JP2018011020A - Composite substrate and electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite substrate, etc. by which an electronic module with a high heat dissipation property can be easily manufactured even with an insulative substrate with a relatively thick second metal plate.SOLUTION: A composite substrate 10 and an electronic device are disclosed. The composite substrate comprises: an insulative substrate 1 having top and bottom faces; a first metal plate 2 having a bottom face bonded to the top face of the insulative substrate 1; a second metal plate 3 thicker than the first metal plate 2, which has a top face bonded to the bottom face of the insulative substrate 1; and a bonding portion 4 bonding between the insulative substrate 1 and the second metal plate 3. The bonding portion 4 includes an active brazing filler metal including a brazing filler metal and an active metal added to the brazing filler metal. The bonding portion includes: a first bonding portion 4a interposed between the bottom face of the insulative substrate 1 and the top face of the second metal plate 3; and a fillet-like second bonding portion 4b including the active brazing filler metal and a granular material 4m made of a material smaller than the brazing filler metal in thermal expansion coefficient, and formed so as to spread from the outer periphery of the first bonding portion 4a to the side face of the second metal plate 3 and over the bottom face of the insulative substrate 1.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a composite substrate including a metal plate bonded to an insulating substrate and an electronic device.

As a composite substrate on which electronic parts such as IGBTs (Insulated Gate Bipolar Transistors) such as power modules or switching modules are mounted, an insulating substrate made of a ceramic sintered body and a metal bonded to the insulating substrate via a brazing material A composite substrate including a plate is used (for example, see Patent Document 1).

  For example, an electronic component is mounted on a metal plate on the upper surface side of an insulating substrate to form an electronic device, and the composite substrate is mounted on an external member such as a mother board or a heat radiator included in various electronic devices.

  In recent years, it has become necessary for the composite substrate and the electronic device to cope with an increase in the amount of heat generated from the electronic components to be mounted. For this, it is conceivable to increase the heat dissipation to the outside by making the lower metal plate thicker than the upper metal plate.

JP-A-3-261669

  However, if the metal plate on the lower surface of the insulating substrate is made thicker than the metal plate on the upper surface, thermal stress generated between the metal portion including the metal plate and the brazing material on the lower surface side of the insulating substrate and the insulating substrate becomes larger. There is a possibility that it is difficult to improve the reliability of bonding between the metal plate on the lower surface side and the insulating substrate.

  A composite substrate according to one aspect of the present invention includes an insulating substrate having an upper surface and a lower surface, a first metal plate having a lower surface bonded to the upper surface of the insulating substrate, and an upper surface bonded to the lower surface of the insulating substrate. And a second metal plate that is thicker than the first metal plate, and a joint that joins the insulating substrate and the second metal plate. The joining portion is made of an active brazing material to which an active metal is added, and has a first joining portion interposed between the lower surface of the insulating substrate and the upper surface of the second metal plate, and more heat than the brazing material. A fillet-like second joint formed of an active brazing material containing a granular material made of a material having a small expansion coefficient, formed from the outer periphery of the first joint to the side surface of the second metal plate and the lower surface of the insulating substrate. Including.

  An electronic device according to an aspect of the present invention includes the composite substrate having the above-described configuration and an electronic component mounted on the first metal plate.

According to the composite substrate according to one aspect of the present invention, the reliability is improved because it has the above-described configuration and includes the first and second joint portions. That is, since the 2nd junction contains the above-mentioned particles, the thermal expansion of the 2nd junction located in the perimeter of a junction is comparatively small. Therefore, the thermal expansion of the joint portion is reduced, and the thermal stress generated between the metal portion including the joint portion and the insulating substrate is reduced. Therefore, it is possible to provide a composite substrate in which the reliability of bonding between the second metal plate and the insulating substrate is effectively improved.

  According to the electronic device of one aspect of the present invention, since the composite substrate having the above-described configuration is included, the reliability of the bonding between the second metal plate and the insulating substrate is high, and it is also effective in improving heat dissipation. An electronic device can be provided.

