Electronic-component-mounted module design to reduce linear expansion coefficient mismatches

An electronic-component-mounted module has an electronic component, a first silver-sintered bonding layer bonded on one surface of the electronic component, a circuit layer made of copper or copper alloy and bonded on the first silver-sintered bonding layer, and a ceramic substrate board bonded on the circuit layer, and further has an insulation circuit substrate board with smaller linear expansion coefficient than the electronic component, a second silver-sintered bonding layer bonded on the other surface of the electronic component, and a lead frame with smaller linear expansion coefficient than the electronic component bonded on the second silver-sintered bonding layer; and a difference in the linear expansion coefficient between the insulation circuit substrate board and the lead frame is not more than 5 ppm/° C.

BACKGROUND OF THE INVENTION

Technical Field

The present invention relates to an electronic-component-mounted module on which power components, LED components, thermoelectric components, and the other electronic components are mounted.

Background Art

Among electronic-component-mounted module, power modules used for semiconductor device controlling large electric current and high voltage are required to deal with large electric current capacity and reduce wiring resistance. In Patent Document 1 for example employs a structure in which wiring connected to semiconductor components are formed from lead frames made of copper; and electronic components (power components and controlling semiconductor components) and the connection parts of the lead frames (an external lead frame and an internal lead frame) are resin-sealed by epoxy resin and the like.

For the electronic-component-mounted modules, as shown in Patent Document 2 for example, an insulation circuit substrate board (a power module substrate) in which a circuit layer made of an aluminum board or the like is bonded on one surface of an insulation substrate board such as aluminum nitride and a metal layer made of an aluminum board or the like is bonded on the other surface is used. The metal layer of this insulation circuit substrate board is bonded on a heat sink made of copper or the like.

In a case in which the electronic component and the lead frame are bonded on this insulation circuit substrate board to form the electronic-component-mounted module, for example, on the circuit layer of the insulation circuit substrate board in which the circuit layer and the metal layer are bonded on surfaces of the insulation substrate board, the electronic component is bonded by methods such as silver-sintering, soldering, or the like. After that, the lead frame made of copper is bonded on this electronic component by soldering or the like.

CITATION LIST

Patent Document

SUMMARY OF INVENTION

Technical Problem

In the above-described electronic-component-mounted module, aluminum, aluminum alloy, copper, and copper alloy used for the circuit layer and the lead frame have larger linear expansion coefficient than that of the electronic component. Therefore, in a case in which the electronic component and the lead frame are mounted on the circuit layer by soldering, owing to change in usage environment and resistance heat of the electronic component and the like, thermal stress is generated in solder bonding layers between the electronic component or the lead frame and the circuit layer repeatedly, cracks may be generated in the solder bonding layer. In a case in which silver-sinter bonding substitutes soldering for mounting the electronic component and the lead frame, the silver-sintered bonding layer has higher bonding reliability in high temperature environment than the solder bonding layer and good thermal transference. However, the silver-sintered bonding layer is thinner and harder than the solder bonding layer; so large thermal stress acts on the electronic component itself and the electronic component may be broken.

The present invention is achieved in consideration of the above circumstances, and has an object of provide an electronic-component-mounted module which can prevent the breakage of the electronic component with improving the bonding reliability of the circuit layer, the electronic component, and the lead frame by the silver-sintered bonding layer.

Solution to Problem

Electronic-component-mounted module of the present invention includes: an electronic component; a first silver-sintered bonding layer bonded on one surface of the electronic component; an insulation circuit substrate board including a circuit layer made of copper or copper alloy bonded on the first silver-sintered bonding layer and a ceramic substrate board bonded on the circuit layer, and having a smaller linear expansion coefficient than the electronic component; a second silver-sintered bonding layer bonded on the other surface of the electronic component; and a lead frame bonded on the second silver-sintered bonding layer and having a smaller linear expansion coefficient than the electronic component; and a difference in the linear expansion coefficient between the insulation circuit substrate board and the lead frame is not more than 5 ppm/° C.

