Manufacturing method of the joint

Abstract

To enable the positional adjustment of the relative positions of members by self-alignment and form a joint layer composed of a metal sintered body with superior heat resistance and joint strength.SOLUTION: A method for producing a joint body 100 includes steps of: disposing a joining paste 10 between a first member 20 and a second member 30 at 35°C or lower, and forming a laminate 100A; increasing the temperature of the laminate 100A to a level that is equal to or higher than the onset temperature for liquid phase formation but is lower than the liquid phase dissolution temperature of the joining paste 10, thereby forming a liquid phase between the first member 20 and the second member 30, and then volatilizing the liquid phase; and increasing the temperature of the laminate 100A to a heating temperature that is higher than the liquid phase dissolution temperature to form a metal sintered body, thereby forming the joint body 100 consisting of the first member 20 and the second member 30. At least one of the first member 20 and the second member 30 has a developed surface area ratio (Sdr) of 0.4 or more on the side in contact with the joining paste 10.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a bonded body.

Background Art

[0002] For example, a semiconductor device such as an LED or a power module has a structure in which a semiconductor element is bonded onto a circuit layer made of a metal member. Here, when bonding an electronic component such as a semiconductor element onto a circuit layer, for example, as shown in Patent Document 1, a method using a solder material is widely used. In addition, Patent Document 2 proposes a technique of forming a plating film and a Sn-based solder layer, alloying them by heat treatment to form an alloy layer, and mounting an electronic component on a substrate.

[0003] Furthermore, Patent Document 3 proposes a technique of bonding an electronic component such as a semiconductor element onto a circuit using a metal paste containing metal powder. In this metal paste, a bonding layer made of a conductive sintered body is formed, and an electronic component such as a semiconductor element is bonded onto the circuit through this bonding layer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, as described in Patent Documents 1 and 2, when joining components using solder, a liquid phase is generated during the heating process at the time of joining. At this time, the relative positions of the components are adjusted by the surface tension of the liquid phase. In other words, the relative positions of the components are self-aligned. However, when solder is used for joining, intermetallic compounds are formed in the joint layer between the components, which may result in relatively low thermal conductivity. Furthermore, cracks are more likely to occur in the joint layer when subjected to temperature cycling, potentially reducing the reliability of the joint.

[0006] Furthermore, when electronic components such as semiconductor elements and circuit layers are joined via solder, there was a risk that some of the solder would melt when used in a high-temperature environment, potentially reducing the reliability of the joint between the electronic components such as semiconductor elements and the circuit layer. In particular, with the recent improvement in the heat resistance of semiconductor devices themselves, and the fact that semiconductor devices are sometimes used in high-temperature environments such as the engine compartments of automobiles, conventional structures joined with solder are becoming insufficient.

[0007] On the other hand, in the metal paste described in Patent Document 3, since the bonding layer is composed of a sintered metal, it has excellent thermal conductivity and excellent bonding reliability. Furthermore, when the bonding layer is formed using a sintered metal body, the bonding layer can be formed under relatively low temperature conditions, and the melting point of the bonding layer itself is high, so the bonding strength does not decrease significantly even in high-temperature environments. However, when joining components using metal paste, a liquid phase is not generated during the heating process. Therefore, it was not possible to self-align the relative positions of the components.

[0008] This invention has been made in view of the circumstances described above, and aims to provide a method for manufacturing a joined body that can adjust the relative positions of members by self-alignment and can form a joined layer made of a metal sintered body with excellent heat resistance and bonding strength. [Means for solving the problem]

[0009] A method for manufacturing a bonded body according to the present disclosure includes the steps of: placing a bonding paste containing metal powder, copper salt, amine, and alcohol, wherein the ratio A / B of the weight A of Cu in the copper salt to the weight B of the metal powder is 0.02 or more and 0.25 or less, between a first member and a second member at 35°C or less to form a laminate; raising the temperature of the laminate to a temperature above the liquid phase generation start temperature of the bonding paste and below the liquid phase disappearance temperature to generate a liquid phase between the first member and the second member and to volatilize the liquid phase; and raising the temperature of the laminate to a heating temperature higher than the liquid phase disappearance temperature to form a metal sintered body, thereby forming a bonded body in which the first member and the second member are joined, wherein at least one of the first member and the second member has a surface area ratio Sdr of 0.4 or more on the side that contacts the bonding paste.

