JPH05206448A - Press contact type semiconductor element - Google Patents

Abstract

PURPOSE:To make uniform current distribution in an element and to enhance characteristics by setting the outer diameter of a thermal buffer board, to be press contacted with one main electrode, larger than the area of one main electrodes distributed while being surrounded by control electrodes and connected with external electrodes by press contact with a semiconductor through the thermal buffer board. CONSTITUTION:Main electrodes are disposed on the main surface of a semiconductor substrate, i.e., a wafer 3, and one main electrode regions, i.e., cathode electrodes 6, are distributed while being surrounded by control electrodes, i.e., gate electrode 5. The cathode electrode 6 and the other main electrode, i.e., an anode electrode 2, are connected with external electrode by press contact through a thermal buffer board 8 made of such material as having substantially identical thermal expansion coefficient as silicon. The thermal buffer board 8 coming into press contact with the cathode electrode 6 has outer diameter larger than the region of the cathode electrode 6 and positioned, at the outer periphery thereof, on the cathode side main surface through a non-fluidity rubber 13. According to the constitution, cost is reduced and current distribution is made uniform at the time of operation of the element resulting in enhancement of characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure contact type semiconductor device, and more particularly to a positioning structure for a cathode electrode plate of the pressure contact type semiconductor device.

[0002]

2. Description of the Related Art FIG. 4 shows the structure of a conventional pressure contact type gate turn-off thyristor as a pressure contact type semiconductor. In the figure, the parts that are in contact without being adhered by brazing or welding are
It is separated and shown for the sake of explanation. In FIG. 4, 1 is a copper block which is one of the main electrode conductors, 2 is an anode electrode made of molybdenum, tungsten or the like which is a material having a thermal expansion coefficient substantially equal to that of silicon, and 3 is a silicon wafer which is a semiconductor substrate having a PNPN structure. is there. The copper block 1 is brought into pressure contact with the anode electrode 2, and the anode electrode 2 is brazed to one main surface of the silicon wafer 3. Reference numeral 4 is a passivation rubber, 5 is an aluminum vapor deposition layer, and is a gate electrode formed on the central portion of the other main surface of the silicon wafer 3. Reference numeral 6 denotes a cathode electrode, and this cathode electrode 6 is the other main electrode formed of an aluminum vapor deposition layer and formed so as to surround the gate electrode 5 on the main surface of the silicon wafer 3 on which the gate electrode 5 is formed. Reference numerals 7 and 8 are thermal buffer plates, 9 is a cathode copper block, and the thermal buffer plate 7 is a doughnut-shaped thin plate made of a material having a thermal expansion coefficient substantially equal to that of silicon, and has a peripheral wall surrounding the outer periphery of the cathode copper block 9. The thermal buffer plate 8 is a donut-shaped disk made of a material having a thermal expansion coefficient substantially equal to that of silicon, and the cathode copper block 9 is the other main electrode conductor that is pressed into contact with the thermal buffer plate 8. 10 is an insulator, 1
Reference numeral 1 is a gate lead which is made of a metal elastic body and one end of which is pressed against the gate electrode 5 by its spring force, and 12 is an elastic member made of silicon rubber or the like.

The cathode electrodes 6 are formed on slit-shaped cathode emitters radially formed on the silicon wafer 3. Further, since the positioning accuracy between the copper blocks 1 and 9 and the silicon wafer 3 alloyed with the cathode electrode 2 is about ± 1 mm, the outer diameter of the copper block 1 is smaller than the area of the cathode electrode 2. ..

[0004]

In the above conventional pressure contact type semiconductor device, since the thermal buffer plate 8 is fixed and positioned,
Requires extra parts such as the heat buffer plate 7 and the elastic member 12,
The production is troublesome and the cost is high. Further, since the cathode electrode on the outer peripheral side of the thermal buffer plate 8 is not pressure-contacted,
The current distribution during element operation becomes non-uniform, which is not preferable in terms of characteristics. Further, the pressure contact stress is concentrated on the edge of the outer peripheral portion of the thermal buffer plate 8, and the outermost peripheral cathode electrode to which this edge is pressure contacted is extended, which may cause a short circuit with the outer peripheral structure.
It was unreliable.

The present invention solves the above problems,
An object of the present invention is to provide an inexpensive, high-performance and highly reliable pressure contact type semiconductor element.

[0006]

In order to achieve the above-mentioned object, the present invention is provided with main electrodes on both main surfaces of a semiconductor substrate, and one main electrode is surrounded by a control electrode and is provided on the main surface. In a semiconductor device in which both main electrodes are dispersed and are connected to an external electrode by pressure contact with the semiconductor substrate via a heat buffer plate, the outer diameter of the heat buffer plate pressed against the one main electrode is set to It is characterized in that it is made larger than the area of the main electrode.

[0007]

The heat buffer plate has an outer diameter larger than that of one main electrode region and is pressed against one main surface of the semiconductor substrate.
As a result, the pressure contact stress to the main electrode becomes uniform, the current distribution of the element becomes uniform, and the characteristics can be improved.

[0008]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 shows a pressure contact type semiconductor device according to an embodiment of the present invention, in which the same or corresponding parts as those in FIG. 4 are designated by the same reference numerals. The main surface of the wafer 3 which is a semiconductor substrate has a main electrode, and the cathode electrode 6 which is one main electrode is surrounded by the gate electrode which is a control electrode and is dispersedly arranged on the main surface. The cathode electrode 6 and the other main electrode, the anode electrode 2, are connected to the external electrode by pressure welding through a thermal buffer plate such as molybdenum or tungsten, which is a material having a thermal expansion coefficient substantially equal to that of silicon. The gate electrode 5 is connected to an external electrode by a gate lead 11 which is pressed against the center of the device.