The electronic-component-mounted module has high bonding reliability even in high temperature environment because the insulation circuit substrate board and the lead frame have lower linear expansion coefficient than the electronic component and both the surfaces of the electronic component are bonded on the insulation circuit substrate board and the lead frame with the silver-sintered bonding layers (the first silver-sintered bonding layer and the second silver-sintered bonding layer) therebetween. Heat generated in the electronic component can be quickly released since thermal conductivity of the silver-sintered bonding layers is excellent. Moreover, thermal stress in the electronic component is reduced and the breakage thereof can be prevented since members bonded on both the surfaces of the electronic component have smaller linear expansion coefficient than the electronic component so as to decrease the difference in the linear expansion to the electronic component. In this case, it is not desirable that the difference in the linear expansion coefficient between the insulation circuit substrate board and the lead frame is more than 5 ppm/° C. because the thermal stress in the electronic component is large by the difference in the linear expansion.

As a preferred aspect of the electronic-component-mounted module of the present invention, it is preferable that a thickness of the circuit layer is t1; and a thickness of the lead frame is t2; and a thickness ratio (t1/t2) of the thickness t1 and the thickness t2 be not less than 0.2 and not more than 5.0. It is preferable that the lead frame be made of copper-type low linear-expansion material including a composite material which is a combination of copper and low linear-expansion material such as tungsten, molybdenum, chrome, or the like; and copper boards bonded on both surfaces of the composite material. It is preferable that the electronic-component-mounted module further have molding resin sealing the insulation circuit substrate board, the electronic component, and the lead frame integrally.

Although copper or copper alloy has larger linear expansion coefficient comparing with the electronic component, since the circuit layer made of copper or copper alloy is bonded on the ceramic substrate board in a laminated state, the linear expansion of the insulation circuit substrate board is influenced by the linear expansion of the ceramic substrate board. Accordingly, the insulation circuit substrate board itself is lower in the linear expansion than the electronic component. In this case, if the thickness ratio (t1/t2) of the thickness t1 of the circuit layer and the thickness t2 of the lead frame is less than 0.2 or more than 5.0, an effect of arranging the insulation circuit substrate board and the lead frame made of the low linear-expansion material on both the surfaces of the electronic component to balance is deteriorated. As a result, the linear expansion of thicker one of the circuit layer or the lead frame dominant, and breakages of the electronic component may occur.

An electronic-component-mounted module of the present invention has: an electronic component; a first silver-sintered bonding layer bonded on one surface of the electronic component; an insulation circuit substrate board having: a spacing member with smaller linear expansion coefficient than the electronic component bonded on the first silver-sintered bonding layer, a third silver-sintered bonding layer bonded on the spacing member, a circuit layer made of aluminum or aluminum alloy and bonded on the third silver-sintered bonding layer, and a ceramic substrate board bonded on the circuit layer; a second silver-sintered bonding layer bonded on the other surface of the electronic component; and a lead frame bonded on the second silver-sintered bonding layer and having smaller linear-expansion coefficient than the electronic component, wherein a difference in the linear expansion coefficient to the spacing member is not more than 5 ppm/° C.

As a preferred aspect of an electronic-component-mounted module of the present invention, it is preferable that a thickness of the spacing member is t3, a thickness of the lead frame is t2, and a thickness ratio (t3/t2) of the thickness t1 and the thickness t2 be not less than 0.2 and not more than 5.0. It is preferable that the spacing member and the lead frame be made of copper-type low linear-expansion material, having a composite material which is a combination of copper and low linear-expansion material such as tungsten, molybdenum, chrome, or the other low linear-expansion material, and copper boards bonded on both surfaces of the composite material. It is preferable that the electronic-component-mounted module further have molding resin sealing the insulation circuit substrate board, the electronic component, and the lead frame integrally.

The spacing member can adjust a height position (a position in a lamination direction) of the lead frame, and the lead frame can be drawn out from an appropriate position. Also in this case, the thickness ratio (t3/t2) of the spacing member and the lead frame is set to be not less than 0.2 and not more than 5.0 not to break the electronic component.

