JPH11186299A - Pressure-contact semiconductor device and power converter provided therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of keeping a uniform contact between a semiconductor device and electrodes in a pressure-contact semiconductor device and lessening the thermal resistance and electrical resistance. SOLUTION: Semiconductor devices 1 each provided with a first main electrode on its first main surface and a second main electrode on its second main surface are arranged in an array and built inside a flat package insulated from the outside by an insulating sheath and located between a pair of electrode plates 4 and 5 for the formation of a pressure-contact semiconductor device, wherein fine wires formed of soft metal or its assembly 6 is arranged between the semiconductor device 1 and the electrodes of the common electrode plates 4 and 5 or between the intermediate electrodes 2 and 3 arranged on the main surfaces of the semiconductor device 1 and the common electrode plates 4 and 5 respectively.

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 pressure contact type semiconductor device which can ensure a uniform contact state between a semiconductor element and a package electrode and can reduce heat resistance and electric resistance. The present invention relates to a device and a converter using the same.

[0002]

2. Description of the Related Art The technology of power electronics, which controls the main circuit current by making full use of the technology of semiconductor electronics, has been applied in a wide range of fields, and its application is being expanded. In particular, in recent years, an insulated gate bipolar transistor (hereinafter abbreviated as IGBT) which is a MOS control device that controls a main current by an input signal to a MOS structure gate
And MOS type field effect transistor (hereinafter abbreviated as MOSFET)
For example, IGBTs are widely used as power switching devices in applications such as motor PWM control inverters.

Conventionally, in an IGBT, a plurality of chips are mounted mainly in a package form of an electrode connection system using wires, which is mainly called a module type structure. In the case of such a module-type package, heat generated inside the element is released only from one side of the package (the side not connected to the wire), that is, only from the electrode side directly mounted on the base substrate. The number of chips (heat generation, current capacity, or mounting density) that can be mounted on one package is limited.

Recently, in order to cope with such a problem and to meet a demand for a larger capacity, a large number of IGBT chips are incorporated in a press-fit type package, and an emitter electrode and a collector electrode formed on the main surface thereof are respectively provided. Attention has been paid to a semiconductor device having a multi-chip parallel-type pressure contact structure in which a pair of external common electrode plates provided on the package side are brought into surface contact with each other and drawn out. According to this press-fit type package structure, 1) the semiconductor chip can be cooled from both sides, so that the cooling efficiency can be increased, and 2) the inductance and resistance of the connection conductor can be reduced as compared with the above-mentioned module type package. 3) Connection reliability of the main electrode is improved because the connection of the main electrode is no longer a wire bond.

However, in this multi-chip parallel type pressure contact type semiconductor device, variations in height at each chip position due to variations in member dimensions and variations in locations due to warpage or undulation of the common electrode plate are inevitable. As a result, there is a large problem that the pressing force varies from chip to chip and uniform contact cannot be obtained, that is, thermal resistance and electric resistance vary greatly from chip position to chip position, and the element characteristics as a whole are not stable.
In the simplest case, it is possible to cope with the problem by using members having strictly uniform dimensions. However, it is unavoidable to increase the cost of parts and the cost of sorting. To solve this problem,
No. 8240 discloses a method in which a ductile soft metal sheet such as Ag is interposed as a thickness correction plate.

[0006]

The above-described method of sandwiching a soft metal sheet, which is disclosed as a method for coping with the problem of uniform contact between chips in the multi-chip parallel type pressure contact type semiconductor device, is disclosed by the present invention. According to the studies by the users, at least in a practical pressure range where the semiconductor chip is not destroyed, the deformation amount is very small (only deformation due to elastic deformation), and the height at each chip position (and the intermediate electrode member etc. It is clear that when the variation in height is large, the deformation amount is insufficient and uniform contact cannot be ensured.

The cause of this is that, as shown in the schematic diagram of FIG. 8, the electrode member sandwiching the soft metal sheet 43 even when the soft metal sheet surface is pressed in the thickness direction to be plastically deformed in the horizontal direction. It is considered that the frictional force (frictional resistance) 46 generated at the interface with 44 and 45 causes the deformation resistance in the lateral direction to become extremely large even for a soft metal material. Even if the pressing force is increased for deformation, the plastic deformation does not easily occur because the frictional force also increases in proportion to the pressure.