The feature of this embodiment is that the heat buffer plate 8 pressed against the cathode electrode 6 has an outer diameter larger than that of the cathode electrode 6 and has a non-fluid rubber at the outer peripheral portion. That is, it is positioned on the main surface of the cathode side through 13. Further, the outer diameters of the cathode copper block 9 and the anode copper block 9 which are pressed against both main electrodes via a heat buffer plate or the like are equal and smaller than the area of the cathode electrode 6.

According to the above-described embodiment, since the extra parts such as the heat buffer thin plate and the elastic member for fixing the heat buffer plate 8 can be omitted, the cost is reduced. In addition, the cathode electrode 6
Are all pressed against each other by the thermal buffer plate 8, so that the current distribution during the operation of the device becomes uniform and the characteristics are improved. Further, the outer diameter of the heat buffer plate 8 is larger than the outer diameter of the cathode copper block 9, and the edge of the outer peripheral portion of the heat buffer plate 8 has the cathode electrode 6.
Since it is not pressure-welded to the outer periphery, the cathode electrode on the outermost periphery is not stretched and short-circuited with the structure on the outer periphery unlike the conventional case.

FIG. 2 shows a pressure contact type gate turn-off thyristor as a pressure contact type semiconductor element according to another embodiment of the present invention. The same or corresponding parts as those in FIG. 1 are designated by the same reference numerals. In this embodiment, as shown in FIG. 2, in order to make the pressure contact of the heat buffer plate 8 more uniform, a silver foil 14 which is a metal foil is provided between the heat buffer plate 8 and the copper block 9, The silver foil 14 is also fixed together with the heat buffer plate 8.

Further, the outer diameters of the cathode copper block 9 and the anode copper block 9 pressed against the two main electrodes via a heat buffer plate and the like are equal and smaller than the area of the cathode electrode 6.

According to the embodiment of FIG. 2, even if the silver foil 14 is inserted between the heat buffer plate 8 and the copper block 9 in order to make the pressure contact of the heat buffer plate 8 more uniform, a new component or It is only necessary to fix and position the heat buffer plate 8 at the same time without using a structure, and the same action and effect as those of FIG. 1 can be obtained.

FIG. 3 shows an example in which the present invention is applied to a gate turn-off thyristor having a so-called alloy flow structure in which a thermal buffer plate is not brazed to the anode electrode. In FIG. 3, reference numeral 15 is an anode electrode, which is made of an aluminum vapor deposition layer and is formed on one main surface of the silicon wafer 3. Reference numeral 16 denotes a heat buffer plate, which is a disc-shaped member made of a material having a thermal expansion coefficient substantially equal to that of silicon. A teflon ring 17 protects the outer peripheral portion of the silicon wafer 3.

The embodiment of FIG. 3 is a semiconductor device such as a diode, a thyristor, an electrostatic induction thyristor, an IGBT (insulated gate type bipolar transistor and an insulated gate) which is connected to an external electrode by pressure contact like the gate turn-off thyristor. It is also applicable to thyristors.

[0017]

As described above, the present invention has the main electrodes on both main surfaces of the semiconductor substrate, and the cathode electrode, which is the cathode electrode which is one of the main electrodes, is surrounded by the gate electrode. Dispersed on the surface, both main electrodes are connected to the external electrodes by pressure welding through a thermal buffer plate such as molybdenum or tungsten, which is a material having a thermal expansion coefficient almost equal to that of silicon, and the gate electrode is pressure-welded near the center of the device. In a gate turn-off thyristor connected to an external electrode by a gate lead, the thermal buffer plate pressed against the cathode electrode has an outer diameter larger than that of the cathode electrode, and a non-fluid rubber is used at the outer peripheral portion. Since it is fixed and positioned on the cathode-side main surface, a high performance and highly reliable pressure contact type semiconductor element can be obtained.

[Brief description of drawings]

FIG. 1 is a front sectional view of a pressure contact type semiconductor device according to an embodiment of the present invention.

FIG. 2 is a front sectional view of a pressure contact type semiconductor device according to another embodiment of the present invention.

FIG. 3 is a front sectional view of a pressure contact type semiconductor device according to still another embodiment of the present invention.

FIG. 4 is a front sectional view of a conventional pressure contact type semiconductor device.

[Explanation of symbols]

1 ... Copper block, 2 ... Anode electrode, 3 ... Semiconductor substrate,
4 ... Fashion rubber, 5 ... Gate electrode, 6 ... Cathode electrode, 9 ... Copper block, 11 ... Gate lead, 1
3 ... Silicon rubber, 14 ... Silver foil, 15 ... Anode electrode,
16 ... Thermal buffer plate.

Claims (3)

[Claims] 1. A main electrode is provided on each of the two main surfaces of a semiconductor substrate, one main electrode is surrounded by a control electrode and is dispersedly arranged on the main surface, and both main electrodes are provided with the semiconductor via a thermal buffer plate. In a semiconductor element which is connected to an external electrode by pressure contact with a substrate, the outer diameter of a heat buffer plate pressure-contacted to the one main electrode is larger than the area of the one main electrode. Pressure contact type semiconductor device. 2. The pressure-contact type semiconductor device according to claim 1, wherein the heat-contact plate and the metal block, which are in pressure-contact with one main electrode provided on one main surface of the semiconductor substrate, are interposed. A pressure contact type semiconductor characterized in that a metal foil or a foil inserted between the one electrode and the heat buffer plate is superposed on the heat buffer plate and fixedly positioned on the one main surface. element. 3. The pressure contact type semiconductor device according to claim 1 or 2, wherein the outer diameters of the metal blocks pressed against the both main electrodes are made equal and smaller than the area of the one main electrode. A pressure contact type semiconductor device characterized by being configured.