JP2020173088A - Ceramic tray, and heat treatment method and heat treatment device using the same - Google Patents

Abstract

To provide a ceramic tray which can suppress influence of a step surface on a treatment body, and a heat treatment method using the ceramic tray.SOLUTION: A ceramic tray includes a plurality of through holes having a large diameter part and a small diameter part along a thickness direction. A step surface present between the large diameter part and the small diameter part represents a difference between a cut level in a load length ratio of 25% in a roughness curve of the step surface and a cut level in a load length ratio of 75% in the roughness curve. The cut level difference (Rδc) in the roughness curve is 4 μm or less.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to a ceramic tray having a plurality of through holes having a large diameter portion and a small diameter portion along the thickness direction, a heat treatment method using the ceramic tray, and a heat treatment apparatus.

Conventionally, in order to efficiently heat-treat sensor parts, molded parts, electronic parts such as various substrates, small-diameter wires used for reed switches, spark plugs, etc. (hereinafter, these may be referred to as objects to be processed). A tray with a plurality of through holes is used. That is, after inserting and holding the object to be processed into the plurality of through holes provided in the tray, the tray is conveyed into the heating furnace and heat-treated.

As such a tray, Patent Document 1 proposes a ceramic tray having a thermal conductivity of 30 W / (m · K) or more at room temperature, and forms a large-diameter portion and a large-diameter portion along the thickness direction. A ceramic tray with a through hole having a small diameter portion to be connected is described.

Further, Patent Document 2 proposes a ceramic tray having a plurality of holes having a minimum diameter of 1 mm or less and whose inner surface is a fired skin, and describes that it is particularly suitable as a jig for heat treatment. ..

Since the object to be processed is attached to the hole of the ceramic tray and taken in and out of the heating furnace or transported together with the tray, it may vibrate or move in the hole of the ceramic tray.

At this time, if the object to be processed comes into contact with the stepped surface of the ceramic tray, this contact may cause shedding of grains from the stepped surface of the ceramic tray. The deflated particles are liable to cause adverse effects such as sticking to the surface of the object to be treated during heat treatment.
In particular, since electronic components and the like have been miniaturized in recent years, the effect of shedding caused by the contact of the object to be processed with the stepped surface of the ceramic tray becomes relatively large.

Japanese Unexamined Patent Publication No. 2005-132691 Japanese Unexamined Patent Publication No. 2003-261384

An object of the present disclosure is to provide a ceramic tray capable of suppressing the influence of a stepped surface on an object to be treated and a heat treatment method using the same.

The ceramic tray of the present disclosure for solving the above problems is provided with a plurality of through holes having a large diameter portion and a small diameter portion along the thickness direction, and a step existing between the large diameter portion and the small diameter portion. The surface represents the difference between the cutting level at a load length ratio of 25% in the roughness curve of the stepped surface and the cutting level at a load length ratio of 75% in the roughness curve. The cutting level difference (Rδc) in the above is 4 μm or less.

In the heat treatment method of the present disclosure using the ceramic tray, the object to be processed is inserted into the through hole of the ceramic tray, and the object to be processed is placed on the stepped surface between the large diameter portion and the small diameter portion of the through hole. The process includes a step of accommodating a ceramic tray loaded with the object to be processed in a heat treatment furnace and heat-treating the object to be processed.
The heat treatment apparatus of the present disclosure using the ceramic tray includes a ceramic tray and a heat treatment furnace for accommodating the ceramic tray.

In the ceramic tray of the present disclosure, since the cutting level difference (Rδc) of the stepped surface is 4 μm or less, the unevenness of the stepped surface is small and relatively flat. Therefore, shedding is less likely to occur from the stepped surface, and adverse effects such as sticking to the object to be treated caused by threshing can be suppressed.

It is a top view which shows the ceramic tray which concerns on one Embodiment of this disclosure. It is an enlarged view of the part A of FIG. FIG. 2 is a cross-sectional view taken along line XX of FIG.

