JP6317178B2 - Circuit board and electronic device - Google Patents

Description

The present invention relates to a circuit board contact and the electronic device.

  Conventionally, as a circuit board used for an electronic device on which electronic parts such as an IGBT (Insulated Gate Bipolar Transistor) such as a power module or a switching module are mounted, for example, metal plates are joined to the upper surface and the lower surface of an insulating substrate, respectively. Things are used. Moreover, in patent document 1, each metal plate of an upper surface and a lower surface is provided substantially plane-symmetrically on both sides of the insulating substrate.

  According to such a configuration, the generation of bending stress due to the difference in thermal expansion between the metal plate and the insulating substrate can be reduced, and the generation of cracks in the insulating substrate or the peeling of the metal plate can be suppressed.

JP 2002-343911 A

  However, in the above-described prior art circuit board, for example, when a plurality of metal plates are provided on the lower surface of the insulating substrate, gaps are generated between these metal plates, so that the area of the lower metal plate is reduced. It was easy. Therefore, when the lower surface of the metal plate in such a circuit board is mounted on a heat sink or the like, the area of the lower metal plate that is a heat dissipation path for releasing the heat generated in the electronic component to the heat sink side will be reduced. The heat dissipation efficiency was decreasing.

The purpose of the present invention, in view of the above problems, cracking of the insulating substrate, or while suppressing peeling of the metal plate, to provide an electronic device and contact the circuit board it is possible to prevent deterioration of the radiation efficiency It is in.

A circuit board according to one aspect of the present invention includes an insulating substrate, a plurality of first metal plates bonded to each other on the upper surface of the insulating substrate with a gap therebetween, and the plurality of first metal plates. A second metal plate bonded to the lower surface of the insulating substrate, and a groove formed on the upper surface or the lower surface of the second metal plate so as to overlap the gap in a top view. In the top view, the position of the side surface of the gap is different from the position of the side surface of the groove .

  An electronic device according to one aspect of the present invention includes the above circuit board and an electronic component mounted on the circuit board.

According to the circuit board of the present invention, the groove formed on the upper surface or the lower surface of the second metal plate is provided so as to overlap the gap when viewed from above, so that the first metal plate on both sides of the gap is provided. And the volume of the second metal plate on both sides of the groove are substantially equal across the insulating substrate. Therefore, since the bending stress due to the difference in thermal expansion between the plurality of first metal plates and the insulating substrate is substantially equal to the bending stress due to the difference in thermal expansion between the second metal plate and the insulating substrate, the entire bending stress is reduced. And the occurrence of cracks in the insulating substrate or peeling of the metal plate can be suppressed. In addition, a groove is formed on the upper surface or the lower surface of the second metal plate, and the bottom of the groove does not reach the surface opposite to the groove, so that the lower surface of the second metal plate, which is a heat dissipation path, is formed. Or the reduction of the area of the upper surface can be suppressed. Therefore, the heat dissipation efficiency of the second metal plate can be improved. Further, since the position of the side surface of the gap is different from the position of the side surface of the groove in a top view, the thermal stress generated between the plurality of first metal plates and the heat generated between the second metal plates. It is possible to prevent the stress from overlapping. Therefore, generation of cracks in the insulating substrate can be suppressed.

  According to the electronic device of the present invention, since it has the above-described circuit board, it is possible to suppress the generation of cracks in the insulating substrate or the peeling of the metal plate and to maintain the heat dissipation efficiency. Can do.

(A) is a top view of the circuit board and electronic device of embodiment of this invention, (b) is sectional drawing in the AA of (a), (c) is a bottom view. (A), (b) is sectional drawing which shows the other example of the B section which is the principal part of FIG.1 (b). (A)-(e) is sectional drawing which shows the example of the manufacturing process of the circuit board of embodiment of this invention. (A), (b) is sectional drawing which shows the other example of the B section which is the principal part of FIG.1 (b). (A) is a top view which shows the other example of the circuit board of embodiment of this invention, (b) is sectional drawing in the BB line of (a), (c) is a bottom view. . (A) is a top view which shows the other example of the circuit board of embodiment of this invention, (b) is sectional drawing in CC line of (a), (c) is a bottom view. .

