Ceramic substrate

Abstract

The ceramic substrate includes alumina particles and zirconia particles, has a non-dense layer in which pores are dispersed in the plane direction and a dense layer in which the proportion of pores is less than the proportion of pores in the non-dense layer, and has a structure in which the non-dense layer and the dense layer are arranged in a layered shape in the thickness direction.

Description

Technical Field

[0001] Embodiments of this disclosure relate to ceramic substrates. Background Technology

[0002] From the perspective of high strength, alumina-zirconia ceramics containing alumina particles and zirconia particles have always attracted attention.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2005-211252 Summary of the Invention

[0006] The ceramic substrate disclosed herein comprises alumina particles and zirconium oxide particles. The ceramic substrate has a non-dense layer with pores dispersed in the planar direction and a dense layer with a pore ratio less than that of the non-dense layer. The ceramic substrate has a structure in which the non-dense layer and the dense layer are arranged in layers in the thickness direction. Attached Figure Description

[0007] Figure 1 This is an enlarged cross-sectional view showing an example of the structure of the ceramic substrate involved in the embodiment.

[0008] Figure 2 This is an enlarged cross-sectional view showing an example of the structure of the ceramic substrate involved in other embodiments 1.

[0009] Figure 3 This is an enlarged cross-sectional view showing an example of the structure of the ceramic substrate involved in other embodiments 2.

[0010] Figure 4 This is an enlarged cross-sectional view showing an example of the structure of the ceramic substrate involved in other embodiments 3.

[0011] Figure 5 This is an enlarged cross-sectional view showing an example of the structure of the ceramic substrate involved in other embodiments 4.

[0012] Figure 6 This is an enlarged cross-sectional view showing an example of the structure of the ceramic substrate involved in other embodiments 5.

[0013] Figure 7 This is a cross-sectional SEM image of the ceramic substrate of sample 1. Detailed Implementation

[0014] Hereinafter, a detailed description of the methods for implementing the ceramic substrate of this disclosure (hereinafter referred to as "Embodiments") will be provided with reference to the accompanying drawings. It should be noted that this disclosure is not limited by these embodiments. Furthermore, the various embodiments can be appropriately combined without contradicting the intended content. In the following embodiments, the same reference numerals are used to label the same parts, and repeated descriptions are omitted.

[0015] From the perspective of high strength, alumina-zirconia ceramics containing alumina particles and zirconia particles have always attracted attention.

[0016] However, when using the aforementioned prior art ceramics as ceramic substrates for mounting electrical components, a tendency is observed for the relative permittivity of the substrate to increase due to the presence of zirconium oxide particles, which have a higher relative permittivity than alumina, in their individual components. Therefore, when electrical components operating at high frequencies are mounted on this substrate, dielectric losses may increase.

[0017] Therefore, it is desirable to solve the above problems and realize a ceramic substrate with high strength and a lower relative permittivity.

[0018] <Implementation Method>

[0019] First, refer to Figure 1 The structure of the ceramic substrate 1 involved in the embodiment will be described. Figure 1 This is an enlarged cross-sectional view showing an example of the structure of the ceramic substrate 1 according to the embodiment.

[0020] like Figure 1 As shown, the ceramic substrate 1 according to the embodiment has a non-dense layer 2 and a dense layer 3. Additionally, the ceramic substrate 1 according to the embodiment may also have an electrode 4.

[0021] Both the non-dense layer 2 and the dense layer 3 are composed of ceramic containing alumina particles (not shown) and zirconia particles (not shown). In the non-dense layer 2, pores V (see reference) Figure 7 The pores are distributed in a planar direction. The porosity of the non-dense layer 2 can be, for example, 2% or more.

[0022] The proportion of pores V in the dense layer 3 is less than that in the non-dense layer 2. The porosity of the dense layer 3 can be, for example, less than 0.2%.