In particular, when the thickness is very small compared with the area receiving the resistance, such as a sheet shape, the influence of the frictional force generated on the surface becomes dominant, so that the generally known yielding of the material occurs. Even if a pressure exceeding the stress is applied, practically no plastic deformation (flow) actually occurs, and the thickness of the soft metal sheet hardly changes before and after pressing. In order to reduce the frictional resistance, a method of reducing the roughness of the electrode member surface is considered. However, a practical range of the processing roughness obtained by lapping or the like (Rmax1 to 0.5 μm, Ra0.05 to 0.5). 03
μm), no significant deformation occurs.

An object of the present invention is to provide a method for ensuring a uniform pressure contact state in a large area region, which becomes more and more difficult with the multi-chip parallelization of elements corresponding to the above-mentioned large capacity, That is, variations in the height of the contact surface (warpage, undulation,
It is intended to provide a method capable of absorbing thermal resistance and electrical resistance at the contact interface by absorbing variation in member dimensions.

A second object of the present invention is to provide a converter which is particularly suitable for a large-capacity system by using the semiconductor device obtained as described above.

[0011]

SUMMARY OF THE INVENTION The object of the present invention is to provide a pressurizing method in which a semiconductor element having at least a first main electrode on a first main surface and a second main electrode on a second main surface is incorporated between a pair of common electrode plates. In the contact type semiconductor device, the problem can be solved by disposing a soft metal processed into a thin line or an aggregate thereof between electrodes between the semiconductor element and the common electrode plate. More preferably, the surface of the soft metal processed into a fine wire is softer,
Alternatively, a metal layer having good oxidation resistance is formed, or a soft metal film is formed on the electrode surface facing the soft metal processed into the fine line shape.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a basic application form of the present invention by using an example of a sheet-like fine-wire soft metal aggregate. At least a first main electrode is formed on the first main surface of the semiconductor element 1, and a second main electrode is formed on the second main surface. Intermediate electrode plates 2 and 3 made of Mo, W, or the like are arranged on both main electrode surfaces, and a pair of common electrode plates (main electrode plates) 4 and 5 made of Cu or the like are provided on outer portions of the intermediate electrode plates. Be placed. An assembly 6 of a soft metal processed into a thin line is sandwiched between the intermediate electrode plate 3 and the main electrode plate 5, and the whole is pressurized at once and the members are in contact with each other. In FIG. 1, (a), (b), (c)
The case where the sum of the thicknesses of the components 1, 2, and 3 increases in order at the position is shown. Corresponding to the difference between these heights, the thickness of the thin wire-shaped soft metal aggregate 6 having a constant thickness before the pressure contact is changed to the thickness (a), (b) after the pressure contact. , (C)
It becomes thin in order. That is, the overall height (the parts 1, 2, 3, and 3) including the height of the thin linear soft metal assembly
6 is the same at the positions (a), (b), and (c).

Thus, even when the members 1, 2, 3 have thickness variations, or the main electrode plates 4, 5 have warpage or undulation, a plurality of chip positions (a), (b), (c) The semiconductor element can be mounted while maintaining a good pressure contact state between the two), and a semiconductor device with less variation in thermal resistance and electric resistance can be realized. In FIG. 1, the main electrode plate 5 and the intermediate electrode plate 3
Although the example in which the thin linear soft metal assembly 6 is interposed between the surfaces which are pressed against each other is shown, this position is, of course, the other contact surface, that is, between the main electrode plate 4 and the intermediate electrode plate 2 and between the element 1 and the element 1. It may be between the intermediate electrode plates 2 and 3 or may be applied to a plurality of interfaces at the same time. Also, a thin linear soft metal of a different material may be arranged for each electrode.

FIG. 2 shows representative examples of the soft metal processed into a fine wire according to the present invention and various shapes of the aggregate thereof. FIG.
(A) is a diagram in which bar-shaped soft metals 7 are arranged neatly in a planar manner, and these soft metal bars 7 are adhered 8 to each other and held in an integrated thin plate (sheet shape). This bonded portion 8 is called a neck portion. As a method of forming these neck portions, there is a method of calcining at a high temperature in a state where the fine wires are in contact with each other, or a method of bonding using a low-temperature adhesive such as an organic substance or solder.

FIG. 2 (b) shows that the thin linear soft metals 7 are spirally arranged in a plane, and these soft metals 7 are bonded to each other 8 to be held in an integrated circular thin plate (sheet shape). It is an example. Adhesion between the soft metal wires 7 is not always necessary.