Advantageous Effects of Invention

According to the electronic-component-mounted module of the present invention, by bonding the low linear-expansion material with smaller linear expansion coefficient than that of the electronic component on both the surfaces of the electronic component by the silver-sintered bonding layers, so that the difference in the linear expansion between the low linear-expansion material at both sides is small, it is possible to improve the bonding reliability and the thermal transference and it is possible to reduce the thermal stress in the electronic component and prevent it's breakage.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be explained referring to drawings.

1. First Embodiment

A first embodiment explains an example of applying an electronic-component-mounted module for a power module100. The power module100is provided with semiconductor components (electronic components of the present invention)30; first silver-sintered bonding layer711bonded on one surface of the electronic components30; a power module substrate (an insulation circuit substrate board of the present invention)10bonded on the first silver-sintered bonding layers711; second silver-sintered bonding layers712bonded on the other surface of the semiconductor components30; a lead frame40bonded on the second silver-sintered bonding layers712; and a molding resin50sealing these semiconductor components30, the power module substrate10, and the lead frame40, as shown inFIG. 1.

The power module substrate10has spacing members20bonded on the first silver-sintered bonding layers711; third silver-sintered bonding layers713bonded on the spacing members20; a circuit layer12bonded on the third silver-sintered bonding layers713; and a ceramic substrate board11bonded on the circuit layer12. The other surfaces of the semiconductor components30are mounted on a surface of12of the power module substrate10with the third silver-sintered bonding layers713, the spacing members20, and the first silver-sintered bonding layers711therebetween. The lead frame40is bonded on the other surface of the semiconductor components30with the second silver-sintered bonding layers712therebetween.

For the ceramic substrate board11forming the power module substrate10, nitride-type ceramics such as MN (aluminum nitride), Si3N4(silicon nitride) and the like, or oxide-type ceramics such as Al2O3(alumina) and the like can be used, for example. A thickness of the ceramic substrate board11is in a range of 0.2 mm to 1.5 mm.

The circuit layer12and a heat radiation layer13are made of aluminum with purity 99.00% by mass or higher (so-called 2N aluminum), aluminum with purity 99.99% by mass or higher (so-called 4N aluminum), or aluminum alloy. Thickness of the circuit layer12and the heat radiation layer13are 0.1 mm to 5.0 mm for example. The circuit layer12and the heat radiation layer13are normally formed into a flat rectangular shape smaller than the ceramic substrate board11. The circuit layer12and the heat radiation layer13are bonded on the ceramic substrate board11by brazing material of alloy such as Al—Si type, Al—Ge type, Al—Cu type, Al—Mg type, or Al—Mn type. The circuit layer12and the heat radiation layer13are formed into a desired shape by any of: punching to have the desired outline by press machining and bonding it on the ceramic substrate board11; or bonding a flat piece on the ceramic substrate board11and then forming into the desired outline by etching.

The spacing members20are made of material having lower linear expansion than the linear expansion coefficient of the semiconductor components30: e.g., copper-type low linear-expansion material, having a composite material in which copper (Cu) having high thermal conductivity is combined with tungsten (W), molybdenum (Mo), chrome (Cr) or the other low linear expansion coefficient material together; and copper boards bonded on both surfaces of the composite materials. A thickness t3 of the spacing members20is preferably in a range of 0.5 mm to 6.0 mm. For the spacing members20, for example, a clad board in which pure copper boards with a thickness 0.1 mm to 2.0 mm are bonded on both surfaces of a composite material with a thickness 0.3 mm to 5.0 mm can be used. A composite material of Cu—Mo is appropriately used as the composite material; in this case, it is preferable to contain Mo in a range of 55% by mass to 75% by mass. The composite material of Cu—Mo is formed by forming mixed powder in which Cu powder and Mo powder are mixed and sintering it.

The copper-type low linear-expansion material can be adjusted in the linear expansion coefficient and thermal conductivity by changing content ratio of the low linear-expansion material and a ratio of a thickness to the cladded copper board. The linear expansion coefficient of the copper-type low linear-expansion material will be described later. The thermal conductivity of the copper-type low linear-expansion material is 180 to 200 W/m·K for example.

InFIG. 1, the two spacing members20are bonded on the circuit layer12aligning in a surface direction.

