JPH11186471A - Multi-chip parallel mounting type semiconductor device - Google Patents

Abstract

(57) Abstract: The present invention relates to a multi-chip parallel mounting type semiconductor device, and more particularly to a uniform contact state between semiconductor chips having different heights and a heat radiating member for dissipating heat generated from the semiconductor chips. An object of the present invention is to provide a structure that can secure the heat resistance and reduce the heat resistance. In a multi-chip parallel mounting type semiconductor device,
A metal obtained by processing a thin plate into a roll or an aggregate thereof is disposed between the semiconductor chip and the heat radiating member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-chip parallel mounting type semiconductor device, and more particularly to a multi-chip parallel mounting type semiconductor device capable of ensuring uniform contact with a heat radiating member for dissipating heat generated from a semiconductor chip and reducing thermal resistance. The present invention relates to a chip-parallel-mounted semiconductor device and a converter or an operation control device using the same.

[0002]

2. Description of the Related Art In recent years, in order to respond to the demand for high-speed processing in computers and various arithmetic and control systems, the integration and speed of semiconductor chips have been increased, and a plurality of semiconductor chips have been mounted on a single wiring board on the mounting side. To shorten the wiring length,
Multi-chip parallel mounting for realizing high speed has been performed. Due to the above, the amount of heat generated by the semiconductor chip has increased, and since the mounting density of the semiconductor chip has increased, the heat generation density on the mounting surface has also increased. Dissipating this heat has become a very important issue. ing. Furthermore, in the case of multi-chip parallel mounting, since the height at which chips are mounted varies between chips, a filler with good thermal conductivity is used to absorb this and ensure uniform contact with the cooling member. A flexible material such as rubber or organic paste is used, or an independent piston-type or comb-type cooling member is used for each individual semiconductor chip. On the other hand, in the field of power electronics, in which the main circuit current is controlled by making full use of semiconductor electronics technology, recently, an insulated gate bipolar transistor (hereinafter referred to as I) which is a MOS control device for controlling a main current by an input signal to a MOS structure gate.
GBT) and MOS field-effect transistors (M
For example, IGBTs are widely used as power switching devices in applications such as motor PWM control inverters.

Conventionally, a plurality of chips are mounted in an IGBT in a package form of an electrode connection method using wires, which is mainly called a module type structure. A multi-chip parallel-type press, in which the chip is incorporated in a pressure-contact type package, and the emitter electrode and collector electrode formed on the main surface are brought into surface contact with a pair of external common electrode substrates provided on the package side, respectively, and pulled out. Attention has been focused on a semiconductor device having a contact structure.

According to this package structure, 1) the semiconductor chip can be cooled from both sides, so that the cooling efficiency can be improved as compared with the above-mentioned module type package.
2) The inductance and resistance of the connection conductor are reduced, and 3) the connection of the main electrode is not wire-bonded, so that the connection reliability is improved.

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-mentioned method using a flexible material such as a rubber containing a filler or an organic paste does not have a sufficient thermal conductivity, particularly when the calorific value increases.
Further, it is difficult to reduce the cost by using a piston-type or comb-type cooling member that is independent for each individual semiconductor chip.

On the other hand, according to the method of sandwiching the above-mentioned soft metal sheet, according to the study of the present inventors, the amount of deformation is very small (only deformation due to elastic deformation) at least in a practical pressure range where the semiconductor chip is not broken. When the height of each chip position (and the height including the intermediate member sandwiching the chip, etc.) has a large variation, it is clear that the deformation amount is insufficient and uniform contact cannot be ensured. The cause is that the electrode members 25 and 26 sandwiching the soft metal sheet 24 also when the soft metal sheet surface is subjected to plastic deformation in the lateral direction by applying pressure in the thickness direction as shown in the schematic diagram of FIG. It is considered that due to the frictional force (frictional resistance) 27 generated at the interface with the material, the deformation resistance in the lateral direction becomes extremely large even with 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 contact state with a cooling member in a large-area area, which becomes more and more difficult with the parallelization of the mounting method as described above, that is, a contact surface. It is intended to provide a method capable of absorbing height variations (due to member size variations, warpage, undulations, etc.) and reducing thermal resistance and electrical resistance at the contact interface.

