Supporting plate for firing

Abstract

The support plate for firing has a ceramic base material and a coating layer that covers the surface of the base material, the coating layer having a thickness of 1 μm or more and 20 μm or less and a surface roughness Ra of 1 μm or less.

Description

Technical Field

[0001] This application claims priority to Japanese Patent Application No. 2020-150061, filed on September 7, 2020. The entire contents of that application are incorporated herein by reference. This specification discloses technology related to firing plates for firing. In particular, it discloses technology related to firing plates having a coating layer on the surface of a substrate. Background Technology

[0002] Japanese Patent Application Publication No. 2002-154884 (hereinafter referred to as Patent Document 1) discloses a firing plate for firing in which a coating layer is provided on the surface of a substrate. The purpose of providing the coating layer is to suppress the reaction between the workpiece and the substrate. In Patent Document 1, in order to reliably suppress the reaction between the workpiece and the substrate, two or more coating layers of different materials are provided on the surface of the substrate. In Patent Document 1, a coating layer is formed by providing two or more sprayed layers or by providing a spray-coated layer on the surface of a sprayed layer. In addition, in Patent Document 1, a coating layer with a thickness of 50 to 1000 μm is provided on the surface of the substrate. Summary of the Invention

[0003] By providing a coating layer of 50 to 1000 μm on the substrate surface, as in Patent Document 1, the reaction between the workpiece and the substrate can be effectively suppressed. However, if a thicker coating layer of 50 μm or more is provided on the substrate surface, the heat capacity of the firing plate increases, and the temperature tracking performance of the firing plate decreases. Furthermore, since a thicker coating layer of 50 μm or more is formed using spraying or electroplating, the yield of the coating material is poor (high cost). If the coating layer thickness is reduced, the above problems are solved; however, in this case, uneven coating may occur, and thus, the reaction between the workpiece and the substrate may not be reliably suppressed. In other words, conventionally, to fulfill the function of the coating layer, a thicker coating layer is permissible even with increased heat capacity. This specification provides a technique for achieving a firing plate with a thinner coating layer and better temperature tracking performance.

[0004] The firing plate disclosed in this specification may have a ceramic substrate and a coating layer that covers the surface of the substrate. The coating layer has a thickness of 1 μm or more and 20 μm or less, and a surface roughness Ra of 1 μm or less.

[0005] This specification also discloses a method for manufacturing a firing support plate, which comprises: a ceramic substrate and a coating layer covering the surface of the substrate with a coating thickness of 1 μm or more and 20 μm or less. The manufacturing method includes the step of printing a coating layer forming paste onto the surface of the substrate to produce a molded body having a coating layer forming film on the surface of the substrate. Attached Figure Description

[0006] Figure 1 A perspective view showing the firing support plate for firing according to the first embodiment.

[0007] Figure 2 An enlarged view showing the surface of the firing plate for firing according to the first embodiment.

[0008] Figure 3 An enlarged view showing the cross-section of the firing support plate for the first embodiment.

[0009] Figure 4 An enlarged view showing the surface of the firing plate for firing according to the second embodiment.

[0010] Figure 5 An enlarged view showing the cross-section of the firing support plate for the second embodiment.

[0011] Figure 6 An enlarged view showing the surface of the firing plate for firing according to the third embodiment.

[0012] Figure 7 This represents a summary of the experimental cases. Detailed Implementation

[0013] The firing support plate disclosed in this specification comprises: a substrate and a coating layer covering the surface of the substrate. The firing support plate disclosed in this specification is not particularly limited, but is preferably used in the manufacturing process (firing process) of ceramic electronic components (ceramic capacitors, etc.). Examples of shapes for the firing support plate include polygons such as triangles, quadrilaterals, pentagons, and hexagons. The substrate is plate-shaped and ceramic. Examples of materials for the substrate include: SiC, alumina, and andalusite. In particular, SiC has good thermal conductivity, and the in-plane temperature of the coating layer surface (the surface on which the fired object is placed) is easily made uniform. It should be noted that, as an example of SiC, Si-SiC material can be given. "Si-SiC material" refers to a material mainly composed of SiC particles and containing metallic Si between the SiC particles. The thickness of the substrate can be, for example, 0.1 to 5 mm. The substrate in a firing support plate is the part covered by a film layer. When observing the cross-section of a firing support plate, it refers to the thickest part of the components (substrate and film layer) that make up the firing support plate.

