WO2025206049A1 - Conductive adhesive film, method for joining dissimilar materials, semiconductor device structure, and dicing die-bonding film - Google Patents

Abstract

The present invention pertains to a conductive adhesive film (10) for joining a semiconductor device and a member, the conductive adhesive film (10) comprising: a stress relaxation layer (1) that is composed of a soft high-thermal-conductivity metal having a Young's modulus of 110 GPa or less at 25°C, a thermal conductivity of 100 W/m•K or more at 25°C, and a volume resistivity of 100 μΩ•cm or less; a first adhesive layer (2) that is provided on the side of the stress relaxation layer (1) to which the semiconductor device is joined, the first adhesive layer containing copper (Cu), tin (Sn), a bismaleimide resin, and an organic phosphine and/or an organic sulfide; and a second adhesive layer (3) that is provided on the side opposite the side of the stress relaxation layer (1) to which the semiconductor device is joined, the second adhesive layer containing copper (Cu), tin (Sn), a bismaleimide resin, and an organic phosphine and/or an organic sulfide.

Description

Conductive adhesive film, method for joining different materials, semiconductor device structure, and dicing die bond film

The present invention relates to a conductive adhesive film for bonding semiconductor devices to components such as substrates and lead frames, a method for bonding dissimilar materials using a conductive adhesive film, a semiconductor device structure having a conductive adhesive film, and a dicing die bond film having a conductive adhesive film.

In recent years, high-capacity power semiconductors, such as SiC, have come into widespread use with the aim of reducing power consumption, among other things. Because high-capacity power semiconductors, such as SiC, have a wider bandgap than conventional silicon, they can operate over a wider temperature range and at higher current densities. This allows devices incorporating high-capacity power semiconductors, such as SiC, such as motor inverters, to achieve both high performance and compact size.

However, although high-capacity power semiconductors themselves maintain their switching performance even at high current densities and the resulting high operating temperatures (junction temperatures), when high-capacity power semiconductors are repeatedly exposed to high operating temperatures, the surrounding mounting components, particularly the lead-free solder used in the die bond area, can be destroyed by thermal fatigue caused by repeated exposure to high and low temperatures, resulting in the failure of devices incorporating high-capacity power semiconductors.

In response, it has been proposed to use a silver-based sintered material as a die-bonding material for high-capacity power semiconductors. For example, a semiconductor device bonding member (Patent Document 1) has been proposed that includes a thermal stress relaxation layer made of any of silver, copper, gold, and aluminum, a first silver brazing material layer primarily composed of silver and tin provided on the side of the thermal stress relaxation layer where the semiconductor device is bonded, and a second silver brazing material layer primarily composed of silver and tin provided on the side of the thermal stress relaxation layer where the substrate is bonded.

However, with silver-based sintered materials such as those described in Patent Document 1, in order to achieve a bonded state with excellent reliability and thermal fatigue resistance that can withstand repeated use at high operating temperatures, sintering at extremely high pressures and at high temperatures of over 300°C is required. This poses a major problem in terms of practicality due to the high cost of silver and the difficulty of the sintering process.

Furthermore, in the adhesive layer of Patent Document 1, which is made of a silver brazing material layer whose main components are silver and tin, an oxide film forms on the silver and tin, which poses the problem of inhibiting the transient liquid phase sintering (TLPS) reaction when joining a power semiconductor to a substrate, lead frame, or other component. Therefore, studies are being conducted to prevent the formation of this oxide film by reducing it by adding an alcohol-based or acid-based flux (reducing agent) to the adhesive layer whose main components are silver and tin.

However, when alcohol-based or acid-based fluxes reduce the oxide film, water molecules are generated, and these water molecules cause voids to form in the sintered adhesive layer. Therefore, when using alcohol-based or acid-based fluxes, it is necessary to apply pressure to the semiconductor device structure, in which high-capacity power semiconductors are mounted on a substrate, etc., in order to eliminate the voids. However, there is a problem in that applying pressure to the semiconductor device structure can cause damage such as cracks to the high-capacity power semiconductors.

Japanese Patent Application Laid-Open No. 2022-50871

The present invention was made in consideration of the above circumstances, and aims to provide a conductive adhesive film that has excellent thermal fatigue resistance, ease of sintering, and void prevention properties without using expensive precious metals, a method for joining dissimilar materials using said conductive adhesive film, a semiconductor device structure having said conductive adhesive film, and a dicing die bond film having said conductive adhesive film.

The gist of the configuration of the present invention is as follows.
[1] A stress relaxation layer made of a soft, highly thermally conductive metal having a Young's modulus at 25°C of 110 GPa or less, a thermal conductivity at 25°C of 100 W/m K or more, and a volume resistivity of 100 μΩ cm or less;
a first adhesive layer provided on the side of the stress relaxation layer to which a semiconductor device is bonded, the first adhesive layer including copper (Cu), tin (Sn), a bismaleimide resin, and an organic phosphine represented by the following general formula (1) and/or an organic sulfide represented by the following general formula (2);
a second adhesive layer provided on the side of the stress relaxation layer opposite to the side to which the semiconductor device is bonded, the second adhesive layer including copper (Cu), tin (Sn), a bismaleimide resin, and an organic phosphine represented by the following general formula (1) and/or an organic sulfide represented by the following general formula (2);
A conductive adhesive film for bonding a semiconductor device and a member, comprising:
(Chem.1)
R ¹ -P(R ² )-R ³ -P(R ⁴ )-R ⁵ ...(1)
(In the general formula (1), R ¹ , R ² , R ³ , R ⁴ , and R ⁵ each independently represent an aromatic or aliphatic organic group containing carbon (C) and hydrogen (H), and are each a functional group
does not contain in the structure.)
(Case 3)
R ⁶ -S-R ⁷ ...(2)
(In the general formula (2), R ⁶ and R ⁷ each independently represent an aromatic or aliphatic organic group containing carbon (C) and hydrogen (H), and are each a functional group
does not contain in the structure.)
[2] The first adhesive layer and the second adhesive layer contain an alloy containing copper (Cu) and nickel (Ni) and/or an alloy containing tin (Sn) and nickel (Ni), and have at least one endothermic peak in a temperature range of 100°C to 250°C in differential scanning calorimetry, and do not have the endothermic peak after heating at 250°C for 5 minutes in a nitrogen atmosphere at normal pressure [1]. A conductive adhesive film.
[3] The soft, highly thermally conductive metal has at least one metal selected from the group consisting of aluminum (Al) having a purity of 99.99% by mass or more and zinc (Zn) having a purity of 99% by mass or more. A conductive adhesive film according to [1] or [2].
[4] A conductive adhesive film according to [1] or [2], wherein a first barrier layer containing at least one metal component selected from the group consisting of molybdenum (Mo), chromium (Cr), titanium (Ti), nickel (Ni), tin (Sn) and copper (Cu) is further provided between the stress relief layer and the first adhesive layer, and a second barrier layer containing at least one metal component selected from the group consisting of molybdenum (Mo), chromium (Cr), titanium (Ti), nickel (Ni), tin (Sn) and copper (Cu) is further provided between the stress relief layer and the second adhesive layer.
[5] The conductive adhesive film according to [1] or [2], wherein the melting point of the organic phosphine is 60°C or higher.
[6] The conductive adhesive film according to [1] or [2], wherein the organic phosphine has a xanthene skeleton.
[7] The conductive adhesive film according to [1] or [2], wherein the melting point of the organic sulfide is 60°C or higher.
[8] The conductive adhesive film according to [1] or [2], wherein the organic sulfide has an acrylic group and/or a methacrylic group and/or a vinyl ether group.
[9] The conductive adhesive film according to [1] or [2], wherein the first adhesive layer and the second adhesive layer further contain a compound represented by the following general formula (3):
(C5)
Ar ¹ -C(R ⁸ )(R ⁹ )-C(R ¹⁰ )(R ¹¹ )-Ar ² ...(3)
(In general formula (3), Ar ¹ and Ar ² each independently represent an aromatic group, and R ⁸ , R ⁹ , R ¹⁰ , and R ¹¹ each independently represent an aliphatic group.)
[10] A method for joining dissimilar materials having different linear expansion coefficients, using the conductive adhesive film according to [1] or [2], by pressureless sintering at 275°C or less for less than 10 minutes in a nitrogen atmosphere at normal pressure.
[11] A semiconductor device structure in which the semiconductor device is bonded to the first adhesive layer of the conductive adhesive film described in [1] or [2], and a substrate or lead frame is bonded to the second adhesive layer of the conductive adhesive film described in [1] or [2], and the semiconductor device is mounted on the substrate or lead frame.
[12] A dicing die bond film in which a dicing tape is attached to the second adhesive layer side of the conductive adhesive film according to [1] or [2].