The semiconductor components30are electronic components provided with semiconductor. For the semiconductor components30, various semiconductor components are selected, such as IGBT (Insulated Gate Bipolar Transistor), MOSFET (Metal Oxide Semiconductor Field Effect Transistor), FWD (Free Wheeling Diode), and the like according to necessary functions. On a top surface and a bottom surface of the semiconductor components30, electrodes are provided and electrically connected between the circuit layer12and the lead frame40. In this case, the semiconductor components30are respectively bonded on the two spacing members20and connected to each other by the lead frame40.

The lead frame40is made of the lower linear expansion material than the linear expansion coefficient of the semiconductor components30. The lead frame40is made of copper-type low linear-expansion material as that of the spacing members20for example and formed into a belt-sheet shape. A difference in the linear expansion coefficient between the lead frame40and the spacing members20is 5 ppm/° C. or less. As mentioned above, the copper-type low linear-expansion material can be adjusted in the linear expansion coefficient and the like in proportion to the content ratio of copper and the low linear-expansion material in the composite material and the thickness ratio of the cladded copper board. Linear expansion coefficient of the semiconductor components30is 20 ppm/° C. to 30 ppm/° C. for example. It is good that a thickness t2 of the lead frame40is in a range of not less than 0.05 mm and not more than 3.0 mm. A thickness ratio (t3/t2) of the thickness t3 of the spacing members20and the thickness t2 of the lead frame40is set to not less than 0.2 and not more than 5.0 in order to effectively show an effect of reduction in the difference of the linear expansion coefficient between them.

The spacing members20, the semiconductor components30, the lead frame40are bonded on the circuit layer12of the power module substrate10respectively with the silver-sintered bonding layers711to713therebetween. In the present embodiment, the silver-sintered bonding layers711to713are distinguished as follows: the silver-sintered bonding layers bonding the semiconductor components30and the spacing members20are the first silver-sintered bonding layers711; the silver-sintered bonding layers bonding the semiconductor components30and the lead frame40are the second silver-sintered bonding layers712; and the silver-sintered bonding layers bonding the spacing members20and the circuit layer12are the third silver-sintered bonding layers713.

In order to bond the spacing members20by the third silver-sintered bonding layers713, undercoat metal layers60made of gold (Au), Silver (Ag), nickel (Ni) or the like is formed on a bonding surface of the circuit layer12. While the illustration is omitted, the undercoat metal layers made of gold, silver, nickel, and the like may be formed by plating, spattering or the like on the respective bonding surfaces of the spacing members20, the semiconductor components30, and the lead frame40.

The molding resin50is made of epoxy resin and the like. The molding resin50seals the heat radiation layer13at side surfaces, the ceramic substrate board11, the circuit layer12, the spacing members20, the semiconductor components30, and the lead frame40at the vicinity of a connecting part to the semiconductor components30integrally except for a bottom surface of the heat radiation layer13of the power module substrate10. An end part of the lead frame40is drawn out from the molding resin50.

Manufacturing Method of First Embodiment

Next, a method of manufacturing the power module100structured as above will be explained.

In this method the power module is formed by, as shown inFIG. 2, [a step of forming a power module substrate] forming the power module substrate10; [a step of forming an undercoat metal layer] forming the undercoat metal layers60on a planned-bonding surface of the circuit layer12of the power module substrate10; [a step of batch-bonding] laminating the spacing members20, the semiconductor components30, and the lead frame40on the circuit layer12in order and bonding at one time; and then [a step of resin-sealing] resin-sealing by the molding resin50. Below, it will be explained in order of the process.

——Step of Forming Power Module Substrate——

As shown inFIG. 3A, an aluminum board12′ which will be the circuit layer12and an aluminum board13′ which will be the heat radiation layer13are stacked on the surfaces of the ceramic substrate board11with soldering material15therebetween. A laminate structure body of these is heated in a state of pressed in a stacking direction so as to melt the brazing material15; and the respective aluminum boards12′ and13′ are bonded to the ceramic substrate board11, so that the power module substrate10having the circuit layer12and the heat radiation layer13is formed (refer toFIG. 3B). Specifically, the laminate structure body is put in a furnace with it remain pressed, and heated at temperature 610° C. to 650° C. inclusive for 1 minute to 60 minutes in vacuum atmosphere.

