JP6233152B2 - Modules using overlay blocks - Google Patents

Description

  In this specification, a module including a semiconductor device, a conductor, a cooler, and the like is disclosed.

  It is necessary to join a conductor to the semiconductor device so as to be conductive. Some semiconductor devices require cooling because they generate heat when operated. Therefore, a module in which a semiconductor device, a conductor, and a cooler are stacked in that order is known. Patent Documents 1 and 2 disclose such a module.

  In general, the thermal expansion coefficients of the semiconductor device and the conductor are different, and the thermal expansion coefficients of the conductor and the cooler are different. When a conductor is joined to the semiconductor device, and a cooler is joined to the conductor, the semiconductor device operates to generate heat and the operation is cooled after the operation is repeated, whereby the semiconductor device, the conductor, and the cooler are repeated. Thermal stress acts. The thermal stress impairs the long-term reliability of the module.

JP 2005-019447 A JP 2010-251711 A

(Basic issues)
In the above module, a conductor is interposed between the semiconductor device and the cooler. The conductor is required to have the following characteristics.
(1) Low electrical resistance.
(2) Low thermal resistance (efficient heat transfer from the semiconductor device to the cooler).
(3) To be deformed flexibly (if deformed flexibly, it is possible to prevent the semiconductor device and the conductor from generating a large thermal stress and to prevent the conductor and the cooler from generating a large thermal stress).
However, with the current technology, it is difficult to satisfy all of the above (1) to (3) at a high level. In the present specification, a module capable of satisfying all of the above (1) to (3) at a high level is disclosed.

(Further problem 1)
Some semiconductor devices include a front electrode and a back electrode, and cool by disposing coolers on both the front and back surfaces of the semiconductor device. Some embodiments disclosed herein solve this basic problem in this type of module.

(Further problem 2)
For example, an inverter connects two switching semiconductor devices in series and draws out an output conductor from an intermediate point thereof. In order to make it modular, it is necessary to prevent electrical conduction to two semiconductor devices, cooling of the two semiconductor devices, and generation of large thermal stress due to the heat cycle of the two semiconductor devices. is there. Among the embodiments disclosed in this specification, there is a module that solves the above-described basic problem in a module including two semiconductor devices.
(Further problem 3)
The three-phase inverter requires two semiconductor devices for u-phase, two semiconductor devices for v-phase, and two semiconductor devices for w-phase. Among the embodiments disclosed in the present specification, there is a module that solves the above-described basic problem in a module including a u-phase circuit, a v-phase circuit, and a w-phase circuit.

(Modules that solve basic issues)
The present applicant has developed a member having a low electrical resistance, a low thermal resistance, and a flexible deformation characteristic, and has applied for a patent (Japanese Patent Application No. 2013-256237). Details of the members are disclosed in the specification and drawings of the above patent application. This patent application has not been published yet and does not fall under the publicly known technology.
The present inventors have found that a module that solves the basic problem can be realized by utilizing the member according to the above patent application, and created the following module.

This module includes at least a surface side cooler, a surface side overlapping block, and a semiconductor device. A surface electrode extending along the surface is formed on at least one surface of the semiconductor device. Hereinafter, the side on which the surface electrode is formed is referred to as a surface. When surface electrodes are formed on both the front and back surfaces of the semiconductor device, the side on which the cooler and the overlapping block are arranged is referred to as the surface. As described later, a cooler and an overlapping block may be arranged on both the front and back surfaces of the semiconductor device. In that case, either one is called the front surface and the other is called the back surface.
In this module, the surface of the superposed block on the front side is joined to the back side of the front side cooler, and the surface electrode of the semiconductor device is joined to the back side of the superposed block on the front side so as to be conductive. The surface side overlapping block is composed of a graphite foil and a metal foil, and is arranged in a direction in which a normal line standing on the surface electrode extends along a contact surface of the graphite foil and the metal foil. Graphite foil and metal foil are superposed. However, the graphite foil and the metal foil are simply overlapped, and they are not joined. For example, graphite foil and metal foil can slide along the contact surface. Alternatively, the overlay state of the graphite foil and the metal foil can be changed, and can be changed to an overlap state in which the adhesion force between the two is increased, or can be changed to an overlap state in which the adhesion force between the two is reduced. In the present specification, a state in which the graphite foil and the metal foil are simply overlapped and no further restraint relationship is taken between them is referred to as a non-bonded state.
The surface-side overlapping block used in this module is characterized in that, when observed from the normal direction, the contact surface of the graphite foil and the metal foil is distributed over the entire area of the surface-side overlapping block. For example, by wrapping a long multilayer foil with a long graphite foil and a long metal foil overlapped, the contact surface between the graphite foil and the metal foil is spread over the entire area from the inside to the outside in the radial direction. Will exist. In such a case, the contact surface is distributed over the entire area of the overlapping block. When winding a long multilayer foil in multiple layers, a core may be used. The contact surface is distributed over the entire area of the overlapping block, including the case where the winding core is present.
In order to maintain the state in which the long multilayer foil is wound in multiple layers, the end of the foil located on the outermost periphery may be maintained by being welded or the like. Or it may maintain in the wound state by restraining an outer periphery with metal foil etc. In this case, the outermost foil is flexibly deformed. Since the outermost foil is flexibly deformed, the graphite foil and the metal foil can slide along the contact surface. Alternatively, it can be changed to an overlapping state in which the adhesion force between the graphite foil and the metal foil is increased, or can be changed to an overlapping state in which the adhesion force is reduced. The foil that holds the wound state on the outermost periphery is maintained in a state where the graphite foil and the metal foil are overlapped, and is not restrained any more. The foil that is in the outermost periphery and maintains the rolled state maintains a state in which the graphite foil and the metal foil are superposed in a non-bonded state.
The same applies to the foil surrounding the outer periphery of the laminated body in order of the first graphite foil, the first metal foil, the second graphite foil, the second metal foil, the third graphite foil, the third metal foil, etc. Yes, as long as the foil surrounding the outer periphery is flexibly deformed, the foil simply maintains the graphite foil and the metal foil in a superposed state, and maintains the graphite foil and the metal foil in a non-bonded state.

