JP2015046414A - Circuit board and electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit board and an electronic device excellent in long-term reliability.SOLUTION: A circuit board 10 comprises: an insulation base 11; and a metal plate 12, made up of a plurality of metal portions 1 and 2 sequentially laminated on each other, which is bonded to a main surface of the insulation base 11. The metal plate 12 includes: the first metal portion 1 positioned closest to the insulation base 11 side; and the second metal portion 2 positioned over the first metal portion 1. An undersurface of the second metal portion 2 includes: a first region 2A which comes into contact with the metal part 1 positioned directly under the second metal portion 2; and a second region 2B which does not come into contact with the metal part 1 positioned directly under the second metal portion 2. The second metal portion 2 can release, from the second region 2B, heat inside the metal plate 12 to the ambient air. Therefore, it is possible to reduce heat stress resulting from the difference in heat expansion coefficient between the metal plate 12 and the insulation base 11.

Description

  The present invention relates to a circuit board and an electronic device in which an electronic component is mounted on the circuit board.

Power module or switching module, eg IGBT (Insulated Gate)
As a circuit board used in an electronic device on which an electronic component such as a bipolar transistor is mounted, a ceramic board in which a metal plate made of, for example, copper or aluminum is bonded is used. The electronic component is mounted on a metal plate and is electrically connected to another metal plate by, for example, a bonding wire.

  As the metal plate, a material mainly composed of copper or aluminum having a small electric resistance (resistivity) is used. Moreover, as an example of another metal plate, what contains the metal part which consists of copper or aluminum, and the other metal part which consists of molybdenum etc. arrange | positioned on this is mentioned. According to this configuration, it is possible to suppress mechanical destruction of the insulating base due to thermal stress caused by a difference in thermal expansion coefficient between the metal portion made of copper or aluminum and the insulating base.

Japanese Patent Laid-Open No. 7-061869 JP-A-11-150217

  However, in the prior art circuit board, when heat is generated from the electronic component mounted on the metal plate, the difference in thermal expansion coefficient between the insulating base and the metal portion bonded to the main surface of the insulating base. There is a problem that the metal part may be peeled off from the insulating substrate due to the thermal stress caused by the above.

  In view of the above problems, an object of the present invention is to provide a highly reliable circuit board and electronic device that reduce thermal stress between a metal plate and an insulating substrate and prevent the metal plate from peeling from the insulating substrate. There is to do.

  A circuit board according to one aspect of the present invention includes an insulating base, and a metal plate that is bonded to the main surface of the insulating base and in which a plurality of metal portions are sequentially stacked. A first metal part located closest to the insulating base, and a second metal part located above the first metal part, and a lower surface of the second metal part is located immediately below the second metal part. And a second region not in contact with the metal part located immediately below the second metal part.

  An electronic device according to one aspect of the present invention is an electronic device including the above-described circuit board and an electronic component mounted on the upper surface of the metal plate.

According to the circuit board according to one aspect of the present invention, the lower surface of the second metal part includes the first region in contact with the metal part located immediately below the second metal part, and the metal part located directly below the second metal part. The second metal part is in contact with the metal part located immediately below, even when heat is generated from the electronic component mounted on the metal plate. The heat transmitted from the electronic component can be efficiently radiated to the outside air from the second region that is not. Therefore, the thermal stress resulting from the difference in thermal expansion coefficient between the metal plate and the insulating substrate can be reduced.

  According to the electronic device according to one aspect of the present invention, the heat generated from the electronic component can be efficiently radiated, and the thermal stress between the metal plate and the insulating base can be reduced.

(A) is sectional drawing which shows the electronic device of embodiment of this invention, (b) is sectional drawing which shows the other example of the electronic device of embodiment of this invention. (A), (b) is sectional drawing which shows the other example of the circuit board of embodiment of this invention. It is sectional drawing which shows the other example of the electronic device of embodiment of this invention. It is sectional drawing which shows the other example of the electronic device of embodiment of this invention. (A) is sectional drawing which shows the other example of the electronic device of embodiment of this invention, (b) is a top view of the electronic device shown to (a).

  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 base 11 and a metal plate 12. In the example shown in FIG. 1, the electronic device 13 includes a circuit board 10 and an electronic component 5.

