JP2007123644A - Power semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power semiconductor device which is compact, improves assembly property and productivity, and is highly reliable by adopting a ceramic capacitor as a smoothing capacitor. <P>SOLUTION: A power semiconductor device includes a semiconductor device 1 for performing power conversion from DC to AC or from AC to DC, a smoothing capacitor 2 for smoothing a DC power source output and a control circuit 6 for controlling the power conversion of the semiconductor device. In the power semiconductor device; the smoothing capacitor 2 is a ceramic capacitor, the semiconductor device 1 and the smoothing capacitor 2 are electrically bonded to a Cu pattern (wiring) 5a on a metal base plate 5c having a heat dissipation function. A protection mechanism 3 comprising an element which is fused and disconnected when an overcurrent flows to a circuit of the wiring 5a, and electrodes provided in both terminals of the element and bonded to the wiring 5a, is bonded to the wiring 5a with a bonding member and disposed in series with the smoothing capacitor 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power semiconductor device using a ceramic capacitor as a smoothing capacitor, and more particularly to a power semiconductor device mounted as a control device in an electric vehicle, a hybrid vehicle, and an idling stop vehicle.

In recent years, reduction of CO ₂ emissions has been demanded against the background of global warming prevention, and development of power semiconductor devices such as inverters considering the environment has been promoted. In particular, in-vehicle power semiconductor devices require high quality and high reliability in spite of the harsh environment such as high temperature and high humidity in the engine room. Miniaturization is required for mounting.

  When switching is performed in a power semiconductor device such as an inverter, a smoothing capacitor is used in order to suppress voltage fluctuation of the DC power source and smooth the voltage jump. As this smoothing capacitor, an aluminum electrolytic capacitor is generally used because a sufficiently large capacitance is required.

  However, this aluminum electrolytic capacitor has a large size (volume) and is not suitable for miniaturization of a power semiconductor device.

  If a ceramic capacitor is used as the smoothing capacitor, the power semiconductor device can be greatly reduced in size, but the ceramic capacitor has a short-circuit failure mode due to its structure, and unlike an aluminum electrolytic capacitor or film capacitor. There is no protection mechanism.

  Therefore, for example, as disclosed in Patent Document 1, in order to increase the reliability of the power semiconductor device, a plurality of fuses are provided in parallel connection.

Japanese Patent Laid-Open No. 11-144603 (page 4, FIG. 1)

  In general, high-voltage fuses corresponding to power electronics circuits that handle high voltages and large currents are currently used, and expensive fuses have to be used as a protection mechanism for semiconductor devices.

  In addition, the fuse has low reliability and is connected by a wiring connection portion such as a bus bar, so that the assemblability and productivity are deteriorated.

  The present invention has been made in order to solve the above-described problems, and is reduced in size by adopting a ceramic capacitor as a smoothing capacitor, and has good assembling and productivity, and highly reliable power. An object is to provide a semiconductor device.

A power semiconductor device according to the present invention controls a circuit including a semiconductor element that performs power conversion from direct current to alternating current or from alternating current to direct current, a smoothing capacitor for smoothing a DC power supply output, and controls power conversion of the semiconductor element. A power semiconductor device comprising: a control circuit unit that protects the semiconductor element and a smoothing capacitor when an overcurrent flows in the circuit;
The smoothing capacitor is a ceramic capacitor,
The protection mechanism includes an element that melts and breaks when an overcurrent flows through the circuit, and electrode portions that are provided at both ends of the element.
The circuit wiring is formed on a base plate having a heat dissipation function,
The semiconductor element, the smoothing capacitor, and the electrode portion of the protection mechanism are joined to a circuit wiring formed on the base plate by a joining member.

  According to the power semiconductor device of the present invention, it is possible to provide a highly reliable power semiconductor device that is miniaturized by adopting a ceramic capacitor as a smoothing capacitor and that has good assembling and productivity.

