Ceramic substrate and manufacturing method for the same, ceramic plate, integrated circuit board, and circuit board

Abstract

To provide a ceramic substrate that can be split smoothly while reducing the damage when a scribe line is provided, and a manufacturing method for the ceramic substrate.SOLUTION: A ceramic substrate includes a scribe line formed of a groove on a main surface, in which the difference between the deepest part of the groove and the shallowest part of the groove is 50 μm or less. A manufacturing method for the ceramic substrate includes a step of forming the scribe line by irradiating a main surface of a ceramic sintered body with high-frequency laser light, in which the frequency of the high-frequency laser light is more than 500 kHz.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a ceramic substrate and a manufacturing method thereof, a ceramic plate, an aggregate circuit board, and a circuit board. [Background technology]

[0002] Insulating ceramic plates are sometimes used for circuit boards mounted on electronic devices. A known method for manufacturing such circuit boards is the technology described in Patent Document 1. The technology described in Patent Document 1 involves forming scribe lines on the surface of a ceramic plate using a carbon dioxide laser, a YAG laser, or the like, and then bonding a metal layer to the surface to form a composite substrate. The metal layer on the surface of the composite substrate is then etched into a circuit pattern. The composite substrate is then divided along the scribe lines to produce multiple circuit boards.

[0003] Patent Document 2 discloses a ceramic plate having scribe lines, which has bending strength along the scribe lines within an appropriate range, thereby stabilizing the quality of circuit boards and improving yield. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-324301 [Patent Document 2] Patent No. 7165842 Summary of the Invention [Problem to be solved by the invention]

[0005] By providing scribe lines on a ceramic substrate, the bending strength required to separate the ceramic substrate can be reduced, making it easier to separate the ceramic substrate. The cut surfaces formed when the scribe lines were formed are exposed on the side surfaces of the ceramic substrate separated along the scribe lines. If significant damage occurs when forming the scribe lines, the cut surfaces may degrade the appearance, strength, and other qualities of the ceramic substrate. Therefore, the present disclosure provides a ceramic substrate that reduces damage when forming scribe lines and can be smoothly separated, and a method for manufacturing the same. Furthermore, the present disclosure provides a ceramic substrate with excellent appearance. The present disclosure also provides an aggregate circuit board including such a ceramic substrate, and a circuit board including a ceramic plate. [Means for solving the problem]

[0006] One aspect of the present disclosure provides the following ceramic substrate.

[0007] [1] A ceramic substrate having a scribe line formed by a groove on a main surface, A ceramic substrate, wherein the difference between the deepest and shallowest parts of the groove is 50 μm or less.

[0008] The ceramic substrate of [1] above has scribe lines formed by grooves on its main surface, with the difference between the deepest and shallowest parts of the groove being 50 μm or less. A ceramic substrate having such scribe lines reduces damage associated with the formation of the scribe lines. Furthermore, the bending strength required when dividing along the scribe lines can be reduced. This allows the ceramic substrate to be divided smoothly. Furthermore, the quality of the ceramic substrate obtained by dividing, such as its appearance and strength, can be improved.

[0009] The ceramic substrate of the above [1] may be the following [2] or [3].

[0010] [2] The ceramic substrate according to [1], wherein the width of the groove is less than 10 μm.

[0011] The ceramic substrate of [2] above has a scribe line groove width of less than 10 μm. Such a ceramic substrate can further reduce damage caused by providing the scribe line and can further reduce the bending strength required when dividing along the scribe line.

[0012] [3] The ceramic substrate according to [1] or [2], wherein the depth of the deepest part of the groove, based on the main surface, is 60 to 100 μm.

[0013] In the ceramic substrate [3] above, the depth of the deepest part of the groove relative to the main surface is 60 to 100 μm. Such a ceramic substrate can further reduce damage caused by providing scribe lines and can further reduce the bending strength required when dividing along the scribe lines.

[0014] One aspect of the present disclosure provides the following ceramic plate.

[0015] [4] A ceramic plate having a cut surface and a fracture surface on the side surface, A ceramic plate in which the cut surface and the fracture surface are arranged in this order along the thickness direction from the first main surface to the second main surface, and the difference between the maximum and minimum lengths of the cut surface along the thickness direction is 50 μm or less.

[0016] The ceramic plate of [4] above has a cut surface and a fracture surface on its side, and the difference between the maximum and minimum lengths of the cut surface is 50 μm or less. Such a ceramic plate has excellent appearance because the variation in thickness of the cut surface is reduced.

[0017] The ceramic plate of the above [4] may be the following [5] or [6].

[0018] [5] The ceramic plate according to [4], wherein the maximum length of the cut surface along the thickness direction is 60 to 100 μm.

[0019] In the ceramic plate of [5] above, the maximum length of the cut surface along the thickness direction is 60 to 100 μm. Such a ceramic plate has an even more excellent appearance.

[0020] [6] The ceramic plate according to [4] or [5], which is obtained by dividing a ceramic substrate having scribe lines formed by grooves on its main surface, the difference between the deepest and shallowest parts of the grooves being 50 μm or less, along the scribe lines.

