Joining material and mounting structure using the same

Abstract

The bonding material comprises a first metal particle having a melting point of 200°C or lower, a second metal particle containing a second metal element capable of forming an intermetallic compound with the first metal element contained in the first metal particle, TiO2 nanoparticles, and a flux. The first metal particle is either a first metal element that forms an intermetallic compound with the second metal element, or a composite comprising a first metal element that forms an intermetallic compound with the second metal element and a third metal element that does not form an intermetallic compound with the second metal element and has a melting point of 250°C or higher. The ratio of the first metal particle to the second metal particle is a ratio in which, in the equilibrium phase diagram of the first metal element and the second metal element, both the first metal element contained in the first metal particle and the second metal element contained in the second metal particle become intermetallic compounds.

Description

Technology Field

[0001] The present invention relates to a bonding material for joining two members with a metal material used in devices such as power devices, and a mounting structure joined using said bonding material. Background Technology

[0002] In the case of [unclear],

[0003] In recent years, there has been a growing demand for high-current control aimed at energy conservation in devices such as power devices. Consequently, next-generation power device materials like SiC and GaN, which offer the advantage of high-efficiency power control, are increasingly replacing conventional Si materials.

[0004] These next-generation power device components have the advantage of being able to operate even at high temperatures and can withstand greater heat generation than conventional Si devices; therefore, as high current is controlled, an increase in the amount of heat generated by the device and a rise in temperature occur.

[0005] As a result, the junction temperature Tj between the electrode, such as a lead frame, which carries the controlled current in the device, and the device electrode rises. For example, while it was about 125°C in conventional Si, it rises to 200–250°C in SiC or GaN.

[0006] Therefore, the junction between the device electrode and the lead frame electrode requires thermal conductivity to efficiently dissipate generated heat into the lead frame, and heat resistance to withstand high junction temperatures Tj.

[0007] In addition, SiC and GaN, which are used in next-generation power devices, have higher elastic moduli and higher strength compared to Si. For example, while the elastic modulus of Si is 160 GPa, SiC and GaN are 200 GPa or higher. Consequently, thermal stress during temperature changes caused by the difference in linear expansion coefficients between the two materials increases. Therefore, it is also required to increase the bonding strength of the joint.

[0008] Conventionally, solder materials have been widely used as bonding materials for the joints of mounting structures that bond a device and a lead frame electrode with a conductor, as bonding is possible at low temperatures. However, for commonly used solder materials with Sn or Pb as the main components, 200°C to 250°C is a temperature near or above the melting point and is a very harsh temperature, so it is difficult to ensure heat resistance in mounting structures using these solders.

[0009] As a means of solving such problems, a bonding material of a liquid phase sintering method has been proposed, in which a low-melting-point metal and a second metal that forms an intermetallic compound with it are mixed, and during bonding, the low-melting-point metal melts and reacts with the second metal to form an intermetallic compound, thereby forming a high-melting-point bond.

[0010] As a bonding material for a conventional high-heat-resistant liquid-phase sintering method, there is a bonding material comprising at least two types of metal particles including at least Cu and a polymer having a polydimethylsiloxane backbone, wherein the metal particles are capable of forming an intermetallic compound (e.g., see Patent Document 1). Prior art literature

[0011] WO2016 / 031551 Public Notice

[0012] The bonding material according to the present invention comprises a first metal particle having a melting point of 200°C or lower, a second metal particle comprising a second metal element capable of forming an intermetallic compound with a first metal element included in the first metal particle, TiO2 nanoparticles, and a flux.

[0013] The first metal particle is either a first metal element that forms an intermetallic compound with a second metal element, or a complex comprising a first metal element that forms an intermetallic compound with a second metal element and a third metal element that does not form an intermetallic compound with the second metal element and has a melting point of 250°C or higher.

[0014] The ratio of the first metal particle to the second metal particle is the ratio in which the first metal element contained in the first metal particle and the second metal element contained in the second metal particle both become intermetallic compounds in the equilibrium phase diagram of the first metal element and the second metal element. Brief explanation of the drawing

[0015] [Fig. 1] This is a schematic diagram showing the composition of the bonding material according to the present embodiment 1. [Fig. 2] Table 1 shows the components included in the bonding materials in Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-12, their weight ratios, and evaluation results. [Fig. 3] Table 2 shows the components included in the bonding materials in Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-4, their weight ratios, and evaluation results. [Fig. 4] Table 3 shows the components included in the bonding material in Examples 3-1 to 3-11, their weight ratios, and evaluation results. Specific details for implementing the invention

[0016] In the bonding material described in Patent Document 1, a low-melting-point metal is melted and reacts with Cu to form a high-melting-point intermetallic compound, so it exhibits high heat resistance, but the crystal grains of the intermetallic compound may become coarse, making it difficult to improve bonding strength.

