JP2010087072A - Power semiconductor module and inverter system using the same - Google Patents

Abstract

【Task】
Provided are a semiconductor module that can withstand operation stability under a high temperature environment and a high current load, and an inverter system using the same.
[Solution]
The power semiconductor module of the present invention includes a semiconductor element having a Ni layer formed on an electrode surface, a metal conductor pattern, and a solder that joins the semiconductor element and the conductor pattern, and the composition ratio of the solder is Sn-3 wt%. A power semiconductor module comprising Cu to Sn-10 wt% Cu, wherein the thickness of the intermetallic compound formed in the vicinity of the interface between the semiconductor element and the solder is 6 μm to 50 μm.
[Selection] Figure 1

Description

The present invention relates to a power semiconductor module using Pb-free solder as a joining member and an inverter system using the same. In particular, to vehicle inverter system, such as the mounting structure and a hybrid vehicle power semiconductor module having a power semiconductor element such as IGBT (I nsulated G ate B ipolar T ransistor).

  A power semiconductor module such as an IGBT module is used for an inverter that controls a high output motor such as a motor for a hybrid vehicle. The cooling of the IGBT module in the automobile inverter is generally based on water cooling. At the time of the inverter operation, heat generated from the power semiconductor mounted on the IGBT module is large, and a large cooling capacity is required to maintain the element stable operation. Furthermore, it is because the inverter volume is required to be small for in-vehicle use. That is, in the case of air cooling, the volume of the heat sink portion becomes too large, so that air cooling for in-vehicle use is not allowed.

  In-vehicle inverters are mounted in an engine room under a high temperature environment, and in recent years, higher reliability is required in comparison with conventional specifications. For example, even if the temperature reached by the power semiconductor element rises from 125 ° C to 150 ° C, stable operation guarantee is required, and it is desired to develop an IGBT module that does not break down even if the instantaneous maximum temperature reaches 175 ° C. For this reason, there is an urgent need to develop a high-temperature-compatible IGBT element, and in parallel to this, development of a low thermal resistance power semiconductor module for quickly cooling the heat generated from the power semiconductor.

  Further, Pb—Sn solder materials have been used for a long time as power semiconductor module bonding materials. However, in recent years, it has been pointed out that the Pb component has an adverse effect on the human body, and solder containing Pb has been closed up as a major social problem, and EU WEEE (Waste Electrical and Electronics Equipment Directive) / ROHS ( As represented by the Restriction of Hazardous Substances Directive), there is an active movement to legally restrict the use of harmful substances including Pb.

  Against this background, application of Pb-free bonding materials is also demanded for power semiconductor modules mounted on in-vehicle inverters.

  In Patent Document 1, in addition to a semiconductor element connection material that can maintain connection reliability even if it is used at a high temperature of 200 ° C. or higher for a long period of time with low environmental impact and low cost, a semiconductor device using the connection material and There is a description regarding the invention of an on-vehicle AC generator (alternator).

The present invention includes a semiconductor element, a support electrode body connected to the first surface of the semiconductor element using the first connection material, and a second surface of the semiconductor element supported by the support electrode body. And a lead electrode body connected using a second connection material, the connection portion of the support member and the connection portion of the lead electrode body are subjected to Ni-based plating, In the semiconductor device, the first connection material and the second connection material are Sn-based solder having a composition having a Cu ₆ Sn ₅ phase content higher than that of the eutectic composition.

Further, a semiconductor element, a support electrode body subjected to Ni-based plating connected to one side of the semiconductor element at room temperature to 200 ° C. via an Sn-based solder containing a Cu ₆ Sn ₅ phase, and the support electrode body In a semiconductor device comprising a lead electrode body with Ni-based plating connected to the other side of the supported semiconductor element through Sn-based solder containing a Cu ₆ Sn ₅ phase at room temperature to 200 ° C. There is a description relating to a method for manufacturing a semiconductor device, characterized in that a connecting step using an Sn-based solder containing a Cu ₆ Sn ₅ phase at 200 ° C. is performed in a reducing atmosphere at 220 to 450 ° C.