When the overlapping block described above is interposed between the surface electrode of the semiconductor device and the back surface of the surface side cooler, the following phenomenon is obtained. (1) Both the graphite foil and the metal foil have low electrical resistance in the direction along the contact surface. The overlapping block is also a conductor having a low electric resistance. (2) The graphite foil continuously extends from the semiconductor device side toward the cooler side. The graphite foil has a very low thermal resistance in the direction along the contact surface. Even if the overlapping block is interposed, the thermal resistance between the semiconductor device and the cooler can be maintained at a low value. (3) The overlapping block is flexibly deformed. The graphite foil and the metal foil are in a non-bonded state, and are deformed flexibly so as to slide on each other, overlap strongly, or reduce the contact force. When the cooler expands / shrinks with respect to the semiconductor device, the overlapping block is flexibly deformed, so that no excessive stress is generated in the semiconductor device, or excessive stress is applied to the cooler. It does not occur. High stress relaxation.
When the above-described overlapping block is used, the surface-side overlapping block becomes a conductor and is electrically connected to the surface electrode. Furthermore, the surface-side overlapping block provides a heat transfer path between the semiconductor device and the surface-side cooler, and alleviates thermal stress caused by the difference in thermal expansion coefficient between the semiconductor device and the surface-side cooler. To do. The above overlapping block has low electrical resistance, low thermal resistance, and high stress relaxation properties. When the above-described overlapping block is used, the long-term reliability of the module is improved.

(Module to solve further problem 1)
The semiconductor device includes a front surface electrode and a back surface electrode, and the semiconductor device may be cooled by the front surface side cooler and the back surface side cooler. In that case, the overlapping block is used on both the front and back sides. The module in this case includes a back side cooler and a back side overlapping block in addition to the basic configuration. The back surface of the back surface side overlapping block is bonded to the surface of the back surface side cooler, and the back surface electrode of the semiconductor device is bonded to the surface of the back surface side overlapping block so as to be conductive. The back surface side overlapping block has the same configuration as the front surface side overlapping block. That is, it is composed of a graphite foil and a metal foil, and a normal line standing on the back electrode of the semiconductor device is arranged in a direction extending along the contact surface of the graphite foil and the metal foil. The graphite foil and the metal foil are overlapped in a non-bonded state, and when the back surface side overlapping block is observed from the normal direction, the contact surface is distributed over the entire back surface side overlapping block. .
According to the above module, the back-side overlap block becomes a conductor and is connected to the back-side electrode, and provides a heat transfer path between the semiconductor device and the back-side cooler, and between the semiconductor device and the back-side cooler. The thermal stress generated due to the difference in thermal expansion coefficient between the two is relaxed.

  When it is necessary to insulate the front side cooler from the front electrode and to insulate the rear side cooler from the rear electrode, install a front side insulating plate between the rear side of the front side cooler and the surface of the front side overlapping block. A backside insulating plate is interposed between the front surface of the backside cooler and the backside of the backside overlapping block. Thereby insulation is ensured. Here, the insulating plate may be fixed to the cooler or may be separable from the cooler. In the case where an insulating layer is formed on the surface of the cooler, the insulating plate can be omitted. In the present specification, the case where the cooler and the overlapping block are joined includes the case where the insulation plate is joined between the two. Since the cooler itself may be formed of an insulating material, an insulating plate or an insulating layer is not essential.

  In order to improve the reliability and durability of the module, it is preferable to cover the periphery of the front surface side overlapping block, the semiconductor device, and the back surface side overlapping block with a resin mold. The resin mold referred to here is one obtained by filling a molten resin around a semiconductor device or the like and curing it. When covering with a resin mold, in order to secure a heat transfer path, the surface of the front surface side overlapping block and the back surface of the back surface side overlapping block are exposed from the resin mold. Then, it is possible to obtain a relationship in which the front surface side overlapping block and the front surface side cooler are joined without using the resin mold, and the back surface side overlapping block and the back surface side cooler are joined without going through the resin mold.

(Module to solve further problem 2)
A module incorporating two semiconductor semiconductor devices may be required. Here, one semiconductor device is referred to as a front surface side semiconductor device, and the other semiconductor device is referred to as a back surface side semiconductor device. In the above module, the back electrode of the front surface side semiconductor device and the front surface electrode of the back surface side semiconductor device face each other, and it is difficult to dispose the conductor and the cooler between these electrodes. In the module disclosed in this specification, a member that serves as both a conductor and a heat transfer body is used.
In the module that solves the further problem 2, the front surface side cooler, the front surface side overlapping block, the front surface side semiconductor device, the intermediate overlapping block, the back surface side semiconductor device, the back surface side overlapping block, and the back surface side cooler are arranged in that order. Are stacked. It has the following features.
The surface of the surface side overlapping block is joined to the back surface of the surface side cooler. A surface electrode of the front surface side semiconductor device is joined to the back surface of the front surface side overlapping block so as to be conductive. The surface of the intermediate overlapping block is joined to the back surface electrode of the front surface side semiconductor device so as to be conductive.
The back surface of the back surface side overlapping block is joined to the surface of the back surface side cooler. The back surface electrode of the back surface side semiconductor device is joined to the surface of the back surface side overlapping block so as to be conductive. The back surface of the intermediate overlapping block is joined to the front surface electrode of the back surface side semiconductor device so as to be conductive.
In the module that solves the further problem 2, the surface of the intermediate overlapping block is bonded to the back surface of the front surface side cooler. Similarly, the back surface of the intermediate overlapping block is joined to the surface of the back surface side cooler.
The front side overlapping block, the intermediate overlapping block, and the back side overlapping block are the same as described above. That is, it is composed of a graphite foil and a metal foil, and the normals standing on the surface electrodes of the front surface side semiconductor device and the back surface side semiconductor device are arranged in a direction extending along the contact surface of the graphite foil and the metal foil. . The graphite foil and the metal foil are overlapped in a non-bonded state. When the overlapping block is observed from the normal direction, the contact surface is distributed over the entire area of the overlapping block.