Hereinafter, the ceramic tray according to the embodiment of the present disclosure will be described. As shown in FIGS. 1 and 2, the ceramic tray 1 according to the present embodiment is composed of a ceramic plate body, and a plurality of through holes 2 are formed in the plate body. The plurality of through holes 2 are arranged in the vertical direction and the horizontal direction. The thickness of the ceramic tray 1 is not particularly limited, but is preferably 5 mm or more and 25 mm or less, preferably 8 mm or more and 20 mm or less.

The material of the ceramic tray 1 is preferably one having high heat resistance and strength that does not easily deform or break due to repeated heat cycles. For example, silicon nitride, aluminum oxide, silicon carbide, etc. are used. Examples thereof include a ceramic sintered body as a main component.

As shown in FIG. 3, the through hole 2 is for inserting and holding the heat-treated object 3 to be heat-treated, and the large-diameter portion 2a and the small-diameter portion 2c are inserted along the thickness direction of the ceramic tray 1. The stepped surface 2b is interposed between them. The large diameter portion 2a preferably has a diameter of 10 mm or more and 25 mm or less, preferably 13 mm or more and 20 mm or less. The distance (pitch) between the axes of the adjacent large diameter portions 2a and 2a is preferably as small as possible, and specifically, it is preferably 35 mm or less.
The diameter of the small diameter portion 2c is about 50% or more and 80% or less, preferably 60% or more and 70% or less with respect to the diameter of the large diameter portion 2a in order to secure a stepped surface 2b between the small diameter portion 2c and the large diameter portion 2a. It is good to have it.

The stepped surface 2b represents the difference between the cutting level at a load length rate of 25% on the roughness curve of the stepped surface 2b and the cutting level at a load length rate of 75% on the roughness curve. The cutting level difference (Rδc) in the roughness curve is 4 μm or less, preferably 3.6 μm or less. Further, the cutting level difference (Rδc) of the stepped surface 2b is preferably 0.5 μm or more.

Since the cutting level difference (Rδc) is 4 μm or less, the stepped surface 2b has small irregularities and is relatively flat. Therefore, it is possible to prevent the object to be processed 3 inserted into the through hole 2 from moving during the transportation of the tray 1 and contacting and rubbing against the step surface 2b to cause shedding from the step surface 2b. As a result, adverse effects such as sticking to the object to be treated 3 caused by shedding can be suppressed. On the other hand, when the cutting level difference (Rδc) is 0.5 μm or more, the contact angle of the stepped surface 2b with respect to pure water becomes small and the hydrophilicity becomes high. Therefore, when cleaning with a water-soluble solution, the cleaning efficiency Is improved.

The coefficient of variation of the cutting level difference (Rδc) is preferably 0.5 or less, preferably 0.48 or less. The coefficient of variation is the standard deviation divided by the mean value and is used to evaluate the relative relationship between the data and the variation with respect to the mean value. When the coefficient of variation is 0.5 or less, the variation in the cutting level difference (Rδc) is reduced, and the influence of sticking to the object to be processed 3 caused by shedding can be further suppressed.

The stepped surface 2b preferably has an arithmetic mean roughness (Ra) of 2.3 μm or less, preferably 2.2 μm or less in the roughness curve. When the arithmetic mean roughness (Ra) is 2.3 μm or less, it means that the unevenness of the stepped surface 2b is small and relatively flat. The coefficient of variation of the arithmetic mean roughness (Ra) is preferably 0.5 or less. Further, the arithmetic mean roughness (Ra) of the stepped surface 2b is preferably 0.3 μm or more. When the arithmetic mean roughness (Ra) is 0.3 μm or more, the contact angle of the stepped surface 2b with respect to pure water becomes small and the hydrophilicity becomes further high. Therefore, when cleaning with a water-soluble solution, the cleaning efficiency Is improved.

The cutting level difference (Rδc) and arithmetic mean roughness (Ra) of the roughness curve conform to JIS B 0601: 2001, and are ultra-deep color 3D shape measurement microscopes (for example, VK-9500 manufactured by KEYENCE CORPORATION). Etc.) can be measured. The measurement conditions are: color ultra-depth, gain: 953, ND (dimming) filter: 2, height measurement resolution (pitch): 0.05 μm, magnification: 200 times, cutoff value λ _s : 2 .5 μm, cutoff value λ _c : 0.08 mm.
Here, the measurement range per location may be 1300 μm × 1000 μm.