Furthermore, the connection material used for this semiconductor device is characterized by being a Sn—Cu-based Pb-free solder having a composition having a Cu ₆ Sn ₅ phase content higher than that of the eutectic composition.

JP 2007-67158 A

Although the conventional semiconductor device and the on-vehicle AC generator (alternator) can be used continuously for a long time at a high temperature of 200 ° C. or higher, Sn—Cu-based Pb having a high content of Cu ₆ Sn ₅ phase. When free solder is applied to a large-capacity power semiconductor module, there are the following problems.

  Power semiconductor modules for in-vehicle use are required to have high heat dissipation from the viewpoint of ensuring stable operation of power semiconductor elements, and usually have an IGBT (Insulated Gate Bipolar Transistor) or MOS-FET (Metal Oxide Semiconductor) with a large area of 10 mm × 10 mm or more. Field Emission Transistor) is mounted from 2 to 3 elements per arm. A power semiconductor module for an in-vehicle inverter is used with a large current / voltage of 400 A × 600 V or more as compared with an energization amount of several tens of A of an in-vehicle AC generator (alternator). Therefore, a temperature load due to element heat generation is applied to each joint portion of the power semiconductor module in addition to the use environment temperature. For this reason, since the wire bonding / element bonding interface and the solder under the element are subjected to a temperature change directly from the element, they are exposed to a severe heat load.

  One solution is to reduce the thickness of the power semiconductor element to reduce the amount of strain generated at the wire bonding / element bonding interface due to thermal stress. The thinning of the power semiconductor element can reduce the difference in thermal expansion coefficient between the two by causing the element itself to exhibit malleability and imparting deformability. On the other hand, when an energization load is applied, a complicated fatigue phenomenon occurs in the solder under the element, so it is necessary to take measures individually. The fatigue phenomenon in the solder under the element is that 1) peeling occurs at the element / solder interface due to the difference in the remaining amount of the Ni metallized layer on the back surface of the element. 2) Solder particles grow with the energization cycle. The generation of voids in the emphasis, and 3) the development of cracks inside the solder. Therefore, in order to improve the life of the power cycle accompanied by element heat generation, it is important to take measures against the above-mentioned factors 1) to 3).

  An object of the present invention is to solve the problems of the module described above, in order to solve the problem of the module, the thickness of the Ni metallized layer on the back surface of the power semiconductor element constituting the power semiconductor module, the remaining amount of Ni after solder reflow, the composition of the solder under the element, Semiconductor module that can withstand operation stability and high current load in high temperature environment by defining the shape and amount of intermetallic compound generated at solder interface and solder / conductor layer interface, and inverter system using the same Is to provide.

  In order to solve the above problems, in the present invention, in a power semiconductor module comprising a semiconductor element having a Ni layer formed on an electrode surface, a metal conductor pattern, and a solder that joins the semiconductor element and the conductor pattern, the solder The composition ratio is Sn-3 wt% Cu to Sn-10 wt% Cu, and the thickness of the intermetallic compound formed in the vicinity of the interface between the semiconductor element and the solder is 6 μm to 50 μm. In addition, let the thickness of an intermetallic compound be an average thickness of the intermetallic compound in a joining interface.

  Further, the thickness of the Ni metallized layer is set to 0.1 μm or more to 10 μm or less, and the Ni metallized residual thickness after soldering is set to 0.1 μm or more.

  The power semiconductor module of the present invention includes a wiring board having a conductor pattern on one surface of an insulating substrate and a back conductor layer formed on the other surface, and a power semiconductor element mounted on the conductor pattern and switching current. And a metal base disposed on the surface of the back conductor layer, a Ni layer is formed on the electrode surface of the power semiconductor element, and the composition ratio of the electrode and the conductor pattern is Sn-3 wt% Cu to Sn It is characterized in that the thickness of the intermetallic compound formed in the vicinity of the interface between the solder and the electrode is 6 μm to 50 μm.