[0017] The present invention aims to solve the conventional problem by providing a bonding material capable of exhibiting higher bonding strength.

[0018] A bonding material according to the first aspect comprises a first metal particle having a melting point of 200°C or lower, a second metal particle comprising a second metal element capable of forming an intermetallic compound with a first metal element included in the first metal particle, TiO2 nanoparticles, and a flux.

[0019] The first metal particle is either one of a first metal element that forms an intermetallic compound with a second metal element, or a complex comprising a first metal element that forms an intermetallic compound with a second metal element and a third metal element that does not form an intermetallic compound with the second metal element and has a melting point of 250°C or higher.

[0020] The ratio of the first metal particle to the second metal particle is the ratio in which the first metal element contained in the first metal particle and the second metal element contained in the second metal particle both become intermetallic compounds in the equilibrium phase diagram of the first metal element and the second metal element.

[0021] In the bonding material according to the second aspect, the TiO2 nanoparticles in the first aspect may have a median diameter of 20 to 80 nm.

[0022] The bonding material according to the third aspect may have a content of TiO2 nanoparticles of 0.1 wt% to 1 wt% of the total sum of the first metal particles, the second metal particles, and the TiO2 nanoparticles in the first or second aspect.

[0023] The bonding material according to the fourth aspect is such that, in any one of the first to third aspects, the first metal particle may be at least one selected from the group consisting of Sn-Bi, Sn-In, Sn-Bi-In, Bi-In, and In.

[0024] The bonding material according to the fifth aspect may include, in any one of the first to fourth aspects, the second metal particle may contain Cu.

[0025] The bonding material according to the 6th aspect may include, in any one of the 1st to 5th aspects, at least a first metal particle having a median diameter of 3 to 30 μm.

[0026] In the bonding material according to the 7th sun, in any one of the 1st to 6th suns, the 2nd metal particle may have a median diameter of 100 to 2000 nm.

[0027] The mounting structure according to the eighth aspect comprises a power device element of SiC or GaN and a bonding material according to any one of the first to seventh aspects that bonds the electrode of the power device element and the external electrode.

[0028] According to the bonding material according to the above sun, it is possible to provide a bonding material capable of forming a bond with higher bonding strength by suppressing grain coarsening during the formation of intermetallic compounds in the liquid phase sintering method.

[0029] Hereinafter, the bonding material and mounting structure according to the embodiment will be described in detail with reference to the attached drawings.

[0030] (Embodiment 1)

[0031] <Joining Material>

[0032] FIG. 1 is a schematic diagram showing the composition of a bonding material according to the present embodiment 1.

[0033] The bonding material (101) according to the present embodiment 1 comprises a first metal particle (102) having a melting point of 200°C or lower, a second metal particle (103) containing a second metal element capable of forming an intermetallic compound with the first metal element included in the first metal particle (102), TiO2 nanoparticles (104), and a flux (105).

[0034] It is believed that by including TiO2 nanoparticles, the second metal element of the second metal particle diffuses into the first metal particle (102), and when an intermetallic compound is formed, the formation of primary crystal nuclei is promoted. In addition, it is believed that when the generated crystal nuclei grow, the solid TiO2 inhibits growth. By these, the crystal grains of the intermetallic compound can be refined.

[0035] The first metal particle is either one of a first metal element that forms an intermetallic compound with a second metal element, or a complex comprising a first metal element that forms an intermetallic compound with a second metal element and a third metal element that does not form an intermetallic compound with the second metal element and has a melting point of 250°C or higher.

[0036] The ratio of the first metal particle to the second metal particle is the ratio in which the first metal element contained in the first metal particle and the second metal element contained in the second metal particle both become intermetallic compounds in the equilibrium phase diagram of the first metal element and the second metal element.