  Hereinafter, a circuit board and an electronic device according to embodiments of the present invention will be described with reference to the drawings. In the drawings, the circuit board and the electronic device are provided in a virtual xyz space and are placed on the xy plane. In the present embodiment, the upper, upper, and upper portions indicate the positive direction of the virtual z axis, and the lower, lower surface, and lower portion indicate the negative direction of the virtual z axis.

In the example shown in FIG. 1, the circuit board 10 includes an insulating substrate 1, a plurality of first metal plates 2, and a second one.
And a metal plate 3. In the example shown in FIG. 1, the electronic device 20 includes a circuit board 10 and an electronic component 5.

  The insulating substrate 1 is made of an electrically insulating material, for example, ceramics such as aluminum oxide ceramics, mullite ceramics, silicon carbide ceramics, aluminum nitride ceramics, or silicon nitride ceramics. Among these ceramic materials, silicon carbide ceramics, aluminum nitride ceramics, or silicon nitride ceramics are preferred in terms of thermal conductivity that affects heat dissipation, and silicon nitride ceramics or silicon carbide ceramics in terms of strength. Is preferred.

  When the insulating substrate 1 is made of a ceramic material having relatively high strength such as silicon nitride ceramics, the insulating substrate 1 may be cracked due to thermal stress caused by the difference in thermal expansion coefficient between the metal plate 2 and the insulating substrate 1. Therefore, it is possible to realize a circuit board capable of flowing a larger current while achieving downsizing.

The thinner insulating substrate 1 may be in terms of thermal conductivity, for example, about 0.1 mm to 1 mm, and may be selected according to the size of the circuit board or the thermal conductivity or strength of the material used.

  If the insulating substrate 1 is made of, for example, silicon nitride ceramics, an appropriate organic binder, plasticizer, and solvent are added to and mixed with raw material powders such as silicon nitride, aluminum oxide, magnesium oxide, and yttrium oxide, and then mixed with slurry. A ceramic green sheet (ceramic raw sheet) is formed by adopting a conventionally known doctor blade method or calendar roll method, and then a suitable punching process is applied to the ceramic green sheet to obtain a predetermined shape. If necessary, a plurality of sheets are laminated to form a molded body, and then, this is manufactured by firing at a temperature of 1600 to 2000 ° C. in a non-oxidizing atmosphere such as a nitriding atmosphere.

  The plurality of first metal plates 2 are joined to the upper surface of the insulating substrate 1 with a gap 2a therebetween as in the example shown in FIG. In the example shown in FIG. 1, the lower surfaces of the plurality of first metal plates 2 are bonding surfaces to the insulating substrate 1.

  In the example shown in FIG. 1, three first metal plates 2 </ b> A, 2 </ b> B, and 2 </ b> C are provided on the upper surface of the insulating substrate 1. The first metal plates 2A and 2C are provided on both sides in the x direction on the upper surface of the insulating substrate 1, respectively. The first metal plate 2B is located at the center of the upper surface of the insulating substrate 1, and is sandwiched between the first metal plates 2A and 2C.

  The gap may be interpreted as a space between the plurality of first metal plates 2 provided adjacent to each other. In the example shown in FIG. 1 (a), in the central portion in the y direction, the gap is a space between the first metal plate 2A and the first metal plate 2B, and the first metal plate 2B and the first metal plate 2C. It can be interpreted as a space between. In the example shown in FIG. 1A, the gap can be understood as a space between the first metal plate 2A and the first metal plate 2C at both ends in the y direction.

  The width of the gap 2a is set to such an extent that insulation can be ensured in consideration of the voltage used for the circuit board 10. For example, although it depends on the arrangement and dimensions of the plurality of first metal plates 2, the width of the gap 2a is about 0.5 to 10 mm.

