Surface treatment method for boron nitride plate, method for manufacturing ceramic sintered body, and method for manufacturing boron nitride plate

Abstract

The surface treatment method of the boron nitride plate according to the embodiment includes a first polishing step and a second polishing step. In the first polishing step, a first polishing member having a particle size number in a range of F120 or more and F220 or less or a range of #240 or more and #320 or less is used to polish a surface of a boron nitride plate. In the second polishing step, a second polishing member having a particle size number in a range of #360 or more and #1000 or less is used to polish the surface of the boron nitride plate. The second polishing step is performed after the first polishing step. The boron nitride plate is suitable for a manufacturing method of a silicon nitride substrate. In the first polishing step, a pressing amount of the first polishing member is preferably in a range of 0.2 mm or more and 1.0 mm or less, and a processing point speed is in a range of 80 mm / s or more and 180 mm / s or less.

Description

Technical Field

[0001] The embodiments described below generally relate to methods for surface treatment of boron nitride plates, methods for manufacturing ceramic sintered bodies, and methods for manufacturing boron nitride plates. Background Technology

[0002] Ceramic substrates are used as circuit boards for mounting semiconductor components. Various ceramic substrates have been used, including silicon nitride substrates, aluminum nitride substrates, alumina substrates, zirconium oxide substrates, and Alussil high-silicon heat-resistant aluminum alloy substrates. Alussil high-silicon heat-resistant aluminum alloy substrates are made by mixing zirconium oxide and alumina.

[0003] The manufacturing process of ceramic substrates includes: raw material mixing, forming, debinding, and sintering. The raw material mixing process involves mixing raw material powder with an organic binder to prepare a raw material paste. The forming process involves preparing a sheet-like structure from the raw material paste. The debinding process involves removing the binder from the sheet-like structure. The sintering process involves sintering the debinded sheet-like structure.

[0004] In the degreasing and sintering processes, the sheet-shaped molded body is placed on a mounting plate. In International Publication No. 2013 / 146789 (Patent Document 1), a boron nitride plate is used as the mounting plate. In the sintering process of ceramic substrates, high temperatures of approximately 1600–2000°C are generally reached. Boron nitride plates are used as mounting plates due to their excellent durability at high temperatures.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: International Publication No. 2013 / 146789 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] If a boron nitride plate used as a mounting plate is repeatedly used, foreign matter will adhere to its surface. This foreign matter adheres from the ceramic sintered body to the boron nitride plate. If foreign matter is present on the boron nitride plate, the surface flatness of the ceramic substrate mounted on the boron nitride plate deteriorates. Therefore, conventionally, a process is performed to periodically remove foreign matter from the surface of the boron nitride plate. Honing is a surface treatment method for boron nitride plates, which involves grinding with abrasive jets. While this removes foreign matter, it increases the surface roughness of the boron nitride plate. If the surface roughness of the boron nitride plate increases, the surface roughness of the ceramic substrate also increases. Therefore, a surface treatment method for boron nitride plates that can suppress the increase of surface roughness is sought.

[0010] means for solving problems

[0011] The surface treatment method for a boron nitride plate according to the embodiment includes a first grinding step and a second grinding step. In the first grinding step, a first grinding member with a grit size in the range of F120 or higher and F220 or lower, or #240 or higher and #320 or lower, is used to grind the surface of the boron nitride plate. In the second grinding step, a second grinding member with a grit size in the range of #360 or higher and #1000 or lower is used to grind the surface of the boron nitride plate. The second grinding step is performed after the first grinding step. Attached Figure Description

[0012] Figure 1 This is a diagram illustrating an example of a surface treatment method for a boron nitride plate according to an embodiment.

[0013] Figure 2 This is a diagram showing an example of a ceramic molded body placed on a boron nitride plate.

[0014] Figure 3 This is a diagram showing another example of placing a ceramic molded body on a boron nitride plate.

[0015] Figure 4 This is a diagram showing an example of black whiskers on the surface of a boron nitride plate.

[0016] Figure 5 This is a flowchart illustrating the processing method involved in the implementation.

[0017] Figure 6 This is a flowchart illustrating a method for manufacturing a ceramic sintered body according to an embodiment.

[0018] Figure 7 This is a flowchart illustrating the surface treatment method of the boron nitride plate involved in the embodiment. Detailed Implementation

[0019] The surface treatment method for a boron nitride plate according to the embodiment includes a first grinding step and a second grinding step. In the first grinding step, a first grinding member with a grit size in the range of F120 or higher and F220 or lower, or #240 or higher and #320 or lower, is used to grind the surface of the boron nitride plate. In the second grinding step, a second grinding member with a grit size in the range of #360 or higher and #1000 or lower is used to grind the surface of the boron nitride plate. The second grinding step is performed after the first grinding step.

[0020] Figure 1 An example of a surface treatment method for a boron nitride plate is shown. Figure 1 In the diagram, 1 is a boron nitride plate, and 2 is abrasive paper. The boron nitride plate 1 is formed from a sintered boron nitride body.

[0021] Figure 1The diagram shows a square boron nitride plate 1. The shape of the boron nitride plate 1 is not limited to the example shown. The shape of the boron nitride plate 1 can be square, rectangular, triangular, pentagonal, hexagonal, circular, or elliptical, etc. The shape of the boron nitride plate 1 is arbitrary, as long as it allows for the arrangement of ceramic molded bodies. The longitudinal and transverse dimensions of the boron nitride plate 1 can be appropriately selected according to the size and quantity of the arranged ceramic molded bodies.

[0022] The thickness of the boron nitride plate 1 is preferably 0.5 mm or more. If the thickness is less than 0.5 mm, the strength of the boron nitride plate 1 may decrease. There is no particular upper limit to the thickness of the boron nitride plate 1, but it is preferably 10 mm or less. If the thickness of the boron nitride plate 1 exceeds 10 mm, the space for arranging the ceramic molded body in the processing chamber of the degreasing or sintering process may be reduced. Therefore, it is preferable that the thickness of the boron nitride plate 1 is in the range of 0.5 mm or more and 10 mm or less, and more preferably in the range of 0.8 mm or more and 5 mm or less.