[0037] As a result, the joint produced by the liquid phase sintering process using this bonding material does not remelt at temperatures below 250°C. Therefore, it is possible to exhibit high heat resistance so that the device does not melt even when the operating temperature after bonding is 200°C or higher.

[0038] Below, each component constituting this bonding material is described.

[0039] <First Metal Particle>

[0040] The first metal particle (102) contains a first metal element that becomes a liquid component in the process of liquid phase sintering and reacts with the second metal particle (103) to produce a high melting point intermetallic compound.

[0041] The first metal particle (102) is composed of an alloy or a single metal having a melting point of 200°C or lower. This enables liquid phase sintering at a low temperature of 200°C or lower.

[0042] As for the alloy or single metal constituting the first metal particle (102), it may be an alloy or single metal having a melting point of 200°C or lower, but it is particularly preferred to be one selected from the group consisting of Sn-Bi, Sn-In, Sn-Bi-In, Bi-In, and In.

[0043] The first metal element is, for example, Sn or In. Meanwhile, the first metal element is not limited to one type and may include both Sn and In. The first metal element forms an intermetallic compound with the second metal element contained in the second metal particle (103).

[0044] <Second Metal Particle>

[0045] The second metal particle (103) includes a second metal element capable of forming an intermetallic compound with the first metal element contained in the first metal particle (102). By this, it can be dissolved in the first metal particle in a molten state to form a high-melting-point intermetallic compound with the first metal element contained in the first metal particle (102).

[0046] The second metal particle (103) may include a second metal element capable of forming at least one intermetallic compound with the first metal element included in the first metal particle (102).

[0047] As for the second metallic element, for example, it is Cu. Meanwhile, the second metallic element is not limited to Cu, but it is preferable that it contains Cu.

[0048] Additionally, the first metal particle (102) is one of a composite comprising only the first metal element that forms an intermetallic compound with the second metal element, or the first metal element that forms an intermetallic compound with the second metal element and the third metal element that does not form an intermetallic compound with the second metal element and has a melting point of 250°C or higher.

[0049] The third metallic element is, for example, Bi. Meanwhile, the third metallic element is not limited to Bi.

[0050] Furthermore, the ratio of the first metal particle (102) to the second metal particle (103) is such that, in the equilibrium phase diagram of the first metal element and the second metal element, both the first metal element contained in the first metal particle and the second metal element contained in the second metal particle become intermetallic compounds. As a result, the joint created by the liquid phase sintering process does not remelt at temperatures below 250°C. Therefore, high heat resistance can be exhibited so that the device does not melt even when the operating temperature after joining is 200°C or higher.

[0051] <TiO2 nanoparticles>

[0052] TiO2 nanoparticles (104) exist as a solid at the interface when an intermetallic compound is formed between the first metal particle (102) and the second metal particle (103). It is believed that this promotes the formation of primary crystal nuclei when the second metal element of the second metal particle diffuses into the first metal particle (102) and the intermetallic compound is formed. Additionally, it is believed that the solid TiO2 inhibits growth when the generated crystal nuclei grow. By doing so, they are included to refine the crystal grains of the intermetallic compound.

[0053] It is preferable that the TiO2 nanoparticles (104) make up 0.1 wt% to 1 wt% of the total sum of the first metal particles (102), the second metal particles (103), and the TiO2 nanoparticles (104).

[0054] <Flux>

[0055] The flux (105) is included to remove the oxide film present on the surface of the first metal particle (102) and the second metal particle (103) and to suppress reoxidation. The flux (105) facilitates the melting of the first metal particle (102) and the diffusion of the second metal element on the surface of the second metal particle (103) into the melted first metal particle (102). The flux (105) includes a component for removing the oxide film present on the surface of the first metal particle (102) and the second metal particle (103), and a solvent having a boiling point higher than the melting point of the first metal particle (102) to prevent reoxidation during the process of the liquid phase sintering method.

[0056] (Example)

[0057] To verify the effect of the present embodiment 1, bonding materials (101) are prepared by changing the types of the first metal particles (102) and the second metal particles (103) as Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-12. The components included in the bonding materials (101) in Examples 1-1 to 1-8 and Comparative Examples 1-1 to 1-12, their weight ratios, and evaluation results are shown in Table 1 of FIG. 2. The particle diameters of the first metal particles (102), the second metal particles (103), and the TiO2 nanoparticles (104) shown in Table 1 of FIG. 2 are all median diameters.