(A) is a top view which shows the composite substrate of embodiment of this invention, (b) is sectional drawing in the AA of (a). It is sectional drawing which expands and shows the principal part of the composite substrate shown in FIG. It is sectional drawing which shows the electronic device of embodiment of this invention. It is sectional drawing which shows the modification of the principal part of the composite substrate shown in FIG. FIG. 10 is a cross-sectional view showing a first modification of the electronic device shown in FIG. 3. FIG. 10 is a cross-sectional view showing a second modification of the electronic device shown in FIG. 3.

  Embodiments of the present invention will be described below with reference to the drawings. The distinction between the upper and lower sides in the following description is for convenience, and does not limit the upper and lower sides when the composite substrate and the electronic device are actually used. Moreover, in the following drawings, in order to make the shape and the like easier to understand, dimensions including the curvature may be emphasized more than actual.

(Composite substrate)
FIG. 1A is a plan view showing a composite substrate according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA in FIG. FIG. 2 is an enlarged cross-sectional view showing a main part of the composite substrate shown in FIG. FIG. 3 is a cross-sectional view illustrating an electronic device according to an embodiment of the present invention.

  The composite substrate 10 basically includes an insulating substrate 1, a first metal plate 2 bonded to the upper surface of the insulating substrate 1, and a second metal plate 3 bonded to the lower surface of the insulating substrate 1 for the bonding portion 4. Has been. In the example of this embodiment, the first metal plate 2 is bonded to the insulating substrate 1 by the upper bonding portion 5. The electronic component 6 is mounted on the composite substrate 10 to form the electronic device 20 of the embodiment.

  The insulating substrate 1, the first metal plate 2 and the second metal plate 3 are parts that basically constitute the composite substrate 10. For example, a part of the upper surface of the first metal plate 2 is used as a mounting part for electronic components. Further, a part or all of the lower surface of the second metal plate 3 is used as a part for connection to the external member 21. The external member 21 is an electronic circuit, a heat radiating member, or the like included in various devices such as an electronic device, a vehicle, or an industrial machine, and the composite substrate 10 is electrically and thermally connected thereto. The electronic device 20 is mounted on the external member 21, and the electronic module 30 is formed.

  The insulating substrate 1 functions as a base that holds the first metal plate 2 and the second metal plate 3 while ensuring electrical insulation. The electronic component 6 is mounted on the upper surface of the first metal plate 2 to form an electronic device 20 to be described later, and the electronic module 30 to be described later is formed if the lower surface of the second metal plate 3 is connected to an external member. In this case, heat generated in the electronic component 6 is conducted to the external member through the first metal plate 2, the insulating substrate 1, and the second metal plate 3.

The insulating substrate 1 has a rectangular shape or a plate shape or the like in which a corner is curved (chamfered) in a plan view. The insulating substrate 1 is made of an electrically insulating material, for example, a material such as a silicon nitride sintered body, an aluminum oxide sintered body, a mullite sintered body, a silicon carbide sintered body, or an aluminum nitride sintered body. Become. Among these materials, when importance is attached to thermal conductivity that affects heat dissipation, a silicon nitride sintered body, a silicon carbide sintered body, an aluminum nitride sintered body, or the like is used. In consideration of mechanical strength, for example, a silicon nitride sintered body or a silicon carbide sintered body is used.

  When the insulating substrate 1 is made of a ceramic material having a relatively high mechanical strength such as a silicon nitride sintered body, the first metal plate 2 and the second metal plate 3 having a greater thickness (thickness) are used. However, the possibility of mechanical damage such as cracks occurring in the insulating substrate 1 can be reduced. Therefore, it is possible to realize the composite substrate 10 capable of flowing a larger current while reducing the size.