[0023] Furthermore, in this disclosure, the maximum diameter of the pores V is 0.1 μm or more. Additionally, in this disclosure, the porosity of the non-dense layer 2 or the dense layer 3 is a value obtained by dividing the total area of ​​the pores by the area of ​​the observed region using an image observed with a scanning electron microscope (SEM) (e.g., a range of 300 μm × 50 μm).

[0024] Moreover, such as Figure 1 As shown, the ceramic substrate 1 involved in the embodiment may also have a structure in which the non-dense layer 2 and the dense layer 3 are arranged in a layered manner in the thickness direction.

[0025] The ceramic substrate 1 with this configuration has a non-dense layer 2 with high porosity. Therefore, compared with an alumina-zirconia substrate that does not have a non-dense layer 2, the relative permittivity can be reduced by an amount corresponding to the low relative permittivity of the pores V. Therefore, according to the embodiment, the ceramic substrate 1 can be made to have high strength and a lower relative permittivity.

[0026] For example, in one embodiment, the relative permittivity of the ceramic substrate 1 may be 9 or higher and 15 or lower. Therefore, when an electrical component (not shown) is mounted on the ceramic substrate 1, the electrical characteristics of that component can be well maintained.

[0027] Furthermore, in this embodiment, the dense layer 3 is arranged to overlap with the non-dense layer 2, thus reducing the overall decrease in mechanical strength of the ceramic substrate 1. In this case, there are fewer pores V on the dense layer 3 side, thereby suppressing the generation of cracks originating from the pores V.

[0028] Furthermore, in the embodiment, since the non-dense layer 2 is configured as a layer, the fracture toughness of the ceramic substrate 1 can be well maintained, and since the ceramic substrate 1 is easy to bend and deform, it is not easy to break.

[0029] Additionally, in the implementation method, such as Figure 1 As shown, the thickness t1 of the non-dense layer 2 can be greater than the thickness t2 of the dense layer 3. In this way, by increasing the proportion of the non-dense layer 2 in the ceramic substrate 1 as a whole, the overall porosity of the ceramic substrate 1 can be increased, thereby further reducing the relative permittivity of the ceramic substrate 1.

[0030] Furthermore, in the embodiment, the thickness ratio t1 / t2 of the non-dense layer 2 and the dense layer 3 can be 2 or more and 20 or less, and more preferably 5 or more and 15 or less. This achieves a good balance between the mechanical strength and low relative permittivity of the ceramic substrate 1, enabling its use in a variety of applications.

[0031] Furthermore, the thickness t1 of the non-dense layer 2 and the thickness t2 of the dense layer 3 are measured, for example, using a digital microscope on a cross-section after the ceramic substrate 1 has been cut and ground. The measurement range, defined as the length of the ceramic substrate 1 in the planar direction, can be set to a length of 500 μm or more. Approximately 10 measurements are taken at equal intervals within this measurement range, and their average values ​​are calculated as the thickness t1 and thickness t2, respectively.

[0032] In the case where the ceramic substrate 1 is a structure with dense layers 3 on both sides of the non-dense layer 2, the thickness of the dense layer 3 on both sides is measured respectively, and the average value is taken as the thickness t2 of the dense layer 3. Figure 7 As shown, in a cross-section of the ceramic substrate 1, the method for separating the region of the non-dense layer 2 and the region of the dense layer 3 is to determine, among the plurality of pores V present in the observed cross-section of the ceramic substrate 1, the pores V closest to the surface and back surface of the ceramic substrate 1, and to draw straight lines through these pores V. These straight lines are configured to be approximately parallel to the surface or back surface of the ceramic substrate 1. For example, pores V with a maximum diameter of 2 μm or more are selected.

[0033] Furthermore, in this embodiment, the pores V can also be located at the position in contact with the zirconia particles. Therefore, the pores V can be used to prevent the development of cracks at the grain boundaries between the zirconia particles, thus enabling the ceramic substrate 1 to have high strength, high toughness, and increased bending deformation rate.

