Water-based boron nitride slurry, its preparation method and application

Abstract

This application relates to a water-based boron nitride slurry, its preparation method, and its application. The water-based boron nitride slurry comprises boron nitride powder, a mixed solvent, a binder emulsion, and a defoamer. The mixed solvent comprises the following components in the following mass percentages: 49%~74% deionized water, 0.8%~2% dispersant, and 25%~50% wetting agent. The wetting agent includes a polyol, which includes at least one selected from ethylene glycol, propylene glycol, glycerol, butanediol, and diethylene glycol. This improves the strength of water-based silicon nitride ceramic substrates prepared by water-based casting and enhances the environmental friendliness of the water-based boron nitride slurry.

Description

Technical Field

[0001] This application relates to the field of ceramic slurry technology, and in particular to a water-based boron nitride slurry, its preparation method, and its application. Background Technology

[0002] As power modules develop towards higher voltage, higher current, smaller size and higher power density, heat dissipation has become one of the important technical bottlenecks. At present, the mainstream high thermal conductivity heat dissipation ceramic substrates are mainly silicon nitride and aluminum nitride substrates, among which silicon nitride ceramic substrates have the best overall performance.

[0003] To improve production efficiency, silicon nitride or aluminum nitride ceramic substrates are stacked in a boron nitride crucible during sintering, with the number of stacks ranging from 5 to 20. Because some liquid phase is generated during high-temperature sintering, the stacked layers easily stick together. Therefore, a separating powder is needed between the ceramic blanks for high-temperature isolation. Boron nitride powder is commonly used as the separating powder. However, traditional boron nitride slurries containing boron nitride powder are highly polluting, have a strong odor, and are harmful to human health. The organic solvents in the boron nitride slurry can dissolve the binder in the ceramic blanks, destroying the surface density of the ceramic blanks and affecting the strength of the ceramic substrate. Summary of the Invention

[0004] Based on this, this application provides a water-based boron nitride slurry, its preparation method, and its application, to improve the strength of ceramic substrates and the environmental friendliness of the water-based boron nitride slurry.

[0005] A first aspect of this application provides a water-based boron nitride slurry, the water-based boron nitride slurry comprising boron nitride powder, a mixed solvent, a binder emulsion, and a defoamer, wherein the mixed solvent comprises the following components in the following mass percentages: 49%~74% deionized water, 0.8%~2% dispersant, and 25%~50% wetting agent, wherein the wetting agent comprises a polyol, the polyol comprising at least one selected from ethylene glycol, propylene glycol, glycerol, butanediol, and diethylene glycol.

[0006] In some embodiments, the water-based boron nitride slurry comprises, by weight percentage, 45% to 58% of the boron nitride powder, 32% to 46% of the mixed solvent, 8% to 20% of the binder emulsion, and 0.01% to 1% of the defoamer.

[0007] In some embodiments, the solid content of the adhesive emulsion is 25% to 45%.

[0008] In some embodiments, the solvent in the adhesive emulsion includes water.

[0009] In some embodiments, the adhesive emulsion contains an adhesive, which includes at least one of polyvinyl alcohol adhesives and waterborne acrylic resin adhesives.

[0010] In some embodiments, the boron nitride powder has a hexagonal crystal form.

[0011] In some embodiments, the boron nitride powder has a sheet-like structure.

[0012] In some embodiments, the average particle size D50 of the boron nitride powder is 5 μm to 15 μm.

[0013] In some embodiments, the mass percentage of oxygen in the boron nitride powder is ≤0.5%.

[0014] In some embodiments, the dispersant includes at least one of polyacrylamide, polyacrylamide, tributyl phosphate, polymethacrylamide, and succinimide.

[0015] In some embodiments, the defoamer includes at least one of octanol, trioctyl phosphate, nonylphenol polyoxyethylene ether, and distearate ethylenediamine.

[0016] A second aspect of this application provides a method for preparing a water-based boron nitride slurry, comprising the following steps:

[0017] Boron nitride powder, mixed solvent and part of defoamer are mixed to obtain a mixed slurry;

[0018] The mixed slurry is subjected to a first ball milling process;

[0019] The slurry obtained from the first ball milling process is mixed with the binder emulsion and the remaining defoamer, and then subjected to a second ball milling process.