In the case of the above-described module, the event described in the item “module for solving basic problems” is obtained between the surface-side cooler and the surface electrode of the surface-side semiconductor device. In addition, the phenomenon described in the item of “module for solving further problem 1” is also obtained between the back surface side cooler and the back surface electrode of the back surface side semiconductor device.
An intermediate overlapping block is bonded to the back electrode of the front surface side semiconductor device and the front surface electrode of the back surface side semiconductor device. The intermediate overlapping block is composed of graphite foil and metal foil. Since the electrical resistance in the direction along the contact surface between the graphite foil and the metal foil is low, a low resistance conduction path is ensured for the back electrode of the front surface side semiconductor device and the front surface electrode of the back surface side semiconductor device.
The intermediate overlapping block is joined to the front surface side cooler and the back surface side cooler. The graphite foil constituting the intermediate overlapping block continuously extends from the back surface electrode of the front surface side semiconductor device to the front surface side cooler and the back surface side cooler. The thermal resistance in the direction along the development surface of the graphite foil is very low. The intermediate superposed block with low thermal resistance secures a heat transfer path from the back electrode of the front surface side semiconductor device to the front surface side cooler and the back surface cooler, and the heat resistance of the heat transfer path is kept low. Similarly, the thermal resistance of the heat transfer path from the front surface electrode of the back surface side semiconductor device to the front surface side cooler and the back surface side cooler can be kept low.
Moreover, the intermediate overlapping block is deformed flexibly. No great stress is generated in the front-side semiconductor device, the back-side semiconductor device, the intermediate overlapping block, the front-side cooler, or the back-side cooler. The intermediate overlap block relieves stress well.
A front-side insulating plate is interposed between the back surface of the front-side cooler and the front surface-side overlapping block, and a rear-side insulating plate is interposed between the front surface of the back-side cooler and the back surface of the rear-side overlapping block. By doing so, the insulation state can be secured.

  It is preferable that the development surface of the graphite foil constituting the front surface side overlapping block and the back surface side overlapping block and the development surface of the graphite foil constituting the intermediate overlapping block be orthogonal to each other. The coefficient of thermal expansion in the direction along the development surface of the graphite foil is low. When there is the above-described orthogonal relationship, deformation of the module in two directions in which the graphite foil is orthogonal is suppressed. It becomes possible to eliminate the need for sealing and protecting with a resin mold.

If the periphery of the front surface side overlapping block, the front surface side semiconductor device, the intermediate overlapping block, the back surface side semiconductor device, and the back surface side overlapping block is covered with a resin mold, the reliability and durability of the module are improved.
If the surface of the surface-side overlapping block and the surface of the intermediate overlapping block are exposed from the resin mold, the surface-side overlapping block and the intermediate overlapping block can be joined to the surface-side cooler. If the back surface of the back surface side overlapping block and the back surface of the intermediate surface block are exposed from the resin mold, the back surface side overlapping block and the intermediate surface block can be joined to the back surface cooler.
If a part of the front side overlapping block, a part of the intermediate overlapping block, and a part of the back side overlapping block protrude from the resin mold, it is possible to connect a conductor to the protruding part, and It is possible to complete a static conduction path.

(Module to solve further problem 3)
The front side semiconductor device and the back side semiconductor device can constitute one phase. In the case of three phases, a u-phase circuit, a v-phase circuit, and a w-phase circuit can be combined into a module. At this time, the u-phase surface-side overlapping block, the v-phase surface-side overlapping block, and the w-phase surface-side overlapping block can be formed of a single member. This is because these blocks have the same potential. Similarly, the u-phase backside block, the v-phase backside block, and the w-phase backside block can be formed of a single member.

  “Foil” as used in the present specification refers to a thinned foil to such an extent that flexibility that can be easily bent with relative expansion / contraction between the semiconductor device and the cooler or the like appears. It should be contrasted with a “plate” that does not flex easily. What is called a film sheet is also a kind of “foil”.

The disassembled perspective view of the module of 1st Example. The disassembled perspective view of the module of 2nd Example. The circuit diagram of the module of the 2nd example. The disassembled perspective view of the module of 3rd Example. VV sectional view taken on the line of FIG. FIG. 6 is a sectional view taken along line VI-VI in FIG. 5. The top view of the module of 3rd Example. The circuit diagram of the module of the 3rd example.

The features of the technology disclosed in this specification will be summarized below. The items described below have technical usefulness independently.
(First feature) An overlapping block is formed of graphite foil and aluminum foil. Aluminum foil is used for the metal foil.
(Second feature) The outer periphery of a metal foil laminated with graphite foil is wrapped with a metal foil to constrain the outer shape. (Third feature) A long metal graphite foil and metal foil are wound around the outermost metal. The foil is fixed to the metal foil inside and maintained in a wound state.
(Fourth feature) The intermediate overlapping block is substantially H-shaped.
(5th characteristic) The contact surface of graphite foil and metal foil is extended in the longitudinal direction of a superposition block.

