JPH11177021A - Electrode structure for semiconductor switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide electrode structure of a semiconductor switch, in which generation of a switching loss or a serge voltage can be reduced by preventing generation of inductance. SOLUTION: Plural semiconductor chips 2 are directly placed on a drain electrode 3 used also as a heat radiating plate, and source electrodes 4 and 5 and a gate electrode 6 are placed on positions so that the semiconductor chip 2 can be surrounded. The source electrodes 4 and 5 and the gate electrode 6 are placed by strongly fixing resin 7 for insulation between those electrodes and the drain electrode 3 and electrically insulating them, and each electrode is connected through plural thin bonding wires 8 with the semiconductor chip 2 in parallel. The source electrode 4 is formed in a 'U' shape so that the top plate can be made wide and large, and the top plate of the 'U'-shaped source electrode and the drain electrode are arranged adjacent in parallel. Thus, currents are allowed to flow on each electrode so that inductance on each electrode can be offset by the mutual inductance effect.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packaged power semiconductor switch, and more particularly to an improved electrode structure for reducing a surge voltage and a switching loss due to an inductance of wiring in a package.

[0002]

2. Description of the Related Art Today, power semiconductor switches for switching large currents are widely used. For example, in a motor control device used for an electric motor-driven vehicle such as an electric vehicle or a battery forklift, the semiconductor switching device described above is used as a switching device of an inverter that supplies power to a traveling or cargo handling motor. Switch is used. Such a semiconductor switch generates heat due to switching of a large current. For this reason, the internal circuit of the semiconductor switch is covered with a metal package case for radiating heat.

FIG. 3 shows that this semiconductor switch 1 is, for example, M
This shows an example of a specific configuration of an internal circuit in the case of using an OSFET (hereinafter, a MOSFET structure is described as a specific example of a semiconductor switch). In this figure, a plurality of semiconductor chips 2 are directly mounted on a drain electrode 3 also serving as a heat sink, and further, a source electrode 4 and a gate electrode 6 are mounted at positions so as to sandwich the semiconductor chip 2. Here, the source electrode 4 and the gate electrode 6 are placed after being electrically insulated by tightly attaching an insulating resin 7 between the drain electrode 3 and a plurality of thin bonding wires 8 in parallel with each electrode. Thus, the configuration is such that the semiconductor chip 2 is connected.

In the internal circuit configured as described above,
By applying an input voltage to the gate electrode 6, the semiconductor chip 2
Is turned on, and an operation is performed in which a current flows in the order of drain electrode 3 → back surface of semiconductor chip 2 → front surface of semiconductor chip 2 → bonding wire 8 → source electrode 4.

[0005] The internal circuit thus configured is
The electrodes are integrated into one resin package, and each electrode is exposed outside the package and connected to an external terminal connected to the outside.

Furthermore, in order to prevent the internal circuit from causing a chemical reaction with oxygen or ions present in the air, the cavity inside the package is filled with gel and epoxy resin from below. .

In the semiconductor switch 1 configured as described above, the switching frequency usually used in, for example, the above-described electric vehicle or the like is about 10 kHz.

[0008]

In the case where the semiconductor switch constructed as described above is actually used at the switching frequency as described above, each of the electrodes and the bonding shown in FIG. In a thin wiring such as a wire, a current flows intensively in a narrow space geometrically, so that it is inevitable that a large inductance is generated.As a result, a considerable loss of switching power is caused when the switching element is turned off. (Hereinafter, referred to as switching loss), and is one of the causes of generating a considerably large surge voltage when the switching element is turned on.

The switching loss is a power loss that occurs internally when a device having a control terminal such as the semiconductor switch performs switching. Usually, 5 to 6 switching devices are included in the motor control device. Since semiconductor switches are used, the switching losses that occur in these switches have been enormous when accumulated. The large loss has a great effect on, for example, the driving and operation of the electric vehicle and the like, and the power of the loss changes into heat generation, which causes heat damage to the semiconductor switch.

[0010] On the other hand, the occurrence of a surge voltage has also caused electrical and thermal damage to the switching element. The present invention has been made in view of the above problems, and an object of the present invention is to provide an electrode structure of a semiconductor switch capable of reducing the occurrence of switching loss and surge voltage by preventing the occurrence of inductance. I do.

[0011]

The present invention mainly relates to the above-mentioned MO.
The present invention solves the problem of the semiconductor switch composed of the SFET, but is not limited thereto, and is applicable to other semiconductor switches such as a bipolar transistor and a thyristor having the same problem. Since the names of the electrodes differ depending on the type of the semiconductor switch, for convenience, the “main current input electrode”, “main current output electrode”, “
The term "control electrode" is used. For example, MOSFET
In the case of, the drain electrode is the main current input electrode, the source electrode is the main current output electrode, the gate electrode is the control electrode,
Each corresponds.