——Step of Forming Undercoat Metal Layer——

Before the step of batch-bonding, the undercoat metal layers60made of gold, silver, nickel, or the like are formed on the planned-bonding surface of the circuit layer12. The undercoat metal layers60can be obtained by forming into a thin film shape by plating or spattering of gold, silver, nickel, or the like. The undercoat metal layers60also can be formed of glass-contained silver paste by applying on the surface of the circuit layer12and sintering them.

(Method of Forming Undercoat Metal Layer with Glass-Contained Silver Paste)

A method of forming the undercoat metal layers60with the glass-contained silver paste on the surface of the circuit layer12will be explained. The glass-contained silver paste contains silver powder, glass (lead-free glass) powder, resin, solvent, and dispersing agent; a content of powder component consisting of the silver powder and the glass powder is 60% by mass to 90% by mass inclusive to the whole glass-contained silver paste, and the remaining is the resin, the solvent, and the dispersing agent. A particle size of the silver powder is 0.05 μm to 1.0 μm inclusive; for example, an average particle size 0.8 μm is appropriate. The glass powder contains one or two or more of bismuth oxide (Bi2O3), zinc oxide (ZnO), boron oxide (B2O3), lead oxide (PbO2), and phosphorus oxide (P2O5); and glass transition temperature thereof is 300° C. to 450° C. inclusive; softening temperature is not more than 600° C.; and crystallization temperature is not less than 450° C. For example, the glass powder with the average particle size 0.5 μm containing lead oxide, zinc oxide and boron oxide is appropriate.

A weight ratio A/G of a weight A of the silver powder and a weight G of the glass powder is adjusted in a range between 80/20 and 99/1, e.g., A/G=80/5. The solvent is appropriate to have a boiling point of 200° C. or higher, e.g., diethylene glycol dibutyl ether is used. The resin adjusts a viscosity of the glass-contained silver paste; it is appropriate to be decomposed at 350° C. or higher. For example, ethyl cellulose is used. Moreover, the dispersing agent of dicarboxylic acid type is suitably added. The glass-contained silver paste may be composed without the dispersing agent.

This glass-contained silver paste is manufactured by pre-mixing mixed powder of the silver powder and the glass powder and an organic mixed compound of the solvent and the resin with the dispersing agent in a mixer to obtain a pre-mixed compound; kneading the pre-mixed compound in a rolling-mill device to obtain a kneaded object; and filtering the kneaded object by a paste filtering device. This glass-contained silver paste is adjusted to have the viscosity of 10 Pa·s to 500 Pa·s inclusive, more preferably, 50 Pa·s to 300 Pa·s inclusive.

This glass-contained silver paste is applied on the planned-bonding surface of the circuit layer12by screen printing or the like; and after drying, it is burned at temperature of 350° C. to 645° C. inclusive for 1 minute to 60 minutes inclusive. As a result, as shown inFIG. 4, the undercoat metal layers60are formed to have a double structure of a glass layer61formed on the planned-bonding surface side and a silver layer62formed on this glass layer61. While the glass layer61is formed, an aluminum oxide film12anaturally generated on the surface of the circuit layer12is melted and removed, so that the glass layer61is directly formed on the circuit layer12; and the silver layer62is formed on this glass layer61. The silver layer62is certainly held and fixed on the circuit layer12, by the glass layer61firmly adhered on the circuit layer12.

In the glass layer61, conductive particles (crystalline particles)63containing at least one of silver or aluminum are dispersed. It is inferred that the conductive particles63deposited inside the glass layer61while burning. Also inside the silver layer62, minute glass particles64are dispersed. It is inferred that the glass particles64are coagulated objects of glass component remained in process of burning silver particles.

An average crystalline size of the silver layer62in the undercoat metal layers60formed as above is adjusted in a range of 0.5 μm to 3.0 μm inclusive. Here, in a case in which the heating temperature while burning the undercoat metal layers60is lower than 350° C. and the holding time at the heating temperature is less than one minute, the undercoat metal layers60cannot sufficiently formed. In contrast, in a case in which the heating temperature is higher than 645° C. and in a case in which the holding time at the heating temperature is more than 60 minutes, it is excessively burned, so that there is concern that the average crystalline size of the silver layer62in the undercoat metal layers60formed after the heat treatment be not in the range of 0.5 μm to 3.0 μm.

