JP5202365B2 - Semiconductor device - Google Patents

Description

  The present invention relates to a semiconductor device in which a semiconductor element is mounted on a heat sink via an insulating layer.

As a power conversion device that converts DC power and AC power, a device using a semiconductor device in which a plurality of semiconductor elements are mounted on the upper surface of a heat sink is known (see, for example, Patent Document 1).
In the semiconductor device described in Patent Document 1, an insulating layer is provided on the upper surface of the heat sink, and a first conductive layer connected to the positive electrode of the DC power source is formed on the insulating layer, and a second conductive layer is connected to the signal line. A conductive layer is provided. A flat conductor connecting piece connected to the negative electrode of the DC power source is disposed in parallel above the first conductive layer, and a power semiconductor element (for example, between the first conductive layer and the connecting piece, for example, An IGBT (Insulated Gate Bipolar Transistor) is fixed by soldering. In the power semiconductor element, the collector electrode portion is connected to the first conductive layer, and the emitter electrode portion is connected to the connection piece. The second conductive layer provided on the insulating layer is connected to the gate electrode portion of the power semiconductor element by wire bonding or the like.

JP-A-2005-236108

By the way, the insulating layer integrated on the upper surface of the heat sink is usually formed of a material such as ceramic having a small linear expansion coefficient with respect to the material of the heat sink. For this reason, when the power semiconductor element generates heat, the heat sink and the insulating layer are likely to be bent and deformed due to the difference in coefficient of linear expansion.
In particular, when the positive-side power semiconductor element and the negative-side power semiconductor element are arranged in parallel on the upper surface of one heat sink, and the upper surface shape of the heat sink is a square shape, the diagonal direction of the heat sink having a long distance from the center Large warpage tends to occur. When a large warp occurs in the diagonal direction of the heat sink, a large stress acts on the power semiconductor element sandwiched between the heat sink and the connection piece that does not warp.

  Accordingly, the present invention is intended to provide a semiconductor device capable of reducing the stress acting on the power semiconductor element when the heat sink is deformed.

The invention according to claim 1, which solves the above problem, includes a positive power semiconductor element (for example, a high-side transistor UH in an embodiment described later) and a negative power semiconductor element (for example, the low side in an embodiment described later). The transistor UL) is provided on an upper surface of a substantially square heat sink (for example, a heat sink 31 in an embodiment described later) via an insulating layer (for example, an insulating layer 44 in an embodiment described later) having a linear expansion coefficient different from that of the heat sink. The positive electrode of the DC power source (for example, the battery 3 in the embodiment described later) is arranged in parallel, and the collector electrode portion of the positive power semiconductor element is connected to the DC power source (for example, the battery 3 in the embodiment described later) via the first conductor (for example, the P bus bar 20 in the embodiment described later). While the emitter electrode portion of the negative power semiconductor element is electrically connected to a second conductor (for example, described later) The N bus bar 21 in the embodiment is electrically connected to the negative electrode of the DC power source, and the emitter electrode portion of the positive power semiconductor element and the collector electrode portion of the negative power semiconductor element are connected to a third conductor (for example, A semiconductor device electrically connected to an AC device (for example, a motor 4 in an embodiment described later) via an Out bus TrU22) in an embodiment described later, the first, second, third At least one of the conductors is provided with a flat connection piece (for example, connection pieces 21a and 22a in the embodiments described later), and this connection piece is one of the positive power semiconductor element and the negative power semiconductor element. been the top polymerization fixed to the connection piece, a pair of bent border of extension of spaced width toward the center side of the heat sink are provided, these bending By a boundary line, wherein the allowable section deflection to facilitate bending deformation of the diagonal direction of the connecting piece of the heat sink is formed.
As a result, when the heat semiconductor element generates heat and the heat sink and the insulating layer are bent and deformed due to the difference between the linear expansion coefficients thereof, the bending stress is input to the connection piece through the power semiconductor element. At this time, since the heat sink is square, it is greatly bent and deformed in the diagonal direction. The connection piece receives an input from the heat sink and easily bends and deforms in the diagonal direction of the heat sink along the pair of bending boundary portions .

The invention described in claim 2, in the semiconductor device according to claim 1, wherein the connecting piece, the curved portion (e.g., embodiment described below the center of the cross section toward the side radius of the heat sink increases continuously A bending portion 38) is provided, and the bending allowing portion is constituted by the bending portion.
As a result, when the heat sink and the insulating layer are bent and deformed due to the difference between the linear expansion coefficients of the power semiconductor element, the connection piece is easily bent and deformed along both edges of the curved portion.

According to the first aspect of the present invention, the connection piece is provided with a pair of bending boundary lines whose width increases toward the center side of the heat sink, and the connection piece follows the pair of bending boundary lines when the heat sink is deformed. Therefore, the stress acting on the power semiconductor element can be surely reduced because the heat sink is easily deformed in the diagonal direction.