[0021] The ceramic plate [6] above is a ceramic substrate having scribe lines formed by grooves on its main surface, and is obtained by dividing a ceramic substrate along the scribe lines, the difference between the deepest and shallowest parts of the grooves being 50 μm or less. Such a ceramic plate further reduces damage caused by providing the scribe lines and further reduces the bending strength required when dividing along the scribe lines, resulting in a ceramic plate with a more excellent appearance and further improved qualities such as strength.

[0022] One aspect of the present disclosure provides the following method for manufacturing a ceramic substrate.

[0023] [7] A step of irradiating a main surface of the ceramic sintered body with a high-frequency laser beam to form a scribe line, The method for manufacturing a ceramic substrate, wherein the frequency of the high-frequency laser light is greater than 500 kHz.

[0024] The method for manufacturing a ceramic substrate according to [7] above includes a step of irradiating a main surface of a ceramic sintered body with high-frequency laser light having a frequency greater than 500 kHz to form scribe lines. By irradiating a high-frequency laser light having a frequency greater than 500 kHz, damage to the ceramic sintered body associated with forming the scribe lines can be reduced. Furthermore, a ceramic substrate can be obtained in which the bending strength required when dividing along the scribe lines is reduced. Furthermore, by reducing damage associated with forming the scribe lines, the quality of the ceramic substrate obtained by dividing along the scribe lines, such as the appearance and strength, can be improved.

[0025] The method for manufacturing a ceramic substrate according to the above [7] may be the following [8].

[0026] [8] The method for producing a ceramic substrate according to [7], wherein the high-frequency laser beam is an ultrashort pulse laser beam.

[0027] In the method for manufacturing a ceramic substrate described above in [8], the high-frequency laser beam is an ultrashort pulse (USP) laser beam. By using a USP laser beam, a ceramic substrate can be obtained in which the bending strength required when dividing along the scribe lines is further reduced. Furthermore, damage to the ceramic sintered body caused by forming the scribe lines can be further reduced, thereby further improving the quality of the ceramic substrate obtained by dividing along the scribe lines, such as the appearance and strength.

[0028] One aspect of the present disclosure provides the following aggregate circuit board and circuit board.

[0029] [9] The ceramic substrate according to any one of [1] to [3] above, and a metal plate bonded to the ceramic substrate.

[10] The ceramic plate according to any one of [4] to [6] above, a metal plate bonded to the ceramic plate.

[0030] The aggregate circuit board of [9] above includes the ceramic substrate of any one of [1] to [3]. Such an aggregate circuit board can be separated smoothly with little force. Furthermore, the quality of the appearance, strength, etc. can be improved.

[0031] The circuit board of the above item

[10] includes the ceramic plate according to any one of items [4] to [6]. Such a circuit board has excellent appearance. [Effects of the Invention]

[0032] The present disclosure provides a ceramic substrate that can be smoothly separated while reducing damage caused when forming scribe lines, and a method for manufacturing the same. Furthermore, it also provides a ceramic plate with excellent appearance. It also provides an aggregate circuit board including such a ceramic substrate, and a circuit board including a ceramic plate. [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 is a perspective view showing an example of a ceramic substrate. [Figure 2] FIG. 2 is a diagram showing an example of a scribe line on a ceramic substrate. [Figure 3] Fig. 3(a) is a diagram showing another example of a scribe line on a ceramic substrate, and Fig. 3(b) is a cross-sectional view taken along line IIIb-IIIb in Fig. 3(a). [Figure 4] Fig. 4(a) is a diagram showing yet another example of a scribe line on a ceramic substrate, and Fig. 4(b) is a cross-sectional view taken along line IVb-IVb in Fig. 4(a). [Figure 5] FIG. 5 is a perspective view showing an example of a ceramic plate. [Figure 6] FIG. 6 is a diagram showing an example of the side surface of a ceramic plate. [Figure 7] FIG. 7 is a perspective view showing an example of an aggregate circuit board. [Figure 8] FIG. 8 is a perspective view showing an example of a composite substrate. [Figure 9] FIG. 9 is a perspective view showing an example of a circuit board. [Figure 10] FIG. 10 is a photograph (magnification: 200 times) of the main surface of the ceramic substrate of Example 1 observed with a microscope. [Figure 11] FIG. 11 is a photograph (magnification: 200 times) of the side surface of each ceramic plate obtained by dividing the ceramic substrate of Example 1 along the scribe lines, observed with a microscope. [Figure 12] FIG. 12 is a photograph (magnification: 200 times) of the main surface of the ceramic substrate of Example 2 observed with a microscope. [Figure 13] FIG. 13 is a photograph (magnification: 200 times) of the side surface of each ceramic plate obtained by dividing the ceramic substrate of Example 2 along the scribe lines, observed with a microscope. [Figure 14] FIG. 14 is a photograph (magnification: 200 times) of the main surface of the ceramic substrate of Comparative Example 1 observed with a microscope. [Figure 15] FIG. 15 is a photograph (magnification: 200 times) of the side surfaces of the ceramic plates obtained by dividing the ceramic substrate of Comparative Example 1 along the scribe lines, observed with a microscope. DETAILED DESCRIPTION OF THE INVENTION

[0034] Hereinafter, embodiments of the present disclosure will be described. However, the following embodiments are merely examples for explaining the present disclosure and are not intended to limit the present disclosure to the following content. The upper or lower limit of a numerical range specified in this disclosure may be replaced with any value shown in the examples. Furthermore, the upper and lower limits individually stated may be arbitrarily combined. The symbol "~" used in a numerical range indicates a numerical range that includes the upper and lower limit. For example, "X~Y" indicates a numerical range of "greater than or equal to X and less than or equal to Y." Unless otherwise specified, the materials or components exemplified in this disclosure can be used alone or in combination of two or more.

