JP2005116843A - Metallic plate circuit and ceramic circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve heat and shock resistance against heat and shock which may be repeatedly applied to a ceramic circuit board, and to provide a metallic plate circuit which can prevent a short circuit of a current among a plurality of metallic plates constituting the metallic plate circuit and the ceramic circuit board using the metallic plate circuit. <P>SOLUTION: The metallic plate circuit is provided with a bottom which is to be joined with a ceramic substrate and an upper surface which becomes a circuit face and having thickness T formed by a mechanical processing means. Respective metallic plates are integrated through respective bridge parts whose thickness t is narrower than the thickness T of the metallic plate circuit, and vertical wall surfaces erected from the bottom and inclined wall surfaces which are inclined upward from the upper ends of respective vertical wall surfaces in the upper surface direction are formed on the side faces of the metallic plate circuit. After brazing the metallic plate circuit to the main surface of the ceramic substrate, respective bridge parts are removed to constitute the ceramic circuit board. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a ceramic circuit board, in particular, a circuit metal plate to be a conductive circuit board used for a power semiconductor module, and a ceramic circuit board in which the circuit metal plate is joined by brazing.

  As a substrate used for a power semiconductor module, a conductive metal plate to be a circuit is joined to one surface (main surface) of an insulating ceramic substrate made of aluminum nitride or silicon nitride, and the other surface is also used for heat dissipation. Ceramic circuit boards joined with metal plates are widely used. As this metal plate, a copper plate or an aluminum plate is used. And a semiconductor chip etc. are connected to the upper surface of the conductive metal plate used as a circuit. In addition, an active metal method using a brazing material is widely used for joining the ceramic substrate and the metal plate.

  In recent years, power semiconductor modules (IGBT, MOS FET, etc.) capable of high voltage and large current operation are used as inverters for electric vehicles. In such a high power module, the amount of heat generated from a semiconductor chip connected to a metal plate such as a copper plate serving as a circuit also increases. As a result, the thermal stress repeatedly generated on the ceramic circuit board is also increased. If it becomes impossible to withstand this thermal stress, problems such as warping and cracking will occur in the ceramic substrate. A ceramic substrate made of aluminum nitride or silicon nitride has excellent electrical insulation and thermal conductivity, but as described above, a highly reliable ceramic circuit that can further cope with thermal shocks repeatedly applied to the ceramic circuit substrate. Substrate development is required.

  Conventionally, various improved techniques have been proposed for ceramic circuit boards that can cope with the repeated thermal shock as described above. For example, the following patent documents have been proposed.

Japanese Patent No. 2797011 (Specifications, pages 2 to 4, FIG. 1) Japanese Patent Application Laid-Open No. 11-340598 (Specifications, pages 3 to 5, FIGS. 1, 2, and 4) Japanese Patent Laid-Open No. 11-322455 (specifications, pages 2 to 4, FIG. 3) Japanese Patent Laid-Open No. 3-21095 (Specifications, pages 2 to 3, FIGS. 1 and 5) JP-A-4-96258 (Specifications, pages 3 to 6, FIGS. 1 to 6) Japanese Patent Laid-Open No. 11-4061 (Specifications, pages 2 to 4, FIGS. 1 and 3) JP-A-2002-359453 (specifications, pages 12 to 13, FIGS. 12 and 14)

  Patent Document 1 discloses a ceramic member surface for suppressing cracking due to thermal shock in an insulating substrate for mounting an electronic component composed of a joined body of an alumina or aluminum nitride ceramic member and a copper or copper alloy metal member. There is described a joined body in which a fillet (exposed member of brazing material) surrounding the periphery of a metal member with a width of at least 0.25 mm or more is formed by a firing paste.

  In Patent Document 2, for the purpose of providing a ceramic circuit board that can be bent greatly without causing breakage or breakage, a metal plate is joined to at least the main surface of the ceramic substrate via a brazing material layer, In a ceramic circuit board in which a predetermined metal circuit pattern is formed by etching a metal plate, a ceramic circuit board in which a brazing material layer is formed so as to protrude outward from the side surface of the metal circuit pattern is described. Yes. Further, Patent Document 2 describes that the stress on the side surface of the metal circuit pattern is reduced by forming a smooth curved inclined surface by an etching process, thereby reducing the concentrated stress acting on the joint end.

  In Patent Document 3, for the purpose of providing a ceramic / metal joined body having excellent thermal shock resistance, the end of the metal plate is inclined so that the end surface approaches the ceramic substrate side as it goes to the edge of the metal plate. In addition, a ceramic / metal joined body is described in which the shape of the end face cut along a plane perpendicular to the metal plate is convex toward the ceramic substrate side.

  In Patent Document 4, a punched circuit pattern in which adjacent circuit conductors are connected by a thin bridge is formed by punching for the purpose of ease of manufacture and improvement of unevenness on the surface of the circuit board. A method of manufacturing a high-current circuit board is described in which a pattern and a prepreg sheet are laminated, hot pressed and pressed to embed a punched circuit pattern on an insulating substrate surface, and then the bridge is cut.

  In Patent Document 5, for the purpose of providing a method of manufacturing an insulating substrate for a semiconductor device that can be manufactured with high dimensional accuracy and at low cost, it has a planar shape corresponding to each part of a circuit pattern and is relatively thick. A metal pattern plate in which a plurality of formed main body portions and the plurality of main body portions are connected to each other and a relatively thin connection portion is integrated is fixed on an insulating film. Thereafter, a method for manufacturing an insulating substrate in which the thinly formed connection portion is removed is described. Further, it is described that this connection portion is removed by etching or mechanical cutting.

