Semiconductor device for suppressing a temperature increase in beam leads

Abstract

Provided is a semiconductor device that can suppress a temperature increase in beam leads while reducing the number of wiring lines and can suppress an increase in manufacturing costs. The semiconductor device is provided with a power module including an upper arm and a lower arm each configured by connecting in parallel a plurality of power elements and a plurality of rectifying elements. Current to one arm flows through a plurality of separately wired beam leads. A portion of the power elements and a portion of the rectifying elements in one arm form a pair and are connected by a common beam lead.

Claims

1. A semiconductor device comprising: a plurality of first power elements and a plurality of first rectifying elements in an upper arm; a positive side conductive pattern on which the plurality of first power elements and the plurality of first rectifying elements are disposed alternately in a line; a plurality of second power elements and a plurality of second rectifying elements in a lower arm; an output side conductive pattern on which the plurality of second power elements and the plurality of second rectifying elements are disposed alternately in a line; a negative side conductive pattern; a plurality of first beam leads, each of the plurality of first beam leads connecting a pair of one of the first power elements and an adjacent first rectifying element to the output side conductive pattern; and a plurality of second beam leads, each of the plurality of second beam leads connecting a pair of one of the second power elements and an adjacent second rectifying element to the negative side conductive pattern.

2. The semiconductor device according to claim 1, wherein the plurality of first beam leads and the plurality of second beam leads are T-shaped in a plan view, and wherein the positive side conductive pattern, the output side conductive pattern and the negative side conductive pattern are disposed in the same plane, and wherein a connecting point of each of the first beam leads to the output side conductive pattern is adjacent to a connecting point of each of the second beam leads to the negative side conductive pattern.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The present invention will be further described below with reference to the accompanying drawings, wherein:

(2) FIG. 1 illustrates the layout of power elements, rectifying elements, and the like, as well as the flow of current therein, in a semiconductor device according to an embodiment of the present invention;

(3) FIG. 2 is a circuit diagram of a semiconductor device according to a conventional technique, in which two-chip sets of power elements are connected by beam leads;

(4) FIG. 3 illustrates the layout and the direction of current in a semiconductor device according to a conventional technique, in which each element in a two-chip set of power elements is individually connected by a beam lead; and

(5) FIG. 4 illustrates the layout and the direction of current in a semiconductor device according to a conventional technique, in which a two-chip set of power elements is collectively connected by one beam lead.

DESCRIPTION OF EMBODIMENTS

(6) The following describes embodiments of the present invention in detail, based on the embodiment illustrated in the drawings.

(7) First, the overall configuration of a semiconductor device according to the present embodiment is described.

(8) The semiconductor device of the present embodiment is, for example, used in an inverter that controls power supplied to an electric motor for driving that is mounted in an electric vehicle.

(9) As illustrated in FIG. 1, the semiconductor device of the present embodiment as well is provided with a power module including an upper arm 10 configured by connecting in parallel two IGBTs 1a and 1b and two diodes 2a and 2b. The semiconductor device is also provided with a power module including a lower arm 11 configured by connecting in parallel two IGBTs 1c and 1d and two diodes 2c and 2d. These power modules are a portion of the above-mentioned inverter.

(10) An insulating substrate 5 has fixed thereon the following: a rectangular positive side pattern 4a, formed from conducting metal, at the right in FIG. 1 (the upper arm side); a negative side pattern 4b, formed from conducting metal, extending horizontally from the left of FIG. 1 to near the approximate center and then turning downward and extending vertically downward to form an inverted L shape; and an output side pattern 4c, formed from conducting metal, extending from the top edge to the bottom edge in FIG. 1 at approximately the center position of FIG. 1 and then turning to the left (the bottom arm side), extending horizontally to the left edge, and rising vertically from the lower left edge to near the positive side pattern 4b to form a U shape.