[0020] The slurry obtained from the second ball milling process is subjected to defoaming treatment to obtain the water-based boron nitride slurry;

[0021] The water-based boron nitride slurry comprises the boron nitride powder, the mixed solvent, the binder emulsion, and the defoamer. The defoamer comprises the partial defoamer and the remaining defoamer. The mixed solvent comprises the following components in the following mass percentages: 49%~74% deionized water, 0.8%~2% dispersant, and 25%~50% wetting agent. The wetting agent comprises a polyol, which comprises at least one of ethylene glycol, propylene glycol, glycerol, butanediol, and diethylene glycol.

[0022] In some embodiments, the water-based boron nitride slurry comprises, by weight percentage, 45% to 58% of the boron nitride powder, 32% to 46% of the mixed solvent, 8% to 20% of the binder emulsion, and 0.01% to 1% of the defoamer.

[0023] In some embodiments, the process conditions for the first ball milling treatment include: the diameter of the ball milling media is 1 mm to 10 mm, the rotation speed of the ball milling treatment is 180 r / min to 300 r / min, and the ball milling treatment time is 0.5 h to 4 h.

[0024] In some embodiments, the average particle size of the particles in the slurry obtained from the first ball milling process is 3 μm to 10 μm.

[0025] In some embodiments, the process conditions for the second ball milling treatment include: the diameter of the ball milling media is 1 mm to 10 mm, the rotation speed of the ball milling treatment is 100 r / min to 200 r / min, and the ball milling treatment time is 1 h to 5 h.

[0026] In some embodiments, the defoamer accounts for 20% to 70% of the total mass of the defoamer, and the remaining defoamer accounts for 30% to 80% of the total mass of the defoamer.

[0027] In some embodiments, the method for preparing the mixed solvent includes the following steps: mixing the deionized water, the dispersant, and the wetting agent, thereby dispersing the dispersant and the wetting agent in the deionized water to obtain the mixed solvent.

[0028] A third aspect of this application provides the application of the water-based boron nitride slurry described in the first aspect of this application or the water-based boron nitride slurry prepared by the preparation method described in the second aspect of this application in the preparation of ceramic isolation powder.

[0029] Compared with traditional technologies, the above-mentioned water-based boron nitride slurry has at least the following advantages:

[0030] The aforementioned water-based boron nitride slurry uses deionized water as a solvent, which can reduce the dissolution of the binder in the ceramic blank, increase the density of the ceramic blank, and thus improve the density and strength of the ceramic substrate after sintering. At the same time, the slurry is more environmentally friendly, reduces harm to the human body, and is more environmentally friendly. Detailed Implementation

[0031] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, a detailed description of specific embodiments of this application is provided below. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0032] In this application, terms such as "first aspect," "second aspect," and "third aspect" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, terms such as "first," "second," and "third" serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0033] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0034] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0035] In this application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0036] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used in this application and in its specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used in this application includes any and all combinations of one or more of the associated listed items. The term "multiple" in this application means at least two, such as two, three, etc., unless otherwise expressly specified.

[0037] One embodiment of this application provides a water-based boron nitride slurry, which includes boron nitride powder, a mixed solvent, a binder emulsion, and a defoamer. The mixed solvent includes the following components in the following mass percentages: 49%~74% deionized water, 0.8%~2% dispersant, and 25%~50% wetting agent. The wetting agent includes a polyol, which includes at least one of ethylene glycol, propylene glycol, glycerol, butanediol, and diethylene glycol.

[0038] In the above embodiments, the water-based boron nitride paste uses deionized water as a solvent, which can reduce the dissolution of binders in ceramic blanks, increase the density of ceramic blanks, and thus improve the density and strength of the sintered ceramic substrate. This paste is more environmentally friendly, reducing harm to the human body and improving environmental protection. Furthermore, traditional boron nitride pastes require explosion-proof measures during drying, and the exhaust gas from the drying oven needs to be treated to render it harmless, increasing operating costs. The reduction in the amount of organic solvent in the above-mentioned water-based boron nitride paste can significantly reduce operating costs. In addition, the above-mentioned water-based boron nitride paste has good printability and can be used as a printing paste.

