WO2004112131A1

WO2004112131A1 - Semiconductor device

Info

Publication number: WO2004112131A1
Application number: PCT/JP2004/005948
Authority: WO
Inventors: Yoshinari Tsukada; Tsugio Masuda; Shinya Watanabe; Fumitomo Takano; Yasuro Yamanaka
Original assignee: Honda Motor Co., Ltd.
Priority date: 2003-06-10
Filing date: 2004-04-23
Publication date: 2004-12-23
Also published as: JP2005005400A

Abstract

A semiconductor device is disclosed wherein a semiconductor element can be cooled well by conducting the heat generated in the semiconductor element to the whole of a carbon fiber composite material. A semiconductor device (10) comprises a laminate (16) arranged between a semiconductor element (11) and a heatsink (12). The laminate (16) is composed of a heat transfer metal sheet (14), a carbon fiber composite material layer (13), an intermediate heatsink (15) for heat buffering, an insulator (18), and a lower metal sheet (19). Preferably, the carbon fiber composite material layer (13) is composed of a carbon-copper composite material and the intermediate heatsink (15) is composed of a copper sheet.

Description

Description Semiconductor device technology

The present invention relates to a semiconductor device, and more particularly to a semiconductor device that efficiently radiates heat from a semiconductor element using a carbon fiber composite material. Background art

In recent years, semiconductor devices called power devices are often used for the purpose of power conversion, power control, or high-power amplification / oscillation. This semiconductor device includes a bipolar transistor, an IGBT (Insulated Gate Bipolar Transistor), a power IC, and a MOSFET, all of which have the advantage of high conversion and control efficiency and small size.

However, the semiconductor element generates a large amount of heat due to the flow of a large current, and the heat generated by the semiconductor element may cause destruction or change in characteristics. Therefore, it is necessary to efficiently cool the semiconductor element. For this reason, various cooling structures have been proposed so far. As an example, FIG. 7 shows a conventional semiconductor device having a cooling structure.

Referring to FIG. 7, the semiconductor device 100 is formed by providing an insulating plate 103 and a metal plate 104 between the semiconductor element 101 and the heat sink 102. The semiconductor element 101 is a power device such as a power transistor, power FET, or IGBT, and is formed of a silicon semiconductor or the like. When the semiconductor element 101 operates, heat is generated by Joule heat and the temperature rises. When the temperature of the semiconductor element 101 rises, the on-resistance increases, and when performing feedback control or the like, a voltage is applied in an attempt to allow current to flow further, causing a current to flow, thereby increasing the regenerative heat. , The temperature will rise further. As a result, the semiconductor element 101 is damaged. To prevent this, a heat sink 102 is provided in the semiconductor device 100.

The heat sink 102 is made of copper or aluminum with good thermal conductivity. And dissipates the heat generated from the semiconductor element # 1. Therefore, it is possible to prevent the temperature of the semiconductor element 101 from rising. Therefore, it is formed so as to increase the heat radiation area.

The insulating plate 103 electrically insulates the semiconductor element 101 from the heat sink 102. Therefore, a material having good thermal conductivity, such as SiN, but having electrical insulation properties is used.

The metal plate 104 is for supporting the semiconductor element 101 and the insulating plate 103, and for conducting heat from the semiconductor element 101 to the heat sink 102. . For this purpose, a copper plate or the like, which has good thermal conductivity and is a strong material, is used.

The heat sink 102 is for dissipating the heat generated in the semiconductor element 101 and transmitted through the insulating plate 103 and the metal plate 104, thereby increasing the contact area with air. It is made of aluminum, copper, aluminum, etc. These semi-conductor elements 1 0 1 and the insulating plate 1 0 3 and the metal plate 1 0 4 and the heat sink ¹ 0 2, the solder or are by re joined to like brazing material.

In the above-described conventional semiconductor device, since the coefficient of thermal expansion of a metal such as copper or aluminum is larger than the coefficient of thermal expansion of the semiconductor element, the metal expanded due to the heat generated by the semiconductor element generates thermal stress, and the device itself However, there is a disadvantage that the steel sheet is curved, and peeling, Z or cracks are generated.

