Ceramic substrate, composite substrate, circuit substrate, and method of manufacturing ceramic substrate, method of manufacturing composite substrate, method of manufacturing circuit substrate, and method of manufacturing multiple circuit substrates

Abstract

This ceramic substrate has a rectangular shape in a plane view. A value obtained by dividing the maximum height difference of the ceramic substrate by the length of a diagonal of the ceramic substrate is 1 μm / mm or less. A plurality of cracks are formed in the end portions of the ceramic substrate so as to extend in an in-plane direction from a main surface end portion of the ceramic substrate and span from one end to the other end in the substrate thickness direction.

Description

[Technical Field]

[0001] The present invention relates to a ceramic substrate, a composite substrate, a circuit substrate, and a method for manufacturing a ceramic substrate, a method for manufacturing a composite substrate, a method for manufacturing a circuit substrate, and a method for manufacturing a plurality of circuit substrates. [Background technology]

[0002] For example, as in Patent Document 1, a circuit board is known in which metal layers are fixed to both sides of a ceramic substrate to form a composite substrate, and a circuit pattern is formed on one of the metal layers of this composite substrate. This circuit board is excellent in terms of high thermal conductivity and high insulation, and is therefore used for power modules, for example.

[0003] Such a ceramic substrate is then processed into a circuit board through various steps, including a metal layer forming step in which a metal layer (e.g., a copper plate) is fixed to both sides of the substrate, a circuit pattern forming step in which a circuit pattern is formed on at least one of the metal layers, and a scribe line forming step. In each of these processes, the ceramic substrate and copper plate, which have different thermal expansion coefficients, are bonded together and subjected to various thermal histories, so it is inevitable that some degree of thermal distortion and thermal stress will remain inside the final circuit board. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-18971 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, there has been an increasing demand for flatness in circuit boards, and in order to meet this demand, it is necessary to reduce the thermal distortion and thermal stress remaining inside the circuit board to a higher level.

[0006] An object of the present invention is to provide a ceramic substrate from which circuit boards having excellent flatness and in which residual thermal distortion and residual thermal stress are significantly reduced can be fabricated. [Means for solving the problem]

[0007] A ceramic substrate according to a first aspect of the present invention is a ceramic substrate that is rectangular in plan view, in which the value obtained by dividing the maximum height difference in the thickness direction of the ceramic substrate by the length of a diagonal of the ceramic substrate is 1 μm / mm or less, and a plurality of cracks are formed at the end of the ceramic substrate, extending in the in-plane direction from the end of the main surface of the ceramic substrate to one end of the thickness direction.

[0008] A ceramic substrate according to a second aspect of the present invention is the ceramic substrate, wherein the plurality of cracks are formed along the entire periphery of the end portion.

[0009] The ceramic substrate according to a third aspect of the present invention is the ceramic substrate described above, which contains silicon nitride or aluminum nitride.

[0010] A composite substrate according to one embodiment of the present invention comprises the ceramic substrate, a first metal layer fixed to the front surface side of the ceramic substrate, and a second metal layer fixed to the back surface side of the ceramic substrate.

[0011] A circuit board according to one aspect of the present invention comprises the ceramic substrate, a circuit pattern formed on the front surface side of the ceramic substrate, and a metal layer fixed to the back surface side of the ceramic substrate.

[0012] A first aspect of the present invention is a method for manufacturing a ceramic substrate, which includes a strip green sheet cutting step of cutting a strip green sheet containing ceramic powder to obtain single green sheets; a sintering step of placing the single green sheets in a firing chamber, heating the firing chamber until the temperature therein reaches at least 1600°C or higher, and then cooling the firing chamber to sinter the single green sheets to obtain the ceramic substrate; and a ceramic substrate cutting step of cutting the entire peripheral edge portion of the ceramic substrate cooled after the sintering step.

[0013] A second aspect of the present invention is a method for manufacturing a ceramic substrate, wherein in the step of cutting the ceramic substrate, a laser light source is scanned around the entire circumferential direction of the entire peripheral edge portion of the ceramic substrate while intermittently irradiating the ceramic substrate with laser light, thereby forming cracks at the edge portions created by cutting the ceramic substrate.

[0014] A third aspect of the present invention is a method for manufacturing a ceramic substrate, wherein in the sintering step, the temperature inside the firing chamber is rapidly cooled when the temperature inside the firing chamber reaches 650°C or lower during cooling inside the firing chamber.

[0015] A fourth aspect of the present invention is a method for producing a ceramic substrate, wherein the ceramic powder contains silicon nitride powder or aluminum nitride powder.

[0016] A method for manufacturing a composite substrate according to one embodiment of the present invention includes the method for manufacturing a ceramic substrate described above and a fixing step of fixing a first metal layer to the front surface side of the ceramic substrate and a second metal layer to the back surface side thereof.

[0017] A method for manufacturing a circuit board according to one aspect of the present invention includes the method for manufacturing a composite substrate, and a pattern forming step of forming at least one circuit pattern on either the first metal layer or the second metal layer.

[0018] A method for manufacturing multiple circuit boards according to one embodiment of the present invention includes the method for manufacturing the composite substrate, a pattern formation process for forming multiple circuit patterns on either the first metal layer or the second metal layer, and a division process for dividing the composite substrate on which the multiple circuit patterns have been formed into multiple circuit boards, each having one of the circuit patterns. [Effects of the Invention]

[0019] The ceramic substrate of the present invention can effectively reduce warpage and internal stress in a bonded substrate and circuit board in which a ceramic substrate and a metal layer are bonded, which are produced after each process including the subsequent metal layer formation process, the circuit pattern formation process in which a circuit pattern is formed on at least one of the metal layers, and the scribe line formation process. Accordingly, the ceramic substrate of the present invention and a composite substrate including the ceramic substrate of the present invention can produce a circuit board with excellent flatness and significantly reduced residual thermal strain and residual thermal stress. Furthermore, the circuit board of the present invention has high reliability, excellent flatness, and significantly reduced residual thermal strain and residual thermal stress. When a circuit board is produced using the ceramic substrate of the present invention, a highly reliable circuit board with excellent flatness and in which residual thermal distortion and residual thermal stress are significantly reduced can be obtained. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 4 is a flowchart showing a method for manufacturing a plurality of mounting substrates according to the present embodiment. [Figure 2A] FIG. 10 is a flow diagram of a green sheet forming step included in the method for manufacturing a plurality of mounting substrates according to the present embodiment. [Figure 2B] This is a diagram for explaining the molding process included in the green sheet formation process of this embodiment, and is a schematic diagram for explaining the state in which a strip-shaped green sheet is produced from slurry using a doctor blade molding device. [Figure 2C]It is a diagram for explaining a cutting process included in the green sheet forming process of the present embodiment, and is a schematic diagram (side view) for explaining a state in which a strip-shaped green sheet is cut using a cutting device to produce a single green sheet. [Figure 2D] It is a schematic diagram of FIG. 2C viewed from the front side. [Figure 3A] It is a diagram for explaining from the deposition process included in the green sheet forming process of the present embodiment to the sintering process in the manufacturing method of a plurality of mounting substrates of the present embodiment. [Figure 3B] It is a graph showing the profile of the firing temperature in the sintering process (including the conditions examined by tests). [Figure 3C] It is a graph showing the relationship between the rapid cooling start temperature (including the conditions examined by tests) in the firing process and the amount of warpage. [Figure 3D] It is a plan view of the ceramic substrate of the first example of the present embodiment, and is a height distribution diagram in a state where a profile of the height level (degree of depression) in the plate thickness direction is attached. [Figure 3E] It is a cross-sectional view of the ceramic substrate of the first example of FIG. 3D, and is a cross-sectional view cut along the cutting line A-A. [Figure 3F] It is a cross-sectional view of the ceramic substrate of the first example of FIG. 3D, and is a cross-sectional view cut along the cutting line B-B. [Figure 3G] It is a plan view of the ceramic substrate of the second example of the present embodiment, and is a height distribution diagram in a state where a profile of the height level (degree of depression) in the plate thickness direction is attached. [Figure 3H] It is a cross-sectional view of the ceramic substrate of the second example of FIG. 3G, and is a cross-sectional view cut along the cutting line A-A. [Figure 3I] It is a cross-sectional view of the ceramic substrate of the second example of FIG. 3G, and is a cross-sectional view cut along the cutting line B-B. [Figure 3J] It is a plan view of the ceramic substrate of the third example of the present embodiment, and is a height distribution diagram in a state where a profile of the height level (degree of depression) in the plate thickness direction is attached. [Figure 3K]Cross-sectional view of the ceramic substrate of the third example in FIG. 3J, which is a cross-sectional view taken along the cutting line A-A. [Figure 3L] Cross-sectional view of the ceramic substrate of the third example in FIG. 3J, which is a cross-sectional view taken along the cutting line B-B. [Figure 3M] Planar view of the ceramic substrate of the fourth example of the present embodiment, which is a height distribution diagram with a profile of the height degree (concavity) in the plate thickness direction attached. [Figure 3N] Cross-sectional view of the ceramic substrate of the fourth example in FIG. 3M, which is a cross-sectional view taken along the cutting line A-A. [Figure 3O] Cross-sectional view of the ceramic substrate of the fourth example in FIG. 3M, which is a cross-sectional view taken along the cutting line B-B. [Figure 3P] Planar view of the ceramic substrate of the fifth example of the present embodiment, which is a height distribution diagram with a profile of the height degree (concavity) in the plate thickness direction attached. [Figure 3Q] Cross-sectional view of the ceramic substrate of the fifth example in FIG. 3P, which is a cross-sectional view taken along the cutting line A-A. [Figure 3R] Cross-sectional view of the ceramic substrate of the fifth example in FIG. 3P, which is a cross-sectional view taken along the cutting line B-B. [Figure 3S] Planar view of the ceramic substrate of the sixth example of the present embodiment, which is a height distribution diagram (70μm span) with a profile of the height degree (concavity) in the plate thickness direction attached. [Figure 3T] Planar view of the ceramic substrate of the sixth example of the present embodiment, which is a height distribution diagram (100μm span) with a profile of the height degree (concavity) in the plate thickness direction attached. [Figure 3U] Planar view of the ceramic substrate of the sixth example of the present embodiment, which is a height distribution diagram (200μm span) with a profile of the height degree (concavity) in the plate thickness direction attached. [Figure 3V] Planar view of the ceramic substrate of the sixth example of the present embodiment, which is a height distribution diagram (300μm span) with a profile of the height degree (concavity) in the plate thickness direction attached. [Figure 3W] 3B is a graph showing the distribution of displacement measured with a laser three-dimensional shape measuring device along the line CC in FIGS. 3S to 3V. [Figure 4A] 10A and 10B are schematic views for explaining a peripheral partial cutting step included in the method for manufacturing a plurality of mounting substrates according to the present embodiment. [Figure 4B] 10 is a graph showing the relationship between the cutting width of the outer periphery and the amount of warpage in the outer periphery cutting step. [Figure 5] 10A to 10C are diagrams for explaining a scribe line forming step included in the method for manufacturing a plurality of mounting substrates according to the present embodiment. [Figure 6A] 10A to 10C are diagrams for explaining a metal layer forming step included in the method for manufacturing a plurality of mounting substrates according to the present embodiment. [Figure 6B] 6B is a cross-sectional view of the ceramic substrate of FIG. 6A taken along section line 6B-6B. [Figure 6C] FIG. 2 is a partial perspective view of the ceramic substrate of the present embodiment. [Figure 7] 10A to 10C are diagrams for explaining a resist printing step included in the method for manufacturing a plurality of mounting substrates according to the present embodiment. [Figure 8] 10A to 10C are diagrams for explaining an etching step included in the method for manufacturing a plurality of mounting substrates according to the present embodiment. [Figure 9] 10A to 10C are diagrams for explaining a dividing step included in the method for manufacturing a plurality of mounting substrates according to the present embodiment. [Figure 10] FIG. 10 is a view for explaining a metal layer forming step of the first modified example. [Figure 11A] FIG. 10 is a plan view of a ceramic substrate of a second modified example, showing a height distribution diagram with a profile of the height degree (depression degree) in the thickness direction of the substrate. [Figure 11B] 11B is a cross-sectional view of the ceramic substrate of FIG. 11A, in which a longitudinal cross-sectional view taken along the X0-X0 cutting line, a longitudinal cross-sectional view taken along the X1-X1 cutting line, and a longitudinal cross-sectional view taken along the X2-X2 cutting line are arranged along the X direction. [Figure 11C]11B is a cross-sectional view of the ceramic substrate of FIG. 11A, in which a cross-sectional view taken along the Y0-Y0 cutting line, a cross-sectional view taken along the Y1-Y1 cutting line, and a cross-sectional view taken along the Y2-Y2 cutting line are arranged along the Y direction. DETAILED DESCRIPTION OF THE INVENTION