[0035] [Ceramic substrate] FIG. 1 is a perspective view showing an example of a ceramic substrate according to one embodiment. The ceramic substrate 100 shown in FIG. 1 is, for example, a silicon nitride plate or an aluminum nitride plate. The ceramic substrate 100 has a flat plate shape. The ceramic substrate 100 has a first main surface 100A and a second main surface 100B on the opposite side. The first main surface 100A is divided into multiple sections by scribe lines. In the example shown in FIG. 1, a scribe line L1 and a scribe line L2 are provided on the first main surface 100A.

[0036] The ceramic substrate 100 is divided into a plurality of (nine in FIG. 1 ) partitions 10 by a plurality of scribe lines L1 and a plurality of scribe lines L2. That is, the ceramic substrate 100 has a plurality of partitions 10 defined by the scribe lines L1 and L2. Each of the plurality of partitions 10 is composed of an area on the first main surface 100A surrounded by the scribe lines L1 and L2 and a three-dimensional area surrounded by the side surface 100C. In FIG. 1 , portions of the scribe lines L1 and L2 are also depicted on the side surface 100C.

[0037] 1, the scribe lines L1 and L2 are formed on the first main surface 100A and not on the second main surface 100B, but the location of the scribe lines is not limited thereto. At least one of the scribe lines L1 and L2 may be formed on the first main surface 100A, or on both the first main surface 100A and the second main surface 100B.

[0038] The thickness of the ceramic substrate 100 may be, for example, 0.2 to 2.0 mm, or 0.3 to 1.5 mm. When the thickness is in this range, the ceramic substrate 100 can be suitably used as a material for an aggregate circuit board.

[0039] Fig. 2 shows an example of a scribe line on a ceramic substrate. Fig. 2 shows an enlarged example of a scribe line L1 provided on a portion of the first main surface 100A of the ceramic substrate 100. The scribe line L1 is made up of a groove 20 extending along its longitudinal direction (direction D1). Similarly, the scribe line L2 is made up of a groove 20 extending along its longitudinal direction (direction D2).

[0040] FIG. 3(a) shows another example of a scribe line on a ceramic substrate. FIG. 3(b) shows a cross-sectional view taken along line IIIb-IIIb in FIG. 3(a). That is, FIG. 3(b) is a cross-sectional view of the ceramic substrate 100 cut along a plane passing through the center of the scribe line L1 and perpendicular to the first main surface 100A in the thickness direction. In FIG. 3(b), the difference Δd1 between the deepest portion d1 and the shallowest portion d2 of the groove 20 forming the scribe line L1 (L2) is 50 μm or less. By setting Δd1 within this range, the bending strength required for dividing along the scribe line can be reduced. Furthermore, damage to the ceramic substrate obtained by division can be reduced, thereby improving the quality, such as the appearance and strength, of the ceramic substrate obtained by division. This allows the ceramic substrate 100 to be divided smoothly with less force. Δd1 may be 40 μm or less, 30 μm or less, or 25 μm or less. By setting Δd1 in this range, the bending strength required when dividing along the scribe lines can be further reduced.

[0041] Δd1 may be 1 μm or more, 5 μm or more, or 10 μm or more. When Δd1 is in this range, the groove 20 can be easily formed. The difference Δd1 between d1 and d2 may be, for example, 1 to 50 μm.

[0042] The depth d1 of the deepest portion of the groove 20, based on the first main surface 100A, may be 60 to 100 μm, 65 to 90 μm, or 68 to 85 μm. By keeping d1 within the above range, the bending strength required when dividing along the scribe lines L1 (L2) can be further reduced. This allows the ceramic substrate 100 to be divided more smoothly.

[0043] The depth d2 of the shallowest portion of the groove 20 relative to the first main surface 100A may be 20 to 70 μm, 30 to 60 μm, or 40 to 55 μm. By keeping d2 within the above range, the bending strength required when dividing along the scribe lines L1 (L2) can be further reduced. This allows the ceramic substrate 100 to be divided more smoothly.

[0044] The d1, d2, and Δd1 of the ceramic substrate 100 can be determined by image analysis of an image of a cross section of the ceramic substrate 100 captured with a microscope, as shown in Fig. 3(b). In the present disclosure, the microscope that can be used is, for example, "Dino-Lite" (trade name, manufactured by OPTO SCIENCE).

