Bonding member and semiconductor device

Abstract

A joining member (1) joins a first object (2) and a second object (3). The joining member (1) contains: metal particles (11) containing Ni as a main component; a low-melting-point phase (12) containing Sn as a main component and having a melting point of less than 300 DEG C; and an intermetallic compound (13) having a melting point of 300 DEG C or higher, said intermetallic compound (13) being generated by interdiffusion between Sn and the metal particles (11). The ratio of the amount of the low-melting-point phase (12) to the total amount of the bonded member (1) is 2 vol% or more and less than 20 vol%. The thermal expansion coefficients of the first object (2) and the second object (3) are 3 * 10 <-6 > / K or more and less than 13 * 10 <-6 > / K, and the difference between the thermal expansion coefficients of the first object (2) and the second object (3) is less than 5 * 10 <-6 > / K. The thermal expansion coefficient of the joining member (1) is at least 16 * 10 <-6 > / K and less than 20 * 10 <-6 > / K.

Description

Technical Field

[0001] The present disclosure relates to a bonding member and a semiconductor device. Background Art

[0002] In recent years, the reliability requirements for semiconductor devices have gradually increased, especially the life reliability of the joints between components with different thermal expansion coefficients (for example, the joint between a semiconductor element and a circuit board, or the joint between a circuit board and a heat sink) has been required to be improved.

[0003] Conventionally, semiconductor elements having substrates using silicon (Si), gallium arsenide (GaAs), etc., are widely used. The operating temperature of such semiconductor elements is 100°C to 125°C. The solder material used for joining these semiconductor elements and circuit boards is required to have a high melting point to cope with multi-stage soldering during manufacturing, crack resistance to repeated thermal stress associated with startup and shutdown, and device contamination resistance.

[0004] In response to these requirements, for example, 95Pb-5Sn (mass %) is used as a solder material for Si devices, and 80Au-20Sn (mass %) is used as a solder material for gallium arsenide devices.

[0005] However, 95Pb-5Sn, which contains a large amount of harmful lead (Pb), has problems from the perspective of reducing environmental load. In addition, 80Au-20Sn, which contains a large amount of precious metals, has problems from the perspective of rising prices or landfills of precious metals. Therefore, alternative materials are strongly desired for both.

[0006] On the other hand, from the viewpoint of energy saving, the development of devices using silicon carbide (SiC) or gallium nitride (GaN) as next-generation devices is booming. Their operating temperature is 175°C or higher, and may reach 300°C in the future.

[0007] This means that the temperature of the junction between the semiconductor element and the circuit substrate reaches 175°C. In addition, the temperature of the junction between the circuit substrate and the heat sink also rises to a temperature close to this value depending on the operating conditions and heat dissipation performance. Therefore, high reliability is required for the junction between the semiconductor element and the circuit substrate, and the junction between the circuit substrate and the heat sink.

[0008] As described above, in conventional and next-generation devices, there is a demand for a member (joining member) constituting the above-mentioned joint portion having a high melting point and excellent heat resistance.

[0009] As a method for manufacturing a highly heat-resistant joint body in the past, the following method is known: a large amount of metal particles such as Ag and Cu are added to Sn, and a joining layer is formed by metal diffusion caused by heating (below 300°C) during joining with a Ag-Sn alloy phase (for example, Ag3Sn: melting point 480°C), a Cu-Sn alloy (for example, Cu6Sn5: melting point 415°C; Cu3Sn: melting point 676°C), etc.

[0010] For example, Patent Document 1 (Japanese Patent Publication No. 2002-314241) discloses a connection method or electronic device using solder, wherein the Sn of the solder ball melts and forms an intermetallic compound at the interface with the Cu of the metal ball, and the Cu metal balls are connected to each other. In addition, the melted Sn also forms an intermetallic compound with the electrodes of the semiconductor chip, the electrodes of the intermediate substrate, etc., so the Cu metal balls and these electrodes are connected.

