Ceramic circuit board

Abstract

To improve a TCT characteristic in a ceramic circuit board having a ceramic substrate and a circuit board while suppressing a decrease in an area of an upper surface of a circuit board on which an electronic component is mounted.SOLUTION: A ceramic circuit board 1 includes: a ceramic substrate 2; and a first circuit board 3 and a second circuit board 4 bonded to one surface 2a of the ceramic substrate 2. The first circuit board 3 and the second circuit board 4 respectively have side surfaces 33 and 43 inclined with respect to a direction perpendicular to the ceramic substrate 2, and the side surface 33 of the first circuit board 3 has a first facing part 34 facing the side surface 43 of the second circuit board 4 and a first non facing part 35 not facing the side surface 44 of the second circuit board 4. When the ceramic substrate 2 as viewed from a direction perpendicular to a width of the side surfaces 33 and 34 is defined as a width, a side surface width W35 in a first non-opposite part 35 of the first circuit board 3 is narrower than a side surface width W34 in the first opposite part 34.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a ceramic circuit board including a ceramic substrate, and a first circuit board and a second circuit board bonded to one surface of the ceramic substrate. [Background technology]

[0002] In recent years, with the progress in miniaturization, power generation, and performance improvement of motors, power conversion equipment, etc., circuit boards for the power semiconductor elements mounted thereon are required to have a long temperature cycle life and high thermal conductivity. To meet this requirement, various proposals have been made for ceramic circuit boards for power semiconductor elements.

[0003] For example, Patent Document 1 describes a ceramic circuit board including a ceramic substrate and a circuit board bonded to the ceramic substrate. The document also describes that by forming an inclined portion on the side surface of the circuit board, thermal stress generated between the ceramic substrate and the circuit board is alleviated, thereby improving the TCT characteristics (Temperature Cycling Test: heat resistance characteristics in a temperature cycling test). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 221174 Summary of the Invention [Problem to be solved by the invention]

[0005] Forming an inclined portion on the side surface of a circuit board, as described in Patent Document 1, improves the TCT characteristics, but reduces the area of ​​the top surface of the circuit board on which electronic components such as semiconductor elements are mounted, which creates problems such as restrictions on the size of the electronic components that can be mounted or requires the entire ceramic circuit board to be larger.

[0006] To solve this problem, the inventors identified areas on a ceramic circuit board where thermal stress is likely to concentrate, and discovered that by increasing the slope width of the side surface of the circuit board in those areas, it is possible to improve the TCT characteristics while minimizing the decrease in the ratio of the area of ​​the top surface of the circuit board to the area of ​​the ceramic substrate, which led to the creation of the present invention.

[0007] That is, an object of the present invention is to improve the TCT characteristics of a ceramic circuit board having a ceramic substrate and a circuit board while suppressing a reduction in the area of ​​the upper surface of the circuit board on which electronic components are mounted. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the present invention provides a ceramic circuit board comprising a ceramic substrate, and a first circuit board and a second circuit board bonded to one side of the ceramic substrate, wherein each side of the first circuit board and the second circuit board is inclined with respect to a direction perpendicular to the ceramic substrate, the side of the first circuit board has a first opposing portion facing the side of the second circuit board and a first non-facing portion not facing the side of the second circuit board, and when the width of the side as viewed in a direction perpendicular to the ceramic substrate is defined as the side width, the side width at the first non-facing portion of the first circuit board is narrower than the side width at the first opposing portion. [Effects of the Invention]

[0009] According to the ceramic circuit board of the present invention, it is possible to improve the TCT characteristics while suppressing a reduction in the area of ​​the top surface of the circuit board on which electronic components are mounted. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a perspective view showing a ceramic circuit board according to an embodiment of the present invention. [Figure 2]1A is a plan view showing the front side of a ceramic circuit substrate, and FIG. 1B is a plan view showing the back side of the ceramic circuit substrate. [Figure 3] 2(a) is a cross-sectional view of the ceramic circuit substrate taken along line AA in FIG. 2(a), (b) is a cross-sectional view of the ceramic circuit substrate taken along line BB in FIG. 2(a), and (c) is a cross-sectional view of the ceramic circuit substrate taken along line CC in FIG. 2(a). [Figure 4] 2 is an enlarged plan view showing the vicinity of the center portion in the longitudinal direction of the ceramic substrate of the ceramic circuit substrate as viewed from the vertical direction. FIG. [Figure 5] 5A is a cross-sectional view taken along line EE in Fig. 4, (b) is a cross-sectional view taken along line FF in Fig. 4, and (c) is a cross-sectional view taken along line GG in Fig. 4. [Figure 6] 5(a) is a cross-sectional view taken along line HH in FIG. 4. FIG. 5(b) is a cross-sectional view taken along line II in FIG. [Figure 7] 5(a) and 5(b) are enlarged views of parts of FIG. [Figure 8] 1 is a graph showing an example of the amount of deformation of a ceramic circuit substrate when the temperature of the ceramic circuit substrate increases. [Figure 9] 10 shows the analysis results of stress distribution when the side width of the tip-side cross-direction extending portion of the first circuit board is 0.10 mm. [Figure 10] 10 shows the analysis results of stress distribution when the side width of the tip-side cross-direction extending portion of the first circuit board is 0.382 mm. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A ceramic circuit board according to an embodiment of the present invention and a method for manufacturing the same will now be described with reference to the drawings.

[0012] FIG. 1(a) is a perspective view showing the front surface side of a ceramic circuit substrate 1 according to an embodiment of the present invention. FIG. 1(b) is a perspective view showing the back surface side of the ceramic circuit substrate 1. FIG. 1(c) is a side view of the ceramic circuit substrate 1. FIG. 2(a) is a plan view showing the front surface side of the ceramic circuit substrate 1. FIG. 2(b) is a plan view showing the back surface side of the ceramic circuit substrate 1. FIG. 3(a) is a cross-sectional view of the ceramic circuit substrate 1 taken along line AA in FIG. 2(a). FIG. 3(b) is an enlarged view of part B in FIG. 3(a). FIG. 3(c) is an enlarged view of part C in FIG. 3(a).