[0045] The grooves 20 can be formed by providing multiple holes 22 along the longitudinal direction D1 of the first main surface 100A of the ceramic substrate 100 so that adjacent holes 22 are connected to each other. When the arrangement pitch p, which is the distance between the centers of adjacent holes 22, is so small that it cannot be measured, the outer edge 20E of the groove 20 is approximately linear, as shown in FIG. 2. On the other hand, as the arrangement pitch p increases, it can be confirmed that the outer edge 22E becomes arc-shaped, as shown in FIGS. 3(a) and 4(a). Such grooves 20 can be formed using high-frequency laser light. The width W of the groove 20 may be less than 10 μm, 8 μm or less, or 5 μm or less. By keeping the width W within this range, the bending strength required for dividing along the scribe lines can be further reduced. This allows the ceramic substrate to be divided more smoothly. The width W of the groove 20 may be 1 μm or more. The width W can be adjusted by adjusting the hole diameter of the area irradiated with high-frequency laser light. Even when the outer edge 22E is arc-shaped as shown in FIGS. 3 and 4, the hole diameter of the part to be irradiated with high-frequency laser light is defined as the width W.

[0046] FIG. 4(a) is a diagram showing yet another example of a scribe line on a ceramic substrate. FIG. 4(b) is a cross-sectional view taken along line IVb-IVb in FIG. 4(a). That is, FIG. 4(b) is a cross-sectional view taken along the thickness direction of the ceramic substrate 100, cut along a plane that passes through the center of the scribe line L1 and is perpendicular to the first main surface 100A. FIGS. 4(a) and 4(b) show a case where the arrangement pitch p is larger than that shown in FIGS. 3(a) and 3(b). Increasing the arrangement pitch p, which is the distance between the centers of adjacent holes 22, increases the distance between the deepest portions d1 of the grooves 20, thereby increasing Δd1. Reducing the arrangement pitch p allows Δd1 to be reduced.

[0047] The arrangement pitch p can be determined by image analysis of a microscope image of the first main surface 100A. The arrangement pitch p may be 50 μm or less, 30 μm or less, or 10 μm or less. The arrangement pitch p may be so small that it cannot be measured by image analysis. In this case, it can be determined by calculation using the following formula (1). When the arrangement pitch p is calculated using the following formula (1), the arrangement pitch p may be 0.01 μm or more, 0.03 μm or more, or 0.05 μm or more. By setting the arrangement pitch p within the above range, the bending strength required when dividing along the scribe lines can be further reduced. Furthermore, damage to the ceramic substrate obtained by division can be further reduced, and the quality of the ceramic substrate obtained by division, such as its appearance and strength, can be further improved. p = scanning speed (mm / s) ÷ frequency (Hz) (1)

[0048] The bending strength of the ceramic substrate 100 at the position where the scribe line L1 (L2) is provided may be 300 MPa or less, 290 MPa or less, or 280 MPa or less. When the bending strength is in this range, the ceramic substrate 100 can be divided smoothly. Furthermore, damage after division can be reduced, and the quality of the ceramic substrate obtained after division, such as the appearance and strength, can be improved. The bending strength may be 240 MPa or more, 250 MPa or more, or 260 MPa or more. When the bending strength is in this range, the strength of the ceramic substrate 100 can be maintained.

[0049] The bending strength of the ceramic substrate 100 can be measured by a three-point bending strength test specified in JIS R 1601-2008. Specifically, the sample is placed with the first main surface 100A, on which the scribe line L1 (L2) of the ceramic substrate 100 to be evaluated, facing downward, so that the scribe line is located at the midpoint of a pair of supports. Then, a load is applied to a position on the second main surface 100B corresponding to the scribe line L1 (L2) (the back side of the scribe line), and the bending strength is measured. In this manner, the bending strength required to separate the ceramic substrate 100 can be measured.

[0050] [Ceramic plate] 5 is a perspective view showing an example of a ceramic plate according to one embodiment. The ceramic plate 50 has a first main surface 50A and a second main surface 50B opposite thereto. The ceramic plate 50 also has a side surface 50C.

[0051] The thickness of the ceramic plate 50 from the first main surface 50A to the second main surface 50B may be, for example, 0.2 to 2.0 mm, or 0.3 to 1.5 mm. With a thickness in this range, the ceramic plate 50 can be suitably used as a material for circuit boards.

[0052] FIG. 6 is a diagram showing an example of a side surface of a ceramic plate 50. The side surface 50C of the ceramic plate 50 includes a cut surface 52 and a fracture surface 54 in this order along the thickness direction from the first main surface 50A to the second main surface 50B. The difference Δd3 between the maximum length d3 and the minimum length d4 of the cut surface 52 along the thickness direction is 50 μm or less. This ceramic plate 50 has reduced variation in the thickness of the cut surface 52, resulting in an excellent appearance. Δd3 may be 40 μm or less, 30 μm or less, or 25 μm or less. A ceramic plate 50 having Δd3 in this range has an even more excellent appearance. At least one of the side surfaces 50C of the ceramic plate 50 may have the cut surface 52 and the fracture surface 54, or all of the side surfaces 50C may have the cut surface 52 and the fracture surface 54.

[0053] Δd3 may be 1 μm or more, 5 μm or more, or 10 μm or more. Δd3 may be, for example, 1 to 50 μm.

[0054] The maximum length d3 of the cut surface 52 along the thickness direction of the ceramic plate 50 may be 60 to 100 μm, 65 to 90 μm, or 68 to 85 μm. A ceramic plate 50 having d3 in the above range has a more excellent appearance.