In the above aspect [1], the first adhesive layer is sintered by transient liquid phase sintering (TLPS) or the like, so that a semiconductor device such as a power semiconductor is bonded to the stress relief layer made of a soft, highly thermally conductive metal via the sintered first adhesive layer, and the second adhesive layer is sintered by transient liquid phase sintering (TLPS) or the like, so that a component such as a substrate or lead frame is bonded to the stress relief layer made of a soft, highly thermally conductive metal via the sintered second adhesive layer. Furthermore, in the present invention, "normal pressure" means atmospheric pressure.

According to an embodiment of the conductive adhesive film of the present invention, by providing a stress relaxation layer made of a soft, highly thermally conductive metal having a Young's modulus at 25°C of 110 GPa or less, a thermal conductivity at 25°C of 100 W/m·K or more, and a volume resistivity of 100 μΩ·cm or less, the film has excellent thermal conductivity and electrical conductivity. Furthermore, even if the thermal expansion coefficients of the semiconductor device and the member on which the semiconductor device is mounted differ, thermal fatigue and stress accumulation are suppressed, preventing damage to the semiconductor device structure on which the semiconductor device is mounted. Furthermore, according to an embodiment of the conductive adhesive film of the present invention, by providing a first adhesive layer and a second adhesive layer containing copper (Cu), tin (Sn), a bismaleimide resin, and an organic phosphine represented by the above general formula (1) and/or an organic sulfide represented by the above general formula (2), a conductive adhesive film with excellent thermal fatigue resistance, ease of sintering, and void prevention can be obtained without using expensive precious metals.

Furthermore, according to an embodiment of the conductive adhesive film of the present invention, the first adhesive layer and the second adhesive layer contain an alloy containing copper (Cu) and nickel (Ni) and/or an alloy containing tin (Sn) and nickel (Ni), and have at least one endothermic peak within the temperature range of 100°C to 250°C in differential scanning calorimetry, and do not have this endothermic peak after heating at 250°C for 5 minutes in a nitrogen atmosphere at atmospheric pressure.This allows the first adhesive layer and the second adhesive layer to be sintered at atmospheric pressure, at a low temperature, and in a short time, thereby reliably improving the ease of sintering.

Furthermore, according to an embodiment of the conductive adhesive film of the present invention, the soft, highly thermally conductive metal contains at least one metal selected from the group consisting of aluminum (Al) with a purity of 99.99% by mass or more and zinc (Zn) with a purity of 99% by mass or more. This makes it possible to more reliably prevent damage to the semiconductor device structure on which the semiconductor device is mounted, even if the thermal expansion coefficients of the semiconductor device and the member on which the semiconductor device is mounted differ.

Furthermore, according to an embodiment of the conductive adhesive film of the present invention, a first barrier layer containing at least one metal component selected from the group consisting of molybdenum (Mo), chromium (Cr), titanium (Ti), nickel (Ni), tin (Sn), and copper (Cu) is further provided between the stress relaxation layer and the first adhesive layer, and a second barrier layer containing at least one metal component selected from the group consisting of molybdenum (Mo), chromium (Cr), titanium (Ti), nickel (Ni), tin (Sn), and copper (Cu) is further provided between the stress relaxation layer and the second adhesive layer. This prevents the metal component of the stress relaxation layer from diffusing into the first adhesive layer and the second adhesive layer, thereby preventing the formation of an alloy phase containing copper and tin from being inhibited by the metal component of the stress relaxation layer and further improving sinterability.

Furthermore, according to an embodiment of the conductive adhesive film of the present invention, the first adhesive layer and the second adhesive layer further contain a compound represented by the above general formula (3), which acts as a curing agent for the bismaleimide resin, thereby improving the heat resistance of the first adhesive layer and the second adhesive layer. Furthermore, the compound represented by the above general formula (3) is a non-oxide compound and does not interfere with the reducing agent, the organic phosphine represented by the above general formula (1) and/or the organic sulfide represented by the above general formula (2), thereby preventing the loss of void prevention properties.

1 is a cross-sectional view schematically illustrating an outline of a conductive adhesive film according to one embodiment of the present invention. FIG. 2 is a cross-sectional view schematically illustrating an outline of a conductive adhesive film according to another embodiment of the present invention. 1 is a cross-sectional view showing an outline of a semiconductor device structure according to an embodiment of the present invention; 1 is a cross-sectional schematic diagram showing an overview of a dicing die bond film in one embodiment of the dicing die bond film according to the present invention.

Embodiments of the conductive adhesive film of the present invention, a method for joining dissimilar materials using a conductive adhesive film, a semiconductor device structure having a conductive adhesive film, and a dicing die bond film having a conductive adhesive film are described in detail below with reference to the drawings.

