Firing setter

Abstract

This firing setter has a platinum or platinum alloy coating layer provided on a surface of a ceramic base material.

Description

Technical Field

[0001] This application claims priority based on Japanese Patent Application No. 2023-032923 filed on March 3, 2023. All the contents of that application are incorporated herein by reference. This specification discloses a technology related to a setter for firing.

Background Art

[0002] Japanese Patent Application Laid-Open No. 10-139572 (hereinafter referred to as Patent Document 1) discloses a setter for firing in which a zirconia-based coating layer is provided on the surface of a ceramic substrate. In Patent Document 1, CaO is used as a stabilizer for the zirconia-based coating material. More specifically, in Patent Document 1, a zirconia-based coating material containing CaO in an amount equal to or more than the fully stabilized amount is used as the coating material. In Patent Document 1, by using Ca-stabilized zirconia as the coating material, the reaction between the coating layer and the fired object (electronic component) is suppressed.

Summary of the Invention

Problems to be Solved by the Invention

[0003] As disclosed in Patent Document 1, zirconia-based coating materials use stabilized zirconia containing stabilizers such as CaO to suppress the phase transition of zirconia. However, when stabilized zirconia is used as a coating material, repeated use of the firing setter causes the stabilizers contained in the coating layer (stabilized zirconia) to de-solidify, changing the properties of the coating layer. For example, the thermal expansion coefficient of the coating layer may change, or the reactivity between the coating layer and the workpiece may change. Therefore, using a zirconia-based coating material shortens the lifespan of the coating layer, and consequently shortens the lifespan of the firing setter. Thus, it is necessary to use a material that replaces zirconia-based coating materials as the material for the coating layer of the firing setter. This specification aims to provide a firing setter equipped with a coating layer using a material that replaces zirconia-based coating materials. [Means for solving the problem]

[0004] The firing setter disclosed herein may have a coating layer of platinum or a platinum alloy provided on the surface of the ceramic substrate. [Brief explanation of the drawing]

[0005] [Figure 1] The results of the example are shown. [Modes for carrying out the invention]

[0006] The firing setter disclosed herein can be suitably used, for example, as a setter for firing ceramic capacitors mainly composed of barium titanate (TiBaO3) and ferrite (Fe2O3). This firing setter may comprise a ceramic substrate and a coating layer covering the surface of the ceramic substrate. The coating layer may cover not only the surface of the ceramic substrate (the contact surface with the object to be fired, such as a ceramic capacitor), but also the back and / or side surfaces of the ceramic substrate. The material of the coating layer may be platinum or a platinum alloy. Examples of platinum alloys include Pt, which contains at least one of Pd, Cu, Ru, Ir, Co, W, and Rh.

[0007] Platinum and platinum alloys can be used as coating materials for firing setters without the need for stabilizers. Therefore, compared to coating materials that require stabilizers, such as zirconia-based coating materials, changes in the properties of the coating layer can be suppressed. In addition, the platinum or platinum alloy coating layer has low reactivity with barium titanate and other materials, and its properties are less likely to change. As a result, firing setters equipped with a platinum or platinum alloy coating layer are less prone to changes in the properties of the coating layer and have a longer lifespan.

[0008] The thickness of the coating layer may be between 1 μm and 100 μm. If the thickness of the coating layer is 1 μm or more, adhesion to the ceramic substrate is improved and peeling of the coating layer is suppressed. Also, if the thickness of the coating layer is 100 μm or less, the temperature applied to the workpiece during firing can be made uniform (large in-plane temperature distribution can be suppressed). The thickness of the coating layer may be 5 μm or more, 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, or 50 μm or more. Also, the thickness of the coating layer may be 50 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, 10 μm or less, or 5 μm or less. The surface of the coating layer may be flat or may have irregularities. If irregularities are formed on the surface of the coating layer, the workpiece to be fired will not slide as easily on the setter surface, and gases generated during de-bypassing will escape more easily from the coating layer.

[0009] The particle size of the material (platinum or platinum alloy) constituting the coating layer may be between 0.3 μm and 60 μm. If the particle size of the material constituting the coating layer is 0.3 μm or larger, the strength of the coating layer can be maintained at a high level. Furthermore, if the particle size of the material constituting the coating layer is 0.3 μm or larger, aggregation of the material during coating is suppressed, and a high-quality coating layer can be obtained. If the particle size of the material constituting the coating layer is 60 μm or smaller, the adhesion of the coating layer is improved, and peeling of the coating layer can be suppressed.