The plurality of first metal plates 2 are joined to the upper surface of the insulating substrate 1 via, for example, an Ag—Cu-based brazing material 4. The brazing material 4 contains, for example, at least one active metal material of titanium, hafnium, and zirconium in order to be firmly bonded to the insulating substrate 1 by being wetted. Moreover, this brazing material may have at least one of In and Sn, for example. In addition, the thickness of this brazing material 4 should just be about 5-100 micrometers, for example.

The plurality of first metal plates 2 are, for example, flat copper plates, and the thickness thereof is, for example, 20 to 600 μm.
m. The copper plate is preferable as a member constituting the first metal plate 2 because it has low electrical resistance and high thermal conductivity.

  When the first metal plate 2 is a copper plate, the first metal plate 2 is, for example, oxygen-free copper. When oxygen-free copper is used as the first metal plate 2, the surface of the first metal plate 2 is oxidized by oxygen present in the copper when the first metal plate 2 and the insulating substrate 1 are joined. And the wettability with the brazing material is improved, so that the bonding strength with the insulating substrate 1 is improved.

  In addition, when the first metal plate 2 is a copper plate and the brazing material has a copper component, the copper component in each member diffuses at the joint portion of both the brazing material and the first metal plate 2. Since the diffusion layer is formed by fitting, the first metal plate 2 and the brazing material are preferably firmly bonded to each other.

  Moreover, in the example shown in FIG. 1, the electronic component 5 is mounted on the upper surface of the first metal plate 2B at the center via a bonding material, and the electronic component 5 includes the other first metal plates 2A and 2C. Are connected by a conductive connecting material such as a bonding wire 6. Thus, in the example shown in FIG. 1, the first metal plate 2 functions as a circuit conductor. The first metal plate 2 can also be used as a metal member for mounting the electronic component 5 mounted on the circuit board and a metal member for the ground conductor. Moreover, the 2nd metal plate 3 mentioned later is mainly used as a heat sink. As described above, the first metal plate 2 is used by being bonded to the insulating substrate 1 made of ceramics or the like as a conductive path for supplying a relatively large current of, for example, several tens of A.

The electronic component 5 is, for example, a transistor or an LS for a CPU (Central Processing Unit).
It is a semiconductor element such as I (Large Scale Integrated circuit), IGBT (Insulated Gate Bipolar Transistor), or MOS-FET (Metal Oxide Semiconductor-Field Effect Transistor).

  The bonding material for bonding the electronic component 5 to the metal plate 2 is made of, for example, metal or conductive resin. The bonding material made of metal is, for example, solder, a gold-tin (Au—Sn) alloy, or a tin-silver-copper (Sn—Ag—Cu) alloy. The bonding material made of conductive resin is, for example, an adhesive with high thermal conductivity such as Ag epoxy resin.

  A plating film may be formed on the surface of the first metal plate 2 by a plating method. According to this configuration, since the wettability with the bonding material is improved, the electronic component 5 can be firmly bonded to the surface of the first metal plate 2. The plating film may be made of a metal having high conductivity and corrosion resistance, and examples thereof include nickel, cobalt, copper, gold, and alloy materials containing these metal materials as main components. The thickness of the plating film may be, for example, 1.5 to 10 μm.

  The plating film preferably contains phosphorus inside. For example, a nickel-phosphorus amorphous alloy plating film is preferable because surface oxidation of the nickel plating film can be suppressed and wettability of a bonding material or the like can be maintained for a long time. Further, when the content of phosphorus with respect to nickel is about 8 to 15 mass, an amorphous alloy of nickel-phosphorus is easily formed, and the adhesive strength of a bonding material or the like to the plating film can be further improved.