[0021] Overview The present embodiment will be described below with reference to the drawings. First, the ceramic substrate 40 (see FIGS. 3A, 3D, 3G, 3J, 3M, 3P, 3S, etc.), the motherboard 60 (an example of a composite substrate, see FIGS. 6A and 6B), the aggregate substrate 60B (another example of a composite substrate, see FIGS. 8 and 9), and the circuit board 60C (see FIG. 9) of the present embodiment will be described. Next, a method for manufacturing a plurality of mounting substrates (not shown) according to this embodiment will be described in the order of the steps shown in FIG. 1 with reference to FIG. Next, the effects of this embodiment will be described. Next, a modification of this embodiment will be described with reference to, for example, FIG. 10 and FIGS. 11A to 11C. In addition, in all drawings referred to in the following description, similar components are denoted by similar reference numerals, and descriptions thereof will be omitted where appropriate.

[0022] <Ceramic substrate of this embodiment> The ceramic substrate 40 of this embodiment will be described below with reference to FIGS. 3D to 3W and 6B to 6C.

[0023] The ceramic substrate 40 of this embodiment has the following basic features: The ceramic substrate 40 is rectangular in plan view, the value obtained by dividing the maximum height difference in the thickness direction of the ceramic substrate 40 by the length of the diagonal of the ceramic substrate 40 is 1 μm / mm or less, and a plurality of cracks MC are formed at the end of the ceramic substrate 40, extending in the in-plane direction from the end of the main surface of the ceramic substrate 40 to one end of the thickness direction. That is, the ceramic substrate 40 of this embodiment is substantially flat or completely flat, and has a plurality of cracks MC formed at its edge, spanning from one end to the other end of the ceramic substrate 40 in the thickness direction. The maximum height difference in this embodiment will be described in the description of Example 6. The "maximum height value" is defined as "the value obtained by dividing the maximum height difference in the thickness direction of the ceramic substrate 40 by the length of the diagonal line of the ceramic substrate 40."

[0024] Furthermore, the ceramic substrate 40 of this embodiment may have slight unevenness in its thickness direction, as long as it satisfies the requirement for the maximum height difference, which is one of the basic characteristics described above. That is, at least one convex portion that is convex toward one side or the other side in the thickness direction may be formed. Examples of the formation of such a convex portion include the following. For example, one aspect of the ceramic substrate 40 of this embodiment has at least one convex portion formed thereon that is convex toward one side or the other in the thickness direction of the substrate (see Figures 3D, 3G, 3J, 3M, 3P, and 3S). Furthermore, for example, in one aspect of the ceramic substrate 40 of the present embodiment, at least one convex portion is a plurality of convex portions, and the plurality of convex portions are each formed in two regions partitioned by one of a pair of diagonal lines in the ceramic substrate 40 (see Figures 3D, 3G, 3J, and 3M). Furthermore, for example, in one aspect of the ceramic substrate 40 of the present embodiment, the at least one convex portion is a plurality of convex portions, and the plurality of convex portions are each formed in four regions defined by a pair of diagonal lines on the ceramic substrate 40 (see FIG. 3M). Furthermore, for example, in one aspect of the ceramic substrate 40 of the present embodiment, the at least one convex portion is a plurality of convex portions, and some of the plurality of convex portions are formed so as to be convex toward one side in the plate thickness direction of the ceramic substrate 40, The remaining part of the plurality of convex portions is formed so as to be convex toward the other side in the plate thickness direction (see FIGS. 3D, 3M, and 3P).

[0025] Next, examples of ceramic substrate 40 will be described with reference to Figures 3D to 3W using first to sixth examples. In these examples, surface 40A1 of ceramic substrate 40 is a substantially flat surface, although it has some irregularities. However, the present invention is not limited to these examples, and surface 40A1 of ceramic substrate 40 may be a completely flat surface without any convex portions. The first to sixth examples described below are merely examples of ceramic substrate 40 of this embodiment, and any ceramic substrate having the above basic characteristics is included in ceramic substrate 40 of this embodiment.

[0026] [First example ceramic substrate] The ceramic substrate 40 of the first example will be described with reference to FIGS. 3D to 3F. Here, Fig. 3D is a plan view of a ceramic substrate 40 of a first example of this embodiment, and is a height distribution diagram with a profile of the height degree (depression level) in the plate thickness direction (Z direction). Fig. 3E is a cross-sectional view of the ceramic substrate 40 of the first example, taken along the AA cutting line in Fig. 3D. Fig. 3F is a cross-sectional view of the ceramic substrate 40 of the first example, taken along the BB cutting line in Fig. 3D. The ceramic substrate 40 of the first example has the following features.

[0027] In the first example ceramic substrate 40, multiple microcracks MC are formed at the end of the ceramic substrate 40, extending in the in-plane direction from the main surface end 40A3 of the ceramic substrate 40 to one end (front surface 40A1) in the thickness direction (Z direction) of the ceramic substrate 40 and the other end (back surface 40A2) (see Figures 6B and 6C). The microcracks MC are formed along the entire circumference of the end portion, i.e., the entire outer peripheral surface (hereinafter referred to as the first feature). The microcracks MC are arranged at a predetermined interval p1 in the circumferential direction of the end portion. For example, in a ceramic substrate with a thickness of 320 μm, the predetermined interval p1 is, for example, 90 μm or more and 110 μm or less. The length L11 of the microcracks MC on the main surface side (surface 40A1 side) is, for example, 15 μm or more and 25 μm or less.

[0028] Furthermore, in the ceramic substrate 40 of the first example, at least one convex portion (convex portions CX1 and CX2 in the first example) that is convex toward one side or the other in the thickness direction (Z direction) is formed at a position shifted from the intersection O formed by the pair of diagonal lines (the pair of dashed lines in FIG. 3D) in a plan view, and the maximum height value is 1 μm / mm or less (hereinafter referred to as the second feature). The ceramic substrate 40 of the first example and the ceramic substrates 40 of the second to fifth examples described below each have, for example, a length of 206 mm and a width of 146 mm, resulting in a diagonal length of approximately 252.5 mm. The convex amounts of the convex portions CX1 and CX2 (the amount of the convex or concave portion compared to a flat surface (the reference in the drawing)) are denoted by ΔZ1 and ΔZ2, respectively. The convex amounts ΔZ1 and ΔZ2 are, for example, 252 μm or less. In other words, in the first example, the maximum height difference is 252 μm or less. Therefore, the maximum height difference of the ceramic substrate 40 of the first example is 1 μm / mm or less.

[0029] Furthermore, assuming that the maximum height value of the ceramic substrate 40 in the first example is 1 μm / mm or less, the multiple convex portions (in the first example, convex portions CX1 and CX2) are each formed in two regions defined by one of a pair of diagonals on the ceramic substrate 40 (in the first example, both diagonals) (hereinafter referred to as the third feature).

[0030] Furthermore, assuming that the maximum height value of the ceramic substrate 40 of the first example is 1 μm / mm or less, some (one of the convex portions CX1, CX2) of the multiple convex portions (in the first example, the convex portions CX1, CX2) are formed so as to be convex toward one side in the plate thickness direction (Z direction), and the remaining part (the other of the convex portions CX1, CX2) is formed so as to be convex toward the other side in the plate thickness direction (hereinafter referred to as the fourth feature).

[0031] The above is a description of the ceramic substrate 40 of the first example.

[0032] [Second example ceramic substrate] The ceramic substrate 40 of the second example will be described with reference to FIGS. 3G to 3I. Here, Fig. 3G is a plan view of a ceramic substrate 40 of a second example of this embodiment, and is a height distribution diagram with a profile of the height degree (depression level) in the plate thickness direction (Z direction). Fig. 3H is a cross-sectional view of the ceramic substrate 40 of the second example, taken along the AA cutting line in Fig. 3G. Fig. 3I is a cross-sectional view of the ceramic substrate 40 of the second example, taken along the BB cutting line in Fig. 3G. The ceramic substrate 40 of the second example differs from the first example (see FIG. 3D) in that the convex portions CX1 and CX2 are each convex on one side (the surface 40A1 side) in the plate thickness direction (Z direction). The ceramic substrate 40 of the second example also has the first to third features of the first example.

[0033] This concludes the description of the ceramic substrate 40 of the second example.

[0034] [Third example ceramic substrate] The ceramic substrate 40 of the third example will be described with reference to FIGS. 3J to 3L. Here, Fig. 3J is a plan view of a ceramic substrate 40 according to a third example of this embodiment, and is a height distribution diagram showing a profile of the height degree (depression level) in the plate thickness direction (Z direction). Fig. 3K is a cross-sectional view of the ceramic substrate 40 according to the third example, taken along the AA cutting line in Fig. 3J. Fig. 3L is a cross-sectional view of the ceramic substrate 40 according to the third example, taken along the BB cutting line in Fig. 3J. The ceramic substrate 40 of the third example differs from the first example (see FIG. 3D) and the second example (see FIG. 3G) in that the convex portions CX1 and CX2 are each convex on the other side (back surface 40A2 side) in the plate thickness direction (Z direction). The ceramic substrate 40 of the third example also has the first to third features of the first example.