According to the first aspect of the present invention, there is provided a semiconductor switch for supplying a current from a main current input electrode to a main current output electrode via a semiconductor chip in accordance with a control signal supplied to a control electrode. In the electrode structure, by providing an electrode structure of a semiconductor switch in which at least one of the main current input electrode and the main current output electrode is formed so as to be large enough to reduce the occurrence of inductance due to current concentration. Can be achieved.

In this case, the thickness of each electrode can be arbitrarily set to a value larger than that usually used, and the larger the surface area, the more effective. In other words, the main current output electrode and the main current input electrode are formed to have an appropriate thickness and have a larger surface area, so that the flowing current can be spatially diffused, thereby reducing inductance due to current concentration. Can be prevented.

According to a second aspect of the present invention, in the first aspect of the present invention, the main current output electrode and the main current input electrode are arranged so as to be close to each other in parallel. In this case, the interval between the two electrodes can be set arbitrarily, and the closer the electrode is, the more effective. That is, the size of the entire semiconductor switch is increased by the size of the electrode according to the first aspect of the present invention. However, by arranging both electrodes in parallel and close to each other, the size of the entire semiconductor switch is reduced, and Due to the effect of the inductance, the inductance generated at both electrodes is canceled out, and the overall inductance can be reduced.

According to a third aspect of the present invention, in the second aspect of the present invention, the current flowing through the main current output electrode is in a geometrically (spatially) opposite direction to the current flowing through the main current input electrode. Further, both electrodes are arranged so as to flow in parallel.

Accordingly, if the directions of the currents flowing through the two electrodes are opposite, the directions of the magnetic fields and magnetic fluxes generated at the two electrodes are also completely opposite, that is, the mutual inductance in the invention of the second aspect more effectively cancels out the inductance. It will be more effective.

[0017] Claim 4 describes the first to third aspects.
In the invention according to any one of the above,
The main current input electrode or the main current output electrode is also used as one of the main current input electrode and the main current output electrode, and is connected to a wide and large substrate.

Thus, the inductance between the main current electrode, which also serves as the substrate, and the semiconductor chip is reduced, and the semiconductor chip is efficiently radiated.
According to a fifth aspect of the present invention, in the invention according to any one of the first to third aspects, a plurality of the semiconductor switches are incorporated in one package, and each of the semiconductor switches is provided in two adjacent semiconductor switches. The electrodes and the main current output electrodes have a line-symmetric structure with a boundary line set between the two semiconductor switches as a center line of symmetry.

As a result, the mutual influence of the adjacent semiconductor switch units affects each other, and the mutual inductance is more effectively offset.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiment, the above-described semiconductor switch is a MOSFET.
The main current input electrode is a drain electrode, the main current output electrode is a source electrode, and the control electrode is a gate electrode.

FIG. 1 is a view for explaining an electrode structure of a semiconductor switch according to a first embodiment of the present invention. FIG. 1 (a) is a perspective view, and FIG. 1 (b) is a side sectional view as seen from the direction of arrow A. Becomes
Also, in this figure, the package case and the gel and epoxy resin filling the inside are omitted, and only the internal circuit is shown.

First, in FIG. 1A, a plurality of semiconductor chips 2 are directly mounted on a drain electrode 3 also serving as a heat sink, and further, source electrodes 4, 5 and a gate electrode 6 sandwich the semiconductor chip 2. It is placed in such a position. The source electrodes 4 and 5 and the gate electrode 6 are placed after being electrically insulated by tightly attaching an insulating resin 7 between the drain electrode 3 and each electrode having a plurality of thin bonding wires 8 arranged in parallel. Thus, the configuration is such that the semiconductor chip 2 is connected.

Here, the difference from the conventional semiconductor switch is that the source electrode 4 is formed wider and larger upward from the side as shown in FIG. Is bent at a right angle to the inside direction of "." To form a "U" shape as shown in FIG. The drain electrode 3 and the source electrode 4 have terminal holes 9, 1, to which external terminals are connected, at positions shown in the figure.
0 are respectively formed, from which current is input and output. The source electrode 5 is used for floating, and no main switching current flows.

According to the semiconductor switch electrode structure of the present invention,
With this configuration, the following operation and effect can be obtained. First, by forming the source electrode 4 to be wide and large (like the drain electrode 3 substrate as shown in the figure in this example), the current flowing in the electrode is spatially dispersed, and the conventional current is reduced. It is possible to reduce the occurrence of inductance as compared with the case of a thin electrode flowing in a concentrated manner. On the other hand, since the size of the entire internal circuit increases when the electrodes are formed to be large, the entire internal circuit can be made compact by forming and installing it in a U-shape on the cross section as described above. However, by forming this U-shape, at the same time, the upper top plate portion of the source electrode 4 and the substrate of the drain electrode 3 are arranged at positions parallel and close to each other. Electromagnetic effects such as canceling out (cancelling) each other's inductance (magnetism) occur, and by utilizing this, it is possible to further reduce the inductance. The effect due to the mutual inductance can be expected to be highest when the distance between the upper top plate of the source electrode 4 and the substrate of the drain electrode 3 is as small as possible (as small as possible), and the directions of flowing currents are opposite to each other. .