[0058] <Joining material (101)>

[0059] In the first embodiment, Sn-58Bi, Sn-51In, Sn-55Bi-20In, In, Sn, Sn-3.5Ag, and Sn-5Sb are evaluated as the first metal particles (102). Additionally, Cu, Cu-20Sn, and Zn are evaluated as the second metal particles (103). TiO2 nanoparticles of 30 nm are used.

[0060] The bonding material (101) is manufactured as follows.

[0061] (1) First, the first metal particle (102), the second metal particle (103), and the TiO2 nanoparticle are weighed and mechanically kneaded to be uniformly mixed.

[0062] (2) After that, flux is weighed and added, and mixed with a twin-screw planetary mixer to obtain a bonding material (101).

[0063] <Joining Process>

[0064] To verify the effects of Embodiment 1, a mounting structure is fabricated. The bonding process is as follows.

[0065] First, bonding is performed using the bonding material (101) that was manufactured.

[0066] (a) A bonding material (101) is supplied onto a Cu plate using a metal mask with a thickness of 100 μm and an opening of 1 mm × 1 mm.

[0067] (b) A SiC element is mounted on the supplied bonding material (101). The electrode of the SiC element bonded to the bonding material (101) is composed of a Ti / Ni / An plating from the SiC side.

[0068] (c) A load of 1 MPa is applied from above the mounted SiC element, and heating is performed at 200°C for 10 min in an N2 atmosphere to produce a mounting structure in which the electrode of the SiC element and the Cu plate are bonded with a bonding material (101).

[0069] <Synthesis Evaluation>

[0070] The results of the evaluation to confirm the effects of the present embodiment 1 are also shown in Table 1 of FIG. 2.

[0071] After performing this series of bonding processes, it is checked whether the electrodes of the Cu plate and the SiC device are bonded. In Table 1 of FIG. 2, Yes is indicated if they are bonded, and No is indicated if they are not bonded.

[0072] Next, the heat resistance of the bonded mounting structure is evaluated. The fabricated mounting structure is heated again to 200°C to evaluate whether the bonding material (101) remelts. In Table 1 of FIG. 2, if the bond is secured without remelting (i.e., if the bonding material (101) has heat resistance), it is indicated as Yes, and if remelting occurs (i.e., if the bonding material (101) does not have heat resistance), it is indicated as No.

[0073] Furthermore, the bonding strength is evaluated for a bonded structure in which remelting does not occur. A shear direction force is applied to the SiC element of the fabricated bonded structure, and the fracture strength is measured. If the value is greater than the average of conventional solder, 20 MPa, it is determined as B (good), if it is greater than 30 MPa, it is determined as A (better), and if it is 20 MPa or less, it is determined as C (bad).

[0074] As shown in Table 1 of FIG. 2, among Examples 1-1 to 1-8, in Examples 1-1 to 1-6, the bonding and heat resistance are Yes and the strength is A, and in Examples 1-7 and 1-8, the bonding and heat resistance are Yes and the strength is B, all exceeding the evaluation criteria. In these examples, the second metal particle (103) contains Cu, such as Cu or Cu-20Sn, and the first metal particle (102) reacts with one or more metal elements to form an intermetallic compound, whichever is Sn-58Bi, Sn-51In, Sn-55Bi-20In, or In. The third metal element (here, Bi) that does not form an intermetallic compound has a melting point of 271°C.

[0075] Furthermore, the ratio of the first metal particle (102) to the second metal particle (103) is 40:60, and in any embodiment, the first metal element and the second metal element Cu in the first metal particle (102) are both in a ratio where they become intermetallic compounds in the equilibrium phase diagram.

[0076] Meanwhile, in Comparative Examples 1-10, 1-11, and 1-12, even if a series of bonding processes are performed, no bond is formed. This is thought to be because the composition of the first metal particles (102) used in Comparative Examples 1-10, 1-11, and 1-12 is Sn, Sn-3.5Ag, and Sn-5Sb, respectively, and their melting points are 232°C, 221°C, and 235°C, respectively, which are higher than the heating temperature of 200°C. In other words, it is thought that in a series of bonding processes, the first metal particles (102) do not melt and liquid phase sintering does not occur, so sufficient bonding is not secured.