<Conductive adhesive film>
1 , the conductive adhesive film 10 of the present invention is a conductive adhesive film for bonding a semiconductor device and a member, and comprises a predetermined stress relaxation layer 1, a predetermined first adhesive layer 2 provided on the side of the stress relaxation layer 1 to which the semiconductor device is bonded, and a predetermined second adhesive layer 3 provided on the side of the stress relaxation layer 1 opposite to the side to which the semiconductor device is bonded. The stress relaxation layer 1 has a first main surface and a second main surface opposite to the first main surface, and the first adhesive layer 2 is provided on the first main surface, which is the side to which the semiconductor device is bonded, and the second adhesive layer 3 is provided on the second main surface, which is the side to which a member is bonded.

The overall thickness of the conductive adhesive film of the present invention can be selected appropriately depending on the conditions of use of the conductive adhesive film, etc., but the lower limit is preferably 10 μm, more preferably 30 μm, and particularly preferably 50 μm, from the viewpoint of further alleviating the thermal stress that occurs between the semiconductor device and the member on which the semiconductor device is mounted. On the other hand, the upper limit of the overall thickness of the conductive adhesive film is preferably 300 μm, more preferably 250 μm, and particularly preferably 200 μm, from the viewpoint of preventing an increase in the thermal resistance of the conductive adhesive film and improving its heat dissipation characteristics.

(1) Stress Relief Layer The stress relief layer in the conductive adhesive film of the present invention is composed of a soft, highly thermally conductive metal having a Young's modulus at 25°C of 110 GPa or less, a thermal conductivity at 25°C of 100 W/m·K or more, and a volume resistivity of 100 μΩ·cm or less. The stress relief layer is a layer that relieves thermal stress that occurs between a semiconductor device and a member on which the semiconductor device is mounted. The conductive adhesive film of the present invention has a stress relief layer composed of the above-mentioned soft, highly thermally conductive metal, which provides excellent thermal conductivity and electrical conductivity. Furthermore, even if the thermal expansion coefficients of the semiconductor device and the member on which the semiconductor device are mounted are different, the conductive adhesive film can flexibly deform in response to thermal stress. This suppresses thermal fatigue and stress accumulation between the semiconductor device and the member on which the semiconductor device is mounted, thereby preventing damage to the semiconductor device structure on which the semiconductor device is mounted.

The soft, highly thermally conductive metal is not particularly limited as long as it is a metal member having the following characteristics: Young's modulus at 25°C of 110 GPa or less, thermal conductivity at 25°C of 100 W/m·K or more, and volume resistivity of 100 μΩ·cm or less. However, even if the thermal expansion coefficients of the semiconductor device and the member on which the semiconductor device is mounted differ, aluminum (Al) with a purity of 99.99% by mass or more and zinc (Zn) with a purity of 99% by mass or more are preferred, and aluminum (Al) with a purity of 99.99% by mass or more is particularly preferred, as these can more reliably suppress thermal fatigue and stress accumulation between the semiconductor device and the member on which the semiconductor device is mounted, thereby more reliably preventing damage to the semiconductor device structure on which the semiconductor device is mounted.

The stress relaxation layer may be composed of a single layer of the soft, highly thermally conductive metal, or multiple layers of the soft, highly thermally conductive metal. If the stress relaxation layer is composed of multiple layers of the soft, highly thermally conductive metal, it may be composed solely of layers of aluminum (Al) with a purity of 99.99% by mass or more, or solely of layers of zinc (Zn) with a purity of 99% by mass or more, or may be composed of layers of aluminum (Al) with a purity of 99.99% by mass or more and layers of zinc (Zn) with a purity of 99% by mass or more.

As a physical property of the soft, highly thermally conductive metal, the Young's modulus at 25°C is preferably 100 GPa or less, and more preferably 80 GPa or less. On the other hand, the lower limit of the Young's modulus at 25°C is not particularly limited, but from the perspective of imparting a certain level of strength to the stress relaxation layer, it is preferably 17 GPa or more.

Furthermore, the thermal conductivity of the soft, highly thermally conductive metal at 25°C is preferably 150 W/m·K or more, and more preferably 200 W/m·K or more.

Furthermore, the volume resistivity of the soft, highly thermally conductive metal is preferably 40 μΩ·cm or less, and more preferably 10 μΩ·cm or less.

The thickness of the stress relaxation layer can be selected appropriately depending on the conditions of use of the conductive adhesive film of the present invention, but the lower limit is preferably 5 μm, more preferably 20 μm, and particularly preferably 40 μm, from the viewpoint of further relaxing the thermal stress that occurs between the semiconductor device and the member on which the semiconductor device is mounted. On the other hand, the upper limit of the thickness of the stress relaxation layer is preferably 250 μm, more preferably 200 μm, and particularly preferably 150 μm, from the viewpoint of preventing an increase in the thermal resistance of the conductive adhesive film and improving its heat dissipation characteristics.

(2) First Adhesive Layer The first adhesive layer is provided on the side of the above-mentioned stress relaxation layer to which the semiconductor device is bonded, and contains copper (Cu), tin (Sn), a bismaleimide resin, and an organic phosphine represented by the following general formula (1) and/or an organic sulfide represented by the following general formula (2).
(C6)
R ¹ -P(R ² )-R ³ -P(R ⁴ )-R ⁵ ...(1)
(In the general formula (1), R ¹ , R ² , R ³ , R ⁴ , and R ⁵ each independently represent an aromatic or aliphatic organic group containing carbon (C) and hydrogen (H), and are each a functional group
does not contain in the structure.)
(Chem.8)
R ⁶ -S-R ⁷ ...(2)
(In the general formula (2), R ⁶ and R ⁷ each independently represent an aromatic or aliphatic organic group containing carbon (C) and hydrogen (H), and are each a functional group
does not contain in the structure.)

When the conductive adhesive film of the present invention is heat-treated, the copper (Cu) and tin (Sn) components in the first adhesive layer are sintered by a transient liquid phase sintering (TLPS) reaction or the like, and in the state after sintering (sintered state), they become an alloy phase containing copper (Cu) and tin (Sn), resulting in an increase in the melting point. Furthermore, a semiconductor device is bonded to the first adhesive layer with its melting point increased. Therefore, even when the operating temperature of semiconductor devices such as power semiconductors is high, the bonding reliability between the first adhesive layer and the semiconductor device is excellent.

The first adhesive layer contains at least copper (Cu) and tin (Sn) as metal components, but does not contain precious metal components such as silver. Therefore, the first adhesive layer does not contain expensive precious metals.