[0013] The ceramic circuit board 1 includes a flat ceramic substrate 2, a first circuit board 3 and a second circuit board 4 bonded to one surface 2a of the ceramic substrate 2, and a heat sink 5 bonded to the other surface 2b of the ceramic substrate 2. As shown in Figures 3(b) and 3(c), the first circuit board 3 and the second circuit board 4 are bonded to one surface 2a of the ceramic substrate 2 by a brazing filler metal layer 61. The heat sink 5 is bonded to the other surface 2b of the ceramic substrate 2 by a brazing filler metal layer 62.

[0014] In this embodiment, for convenience of explanation, the first circuit board 3 and second circuit board 4 side may be referred to as "upper" and the heat sink 5 side as "lower" in the thickness direction of the ceramic substrate 2, but this "upper" and "lower" do not necessarily refer to the top and bottom in the vertical direction when the ceramic circuit board 1 is in use. In the following explanation, the direction perpendicular to the ceramic substrate 2 will be referred to as the "vertical direction," and the direction parallel to the ceramic substrate 2 will be referred to as the "horizontal direction."

[0015] Specific examples of the ceramic substrate 2 include a silicon nitride (Si3N4) substrate, an aluminum nitride (AlN) substrate, an aluminum oxide (Al2O3) substrate, a silicon carbide (SiC) substrate, an alumina zirconia (ZTA) substrate, and a beryllium oxide (BeO) substrate. The thickness T2 (see FIG. 3(b)) of the ceramic substrate 2 is, for example, 0.32 mm. For example, when the ceramic substrate 2 is a silicon nitride substrate, the thickness T2 can be set to 0.15 mm or more and 2.0 mm or less.

[0016] The brazing filler metal layers 61 and 62 are formed of a silver (Ag)-copper (Cu)-titanium (Ti) based active brazing metal. The brazing filler metal layers 61 and 62 each have a thickness of, for example, 20 μm, and can be set to 10 μm or more and 40 μm or less.

[0017] The first circuit board 3, the second circuit board 4, and the heat sink 5 are made of flat metal plates, such as copper plates. However, any or all of the first circuit board 3, the second circuit board 4, and the heat sink 5 may be aluminum plates. The thicknesses T3, T4, and T5 of the first circuit board 3, the second circuit board 4, and the heat sink 5 are, for example, 0.4 mm or more and 2.0 mm or less.

[0018] It is desirable that the thicknesses T3, T4, and T5 of the first circuit board 3, the second circuit board 4, and the heat sink 5 are thicker than the thickness T2 of the ceramic substrate 2. By making the thicknesses T3, T4, and T5 of the first circuit board 3, the second circuit board 4, and the heat sink 5 thicker than the thickness T2 of the ceramic substrate 2 and by making them 0.4 mm or more, the thermal conductivity of the ceramic circuit board 1 can be increased, and heat dissipation can be improved. Furthermore, by making the thicknesses T3, T4, and T5 of the first circuit board 3, the second circuit board 4, and the heat sink 5 2.0 mm or less, the ceramic circuit board 1 can be made smaller and lighter.

[0019] The ceramic substrate 2 has a rectangular shape when viewed vertically. The first circuit board 3 and the second circuit board 4 are formed to have the same shape. When the ceramic circuit substrate 1 is viewed vertically, the first circuit board 3 and the second circuit board 4 are aligned along the long side of the ceramic substrate 2. In FIG. 2(a), the direction in which the first circuit board 3 and the second circuit board 4 are aligned on one surface 2a of the ceramic substrate 2 is indicated by arrow D. Also, FIG. 2(a) shows the center positions C1 and C2 of the first circuit board 3 and the second circuit board 4 when viewed vertically. FIG. 2(b) shows the center position C3 of each heat sink 5 when viewed vertically.

[0020] When viewed from the vertical direction, the first circuit board 3 has a shape in which a rectangular base portion 301 and a rectangular protruding portion 302 protruding from the base portion 301 are integrated together. Similarly, when viewed from the vertical direction, the second circuit board 4 has a shape in which a rectangular base portion 401 and a rectangular protruding portion 402 protruding from the base portion 401 are integrated together. The protruding portions 302, 402 are formed smaller than the base portions 301, 401. In the following description, in the first circuit board 3 and the second circuit board 4, the tip side of the protruding direction of the protruding portions 302, 402 from the base portions 301, 401 may be simply referred to as the "tip side," and the base side of the protruding direction may be simply referred to as the "base side."

[0021] The protruding portion 302 of the first circuit board 3 protrudes from an end of the base portion 301 of the first circuit board 3 that faces the second circuit board 4 toward the base portion 401 of the second circuit board 4. The protruding portion 402 of the second circuit board 4 protrudes from an end of the base portion 401 of the second circuit board 4 that faces the first circuit board 3 toward the base portion 301 of the first circuit board 3. The protruding portion 302 of the first circuit board 3 and the protruding portion 402 of the second circuit board 4 are aligned along the short side direction of the ceramic substrate 2.

[0022] A crank-shaped gap 10 is formed between the first circuit board 3 and the second circuit board 4. The gap 10 has a first portion 11 extending in the long-side direction of the ceramic substrate 2 between the protruding portion 302 of the first circuit board 3 and the protruding portion 402 of the second circuit board 4, a second portion 12 extending in the short-side direction of the ceramic substrate 2 between the protruding portion 302 of the first circuit board 3 and the base portion 401 of the second circuit board 4, and a third portion 13 extending in the short-side direction of the ceramic substrate 2 between the base portion 301 of the first circuit board 3 and the protruding portion 402 of the second circuit board 4, and one end of the second portion 12 and one end of the third portion 13 are connected by the first portion 11.