[0023] Examples of abrasive components include abrasive paper, abrasive cloth, abrasive resin film, and grinding stones. Abrasive paper is a component with abrasive material adhered to its surface. Abrasive cloth is a component with abrasive material adhered to its surface. Abrasive resin film is a component with abrasive material adhered to its surface. A grinding stone is a component made by bonding abrasive materials together using an adhesive. All abrasive components utilize abrasive materials.

[0024] The size of abrasive materials is indicated by a grit number. The grit number is shown as a number followed by "F" or "#". A smaller grit number indicates a coarser abrasive material. The grit number is determined by the particle size of the abrasive material. Grit numbers are specified in JIS-R-6001-1(2017) and JIS-R-6001-2(2017). For abrasive paper, refer to JIS-R-6252(2006), JIS-R-6253(2006), JIS-R-6111(2020), JIS-R-6010(2020), and JIS-R-6004(2020). These JIS standards correspond to ISO 3366(1999), ISO 21948(2001), and ISO 21950(2001).

[0025] In the JIS standard, the distinction is as follows: coarse abrasive materials are used for grit sizes below F220, while fine abrasive materials are used for grit sizes above #240. Abrasive materials (grits) with F120 or higher but below F220 have their particle size determined by sieving. Furthermore, abrasive materials with #240 or higher but below #1000 have their particle size determined by the settling tube test.

[0026] For example, in the F120 Grade 1 test sieve, the nominal sieve aperture for which the entire amount of abrasive material passes through is defined as 180 μm. The nominal sieve aperture for the Grade 5 test sieve is defined as 63 μm. Furthermore, the nominal sieve aperture for the Grade 5 test sieve is defined as the nominal sieve aperture at which the maximum mass fraction of abrasive material passing through the Grade 5 sieve is 3%.

[0027] In the F220 Class 1 test sieve, the nominal sieve aperture for passing through the entire amount of abrasive material is defined as 106 μm. The nominal sieve aperture for Class 3 test sieves is defined as 53 μm. The nominal sieve aperture for Class 4 test sieves is defined as 43 μm. The minimum mass fraction of abrasive material that must remain on both Class 3 and Class 4 sieves is defined as 60%.

[0028] For #240 to #1000, the particle size is determined using the settling tube test method. For example, for #240, the particle size (d) with a cumulative height fraction of 50% is used. 50 The value is defined as 60 μm ± 4.0 μm. For #320, the particle size (d) with a cumulative height fraction of 50% is defined as... 50 The value is defined as 46 μm ± 2.5 μm. Regarding #360, the particle size (d) with a cumulative height fraction of 50% is defined as... 50 The value is defined as 40 μm ± 2.0 μm. For #1000, the particle size (d) with a cumulative height fraction of 50% is defined as... 50 It is defined as 15.5μm±1.0μm.

[0029] Alumina, zirconium oxide, and silicon carbide are used as abrasive materials. When the ceramic body is an oxide-based ceramic, alumina or zirconium oxide are preferred as abrasive materials. When the ceramic body is a nitride-based ceramic, silicon carbide is preferred as abrasive material.

[0030] The preferred abrasive component is abrasive paper. Abrasive paper is also called sandpaper or sandpaper. In abrasive paper, paper is used as the substrate. In the process of abrading the boron nitride plate 1 by pressing the abrasive component, if the substrate is paper, the abrasive surface of the boron nitride plate 1 is less affected by the unevenness of the substrate. Therefore, it is easier to obtain a flat surface of the boron nitride plate 1. If the substrate is cloth, the abrasive surface of the boron nitride plate 1 is affected by the coarseness of the cloth fibers. Furthermore, compared with abrasive cloth, abrasive paper is inexpensive. Abrasive resin films or grinding stones are more expensive components compared to abrasive cloth.

[0031] If grinding is performed with a specified pressure, the grinding paper and grinding cloth may sometimes break. The exchange frequency of the grinding paper and the exchange frequency of the grinding cloth are at the same level. Therefore, it is preferable to use grinding paper. Hereinafter, examples of using grinding paper as a grinding component will be described. When using grinding cloth, grinding resin film, or grinding stone, the grinding paper in the following description can be read as those grinding components.

[0032] Figure 1 The diagram shows an example of abrasive paper 2 being mounted on a roller. Besides rollers, abrasive paper 2 can also be mounted on a rotating disk. By mechanically performing the abrasive process using mounting fixtures such as rollers and rotating disks, uneven abrasiveness can be controlled. Mounting the abrasive paper 2 on a roller is more preferable than using a rotating disk. By making the length of the roller match the length of the boron nitride plate 1, uneven abrasiveness can be further suppressed. Furthermore, multiple rollers can be used to form an abrasive belt.

[0033] The surface treatment method for a boron nitride plate according to the embodiment includes a first grinding step and a second grinding step. The first grinding step is a step of grinding the surface of the boron nitride plate using a first abrasive paper. First, the surface is ground with a first abrasive paper with a grit size of F120 or higher and F220 or lower, or #240 or higher and #320 or lower. The first abrasive paper is an example of a first abrasive member. If the grit size is less than F120, grinding marks are easily formed on the surface of the boron nitride plate 1 because the abrasive material is coarse. If the grit size is greater than #320, grinding the surface of the boron nitride plate 1 takes time because the abrasive material is fine. Therefore, the grit size of the first abrasive paper used in the first grinding step is preferably in the range of F120 or higher and F220 or lower, or #240 or higher and #320 or lower. The grit size of the first abrasive paper is more preferably in the range of #220 or higher and #280 or lower.

[0034] The second grinding step is a process of grinding the surface of the boron nitride plate 1 using a second grinding paper. After the first grinding step, the surface is ground with a second grinding paper having a grit size in the range of #360 or higher and #1000 or lower. The second grinding paper is an example of a second grinding component. If the grit number is less than #360, the second grinding step becomes the same as the first grinding step. If the grit size is greater than #1000, the grinding of the surface of the boron nitride plate 1 takes time due to the fineness of the abrasive material. Therefore, the grit size of the second grinding paper used in the second grinding step is preferably in the range of #360 or higher and #1000 or lower, more preferably in the range of #400 or higher and #800 or lower.