[0014] As described above, a coating layer is applied to the surface of a substrate, covering the substrate surface. The coating thickness (thickness of the substrate surface) can be 1 μm or more and 20 μm or less. Furthermore, the coating layer can be a single layer or a multilayer structure obtained by stacking multiple layers. In the case of a multilayer structure, the material of each layer can be varied, for example, suppressing coating layer deterioration caused by differences in thermal expansion rates. Additionally, in the case of a multilayer structure, the total thickness of the multiple layers can be 1 μm or more and 20 μm or less as described above. If the total thickness of the coating layer is 1 μm or more, contact between the substrate and the workpiece can be suppressed, thereby preventing a reaction between the substrate and the workpiece. Furthermore, if the total thickness of the coating layer is 20 μm or less, the heat capacity of the coating layer is reduced, suppressing the deviation of the surface temperature of the coating layer (the temperature of the portion in contact with the workpiece) from the substrate temperature. In other words, if the total thickness of the coating layer is 20 μm or less, a firing support plate with good temperature tracking can be achieved. Furthermore, if the film thickness is 1 μm or more and 20 μm or less, and a SiC substrate with high thermal conductivity is used, the reduction in thermal conductivity caused by oxide films with lower thermal conductivity than SiC can be effectively suppressed.

[0015] The thickness of the coating layer (total thickness) can be obtained as follows: using a scanning electron microscope (SEM), an SEM image of a cross-section (near the surface) of the firing support plate is obtained. The thickness of the coating layer in the SEM image of this cross-section is measured at 5 locations, and the average value of the measured values ​​is calculated. It should be noted that the total thickness of the coating layer can be 2 μm or more, 4 μm or more, 6 μm or more, 8 μm or more, 10 μm or more, or 12 μm or more. Furthermore, the total thickness of the coating layer can be less than 18 μm, less than 16 μm, less than 14 μm, less than 12 μm, or less than 10 μm.

[0016] The surface roughness Ra of the coating layer can be less than 1 μm. If the surface roughness Ra is less than 1 μm, even a thin coating layer can suppress uneven coating on the substrate surface. Such a thin film with low surface roughness can be manufactured using printing techniques such as screen printing. Specifically, the raw material particles used to form the coating layer are mixed with an organic solvent to prepare a coating layer forming paste. This paste is then printed onto the substrate surface to create a molded body (intermediate molded body). The molded body is then fired to produce the coating layer. When using printing techniques to manufacture the coating layer, the freedom of raw material size (particle size) increases. Therefore, particulate raw materials that are difficult to use in spraying, electroplating, etc., can be used in the printing method. By using particulate raw materials to form the coating layer, a thin film with low surface roughness can be formed. The surface roughness Ra of the coating layer can be less than 0.5 μm or less, or less than 0.2 μm. Furthermore, there is no particular limitation on the lower limit of the surface roughness Ra, which can be greater than 0.05 μm. It should be noted that the surface roughness Ra of the film layer can be determined using a stylus-type contact method.

[0017] The thickness deviation of the coating layer (in the case of a multilayer structure, the deviation of the total thickness) can be less than 40% of the coating thickness and ±3 μm of the coating thickness. For example, when the coating thickness is 1 μm, applying the condition of "less than 40% of the coating thickness", the coating thickness can be 1 ± 0.4 μm. Similarly, when the coating thickness is 20 μm, applying the condition of "±3 μm of the coating thickness", the coating thickness can be 20 ± 3 μm. It should be noted that SEM images of cross-sections (near the surface) of the coating layer can be obtained by randomly selecting 10 locations. For each image, the maximum and minimum coating thicknesses are measured, and the ratio of the maximum and minimum coating thicknesses to the total coating thickness in each image is calculated. This yields the coating thickness deviation.