  Patent Document 6 discloses a circuit board manufacturing method that enables manufacturing with a small-scale processing facility by forming a circuit pattern by mechanical processing, and that facilitates circuit changes and small-scale manufacturing. For the purpose of providing a circuit board, a circuit pattern is formed by separating a plurality of wiring paths that form a desired circuit by dividing a conductor plate into a groove shape, and the circuit board is manufactured by joining the conductor plate to a base material. A method is described. Further, in Patent Document 6, the dividing band is formed by connecting openings by perforation, and the formation of the dividing band is interrupted at an arbitrary position to form a bridging portion that partially connects the separated wiring paths. In addition, it is described that the bridging portion is removed after the conductor plate is joined to the base plate.

  In Patent Document 7, the etching residue remaining on the insulating substrate can be easily removed, and the warpage of the entire joined body can be controlled so that a metal cooling fin or the like can be firmly fixed. For the purpose of providing a circuit board, when a metal plate is pressed to form a circuit pattern, a bridge that connects the circuits is also formed. After the metal plate is joined to the insulating board, the bridge is punched. Alternatively, cutting using a nipper or the like is described.

  In the inventions described in Patent Document 1 and Patent Document 2, when a circuit metal plate is connected to a ceramic substrate via a brazing material, the brazing material has a predetermined length from the side surface (end surface) of the circuit metal plate. By providing the protruding portion, the concentration of thermal stress on the joint surface between the ceramic substrate and the end surface of the circuit metal plate is alleviated. Further, in the invention described in Patent Document 2, the end surface of the circuit metal plate is smoothed. It is intended to further reduce the concentration of thermal stress by inclining into a curved surface.

  However, ceramic circuit boards used in power semiconductor modules are strongly required to simplify manufacturing processes and reduce manufacturing costs, in addition to improving thermal conductivity and strength against thermal shock. For this purpose, in forming a pattern of a circuit metal plate to be bonded to a ceramic substrate, the shape of the circuit metal plate that can eliminate the time-consuming etching process as much as possible and the manufacturing method thereof are important. Patent Document 1 and Patent Document 2 do not describe a manufacturing method and shape of a circuit metal plate that simplifies such a manufacturing process.

  Patent Document 2 and Patent Document 3 describe that an inclined surface is formed on a side surface of a circuit metal plate by an etching process, and this inclined surface prevents stress concentration on the end surfaces of the ceramic substrate and the circuit metal plate. Has been. However, when an inclined surface is formed on the side surface of the circuit metal plate by the etching process, the linearity is lowered at the lower end portion of the inclined surface, which becomes a bonding boundary line with the ceramic substrate, and fine irregularities are generated. In recent ceramic circuit boards, improvement in integration density is also required, and the interval between a plurality of circuit metal plates is required to be set to 1.5 mm or less. When such a minute interval and the inclined surface are formed by etching, the linearity is lowered due to the occurrence of the unevenness as described above, and there is a risk that a short circuit of current occurs during use. Furthermore, an expensive photoresist device is also required, resulting in a complicated manufacturing process and high cost.

The inventions described in Patent Documents 4 to 7 are manufactured by punching a plurality of circuit metal plates connected at a bridging portion, and joining the circuit metal plate to a substrate such as ceramics. Is cut using an etching process or a tool such as a nipper. However, these patent documents do not describe that an inclined surface is formed on the end surface portion of the circuit metal plate to reduce thermal stress.
Patent Document 7 discloses a method of efficiently removing the brazing material layer using sandblasting, but in this case, the protruding portion of the brazing material cannot be formed.

  The object of the present invention is to improve the thermal stress resistance of a conventional ceramic circuit board, to prevent a short circuit of current between a plurality of metal plates constituting a circuit metal plate, and to simplify the manufacturing process for manufacturing. An object of the present invention is to provide a circuit metal plate and a ceramic circuit board using the circuit metal plate, which can further reduce the cost.

The present invention is a circuit metal plate having a thickness T, which is formed by mechanical processing means and includes a bottom surface bonded to a ceramic substrate and an upper surface serving as a circuit surface. It is integrated through a narrow bridging portion with a smaller thickness t, and on the side surface of the circuit metal plate, there is a vertical wall surface standing from the bottom surface, and an upward slope from the upper end of the vertical wall surface toward the upper surface direction. It is the metal plate for circuits provided with the inclined wall surface which becomes.
Furthermore, the metal plate for a circuit of the present invention is a metal plate having a flat surface parallel to the bottom surface between the vertical wall surface and the inclined wall surface. The metal plate for circuit of the present invention is made of a kind of material such as copper, copper alloy, aluminum, and aluminum alloy. In particular, when copper is used, it is desirable to use oxygen-free copper having high copper purity.

  Furthermore, the circuit metal plate of the present invention is configured such that the total volume of the bridging portion formed on the circuit metal plate is 0.1 to 2% of the total volume of the entire circuit metal plate including the circuit surface. In addition, the circuit metal plate is configured such that (thickness T of the circuit metal plate) − (thickness t of the bridging portion) is equal to or greater than 0.1 mm. .

  The circuit metal plate of the present invention is a circuit metal plate provided with alignment means for aligning the ceramic substrate and the circuit metal plate when bonded to the ceramic substrate. As the alignment means, a means constituted by an alignment protrusion protruding from the side surface of the circuit metal plate in the outward direction of the circuit metal plate, or a means constituted by a hole formed in the bridging portion, Or it is a metal plate for circuits provided with both the means comprised from these alignment protrusion parts, and the means comprised from the hole formed in the bridge | bridging part.

  Furthermore, the present invention is a ceramic circuit board in which the circuit metal plate having the above-described structure is bonded to the ceramic substrate via a brazing material layer, and after the circuit metal plate is bonded to the ceramic substrate, It is the ceramic circuit board which is the structure from which the alignment protrusion part was removed. Further, in the ceramic circuit board of the present invention, a ceramic circuit board in which an inclined wall surface along the inclined wall surface of the circuit metal plate or a remaining surface other than the inclined wall surface is formed on the removal trace of the bridge portion and the alignment protrusion portion. It is.