[0035] The second grinding step is a further grinding step on the surface that has undergone the first grinding step. That is, the surface of the boron nitride plate 1 undergoes two grinding steps: the first grinding step and the second grinding step. The grit size of the abrasive paper used in the second grinding step is larger than that used in the first grinding step. After the first grinding step using coarse-grit abrasive paper, the second grinding step using fine-grit abrasive paper is performed. This improves the flatness of the boron nitride plate 1.

[0036] In the first grinding step, it is preferable that the pressure of the first grinding paper is in the range of 0.2 mm or more and 1.0 mm or less, and preferably that the processing speed is in the range of 80 mm / s or more and 180 mm / s or less. The pressure of the grinding paper is the force with which the grinding paper 2 is pressed perpendicularly against the boron nitride plate 1. The roller on which the grinding paper 2 is wound is called the grinding roller. The distance by which the grinding roller is placed on the boron nitride plate 1 and pressed from there is called the pressure. If the pressure is in the range of 0.2 mm or more and 1.0 mm or less, it is possible to achieve both flatness and grinding efficiency. If the pressure is less than 0.2 mm, the grinding efficiency may decrease due to insufficient pressure. If the pressure exceeds 1.0 mm, over-grinding may occur, and the unevenness of the ground surface may increase. Therefore, in the first grinding step, it is preferable that the pressure of the grinding paper is in the range of 0.2 mm or more and 1.0 mm or less, and more preferably in the range of 0.3 mm or more and 0.7 mm or less.

[0037] The clamping amount can be adjusted by the hardness of the roller body of the grinding roller and the clamping pressure. The roller body is the roller body on which the grinding paper is mounted. The roller body can be made of various materials such as rubber, metal, and ceramic. Rubber is preferred. If the roller body is made of rubber, it can suppress the breakage of the ceramic substrate. When the roller body is made of rubber, its hardness is preferably in the range of 10° to 90°. JIS-K-6253-3 (2012) specifies the method for determining the hardness of rubber. JIS-K-6253-3 corresponds to ISO7619-1 (2010). In addition, the clamping pressure is preferably in the range of 10 N (Newtons) to 200 N.

[0038] The processing point speed refers to the distance the abrasive paper moves per unit time. The unit "mm / s" represents the distance (mm) the abrasive paper moves in one second. For example, when the abrasive paper is wound on a roller, the unit "mm / s" represents the rotational speed of the roller. When the abrasive paper is mounted on a rotating disk, the unit "mm / s" is the rotational speed of the rotating disk. The processing point speed is a parameter used to control the stress applied to the boron nitride plate 1 by the abrasive paper 2. If the processing point speed is in the range of 80 mm / s or more and 180 mm / s or less, the processing efficiency can be improved. If the processing point speed is less than 80 mm / s, the processing efficiency may decrease. If the processing point speed is higher than 180 mm / s, there is a possibility of processing deviations that increase the unevenness on the surface of the boron nitride plate 1. Therefore, it is preferable that the processing point speed is in the range of 80 mm / s or more and 180 mm / s or less, and more preferably in the range of 100 mm / s or more and 150 mm / s or less. Furthermore, a synergistic effect can be achieved by combining and adjusting the processing point speed and the pressure of the abrasive paper.

[0039] In the second grinding step, the pressure of the grinding paper is preferably in the range of 0.2 mm or more and 1.0 mm or less, and the processing speed is preferably in the range of 20 mm / s or more and 100 mm / s or less. The pressure of the second grinding step is preferably in the range of 0.2 mm or more and 1.0 mm or less, more preferably in the range of 0.3 mm or more and 0.7 mm or less. The processing speed of the second grinding step is preferably in the range of 20 mm / s or more and 100 mm / s or less, more preferably in the range of 30 mm / s or more and 80 mm / s or less. Even in the second grinding step, by controlling the pressure and processing speed, processing efficiency can be improved.

[0040] Preferably, the processing speed of the first grinding step is faster than that of the second grinding step. The grit size of the abrasive paper used in the first grinding step is smaller than that used in the second grinding step. Therefore, the first grinding step is a rougher process compared to the second grinding step. By increasing the processing speed of the first grinding step, the surface roughness of the boron nitride plate can be reduced while achieving a rougher surface finish in a shorter time. Furthermore, if the surface is roughened using the first grinding step, it is easier to perform a finer surface finish using the larger grit abrasive paper used in the second grinding step. In this case, by slowing down the processing speed, a smoother surface can be obtained.

[0041] By performing the above-described polishing process on the boron nitride plate 1, a flat surface can be obtained. A "flat surface" refers to a surface without recesses deeper than 40 μm. Furthermore, a flat surface without needle-like silicon nitride grains can be obtained on the surface of the boron nitride plate 1. Additionally, a third polishing process can be performed after the second polishing process if necessary. In the third polishing process, a polishing element with a larger grit size is used compared to the second polishing process.

[0042] A boron nitride plate 1 is used in the degreasing or sintering process of the ceramic molded body. In these processes, the ceramic molded body is placed on the boron nitride plate 1. Both the degreasing and sintering processes are heating processes. Heating the ceramic molded body results in grain growth of the ceramic raw material powder and shrinkage of the molded body. If the surface of the boron nitride plate 1 has a recess with a depth of 40 μm or more, it is easy to form a protrusion of 40 μm or more in the resulting sintered ceramic body. When the sintered ceramic body is plate-shaped, it is not preferable to form a protrusion of 40 μm or more. The plate-shaped sintered ceramic body is called a ceramic substrate. A ceramic substrate can be formed by bonding it to a metal plate to form a ceramic circuit board. Furthermore, a press-fit structure type module structure can be formed by pressing semiconductor elements onto the ceramic substrate. The ceramic substrate used in the press-fit structure type module is used as a single plate without bonding to the metal plate.

[0043] In ceramic circuit boards, a solder layer is used to bond the ceramic substrate and a metal plate. Large protrusions on the surface of the ceramic substrate negatively impact the bonding between the ceramic substrate and the metal plate. Furthermore, large protrusions on the surface of the ceramic substrate used in press-fit structural modules negatively affect the adhesion between the ceramic substrate and the semiconductor element. Therefore, it is preferable that there are no protrusions larger than 40 μm on the surface of the ceramic substrate. In other words, the boron nitride plate 1 according to the embodiment is suitable for use in the process of obtaining the ceramic substrate.