[0034] Furthermore, in this embodiment, by positioning the pores V in contact with the zirconia particles, the constraint force exerted by the alumina particles can be reduced, thus facilitating the phase transformation of the zirconia particles and improving the resistance to crack development caused by the phase transformation of the zirconia particles.

[0035] In addition, in the embodiment, when the average particle size of the alumina particles contained in the non-dense layer 2 and the dense layer 3 is set as D1 and the average particle size of the zirconia particles is set as D2, D1 can be greater than D2.

[0036] Thus, in this embodiment, the size of the alumina particles is larger than that of the zirconia particles, thereby the alumina particles can contribute to the overall rigidity and hardness of the ceramic substrate 1.

[0037] Furthermore, in this embodiment, due to the small size of the zirconia particles, the three-point bending strength and fracture toughness of the ceramic substrate 1 are improved, and the deflection of the ceramic substrate 1 can be increased.

[0038] Furthermore, in the embodiment, when the average particle size of the alumina particles contained in the non-dense layer 2 and the dense layer 3 is set to D1 and the average particle size of the zirconia particles is set to D2, the particle size ratio D1 / D2 can be 3 or more and 10 or less.

[0039] Therefore, alumina particles can further contribute to the overall rigidity and hardness of the ceramic substrate 1. In addition, the three-point bending strength and fracture toughness of the ceramic substrate 1 are further improved, and the deflection of the ceramic substrate 1 can be further increased.

[0040] Additionally, in the implementation method, such as Figure 1 As shown, the exposed surface of the dense layer 3 can also be the mounting surface 1a of an electrical component (not shown). That is, in the embodiment, the electrode 4 that mounts the electrical component can also be located on the exposed surface of the dense layer 3, i.e., the mounting surface 1a.

[0041] Therefore, the ceramic layer located near the electrical components becomes a dense layer 3 with higher rigidity than the non-dense layer 2, thereby improving the reliability of the electrical device comprising the ceramic substrate 1 and the electrical components.

[0042] In addition, in this embodiment, the non-dense layer 2 and the dense layer 3 may contain a glassy phase in addition to the alumina particles and zirconia particles. The glassy phase may, for example, be present around the alumina particles and zirconia particles.

[0043] In this embodiment, the glass phase, which is present adjacent to the alumina particles and the zirconia particles, weakens the binding forces between the alumina particles, between the zirconia particles, and between the alumina particles and the zirconia particles.

[0044] The glassy phase contained in the non-dense layer 2 and the dense layer 3 is a grain boundary phase surrounding the alumina particles and zirconia particles. The glassy phase may contain a small amount of crystalline phase. The glassy phase can be present in a proportion that is uniformly distributed around the alumina and zirconia particles, provided that the ceramic substrate 1 achieves or exceeds specified values ​​for properties such as flexural strength, fracture toughness, and three-point bending strength. In this case, the proportion of the glassy phase, in terms of area, can be 1% or more and 7% or less.

[0045] The Young's moduli of alumina particles, zirconia particles, and the glass phase are different. Specifically, the Young's moduli increase in the order of glass phase < zirconia particles < alumina particles. In the ceramic substrate 1 according to the embodiment, the zirconia particles have a smaller contact area compared to the alumina particles with high Young's moduli, and a glass phase with a lower Young's moduli exists around the alumina and zirconia particles. As a result, a ceramic substrate 1 with large flexural capacity and high deformation can be obtained.

[0046] In an embodiment, for example, the area ratio per unit area of ​​alumina particles and zirconia particles contained in the ceramic substrate 1 may be 40% or more and 60% or less for alumina particles and 30% or more and 40% or less for zirconia particles. The remaining glass phase may be 5% or more and 20% or less.

[0047] <Other Implementation Method 1>

[0048] Next, refer to Figures 2-6 Various other embodiments of this disclosure will be described. Figure 2 This is an enlarged cross-sectional view showing an example of the structure of the ceramic substrate 1 in another embodiment 1.