Further, the stepped surface 2b has an absolute value of skewness (Rsk) (skewness) of 0.6 or less in the roughness curve, and Kurtosis (Rku) (kurtosis) of 2.5 or less in the roughness curve. Is preferable. Skewness (Rsk) is a kind of index showing the surface texture, and shows the degree of bias of the uneven shape formed on the surface. The larger the skewness (Rsk), the more steep protrusions and gentle recesses in the roughness curve. On the other hand, the smaller the skewness (Rsk), the more steep concave portions and gentle convex portions in the roughness curve.

Kurtsis (Rku) is a kind of index showing the surface texture, and shows the degree of sharpness of the uneven shape formed on the surface. As the cultosis (Rku) becomes larger, the uneven shape on the roughness curve becomes steeper. On the other hand, the smaller the Kurtosis (Rku), the gentler the uneven shape.

It is more preferable that the absolute value of skewness (Rsk) is 0.52 or less and that of Kurtosis (Rku) is 2.2 or less. Skewness (Rsk) and Kurtosis (Rku) can be measured with the measuring device and measuring conditions used to measure the cutting level difference (Rδc) and the arithmetic mean roughness (Ra).

The tray of the present embodiment has closed pores, and a value obtained by subtracting the average value of the equivalent circle diameters of the closed pores from the distance between the centers of gravity of the adjacent closed pores (hereinafter, this value is referred to as an interval between the closed pores). It is preferably 8 μm or more and 18 μm.
When the distance between the closed pores is 8 μm or more, the closed pores exist in a relatively dispersed state, so that the mechanical strength becomes high. On the other hand, when the distance between the closed pores is 12 μm or less, even if microcracks originating from the contour of the closed pores are generated due to repeated exposure to a temperature rise to about 400 ° C. and a temperature decrease to the room temperature after the temperature rise. The surrounding air closures increase the likelihood that the extension will be blocked. From this, if the distance between the closed pores is 8 μm or more and 12 μm or less, the ceramic tray can be used for a long period of time.

To determine the distance between the closed pores, first, the average particle size D ₅₀ is 3 μm from the main surface on the side where the large diameter portion of the ceramic tray is located to the range of 10% to 50% of the wall thickness in the depth direction. Polish with a copper plate using diamond abrasive grains. Then, by polishing on a tin plate using diamond abrasive grains having an average particle size D ₅₀ of 0.5 μm, a polished surface having an arithmetic mean roughness (Ra) of 0.2 μm or less in the roughness curve is obtained.

The arithmetic mean roughness Ra of the polished surface is the same as the measurement method described above.
Observe the polished surface at a magnification of 200 times and select an average range, for example, an area of 7.2 x 10 ⁴ μm ² (horizontal length 310 μm, vertical length 233 μm). The area is photographed with a CCD camera to obtain an observation image.
For this observation image, the distance between the centers of gravity of the closed pores is measured by using the image analysis software "A image-kun (ver2.52)" (registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd.). Just find the distance. Hereinafter, when the image analysis software "A image-kun" is described, the image analysis software manufactured by Asahi Kasei Engineering Co., Ltd. is shown.
As the setting conditions of this method, for example, the threshold value indicating the brightness of the image may be 165, the brightness may be dark, the small figure removal area may be 1 μm ² , and the noise removal filter may be omitted. The threshold value may be adjusted according to the brightness of the observed image, the brightness is darkened, the binarization method is manual, the small figure removal area is 1 μm ^2, and the noise removal filter is provided. , The threshold value may be adjusted so that the marker appearing in the observation image matches the shape of the pores.