[0039] It should be noted that wetting agents can improve the wettability of water-based boron nitride slurries, thereby extending the slurry's service life. Ethylene glycol, propylene glycol, glycerol, butanediol, and diethylene glycol, among other alcohol solvents, have strong dissolving power, low toxicity and volatility, and significantly less odor than terpineol and isopropanol. Therefore, although the aforementioned water-based boron nitride slurries contain at least one of ethylene glycol, propylene glycol, glycerol, butanediol, and diethylene glycol, they are significantly more environmentally friendly than traditional boron nitride slurries, greatly reducing harm to human health. It is understood that the mass percentage of deionized water includes, but is not limited to: 49%, 50%, 53%, 56%, 60%, 63%, 66%, 70%, 72%, and 74%; the mass percentage of dispersant includes, but is not limited to: 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, and 2%; and the mass percentage of wetting agent includes, but is not limited to: 25%, 28%, 30%, 33%, 36%, 40%, 43%, 46%, and 50%.

[0040] In some embodiments, the water-based boron nitride paste comprises, by weight percentage, 45%–58% boron nitride powder, 32%–46% mixed solvent, 8%–20% binder emulsion, and 0.01%–1% defoamer. Maintaining the weight percentages of boron nitride powder, mixed solvent, binder emulsion, and defoamer within the aforementioned range further enhances the printability of the water-based boron nitride paste. It is understood that the mass percentage of boron nitride powder includes, but is not limited to: 45%, 46%, 47%, 48%, 49%, 50%, 52%, 54%, 56%, 58%; the mass percentage of mixed solvents includes, but is not limited to: 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%; the mass percentage of binder emulsion includes, but is not limited to: 8%, 10%, 12%, 14%, 16%, 18%, 20%; and the mass percentage of defoamer includes, but is not limited to: 0.01%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%.

[0041] In some embodiments, the solid content of the adhesive emulsion is 25% to 45%. It is understood that the solid content of the adhesive emulsion includes, but is not limited to: 25%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, and 45%. The aforementioned adhesive emulsion can be in emulsion or colloidal form.

[0042] In some embodiments, the solvent in the adhesive emulsion includes water.

[0043] In some embodiments, the binder emulsion contains a binder, which includes at least one of polyvinyl alcohol binders and waterborne acrylic resin binders. These types of binders are beneficial for improving the bonding performance of water-based boron nitride slurries.

[0044] In some embodiments, the polyvinyl alcohol (PVA) adhesive includes at least one of PVA 17-99, PVA 24-88, and PVA GH-22. Optionally, the PVA adhesive includes PVA GH-22.

[0045] In some embodiments, the waterborne acrylic resin adhesive includes at least one of acrylic resin S-74, acrylic resin S-160, and acrylic resin S-820. Optionally, the waterborne acrylic resin adhesive includes acrylic resin S-74.

[0046] In some embodiments, the boron nitride powder has a hexagonal crystal form.

[0047] In some embodiments, the boron nitride powder has a sheet-like structure.

[0048] In some embodiments, the average particle size D50 of the boron nitride powder is 5 μm to 15 μm.

[0049] In some embodiments, the mass percentage of oxygen in the boron nitride powder is ≤0.5%.

[0050] In some embodiments, the dispersant includes at least one selected from polyacrylamide, polyacrylamide, tributyl phosphate, polymethyl methacrylate, and succinimide. Dispersants of these types are beneficial for improving the dispersibility of the components in water-based boron nitride slurries.

[0051] In some embodiments, the defoamer includes at least one of octanol, trioctyl phosphate, nonylphenol polyoxyethylene ether, and distearate ethylenediamine.

[0052] In some embodiments, the mixed solvent comprises the following components in weight percentages: 55%–70% deionized water, 1%–2% dispersant, and 28%–44% wetting agent. The mixed solvent comprising the above-mentioned weight percentages of components can further improve the flowability and screen-passing properties of the water-based boron nitride slurry, while also further enhancing the sintering effect of the water-based boron nitride slurry and the strength of the ceramic plate.