In the conductive adhesive film of the present invention, the organic phosphine represented by the following general formula (1) and the organic sulfide represented by the following general formula (2) function as a reducing agent.
(Chem.10)
R ¹ -P(R ² )-R ³ -P(R ⁴ )-R ⁵ ...(1)
(In the general formula (1), R ¹ , R ² , R ³ , R ⁴ , and R ⁵ each independently represent an aromatic or aliphatic organic group containing carbon (C) and hydrogen (H), and are each a functional group
does not contain in the structure.)
(Chem.12)
R ⁶ -S-R ⁷ ...(2)
(In the general formula (2), R ⁶ and R ⁷ each independently represent an aromatic or aliphatic organic group containing carbon (C) and hydrogen (H), and are each a functional group
does not contain in the structure.)

If an oxide film forms on the copper and tin metal components of the first adhesive layer, when the power semiconductor is bonded to a substrate, lead frame, or other component by sintering such as transient liquid phase sintering (TLPS), the oxide film inhibits the sintering reaction, i.e., inhibits the formation of an alloy phase containing copper and tin. However, the organic phosphine represented by general formula (1) and the organic sulfide represented by general formula (2) reduce the oxide film, preventing the formation of an oxide film on the copper and tin. Therefore, even when using copper and tin, which are metal components that oxidize more easily than noble metals, the formation of an oxide film on the copper and tin can be prevented, promoting sintering reactions such as transient liquid phase sintering, facilitating sintering and promoting the formation of an alloy phase containing copper and tin.

Neither the organic phosphine represented by general formula (1) nor the organic sulfide represented by general formula (2) contains the following functional group in its chemical structure: Therefore, when the organic phosphine represented by general formula (1) reduces the oxide film and chemically changes to an organic phosphine oxide, and when the organic sulfide represented by general formula (2) reduces the oxide film and chemically changes to an organic sulfoxide, no water molecules are generated as a by-product.

When the organic phosphine represented by general formula (1) chemically changes to organic phosphine oxide and the organic sulfide represented by general formula (2) chemically changes to organic sulfoxide, no water molecules are generated as by-products, preventing the formation of voids in the first adhesive layer in a sintered state. In other words, the organic phosphine represented by general formula (1) and the organic sulfide represented by general formula (2) have excellent void prevention properties. From the above, by having the first adhesive layer contain an organic phosphine represented by general formula (1) and/or an organic sulfide represented by general formula (2), it is not necessary to subject a semiconductor device structure in which a power semiconductor is mounted on a substrate or the like to pressure treatment to eliminate voids, and therefore damage such as cracking can be prevented from occurring in the power semiconductor.

The conductive adhesive film of the present invention may contain, as a reducing agent, either an organic phosphine represented by general formula (1) or an organic sulfide represented by general formula (2), or may use both an organic phosphine represented by general formula (1) and an organic sulfide represented by general formula (2) in combination.

The melting point of the organic phosphine represented by general formula (1) is not particularly limited, but from the perspective of storage stability, it is preferable that the organic phosphine maintain a fine crystalline state before being introduced into the semiconductor device mounting process. This suppresses diffusion within the conductive adhesive film composition system, thereby preventing the reaction from proceeding too quickly. However, when the organic phosphine is introduced into the semiconductor device mounting process and heating is initiated, diffusion within the conductive adhesive film composition system begins quickly, allowing the reaction to begin. From this perspective, a melting point of 60°C or higher is preferred, and 80°C or higher is particularly preferred.

Specific examples of organic phosphines represented by general formula (1) include organic phosphines having a xanthene skeleton. Specifically, in general formula (1), R ¹ , R ² , R ⁴ , and R ⁵ are each aromatic and R ³ is an aromatic compound having a xanthene skeleton, and it is particularly preferred that R ¹ , R ² , R ⁴ , and R ⁵ are each an optionally substituted phenyl group, and R ³ is an aromatic compound having a xanthene skeleton. Furthermore, in general formula (1), it is preferred that R ¹ , R ² , R ⁴ , and R ⁵ are each aromatic and R ³ is an aliphatic group, and it is particularly preferred that R ¹ , R ² , R ⁴ , and R ⁵ are each an optionally substituted phenyl group, and R ³ is an aliphatic group having 1 to 10 carbon atoms.

The melting point of the organic sulfide represented by general formula (2) is not particularly limited, but from the perspective of storage stability, it is preferable that the organic sulfide maintain a fine crystalline state before being introduced into the semiconductor device mounting process. This suppresses diffusion within the conductive adhesive film composition system, thereby preventing the reaction from proceeding prematurely, and yet, when introduced into the semiconductor device mounting process and heating begins, it is preferable that diffusion within the conductive adhesive film composition system quickly begins, allowing the reaction to begin. From this perspective, a melting point of 60°C or higher is preferred, and 80°C or higher is particularly preferred.

Specifically, the organic sulfide represented by general formula (2) is preferably an organic sulfide having an acrylic group and/or a methacrylic group and/or a vinyl ether group, i.e., ^R6 and ^R7 are each organic groups having an acrylic group and/or a methacrylic group and/or a vinyl ether group, and particularly preferably an organic group having an acrylic group and/or a methacrylic group, because it can crosslink with the bismaleimide resin described later and contribute to improving thermal fatigue resistance. Note that ^R6 and ^R7 may each be organic groups having an aliphatic group such as an acrylic group and/or a methacrylic group and/or a vinyl ether group and an aromatic group consisting of a phenyl group.

The conductive adhesive film of the present invention uses bismaleimide resin as the thermosetting resin. This resin forms a crosslinked polyimide with excellent heat resistance upon thermosetting, as it can withstand the high operating temperatures of power semiconductors and does not contain protonic hydroxyl groups, preventing the generation of outgassing. Furthermore, bismaleimide resin has stress relaxation properties, which improves the thermal fatigue resistance of the conductive adhesive film after sintering.

The amounts of the metal component containing copper and tin, the reducing agent composed of an organic phosphine represented by general formula (1) and/or an organic sulfide represented by general formula (2), and the bismaleimide resin in the first adhesive layer are not particularly limited. The lower limit of the amount of the metal component containing copper and tin in 100% by mass of the first adhesive layer is preferably 60% by mass, more preferably 70% by mass, and particularly preferably 75% by mass, from the viewpoint of obtaining a sintered first adhesive layer and improving the bonding reliability of the semiconductor device. On the other hand, the upper limit of the amount of the metal component containing copper and tin in 100% by mass of the first adhesive layer is preferably 95% by mass, more preferably 90% by mass, and particularly preferably 85% by mass.