FIG. 2 (c) shows an example in which the thin wire-shaped soft metal 7 is processed into a ring (annular shape) in a plane, and FIG. 2 (d) shows a combination of a plurality of soft metal rings (annular shapes) having different diameters. This is an example. In each case, the cross-sectional shape of the thin line was an example of a circle,
The shape need not necessarily be circular, but may be flat.

FIG. 3 is a model diagram showing the deformation process of the thin linear soft metal of the present invention by pressurization, and shows an example using a sheet-like thin linear soft metal aggregate 70. FIG.
(A) shows a state of slight contact before pressurizing, (b) shows a state in the middle of pressurizing, and (c) shows a state of being pressurized and sufficiently deformed. When a load is initially applied, the area of the round surface of each thin wire-shaped soft metal 7 that is in contact with the electrode 9 to be pressed is very small, so that the pressure applied here becomes very large, and this part is easily formed. Start crushing.

FIG. 3B shows a state before deformation by a dotted line 10 for comparison. The crushed and deformed soft metal material portion 11 microscopically undergoes plastic deformation 12 in a state of firmly contacting (pressing) the interface with the electrode 9,
The contact interface increases. At the same time, the overall height (the thickness of the thin linear soft metal assembly 70) decreases. Eventually, sufficient deformation occurs to reach the state shown in FIG.

In this case, in principle, if an infinite load is applied, the interface can be deformed to a state in which the interface is completely filled. However, in reality, the pressure which can be completely filled due to the limitation of the load can be obtained. It is impossible to use up to the area. Due to the deformation of the thin linear soft metal 7, the electric resistance and the thermal resistance decrease due to the effect of increasing the contact interface and reducing the thickness of the thin linear soft metal aggregate. On the other hand, in the case of a soft metal sheet having a uniform thickness, as described above (FIG. 8), even if a pressure exceeding the yield stress is applied, large deformation due to plastic deformation does not occur, and small deformation corresponding to elastic deformation is caused. Only happens.

Unlike the case of the above-mentioned metal foil (thin plate) having a uniform thickness (FIG. 8), such a thin linear soft metal has voids on its own surface, Since the material receiving the deformation force can be easily moved to this portion, the resistance to the deformation in the pressing direction is small, and a large deformation can be obtained with a relatively small pressure. Further, deformation occurs substantially only in the plate thickness direction (direction in which pressure is applied) in the macro direction due to the resistance due to the frictional force at the contact surface in the horizontal direction.

Since these materials have elasto-plastic deformation ability, when unloaded after deformation, the amount of elastic deformation returns, but the amount of plastic deformation almost corresponding to the variation in height between mounted components is maintained. When pressurizing again, sufficient contact can be ensured at the same pressure by utilizing this elastic deformation. The pressure at which this deformation occurs and the elasto-plastic deformation behavior can be controlled by the type of metal, density (porosity), and wire thickness (surface curvature). The deformation can be selected to occur.

FIG. 4 shows the relationship between the length of the neck portion and the maximum crush amount, normalized by the diameter of the soft metal thin wire. When it is desired to secure a large amount of deformation, it is preferable to reduce the neck portion as much as possible and make the line shape thick. This is because the porosity of the surface of the fine linear soft metal secured before deformation can be increased. It is preferable that the wire diameter is as small as possible from the viewpoint of reducing the thermal resistance and the electric resistance. Therefore, the ratio of the length of the neck portion to the diameter of the soft metal wire is 0.5.
Or less, preferably 0.35 or less.

The contact resistance (electricity, heat) at the interface with the electrode sandwiching the thin linear soft metal is also an important factor. In order to further reduce the contact resistance, it is also important to reduce the contact resistance at the interface between the soft metal fine wire and the electrode. Therefore, a metal layer softer or more resistant to oxidation than the fine linear soft metal material is printed, plated, and vapor-deposited on the surface of the fine linear soft metal.

FIG. 5 shows a flywheel diode (F) connected in anti-parallel with a switching device using IGBT21.
1 shows an example in which the present invention is applied to a reverse conduction type switching device incorporating WD) 22. The figure shows a partial cross section from the outermost part of the press-contact type semiconductor device at the right end to the middle part toward the center. The IGBT chip 21 has an emitter electrode formed on substantially the entire first main surface on the upper surface side and a collector electrode on the second main surface on the lower surface side, and further has a control electrode (gate electrode) on the first main surface. Are formed. Also,
The FWD 22 has an anode electrode formed on the upper surface side of the silicon substrate and a cathode electrode formed on the lower surface side.