[0023] Width W of the horizontal gap 10 10 (See FIG. 3(b)) is, for example, 0.5 mm or more and 3.0 mm or less across the first portion 11, the second portion 12, and the third portion 13. 10 By setting the width W to 0.5 mm or more, it is possible to ensure a sufficient creepage distance between the first circuit board 3 and the second circuit board 4. 10 By setting the width W to 3.0 mm or less, the first circuit board 3 and the second circuit board 4 can be densely arranged on the ceramic substrate 2, and the ceramic circuit substrate 2 can be made small. 10 A more preferable range is 1.0 mm or more and 2.0 mm or less.

[0024] The first circuit board 3 has a lower surface 31, which faces the ceramic substrate 2, joined to one surface 2a of the ceramic substrate 2 by a brazing filler metal layer 61, and an electronic component such as a semiconductor element mounted on its opposite upper surface 32. A side surface 33 between the lower surface 31 and the upper surface 32 is inclined with respect to the vertical direction. Similarly, the second circuit board 4 has a lower surface 41, which faces the ceramic substrate 2, joined to one surface 2a of the ceramic substrate 2 by a brazing filler metal layer 61, and an electronic component such as a semiconductor element is mounted on its opposite upper surface 42. A side surface 43 between the lower surface 41 and the upper surface 42 is inclined with respect to the vertical direction.

[0025] The heat sink 5 has a rectangular shape when viewed vertically and is aligned vertically with the first circuit board 3 and the second circuit board 4. A predetermined width of the other surface 2b of the ceramic substrate 2 is exposed around the heat sink 5. The bonding surface 51 of the heat sink 5, which faces the ceramic substrate 2, is bonded to the other surface 2b of the ceramic substrate 2 by a brazing layer 62, and a heat dissipation member such as a heat sink is disposed on the opposite heat dissipation surface 52. The side surface 53 of the heat sink 5 between the bonding surface 51 and the heat dissipation surface 52 is inclined relative to the vertical direction. In this embodiment, a single heat sink 5 is bonded to the other surface 2b of the ceramic substrate 2, but multiple heat sinks 5 may be bonded to the other surface 2b of the ceramic substrate 2.

[0026] Here, the width of the side surfaces 33, 43, and 53 of the first circuit board 3, the second circuit board 4, and the heat sink 5 as viewed from the vertical direction is defined as the side surface width. As shown in FIG. 3(b), the upper ends 33a, 43a of the side surfaces 33, 43 of the first circuit board 3 and the second circuit board 4, which are the ends on the upper surfaces 32, 42, are located closer to the center positions C1, C2 of the first circuit board 3 and the second circuit board 4 than the lower ends 33b, 43b, which are the ends on the lower surfaces 31, 41. Therefore, the side surface width of the side surfaces 33, 43 is the distance between the lower ends 33b, 43b and the upper ends 33a, 43a of the side surfaces 33, 43 when viewed from the upper surfaces 32, 42. In FIG. 3(b), the side surface width W of the side surface 33 of the first circuit board 3 is defined as the distance between the lower ends 33b, 43b and the upper ends 33a, 43a. 33 , and the side width W at the side 43 of the second circuit board 4 43 This shows:

[0027] 3(c), the end 53a of the side surface 53 of the heat sink 5 is located closer to the center position C3 of the heat sink 5 than the end 53b of the joining surface 51. Therefore, the side width of the side surface 53 of the heat sink 5 is the distance between the end 53b of the joining surface 51 and the end 53a of the heat sink 52 when the heat sink 5 is viewed vertically from the heat sink 52 side. In FIG. 3(c), the side width W of the side surface 53 of the heat sink 5 53 is shown.

[0028] The side surfaces 33 and 43 of the first circuit board 3 and the second circuit board 4 form angles θ with the lower surfaces 31 and 41 at the lower ends 33b and 43b. 31 ,θ 41 , and the angle θ formed by the upper end portions 33a and 43a with the upper surfaces 32 and 42 32 ,θ 42 are acute angles, and the portions between the lower ends 33b, 43b and the upper ends 33a, 43a of the side surfaces 33, 43 in the thickness direction of the first circuit board 3 and the second circuit board 4 are U-shaped recessed toward the central positions C1, C2. The deepest portions 33c, 43c, which are the most recessed portions of the side surfaces 33, 43, are located closer to the central positions C1, C2 than the upper ends 33a, 43a and the lower ends 33b, 43b of the side surfaces 33, 43 in the horizontal direction.

[0029] Angle θ at the lower ends 33b, 43b of the side surfaces 33, 43 of the first circuit board 3 and the second circuit board 4 31 ,θ 41 is, for example, 45°. 32 ,θ 42 is the angle θ at the lower ends 33b and 43b 31 ,θ 41 The angle θ at the upper end portions 33a and 43a is larger than the angle θ at the upper end portions 33a and 43a, for example, 80°. 32 ,θ 42 The side surfaces 33, 43 may be formed to be inclined so that the angle is obtuse and the upper end portions 33a, 43a are closer to the center positions C1, C2. In this case, the side surfaces 33, 43 have a J shape.

[0030] The side surface 53 of the heat sink 5 also has an angle θ 51 , and the angle θ between the end 53a on the heat radiation surface 52 and the heat radiation surface 52 52 are both acute angles, and the portion of the side surface 53 between the end 53a on the heat dissipation surface 52 side and the end 53b on the bonding surface 51 side in the thickness direction of the heat dissipation plate 5 is U-shaped recessed toward the center position C3. The deepest part 53c, which is the most recessed part of the side surface 53, is located closer to the center position C3 than the end 53b on the bonding surface 51 side and the end 53a on the heat dissipation surface 52 side. However, the shape of the side surface 53 is such that the angle θ52 Alternatively, the angle may be an obtuse J-shape, inclined so that the heat radiation surface 52 side approaches the center position C3.