Hereinafter, preferred embodiments of an electronic device apparatus according to the present invention will be described with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a cross-sectional view showing a first embodiment of a power semiconductor device according to the present invention. The power semiconductor device according to the first embodiment includes a semiconductor element 1, a smoothing capacitor 2 and a protection mechanism 3, which are electrically connected to a wiring circuit using a Cu pattern 5a, an input terminal 4a and an output terminal 4b connected to the outside, and an input terminal. 4a and a bus bar 11 connected to the output terminal 4b and electrically connecting the wiring circuit to the input terminal 4a and the output terminal 4b, a metal substrate 5 on which these are mounted and mounted, and a control circuit for controlling the semiconductor element 1 Unit 6, a housing 7 in which the metal substrate 5, the control circuit unit 6 and the input / output terminal 4 are integrated, and a radiator 9 attached to the back surface of the metal base plate 5 c via a grease layer 8.

  For example, a MOSFET that performs switching can be used as the semiconductor element 1. However, the semiconductor element 1 is not limited to the MOSFET, and may be an IGBT, a transistor, or the like. In the first embodiment, the shape of the semiconductor element 1 is a discrete shape, but it may be a bare chip or a power module in which a pair of upper and lower arms are integrated with resin or the like.

  A metal substrate 5 on which electronic components such as a semiconductor element 1, a smoothing capacitor 2, and a protection mechanism 3 are mounted is composed of a Cu pattern (wiring) 5a, an insulating layer 5b, and aluminum (Al) having a thickness of about 2 to 3 mm in order from the upper layer. ) Or copper (Cu), which is provided with a metal base plate 5c having a good thermal conductivity, and the heat of the semiconductor element 1, the smoothing capacitor 2, and the protection mechanism 3 is transferred from the metal substrate 5 to the radiator. 9 is diffused, radiated and cooled. As described above, the semiconductor element 1, the smoothing capacitor 2, and the protection mechanism 3 are joined to the Cu pattern (wiring) 5 a of the metal substrate 5 by the solder 15, and are electrically connected to the input terminal 4 a and the output terminal 4 b through the bus bar 11. It is connected to the.

  In addition, a control circuit unit 6 for performing switching control of the semiconductor element 1 composed of a drive circuit and a power supply circuit on which electronic components such as a microcomputer and a memory are mounted is electrically connected to the Cu pattern (wiring) 5 a of the metal substrate 5. Connected.

  An input terminal 4a, an output terminal 4b, a bus bar 11 and a metal substrate 5 connected to the input terminal 4a and the output terminal 4b are attached to a housing 7 integrally formed of PPS or PBT, and the input terminal 4a and the output terminal 4b. It can be electrically connected to an external load and a DC power source via

  Power electronics circuits such as power semiconductor devices handle large currents and generate large amounts of heat, so heat dissipation and cooling capabilities are required. Therefore, the metal base plate 5 c of the metal substrate 5 is attached to the radiator 9 via the grease layer 8. The radiator 9 has a plurality of fins and is cooled by air, or a cooling water passage provided with water is used.

  On the side facing the radiator 9, a cover 10 having a dustproof and waterproof role is provided so as to cover the housing 7.

  FIG. 2 is a schematic circuit diagram for explaining the operation of the power semiconductor device according to the first embodiment. The power semiconductor device 14 includes a semiconductor element 1 constituting the U phase, the V phase, and the W phase, and a control circuit unit 6 that controls the semiconductor element 1. A circuit configuration for driving an AC load 12 such as a DC power source 13 converts a current from a DC power source 13 into a three-phase AC composed of a U phase, a V phase, and a W phase in the semiconductor element 1 to generate an AC current. The load 12 is driven. Moreover, the three-phase alternating current of the alternating current load 12 is converted into direct current by regeneration and returned to the direct current power source 13.

  The protection mechanism 3 is connected in series with the smoothing capacitor 2, and the protection mechanism 3 and the smoothing capacitor 2 are connected in parallel with the U phase, the V phase, and the W phase.

  In the power semiconductor device according to the first embodiment, a ceramic capacitor is employed as the smoothing capacitor 2 and incorporated in the circuit, thereby realizing a reduction in size of the power semiconductor device.

  Ceramic capacitors have a problem in that they have a high defect rate and a high failure rate in the manufacturing process, and do not have a protective mechanism like an aluminum electrolytic capacitor or a film capacitor. In order to solve this problem, when a protection mechanism 3 is newly provided on the circuit and a short circuit failure occurs in the ceramic capacitor, a current of about several hundred to 1200 A flows in this circuit, and the protection mechanism 3 is activated. Thus, it has been confirmed by experiments that the semiconductor element 1 and the ceramic capacitor are prevented from being destroyed.