The equivalent circle diameter of the closed pores can be determined by the following method.
For the above observation image, the equivalent circle diameter of the closed pores may be obtained by a technique called particle analysis.
The setting conditions of this method may be the same as the setting conditions used in the distance between the centers of gravity of the dispersion measurement.
It is composed of a ceramic sintered body containing aluminum oxide as a main component and containing silicon. In the cross section including the stepped surface 2b, the concentration of silicon on the stepped surface 2b is higher than the concentration of silicon on the virtual surface parallel to the stepped surface. Is preferable.
Since the contact angle of silicon with pure water is small, if the concentration of silicon on the step surface is higher than the concentration of silicon on the virtual surface, the step where dirt easily adheres due to heat treatment when washed with a water-soluble detergent. The efficiency of removing dirt on the surface 2b can be increased.
On the other hand, when the concentration of silicon on the virtual surface is lower than the concentration of silicon on the stepped surface 2b, the generation of mullite having a linear expansion coefficient different from that of aluminum oxide is suppressed inside, so that the surface layer portion including the inside and the stepped surface is suppressed. It is possible to reduce the strain generated between and.
The concentration of silicon is a color mapping image of silicon using an electron probe microanalyzer (EPMA) (horizontal length: 120 μm, vertical length: 90 μm) for a polished cross section including a stepped surface. You just have to observe.

The main component in the ceramic sintered body means a component that accounts for 80% by mass or more of the total 100% by mass of the components constituting the ceramic sintered body.
Regarding the content of the components constituting the ceramic sintered body, the content of the metal element was determined using a fluorescent X-ray analyzer or an ICP emission spectroscopic analyzer, and for example, aluminum (Al) was converted to Al ₂ O ₃ . do it. The constituent components may be identified using an X-ray diffractometer.

Next, an example of the method for manufacturing the ceramic tray of the present disclosure will be described.
A case where the main component of the ceramic sintered body constituting the ceramic tray is aluminum oxide will be described.

Aluminum oxide powder (purity of 99.9% by mass or more), which is the main component, and magnesium hydroxide, silicon oxide, and calcium carbonate powders are put into a crushing mill together with a solvent (ion-exchanged water) to prepare the powder. After pulverizing until the average particle size (D ₅₀ ) becomes 1.5 μm or less, an organic binder and a dispersant for dispersing aluminum oxide powder are added and mixed to obtain a slurry.

Here, the content of magnesium hydroxide powder in a total of 100% by mass of the powder is 0.3 to 0.42% by mass, the content of silicon oxide powder is 0.5 to 0.8% by mass, and that of calcium carbonate powder. The content is 0.06 to 0.1% by mass, and the balance is aluminum oxide powder and unavoidable impurities.
The organic binder is an acrylic emulsion, polyvinyl alcohol, polyethylene glycol, polyethylene oxide and the like.

Next, after spray-granulating the slurry to obtain granules, a substrate-like molded body is formed by pressurizing the molding pressure to 78 MPa or more and 98 MPa or less using a uniaxial press molding device or a cold hydrostatic press molding device. To get.
In the molded body, a first pilot hole having a large diameter portion and a second pilot hole having a small diameter portion after firing are formed in the thickness direction by cutting. Here, an end face on the second pilot hole side of the first pilot hole is formed, and this end face becomes a stepped surface after firing and grinding.

Next, a ceramic sintered body is obtained by firing at a firing temperature of 1580 ° C. or higher and 1780 ° C. or lower and a holding time of 2 hours or longer and 4 hours or lower.
In order to obtain a ceramic tray having a pore spacing of 8 μm or more and 18 μm, the firing temperature may be 1600 ° C. or higher and 1760 ° C. or lower, and the holding time may be 2 hours or longer and 4 hours or shorter.
In order to obtain a ceramic tray in which the concentration of silicon on the stepped surface is higher than the concentration of silicon on the stepped surface parallel to the stepped surface, silicon oxide is contained, and the content thereof is, for example, 0.1% by mass or more and 0. The molded product may be placed on a baking powder having a weight of 5.5% by mass or less and fired.
By grinding the inner peripheral surfaces of the first pilot hole and the second pilot hole and the end faces of the first pilot hole on the second pilot hole side, respectively, the large diameter portion 2a, the step portion 2b, and the small diameter portion 2c are ground. A ceramic tray having the above can be obtained.

Here, in order to obtain a ceramic tray in which the cutting level difference (Rδc) of the stepped surface 2b is 4 μm or less, diamond abrasive grains having a particle size number of 230 or more and 400 or less described in ASTM E11-61 are placed on the outer peripheral surface. Using the mounted columnar tool, the rotation speed of the tool may be set to 6000 rpm or more and 10000 rpm or less, and the end face of the first pilot hole on the second pilot hole side may be ground.