  The ceramic substrate constituting the ceramic circuit board of the present invention uses a ceramic material having high thermal conductivity such as silicon nitride and aluminum nitride.

  The circuit metal plate of the present invention has a structure in which a vertical wall surface and an inclined wall surface are formed on the side surface, or a structure in which a flat surface is formed between the vertical wall surface and the inclined wall surface. By setting it as such a structure, the thermal stress which arises in a ceramic substrate can be disperse | distributed. For example, the stress generated in the ceramic substrate in the vicinity of the end portion was simulated for the example including the vertical wall surface, the flat surface, and the inclined wall surface shown in FIG. That is, the stress reduction was observed when the length r of the flat portion was 0.3 mm, the thickness t of the vertical portion was changed, and a simple rectangular end portion having no vertical wall surface and inclined wall surface was defined as 100. As a result, the thermal stress was 98.6% when t was 0.3 mm, and 88.5% when t was 0.1 mm. The stress reduction effect was able to be confirmed by the above.

  Next, in the metal plate for a circuit of the present invention, the reason why (metal plate thickness T) − (crosslinked portion thickness t) is limited to 0.1 mm or more is as follows. (Tt) is a gap formed under the bridge portion. When the ceramic substrate and the metal plate are joined by brazing, the brazing material oozes out between the ceramic substrate and the metal plate. When the exuded brazing material comes into contact with the lower surface of the bridging portion, it spreads over the lower surface as it is, and a pool portion of the exuding brazing material is formed on the lower surface of the bridging portion. Such a brazing material reservoir may be 0.1 mm or more. Then, when the gap is 0.1 mm or less, the brazing material pool comes into contact with the ceramic substrate, resulting in contact with the adjacent metal plate and causing a short circuit. For this reason, by securing a gap of 0.1 mm or more, even if the brazing material is transmitted to the lower surface of the bridging portion, the brazing material does not contact the ceramic substrate and can prevent a short circuit.

Furthermore, the reason why the total volume of the plurality of bridging portions is limited to 0.1 to 2% of the total volume of the plurality of metal plates to be a circuit is as follows. That is, the thickness of the metal plate for a circuit used in the present invention is a thin plate made of copper or copper alloy having a thickness of 0.2 mm to 1.0 mm. For this reason, if the total volume of the bridging portion is less than 0.1% of the total volume of the metal plate serving as a circuit, the rigidity of the bridging portion decreases. For this reason, distortion occurs in the bridging portion during the heat treatment when joining the metal plate to the ceramic substrate, and the wiring interval of the plurality of metal plates connected at the bridging portion cannot be maintained, resulting in a short circuit or dimension. This is because there is a risk that defects will occur. In order to prevent the occurrence of this short circuit or dimension failure, it is necessary to provide positioning means for the metal plate at the time of joining.
On the other hand, if it exceeds 2%, the above (metal plate thickness T)-(crosslinked portion thickness t) cannot be secured to 0.1 mm or more, and the exuded brazing material contacts the lower surface of the crosslinked portion. This is because it spreads and causes a short circuit between the metal plates, and increases the man-hours for removing the thick bridge portion.

The present invention has the following effects.
(1) Since the circuit metal plate of the present invention is manufactured by mechanical processing means such as press processing, the manufacturing cost and the number of manufacturing steps can be significantly reduced as compared with the conventional method using etching. Furthermore, since the vertical wall surface formed on the side surface of the circuit board is formed by plastic compression or press cutting using a press, the linearity of the side surface is greatly improved. Thereby, since the wiring space | interval between the metal plates for circuits can be ensured, the ceramic circuit board which does not produce a short circuit between circuits can be provided.

(2) Since the vertical wall surface and the inclined wall surface formed on the side surface of the circuit metal plate perform the action of dispersing the thermal stress generated in the ceramic substrate, even if the ceramic circuit substrate of the present invention is used as a power semiconductor module, It is possible to prevent the occurrence of cracks due to repeated thermal stress.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. 1-3 is a figure which shows 1st Embodiment about the metal plate for circuits of this invention, and each shows a top view, an AA longitudinal cross-sectional view, and a BB longitudinal cross-section.

  1 to 3, a circuit metal plate 1 according to the present invention is a thin plate 2 (FIG. 4A) made of a conductive metal having a thickness T of 0.2 to 1.0 mm, for example, oxygen-free copper (C1020). ), And is formed by mechanical processing means such as press working, and the three metal plates 3, 4, 5 are connected via a plurality of narrow bridge portions 6a, 6b, 6c, 6d. It is made up of. That is, between the three metal plates 3, 4, and 5, the portions other than the bridging portions 6 a, 6 b, 6 c, and 6 d are punched to form a linear gap 7. The gap 7 has an interval K, which is a wiring interval (hereinafter referred to as a wiring interval K) between the metal plates 3, 4 and 5 serving as a circuit surface. Although the wiring interval K varies depending on the product specifications, when the metal plates 3, 4, and 5 need to be arranged at high density, it is necessary to set the wiring interval K to 1.2 to 1.5 mm. As a material of the circuit metal plate 1, in addition to the oxygen-free copper, a copper alloy, aluminum, or an aluminum alloy can be used, but the oxygen-free copper is preferably used. This is because when the circuit metal plate 1 is joined to the ceramic substrate with the brazing material, the brazing material is not oxidized by the oxygen contained in the circuit metal plate 1, so that the ceramic substrate 9 (shown in FIG. 5). This is because the circuit metal plate 1 can be firmly brazed.