[0055] The minimum length d4 of the cut surface 52 along the thickness direction of the ceramic plate 50 may be 20 to 70 μm, 30 to 60 μm, or 40 to 55 μm. A ceramic plate 50 having d4 in the above range has a more excellent appearance.

[0056] The d3, d4, and Δd3 of the ceramic plate 50 can be determined by image analysis of a microscope image of the side surface 50C of the ceramic plate 50 as shown in FIG.

[0057] The ceramic plate 50 may be obtained by dividing the ceramic substrate 100 along the scribe line L1 (L2). The ceramic plate 50 may be, for example, one of the multiple partitions 10 obtained by dividing the ceramic substrate 100 shown in FIG. 1 along the scribe line L1 (L2). In this case, the side surface of the ceramic plate 50 divided along the scribe line L1 (L2) has a shape similar to the cross-sectional view of the ceramic substrate 100 divided along the scribe line L1 (L2) shown in FIG. 3. In this case, d1=d3 and d2=d4.

[0058] [Method of manufacturing ceramic substrates] An example of a method for manufacturing the ceramic substrate 100 is described below. First, a ceramic sintered body containing a ceramic material (e.g., silicon nitride powder or aluminum nitride powder) is prepared. The ceramic sintered body can be manufactured, for example, by the following procedure. First, a slurry containing silicon nitride powder or aluminum nitride powder, a binder resin, a sintering aid, a plasticizer, a dispersant, a solvent, etc. is molded to obtain a green sheet. Examples of sintering aids include rare earth metals, alkaline earth metals, metal oxides, fluorides, chlorides, nitrates, and sulfates. These may be used alone or in combination. The use of a sintering aid can promote sintering of the inorganic compound powder. Examples of binder resins include methyl cellulose, ethyl cellulose, polyvinyl alcohol, polyvinyl butyral, and (meth)acrylic resins.

[0059] Examples of plasticizers include purified glycerin, glycerin trioleate, diethylene glycol, phthalate-based plasticizers such as di-n-butyl phthalate, and dibasic acid-based plasticizers such as di-2-ethylhexyl sebacate. Examples of dispersants include poly(meth)acrylates and (meth)acrylic acid-maleate copolymers. Examples of solvents include organic solvents such as ethanol and toluene.

[0060] Examples of methods for forming the slurry include the doctor blade method and extrusion molding. A green sheet is produced by such a method. The green sheet is then degreased and sintered to obtain a substrate containing silicon nitride or aluminum nitride. Degreasing may be performed, for example, by heating the green sheet at 400 to 800°C for 0.5 to 20 hours. This can reduce the amount of residual organic matter (carbon) while suppressing oxidation and deterioration of the silicon nitride or aluminum nitride. Sintering may be performed by heating the green sheet at 1700 to 1900°C in a non-oxidizing gas atmosphere such as nitrogen, argon, ammonia, or hydrogen.

[0061] The above-mentioned degreasing and sintering may be performed with a plurality of green sheets stacked together. When degreasing and sintering are performed with the green sheets stacked together, a release layer made of a release agent may be provided between the green sheets to facilitate separation of the sheets after firing. As the release agent, for example, boron nitride (BN) can be used. The release layer may be formed by applying a slurry of boron nitride powder by spraying, brushing, roll coating, screen printing, or other methods. The number of green sheets to be stacked may be, for example, 10 to 100 sheets, or 20 to 80 sheets, from the viewpoint of efficiently mass-producing ceramic sintered bodies while sufficiently progressing degreasing. A ceramic sintered body can be obtained by this procedure.

[0062] The method for manufacturing the ceramic substrate 100 includes a step of forming scribe lines by irradiating a main surface of the ceramic sintered body obtained by the above-described procedure with high-frequency laser light having a frequency greater than 500 kHz. Examples of high-frequency laser light include UV laser light and fiber laser light. By irradiating the high-frequency laser light to form multiple holes, a ceramic substrate 100 is obtained having scribe lines L1 (L2) composed of grooves 20 on the first main surface 100A, as shown in FIGS. 1 to 4. This reduces damage to the ceramic sintered body. It also reduces the generation of black fumes and discoloration, improving the appearance of the scribe lines.

[0063] The frequency of the high-frequency laser light may be 700 kHz or higher, or may be 900 kHz or higher. By setting the frequency within this range, the speed at which the scribe lines L1 (L2) are formed can be improved. In addition, damage to the ceramic substrate 100 when forming the scribe lines L1 (L2) can be further reduced, and the quality of the ceramic substrate 100 can be further improved.

[0064] The frequency of the high-frequency laser beam may be 1500 kHz or less, 1300 kHz or less, or 1100 kHz or less. By keeping the frequency within this range, damage to the ceramic substrate 100 during the formation of the scribe lines L1 (L2) can be further reduced, and the quality of the ceramic substrate 100 can be further improved. Furthermore, the quality of the appearance, strength, etc. of the side surface 50C of the ceramic plate 50 obtained when the ceramic substrate 100 is divided can be further improved. For example, the frequency of the high-frequency laser beam may be greater than 500 kHz and less than 1500 kHz. By adjusting the frequency of the high-frequency laser beam, the length of the shallowest portion d2 of the groove 20 can be adjusted.