According to the second aspect of the present invention, the connecting piece is provided with the curved portion whose radius of the cross section continuously increases toward the center side of the heat sink, and the connecting piece has both edges of the curved portion when the heat sink is deformed. Accordingly, the stress acting on the power semiconductor element can be reliably reduced.

It is a circuit diagram of the power control unit of one embodiment of this invention. It is a perspective view before attaching the terminal block of the semiconductor device of one Embodiment of this invention. 1 is a perspective view of a semiconductor device according to an embodiment of the present invention. It is a rear view of the semiconductor unit of one Embodiment of this invention. It is an expanded sectional view corresponding to the AA section of Drawing 4 of the power module of one embodiment of this invention. It is a top view of the semiconductor device of one embodiment of this invention. It is a side view of the semiconductor device of one embodiment of this invention. It is an expanded sectional view corresponding to the BB section of Drawing 6 of the connecting piece of one embodiment of this invention.

Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration of a circuit including a power control unit (PCU) 1 for a hybrid vehicle. This hybrid vehicle includes an engine (not shown), a generator (GEN) 2 that is driven by the mechanical output of the engine, and a battery (BAT) that is a high-voltage DC power source that is charged by the power generation output of the generator 2. 3, and a three-phase AC motor (MOT) 4 that drives drive wheels (not shown) using at least one of the discharge output of the battery 3 and the power generation output of the generator 2.

The power control unit 1 includes a converter (DC / DCCONV) 7 that functions as a step-up circuit and a step-down circuit, and converts the direct current power into three-phase alternating current power to drive the motor 4 and the three-phase alternating current generated by the motor 4. A first inverter (Tr / M PDU) 5 that converts electric power into DC power; and a second inverter (GEN PDU) 6 that converts three-phase AC power generated by the generator 2 into DC power. .
When the motor 4 is driven, the DC power of the battery 3 boosted by the converter 7 or the generated power of the generator 2 converted into DC by the second inverter 2 is output by the first inverter 5 to an arbitrary output of three-phase AC power. And the electric power is supplied to the motor 4. When the battery 3 is charged, the regenerative power of the motor 4 converted to DC power by the first inverter 5 or the generated power of the generator 2 converted to DC power by the second inverter 6 is set by the converter 7. The voltage is stepped down to DC power of voltage and the power is supplied to the battery 3.
The converter 7, the first inverter 5, and the second inverter 6 are driven and controlled via a gate drive substrate (GDCB) 9 according to a control command from a control substrate (ECU) 8.

  The first inverter 5 is configured by a pulse width modulation (PWM) PWM inverter provided with a bridge circuit 5a having a plurality of power semiconductor elements (for example, IGBT: Insulated Gate Bipolar Transistor) and a smoothing capacitor 5b. A motor 4 and a converter 7 are connected to the first inverter 5.

  Similar to the first inverter 5, the second inverter 6 is configured by a pulse width modulation (PWM) PWM inverter or the like provided with a bridge circuit 6a including a plurality of power semiconductor elements and a smoothing capacitor 6b. Further, the generator 2 and the converter 7 are connected to the second inverter 6.

  The bridge circuits 5a and 6a of the first inverter 5 and the second inverter 6 include high side (positive side) transistors UH, VH, WH and low side (corresponding to U phase, V phase, and W phase) Negative side transistors) UL, VL, WL are provided. The high-side transistors UH, VH, and WH of each phase are connected to the positive terminal Pt of the converter 7, and the low-side transistors UL, VL, and WL are connected to the negative terminal Nt of the converter 7. Transistors UH and UL, VH and VL, and WH and WL that form a pair for each phase are connected in series, and a pair of transistors for each phase is connected in parallel to converter 7. Further, between the collector electrode portions of the transistors UH, UL, VH, VL, WH, WL and the emitter electrode portions, the diodes DUH, DUL, DVH, DVL, DWH, and DWL are connected to each other.

2 and 3 show blocks of the semiconductor device 70. FIG.
In the semiconductor device 70, the U-phase high-side transistor UH and the low-side transistor UL of the first inverter 5 are integrated on the heat sink 31 together with the corresponding diodes DUH and DUL. The V-phase and W-phase high and low side transistors VH, VL, WH and WL of the first inverter 5 and the diodes DVH, DVL, DWH and DWL, and the high and low sides of each phase of the second inverter 6 are shown. The side transistors UH, UL, VH, VL, WH, WL and the diodes DUH, DUL, DVH, DVL, DWH, DWL are also configured as the semiconductor device 70 having the same configuration. Therefore, hereinafter, the U-phase semiconductor device 70 of the first inverter 5 will be described as a representative, and only the different configurations of the other semiconductor devices 70 will be described.