As shown in FIG. 2, the thickness t of the bridging portion 6a (6b, 6c, 6d) is 1/4 to 1/1 of the thickness T of the circuit metal plate 1 composed of the metal plates 3, 4, and 5. The length L is about 2 and is the same as the wiring interval K between the metal plates 3, 4, 5, and needs to be, for example, 1.2 to 1.5 mm. The width W (length in the direction orthogonal to the length L) of the bridging portion 6a (6b, 6c, 6d) is preferably 1.5 to 3 mm in order to maintain an appropriate strength in consideration of the plate thickness T. . Further, the number of bridging portions connecting the adjacent metal plates 3, 4, 5 is 1 in consideration of the thickness T of the circuit metal plate 1 and the shape of these three metal plates 3, 4, 5. One or more are provided. The number and shape of the metal plates 3, 4, 5, etc. are determined based on the design specifications of the ceramic circuit board. However, it is desirable to avoid the corners of each metal plate for the arrangement of each bridging part. This is because the corner is the site where the maximum stress occurs.

The upper surfaces 3a, 4a and 5a of the metal plates 3, 4 and 5 formed in three divisions become circuit surfaces and are connected to semiconductor chips and the like, and the bottom surfaces 3b, 4b and 5b are ceramic substrates 9 (shown in FIG. 5). ) And brazed joint surface. Vertical wall surfaces 3c, 4c, and 5c standing from the bottom surfaces 3b, 4b, and 5b are formed on the side surfaces of the metal plates 3, 4, and 5, and the upper surface 3a from the upper end of the vertical wall surfaces 3c, 4c, and 5c. Inclined wall surfaces 3d, 4d, and 5d that are inclined upward in the 4a and 5a directions are formed. The vertical wall surfaces 3c, 4c and 5c are formed so as to rise vertically or substantially vertically from the bottom surfaces 3b, 4b and 5b. On the other hand, the inclined wall surfaces 3d, 4d, and 5d are set such that the inclination angle α formed with the vertical direction of the bottom surfaces 3b, 4b, and 5b is 5 ° to 45 °. In addition, said upward inclination means that each area of upper surface 3a, 4a, 5a inclines so that it may become smaller than each area of bottom face 3b, 4b, 5b. The vertical wall surfaces 3c, 4c, and 5c and the inclined wall surfaces 3d, 4d, and 5d are formed on all side surfaces of the metal plates 3, 4, and 5 except for the connection portions with the bridging portions 6a, 6b, 6c, and 6d. . The height T1 of the vertical wall surfaces 3c, 4c, and 5c is preferably 0.1T to 0.3T, where T is the thickness of the circuit metal plate 1. In the present invention, after the circuit metal plate 1 is brazed to the ceramic substrate 9, the bridging portions 6a, 6b, 6c, 6d are removed.

  Furthermore, as shown in FIG. 1, the circuit metal plate 1 of the present invention has alignment protrusions 8a and 8b formed on the outer surface of the circuit metal plate 1 having a substantially rectangular shape. The alignment protrusions 8a and 8b perform alignment when the circuit metal plate 1 is brazed to the ceramic substrate 9, and the distance D1 or the outward direction from the side surface of the circuit metal plate 1 A protruding length of D2 is provided. In the example shown in FIG. 1, the positions where these alignment protrusions are formed are shown as examples in which one is formed on each of the adjacent outer surfaces of the substantially rectangular circuit metal plate 1. One or a plurality of alignment protrusions may be formed on an arbitrary outer surface of the circuit metal plate 1 based on the specifications of an apparatus (a jig) for brazing the circuit metal plate 1. In addition, after the circuit metal plate 1 is brazed to the ceramic substrate 9, the alignment protrusions 8a and 8b are removed.

  In the present invention, the mechanical processing means indicates punching by a press device, plastic compression processing, or the like. Using these processing means, the circuit metal plate 1 can be manufactured from the metal thin plate 2 made of oxygen-free copper shown in FIG. 4A by the following procedure.

Several types of molds having the shapes of the upper surface portion, the bottom surface portion, and the side surface portion of the metal plate for circuit 1 shown in FIG. 2 are prepared, and manufactured by the following processing procedure using a press device, for example.
(step 1)
From the rectangular thin metal plate 2 shown in FIG. 4 (a), as shown in FIG. 4 (b), protrusions 8c and 8d are formed on the outer surface by punching, and the wiring interval K is formed by press cutting. The original form of the circuit metal plate 1 in which the three metal plates 3, 4, 5 are connected by the bridging portions 6a, 6b, 6c, 6d is manufactured. Subsequently, after the projecting portions 8c and 8d and the bridging portions 6a, 6b, 6c and 6d are compressed to a thickness of t by plastic compression, the projecting portions 8c and 8d have a predetermined projecting length. Then, the bridging portions 6a, 6b, 6c and 6d are processed so that the width W becomes a predetermined value.

(Procedure 2)
The side surfaces of the metal plates 3, 4 and 5 are subjected to plastic compression, and as shown in FIGS. 4C and 4D, inclined wall surfaces 3d, 4d and 5d are provided on the side surfaces of the metal plates 3, 4 and 5, respectively. Form. At the same time, by using plastic deformation, protrusions provided with flat portions 3e, 4e, 5e and vertical wall surfaces 3f, 4f, 5f at the ends of the bottom surfaces 3b, 4b, 5b of the metal plates 3, 4, 5 3g, 4g, 5g are formed. The length of the flat portions 3e, 4e, and 5e (the protruding lengths of the protruding portions 3g, 4g, and 5g) r may be about 0.2 mm to 0.4 mm. The flat portions 3e, 4e, and 5e are formed so as to be parallel or substantially parallel to the bottom surfaces 3b, 4b, and 5b.