[0011] In addition, Patent Document 1 states the following: Regarding the connection portion, the Sn of the solder ball becomes a Cu-Sn intermetallic compound (Cu6Sn5, melting point: approximately 630°C), and the contact portion and its vicinity become a high melting point. Even if a portion of the Sn remains, as long as the other portions are not melted, sufficient strength to withstand the subsequent soldering process can be ensured.

[0012] In addition, Patent Document 1 also records the following: The metal ball is not limited to Cu, and Ag, Au, Al, Ni, Cu alloy, Cu-Sn compound, Ag-Sn compound, Au-Sn compound, Al-Ag compound, Zn-Al compound, etc. can also be used. Au has an effect of reducing the porosity of the connecting part due to its excellent wettability.

[0013] In addition, Patent Document 2 (International Publication No. 2012 / 108395) states that in the connection portion, a solder containing a Sn-based metal and a Cu-based metal is heated and melted to form an intermetallic compound having a melting point of 310° C. or higher. In addition, it is disclosed that the proportion of the Sn-based metal component contained in the connection portion is 30% by volume or less.

[0014] Prior art literature

[0015] Patent Document 1: Japanese Patent Application Publication No. 2002-314241

[0016] Patent Document 2: International Publication No. 2012 / 108395 Summary of the invention

[0017] However, in the conventional semiconductor device manufacturing methods disclosed in Patent Documents 1 and 2, no evaluation on crack resistance in a thermal shock test is performed regarding the amount of metal particles added to Sn particles.

[0018] For example, when a large amount of metal particles such as Cu particles and Ag particles are added, the fluidity of Sn deteriorates, so that the parts sealed by the metal particles become unbonded parts, generating voids, and cracks are easily generated when thermal shock is applied to the bonded parts.

[0019] And, when considering from the metal state diagram, the Ag-Sn alloy represented by Ag3Sn or the Cu-Sn alloy represented by Cu6Sn5 has a solid solution region of Ag or Cu and Sn of 5 mass %. However, due to the two-phase separation type, the interface of Ag3Sn and Cu6Sn5 will become a gap if there is no Sn phase with a low melting point, which becomes the starting point of cracks.

[0020] On the other hand, the inventors of the present invention believe that in semiconductor devices operating at high temperatures, what is important is not only the mechanical properties of the material or the heat cycle resistance of the component itself, but also the reliability of the device in the power cycle associated with actual operation (repeated heating and cooling by repeatedly turning on and off the application of power to the semiconductor device).

[0021] An object of the present disclosure is to provide a bonding member having high bonding reliability against power cycles in a semiconductor device operating at high temperatures.

[0022] A joining member joins a first object and a second object.

[0023] The bonding member includes: metal particles containing Ni as a main component; a low melting point phase containing Sn as a main component, having a melting point lower than 300°C; and an intermetallic compound produced by mutual diffusion between Sn and the metal particles, having a melting point of 300°C or higher.

[0024] The ratio of the amount of the low melting point phase to the total amount of the bonding member is 2 volume % or more and less than 20 volume %.

[0025] The thermal expansion coefficient of the first object and the second object is 3×10 -6 / K or more and less than 13×10 -6 / K, the difference in thermal expansion coefficient between the first object and the second object is less than 5×10 -6 / K.

[0026] The thermal expansion coefficient of the joint member is 16×10 -6 / K or more and less than 20×10 -6 / K.

[0027] According to the present disclosure, it is possible to provide a bonding member having high bonding reliability against power cycles in a semiconductor device operating at high temperatures.

[0028] Specifically, in the bonded member of the present disclosure, wettability to the bonded member (bonding object) is ensured by allowing a low melting point phase (eg, Sn single phase) to remain, and longitudinal cracks during power cycling can be suppressed by making the remaining amount appropriate.

[0029] Furthermore, the joining member of the present disclosure is applied to joining a plurality of joining objects having a difference in thermal expansion coefficient within a specific range, and thus can suppress transverse cracks caused by shear stress due to the difference in thermal expansion coefficient between the plurality of joining objects.