[0018] The coating layer can cover the entire substrate surface without gaps, or it can cover the substrate surface with a portion of the substrate surface exposed. Specifically, the coating layer can include multiple coating sheets covering the substrate surface, with gaps between the coating sheets. The gaps between the coating sheets can be 5 μm or more and 50 μm or less. If the gaps between the coating sheets are 5 μm or more, the force exerted on the coating layer due to the difference in thermal expansion coefficients between the coating layer (coating sheet) and the substrate can be suppressed. As a result, damage to the coating layer is suppressed, and the durability of the coating layer is improved. If the gaps between the coating sheets are 50 μm or less, contact between the sintered object and the substrate can be prevented, and the reaction between the sintered object and the substrate is suppressed. The gaps between the coating sheets can be 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, or 40 μm or more. Furthermore, the gaps between the films can be less than 45 μm, less than 40 μm, less than 35 μm, less than 30 μm, less than 25 μm, less than 20 μm, or less than 15 μm. It should be noted that multiple SEM observation samples (samples used to observe cross-sections near the surface) can be selected from a range of 250 μm × 200 μm to obtain SEM images of the cross-sections (cross-sections near the surface). Ten gaps can be selected from the obtained images for measurement, and the average value of the measured values ​​can be calculated to obtain the gaps between the films.

[0019] By employing the above-described printing method, a film layer with gaps between the film sheets can be formed on the surface of a substrate. Furthermore, by using the printing method, film sheets of any shape can be formed on the substrate surface, thereby enabling the formation of geometrically patterned film sheets. The shape of the film sheets is not particularly limited and can be circular, polygonal (triangle, quadrilateral, pentagon, hexagon, etc.). Moreover, by using the printing method, film sheets can be formed at any position on the substrate surface. However, from the viewpoint of uniformly heating the workpiece, it is preferable that the film sheets appear regularly on the substrate surface. For example, film sheets can be formed at equal intervals on the substrate surface, with uniform gaps between the film sheets.

[0020] As described above, the coating layer can be a multilayer structure obtained by stacking multiple layers. In this case, a second coating sheet can be further provided on the surface of the first coating sheet provided on the surface of the substrate. This results in a multilayer structure with gaps between the coating sheets. In this case, the gap between the first coating sheets (the size of the gap) and the gap between the second coating sheets can be different. For example, the gap between the second coating sheets can be larger than the gap between the first coating sheets. This suppresses the migration of substrate components to the coating layer (coating sheet) and reduces the contact area between the coating layer (second coating layer) and the workpiece. A coating layer with different gaps between the first and second coating sheets can also be easily manufactured using a printing method. It should be noted that a third, fourth, ... nth coating sheet can be further provided on the surface of the second coating sheet.

[0021] The material of the coating layer can be appropriately selected based on the substrate material and the type of object to be fired. For example, the material of the coating layer (film) can be ZrO2 / Y2O3 (Y2O3 stabilizes ZrO2), ZrO2 / CaO (CaO stabilizes ZrO2), Y2O3, Al2O3, MgO, andalusite, or a mixture of these materials. It should be noted that when the coating layer has a multilayer structure, for example, the material can be different in each layer, such as the first coating layer (film) being andalusite and the second coating layer (film) being ZrO2 / Y2O3.

[0022] The porosity of the coating layer can be 5% or more and 50% or less. If the porosity is 5% or more, gases generated by the workpiece during firing can pass through the coating layer, preventing gas from becoming trapped between the workpiece and the coating layer. If the porosity is 50% or less, the strength of the coating layer is maintained, and the durability of the firing support plate for firing is improved. The porosity of the coating layer can be 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, or 35% or more. Furthermore, the porosity of the coating layer can be 45% or less, 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, or 15% or less. It should be noted that the porosity of the coating layer can be determined according to JIS R2205-1992.

[0023] Example

[0024] (First Embodiment)

[0025] Reference Figures 1 to 3 The firing support plate 10 for firing will be described below. Figure 1As shown, the firing support plate 10 is flat and includes: a SiC substrate 2 and a coating layer 4 disposed on the surface of the substrate 2. It should be noted that the coating layer 4 has a two-layer structure, comprising: an intermediate layer 6 disposed on the surface of the substrate 2 and a surface layer 8 disposed on the surface of the intermediate layer 6. The intermediate layer 6 and the surface layer 8 will be described in detail below.