  The insulating base 11 has a metal plate 12 bonded to its main surface. The insulating base 11 is made of an electrically insulating material, for example, ceramic 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 base 11 is made of a relatively strong ceramic material such as silicon nitride ceramics, the possibility of cracks in the insulating base 11 is reduced even if a thicker metal plate 12 is used. Thus, it is possible to realize a circuit board capable of allowing a larger current to flow while achieving the above.

The thinner insulating substrate 11 may be thin 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 10 or the thermal conductivity or strength of the material used.

If the insulating substrate 11 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 the slurry is mixed. 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 metal plate 12 is joined to the main surface of the insulating base 11, and a plurality of metal portions 1 and 2 are sequentially laminated. The metal plate 12 has a first metal part 1 located closest to the insulating base 11 and a second metal part 2 located above the first metal part 1. In the example shown in FIG. 1, the second metal part 2 is provided directly on the first metal part 1, but another metal part is provided between the first metal part 1 and the second metal part 2. May be provided.

  In the example shown in FIG. 1, an electronic component 5 is mounted on the upper surface of one metal plate 12, and this electronic component 5 is connected to the other metal plate 12 by a conductive connecting material 7 (bonding wire). Yes. Thus, in the example shown in FIG. 1, the metal plate 12 functions as a circuit conductor. Further, the metal plate 12 is not limited to the circuit conductor, and can be used as a metal member for mounting the electronic component 5 mounted on the circuit board 10, a metal member for the ground conductor, a heat radiating plate, or the like. As described above, the metal plate 12 is used by being bonded to the insulating base 11 made of ceramics or the like as a conductive path for supplying a relatively large current of, for example, several tens of A or a heat dissipation material. In the electronic device 13, the electronic component 5 to which a large current is passed is a heat generation source.

  In the example shown in FIG. 1, the first metal part 1 is provided between the insulating base 11 and the second metal part 2. The thickness of the first metal part 1 is about 5 to 300 μm.

  The metal plate 12 is preferably composed of a combination of a metal part having low electrical resistance and high thermal conductivity and a metal part having a low coefficient of thermal expansion. By such a combination of metal parts, the metal plate 12 functions as a circuit conductor with low electrical resistance, the circuit board 10 functions as a heat dissipation substrate with high heat dissipation efficiency, and thermal expansion of the metal plate 12 is suppressed. The circuit board 10 having high bonding reliability with the insulating base 11 can be provided.

  As the metal portion having low electrical resistance and high thermal conductivity, for example, copper or aluminum, or an alloy material mainly composed of copper or aluminum may be used. From the viewpoint of heat dissipation, a metal material having high thermal conductivity may be used. A certain copper (Cu) is preferably used (Cu thermal conductivity: 395 W / m · K).

  As a metal part with a low thermal expansion coefficient, for example, an iron-nickel (Fe-Ni) alloy such as molybdenum (Mo), tungsten (W), or Invar (invar) having a smaller thermal expansion coefficient than Cu, etc. A metal material may be used.

  In the example shown in FIG. 1, a metal having a low thermal expansion coefficient is used as the first metal part 1, and a metal having low electrical resistance and high thermal conductivity is used as the second metal part. Further, as will be described later, in the example shown in FIG. 2, a metal having low electrical resistance and high thermal conductivity is used as the first metal part 1 and the second metal part 2, and as the third metal part 3, A metal having a low coefficient of thermal expansion is used.

  When the above-described materials (Mo, W, Invar, Fe-Ni alloy, etc.) are used as the first metal part 1, these materials have a Young's modulus smaller than that of the insulating base 11 made of ceramics and the toughness. Therefore, by using these materials as the first metal part 1, the thermal stress of the first metal part 1 can be relaxed by the deformation of the first metal part 1 itself. Therefore, mechanical destruction such as cracks in the first metal part 1 is also effectively suppressed.

The first metal part 1 is preferably made of a metal material having a higher thermal expansion coefficient than that of the insulating base 11 and a lower thermal expansion coefficient than that of the second metal part 2. According to such a configuration, the insulating base
Even when the difference between the thermal expansion coefficients of 11 and 2 is large, since the first metal part 1 is interposed between the two members, the heat caused by the difference in the thermal expansion coefficient between the two members. The stress can be relaxed by the first metal part 1. Therefore, deformation and peeling of the metal plate 12 can be suppressed.