[0030] Moreover, by adopting a bonding member having a thermal expansion coefficient within a specific range, the tensile stress and compressive stress (tensile-compressive stress) caused by the difference in thermal expansion coefficient between the bonding object and the bonding member are suppressed, and excellent bonding reliability is achieved even when working at high temperatures (e.g. 175°C). BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 1 is a flowchart showing a process of manufacturing a semiconductor device (joined member).

[0032] Figure 2 It is shown Figure 1 A schematic cross-sectional view of the first step of the process.

[0033] Figure 3 It is shown Figure 1 A schematic cross-sectional view of the second step.

[0034] Figure 4 It is shown Figure 1 A schematic cross-sectional view of the third step.

[0035] Figure 5 It is shown Figure 1 A schematic cross-sectional view of the fourth step.

[0036] Figure 6 It is shown Figure 1 A schematic cross-sectional view of the 5th step. DETAILED DESCRIPTION

[0037] In the drawings, for the sake of clarity and simplification, the dimensional relationships of length, width, thickness, depth, etc. are appropriately changed and do not represent actual dimensional relationships.

[0038] Implementation method 1.

[0039] <Jointing member>

[0040] The bonding member 1 of the present embodiment is a member for bonding a first object 2 (for example, a heat sink) and a second object 3 (for example, a circuit board having a semiconductor element and a wiring circuit) (see Figure 6 ). In addition, the joining member 1 is different from the solder sheet 10 described later, and is a member composed of solder (solder alloy) that is melted by a heating process and then solidified, and is a member that exists in a state of being joined to both the joined members (the first object 2 and the second object 3).

[0041] The bonded member 1 of the present embodiment includes metal particles 11 , a low melting-point phase 12 , and an intermetallic compound 13 .

[0042] The metal particles 11 contain Ni as a main component. Here, the "main component" refers to the component with the largest amount among the components contained in the metal particles 11. The content of Sn in the metal particles 11 is preferably 60 mass% or more, more preferably 70 mass% or more, and further preferably 80 mass% or more.

[0043] The metal particles 11 may further contain at least one component selected from the group consisting of Fe, Cr, C, Cu, and Si.

[0044] The low melting point phase 12 contains Sn as a main component and has a melting point of less than 300° C. Here, the “main component” refers to the component with the largest amount among the components contained in the low melting point phase 12. The content of Sn in the low melting point phase 12 is preferably 60% by mass or more, more preferably 70% by mass or more, and further preferably 80% by mass or more.

[0045] The low melting point phase may also contain Ag and Cu, for example (in addition to Sn). In this case, for example, the content of Ag may be 3% by mass or more and less than 4% by mass, and the content of Cu may be 0.5% by mass or more and less than 1.0% by mass. In addition, if the content of Ag and Cu is within this range, it is expected that the effect of the present disclosure can be obtained more reliably.

[0046] The intermetallic compound 13 is a compound (phase) generated by mutual diffusion between Sn and the metal particles 11 and has a melting point of 300° C. or higher.

[0047] In addition, in the bonding member 1 of the present embodiment, the ratio of the amount of the low melting point phase 12 to the total amount of the bonding member 1 is 2 volume % or more and less than 20 volume %.

[0048] In addition, the thermal expansion coefficient of the first object 2 and the second object 3 is 3×10 -6 / K or more and less than 13×10 -6 / K, and the difference in thermal expansion coefficient between the first object 2 and the second object 3 is less than 5×10 -6 / K.

[0049] In addition, the thermal expansion coefficient of the bonding member is 16×10 -6 / K or more and less than 20×10 -6 / K.

[0050] Furthermore, the present inventors have conducted reliability tests on semiconductor devices during power cycles and have found that it is important to suppress cracks (vertical cracks) generated in the thickness direction of the layer of the bonding member in order to improve bonding reliability during power cycles.

[0051] Moreover, not only the materials constituting the joining member, such as solder, but also the structure of the joined member (joining object) affects the reliability of the joining portion. Therefore, in order to improve the reliability of the power module, it is considered necessary to study not only the composition of the materials of the joining member, but also the structure of the joined member.