[0053] Another embodiment of this application provides a method for preparing a water-based boron nitride slurry, comprising the following steps:

[0054] Boron nitride powder, mixed solvent and part of defoamer are mixed to obtain a mixed slurry;

[0055] The mixed slurry was subjected to a first ball milling process;

[0056] The slurry obtained from the first ball milling process is mixed with the binder emulsion and the remaining defoamer, and then subjected to a second ball milling process.

[0057] The slurry obtained from the second ball milling process was defoamed to obtain a water-based boron nitride slurry.

[0058] The water-based boron nitride slurry includes boron nitride powder, a mixed solvent, a binder emulsion, and a defoamer. The defoamer includes a portion of the defoamer and the remainder. The mixed solvent includes the following components in the following mass percentages: 49% to 74% deionized water, 0.8% to 2% dispersant, and 25% to 50% wetting agent. The wetting agent includes a polyol, which includes at least one of ethylene glycol, propylene glycol, glycerol, butanediol, and diethylene glycol.

[0059] The above preparation method is relatively simple, highly operable, and has a wide process window, which is conducive to industrial-scale mass production. The water-based boron nitride paste prepared by this method uses deionized water as a solvent, which can reduce the dissolution of binders in ceramic blanks, increase the density of ceramic blanks, and thus improve the density and strength of the sintered ceramic substrate. This paste is more environmentally friendly, reducing harm to human health and exhibiting better environmental performance. Furthermore, traditional boron nitride pastes require explosion-proof measures during drying, and the exhaust gas from the drying oven needs to be treated to render it harmless, increasing operating costs. The reduction in the amount of organic solvent used in the above water-based boron nitride paste can significantly reduce operating costs. In addition, the above water-based boron nitride paste has good printability and can be used as a printing paste.

[0060] In some embodiments, the water-based boron nitride slurry comprises, by weight percentage, 45% to 58% boron nitride powder, 32% to 46% mixed solvent, 8% to 20% binder emulsion, and 0.01% to 1% defoamer.

[0061] In some embodiments, the process conditions for the first ball milling treatment include: a ball milling media diameter of 1 mm to 10 mm, a ball milling rotation speed of 180 r / min to 300 r / min, and a ball milling treatment time of 0.5 h to 4 h. It is understood that the diameter of the ball milling media includes, but is not limited to: 1 mm, 3 mm, 5 mm, 7 mm, 9 mm, and 10 mm; the ball milling rotation speed includes, but is not limited to: 180 r / min, 200 r / min, 220 r / min, 240 r / min, 260 r / min, 280 r / min, and 300 r / min; and the ball milling treatment time includes, but is not limited to: 0.5 h, 1 h, 2 h, 3 h, 4 h, and 5 h.

[0062] In some embodiments, the average particle size of the particles in the slurry obtained from the first ball milling process is 3 μm to 10 μm. This design can further improve the fluidity of the slurry, reduce the risk of screen clogging, and thus further improve the printing performance of the water-based boron nitride slurry. It is understood that the average particle size of the particles in the slurry obtained from the first ball milling process includes, but is not limited to: 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, and 10 μm.

[0063] In some embodiments, the process conditions for the second ball milling treatment include: a ball milling media diameter of 1 mm to 10 mm, a ball milling rotation speed of 100 r / min to 200 r / min, and a ball milling treatment time of 1 h to 5 h. This design can further improve the fluidity of the paste, reduce the risk of screen clogging, and thus further improve the printing performance of water-based boron nitride paste. It is understood that the diameter of the ball milling media includes, but is not limited to: 1 mm, 3 mm, 5 mm, 7 mm, 9 mm, and 10 mm; the ball milling rotation speed includes, but is not limited to: 100 r / min, 120 r / min, 140 r / min, 160 r / min, 180 r / min, and 200 r / min; and the ball milling treatment time includes, but is not limited to: 0.5 h, 1 h, 2 h, 3 h, 4 h, and 5 h.

[0064] In some embodiments, after the step of defoaming the slurry obtained from the second ball milling process, the method further includes: adjusting the viscosity of the slurry obtained from the defoaming process to obtain a water-based boron nitride slurry. This can further improve the printing effect of the water-based boron nitride slurry.