[0010] In the step of volatilizing the liquid phase, it is preferable to raise the temperature of the laminate to a first heating temperature higher than the liquid phase generation start temperature and hold it there, thereby eliminating the liquid phase and reducing the copper salt. In the step of forming the bonded body, it is preferable to raise the temperature of the laminate from which the liquid phase has disappeared to a second heating temperature higher than the first heating temperature, thereby forming the metal sintered body and forming the bonded body.

[0011] Preferably, the process further includes the step of performing DC electroplating on at least one of the first member and the second member, and then performing PR pulse electroplating, thereby forming a roughened plating layer on the surface of at least one of the first member and the second member that is in contact with the bonding paste, wherein the developed area ratio Sdr is 0.4 or more.

[0012] The bonding paste preferably further contains silver salt. [Effects of the Invention]

[0013] According to the present invention, the relative positions of members can be adjusted by self-alignment, and a bonding layer made of a metal sintered body excellent in heat resistance and bonding strength can be formed.

Brief Description of Drawings

[0014] [Figure 1] FIG. 1 is a schematic diagram of the bonding paste according to the present embodiment. [Figure 2] FIG. 2 is a schematic diagram of the first member. [Figure 3] FIG. 3 is a schematic diagram for explaining a method of manufacturing a bonded body. [Figure 4] FIG. 4 is a table showing samples of examples. [Figure 5] FIG. 5 is an explanatory diagram of the mounting position of the second member and the method of confirming self-alignment in the example. [Figure 6] FIG. 6 is an explanatory diagram of the method for evaluating the liquid-phase generation temperature in the example. [Figure 7] FIG. 7 is a table showing the evaluation results of each example.

Embodiments for Carrying Out the Invention

[0015] Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited by the following embodiments for carrying out the invention (hereinafter referred to as embodiments). In addition, the constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those within the so-called equivalent range. Furthermore, the constituent elements disclosed in the following embodiments can be combined as appropriate.

[0016] (Bonding Paste) The bonding paste 10 according to the present embodiment is used when manufacturing a bonded body by bonding a first member and a second member. The bonding paste = 10 is used, for example, when bonding a semiconductor element (second member) as an electronic component to a circuit layer (first member) of an insulating circuit board.

[0017] Figure 1 is a schematic diagram of the bonding paste according to this embodiment. As shown in Figure 1, the bonding paste 10 contains metal powder 12, copper salt 14, amine 16, and alcohol 18.

[0018] (metal powder) The metal powder 12 is preferably one or both of silver and copper. That is, it is preferable that the metal powder 12 contains at least one of silver and copper. The metal powder 12 is preferably in a primary particle state in the range of 100 nm to 3 μm. The average particle size of the primary particles of the metal powder 12 is determined by the following method. First, a scanning electron microscope (SEM) is used to determine the magnification according to the size of the metal powder 12 and to take an SEM image of the metal powder 12. It is preferable to take the image in the range of 10,000 to 50,000 times. Next, the SEM image is analyzed using image analysis software, the Heywood diameter is determined for 300 or more particles per sample, and the arithmetic mean of the Heywood diameter is taken as the average particle size of the primary particles.

[0019] (copper salt) The copper salt 14 can be any compound that forms a copper complex when added together with the amine 16. In this embodiment, it is preferable to use an organic carboxylate copper salt as the copper salt 14. Specifically, copper(II) acetate monohydrate, copper citrate 2.5 hydrate, copper 2-ethylhexanoate, copper oleate, copper gluconate, copper stearate, copper benzoate, etc., can be used as the copper salt 14, and it is preferable to use copper(II) acetate monohydrate as the copper salt 14. In this embodiment, the copper salt 14 may contain two or more types of copper salts.

[0020] (amine) The amine 16 can be any amine that forms a copper complex when added together with the copper salt 14. In this embodiment, it is preferable that the amine 16 includes a linear alkylamine. Specifically, dodecylamine, tetradecylamine, stearinamine, aminodecane, etc. can be used as the amine 16, and it is preferable to use dodecylamine as the amine 16. In this embodiment, amine 16 may contain two or more types of amines.