In order to reliably form the undercoat metal layers60, it is preferable that a lower limit of the heating temperature in the heat treatment be 400° C. or higher, more preferably, 450° C. or higher. It is preferable that the holding time at the heating temperature be five minutes or longer, more preferably, 10 minutes or longer. In contrast, in order to reliably suppress the progress of burning, it is preferable that the heating temperature in the heating treatment be 600° C. or lower, more preferably, 575° C. or lower. It is preferable that the holding time at the heating temperature be 45 minutes or shorter, more preferably, 30 minutes or shorter.

Next, the circuit layer12on which the undercoat metal layers60are formed, the spacing members20, the semiconductor components30, and the lead frame40are laminated with interposing silver paste layers70therebetween.

The silver paste layers70are layers formed by applying silver paste containing silver powder of a particle size 0.05 μm to 100 μm inclusive, resin, and solvent. The resin for the silver paste is ethyl cellulose or the like. The solvent for the silver paste is α-terpineol or the like. It is preferable for composition of the silver paste that content of the silver powder be 60% by mass to 92% by mass inclusive to the whole silver paste, content of the resin be 1% by mass to 10% by mass inclusive to the whole silver paste, and the remaining be solvent.

The silver paste can contain organic metal compound powder of carboxylic acid type metal salt and the like such as silver formate, silver acetate, silver propionate, silver benzoate, silver oxalate and the like with not less than 0% by mass and not more than 10% by mass to the whole silver paste. Reducing agent such as alcohol, organic metal acid or the like can be contained also as necessary, with not less than 0% by mass and not more than 10% by mass to the whole silver paste. This silver paste is adjusted to have a viscosity 10 Pa·s to 100 Pa·s inclusive, more preferably, 30 Pa·s to 80 Pa·s.

This silver paste is applied on the undercoat metal layers60of the circuit layer12, on surfaces of the spacing members20, and the surfaces of the lead frame40by screen printing or the like for example respectively and dried, so that the silver paste layers70are formed. It is sufficient that the silver paste layers70are formed on any of the planned-bonding surfaces facing to each other when bonding. In the example shown inFIG. 3C, the silver paste layers70are formed respectively on the surface of the circuit layer12, the surfaces of the spacing members20at a side facing to the semiconductor components30, and the surface of the lead frame40at a side facing to the semiconductor components30.

As the silver paste layers70, silver oxide paste in which oxide powder is a substitute for the silver powder can be used. The oxide silver paste contains the oxide silver powder, the reducing agent, the resin, and the solvent, and adding to these, further contains organic metal compound powder. A content of the oxide silver powder is 60% by mass to 92% by mass inclusive to the whole oxide silver paste; a content of the reducing agent is 5% by mass to 15% by mass inclusive to the whole oxide silver paste; a content of the organic metal compound powder is 0% by mass to 10% by mass inclusive to the whole oxide silver paste; and the remaining is the solvent.

As shown inFIG. 3C, a laminated state is made by arranging the spacing members20on the silver paste layers70of the circuit layer12, arranging the semiconductor components30on the silver paste layers70of the spacing members20, and arranging the silver paste layers70of the lead frame40on the semiconductor components30. In a state of in which a pressuring forth 1 MPa to 20 MPa inclusive is added in the laminate direction, it is heated to temperature 180° C. to 350° C. inclusive.

A holding time of this temperature is sufficient in a range 1 minute to 60 minutes inclusive. By this heat treatment, the silver paste layers70are sintered and form the silver-sintered bonding layers711to713respectively between the circuit layer12, the spacing members20, the semiconductor components30, and the lead frame40; and these silver-sintered bonding layers711to713bond the circuit layer12, the spacing members20, the semiconductor components30, and the lead frame40integrally.