The thinner the insulating substrate 1, the better in terms of thermal conductivity. However, when considering mechanical strength, electrical insulation, etc., it should not be too thin. The thickness of the insulating substrate 1 is, for example, about 0.1 mm to 1 mm, and may be selected according to the size of the composite substrate 10 or the thermal conductivity or strength of the material used. The size of the insulating substrate 1 is, for example, about 5 to 50 mm in length and about 10 to 60 mm in width in plan view.

  If the insulating substrate 1 is made of, for example, a silicon nitride sintered body, it can be manufactured as follows. First, a slurry prepared by adding and mixing an appropriate organic binder, plasticizer and solvent to raw powders such as silicon nitride, aluminum oxide, magnesium oxide and yttrium oxide is formed into a sheet by a method such as a doctor blade method or a calender roll method. Molding to form a ceramic green sheet. Next, the ceramic green sheet is subjected to an appropriate punching process or the like to obtain a predetermined shape, and a plurality of sheets are laminated and processed into a molded body as necessary. Thereafter, the compact is fired at a temperature of 1600 to 2000 ° C. in a non-oxidizing atmosphere such as a nitrogen atmosphere. The insulating substrate 1 can be manufactured by the above process.

  The first metal plate 2 is bonded to the upper surface of the insulating substrate 1, and the second metal plate 3 is bonded to the lower surface of the insulating substrate 1. The first metal plate 2 and the second metal plate 3 are made of, for example, copper, an alloy containing copper as a main component, or a metal material such as aluminum.

  In the composite substrate 10 and the electronic device 20 of the embodiment, the thickness of the second metal plate 3 is set to be twice or more the thickness of the first metal plate 2. If a specific example is given, the thickness of the 1st metal plate 2 will be set to about 0.4-0.6 mm, and the thickness of the 2nd metal plate 3 will be set to about 0.8-1.2 mm. In this case, the thickness of the second metal plate 3 may be set to a thickness exceeding 1.2 mm in consideration of improvement in heat dissipation, suppression of deformation of the laminated body 9 due to thermal stress, economy, and the like. .

  The first metal plate 2 and the second metal plate 3 are attached to the insulating substrate 1 after a copper original plate (not shown) is formed by a predetermined metal processing such as die punching or etching, for example. Alternatively, the first metal plate 2 or the second metal 3 can be formed by bonding an original copper plate to the upper surface or the lower surface of the insulating substrate 1 and then performing an etching process or the like on the original plate. The first metal plate 2 and the second metal plate 3 are joined to the insulating substrate 1 by a joining method such as brazing. The brazing material is, for example, an active brazing material containing silver brazing as a main component and further adding an active metal material such as titanium to the silver brazing. An active brazing material or the like that joins the second metal plate 3 to the insulating substrate 1 forms the joint 4. The upper joint 5 can also be formed using a brazing material such as an active brazing material. Details of the joint 4 will be described in detail below.

  The joint 4 joining the insulating substrate 1 and the second metal plate 3 is made of an active brazing material containing a brazing material and an active metal added to the brazing material, and the lower surface of the insulating substrate 1 and the second metal. The outer periphery of the 1st junction part 4a which consists of the 1st junction part 4a interposed between the upper surfaces of the board 3, and the active brazing material containing the granular material 4m which consists of a material whose coefficient of thermal expansion is smaller than a brazing material To the side surface of the second metal plate 3 and the lower surface of the insulating substrate 1.

  The 1st junction part 4a and the 2nd junction part 4b may contain the mutually same kind of brazing material. Examples of such a brazing material include brazing materials such as silver brazing (silver-copper brazing), copper brazing, gold alloy brazing, aluminum alloy brazing, brass brazing and the like.

  In the case where the second metal plate 3 is made of copper such as oxygen-free copper, silver brazing (silver-copper brazing) is used as the brazing material in consideration of bonding strength, workability, economy, and the like. Used. The composition of the silver solder may be a silver-copper eutectic composition or a composition having a higher copper content.