In order to solve the above-mentioned drawbacks, a technology of inserting a layer of a unidirectional carbon fiber composite material between a semiconductor element and a heat sink is disclosed in, for example, Japanese Patent Application Laid-Open No. H10-107190. Have been. This unidirectional carbon fiber composite material has the advantage that it has a large thermal conductivity in the thickness direction, has a smaller thermal expansion coefficient in the plane direction than copper or aluminum, and is close to the thermal expansion coefficient of semiconductor elements. Having.

As described above, the conventional semiconductor device shown in FIG. 7 has a difference in thermal expansion coefficient between metal and other materials. However, there is a drawback that such a phenomenon occurs. As a result, the semiconductor element cannot exert its original performance without being subjected to a high load, and a forced air cooling device such as a water cooling device or a fan is required, and the size of the device is increased. was there.

In addition, when the technology disclosed in Japanese Patent Application Laid-Open No. H10-107190 is used, the problem due to the difference in the coefficient of thermal expansion is solved, but the carbon fiber is difficult to diffuse heat in the lateral direction. Due to the characteristics of the composite material, the heat of the semiconductor element did not propagate through the entire carbon fiber composite material, and the heat could not be efficiently transmitted to the heat sink.

Therefore, in a semiconductor device in which a carbon fiber composite material layer is provided between a semiconductor element and a heat sink, heat generated in the semiconductor element is conducted to the entire carbon fiber composite material layer, and the semiconductor element is cooled well. There is a need for technology that can do that. Disclosure of the invention

In the present invention, a semiconductor element, a heat sink, a carbon fiber composite material layer provided between the semiconductor element and the heat seek, and provided between the semiconductor element and the carbon fiber composite material layer, A heat transfer metal plate that conducts heat generated by the semiconductor element to the entire surface of the carbon fiber composite material layer is provided.

Therefore, according to the semiconductor device of the present invention, the heat generated by the semiconductor element is diffused in the plane direction by the heat transfer metal plate provided between the semiconductor element and the carbon fiber composite material layer. Heat is conducted to the entire material layer, and the semiconductor element can be cooled well.

In the semiconductor device of the present invention, preferably, an intermediate heat sink for a heat buffer is further provided between the carbon fiber composite material layer and the heat sink. Therefore, the transient thermal resistance of the semiconductor device can be reduced, and the temperature rise of the semiconductor element can be reduced.

The carbon fiber composite material is preferably made of a carbon-copper composite material, and the intermediate heat sink is made of a copper plate. Therefore, heat is conducted to the entire carbon fiber composite material layer, and the semiconductor element can be cooled well. Further, by using a copper plate for the intermediate heat sink, the transient thermal resistance of the semiconductor device can be reduced, and the temperature rise of the semiconductor element can be reduced.

Further, in the present invention, a semiconductor element, a heat sink, and the semiconductor element And a laminate provided between the heat sink and the heat sink, the laminate including a carbon fiber composite material layer.

As described above, when the laminate includes the carbon fiber composite material layer, the heat generated in the semiconductor element is transmitted to the entire carbon fiber composite material, and is transmitted to the heat sink via the laminate. Good conduction and heat dissipation.

Preferably, the laminated plate is: an upper metal plate that conducts heat generated in the semiconductor element to the entire surface of the carbon fiber composite material layer; and the carbon fiber composite material layer that transmits heat of the upper metal plate in a plate thickness direction. An intermediate heat sink for a heat buffer that accumulates and conducts heat from the carbon fiber composite material layer; and an insulator that is bonded to the intermediate heat sink on a side opposite to a bonding surface with the carbon fiber composite material layer. And a lower metal plate joined on the opposite side to the joint surface of the insulator with the intermediate heat sink. Therefore, the heat generated by the semiconductor element is also diffused in the plane direction by the metal plate between the semiconductor element and the carbon fiber composite material, and the heat is conducted to the entire carbon fiber composite material to cool the semiconductor element well. Can be. Also, since the laminated plate includes a metal plate, it has good thermal conductivity, and the heat generated by the semiconductor element can be well conducted to the heat sink, so that the heat can be efficiently dissipated. BRIEF DESCRIPTION OF THE FIGURES

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

FIG. 2 is a diagram showing a heat flow image of the semiconductor device shown in FIG.