The lower limit of the amount of the reducing agent composed of an organic phosphine represented by general formula (1) and/or an organic sulfide represented by general formula (2) in 100% by mass of the first adhesive layer is preferably 0.1% by mass, more preferably 1.0% by mass, and particularly preferably 1.5% by mass, in order to improve sintering ease and void prevention. On the other hand, the upper limit of the amount of the reducing agent composed of an organic phosphine represented by general formula (1) and/or an organic sulfide represented by general formula (2) in 100% by mass of the first adhesive layer is preferably 20% by mass, more preferably 10% by mass, and particularly preferably 5% by mass.

The lower limit of the amount of bismaleimide resin in 100% by mass of the first adhesive layer is preferably 5% by mass, more preferably 10% by mass, and particularly preferably 15% by mass, in order to further improve thermal fatigue resistance. On the other hand, the upper limit of the amount of bismaleimide resin in 100% by mass of the first adhesive layer is preferably 40% by mass, more preferably 35% by mass, and particularly preferably 30% by mass.

From the above, the conductive adhesive film of the present invention has a first adhesive layer containing copper, tin, bismaleimide resin, and an organic phosphine represented by the above general formula (1) and/or an organic sulfide represented by the above general formula (2), making it possible to obtain a conductive adhesive film with excellent thermal fatigue resistance, ease of sintering, and void prevention properties without using expensive precious metals.

In the conductive adhesive film of the present invention, the first adhesive layer may contain nickel (Ni) as a metal component in addition to copper and tin, as necessary. That is, the metal component may be an alloy containing copper (Cu) and nickel (Ni) and/or an alloy containing tin (Sn) and nickel (Ni). Nickel promotes the formation of an alloy phase (intermetallic compound) containing copper and tin during sintering, thereby shortening the sintering reaction time.

Furthermore, when the first adhesive layer contains nickel (Ni), in differential scanning calorimetry (DSC) analysis, it is preferable that the material has at least one endothermic peak within the temperature range of 100°C to 250°C in the state before sintering (unsintered state), and that after heating at 250°C for 5 minutes in a nitrogen atmosphere at normal pressure, i.e., in the state after sintering (sintered state), the endothermic peak does not exist and the endothermic peak disappears.

In the unsintered state, at least one endothermic peak observed within the above temperature range represents the melting point of at least one metal element that constitutes the metal component containing copper, tin, and nickel. In other words, when the unsintered first adhesive layer is heated (sintered) within the above temperature range, a specific metal component melts and spreads across the surface of the adherend (power semiconductor), advantageously enabling the mounting of power semiconductors at low temperatures. On the other hand, in the sintered state, no endothermic peak is observed within the above temperature range, which means that the melting point of the metal component containing copper, tin, and nickel does not exist within the above temperature range. In other words, once melted, the metal forms an alloy phase (intermetallic compound) containing copper and tin with a high melting point after sintering due to a diffusion reaction between the metals, resulting in excellent heat resistance.

The endothermic peak disappears after heating at 250°C for 5 minutes in a nitrogen atmosphere at normal pressure, meaning the first adhesive layer can be sintered at normal pressure, at low temperature, and in a short time, thereby significantly improving the ease of sintering the first adhesive layer. Furthermore, the first adhesive layer can be sintered at low temperatures (for mounting power semiconductors), yet exhibits excellent heat resistance after sintering (for mounting power semiconductors).

The amount of nickel in 100% by mass of the first adhesive layer is not particularly limited, but the lower limit is preferably 0.01% by mass, more preferably 0.02% by mass, and particularly preferably 0.05% by mass, in order to further improve the sintering reactivity of copper and tin. On the other hand, the upper limit of the amount of nickel in 100% by mass of the first adhesive layer is preferably 20% by mass, more preferably 15% by mass, and particularly preferably 10% by mass.

In the conductive adhesive film of the present invention, the first adhesive layer may further contain a compound represented by the following general formula (3), if necessary.
(Chem.15)
Ar ¹ -C(R ⁸ )(R ⁹ )-C(R ¹⁰ )(R ¹¹ )-Ar ² ...(3)
(In general formula (3), Ar ¹ and Ar ² each independently represent an aromatic group, and R ⁸ , R ⁹ , R ¹⁰ , and R ¹¹ each independently represent an aliphatic group.)

The compound represented by the general formula (3) above is a thermal radical initiator and acts as a curing agent for the bismaleimide resin, improving the heat resistance and thermal fatigue resistance of the first adhesive layer. Furthermore, the compound represented by the general formula (3) above is a non-oxide compound and does not interfere with the reducing agents, the organic phosphine represented by the general formula (1) and/or the organic sulfide represented by the general formula (2), thereby preventing the void prevention properties of the first adhesive layer from being impaired.

In general formula (3), Ar ¹ and Ar ² are each preferably a phenyl group which may have a substituent, and R ⁸ , R ⁹ , R ¹⁰ and R ¹¹ are each preferably independently an aliphatic group having 1 to 10 carbon atoms, and it is particularly preferred that Ar ¹ and Ar ² are each a phenyl group, and R ⁸ , R ⁹ , R ¹⁰ and R ¹¹ are each independently an aliphatic group having 1 to 5 carbon atoms.

The amount of the compound represented by general formula (3) in 100% by mass of the first adhesive layer is not particularly limited, but the lower limit is preferably 0.01% by mass, more preferably 0.05% by mass, and particularly preferably 0.1% by mass, in order to further improve the heat resistance and thermal fatigue resistance of the first adhesive layer. On the other hand, the upper limit of the amount of the compound represented by general formula (3) in 100% by mass of the first adhesive layer is preferably 2% by mass, more preferably 1% by mass, and particularly preferably 0.5% by mass.

The thickness of the first adhesive layer can be selected appropriately depending on the conditions of use of the conductive adhesive film of the present invention, but the lower limit is preferably 1 μm, more preferably 4 μm, and particularly preferably 8 μm, from the viewpoint of ensuring reliable bonding between the semiconductor device and the stress relaxation layer. On the other hand, the upper limit of the thickness of the first adhesive layer is preferably 50 μm, more preferably 40 μm, and particularly preferably 30 μm, from the viewpoint of preventing an increase in the thermal resistance of the conductive adhesive film and improving its heat dissipation characteristics.

(3) Second Adhesive Layer The second adhesive layer is provided on the side of the stress relaxation layer opposite to the side to which the semiconductor device is bonded. For example, the second adhesive layer is provided on the side of the stress relaxation layer to which a member such as a lead frame or a substrate is bonded.