[0035] This concludes the description of the ceramic substrate 40 of the third example.

[0036] [Fourth example ceramic substrate] The ceramic substrate 40 of the fourth example will be described with reference to FIGS. 3M to 3O. Here, Fig. 3M is a plan view of a ceramic substrate 40 according to a fourth example of this embodiment, and is a height distribution diagram with a profile of the height degree (depression level) in the plate thickness direction (Z direction). Fig. 3N is a cross-sectional view of the ceramic substrate 40 according to the fourth example, taken along the AA cutting line in Fig. 3M. Fig. 3N is a cross-sectional view of the ceramic substrate 40 according to the fourth example, taken along the BB cutting line in Fig. 3M. In the ceramic substrate 40 of the fourth example, the maximum height is assumed to be 1 μm / mm or less, and the plurality of convex portions (convex portions CX1, CX2, CX3, and CX4) are formed in four regions defined by a pair of diagonal lines on the ceramic substrate 40 (hereinafter referred to as a fifth feature). The convex amounts ΔZ3 and ΔZ4 of the convex portions CX3 and CX4 are, for example, 252 μm or less. The ceramic substrate 40 of the third example has the first to fourth features of the first example.

[0037] The above is a description of the ceramic substrate 40 of the fourth example.

[0038] [Fifth example ceramic substrate] The ceramic substrate 40 of the fifth example will be described with reference to FIGS. 3P to 3R. Here, Fig. 3P is a plan view of a ceramic substrate 40 according to a fifth example of this embodiment, and is a height distribution diagram with a profile of the height degree (depression level) in the plate thickness direction (Z direction). Fig. 3Q is a cross-sectional view of the ceramic substrate 40 according to the fifth example, taken along the AA cutting line in Fig. 3P. Fig. 3R is a cross-sectional view of the ceramic substrate 40 according to the fifth example, taken along the BB cutting line in Fig. 3P. In the ceramic substrate 40 of the fifth example, the convex portions CX1 and CX2 are each formed in one of four regions defined by a pair of diagonal lines on the ceramic substrate 40. In this respect, the ceramic substrate 40 of the fifth example differs from the first example (see FIG. 3D). The ceramic substrate 40 of the fifth example also has the first and second features of the first example.

[0039] The above is a description of the ceramic substrate 40 of the fifth example.

[0040] [Sixth example ceramic substrate] The ceramic substrate 40 of the sixth example will be described with reference to FIGS. 3S to 3W. 3S to 3V are plan views of a ceramic substrate 40 according to a sixth example of this embodiment, and are elevation distribution diagrams showing profiles of the elevation degree (depression level) in the thickness direction (Z direction). The measurement spans for measuring the amount of warpage, which will be described later, are different in FIGS. 3S to 3V (70 μm, 100 μm, 200 μm, and 300 μm, respectively). FIG. 3W is a graph showing the distribution of displacement measured with a laser three-dimensional shape measuring device along the line CC in FIGS. 3S to 3V. In this embodiment, the amount of warpage of the ceramic substrate 40 was measured as follows: A laser three-dimensional shape measuring instrument (Keyence Corporation: LK-GD500) was used to irradiate the ceramic substrate 40 with laser light, receive the light diffused and reflected from the ceramic substrate 40, calculate the amount of displacement, and measure the amount of warpage of the main surface of the ceramic substrate 40. In this case, the measurement pitch was 1 mm x 1 mm. In this embodiment, the "maximum height difference" refers to the maximum displacement amount when the reference surface 40A1 (or back surface 40A2) is calculated from the displacement measured by the laser 3D shape measuring device and the displacement amount from that reference surface is calculated.

[0041] The above is a description of the ceramic substrate 40 of the sixth example.

[0042] As described above, the ceramic substrates 40 of the first to sixth examples (see FIGS. 3D to 3W) are examples of the ceramic substrate 40 of this embodiment, and the ceramic substrate 40 of this embodiment also includes the following examples. For example, in the case of the ceramic substrate 40 of the first example (see FIG. 3D), the convex portions CX1 and CX2 are formed in two regions defined on both sides in the longitudinal direction (Y direction) with an intersection O sandwiched between four regions defined by a pair of diagonal lines on the ceramic substrate 40. However, for example, the convex portions CX1 and CX2 may be formed in two regions defined on both sides in the lateral direction (X direction) with the intersection O sandwiched between them. Furthermore, for example, in the case of the ceramic substrate 40 of the fourth example (see FIG. 3M), the convex portions CX2 and CX3 are convex toward the back surface 40A2 in the thickness direction (Z direction) of the ceramic substrate 40 (see FIGS. 3N and 3O). However, for example, one or both of the convex portions CX2 and CX3 may be convex toward the front surface 40A1. Also, for example, a ceramic substrate (not shown) may be used in which the ceramic substrate 40 of the first example (see FIG. 3D) is combined with the convex portion CX2 (see FIG. 3P) of the ceramic substrate 40 of the fifth example. Also, for example, the ceramic substrate 40 (see FIG. 3D) of the first example may be a ceramic substrate (not shown) that does not have one of the convex portions CX1 and CX2. Similarly, the ceramic substrate 40 (see FIG. 3P) of the fifth example may be a ceramic substrate (not shown) that does not have one of the convex portions CX1 and CX2.

[0043] The above is a description of the ceramic substrate 40 of this embodiment.

[0044] Motherboard Next, the motherboard 60 of this embodiment will be described with reference to FIGS. 6A and 6B. The motherboard 60 of this embodiment includes a first metal layer 50A fixed to the front surface 40A1 of the ceramic substrate 40, and a second metal layer 50B fixed to the back surface 40A2 of the ceramic substrate 40. 6A and 6B, a ceramic substrate 40A with SL, which will be described later, is used instead of the ceramic substrate 40. The ceramic substrate 40A with SL is a substrate in which, as an example, a plurality of scribe lines SL are formed on the ceramic substrate 40, as will be described later. The above is a description of the motherboard 60 of this embodiment.

[0045] <Circuit board> Next, the circuit board 60C of this embodiment will be described with reference to FIG. The circuit board 60C of this embodiment comprises a ceramic substrate 40, a circuit pattern CP formed on the front surface 40A1 side of the ceramic substrate 40, and a metal layer (second metal layer 50B) fixed to the back surface 40A2 side of the ceramic substrate 40. The above is the description of the circuit board 60C of this embodiment.

[0046] <<Method for manufacturing a plurality of mounting substrates according to this embodiment>> Next, a method S100 for manufacturing a plurality of mounting substrates according to this embodiment (hereinafter referred to as the manufacturing method S100 of this embodiment) will be described with reference to FIG. 1, the manufacturing method S100 of this embodiment includes a green sheet forming step S1, a sintering step S2, a peripheral partial cutting step S3, a scribe line forming step S4 (hereinafter referred to as an SL forming step S4), a metal layer forming step S5, a resist printing step S6, an etching step S7, a surface treatment step S8, a dividing step S9, and a mounting step S10. The manufacturing method S100 of this embodiment is performed in the order in which these steps are listed.

[0047] The relationship between the end of each step in the manufacturing method S100 of this embodiment and the product at that time is as follows. ======================================== Each process at the end of the process ======================================== Sintering step S2: Ceramic substrate 40 (see FIG. 3D) SL formation process S4: SL-equipped ceramic substrate 40A (see FIG. 5) Metal layer formation process S5 Motherboard 60 (see FIGS. 6A and 6B) Etching step S7: aggregate substrate 60B (see FIG. 8) Dividing step S9: Dividing a plurality of circuit boards 60C (see FIG. 9) Mounting process S10: Multiple mounting boards ========================================

[0048] The description of each step in the manufacturing method S100 of this embodiment also includes the description of each of the following inventions. (Invention relating to the manufacturing method of ceramic substrates) The method for manufacturing the ceramic substrate 40 of this embodiment includes a cutting process for the strip green sheet 20, in which the strip green sheet 20 containing ceramic powder is cut to obtain the single green sheet 30; a sintering process for placing the single green sheet 30 in a firing chamber, heating the firing chamber until the temperature therein reaches at least 1600°C or higher, and then cooling the firing chamber to sinter the single green sheet 30 to obtain the ceramic substrate 40; and a cutting process for the ceramic substrate 40, in which the entire peripheral edge portion of the cooled ceramic substrate 40 after the sintering process is cut (see Figures 1 and 4A). Furthermore, in the manufacturing method of the ceramic substrate 40 of this embodiment, in the sintering process, if the temperature inside the firing chamber becomes 650°C or lower during cooling inside the firing chamber, the temperature inside the firing chamber is rapidly cooled (see Figures 1, 2B, 2C, 3B, etc.). (Invention relating to a method for manufacturing a motherboard) The manufacturing method of the motherboard 60 of this embodiment includes the above-mentioned ceramic substrate manufacturing method and a fixing process of fixing a first metal layer 50A to the front surface 40A1 side of the ceramic substrate 40 and fixing a second metal layer 50B to the back surface 40A2 side (see Figure 6A). (Invention relating to the manufacturing method of circuit boards) The manufacturing method of the circuit board 60C of this embodiment includes the manufacturing method of the motherboard 60 described above and a pattern formation process of forming at least one circuit pattern CP on either the first metal layer 50A or the second metal layer 50B (in this embodiment, the first metal layer 50A as an example) (see Figures 7, 8, etc.). (Invention relating to a method for manufacturing multiple circuit boards) The method for manufacturing multiple circuit boards 60C in this embodiment includes the above-mentioned method for manufacturing the motherboard 60, a pattern formation process for forming multiple circuit patterns CP on either the first metal layer 50A or the second metal layer 50B (in this embodiment, the first metal layer 50A is used as an example), and a division process for dividing the motherboard 60 on which the multiple circuit patterns CP have been formed into multiple circuit boards 60C, each having one circuit pattern CP (see Figures 7 to 9, etc.). Each step will be described below.

[0049] <Green sheet forming process and sintering process> In this embodiment, the process of combining the green sheet forming step S1 and the sintering step S2 and performing them in the order described corresponds to a method of manufacturing the ceramic substrate 40. A method for manufacturing the ceramic substrate 40 of this embodiment will be described below with reference to FIGS. 2A to 2D, 3A to 3R, 4A and 4B.