[0010] Examples of materials used for ceramic substrates include oxides such as alumina (Al2O3), mullite (Al2O3-SiO2), alumina-mullite, and cordierite (MgO-Al2O3-SiO2). Examples of non-oxide materials include sintered SiC (SSC), silicon-impregnated SiC (SiSiC), recrystallized SiC (Re-SiC), silicon nitride (Si3N4), and SIALON (a ceramic containing silicon, aluminum, oxygen, and nitrogen).

[0011] When the ceramic substrate is made of SiC, an intermediate layer mainly composed of alumina or mullite may be provided between the ceramic substrate and the coating layer. Note that "SiC" refers to the sintered SiC, silicon-impregnated SiC, and recrystallized SiC mentioned above. Providing an intermediate layer mainly composed of alumina or mullite improves the adhesion between the SiC substrate and the platinum or platinum alloy coating layer. Furthermore, providing an intermediate layer mainly composed of alumina or mullite can suppress peeling of the coating layer caused by the difference in thermal expansion coefficients between the SiC substrate and the coating layer. The coating layer may completely cover the surface of the ceramic substrate or the intermediate layer, or it may cover the surface of the ceramic substrate or intermediate layer so that it is partially exposed. Since platinum or platinum alloys have poor wettability, even if the surface of the ceramic substrate or intermediate layer is partially exposed, the components of the fired material do not easily penetrate into the coating layer.

[0012] The method for forming the coating layer is not particularly limited, but methods such as thermal spraying, printing, spray coating, vapor deposition, and plating can be used. Alternatively, a platinum film (platinum alloy film) can be placed on the surface of a ceramic substrate or intermediate layer and the coating layer can be formed by firing. Furthermore, when forming a thin film (approximately 20 μm or less), the thickness of the coating layer can be well controlled by using methods such as printing, vapor deposition, or plating. [Examples]

[0013] Samples with different substrate thicknesses, intermediate layer thicknesses, and coating layer thicknesses were prepared, and the properties of each sample were evaluated (Samples 1-30). SiC was used as the substrate, mullite as the intermediate layer, and platinum or zirconia as the coating layer. The conditions for each sample are shown in Figure 1.

[0014] As shown in Figure 1, samples 1-9 and 21-25 did not form an intermediate layer. For the other samples, first, mullite powder was applied to the surface of the SiC substrate to a predetermined thickness using a spray method, and each sample was fired in an air atmosphere at 1200-1360°C for 2-5 hours to form an intermediate layer. Subsequently, a platinum layer (coating layer) was formed on the surface of the substrate or intermediate layer for samples 1-25, and a zirconia layer (coating layer) was formed on the surface of the intermediate layer for samples 26-30.

[0015] For samples 1-20 and 26-29, the coating layer was formed using a printing method. Specifically, platinum paste was printed onto the substrate or intermediate layer using a screen printing machine (LZ-9601NS), and then baked at 1300°C for 3 hours. For sample 21, the coating layer was formed using a plating method. Specifically, the substrate was immersed in a platinum solution (Plating Studio Platinum Plating Solution), and then plated using a commercially available plating device (PROMEX). For sample 22, the coating layer was formed using platinum foil. Specifically, 1 μm platinum foil was placed on the surface of the substrate, and then baked at 1300°C for 3 hours. For sample 23, the coating layer was formed using a vapor deposition method. Specifically, platinum was vapor-deposited using an ion sputtering device (JEOL JFC-1500). For samples 24 and 30, the coating layer was formed using a spray method. Specifically, a predetermined thickness of platinum powder was applied to the substrate surface, and each sample was fired at 1300°C for 3 hours in an air atmosphere. For sample 25, a coating layer was formed using a thermal spraying method. Specifically, platinum powder was thermal sprayed onto the substrate surface.