Moreover, both the 1st junction part 4a and the 2nd junction part 4b may add the active metal to the brazing material with the same content rate. Examples of the active metal include zirconium and hafnium in addition to titanium. The ratio of the addition of the active metal to the brazing material is, for example, 1.7 to 4.3% by mass in the external addition when the brazing material is 100 parts by mass in consideration of the brazing strength, workability, economy, etc. Good. Or the content rate of the active metal in an active brazing material should just be about 1.6-3.8 mass%.

  As the material having a relatively high melting point forming the granular material 4m, when the brazing material is silver brazing as described above, a metal material having a melting point higher than that of copper can be used. Examples of such a metal material include metal materials such as molybdenum, tungsten, and nickel.

  Even when the brazing material is a brazing material other than silver brazing material, a granular material 4m made of a metal material or a semi-metal material higher than the melting point of each brazing material component can be used. For example, when the brazing material is an aluminum alloy brazing, chromium can be used, and when the brazing material is brass brazing, at least one of nickel and silicon can be used.

(Production method of composite substrate)
The composite substrate 10 of the embodiment can be manufactured by a manufacturing method including the following processes, for example. However, the manufacturing method of the composite substrate 10 is not limited to this example, and can be appropriately changed according to the type or size of the material to be used, productivity, economy, and the like.

First, the insulating substrate 1 is produced by the method as described above. The insulating substrate 1 is set in accordance with the outer dimensions, predetermined characteristics, economy, etc. of the composite substrate 10 to be manufactured, and the material to be used is selected. For example, the insulating substrate 1 having a rectangular shape (square shape or rectangular shape) having a thickness of about 0.1 mm to 1 mm and a side dimension of about 5 to 60 mm in plan view is manufactured by a method of firing a ceramic green sheet. To do.

  Next, the first metal plate 2 and the second metal plate 3 are produced. The 1st metal plate 2 and the 2nd metal plate 3 can be produced by giving predetermined metal processing, such as cutting, rolling, and etching, to a copper original plate, such as oxygen free copper, for example. The first metal plate 2 and the second metal plate 3 are produced, for example, as flat plates having outer dimensions slightly smaller than those of the insulating substrate 1 in plan view.

  At this time, in order to increase (thicken) the thickness of the second metal plate 3 to about twice the thickness of the first metal plate 2, for example, the dimensions at the time of metal processing may be adjusted. The size (dimension) in plan view of the first metal plate 2 and the second metal plate 3 depends on the size in plan view of the first metal plate 2 and the second metal plate 3 in the composite substrate 10 to be manufactured. It may be adjusted appropriately. For example, at least one of the first metal plate 2 and the second metal plate 3 to be manufactured may be larger than the insulating substrate 1 in plan view.

  Next, the first metal plate 2 and the second metal plate 3 are joined to the insulating substrate 1. In this joining, for example, the first metal plate 2 and the second metal are firstly passed through the paste or preform of the active brazing material to be the first joining part 4a, the second joining part 4b and the upper joining part 5, respectively. Each plate 3 is aligned with the insulating substrate 1. Thereafter, the above brazing can be performed by heating in a furnace while temporarily fixing them with a jig or the like. At this time, the granular material 4m may be added to the paste or preform to be the second joint portion 4b.

  In addition, said brazing may be performed simultaneously with the 1st metal plate 2 and the 2nd metal plate 3, and may be performed separately (sequentially). Also, for the bonding of the second metal plate 3 to the insulating substrate 1, the bonding via the first bonding portion 4a and the formation of the second bonding portion 4b are separately performed (the first bonding portion 4a and the second bonding portion 4b). In order) or at the same time.

  When the first joint 4a and the second joint 4b are simultaneously performed at the time of brazing (that is, under the same temperature condition), the granular material 4m that becomes the second joint 4b is contained. The flowability of the active brazing material is smaller than that of the active brazing material that forms the first joint 4a. Therefore, the flow out to the outer side of the 2nd junction part 4b is suppressed. As a result, the entire joint 4 including the fillet portion is prevented from flowing out from the region effective for the joint strength between the second metal plate 3 and the insulating substrate 1. Therefore, the bonding strength between the relatively thick second metal plate 3 and the insulating substrate 1 can also be effectively increased.