The second metal plate 3 faces the plurality of first metal plates 2 and is bonded to the lower surface of the insulating substrate 1. In the example shown in FIG. 1, a groove 3a is formed on the upper surface of the second metal plate 3 so as to overlap the gap 2a when viewed from above. According to this configuration, the volume of the first metal plate 2 on both sides of the gap 2a and the volume of the second metal plate 3 on both sides of the groove 3a are substantially equal across the insulating substrate 1. In addition, the shape of the joint surface between the plurality of first metal plates 2 and the insulating substrate 1 is substantially plane symmetric with respect to the shape of the joint surface between the second metal plate 3 and the insulating substrate 1. Therefore, the bending stress resulting from the difference in thermal expansion between the plurality of first metal plates 2 and the insulating substrate 1 is substantially equal to the bending stress resulting from the difference in thermal expansion between the second metal plate 3 and the insulating substrate 1. The overall bending stress is reduced, and cracks in the insulating substrate 1 or peeling of the metal plates 2 and 3 can be suppressed. Further, the groove 3a is formed on the upper surface of the second metal plate 3, and the bottom of the groove 3a does not reach the lower surface, so that the reduction of the area of the lower surface of the second metal plate 3 can be suppressed. Therefore, the heat dissipation efficiency from the lower surface of the second metal plate 3 can be maintained.

  The material and dimensions of the second metal plate 3, the plating film on the second metal plate 3, and the method of joining the second metal plate 3 to the insulating substrate 1 are the same as those of the first metal plate 2.

  In the example shown in FIG. 1, the upper surface of the second metal plate 3 is a bonding surface to the insulating substrate 1.

  As in the example shown in FIGS. 1B and 1C, the groove 3 a is formed on the upper surface of the second metal plate 3. The bottom of the groove 3 a does not reach the lower surface of the second metal plate 3. Therefore, as in the example shown in FIGS. 1B and 1C, the second metal plate 3 has a plurality of facing regions that face each of the first metal plates 2A, 2B, and 2C via the insulating substrate 1. In addition, the plurality of facing regions are connected to each other on the lower surface side (the negative side in the z direction).

The width of the groove 3a is, for example, about 0.5 to 12 mm, although it depends on the shape and dimensions of the second metal plate 3. Moreover, although the depth of the groove | channel 3a is based also on the thickness of the 2nd metal plate 3, it is about 5-500 micrometers, for example.

  As in the example shown in FIG. 1 (b), it is preferable that the groove 3a and the gap 2a have the same side surface position in a top view, and the width of the groove 3a is the same as the width of the gap 2a. In this case, the bonding surfaces of the plurality of first metal plates 2 and the insulating substrate 1 are the same as the bonding surfaces of the second metal plate 3 and the insulating substrate 1 not only in shape but also in size. Therefore, the difference in thermal expansion with the first metal plate 2 on the upper surface of the insulating substrate 1 and the difference in thermal expansion with the second metal plate 3 on the lower surface of the insulating substrate 1 are further equal. The peeling of the metal plates 2 and 3 can be further suppressed.

  The above “same” includes not only completely the same but also substantially the same. The case where it is substantially the same is a case where the difference is about 0.1 to 1 mm, for example.

  Further, as in the example shown in FIG. 1B, the width of the groove 3a is the same as the width of the gap 2a, and the depth of the groove 3a is more than half of the thickness of the second metal plate 3. It is preferable. If the width of the groove 3a is the same as the width of the gap 2a as in this configuration, the metal amount of the second metal plate 3 increases as the depth of the groove 3a increases. Since it is close to the amount, the amount of thermal expansion of both members is also approximated. Accordingly, the difference in thermal expansion with the first metal plate 2 on the upper surface of the insulating substrate 1 and the difference in thermal expansion with the second metal plate 3 on the lower surface of the insulating substrate 1 are further equal. The peeling of the metal plates 2 and 3 can be further suppressed.

  Next, an example of another embodiment of the present invention will be described with reference to FIG. The cross-sectional views of FIGS. 2A and 2B show other examples of the B part, which is the main part of FIG.

In the example shown in FIGS. 2A and 2B, the plurality of first metal plates 2 are interposed via gaps 2a.
The side surfaces are opposed to each other, and the central portions in the thickness direction of the side surfaces protrude from the upper surface side and the lower surface side of the first metal plate 2. With this configuration, the creeping distance between the first metal plates 2 is not close on the lower surface side that does not protrude, so that the occurrence of creeping discharge can be suppressed. Moreover, since the distance between the corners of the first metal plate 2 is not close even on the upper surface side, discharge in the air can be suppressed. Moreover, since the discharge can be suppressed on the lower surface side and the upper surface side in this way, the central portion in the thickness direction protrudes, so that the volume of the first metal plate 2 can be increased and the electrical resistance can be reduced. Can do.