  According to the present invention, it is possible to realize a power semiconductor module excellent in power cycle characteristics with stable operation stability even when the load applied to the semiconductor element is large, such that the energization amount to the power semiconductor module exceeds 400A. Become.

  It is characterized by a power semiconductor module having improved cooling performance and reliability in a high temperature environment, in particular, a long life in a high temperature power cycle test under the condition that the element temperature reaches 150 ° C.

  That is, the present invention comprises a semiconductor element having a Ni layer formed on the surface thereof, a metal conductor pattern, the semiconductor and the conductor pattern, and a solder having a composition ratio of Sn-3 wt% to Sn-10 wt%, The thickness of the intermetallic compound formed in the vicinity of the interface between the semiconductor element and the solder is 6 μm to 50 μm, and the heat generated in the semiconductor element is transferred from the interface to the pattern, and is passed through the conductor pattern. This is a power semiconductor module that dissipates heat.

  In the present invention, the area ratio of the intermetallic compound in a vertical cross section with respect to the interface between the semiconductor element and the solder is in the range of 20% to 100%.

  Further, the present invention is characterized in that the residual amount of the Ni layer after soldering is 0.1 μm or more.

  Further, the present invention is characterized in that the thickness of the Ni layer formed on the surface of the semiconductor element is 0.1 μm to 10 μm.

  In addition to the metal conductor pattern, the present invention is characterized in that fins are provided in a region on the surface opposite to the contact surface between the second conductor layer and the base plate.

  Further, the present invention is characterized in that fins are provided in a region of a surface opposite to the contact surface of the base plate with the second conductor layer.

  Further, the present invention is an in-vehicle inverter device using the semiconductor module, wherein a cooling water flow path is formed below a surface opposite to a contact surface between the second conductor layer and the base plate. This is an in-vehicle inverter device.

  The present invention will be described below with reference to the drawings.

  The following technologies were introduced as measures to improve reliability in high temperature environments.

  In order to improve the power cycle characteristics, it is necessary to reduce the difference in thermal expansion coefficient between the element and the wire at the wire bonding and the element bonding surface, and to reduce the amount of distortion of the solder under the element due to energization on / off. Therefore, the effect of thinning the element can be expected. In the latter case, it is necessary to control the thickness and generation amount of the intermetallic compound generated near the element back surface and the solder interface, and to control the Ni thickness remaining at the element / solder interface after soldering. Each will be described below.

  FIG. 1 is an explanatory view of the structure of the present invention. FIG. 1A is a schematic plan view, and FIG. 1B is a schematic cross-sectional view taken along AA in FIG. In the cross-sectional schematic diagram, the conductor layer pattern on the surface of the insulator, the back surface metal pattern for bonding, the conductor layer pattern of the semiconductor element and the insulator, and the heat dissipation base are included.

  Embodiments of the present invention will be described below in detail with reference to the drawings.

Example 1
The first embodiment will be described in detail with reference to FIG. It is an example of a three-phase IGBT module applied to a 50 kW class water-cooled three-phase inverter.

  FIG. 1A is a schematic plan view, and FIG. 1B is a schematic cross-sectional view of FIG. In the schematic cross-sectional view, the silicon nitride substrate 5, the copper fin base 8, the main terminal electrode 13, and the control, in which the conductor layer 4 on the front surface and the conductor layer 6 on the rear surface 6 are made of copper. The terminal electrode 12, the adhesive layer 3 under the element 3, the back conductor layer pattern 6 of the insulator 4, and the adhesive layer 7 of the metal base 8 are shown.