  Moreover, since the flow-out of the junction part 4 is suppressed effectively, the electrical insulation fall and the electrical short circuit by the brazing material etc. which flowed out of the 2nd metal plate 3 and another metal plate (not shown) are also effective. Can be suppressed. A specific example of ion migration in the portion including the second metal plate 3 will be described later.

(Modification)
FIG. 4 is a cross-sectional view showing a modification of the main part of the composite substrate 10 shown in FIG. 4, parts similar to those in FIG. 2 are denoted by the same reference numerals.

  In the example shown in FIG. 4, both the first joint 4 a and the second joint 4 b contain the primary crystal 4 p of the component in the brazing material. The brazing material in this case contains a plurality of metal materials or metalloid materials, and any metal material or metalloid material is crystallized as a primary crystal. In this case, the plurality of metal materials or metalloid materials may be a plurality of metal materials or metalloid materials having different coefficients of thermal expansion.

  The presence or absence of crystallization of the primary crystal 4p, the crystallization temperature, the composition of the brazing material that can be crystallized, and the like can be confirmed by a phase diagram of the metal material or semi-metal material constituting the brazing material of the joint portion 4. For example, the composition corresponding to the eutectic phase diagram can be used.

  Examples of such a brazing material include silver-copper eutectic brazing and aluminum alloy brazing.

  For example, if the brazing material is silver brazing, the metal material having the smaller coefficient of thermal expansion (linear expansion coefficient) is copper. If the brazing material is an aluminum alloy brazing material, the metal material or metalloid material having the smaller coefficient of thermal expansion is silicon.

  In addition, the thermal expansion coefficient of the metal material or metalloid material having the smaller thermal expansion coefficient may be smaller, larger, or the same as the thermal expansion coefficient of the granular material 4m.

In this case, a primary crystal of a metal material or a semi-metal material having a smaller thermal expansion coefficient may be present, and the primary crystal 4p in the second joint 4b is more than the proportion of the primary crystal 4p in the first joint 4a. The ratio may be larger.

  When the primary crystal 4p of the metal material or the semimetal material having the smaller thermal expansion coefficient exists and the ratio of the primary crystal 4p is larger in the second joint 4b than in the first joint 4a, The thermal expansion (apparent thermal expansion coefficient) of the two joint portions 4b can be further reduced. Therefore, the thermal stress generated between the relatively thick second metal plate 3 and the insulating substrate 1 can be effectively reduced. Therefore, the composite substrate 10 in which the reliability of bonding between the insulating substrate 1 and the second metal plate 3 is effectively improved can be obtained.

  In the configuration in which the joint portion 4 includes the primary crystal of the brazing material as in the example illustrated in FIG. 4, the brazing material constituting the joint portion 4 includes a plurality of metal materials that are different from each other in ion migration. The primary crystal of the metal material that is less likely to cause ion migration (electrochemical migration) among the plurality of metal materials is present on the outer peripheral portion of the second joint portion 4b. May be.

  In this case, the primary crystal 4p of the component in the brazing material is formed by first crystallizing the metal material that is less susceptible to ion migration during brazing. Examples of such a brazing material include silver-copper eutectic brazing and aluminum alloy brazing.

The primary crystal 4p of the metal material that is less likely to cause ion migration is present at least in the outer peripheral portion of the second joint portion 4b, whereby the ion migration of the joint portion 4 can be effectively suppressed. As a result, a decrease in electrical insulation or an electrical short circuit between the second metal plate 3 and another conductor such as another metal plate (not shown) due to the above-mentioned ion migration is also effective. Can be suppressed.