(Examples that solve basic problem and further problem 1)
FIG. 1 shows a module according to the first embodiment in which a front side cooler 20a, a front side overlapping block 30a, a semiconductor device 40, a back side overlapping block 30b, and a back side cooler 20b are sequentially stacked. 10 is an exploded perspective view of FIG.
The surface side cooler 20a is made of a metal (aluminum) having a low thermal resistance, and a passage for the coolant is formed inside. A cooling liquid inflow pipe and an outflow pipe are formed in the surface side cooler 20a. The back side cooler 20b has the same shape and structure as the front side cooler 20a. An insulating layer is formed on the back surface of the front surface side cooler 20a and the surface of the back surface side cooler 20b, thereby ensuring insulation between the overlapping block and the cooler described later. The back surface of the front surface side cooler 20a and the front surface of the back surface side cooler 20b extend along the xy plane.
The surface-side overlapping block 30a includes a block 36a in which a large number of graphite foils 32a and a large number of metal foils 34a are alternately stacked, and a metal plate 38a that is connected to the block 36a in a conductive manner. Yes. The metal plate 38a extends long in the y direction, and the individual graphite foils 32a and the individual metal foils 34a extend along the yz plane. The contact surface of the graphite foil 32a and the metal foil 34a extends along the normal line (z axis) standing on the surface electrode of the semiconductor device 40, and extends along the longitudinal direction (y axis) of the surface side overlapping block 30a. ing. In the figure, the thicknesses of the individual graphite foils 32a and the individual metal foils 34a are displayed thicker than actual. The actual number of stacked sheets is much larger. The back side overlapping block 30b is formed in the same structure and shape as the front side overlapping block.
The semiconductor device 40 includes a front electrode and a back electrode (not shown), and also includes a control electrode (not shown). The semiconductor device 40 switches the resistance between the front electrode and the back electrode by a voltage applied to the control electrode. It switches large current and generates heat when it operates. If it is not cooled, the semiconductor device 40 will be overheated, so cooling is required.

  If a metal plate is interposed between the surface electrode of the semiconductor device 40 and the back surface of the surface side cooler 20a, the metal plate becomes a conductor and a conductive path to the surface electrode of the semiconductor device 40 is secured. However, the thermal resistance of the metal plate is larger than the thermal resistance of the overlapping block used in this embodiment. In the technique in which the metal plate is interposed, the thermal resistance between the semiconductor device 40 and the surface side cooler 20a is increased, and the semiconductor device 40 is overheated. Further, since the thermal expansion coefficient of the semiconductor device 40 and the thermal expansion coefficient of the metal plate are different, a large thermal stress develops in the semiconductor device and the metal plate, which impairs the long-term reliability of the module. In order to solve the problem, the front surface side overlapping block 30a is used between the front surface electrode of the semiconductor device 40 and the back surface of the front surface side cooler 20a.

  In the first embodiment of FIG. 1, a block 36a is formed by alternately stacking a large number of graphite foils 32a and a large number of metal foils 34a. The graphite foil 32a and the metal foil 34a are merely overlapped, and there is no further constraint relationship. In order to maintain the overlapped shape, the outer peripheral side surface of the block 36a is wrapped with metal foil. The metal foil covering the outermost periphery is flexible and does not prevent the graphite foil 32a and the metal foil 34a from being deformed / displaced. The metal plate 38a is electrically connected to the metal foil covering the outermost periphery, and each graphite foil 32a and each metal foil 34a are electrically connected to the metal foil covering the outermost periphery of the block 36a. All the graphite foils 32a and all the metal foils 34a are electrically connected to the metal plate 38a.

  The surface of the block 36a is brazed to the back surface of the front side cooler 20a. The back surface of the block 36 a is brazed to the front surface electrode of the semiconductor device 40. At the stage of forming the module 10, the surface of the surface side overlapping block 36 a is constrained by the surface side cooler 20 a, and the back surface of the surface side overlapping block 36 a is constrained by the semiconductor device 40.

  The relationship between the back side cooler 20b, the back side overlapping block 30b, and the semiconductor device 40 is the same on the front side. However, the vertical relationship is reversed between the front side and the back side. The back surface of the front surface side member is the surface of the back surface side member, and the front surface of the front surface side member is the back surface of the back surface side member. The description which overlaps substantially is abbreviate | omitted. Reference number 40p indicates a range where the surface of the back surface side overlapping block 30b and the back surface electrode of the semiconductor device 40 contact, and reference number 36p indicates a range where the back surface of the back surface side overlapping block 36b contacts the surface of the back surface side cooler 20b. Is shown.

Power is supplied to the surface electrode of the semiconductor device 40 through the surface side overlapping block 30a. The metal plate 38a, the metal foil 34a, and the graphite foil 32a are conductors. The electric resistance in the y direction of the metal foil 34a and the graphite foil 32a is low. Similarly, power is supplied to the back surface electrode of the semiconductor device 40 via the back surface side overlapping block 30b.
When the semiconductor device 40 operates, the semiconductor device 40 generates heat. The relationship of the temperature of the semiconductor device 40> the temperature of the front surface side overlapping block 30a> the temperature of the front surface side cooler 20a is established. In the present embodiment, the graphite foil 32a constituting the surface-side overlapping block 30a extends in the z direction to provide a heat transfer path between the semiconductor device 40 and the surface-side cooler 20a. The thermal resistance of the graphite foil 32a extending in the z direction is lower than the thermal resistance of the metal plate 38a. The thermal resistance between the semiconductor device 40 and the surface side cooler 20a is very low. The temperature difference between the semiconductor device 40 and the surface side cooler 20a can be kept small compared to the case where heat is transferred by the metal plate 38a.
The back side is the same, and the temperature difference between the semiconductor device 40 and the back side cooler 20b can be kept small.

Since the thermal expansion coefficient of the surface-side cooler 20 a is much larger than the thermal expansion coefficient of the semiconductor device 40, when the semiconductor device 40 generates heat, the surface-side cooler 20 a is more relative than the semiconductor device 40. Greatly expands. In the illustrated case, the surface side cooler 20 a expands in the x direction and the y direction with respect to the semiconductor device 40.
The surface of the front surface side overlapping block 30a is restrained by the front surface side cooler 20a, and the back surface of the front surface side overlapping block 30a is restrained by the semiconductor device 40. If the front side cooler 20a expands relatively larger than the semiconductor device 40, and the front side deforms relatively larger than the back side of the front side overlapping block 30a. No great thermal stress is generated in the semiconductor device 40 or the surface side cooler 20a.