The ceramic substrate (here, a silicon nitride substrate) 5 has a size of 32 mm × 52 mm, an element size of 14.0 mm × 12.5 mm, a thickness of 0.09 mm, an element size of 12.5 mm × 7 Two elements of 0.0 mm FWD element 2 are bonded with Pb-less solder having a melting point of 210 ° C. or higher. Here, the Sn—Cu solder and the Sn—Ag—Cu solder shown in Table 1 were used. The solder thickness is about 0.1 mm. The voltage / current rating of each element is 600 V / 200 A, and a module with a rating of 600 V / 400 A is obtained by connecting two elements in parallel. Further, a resonance preventing gate resistance element (not shown) and a temperature detection thermistor (not shown) when the IGBTs are driven in parallel are bonded to the silicon nitride substrate 5 with the same Pb-less solder as described above. . The connection between the IGBT element 1 and the FWD element 2 and the conductor layer pattern 4 which is a copper pattern on the ceramic substrate 5 is made by aluminum wires 10, 11 and 12.
The wire diameter of this wire is 400 μmφ. The aluminum wires 10, 11, and 12 represent only representative wires, not the total number. The power semiconductor-mounted silicon nitride substrate 5 and the copper base 8 are bonded to each other with a Pb-less solder such as Sn—Cu base having a melting point of 210 ° C. or higher. The solder thickness is about 0.18 mm. The silicon nitride substrate 5 and the main terminal 13 are ultrasonically bonded by metal bonding. The connection to the control terminal electrode 12 is also made by the aluminum wire 9. The wire diameter is 400 μmφ. Since the aluminum wires 10 and 11 are bonded to the surface of the semiconductor element, it is necessary to consider low damage, and it is essential to optimize the bonding conditions.

  Each arm of the three-phase module is composed of one silicon nitride substrate 5, and a total of six substrates 5 are soldered to a finned copper base 8 having a size of 126 mm × 145 mm and a flat plate portion of 3 mm. . The width 115, interval 116, and height 118 of the fin 114 are 2 mm, 4.5 mm, and 8 mm, respectively. The length is 8 mm. The number of fins 114 is 784, and the width of the entire fin is 2 mm. Of course, the fins 114 are arranged in a region under the silicon nitride substrate 100. The shape of the fin was set to a shape that can realize the maximum heat transfer in consideration of the flow velocity when the cooling water is passed and the fin efficiency.

  FIG. 2 shows a schematic cross-sectional view of an embodiment in which this module is attached to a water-cooling jacket using a fastening bolt screw 17. The bottom surface of the fin 0 is in contact with the Al die-cast cooling jacket 15. The cooling water is sealed by attaching the cooling jacket with the O-ring 16. A groove (not shown) is provided in the cooling jacket 15 made of Al die casting for attaching the O-ring. The O-ring has a wire diameter of 1.9 mmφ and a groove depth of 1.4 mm. The module was attached with M6 bolts, and the tightening torque was 2.45 N · m. This torque is comparable to the normal module mounting torque.

  The water cycle of ethylene glycol 50 vol.% Was passed from the water supply port 18 at a flow rate of 10 L / min to the water channel of the cooling jacket 15 in which the module having the above configuration was brought into contact, and a power cycle test was performed. The power cycle life test was carried out in advance by confirming the conditions for the element temperature to reach 150 ° C., DC500A per arm (DC250A per element), ON time 2 sec, OFF time 15 sec. As the cooling water, 50% LCC was used and the temperature was set to 50 ° C. using a heating / cooling circulation device. The power cycle life was defined as the number of times that the ΔVce value of the IGBT element was 1.2 times the initial value.

  The thickness of the Ni metallized layer of the IGBT element was observed using a scanning electron microscope (Hitachi S-4500).

  The solder under the element is Sn-Cu (Senju Metal), Sn-3.5% Ag-0.5% Cu-Ni-Ge (Nihon Solder) and Sn-3% Ag-0.5% Cu (Nihon Solder). The under-substrate solder was Sn-3% Ag-0.5% Cu-5% In (manufactured by Senju Metal) and used for module fabrication.