  3 is a cross-sectional view of the protection mechanism 3 according to the first embodiment, and FIG. 4 is a plan view of the protection mechanism 3 according to the first embodiment. As shown in FIGS. 3 and 4, in the protection mechanism 3, the element 3 a and the electrode portion 3 b are composed of the same conductive member. The electrode portion 3 b is joined to the Cu pattern (wiring) 5 a that is the wiring portion of the metal substrate 5 by the solder 15 that is a joining member.

  In this way, by joining the protection mechanism 3 to the wiring, even if a ceramic capacitor is short-circuited and a sudden overcurrent flows in the circuit, the element 3a of the protection mechanism 3 is immediately melted and disconnected. Thus, it is possible to prevent the occurrence of a situation such as destruction, burning, smoke generation, or ignition in the ceramic capacitor or the power semiconductor device 1.

  The electrode portion 3b is bonded to the Cu pattern (wiring) 5a that is the wiring portion of the metal substrate 5 with the solder 15 that is a bonding member, and the thermal conductivity of the insulating layer 5b of the metal substrate 5 is about 1.5. Since it is good at 2.5 W / mk, in a steady state, Joule heat generated in the element 3a and the electrode part 3b is radiated from the electrode part 3b to the metal base plate 5c having a heat radiation function (heat radiator 9). 3a can be prevented from fusing, solder 15 as a joining member can be prevented from melting, and when overcurrent flows into element 3a, it can be blown out by Joule heat due to overcurrent, so that the power semiconductor device Can be made highly reliable. Moreover, since the protection mechanism 3 can be mounted simultaneously with the mounting of the semiconductor element 1 and the smoothing capacitor, the assemblability is improved and the productivity is improved.

  Further, the elastic modulus of the insulating layer 5b is set to about 100 to 1000 MPa, and the metal substrate 5 is made to have a low elastic modulus. For example, the structure of the electrode portion 3b is high even in a high temperature severe environment such as an engine room. Reliability can be obtained, and electrical characteristics and sufficient heat dissipation can be maintained. Productivity is also improved.

  In addition, since the element 3a and the electrode portion 3b are made of the same conductive member, the protection mechanism can be made simple and manufactured by a press using a mold, etc., so that the mass productivity is improved. Can do.

  The element 3a has a thin line shape such that the length of one side of the cross section is approximately 0.1 mm to 2.0 mm, whereas the mounting area of the electrode portion 3b is the Joule heat generated in the element 3a at the normal time. Is preferably as large as possible in order to dissipate heat to the metal substrate 5 through the electrode portion 3b joined with the solder 15.

  In addition, since the element 3a has the same length and a plurality of fine wires arranged in parallel, the element 3a can be shortened, and the power semiconductor device can be downsized.

  Further, by providing the element 3a with a plurality of thin wires arranged in parallel, it is possible to disperse the current and suppress the temperature rise of the solder 15.

  The number of parallel thin wires in the element 3a depends on the fusing characteristics as a protective function. That is, since the number of parallel thin wires in element 3a, the length of the thin wires, the cross-sectional area of the thin wires, and the fusing characteristics are strictly related, the Joule heat is calculated from the resistance of element 3a and the flowing current, Find a number. As an example, FIG. 4 shows a case where the number of parallel thin lines in the element 3a is three, but the number of fine lines in the element 3a may be one.

  In order to reduce the size of the protection mechanism 3, for example, the length of the element 3a is shortened, the cross-sectional area is reduced, or the length of the element 3a is shortened, and a plurality of fine wires are arranged in parallel. .

  In the first embodiment, the protection mechanism 3 needs to be disconnected or blown within about 1 s (about 100 ms) with respect to a large overcurrent of about 100 to 2000 A, and in a steady state, about 50 A or less. The condition that the element 3a is not disconnected or fused with respect to the current must be satisfied. Moreover, since it is necessary to suppress the temperature rise of the solder 15 so that the joining part of the electrode part 3b and the metal substrate 5, that is, the solder 15, does not melt due to the heat effect generated by the element 3a or the electrode part 3b. As described above, the electrode portion 3b of the protection mechanism 3 is joined to the wiring portion of the metal substrate 5 having a heat dissipation function.