Further, in order to obtain a ceramic tray having a coefficient of variation of the cutting level difference (Rδc) of 0.5 or less, a tool equipped with diamond abrasive grains having a particle size number in the above range is used, and the rotation speed of the tool is 6000 rpm or more. The end face of the first pilot hole on the second pilot hole side may be ground at 9500 rpm or less.

To obtain a ceramic tray with an arithmetic mean roughness (Ra) of 2.3 μm or less on the roughness curve, use a tool equipped with diamond abrasive grains with a particle size number in the above range, and rotate the tool at 6000 rpm or more. The end face of the first pilot hole on the second pilot hole side may be ground at 9000 rpm or less.

To obtain a ceramic tray with a coefficient of variation of arithmetic mean roughness (Ra) of 0.4 or less, use a tool equipped with diamond abrasive grains with a particle size number in the above range, and rotate the tool at 6000 rpm or more and 8500 rpm. As follows, the end face of the first pilot hole on the second pilot hole side may be ground.

In order to obtain a ceramic tray in which the absolute value of skewness (Rsk) on the roughness curve is 0.9 or less, diamond abrasive grains having a particle size number of 270 or more and 400 or less described in ASTM E11-61 are placed on the outer peripheral surface. Using the mounted columnar tool, the rotation speed of the tool may be set to 6000 rpm or more and 8500 rpm or less, and the end face of the first pilot hole on the second pilot hole side may be ground.

In order to obtain a ceramic tray having a Kurtosis (Rku) of 2.5 or less in the roughness curve, a diamond having a particle size number of 325 or more and 400 or less and having an abrasive grain of 270 or more and 400 or less described in ASTM E11-61 is obtained. The end face of the first pilot hole on the second pilot hole side may be ground by using a columnar tool on which the abrasive grains of the above are mounted on the outer peripheral surface and setting the rotation speed of the tool to 6000 rpm or more and 8500 rpm or less.

In order to heat-treat the object to be processed 3 using the ceramic tray 1 of the present embodiment obtained as described above, first, the object to be processed 3 is inserted into the through hole 2 of the ceramic tray 1 and has a large diameter. The object to be processed 3 is placed on the surface of the stepped surface 2b between the portion 2a and the small diameter portion 2c. Next, the ceramic tray 1 loaded with the object to be processed 3 is housed in a heat treatment furnace (not shown) to heat-treat the object to be processed 3. The heat treatment temperature varies depending on the type of the target object 3 and the like, but is, for example, about 400 to 1000 ° C. The heat treatment is applied, for example, in the manufacture of a pressure sensor obtained by melting a glass for joining a diaphragm that bends due to pressure and a sensor element that outputs a sensor signal corresponding to the distortion of the diaphragm.

Since the ceramic tray of the present disclosure has small irregularities on the stepped surface 2b and is relatively flat, it is difficult for shedding of particles from the inner peripheral surface to occur, and the shed particles have an adverse effect such as sticking to the object to be processed 3. It can be suppressed.

Hereinafter, the ceramic tray of the present disclosure will be described in detail with reference to examples. The ceramic tray of the present disclosure is not limited to the following examples.

First, aluminum oxide powder (purity: 99.9% by mass), which is the main component, and magnesium hydroxide, silicon oxide, and calcium carbonate powders are put into a crushing mill together with a solvent (ion-exchanged water) to form a powder. After pulverizing until the average particle size (D ₅₀ ) of the above was 1.5 μm or less, an organic binder and a dispersant for dispersing aluminum oxide powder were added and mixed to obtain a slurry.
Here, the content of the magnesium hydroxide powder is 0.36% by mass, the content of the silicon oxide powder is 0.65% by mass, and the content of the calcium carbonate powder is 0.08% by mass in the total 100% by mass of the powder. The balance is aluminum oxide powder and unavoidable impurities.
Organic binders are acrylic emulsions, polyvinyl alcohols, polyethylene glycols, and polyethylene oxides.
Next, the slurry was spray-granulated to obtain granules, and then a substrate-like molded product was obtained by pressurizing the molding pressure to 88 MPa using a cold hydrostatic press molding apparatus.
In the molded body, a first pilot hole having a large diameter portion and a second pilot hole having a small diameter portion after firing were formed in the thickness direction by cutting.
Next, a ceramic sintered body was obtained by firing at a firing temperature of 1700 ° C. and a holding time of 3 hours.
By grinding the inner peripheral surfaces of the first pilot hole and the second pilot hole and the end faces of the first pilot hole on the second pilot hole side, respectively, the large diameter portion 2a, the stepped surface 2b, and the small diameter portion 2c are ground. A ceramic tray 1 having the above was obtained.
Here, the stepped surface of the first pilot hole is ground by using a cylindrical tool having diamond abrasive grains having a particle size number of 400 described in ASTM E11-61 mounted on the outer peripheral surface, and the tool is rotated. The number was set to 6000 rpm or more and 8500 rpm or less.