In the surface-side overlapping block 30a, only the graphite foil 32a and the metal foil 34a are overlapped, and if the graphite foil 32a and the metal foil 34a can slide along the contact surface, the adhesion between them increases. If it can change to a state, it can also change to a state in which the adhesion between the two has decreased. The surface side overlapping block 30a can be flexibly deformed. When the surface side cooler 20a expands and contracts with respect to the semiconductor device 40, the overlapping block 30a is flexibly deformed. Even if the surface side cooler 20a expands and contracts with respect to the semiconductor device 40, no large thermal stress is generated in the semiconductor device 40, and no large thermal stress is generated in the surface side cooler 20a. Further, no large thermal stress is generated in the surface side overlapping block 30a itself.
The back side overlapping block 30b also exhibits the same stress relaxation effect as described above. No large thermal stress is generated in the semiconductor device 40, no large thermal stress is generated in the back side cooler 20b, and no large thermal stress is generated in the back side overlapping block 30b.
In the module 10 shown in FIG. 1, the electrical resistance of the conductive path with respect to the surface electrode of the semiconductor device 40 is low, the thermal resistance of the heat transfer path between the semiconductor device 40 and the surface side cooler 20a is low, and a sufficiently flexible overlay The use of the block 30a prevents the generation of large thermal stress. Similarly, the electrical resistance of the conductive path with respect to the back electrode of the semiconductor device 40 is low, the heat resistance of the heat transfer path between the semiconductor device 40 and the back side cooler 20b is low, and a sufficiently flexible overlapping block 30b is used. This prevents a large thermal stress from being generated.

  In the present embodiment, each graphite foil 32a and each metal foil 34a extend along the yz plane. In this case, the electrical resistance in the y direction of the block 36a is low. Therefore, instead of using the metal plate 38a, the block 36 itself may be extended in the y direction to form a conductive path. When the metal plate 38a is used in combination, each graphite foil 32a and each metal foil 34a may extend along the xz plane. Further, the overlapping block 36 may be formed by wrapping multiple layers of a long graphite foil and a long metal foil.

Although not shown in FIG. 1, the surface-side overlapping block 30 a, the semiconductor device 40, and the back-side overlapping block 30 b are joined together in an injection mold, and the surface-side overlapping block 30 a and the semiconductor device 40 are combined. The semiconductor device 40 and the like can be sealed with a resin mold in which the molten resin is filled around the back side overlapping block 30b and the molten resin is cured. Thereby, the reliability and durability of the module can be improved.
The resin mold covers the side of the block 36 a so that the outer shape in the vicinity of the surface is indicated by a virtual line 90. A part of the overlapping block 30a protrudes from the resin mold and can be connected to a conductor (not shown). The surface of the resin mold 90 is flush with the surface of the block 36 a, and the surface of the block 36 a is exposed on the surface of the resin mold 90. Therefore, the surface of the block 36a can be joined to the back surface of the front surface side cooler 20a (without using a resin mold). Similarly, the back surface of the resin mold 90 is flush with the back surface of the back surface side block 36 b, and the back surface of the back surface side block 36 b is exposed on the back surface of the resin mold 90. Therefore, the back surface of the block 36b can be joined to the surface of the back surface side cooler 20b (without using a resin mold).

In the present embodiment, the same structure as that on the front surface side is arranged on the back surface side. This embodiment corresponds to the case where the semiconductor device 40 is provided with electrodes on both front and back surfaces, and coolers are disposed on both front and back surfaces. That is, it is for the solution of the further subject 1.
On the other hand, the back surface of the semiconductor device 40 may be fixed to the insulating substrate, or the back surface of the semiconductor device 40 may be exposed to the atmosphere. In such a case, the front surface side cooler 20a and the front surface side overlapping block 30a are used, but the back surface side cooler 20b and the back surface side overlapping block 30b are not used. In the above case, the problem (basic problem) can be solved only by using the surface-side cooler 20a and the surface-side overlapping block 30a.

(Example that solves basic problem and further problem 2)
As shown in FIG. 2, the module 80 of this embodiment incorporates two semiconductor devices 40a and 40b. In this specification, one semiconductor device 40a is referred to as a front surface side semiconductor device, and the other semiconductor device 40b is referred to as a back surface side semiconductor device. In FIG. 2, the front surface side semiconductor device 40a and the front surface side overlapping block 30a are shown in a position assembled to the intermediate overlapping block 70, and the back surface side semiconductor device 40b and the back surface side overlapping block 30b are intermediately stacked. It is shown separated from the mating block 70. A subscript a indicates a member on the front surface side, a subscript b indicates a member on the back surface side, and a member having the same reference numeral as that in FIG. 1 corresponds to the member in FIG. .

  As shown in FIG. 3, the surface-side semiconductor device 40a includes a diode and an IGBT. Similarly, the back side semiconductor device 40b also includes a diode and an IGBT. The surface electrode of the surface side semiconductor device 40a is a drain electrode of the IGBT, and is connected to the positive electrode of the DC power supply via the surface side overlapping block 30a which is also a conductor. Actually, it is connected to the positive electrode of the DC power source using a metal plate 38a protruding from a resin mold 90 described later. The back surface electrode of the back surface side semiconductor device 40b is a source electrode of the IGBT, and is connected to the negative electrode of the DC power supply via the back surface side overlapping block 30b which is also a conductor. Actually, it is connected to the negative electrode of the DC power source using a metal plate 38b protruding from a resin mold 90 described later. The back electrode of the front surface side semiconductor device 40a is an IGBT source electrode, the front surface electrode of the back surface side semiconductor device 40b is an IGBT drain electrode, and both are connected by an intermediate overlapping block 70 which is also a conductor. An electronic circuit in which two IGBTs are connected in series is obtained. A part 78 of the intermediate overlapping block 70 protrudes from the resin mold 90, and a conductor can be connected to the protrusion 78. A terminal for applying a control voltage to the gate electrode of the IGBT also protrudes from the resin mold 90 (not shown). Module 80 incorporates the boost converter circuit shown in FIG.