It is a second object of the present invention to provide a converter and a high-speed operation control device particularly suitable for a large-capacity system by using the semiconductor device obtained as described above.

[0011]

The object of the present invention is to provide a semiconductor device in which a plurality of semiconductor chips are incorporated side by side on one electrode substrate or a wiring substrate, and the heat generated from the semiconductor chips is generated by the plurality of semiconductor chips. In a semiconductor device having a structure for dissipating heat via a common heat dissipating member, the problem can be solved by disposing a metal obtained by processing a thin plate into a roll or an aggregate thereof between the semiconductor chip and the heat dissipating member. More preferably, a soft or oxidation-resistant metal layer is formed on the surface of the metal processed into the roll shape, or a soft metal film is formed on an electrode surface facing the metal processed into the roll 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 an example of a basic application of the present invention using an aggregate in which a plurality of sheet metal rolls are arranged in a sheet. At least a first main electrode is formed on the first main surface of the semiconductor chip 1, and a second main electrode is formed on the second main surface. Intermediate electrode plates (intermediate members) 2 and 3 made of Mo, W, or the like are arranged on both main electrode surfaces, and a common electrode substrate also serving as a pair of heat-dissipating members made of a pair of Cu and the like outside the intermediate electrode plates. (Main electrode plates) 4 and 5 are arranged. Between the intermediate electrode plate 3 and the common electrode substrate 5, an assembly 6 in which a plurality of thin-plate roll-shaped metals are arranged is sandwiched, and the whole is pressed at once and the members are in contact with each other. In FIG. 1, (a), (b),
The case where the sum of the thicknesses of the components 1, 2, 3 increases in order at the position (c) is shown.

According to the difference between these heights, the thickness of the roll-shaped metal assembly 6 having a constant thickness before the pressure contact is changed to (a), ( b) and (c) become thinner in this order. That is, the overall height including the height of the roll-shaped metal assembly (the sum of the thicknesses of the components 1, 2, 3, and 6) is the same at the positions (a), (b), and (c). Thus, the thickness of the roll-shaped metal aggregate changes.

Accordingly, 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) are required. The semiconductor element can be mounted while maintaining a good pressure contact state between (1) and (2), so that a pressure contact type semiconductor device with little variation in thermal resistance and electric resistance can be realized. In FIG. 1, the main electrode substrate 5
Although the example in which the roll-shaped metal assembly 6 is interposed between the surfaces of the metal electrode 6 and the intermediate electrode plate 3 which are pressed against each other is shown, this position is of course the other contact surface, that is, between the main electrode substrate 4 and the intermediate electrode plate 2. Or between the semiconductor chip 1 and the intermediate electrode plates 2 and 3, or may be applied to a plurality of interfaces simultaneously. Further, a roll-shaped metal of a different material may be arranged for each electrode.

Flywheel diode (FWD) connected in anti-parallel with a switching device using IGBT
In the embodiment of the reverse conduction type switching device in which the thickness of each mounted chip is 200 μm at the maximum, even if the thickness is 0.05 mm and the number of turns is 1
A roll-shaped metal assembly having a thickness of 0.5 mm and a thickness of 1.5 mm is sandwiched between the intermediate electrode plate 3 and the common main electrode substrate 5, and the pressure distribution is measured by sandwiching a pressure-sensitive paper between the intermediate electrode plate 2 and the common main electrode substrate 4. As a result, it was found that the pressure difference was small and the pressure was almost uniformly applied.

FIG. 2 shows a typical example of a metal obtained by processing a thin plate of the present invention into a roll, and various shapes of an aggregate thereof. FIG. 2 (a) shows a thin sheet metal 7 wound in a bar shape and arranged in a clean and flat manner, and these metal bars 7 are adhered 8 to each other and held in an integrated thin plate (sheet shape). It is. As a method of forming these bonding portions, there is a method in which high-temperature heating is performed in a state where the fine wires are in contact with each other to lightly fuse them, or bonding is performed using a low-temperature bonding material such as an organic bonding material or solder.