[0065] The high-frequency laser beam may be an ultrashort pulse laser beam (USP laser beam). In the present disclosure, USP laser beam has a pulse width of 1.0×10 -15 This refers to high-frequency laser light having a pulse width of at least 1 / 2 second. By using USP laser light, the pulse width can be shortened, which further reduces damage to the ceramic substrate 100 when forming the scribe lines L1 (L2), thereby further improving the quality of the ceramic substrate 100. In addition, the quality of the appearance and strength of the side surfaces of the ceramic plate 50 obtained when the ceramic substrate 100 is divided can be further improved.

[0066] The pulse width of the USP laser light is 5.0 × 10 -15 may be 1.0 x 10 seconds or more -13 may be 1.0 x 10 seconds or more -12 The pulse width may be 1.0 × 10 -10 It may be less than 0.5 x 10 seconds -10 seconds or less, 2.0 x 10 -11The pulse width may be 1.0 femtoseconds (fs) to 100.0 picoseconds (ps). When the pulse width of the USP laser light is in this range, damage to the ceramic substrate 100 when forming the scribe line L1 (L2) can be reduced, and the quality of the ceramic substrate 100 can be further improved. Furthermore, by adjusting the pulse width of the high-frequency laser light, the length of the shallowest portion d2 of the groove 20 can be adjusted more precisely.

[0067] The maximum irradiation depth of the high-frequency laser light may be 60 to 100 μm, 65 to 90 μm, or 68 to 85 μm. By adjusting the maximum irradiation depth, the length of the deepest part d1 of the groove 20 can be adjusted. When the maximum irradiation depth is within the above range, the bending strength along the scribe line L1 (L2) formed in the ceramic substrate 100 can be further reduced. This allows the ceramic substrate 100 to be divided more smoothly.

[0068] The hole diameter of the irradiated portion of the high-frequency laser light may be less than 10 μm, may be 8 μm or less, or may be 5 μm or less. The width W of the groove 20 can be adjusted by changing the hole diameter of the irradiated portion. By keeping the hole diameter of the irradiated portion within this range, the width W of the groove 20 can be reduced, making the scribe line on the main surface of the ceramic substrate 100 less noticeable. Furthermore, the bending strength along the scribe line can be further reduced. This makes it easier to divide the ceramic substrate. The hole diameter of the irradiated portion may be 1 μm or more.

[0069] The output of the high frequency laser light may be 10 to 150 W, 15 to 125 W, or 20 to 100 W. When the output is in this range, the grooves 20 that make up the scribe lines L1 (L2) can be easily formed.

[0070] The scribe lines can be formed by moving the laser beam relative to the ceramic sintered body. The scanning speed of the laser beam may be 200 mm / s or less, 175 mm / s or less, or 160 mm / s or less. When the scanning speed of the laser beam is within this range, damage to the ceramic sintered body can be further reduced. The scanning speed of the laser beam may be 30 mm / s or more, 50 mm / s or more, or 70 mm / s or more. When the scanning speed of the laser beam is within this range, the manufacturing speed of the ceramic substrate 100 can be improved.

[0071] [Collective circuit board] 7 is a perspective view showing an example of an aggregate circuit board according to one embodiment. The aggregate circuit board 200 has a ceramic substrate 100 and a plurality of conductor portions 220 bonded to the main surface of the ceramic substrate 100. Each of the plurality of conductor portions 220 is provided independently for each partition portion 10 on the first main surface 100A and the second main surface 100B. The aggregate circuit board 200 can be cut along scribe lines L1 and L2 to separate it into a plurality of circuit boards 150.

[0072] The aggregate circuit board 200 can be manufactured using a composite substrate 230 including a ceramic substrate 100 shown in FIG. 8 and a pair of metal plates 210 facing each other. The metal plates 210 are bonded to the ceramic substrate 100 so as to cover the first and second main surfaces 100A and 100B of the ceramic substrate 100 and the scribe lines L1 and L2 formed on the first main surface 100A. Examples of the metal plate 210 include a copper plate. A solder paste can be used for bonding. The ceramic substrate 100 and the metal plate 210 may have the same shape and size or may differ from each other. The aggregate circuit board 200 can be manufactured by forming a circuit pattern on the metal plate 210. The circuit pattern may be formed by etching the metal plate using a resist. This makes it possible to form a circuit board or a heat sink that can sufficiently suppress leakage current, etc.

[0073] [Circuit board] 9 is a perspective view showing an example of a circuit board according to one embodiment. The circuit board 150 has a pair of conductors 170 arranged on a ceramic plate 50 so as to face each other. The pair of conductors 170 are joined to the ceramic plate 50 so as to cover the first main surface 50A and the second main surface 50B of the ceramic plate 50. An example of the conductors 170 is a copper plate. A solder paste can be used for joining. The ceramic plate 50 and the conductors 170 may have the same shape and size or may differ from each other.

[0074] Circuit board 150 may be obtained by joining conductor portion 170 to ceramic plate 50, or by dividing aggregate circuit board 200 along scribe lines L1, L2. Because aggregate circuit board 200 has ceramic substrate 100 with scribe lines L1, L2, damage to circuit board 150 during division can be reduced, and the appearance, strength, and other qualities of circuit board 150 can be improved.