(Measurement of surface properties)
The obtained ceramic tray 1 was subjected to a load length ratio of 25% on the roughness curve of the stepped surface 2b under the following measurement conditions using an ultra-depth color 3D shape measuring microscope (VK-9500 described above). The cutting level difference (Rδc) of the roughness curve, which represents the difference between the cutting level and the cutting level at a load length rate of 75% in the roughness curve, was measured. Arithmetic mean roughness (Ra), skewness (Rsk) and kurtosis (Rku) in this roughness curve were also measured. The results are shown in Table 1.
As for the measurement positions, a total of 10 points were measured, 2 points each for 5 through holes 3 in the vertical direction (arrow Y direction shown in FIG. 1) of the ceramic tray 1.
The measurement conditions are as follows.
Gain: 953
ND (dimming) filter: 2
Magnification: 200 times Cutoff value λs: 2.5 μm
Cutoff value λc: 0.08 mm
Measurement resolution (pitch) in the height direction: 0.05 μm
The measurement range per location was 1300 μm × 1000 μm.

1 Ceramic tray 2 Through hole 2a Large diameter part 2b Step surface 2c Small diameter part 3 Object to be processed

Claims (10)

A plurality of through holes having a large diameter portion and a small diameter portion along the thickness direction are provided, and the stepped surface existing between the large diameter portion and the small diameter portion is 25% of the roughness curve of the stepped surface. Ceramic having a cutting level difference (Rδc) of 4 μm or less, which represents the difference between the cutting level at the load length rate and the cutting level at a load length rate of 75% in the roughness curve. tray. The ceramic tray according to claim 1, wherein the coefficient of variation of the cutting level difference (Rδc) is 0.5 or less. The ceramic tray according to claim 1 or 2, wherein the stepped surface has an arithmetic mean roughness (Ra) of 2.3 μm or less in the roughness curve. The ceramic tray according to claim 3, wherein the coefficient of variation of the arithmetic mean roughness (Ra) is 0.4 or less. The ceramic tray according to any one of claims 1 to 4, wherein the stepped surface has an absolute value of skewness (Rsk) of 0.9 or less in the roughness curve. The ceramic tray according to any one of claims 1 to 5, wherein the stepped surface has a Kurtosis (Rku) of 2.5 or less in the roughness curve. The invention according to any one of claims 1 to 6, wherein the value obtained by subtracting the average value of the equivalent circle diameters of the closed pores from the distance between the centers of gravity of the adjacent closed pores is 8 μm or more and 18 μm. Ceramic tray. It is composed of a ceramic sintered body containing aluminum oxide as a main component and containing silicon. In the cross section including the stepped surface, the concentration of silicon on the stepped surface is higher than the concentration of silicon on the virtual surface parallel to the stepped surface. The high ceramic tray according to any one of claims 1 to 7. The object to be processed is inserted into the through hole of the ceramic tray according to any one of claims 1 to 8, and the object to be processed is placed on a stepped surface between the large diameter portion and the small diameter portion in the through hole. The process of mounting and
A heat treatment method comprising a step of accommodating the ceramic tray loaded with the object to be processed in a heat treatment furnace and heat-treating the object to be processed. A heat treatment apparatus including the ceramic tray according to any one of claims 1 to 8 and a heat treatment furnace for accommodating the ceramic tray.