The second adhesive layer has the same component composition as the first adhesive layer described above, i.e., the second adhesive layer contains copper (Cu), tin (Sn), a bismaleimide resin, and an organic phosphine represented by the following general formula (1) and/or an organic sulfide represented by the following general formula (2):
(Chem.16)
R ¹ -P(R ² )-R ³ -P(R ⁴ )-R ⁵ ...(1)
(In the general formula (1), R ¹ , R ² , R ³ , R ⁴ , and R ⁵ each independently represent an aromatic or aliphatic organic group containing carbon (C) and hydrogen (H), and are each a functional group
does not contain in the structure.)
(Chem.18)
R ⁶ -S-R ⁷ ...(2)
(In the general formula (2), R ⁶ and R ⁷ each independently represent an aromatic or aliphatic organic group containing carbon (C) and hydrogen (H), and are each a functional group
does not contain in the structure.)

The second adhesive layer, like the first adhesive layer, may further contain nickel (Ni) as a metal component in addition to copper and tin, if necessary. Also, like the first adhesive layer, the second adhesive layer may further contain a compound represented by the following general formula (3), if necessary.
(C20)
Ar ¹ -C(R ⁸ )(R ⁹ )-C(R ¹⁰ )(R ¹¹ )-Ar ² ...(3)
(In general formula (3), Ar ¹ and Ar ² each independently represent an aromatic group, and R ⁸ , R ⁹ , R ¹⁰ , and R ¹¹ each independently represent an aliphatic group.)

The second adhesive layer has the same component composition as the first adhesive layer described above, so detailed explanations of each component and their effects will be omitted.

The thickness of the second adhesive layer can be selected appropriately depending on the conditions of use of the conductive adhesive film of the present invention, but the lower limit is preferably 1 μm, more preferably 4 μm, and particularly preferably 8 μm, from the viewpoint of ensuring reliable bonding between the stress relief layer and components such as a lead frame or substrate. On the other hand, the upper limit of the thickness of the first adhesive layer is preferably 50 μm, more preferably 40 μm, and particularly preferably 30 μm, from the viewpoint of preventing an increase in the thermal resistance of the conductive adhesive film and improving its heat dissipation characteristics.

(4) First Barrier Layer As shown in FIG. 2, in the conductive adhesive film 10 of the present invention, if necessary, a first barrier layer 4 containing at least one metal component selected from the group consisting of molybdenum (Mo), chromium (Cr), titanium (Ti), nickel (Ni), tin (Sn) and copper (Cu) may further be provided between the stress relief layer 1 and the first adhesive layer 2.

By further providing a first barrier layer 4 between the stress relaxation layer 1 and the first adhesive layer 2, the metal components of the stress relaxation layer 1 can be prevented from diffusing into the first adhesive layer 2, preventing the formation of an alloy phase containing copper and tin in the first adhesive layer 2 from being inhibited by the metal components of the stress relaxation layer 1, further improving the ease of sintering of the first adhesive layer 2.

(5) Second Barrier Layer As shown in FIG. 2, in the conductive adhesive film 10 of the present invention, if necessary, a second barrier layer 5 containing at least one metal component selected from the group consisting of molybdenum (Mo), chromium (Cr), titanium (Ti), nickel (Ni), tin (Sn) and copper (Cu) may be further provided between the stress relief layer 1 and the second adhesive layer 3.

By further providing a second barrier layer 5 between the stress relaxation layer 1 and the second adhesive layer 3, the metal components of the stress relaxation layer 1 can be prevented from diffusing into the second adhesive layer 3, preventing the formation of an alloy phase containing copper and tin in the second adhesive layer 3 from being inhibited by the metal components of the stress relaxation layer 1, further improving the ease of sintering of the second adhesive layer 3.

<Method of manufacturing conductive adhesive film>
Next, an example of a method for producing the conductive adhesive film of the present invention will be described. First, the components constituting the first adhesive layer and the second adhesive layer are dissolved in an organic solvent such as toluene to prepare a conductive composition constituting the first adhesive layer and the second adhesive layer. The prepared conductive composition is then applied to both sides of a film-like soft, highly thermally conductive metal constituting the stress relief layer to a desired thickness. The application method is not particularly limited, and examples include known application methods such as a comma coater, screen printing, bar coater, applicator, blade coater, knife coater, roll coater, and gravure coater. After application of the conductive composition, a drying process is performed at 100°C to 150°C for 1 minute to 30 minutes, thereby forming a first adhesive layer on the first main surface of the stress relief layer, which is the side to which the semiconductor device is bonded, and a second adhesive layer on the second main surface, which is the side to which the member is bonded.

If a first barrier layer and a second barrier layer are further provided, before applying the conductive composition to the soft, highly thermally conductive metal, the first barrier layer and the second barrier layer are formed on both sides of the soft, highly thermally conductive metal by sputtering or the like, and the conductive composition is then applied onto the first and second barrier layers.

<Method for joining different materials using conductive adhesive film>
As described above, the conductive adhesive film of the present invention can bond components with different thermal expansion coefficients while suppressing thermal fatigue and stress accumulation, so that the conductive adhesive film can be used to bond different materials with different linear expansion coefficients. Furthermore, as described above, the conductive adhesive film of the present invention can bond different materials under easy sintering conditions because the first adhesive layer and the second adhesive layer are sintered at normal pressure, at low temperature, and in a short time.

First, components with different thermal expansion coefficients are prepared, such as a SiC power semiconductor and a lead frame or substrate on which the SiC power semiconductor is mounted. Next, a structure is formed in which the conductive adhesive film of the present invention is sandwiched between the SiC power semiconductor and the lead frame or substrate. The formed structure is then heat-treated at atmospheric pressure in an inert gas (e.g., nitrogen gas) atmosphere at a temperature of 275°C or less for less than 10 minutes. The above heat treatment (pressureless sintering) puts the first adhesive layer and second adhesive layer into a sintered state, making it possible to bond dissimilar materials (SiC power semiconductor and lead frame or substrate) with different linear expansion coefficients.

The lower limit of the heating temperature for the above heat treatment is, for example, 230°C, and preferably 250°C. The lower limit of the heating time for the above heat treatment is, for example, 3 minutes, and preferably 5 minutes.

<Semiconductor device structure>
3, the semiconductor device structure 100 of the present invention has a structure in which a semiconductor device 20 such as a power semiconductor is mounted on a member such as a substrate or lead frame 30. In this structure, in the semiconductor device structure 100, the semiconductor device 20 is bonded to the first adhesive layer of the conductive adhesive film 10 of the present invention described above, and the substrate or lead frame 30 is bonded to the second adhesive layer of the conductive adhesive film 10 of the present invention described above.

As described above, the semiconductor device structure of the present invention has a structure in which a semiconductor device such as a power semiconductor is mounted on a member such as a substrate or lead frame via the conductive adhesive film of the present invention. Furthermore, in the semiconductor device structure of the present invention, the conductive adhesive film of the present invention has the function of bonding the semiconductor device such as a power semiconductor to a member such as a substrate or lead frame.