[0052] In addition, regarding the longitudinal cracks, the following is recorded in the reference (Hiroji Yamazaki, "Study on the Conditions for Occurrence of Thread Cutting in Lead-Free Joints", 26th Electronix Real-Time Science Conference, 9C-14): When a high-speed thermal cycle test (+50°C / +175°C, temperature difference: 125°C) was performed on a sample in which Cu plates were welded to each other and a sample in which Mo plates were welded to each other, although the same solder material was used for the joining, no longitudinal cracks were generated in the former, but longitudinal cracks were generated in the latter.

[0053] This is related to the tensile stress and compressive stress (tensile-compressive stress) caused by the difference in thermal expansion coefficient between the solder material and the member being joined. When constrained by a member with low thermal expansion, tensile-compressive stress is applied to the solder with a large thermal expansion coefficient, and dynamic recrystallization occurs in the solder due to heating, resulting in longitudinal cracks along the grain boundaries or internal precipitates of Sn, which is the main component of the solder.

[0054] Furthermore, it is known that when there is a large difference in thermal expansion coefficient between members to be joined (between two objects to be joined), transverse cracks rather than longitudinal cracks are mainly generated.

[0055] Based on the results of the above-mentioned studies, the present inventors have found a bonding member of the present disclosure having high bonding reliability against power cycles in a semiconductor device that operates at high temperatures.

[0056] Implementation method 2.

[0057] <Semiconductor Device>

[0058] The semiconductor device according to this embodiment includes a heat sink 2 and a circuit board 3 (a board having semiconductor elements and wiring circuits). The heat sink 2 and the circuit board 3 are bonded via the bonding member 1 having high bonding reliability described in Embodiment 1. Thus, a semiconductor device with high reliability is provided.

[0059] The heat sink and the circuit board can be bonded together by a process (see Figure 1 to Figure 6 ) is used to manufacture the semiconductor device of this embodiment.

[0060] Below, refer to Figure 1 The flowchart shown in the figure explains an example of a process when a circuit substrate and a heat sink are bonded together in the method for manufacturing a semiconductor device according to the present embodiment.

[0061] First, as a first step (S1), the solder sheet 10 is cut into a predetermined size (see Figure 2 ), wherein the solder sheet 10 is a solder sheet obtained by dispersing metal particles 11 composed of Ni in a low melting point phase 12 containing Sn as a main component and having a melting point of 300° C. or less.

[0062] Specifically, as a representative example of the solder composition of the low melting point phase 12, each element is added and melted to form a composition represented by Sn-3.3Ag-0.5Cu (numerical values ​​represent mass %), thereby preparing a bulk body.

[0063] Next, the solder sheet 10 in a roll shape is produced by a rolling process at 100° C. or lower so as to have a thickness of 100 μm.

[0064] Then, Ni particles (metal particles 11) are uniformly dispersed in the solder sheet 10, and a sheet composed of the low melting point phase 12 is stacked from above to produce a mixed sheet. In this embodiment, the thickness is set to 100 μm, but it is not limited to this. In addition, the cutting size is cut into the same size as the upper member, 10 mm×10 mm.

[0065] In addition, regarding the manufacture of the solder sheet 10, the solder sheet 10 can be manufactured not only by rolling, but also by melting the substrate body and allowing the molten solder to flow in from a thin slit in sequence. In addition, in the case where the combination of elements is more than 3 elements as described above (for example, when Bi, In, Sb, etc. are added to Sn-Ag-Cu), the composition of the substrate body sometimes becomes uneven due to the temperature deviation of the melting furnace. In this case, it is also possible to adjust the solder composition by first manufacturing the substrate body of Sn-Ag-Cu, and then melting it again and adding a predetermined amount of the remaining Bi, In, Sb, etc. In addition, it is also possible to temporarily form solder balls, evenly spread the solder balls on the flat plate and perform compression molding to manufacture the solder sheet 10.