[0049] like Figure 2 As shown, in the ceramic substrate 1 of other embodiments 1, the thicknesses t1 and t2 of the non-dense layer 2 and the dense layer 3 are the same as those in the above-described embodiments (refer to...). Figure 1 The thickness t2 of the dense layer 3 can be greater than the thickness t1 of the non-dense layer 2. Specifically, in other embodiments 1, the thickness t2 of the dense layer 3 can be greater than the thickness t1 of the non-dense layer 2.

[0050] In this way, by increasing the proportion of the dense layer 3 in the ceramic substrate 1 as a whole, the three-point bending strength of the ceramic substrate 1 can be well maintained.

[0051] <Other Implementation Method 2>

[0052] Figure 3 This is an enlarged cross-sectional view showing an example of the structure of the ceramic substrate 1 according to another embodiment 2. For example... Figure 3 As shown, in the ceramic substrate 1 of other embodiments 2, the non-dense layer 2 may also be sandwiched between two dense layers 3.

[0053] Thus, in other embodiment 2, since the structure has two dense layers 3 sandwiching a non-dense layer 2, it is possible to reduce the situation where one side of the ceramic substrate 1 is deformed into a convex shape and the other side into a concave shape. Therefore, according to other embodiment 2, a ceramic substrate 1 with high flatness can be obtained.

[0054] Furthermore, in another embodiment 2, the thickness t1 of the non-dense layer 2 can be greater than the thickness t2 of each of the two dense layers 3. In this way, by increasing the proportion of the non-dense layer 2 in the ceramic substrate 1 as a whole, the overall porosity of the ceramic substrate 1 can be increased, thereby further reducing the relative permittivity of the ceramic substrate 1.

[0055] Furthermore, in other embodiments 2, the thickness ratio t1 / t2 of the non-dense layer 2 to the dense layer 3 can be 3 or more and 20 or less, and more preferably 5 or more and 15 or less. This achieves a good balance between the mechanical strength and low relative permittivity of the ceramic substrate 1, enabling its use in a variety of applications.

[0056] <Other Implementation Methods 3>

[0057] Figure 4 This is an enlarged cross-sectional view showing an example of the structure of the ceramic substrate 1 according to another embodiment 3. For example... Figure 4As shown, in the ceramic substrate 1 of other embodiments 3, the thickness of the dense layer 3 is the same as that of other embodiments 2 (see above). Figure 3 )different.

[0058] Specifically, in another embodiment 3, the thickness t2a of the dense layer 3A having the mounting surface 1a can be less than the thickness t2b of the dense layer 3B on the opposite side of the dense layer 3A. The dense layer 3A is an example of one type of dense layer 3, and the dense layer 3B is an example of the other type of dense layer 3. Furthermore, the exposed surface of the dense layer 3B is the back surface 1b of the ceramic substrate 1.

[0059] In this way, by making the thickness t2a of the dense layer 3A smaller than the thickness t2b of the dense layer 3B, the distance between the non-dense layer 2, which has a low relative permittivity, and the electrical component (not shown) can be shortened. Therefore, according to another embodiment 3, when the electrical component is mounted on the ceramic substrate 1, the electrical characteristics of the electrical component can be well maintained.

[0060] In addition, in other embodiments 3, the thickness t1 of the non-dense layer 2 can also be greater than the thicknesses t2a and t2b of the two dense layers 3. In this way, by increasing the proportion of the non-dense layer 2 in the ceramic substrate 1 as a whole, the porosity of the ceramic substrate 1 as a whole can be increased, and thus the relative permittivity of the ceramic substrate 1 can be further reduced.

[0061] Furthermore, in other embodiments 3, the thickness ratios t1 / t2a and t1 / t2b of the non-dense layer 2 and the dense layers 3A and 3B can be 3 or more and 20 or less, and more preferably 5 or more and 15 or less. This achieves a good balance between the mechanical strength and low relative permittivity of the ceramic substrate 1, enabling its use in a variety of applications.