[0031] 2(a), the side surface 33 of the first circuit board 3 has a first facing portion 34 that faces the side surface 43 of the second circuit board 4 in the horizontal direction, and a first non-facing portion 35 that does not face the side surface 43 of the second circuit board 4. The side surface 43 of the second circuit board 4 has a second facing portion 44 that faces the side surface 33 of the first circuit board 3 in the horizontal direction, and a second non-facing portion 45 that does not face the side surface 33 of the first circuit board 3. The first facing portion 34 of the first circuit board 3 and the second facing portion 44 of the second circuit board 4 face each other with a gap 10 between them.

[0032] FIG. 4 is an enlarged plan view showing the vicinity of the longitudinal center of the ceramic substrate 2 of the ceramic circuit board 1 as viewed from the vertical direction. FIG. 5(a) is a cross-sectional view taken along line EE in FIG. 4. FIG. 5(b) is a cross-sectional view taken along line FF in FIG. 4. FIG. 5(c) is a cross-sectional view taken along line GG in FIG. 4. FIG. 6(a) is a cross-sectional view taken along line HH in FIG. 4. FIG. 6(b) is a cross-sectional view taken along line II in FIG. 4. FIGS. 7(a) and (b) are enlarged views of portions of FIG. 4.

[0033] The first opposing portion 34 on the side surface 33 of the first circuit board 3 has an arrangement direction extending portion 341 extending along the arrangement direction of the first circuit board 3 and the second circuit board 4, a tip-side intersecting direction extending portion 342 extending at the tip side of the protruding portion 302 in a direction intersecting the arrangement direction of the first circuit board 3 and the second circuit board 4, and a base-side intersecting direction extending portion 343 extending at the base end side of the protruding portion 302 in a direction intersecting the arrangement direction of the first circuit board 3 and the second circuit board 4. The arrangement direction extending portion 341 in the first opposing portion 34 corresponds to the "first arrangement direction extending portion" in the present invention. The tip-side intersecting direction extending portion 342 in the first opposing portion 34 corresponds to the "first intersecting direction extending portion" in the present invention.

[0034] Similarly, the second opposing portion 44 on the side surface 43 of the second circuit board 4 has an arrangement direction extending portion 441 extending along the arrangement direction of the first circuit board 3 and the second circuit board 4, a tip-side intersecting direction extending portion 442 extending in a direction intersecting the arrangement direction of the first circuit board 3 and the second circuit board 4 at the tip side of the protruding portion 402, and a base-side intersecting direction extending portion 443 extending in a direction intersecting the arrangement direction of the first circuit board 3 and the second circuit board 4 at the base end side of the protruding portion 402. The arrangement direction extending portion 441 in the second opposing portion 44 corresponds to the "second arrangement direction extending portion" in the present invention. The tip-side intersecting direction extending portion 442 in the second opposing portion 44 corresponds to the "second intersecting direction extending portion" in the present invention.

[0035] The parallel direction extending portion 341 and the tip side cross direction extending portion 342 in the first opposing portion 34 of the first circuit board 3 form an approximately right-angle corner portion 303 at the end of the parallel direction extending portion 341 on the base portion 401 side of the second circuit board 4, and the parallel direction extending portion 341 and the base end side cross direction extending portion 343 form an approximately right-angle recessed corner portion 304 at the end of the parallel direction extending portion 341 on the base portion 301 side of the first circuit board 3. In this embodiment, the side-by-side extending portion 341 extends in the longitudinal direction of the ceramic substrate 2, the tip-side intersecting direction extending portion 342 and the base-side intersecting direction extending portion 343 extend in the short direction of the ceramic substrate 2, and the angle formed between the side-by-side extending portion 341 and the tip-side intersecting direction extending portion 342 and the angle formed between the side-by-side extending portion 341 and the base-side intersecting direction extending portion 343 are each 90°. However, the angle formed between the side-by-side extending portion 341 and the tip-side intersecting direction extending portion 342 and the angle formed between the side-by-side extending portion 341 and the base-side intersecting direction extending portion 343 may be approximately right angles, for example, between 80° and 100°.

[0036] Similarly, the parallel direction extending portion 441 and the tip side cross direction extending portion 442 in the second opposing portion 44 of the second circuit board 4 form an approximately right-angle corner portion 403 at the end of the parallel direction extending portion 441 on the base portion 301 side of the first circuit board 3, and the parallel direction extending portion 441 and the base side cross direction extending portion 443 form an approximately right-angle recessed corner portion 404 at the end of the parallel direction extending portion 441 on the base portion 401 side of the second circuit board 4. In the present embodiment, the side-by-side extending portion 441 extends in the longitudinal direction of the ceramic substrate 2, the tip-side intersecting direction extending portion 442 and the base-side intersecting direction extending portion 443 extend in the short direction of the ceramic substrate 2, and the angle formed between the side-by-side extending portion 441 and the tip-side intersecting direction extending portion 442 and the angle formed between the side-by-side extending portion 441 and the base-side intersecting direction extending portion 443 are each 90°. However, the angle formed between the side-by-side extending portion 441 and the tip-side intersecting direction extending portion 442 and the angle formed between the side-by-side extending portion 441 and the base-side intersecting direction extending portion 443 may be approximately right angles, for example, between 80° and 100°.