[0066] Next, as a second step (S2), the solder sheet 10 is placed on the first object 2 (lower member) (see Figure 3 ).

[0067] In addition, in order to prevent oxidation, a predetermined amount of a rust inhibitor having a decomposition temperature of 100°C or less that does not affect the bonding property may be applied to the outermost surface of the CuMo alloy plate. In addition, when placing the solder sheet 10, an organic agent that thermally decomposes at a high temperature of 100°C or more may be used as a viscous material in order to prevent the solder sheet 10 from deviating from the predetermined position. The viscosity of the viscous material is preferably 200 Pa·s or more. Alternatively, in order to prevent the solder sheet 10 from deviating, a resist film may be applied except for the bonding portion of the first object 2.

[0068] The solder sheet 10 may be slightly bent when being cut or handled. This is because the solder sheet 10 melts to a certain extent due to heating, so the influence caused by the initial shape of the solder sheet is small. However, since the second object 3 (upper member) is placed in the next step, if the solder sheet 10 is bent to a large extent to the extent that the second object 3 (upper member) cannot be placed, the solder sheet 10 is corrected to be parallel on another flat plate.

[0069] Next, as a third step (S3), the second object 3 (upper member) is placed on the solder sheet 10 (see Figure 4 ).

[0070] Furthermore, the above-mentioned adhesive material may be applied between the member to be joined (upper member) 1 and the solder sheet 10 in order to fix the mounting position.

[0071] In addition, the surfaces of the bonding side of the bonded members (the first object 2 and the second object 3) are preferably plated with Cu or Ni, or coated with an Au film, Ag film, Pt film, etc. of the order of tens of nanometers.

[0072] Next, as a fourth step (S4), the stacked body of each member obtained in the above steps is placed on a heating plate 5 in a heating furnace 5 (see Figure 5 ). Then, formic acid, which is a typical organic acid capable of reducing the oxide film, is charged into the heating furnace 5 and heated at 180° C. for 5 minutes and then at 260° C. for 3 minutes to melt the solder sheet 10 and form the bonding member 1.

[0073] Here, the low melting point phase 12 and the metal particles 11 in the solder sheet 10 form a compound by thermal diffusion. The formation ratio of the compound (intermetallic compound) of the metal particles 11 and Sn changes depending on the particle size and addition amount of the metal particles 11. Therefore, it is preferable to adjust the particle size and addition amount of the metal particles 11 so that the low melting point phase 12 remains.

[0074] The reason for this is that, first, if most of the bonded member 1 is formed of the metal particles 11 and the intermetallic compound 13 , Sn in the low melting point phase 12 cannot be deformed, so there is no problem in terms of bonding reliability.

[0075] On the other hand, there may be a situation where the surface of the common joined components (the first object 2 and the second object 3) has a roughness, and the surface roughness (concavity and convexity) is on the order of several μm. Therefore, when joining in a non-pressurized manner, it is also necessary to wet and diffuse the low-melting point phase 12 by an amount corresponding to the volume of the concavity and convexity on the surface. However, when a large amount of metal particles 11 are present, the surface area of ​​the metal particles 11 in the solder sheet 10 becomes larger, and the low-melting point phase 12 reacts preferentially with the metal particles 11, resulting in the low-melting point phase 12 not fully wetting the surface of the joined component.

[0076] Therefore, in the present embodiment, it is preferred to adjust the particle size and addition amount of the metal particles 11 so as to leave the low melting point phase 12. For example, the particle size (average particle size: D50) of the metal particles 11 added to the solder sheet 10 is 5 to 20 μm, and the mixing ratio of the metal particles in the solder sheet 10 is 8 to 30 mass %.

[0077] Furthermore, bonding can be performed by applying pressure without worrying about damaging the members to be bonded.

[0078] Next, as a fifth step (S5), the sample formed with the bonded member 1 is placed on a cooling plate 6 and cooled (see Figure 6 ).