[0062] <Other Implementation Methods 4>

[0063] Figure 5 This is an enlarged cross-sectional view showing an example of the structure of the ceramic substrate 1 according to another embodiment 4. For example... Figure 5 As shown, in the ceramic substrate 1 of other embodiments 4, the thickness of the dense layer 3 is the same as that of other embodiments 2 (see reference 1). Figure 3 ) and other implementation methods 3 (see Figure 4 )different.

[0064] Specifically, in other embodiments 4, the thickness t2a of the dense layer 3A having the mounting surface 1a can be greater than the thickness t2b of the dense layer 3B on the opposite side of the dense layer 3A.

[0065] In this way, by making the thickness t2a of the dense layer 3A greater than the thickness t2b of the dense layer 3B, the thickness t2a of the dense layer 3A, which is located near the electrical components and has high rigidity, can be increased, thereby improving the reliability of the electrical device comprising the ceramic substrate 1 and the electrical components.

[0066] In addition, in other embodiments 4, the thickness t1 of the non-dense layer 2 can also be greater than the thicknesses t2a and t2b of the two dense layers 3. In this way, by increasing the proportion of the non-dense layer 2 in the ceramic substrate 1 as a whole, the porosity of the ceramic substrate 1 as a whole can be increased, and thus the relative permittivity of the ceramic substrate 1 can be further reduced.

[0067] Furthermore, in other embodiments 4, the thickness ratios t1 / t2a and t1 / t2b of the non-dense layer 2 and the dense layers 3A and 3B can be 3 or more and 20 or less, and more preferably 5 or more and 15 or less. This achieves a good balance between the mechanical strength and low relative permittivity of the ceramic substrate 1, enabling its use in a variety of applications.

[0068] <Other Implementation Methods 5>

[0069] Figure 6 This is an enlarged cross-sectional view showing an example of the structure of the ceramic substrate 1 according to another embodiment 5. For example... Figure 6 As shown, in the ceramic substrate 1 of other embodiments 5, the thickness t2 of the dense layer 3 is the same as that of other embodiments 2 to 4 (see above). Figures 3-5 )different.

[0070] Specifically, in another embodiment 5, the thickness t1 of the non-dense layer 2 can be less than the thickness t2 of each of the two dense layers 3. In this way, by increasing the proportion of dense layers 3 in the ceramic substrate 1 as a whole, the three-point bending strength of the ceramic substrate 1 can be well maintained.

[0071] (Example)

[0072] The embodiments of this disclosure are described in detail below. It should be noted that this disclosure is not limited to the following embodiments.

[0073] <Sample 1>

[0074] First, as a primary mixed powder, a mixture of 70% by mass of alumina particles (average particle size 1.3 μm) and 30% by mass of zirconium oxide powder (average particle size 0.2 μm) is prepared. Next, relative to 100 parts by mass of this primary mixed powder, 3.6 parts by mass of glass powder (borosilicate glass) is added to prepare a secondary mixed powder.

[0075] Next, relative to 100 parts by weight of the prepared secondary mixed powder, 15 parts by weight of binder (butyraldehyde resin) and 5 parts by weight of plasticizer (dioctyl phthalate (DOP)) are added, and toluene is used as a solvent to prepare a slurry.

[0076] Next, alumina-zirconia green sheets with a thickness of 70 μm were made from the prepared slurry using a scraper method.

[0077] In addition, alumina green sheets are produced in parallel with the production of alumina-zirconia green sheets described above. It should be noted that, at this time, a binder (butyraldehyde resin) and a plasticizer (dioctyl phthalate (DOP)) are added to alumina particle powder (average particle size 3 μm), and toluene is used as a solvent to prepare a slurry.

[0078] Next, two 150 μm thick alumina green sheets were made from the prepared slurry using a scraper method.

[0079] Next, a laminate consisting of two alumina green sheets sandwiching one alumina-zirconia green sheet is formed, and the laminate is fired at a maximum temperature of 1550°C for 5 hours.