[0037] The alignment direction extending portion 341 of the first circuit board 3 and the alignment direction extending portion 441 of the second circuit board 4 face each other across a first portion 11 of the gap 10. The tip-side cross-direction extending portion 342 of the first circuit board 3 and the base-side cross-direction extending portion 443 of the second circuit board 4 face each other across a second portion 12 of the gap 10. The base-side cross-direction extending portion 343 of the first circuit board 3 and the tip-side cross-direction extending portion 442 of the second circuit board 4 face each other across a third portion 13 of the gap 10.

[0038] In FIG. 5(a), the side width W 341 , and the side width W of the extending portion 441 of the second circuit board 4 in the arrangement direction 441 In FIG. 5(b), the side width W 342 , and the side width W of the base end side cross direction extending portion 443 of the second circuit board 4 443 In FIG. 5(c), the side width W 343 , and the side width W of the tip-side cross-direction extending portion 442 of the second circuit board 4442 In FIG. 6(a), the side width W 35 In FIG. 6(b), the side width W 45 This shows:

[0039] 7(a) is an enlarged view showing the periphery of the corner portion 303 of the first circuit board 3. In FIG. 7(a), the extension line L of the arrangement direction extending portion 341 of the first circuit board 3 is 341 and the extension line L of the tip-side cross-direction extending portion 342 342 are shown by dashed lines. These extension lines L 341 and extension line L 342 is a straight line extending from the alignment direction extending portion 341 and the tip-side cross direction extending portion 342 at the lower end portion 33b of the side surface 33 of the first circuit board 3, and intersects at a right angle at the first intersection 340. The cross section of line FF in FIG. 4 shown in FIG. 5(b) is a straight line extending from the first intersection 340 to the tip-side cross direction extending portion 342, as shown in FIG. 7(a). 342 1 shows a cross section of the tip-side intersecting direction extending portion 342 at a position 1 mm (1.00 mm) away from the tip-side intersecting direction extending portion 342 along the line.

[0040] 7(b) is an enlarged view showing the periphery of the corner 403 of the second circuit board 4. In FIG. 7(b), the extension line L of the arrangement direction extending portion 441 of the second circuit board 4 is 441 and the extension line L of the tip-side cross-direction extending portion 442 442 are shown by dashed lines. These extension lines L 441 and extension line L 442 is a straight line extending from the alignment direction extending portion 441 and the tip-side cross direction extending portion 442 at the lower end portion 43b of the side surface 43 of the second circuit board 4, and intersects at a right angle at the second intersection 440. The cross section of line GG in FIG. 4 shown in FIG. 5(c) is a straight line extending from the second intersection 440 to the extension line L of the tip-side cross direction extending portion 442, as shown in FIG. 7(b). 442 1 shows a cross section of the tip-side intersecting direction extending portion 442 at a position 1 mm (1.00 mm) away from the tip-side intersecting direction extending portion 442 along the line.

[0041] The side width W of the alignment direction extending portion 341, the distal end side cross direction extending portion 342, and the proximal end side cross direction extending portion 343 in the first opposing portion 34 341 ,W 342 ,W 343 are collectively referred to as the side width W of the first opposing portion 34 34 When the side width W of the first non-opposing portion 35 is 35 is the side width W of the first opposing portion 34 34 In addition, the side width W of the juxtaposition direction extending portion 441, the distal end side cross direction extending portion 442, and the proximal end side cross direction extending portion 443 of the second opposing portion 44 is 441 ,W 442 ,W 443 are collectively referred to as the side width W of the second opposing portion 44 44 When the side width W of the second non-opposing portion 45 is 45 is the side width W of the second opposing portion 44 44 That is, the side width W 35 is the side width W of the first opposing portion 34 throughout 341 ,W 342 ,W 343 and the side width W of the second non-opposing portion 45 is narrower than either of the above. 45 is the side width W of the second opposing portion 44 throughout 441 ,W 442 ,W 443 It is narrower than either of the above.

[0042] In addition, the side width W of the side surface 53 of the heat sink 5 53 is the side width W of the first opposing portion 34 34 and the side width W of the second circuit board 4 at the second facing portion 44 44 That is, the side width W of the side surface 53 of the heat sink 5 is narrower than 53 is the side width W of the first opposing portion 34 and the second opposing portion 44 throughout the entire 341 ,W 342 ,W 343 ,W 441 ,W 442 ,W 443 It is narrower than either of the above.

[0043] The side width W of the heat sink 5 at the side surface 53 53 is the side width W of the first non-opposing portion 35 35 or the side width W of the second non-opposing portion 45 45 However, the side width W of the first non-opposing portion 35 may be the same as 35 and the side width W of the second non-opposing portion 45 45 The side width W of the heat sink 5 at the side surface 53 may be narrower. 53 is, for example, 0.2 mm or more, and the side width W 35 and the side width W of the second non-opposing portion 45 45 is, for example, 0.3 mm or more.

[0044] The side width W of the tip-side intersecting direction extending portion 342 in the cross section shown in FIG. 342 In other words, the extension line L from the first intersection 340 to the tip-side crossing direction extending portion 342 is 0.36 mm or more and 0.60 mm or less. 342 The side width W of the tip-side cross-direction extending portion 342 at a position 1 mm away from the tip-side cross-direction extending portion 342 along the 342 In this embodiment, the side width W of the tip-side cross-direction extending portion 342 of the first circuit board 3 is 0.36 mm or more and 0.60 mm or less. 342 is between 0.36 mm and 0.60 mm throughout.

[0045] In addition, the side width W of the tip-side intersecting direction extending portion 442 in the cross section shown in FIG. 442 In other words, the extension line L of the tip-side crossing direction extending portion 442 from the second crossing point 440 is 0.36 mm or more and 0.60 mm or less. 442 The side width W of the tip-side cross-direction extending portion 442 at a position 1 mm away from the tip-side cross-direction extending portion 442 along the 442 In this embodiment, the side width W of the tip-side cross-direction extending portion 442 of the second circuit board 4 is 0.36 mm or more and 0.60 mm or less. 442 is between 0.36 mm and 0.60 mm throughout.