  As in the example illustrated in FIG. 2A, the central portion in the thickness direction may protrude in a protruding shape on the side surfaces of the plurality of first metal plates 2.

  As in the example shown in FIG. 2B, the side surfaces of the plurality of first metal plates 2 are preferably convex curved surfaces. In this case, it is possible to further reduce the possibility that air discharge occurs between the central portions protruding on the side surfaces.

  Next, a method for manufacturing the circuit board 1 according to the embodiment of the example shown in FIG. 2 of the present invention will be described with reference to FIGS.

  (1) First, as a first step, an insulating substrate 1 and a plurality of first metal plate regions 22A, 22B, and 22C that have a first groove 22a on the lower surface and are disposed with the first groove 22a therebetween are provided. A first metal plate base material 22 and a second metal plate 3 provided with a second groove 3a (symmetrical to the first groove 22a) on the upper surface (the groove 3a described above) are prepared. Here, for example, copper is used as the material for the first metal plate base material 22 and the second metal plate 3.

  In order to form the first metal plate base material 22 having the first groove 22a, a groove is formed by performing, for example, an etching process on the joining surface side of the flat metal plate 21 with the insulating substrate 1. For example, ferric chloride is used as the etching solution. In the etching process, masking 7 is first applied to the portions corresponding to the first metal plate regions 22A, 22B, and 22C as shown in FIG.

  Next, etching is performed to a depth of about 60% of the thickness of the metal to form the first groove 22a at a predetermined position. Thereafter, the masking 7 is peeled off to obtain the first metal plate base material 22 in which the first grooves 22a are formed as shown in FIG.

  By using the etching process as described above and adjusting the conditions such as the etching time, the first groove 22a whose width is narrowed from the joint surface side with the insulating substrate 1 toward the central portion in the thickness direction is formed. It can be formed easily.

  The second metal plate 3 is provided with a second groove 3a (the groove 3a described above) having a shape symmetrical to the first groove 22a on the upper surface (bonding surface with the insulating substrate 1). The method of forming the second groove 3a is the same as the method of forming the first groove 22a described above.

  (2) Next, as a second step, as shown in FIG. 3C, the lower surface of the first metal plate base material 22 is disposed on the upper surface of the insulating substrate 1, and the second groove 3a is formed when viewed from above. The upper surface of the second metal plate 3 is placed on the lower surface of the insulating substrate 1 so as to overlap the first groove 22a and so that the second metal plate 3 faces the first metal plate regions 22A, 22B, 22C. To place. As a result of this arrangement, the first groove 22a and the second groove 3a have a plane-symmetric shape through the insulating substrate 1.

In this step, before placing the first metal plate base material 22 and the second metal plate 3, as shown in FIG. 3C, a brazing material is previously placed on both main surfaces of the insulating substrate 1 at predetermined positions. For example, it is applied in a predetermined shape by a method such as screen printing. As this brazing material, for example, a material mainly composed of silver and copper, further containing Ti, and having a melting point adjusted to about 790 ° C. with In or Sn is used.

  (3) Next, as a third step, the first metal plate base material 22 and the second metal plate 3 are joined to the insulating substrate 1 by heat treatment. In this step, the laminated body obtained in the second step is placed in a vacuum furnace, and heat treatment is performed at about 830 ° C. in a vacuum state. Thus, the brazing material is melted and cooled to solidify the brazing material, and the first metal plate base material 22 and the second metal plate 3 are joined to the insulating substrate 1.

  (4) Next, as a fourth step, a plurality of first metal plates 2 separated from each other with a gap 2a are removed by removing a portion from the upper surface of the first metal plate base material 22 to the bottom of the first groove 22a. Form.