[0026] like Figure 2 and Figure 3 As shown, the intermediate layer 6 covers the entire surface of the substrate 2. The material of the intermediate layer 6 is andalusite. The intermediate layer 6 is formed on the surface of the substrate 2 by a printing method, and its thickness T6 is approximately 1 μm. A surface layer 8 is disposed on the surface of the intermediate layer 6. The material of the surface layer 8 is yttrium oxide. The surface layer 8 is composed of multiple films 8a. The films 8a are quadrilateral, and the gap G8 between each film 8a is approximately 10 μm. The surface layer 8 (films 8a) is formed on the surface of the intermediate layer 6 by a printing method, and its thickness T8 is approximately 1 μm. In addition, the surface roughness Ra of the surface of the film layer 4 (the surface of the surface layer 8) is suppressed to less than 1 μm.

[0027] In the firing plate 10, since the coating layer 4 (intermediate layer 6, surface layer 8) is formed by printing, it is easy to achieve a coating layer 4 with a thin thickness and a small surface roughness Ra. By reducing the thickness of the coating layer 4, the heat capacity of the coating layer 4 is reduced, and the in-plane temperature deviation of the firing plate 10 during firing is suppressed, thereby improving the temperature tracking performance of the firing plate 10. In addition, the surface layer 8 has multiple coating sheets 8a, and gaps are provided between each coating sheet 8a. Therefore, the force exerted on the coating layer 4 due to the difference in thermal expansion rates between the substrate 2 and the coating layer 4 can be suppressed, thereby suppressing damage to the coating layer 4.

[0028] Hereinafter, modified examples (second and third embodiments) of the firing support plate 10 will be described. In the firing support plates 10a and 10b described below, reference numerals that are the same as those used for the firing support plate 10 are marked for features that are common to the firing support plate 10, and therefore descriptions are sometimes omitted.

[0029] (Second Embodiment)

[0030] Reference Figure 4 and Figure 5The firing support plate 10a for firing will be described below. In the firing support plate 10a, the coating layer 4 has a three-layer structure, comprising: an intermediate layer 6 disposed on the surface of the substrate 2, a surface layer 8 disposed on the surface of the intermediate layer, and an outermost layer 9 disposed on the surface of the surface layer 8. The intermediate layer 6 is made of andalusite, and the surface layer 8 and the outermost layer 9 are made of yttrium oxide. The outermost layer 9 is composed of multiple coating sheets 9a. Each coating sheet 9a is quadrilateral, and one coating sheet 9a is disposed on the surface of one coating sheet 8a. The size of each coating sheet 9a is smaller than the size of each coating sheet 8a. Therefore, the gap G9 between each coating sheet 9a is larger than the gap G8 between each coating sheet 8a. Specifically, the gap G9 is approximately 20 μm. It should be noted that the thickness of the outermost layer 9 (coating sheet 9a) is approximately 1 μm.

[0031] like Figure 5 As shown, when the workpiece 20 is placed on the firing plate 10a, the workpiece 20 contacts the outermost layer 9. As described above, the size of the film 9a is smaller than the size of the film 8a. Therefore, compared with the firing plate 10, the firing plate 10a can reduce the contact area between the workpiece 20 and the film layer 4. By reducing the contact area between the workpiece 20 and the film layer 4, it is possible to suppress the retention of gases generated by the workpiece during firing around the workpiece 20, thereby suppressing uneven firing of the workpiece.

[0032] (Third Embodiment)

[0033] Reference Figure 6 The firing support plate 10b for firing will be described below. In the firing support plate 10b, the coating layer 4 has a two-layer structure. The coating layer 4 comprises: a substrate (refer to...) Figure 1 The intermediate layer 6 covers the entire surface of the firing plate 10b, and the surface layer 8 is disposed on the surface of the intermediate layer 6. The surface layer 8 is composed of a plurality of circular film sheets 8a. The gap (shortest distance) G8 between each film sheet 8a is about 10 μm. That is, the shape of the film sheets 8a constituting the surface layer 8 is different from that of the firing plate 10b and the firing plate 10.