  The Sn—Cu solder composition was evaluated by ICP emission analysis. For the surface treatment of the conductor layer (circuit board of the circuit board), Ni-P plating and plating-free ones were used.

  The shape of the intermetallic compound after reflow (thickness, generation amount) and the remaining thickness of Ni metallization were determined by scanning the electron microscope (Hitachi S -4500).

3 and 4 show cross-sectional observation images of the element / solder interface and the solder / conductor layer interface.
3 (a) and 3 (b) are observed at x1000 times and x3000 times the element / solder interface. 4 (a) and 4 (b) are observed at x1000 times and x3000 times the solder / conductor layer interface. The thickness and amount of the intermetallic compound are measured from FIGS. 3A and 4A, and the remaining thickness of Ni metallization is measured from FIG. 3B.

  In Table 1, as Examples No.1 to No.4, the power cycle life of the semiconductor module was evaluated when the Ni metallized layer thickness on the back surface of the IGBT element was set to 0.2 μm to 4.5 μm.

  As Examples No. 5 to 9, the reflow time of Example No. 2 was evaluated up to 3 minutes on the short side and 60 minutes on the long side. Further, as Examples Nos. 10 and 11, the conditions of the reflow times of Examples No. 6 and No. 7 were similarly set, and the Ni metallized layer thickness on the back surface of the IGBT element was evaluated to be 2.5 μm. Further, as Examples No. 12 to 15, the reflow temperatures of Examples No. 2 and No. 6 were evaluated at 300 ° C. and 355 ° C. In addition, as Examples No. 16 and 17, evaluation was performed by using the same reflow conditions as in Examples No. 2 and No. 14 but changing the solder composition to Sn-3% Cu. Further, as Examples No. 18 and 19, evaluation was performed by using the same reflow conditions as in Examples No. 2 and No. 14 but changing the solder composition to Sn-5% Cu. In addition, as Examples No. 20 and 21, the reflow conditions of Examples No. 2 and No. 14 were similarly used and the solder composition was changed to Sn-9% Cu for evaluation. As Example Nos. 22 and 23, the reflow conditions of Examples No. 2 and No. 14 were similarly evaluated using the solder composition changed to Sn-10% Cu. Further, as Example No. 24, the reflow condition of Example No. 2 was changed from 255 ° C. to 355 ° C., and the holding time was changed from 6 min to 12 min. Also, as Example No. 25, the conductor layer material of Example No. 2 was changed from Cu to Ni, and as Example 26, the reflow temperature of Example No. 25 was changed from 255 ° C. to 355 ° C. It evaluated using what was done.

  As a result, in Examples Nos. 1 to 26, the target specification value 18000 cycles of the power cycle test could be cleared, and a semiconductor module excellent in power cycle characteristics under a high temperature environment was obtained.

  Next, in No. 31-42 of the comparative example of Table 1, the power cycle characteristic of the semiconductor module could not be maintained.

  In Comparative Example No. 31, in the semiconductor module of Example No. 2, the Ni metallization thickness on the back surface of the element was changed to 0.1 μm. No. 31 was less than 18,000 cycles of the target specification in the power cycle test. The thickness of the intermetallic compound was 10 μm, and the remaining Ni metallized thickness was as thin as 0.02 μm. For this reason, peeling at the element / solder interface occurred during the power cycle test. In Comparative Example No. 32, in the semiconductor module of Example No. 2, the Ni metallization thickness on the back surface of the element was increased to 12 μm. In this case, since the thickness ratio of the Ni metallized layer increases with respect to the element thickness of 90 μm, a large strain is generated due to the thermal stress load at the interface between the Ni metallized layer and the element, so that the IGBT element is cracked immediately after reflow. A malfunction occurred.