  In the example shown in FIG. 1, for example, a brazing material (not shown) is used for joining the first metal part 1 to the insulating base 11. The brazing material is made of a metal material containing, for example, silver, tin and indium. The thickness of the brazing material may be about 5 to 100 μm, for example.

As a more detailed composition of the brazing material, for example, silver is about 30 to 50% by mass, tin is about 1 to 40% by mass, and indium is about 1 to 5% by mass. As a more specific example, 41.69% by mass of silver
Tin is 37% by mass and indium is 3% by mass.

  The brazing material may contain other metal material of about 1 to 20% by mass or components of the first metal part 1 in addition to silver, tin and indium.

  The brazing material preferably further contains at least one metal material of titanium, hafnium and zirconium. In this case, a metal material such as titanium which is an active metal material is firmly bonded to the first metal portion 1 and the insulating base 11. The first metal portion is firmly bonded to the insulating base 11 via the active metal.

  In the example shown in FIG. 1, the second metal part 2 is provided on the upper surface of the first metal part 1. The second metal part 2 is located on the uppermost part of the metal plate 12. For joining the second metal part 2 to the first metal part 1, for example, joining with a brazing material or a cold rolling method is used. The brazing material used here is the same as described above.

  The lower surface of the second metal part 2 includes a first region 2A in contact with the metal part (first metal part 1) located immediately below the second metal part 2, and a metal part (first metal part located immediately below the second metal part 2). 1 metal part 1) and 2nd area | region 2B which does not contact | connect. In the example shown in FIG. 1, the metal part located immediately below the second metal part 2 corresponds to the first metal part 1.

  With such a configuration, the second metal part 2 can dissipate heat inside the metal plate 12 to the outside air from the second region 2B that is not in contact with the metal part (first metal part 1) located immediately below. . Therefore, the thermal stress resulting from the difference in thermal expansion coefficient between the metal plate 12 and the insulating base 11 can be reduced.

  Further, since the area where the second metal part 2 is joined to the first metal part 1 is reduced, thermal stress and thermal stress due to the difference in thermal expansion coefficient between the second metal part 1 and the first metal part 1 are generated. It is greatly reduced. Thereby, the thermal stress resulting from the difference in thermal expansion coefficient between the second metal part and the first metal part 1 inside the metal plate 12 can also be reduced.

  In the example shown in FIG. 1, it is preferable to use a metal material having low electrical resistance and high thermal conductivity as the second metal part 2 because the heat radiation efficiency of heat generated in the electronic component 5 is further increased.

  Moreover, copper which is an example of the metal material used for the 2nd metal part 2 is oxygen-free copper, for example. When oxygen-free copper is used as the material of the second metal part 2, it is reduced that the surface of the copper is oxidized by oxygen present in the copper when the metal plate 12 and the insulating base 11 are joined as will be described later. In addition, since the wettability with the bonding material 6 (described later) is improved, the bonding strength between the metal plate 12 and the insulating substrate 11 is improved.

The second metal layer 2 made of Cu is formed, for example, by applying a metal processing method such as a mechanical processing such as a rolling method or a punching method or a chemical processing such as etching to a Cu ingot. Is formed in a flat plate shape having a thickness of 10 to 300 μm and a predetermined pattern.

  An electronic component 5 is mounted on the second metal layer 2 of the circuit board 10 in the example shown in FIG. In the example shown in FIG. 1, the electronic component 5 is bonded to one metal plate 12 by a bonding material 6 and connected to the other metal plate 12 via a conductive connection material 7 such as a bonding wire. .

  In the example shown in FIG. 1A, the electronic component 5 is provided on the upper surface of the second metal layer 2 and above the first region 2A. In this case, since the first region 2A is supported by the first metal part 1, the electronic component 5 can be placed in a stable location.

  In the example shown in FIG. 1B, the electronic component 5 is provided on the upper surface of the second metal layer 2 and above the second region 2B. In this case, even when the electronic component 5 generates heat, a large amount of heat generated in the electronic component 5 is transmitted from the second region 2B before the heat is transferred to the insulating base 11 via the first metal part 1. It can dissipate heat.