  Examples of the metal that easily causes ion migration include silver, copper, and lead. These metal materials are likely to cause migration in the above order.

  In addition, it is a composition containing said metal material or semi-metal material which can form the junction part 4, ie, silver, copper, gold | metal | money, aluminum, silicon, brass (zinc) etc., Comprising: Examples include copper and silicon.

  For example, from the above composition, the composition of the brazing material can be determined by appropriately considering the above conditions such as the coefficient of thermal expansion or the difficulty of occurrence of ion migration.

  In addition, about the upper junction part 5 which joins the 1st metal plate 2 and the insulated substrate 1, it can include an initial crystal similarly to the 2nd junction part 4, for example. In this case, the upper joint 5 can obtain the same effect as that of the joint 4.

  In the above modification, when the brazing material is silver brazing and the material having a low coefficient of thermal expansion is at least one metal material selected from molybdenum and tungsten, the first metal plate 2 made of oxygen-free copper or the like. It is easy to improve the wettability and the like of the active brazing material including the brazing material with respect to the second metal plate 3. Therefore, the bonding strength of the first metal plate 2 and the second metal plate 3 to the insulating substrate 1 through the bonding portion 4 and the upper bonding portion 5 can be effectively improved.

In a configuration in which the brazing material is silver brazing and the material having a low coefficient of thermal expansion is at least one metal material selected from molybdenum and tungsten, the brazing material has a copper content higher than the silver-copper eutectic composition. May be a silver solder having a large thermal expansion coefficient and molybdenum. In this case, it is easy to crystallize the primary crystal 4p in the active brazing material (brazing material) to be the joint portion 4, and the joint portion 4 including the primary crystal 4p is easy to realize.

  In each example including the embodiment and the modification described above, the second bonding portion 4b is, for example, in a longitudinal sectional view as shown in FIG. 2, than the dimension (width) L1 in the direction along the lower surface of the insulating substrate 1. The dimension (height) L2 in the direction along the side surface of the second metal plate 3 may be larger (L1 <L2).

  In this case, a base portion (not indicated as a base portion) composed of the insulating substrate 1, the first metal plate 2 and the second metal plate 3 is joined to the second joint by joining to the side surface of the second metal plate 3. Other metal plates (not shown) joined to the same surface as the second metal plate 3 of the insulating substrate 1 and the second metal plate 3 through the second joint 4b while increasing the joint strength with the portion 4b It is also possible to effectively suppress a decrease in electrical insulation and an electrical short circuit.

  As described above, when L1 <L2, the contact angle θ2 with respect to the side surface of the second metal plate 3 is smaller than the contact angle θ1 with respect to the lower surface of the insulating substrate 1 in the second bonding portion 4b. For example, θ1 is about 30 to 70 degrees, and θ2 is about 10 to 50 degrees, for example.

(Electronic device)
As described above, FIG. 3 is a cross-sectional view showing the electronic device 20 according to the embodiment of the present invention. The electronic device 20 of the embodiment is basically configured by the composite substrate 10 having the above configuration and the electronic component 6 mounted on the first metal plate 2. The electronic device 20 is mounted on the external member 21 in the direction of an arrow, for example. Also in the following drawings, the direction of mounting or mounting may be indicated by an arrow as in FIG.

The electronic component 6 is mounted, for example, at the center of the upper surface of the first metal plate 2 that is rectangular in plan view. The electronic component 6 is, for example, a semiconductor element such as a transistor, an LSI (Large Scale Integrated circuit) for a CPU (Central Processing Unit), an IGBT (Insulated Gate Bipolar Transistor), or a MOS-FET (Metal Oxide Semiconductor-Field Effect Transistor). is there. The electronic component 6 is not limited to a semiconductor element, and may be appropriately selected from various electronic components including a sensor element such as a temperature sensor element and a passive component such as a capacitive element, or may be plural. Different types of electronic components (not shown) may be mounted.