Fig. 3 shows the speed change during acceleration / deceleration in an electric vehicle by (a), the time change of the current flowing through the semiconductor element by (b), and the temperature change of the semiconductor element by (c). It is the graph shown.

FIGS. 4A and 4B are diagrams showing the temperature and the amount of heat transport in a conventional semiconductor device in a steady state, wherein FIG. 4A shows the thermal resistance of the semiconductor device, and FIG. It is a figure showing the temperature of each part.

FIG. 5 is a diagram for explaining the temperature and the amount of heat transport in a transient state. FIG. 5 (a) shows the shape of a substance, and FIG. 5 (b) shows an equivalent circuit.

FIG. 6 is a diagram showing a time change of the energy and the temperature difference. FIG. 7 is a cross-sectional view of a conventional semiconductor device.

Best mode for carrying out the invention

The semiconductor device 10 of the present embodiment shown in FIG. 1 includes a carbon fiber composite material layer 13 provided between the semiconductor element 11 and the heat sink 12, a semiconductor element 11 and the carbon fiber composite material layer 13. A heat transfer metal plate (upper metal plate) 14 that conducts the heat generated by the semiconductor element 11 to the entire surface of the carbon fiber composite material layer 13, and heats the carbon fiber composite material layer 13. And a heat buffer intermediate heat sink 15 provided between the sinks 12. Preferably, it is formed by providing a laminate 16 including the carbon fiber composite material layer 13 between the semiconductor element 11 and the heat sink 12.

The semiconductor element 11 is a power device such as a power transistor, a power FET, or an IGBT, and is formed of a silicon semiconductor or the like. When the semiconductor element 11 operates, heat is generated by Joule heat and the temperature rises. When the temperature of the semiconductor element 11 rises, the on-resistance increases, and when performing feedback control or the like, if a voltage is applied in order to allow more current to flow, Joule heat increases and the temperature further rises. As a result, the semiconductor element 11 is damaged. To prevent this, the semiconductor device 10 is provided with a heat sink 12.

The heat sink 12 is formed of copper, aluminum, or the like having good thermal conductivity, and radiates heat generated from the semiconductor element 11. Thereby, the temperature of semiconductor element 11 can be prevented from rising. Therefore, it is formed to increase the heat radiation area.

The laminated plate 16 is where the heat generated in the semiconductor element 11 is conducted to the heat sink 12 and radiated.

The laminated plate 16 is composed of an upper metal plate 14 that conducts heat generated by the semiconductor element 11 to the entire surface of the carbon fiber composite material layer 13 and a carbon plate that transfers heat of the upper metal plate 14 in the thickness direction. Bonding of the fiber composite material layer 13, the heat buffer intermediate heat sink 15 for storing and conducting heat from the carbon fiber composite material layer 13, and the carbon fiber composite material layer 13 of the intermediate heat sink 15 An insulator 18 joined to the opposite side of the surface, and a lower metal plate 19 joined to the opposite side of the joint between the insulator 18 and the intermediate heat sink 15 ing.

On the surface of the upper metal plate 14 on the side where the semiconductor element 11 is bonded, Ni plating 20 is applied to the surface. The Ni plating 20 is for securing the brazing property and the wire pounding property of the semiconductor element. The metal plate 14 is for ensuring the brazing property and the bonding property of the semiconductor element 11 and for diffusing heat in the plane direction. For this purpose, a relatively thin copper plate with high thermal conductivity is used.