(Procedure 3)
The protrusions 3g, 4g, and 5g are press-cut to form vertical wall surfaces 3c, 4c, and 5c as shown in FIG. By forming the vertical wall surfaces 3c, 4c, and 5c by press cutting in this manner, the side surfaces of the metal plates 3, 4, and 5 are linear with extremely high accuracy, so that the wiring interval K with high dimensional accuracy is ensured. It becomes possible.

(Procedure 4)
Cut so that the protruding lengths of the alignment protrusions 8c and 8d are D1 and D2. As a result, as shown in FIG. 2, the joint surfaces 3a, 4a, 5a of the metal plates 3, 4, 5 with the semiconductor chip are coplanar, except for the bridging portions 6a, 6b, 6c, 6d, The circuit metal plate 1 shown in FIG. 1 in which the vertical wall surfaces 3c, 4c, and 5c and the inclined wall surfaces 3d, 4d, and 5d are formed on the side surfaces of the metal plates 3, 4, and 5 can be obtained.

  In the ceramic circuit board of the present invention, as shown in FIG. 5, a metal plate 13 made of oxygen-free copper or the like is brazed to the heat radiating side surface (back surface) of the ceramic substrate 9. The metal plate 13 does not need to form a plurality of metal plates 3, 4, and 5 like the circuit metal plate 1, but the vertical wall surface 13 c, the inclined wall surface 13 d, Alignment protrusions 8a and 8b (not shown) are formed.

  Next, a configuration example of the ceramic circuit board of the present invention will be described with reference to FIG. In FIG. 5, 9 is a ceramic substrate made of silicon nitride having a thickness of 0.2 to 1.0 mm and a thermal conductivity of 70 W / m · K or more. On one surface (main surface) of the ceramic substrate 9, metal plates 3, 4, 5 constituting the circuit metal plate 1 of the present invention are joined via brazing material layers 10, 11, 12. At this time, the ceramic substrate 9 and the metal plates 3, 4, 5 are joined by joining the joint surfaces 3 b, 4 b, 5 b of the metal plates 3, 4, 5 to the main surface of the ceramic substrate 9. That is, the metal plates 3, 4, and 5 are bonded to the ceramic substrate 9 at the bonding surfaces (bottom surfaces) 3 b, 4 b, and 5 b that are surfaces that increase the bonding area. Note that the thickness S of the brazing filler metal layers 10, 11 and 12 is preferably 5 to 50 μm.

  On the other hand, a flat metal plate (copper plate) 13 is bonded to the other surface of the ceramic substrate 9 (the lower surface on the heat dissipation side) via a brazing material layer 14. The copper plate 13 is also formed with a vertical wall surface 13 c and an inclined wall surface 13 d on the entire circumference of the side surface, and a surface 13 b with a large surface area of the copper plate 13 is joined to the lower surface of the ceramic substrate 9. The vertical wall surface 13c and the inclined wall surface 13d are formed by the above-described mechanical processing means, for example, a press device, and the inclination angle of the inclined wall surface 13d is 5 ° to 45 ° similarly to the inclination angle α of the inclined wall surfaces 3a, 4a, and 5a. (CAE) should be set. The thickness of the brazing material layer 14 is preferably 5 to 50 μm.

  In the ceramic circuit board of the present invention, when the metal plates 3, 4, 5, and the copper plate 13 are joined to the ceramic substrate 9 by the brazing material layer, the brazing material layers 10, 11, 12, and 14 are made of each metal. It is preferable to protrude from the side surfaces of the rotating plates 3, 4, 5 and the copper plate 13 by a predetermined distance H. When the protruding length H is at least 0.2 mm or more, preferably 0.25 to 0.5 mm, the ceramic substrate 9 and the metal plates 3, 4, 5 are used when the ceramic circuit board of the present invention is used. And thermal stress concentrated on the side surface of the copper plate 13 can be relaxed. Furthermore, in the present invention, since the vertical wall surfaces 3c, 4c, 5c, and 13c and the inclined wall surfaces 3d, 4d, 5d, and 13d are formed on the side surfaces of the respective metal plates 3, 4, 5, and 13, the ceramic substrate 9 and the thermal stress concentrated on the side surfaces of the metal plates 3, 4, 5 and the copper plate 13 can be relaxed.

  The brazing materials 10, 11, 12, and 14 can be applied to the ceramic substrate 9 by screen printing. However, the brazing materials 10, 11, 12, and 14 can be applied directly to the surface of the metal plates 3, 4, 5, and 13 on the ceramic substrate side. May be formed.

  In the circuit metal plate 1 of the present invention described above, as shown in FIG. 8A, the thickness of the circuit metal plate 1 is T, and the thickness of each bridging portion 6a (6b, 6c, 6d) is t. In this case, it is important to set the gap t1 = (T−t) to 0.1 mm or more. The reason for this is as follows. As the metal plate for circuit 1 used in the present invention, a thin plate made of oxygen-free copper or the like having a thickness of 0.2 mm to 1.0 mm is used. Therefore, when the gap t1 is smaller than 0.1 mm, when the ceramic substrate 9 and the circuit metal plate 1 are heat-bonded by brazing, for example, as shown in FIG. 8B, the ceramic substrate 9 and the metal plate 3 ( 4 and 5), the brazing filler metal 15 oozing out from the brazing filler metal layer 10 (11, 12) extends while connecting to the lower surface 60a of the bridging portion 6a (6b, 6c, 6d), and the brazing material is accumulated. There are things to do. Then, it finally flows along the gap t1 on the ceramic substrate 9, and when this progresses, it contacts the adjacent metal plate 4 and causes a short circuit.