[0046] The side width W of the tip-side cross-direction extending portions 342, 442 of the first circuit board 3 and the second circuit board 4 342 ,W 442 The reason why the side width W is set to 0.36 mm or more is that thermal stress tends to concentrate on the tip-side cross-direction extending portions 342, 442. 342 ,W 442 By setting the gap to 0.36 mm or more, it becomes possible to prevent cracks from occurring in the ceramic substrate 2.

[0047] FIG. 8 is a graph showing an example of the amount of deformation (warpage) of the ceramic substrate 2 when the temperature of the ceramic circuit substrate 1 increases. In FIG. 8, the outlines of each component at room temperature are indicated by thin black lines. Also, in FIG. 8, the amount of displacement of each component from room temperature is indicated by shading, with the greater the amount of displacement, the darker the color. As shown in FIG. 8, when the temperature of the ceramic circuit substrate 1 increases, warpage occurs in the ceramic substrate 2 due to differences in the expansion coefficients of the components. If this warpage becomes large and stress concentrates in a specific component of the ceramic substrate 2, cracks will occur in the ceramic substrate 2. Note that FIG. 8 exaggerates the amount of deformation of the shape of the ceramic circuit substrate 1 at high temperatures.

[0048] FIG. 9 shows the side width W of the leading end side cross-direction extending portion 342 of the first circuit board 3. 342 10 shows the analysis results of the stress distribution when the side width W of the leading-end cross-direction extending portion 342 of the first circuit board 3 is 0.10 mm. 342 9 and 10, the magnitude of stress is indicated by shading, with the darker color indicating the area with greater stress.

[0049] 9 and 10, when the temperature of the ceramic circuit board 1 rises, stress concentrates in the vicinity of the tip-side cross-direction extending portion 342 of the first circuit board 3, and the stress is particularly high at a position 1 mm away from the first intersection 340. Furthermore, as is clear from a comparison of FIGS. 9 and 10, the W of the tip-side cross-direction extending portion 342 342 The larger the value, the smaller the generated stress.

[0050] Next, we will explain the method for manufacturing the ceramic circuit board 1. In the method for manufacturing the ceramic circuit board 1 of this embodiment, metal plates are placed on one surface 2a and the other surface 2b of the ceramic substrate 2 via a paste-like brazing filler metal containing an active metal such as titanium, and the temperature is raised until the brazing filler metal melts, and then the bonding is performed by lowering the temperature to room temperature at a rate of, for example, 5°C / min or less to prevent cracks from occurring due to a sudden change in temperature.

[0051] The thickness of the applied brazing filler metal is preferably 10 μm or more and 40 μm or less. The joining step of melting the brazing filler metal to join the metal plates is preferably carried out at a temperature of 600°C or more and 950°C or less. When the active metal of the brazing filler metal contains at least one element selected from Ti, Zr, Hf, and Nb, the step is preferably carried out at a temperature of 800°C or more and 950°C or less. When the active metal contains Al, the step is preferably carried out at a temperature of 600°C or more and 800°C or less. The heating atmosphere is preferably a non-oxidizing atmosphere.

[0052] At this time, for example, metal plates are bonded to one surface 2a and the other surface 2b of the ceramic substrate 2 so as to cover most of the surface, and the bonded metal plates are then etched. By this etching, a pattern is formed on the one surface 2a of the ceramic substrate 2, in which the first circuit board 3 and the second circuit board 4 are separated by a gap 10. The metal plate bonded to the other surface 2b of the ceramic substrate 2 becomes the heat sink 5. Furthermore, the brazing material layer that was bonded to the ceramic substrate 2 by the metal plate in the portion removed by etching is also etched, thereby removing the brazing material layer in that portion and exposing the ceramic substrate 2. The U-shaped portions on the side surfaces 33, 43, and 53 of the first circuit board 3, the second circuit board 4, and the heat sink 5 are also formed by etching.

[0053] In the etching process, etching is performed so that the side widths of the respective portions of the side surfaces 33, 43, and 53 of the first circuit board 3, the second circuit board 4, and the heat sink 5 become the above-mentioned dimensions. For this etching process, it is preferable to use an etching solution containing, for example, cupric chloride or ferric chloride. When the metal plate is a copper plate, using an etching solution containing cupric chloride allows the processing solution after etching the copper plate to be regenerated and reused.

[0054] The side widths of the respective portions of the side surfaces 33, 43 of the first circuit board 3 and the second circuit board 4 can be controlled, for example, by the etching time. The side widths can also be controlled by the concentration of copper (II) chloride or ferric chloride. The first circuit board 3, the second circuit board 4, and the heat sink 5 may be formed by a single etching process, or may be formed by multiple etching processes.

[0055] (Examples and Experimental Results) Next, the side width W of the tip-side cross-direction extending portions 342, 442 of the first circuit board 3 and the second circuit board 4 342 ,W 442 The temperature cycle test (TCT) was carried out by changing the temperature, and the rate of crack occurrence after the TCT was investigated. The specifications of each member of the ceramic circuit board 1 used in this experiment are as follows: (1) Ceramic substrate 2 Material: Silicon nitride, Thermal conductivity: 90 W / m·K, 3-point bending strength: 700 MPa, Size: 47.3 mm x 23.6 mm, Thickness: 0.32 mm (2) First circuit board 3, second circuit board 4, heat sink 5 Material: Copper (oxygen-free copper), thickness: 0.8 mm

[0056] The brazing filler metal used to join the first circuit board 3, the second circuit board 4, and the heat sink 5 to the ceramic substrate 2 was an active metal brazing filler metal in paste form, prepared by adding 0.3 parts by mass of TiH2 to an alloy powder (total of 100 parts by mass) consisting of 70% by mass of Ag, 3% by mass of In, and 27% by mass of Cu, and further adding an organic solvent and a binder component.