  The heat sink 31 is made of an aluminum material, and a plurality of pin-shaped fins 40 (see FIGS. 4 and 5) projecting downward are integrally formed on the lower surface of a rectangular plate-like pedestal 43. An insulating layer 44 of aluminum nitride having excellent thermal conductivity is integrally formed on the upper surface of the pedestal 43, and a pair of base electrodes 45 and 46 are installed in parallel on the upper surface of the insulating layer 44. . The linear expansion coefficient of the aluminum nitride insulating layer 44 is smaller than the linear expansion coefficient of the heat sink 31 made of an aluminum material.

  One base electrode 45 is connected to the P bus bar 20 (first conductor) that is electrically connected to the positive terminal Pt (see FIG. 1) of the converter 7, and the other base electrode 46 is connected to the U-phase terminal of the motor 4. It is connected to the Out bus TrU22 (third conductor). Above one base electrode 45, a connecting piece 22a extending from the Out bus TrU22 is arranged in parallel, and a high-side transistor UH and a diode DUH are connected between the base electrode 45 and the connecting piece 22a. In the high-side transistor UH, the collector electrode portion is connected to the base electrode 45 (P bus bar 20), and the emitter electrode portion is connected to the connection piece 22a (Out bus TrU22).

Above the other base electrode 46, the connection piece 21a of the N bus bar 21 (second conductor) that is electrically connected to the negative terminal Nt (see FIG. 1) of the converter 7 is disposed in parallel. A low-side transistor UL and a diode DUL are connected between 21 connection pieces 21a. The low-side transistor UL has a collector electrode portion connected to the base electrode 46 (Out bus TrU22) and an emitter electrode portion connected to the N bus bar 21.
In the V-phase and W-phase semiconductor devices 70, instead of the Out bus TrU22, an Out bus TrV23 (see FIG. 1) connected to the V-phase terminal of the motor 4 and a W-phase terminal of the motor 4 are connected. Out bus TrW24 (see FIG. 1) is used. Further, in the semiconductor device 70 of each phase of U, V, and W of the second inverter 6, an Out bus TrU25, an Out bus TrV26, and an Out bus TrW27 (see FIG. 1) are used.

  The connection piece 22 a of the Out bus TrU 22 and the connection piece 21 a of the N bus bar 21 are formed in a substantially rectangular shape, and are arranged so that the long sides thereof are parallel to the side of the base 43 of the heat sink 31. A curved portion 38 that bulges upward (in a direction away from the heat sink 31) is formed at a substantially intermediate position in the longitudinal direction of both connection pieces 22a and 21a. The curved portion 38 will be described in detail later.

  Further, as shown in FIG. 3, a terminal block 69 for holding signal lines connected to the gate electrode portions of the transistors UH and UL and other electronic devices is attached to the upper surfaces of the connection pieces 22 and 21. ing. The terminal block 69 is made of an insulating material, and is constituted by a long block that extends over the entire width direction of the connection pieces 22 and 21. A signal terminal 39 to which a signal line is connected is provided on the upper surface of the terminal block 69, and the signal terminal 39 and the transistors UH, UL and other electronic devices are connected by wire bonding. In the figure, reference numeral 48 denotes a connection line by wire bonding.

4 shows the semiconductor unit 32 in which the three semiconductor devices 70 of the first inverter 5 of U phase, V phase, and W phase are held by the resin case 34. FIG. The power module 30 to which the road case 41 is attached is shown.
In this embodiment, the three semiconductor devices 70 of the U-phase, V-phase, and W-phase of the first inverter 5 are integrated as one power module 30.

The three semiconductor devices 70 are arranged in a line, and the peripheral portion and the upper surface side of these semiconductor devices 70 are covered with the resin case 34.
The resin case 34 is first integrated with the semiconductor device 70 and then potted in the frame so as to cover the upper part of each semiconductor device 70. For this reason, although the upper part of each semiconductor device 70 is embedded in the podding part of the resin case 34, the connection terminal parts of the P bus bar 20, the Out bus TrU 22, and the N bus bar 21 and the signal pins drawn from the terminal block 69. 37 is exposed to the outside of the resin case 34.

The flow path case 41 is coupled to the lower surface of the resin case 34 of the semiconductor unit 32 and forms a flow path for the cooling medium between the resin case 34. A recess 42 for receiving the fin 40 is formed. Further, as shown in FIG. 4, an introduction pipe 52 for introducing a refrigerant into the recess 42 is connected to one end in the longitudinal direction of the flow path case 41, and the coolant is supplied from the recess 42 to the other end in the longitudinal direction. A discharge pipe 53 for discharging is connected.
A resin case 34 is superposed on the upper surface of the flow path case 41, and the resin case 34 and the flow path case 41 are fastened and fixed by bolts 50 in this state. An annular seal member 47 is interposed between the resin case 34 and the flow path case 41.