Furthermore, in the circuit metal plate 1 of the present invention, the total volume of the plurality of bridging portions 6a, 6b, 6c, 6d is 0. 0 of the volume of all the circuit metal plates 3, 4, 5 including the circuit portion. It is important to make it 1 to 2%. The reason is as follows.
The metal plate for circuit 1 used for the ceramic circuit board of the present invention uses a copper thin plate having a thickness of 0.2 mm to 1.0 mm and low rigidity as described above. For this reason, when the total volume of the bridging portions 6a, 6b, 6c, 6d is less than 0.1% of the total volume of the metal plates 3, 4, 5 serving as a circuit, the rigidity of the bridging portions 6a, 6b, 6c, 6d is remarkably high. Since the metal plate 3, 4, 5 is brazed to the ceramic substrate 9 between the plurality of metal plates 3, 4, 5 connected by the bridging portions 6 a, 6 b, 6 c, 6 d. This is because the wiring interval K cannot be maintained, and there is a risk that a short circuit or a dimensional defect of the wiring interval K occurs. In order to prevent the occurrence of a dimensional defect of the wiring interval K, it is necessary to provide positioning means for each metal plate at the time of joining. However, in order to automate this positioning, expensive equipment is required.

  Further, if the total volume of the bridging portion is larger than 2%, it becomes difficult to secure the gap t1 of 0.1 mm or more, and the brazing filler metal 15 that has exuded is formed between the bridging portions 6a, 6b, 6c, 6d and the ceramic substrate 8. Since it flows along the gap, it causes a short circuit between the metal plates 3, 4, 5, and the number of work steps for removing the bridging portions 6 a, 6 b, 6 c, 6 d to which the brazing material has adhered increases. This is because a process for removing the brazing filler metal 15 accumulated in the portion where the brazing filler metal has exuded by an interval H is required.

  Furthermore, in the ceramic circuit board of the present invention, as shown in FIGS. 8A and 8B, the wiring interval K between the adjacent metal plates 3, 4 and 5 is preferably 1.3 mm or more, The interval P between the end portions of the brazing filler metal layer protruding into the wiring interval K is preferably set to 0.8 mm or more. The reason for this is that if the thickness S of the brazing filler metal layers 10, 11, 12 applied to the ceramic substrate 9 is 5 to 50 μm, the exuded brazing filler metal 15 can be prevented from flowing out and coming into contact with the adjacent brazing filler metal layer. Because it becomes like this.

  Then, the manufacturing method of the ceramic circuit board of this invention is demonstrated. First, a ceramic substrate 9 having a dimension slightly larger than the vertical and horizontal dimensions of the circuit metal plate 1 having a substantially rectangular shape as shown in FIG. 1 is prepared. The ceramic substrate 9 can be manufactured by the following method. First, a thin green sheet mainly composed of silicon nitride is manufactured by a known doctor blade method or the like. Subsequently, after degreasing and sintering the green sheet, the ceramic substrate 9 having a thickness of 0.2 to 1.0 mm can be obtained by cutting the green sheet into a desired size, for example, 80 mm × 100 mm. it can.

  Next, as shown in FIG. 6, brazing material layers 10, 11, and 12 having a thickness of 5 to 50 μm are applied to the main surface of the ceramic substrate 9 by screen printing. At this time, the range in which the brazing material is applied to the main surface of the ceramic substrate 9 is applied so as to protrude outward by an interval H, that is, 0.2 to 1.2 mm from the range in which the metal plates 3, 4, and 5 are joined. Similarly, the brazing material layer 14 is applied to the heat radiation side surface (back surface) of the ceramic substrate 9.

  Subsequently, as shown in FIG. 7, the circuit metal plate 1 shown in FIG. 1 is accurately aligned with the main surface of the ceramic substrate 9 coated with the brazing material, and the copper plate 13 is accurately aligned with the heat radiation side surface of the ceramic substrate 9. And hold | maintain in a pressurized state. At this time, circuit metal is respectively provided on the front and back surfaces of the ceramic substrate 9 so that the brazing filler metal layers 10, 11, 12, and 14 protrude from the entire circumference of the side surfaces of the metal plates 3, 4, 5 and the copper plate 13 by the distance H It is necessary to accurately position the plate 1 and the copper plate 13. Furthermore, when the circuit metal plate 1 is aligned with the ceramic substrate 9, predetermined distances D1 and D2 are secured between the side surfaces of the metal plates 3, 4, and 5 and the side surface of the ceramic substrate 7. Need to be aligned. In the present invention, the ceramic substrate 9, the circuit metal plate 1, and the copper plate 13 are aligned using alignment means such as alignment protrusions 8a and 8b.

Next, alignment means for brazing the circuit metal plate 1 and the copper plate 13 to the ceramic substrate 9 will be described. This alignment can be performed according to the following procedures 1-5.

(Positioning procedure 1)
First, as shown in FIG. 9A, an alignment jig 18 provided with vertical walls 16 and 17 extending in the vertical direction along adjacent side surfaces of the ceramic substrate 9 is prepared. Then, the tips of the positioning projections 8a and 8b formed on the metal plate 13 to be brazed to the heat radiating side are in contact with the inner wall surfaces 16a and 17a of the jig 18 as shown in FIG. As shown, it is placed on the bottom 18 a of the alignment jig 18.

(Positioning procedure 2)
Subsequently, the adjacent side surfaces of the ceramic substrate 9 coated with the brazing filler metal layers 10, 11, 12, and 14 are placed on the copper plate 13 in a state where the side surfaces are in contact with the inner wall surfaces 16 a and 17 a of the alignment jig 18. Thereby, the metal plate 13 and the ceramic substrate 9 can be overlapped in a state where the alignment is performed accurately.