  In Comparative Example No. 33, the semiconductor module of Example No. 2 was evaluated by changing the under-element solder composition from Sn-7% Cu to Sn-2% Cu. In this case, the generation thickness of the intermetallic compound at the element / solder interface and the solder / conductor interface is 6 μm or less, and element / solder peeling occurs.

In Comparative Example No. 34, the semiconductor module of Example No. 2 was evaluated by changing the under-element solder composition from Sn-7% Cu to Sn-12% Cu. In this case, in addition to the (Cu, Ni) ₆ Sn ₅ intermetallic compound at the element / solder interface and the solder / conductor interface, fragile Cu ₃ Sn is generated at the interface between the (Cu, Ni) ₆ Sn ₅ and the conductor layer. To do. In this case, during the power cycle test, peeling occurred at the interface between the generated Cu ₃ Sn and the conductor layer, so that the power cycle life was reduced.

  In Comparative Example No. 35, the semiconductor module of Example No. 2 with the reflow temperature increased from 255 ° C. to 450 ° C. was used. In this case, the remaining amount of the Ni metallized layer was 0.01 μm, and peeling occurred at the element / solder interface during the power cycle test.

  In Comparative Example No. 36, the semiconductor module of Example No. 2 was evaluated using the reflow temperature and holding time increased from 255 ° C. to 355 ° C. and extended from 6 min to 60 min. Also in this case, the remaining amount of the Ni metallized layer was 0.08 μm, and peeling at the element / solder interface occurred during the power cycle test.

  Comparative Examples No. 37 and 38 were obtained by changing the under-element solder compositions of Example No. 2 and Example No. 14 from Sn-7% Cu to Sn-3.5% Ag. Nos. 39 and 40 were obtained by changing the under-element solder composition of the example from Sn-7% Cu to Sn-3.5% Ag-0.5% Cu-Ni-Ge, and Comparative Example No. .41 and 42 were evaluated using the under-element solder composition of the same example changed from Sn-7% Cu to Sn-3% Ag-0.5% Cu. As a result, the intermetallic compound produced at the element / solder interface from No. 37 to No. 42 is Ni-Sn, and in this case, the formation reaction of this intermetallic compound is promoted during reflow, so The metallized layer is greatly reduced compared to the Sn—Cu system. For this reason, peeling at the element / solder interface occurs during the power cycle test, resulting in a reduction in life.

  From the above results, the Ni metallization layer thickness on the back surface of the power semiconductor element is preferably 0.2 μm or more and 10 μm or less.

  The under-element solder composition is preferably Sn-3% Cu to Sn-10% Cu. Since Sn-Ag and Sn-Ag-Cu solders easily generate Ni-Sn compounds, the disappearance rate of the Ni metallized layer is high, and improvement in power cycle life cannot be expected.

Furthermore, the intermetallic compound is desirably 10 μm or more and 40 μm or less.
Further, the remaining thickness of the Ni metallized layer is preferably 0.1 μm or more.

When Sn—Ag and Sn—Ag—Cu based solder is used, the cause of interfacial delamination at the center of the element involves the disappearance of the Ni metallized layer. That is, in the SnAgCuNiGe solder, it reacts with the solder component Sn in the reflow process to generate a Ni—Sn compound, so-called Ni erosion by the solder occurs, and the Ni metallized layer disappears. Therefore, it becomes a new interface between the Ti layer of the Ni layer base film, the Ni—Sn phase, and the main phase Sn. In this case, in order to guarantee the bonding strength at the Ti / solder interface, it is necessary to generate a Ti—Sn compound by the reaction of Ti and Sn, but a Ti ₆ Sn ₅ intermetallic compound is formed at 231 ° C. Since this is a temperature lower than the reflow temperature at the time of module trial manufacture, Ti-Sn alloying can occur in the reflow process. However, the formation of the Ti—Sn layer and the amount of oxygen contained in the Ti layer are closely related, and the adhesive strength is reduced by the fluctuation of the amount of oxygen incorporated in the formation of the Ti layer in the previous process of the semiconductor element. There is a possibility that a weak interface may be formed, and in the power cycle process, due to the thermal stress load generated by repeated heating and cooling of the element due to energization, peeling occurred at the solder joint interface with Ti with weak adhesion Inferred.