  The metal plate 12 on which the electronic component 5 is mounted and the metal plate 12 on which the conductive connecting material 7 is mounted are likely to generate heat due to large current flow, but the metal plate having the second metal portion 2. 12 each serve as a heat radiating section. The metal plate 12 functions as a circuit conductor and also serves to electrically connect the electronic component 5 and an external electric circuit (not shown).

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 6 is made of, for example, a metal or a conductive resin. The bonding material 6 is, for example, solder, a gold-tin (Au—Sn) alloy, or a tin-silver-copper (Sn—Ag—Cu) alloy.

  In the example shown in FIG. 2A, the difference from the example shown in FIG. 1 in the structure is that a third metal part 3 is provided between the first metal part 1 and the second metal part 2.

  In the example shown in FIG. 2A, the metal plate 12 is bonded to the main surface of the insulating base 11, and the first metal part 1, the third metal part 3, and the second metal part 2 are formed from the insulating base 11 side. It is made up of layers in order. The metal plate 12 has a first metal part 1 located closest to the insulating base 11 and a second metal part 2 located above the first metal part 1. In addition, as described above, in the example shown in FIG. 2A, the third metal part 3 is provided between the first metal part 1 and the second metal part 2.

  In the example shown in FIG. 2A, the materials and thicknesses of the first metal part 1 and the second metal part 2 are the same as those of the second metal part 2 used in the example shown in FIG. In the example shown in FIG. 2A, the material and thickness of the third metal part 3 are the same as those of the first metal part 1 used in the example shown in FIG.

  Further, the example shown in FIG. 2B is different from the example shown in FIG. 2A only in the dimension of the first metal part 1 in the y-axis direction. In the example shown in FIG. 2A, the first metal part 1 has the same dimension in the y-axis direction as the third metal part 3, but the first metal part 1 as in the example shown in FIG. Unlike the third metal part 3, 1 may be longer in the y-axis direction than the third metal part 3. In addition, it is not specifically limited whether the dimension of the x-axis direction of the 1st metal part 1 and the 3rd metal part 3 is also the same or different.

  In the example shown in FIG. 2, the method of joining the first metal part 1 to the insulating base 11 is the same as that in the example shown in FIG. 1, and the first metal part 1 and the second metal of the third metal part 3. The joining method to the part 2 is also the same as the joining method of the second metal part 2 to the first metal part 1 in the example shown in FIG.

  In the example shown in FIG. 2, the third metal part 3 is preferably made of a metal material having a larger coefficient of thermal expansion than that of the insulating base 11 and a smaller coefficient of thermal expansion than that of the second metal part 2. According to such a configuration, even when the difference in thermal expansion coefficient between the insulating base 11 and the second metal part 2 is large, the third metal part 3 is interposed between the two members. The third metal part 3 can relieve the thermal stress caused by the difference in thermal expansion coefficient. Therefore, deformation and peeling of the metal plate 12 can be suppressed.

  Next, a method for manufacturing the circuit board 10 of the present invention will be described. Here, a method for manufacturing the circuit board 10 of the example shown in FIG. 2 will be described.

  (1) First, the metal parts 1, 2, and 3 constituting the metal plate 12 are patterned into a desired shape. A specific patterning method for the metal plate 12 includes, for example, an etching process using masking together. Further, laser processing or punching processing may be used. When Cu is used as the first metal part 1 and the second metal part 2, ferric chloride is used for the etching solution for the first metal part 1 and the second metal part 2. When Mo is used as the third metal part 3, an oxidizing acidic solution in which concentrated nitric acid, concentrated sulfuric acid, and water are mixed at a volume ratio of 1: 1: 3 in the etching solution for the third metal part 3. Is used. When Invar is used as the third metal part 3, ferric chloride is used as the etching solution for the third metal part 3. When the third metal part 3 is made of an alloy of W and Mo, an alkaline solution containing ferricyanate is used as the etching solution for the third metal part 3.

  (2) Next, the patterned metal parts 1, 2, and 3 are joined to the insulating base 11. In this step, for example, the metal parts 1, 2, and 3 may be bonded to each other and then bonded to the insulating substrate 11 with a brazing material. The metal parts 1, 2, and 3 are joined to each other by, for example, a cold rolling method. After applying a paste-like brazing material to the lower surface of the joined body of the metal parts 1, 2, and 3, it is placed on the insulating substrate 11 with its surface down, cooled at a predetermined temperature in an electric furnace, and then cooled. By doing so, the metal parts 1, 2, and 3 are joined to the insulating base 11.