  As shown in FIG. 2, the back surface of the front surface side overlapping block 30a is bonded to the front surface electrode of the front surface side semiconductor device 40a, and the back surface of the front surface side cooler 20a is bonded to the front surface of the front surface side overlapping block 30a. The back surface of the surface side cooler 20a is covered with an insulating layer, and the surface side overlapping block 36a, which is a conductor, and the surface side cooler 20a are insulated. The surface side overlapping block 30a has the same structure and the same shape as the overlapping block 30 described in FIG. 1, and a plurality of graphite foils 32a and metal foils 34a extending in the yz plane are alternately stacked to form a block 36a. And a metal plate 38a extends therefrom. The metal plate 38a protrudes from the resin mold 90. The operation and effect obtained by the above configuration is as described with reference to FIG. 1, and a conductive path having a low electrical resistance with respect to the surface electrode of the surface-side semiconductor device 40a is secured, and the surface-side cooler 20a is connected from the surface-side semiconductor device 40a. A heat transfer path having a low thermal resistance is secured, and a large thermal stress is prevented from being generated in the surface-side semiconductor device 40a, the surface-side overlapping block 30a, and the surface-side cooler 20a.

  The same applies to the back surface side, and the surface of the back surface side overlapping block 30b is bonded to the back surface electrode of the back surface side semiconductor device 40b, and the surface of the back surface side cooler 20b is bonded to the back surface of the back surface side overlapping block 30b. The same relationship as that of the front surface side is obtained, a low electrical resistance conductive path to the back surface electrode of the back surface side semiconductor device 40b is secured, and a low heat resistance heat transfer path from the back surface side semiconductor device 40b to the back surface side cooler 20b is secured. Further, it is possible to prevent a large thermal stress from being generated in the back side semiconductor device 40b, the back side overlapping block 30b, and the back side cooler 20b.

  The back electrode of the front surface side semiconductor device 40 a is bonded to the surface of the intermediate overlapping block 70, and the front surface electrode of the back surface side semiconductor device 40 b is bonded to the back surface of the intermediate overlapping block 70. The intermediate overlapping block 70 is formed of an H-shaped block 76 and a metal plate 78 joined to the H-shaped block 76 so as to be conductive. The H-type block 76 is formed by alternately superimposing H-shaped graphite foil 72 and H-shaped metal foil 74 in the y direction. Each of the graphite foil 72 and the metal foil 74 extends in the xz plane. The graphite foil 72 and the metal foil 74 are merely overlapped, and no further constraint is taken. In order to maintain the overlapped state, the outer surface of the H-shaped block 76 is covered with a thin metal foil. The metal foil is extremely flexible and does not interfere with the flexible deformation of the graphite foil 72 and the metal foil 74 forming the H-shaped block 76. The heat resistance and electrical resistance in the x direction and z direction of the H-type block 76 are low. The tip of the metal plate 78 extending from the H block 76 protrudes from the resin mold 90.

  The H-shaped block 76 includes two overlapping portions extending in the z direction from both ends in the x direction. The surface of each overlapping portion in the z direction is flush with the surface of the surface side block 36a. In addition, the back surface of each z-direction overlapping portion is flush with the back surface of the back block 36b.

The side of the front surface side overlapping block 30a and the front surface side semiconductor device 40a (including the gap between the intermediate overlapping block 70), and the side surface of the back surface side overlapping block 30b and the back surface side semiconductor device 40b (intermediate overlapping block 70). And the side of the intermediate overlapping block 70 is covered with a resin mold 90. However, the surface of the surface side block 36 a and the surface of the H-type block 76 are exposed on the surface of the resin mold 90. Further, the back surface of the back surface side block 36 b and the back surface of the H-type block 76 are exposed on the back surface of the resin mold 90.
If the surface of the resin mold 90 is covered with the back surface of the front surface side cooler 20a, the surface of the front surface side overlapping block 30a and the surface of the intermediate overlapping block 70 are in contact with the back surface of the front surface side cooler 20a. When the surface of the back surface side cooler 20b is put on the back surface of the resin mold 90, the back surface of the back surface side overlapping block 30b and the back surface of the intermediate overlapping block 70 are in contact with the surface of the back surface side cooler 20b.
The surface side overlapping block 30a provides a heat transfer path having a low thermal resistance between the surface side semiconductor device 40a and the surface side cooler 20a. The back side overlapping block 30b provides a heat transfer path having a low thermal resistance between the back side semiconductor device 40b and the back side cooler 20b. Further, the intermediate overlapping block 70 provides a low heat resistance heat transfer path among the front surface side semiconductor device 40a, the back surface side semiconductor device 40b, the front surface side cooler 20a, and the back surface side cooler 20b.

  According to the above embodiment, by using the intermediate overlapping block 70, a low electrical resistance conductive path is ensured for the back electrode of the front surface side semiconductor device 40a and the front surface electrode of the back surface side semiconductor device 40b, and the front surface side semiconductor device 40a. A low heat resistance heat transfer path from the back surface electrode to the front surface side cooler 20a is ensured, and a low heat resistance heat transfer path from the back surface electrode of the front surface side semiconductor device 40a to the back surface cooler 20b is ensured. A low heat resistance heat transfer path from the surface electrode of the device 40b to the surface side cooler 20a is ensured, and a low heat resistance heat transfer path from the surface electrode of the back surface side semiconductor device 40b to the back surface cooler 20b is ensured. Side cooler 20a, front surface side overlapping block 30a, front surface side semiconductor device 40a, intermediate overlapping block 70, back surface side semiconductor device 40b, and back surface side overlapping block Tsu large thermal stress in the click 30b and the back-side cooler 20b can be prevented.