[0050] Here, the ceramic substrate 40 is used, for example, as a circuit board or mounting substrate for a power module installed in an electric vehicle, a railroad car, or other industrial equipment. The ceramic substrate 40 is obtained, for example, by stacking and sintering (see FIG. 3A) single-layer green sheets 30 (see FIG. 2C), which will be described later. The single-layer green sheets 30 are also obtained by cutting a strip-shaped green sheet 20 (see FIGS. 2B and 2C). That is, the ceramic substrate 40 and the single-layer green sheets 30 have a relationship similar to that between a finished product and an intermediate product (a product manufactured in a process before becoming a finished product), or a relationship similar to that between a first intermediate product and a second intermediate product (a product manufactured in a process before becoming the first intermediate product). Therefore, the single-layer green sheets 30 of this embodiment are manufactured up to an intermediate stage in the manufacturing method for the ceramic substrate 40 of this embodiment. The ceramic substrate 40 of this embodiment is, for example, a rectangular plate (see FIGS. 3D, 3G, 3J, 3M, 3P, 5, etc.).

[0051] <Green sheet formation process> The green sheet forming step S1 will be described below with reference to Figures 2A, 2B, 2C, and 2D. The green sheet forming step S1 of this embodiment includes a slurry preparing step S11, a molding step S12, a cutting step S13, a depositing step S14, and a degreasing step S15, which are performed in the order listed (see Figures 1 and 2A).

[0052] [Slurry preparation process] The slurry preparation step S11 will be described. In this step, a raw material powder and an organic solvent, which will be described later, are mixed to prepare a slurry 10. The slurry 10 (see FIG. 2B) prepared in this step is formed into a strip-shaped green sheet 20 in the next step (forming step S12).

[0053] The raw material powder of the slurry 10 is a powder containing a main component and a sintering aid, which will be described later. The main component is, for example, 80% to 98.3% by mass of silicon nitride (Si3N4), and the sintering aid is, for example, 1% to 10% by mass (oxide equivalent) of at least one rare earth element and 0.7% to 10% by mass (oxide equivalent) of magnesium (Mg). The alpha conversion rate of the silicon nitride powder is preferably 20% to 100%, taking into account the density, bending strength, and thermal conductivity of the ceramic substrate 40. Here, to clarify the meaning of "to" used in this specification, for example, "20% to 100%" means "20% or more and 100% or less." Furthermore, "to" used in this specification means "more than the part written before 'to' and less than the part written after 'to'."

[0054] The reason why the proportion of silicon nitride (Si3N4) in the raw material powder is set to 80% by weight to 98.3% by mass is to ensure that the bending strength and thermal conductivity of the resulting ceramic substrate 40 are not too low, and to ensure the density of the ceramic substrate 40 due to a lack of sintering aids.

[0055] For ease of explanation, the silicon nitride raw material powder will be referred to as Si3N4 powder (also known as silicon nitride powder, an example of ceramic powder), the Mg raw material powder as MgO powder, and the rare earth element raw material powder as YO3 powder. However, the silicon nitride raw material powder and the sintering aid raw material powder do not have to be Si3N4 powder, MgO powder, and YO3 powder, respectively.

[0056] Then, the SiN powder, MgO powder, and YO powder blended as described above are mixed with a plasticizer, an organic binder, and an organic solvent to prepare the slurry 10. Therefore, the slurry 10 prepared in this step contains ceramic powder.

[0057] This concludes the description of the slurry preparation step S11.

[0058] [Molding process] Next, the molding step S12 will be described. In this step, a strip-shaped green sheet 20 is produced from the slurry 10, as shown in FIG.

[0059] This step is performed, for example, using a doctor blade molding apparatus 100 shown in FIG. 2B . The doctor blade molding apparatus 100 includes a belt conveying mechanism 110, a molding unit 120, and a heating unit 130. The belt conveying mechanism 110 has an upstream roller 112A, a downstream roller 112B, and a belt 114, and drives the downstream roller 112 to move the belt 114 from the upstream roller 112 to the downstream roller 112 (along the X direction). The molding unit 120 is disposed above the belt 114 (closer to the Z direction than the belt 114) and faces the belt 114. The molding unit 120 includes a storage section 122 that stores the slurry 10 and a doctor blade 124.

[0060] 2B, the forming unit 120 uses a doctor blade 124 to regulate the slurry 10, which is carried out of the storage section 122 by its own weight and the adhesive force with the moving belt 114, into a sheet having a predetermined thickness. The heating unit 130 blows hot air WC onto the slurry 10 on the belt 114, which has been formed to the predetermined thickness, to form the slurry 10 into a sheet (evaporating the organic solvent). As a result, in the forming step S12, a strip-shaped green sheet 20 having a predetermined width (the Y direction in the drawing corresponds to the width direction) is produced from the slurry 10. That is, in the forming step S12, the slurry 10 is formed into a strip-shaped green sheet 20 by doctor blade forming to obtain, as an example, a strip-shaped green sheet 20 containing Si3N4 (ceramic).

[0061] As an example, this step is performed after the slurry 10 prepared in the slurry preparation step S11 has been degassed and thickened. The thickness of the belt-shaped green sheet 20 prepared in this step is set in consideration of the thickness of the ceramic substrate 40 to be finally manufactured. Accordingly, the conditions for controlling the doctor blade 124 (such as the distance from the belt 114) for controlling the thickness of the slurry 10 to a predetermined thickness are also set in consideration of the thickness of the ceramic substrate 40 to be finally manufactured.

[0062] This concludes the description of the molding step S12.

[0063] [Cutting process] Next, a description will be given of the cutting step S13 of the belt-shaped green sheet 20. In this step, the belt-shaped green sheet 20 is cut to produce single green sheets 30, as shown in Fig. 2C.

[0064] 2C, the cutting device 200 includes a sheet conveying mechanism 210 and a cutting section 220. The sheet conveying mechanism 210 has a support unit 212, a first conveying unit 214, and a second conveying unit 216. The support unit 212 rotatably supports a roller 112B (see FIGS. 2B and 2C) around which the strip green sheet 20 produced in the forming step S12 is wound. The first conveying unit 214 adjusts the orientation of the strip green sheet 20 conveyed from the support unit 212 and conveys the strip green sheet 20 along the X direction (along the longitudinal direction of the strip green sheet 20) to the cutting unit 220. The second conveying unit 216 conveys the individual green sheets 30 produced by cutting the strip green sheet 20 in the cutting unit 220 further downstream (in the X direction). The cutting unit 220 also has a housing 222, an irradiation unit 224, and a movement mechanism 226. The irradiation unit 224, for example, irradiates laser light LB. The movement mechanism 226 scans the irradiation unit 224 from one end to the other in the short-side direction (Y direction in the figure) of the strip-shaped green sheet 20. The irradiation unit 224 and the movement mechanism 226 are attached to the housing 222.

[0065] In the cutting device 200 of this embodiment, the sheet conveying mechanism 210 conveys the strip green sheet 20 by the length of the individual green sheets 30, stops the strip green sheet 20, and cuts the strip green sheet 20 using the cutting unit 220. In this case, the cutting unit 220 irradiates the irradiation unit 224 with laser light LB while moving the irradiation unit 224 along the Y direction from one end to the other end in the short direction of the strip green sheet 20 using the movement mechanism 226 (see FIG. 2D). The irradiation unit 224, which is scanned by the movement mechanism 226, intermittently irradiates the laser light LB. Here, "intermittently" means that irradiation is performed for a certain period of time and then not irradiated for a certain period of time alternately. Therefore, the movement mechanism 226 scans the irradiation unit 224 by repeatedly moving and stopping the irradiation unit 224 (see FIG. 2D). As described above, in this process, the strip green sheet 20 is cut by irradiating it with laser light LB to obtain single-leaf green sheets 30. Note that the laser light LB may be a carbon dioxide laser, an infrared laser, an ultraviolet laser, or any other laser light as long as it can cut the strip green sheet 20. In addition, in the description of this process, the strip green sheet 20 is cut using the cutting device 200 shown in FIG. 2C as an example to produce the single-leaf green sheets 30, but other methods may be used as long as they can produce the single-leaf green sheets 30 from the strip green sheet 20. For example, the single-leaf green sheets 30 may be produced by punching the strip green sheet 20 using a press processing device (not shown).

[0066] The above is the description of the cutting step S13 of the belt-shaped green sheet 20.

[0067] [Deposition process] Next, the stacking step S14 will be described. In this step, a plurality of single-layered green sheets 30 are stacked in the thickness direction as shown in Fig. 3A. This step is performed to efficiently sinter the single-layered green sheets 30 in the subsequent step (sintering step S2).

[0068] In this step, as shown in FIG. 3A, multiple single-leaf green sheets 30 are stacked with a non-reactive powder layer (not shown) interposed therebetween, which will be described later. If the number of stacked single-leaf green sheets 30 is small, the number that can be processed at one time in a sintering furnace (not shown) in the subsequent sintering step S2 will be reduced (production efficiency will be reduced). On the other hand, if the number of stacked single-leaf green sheets 30 is large, the binder contained in the single-leaf green sheets 30 will be difficult to decompose in the next step (debinding step S15). For the above reasons, the number of stacked single-leaf green sheets 30 in this step is 8 to 100, preferably 30 to 70.

[0069] In addition, the non-reactive powder layer in this embodiment is, for example, a boron nitride powder layer (BN powder layer) having a film thickness of approximately 1 μm to 20 μm. The BN powder layer has the function of easily separating the ceramic substrate 40 after the next step (sintering step S2). The BN powder layer is applied as a BN powder slurry to one side of each green sheet 30 by, for example, spraying, brush coating, roll coating, screen printing, or the like. The BN powder has a purity of 85% or more and preferably has an average particle size of 1 μm to 20 μm.

[0070] This concludes the description of the depositing step S14.

[0071] [Degreasing process] Next, the degreasing step S15 will be described. In this step, the binder and plasticizer contained in the single green sheet 30 are degreased before the next step (sintering step S2). In this step, for example, the plurality of green sheets 30 (see FIG. 3A) stacked in the stacking step S14 are held for 0.5 to 20 hours in a temperature environment of 450° C. to 750° C. As a result, the binder and plasticizer contained in the plurality of green sheets 30 are degreased.

[0072] The above is a description of the degreasing step S15. The above is a description of the green sheet forming step S1 of this embodiment.

[0073] <Sintering process> Next, the sintering step S2 will be described with reference to Figures 3A to 3R. In this step, a plurality of single green sheets 30 (hereinafter referred to as the plurality of single green sheets 30 in Figure 3A) that have been stacked in the stacking step S14 and from which the binder and plasticizer have been degreased in the degreasing step S15 are sintered using a sintering device (not shown).

[0074] The sintering apparatus includes a sintering furnace and a control device. The sintering furnace has a temperature adjustment mechanism, a firing chamber, and a thermometer that measures the temperature inside the firing chamber. The temperature adjustment mechanism has a heating section (e.g., a heater) that heats the firing chamber and a cooling section (e.g., a water cooling tube) that cools the firing chamber. In this process, with the plurality of single-sheet green sheets 30 shown in FIG. 3A placed inside the sintering chamber, the control device controls the temperature adjustment mechanism so that the temperature inside the firing chamber changes according to a temperature control program described below.