[0044] Therefore, it is preferable that there are no recesses with a depth of 40 μm or more on the surface of the boron nitride plate. Furthermore, recesses with a depth of 40 μm or more are mainly formed through a grinding process. Therefore, recesses with a depth of 40 μm or more on the surface of the boron nitride plate 1 are sometimes referred to as grinding marks. Recesses with a depth of 40 μm or more on the surface of the boron nitride plate 1 can be measured using a three-dimensional shape measuring machine. The entire surface of the boron nitride plate 1, on the side where the ceramic molded body is placed, is measured. As the three-dimensional shape measuring machine, a Keyence one-shot 3D shape measuring machine VR series or an equivalent device is used.

[0045] Furthermore, the statement that there are no recesses with a depth of 40 μm or more on the surface of the boron nitride plate means that there are no recesses with a depth of 40 μm or more in the areas where the ceramic molded body is disposed. In other words, recesses with a depth of 40 μm or more can exist even in areas where the ceramic molded body is not disposed. Moreover, it is most preferable that there are no recesses with a depth of 40 μm or more on the entire surface of the boron nitride plate. In this way, the placement location of the ceramic molded body is not restricted.

[0046] Preferably, there are no needle-shaped silicon nitride grains on the surface of the boron nitride plate 1. During the sintering process of the ceramic molded body, the ceramic raw material powder gradually undergoes grain growth. In particular, the round silicon nitride powder of the silicon nitride molded body gradually transforms into elongated silicon nitride grains. These elongated silicon nitride grains grow to an aspect ratio of 2 or more. Silicon nitride grains with an aspect ratio of 2 or more are referred to as needle-shaped silicon nitride grains. The elongated silicon nitride grains are mainly composed of β-type silicon nitride grains. The needle-shaped silicon nitride grains that grow through the sintering process become protrusions on the surface of the sintered silicon nitride body. These protrusions penetrate into the boron nitride plate 1, resulting in needle-shaped silicon nitride grains on the surface of the boron nitride plate 1. The needle-shaped silicon nitride grains are hard materials. The first and second grinding processes are also effective in removing the needle-shaped silicon nitride grains from the surface of the boron nitride plate 1. In particular, by using abrasive paper containing silicon carbide abrasive, needle-like silicon nitride grains can be removed efficiently. In other words, the surface treatment method for boron nitride plates according to the embodiments is suitable for boron nitride plates used in the degreasing or sintering processes of silicon nitride molded bodies.

[0047] The presence or absence of needle-like silicon nitride grains on the surface of boron nitride plate 1 can be analyzed using energy-dispersive X-ray diffraction (EDX). It is sufficient to investigate the presence or absence of silicon on the surface of boron nitride plate 1. Furthermore, the presence or absence of needle-like silicon nitride grains can be confirmed by observing areas where silicon is detected using scanning electron microscopy (SEM). For example, when the boron nitride plate does not contain sintering aids, the presence or absence of needle-like silicon nitride grains can be confirmed by EDX analysis alone. When the boron nitride plate contains sintering aids, the presence or absence of needle-like silicon nitride grains can be confirmed by combining EDX and SEM. The presence or absence of needle-like silicon nitride grains can be confirmed by analyzing the entire surface of the boron nitride plate on which the ceramic mold is mounted.

[0048] For SEM-EDX, a Keyence VE9800 or equivalent device was used. During observation, the magnification was set to 200x and the applied voltage to 12kV. Furthermore, areas where the silicon nitride content determined by SEM-EDX was below the detection limit were considered to be free of needle-like silicon nitride grains. This can also be easily determined by the silicon content. The absence of needle-like silicon nitride grains in the area where the ceramic molded body is mounted is effective. The absence of needle-like silicon nitride grains across the entire surface of the boron nitride plate increases the freedom of choice in the placement of the ceramic molded body. Therefore, it is preferable that the entire surface of the boron nitride plate is free of needle-like silicon nitride grains.

[0049] Figure 4 An example of needle-like silicon nitride grains and grinding marks is shown. Figure 4 In the diagram, 4 represents needle-like silicon nitride grains, and 5 represents a grinding mark. If a color distribution is plotted on the surface measured by a 3D shape measuring machine, the needle-like silicon nitride grains 4 and the grinding mark 5 appear discolored due to their height difference from other parts. For example, if the measurement is performed using the default settings of the Keyence VR series one-shot 3D shape measuring machine, the needle-like silicon nitride grains 4 appear reddish because they are protrusions. Furthermore, the grinding mark 5 appears bluish because it is a recess.

[0050] By applying the surface treatment method according to the embodiment to the boron nitride plate 1, the warpage of the boron nitride plate 1 can be reduced to 0.1 mm or less. Furthermore, by applying the surface treatment method according to the embodiment to the boron nitride plate 1, the maximum height roughness Rz of the boron nitride plate 1 can be reduced to 40 μm or less. The warpage of the boron nitride plate 1 is defined as flatness in JIS-B-0621 (1984). The maximum height roughness Rz is specified in JIS-B-0601 (2013). Both the warpage and the maximum height roughness Rz are measured using a three-dimensional shape measuring machine. Moreover, JIS-B-0601 (2013) corresponds to ISO 4287 (2009).

[0051] If the warpage of the boron nitride plate 1 is 0.1 mm or less, the warpage of the resulting ceramic sintered body can be further reduced. Furthermore, if the maximum height roughness Rz of the boron nitride plate 1 is 40 μm or less, the maximum surface protrusion of the resulting ceramic sintered body can be reduced to 20 μm or less. By controlling the warpage and maximum height roughness Rz of the boron nitride plate 1, the warpage and surface protrusion of the resulting ceramic sintered body can be reduced. Reducing the warpage and surface protrusion is effective for manufacturing ceramic substrates with a thickness of 1 mm or less. In other words, the surface treatment method according to the embodiment is suitable for the boron nitride plate 1 used to manufacture ceramic substrates with a thickness of 1 mm or less. Furthermore, by setting the maximum height roughness Rz of the boron nitride plate 1 to 40 μm or less, it becomes difficult for needle-like silicon nitride grains to penetrate. Therefore, the warpage of the boron nitride plate is preferably 0.1 mm or less, more preferably 0.06 mm or less. The maximum height roughness Rz of the boron nitride plate is preferably 40 μm or less, more preferably 20 μm or less. Furthermore, if a boron nitride plate is used for the degreasing or sintering process, the surface of the boron nitride plate 1 gradually deteriorates. The surface treatment method described in this embodiment is effective when implemented after the deterioration of the boron nitride plate 1 occurs or before signs of deterioration appear. This improves the yield of the ceramic substrate.