The carbon fiber composite material layer 13 quickly transmits heat generated in the semiconductor element 11 and diffused in the surface direction of the upper metal plate 14 to the heat sink direction. Further, the carbon fiber composite material layer 13 reduces the thermal stress caused by the difference between the thermal expansion of the semiconductor element 11, the thermal expansion of each layer of the laminated plate, and the thermal expansion of the heat sink due to heat generated in the semiconductor element 11. ease. For this purpose, a material having a small elastic constant in the laminating plane direction is used, for example, a carbon fiber composite material such as a carbon-copper composite material is used. In the carbon fiber composite material, individual carbon fibers are arranged in the thickness direction, and a metal material such as copper or aluminum is contained between the fibers. This carbon fiber composite material has the property that the thermal conductivity in the thickness direction (longitudinal direction) is higher than the thermal conductivity in the plane direction (lateral direction).

The intermediate heat sink 15 temporarily stores heat generated in the semiconductor element 11 and conducted through the upper metal plate 14 and the carbon fiber composite material layer 13, and the insulator 18 bonded to the lower surface and the lower metal plate 1 Conduct heat to the heat sink 1 through 9. For this reason, a relatively thick copper plate with high thermal conductivity is used.

The insulating plate 18 is for electrically insulating the semiconductor element 11 and the heat sink 12. Therefore, a substance having good thermal conductivity and electrical insulation such as SiN is used.

The lower metal plate 19 is for supporting the laminated structure on the upper side, and is for conducting heat from the semiconductor element 11 to the heat sink 12. For this purpose, use a copper plate that has good thermal conductivity and is strong.

The heat sink 12 is for dissipating the heat generated by the semiconductor element 11 and conducted through the upper laminated structure, and has a structure that increases the contact area with air, and is formed of copper, aluminum, or the like. Have been.

Incidentally, these plate members are sandwiched T i one C u foil dusted powder M g, of N ₂ Kiri Bonding may be performed by applying pressure and annealing in an atmosphere.

Next, the operation of the semiconductor device 10 according to the present embodiment will be described.

The heat generated during the operation of the semiconductor element 11 of the semiconductor device 10 is conducted to the upper metal plate 14, and the upper metal plate 14 has good thermal conductivity. It also spreads in the direction and conducts. Further, the temperature of the upper metal plate 14 also increases. Thereby, thermal expansion occurs before the temperature is generated.

The heat conducted in the upper metal plate 14 is conducted to the carbon fiber composite material layer 13 and the temperature of the carbon fiber composite material layer 13 also rises. The heat conducted to the carbon fiber composite material layer 13 is conducted to the intermediate heat sink 15, the temperature of the intermediate heat sink 15 rises, and the intermediate heat sink 15 expands.

The heat conducted to the intermediate heat sink 15 is conducted to the insulator 18 and the lower metal plate 19, conducted to the heat sink 12, and dissipated by the heat sink 12, so that the heat of the semiconductor element 11 is Dissipates and reduces the amount of temperature rise.

FIG. 2 shows heat transmission of the semiconductor device 10.

At this time, the temperatures of the semiconductor element 11, the upper metal plate 14, the carbon fiber composite material layer 13, the intermediate heat sink 15, the insulating plate 18, the lower metal plate 19, and the heat sink 12 are as follows. Is hotter than before it generates heat. This causes each layer to expand thermally with the thermal expansion coefficient of the respective material. At that time, thermal stress occurs. The carbon fiber composite material layer 13 made of a carbon-copper composite material or the like having a small elastic coefficient in the plane direction alleviates the thermal stress, reduces the thermal stress generated in the semiconductor device 10 and reduces warpage. be able to.

By disposing the intermediate heat sink 15 below the semiconductor element 11, the transient thermal resistance of the semiconductor apparatus 10 can be reduced, and the temperature rise of the semiconductor element 11 can be reduced. Further, when an electric vehicle using the semiconductor device 10 travels, the reliability of a power module using the semiconductor device 11 can be improved. Also, by reducing the chip size with reliability and tradeoff, miniaturization and cost reduction can be achieved.