The lower main electrodes (collector, cathode) of each of these semiconductor chips are Au electrodes.
The u-plated film is in pressure contact with the intermediate electrode 24 having a thickness of 1 to 3 μm. On the other hand, an Au plating film having a thickness of 2 to 3 μm is formed on the surface of the intermediate electrode 23 and is bonded to each semiconductor chip. These further have a Ni plating film on the surface of 2 to 4
It is sandwiched between a first common main electrode plate (Cu) 25 and a second common main electrode plate (Cu) 26 formed in μm. The pin 27 for taking out the gate control electrode from the chip is an IGBT.
It is formed in the center of the chip. A gold O-ring 35 having a wire diameter of 1 mm for absorbing height variations is provided on the intermediate electrode plate 23.
And the common electrode plate 25 and the pin 27 and the pin insulating member 28.

In this method, an individual soft metal O-ring 3
The position 5 can be prevented from being displaced by the insulating member 28 of the center pin, so that assembling workability and the like are good. Gate wiring 29
Are grooves 3 provided in the first common main electrode plate (Cu) 25.
And is drawn out to the outer peripheral portion of the package, and further taken out of the package by wirings 31 and 33. The space between the pair of common main electrode plates 25 and 26 is externally insulated by an insulating outer cylinder 32 made of ceramic or the like, and the interior of the package is sealed and sealed between the common main electrode plate and the insulating outer cylinder by a metal plate 34. It has a stopped hermetic structure. The gate electrode wiring is led out of the package by a sealed wiring 33 penetrating the outer cylinder 32.

Although the thickness variation at each chip position mounted in this embodiment was set to a maximum of 100 μm, the pressure difference was measured with a pressure-sensitive paper sandwiched between the intermediate electrode plate 24 and the common main electrode plate 26. It was found that the pressure was small and almost uniform.

In order to optimally realize the height correction and the reduction of the electric resistance and the thermal resistance, not only the soft metal or the aggregate thereof formed into a thin wire shape is sandwiched between the electrodes, but also the soft metal foil is arranged at the same time. May be. For example, a method of inserting an Au foil between the upper main electrode plate and the intermediate electrode plate, and inserting a soft metal thin wire assembly between the lower main electrode plate and the intermediate electrode plate is also effective. In the case where different types of semiconductor chips are mounted in parallel in one package as described above, when the thickness differs greatly for each type, the average thickness of the intermediate electrode plate was changed according to the type of chip. A method of preparing a material, adjusting a large difference in chip thickness, and further using the deformation caused by the soft metal processed into a fine wire shape or the aggregate thereof according to the present invention mainly for absorbing thickness variations of the intermediate electrode plate and the semiconductor chip. Is also effective.

Conventionally, the surface of the common electrode plate and the intermediate electrode plate generally have a surface roughness (Rmax) in order to reduce the contact resistance.
Was required to be finished to 1 μm or less, but the surface of the common electrode plate and the intermediate electrode plate sandwiching the soft metal processed into the fine wire or the aggregate thereof and the intermediate electrode plate had a maximum surface roughness (Rmax) of 1 μm.
Even in a rough state exceeding m, the material is deformed according to the surface unevenness, the contact area is microscopically increased, and the contact resistance can be reduced, so that the processing cost can be reduced. Rather, since the space for deformation increases, it is suitable when a particularly large amount of deformation is desired. In this case, the surfaces of the common electrode plate and the intermediate electrode plate preferably have a maximum surface roughness (Rmax) exceeding 3 μm.

As soft metals, copper, aluminum,
Silver, gold, solder, etc. are particularly preferred. Depending on the usage of the semiconductor device, it is important to select the most suitable material and surface treatment depending on whether thermal resistance, electrical resistance is reduced, or the deformability is improved. preferable.

As the material for the intermediate electrode, a material having a thermal expansion coefficient between that of Si and the external main electrode material and having good thermal conductivity and electric conductivity is used. Specifically, tungsten
Metal such as (W) and molybdenum (Mo), or Cu-W, Ag-W, Cu-M using them as main constituent materials
o, Ag-Mo, Cu-FeNi or other composite materials or alloys, and further, composite materials of metals and ceramics or carbon, such as Cu / SiC, Cu / C, Al / SiC,
Al / AlN and the like are preferable. On the other hand, for the main electrode, it is preferable to use copper or aluminum having good electrical conductivity and thermal conductivity, or the above-mentioned alloy or composite material containing them.