[0077] In addition, in Comparative Example 1-9, remelting occurs during the heat resistance evaluation. This is thought to be because the In of the first metal particle (102) and the Zn of the second metal particle (103) used in Comparative Example 1-9 do not form an intermetallic compound. It is thought to be because liquid phase sintering does not proceed during the bonding process, and In and Zn remain, causing In to remelt upon reheating.

[0078] As with Comparative Examples 1-2, 1-4, 1-6, 1-8 and Comparative Example 1-9, remelting occurs during the heat resistance evaluation.

[0079] This can be understood by paying attention to the mixing ratio of the first metal element (Sn in Comparative Example 1-2, Sn and In in Comparative Example 1-4 and Comparative Example 1-6, and In in Comparative Example 1-8) and the second metal element Cu in the first metal particle (102). That is, in Comparative Examples 1-2, 1-4, 1-6, and 1-8, the mixing ratio of the first metal particle (102) and the second metal particle (103) is 70:30. In this case, it is thought that the first metal element in the first metal particle (102) exists in excess of the ratio in which it becomes an intermetallic compound with the second metal element in the equilibrium phase diagram.

[0080] For this reason, in the bonding material (101) after undergoing the bonding process, Sn remains in Comparative Example 1-2, Sn and In remain in Comparative Example 1-4 and Comparative Example 1-6, and In remains in Comparative Example 1-8, and since their melting points are lower than 200°C, it is thought that remelting occurs at 200°C or lower.

[0081] Furthermore, looking at Comparative Examples 1-1, 1-3, 1-5, and 1-7, although the initial bonding and heat resistance exceed the standard values, the bonding strength is 16.8, 13.4, 14.7, and 12.2 MPa, respectively, which is not that great, so the judgment is C.

[0082] When comparing Comparative Examples 1-1, 1-3, 1-5, and 1-7 with Examples 1-1, 1-3, 1-5, and 1-7, it can be seen that the bonding strength increases by more than double by adding 30 nm TiO2 nanoparticles (104).

[0083] From the results of the present embodiment 1, the following is confirmed.

[0084] In order to exhibit the effects of the present disclosure, first, it is necessary to have a bonding material comprising a first metal particle with a melting point of 200°C or lower, a second metal particle (103) containing a second metal element capable of forming an intermetallic compound with the first metal element included in the first metal particle (102), TiO2 nanoparticles (104), and a flux (105).

[0085] Furthermore, it is necessary that the first metal particle (102) be one of the following: a first metal element that forms an intermetallic compound with a second metal element, or a complex comprising a first metal element that forms an intermetallic compound with a second metal element and a third metal element that does not form an intermetallic compound with a second metal element and has a melting point of 250°C or higher.

[0086] And, the ratio of the first metal particle (102) and the second metal particle (103) is such that, in the equilibrium phase diagram of the first metal element and the second metal element, the first metal element contained in the first metal particle and the second metal element contained in the second metal particle are both intermetallic compounds.

[0087] In a bonding material (101) that satisfies these conditions, it is possible to provide a bonding material capable of forming a bond with high bonding strength.

[0088] (Embodiment 2)

[0089] In this embodiment 2, the influence of the particle size and content of TiO2 nanoparticles (104) is evaluated. The components included in the bonding material (101), their weight ratios, and evaluation results in Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-4 of this embodiment 2 are shown in Table 2 of FIG. 3. The method of manufacturing the bonding material (101), the bonding process, and the evaluation method are the same as in embodiment 1.

[0090] In the 2020,

[0091] Meanwhile, in Comparative Examples 2-1 and 2-2, where the particle size of the TiO2 nanoparticles (104) is 100 nm and 300 nm, the bonding strength is not high, so the judgment is C.

[0092] This is because, since the particle size of the TiO2 nanoparticles (104) is large, the number of nucleation sites during liquid phase sintering is reduced, and also, after bonding, large foreign substances are mixed between the intermetallic compounds.

[0093] For this reason, it is thought that the effect of containing TiO2 nanoparticles (104) is reduced, and the area near the interface is structurally weakened, and the bonding strength is reduced.

[0094] Next, looking at the content of TiO2 nanoparticles (104), in Examples 2-4 to 2-6, where the content of TiO2 nanoparticles is 0.1, 0.2, and 1.0 wt%, respectively, the bonding and heat resistance are Yes and the strength is A, both exceeding the evaluation criteria.