For example, consider the case where acceleration and deceleration are performed in an electric vehicle as shown in FIG. In Fig. 3 (a), the horizontal axis represents time, the vertical axis represents speed, and acceleration and deceleration are repeated. Let's hang. FIG. 3 (b) shows the time change of the current flowing through the semiconductor element at that time. During acceleration, current flows rapidly, and during deceleration, current flows rapidly in the opposite direction. FIG. 3 (c) shows the temperature change of the semiconductor element at that time. A curve C 10 is a temperature change of the semiconductor element 101 in the conventional semiconductor device 100 shown in FIG. 7, and a curve C 11 is a temperature change of the semiconductor element 11 in the semiconductor device 10 according to the present invention. Indicates a change.

As shown in FIG. 3 (c), the temperature rise of the semiconductor element 11 in the semiconductor device 10 according to the present invention is smaller than that of the conventional device, and it can be seen that the temperature stress is reduced. . Therefore, when the reliability is improved and the temperature does not exceed 150 ° C when using a normal semiconductor device, the IGBT is typically 1.5 to 2 times faster than the conventional one if the temperature does not exceed 150 ° C. A current can flow. As a result, the chip size can be reduced, and the cost can be reduced.

Next, instead of the operation principle of the semiconductor device according to the present invention, the operation principle of the conventional semiconductor device shown in FIG. 7 will be described with reference to FIG.

FIG. 4 is a diagram showing a temperature and a heat transport amount in a steady state in the conventional semiconductor device 100 shown in FIG. 7, and shows the temperature at each part. FIG. 4A shows the thermal resistance of the semiconductor device 100. R1 is the thermal resistance at the junction between the semiconductor element 101 and the insulating substrate 103. R 12 is the thermal resistance of the insulating substrate 103. R2 is the thermal resistance at the junction between the insulating substrate (insulated plate) 103 and the copper base (metal plate) 104. R23 is the thermal resistance of the copper base 104. R3 is the thermal resistance at the junction between the copper base 104 and the heat sink 102. R 3 G is the thermal resistance of the heat sink 102. R4G is the thermal resistance at the contact between the heat sink 102 and the air.

FIG. 4B shows the temperature of each part in the semiconductor device 100 in a steady state. When the semiconductor element 101 operates and the temperature T 1 = 150 ° C, the thermal resistance R 1 causes the temperature T 12 on the upper surface of the insulating substrate 103 and the thermal resistance R 12 causes the insulating substrate 103 The temperature difference between the lower surface and the upper surface is large, and the temperature becomes T2.

Due to the thermal resistance R 2, the temperature becomes T 23 on the upper surface of the copper base 104 and the temperature T 3 on the lower surface of the copper base 104.

Due to the thermal resistance R 3, the temperature becomes T 34 on the upper surface of the heat sink 102, and the thermal resistance R 3 G becomes the temperature T 4 on the lower surface of the heat sink 102. Due to the thermal resistance R 4 G, the temperature immediately below the heat sink 102 becomes T 4 G = TG.

The temperature is determined from the thermal resistance and the heat transport rate as shown in equation (1).

The amount of heat transport can be obtained from the temperature difference and thermal resistance, or the thermal conductivity, cross-sectional area and temperature difference, and the length or thickness, as shown in equation (2).

[Temperature (° C)] = [Thermal resistance (° C / W)] X [Heat transport (W)] ■■■ '(1)

[Temperature difference (° 0)

[Heat transport J

[Thermal resistance (° c / w)]

[Thermal conductivity (W / m ° C)] X [Cross-sectional area (m ² )] X [Temperature difference (° C)]

2) [Length or thickness (m)] As described above, in order to reduce the temperature rise of the semiconductor element in a steady state, the thermal conductivity is increased. Increase and reduce heat transfer area. Increase the temperature difference. It is clear that it is necessary to reduce the amount of heat transport.