In FIG. 1B, an external current is first input to the terminal hole 9 in the drain electrode 3, and the semiconductor chip 2 is supplied from the drain electrode 3 through the flow path indicated by the arrow Id.
And is output from the source electrode 4 to the terminal hole 10 in the source electrode 4 through the flow path indicated by the arrow Is. Therefore, the currents flowing through the two current flow paths indicated by the arrows Id and Is are flowing in substantially opposite directions, so that the effect of the mutual inductance can be further exhibited.

As described above, the drain electrode 3 and the source electrode 4
(Electromagnetic) connection between them is improved, switching loss,
Generation of a surge voltage can be reduced. 2A and 2B are views for explaining the electrode structure of a semiconductor switch according to a second embodiment of the present invention, wherein FIG. 2A is a top view and FIG. 2B is a front view. Also in this figure, the package case and the gel and epoxy resin filling the inside are omitted, and only the internal circuit is shown.

As shown in FIGS. 2A and 2B, the semiconductor switch 1 of the present embodiment is obtained by making the semiconductor switch of the first embodiment into a symmetrical structure when viewed from the front. Three semiconductor switches are arranged side by side and the drain electrode 3
Are connected so as to be integrated, and the central gate electrode 6 and the source electrode 5 are combined into one and shared. That is, except for the arrangement of the gate electrode 6 and the source electrode 5, the configuration is substantially symmetrical. The source electrode 5 is used for floating, and no main switching current flows.

By symmetrically arranging two circuits in one package rather than arranging two individually in this manner, the symmetrical arrangement between the electrodes, that is, between the source electrodes 4 and 4 ′ in this example, is not required. The effect of inductance works,
The inductance of the entire semiconductor switch 1 can be further reduced.

In the electrode structure of the semiconductor switch of the present invention, the shape of the bonding wire 8 is not limited to the semicircular shape shown in FIG. A configuration that cancels out is also possible.

The mutual inductance function described above can be made to work more effectively by selecting the material of each electrode. Note that the electrode structure of the semiconductor switch described above is not limited to the MOSFET structure of the above embodiment, but can be applied to other bipolar or thyristor. In this case, the main current input electrode corresponds to the collector electrode and the anode electrode, the main current output electrode corresponds to the emitter electrode and the cathode electrode, and the control electrode corresponds to the base electrode and the gate electrode.

[0031]

As described above, it is possible to reduce the occurrence of inductance in the semiconductor switch of the present invention, and it is also possible to reduce the surge voltage at the time of turn-on and the switching at the time of turn-off in the operation of the semiconductor switch as described above. Loss can be reduced. Furthermore, this makes it possible to reduce heat generation and power loss during operation of the semiconductor switch, thereby reducing the size of the heat sink, reducing the need for snubbers, and reducing the number of semiconductor chips required to reduce derating. The manufacturing cost can be reduced along with the improvement of the performance.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams illustrating an electrode structure of a semiconductor switch according to a first embodiment of the present invention, wherein FIG. 1A is a perspective view and FIG.

FIGS. 2A and 2B are diagrams illustrating an electrode structure of a semiconductor switch according to a second embodiment of the present invention, wherein FIG. 2A is a top view and FIG.

FIG. 3 shows a specific example of an electrode structure of a conventional semiconductor switch.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Semiconductor switch 2 Semiconductor chip 3 Drain electrode 4, 4 'source electrode 5 Source electrode (for floating) 6 Gate electrode 7 Insulating resin 8 Bonding wire 9 Drain electrode terminal hole 10, 10' Source electrode terminal hole

Claims (5)

[Claims] In an electrode structure of a semiconductor switch for supplying a current from a main current input electrode to a main current output electrode via a semiconductor chip in accordance with a control signal supplied to a control electrode, generation of inductance due to concentration of the current is reduced. An electrode structure for a semiconductor switch, wherein both the main current input electrode and the main current output electrode are formed to be wide and large to the extent that they can be reduced. 2. The electrode structure of a semiconductor switch according to claim 1, wherein said main current input electrode and said main current output electrode are arranged in parallel and close to each other. 3. A current flowing through the main current output electrode,
3. The electrode structure of a semiconductor switch according to claim 1, wherein both electrodes are arranged so as to be spatially parallel to a current flowing through the main current input electrode and to flow in opposite directions. 4. The semiconductor chip according to claim 1, wherein said semiconductor chip is used on one of said main current input electrode and said main current output electrode, and is connected to a large substrate which is widely formed. 4. The electrode structure of a semiconductor switch according to any one of items 3 to 3. 5. A plurality of the semiconductor switches are incorporated in one package, and main current input electrodes and main current output electrodes included in two adjacent semiconductor switches are respectively connected to the two semiconductor switches. The electrode structure of a semiconductor switch according to any one of claims 1 to 3, wherein the electrode structure has a line-symmetrical structure with a boundary line set between them as a center line of symmetry.