[0080] Finally, the sintered alumina body originating from the alumina green sheet is peeled off from both sides of the sintered laminate to obtain the ceramic substrate 1 of sample 1.

[0081] <Sample 2>

[0082] Except for setting the holding time in the firing process of the laminate to 10 hours, the ceramic substrate 1 of the sample 2 was obtained by the same method and conditions as the sample 1 described above.

[0083] <Sample 3>

[0084] Using the same method as for sample 1 above, two green sheets of alumina and zirconia and two green sheets of alumina were prepared. Then, two laminates consisting of one green sheet of alumina and one green sheet of alumina were prepared.

[0085] Next, the alumina and zirconia green sheets are placed face to face, and release powder (alumina powder) is spread between them. The two laminates are then overlapped to form a single laminate. The laminate is then fired at a maximum temperature of 1550°C for 5 hours.

[0086] Next, the sintered body is divided into two parts from the interface covered with release powder. The alumina sintered body originating from the alumina green sheet is peeled off from one side of the divided sintered body to obtain the ceramic substrate 1 of sample 3.

[0087] <Sample 4>

[0088] Using the same method as for sample 1, a green alumina-zirconia sheet was prepared. Next, the green alumina-zirconia sheet was placed on a substrate of the alumina sintered body. Finally, the green alumina-zirconia sheet placed on the substrate was fired at a maximum temperature of 1550°C for 5 hours to obtain the ceramic substrate 1 of sample 4. The thickness of samples 1-4 after firing was approximately 50 μm.

[0089] <Various Reviews>

[0090] Next, the ceramic substrate 1 of each of the above-obtained samples was cut off, the cut surface was mirror-polished, and the cross-section was observed using a scanning electron microscope (SEM). Figure 7 This is a cross-sectional SEM image showing the ceramic substrate 1 of sample 1. Furthermore, in Figure 7 The example shown illustrates a sample in which electrodes 4 are formed on the mounting surface 1a and the back surface 1b of a ceramic substrate 1.

[0091] like Figure 7 As shown, sample 1 has a structure in which a non-dense layer 2 with many pores (V) and a dense layer 3 with few pores (V) are arranged in a layered manner in the thickness direction. In addition, in sample 1, the non-dense layer 2 is sandwiched between two dense layers 3.

[0092] Furthermore, although not shown in the figure, the cross-sectional SEM image of sample 2 shows that the dense layers 3 on both sides are thicker than those in sample 1. Additionally, in the cross-sectional SEM image of sample 3, as shown... Figure 1 As shown schematically, a cross-sectional structure is observed with one thick non-dense layer 2 and one thin dense layer 3.

[0093] In addition, in the cross-sectional SEM image of sample 4, a cross-sectional structure with pores V was observed to be distributed integrally from the mounting surface 1a to the back surface 1b.

[0094] In addition, flexural tests were performed on each sample of the obtained ceramic substrate 1 to determine the flexural amount of each sample. Specifically, in the flexural test, a test sample was cut from the prepared sample and a three-point bending strength test was performed. The change from the flat state at the point of fracture was taken as the flexural amount. The sample dimensions were approximately as follows: length 40 mm, width 4 mm, and thickness 50 μm.

[0095] In addition, the fracture toughness of each specimen of the obtained ceramic substrate 1 was determined according to the indenter indentation method (IF method) specified in JIS R1607-1995. In this case, a specimen with a thickness of 2 mm was also prepared.

[0096] In addition, using the obtained ceramic substrate 1, the relative permittivity at a frequency of 1 MHz was determined using a Q meter (manufactured by Yokokawa Hewlett-Packard Co., Ltd.) and a PNA network analyzer (N5227A, N5261A, and Keyence Co., Ltd.), according to JIS C2138:2007, under the following measurement conditions. The fabricated ceramic substrate was cut into 10 mm × 10 mm (t 50 μm) wafers, and In-Ga was coated on both sides as electrode material to prepare samples. Measurements were performed at a temperature of 23–25 °C and a humidity of 30–50% RH.