[0057] When preparing the sample for the experiment, the active metal brazing paste was applied to both sides of a silicon nitride substrate as the ceramic substrate 2 and dried. Copper plates were then placed on both sides of the silicon nitride substrate and heated to 800°C under pressure in a vacuum to bond the copper plates to both sides of the silicon nitride substrate. Then, an etching process was carried out. At this time, the etching process conditions were changed to change the side width W 342 ,W 442 We created several samples with different side widths W 342 ,W 442 The side width W of each sample was controlled by the etching time. 342 ,W 442 The evaluation results are shown in Table 1. In the TCT, a cycle of holding at -40°C for 30 minutes and then at 160°C for 30 minutes was repeated 750 times, after which the number of samples in which cracks had occurred in the silicon nitride substrate and the probability of crack occurrence were confirmed.

[0058] [Table 1]

[0059] As shown in Table 1, the side width W 342 ,W 442 It was found that the occurrence of cracks can be suppressed in TCT by setting the side width W to 0.360 mm or more. 342 ,W 442 It was found that even when the side width W is 0.28 mm or more, the occurrence of cracks can be suppressed compared to when it is less than 0.28 mm. 342 ,W 442If the side width W is made too large, the area of ​​the upper surfaces 32, 42 of the first circuit board 3 and the second circuit board 4 will become small. 342 ,W 442 It is desirable to keep the thickness below 0.60 mm.

[0060] (Effects of the embodiment) According to the embodiment described above, the side width W 35 is the side width W of the first opposing portion 34 34 and the side width W 45 is the side width W of the second opposing portion 44 44 9 and 10, since the side width W 35 ,W 45 On the other hand, in the first opposing portion 34 and the second opposing portion 44 where relatively large thermal stress is likely to occur, the side width W 34 ,W 44 By widening the gap, it is possible to suppress the occurrence of cracks.

[0061] According to this embodiment, the side surface width W of the side surface 53 of the heat sink 5 53 is the side width W of the first opposing portion 34 34 and the side width W of the second opposing portion 44 44 Since the area is narrower than the area of ​​the heat dissipation surface 52 of the heat dissipation plate 5, the area of ​​the heat dissipation surface 52 can be increased.

[0062] Furthermore, according to this embodiment, the side width W of the tip-side cross-direction extending portion 342, which corresponds to the tip of the protruding portion 302 of the first circuit board 3 where large thermal stress is likely to occur, is 342 , and the side width W of the tip-side cross-direction extending portion 442 which corresponds to the tip of the protruding portion 402 of the second circuit board 4. 442By setting the width W to 0.36 mm or more, it is possible to suppress the occurrence of cracks during TCT. In particular, the side width W of the tip-side intersecting direction extending portions 342, 442 at positions 1 mm away from the first intersection 340 and the second intersection 440 where the thermal stress becomes maximum is set to 0.36 mm or more. 342 ,W 442 Side width W 342 By setting the side width W to 0.36 mm or more, the occurrence of cracks can be effectively suppressed. 342 ,W 442 Side width W 342 By setting the distance to 0.60 mm or less, it is possible to prevent the areas of the upper surfaces 32, 42 of the first circuit board 3 and the second circuit board 4 from being narrowed.

[0063] (Summary of the embodiment) Next, the technical ideas grasped from the above-described embodiments will be described by using the reference numerals and the like in the embodiments. However, the reference numerals in the following description do not limit the components in the claims to the members and the like specifically shown in the embodiments.

[0064] [1] A ceramic substrate (2), and a first circuit board (3) and a second circuit board (4) bonded to one surface (2a) of the ceramic substrate (2), wherein the first circuit board (3) and the second circuit board (4) each have a side surface (33, 43) that is inclined with respect to a direction perpendicular to the ceramic substrate (2), the side surface (33) of the first circuit board (3) has a first opposing portion (34) that faces the side surface (43) of the second circuit board (4) and a first non-opposing portion (35) that does not face the side surface (43) of the second circuit board (4), and when the width of the side surfaces (33, 43) as viewed in a direction perpendicular to the ceramic substrate (2) is defined as the side surface width, the side surface width (W) of the first circuit board (3) at the first non-opposing portion (35) is 35 ) is the side width (W 34 ) and narrower than ceramic circuit boards (1).

[0065] [2] The side surface (43) of the second circuit board (4) has a second facing portion (44) facing the side surface (33) of the first circuit board (3) and a second non-facing portion (45) not facing the side surface (33) of the first circuit board (3), and the side surface width (W) of the second non-facing portion (45) of the second circuit board (4) is 45 ) is the side width (W 44 ) The ceramic circuit board (1) according to the above [1].

[0066] [3] A heat sink (5) is provided which is joined to the other surface (2b) of the ceramic substrate (2), and the side surface (53) of the heat sink (5) is inclined with respect to a direction perpendicular to the ceramic substrate (2), and the side surface width (W 53 ) is the side width (W 34 The ceramic circuit board (1) according to the above [1] or [2], wherein the width is narrower than the width of the ceramic circuit board (1).

[0067] [4] The first opposing portion (34) of the first circuit board (3) has a first parallel extension portion (341) extending along the parallel arrangement direction of the first circuit board (3) and the second circuit board (4), and a first intersecting extension portion (tip-side intersecting extension portion 342) extending in a direction intersecting the parallel arrangement direction, and the first parallel extension portion (341) and the first intersecting extension portion (342) form a substantially right-angled corner portion (303) at an end of the first parallel extension portion (341) on the second circuit board (4) side, and an extension line (L) of the first parallel extension portion (341) when the first circuit board (3) is viewed from a direction perpendicular to the ceramic substrate (2). 341 ) and the extension line (L) of the first intersecting direction extending portion (342). 342 ) is defined as a first intersection point (340), the extension line (L) of the first intersecting direction extending portion (342) from the first intersection point (340) is 342 ) along the first intersecting direction extending portion (341) at a position 1 mm away from the first intersecting direction extending portion (342) side. 341) is 0.36 mm or more.