In a case in which the silver paste layers70made of the silver oxide paste containing silver oxide and the reducing agent is used, reduced silver particles precipitated by reducing the silver oxide while bonding (burning) are so minute to have a particle size 10 nm to 1 μm, for example. Thus the dense silver-sintered bonding layers711to713are formed, and it is possible to firmly bond the circuit layer12, the spacing members20, the semiconductor components30, and the lead frame40.

As described above, after bonding the spacing members20, the semiconductor components30, and the lead frame40on the power module substrate10; the power module substrate10, the spacing members20, the semiconductor components30, and the vicinity of the connecting part of the lead frame40are sealed by the molding resin50integrally, except for the bottom surface of the heat radiation layer13of the power module substrate10. Specifically, the molding resin50is formed by sealing material made of epoxy resin by a transfer molding method and sealing is carried out, for example.

An external end part of the lead frame40is exposed from the molding resin50.

In the power module100manufactured as above, the warp is reduced since the semiconductor components30are bonded and pressed between the power module substrate having high rigidity and the lead frame40. Therefore, the semiconductor components30, the power module substrate10, and the lead frame40can get a good bonded state without breaking the semiconductor components30. It is facilitated to manufacture since the spacing members20, the semiconductor components30, and the lead frame40are bonded on the power module substrate10at one time.

In this power module100, both the surfaces of the semiconductor components30are bonded on the spacing members20and the lead frame40by the first silver-sintered bonding layers711and the second silver-sintered bonding layers712, so that it has high bonding reliability even under high temperature environment. The heat of the semiconductor components30can be quickly released since the thermal conductivity of the silver-sintered bonding layers711and712is excellent. Moreover, the spacing members20and the lead frame40arranged on both the surfaces of the semiconductor components30are made of the copper-type low linear-expansion material and the spacing members20and the lead frame40have small difference in the linear expansion to the semiconductor components30, so that thermal stress on the semiconductor components30is reduced and the breakages thereof can be prevented.

In the power module100, the power module substrate10, the semiconductor components30, and the lead frame40are sealed by the molding resin50as one assembly. Accordingly, the respective bonding states can be maintained fine by the molding resin50; and even higher bonding reliability can be obtained.

2. Second Embodiment

FIG. 5shows a power module101of a second embodiment.

In the power module101of the second embodiment, there is no spacing members20which are provided in the first embodiment; one surface of the semiconductor components30is bonded on a circuit layer17of a power module substrate16with the first silver-sintered bonding layers711therebetween, and the lead frame40is bonded on the other surface of the semiconductor components30with the second silver-sintered bonding layers712therebetween.

InFIG. 5, on the ceramic substrate board1of the power module substrate16, two small-circuit parts17aand17bas the circuit layer17are bonded in a laminated state aligning in a surface direction. On the small-circuit parts17aand17b, the first silver-sintered bonding layers711are bonded respectively, and the semiconductor components30are bonded respectively on each of the first silver-sintered bonding layers711.

The circuit layer17and a heat radiation layer18of the power module substrate16are made of copper or copper alloy. Copper or copper alloy has relatively large linear expansion coefficient, however it is hard to be deformed in comparing with aluminum and the other alloy in the first embodiment. Therefore, linear expansion of the ceramic substrate board11is dominant over linear expansion of the circuit layer17at the surface. Accordingly, the whole power module substrate16is low linear-expansion material having smaller linear expansion coefficient than the semiconductor components30. In the present embodiment, oxygen-free copper is used for the circuit layer17and the heat radiation layer18.

The lead frame40is made of copper-type low linear-expansion material having a composite material and copper boards bonded on both surfaces of the composite material, as in the first embodiment. The composite material is a combination of copper (Cu) and the low linear expansion coefficient material, such as tungsten (W), molybdenum (Mo), chrome (Cr) and the other. The difference of the linear expansion coefficient between the power module substrate16and the lead frame40is set to be 5 ppm/° C. or lower. A thickness ratio (t1/t2) of a thickness t1 of the circuit layer16of the power module substrate15and a thickness t2 of the lead frame40is set to be 0.2 to 5.0 inclusive.