  In this step, for example, a portion from the upper surface of the first metal plate base material 22 to the bottom of the first groove 22a is removed by an etching process. When performing the etching process, first, masking 7 is applied to the upper surface of the first metal plate base material 22 and the lower surface of the second metal plate 3 as shown in FIG. The masking 7 on the upper surface of the first metal plate base material 22 excludes a portion corresponding to the first groove 22a.

  Then, after the second etching process with ferric chloride as described above, the masking 7 is removed to obtain the circuit board 10 of the present invention as shown in FIG.

  Thus, the width of the portion removed by using the etching process becomes narrower from the upper surface toward the central portion in the thickness direction by adjusting the conditions such as the etching time. Therefore, as in the example shown in FIG. 2, it is possible to form side surfaces in which the central portion in the thickness direction protrudes from the upper surface side and the lower surface side of the first metal plate 2.

  Further, in order to make the side surface of the first metal plate 2 have a convex curved surface, the side surface from which the central portion protrudes may be further subjected to etching treatment to remove the projection shape and the like.

  In the example manufacturing method shown in FIG. 2, the side surface with the central portion protruding may be formed by machining such as cutting. In this case, the cutting blade may be adjusted to a predetermined shape.

  Moreover, you may nickel-plat on the surface of the 1st metal plate 2 and the 2nd metal plate 3 as needed.

  As described above, in the manufacturing method of the present invention, the step of forming the gap 2a is divided into two times. In the first of the two times, the first metal plate base material 22 is subjected to an etching process after masking 7 on the joint surface with the insulating substrate 1 to form a first groove 22a which is a part of the gap 2a. To do.

On the other hand, in general, the depth of the groove formed by etching increases as the depth increases. Therefore, for example, after brazing the first metal plate base material not having the first groove, the gap 2a is formed by etching only once from the surface (upper surface) opposite to the bonding surface with the insulating substrate 1. When formed, the gap 2a between the plurality of first metal plates 2 on the surface of the insulating substrate 1 becomes relatively large. Therefore, when the formation of the gap 2a is divided into two times and the first etching is performed from the bonding surface side with the insulating substrate 1 to form the first groove 22a, the first metal plate 2 can be arranged at high density. .

  The above effect is the same not only when the first groove 22a is formed by etching but also when it is formed by machining as described above.

In the manufacturing method of the present invention, the formation process of the gap 2a is divided into two, and the formation is stopped in the state of the groove (first groove 22a) in the first formation process. Therefore, since the bottom of the first groove 22a does not reach the upper surface of the first metal plate base material 22, the plurality of first metal plate regions 22A, 22B, and 22C are connected to each other during the heat treatment in the third step. It is in a state. Therefore, for example, the bending deformation in the insulating substrate 1 during heating is suppressed by the first metal plate base material 22 as compared with the case where the heat treatment is performed in a state where the plurality of first metal plates are separated from each other. Therefore, the generation of cracks in the insulating substrate 1 or the peeling of the metal plates 2 and 3 during manufacture can be suppressed.

  Next, the manufacturing method of the circuit board 1 according to the embodiment of the example shown in FIG. 1 of the present invention will be described while referring to differences from the example of FIG.

  First, in the first step of forming the first metal plate base material 22 having the first groove 22a, for example, a cutting tool having a flat side surface is provided on the side of the flat metal plate 21 joined to the insulating substrate 1. The first groove 22a is formed by the used machining. By such machining, the first groove 22a having a flat inner surface can be easily formed.

  Further, in the fourth step of removing the portion from the upper surface of the first metal plate base material 22 to the bottom of the first groove 22a, the first metal plate base is performed by machining using a cutting tool having a flat side surface, for example. The part from the upper surface of the material 22 to the bottom of the first groove 22a is removed. By such machining, a plurality of first metal plates 2 whose side surfaces are flat can be easily formed.

  In the manufacturing method of the example shown in FIG. 1, a plurality of first metal plates 2 whose side surfaces are flat may be formed by, for example, etching. In this case, the etching conditions may be adjusted as appropriate.

  Next, an example of another embodiment of the present invention will be described with reference to FIG. The cross-sectional views of FIGS. 4A and 4B show other examples of the B part, which is the main part of FIG.