  The electronic component 6 is bonded to the upper surface of the first metal plate 2 by a bonding method such as bonding via a bonding material (not shown) for components. The bonding material for parts is made of, for example, metal or conductive resin. The bonding material for components is, for example, solder (tin-lead eutectic solder or the like), gold-tin (Au-Sn) alloy, tin-silver-copper (Sn-Ag-Cu) alloy, or the like.

A plating film (not shown) may be formed on the surface of the first metal plate 2 by a plating method. According to this configuration, since the wettability of the bonding material for components is improved, the bonding strength of the electronic component 6 to the upper surface of the first metal plate 2 can be improved. As the plating film, a metal having high conductivity and corrosion resistance may be used. For example, a plating film of nickel, cobalt, silver, copper, gold, or the like is used. The plating film may be an alloy material mainly composed of these metal materials, or may be one in which a plurality of layers are sequentially deposited. The thickness of the plating film may be, for example, 0.1 to 10 μm.

  The semiconductor element mounted as the electronic component 6 is electrically connected to an external electric circuit (not shown) by a conductive connecting material (not shown) such as a bonding wire. The external electric circuit is included in the external member 21, and various signals or predetermined potentials such as ground are exchanged between the semiconductor element and the external electric circuit.

  For example, when the external member 21 is a circuit board (motherboard or the like) of a device having an electronic control mechanism such as a computer or an automobile, information serving as a basis for calculation is transmitted from the external member 21 to the electronic component 6 and from the electronic component 6 to the outside. An operation result or stored information is transmitted to the electric circuit.

  Further, the heat generated by the operation of the electronic component 6 is conducted to, for example, the second metal plate 3, and is conducted from the second metal plate 3 to the external member 21. In this case, the circuit board may promote heat transfer and heat dissipation to the outside. Further, an external member 21 for heat dissipation other than the external electric circuit may be joined to the second metal plate 3 to promote heat dissipation to the outside.

(Modification of electronic device)
FIG. 5 is a cross-sectional view showing a first modification of the electronic device 20 shown in FIG. In FIG. 5, parts similar to those in FIGS.

  In the example shown in FIG. 5, the composite substrate 10 is turned upside down and used to form the electronic device 20. As described above, the upper and lower sides when the composite substrate 10 is actually used are not limited to the above-described embodiment and its modified examples (examples shown in FIGS. 1 to 6), but as in the example of FIG. The second metal plate 3 may be used in an upward direction, and the electronic component 6 may be mounted on the second metal plate 3. Further, the first metal plate 2 may be mounted to face the external member 21.

  The example shown in FIG. 5 can be regarded as an example in which the relatively thick second metal plate 3 is used as the metal plate for mounting the electronic component 6 disposed on the upward surface of the insulating substrate 1. In this case, the second metal plate 3 may be divided into a plurality of parts (not shown) in plan view. The second metal plate 3 divided into a plurality includes one on which the electronic component 6 is directly mounted and one on which the electrode of the electronic component 6 is connected.

  At this time, as described above, if ion migration at the outer peripheral portion of the second joint portion 4b (the outermost peripheral portion of the joint portion 4) is suppressed, the electrical insulation between the plurality of second metal plates 3 is reduced and An electrical short can be effectively suppressed. That is, for each second metal plate 3, if the primary crystal 4p of a metal material (copper or the like) that is less prone to ion migration exists, ion migration of a metal material (silver or the like) that is more likely to cause migration. Can be suppressed.

  Even in the case of the electronic device 20 of the form shown in FIG. 5, since the composite substrate 10 having the above configuration is included, the reliability of the bonding between the relatively thick second metal plate 3 and the insulating substrate 1 is high, and the heat dissipation is good. It is possible to provide the electronic device 20 that is effective for improvement and the like.

  FIG. 6 is a cross-sectional view showing a second modification of the electronic device 20 shown in FIG. In the example shown in FIG. 6, the composite substrate 10 is mounted on the external member 21 in the vertical direction. As described above, the direction including the top and bottom when the composite substrate 10 is actually used is not limited to the above-described embodiment and its modification.