[0079] At this time, when a completely molten material such as a normal solder is used to form a welded component, there is a possibility that the joined component (upper component or lower component) may be warped or undulated (produce unevenness) due to thermal shrinkage. Therefore, it is preferred to cool gradually in the cooling process. For example, generally, it is cooled to 100°C within 60 seconds, but when it is desired to reduce warping, it sometimes takes about 400 seconds to cool to 100°C.

[0080] In the present disclosure, the main component of the metal particles 11 is Ni, which has a lower thermal expansion coefficient than Sn, so the thermal shrinkage of the solder sheet 10 is small. In addition, the thermal expansion coefficients of the members to be joined (the first object 2 and the second object 3) are 3×10 -6 / K or more and less than 13×10 -6 / K, the difference in thermal expansion coefficient between the first object 2 and the second object 3 is less than 5×10 -6 / K, the warpage is small and the residual stress generated in the bonded member 1 can be reduced. Therefore, there is no need to particularly extend the time of the cooling step.

[0081] When actually applied to a power module, for example, a circuit substrate and a heat sink formed with semiconductor elements and circuit patterns can be joined via the above-mentioned joining member 1. The joining member 1 (solder sheet 10) is independent of the size of the joining area and can be applied to the chip joining portion, base mounting portion, etc. of the power module.

[0082] In addition, the oxygen concentration in the solder sheet 10 is also important. The metal particles 11 contain Ni that is easily oxidized, and the surface area of ​​the metal particles 11 is large. Therefore, even if a small amount of surface oxidation of the metal particles 11 occurs, when the oxidation develops from the interface of the metal particles 11, the overall oxidation amount will also increase, greatly affecting the wettability. Therefore, when the oxygen concentration in the solder sheet 10 is high, a good bonding member cannot be formed if it is not stored in a vacuum dryer. Therefore, in order to form a good bonding member, the oxygen concentration in the solder sheet 10 is preferably greater than 0 and less than 500ppm.

[0083] Example

[0084] Hereinafter, the present disclosure will be described in more detail with reference to examples, but the present disclosure is not limited to these examples.

[0085] (Test Example 1)

[0086] In reference Figure 1In the process of the above embodiment described, the thermal expansion coefficients of the first object 2 and the second object 3 were changed as shown in Table 1 to prepare bonding samples (samples 1 to 7). The particle size (average particle size: D50) of the metal particles 11 added to the solder sheet 10 was 10 μm.

[0087] A CuMo alloy plate (thickness: 1 mm, size: 20 mm×20 mm) was used as the first object 2. The outermost surface of the CuMo alloy plate was pure copper, and no plating treatment was performed on the outermost surface. In the CuMo alloy plate, the mixing ratio of Cu and Mo was changed to change the thermal expansion coefficient as shown in Table 1. Among them, as the first object with a thermal expansion coefficient of 2, invar alloy was used.

[0088] In addition, in a DBC (Direct Bonded Copper) substrate or a CIC (Copper-Invar-Copper) substrate, the thermal expansion coefficient can be arbitrarily adjusted by using the thickness of three layers constituting these substrates.

[0089] The second object 3 has a thickness of 100 μm and a size of 10 mm×10 mm. The thermal expansion coefficient of the second object 3 changes as shown in Table 1 depending on the mixing ratio of the CuMo alloy and the Invar alloy, similarly to the first object 2 .

[0090] In order to prevent the wettability from being different depending on the type of the member to be joined, Ni plating with a thickness of 3 μm was applied to the surface of each of the first object 2 and the second object 3 on the joining side.

[0091] A high-speed thermal shock test simulating a power cycle test was performed on the bonded samples of the combination shown in Table 1 obtained as described above. Specifically, the following thermal shock test was performed: a cycle consisting of 10 seconds of power-on (reaching temperature: 175°C) and 10 seconds of power-off (reaching temperature: 50°C) was repeated 100,000 times.

[0092] After the thermal shock test, a cross section in the thickness direction of the layer of the bonding member of the bonding sample is made, and the transmission X-ray image of the cross section is binarized for image analysis, thereby measuring the area ratio of the voids generated in the bonding member relative to the area of ​​the entire bonding member in the cross section (100%). In addition, the case where the area ratio of the voids is 10% or more is evaluated as "NG", and if it is less than 10%, there is no problem in practical use, so it is evaluated as "OK". Table 1 shows the evaluation results.

