished, performing heat preservation for 4 hours, performing annealing treatment, naturally cooling, and discharging to obtain 1 ceramic block with the thickness of 40mm and the length of 385mm and the width of 280 mm;
4) The silicon nitride ceramic substrate with 138 multiplied by 190mm and 0.4 mu m roughness can be obtained by adopting a diamond wire saw to divide, cut and polish, and the bending strength 1180MPa and the thermal conductivity 136W/m.K of the material can be obtained by block sampling.
2. The preparation method of the high-strength high-heat-conductivity large-size silicon nitride ceramic is characterized by comprising the following steps in sequence:
1) A certain amount of silicon nitride powder and a sintering aid are taken for proportioning, wherein d50=0.7 μm, the oxygen content is 1wt.% of self-propagating combustion synthetic powder silicon nitride powder 55.2%, d50=0.8 μm silicon imine decomposition method silicon nitride powder 36.8%, and the sintering aid MgSiN are calculated according to mass percent 2 4%、YF 3 4%；
2) Ball milling is carried out on silicon nitride balls in an alcohol medium for 6 hours, and slurry is dried and sprayed for granulation in a nitrogen protective atmosphere to obtain evenly mixed formula powder;
3) Filling powder into a rubber mold, carrying out cold isostatic pressing molding under 200MPa after vacuumizing, stacking 2 layers of carbon fiber reinforced carbon-carbon composite material molds after machining, separating the stacked layers by using high-strength graphite plates, carrying out heat preservation for 4 hours under the condition of bidirectionally applying 35MPa pressure in a nitrogen protective atmosphere at 1820 ℃, carrying out hot pressing sintering, cooling to 1400 ℃ with a furnace after the high-temperature heat preservation is finished, carrying out heat preservation for 4 hours, carrying out annealing treatment, then naturally cooling, and discharging to obtain 2 ceramic blocks with the thickness of 30mm and the length of 190mm and the width of 280 mm;
4) The silicon nitride ceramic substrate with 138 multiplied by 190mm and 0.4 mu m roughness can be obtained by adopting a diamond wire saw to divide, cut and polish, and the bending strength 970MPa and the thermal conductivity 118W/m.K of the material can be measured by block sampling.
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