[0075] The temperature control program is stored in a storage device (e.g., ROM) of the control device. Using the temperature control program, the control device controls the temperature (e.g., PID control) using a temperature adjustment mechanism while referring to temperature information from a thermometer. Specifically, the temperature control program configures the temperature profile inside the firing chamber to consist of a temperature-rising region F1 having a cooling region, a temperature-holding region F2, and a cooling region F3, and the profile progresses in the listed order (see FIG. 3B). The technical significance of the temperature-rising region F1, temperature-holding region F2, and cooling region F3 will be explained below.

[0076] [Temperature rise range] The temperature-rising region F1 is a temperature region in which the sintering aid contained in each green sheet 30 reacts with the oxide layer on the surface of the silicon nitride particles to generate a liquid phase. In the temperature-rising region F1 of this embodiment, as shown in FIG. 3B, the temperature is preferably raised stepwise from room temperature to a temperature within the range of 1600°C to 2000°C (approximately 1800°C in this embodiment) over, for example, approximately 12 hours. In the temperature-rising region F1, the grain growth of α-silicon nitride is suppressed, and the silicon nitride particles are rearranged and densified in the liquid-phase sintering aid. As a result, after passing through the next temperature-holding region F2, a ceramic substrate 40 with small pore size and porosity, high bending strength, and high thermal conductivity is obtained.

[0077] [Temperature holding range] The temperature holding region F2 is a temperature region for promoting rearrangement of silicon nitride particles, generation of β-type silicon nitride crystals, and grain growth of the silicon nitride crystals from the liquid phase generated in the temperature rising region F1, thereby further densifying the ceramic substrate 40, which is a sintered body. The temperature in the temperature holding zone F2 is preferably set within a range of 1600°C to 2000°C, taking into consideration the size and aspect ratio (ratio of major axis to minor axis) of the β-type silicon nitride particles, the formation of voids due to volatilization of the sintering aid, and the like, and the holding time is preferably set within a range of 1 hour to 30 hours (approximately 8 hours in the present embodiment, for example). If the temperature in the temperature holding zone F2 is below 1600°C, the ceramic substrate 40 is difficult to densify. On the other hand, if the temperature in the temperature holding zone F2 exceeds 2000°C, the volatilization of the sintering aid and the decomposition of the silicon nitride become intense, making it difficult to densify the ceramic substrate 40. Note that, as long as the temperature in the temperature holding zone F2 is within a range of 1600°C to 2000°C, the temperature in the temperature holding zone F2 may be set to change over time (for example, to gradually increase). Here, the temperature in the temperature holding zone F2 is more preferably within the range of 1750°C to 1950°C, and even more preferably within the range of 1800°C to 1900°C. Furthermore, the temperature in the temperature holding zone F2 is preferably at least 50°C higher than the upper limit of the temperature in the cooling zone F1, and even more preferably at least 100°C to 300°C higher. The holding time in the temperature holding zone F2 is more preferably 2 hours to 20 hours, and even more preferably 3 hours to 10 hours.

[0078] [Cooling region (including quenching region)] The cooling region F3 is a temperature region for cooling and solidifying the liquid phase maintained in the temperature holding region F2, and fixing the position of the resulting grain boundary phase. Note that the cooling region F3 in this embodiment includes a quenching region F4, which will be described later.

[0079] The cooling rate in cooling region F3 is preferably 100°C / hour or more, more preferably 300°C / hour or more, and even more preferably 500°C / hour or more in order to rapidly solidify the liquid phase and maintain uniformity in the grain boundary phase distribution. A practical cooling rate is preferably 500°C to 600°C / hour. Cooling the liquid phase at such a cooling rate suppresses crystallization of the solidifying sintering aid, and a grain boundary phase mainly composed of a glass phase is formed. As a result, the bending strength of ceramic substrate 40 can be increased. As described above, the cooling region F3 is the temperature region following the temperature rise region F1 and the temperature holding region F2 in the temperature control program (see FIG. 3B). Therefore, the cooling region F3 in this embodiment can be said to be a temperature region in which the inside of the firing chamber is cooled after being heated by the temperature rise region F1 and the temperature holding region F2 until the temperature inside the firing chamber reaches at least 1600°C (see FIG. 3B).

[0080] Next, the quenching region F4 will be described with reference to FIG. 3B. The cooling region F3 of this embodiment has a temperature region where the cooling rate is further increased during its progress. In this embodiment, this "temperature region where the cooling rate is further increased" is referred to as the quenching region F4. As an example, the quenching region F4 of this embodiment is initiated when the temperature inside the firing chamber reaches any temperature below 650°C. Note that, in this embodiment, the time period during which the quenching region F4 is performed is, as an example, approximately half or less of the time period during which the cooling region F3 is performed. Note that the technical significance of setting the quenching region F4 in the cooling region F3 (see FIGS. 3C to 3R, etc.) will be described later. When this process is completed, a plurality of ceramic substrates 40 are manufactured in a stacked state (see FIG. 3A).

[0081] This concludes the description of the sintering step S2.

[0082] <Outer circumference cutting process> Next, the peripheral portion cutting step S3 will be described with reference to FIG. 4A. This step (cutting step) is a step of cutting the entire peripheral edge portion of the ceramic substrate 40 manufactured through the sintering step S2. Specifically, in this step, a laser processing machine (not shown) is used to cut a portion of the entire peripheral edge portion of the ceramic substrate 40 after the sintering step S2, which is, for example, a width of 3 mm or less. In this case, the laser light source of the laser processing machine intermittently irradiates laser light along the portion to be cut. As a result, a scribe line SL consisting of multiple linearly arranged depressions is formed at a position that will become the cut surface (edge ​​surface) of the ceramic substrate 40, at a predetermined interval p1 determined by the scanning speed and irradiation time of the laser light source. Then, for example, when the predetermined interval p1 is 90 μm or more and 110 μm or less, microcracks MC (an example of a crack) are formed from each depression throughout the entire area in the plate thickness direction at the edge (see FIG. 6B). FIG. 6C shows a partial perspective view (here, a perspective view of one corner of a rectangle) of the ceramic substrate 40 after cutting a predetermined width along the entire peripheral edge along the scribe lines SL. The thickness T1 of the ceramic substrate 40 is 320 μm. Multiple recesses are formed at the above-mentioned intervals p1 at the end (main surface end 40A3) of the front surface 40A1 of the ceramic substrate 40, corresponding to the scribe lines SL. Multiple microcracks MC are formed in the in-plane direction from the recesses at the main surface end 40A3, extending from one end (front surface 40A1) to the other end (rear surface 40A2) in the thickness direction. In this case, the length L11 of each microcrack MC (i.e., the length L11 of the microcracks MC appearing on the main surface (i.e., front surface 40A1) so as to extend in the in-plane direction from the main surface end 40A3) is, for example, 15 to 25 μm. Furthermore, the length L21 of the portion of the microcracks MC appearing at the end surface 40A4 is 250 to 320 μm. As described above, when this step is completed, the entire peripheral edge portion is cut off, and a ceramic substrate 40 is manufactured in which a plurality of microcracks MC are formed over the entire peripheral area of ​​the edge portion.

[0083] [Technical significance of setting the quenching region F4 in the cooling region F3] First, the technical significance of providing the quenching zone F4 in the cooling zone F3 will be explained with reference to FIGS. 3B and 3C. FIG. 3B is a graph showing the firing temperature profile (including conditions examined through testing) in the sintering step S2. As described above, in this embodiment, the quenching zone F4 is initiated when the temperature in the firing chamber reaches any temperature below 650°C, for example. As shown in the graph in FIG. 3B, the inventors conducted a test to measure the amount of warpage of the ceramic substrate 40 when the start temperature (quenching start temperature) of the quenching zone F4 was set to 1200°C, 1050°C, 800°C, 650°C, and 400°C. FIG. 3C is a graph showing the results, i.e., a relationship between the quenching start temperature in the sintering step S2 and the amount of warpage (the maximum high and low values ​​mentioned above). The graph in FIG. 3C indicates that the lower the quenching start temperature, the smaller the amount of warpage of the ceramic substrate 40 tends to be. For example, the amount of warpage is preferably a maximum of 6 μm or less. This is because the ceramic substrate 40 can be easily handled during the circuit pattern forming process (resist printing process S6 and etching process S7) or the electronic component mounting process S10. As can be seen from the graph in Fig. 3C, the higher the quenching start temperature, the greater the amount of warpage and the greater the variation in the amount of warpage. This means that the higher the quenching start temperature, the greater the impact of partial distortion of the ceramic substrate 40 due to quenching. 3C, when the quenching start temperature is 400°C and 650°C, even when variations in the amount of warpage are taken into consideration, the amount of warpage of the ceramic substrate 40 is less than the maximum allowable value (less than 4 μm in this case). Also, if the quenching start temperature is drastically lowered (for example, to 400°C or lower), the firing time will be extended, which will lead to a decrease in productivity. Therefore, in this embodiment, the appropriate range for the rapid cooling start temperature is set to 400°C to 650°C, taking into consideration the balance between the amount of warpage and shortening of the firing time. If shortening the firing time is not a consideration, the rapid cooling start temperature may be set to less than 400°C. The above is the technical significance of providing the rapid cooling region F4 in the cooling region F3.

[0084] [Technical significance of performing the outer peripheral partial cutting step S3] Next, the technical significance of performing the outer periphery partial cutting step S3 will be described with reference to FIG. 4B. The inventors of the present application conducted a test to measure the amount of warpage (the aforementioned maximum value) of ceramic substrate 40 when the cutting width of the peripheral portion was set to 0 mm (no cutting), 3 mm, 6 mm, and 9 mm, using a rapid cooling start temperature of 650°C as an example. FIG. 4B is a graph showing the results, i.e., the relationship between the cutting width of the peripheral portion and the amount of warpage in the peripheral portion cutting step S3. As can be seen from the graph in FIG. 4B, the larger the cutting width of the peripheral portion, the smaller the amount of warpage. It can also be seen that the larger the cutting width of the peripheral portion, the smaller the variation in the amount of warpage. This is because the ceramic substrate 40 is subjected to compressive or tensile stress due to cooling in the portions closer to the peripheral portion, and cutting these portions is thought to relieve these stresses. Considering the results of the graph in FIG. 4B, it is necessary to cut the peripheral portion. However, since the cut peripheral portion of the ceramic substrate 40 is discarded, i.e., the larger the cutting width, the greater the amount of waste. Therefore, a narrower cutting width of the peripheral portion is preferable. Therefore, in this embodiment, it is preferable that the cutting width of the outer peripheral portion is 3 mm or less. Furthermore, a plurality of microcracks MC are formed around the entire periphery of the end portion of the ceramic substrate 40 of this embodiment. The microcracks MC are arranged at a predetermined interval p1 in the circumferential direction of the end portion. Therefore, the microcracks MC facilitate the release of permanent strain remaining near the end portion. That is, in areas where tensile stress is applied, the microcracks MC deform to close, thereby releasing the tensile stress in those areas. In addition, in areas where compressive stress is applied, the microcracks MC deform to open, thereby releasing the compressive stress in those areas. From the above, it is believed that the microcracks MC formed around the end portion release permanent strain near the end portion of the ceramic substrate 40, thereby ultimately reducing the amount of warpage of the ceramic substrate 40. The above is the technical significance of performing the outer periphery partial cutting step S3.