[0065] In some embodiments, the partial defoamer accounts for 20% to 70% of the total mass of the defoamer, and the remaining defoamer accounts for 30% to 80% of the total mass of the defoamer. It is understood that the partial defoamer's mass percentage in the defoamer includes, but is not limited to, 20%, 30%, 40%, 50%, 60%, and 70%, and the remaining defoamer's mass percentage includes, but is not limited to, 30%, 40%, 50%, 60%, 70%, and 80%. Optionally, the partial defoamer and the remaining defoamer each independently include at least one of octanol, trioctyl phosphate, nonylphenol polyoxyethylene ether, and distearate ethylenediamine.

[0066] In some embodiments, the method for preparing the mixed solvent includes the following steps: mixing deionized water, a dispersant and a wetting agent, dispersing the dispersant and the wetting agent in the deionized water to obtain the mixed solvent.

[0067] In other embodiments, the method for preparing the mixed solvent includes the following steps: mixing deionized water, dispersant and wetting agent in a rapid dispersion device, with the paddle speed being 2000 r / min to 5000 r / min and the dispersion time being 10 min to 30 min, to obtain the mixed solvent.

[0068] In some embodiments, the method for preparing the adhesive emulsion includes the following steps: mixing the adhesive and water, heating to dissolve the adhesive in the water, thereby obtaining the adhesive emulsion. Optionally, the heating temperature is 80°C to 95°C. For example, the heating temperature can be 80°C, 82°C, 84°C, 86°C, 88°C, 90°C, 92°C, or 95°C.

[0069] In some embodiments, the step of mixing boron nitride powder, the mixed solvent, and a portion of the defoamer includes: adding boron nitride powder to the mixed solvent in multiple portions, then adding a portion of the defoamer, and dispersing the resulting slurry. The dispersion conditions include: a paddle speed of 500 r / min to 2000 r / min and a dispersion time of 15 min to 60 min. Optionally, the boron nitride powder can be gradually added to the mixed solvent in 2 to 5 portions.

[0070] It should be noted that by adjusting the process parameters or process conditions in the above preparation method, the water-based boron nitride slurry provided in one embodiment of this application can be obtained.

[0071] Another embodiment of this application provides the application of the water-based boron nitride slurry described above or prepared by the method described above in this application in the preparation of ceramic isolation powder.

[0072] In some embodiments, a water-based boron nitride paste is printed onto the surface of a ceramic blank, followed by stacking of the ceramic blanks, and then sequentially performing a debinding process and sintering to obtain a ceramic substrate with boron nitride powder on its surface. Optionally, a screen printing machine is used to print the water-based boron nitride paste onto the surface of the ceramic blank. By adjusting the screen printing process, the thickness of the printed layer can be precisely controlled, reducing product quality problems caused by boron nitride powder agglomeration.

[0073] To further illustrate this application, the technical solution of this application is described in detail below with reference to specific embodiments. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0074] The boron nitride powder used in each embodiment and comparative example has a hexagonal crystal form and a lamellar structure, with an average particle size D50 of 10 μm and an oxygen content of 0.3% by mass.

[0075] Example 1

[0076] A method for preparing a water-based boron nitride slurry includes the following steps:

[0077] (1) Take 70g of deionized water, add 30g of adhesive polyvinyl alcohol GH-22 under stirring, heat to 90℃ until the adhesive is completely dissolved, stir evenly to obtain adhesive emulsion;

[0078] (2) Take 55g of deionized water, add 1g of dispersant polymethacrylic acid amine and 44g of wetting agent ethylene glycol to it, stir for 20min through a rapid dispersion device until completely mixed, and adjust the speed of the paddle to 3000r / min to obtain a mixed solvent.

[0079] (3) Add 100g of boron nitride powder to 80g of mixed solvent in two portions, and add 0.5g of trioctyl phosphate (partial defoamer). Stir quickly for 30min until the boron nitride powder is completely dispersed in the mixed solvent. Adjust the stirring speed to 1000r / min.

[0080] (4) The initially dispersed slurry was transferred to a planetary high-speed ball mill for the first ball milling treatment. The ball milling media were a mixture of 3 mm and 8 mm diameter media. The ball milling speed was 250 r / min and the ball milling was performed for 1 h. The average particle size of the particles in the slurry obtained from the first ball milling treatment was 7 μm.