(11) At one edge of the insulating substrate 5 (at the top edge in FIG. 1), a positive side input terminal P is provided and connected to the positive side pattern 4a. At the same edge of the insulating substrate 5, a negative side input terminal N is provided and connected to the negative side pattern 4b. At the other edge of the insulating substrate 5 (at the bottom edge in FIG. 1), an output terminal O is provided and connected to the output side pattern 4c.

(12) At the upper arm side, the IGBT 1a and the diode 2a, for which to current flows in opposite directions, form a pair. For example, in the case of the IGBT 1a being an n-channel type, the collector side of the IGBT 1a and the cathode side of the diode 2a are fixed to the positive side pattern 4a provided on the insulating substrate 5. The emitter side of the IGBT 1a and the anode side of the diode 2a are grouped and connected to each other by one side of a beam lead 3a, and the other side of the beam lead 3a is connected to the output side pattern 4c provided on the insulating substrate 5. The IGBT 1a and the diode 2a are thus made conductive with each other by the beam lead 3a.

(13) Similarly, the IGBT 1b and the diode 2b of the upper arm, for which current flows in opposite directions, form another pair. For example, in the case of the IGBT 1b being an n-channel type, the collector side of the IGBT 1b and the cathode side of the diode 2b are fixed to the positive side pattern 4a. The emitter side of the IGBT 1b and the anode side of the diode 2b are grouped and connected to each other by one side of a beam lead 3b, and the other side of the beam lead 3b is connected to the output side pattern 4c. The IGBT 1b and the diode 2b are thus made conductive with each other by the beam lead 3b.

(14) On the other hand, at the lower arm side, the IGBT 1c and the diode 2c, for which current flows in opposite directions, form a pair. For example, in the case of the IGBT 1c being an n-channel type, the collector side of the IGBT 1c and the cathode side of the diode 2c are fixed to the output side pattern 4c. The emitter side of the IGBT 1c and the anode side of the diode 2c are grouped and connected to each other by one side of a beam lead 3c, and the other side of the beam lead 3c is connected to the negative side pattern 4b provided on the insulating substrate 5. The IGBT 1c and the diode 2c are thus made conductive with each other by the beam lead 3c.

(15) Similarly, the IGBT 1d and the diode 2d of the lower arm, for which current flows in opposite directions, form another pair. For example, in the case of the IGBT 1d being an n-channel type, the collector side of the IGBT 1d and the cathode side of the diode 2d are fixed to the output side pattern 4c. The emitter side of the IGBT 1d and the anode side of the diode 2d are grouped and connected to each other by one side of a beam lead 3d, and the other side of the beam lead 3d is connected to the negative side pattern 4b. The IGBT 1d and the diode 2d are thus made conductive with each other by the beam lead 3d.

(16) While not illustrated, a gate signal for control, determined by a control unit (not illustrated) in accordance with the amount of accelerator depression, vehicle speed, or the like, can be applied to the gate of each of the IGBTs 1a to 1d.

(17) Three combinations that are similar to the combination of the upper arm 10 and the lower arm 11 are provided, and the output terminals thereof are connected to respective coils of a three-phase AC electric motor.

(18) Next, the operations of the inverter that is a semiconductor device with the above-described configuration are described.

(19) In the above-described semiconductor device, the IGBTs 1a and 1b of the upper arm 10 and the diodes 2c and 2d of the lower arm 11 form a step-down chopper, and the IGBTs 1c and 1d of the lower arm 11 and the diodes 2a and 2b of the upper arm 10 form a step-up chopper.

(20) By complementary switching of the IGBTs 1a, 1b and 1c, 1d of the upper and lower arms 10 and 11, power conversion can be performed regardless of the polarity of the current.

(21) In other words, by turning the IGBTs 1a and 1b of the upper arm 10 ON and the IGBTs 1c and 1d of the lower arm 11 OFF, positive reactor current flows through the IGBTs 1a and 1b of the upper arm 10 into the electric motor coil connected to the output terminal O. Conversely, by turning the IGBTs 1c and 1d of the lower arm 11 ON and the IGBTs 1a and 1b of the upper arm 10 OFF, negative reactor current flows through the IGBTs 1c and 1d.