Next, the transient temperature and the heat transport amount will be described. Fig. 5 (a) shows the shape of the substance, and Fig. 5 (b) shows its equivalent circuit. The thermal conductivity of the material is λ (WZm-K), the density is p (g / m ³ ), the specific heat at constant pressure is C p (JZg'K), the width b (m), the height h (m), and the thickness t (m), the thermal resistance R (KZW) is expressed by equation (3), the heat capacity C (J / K) is expressed by equation (4), and the thermal diffusivity a is expressed by equation (5). You. At this time, the amount of heat transport and the temperature are expressed by equations (6) and (f), respectively.

C = Cp- 'b'h't (4

Δ Τ 二 Wi. -R (1—e GR

Figure 6 shows the change over time in energy and temperature difference. W _{i R} in equation (6) increases over time, and W i. Decreases over time. The temperature difference ΔΤ shown in equation (7) increases with time. Wic is accumulated as the kinetic energy of the crystal lattice and free electrons and the transition energy of electrons. In the present invention, the use of the intermediate heat sink reduces the rate of temperature rise.

From Eq. (7), to delay the temperature rise in the transient state, increase the thermal resistance. Further, the density, specific heat and volume are increased by the equation (5). In particular, it is necessary to increase the thickness.

To reduce the temperature rise, increase the thermal conductivity and heat transfer area, reduce the heat resistance by reducing the heat transfer section, and increase the temperature difference by increasing the cooling capacity. can do.

To delay the temperature rise, increase the thermal resistance by reducing the thermal conductivity and heat transfer area, increase the density / specific heat, and increase the heat capacity by increasing the thickness of the heat transfer section. Good. Under these conditions, material selection, material combination, structural design, and optimal design were performed.

Based on the above considerations, a theoretical study of the structure and an appropriate material and thickness were determined by experimental design.

As a result, by providing a carbon-copper composite material of appropriate thickness as an intermediate layer, It has been found that warpage can be reduced by adjusting the thickness of the upper metal plate 14, the thickness of the intermediate heat sink 15 and the thickness of the lower metal plate 19 in the laminate. By providing the carbon fiber composite material layer as an intermediate layer for relaxing thermal stress between the semiconductor element and the heat sink, warpage of the semiconductor device due to heat can be reduced.

Industrial applicability

INDUSTRIAL APPLICABILITY The semiconductor device according to the present invention can efficiently transmit heat generated in a semiconductor element to a heat sink to effectively cool the semiconductor element, and is useful for industries requiring a power device.

Claims

The scope of the claims

1. a semiconductor device;

Heat sink;

A carbon fiber composite material layer provided between the semiconductor element and the heat seek; a carbon fiber composite material layer provided between the semiconductor element and the carbon fiber composite material layer; A heat transfer metal plate that conducts over the entire surface of the layer.

2. The semiconductor device according to claim 1, further comprising an intermediate heat sink for heat buffer provided between the carbon fiber composite material layer and the heat sink.

3. The semiconductor device according to claim 2, wherein the carbon fiber composite material layer is made of a carbon-copper composite material, and the intermediate heat sink is made of a copper plate.

4. semiconductor devices;

Heat sink;

A laminate provided between the semiconductor element and the heat sink, the laminate including a carbon fiber composite material layer;

A semiconductor device comprising:

5. The laminate is

An upper metal plate that conducts heat generated by the semiconductor element to the entire surface of the carbon fiber composite material layer;

The carbon fiber composite material layer for transmitting the heat of the upper metal plate in the thickness direction; an intermediate heat sink for a heat buffer for accumulating and conducting heat from the carbon fiber composite material layer;

Opposite to the bonding surface of the intermediate heat sink with the carbon fiber composite material layer An insulator to be bonded to;

A lower metal plate joined to a side opposite to a joining surface of the insulator with the intermediate heat sink;

5. The semiconductor device according to claim 4, comprising:

6. The semiconductor device according to claim 5, wherein the carbon fiber composite material is made of a copper composite material, and the intermediate heat sink is made of a copper plate.