[0081] (5) Add 19g of binder emulsion and 0.5g of trioctyl phosphate (remaining defoamer) to the slurry obtained from the first ball milling treatment and perform a second ball milling treatment. Adjust the speed of the second ball milling treatment to 150r / min and ball mill for 1h.

[0082] (6) The ball-milled slurry was filtered through a 400-mesh sieve and defoamed quickly by centrifugation to obtain a water-based boron nitride slurry.

[0083] By weight percentage, the water-based boron nitride slurry comprises 50% boron nitride powder, 40% mixed solvent, 9.5% binder emulsion, and 0.5% defoamer. The mixed solvent comprises the following components by weight percentage: 55% deionized water, 1% dispersant, and 44% wetting agent.

[0084] Example 2

[0085] The preparation method of water-based boron nitride slurry is basically the same as that in Example 1, except that step (2) is different;

[0086] In step (2) of this embodiment, 70g of deionized water is taken, and 1.5g of dispersant polymethacrylic acid amine and 28.5g of wetting agent ethylene glycol are added to it respectively. The mixture is stirred for 20 minutes by a rapid dispersion device until it is completely mixed. The speed of the paddle is adjusted to 3000r / min to obtain a mixed solvent.

[0087] The mixed solvent in the resulting water-based boron nitride slurry comprises the following components in the following mass percentages: 70% deionized water, 1.5% dispersant, and 28.5% wetting agent.

[0088] Example 3

[0089] The preparation method of water-based boron nitride slurry is basically the same as that in Example 1, except that step (2) is different;

[0090] In step (2) of this embodiment, 50g of deionized water is taken, and 1g of dispersant polymethacrylic acid amine and 49g of wetting agent ethylene glycol are added to it respectively. The mixture is stirred for 20 minutes by a rapid dispersion device until it is completely mixed. The speed of the paddle is adjusted to 3000r / min to obtain a mixed solvent.

[0091] The mixed solvent in the resulting water-based boron nitride slurry comprises the following components by mass percentage: 50% deionized water, 1% dispersant, and 49% wetting agent.

[0092] Example 4

[0093] The preparation method of water-based boron nitride slurry is basically the same as that in Example 1, except that step (5) is different;

[0094] In step (5) of this embodiment, 29g of binder emulsion and 0.5g of trioctyl phosphate (remaining defoamer) are added to the slurry obtained by the first ball milling treatment for a second ball milling treatment. The rotation speed of the second ball milling treatment is adjusted to 150r / min and the ball milling is carried out for 1h.

[0095] The resulting water-based boron nitride slurry comprises, by mass percentage, 47.6% boron nitride powder, 38.1% mixed solvent, 13.8% binder emulsion, and 0.5% defoamer.

[0096] Comparative Example 1

[0097] A method for preparing an organic solvent boron nitride slurry includes the following steps:

[0098] (1) Dissolve 20g of the adhesive polyvinyl butyral in 40g of ethanol and 40g of terpineol, heat to 80℃, and stir continuously until the adhesive is completely dissolved to prepare an organic adhesive carrier.

[0099] (2) Add 100g of boron nitride powder, 2g of dispersant tributyl phosphate, 35g of ethanol and 35g of terpineol to a ball milling jar and ball mill at 250r / min for 1h.

[0100] (3) Add 25g of organic binder carrier and 3g of leveling agent ethylene glycol methyl ether to the ball mill jar, and mill at 150r / min for 1h.

[0101] (4) The ball-milled slurry was filtered through a 400-mesh sieve and defoamed quickly by centrifugation to obtain an organic solvent boron nitride slurry.

[0102] By weight percentage, the organic solvent boron nitride slurry comprises 50% boron nitride powder, 35% solvent, 12.5% ​​organic binder carrier, 1% dispersant, and 1.5% leveling agent, wherein the solvents are ethanol and terpineol. The organic binder carrier comprises the following components by weight percentage: 20% binder and 80% solvent, wherein the solvents in the organic binder carrier are ethanol and terpineol.

[0103] Comparative Example 2

[0104] The preparation method of water-based boron nitride slurry is basically the same as that in Example 1, except that step (2) is different;

[0105] In step (2) of this embodiment, 85g of deionized water is taken, and 1g of dispersant polymethacrylic acid amine and 14g of wetting agent ethylene glycol are added to it respectively. The mixture is stirred for 20 minutes by a rapid dispersion device until it is completely mixed. The speed of the paddle is adjusted to 3000r / min to obtain a mixed solvent.