(Positioning procedure 3)
Subsequently, the tip ends of the alignment protrusions 8 a and 8 b provided on the side surface of the circuit metal plate 1 are overlaid on the ceramic substrate 9 in a state of being in contact with the inner wall surfaces 16 a and 17 a of the jig 18. Accordingly, the circuit metal plate 1 can be accurately superimposed on the main surface of the ceramic substrate 9 in a state in which the intervals D1 and D2 shown in FIG. 7 and the protruding interval H of the brazing material are secured.

(Alignment procedure 4)
A spacer plate 19 is placed on the aligned circuit metal plate 1. The spacer plate 19 may be a thin carbon plate having heat resistance and a low coefficient of thermal expansion.

(Alignment procedure 5)
Next, the above alignment procedures 1 to 4 are repeated several times, and the ceramic substrate 9 in which the metal plate 1 for circuit is superimposed on the main surface (upper surface) and the metal plate 13 is superimposed on the lower surface is positioned via the spacer plate 19. The stacking jig 18 is stacked in several stages and is held using a clamping device or the like so that a pressing force acts in the vertical direction of the stack. Then, after heating these stacked ceramic substrates 9 in a pressurized state at a temperature of about 800 ° C. for a predetermined time and then cooling, the circuit board metal plate 1 is dissipated on the main surface of the ceramic substrate 9. The metal plate 13 can be joined to the side surface via a brazing material layer.

  Subsequently, the bridge portions 6a, 6b, 6c and 6d provided on the circuit metal plate 1 and the alignment projections 8a and 8b of the circuit metal plate 1 and the metal plate 13 are replaced with numerically controlled machine tools. When used and removed with an ultra-fine end mill tool, a ceramic circuit board as shown in FIG. 5 can be obtained. When removing the bridging portion 6a and the like with the end mill tool, the bridging portions 6a, 6b, 6c and 6d and the alignment projections 8a and 8b are connected to the metal plates 3, 4 and 5, that is, the bridging portion. The removal marks of the portions 6a and the alignment protrusions 8a and 8b are also provided with inclined wall surfaces 3d, 4d, and 5d of a metal plate that are formed in advance and inclined wall surfaces and vertical wall surfaces that are connected to the vertical wall surfaces 3c, 4c, and 5c. It is good to form. The alignment protrusions 8a and 8b formed on the metal plate 13 brazed to the heat radiating side can also be removed by an end mill tool in the same manner as described above.

In the present invention, the thicknesses, lengths, and widths of the bridging portions 6a, 6b, 6c, 6d and the alignment projections 7a, 7b are extremely small, so that the time is short as in the prior art. It is also possible to remove the bridging portions 6a, 6b, 6c, 6d and the alignment protrusions 8a, 8b by etching. Moreover, you may remove these bridge | crosslinking parts and the alignment protrusion part by manual operation using cutting tools, such as a nipper.

  In the present invention, when the bridging portions 6a, 6b, 6c, 6d and the alignment protrusions 8a, 8b are removed by a cutting tool using an end mill or the like, the removal traces are separated from other side portions. Although it is desirable to form the same vertical wall surface and inclined wall surface, the width W of the bridging portions 6a, 6b, 6c, 6d and the width of the alignment projections 8a, 8b are very small. The effects of the present invention can be exerted even with the appropriate remaining surface after removal of the alignment protrusion. Normally, the maximum stress generation site is a corner portion of the circuit surface, so it is desirable that the bridge portion avoids the circuit corner portion. Furthermore, it is effective to utilize stress analysis by computer simulation or the like when determining the optimum position of the bridge portion.

Then, the 2nd form of the metal plate for circuits for implementing this invention is demonstrated based on FIG. The circuit metal plate 1a according to the second embodiment is obtained by forming an alignment hole 20 in the bridging portions 6a, 6b and the like in the first embodiment shown in FIG. The hole 20 does not need to be formed in all the bridging portions 6a, 6b, 6c, 6d, but is formed in 1 to 3 bridging portions. Further, a plurality of hole portions 20 may be formed in one bridging portion. The diameter of the hole 20 may be set to about 1 to 2 mm when the width W of the bridge portion is set to about 3 mm. The hole 20 can be formed by punching with a press when the above-described circuit metal plate is manufactured by mechanical processing means.

  The alignment hole 20 functions as an alignment means when the circuit metal plate 1a is joined to the ceramic substrate 9, and after the alignment, in particular, the ceramic substrate 9 is heated to melt the brazing material. In addition, it is possible to exert the effect of preventing the positional deviation between the circuit metal plate 1a and the ceramic substrate 9.

When the circuit metal plate 1a is brazed to the ceramic substrate 7, the procedure for aligning the circuit metal plate 1a with the ceramic substrate 7 is substantially the same as the alignment procedures 1 to 5 described above. The difference from the alignment procedure is that, as shown in FIG. 11, a protrusion 19a is provided on the spacer plate 19, and this protrusion 19a is fitted into an alignment hole 20 formed in the bridging portion of the circuit metal plate 1a. It is to let you let it. By fitting the projection 19a with the alignment hole 20, the circuit metal plate 1a can be accurately aligned at a predetermined position on the ceramic substrate 9, and the circuit metal plate 1a Since the protrusion 19a of the spacer plate 19 is fitted, it is possible to prevent the positional deviation between the ceramic substrate 9 and the circuit metal plate 1a.

  In the above-described second embodiment of the present invention, the alignment protrusions 8a and 8b of the circuit metal plate 1a can be omitted. In this case, the operation of aligning the circuit metal plate 1a on the ceramic substrate 9 can be performed as follows. First, the protrusion 19a of the spacer 19 is fitted into the hole 20 formed in the circuit metal plate 1a. Subsequently, the spacer 19 is placed on the ceramic substrate 9 placed on the alignment jig 18 with the side surfaces being in contact with the inner wall surfaces 16 a and 17 a of the alignment jig 18 to accurately position the spacer 19. It can be performed. In this embodiment, it is desirable to form alignment protrusions 8a and 8b on the metal plate 13 to be brazed to the heat dissipation side of the ceramic substrate 9.