6 shows one semiconductor device 70 as viewed from the upper surface side, FIG. 7 shows a side surface of the semiconductor device 70, and FIG. 8 shows a connection piece 21a (N) corresponding to the BB cross section of FIG. A cross section of the bus bar 21) is shown.
As shown in these drawings, the curved portion 38 of each connection piece 22a, 21a has an arc-shaped cross section formed over the width direction of the connection piece 22a, 21a. The heat sink 31 continuously increases toward the center (intersection of diagonal lines). Therefore, the two boundary lines L 1 and L 2 (bending boundary lines) between the flat general surfaces of the connection pieces 22 a and 21 a and the curved portion 38 are widened toward the center side of the heat sink 31. In this embodiment, the curved portions 38 provided on the connection pieces 22a and 21a, or the boundary lines L1 and L2 at both edges of the curved portions 38 constitute a bending allowance portion.

  In each semiconductor device 70, since the insulating layer 44 of aluminum nitride having a smaller linear expansion coefficient than aluminum is integrally provided on the upper surface of the heat sink 31 made of an aluminum material, the linear expansion coefficient is generated when the transistors UH and UL generate heat. Due to this difference, the heat sink 31 and the insulating layer 44 may be bent and deformed. Since the upper surface of the heat sink 31 and the insulating layer 44 attached to the upper surface are formed in a square shape, the heat sink 31 and the insulating layer 44 are arranged in a diagonal direction with a long separation distance from the center of the heat sink 31. Large bending deformation (warp deformation) is likely to occur.

Each semiconductor device 70 of the power module 30 has a connection between the Out bus TrU22 and the N bus bar 21 above the transistors UH, UL and diodes DUH, DUL installed on the heat sink 31 via the insulating layer 44 and base electrodes 45, 46. The pieces 22a and 21a are joined, but each connecting piece 22a and 21a is provided with a curved portion 38 so that the radius of the arc continuously increases toward the center side of the heat sink 31, so that the transistor When the heat sink 31 and the insulating layer 44 are greatly bent and deformed in the diagonal direction due to heat generated by UL and UL, the connection pieces 22a and 21a are easily deformed following the boundary lines L1 and L2 of both edges of the curved portion 38. .
Therefore, since the connecting pieces 22a and 21a are easily bent and deformed following the heat sink 31 and the insulating layer 44, a large stress does not act on the transistors UH and UL and the diodes DUH and DUL. Therefore, in the semiconductor device 70, deterioration of the diodes DUH and DUL and the transistors UH and UL can be prevented beforehand by devising the shapes of the connection pieces 22a and 21a.

  In addition, this invention is not limited to said embodiment, A various design change is possible in the range which does not deviate from the summary.

3 ... Battery (DC power supply)
4 ... Motor (AC equipment)
20 ... P bus bar (first conductor)
21 ... N bus bar (second conductor)
22 ... Out bus TrU (third conductor)
21a, 22a ... connecting piece 31 ... heat sink 38 ... curved portion 44 ... insulating layer 70 ... semiconductor device UH ... high side transistor (positive power semiconductor element)
UL ... Low-side transistor (negative-side power semiconductor element)
DUH: High-side diode (positive-side power semiconductor element)
DUL ... Low side diode (negative power semiconductor element)
L1, L2 ... boundary line (bending boundary line)

Claims (2)

The positive power semiconductor element and the negative power semiconductor element are arranged in parallel on the upper surface of the substantially square heat sink via an insulating layer having a different linear expansion coefficient from the heat sink.
While the collector electrode portion of the positive power semiconductor element is electrically connected to the positive electrode of the DC power source through the first conductor,
An emitter electrode portion of the negative power semiconductor element is electrically connected to a negative electrode of the DC power source via a second conductor;
A semiconductor device in which the emitter electrode part of the positive power semiconductor element and the collector electrode part of the negative power semiconductor element are electrically connected to an AC device via a third conductor;
A flat connection piece is provided on at least one of the first, second, and third conductors, and the connection piece is superimposed on one upper surface of the positive power semiconductor element and the negative power semiconductor element. Fixed,
The connection piece is provided with a pair of bent boundary lines whose separation width is widened toward the center side of the heat sink, and these bent boundary lines facilitate bending deformation of the connection piece in the diagonal direction of the heat sink. A semiconductor device comprising a bending allowance portion . Claim 1, the connecting piece, the curved portion is provided radially cross-section toward the center side of the heat sink increases continuously, permitting portion bending said by the curved portion is characterized by being composed A semiconductor device according to 1.

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