[0075] A power module may be manufactured using the collective circuit board 200 or the circuit board 150. The power module can be manufactured by mounting a semiconductor element electrically connected by soldering, wire bonding, or the like on a copper plate of the circuit board, and housing the circuit board and the semiconductor element in the housing space of a housing, followed by resin sealing.

[0076] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments. [Example]

[0077] The present disclosure will be described in more detail with reference to examples and comparative examples, but the present disclosure is not limited to the following examples.

[0078] Example 1 [Ceramic substrate fabrication] Silicon nitride powder and, as sintering aids, magnesium oxide powder and yttrium oxide powder were prepared. These were blended in a mass ratio of Si3N4:YO3:MgO = 94.0:3.0:3.0 to obtain a raw material powder. This raw material powder was uniaxially pressed to produce a compact. This compact was placed in an electric furnace equipped with a carbon heater and sintered in a nitrogen gas atmosphere at 1800°C for 12 hours to obtain a flat-plate-shaped silicon nitride sintered body.

[0079] A ceramic substrate 100 having a scribe line formed by a groove 20 was fabricated by irradiating a high-frequency laser beam onto the main surface of the obtained silicon nitride sintered body. UV laser beam was used as the high-frequency laser beam, with an output of 24 W, a frequency of 1000 kHz, a pulse width of 15 picoseconds, and a maximum irradiation depth of 75 μm. The hole diameter of the irradiated portion of the laser beam was less than 10 μm. The scanning speed of the laser beam during scribe line formation was 75 mm / s.

[0080] Under the above laser light irradiation conditions, the width W of the grooves 20 formed on the first main surface 100A was less than 10 μm, and the depth d1 of the deepest part was 75 μm. The arrangement pitch p of the holes 22 was too small to be measured. On the other hand, the arrangement pitch p was calculated using the following formula (1) and was found to be 0.075 μm. p = scanning speed (mm / s) ÷ frequency (Hz) (1)

[0081] A microscope photograph (magnification: 200 times) of the first main surface 100A of the obtained ceramic substrate 100 is shown in Fig. 10. As shown in Fig. 10, scribe lines L1 composed of grooves 20 were formed on the first main surface 100A of the ceramic substrate 100.

[0082] <Measurement of bending strength of ceramic substrate> The bending strength of the produced ceramic substrate 100 at the scribe line was measured by a three-point bending strength test specified in JIS R 1601-2008. Specifically, the sample was placed with the first main surface 100A, on which the scribe line L1 of the ceramic substrate 100 to be evaluated, facing downward, so that the scribe line L1 was located at the midpoint of a pair of supports. A load was applied to a position on the second main surface 100B corresponding to the scribe line L1 (the back side of the scribe line L1), and the bending strength was measured. In this way, the bending strength required to separate the ceramic substrate 100 was measured. Three ceramic substrates 100 were produced, and one measurement was performed for each ceramic substrate 100. The average and standard deviation of the three measured values are shown in Table 1.

[0083] <Side view of ceramic plate 50> FIG. 11 shows a microscope photograph (magnification: 200x) of the side surface 50C of the ceramic plate 50 obtained by dividing the ceramic substrate 100 along the scribe line. As shown in FIG. 11, no color change was observed on the cut surface 52 of the side surface 50C of the ceramic plate 50. This confirmed that there was little deterioration of the ceramic plate 50. Furthermore, the difference Δd3 between the maximum value d3 and the minimum value d4 of the length of the cut surface 52 in the thickness direction of the ceramic plate 50 was measured by image analysis of the microscope image. Because the ceramic substrate 100 was divided in the thickness direction along the scribe line L1 of the ceramic substrate 100, Δd3 is the same value as the difference Δd1 in depth between the deepest part d1 and the shallowest part d2 of the ceramic substrate 100. The results are shown in Table 1.

[0084] Example 2 A silicon nitride sintered body was produced using the same procedure as in Example 1. A high-frequency laser beam was irradiated onto the main surface of the produced silicon nitride sintered body to produce a ceramic substrate 100 having a scribe line formed by grooves 20. A fiber laser beam was used as the high-frequency laser beam, with an output of 80 W, a frequency of 1000 kHz, a pulse width of 1.6 picoseconds, and an irradiation depth of 80 μm. The hole diameter of the irradiated portion of the laser beam was less than 10 μm. The scanning speed of the laser beam during scribe line formation was 150 mm / s.

[0085] Under the above laser light irradiation conditions, the width W of the grooves 20 formed on the first main surface 100A was less than 10 μm, and the depth d1 of the deepest part was 80 μm. The arrangement pitch p of the holes 22 was too small to be measured. On the other hand, the arrangement pitch p was calculated using equation (1) and was found to be 0.150 μm.

[0086] Fig. 12 shows a microscope photograph (magnification: 200x) of the first main surface 100A of the ceramic substrate 100 obtained in the same manner as in Example 1. As shown in Fig. 12, a scribe line L1 composed of a groove 20 was formed on the first main surface 100A of the ceramic substrate 100.