[0068] [5] The side width (W 342 ) is 0.36 mm or more and 0.60 mm or less throughout the ceramic circuit board (1) according to [4] above.

[0069] [6] The second opposing portion (44) of the second circuit board (4) has a second parallel extension portion (441) extending along the parallel arrangement direction of the first circuit board (3) and the second circuit board (4), and a second intersecting extension portion (tip-side intersecting extension portion 442) extending in a direction intersecting the parallel arrangement direction, and the second parallel extension portion (441) and the second intersecting extension portion (442) form a substantially right-angled corner portion (403) at an end of the second parallel extension portion (441) on the first circuit board (3) side, and an extension line (L) of the second parallel extension portion (441) when the second circuit board (4) is viewed from a direction perpendicular to the ceramic substrate (2). 441 ) and the extension line (L) of the second cross-direction extending portion (442) 442 ) is defined as a second intersection point (440), the extension line (L) of the second intersecting direction extending portion (442) from the second intersection point (440) is 442 ) at a position 1 mm away from the second cross-direction extending portion (442) along the 442 ) is 0.36 mm or more.

[0070] [7] The side width (W 442 ) is 0.36 mm or more and 0.60 mm or less throughout the ceramic circuit board (1) according to [6] above.

[0071] The invention made by the inventor has been specifically described above based on the embodiments thereof, but it goes without saying that the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the invention. [Explanation of symbols]

[0072] 1...Ceramic circuit board 2...Ceramic substrate 2a...One side 2b...the other side 3...First circuit board 4...Second circuit board 5...Heat sink 33,43...Side 34...First opposing portion 35...First non-opposing portion 44...Second opposing portion 45...Second non-opposing portion 53...Side 303...Corner 340...First intersection 341...Arrangement direction extension part 342...Tip side cross direction extension part 343…Proximal side cross direction extension part 403...Corner 440...Second intersection 441...Line-up direction extension part 442...Tip side cross direction extension part 443...Proximal side cross direction extension part L 341 ,L 342 ,L 441 ,L 442 …extension line W 33 ,W 34 ,W 35 ,W 43 ,W 44 ,W 45 ,W 53 …Side width W 341 ,W 342 ,W 343 ,W 441 ,W 442 ,W 443 …Side width

Claims

1. a ceramic substrate; and a first circuit board and a second circuit board bonded to one surface of the ceramic substrate; the first circuit board and the second circuit board have respective side surfaces inclined with respect to a direction perpendicular to the ceramic substrate; the side surface of the first circuit board has a first facing portion facing the side surface of the second circuit board and a first non-facing portion not facing the side surface of the second circuit board; When the width of the side surface as viewed in a direction perpendicular to the ceramic substrate is defined as a side surface width, the side surface width of the first non-facing portion of the first circuit board is narrower than the side surface width of the first facing portion. Ceramic circuit board.

2. the side surface of the second circuit board has a second facing portion facing the side surface of the first circuit board and a second non-facing portion not facing the side surface of the first circuit board; a side width of the second non-opposing portion of the second circuit board is narrower than a side width of the second opposing portion; The ceramic circuit board according to claim 1 .

3. a heat sink bonded to the other surface of the ceramic substrate; a side surface of the heat sink is inclined with respect to a direction perpendicular to the ceramic substrate; a side width of the side surface of the heat sink is narrower than a side width of the first opposing portion; 3. The ceramic circuit board according to claim 1 or 2.

4. the first opposing portion of the first circuit board has a first alignment direction extending portion that extends along an alignment direction of the first circuit board and the second circuit board, and a first intersecting direction extending portion that extends in a direction intersecting the alignment direction; the first alignment direction extending portion and the first intersecting direction extending portion form a substantially right-angled corner at an end portion of the first alignment direction extending portion on the second circuit board side, When the first circuit board is viewed in a direction perpendicular to the ceramic substrate, a point where an extension line of the first alignment direction extending portion intersects with an extension line of the first intersecting direction extending portion is defined as a first intersection point, and a side width of the first intersecting direction extending portion at a position 1 mm away from the first intersection point along the extension line of the first intersecting direction extending portion toward the first intersecting direction extending portion is 0.36 mm or more. The ceramic circuit board according to claim 1 .

5. The side width of the first intersecting direction extending portion is 0.36 mm or more and 0.60 mm or less throughout. The ceramic circuit board according to claim 4.

6. the second opposing portion of the second circuit board has a second alignment direction extending portion that extends along an alignment direction of the first circuit board and the second circuit board, and a second intersecting direction extending portion that extends in a direction intersecting the alignment direction; the second alignment direction extending portion and the second intersecting direction extending portion form a substantially right-angled corner at an end of the second alignment direction extending portion on the first circuit board side, when the point at which an extension line of the second alignment direction extending portion intersects with an extension line of the second intersecting direction extending portion when the second circuit board is viewed in a direction perpendicular to the ceramic substrate is defined as a second intersection point, a side width of the second intersecting direction extending portion at a position 1 mm away from the second intersection point along the extension line of the second intersecting direction extending portion toward the second intersecting direction extending portion is 0.36 mm or more; The ceramic circuit board according to claim 2 .

7. The side width of the second intersecting direction extending portion is 0.36 mm or more and 0.60 mm or less throughout. The ceramic circuit board according to claim 6.

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