[0085] This concludes the description of the peripheral portion cutting step S3, and also concludes the description of the method for manufacturing the ceramic substrate 40 of this embodiment.

[0086] <Scribe line formation process> Next, the SL forming step S4 will be described with reference to Fig. 5. In this step, a plurality of scribe lines SL (three in this embodiment, for example) are formed on one surface (front surface 40A1 in this embodiment, for example) of the ceramic substrate 40. When this step is completed, the ceramic substrate 40A with SLs is manufactured. In this process, a laser beam is irradiated from an irradiation unit (not shown) onto the surface 40A1 of the ceramic substrate 40, forming, for example, three straight line segments: one in the center in the width direction and two that divide the length direction into thirds, thereby dividing the entire area of ​​the surface 40A1 into six equal areas. Here, for example, each scribe line SL is composed of a plurality of recesses arranged in a straight line (see FIG. 6B). Therefore, the irradiation unit (for example, a carbon dioxide laser light source, a YAG laser light source, or the like) used in this process is capable of, for example, intermittently irradiating the laser beam. The scribe lines SL are used as cutting lines when dividing the ceramic substrate 40 into a plurality of pieces (six pieces in this embodiment) in a subsequent dividing step S9 (see FIG. 1).

[0087] This concludes the description of the SL forming step S4.

[0088] <Metal layer formation process> Next, the metal layer forming step S5 will be described with reference to FIGS. 6A and 6B. In this process, the first metal layer 50A and the second metal layer 50B are fixed to the front surface 40A1 and the back surface 40A2 of the ceramic substrate 40A with the SL, respectively. In this process, the first metal layer 50A and the second metal layer 50B are fixed to the front surface 40A1 and the back surface 40A2, respectively, via a brazing filler metal (not shown). Specifically, a brazing filler metal paste is uniformly applied to the front surface 40A1 and the back surface 40A2 of the ceramic substrate 40 by a roll coater method, a screen printing method, a transfer method, or the like. The first metal layer 50A and the second metal layer 50B are then bonded to the front surface 40A1 and the back surface 40A2 of the ceramic substrate 40, respectively, via the uniformly applied brazing filler metal paste. In this process, the screen printing method is preferred because it allows the brazing filler metal paste to be uniformly applied. In this case, the viscosity of the brazing filler metal paste is preferably controlled to 5 Pa·s to 20 Pa·s. An excellent paste-like brazing material can be obtained by blending the organic solvent content in the paste-like brazing material in the range of 5% by mass to 7% by mass and the binder content in the range of 2% by mass to 8% by mass. When this process is completed, the motherboard 60 is manufactured. 6B shows a state in which microcracks MC are formed from each of the plurality of recesses constituting the scribe line SL to the back surface 40A2, but the microcracks MC are formed during the dividing step S9 described below. The microcracks MC are also formed during the peripheral partial cutting step S3 described above.

[0089] This concludes the description of the metal layer forming step S5.

[0090] <Resist printing process> Next, the resist printing step S6 will be described with reference to FIG. 7. In this step, a photosensitive resist film PRF is coated on the first metal layer 50A of the motherboard 60, and resist patterns PRP corresponding to each circuit pattern CP described below are formed in six areas defined by three scribe lines SL in the first metal layer 50A. Specifically, in this step, the resist pattern PRP is printed on the resist film PRF using an exposure device (not shown), for example (the resist pattern PRP is hardened, and the portions of the resist film PRF other than the resist pattern PRP are left unhardened). As a result, a motherboard 60A with PRP is manufactured.

[0091] This concludes the description of the resist printing step S6.

[0092] <Etching process> Next, the etching step S7 (an example of a circuit pattern forming step) will be described with reference to FIG. 8. In this step, uncured resist film PRF in the resist film PRF of the PRP-equipped motherboard 60A is removed, the exposed portion of the first metal layer 50A is etched, and then the remaining resist pattern PRP is removed to form a circuit pattern CP. As a result, the PRP-equipped motherboard 60A before this step becomes an aggregate substrate 60B on which circuit patterns CP are formed in six areas defined by three scribe lines SL. Furthermore, once the aggregate substrate 60B is formed, all portions of the three scribe lines SL formed in the SL forming step S4 become exposed as a result of etching the first metal layer 50A. In addition, electronic components (not shown) such as ICs, capacitors, resistors, etc. are mounted on each circuit pattern CP formed in this process in a mounting process S10 described later. In addition, in the above explanation, the etching process S7 is an example of a circuit pattern forming process, but the combination of the resist printing process S6 and the etching process S7 may also be considered as an example of a circuit pattern forming process.

[0093] This concludes the description of the etching step S7.

[0094] <Surface treatment process> Next, the surface treatment step S8 will be described. In this step, the surface of the surface of the aggregate substrate 60B on which the plurality of (six in this embodiment) circuit patterns CP are formed is covered with a protective layer (not shown) such as solder resist, except for the bonding areas where the electronic components are bonded, and the surface treatment is performed on the areas other than the bonding areas. In this step, the bonding areas where the electronic components are bonded are plated, for example, by electrolytic plating, to perform surface treatment on the bonding areas. Here, in the above explanation, the product at the end of the etching step S7 is referred to as aggregate substrate 60B, but the product at the end of the surface treatment step S8, i.e., aggregate substrate 60B coated with a protective layer, may also be considered to be the aggregate substrate.

[0095] This concludes the description of the surface treatment step S8.

[0096] <Dividing process> Next, the dividing step S9 will be described with reference to Fig. 9. In this step, the aggregate substrate 60B (or the ceramic substrate 40A with SL) is cut along a plurality of scribe lines SL (three in this embodiment, as an example), and the aggregate substrate 60B is divided into a plurality of circuit substrates 60C (six in this embodiment, as an example).

[0097] When this step is completed, a plurality of circuit boards 60C are manufactured. In this embodiment, the first metal layer 50A becomes the circuit pattern CP of each circuit board 60C through the steps up to this point. In contrast, the area of ​​the second metal layer 50B defined by the three scribe lines SL becomes the metal layer on the side opposite to the side on which the circuit pattern CP is formed on each circuit board 60C through the steps up to this point. This metal layer then functions as a heat dissipation layer for dissipating heat generated by electronic components mounted on the circuit pattern CP when a mounting board (not shown) manufactured through a mounting step S10 (described later) is used. In this step, the aggregate substrate 60B is divided into a plurality of circuit substrates 60C along scribe lines SL, and thus a plurality of microcracks MC are formed at the edge of each of the circuit substrates 60B formed by the division, as in the peripheral partial cutting step S3. That is, when attention is focused on the ceramic substrate 40 of the circuit substrate 60B, a plurality of microcracks MC are formed in the manner shown in FIG. 6C. Therefore, when this step is completed, the amount of warping of each circuit substrate 60B after division is reduced compared to the amount of warping of each circuit substrate 60C in the aggregate substrate 60B (before division).

[0098] This concludes the description of the dividing step S9. In the above description of the manufacturing method of this embodiment, the metal layer forming step S5 is performed on the motherboard 60, and then the dividing step S9 is performed. However, for example, the dividing step S9 may be performed after the scribe line forming step S4, and then the metal layer forming step S5 to the surface treatment step S8 may be performed.

[0099] <Mounting process> Next, the mounting process S10 will be described. In this process, electronic components (not shown) are mounted on each circuit board 60C (see FIG. 9). In this process, a mounting device (not shown) is used to apply solder (not shown) to the joint portions of the circuit pattern CP (see FIG. 9) of each circuit board 60C where the electronic components are to be joined, thereby joining the joining terminals of the electronic components to the joint portions. In this case, since multiple microcracks MC are formed at the end portions of each circuit board 60C, deformation of each circuit board 60C due to heat generated during joining causes the microcracks MC to open and close. As a result, the opening and closing of the microcracks MC suppresses misalignment between the joint portions of the circuit pattern CP and the joining terminals of the electronic components during joining.

[0100] When this step is completed, a plurality of mounting substrates are manufactured. In the above description, this step is described as being performed after the dividing step S9, but the dividing step S9 may be performed after this step. That is, the manufacturing method S100 of this embodiment may be performed in the order of the surface treatment step S8, the mounting step S10, and the dividing step S9.

[0101] This concludes the description of the mounting step S10. After the manufacturing of the plurality of mounting boards, an inspection device (not shown) is used to inspect the circuit patterns CP, inspect the operation of the electronic components, and so on. This concludes the description of the manufacturing method S100 of this embodiment.

[0102] Effect of this embodiment Next, the effects of this embodiment will be described.

[0103] <First effect> The ceramic substrate 40 of this embodiment (see Figures 3A, 3D, 3G, 3J, 3M, 3P, etc.) is a ceramic substrate 40 that is rectangular in plan view, and the value obtained by dividing the maximum height difference in the thickness direction of the ceramic substrate 40 by the length of the diagonal of the ceramic substrate 40 is 1 μm / mm or less, and multiple microcracks MC are formed at the end portion thereof, extending in the in-plane direction from the main surface end portion 40A3 of the ceramic substrate 40 to one end in the thickness direction. As described above, the ceramic substrate 40 of this embodiment has the first metal layer 50A and the second metal layer 50B fixed to both sides thereof, respectively, and is processed into the circuit board 60C (see FIG. 9). Therefore, the ceramic substrate 40 of this embodiment is subjected to various thermal histories while the first metal layer 50A and the second metal layer 50B are fixed to both sides thereof (in the state of the motherboard 60). In other words, thermal distortion and thermal stress occur inside the motherboard 60. In particular, the thermal distortion and thermal stress may remain near the outer periphery of the motherboard 60. For the above reasons, strain energy is likely to remain near the outer periphery of the ceramic substrate 40 in the state of the motherboard 60. However, in the ceramic substrate 40 of this embodiment, a plurality of microcracks MC are formed at its end (outer peripheral surface) in the in-plane direction from the end 40A3 of the main surface of the ceramic substrate 40 to one end in the plate thickness direction (Z direction). Each microcrack MC functions to release, i.e., reduce, strain energy in the vicinity of the outer peripheral edge of the ceramic substrate 40. As described above, the ceramic substrate 40 of this embodiment includes various forms of unevenness (warpage) in the thickness direction, such as the first to fifth examples of the ceramic substrate 40 (see FIGS. 3A, 3D, 3G, 3J, 3M, 3P, etc.) and other examples. However, the ceramic substrate 40 of this embodiment has a maximum height of 1 μm or less in any case. Furthermore, at the end (outer peripheral surface) of the ceramic substrate 40 of this embodiment, multiple microcracks MC are formed extending in-plane from the end 40A3 of the main surface of the ceramic substrate 40 to the other end in the thickness direction (Z direction) (see FIGS. 6B and 6C). Therefore, it can be said that the ceramic substrate 40 of this embodiment can maintain a maximum height of 1 μm or less in any case due to the above function of the multiple microcracks MC. Therefore, by using the ceramic substrate 40 of this embodiment, it is possible to manufacture a highly reliable circuit board with excellent flatness and in which residual thermal distortion and residual thermal stress are significantly reduced.