In the power module101, the power module substrate16is manufactured by laminating the circuit layer17and the heat radiation layer18on the respective surfaces of the ceramic substrate board11with active-metal brazing material therebetween, such as silver-titanium (Ag—Ti) type brazing material or silver-copper-titanium (Ag—Cu—Ti) type brazing material; and heating to 800° C. to 930° C. inclusive in a state in which a pressure of 0.05 MPa to 1.0 MPa inclusive is added in the lamination direction, for example. After that, the circuit layer17, the semiconductor components30, and the lead frame40are laminated on respective planned-bonding surfaces with silver paste layers therebetween, and pressed and heated by batch as in the first embodiment; so that the circuit layer12and the semiconductor components30are bonded with the first silver-sintered bonding layers711therebetween, and the semiconductor components30and the lead frame40are bonded with the second silver-sintered bonding layers712therebetween. At the last, the vicinity of connection parts of the power module substrate16with the semiconductor components30and the lead frame40are sealed by the molding resin50as one assembly.

Since the circuit layer17of the power module substrate16of the present embodiment is made of copper or copper alloy, it is not necessary to provide the undercoat metal layers60formed on the circuit layer12made of aluminum or alloy thereof as in the first embodiment; however, the similar undercoat metal layers may be formed. Moreover, on the respective planned-bonding surfaces of the semiconductor components30and the lead frame40, undercoat metal layers such as gold, silver, nickel, or the like may be formed by plating, spattering, or the like.

In the power module101manufactured as above, the lead frame40and the brazing material15arranged on both the surfaces of the semiconductor components30are made of copper-type low linear-expansion material having smaller linear expansion coefficient than the semiconductor components30. Accordingly, thermal stress in the semiconductor components30is reduced and it is possible to effectively prevent the breakage. Since the power module substrate16, the semiconductor components30which are bonded on the power module substrate16, and the lead frame40are sealed by the molding resin50as one body, it is possible to maintain the bonding states to be good by the molding resin50respectively and even higher bonding reliability can be obtained.

Besides, the present invention is not limited to the above-described embodiments and various modifications may be made without departing from the scope of the present invention.

EXAMPLES

The circuit layer of the power module substrate, the spacing members, and the lead frame were prepared at the material and the thickness shown in Table 1. The silver paste was applied on any of the planned-bonding surfaces facing each other, and they were laminated and batch-bonded. In this case, regarding Invention Examples 1 to 4 and Comparative Example 1, the undercoat metal layer was formed on the surface of the circuit layer made of aluminum using the above-described glass-contained silver paste. Regarding Invention Example 5 and 6 and Comparative Example 2, the semiconductor component was bonded on the circuit layer without the spacing member. In any case, temperature was 300° C. and pressure was 10 MPa while bonding.

On the power module on which the semiconductor component was bonded, a cold/hot impact test was carried out at lower temperature −40° C. and higher temperature 150° C., with 1000 cycles, and the semiconductor was evaluated whether broken or not. The breakage of the semiconductor component was examined using an ultrasonic imaging device, and evaluated as “good” if a probability of cracks were found in the semiconductor was 10% or lower; or as “not good” if the probability of cracks were found in the semiconductor was more than 10%.

Results are shown in Table 2. In table 1, “4N—Al” is aluminum with purity 99.99% by mass or higher; “C1020” is oxygen-free copper; “Cu—Mo” is a clad material of pure copper/copper molybdenum composite material/pure copper; and “Cu—W” is a clad material of pure copper/copper tungsten composite material/pure copper.

As recognized from Tables 1 and 2, the breakage of the semiconductor component was not found in the power modules in which the difference of the linear expansion coefficient between materials on both the surfaces of the semiconductor component was not more than 5 ppm/° C., and the thickness ratio (t1/t2) or the ratio (t3/t2) was 0.2 to 5.0 inclusive.

INDUSTRIAL APPLICABILITY

By bonding the low linear-expansion material having lower linear expansion coefficient than the electronic component on both the surfaces of the electronic component with the silver-sintered bonding layers therebetween and reducing the difference of the linear expansion between the low linear-expansion material, it is possible to improve the bonding reliability and the thermal transference of the electronic-component-mounted module, and it is possible to reduce the thermal stress in the electronic component and prevent the breakage thereof.

REFERENCE SIGNS LIST