  In the above embodiment, the graphite foils 32a and 32b constituting the front surface side overlapping block 30a and the back surface side overlapping block 30b are developed along the yz plane, and the graphite foil 72 constituting the intermediate overlapping block 70 is It develops along the xz plane, and both development planes are orthogonal. The coefficient of thermal expansion in the direction along the development surface of the graphite foil is very low. The graphite foils 32a and 32b suppress the deformation of the module in the y direction and suppress the deformation in the z direction. The graphite foil 72 suppresses deformation of the module in the x direction and suppresses deformation in the z direction. The graphite foils 32a, 32b, 72 prevent the module from being deformed in all directions of x, y, z. If the module is restrained from being deformed in all three orthogonal directions, it is possible to eliminate the need for protection by sealing with a resin mold. The resin mold can be made unnecessary.

(Example in which a three-phase inverter circuit is modularized)
As shown in FIG. 4, the three-phase inverter circuit can be modularized. In this case, the structure of FIG. 2 is used for each phase. The subscripts indicate the u phase, the v phase, and the w phase. As shown in FIG. 8, the drains of the surface side semiconductor devices 40au, 40av, 40aw are connected to a common potential. Therefore, as shown in FIG. 4, a metal plate 38a extending over the u phase, the v phase, and the w phase is used. Three openings are formed in the metal plate 38a, and a u-phase surface-side overlapping block 36au, a v-phase surface-side overlapping block 36av, and a w-phase surface-side overlapping block 36aw are fitted therein. ing. Instead of combining the metal plate 38a and the blocks 36au, 36av, 36aw, a single overlapping block 30a extending over the u-phase, v-phase, and w-phase may be used as shown by the phantom lines in FIG. If each graphite foil 32a and each metal foil 34a extend long in the y direction, necessary conductivity can be secured.
Similarly, as shown in FIG. 8, the sources of the back-side semiconductor devices 40bu, 40bv, and 40bw are connected to a common potential. Therefore, as shown in FIG. 4, a metal plate 38b extending over the u phase, the v phase, and the w phase is used. Three openings are formed in the metal plate 38b, and a u-phase backside overlapping block 36bu, a v-phase backside overlapping block 36bv, and a w-phase backside overlapping block 36bw are fitted therein. ing. Instead of combining the metal plate 38b and the blocks 36bu, 36bv, 36bw, although not shown, a single overlapping block extending over the u phase, the v phase, and the w phase may be used. If each graphite foil 32b and each metal foil 34b extend in the y direction, necessary conductivity can be secured.
In this embodiment, the u-phase, v-phase, and w-phase circuits are sealed in a common resin mold 90. One end of each of the metal plates 38a, 38b, 78u, 78v, 78w extends out of the resin mold 90.

  FIG. 5 shows a cross-sectional view taken along line VV in FIG. A cross section of the coolant path inside the coolers 20a, 20b is shown. Reference number 22a is an insulating plate extending along the back surface of the front surface side cooler 20a, and reference number 22b is an insulating plate extending along the surface of the back surface side cooler 20b. The insulating plates 22a and 22b may be fixed to the cooler, or may be formed on the surface of the cooler. It can be seen that the resin mold 90 insulates between conductors having different potentials.

  6 shows a cross-sectional view taken along line VI-VI in FIG. 5, and FIG. 7 shows a plan view of the module. Reference numeral 42 indicates a control terminal. The u-phase control terminal 42 u, the v-phase control terminal 42 v, and the w-phase control terminal 42 w extend outside the resin mold 90. The surfaces of the surface-side overlapping blocks 30au, 30av, and 30aw and the surfaces of the H-side overlapping blocks 70u, 70v, and 70w are exposed on the surface of the resin mold 90. Similarly, although not shown, the back surfaces of the back surface side overlapping blocks 30bu, 30bv, 30bw and the back surface of the H side overlapping blocks 70u, 70v, 70w are exposed on the back surface of the resin mold 90.

In the above-described embodiment, the surface-side overlapping block 30a is configured by assembling the three surface-side blocks 36au, 36av, 36aw to the metal plate 38a. Instead, the overlapping block 36a itself of the graphite foil 32a and the metal foil 34a extending across the u phase, the v phase, and the w phase may be used as the surface side overlapping block 30a. That is, there is an embodiment in which the metal plate 38a is not used. The contact surface of the graphite foil 32a and the metal foil 34a constituting the surface side overlapping block 30a is perpendicular to the surface of the semiconductor device 40a (that is, extends in the z direction), and the surface side overlapping block 30a has a contact surface. If it extends in the longitudinal direction (that is, if it extends in the y direction), it is possible to ensure necessary heat conductivity and conductivity. When the metal plate 38a is not used in order to use the surface-side overlapping block 30a itself as a conductor, in the plan view of FIG. 7, the surface of the surface-side overlapping block 30a that is long in the y direction is exposed on the surface of the module. Adhere closely to the side cooler. The same applies to the back side overlapping block 30b.
In the above embodiment, the graphite foils 32a and 32b extend in the yz direction. The graphite foil has a very low coefficient of thermal expansion in the direction along the development surface. Therefore, the deformation rate in the y direction and the deformation rate in the z direction of the module of FIG. 4 are very low. Further, the graphite foil 72 extends in the xz direction. Therefore, the deformation rate in the x direction and the deformation rate in the z direction of the module of FIG. 4 are very low. As a result, in the module of FIG. 4, the deformation rate of expansion and contraction due to heat is small in any of the x, y, and z directions. Therefore, it is not necessary to protect the resin mold 90. Necessary reliability can be ensured without protection by the resin mold 90. The manufacturing cost can be reduced by omitting the resin mold 90.
In the above embodiment, the front surface side overlapping block 30a and the back surface side overlapping block 30b, which are conductors, extend facing each other with a slight distance. During the operation of the inverter circuit, a current in the opposite direction flows through conductors parallel to each other with a small distance. Therefore, mutual inductance can be kept low. Heat generation due to the parasitic inductance can be suppressed, and generation of a large surge voltage due to the parasitic inductance can be prevented.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
In addition, the technical elements described in the present specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