(22) The diodes 2a to 2d are used because, by causing the induced voltage energy generated by the electric motor to flow to the DC power source, the diodes 2a to 2d prevent the terminal voltage of the motor from rising due to the induced voltage, which would cause the IGBTs 1a to 1d to be damaged by overvoltage.

(23) Furthermore, in the former case mentioned above in which positive reactor current flows, the diodes 2a and 2b of the upper arm 10 block current from flowing through these diodes 2a and 2b, whereas in the latter case mentioned above in which negative reactor current flows, the diodes 2c and 2d of the lower arm 11 block current from flowing through these diodes 2c and to 2d.

(24) Accordingly, current does not flow simultaneously through both the IGBTs 1a and 1b and the diodes 2a and 2b of the upper arm 10, and similarly, current does not flow simultaneously through both the IGBTs 1c and 1d and the diodes 2c and 2d of the lower arm 11.

(25) The IGBTs 1a and 1b of the upper arm 10 are connected individually by different beam leads 3a and 3b, and when the IGBTs 1a and 1b are ON, current does not flow to the diodes 2a and 2b connected to the beam leads 3a and 3b. Therefore, the current flowing through the beam leads 3a and 3b decreases.

(26) Similarly, the IGBTs 1c and 1d of the lower arm 11 are connected individually by different beam leads 3c and 3d, and when the IGBTs 1c and 1d are ON, current does not flow to the diodes 2c and 2d connected to the beam leads 3c and 3d. Therefore, the current flowing through the beam leads 3c and 3d decreases.

(27) Note that in FIG. 1, arrows depicted with solid lines indicate the direction of current when the IGBTs are operating, and arrows depicted with dashed lines indicate the direction of current when the diodes are operating.

(28) As is clear from the above description, in the semiconductor device of the present embodiment, the power module includes the upper arm 10 and the lower arm 11 each configured by connecting the plurality of IGBTs 1a to 1d and the plurality of diodes 2a to 2d in parallel, and the current in one arm 10 (or 11) flows through the plurality of separately wired beam leads 3a to 3d. At this time, in the semiconductor device, a portion of the IGBTs 1a and 1b (and/or 1c and 1d) and a portion of the diodes 2a and 2b (and/or 2c and 2d) in the one arm 10 (or 11) form pairs and are connected by common beam leads 3a to 3d. Therefore, in these pairs, the IGBT and diode do not turn ON simultaneously, and hence current does not flow simultaneously to both elements.

(29) In other words, only one chip's worth (either the IGBT or the diode in the pair) of current flows simultaneously through the beam leads 3a to 3d.

(30) Accordingly, the amount of current flowing through the beam leads 3a to 3d can be suppressed and equalized. Therefore, the beam leads 3a to 3d can be prevented from reaching a high temperature, and the beam leads 3a to 3d need not be made large.

(31) Furthermore, the beam leads 3a to 3d are fewer in number as compared to when beam leads are individually wired, thus suppressing an increase in manufacturing costs.

(32) The present invention has been described based on the above embodiments, yet the present invention is not limited to these embodiments and includes any design modification or the like within the spirit and scope of the present invention.

(33) For example, in the embodiment, each arm is configured to include two IGBTs and two diodes, yet this embodiment is not limiting. The case of one arm being configured with three or more each of the power elements and rectifying elements is included, and the semiconductor device may have a plurality of sets.

(34) The present invention may also be applied just to a pair of only a portion of the plurality of power elements and rectifying elements in one arm.

REFERENCE SIGNS LIST

(35) 1a, 1b: IGBT (power element) at upper arm side 1c, 1d: IGBT (power element) at lower arm side 2a, 2b: Diode (rectifying element) at upper arm side 2c, 2d: Diode (rectifying element) at lower arm side 3a to 3d: Beam lead 4a: Positive side pattern 4b: Negative side pattern 4c: Output side pattern 5: Insulating substrate 10: Upper arm 11: Lower arm N: Negative side input terminal P: Positive side input terminal O: Output terminal