[0016] For the obtained samples 1 to 30, the ratio of the thickness of the coating layer (and intermediate layer) to the thickness of the substrate was calculated. The results are shown in Figure 1. The ratio of the thickness of the coating layer to the thickness of the substrate was calculated using the following formula (1). In the following formula, T1 represents the thickness of the coating layer, T2 represents the thickness of the intermediate layer, and T3 represents the thickness of the substrate. Ratio (%) = (T1 + T2) / T3 × 100 ... (1)

[0017] Reaction tests and peel tests were performed on the obtained samples 1 to 30. For the reaction tests, first, 0.8 g of BaTiO3 aqueous solution was applied to a 30 mm x 30 mm area in the center of the sample surface (coating layer surface). The BaTiO3 aqueous solution used was BaTiO3:water = 2:8 by mass ratio. Then, it was heated at 1200°C for 2 hours in an air atmosphere, and the appearance after heating was observed visually. Samples in which no reaction marks were observed on the surface of the coating layer were classified as "A", samples in which minute reaction marks were observed (less than 50% of the area where the BaTiO3 aqueous solution was applied) were classified as "B", and samples in which clear reaction marks were observed (more than 51% of the area where the BaTiO3 aqueous solution was applied) were classified as "C". The results are shown in Figure 1.

[0018] Ratings "A" and "B" indicate low reactivity with BaTiO3 and high reactivity resistance to the fired material. In other words, samples with ratings "A" and "B" have a long coating layer life and a long firing setter life. On the other hand, rating "C" indicates high reactivity with BaTiO3 and low reactivity resistance to the fired material. Samples with a rating "C" have a short coating layer life and a short firing setter life.

[0019] The peel test involved placing 30mm x 20mm pieces of masking tape at 16 locations on the sample surface (coating layer surface), placing a 2kg weight on the tape, and then attaching the tape to the sample surface. After that, the masking tape was peeled off, and the number of locations where the coating layer had peeled was measured. Samples with no peeling of the coating layer were classified as "A," samples with 1 to 7 locations of peeling were classified as "B," and samples with 8 or more locations of peeling were classified as "C." The results are shown in Figure 1. Evaluations "A" and "B" indicate high adhesion between the substrate and the coating layer, and high peel resistance of the coating layer. On the other hand, evaluation "C" indicates low adhesion between the substrate and the coating layer, and low peel resistance of the coating layer.

[0020] As shown in Figure 1, all samples with a platinum coating (samples 1-25) exhibited a reactivity resistance rating of "A". On the other hand, all samples with a zirconia coating (samples 26-30) exhibited a reactivity resistance rating of "C". This result indicates that using platinum as the coating material suppresses the reaction between the workpiece and the firing setter compared to a zirconia coating layer, thereby improving the lifespan of the firing setter.

[0021] Furthermore, samples 1-25 all had a peel resistance rating of "A" or "B," while samples 26-35 all had a peel resistance rating of "C." These results confirm that using platinum as the coating layer material improves the lifespan of the firing setter compared to a zirconia coating layer.

[0022] The samples with an intermediate layer (samples 10-20), with the exception of sample 10, had a peel resistance rating of "A". This result confirms that peel resistance is significantly improved by adding an intermediate layer and adjusting the thickness of the platinum coating layer to 5 μm or more. Furthermore, the results for samples 26-30 indicate that simply adding an intermediate layer and adjusting the coating layer thickness to 5 μm or more does not improve peel resistance; the fact that the coating layer material is platinum is also important.

[0023] For samples without an intermediate layer (Samples 1 to 9, 21 to 25), it was confirmed that the thickness of the platinum layer does not affect the characteristics (reactivity resistance, peel resistance). Specifically, it was confirmed that good characteristics can be obtained in samples where the thickness of the coating layer is 1 μm or more and 100 μm or less. Also, it was confirmed that the method of forming the coating layer does not affect the characteristics (Samples 21 to 25). That is, it was confirmed that various means can be taken as the method of forming the coating layer. In this test, the influence of the difference in the ratio of the thickness of the coating layer and the substrate on the characteristics was not confirmed.

[0024] As described above, specific examples of the present invention have been described in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. Also, the technical elements described in this specification or the drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Further, the technology illustrated in this specification or the drawings can achieve multiple purposes simultaneously, and achieving one of those purposes itself has technical utility.

Claims

1. A coating layer of platinum or a platinum alloy is provided on the surface of a ceramic substrate, with an intermediate layer mainly composed of alumina or mullite in between. A firing setter having an intermediate layer thickness of 5 μm or more and 50 μm or less, and a coating layer thickness of 10 μm or more and 50 μm or less.

2. The firing setter according to claim 1, wherein the ceramic substrate is made of SiC.

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