[0093] [Table 1]

[0094]

[0095] From the results shown in Table 1, it can be seen that the thermal expansion coefficient of the first object 2 and the second object 3 is 3×10 -6 / K(3.0×10 -6 / K) and less than 13×10 -6 / K(13.0×10 -6 / K), and the difference in thermal expansion coefficient between the first object 2 and the second object 3 is less than 5×10 -6 / K(5.0×10 -6 / K), the evaluation result is OK, and voids are not easily generated in the bonding component after the high-speed thermal shock test. Therefore, according to the present disclosure, it is known that a bonding component with high bonding reliability for power cycling in a semiconductor device operating at high temperatures and a semiconductor device using the bonding component can be provided.

[0096] In addition, as a result, it is also related to the thermal expansion coefficient of the joint (joining member and joined member). As described above, a lateral tensile and compressive stress is applied to the joining member constrained by the joined member (the first object 2 and the second object 3), resulting in a longitudinal crack. That is, if the thermal expansion coefficient of the joining member 1 is small, the stress generated can also be reduced. In the present disclosure, a metal particle 11 containing Ni as a main component is used. It is difficult to predict from the known literature to what extent the thermal expansion coefficient of the joining member 1 using the metal particle 11 will affect the joining reliability.

[0097] The inventors of the present invention have actually studied the thermal expansion coefficient of the bonding member 1 and found that the thermal expansion coefficient of the bonding member is 16×10 -6 / K or more and less than 20×10 -6 / K, and when the ratio of the area of ​​the above-mentioned low-melting-point phase (a phase containing Sn as a main component and having a melting point less than 300°C) in the cross-section of the bonding member (the cross-section in the thickness direction of the layer of the bonding member) to the overall area (100%) of the bonding member is 2% or more and less than 20% (that is, the ratio of the amount of the low-melting-point phase 12 to the total amount of the bonding member 1 is 2% by volume or more and less than 20% by volume), good results were obtained (Samples 2 to 4 in Table 1).

[0098] It should be understood that the embodiments and examples disclosed this time are illustrative in all points and are not restrictive. The scope of the present disclosure is indicated by the claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0099] Explanation of symbols

[0100] 1: Joining member; 10: Solder sheet; 11: Metal particles; 12: Low melting point phase; 13: Intermetallic compound; 2: First object (heat sink); 3: Second object (circuit board); 4: Heating furnace; 5: Heating plate; 6: Cooling plate.

Claims

1. A joining member for joining a first object and a second object, wherein: The joining member comprises: Metal particles containing Ni as a main component; The low melting point phase containing Sn as a main component has a melting point lower than 300° C.; and The intermetallic compound produced by mutual diffusion between Sn and the metal particles has a melting point of 300° C. or more. The ratio of the amount of the low melting point phase to the total amount of the bonding member is 2 volume % or more and less than 20 volume %, The thermal expansion coefficient of the first object and the second object is 3×10 -6 / K or more and less than 13×10 -6 / K, the difference in thermal expansion coefficient between the first object and the second object is less than 5×10 -6 / K, The thermal expansion coefficient of the joint member is 16×10 -6 / K or more and less than 20×10 -6 / K.

2. The joining member according to claim 1, wherein The low melting point phase further includes Ag and Cu.

3. The joining member according to claim 1 or 2, wherein: The metal particles further include at least one component selected from the group consisting of Fe, Cr, C, Cu, and Si.

4. The joining member according to any one of claims 1 to 3, wherein: The first object is a heat sink, The second object is a circuit board having a semiconductor element and a wiring circuit.

5. A semiconductor device, wherein: The semiconductor device comprises a heat sink and a circuit substrate having a semiconductor element and a wiring circuit. The heat sink and the circuit board are joined via the joining member according to claim 4 .

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