[0104] <Second effect> Furthermore, in the ceramic substrate 40 of this embodiment, the plurality of microcracks MC are formed all around the edge of the ceramic substrate 40. Therefore, by using the ceramic substrate 40 of this embodiment, it is possible to manufacture a highly reliable circuit board with excellent flatness and in which residual thermal distortion and residual thermal stress are significantly reduced all around its periphery.

[0105] <Third Effect> In the ceramic substrate 40 of this embodiment, the microcracks MC are arranged in the circumferential direction of the end portion of the ceramic substrate 40 at a predetermined interval p1. Therefore, by using the ceramic substrate 40 of this embodiment, it is possible to manufacture a highly reliable circuit board with excellent flatness and with significantly reduced residual thermal distortion and residual thermal stress in a well-balanced manner over the entire periphery.

[0106] <Fourth Effect> Furthermore, in the ceramic substrate 40 of this embodiment, multiple microcracks MC are not simply arranged in the circumferential direction of the end of the ceramic substrate 40, but are arranged at intervals of 90 μm or more and 110 μm or less, and the length L11 of the multiple microcracks MC (i.e., the length L11 of the microcracks MC that appear to extend in the in-plane direction from the main surface end 40A3 of the surface 40A1, which is the main surface) is 15 μm or more and 25 μm or less. Therefore, when the ceramic substrate 40 of this embodiment is used, the third effect described above can be more significantly achieved.

[0107] <Fifth Effect> As shown in Figures 6A and 6B, the motherboard 60 of this embodiment comprises a ceramic substrate 40, a first metal layer 50A fixed to the front surface 40A1 side of the ceramic substrate 40, and a second metal layer 50B fixed to the back surface 40A2 side of the ceramic substrate 40. The ceramic substrate 40 included in the motherboard 60 of this embodiment provides the first to fourth effects described above. Therefore, by including the ceramic substrate 40 of this embodiment, the motherboard 60 of this embodiment has significantly reduced residual thermal distortion and residual thermal stress, and is excellent in flatness.

[0108] <Sixth Effect> As shown in FIG. 9, the circuit board 60C of this embodiment comprises a ceramic substrate 40, a circuit pattern CP formed on one surface side of the ceramic substrate 40 (in this embodiment, as an example, the front surface 40A1 side), and a metal layer (second metal layer 50) fixed to the other surface side of the ceramic substrate 40 (in this embodiment, as an example, the back surface 40A2 side). The ceramic substrate 40 included in the circuit board 60C of this embodiment provides the first to fourth effects described above. Therefore, by including the ceramic substrate 40 of this embodiment, the circuit board 60C of this embodiment has significantly reduced residual thermal distortion and residual thermal stress, and is excellent in flatness.

[0109] <Seventh Effect> In addition, the manufacturing method of the ceramic substrate 40 of this embodiment includes a cutting process in which a strip-shaped green sheet 20 containing ceramic powder is cut to obtain a single green sheet 30, a sintering process in which the single green sheet 20 is placed in a firing chamber, the firing chamber is heated until the temperature inside the firing chamber reaches at least 1600°C or higher, and then the firing chamber is cooled to sinter the single green sheet 30 to obtain a ceramic substrate 40, and a cutting process in which the entire peripheral portion of the cooled ceramic substrate 40 after the sintering process is cut. Therefore, in the cutting step, the portion of the ceramic substrate 40 near the outer periphery where a large amount of strain energy remains due to the influence of cooling is cut. As a result, the ceramic substrate 40, whose entire peripheral edge has been cut, is released from the compressive or tensile stress that was applied thereto due to the effect of cooling, that is, the stress on the outer peripheral edge in particular. As a result, according to the method for manufacturing ceramic substrate 40 of this embodiment, it is possible to manufacture ceramic substrate 40 with significantly reduced residual thermal distortion and residual thermal stress and excellent flatness (see FIG. 4B).

[0110] <Eighth Effect> In addition, in the cutting process of the manufacturing method of the ceramic substrate 40 of this embodiment, a laser light source is scanned around the entire circumferential direction of the entire peripheral edge portion of the ceramic substrate 40, and laser light is intermittently irradiated to form microcracks MC at the end portion created by cutting the ceramic substrate 40. Therefore, when the ceramic substrate 40 is cut along the scribe lines SL, a plurality of microcracks MC are formed at the end formed by the cut, extending in the in-plane direction from the end 40A3 of the main surface of the ceramic substrate 40 to one end in the plate thickness direction (Z direction) of the ceramic substrate 40. Therefore, as described above, the plurality of microcracks MC function to release, i.e., reduce, strain energy near the outer peripheral edge of the ceramic substrate 40. Therefore, according to the method for manufacturing the ceramic substrate 40 of this embodiment, it is possible to manufacture a ceramic substrate 40 that has excellent flatness and in which residual thermal distortion and residual thermal stress are significantly reduced.

[0111] <9th effect> Furthermore, in the manufacturing method of ceramic substrate 40 of this embodiment, in the sintering step, when the temperature inside the firing chamber reaches 650°C or lower during cooling inside the firing chamber, the temperature inside the firing chamber is rapidly cooled (see FIG. 3B). In the method for manufacturing the ceramic substrate 40 of this embodiment, the cooling zone F3 of the sintering step S2 is followed by a rapid cooling zone F4 (see FIG. 3B). The rapid cooling start temperature for the rapid cooling zone F4 is set to 650°C or lower, for example (see FIG. 3B). As a result, the method for manufacturing ceramic substrate 40 of this embodiment can manufacture ceramic substrate 40 with excellent flatness and significantly reduced residual thermal distortion and residual thermal stress by performing the cooling region F4 in the cooling region F3 of sintering process S2 while performing the peripheral partial cutting process S3 (see Figures 1, 4A, and 4B).

[0112] The above is a description of the effects of this embodiment. Also, the above is a description of this embodiment.

[0113] <<Variations>> Next, a modification of this embodiment will be described.

[0114] <First Modification> In the manufacturing method S100 of this embodiment, the SL forming step S4 is described as being performed (see FIG. 1). However, as in a first modified example shown in FIG. 10, the metal layer forming step S5 may be performed after the peripheral partial cutting step S3 without performing the SL forming step S4. In this modified example, if the mounting step S10 is performed after the surface treatment step S8 without performing the dividing step S9 (see FIG. 1), one mounting substrate is manufactured from one motherboard 60. The above is the description of the first modified example.

[0115] <Second Modification> In the description of this embodiment, first to fifth examples (see FIGS. 3D to 3R) are used as examples of the ceramic substrates 40. However, the ceramic substrate 40 may also be, for example, the ceramic substrate 40 of a second modified example shown in FIGS. 11A to 11C. Hereinafter, this modified example will be described with reference to FIGS. 11A to 11C, focusing only on the differences between this modified example and the above-described embodiment.

[0116] [Configuration, etc.] Fig. 11A is a plan view of ceramic substrate 40 of this modification, showing a height distribution diagram with a profile of the height (depression) in the thickness direction (Z direction). Fig. 11B is a cross-sectional view of ceramic substrate 40 of Fig. 11A, showing a longitudinal cross-section taken along X0-X0 line (X0-X0 cross-section), a longitudinal cross-section taken along X1-X1 line (X1-X1 cross-section), and a longitudinal cross-section taken along X2-X2 line (X2-X2 cross-section), all aligned along the X direction. Fig. 11C is a cross-sectional view of ceramic substrate 40 of Fig. 11A, showing a transverse cross-section taken along Y0-Y0 line, a transverse cross-section taken along Y1-Y1 line, and a transverse cross-section taken along Y2-Y2 line, all aligned along the Y direction.

[0117] The ceramic substrate 40 of this modified example has the following features.

[0118] In ceramic substrate 40 of this modification, when viewed in plan, an intersection O formed by a pair of diagonal lines (broken lines in FIG. 11A) is used as a reference in the thickness direction of ceramic substrate 40. Of the four regions divided by the pair of diagonal lines, one of a pair of first regions and a pair of second regions facing each other across the intersection O is located on one side of the intersection O in the thickness direction, and the other is located on the other side of the intersection O in the thickness direction. The maximum height difference is 1 μm / mm or less. Here, as shown in FIG. 11B , a cut surface (first cut surface) cut along a line L1 in the Y direction passing through the center O has an arc-shaped portion at the center O that is convex toward one side in the thickness direction. In other words, the first cut surface forms an arc-shaped surface that is convex toward one side in the thickness direction, with the position of the center O being an inflection point. In yet another way, the first cut surface forms an arc-shaped surface that is convex toward one side in the thickness direction, with the position of the center O being the furthest one of the positions on one side in the thickness direction. In this case, the convex amount of the convex portion at the center O (the amount of the convex or concave portion compared to the flat case ((reference in the figure))) is defined as ΔZ1. Then, from the center O to the end in the width direction, the convex amount decreases to ΔZ2 (<ΔZ1) and ΔZ3 (<ΔZ2). Here, the convex amount ΔZ1 is, for example, 252 μm or less. As shown in FIG. 11C , the cut surface (second cut surface) cut along a straight line L2 in the X direction passing through the center O has an arc-shaped surface at the center O that is convex toward the other side in the thickness direction. In other words, the second cut surface forms an arc-shaped surface that is convex toward the other side in the thickness direction, with the center O serving as an inflection point. In yet another way, the second cut surface forms an arc-shaped surface that is convex toward the other side in the thickness direction, with the center O serving as the furthest position on the other side in the thickness direction. The convexity of the convex portion at the center O in this case (the amount of convexity or concavity compared to a flat surface) is defined as ΔZ1. The convexity increases from the center O to the end in the width direction, with ΔZ2 (>ΔZ1) and ΔZ3 (>ΔZ2). Here, the convexity ΔZ1 is, for example, 252 μm or less. The ceramic substrate 40 of this modified example is warped in a line-symmetrical manner with respect to the line L1 and a line L2 (described later). That is, the ceramic substrate 40 of this modified example has a three-dimensional shape that is line-symmetrical with respect to the line L1 and the line L2. As described above, in ceramic substrate 40 of this modified example, the maximum protrusion amount is 252 μm or less, and the length of the diagonal line is approximately 252.5 mm, so the maximum height difference is 1 μm / mm or less.