  Then, the vehicle-mounted inverter apparatus carrying the power semiconductor module of this invention is demonstrated.

  FIG. 5 is a block diagram of a hybrid electric vehicle that combines an in-vehicle electric machine system configured using a power converter INV using a power semiconductor module according to an embodiment of the present invention and an engine system of an internal combustion engine.

  The HEV of this embodiment includes front wheels FRW, FLW, rear wheels RPW, RLW, front wheel axle FDS, rear wheel axle RDS, differential gear DEF, transmission T / M, engine ENG, electric motors MG1, MG2, power converter INV, A battery BAT, an engine control unit ECU, a transmission control unit TCU, an electric motor control unit MCU, a battery control unit BCU, and an in-vehicle local area network LAN are provided.

  In this embodiment, the driving force is generated by the engine ENG and the two electric motors MG1 and MG2, and is transmitted to the front wheels FRW and FLW through the transmission T / M, the differential gear DEF, and the front wheel axle FDS.

  The transmission T / M is a device that includes a plurality of gears and can change a gear ratio according to an operation state such as a speed.

  The differential gear DEF is a device that appropriately distributes power to the left and right when there is a speed difference between the left and right wheels FRW and FLW due to a curve or the like.

  The engine ENG includes a plurality of components such as an injector, a slot valve, an ignition device, and an intake / exhaust valve (all not shown). The injector is a fuel injection valve that controls the fuel injected into the cylinder of the engine ENG. The slot valve is a throttle valve that controls the amount of air supplied into the cylinder of the engine ENG. The ignition device is a fire source that burns the air-fuel mixture in the cylinder of the engine ENG. The intake / exhaust valves are open / close valves provided for intake and exhaust of the cylinders of the engine ENG.

  Electric motors MG1 and MG2 are three-phase AC synchronous, that is, permanent magnet rotating electric machines.

  As the electric motors MG1 and MG2, a three-phase AC induction type rotating electric machine or a reluctance type rotating electric machine may be used.

  Electric motors MG1 and MG2 include a rotating rotor and a stator that generates a rotating magnetic field.

  The rotor is configured by embedding a plurality of permanent magnets in the iron core or by arranging a plurality of permanent magnets on the outer peripheral surface of the iron core. The stator is formed by winding a copper wire around a magnetic steel sheet.

  By flowing a three-phase alternating current through the stator winding, a rotating magnetic field is generated, and the motors MG1 and MG2 can be rotated by torque generated by the rotor.

  The power converter INV controls the electric power of the electric motors MG1, MG2 by switching power semiconductors. In short, the motors MG1 and MG2 are controlled by connecting (on) and turning off (off) the DC source of the high voltage battery BAT to the motors MG1 and MG2. In the present embodiment, since the motors MG1 and MG2 are three-phase AC motors, three-phase AC voltages are generated by controlling the time width of switching (on and off) to control the driving force of the motors MG1 and MG2 (PWM) control).

  The power converter INV includes a capacitor module CM that instantaneously supplies power during switching, a power semiconductor module PMU that performs switching, a drive circuit unit DCU that performs switching of the power semiconductor module, and an electric motor control unit MCU that determines the density of the switching time width. Constitute.

  The power conversion device INV of the present invention has high reliability by mounting a power semiconductor module having excellent heat dissipation.

  According to the present embodiment, it is possible to achieve further downsizing of the power semiconductor module, and thus the inverter device INV, which saves mounting space by maintaining the low thermal resistance and reducing the number of mounted elements. As a result, a small and highly reliable electric drive system for a hybrid electric vehicle can be provided at a low price.