In FIG. 2B, roll-shaped metal wires 7 are arranged in a spiral shape in a plane, and these metal wires 7 are bonded to each other 8 to be held in an integrated circular thin plate (sheet shape). It is an example. In addition to these, a ring in a plane
Examples of processing into a shape, examples in which a plurality of rings (rings) having different diameters are combined, and the like are also possible. Adhesion between the metal wires 7 is not always necessary. In each case, the cross-sectional shape of the thin line is an example of a circular shape, but it is not necessarily required to be a circular shape, but may be a flat shape.

In the case of the metal obtained by processing the thin plate of the present invention into a roll shape, unlike the case of the above-mentioned metal foil (thin plate) having a uniform thickness (FIG. 6), there is a gap inside itself. Since the material receiving the deforming force can be easily moved by utilizing 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. Due to the deformation of the rolled metal, the electrical resistance and the thermal resistance decrease due to the effect of increasing the contact interface and reducing the thickness of the rolled metal aggregate.

On the other hand, in the case of a soft metal thin plate having a uniform thickness, as described above (FIG. 6), even if a pressure exceeding the yield stress is applied, large deformation due to plastic deformation does not occur, and elastic deformation does not occur. Only a small deformation of.

Since these materials have elasto-plastic deformation ability, when the load is removed after the deformation, the elastic deformation returns, but the plastic deformation corresponding to the height variation between the 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, the apparent density (porosity), the thickness of the thin plate, and the number of windings. Pressure can be selected to produce an optimal amount of deformation. In order to increase the amount of deformation under a small pressure, it is preferable to reduce the thickness of the sheet and the number of turns and the density of the turns. From the viewpoint of reduction of thermal resistance and electric resistance, the number of turns,
It is preferable to increase the winding density.

The contact resistance (electricity, heat) at the interface with the electrode sandwiching the metal obtained by processing the thin plate into a roll shape is also an important factor.
In order to further reduce the contact resistance, it is important to reduce the contact resistance at the interface with the member sandwiching the roll-shaped metal. For this purpose, it is preferable to form a metal layer that is softer than the fine linear soft metal material or has better oxidation resistance on the surface of the roll-shaped metal by printing, plating, vapor deposition, or the like.

In order to optimally realize the height correction and the reduction of the electric resistance and the thermal resistance, at least one of the main electrode, the intermediate electrode plate and the common electrode plate of each semiconductor element is opposed to at least one of the opposing contact surfaces. In addition to sandwiching a metal processed into a roll or an aggregate thereof, a softer metal foil may be simultaneously arranged. 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. Alternatively, it is also effective to form a soft metal thin film on at least one surface of the intermediate electrode or the common electrode plate.

In the case where different types of semiconductor chips are mounted in parallel in one package as described above, and when the thickness of each type is greatly different, the average thickness of the intermediate electrode plate depends on the type of chip. By preparing a material with a different thickness, adjusting the large difference in chip thickness, and further absorbing the deformation due to the rolled metal of the present invention or the aggregate thereof mainly by absorbing the thickness variation of the intermediate electrode plate and the semiconductor chip Is also effective.

As the metal to be processed into a roll, Ni,
Any metal such as SUS, copper, aluminum, silver, gold, solder, etc. can be used. In particular, soft high heat conductive metals such as copper, aluminum, silver, gold, etc. are used to reduce deformation and thermal resistance under low pressure. Is preferred. The optimum material and surface treatment can be selected depending on whether the reduction of thermal resistance and electric resistance or the improvement of deformability is prioritized, depending on the usage form and purpose of the semiconductor device.

As the material of the intermediate electrode, a material having a thermal expansion coefficient between that of Si and the material of the external main electrode 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 substrate, 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.