The mounting method of the present invention can of course be used for a pressure contact type semiconductor device comprising only a switching semiconductor such as an IGBT which does not include a diode. For example, a large number of diode chips alone can be used in a pressure contact type package by the above method. Implementation is of course also effective. Further, in the above embodiment, the description has been made mainly using the IGBT.
The present invention is directed to a general semiconductor device having at least a first main electrode on a first main surface and a second main electrode on a second main surface, and uses an insulated gate transistor (MOS) other than an IGBT.
Transistor), IGCT (Insulated Gate Control)
led Thyristor) and other insulated gate thyristors (M
An OS control thyristor), a GTO, a thyristor, a diode, and the like can be similarly implemented. In addition, Si
The present invention is similarly effective for compound semiconductor devices such as SiC and GaN other than the device.

In the press-contact type semiconductor device of the present invention,
Even if (capacity is increased), a stable contact state between the electrodes can be obtained, so that a semiconductor device having small electric resistance and thermal resistance can be obtained. Therefore, by using this press-contact type semiconductor device, it becomes possible to realize a large-capacity converter in which the volume and cost of the converter are greatly reduced. FIG. 6 shows an IG according to the present invention.
FIG. 3 is a circuit diagram showing a configuration of one bridge in a case where a pressure contact type semiconductor device of BT is applied to a power converter as a main conversion element.

An IGBT element 40 and a diode element 41 serving as main conversion elements are arranged in anti-parallel, and n pieces are connected in series. These IGBTs and diodes represent a press-contact type semiconductor device in which a number of semiconductor chips according to the present invention are mounted in parallel. In the case of the reverse conducting IGBT pressure contact type semiconductor device of the embodiment shown in FIG. 5, the IGBT chip and the diode chip in the drawing are put together in one package. This is a snubber circuit 4
2, and a current limiting circuit.

FIG. 7 shows the configuration of a self-excited converter in which the three-phase bridge of FIG. 6 is multiplexed by four. The press-contact type semiconductor device of the present invention is mounted in a so-called stack structure in which a plurality of the press-contact semiconductor devices are connected in series with a water-cooled electrode interposed therebetween so as to make surface contact with the outside of the main electrode plate, and pressurize the entire stack at once. According to the present invention, uniform contact can be obtained even with a lower pressing force than in the past, so that the stack structure and the like can be simplified.

The pressure-contact type semiconductor device of the present invention is not particularly limited to the above example, and is particularly suitable for a self-excited large-capacity converter used in a power system or a large-capacity converter used as a converter for a mill.
Variable speed pumped storage power generation, substation facilities in buildings, substation facilities for railways,
It can also be used in converters for sodium-sulfur (NaS) battery systems and vehicles.

[0038]

According to the present invention, uniformity over a large area becomes increasingly difficult with the increase in the size of the package due to the increase in the diameter of the wafer and the parallelization of elements corresponding to the increase in the capacity. Pressure welding can be easily realized with relatively low pressure, that is, it absorbs variations in the height of the contact surface sufficiently,
In addition, the thermal resistance and electric resistance at the contact interface can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a pressure contact type semiconductor device which is a basic configuration of the present invention.

FIG. 2 is a diagram showing a typical example of an embodiment of a soft metal fine wire aggregate.

FIG. 3 is a model diagram showing a deformation behavior of the soft metal fine wire material of FIG. 2;

FIG. 4 is a characteristic diagram showing a relationship between a normalized neck length and a maximum crushing amount.

FIG. 5 is a side sectional view showing an embodiment of the present invention applied to an IGBT.

FIG. 6 is a configuration circuit diagram of one bridge using the semiconductor device of the present invention.

FIG. 7 is a configuration diagram of a self-excited converter in which the three-phase bridge of FIG.

FIG. 8 is a diagram illustrating the deformation behavior of a soft metal when pressurized by a conventional method.