  In the embodiment of the circuit metal plate of the present invention described above, the example in which the protruding portions 3g, 4g, and 5g are press-cut to form the vertical wall surfaces 3c, 4c, and 5c has been described. As shown in FIG. 12, it is good also as a metal plate for circuits which left these protrusion parts 3g, 4g, and 5g. Such a circuit metal plate is preferably applied to a ceramic circuit board capable of increasing the wiring interval K. Thereby, the process of press-cutting the protrusions 3g, 4g, and 5g becomes unnecessary, and the cost can be reduced.

It is a top view which shows 1st Embodiment about the metal plate for circuits of this invention. It is a longitudinal cross-sectional view of the AA line of FIG. It is a longitudinal cross-sectional view of the BB line of FIG. It is a figure for demonstrating the manufacturing procedure of the metal plate for circuits shown in FIG. 1, (a) is a top view which shows the shape before a process, (b) The top view which shows the shape when press forming the wiring space | interval, (C) is a longitudinal sectional view taken along line AA when a vertical wall surface and an inclined wall surface are formed on the circuit metal plate shown in (b), (d) is an enlarged view of the O portion in (c), and (e). These are figures which show a shape when the protrusion part 3g is cut | disconnected in (d). It is a longitudinal cross-sectional view which shows the structure of the ceramic circuit board of this invention. It is a top view which shows a state when apply | coating a brazing filler metal layer to a ceramic substrate when manufacturing the ceramic circuit board shown in FIG. FIG. 6 is a plan view showing a state in which the ceramic substrate and the circuit metal plate are superposed when the circuit metal plate shown in FIG. 1 is brazed to the ceramic substrate shown in FIG. 5. It is principal part sectional drawing for demonstrating the state of the brazing process which manufactures the ceramic circuit board of this invention, (a) is thickness of a bridge | crosslinking part, (b) is thickness of a bridge | crosslinking part. It is a figure which shows the behavior of the oozing brazing material when is too large. It is a figure for demonstrating the procedure which positions the metal plate for a circuit on a ceramic substrate when manufacturing the ceramic circuit board of this invention, (a) is a top view, (b) is a principal part longitudinal cross-sectional view. . It is a top view which shows 2nd Embodiment about the metal plate for circuits of this invention. It is a figure for demonstrating the procedure which positions the metal plate for a circuit on a ceramic substrate, when manufacturing the ceramic circuit board of this invention using the metal plate for a circuit shown in FIG. 10, (a) is a top view, (B) is a principal part longitudinal cross-sectional view. It is a longitudinal cross-sectional view which shows another structure about the ceramic circuit board of this invention.

Explanation of symbols

1: Circuit metal plates 2, 3, 4: Metal plates 3c, 4c, 5c: Vertical wall surfaces 3d, 4d, 5d: Inclined wall surfaces 3e, 4e, 5e: Flat surfaces 3f, 4f, 5f: Vertical wall surfaces 6a, 6b, 6c, 6d: bridging sections 8a, 8b: positioning protrusions 9: ceramic substrates 10, 11, 12: brazing material layer 18: alignment jig 19: spacer plate 20: hole T: thickness t of circuit metal plate : Cross-linked thickness

Claims (11)

A circuit metal plate having a thickness T formed by mechanical processing means, having a bottom surface bonded to a ceramic substrate and an upper surface serving as a circuit surface, wherein the circuit metal plate has a thickness smaller than the thickness T. And being integrated through a narrow cross-linked portion of t,
The circuit metal plate is characterized in that a side wall of the circuit metal plate is provided with a vertical wall surface standing from the bottom surface and an inclined wall surface inclined upward from the upper end of the vertical wall surface in the upper surface direction. . The metal plate for a circuit according to claim 1, further comprising a flat surface substantially parallel to the bottom surface between the vertical wall surface and the inclined wall surface. 3. The circuit according to claim 1, wherein the total volume of the bridging portion is configured to be 0.1 to 2% of the total volume of the circuit metal plate including the circuit surface. Metal plate. (Thickness T of the circuit metal plate) − (thickness t of the bridging portion) is configured to be 0.1 mm or more. The metal plate for a circuit according to any one of the above. The said circuit metal plate is equipped with the alignment means for aligning the said ceramic substrate and the said circuit metal plate at the time of joining to a ceramic substrate, The claim | item 1 characterized by the above-mentioned. The metal plate for a circuit according to claim 3. The circuit metal plate according to claim 5, wherein the alignment unit includes an alignment protrusion that protrudes from a side surface of the metal plate toward an outer side of the metal plate. 6. The metal plate for a circuit according to claim 5, wherein the alignment means is constituted by a hole formed in the bridging portion. The alignment means comprises means comprising an alignment protrusion that protrudes from the side surface of the metal plate toward the outside of the metal plate, and a hole formed in the bridging portion. The metal plate for a circuit according to claim 5. The circuit metal plate according to any one of claims 1 to 8, wherein the circuit metal plate is made of oxygen-free copper, copper, copper alloy, aluminum, or an aluminum alloy. 10. The circuit metal plate according to claim 1, wherein the circuit metal plate is a ceramic circuit board bonded to a main surface of the ceramic substrate via a brazing material layer, and the circuit metal is attached to the ceramic substrate. A ceramic circuit board having a structure in which the bridging portion and the alignment protrusion are removed after joining the plates. 11. The ceramic according to claim 10, wherein a remaining surface other than the inclined wall surface or the inclined wall surface along the inclined wall surface of the circuit metal plate is formed on the removal trace of the bridging portion and the alignment protrusion. Circuit board.

Images