FIG. 3 shows an example of a multi-chip parallel mounting type semiconductor device in which a plurality of LSI chips 10 as semiconductor chips are mounted on a multilayer wiring board 17 in parallel. In this embodiment, LS
The I chip 10 is mounted on a small ceramic substrate 12 by flip chip connection using solder balls 11. In this case, a cap 13 having high thermal conductivity is further soldered 14 to hermetically seal the LSI chip 10. L
The back surface (the surface on which no elements are formed, the upper surface in the figure) of the SI chip 10 is solder-bonded 15 to the cap material 13 to reduce thermal resistance.

A plurality of these LSI chips previously mounted in a small package were mounted on a multilayer circuit board 17 using solder balls 16. Due to variations in the height of the small package and the height of the solder balls, the height of the upper surface of the small package differs for each position of the LSI chip. Therefore, if the heat dissipating member 19 is kept in contact with the small package, the small package having a small height may not be contacted.

In this embodiment, the metal 7 obtained by processing the thin plate of the present invention into a roll is disposed between the upper surface of the small package and the heat radiating member 19. In this embodiment, first, the rolled metal 7
Were arranged in advance and a material held by the solder 20 was prepared in advance. The internal space of the roll-shaped metal 7 is not filled with solder, and the deformability is secured. This is arranged between the upper surface of the small package and the heat dissipating member (cooling member) 19, and is deformed by applying pressure to absorb height variations. Then solder 2
0 was melted and bonded to the upper surface of the small package and the lower surface of the heat dissipating member 19. Instead of the above method, it is also possible to press and heat a plurality of roll-shaped metals and solder foils therebetween.
Alternatively, a solder layer can be printed on the surface of the roll-shaped metal assembly using a solder paste. This multilayer circuit board 1
A large number of I / O pins or power supply pins 18 are provided on the surface opposite to the semiconductor chip mounting surface of No. 7 to perform wiring connection with the LSI.

As the multilayer circuit board 17, a ceramic board, a printed board, or the like is used. For the wiring connection between the semiconductor chip 10 and the small substrate 12, a method such as TAB, PGA, BGA, wire bonding or the like can be used as appropriate in addition to the method using solder balls. Further, it is also possible to mount the semiconductor chip 10 directly on the multilayer circuit board 17 without mounting the semiconductor chip 10 in a small package as in the present embodiment, that is, a so-called bare chip mounting. In this case, if air-tight sealing is required, a structure in which the side surface is sealed (not shown) between the substrate 17 and the cooling member 19 may be adopted. As a cooling method, a method such as air cooling, water cooling, or other liquid cooling can be used. The heat dissipating member 19 has a cooling medium flow path formed inside or a fin-shaped processing having good heat dissipating efficiency on the outer surface. To improve the cooling efficiency.

In the multi-chip parallel mounting type semiconductor device of the present invention, a uniform contact state with a heat dissipating member that dissipates heat can be obtained even when the size (capacity) is increased, so that a semiconductor device with low thermal resistance is obtained. Can be Therefore, by using this semiconductor device, a large-capacity converter can be realized as a power converter in which the volume and cost of the converter are significantly reduced. On the other hand, as an arithmetic and control unit, a high-speed arithmetic unit and a high-performance control unit that generate a large amount of heat can be realized.

FIG. 4 shows a case where the IGBT semiconductor device according to the present invention is applied to a power converter as a main conversion element.
FIG. 3 shows a configuration circuit diagram for a bridge. IG to be the main conversion element
The BT element 21 and the diode element 22 are arranged in anti-parallel, and n pieces are connected in series.
These IGBTs and diodes represent a 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 semiconductor device of the above embodiment, I in FIG.
The GBT chip and the diode chip are put together in one package.

This is provided with a snubber circuit 23 and a current limiting circuit. FIG. 5 shows a configuration of a self-excited converter in which the three-phase bridge of FIG. 4 is multiplexed by four. The semiconductor device of the present invention is mounted in a so-called stack structure in which a plurality of semiconductor devices are connected in series with a water-cooled electrode therebetween in such a manner 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 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 mill converter. It can also be used for converters in internal substation facilities, substation facilities for electric railways, sodium sulfur (NaS) battery systems, vehicles and the like.