[Explanation of symbols]

1: semiconductor element, 2, 3, 23, 24 ... intermediate electrode plate
4, 5, 25, 26 ... common electrode plate, 6, 17, 30, 3
6 ... Soft metal processed into a thin wire or its aggregate, 7 ...
Soft metal fine wire, 8: bonded portion (neck portion), 9: pressurized electrode, 10: state before deformation, 11: deformed soft metal material portion, 12: plastically deformed portion, 21: IGBT, 2
2 ... flywheel diode, 27 ... pin, 28 ... insulating member, 29, 31, 33 ... gate wiring, 30 ... groove,
32: insulating outer cylinder, 34: metal plate, 35: O-ring, 4
0: IGBT element, 41: Diode element, 42: Snubber circuit, 43: Soft metal sheet, 44, 45: Electrode member, 46: Friction force (friction resistance), 70: Fine linear soft metal aggregate.

Claims (12)

[Claims] A flat package in which a pair of common electrode plates exposed on both sides is externally insulated by an insulating outer cylinder.
A semiconductor device in which a plurality of semiconductor elements having at least a first main electrode on a first main surface and a second main electrode on a second main surface are juxtaposed and incorporated, and the electrodes of the semiconductor element and a common electrode plate are provided. A pressure contact type semiconductor device, wherein a soft metal processed into a fine wire or an aggregate thereof is disposed between the soft metal and the soft metal. 2. A flat package in which a pair of common electrode plates exposed on both sides are externally insulated by an insulating outer cylinder.
A semiconductor device in which a plurality of semiconductor elements having at least a first main electrode on a first main surface and a second main electrode on a second main surface are juxtaposed and incorporated, and the main electrode of each semiconductor element and the Conductive, between the opposing common electrode plate, and an intermediate electrode plate also serving as heat dissipation is interposed, further soft metal processed into a thin wire between at least one of the intermediate electrode plate and the common electrode plate opposed thereto A pressure contact type semiconductor device wherein the aggregate is arranged. 3. The pressure contact type semiconductor device according to claim 1, wherein the aggregate of the soft metal processed into a thin wire is arranged in a plane and held as an integral thin plate. . 4. The pressure contact type semiconductor device according to claim 1, wherein the soft metal processed into a fine wire or an aggregate thereof is formed in a ring shape. 5. The pressure contact type semiconductor device according to claim 1, wherein said soft metal processed into a fine wire shape is mainly made of Cu, Al, Ag, Au or solder. 6. A pressure contact type semiconductor device according to claim 1, wherein a softer or better oxidation-resistant metal layer is formed on the surface of said soft metal. 7. A main electrode and an intermediate electrode plate of each of the semiconductor elements,
7. The pressure contact type semiconductor device according to claim 1, further comprising a soft metal foil interposed between at least one contact surface of the common electrode plate and the contact surface facing each other. 8. A pressure contact type semiconductor device according to claim 1, wherein a soft metal thin film is formed on at least one surface of said intermediate electrode or common electrode plate. 9. A method according to claim 1, wherein at least one surface of said common electrode plate and said intermediate electrode plate is roughened to have a maximum surface roughness (Rmax) exceeding 1 μm.
The pressure contact type semiconductor device according to the above. 10. The semiconductor device is an insulated gate device having a first main electrode and a control electrode on a first main surface and a second main electrode on a second main surface. A flywheel diode having a first main electrode on one main surface and a second main electrode on a second main surface, a plurality of flywheel diodes each being incorporated in parallel in anti-parallel with the insulated gate element. 10. A pressure contact type semiconductor device according to any one of 1 to 9. 11. A flat package in which a pair of common electrode plates exposed on both sides are externally insulated by an insulating outer cylinder, at least a first main electrode on a first main surface and a second main electrode on a second main surface. A pressure contact type semiconductor device in which a plurality of semiconductor elements are juxtaposed and incorporated, and a soft metal or an aggregate thereof formed into a thin wire between the semiconductor element and a common electrode plate is used as a main conversion element. A power converter characterized by using: 12. A flat package in which a pair of common electrode plates exposed on both sides are externally insulated by an insulating outer cylinder, at least a first main electrode on a first main surface and a second main electrode on a second main surface. A plurality of semiconductor elements having main electrodes are juxtaposed and incorporated, and an intermediate electrode plate that also serves as a conductive and heat radiator is interposed between the main electrode of each semiconductor element and a common electrode plate opposed thereto, Further, a pressure contact type semiconductor device in which a soft metal processed into a fine wire or an aggregate thereof is disposed on at least one between the intermediate electrode plate and a common electrode plate opposed thereto is used as a main conversion element. Power converter.