[0097] Here, the evaluation results of deflection, fracture toughness, three-point bending strength and relative permittivity for specimens 1 to 4 are shown in Table 1.

[0098] (Table 1)

[0099] As shown in Table 1, based on the comparison of the evaluation results of sample 4 with those of samples 1 to 3, it can be seen that by configuring a layered structure in the thickness direction of a non-dense layer 2 with many pores V and a dense layer 3 with few pores V, the ceramic substrate 1 can achieve high strength and reduce the relative permittivity.

[0100] Furthermore, according to the evaluation results of samples 1 to 3 in the embodiment, by configuring the non-dense layer 2 in a layered manner on the ceramic substrate 1, the deflection, fracture toughness and three-point bending strength of the ceramic substrate 1 can be well maintained.

[0101] In addition, in the cross-sectional SEM images of samples 1 to 3, it was observed that the pores V formed in the non-dense layer 2 were in a state that were more adjacent to the zirconium oxide particles than the alumina particle side.

[0102] Furthermore, in the cross-sectional SEM images of samples 1–3, it was observed that the average particle size D1 of alumina particles was greater than the average particle size D2 of zirconia particles (i.e., D1>D2). Additionally, in the cross-sectional SEM images of samples 1–3, the particle size ratio D1 / D2 was observed to be approximately 7, and the average diameter of the pores V was approximately 3 μm.

[0103] Furthermore, it was observed that the total thickness ratio t1 / t2 (t2) of the non-dense layer 2 and the dense layer 3 in sample 1 was approximately 4, and the thickness ratio t1 / t2 in sample 3 was approximately 9. The total thickness ratio t1 / 2 (t2) of sample 2 was approximately 2. Thickness t1 and thickness t2 were measured using the method described above.

[0104] The embodiments of this disclosure have been described above, but this disclosure is not limited to the above embodiments. Various changes can be made as long as they do not depart from its spirit.

[0105] For example, in the above embodiments, cases where the thickness t1 of the non-dense layer 2 is larger than and smaller than the thickness t2 of the dense layer 3 are shown. However, this disclosure is not limited to such examples; for instance, the thickness t1 of the non-dense layer 2 may also be approximately equal to the thickness t2 of the dense layer 3. This also enables the ceramic substrate 1 to achieve high strength and reduce its relative permittivity.

[0106] Further effects and other embodiments can be readily derived by those skilled in the art. Therefore, the broader aspects of this disclosure are not limited to the specific details and representative embodiments shown and described above. Thus, various modifications are possible without departing from the spirit or scope of the general concept of the invention as defined by the appended claims and their equivalents.

[0107] It should be noted that this technology can also be configured in the following ways.

[0108] (1) A ceramic substrate, wherein

[0109] Contains alumina particles and zirconium oxide particles. The ceramic substrate has a non-dense layer with pores distributed in a planar direction and a dense layer with a smaller proportion of pores than the non-dense layer. The ceramic substrate has a structure in which the non-dense layer and the dense layer are arranged in layers in the thickness direction.

[0110] (2) The ceramic substrate according to (1), wherein, The non-dense layer is sandwiched between two dense layers.

[0111] (3) The ceramic substrate according to (1) or (2), wherein, When the thickness of the non-dense layer is set to t1 and the thickness of the dense layer is set to t2, the thickness ratio t1 / t2 is greater than 2 and less than 20.

[0112] (4) The ceramic substrate according to any one of (1) to (3) above, wherein, When the thickness of the non-dense layer is set to t1 and the thickness of the dense layer is set to t2, the thickness ratio t1 / t2 is 5 or more and 15 or less.

[0113] (5) The ceramic substrate according to any one of (1) to (4) above, wherein, The thickness of the non-dense layer is greater than the thickness of the dense layer.

[0114] (6) The ceramic substrate according to (1) or (2), wherein, The thickness of the dense layer is greater than the thickness of the non-dense layer.