[0095] Meanwhile, in Comparative Example 2-3, where the content of TiO2 nanoparticles (104) is small at 0.05 wt%, the bonding strength is not high at 18.1 MPa.

[0096] This is thought to be because the effect of the addition is small due to the low content of TiO2 nanoparticles (104).

[0097] In addition, in Comparative Example 2-4, where the content of TiO2 nanoparticles (104) is 2.0 wt.%, the bonding strength is small at 14.3 MPa, so the judgment is ×. This is thought to be because the high content of TiO2 nanoparticles (104) reduces the strength between the intermetallic compounds formed between the first metal particle (102) and the second metal particle (103).

[0098] From the results of the present embodiment 2, the following is confirmed.

[0099] The particle size of the TiO2 nanoparticles (104) is preferably a median diameter of 20 to 80 nm.

[0100] In addition, the content of TiO2 nanoparticles (104) is preferably 0.1 to 1 wt.%.

[0101] In a bonding material (101) that satisfies these conditions, it is possible to provide a bonding material capable of forming a bond with high bonding strength.

[0102] (Embodiment 3)

[0103] In this embodiment 3, the influence of the particle size of the first metal particle (102), the second metal particle (103), and the TiO2 nanoparticle (104) is evaluated.

[0104] The components included in the bonding material (101) and their weight ratios, and the evaluation results in Examples 3-1 to 3-11 of the present embodiment 3 are shown in Table 3 of FIG. 4. The method of manufacturing the bonding material (101), the bonding process, and the evaluation method are the same as those in Embodiments 1 and 2.

[0105] From the results of Table 3 in FIG. 4, focusing on the particle size of the first metal particle (102), in the case of Examples 3-2 to 3-4 where the particle size of the first metal particle (102) is 3, 20, and 30 μm, respectively, the judgment of bonding and heat resistance is Yes and the judgment of strength is A, and in the case of Examples 3-1 and 3-5 where the particle size is 0.5 and 45 μm, the judgment of bonding and heat resistance is Yes and the judgment of strength is B.

[0106] In the case of Example 3-1, where the particle size of the first metal particle (102) is small, the particle size of the second metal particle (103) is close to that of the second metal particle (103), so there are many places in contact with the second metal particle (103). Therefore, the rate of liquid phase sintering during heating in the bonding process is very high, and the formation of the intermetallic compound is completed before it is sufficiently wetted and spread on the electrodes of the two members to be bonded, so it is thought that the strength is lower compared to other examples.

[0107] Conversely, in the case of Example 3-5, where the particle size of the first metal particle (102) is large, the particle size of the first metal particle (102) is very large compared to the second metal particle (103), so the uniformity when making the bonding material (101) is reduced, and thus the bonding strength is also thought to be relatively smaller compared to other examples.

[0108] Looking at the particle size of the second metal particle (103), in the case of Examples 3-7 to 3-10, where the particle size of the second metal particle (103) is 100, 400, 1200, and 2000 nm respectively, the judgment of bonding and heat resistance is Yes and the judgment of strength is A, and in the case of Examples 3-6 and 3-11, where the particle size is 50 and 6000 nm, the judgment of bonding and heat resistance is Yes and the judgment of strength is B.

[0109] In Examples 3-6, where the particle size of the second metal particle (103) is small, it is thought that the bonding strength is relatively smaller compared to other examples because the uniformity is reduced due to the aggregation of the second metal particle (103) during the production of the bonding material (101) or during heating of the bonding process, as the particle size of the second metal particle (103) is very small.

[0110] In Example 3-11, where the particle size of the second metal particle (103) is large, it is thought that because the particle size of the second metal particle (103) is large, the diffusion into the first metal particle (102) that is melting during the bonding process is slow, and thus the particle size of the intermetallic compound becomes larger.

[0111] From the results of the present embodiment 3, the following is confirmed.

[0112] The first metal particle (102) preferably contains at least a particle with a median diameter of 3 to 30 μm.

[0113] The second metal particle (103) preferably has a median diameter of 100 to 2000 nm. In a bonding material (101) satisfying these conditions, it is possible to provide a bonding material capable of forming a bond with high bonding strength.