  In general, the protection mechanism or fuse is extremely thin at the center of the element. When the center of the element is extremely thin, it is disconnected or melted within about 1 s (about 100 ms) against a large overcurrent, and at steady state. However, in the first embodiment, it is difficult to set the shape and dimension so as to satisfy the condition that the element 3a is not melted or disconnected with respect to a current of about 50 A or less. Since the cross-sectional area in the length direction of 3a is made uniform, and the element 3a is composed of a plurality of fine lines, the lengths of the thin lines are also the same, so that the shape dimension can be easily set.

  Experiments have shown that the fusing characteristics of the protection mechanism 3 in the overcurrent of the power semiconductor device are substantially the same fusing time regardless of the length when the length exceeds a certain length. FIG. 5 is a diagram showing the relationship between the fusing time and the fusing current when the cross-sectional area of the element 2a made of nickel (Ni) is 0.2 mm × 0.25 mm and the length is 5 mm, 10 mm, and 20 mm. From the result of FIG. 5, when viewed at a cutting current of 30 A, the cutting time is 100 ms regardless of the length at C: 20 mm and B: 10 mm, and the influence of the length can be ignored. Therefore, the length of the element 3a does not need to be unnecessarily long such as 20 mm, and may be 10 mm or less.

  It is preferable to use nickel (Ni) or aluminum (Al) as the material of the protection mechanism made of the same conductive material. Ni and Al increase in resistivity as the temperature increases. That is, in a steady state, the temperature is low, the resistivity is small, the generation of Joule heat is small, and it does not melt or break. When an overcurrent flows, the resistivity increases due to a temperature rise, and a large Joule heat is generated and the temperature rises, so that it can be melted and disconnected instantly, which is most suitable for a power semiconductor device.

  In the protection mechanism 3, in particular, the wettability of the solder 15 can be improved by plating the electrode portion 3 b that is a joint portion to the metal substrate 5 with Sn, solder, or the like.

  Further, the bonding between the electrode portion 3 b and the wiring portion of the metal substrate 5 is not limited to the solder 15, and a conductive adhesive resin can be used instead of the solder 15.

Embodiment 2. FIG.
FIG. 6 is a cross-sectional view for explaining the power semiconductor device according to the second embodiment of the present invention, and shows the structure of the protection mechanism. The second embodiment is the same as the first embodiment except for the protection mechanism, and the difference from the first embodiment is the structure of the protection mechanism.

  As shown in FIG. 6, the element 3a of the protection mechanism 3 according to the second embodiment has a curved shape, and the distance between the electrode portions 3b is the same when the length of the element 3a is the same when the shape is linear. It is possible to reduce the size of the protection mechanism 3 by shortening.

  Further, by making the element 3a curved, as shown in the figure, the narrow space of the element 3a is arranged in the vertical direction by effectively utilizing the limited space between the electrode portions 3b, and the necessary and sufficient length of the element 3a is provided. Therefore, the protection mechanism 3 can be downsized.

Embodiment 3 FIG.
FIG. 7 is a cross-sectional view for explaining a third embodiment of the power semiconductor device according to the present invention, and shows the structure of the protection mechanism. The third embodiment is the same as the first embodiment except for the protection mechanism, and the difference from the first embodiment is the structure of the protection mechanism.

  As shown in FIG. 7, in the protection mechanism 3 according to the third embodiment, at least the element 3a is covered with an insulating material 16 made of resin, flame retardant material, or the like.

  The insulating material 16 does not need to cover the entire element 3a, and may be provided so as to cover a part of the element 3a, particularly the central portion of the element 3a.

  According to the protection mechanism 3 of the third embodiment, the fragments of the element 3a melted and disconnected by the insulating material 16 at high heat are prevented from being scattered and scattered, and the melted and disconnected element 3a is connected to the wiring connection portion and the electronic component. It is possible to prevent contact with the electrodes and the like, and to prevent short circuit, burnout, smoke generation, and the like.

  The insulating material 16 can be formed by a method such as potting resin after mounting electronic components such as the semiconductor element 1, the smoothing capacitor 2, and the protection mechanism 3 on the metal substrate 5. Productivity can be improved.