[0087] As in Example 1, the average value and standard deviation of the bending strength at the scribe line L1 were measured. The results are shown in Table 1. Also, as in Example 1, a microscope photograph (magnification: 200x) of the side surface 50C of the ceramic plate 50 obtained by cutting the ceramic substrate 100 along the scribe line is shown in Figure 13. As shown in Figure 13, the cut surface 52 of the side surface 50C of the ceramic plate 50 showed no noticeable discoloration, confirming that the ceramic plate 50 had undergone little deterioration. Furthermore, d3, d4, and Δd3 on the cut surface of the ceramic plate 50 were measured by image analysis of the microscope image. d3, d4, and Δd3 refer to d1, d2, and Δd1. The results are shown in Table 1.

[0088] (Comparative Example 1) A silicon nitride sintered body was produced using the same procedure as in Example 1. A ceramic substrate with scribe lines was produced by irradiating the main surface of the produced silicon nitride sintered body with laser light. A CO2 laser was used as the laser light, with an output of 80 W, a frequency of 3.6 kHz, a pulse width of 19.04 microseconds, and an irradiation depth of 70 μm. The hole diameter of the laser light irradiated portion was 110 μm. The arrangement pitch p was 100 μm. The scanning speed of the laser light during scribe line formation was 360 mm / s.

[0089] A microscope photograph (magnification: 200 times) of the main surface of the ceramic substrate obtained in the same manner as in Example 1 is shown in Fig. 14. As shown in Fig. 14, a scribe line L3 was formed on the main surface of the ceramic substrate. In addition, the area where the scribe line L3 was formed had turned black due to the generation of fumes, deteriorating the appearance. Furthermore, the blackening of the scribe line L3 clearly confirmed the traces of laser light irradiation.

[0090] As in Example 1, the average value of the bending strength at the scribe line L3 was measured. The results are shown in Table 1. Also, as in Example 1, a microscope photograph (magnification 200x) of the side of a ceramic plate obtained by dividing the ceramic substrate along the scribe line L3 is shown in Figure 15. As shown in Figure 15, fumes were generated on the side of the ceramic plate, turning the scribe line L3 black, and the cut surface was clearly visible. The d3, d4, and Δd3 of the cut surface of the ceramic plate, i.e., d1, d2, and Δd1, were measured by image analysis of the microscope image. The results are shown in Table 1.

[0091] [Table 1]

[0092] As shown in Table 1, it was confirmed that a ceramic substrate 100 having a small difference Δd1 between the deepest part d1 and the shallowest part d2 of the groove 20 that constitutes the scribe line L1 has a small bending strength. Therefore, it was confirmed that damage caused when forming the scribe line can be reduced, and the appearance and strength of the ceramic plate 50 after dividing the ceramic substrate 100 can be improved. [Industrial Applicability]

[0093] According to the present disclosure, a ceramic substrate that can be smoothly separated while reducing damage caused when forming scribe lines and a method for manufacturing the same are provided. Furthermore, a ceramic plate with excellent appearance is also provided. Furthermore, an aggregate circuit board including such a ceramic substrate and a circuit board including such a ceramic plate are also provided. [Explanation of symbols]

[0094] 100...ceramic substrate, 50...ceramic plate, 10...partition portion, 100A, 50A...first main surface, 100B, 50B...second main surface, 100C, 50C...side surface, L1, L2, L3...scribe line, 20...groove, 22...hole, 20E, 22E...outer edge, D1, D2...direction, W...width, 52...cutting surface, 54...fracture surface, d1...deepest part, d2...shallowest part, Δd1...difference between d1 and d2, d3...maximum value in the thickness direction at the cutting surface, d4...minimum value in the thickness direction at the cutting surface, Δd3...difference between d3 and d4, 200...aggregate circuit board, 150...circuit board, 170, 220...conductor portion, 230...composite substrate, 210...metal plate.

Claims

1. A ceramic substrate having a scribe line formed by a groove on a main surface, A ceramic substrate, wherein the difference between the deepest and shallowest portions of the groove is 50 μm or less.

2. The ceramic substrate of claim 1 , wherein the groove has a width of less than 10 μm.

3. 3. The ceramic substrate according to claim 1, wherein the depth of the deepest part of said grooves relative to said main surface is 60 to 100 μm.

4. A ceramic plate having a cut surface and a fracture surface on a side surface, A ceramic plate, wherein the cut surface and the fracture surface are arranged in this order along the thickness direction from the first main surface to the second main surface, and the difference between the maximum and minimum lengths of the cut surface along the thickness direction is 50 μm or less.

5. 5. The ceramic plate according to claim 4, wherein the maximum length of the cut surface along the thickness direction is 60 to 100 μm.

6. 6. The ceramic plate according to claim 4 or 5, obtained by dividing a ceramic substrate having scribe lines formed by grooves on a main surface, the difference between the deepest and shallowest parts of the grooves being 50 μm or less, along the scribe lines.

7. a step of irradiating a main surface of the ceramic sintered body with a high-frequency laser beam to form a scribe line; The method for manufacturing a ceramic substrate, wherein the frequency of the high-frequency laser light is greater than 500 kHz.

8. The method for producing a ceramic substrate according to claim 7, wherein the high-frequency laser light is an ultrashort pulse laser light.

9. The ceramic substrate according to claim 1 or 2; and a metal plate bonded to the ceramic substrate.

10. The ceramic plate according to claim 4 or 5; a metal plate bonded to the ceramic plate.

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