The basic structure of this invention is shown, (a) Planar structure figure, (b) Cross-section structure schematic diagram. It is sectional drawing which shows the cooling structure of the semiconductor module by embodiment of this invention. Microstructure (a) × 1000 times (b) × 3000 times magnified image of element / solder interface. Microstructure of solder / conductor layer interface (a) × 1000 times (b) × 3000 times magnified image. 1 is a block diagram of a hybrid electric vehicle that combines an in-vehicle electric system configured using a power converter INV according to an embodiment of the present invention and an engine system of an internal combustion engine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 IGBT element 2 FWD element 3 Element lower adhesive layer 4 Surface conductor layer 5 Insulator 6 Back conductor layer 7 Back conductor layer lower adhesive layer 8 Copper fin bases 9, 10, and 11 Aluminum wire 12 Control terminal electrode 13 Main terminal electrode 14 PPS resin case 15 Al die-cast cooling jacket 16 O-ring 17 Fastening bolt screw 18 Water supply port

Claims (10)

In a power semiconductor module comprising a semiconductor element in which a Ni layer is formed on the electrode surface, a metal conductor pattern, and a solder joining the semiconductor element and the conductor pattern,
The composition ratio of the solder is Sn-3 wt% Cu to Sn-10 wt% Cu, and the thickness of the intermetallic compound formed in the vicinity of the interface between the semiconductor element and the solder is 6 μm to 50 μm, Power semiconductor module. The power semiconductor module according to claim 1,
A power semiconductor module, wherein an area ratio of the intermetallic compound in a vertical section with respect to an interface between the semiconductor element and the solder is in a range of 20% to 100%. The power semiconductor module according to claim 1,
The power semiconductor module, wherein the remaining amount of the Ni layer after soldering is 0.1 μm or more. The power semiconductor module according to claim 1,
A power semiconductor module, wherein the Ni layer formed on the surface of the semiconductor element has a thickness of 0.1 μm to 10 μm.   2. The power semiconductor module according to claim 1, wherein an energization amount to the power semiconductor module is 400 A or more. A wiring board having a conductor pattern formed on one surface of the insulating substrate and a back conductor layer formed on the other surface; a power semiconductor element mounted on the conductor pattern for switching current; and disposed on the surface of the back conductor layer. In a power semiconductor module comprising a metal base,
Ni layer is formed on the electrode surface of the power semiconductor element,
The electrode and the conductor pattern are joined by a solder having a composition ratio of Sn-3 wt% Cu to Sn-10 wt% Cu,
A power semiconductor module, wherein a thickness of an intermetallic compound formed in the vicinity of an interface between the solder and the electrode is 6 μm to 50 μm. The power semiconductor module according to claim 6, wherein
A power semiconductor module, wherein an area ratio of the intermetallic compound in a vertical section with respect to an interface between the semiconductor element and the solder is in a range of 20% to 100%. The power semiconductor module according to claim 6, wherein
The power semiconductor module, wherein the Ni layer has a thickness of 0.1 μm to 10 μm.   The power semiconductor module according to claim 6, wherein fins are provided on a surface of the metal base plate. A wiring board having a conductor pattern formed on one surface of the insulating substrate and a back conductor layer formed on the other surface; a power semiconductor element mounted on the conductor pattern for switching current; and disposed on the surface of the back conductor layer. A vehicle-mounted inverter device comprising a metal base and a cooling water passage disposed on the back surface of the metal base plate,
Ni layer is formed on the electrode surface of the power semiconductor element,
The electrode and the conductor pattern are joined by a solder having a composition ratio of Sn-3 wt% Cu to Sn-10 wt% Cu,
The in-vehicle inverter device, wherein a thickness of an intermetallic compound formed in the vicinity of an interface between the solder and the electrode is 6 μm to 50 μm.

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