  In the example shown in FIG. 6, a plurality of electronic components 6 are mounted on the composite substrate 10. The number of electronic components 6 is not limited to one, and a plurality of electronic components 6 may be mounted. When a plurality of electronic components 6 are mounted, high functionality as the electronic device 30 is effectively performed.

  Even in the case of the electronic device 20 of the form shown in FIG. 6, since the composite substrate 10 of the embodiment is included as in the case of the electronic device 20 of FIG. Thus, the electronic module 30 having high adhesion between the external member 21 and the external member 21 can be obtained.

  The plurality of electronic components 6 to be mounted may be of the same type (for example, a plurality of semiconductor elements for storage) or different from each other (for example, a semiconductor integrated circuit element, a sensor element, and a passive component). Or a combination thereof.

  The external member 21 on which the electronic device 20 is mounted is not limited to the mother board or the like in the above-described example, and may be a heat radiating member 21 (21A) including heat radiating fins. Thereby, a mounting structure of the electronic device 20 with improved heat dissipation can be formed.

  Further, the external member 21 may be a bus bar 21B or the like. The bus bar 21 (21B) is electrically connected to a power source portion such as a battery in various vehicles on which an electric motor is mounted, for example. Thereby, the management and control of the power source of the vehicle having a conductive mechanism such as a hybrid vehicle or an electric vehicle can be effectively performed.

1 .. Insulating substrate 2 .. 1st metal plate 3 .. 2nd metal plate 4 .. Joining part 4 a .. 1st joining part 4 b .. 2nd joining part 4 m .. Granular material 4 p.・ Upper joint 6 ・ ・ Electronic parts
10. ・ Composite substrate
20 ・ ・ Electronic equipment
21 ・ ・ External material
30 ・ ・ Electronic module

Claims (7)

An insulating substrate having an upper surface and a lower surface;
A first metal plate having a lower surface bonded to the upper surface of the insulating substrate;
A second metal plate having an upper surface bonded to the lower surface of the insulating substrate and being thicker than the first metal plate; and a bonding portion for bonding the insulating substrate and the second metal plate. ,
The joint is
A first bonding portion made of an active brazing material containing an active metal added to the brazing material and the brazing material, and interposed between the lower surface of the insulating substrate and the upper surface of the second metal plate;
It contains the active brazing material and a granular material made of a material having a smaller coefficient of thermal expansion than the brazing material, and extends from the outer periphery of the first joint to the side surface of the second metal plate and the lower surface of the insulating substrate. A composite substrate including the formed fillet-shaped second bonding portion. The brazing material contains a plurality of metal materials or metalloid materials having different coefficients of thermal expansion,
In the first joint portion and the second joint portion, an initial crystal of a metal material or a semimetal material having a smaller coefficient of thermal expansion among the plurality of metal materials or semimetal materials exists, and the first joint portion 2. The composite substrate according to claim 1, wherein a ratio of the primary crystal in the second bonding portion is larger than a ratio of the primary crystal in. The brazing material contains a plurality of metal materials that are different from each other in ion migration, and a metal material that is less prone to ion migration among the plurality of metal materials on the outer periphery of the second joint portion. The composite substrate according to claim 1, wherein the primary crystal is present. The composite substrate according to claim 2, wherein the brazing material is silver brazing, and the material forming the granular material is at least one metal material selected from molybdenum and tungsten. The composite substrate according to claim 4, wherein the brazing material is a silver brazing material having a copper content larger than that of the silver-copper eutectic composition, and the material forming the granular material is molybdenum. The second joint portion has a dimension in a direction along a side surface of the second metal plate larger than a dimension in a direction along a lower surface of the insulating substrate in a longitudinal sectional view. A composite substrate according to any one of the above. The composite substrate according to any one of claims 1 to 6,
And an electronic component disposed on the first metal plate.