[0052] The boron nitride plate subjected to the above-described surface treatment method can be used in the manufacturing process of ceramic sintered bodies. The manufacturing process of ceramic sintered bodies includes a raw material mixing process, a forming process, a debinding process, and a sintering process. The raw material mixing process is the process of mixing raw material powders and organic binders to prepare a raw material paste. The forming process is the process of preparing a ceramic molded body from the raw material paste. The debinding process is the process of removing the binder from the ceramic molded body. The sintering process is the process of sintering the debinded ceramic molded body. The debinding and sintering processes are performed by placing the ceramic molded body on the boron nitride plate 1. Figure 2 and Figure 3 An example is shown of a ceramic molded body mounted on a boron nitride plate.

[0053] exist Figure 2 and Figure 3 In the diagram, 1 is a boron nitride plate and 3 is a ceramic molded body. Figure 2 An example is shown where a single-layer ceramic molded body is placed on a boron nitride plate. Figure 3The diagram shows an example of ceramic molded bodies stacked one on top of another on a boron nitride plate. A pressure plate (not shown) can also be disposed on the ceramic molded body 3. The boron nitride plate can also be used as the pressure plate. A structure in which the boron nitride plate 1 and the ceramic molded body 3 are alternately stacked in the manner of boron nitride plate 1 / ceramic molded body 3 / boron nitride plate 1 / ceramic molded body 3. When the ceramic molded bodies 3 are stacked one on top of another, powder can also be disposed between them. By using the pressure plate, the effect of suppressing warping of the ceramic sintered body can also be obtained. Similarly, by alternately stacking the boron nitride plate 1 and the ceramic molded body 3, the effect of suppressing warping of the ceramic sintered body can also be obtained. Warping suppression is suitable for manufacturing plate-shaped ceramic sintered bodies. Here, the plate-shaped ceramic sintered body is referred to as a ceramic substrate.

[0054] Examples of ceramic substrates include silicon nitride substrates, aluminum nitride substrates, alumina substrates, zirconia substrates, and Alusser high-silicon heat-resistant aluminum alloy substrates. Silicon nitride and aluminum nitride substrates are referred to as nitride-based ceramic substrates. Alumina substrates, zirconia substrates, and Alusser high-silicon heat-resistant aluminum alloy substrates are referred to as oxide-based ceramic substrates. They are classified according to their content of 50% by mass or more. A content of 50% by mass or more is considered the main component. For example, a ceramic substrate containing 50% by mass or more silicon nitride is called a silicon nitride substrate.

[0055] The following describes a method for manufacturing a ceramic substrate. The manufacturing process of the ceramic substrate includes a raw material mixing process, a forming process, a debinding process, and a sintering process. In the raw material mixing process, ceramic powder, which is the main component, is mixed with sintering aid powder to prepare a raw material powder. An organic binder is mixed into the raw material powder to prepare a raw material paste. In the forming process, a sheet-shaped ceramic body is prepared from the raw material paste. Methods for preparing the sheet-shaped ceramic body include scraping, die forming, and injection molding. When manufacturing ceramic substrates with a thickness of 1 mm or less, scraping is preferred. The sheet-shaped ceramic body is then cut as needed.

[0056] The boron nitride plate, having undergone the surface treatment method described in the embodiments, can be used as a component for arranging ceramic molded bodies in either the degreasing or sintering process. The boron nitride plate can also be used in both the degreasing and sintering processes. In other words, a ceramic molded body can be arranged on the boron nitride plate, and after the degreasing process, the sintering process can be performed directly.

[0057] The degreasing process is a process of removing the binder from the sheet-like ceramic molded body. Here, the sheet-like ceramic molded body is simply referred to as ceramic molded body 3. The ceramic molded body 3 is disposed on the boron nitride plate 1. Preferably, the degreasing process is carried out in a temperature range of 350°C or higher and 600°C or lower. The organic binder can be removed by the degreasing process.

[0058] The sintering process is a process of sintering the degreased ceramic molded body 3. Preferably, the sintering process is carried out in a temperature range of 1600°C or higher and 2000°C or lower. Examples of atmospheres for the sintering process include vacuum, atmosphere, and inert atmospheres. The pressure during the sintering process can be atmospheric pressure or pressurized pressure. During the sintering process, the ceramic powder gradually undergoes grain growth. In the fabrication of a silicon nitride substrate, spherical silicon nitride powder gradually grows into elongated silicon nitride grains. The aspect ratio of these elongated silicon nitride grains is 1.5 or higher, and more specifically 2 or higher. Here, silicon nitride grains with an aspect ratio of 1.5 or higher are referred to as needle-shaped silicon nitride grains.

[0059] Needle-shaped silicon nitride grains grown through the sintering process become protrusions on the surface of the sintered silicon nitride body. These protrusions penetrate into the boron nitride plate 1, resulting in needle-shaped silicon nitride grains on the surface of the boron nitride plate. If a pressure plate is placed on the silicon nitride molded body, the adhesion between the boron nitride plate 1 and the silicon nitride molded body is improved. This improved adhesion is effective in preventing warping of the silicon nitride substrate. On the other hand, the needle-shaped silicon nitride grains become easier to penetrate into the boron nitride plate 1. If needle-shaped silicon nitride grains are present on the surface of the boron nitride plate 1, it will adversely affect the obtained silicon nitride substrate, potentially reducing the yield. Adhesion can also be improved when silicon nitride molded bodies are stacked together, or when a stacked structure of boron nitride plate 1 and ceramic molded body 3 is formed. Similarly, on the other hand, the needle-shaped silicon nitride grains become easier to penetrate into the boron nitride plate.