[0106] The mixed solvent in the resulting water-based boron nitride slurry comprises the following components by mass percentage: 85% deionized water, 1% dispersant, and 14% wetting agent.

[0107] Comparative Example 3

[0108] The preparation method of water-based boron nitride slurry is basically the same as that in Example 1, except that step (2) is different;

[0109] In step (2) of this embodiment, 40g of deionized water is taken, and 1g of dispersant polymethacrylic acid amine and 59g of wetting agent ethylene glycol are added to it respectively. The mixture is stirred for 20 minutes by a rapid dispersion device until it is completely mixed. The speed of the paddle is adjusted to 3000r / min to obtain a mixed solvent.

[0110] The mixed solvent in the resulting water-based boron nitride slurry comprises the following components by mass percentage: 40% deionized water, 1% dispersant, and 59% wetting agent.

[0111] Performance testing

[0112] (1) Flowability and screen-passing properties of boron nitride slurry

[0113] The fluidity of boron nitride paste is judged by its viscosity. If the viscosity is too low, it is easy for the paste to seep through the screen, and the paste will flow down the screen naturally without the action of the doctor blade, affecting the uniformity of printing. If the viscosity is too high and the fluidity is poor, it is easy to cause screen clogging or incomplete printing.

[0114] The screen passability of boron nitride paste is judged based on the integrity of the printed pattern and the number of consecutive normal working cycles. A 200-mesh screen is used. 300 consecutive normal printing cycles are considered excellent, 200 cycles are good, 100 cycles are acceptable, and less than 100 cycles are poor.

[0115] (2) Tests on the heat insulation effect of boron nitride slurry and the strength of ceramic substrates.

[0116] The boron nitride slurry prepared in each embodiment or comparative example was screen-printed onto water-based cast silicon nitride ceramic blanks. The blanks were stacked in 10 layers for debinding, with boron nitride slurry applied between adjacent blanks. The debinding temperature was between 500 and 650°C, and the temperature was maintained for 2 to 8 hours. The debinded blanks were then sintered in a nitrogen atmosphere at 1900°C for 4 to 6 hours. After sintering, the stacked ceramic substrates were separated into pieces. The separability of the ceramic substrates was used to determine the sintering effect of the boron nitride slurry, and the strength of the separated ceramic substrates was tested. For the separability test, 50 ceramic substrates were taken, and the number of separable pieces was measured. Better separability indicated a better sintering effect of the boron nitride slurry. The strength of the ceramic substrates was tested according to GB / T 6569-2006 "Test Method for Bending Strength of Fine Ceramics".

[0117] Table 1

[0118]

[0119] As shown in Table 1, the use of water-based printing paste and organic solvent-based printing paste affects the strength of ceramic substrates prepared by water-based casting. Compared with Comparative Examples 1-3, the ceramic substrates of Examples 1-4 have higher strength, indicating that the water-based boron nitride paste of Examples 1-4 can improve the strength of ceramic substrates. Compared with the organic solvent-based boron nitride paste of Comparative Example 1, the water-based boron nitride paste of Examples 1-4 does not contain terpineol; therefore, the water-based boron nitride paste of Examples 1-4 is more environmentally friendly.

[0120] Compared with Comparative Examples 2-3, the water-based boron nitride slurries of Examples 1-4 showed better flowability and screen passing properties, and a greater number of separated sheets on the ceramic substrate. This indicates that controlling the mixed solvent of the water-based boron nitride slurry to include 49%-74% deionized water, 0.8%-2% dispersant, and 25%-50% wetting agent can improve the flowability and screen passing properties of the water-based boron nitride slurry, while also improving the sintering effect of the water-based boron nitride slurry.

[0121] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0122] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A water-based boron nitride slurry for ceramic insulating powder, characterized in that, The water-based boron nitride slurry, by mass percentage, comprises 45%–58% boron nitride powder, 32%–46% mixed solvent, 8%–20% binder emulsion, and 0.01%–1% defoamer. The mixed solvent comprises the following components by mass percentage: 49%–74% deionized water, 0.8%–2% dispersant, and 25%–50% wetting agent. The wetting agent is a polyol, which includes at least one of ethylene glycol, propylene glycol, glycerol, butanediol, and diethylene glycol.