[0034] (Other implementation methods)

[0035] In the above embodiments, firing plates with the surface layer 8 and the outermost layer 9 having shapes of quadrilaterals (first and second embodiments) and circles (third embodiment) are illustrated. However, the shape of the surface layer 8 (outermost layer 9) can be a polygon such as a triangle, pentagon, or hexagon. Alternatively, the surface layer 8 (outermost layer 9) can cover the entire surface of the intermediate layer 6. That is, the surface layer 8 (outermost layer 9) may not be formed of a film sheet. In addition, in the firing plate 10b of the third embodiment, similar to the firing plate 10a of the second embodiment, an outermost layer 9 can be further provided on the surface of the surface layer 8. It should be noted that when the outermost layer 9 is provided on the surface of the surface layer 8, the shape of the film sheet 8a of the surface layer 8 and the shape of the film sheet 9a of the outermost layer 9 can be different. Furthermore, three or more surface layers can be provided on the surface of the intermediate layer 6.

[0036] In the above embodiments, the method of providing the intermediate layer 6 on the surface of the substrate 2 has been described; however, the intermediate layer 6 may be omitted. If the intermediate layer 6 is omitted, the surface layer 8 (outermost layer 9) can cover the entire surface of the substrate 2, or it may be formed from multiple films.

[0037] (Experimental Example)

[0038] Fabrication: Firing support plates 10 with different morphologies of the coating layer 4 (samples 1 to 4) were used to evaluate the in-plane temperature deviation of the firing support plates 10 during heating and cooling. Figure 7 The characteristics of each sample are shown in the figure. First, the manufacturing methods of samples 1 to 4 will be described.

[0039] Regarding Sample 1, firstly, 0.5 μm (D50) andalusite particles were mixed with an organic solvent to prepare an andalusite paste (paste for coating formation). Next, the andalusite paste was printed with a thickness of 1 μm onto the entire surface of a 150 mm × 150 mm × 1 mm SiC substrate and fired at 1300 °C for 2 hours, thereby creating an andalusite layer (intermediate layer) on the surface of the SiC substrate. Then, 0.5 μm (D50) yttrium oxide particles were mixed with an organic solvent to prepare a yttrium oxide paste. This yttrium oxide paste was then printed with a thickness of 1 μm onto the surface of the andalusite layer and fired at 1350 °C for 2 hours, thereby creating a yttrium oxide layer (surface layer) on the surface of the andalusite layer. Thus, sample 1 was obtained, which has a 2 μm coating layer (1 μm of andalusite layer and 1 μm of yttrium oxide layer) on the surface of the SiC substrate. It should be noted that the yttrium oxide layer was not printed on the entire surface of the andalusite layer; instead, multiple quadrilateral coating sheets were printed with a 10 μm gap between adjacent sheets. The surface roughness of the obtained sample was 0.5 μm.

[0040] Regarding sample 2, except that the thickness of the andalusite layer is 5 μm and the thickness of the yttrium oxide layer is 5 μm, it was prepared using the same raw materials and manufacturing method as sample 1. The surface roughness of sample 2 is 0.2 μm.

[0041] Regarding sample 3, 70 μm (D50) andalusite particles were sprayed onto the entire surface of the SiC substrate, creating a 50 μm andalusite layer. Then, 20 μm (D50) yttrium oxide particles were sprayed onto the entire surface of the andalusite layer, creating a 50 μm yttrium oxide layer (surface layer). The resulting sample had a surface roughness of 5 μm.

[0042] Regarding sample 4, the andalusite particles used in the preparation of sample 1 (sample 2) were sprayed onto the entire surface of the SiC substrate in the same manner as sample 3. Then, yttrium oxide particles used in the preparation of sample 1 (sample 2) were sprayed onto the entire surface of the andalusite layer. However, in sample 4, the particles (andalusite particles and yttrium oxide particles) were not sufficiently adhered to the surface of the SiC substrate, resulting in an unstable film layer. As mentioned above, the particle size (D50) of the particles used in samples 1 and 2 is relatively small, only 0.5 μm. It is speculated that because the particles are too light, they bounce off the coating surface (the surface of the SiC substrate), thus failing to adhere sufficiently to the surface of the SiC substrate.