[0119] Furthermore, in ceramic substrate 40 of this modification, a first cut surface obtained by cutting ceramic substrate 40 along a first straight line (an example of a first straight line) that passes through center O and is parallel to any one of the four sides in a plan view of ceramic substrate 40 has a central portion in the length direction (Y direction) that is convexly curved toward one side in the plate thickness direction (see FIG. 11B).A second cut surface obtained by cutting ceramic substrate 40 along a straight line L2 (an example of a second straight line) that passes through center O and is perpendicular to line L1 has a central portion in the length direction that is convexly curved toward the other side in the plate thickness direction (see FIG. 11C), and the maximum height difference is 1 μm / mm or less.

[0120] Furthermore, in the ceramic substrate 40 of this modified example, first parallel cross sections (X1-X1 cross section and X2-X2 cross section in FIG. 11B) parallel to the first cross section (X0-X0 cross section) at each position from the center O to both ends of the ceramic substrate 40 in the direction along the straight line L1 (Y direction) have central portions in the longitudinal direction that are convexly curved toward one side in the plate thickness direction, and the curvature of the first parallel cross sections at each position continuously increases from the center O to both ends of the ceramic substrate 40 in the direction along the straight line L1 (X direction) (see FIG. 11B).

[0121] Furthermore, in the ceramic substrate 40 of this modified example, second parallel cut surfaces (X1-X1 cross section and X2-X2 cross section in FIG. 11C ) parallel to the second cut surface at each position from the center O to both ends of the ceramic substrate 40 in the direction along the straight line L2 (X direction) have central portions in the longitudinal direction that are convexly curved toward the other side in the plate thickness direction, and the curvature of the second parallel cut surfaces at each position continuously decreases from the center O to both ends of the ceramic substrate 40 in the direction along the straight line L1 (Y direction) (see FIG. 11C ).

[0122] The above is a description of the characteristics of the ceramic substrate 40 of this modified example. By having these characteristics, the ceramic substrate 40 of this modified example forms a substrate with a so-called saddle shape, with the center O being a saddle point.

[0123] 〔effect〕 Next, the effects of this modification will be described.

[0124] Other effects of the ceramic substrate 40 of this modified example are similar to those of the ceramic substrate 40 of the above-described embodiment.

[0125] The above is a description of the effects of this modification. Also, the above is a description of this modification. As described above, one example of the present invention has been described with reference to the above-described embodiment (see FIGS. 1 to 9), but the present invention is not limited to the above-described embodiment. The technical scope of the present invention also includes, for example, the following embodiments (modifications).

[0126] For example, in the description of the present embodiment, silicon nitride is used as an example of the ceramic powder, but the ceramic powder may be other ceramic powders, such as aluminum nitride powder.

[0127] In addition, in the description of the molding step S12 (see FIG. 2A) included in the green sheet forming step S1 of this embodiment, it is performed using doctor blade molding. However, the molding step S12 may be performed by other methods as long as the slurry 10 can be molded into the strip-shaped green sheet 20. For example, the molding step S12 may be performed by extrusion molding.

[0128] Furthermore, in the description of the cutting step S13 (see FIG. 2A ) included in the green sheet forming step S1 of this embodiment, the strip green sheet 20 is cut while the irradiation unit 224 is moved from one end side to the other end side in the widthwise direction of the strip green sheet 20. However, as long as the strip green sheet 20 can be cut to obtain a single green sheet 30 as a result, the cut portion of the strip green sheet 20 does not have to be a straight portion extending from one end side to the other end side in the widthwise direction of the strip green sheet 20 as in this embodiment. For example, the strip green sheet 20 may be cut so as to separate (or hollow out) the single green sheet 30 from the strip green sheet 20 by opening a hole in the strip green sheet 20 in the shape of the single green sheet 30. In other words, it is sufficient that at least a portion of all edge surfaces of the single green sheet 30 obtained by cutting the strip green sheet 20 are cut surfaces.

[0129] In addition, in the present embodiment, the circuit pattern CP is described as being formed on the first metal layer 50A. However, the circuit pattern CP may be formed on the second metal layer 50B without being formed on the first metal layer 50A. That is, in the pattern forming process (resist printing process S6 and etching process S7), at least one circuit pattern CP may be formed on either the first metal layer 50A or the second metal layer 50B.

[0130] In this embodiment, the scribe lines SL have been described as being multiple recesses arranged in a straight line (see FIG. 6B). However, as long as they can fulfill their function, the scribe lines SL may be, for example, continuous grooves or multiple recesses with different lengths, widths, etc.

[0131] In addition, in this embodiment, the multiple scribe lines SL have been described as being three scribe lines SL (see FIG. 5). However, the multiple scribe lines SL may be at least one.

[0132] In addition, in this embodiment, the scribe lines SL are described as dividing the motherboard 60 into six equal parts (see FIG. 5). However, the scribe lines SL do not necessarily have to divide the motherboard 60 into six equal parts.

[0133] This application claims priority based on Japanese Patent Application No. 2019-206752, filed November 15, 2019, the disclosure of which is incorporated herein by reference in its entirety. [Explanation of symbols]

[0134] 10 Slurry 20 Strip-shaped green sheet 30 green sheets 40 Ceramic substrate 40 Ceramic substrate 40A SL with ceramic substrate 40A1 surface 40A2 back 40A3 Main surface edge 40A4 end face 50A 1st metal layer 50B 2nd metal layer 60 Motherboard (an example of a composite board) Motherboard with 60A PRP 60B collective board 60C circuit board 100 Doctor blade molding device 110 Belt conveying mechanism 112 Laura 112A Roller 112B Laura 114 Belt 120 molding unit 122 Storage unit 124 Doctor Blade 130 Heating Unit 200 Cutting equipment 210 Sheet transport mechanism 212 Support part 214 First conveying section 216 Second conveying section 220 Cutting section 222 Case 224 Irradiation unit 226 Moving mechanism CX1 convex part CX2 convex part CX3 convex part CX4 convex part CP circuit pattern F1 temperature rise range F1 slow heat range F2 temperature holding range F3 cooling area F4 Quenching region L1 straight line (first straight line) L2 straight line (second straight line) LB laser light MC Microcrack O intersection, center PRF resist film PRP resist pattern S1 Green sheet forming process S10 Mounting process S11 Slurry preparation process S12 Molding process S13 Cutting process S14 Deposition process S15 Degreasing process S2 Sintering process S3 Outer circumference cutting process S4 SL formation process (scribe line formation process) S5 Metal layer formation process S6 Resist printing process S7 Etching process S8 Surface treatment process S9 splitting process S100 Manufacturing method for multiple mounting boards SL Scribe Line WC hot air ΔZ1 convex amount ΔZ2 convex amount ΔZ3 convex amount ΔZ4 convexity

Claims

1. A ceramic substrate having a rectangular shape in a plan view, a value obtained by dividing a maximum height difference in a thickness direction of the ceramic substrate by a diagonal length of the ceramic substrate is 1 μm / mm or less; At the end portion, a plurality of cracks are formed in the in-plane direction, extending from one end to the other end in the plate thickness direction, with each of the plurality of recesses provided at the end portion of the main surface of the ceramic substrate as a base point, When the length of the crack appearing on the end surface is L21 and the plate thickness is T1, the ratio L21 / T1 is 0.78 or more and 1.0 or less, Ceramic substrate.

2. The plurality of cracks are formed around the entire periphery of the end portion. The ceramic substrate according to claim 1 .

3. including silicon nitride or aluminum nitride, The ceramic substrate according to claim 1 or 2.

4. 4. The ceramic substrate according to claim 1, wherein the distance between adjacent recesses is 90 μm or more and 110 μm or less.

5. 5. The ceramic substrate according to claim 1, wherein the length of the crack appearing on the end surface is 250 μm or more and 320 μm or less.

6. 6. The ceramic substrate according to claim 1, wherein the crack also extends to the main surface, and the length of the extending portion is 15 μm or more and 25 μm or less.

7. The ceramic substrate according to any one of claims 1 to 6, a first metal layer fixed to the front surface side of the ceramic substrate; a second metal layer fixed to a back surface side of the ceramic substrate; A composite substrate comprising:

8. The ceramic substrate according to any one of claims 1 to 6, a circuit pattern formed on the front surface side of the ceramic substrate; a metal layer fixed to a back surface side of the ceramic substrate; A circuit board comprising:

9. A method for manufacturing a ceramic substrate according to any one of claims 1 to 6, a cutting step of the belt-shaped green sheet by cutting the belt-shaped green sheet containing the ceramic powder to obtain a single green sheet; a sintering step of placing the single-sheet green sheet in a firing chamber, heating the inside of the firing chamber until the temperature inside the firing chamber reaches at least 1600°C or higher, and then cooling the inside of the firing chamber to sinter the single-sheet green sheet to obtain the ceramic substrate; a cutting step of cutting the entire peripheral edge portion of the ceramic substrate cooled after the sintering step; Including, In the cutting step, a laser light source is scanned around the entire circumferential direction of the entire peripheral edge portion of the ceramic substrate, and laser light is intermittently irradiated to form a plurality of depressions, and the ceramic substrate is cut along a scrub line formed by the plurality of depressions. At the cut end, a crack is formed in the in-plane direction, starting from the depression and extending from one end to the other end in the plate thickness direction, and when the length of the crack appearing on the end surface is L21 and the plate thickness is T1, the ratio L21 / T1 is 0.78 or more and 1.0 or less.

10. In the sintering step, when the temperature inside the firing chamber becomes 650°C or lower during cooling inside the firing chamber, the temperature inside the firing chamber is rapidly cooled. The method for manufacturing a ceramic substrate according to claim 9 .

11. The ceramic powder includes silicon nitride powder or aluminum nitride powder. The method for manufacturing a ceramic substrate according to claim 9 or 10.

12. A method for producing a ceramic substrate according to any one of claims 9 to 11; a fixing step of fixing a first metal layer to the front surface side of the ceramic substrate and a second metal layer to the back surface side of the ceramic substrate; Including, A method for manufacturing a composite substrate.

13. The method for manufacturing a composite substrate according to claim 12; a pattern forming step of forming at least one circuit pattern on either the first metal layer or the second metal layer; Including, A method for manufacturing a circuit board.

14. The method for manufacturing a composite substrate according to claim 12; a pattern forming step of forming a plurality of circuit patterns on either the first metal layer or the second metal layer; a dividing step of dividing the composite substrate on which the plurality of circuit patterns are formed into a plurality of circuit substrates, each of which has one of the circuit patterns; Including, A method for manufacturing a plurality of circuit boards.

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