As a metal material (brazing material) for joining the first metal part 1 and the insulating base 11, for example, a material having a melting point of about 600 ° C. is used. The melting point is adjusted by adjusting the amount of tin and indium with respect to the amount of silver which is the main component of the brazing material. The suitable composition in that case is as described above. The brazing material may be heated at a temperature higher by about 50 ° C. than the melting point of the brazing material. When the heating temperature of the brazing material is set in the vicinity of the melting point, the heat treatment time is preferably set to 1 hour or more.

  In the above process, the metal parts 1, 2, and 3 may be joined to each other by a brazing material instead of the cold rolling method. In that case, it is preferable to use a brazing material having a melting point higher than that of the metal material (brazing material) for joining the first metal part 1 and the insulating base 11. In this case, even when heating is performed to join the first metal part 1 and the insulating base 11, the brazing material that fixes the metal parts 1, 2, and 3 does not melt. Lamination displacement and deformation between 1, 2, and 3 can be suppressed.

In the above process, the joined body of the metal parts 1, 2, 3 joined in advance to the insulating base 11, but the joining of the metal parts 1, 2, 3 and the metal parts 1, 2, 3 Bonding to the insulating substrate 11 may be performed simultaneously. In this case, paste-like brazing material is used between the insulating base 11 and the first metal part 1, between the first metal part and the third metal part 3, and between the second metal part 2 and the third metal part 3. The members are temporarily fixed to each other, and then the members are joined together by heating and cooling together. As the brazing material in this case, for example, a material containing silver, tin and indium described above may be used.

  In the above-described process, the metal parts 1, 2, and 3 that have been patterned in advance have been described as being bonded to the insulating base 11. However, the patterning may be performed after the bonding to the insulating base 11 is performed first. In this case, not only the metal parts 1, 2, and 3 but also the brazing material between the first metal part 1 and the insulating base 11 must be removed by etching. Thus, for example, the first metal part 1 (Cu), the second metal part 2 (Cu), the third metal part 3 (Mo), and the brazing material are sequentially removed by etching while changing the etching solution. do it. For example, hydrofluoric acid is used as an etching solution for the brazing material. In addition, when the 1st metal part, the 2nd metal part 2, and the 3rd metal part 3 are joined by the brazing material, what is necessary is just to remove these brazing materials also by etching.

  A metal having high conductivity and corrosion resistance and good wettability with the bonding material 6 may be deposited on the surface of the metal plate 12 by a plating method. In this case, the metal plate 12 and the external electric circuit, the bonding material 7 and the like can be easily and firmly bonded. Further, the electrical connection between the metal plate 12 and the external electric circuit or the like can be made better.

  Examples of the plating metal include metal materials such as nickel, cobalt, copper, and gold, or alloy materials containing these metal materials as main components. For example, in the case of a nickel-phosphorus amorphous alloy plating layer containing 8 to 15% by mass of phosphorus inside, the surface oxidation of the nickel plating layer can be suppressed and the wettability of the bonding material 7 and the like can be maintained for a long time. It is preferable because it is possible. When the content of phosphorus with respect to nickel is about 8 to 15 masses, a nickel-phosphorus amorphous alloy is easily formed, and the adhesive strength of the bonding material 6 and the like to the plating layer can be improved. The thickness of this nickel plating layer should just be about 1.5-10 micrometers, for example.

  3 is different from the example shown in FIG. 1A in that the metal plate 12 is also bonded to the other main surface (lower surface) of the insulating base 11. FIG. In addition, the member with the same code | symbol is using the same thing as the example shown in FIG. With such a configuration, the thermal expansion amount of the metal plate 12 on each of the lower surface and the upper surface of the insulating base 11 is approximated, so that the thermal stress applied to each of the lower surface and the upper surface of the insulating base 11 is also approximated. Therefore, the amount of warping of the insulating base 11 can be reduced.