[0037]

According to the present invention, a heat dissipating member for dissipating heat in a large area, which is becoming more and more difficult with the multi-chip parallel mounting of semiconductor chips corresponding to high speed and large capacity, is required. Uniform contact can be achieved relatively easily, that is, variations in the height of the contact surface can be sufficiently absorbed, and thermal resistance at the contact interface can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a part of a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a view showing a typical example of an embodiment of a metal aggregate processed into a roll.

FIG. 3 is a side sectional view showing an embodiment of the present invention applied to LSI mounting.

FIG. 4 is a configuration circuit diagram of one bridge using the semiconductor device of the present invention.

5 is a configuration diagram of a self-excited converter in which the three-phase bridge of FIG. 4 is multiplexed by four.

FIG. 6 is a view for explaining the deformation behavior of a soft metal when pressurized by a conventional method.

[Explanation of symbols]

1 ... semiconductor chip, 2, 3 ... intermediate electrode plate (intermediate member),
4, 5: common electrode substrate, 6: metal processed into a roll shape or an aggregate thereof, 7: thin metal wire processed into a roll shape, 8
... Adhesive part, 10 ... LSI chip, 11, 16 ... Solder ball, 12 ... Small ceramic substrate, 13 ... Cap, 1
4, 15, 20 solder, 17 multilayer circuit board, 18 pin, 19 heat dissipation member (cooling member), 21 IGBT element, 22 diode element, 23 snubber circuit, 24
Soft metal sheet, 25, 26 ... electrode member, 27 ... frictional force (frictional resistance).

Claims (9)

[Claims] A plurality of semiconductor chips each comprising one electrode substrate;
Or a semiconductor device having a structure which is incorporated in juxtaposition on a wiring substrate and radiates heat generated from the semiconductor chip to the plurality of semiconductor chips through a common heat radiating member. A multi-chip parallel mounting type semiconductor device, wherein a metal obtained by processing a thin plate into a roll or an aggregate thereof is disposed between the heat radiating member and the heat radiating member. 2. 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 between a pair of common electrode substrates serving also as heat radiating members. A multi-chip parallel mounting type semiconductor device, wherein a metal or a set of rolled thin plates is arranged between the semiconductor chip and an electrode of a common electrode substrate. 3. The multi-chip parallel mounted semiconductor according to claim 1, wherein said semiconductor chips are packaged and mounted side by side on one electrode substrate or a wiring substrate. apparatus. 4. An intermediate member having a thermal expansion coefficient between the semiconductor chip and an electrode substrate, a wiring substrate, or a heat radiating member on which the semiconductor chip is mounted. 4. The multi-chip parallel mounting type semiconductor device according to any one of items 3 to 3. 5. A multi-chip parallel mounting type semiconductor device as set forth in claim 1, wherein an assembly of metal obtained by processing said thin plate into a roll is arranged in a plane and held as an integral plate. . 6. The multi-chip parallel mounting type semiconductor device according to claim 1, wherein the metal obtained by processing the thin plate into a roll is mainly made of Cu, Al, Ag, Au or solder. 7. The multichip parallel mounting according to claim 1, wherein a softer or more oxidation-resistant metal layer is formed on a surface of the metal obtained by processing the thin plate into a roll. Type semiconductor device. 8. The method according to claim 8, wherein the plurality of semiconductor chips are one electrode substrate.
Or a structure in which heat generated from the semiconductor chip is radiated through a common heat radiating member to the plurality of semiconductor chips, and the semiconductor chip and the heat radiating member are combined. A power converter characterized by using a multi-chip parallel mounting type semiconductor device in which a metal obtained by processing a thin plate into a roll or an aggregate thereof is used as a main conversion element. 9. The method according to claim 9, wherein the plurality of semiconductor chips are one electrode substrate.
Or a structure in which heat generated from the semiconductor chip is radiated through a common heat radiating member to the plurality of semiconductor chips, and the semiconductor chip and the heat radiating member are combined. An arithmetic and control unit characterized by using a multi-chip parallel mounting type semiconductor device in which a metal obtained by processing a thin plate into a roll or an aggregate thereof is disposed.