The semiconductor device structure of the present invention can be manufactured, for example, by placing a semiconductor device such as a power semiconductor on the surface of a substrate or lead frame or other member via the conductive adhesive film of the present invention, and then performing a heat treatment (e.g., reflow treatment) at atmospheric pressure in an inert gas (e.g., nitrogen gas) atmosphere at a temperature of 275°C or less for less than 10 minutes.

The lower limit of the heating temperature for the above heat treatment is, for example, 230°C, and preferably 250°C. The lower limit of the heating time for the above heat treatment is, for example, 3 minutes, and preferably 5 minutes.

<Dicing die bond film>
4, the dicing die bond film 200 of the present invention has a structure in which a dicing tape 40 is attached to the second adhesive layer side of the above-described conductive adhesive film 10 of the present invention. That is, the dicing die bond film 200 of the present invention has an embodiment in which the conductive adhesive film 10 of the present invention and the dicing tape 40 are integrated.

By attaching a semiconductor wafer to the first adhesive layer of the conductive adhesive film of the present invention, the semiconductor wafer can be attached to the dicing tape via the conductive adhesive film of the present invention. The dicing die bond film of the present invention allows the semiconductor wafer to be attached to the dicing tape via the conductive adhesive film of the present invention, preventing the semiconductor chips from flying off when the semiconductor wafer is diced to a predetermined size to produce semiconductor chips.

Next, examples of the present invention will be described, but the present invention is not limited to these examples as long as they do not deviate from the spirit of the invention. Room temperature is defined as being within the range of 25°C ± 5°C.

[0049] The components shown in Tables 1 to 3 below were dissolved in 100 ml of toluene in the formulations shown in Tables 1 to 3 below to prepare conductive compositions constituting the first adhesive layer and the second adhesive layer used in Examples 1 to 12 and Comparative Examples 1 to 4. The prepared conductive compositions were then applied using a comma coater to both sides of the metal films constituting the stress relaxation layers shown in Tables 1 to 3 below, and dried at 130°C for 3 minutes to form a first adhesive layer on the first main surface of the stress relaxation layer and a second adhesive layer on the second main surface, thereby preparing the conductive adhesive films of Examples 1 to 12 and Comparative Examples 2 to 4. In Comparative Example 1, the first adhesive layer and the second adhesive layer were directly bonded together to prepare the conductive adhesive film.

In Examples 7 to 12, the first and second barrier layers were formed by sputtering on both sides of the metal film that constitutes the stress relaxation layer before the conductive composition was applied to the metal film that constitutes the stress relaxation layer, and then the conductive composition was applied to the formed first and second barrier layers using a comma coater.

Dicing tape having an acrylic adhesive on a polyolefin substrate was attached to the conductive adhesive film prepared as described above to obtain dicing die bond films for Examples 1 to 12 and Comparative Examples 1 to 4.

Details of each component in Tables 1 to 3 are as follows:
Nofumer BC (non-oxide): 2,3-dimethyl-2,3-diphenylbutane, a curing agent for bismaleimide resin, manufactured by NOF Corporation.

Mounting Process Using the dicing die bond film of Examples 1 to 12 and Comparative Examples 1 to 4, a 0.2 mm thick Ag metallized SiC chip was bonded at 70 °C, and then diced to a size of 5 mm x 5 mm to obtain a SiC chip with a conductive adhesive film. The obtained SiC chip with the conductive adhesive film was picked up with a pickup die bonder and die-attached to an active metal copper circuit board (AMC board) with a Cu outer surface at 90 °C for 2 seconds. The die-attached sample was then mounted using a reflow furnace in a nitrogen atmosphere at normal pressure at the sintering temperatures and times listed in Tables 1 to 3, to obtain mounted samples of Examples 1 to 12 and Comparative Examples 1 to 4.

The evaluation and measurement items are as follows:

(1) Thermal fatigue resistance 1
The mounted samples of Examples 1 to 12 and Comparative Examples 1 to 4 were subjected to a thermal shock test (TCT) in a temperature range of -45°C to 200°C for 500 cycles, and the mounted samples after the test were visually inspected for peeling of the SiC chip and evaluated according to the following criteria, with a rating of △ or higher being considered a pass.
◯: No peeling △: Partial peeling ×: Peeling over the entire surface

(2) Thermal fatigue resistance 2
The mounted samples of Examples 1 to 12 and Comparative Examples 1 to 4 were subjected to a thermal shock test (TCT) in a temperature range of -45°C to 230°C for 1000 cycles, and the mounted samples after the test were visually inspected for peeling of the SiC chip and evaluated according to the following criteria, with a rating of △ or higher being considered a pass.
◯: No peeling △: Partial peeling ×: Peeling over the entire surface

(3) Shortest sintering time A conductive adhesive film was collected from the mounting samples of Examples 1 to 12, weighed out to 10 mg, and sealed in a dedicated aluminum pan to prepare a measurement sample. Using a high-sensitivity differential scanning calorimeter (Hitachi High-Tech Science Corporation, DSC7000X), a DSC chart was obtained in a nitrogen atmosphere (nitrogen flow rate 20 mL/min) in the range of room temperature to 350°C at a temperature increase rate of 5°C/min. The obtained DSC chart gave the shortest sintering time at which the disappearance of the endothermic peak in the temperature range of 200 to 250°C was observed.

For the mounted samples of Comparative Examples 1 to 3, the sintering temperature in the mounting process was set to 350°C, and for the mounted sample of Comparative Example 4, the sintering temperature in the mounting process was set to 350°C and pressure was applied with a 250g tungsten weight. The shortest sintering time at which the endothermic peak disappeared was obtained in the same manner as in Examples 1 to 12.

(4) Void occurrence rate in sintered state For the mounted samples of Examples 1 to 12 and the mounted samples of Comparative Examples 1 to 4, the void occurrence rate (%) in the first adhesive layer and the second adhesive layer in the sintered state was detected by non-destructive internal inspection using ultrasonic flaw detection (SAT). Note that only the mounted sample of Comparative Example 4 was pressed using a tungsten weight during the mounting process. The void occurrence rate in the sintered state was evaluated according to the following criteria.
◎: Less than 3% 〇: 3% to 5% ×: More than 5%

(5) Reflow Workability A product having atmospheric pressure and a shortest sintering time of 10 minutes or less, which after reflowing under said conditions had a void generation rate in the sintered state rated as "○" or better, and which was also rated as "△" or better in a thermal shock test (TCT) in which 500 cycles were performed in a temperature range of -45°C to 200°C, was evaluated as "Excellent ◎". A product having atmospheric pressure and a shortest sintering time of more than 10 minutes, which after reflowing under said conditions had a void generation rate in the sintered state rated as "○" or better, and which was also rated as "△" or better in a thermal shock test (TCT) in which 500 cycles were performed in a temperature range of -45°C to 200°C, was evaluated as "○ Good". A product that did not satisfy even one of the conditions of atmospheric pressure, a shortest sintering time of 30 minutes or less, a void generation rate in the sintered state rated as "○" or better, and which was also rated as "△" or better in a thermal shock test (TCT) in which 500 cycles were performed in a temperature range of -45°C to 200°C, was evaluated as "× Poor".