[0114] <Suitable Conditions of the Present Invention>

[0115] From the results of embodiments 1 to 3 above, as a suitable condition for exhibiting the effect of the bonding material of the present disclosure, the bonding material is a bonding material (101) comprising a first metal particle (102) having a melting point of 200°C or lower, a second metal particle (103) containing a second metal element capable of forming an intermetallic compound with the first metal element included in the first metal particle (102), TiO2 nanoparticles (104), and flux (105).

[0116] Additionally, the first metal particle (102) is one of a composite comprising only the first metal element that forms an intermetallic compound with the second metal element, or the first metal element that forms an intermetallic compound with the second metal element and the third metal element that does not form an intermetallic compound with the second metal element and has a melting point of 250°C or higher.

[0117] Furthermore, the ratio of the first metal particle (102) to the second metal particle (103) is such that, in the equilibrium phase diagram of the first metal element and the second metal element, both the first metal element contained in the first metal particle (102) and the second metal element contained in the second metal particle (103) become intermetallic compounds.

[0118] As a more favorable condition, the TiO2 nanoparticles (104) may have a median diameter of 20 to 80 nm.

[0119] As a more favorable condition, the content of TiO2 nanoparticles (104) may be 0.1 wt% to 1 wt% of the total sum of the first metal particle (102), the second metal particle (103), and the TiO2 nanoparticles (104).

[0120] As a more favorable condition, the first metal particle (102) may be at least one selected from the group consisting of Sn-Bi, Sn-In, Sn-Bi-In, Bi-In, and In.

[0121] As a more favorable condition, the second metal particle (103) may contain Cu.

[0122] As a more favorable condition, the first metal particle (102) may include at least a particle with a median diameter of 3 to 30 μm.

[0123] As a more favorable condition, the second metal particle (103) may have a median diameter of 100 to 2000 nm.

[0124] In addition, the mounting structure comprises a power device element of SiC or GaN and the bonding material (101) that bonds the electrode of the power device element and the external electrode.

[0125] Meanwhile, in this embodiment, the electrode of the SiC device used for evaluation is Ti / Ni / Au, but the present disclosure is not limited to this, and any electrode that can be bonded with the first metal particle (102) can exhibit the effects of the present disclosure.

[0126] Meanwhile, the present disclosure includes appropriately combining any of the various embodiments and / or examples described above, and can produce the effects of each embodiment and / or example. Industrial applicability

[0127] According to the bonding material of the present invention, by using a high-modulus material such as SiC or GaN, it is possible to realize a mounting structure having heat resistance and high strength required for a device that performs high-temperature operation. Explanation of the symbols

[0128] 101 Bonding Materials 102 First metal particles 103 Second metal particles 104 TiO2 nanoparticles 105 flux

Claims

Claim 1 A bonding material comprising a first metal particle having a melting point of 200°C or lower, a second metal particle comprising a second metal element capable of forming an intermetallic compound with a first metal element included in the first metal particle, TiO2 nanoparticles, and a flux, wherein the first metal particle is either only the first metal element that forms an intermetallic compound with the second metal element, or a composite comprising the first metal element that forms an intermetallic compound with the second metal element and a third metal element that does not form an intermetallic compound with the second metal element and has a melting point of 250°C or higher for the metal element body, and the ratio of the first metal particle to the second metal particle is such that, in the equilibrium phase diagram of the first metal element and the second metal element, both the first metal element included in the first metal particle and the second metal element included in the second metal particle become intermetallic compounds. ingredient. Claim 2 A bonding material according to claim 1, wherein the TiO2 nanoparticles have a median diameter of 20 to 80 nm. Claim 3 A bonding material according to claim 1, wherein the content of the TiO2 nanoparticles is 0.1 wt% to 1 wt% of the total sum of the first metal particles, the second metal particles, and the TiO2 nanoparticles. Claim 4 A bonding material according to claim 1, wherein the first metal particle is at least one selected from the group consisting of Sn-Bi, Sn-In, Sn-Bi-In, Bi-In, and In. Claim 5 A bonding material according to claim 1, wherein the second metal particle comprises Cu. Claim 6 A bonding material according to claim 1, wherein the first metal particles comprise at least particles with a median diameter of 3 to 30 μm. Claim 7 A bonding material according to claim 1, wherein the second metal particle has a median diameter of 100 to 2000 nm. Claim 8 A mounting structure comprising a power device element of SiC or GaN and a bonding material described in any one of claims 1 to 7, which bonds an electrode of the power device element and an external electrode.

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