[0115] (7) The ceramic substrate according to any one of (1) to (6) above, wherein, The pores are located at the positions where they are in contact with the zirconium oxide particles.

[0116] (8) The ceramic substrate according to any one of (1) to (7) above, wherein, When the average particle size of the alumina particles is set to D1 and the average particle size of the zirconium oxide particles is set to D2, D1>D2.

[0117] (9) The ceramic substrate according to (8) above, wherein, D1 / D2 is 3 or higher and 10 or lower.

[0118] (10) The ceramic substrate according to any one of (1) to (9) above, wherein, The exposed surface of the dense layer is the mounting surface for electrical components.

[0119] (11) The ceramic substrate according to any one of (1) to (10) above, wherein, The non-dense layer is sandwiched between two dense layers. The exposed surface of the dense layer on one side serves as the mounting surface for electrical components. The thickness of the dense layer of one party is less than the thickness of the dense layer of the other party.

[0120] (12) The ceramic substrate according to any one of (1) to (10) above, wherein, The non-dense layer is sandwiched between two dense layers. The exposed surface of the dense layer on one side serves as the mounting surface for electrical components. The thickness of the dense layer of one party is greater than the thickness of the dense layer of the other party.

[0121] Explanation of reference numerals in the attached figures: 1. Ceramic substrate 1a Mounting surface 1b Back 2 Non-dense layer 3. Dense layer 3A Tight Layer (An example of a tight layer on one side) 3B Dense layer (an example of the dense layer of the other party) 4 electrodes Thicknesses of t1, t2, t2a, and t2b V pores

Claims

1. A ceramic substrate, wherein, Contains alumina particles and zirconium oxide particles. The ceramic substrate has a non-dense layer with pores distributed in a planar direction and a dense layer with a smaller proportion of pores than the non-dense layer. The ceramic substrate has a structure in which the non-dense layer and the dense layer are arranged in layers in the thickness direction.

2. The ceramic substrate according to claim 1, wherein, The non-dense layer is sandwiched between two dense layers.

3. The ceramic substrate according to claim 1 or 2, wherein, When the thickness of the non-dense layer is set to t1 and the thickness of the dense layer is set to t2, the thickness ratio t1 / t2 is greater than 2 and less than 20.

4. The ceramic substrate according to any one of claims 1 to 3, wherein, When the thickness of the non-dense layer is set to t1 and the thickness of the dense layer is set to t2, the thickness ratio t1 / t2 is 5 or more and 15 or less.

5. The ceramic substrate according to any one of claims 1 to 4, wherein, The thickness of the non-dense layer is greater than the thickness of the dense layer.

6. The ceramic substrate according to claim 1 or 2, The thickness of the dense layer is greater than the thickness of the non-dense layer.

7. The ceramic substrate according to any one of claims 1 to 6, wherein, The pores are located at the positions where they are in contact with the zirconium oxide particles.

8. The ceramic substrate according to any one of claims 1 to 7, wherein, When the average particle size of the alumina particles is set to D1 and the average particle size of the zirconium oxide particles is set to D2, D1>D2.

9. The ceramic substrate according to claim 8, wherein, D1 / D2 is 3 or higher and 10 or lower.

10. The ceramic substrate according to any one of claims 1 to 9, wherein, The exposed surface of the dense layer has a mounting surface for electrical components.

11. The ceramic substrate according to any one of claims 1 to 10, wherein, The non-dense layer is sandwiched between two dense layers. The exposed surface of the dense layer on one side serves as the mounting surface for electrical components. The thickness of the dense layer of one party is less than the thickness of the dense layer of the other party.

12. The ceramic substrate according to any one of claims 1 to 10, wherein, The non-dense layer is sandwiched between two dense layers. The exposed surface of the dense layer on one side serves as the mounting surface for electrical components. The thickness of the dense layer of one party is greater than the thickness of the dense layer of the other party.

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