  In the example shown in FIGS. 4A and 4B, the position of the side surface of the gap 2a is different from the position of the side surface of the groove 3a in the top view. According to such a configuration, the insulating substrate 1 has the thermal stress generated between the plurality of first metal plates 2 and the heat generated between the second metal plates 3 at a specific position when viewed from above. It is possible to prevent the stress from overlapping. Therefore, generation of cracks in the insulating substrate 1 can be suppressed.

  As in the example shown in FIG. 4A, the width of the groove 3a is preferably narrower than the width of the gap 2a. In this case, the bonding area to the insulating substrate 1 is larger in the second metal plate 3 than in the first metal plate 2 around the groove 3a. Accordingly, the width of the path when the heat generated by the operation of the electronic component 5 is transmitted to the second metal plate 3 via the plurality of first metal plates 2 is widened. Therefore, since the heat transmitted to the second metal plate 3 spreads not only in the thickness direction but also in the xy plane direction, the heat dissipation efficiency can be increased and the difference in thermal expansion can be reduced. Or peeling of the metal plates 2 and 3 can be suppressed.

  As an example of the dimensions shown in FIG. 4A, for example, when the width of the gap 2a is about 5 mm, the width of the groove 3a may be about 0.5 to 4 mm.

4A, the width of the groove 3a is narrower than the width of the gap 2a, and the depth of the groove 3a is not less than half the thickness of the second metal plate 3. In the example shown in FIG. preferable. In this configuration, the amount of metal in the second metal plate 3 is larger than the amount of metal in the plurality of first metal plates 2 because the width of the groove 3a is narrower than the width of the gap 2a. As the depth of the groove 3a becomes deeper, the amount of metal of the second metal plate 3 is closer to the amount of metal of the plurality of first metal plates 2, so that the amount of thermal expansion of both members can be approximated. Accordingly, the difference in thermal expansion with the first metal plate 2 on the upper surface of the insulating substrate 1 and the difference in thermal expansion with the second metal plate 3 on the lower surface of the insulating substrate 1 are further equal. The peeling of the metal plates 2 and 3 can be further suppressed.

  As in the example shown in FIG. 4B, the width of the groove 3a is preferably wider than the width of the gap 2a. In the example shown in FIG. 4B, the amount of metal is more than that of the plurality of first metal plates 2 that are completely separated on both sides of the gap 2a because the second metal plate 3 is not completely separated on both sides of the groove 3a. However, since the metal amount of the second metal plate 3 is close to the metal amount of the plurality of first metal plates 2 by making the width of the groove 3a wider than the width of the gap 2a, The amount of thermal expansion is also approximate. Accordingly, the difference in thermal expansion with the first metal plate 2 on the upper surface of the insulating substrate 1 and the difference in thermal expansion with the second metal plate 3 on the lower surface of the insulating substrate 1 are further equal. The peeling of the metal plates 2 and 3 can be further suppressed.

  As an example of the dimensions shown in FIG. 4B, for example, when the width of the gap 2a is about 1 mm, the width of the groove 3a may be about 2 to 5 mm.

  Further, as in the example shown in FIG. 4B, the width of the groove 3 a is wider than the width of the gap 2 a and the depth of the groove 3 a is less than half the thickness of the second metal plate 3. preferable. According to this structure, since the thickness of the 2nd metal plate 3 can be ensured from the bottom part of the groove | channel 3a to the lower surface of the 2nd metal plate 3, the heat capacity which passes the said thickness part can be increased, and the 2nd metal plate The amount of heat released from 3 can be increased.

  Next, an example of another embodiment of the present invention will be described with reference to FIG. 5A shows a top view of the other embodiment, FIG. 5B shows a cross-sectional view of the other embodiment, and FIG. 5C is a bottom view.

  Also in the example shown in FIG. 5, as in FIG. 4, the position of the side surface of the gap 2a and the position of the side surface of the groove 3a are different in a top view. Therefore, it has an effect similar to the above.