[0043] As described above, a stable coating layer could not be obtained from sample 4. Therefore, heating and cooling tests were conducted on samples 1 to 3 to evaluate the in-plane temperature deviation of the firing support plate 10 during heating and cooling. In the heating and cooling tests, each sample was placed in a heating furnace, and the furnace temperature was increased from room temperature to 1200°C at a rate of 600°C / min. The temperature difference between the two ends of the firing support plate 10 at the furnace temperature of 1200°C was measured. Furthermore, the furnace temperature was decreased from 1200°C to room temperature at a rate of 600°C / min, and the temperature difference between the two ends of the firing support plate 10 at the furnace temperature of room temperature was measured. Figure 7 The results are shown in the figure.

[0044] like Figure 7As shown, it was confirmed that samples 1 and 2, with thinner coating layers (below 20 μm), exhibited smaller in-plane temperature deviations on the firing plate 10 during heating and cooling (temperature difference less than 15°C during heating, and less than 10°C during cooling). Conversely, sample 3, with thicker coating layers (above 20 μm), showed larger in-plane temperature deviations on the firing plate 10 during heating and cooling (temperature difference greater than 15°C during heating, and greater than 10°C during cooling). This result indicates that because samples 1 and 2 have thinner coating layers compared to sample 3, their heat capacity is smaller, and their temperature follows the furnace temperature well. It should be noted that the surface roughness Ra of samples 1 and 2 is smaller than that of sample 3. This result reflects the different particle sizes of the raw materials used. That is, the particle size of the raw material particles in samples 1 and 2 is small, therefore, the surface roughness Ra of the coating layer is small (less than 1 μm). In other words, by using raw materials with a particle size such as Ra of less than 1 μm to form the coating layer, the thickness of the coating layer can be reduced.

[0045] The specific examples of the present invention have been described in detail above; however, these examples are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes solutions obtained by various modifications and alterations to the specific examples illustrated above. Furthermore, the technical elements described in this specification or drawings exert their technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of application. Additionally, the technology illustrated in this specification or drawings can achieve multiple objectives simultaneously, and the solution for achieving one of these objectives is itself technically useful.

[0046] Symbol Explanation

[0047] 2: Substrate

[0048] 4: Coating layer

[0049] 10: Firing support plate for firing

Claims

1. A firing support plate for firing, characterized in that, have: Ceramic substrate; and A coating layer that covers the surface of a substrate, the coating thickness being greater than 1 μm and less than 20 μm, and the surface roughness Ra being less than 1 μm. The thickness deviation of the coating layer is less than 40% of the coating thickness, and is within ±3 μm of the coating thickness. The coating layer comprises: multiple films covering the surface of the substrate. A second diaphragm is disposed on the surface of each diaphragm. The spacing between the diaphragms is different from the spacing between the second diaphragm.

2. The firing support plate according to claim 1, characterized in that, A gap of 5 μm or more and 50 μm or less is provided between each membrane sheet.

3. The firing support plate according to claim 2, characterized in that, The diaphragms are in a prescribed circular or polygonal shape and appear regularly on the surface of the substrate.

4. The firing support plate according to claim 1, characterized in that, The coating material includes: ZrO2 / Y2O3, ZrO2 / CaO, Y2O3, Al2O3, MgO, andalusite, or a mixture of these materials.

5. The firing support plate according to claim 1, characterized in that, The substrate material is SiC.

6. The firing support plate according to claim 1, characterized in that, The coating layer has a multilayer structure with two or more layers.

7. The firing support plate according to claim 1, characterized in that, The porosity of the coating layer is above 5% and below 50%.

8. A method for manufacturing a firing support plate according to any one of claims 1 to 7, wherein the firing support plate comprises: a ceramic substrate and a film layer covering the surface of the substrate with a film thickness of 1 μm or more and 20 μm or less. The manufacturing method is characterized by having the following steps: A coating film forming paste is printed on the surface of the substrate in such a way that the thickness deviation of the coating film is less than 40% of the coating film thickness and is ±3 μm of the coating film thickness, thereby producing a molded body having a coating film forming film on the surface of the substrate.

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