[0060] By performing the surface treatment described in this embodiment on the boron nitride plate, a surface can be obtained in which needle-like silicon nitride grains are difficult to penetrate into the boron nitride plate 1. If the surface of the boron nitride plate 1 has recesses, needle-like silicon nitride grains can easily penetrate into these areas. By making the maximum height roughness Rz of the boron nitride plate less than 40 μm, a surface in which needle-like silicon nitride grains are difficult to penetrate can be obtained. Since needle-like silicon nitride particles are difficult to penetrate, the boron nitride plate 1 can be reused. The frequency of surface treatment of the boron nitride plate can be reduced, thereby improving efficiency and reducing costs.

[0061] In the fabrication of aluminum nitride substrates, alumina substrates, and zirconia substrates, the grains are grown using the same method as in the fabrication of silicon nitride substrates. However, in these substrates, grains with an aspect ratio of less than 2 are predominant. Therefore, compared to silicon nitride substrates, the likelihood of needle-like grains penetrating the boron nitride plate 1 is lower. In other words, the surface treatment method and the method for manufacturing the ceramic sintered body using the method described in the embodiments are suitable for manufacturing silicon nitride substrates.

[0062] The resulting ceramic sintered body is plate-shaped, preferably with a warpage of 0.1 mm or less, and preferably with a maximum surface protrusion of 20 μm or less. According to the above-described method for manufacturing a ceramic sintered body, the warpage of the plate-shaped ceramic sintered body can be kept below 0.1 mm. Furthermore, the maximum surface protrusion of the plate-shaped ceramic sintered body can be kept below 20 μm. The plate-shaped ceramic sintered body is a ceramic substrate. Most ceramic substrates have a thickness of 1 mm or less. When a silicon nitride substrate is used as the ceramic substrate, the thickness of the silicon nitride substrate can be further reduced to 0.1 mm or more and 0.4 mm or less. According to the method for manufacturing a ceramic sintered body according to the embodiment, ceramic substrates with a thickness of 1 mm or less, and further 0.4 mm or less, can be manufactured, reducing warpage and surface protrusion. Therefore, the yield can be improved. Furthermore, since the surface treatment frequency of the boron nitride plate 1 can be reduced, the cost can also be reduced.

[0063] The warpage and maximum value of surface protrusions of the silicon nitride substrate were also measured using a three-dimensional shape measuring machine. The above describes a method for manufacturing a silicon nitride substrate, but the same method can be applied to other ceramic substrates.

[0064] Figure 5 This is a flowchart illustrating the processing method involved in the implementation method. For example... Figure 5 As shown, firstly, a boron nitride plate is prepared (step S1). The boron nitride plate can be obtained, for example, by sintering a molded body containing boron nitride powder. Commercially available boron nitride plates can also be used. Next, a ceramic sintered body is manufactured using the boron nitride plate (step S2). After the ceramic sintered body is manufactured, the boron nitride plate undergoes surface treatment (step S3). Then, a ceramic sintered body is manufactured again using the treated boron nitride plate (step S2).

[0065] Figure 6 This is a flowchart illustrating a method for manufacturing a ceramic sintered body according to an embodiment. For example... Figure 6 As shown, in the manufacture of the ceramic sintered body (step S2), a ceramic molded body is disposed on a boron nitride plate (step S2a). The ceramic molded body undergoes a degreasing process and a sintering process (steps S2b and S2c). Thus, a ceramic sintered body is obtained.

[0066] Figure 7 This is a flowchart illustrating a surface treatment method for a boron nitride plate according to an embodiment. For example... Figure 7As shown, a first grinding process (step S3a) is performed on the boron nitride plate used in the manufacture of the ceramic sintered body. Next, a second grinding process (step S3b) is performed on the boron nitride plate. During the manufacture of the ceramic sintered body (step S2), needle-like silicon nitride grains penetrate the surface of the boron nitride plate. These needle-like silicon nitride grains can be effectively removed through the first and second grinding processes. According to the first and second grinding processes, the maximum height roughness Rz of the boron nitride plate can be reduced, thereby reducing warpage.

[0067] exist Figure 5 In the flowchart shown, the manufacturing of the ceramic sintered body (step S2) can be repeated multiple times. The manufacturing of the ceramic sintered body and the surface treatment of the boron nitride plate can also be repeated alternately. By performing surface treatment on the boron nitride plate, the yield of the subsequently manufactured ceramic sintered body can be improved. Furthermore, if necessary, the surface treatment of the boron nitride plate (step S3) can be performed between the preparation of the boron nitride plate (step S1) and the manufacturing of the ceramic sintered body (step S2).

[0068] Furthermore, when treating the surface of the boron nitride plate 1, it is not necessary to treat the entire surface. The scope of surface treatment can be appropriately varied as long as at least the area where the ceramic molded body is disposed is treated. Moreover, during the manufacture of the ceramic sintered body, when the boron nitride plate 1 is disposed on the ceramic molded body, there is a possibility that needle-like silicon nitride grains may also penetrate the back surface of the boron nitride plate 1. Therefore, when the boron nitride plate 1 is disposed on the ceramic molded body, it is preferable to also perform the surface treatment method described in the embodiment on the back surface of the boron nitride plate 1.

[0069] (Example)

[0070] (Examples 1-5, Comparative Examples 1-3)

[0071] First, a boron nitride plate was prepared. The boron nitride plate had a longitudinal dimension of 240 mm, a transverse dimension of 180 mm, and a thickness of 1.5 mm. A silicon nitride molded body was prepared as the ceramic molded body. The silicon nitride molded body was formed using a scraper method to create a sheet-like molded body. The silicon nitride molded body was placed on the boron nitride plate, and degreasing and sintering processes were performed. The degreasing process was carried out within a temperature range of 350°C to 600°C. The sintered silicon nitride body was moved, and other silicon nitride molded bodies were placed on the same boron nitride plate, and degreasing and sintering processes were performed. These processes were repeated 5 times as a group. As a result, multiple locations with needle-like silicon nitride grains were observed on the surface of the boron nitride plate.