  As in the example shown in FIG. 5, the side surface of the groove 3a on the substrate inner side is preferably close to the side surface of the gap 2a on the outer edge side of the substrate. According to such a structure, the width | variety of the opposing area | region with respect to the 1st metal plate 2B in which the electronic component 5 was mounted in the 2nd metal plate 3 can be made significantly wider than the width | variety of the 1st metal plate 2B. Therefore, the heat generated in the electronic component 5 and transmitted through the first metal plate 2B can be radiated favorably from the region facing the first metal plate 2B.

  In addition, the metal plate of this invention is not limited to the example of the said embodiment, A various change is possible if it is in the range of the summary of this invention.

  For example, the structure in which the first metal plate 2 and the second metal plate 3 are bonded to the upper and lower surfaces of the insulating substrate 1 with the brazing material 4 containing active metal has been described. Instead of brazing, a copper direct bonding method (DBC method) is used. ) May be used.

  Moreover, as a material of the plurality of first metal plates 2 and the second metal plate 3, for example, aluminum may be used instead of the copper described above. When joining the metal plates 2 and 3 made of aluminum to the insulating substrate 1, for example, an aluminum brazing is used.

  Next, an example of another embodiment of the present invention will be described with reference to FIG. 6A shows a top view of the other embodiment, FIG. 6B shows a cross-sectional view of the other embodiment, and FIG. 6C is a bottom view.

  In the example shown in FIG. 6, a groove 3a is formed on the lower surface of the second metal plate 3 so as to overlap the gap 2a when viewed from above. According to this configuration, the volume of the first metal plate 2 on both sides of the gap 2a and the volume of the second metal plate 3 on both sides of the groove 3a are substantially equal across the insulating substrate 1. Therefore, the bending stress resulting from the difference in thermal expansion between the plurality of first metal plates 2 and the insulating substrate 1 is substantially equal to the bending stress resulting from the difference in thermal expansion between the second metal plate 3 and the insulating substrate 1. The overall bending stress is reduced, and cracks in the insulating substrate 1 or peeling of the metal plates 2 and 3 can be suppressed. In addition, the groove 3a is formed on the lower surface of the second metal plate 3, and the bottom of the groove 3a does not reach the upper surface, so that a reduction in the area of the upper surface of the second metal plate 3 can be suppressed. Therefore, the heat transferred to the insulating substrate 1 through the first metal plate 2 is efficiently transferred to the second metal plate 3, so that the heat radiation efficiency from the lower surface of the second metal plate 3 can be improved.

DESCRIPTION OF SYMBOLS 1 ... Insulating substrate 2 ... 1st metal plate 2a ... Gap 3 ... 2nd metal plate 3a .... groove | channel (2nd groove | channel)
4 ... brazing material 5 ... electronic component 6 ... bonding wire 7 ... masking
10 ... Circuit board
20 ... Electronic device
22 ... 1st metal plate base material
22a ... 1st groove
22A, 22B, 22C ... Multiple first metal plate regions

Claims (8)

An insulating substrate;
A plurality of first metal plates joined to the upper surface of the insulating substrate with a gap therebetween;
A second metal plate facing the plurality of first metal plates and bonded to the lower surface of the insulating substrate;
On the upper surface or the lower surface of the second metal plate, there is provided a groove formed so as to overlap the gap in the top view ,
A circuit board in which a position of a side surface of the gap is different from a position of a side surface of the groove in a top view . The side surfaces of the plurality of first metal plates are opposed to each other through the gap,
The circuit board according to claim 1, wherein a central portion in the thickness direction of the side surface protrudes from an upper surface side and a lower surface side of the first metal plate. The circuit board according to claim 2, wherein the side surface is a convex curved surface. Width of the groove, the circuit board according to any one of the narrow claims 1 to 3 than the width of the gap. The circuit board according to claim 4 , wherein a depth of the groove is at least half of a thickness of the second metal plate. Width of the groove, the circuit board according to any one of a wide claims 1 to 3 than the width of the gap. The circuit board according to claim 6 , wherein a depth of the groove is not more than half of a thickness of the second metal plate. A circuit board according to any one of claims 1 to 7 ,
And an electronic component mounted on the circuit board.

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