10: Module 20 of the first embodiment: Cooler 22: Insulating plate 30: Superposition block 32: Graphite foil 34: Metal foil 36: Block 38: Metal plate 40: Semiconductor device 42: Control terminal 70: Intermediate superposition block 72: Graphite foil 74: Metal foil 76: Block 78: Metal plate 80: Module 90 of the second embodiment 90: Resin mold subscript a: Front side subscript b: Back side

Claims (8)

A module including at least a surface-side cooler, a surface-side overlapping block, and a semiconductor device;
The surface of the surface side overlapping block is bonded to the back surface of the surface side cooler,
The surface electrode of the semiconductor device is joined to the back surface of the front surface side overlapping block so as to be conductive,
The surface side overlapping block is composed of a graphite foil and a metal foil, and a normal line standing on the surface electrode is arranged in a direction extending along a contact surface of the graphite foil and the metal foil, The graphite foil and the metal foil are overlapped in a non-bonded state, and when the surface side overlapping block is observed from the normal direction, the contact surface extends over the entire surface side overlapping block. Distributed,
The surface-side overlapping block is electrically connected to the surface electrode and provides a heat transfer path between the surface-side cooler and the semiconductor device, and a coefficient of thermal expansion between the surface-side cooler and the semiconductor device. A module characterized by relieving thermal stress caused by the difference between the two. The back side cooler and the back side overlapping block are added,
The back side of the back side overlapping block is joined to the surface of the back side cooler,
The back surface electrode of the semiconductor device is joined to the surface of the back surface side overlapping block so as to be conductive,
The back surface side overlapping block is composed of a graphite foil and a metal foil, and a normal line standing on the back electrode is arranged in a direction extending along a contact surface of the graphite foil and the metal foil, The graphite foil and the metal foil are overlapped in a non-bonded state, and when the back surface side overlapping block is observed from the normal direction, the contact surface extends over the entire area of the back surface side overlapping block. Distributed,
The backside overlap block is electrically connected to the backside electrode and provides a heat transfer path between the backside cooler and the semiconductor device, and a thermal expansion coefficient between the backside cooler and the semiconductor device. The module according to claim 1, wherein a thermal stress generated due to the difference is relaxed. The periphery of the front surface side overlapping block, the semiconductor device, and the back surface side overlapping block is covered with a resin mold,
The module according to claim 2, wherein the front surface of the front surface side overlapping block and the back surface of the rear surface side overlapping block are exposed from the resin mold. The front side cooler, the front side superposition block, the front side semiconductor device, the intermediate superposition block, the back side semiconductor device, the back side superposition block, and the back side cooler are stacked in that order,
The surface of the surface side overlapping block is bonded to the back surface of the surface side cooler,
The surface electrode of the front surface side semiconductor device is joined to the back surface of the front surface side overlapping block so as to be conductive,
The surface of the intermediate overlapping block is joined to the back electrode of the front surface side semiconductor device so as to be conductive,
The back side of the back side overlapping block is joined to the surface of the back side cooler,
The back surface electrode of the back surface side semiconductor device is joined to the surface of the back surface side overlapping block so as to be conductive,
The back surface of the intermediate overlapping block is joined to the surface electrode of the back surface side semiconductor device so as to be conductive,
The surface of the intermediate overlapping block is bonded to the back surface of the front surface side cooler,
The back surface of the intermediate overlapping block is bonded to the surface of the back side cooler,
The front surface side overlapping block, the intermediate overlapping block, and the back surface side overlapping block are made of graphite foil and metal foil, and are set up on the surface electrodes of the front surface side semiconductor device and the back surface side semiconductor device. A line is arranged in a direction extending along the contact surface of the graphite foil and the metal foil, and the graphite foil and the metal foil are overlapped in a non-bonded state, and the normal direction is The module, wherein the contact surface is distributed over the entire area of the overlapping block when the overlapping block is observed. When using an x, y, z orthogonal coordinate system in which the direction in which the normal line standing on the surface electrodes of the front surface side semiconductor device and the back surface side semiconductor device extends is the z direction,
The graphite foil constituting the intermediate overlapping block is developed along the xz plane,
The module according to claim 4, wherein the graphite foil constituting the front surface side overlapping block and the back surface side overlapping block is developed along the yz plane. The front surface side overlapping block, the front surface side semiconductor device, the intermediate overlapping block, the back surface side semiconductor device, and the periphery of the back surface side overlapping block are covered with a resin mold,
The front surface of the front surface side overlapping block, the front surface of the intermediate overlapping block, the back surface of the intermediate overlapping block, and the back surface of the back surface side overlapping block are exposed from the resin mold,
6. The part according to claim 4, wherein a part of the front surface side overlapping block, a part of the intermediate overlapping block, and a part of the back surface side overlapping block protrude from the resin mold. module. A composite module in which the u-phase module according to claim 4 or 5, the v-phase module according to claim 4 or 5, and the w-phase module according to claim 4 or 5 are combined.
The surface-side overlapping block of the u-phase module, the surface-side overlapping block of the v-phase module, and the surface-side overlapping block of the w-phase module are continuous so as to be mutually conductive.
The back-side overlapping block of the u-phase module, the back-side overlapping block of the v-phase module, and the back-side overlapping block of the w-phase module are continuous so as to be mutually conductive. Feature composite module. The longitudinal direction of each of the intermediate overlapping block of the u-phase module, the intermediate overlapping block of the v-phase module, and the intermediate overlapping block of the w-phase module is defined as the x direction,
The longitudinal direction of the member that also serves as the surface side overlapping block of the u phase module, the surface side overlapping block of the v phase module, and the surface side overlapping block of the w phase module is defined as the y direction,
When the direction in which the normal extending from the surface electrodes of the front surface side semiconductor device and the back surface side semiconductor device extends is the z direction,
the x, y and z directions are orthogonal to each other,
The graphite foil constituting the intermediate overlapping block extends along the xz plane,
The composite module according to claim 7, wherein the graphite foil constituting the front surface side overlapping block and the back surface side overlapping block extends along the yz plane.

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