The structure, components, and evaluation results of the conductive adhesive films of Examples 1 to 12 are shown in Tables 1 and 2 below, and the structure, components, and evaluation results of the conductive adhesive films of Comparative Examples 1 to 4 are shown in Table 3 below.

As shown in Tables 1 and 2, Examples 1 to 12, in which the first and second adhesive layers contained an organic phosphine represented by general formula (1) or an organic sulfide represented by general formula (2), exhibited excellent sintering ease with the shortest sintering time of 5 to 30 minutes at 270°C and atmospheric pressure. They also exhibited excellent void prevention, with a void generation rate of 5% or less in the sintered state. Furthermore, Examples 1 to 12, in which aluminum (Al) with a purity of 99.99% by mass or higher or zinc (Zn) with a purity of 99% by mass or higher was used as the stress relaxation layer, also exhibited excellent thermal fatigue resistance 1 and thermal fatigue resistance 2.

On the other hand, among Comparative Examples 1 to 4, in which the first and second adhesive layers did not contain either the organic phosphine represented by general formula (1) or the organic sulfide represented by general formula (2), Comparative Examples 1 to 3 did not achieve void prevention properties in the mounting process at normal pressure, and Comparative Example 4 required pressure treatment in the mounting process to achieve void prevention properties. Furthermore, Comparative Examples 1 to 4, in which aluminum (Al) with a purity of 99.99% by mass or higher or zinc (Zn) with a purity of 99% by mass or higher was not used as the stress relaxation layer, did not achieve thermal fatigue resistance in the mounting process at normal pressure.

REFERENCE SIGNS LIST 1 Stress relaxation layer 2 First adhesive layer 3 Second adhesive layer 4 First barrier layer 5 Second barrier layer 10 Conductive adhesive film 20 Semiconductor device 30 Substrate (lead frame)
40 Dicing tape 100 Semiconductor device structure 200 Dicing die bond film

Claims (12)

a stress relaxation layer made of a soft, highly thermally conductive metal having a Young's modulus at 25°C of 110 GPa or less, a thermal conductivity at 25°C of 100 W/m·K or more, and a volume resistivity of 100 μΩ·cm or less;
a first adhesive layer provided on the side of the stress relaxation layer to which a semiconductor device is bonded, the first adhesive layer including copper (Cu), tin (Sn), a bismaleimide resin, and an organic phosphine represented by the following general formula (1) and/or an organic sulfide represented by the following general formula (2);
a second adhesive layer provided on the side of the stress relaxation layer opposite to the side to which the semiconductor device is bonded, the second adhesive layer including copper (Cu), tin (Sn), a bismaleimide resin, and an organic phosphine represented by the following general formula (1) and/or an organic sulfide represented by the following general formula (2);
A conductive adhesive film for bonding a semiconductor device and a member, comprising:
(Chem.1)
R ¹ -P(R ² )-R ³ -P(R ⁴ )-R ⁵ ...(1)
(In the general formula (1), R ¹ , R ² , R ³ , R ⁴ , and R ⁵ each independently represent an aromatic or aliphatic organic group containing carbon (C) and hydrogen (H), and are each a functional group
does not contain in the structure.)
(Case 3)
R ⁶ -S-R ⁷ ...(2)
(In the general formula (2), R ⁶ and R ⁷ each independently represent an aromatic or aliphatic organic group containing carbon (C) and hydrogen (H), and are each a functional group
does not contain in the structure.) The conductive adhesive film according to claim 1, wherein the first adhesive layer and the second adhesive layer contain an alloy containing copper (Cu) and nickel (Ni) and/or an alloy containing tin (Sn) and nickel (Ni), have at least one endothermic peak within a temperature range of 100°C to 250°C in differential scanning calorimetry, and do not have the endothermic peak after heating at 250°C for 5 minutes in a nitrogen atmosphere at normal pressure. The conductive adhesive film according to claim 1 or 2, wherein the soft, highly thermally conductive metal comprises at least one metal selected from the group consisting of aluminum (Al) with a purity of 99.99% by mass or more and zinc (Zn) with a purity of 99% by mass or more. The conductive adhesive film according to claim 1 or 2, further comprising a first barrier layer between the stress relief layer and the first adhesive layer, the first barrier layer containing at least one metal component selected from the group consisting of molybdenum (Mo), chromium (Cr), titanium (Ti), nickel (Ni), tin (Sn), and copper (Cu), and a second barrier layer between the stress relief layer and the second adhesive layer, the second barrier layer containing at least one metal component selected from the group consisting of molybdenum (Mo), chromium (Cr), titanium (Ti), nickel (Ni), tin (Sn), and copper (Cu). The conductive adhesive film according to claim 1 or 2, wherein the melting point of the organic phosphine is 60°C or higher. The conductive adhesive film according to claim 1 or 2, wherein the organic phosphine has a xanthene skeleton. The conductive adhesive film according to claim 1 or 2, wherein the melting point of the organic sulfide is 60°C or higher. The conductive adhesive film according to claim 1 or 2, wherein the organic sulfide has an acrylic group and/or a methacrylic group and/or a vinyl ether group. The conductive adhesive film according to claim 1 or 2, wherein the first adhesive layer and the second adhesive layer further contain a compound represented by the following general formula (3):
(C5)
Ar ¹ -C(R ⁸ )(R ⁹ )-C(R ¹⁰ )(R ¹¹ )-Ar ² ...(3)
(In general formula (3), Ar ¹ and Ar ² each independently represent an aromatic group, and R ⁸ , R ⁹ , R ¹⁰ , and R ¹¹ each independently represent an aliphatic group.) A method for joining dissimilar materials having different linear expansion coefficients, using the conductive adhesive film described in claim 1 or 2, by pressureless sintering at 275°C or less for less than 10 minutes in a nitrogen atmosphere at atmospheric pressure. A semiconductor device structure in which the semiconductor device is bonded to the first adhesive layer of the conductive adhesive film described in claim 1 or 2, and a substrate or lead frame is bonded to the second adhesive layer of the conductive adhesive film described in claim 1 or 2, and the semiconductor device is mounted on the substrate or lead frame. A dicing die bond film in which dicing tape is attached to the second adhesive layer side of the conductive adhesive film described in claim 1 or 2.