Embodiment 4 FIG.
FIG. 8 is a cross-sectional view for explaining a power semiconductor device according to a fourth embodiment of the present invention and shows the structure of the protection mechanism. The fourth embodiment is the same as the first embodiment except for the protection mechanism.

  The difference from the first embodiment is the structure of the protection mechanism. As shown in FIG. 8, in the protection mechanism 3 according to the fourth embodiment, at least the element 3 a is covered with the shield plate 17.

  The shield plate 17 does not need to cover the entire element 3a, and may be provided so as to cover a part of the element 3a, particularly the central portion of the element 3a.

  According to the protection mechanism 3 of the fourth embodiment, the shield plate 17 prevents scattered and scattered pieces of the element 3a melted and disconnected by high heat, and the melted and disconnected element 3a is connected to the wiring connection portion, the electronic It is possible to prevent contact with the electrode of the component and prevent short circuit, burnout, smoke generation, and the like.

  The power semiconductor device according to the invention can be effectively used as a control device for a rotating electrical machine mounted on an electric vehicle, a hybrid vehicle, an idling stop vehicle, or the like.

1 is a cross-sectional view showing a first embodiment of a power semiconductor device according to the present invention. FIG. 5 is a schematic circuit diagram for explaining an operation in the power semiconductor device of the first embodiment. It is sectional drawing of the protection mechanism 3 in this Embodiment 1. FIG. It is a top view of the protection mechanism 3 in this Embodiment 1. FIG. It is a figure which shows the relationship between fusing time and fusing current when the cross-sectional area of the element 2a which consists of nickel (Ni) is 0.2 mm x 0.25 mm and length is 5 mm, 10 mm, and 20 mm. It is sectional drawing for demonstrating Embodiment 2 of the power semiconductor device which concerns on this invention. It is sectional drawing for demonstrating Embodiment 3 of the power semiconductor device which concerns on this invention. It is sectional drawing for demonstrating Embodiment 4 of the power semiconductor device which concerns on this invention.

Explanation of symbols

1 semiconductor element, 2 smoothing capacitor, 3 protection mechanism, 3a element,
3b electrode part, 4 input / output terminal, 4a input terminal, 4b output terminal, 5 metal substrate,
5a Cu pattern, 5b insulating layer, 5c metal base plate, 6 control circuit section, 7 housing, 8 grease layer, 9 radiator, 10 cover, 11 bus bar, 12 AC load,
13 DC power supply, 14 Power semiconductor device, 15 Solder, 16 Insulating material,
17 Shield plate.

Claims (9)

A circuit including a semiconductor element for performing power conversion from direct current to alternating current or alternating current to direct current, a smoothing capacitor for smoothing a DC power supply output, a control circuit unit for controlling power conversion of the semiconductor element, and the circuit In a power semiconductor device comprising a protection mechanism for protecting the semiconductor element and the smoothing capacitor when an overcurrent flows,
The smoothing capacitor is a ceramic capacitor,
The protection mechanism includes an element that melts and breaks when an overcurrent flows through the circuit, and electrode portions that are provided at both ends of the element.
The circuit wiring is formed on a base plate having a heat dissipation function,
The power semiconductor device, wherein the semiconductor element, the smoothing capacitor, and the electrode portion of the protection mechanism are joined to a circuit wiring formed on the base plate by a joining member. The power semiconductor device according to claim 1, wherein the element of the protection mechanism and the electrode portion are made of the same conductive member. 2. The power semiconductor device according to claim 1, wherein the elements of the protection mechanism are formed of two or more thin wires having substantially the same length provided in parallel between the electrodes. The power semiconductor device according to claim 1, wherein the element of the protection mechanism has a substantially uniform cross-sectional area between the electrodes. The power semiconductor device according to claim 1, wherein the element of the protection mechanism has a curved shape between the electrodes. The power semiconductor device according to claim 1, wherein an element of the protection mechanism is 10 mm or less. 3. The power semiconductor device according to claim 2, wherein the element and the electrode portion of the protection mechanism made of the same conductive member are made of nickel or aluminum. The power semiconductor device according to claim 1, wherein at least a part of a central portion of the element of the protection mechanism is covered with an insulating material. 2. The power semiconductor device according to claim 1, wherein at least an element of the protection mechanism is covered with a shield plate.

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