2. The water-based boron nitride slurry for ceramic insulating powder according to claim 1, characterized in that, The water-based boron nitride slurry, by weight percentage, comprises 50% boron nitride powder, 40% mixed solvent, 9.5% binder emulsion, and 0.5% defoamer.

3. The water-based boron nitride slurry for ceramic insulating powder according to claim 1 or 2, characterized in that, The water-based boron nitride slurry has at least one of the following characteristics (1) to (3): (1) The solid content of the adhesive emulsion is 25%~45%; (2) The solvent in the adhesive emulsion includes water; (3) The adhesive emulsion contains an adhesive, which includes at least one of polyvinyl alcohol adhesives and water-based acrylic resin adhesives.

4. The water-based boron nitride slurry for ceramic insulating powder according to claim 1 or 2, characterized in that, The water-based boron nitride slurry has at least one of the following characteristics (1) to (4): (1) The boron nitride powder has a hexagonal crystal form; (2) The structure of the boron nitride powder includes a sheet-like structure; (3) The average particle size D50 of the boron nitride powder is 5μm~15μm; (4) The mass percentage of oxygen in the boron nitride powder is ≤0.5%.

5. The water-based boron nitride slurry for ceramic insulating powder according to claim 1 or 2, characterized in that, The water-based boron nitride slurry has at least one of the following characteristics (1) to (2): (1) The dispersant includes at least one of polyacrylamide, polyacrylamide, tributyl phosphate, polymethyl methacrylate and succinimide; (2) The defoamer includes at least one of octanol, trioctyl phosphate, nonylphenol polyoxyethylene ether and distearate ethylenediamine.

6. A method for preparing a water-based boron nitride slurry for ceramic insulating powder, characterized in that, Includes the following steps: Boron nitride powder, mixed solvent and part of defoamer are mixed to obtain a mixed slurry; The mixed slurry is subjected to a first ball milling process; The slurry obtained from the first ball milling process is mixed with the binder emulsion and the remaining defoamer, and then subjected to a second ball milling process. The slurry obtained from the second ball milling process is subjected to defoaming treatment to obtain the water-based boron nitride slurry; The water-based boron nitride slurry, by mass percentage, comprises 45%–58% boron nitride powder, 32%–46% mixed solvent, 8%–20% binder emulsion, and 0.01%–1% defoamer. The defoamer consists of a portion of the defoamer and the remaining defoamer. The mixed solvent comprises the following components by mass percentage: 49%–74% deionized water, 0.8%–2% dispersant, and 25%–50% wetting agent. The wetting agent is a polyol, including at least one selected from ethylene glycol, propylene glycol, glycerol, butanediol, and diethylene glycol.

7. The preparation method according to claim 6, characterized in that, The water-based boron nitride slurry, by weight percentage, comprises 50% boron nitride powder, 40% mixed solvent, 9.5% binder emulsion, and 0.5% defoamer.

8. The preparation method according to claim 6 or 7, characterized in that, The preparation method satisfies at least one of the following conditions (1) to (4): (1) The process conditions for the first ball milling treatment include: the diameter of the ball milling media is 1 mm to 10 mm, the rotation speed of the ball milling treatment is 180 r / min to 300 r / min, and the ball milling treatment time is 0.5 h to 4 h; (2) The average particle size of the particles in the slurry obtained by the first ball milling treatment is 3μm~10μm; (3) The process conditions for the second ball milling treatment include: the diameter of the ball milling media is 1 mm to 10 mm, the rotation speed of the ball milling treatment is 100 r / min to 200 r / min, and the ball milling treatment time is 1 h to 5 h; (4) The defoamer accounts for 20% to 70% of the total mass of the defoamer, and the remaining defoamer accounts for 30% to 80% of the total mass of the defoamer.

9. The preparation method according to claim 6 or 7, characterized in that, The method for preparing the mixed solvent includes the following steps: mixing the deionized water, the dispersant, and the wetting agent, dispersing the dispersant and the wetting agent in the deionized water to obtain the mixed solvent.

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