[0072] The boron nitride plate with needle-like silicon nitride grains embedded was subjected to the surface treatments shown in Table 1. Abrasive paper was used in Examples 1-4 and Comparative Examples 2-3. The abrasive material was made of silicon carbide. Abrasive cloth was used in Example 5. The abrasive material was made of silicon carbide. The abrasive paper or cloth was rolled onto the roller body for surface treatment. Furthermore, the symbols F for grit sizes 120-220 and # for grit sizes 240-1000 are omitted in Table 1. No surface treatment was performed in Comparative Example 1. A rubber roller with a hardness of 10° or higher and 90° or lower was used as the roller body. The pressing pressure was set within the range of 10N or higher and 200N or lower, thereby adjusting the pressing amount.

[0073] Table 1

[0074]

[0075] The surface treatment conditions in Examples 1-5 were set within the range that satisfy the surface treatment method for boron nitride plates according to the embodiments. In Comparative Example 1, no surface treatment was performed. In Comparative Examples 2 and 3, only one grinding step was performed. That is, in Comparative Examples 2 and 3, no second grinding step was performed.

[0076] After surface treatment, the presence or absence of needle-like silicon nitride grains on the surface of the boron nitride plate was confirmed, the warpage of the boron nitride plate was measured, and the presence or absence of areas with a maximum height roughness Rz exceeding 40 μm was confirmed. For the warpage of the boron nitride plate, flatness according to JIS-B-0621 (1984) was used. The maximum height roughness Rz was based on the value of JIS-B-0601 (2013). The warpage and maximum height roughness Rz of the boron nitride plate were measured using a three-dimensional shape measuring machine. A Keyence VR series one-shot 3D shape measuring machine was used as the three-dimensional shape measuring machine. The entire surface of the ceramic molded body was measured using the three-dimensional shape measuring machine. The presence or absence of needle-like silicon nitride grains on the surface of the boron nitride plate was determined using EDX and SEM. These measurements were also performed on the entire surface of the ceramic molded body. A Keyence VE9800 was used as the SEM-EDX. The results are shown in Table 2.

[0077] Table 2

[0078]

[0079] In Examples 1-3 and 5, the warpage of the boron nitride plate was less than 0.1 mm. No needle-like silicon nitride grains or areas with a maximum height roughness Rz exceeding 40 μm were observed. Therefore, it was determined that the maximum height roughness Rz of the boron nitride plate involved in Examples 1-3 and 5 was less than 40 μm. In Example 4, two recesses with a maximum height roughness Rz exceeding 40 μm were observed. In Example 4, this was believed to be due to the processing point speed being outside the preferred range.

[0080] In Comparative Example 1, since no surface treatment was performed, all properties were poor. In Comparative Examples 2 and 3, only one grinding process was performed. Therefore, although the warpage was reduced, there were needle-like silicon nitride grains and areas with a maximum height roughness Rz exceeding 40 μm. Therefore, it is concluded that performing both the first and second grinding processes is effective as a surface treatment for boron nitride boards.

[0081] Next, a silicon nitride substrate was manufactured using the boron nitride plates of the examples and comparative examples. The thickness of the obtained silicon nitride substrate was set to 0.32 mm. Sheet-shaped silicon nitride molded bodies were placed on the boron nitride plates of the examples and comparative examples, respectively. Ten sheet-shaped silicon nitride molded bodies were stacked on each boron nitride plate, and a pressure plate was placed on them. A degreasing process at 400°C and a sintering process at 1800°C were performed. After repeating the set of steps of placing the sheet-shaped silicon nitride molded bodies, degreasing, and sintering five times, the warpage of the boron nitride plate was measured to confirm the presence or absence of needle-like silicon nitride grains and the presence or absence of areas with a maximum height roughness Rz exceeding 40 μm. Furthermore, after repeating this set of steps eight times, the warpage of the boron nitride plate was also measured to confirm the presence or absence of needle-like silicon nitride grains and the presence or absence of areas with a maximum height roughness Rz exceeding 40 μm. The results are shown in Table 3.

[0082] Table 3

[0083]

[0084] As shown in Table 3, for the boron nitride plates that have undergone the surface treatment described in the embodiments, surface degradation is reduced even with repeated degreasing and sintering processes. In particular, for the boron nitride plates described in Examples 1-3 and Example 5, surface degradation is significantly reduced, thereby demonstrating excellent durability. Therefore, the surface treatment frequency of boron nitride plates can be reduced.

[0085] Next, the warpage and maximum height roughness Rz of the silicon nitride substrates were investigated. Silicon nitride substrates with a warpage of 0.1 mm or less and a maximum height roughness Rz of 20 μm or less were considered "good". The warpage and maximum height roughness Rz of the silicon nitride substrates were also measured using a three-dimensional shape measuring machine (Keyence's one-shot 3D shape measuring machine VR series). 1000 silicon nitride substrates were fabricated in each example and comparative example, and the proportion of good products was investigated. The results are shown in Table 4.

[0086] Table 4

[0087] Example 1 100 Example 2 100 Example 3 100 Example 4 97 Example 5 100 Comparative Example 1 73 Comparative Example 2 81 Comparative Example 3 85

[0088] Table 4 shows that the silicon nitride substrate manufacturing method described in the embodiments has a high yield. Furthermore, it is known that even with repeated use, the boron nitride substrate exhibits minimal degradation. Based on this, cost reduction can also be achieved.

[0089] The embodiments of the present invention include the following features.

[0090] (Postscript 1)

[0091] A surface treatment method for a boron nitride plate includes the following steps:

[0092] The first grinding step involves grinding the surface of a boron nitride plate using a first grinding member with a grit size ranging from F120 to F220 or from #240 to #320; and

[0093] After the first grinding step, a second grinding step is performed by grinding the surface using a second grinding member with a grit size in the range of #360 or higher and #1000 or lower.

[0094] (Postscript 2)

[0095] According to the surface treatment method described in Appendix 1, the first abrasive member and the second abrasive member are abrasive paper.

[0096] (Note 3)

[0097] According to the surface treatment method for boron nitride plates according to any one of Appendix 1 to 2, in the first grinding step, the clamping amount of the first grinding member is 0.2 mm or more and 1.0 mm or less, and the processing point speed is 80 mm / s or more and 180 mm / s or less.