  Further, as in the example shown in FIG. 3, when the metal plate 12 on the upper surface of the insulating base 11 is composed of the first metal portion 1 and the second metal portion 2, the metal plate 12 on the lower surface of the insulating base 11 is also the first. It is preferable that the metal part 1 and the second metal part 2 are included. According to such a configuration, the thermal expansion amounts of the metal plate 12 on the upper surface and the lower surface of the insulating base 11 can be further approximated.

  Further, as in the example shown in FIG. 3, it is preferable that the position and size of the first region 2A on the upper surface and the lower surface of the insulating substrate 11 are symmetrical. According to such a configuration, the region of the second metal portion 2 that receives stress due to thermal expansion is symmetrical between the upper surface and the lower surface of the insulating base 11, so that the warping of the insulating base 11 can be further reduced.

  Further, as in the example shown in FIG. 3, it is preferable that the position and size of the second region 2B of the metal plate 12 on the upper and lower surfaces of the insulating base 11 are also symmetrical. According to such a configuration, the amount of heat released from the second region 2B is also approximated between the upper surface and the lower surface of the insulating base 11, so that the warping of the insulating base 11 can be further reduced.

Further, the metal plate 12 on the lower surface also functions as a heat sink, so that the heat dissipation of the circuit board 10 is improved. Also,
When a via conductor is provided inside the insulating substrate 11 and conduction is established between the upper surface and the lower surface of the insulating substrate 11, it is also used as a circuit conductor.

  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, another metal part may be laminated between the first metal part 1 and the second metal part 2 of the metal plate 12, and another metal part may be laminated on the upper part of the second metal part. Also good.

  Further, the second metal part 2 may extend to the outside from the outer edge of the insulating base 11 in a top view. In this case, a large area of the second region 2B can be secured, so that not only the heat dissipation efficiency is improved, but also the extended end portion of the second metal portion 2 can function as a connection terminal to an external electronic device. it can.

  Further, as in the example shown in FIG. 4, the metal plate 12 may have a plurality of second metal portions 2. In FIG. 4, the metal plate 12 has two second metal parts 2, both of which are located on the upper part of the first metal part 1. The lower second metal part 2 is provided so as to be sandwiched between the first metal part 1 and the third metal part 3, and the upper second metal part 2 is provided on the upper surface of the third metal part 3. ing. Since these two second metal portions 2 each have the second region 2B, the metal plate 12 can dissipate heat from the two second regions 2B. The metal plate 12 may have three or more second metal portions 2. Further, a plurality of third metal portions may be provided in accordance therewith.

  As in the example illustrated in FIG. 5, the second metal portion 2 includes a flat plate portion 2 a and a plurality of linear portions 2 b provided at the distal end portion of the flat plate portion 2 a. By having such a linear portion 2b, a terminal can be easily connected to an external device. Moreover, according to such a structure, it can radiate also from the linear part 2b. Further, in the example shown in FIG. 5, these linear portions 2b are bent upward. According to such a configuration, a connection can be easily made when terminal connection is made to an external electronic device in the Z direction. Moreover, according to such a structure, since heat can be radiated to the space above the circuit board, the heat radiation efficiency can be further enhanced.

DESCRIPTION OF SYMBOLS 1 ... 1st metal part 2 ... 2nd metal part 2A ... 1st area | region 2B ... 2nd area | region 3 ... 3rd metal part 5 ... Electronic component 6 ... Bonding material 7: Conductive connecting material
10 ... Circuit board
11 ... Insulating substrate
12 ... Metal plate
13 ... Electronic device

Claims (5)

An insulating substrate;
A metal plate that is bonded to the main surface of the insulating base and is formed by sequentially laminating a plurality of metal portions;
The metal plate has a first metal portion located closest to the insulating base, and a second metal portion located above the first metal portion,
The lower surface of the second metal part has a first region in contact with the metal part located immediately below the second metal part and a second region not in contact with the metal part located immediately below the second metal part. Circuit board. The circuit board according to claim 1, wherein the second metal part is a metal part located at an uppermost part of the metal plate. The circuit board according to claim 1, wherein the second metal portion extends to the outside from an outer edge of the insulating base in a top view. The circuit board according to claim 1, wherein the metal plate has a plurality of second metal parts. A circuit board according to any one of claims 1 to 4,
An electronic component mounted on the upper surface of the metal plate;
An electronic device.

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