[0098] (Note 4)

[0099] According to any one of the appendices 1 to 3, in the second grinding step, the clamping amount of the second grinding member is 0.2 mm or more and 1.0 mm or less, and the processing point speed is 20 mm / s or more and 100 mm / s or less.

[0100] (Note 5)

[0101] According to any one of the appendices 2 to 4, the surface treatment method for boron nitride plates, wherein the processing point speed in the first grinding step is faster than the processing point speed in the second grinding step.

[0102] (Note 6)

[0103] According to the surface treatment method of boron nitride plate according to any one of Appendix 1 to 5, the surface after the second grinding process is free of needle-like silicon nitride grains and has no recesses with a depth of more than 40 μm.

[0104] (Note 7)

[0105] According to the surface treatment method for boron nitride plates described in any one of Appendices 1 to 6, the warpage of the boron nitride plate after the second grinding process is less than 0.1 mm, and the maximum height roughness Rz is less than 40 μm.

[0106] (Postscript 8)

[0107] A method for manufacturing a ceramic sintered body, comprising the following steps:

[0108] A process of depositing a ceramic molded body on the surface treated by any one of the surface treatment methods described in Appendices 1 to 7;

[0109] The process of degreasing the ceramic molded body; and

[0110] The process of sintering the degreased ceramic molded body.

[0111] (Note 9)

[0112] According to the method for manufacturing ceramic sintered bodies described in Appendix 8, the resulting ceramic sintered body is plate-shaped.

[0113] (Postscript 10)

[0114] According to any one of the methods for manufacturing ceramic sintered bodies described in Appendices 8 to 9, wherein...

[0115] The resulting sintered ceramic body is plate-shaped.

[0116] The warpage of the sintered ceramic body is less than 0.1 mm.

[0117] The maximum height roughness Rz of the sintered ceramic body is below 20 μm.

[0118] (Postscript 11)

[0119] The method for manufacturing a ceramic sintered body according to any one of Appendices 8 to 10, wherein the ceramic sintered body is a silicon nitride sintered body.

[0120] (Postscript 12)

[0121] A method for manufacturing a boron nitride plate, comprising the following steps:

[0122] The process of preparing boron nitride plates formed from boron nitride sintered bodies;

[0123] A first grinding step, employing a first grinding member with a value between F120 and F220 or between #240 and #320, grinding the surface of the boron nitride plate; and

[0124] After the first grinding step, a second grinding step is performed by grinding the surface using a second grinding member in the range of #360 or higher and #1000 or lower.

[0125] The above have illustrated several embodiments of the present invention, but these embodiments are merely examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other ways, and various omissions, substitutions, modifications, etc., can be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope and spirit of the invention, and are also included within the scope of the invention as described in the claims and their equivalents. Furthermore, the above-described embodiments can also be implemented by combining with each other.

[0126] Symbol Explanation

[0127] 1 - Boron nitride plate

[0128] 2-Abrasive paper

[0129] 3-Ceramic molded body

[0130] 4-Needle-shaped silicon nitride grains

[0131] 5 - Grinding marks

Claims

1. A surface treatment method for a boron nitride plate, comprising the following steps: The first grinding step involves grinding the surface of a boron nitride plate using a first grinding member with a grit size ranging from F120 to F220 or from #240 to #320; and After the first grinding step, a second grinding step is performed by grinding the surface using a second grinding member with a grit size in the range of #360 or higher and #1000 or lower. In the first grinding step, the clamping amount of the first grinding component is 0.2 mm or more and 1.0 mm or less, and the processing speed is 80 mm / s or more and 180 mm / s or less. In the second grinding step, the clamping amount of the second grinding component is 0.2 mm or more and 1.0 mm or less, and the processing speed is 20 mm / s or more and 100 mm / s or less. The processing point speed in the first grinding process is faster than the processing point speed in the second grinding process.

2. The surface treatment method for boron nitride plates according to claim 1, wherein, The first abrasive component and the second abrasive component are abrasive paper.

3. The surface treatment method for a boron nitride plate according to claim 1 or 2, wherein, On the surface after the second grinding process, there are no needle-like silicon nitride grains and no recesses with a depth of more than 40 μm.

4. The surface treatment method for a boron nitride plate according to claim 1 or 2, wherein, The warpage of the boron nitride plate after the second grinding process is less than 0.1 mm, and the maximum height roughness Rz is less than 40 μm.

5. The surface treatment method for a boron nitride plate according to claim 1 or 2, wherein, The first abrasive component and the second abrasive component are rollers wound with abrasive paper or rollers wound with abrasive cloth.

6. The surface treatment method for a boron nitride plate according to claim 1 or 2, wherein, The thickness of the boron nitride plate is 0.5 mm or more.

7. A method for manufacturing a ceramic sintered body, comprising the following steps: A process of depositing a ceramic molded body on the surface treated by the surface treatment method according to any one of claims 1 to 6; The process of degreasing the ceramic molded body; and The process of sintering the degreased ceramic molded body.

8. The method for manufacturing a ceramic sintered body according to claim 7, wherein, The resulting ceramic sintered body is plate-shaped.

9. The method for manufacturing a ceramic sintered body according to claim 7, wherein, The resulting sintered ceramic body is plate-shaped. The warpage of the sintered ceramic body is less than 0.1 mm. The maximum height roughness Rz of the sintered ceramic body is below 20 μm.

10. The method for manufacturing a ceramic sintered body according to claim 7, wherein, The ceramic sintered body is a silicon nitride sintered body.

11. A method for manufacturing a boron nitride plate, comprising the following steps: The process of preparing boron nitride plates formed from boron nitride sintered bodies; A first grinding step, employing a first grinding member with a value between F120 and F220 or between #240 and #320, grinding the surface of the boron nitride plate; and After the first grinding step, a second grinding step is performed by grinding the surface using a second grinding member in the range of #360 or higher and #1000 or lower. In the first grinding step, the clamping amount of the first grinding component is 0.2 mm or more and 1.0 mm or less, and the processing speed is 80 mm / s or more and 180 mm / s or less. In the second grinding step, the clamping amount of the second grinding component is 0.2 mm or more and 1.0 mm or less, and the processing speed is 20 mm / s or more and 100 mm / s or less. The processing point speed in the first grinding process is faster than the processing point speed in the second grinding process.

Images