[0021] (alcohol) Alcohol 18 may be any alcohol, but glycerin, α-terpineol, diethylene glycol (DEG), etc., can be used. In particular, it is preferable to use glycerin as alcohol 18. In this embodiment, the alcohol 18 may contain two or more types of alcohol.

[0022] (Percentage of each component) In the bonding paste 10, the ratio A / B of the weight A of Cu in the copper salt 14 to the weight B of the metal powder 12 is set to be within the range of 0.02 to 0.25. Here, if the ratio A / B of the weight of Cu in the copper salt 14 to the weight of the metal powder 12 is less than 0.02, the content of the copper salt 14 will be insufficient, and the liquid phase may not be sufficiently formed during the heating process when joining, which may impair the self-alignment properties. On the other hand, if the above weight ratio A / B exceeds 0.25, an excessive amount of liquid phase will be generated, the amount of volatile organic matter will increase, the density of the metal sintered body after firing will decrease, and the joint strength may decrease. Therefore, in this embodiment, the ratio A / B of the weight A of Cu in the copper salt 14 to the weight B of the metal powder 12 is set within the range of 0.02 to 0.25. Furthermore, the weight ratio A / B mentioned above is preferably 0.04 or higher, and more preferably 0.06 or higher. In addition, the weight ratio A / B mentioned above is preferably 0.20 or lower, and more preferably 0.15 or lower.

[0023] The bonding paste 10 preferably contains metal powder 12 in the range of 25 mass% to 75 mass%. Furthermore, it is preferable that the bonding paste 10 contains copper salt 14 within the range of 4 mass% to 16 mass%. Furthermore, it is preferable that the bonding paste 10 contains amine 16 in the range of 16 mass% to 54 mass%. Furthermore, it is preferable that the bonding paste 10 contains alcohol 18 within the range of 1 mass% to 10 mass%. Note that each content is based on the bonding paste being 100 mass%.

[0024] (Characteristics of bonding paste) Preferably, the bonding paste 10 is in paste form within a temperature range of 15°C to 35°C, a liquid phase is generated during the heating process from 35°C, the liquid phase disappears during the heating process above the liquid phase generation start temperature, and a metal sintered body is formed above the liquid phase disappearance temperature. In this embodiment, as described above, since it contains copper salt 14 and amine 16, a metal complex (copper complex) is formed by mixing these. This metal complex becomes paste-like within a temperature range of 15°C to 35°C, and a liquid phase is generated by further heating.

[0025] (Silver halide) The bonding paste 10 may further contain a silver salt. The silver salt contained in the bonding paste 10 should be one that forms a silver complex when added together with an amine. In this embodiment, silver acetate, silver oxalate, silver propionate, silver myristate, silver butyrate, etc. can be used as the silver salt. In particular, it is preferable to use silver acetate as the silver salt. In this embodiment, two or more types of silver salts may be contained as the silver salt. The bonding properties can be further improved by including a silver salt.

[0026] When the bonding paste 10 contains silver salt, the ratio C / B of the weight of Ag in the silver salt to the weight of metal powder 12 is preferably in the range of 0.01 to 0.25, more preferably 0.02 to 0.2, and even more preferably 0.03 to 0.1. A ratio C / B within this range can further improve bonding performance. Furthermore, if the bonding paste 10 contains silver salt, it is preferable that the silver salt content is within the range of 0.1 mass% to 12 mass%.

[0027] The bonding paste 10 of this embodiment can be manufactured by weighing the above-mentioned metal powder 12, copper salt 14, amine 16, and optionally alcohol 18 or silver salt in a predetermined proportion and mixing them.

[0028] (First member and second member) Figure 2 is a schematic diagram of the first member. In this embodiment, the first member 20 and the second member 30 are joined together using a bonding paste 10 as a bonding layer to manufacture the bonded body 100. The first member 20 and the second member 30 can be any material, but for example, one of the first member 20 and the second member 30 may be a substrate and the other may be an electronic component. That is, a semiconductor module in which a substrate and an electronic component are joined by a bonding layer may be manufactured as the bonded body 100. The substrate is not particularly limited, but examples include oxygen-free copper plates, copper-molybdenum plates, high heat dissipation insulating substrates (e.g., DCB (Direct Copper Bond)), and substrates for mounting semiconductor elements such as LED (Light Emitting Diode) packages. Examples of electronic components include semiconductor elements such as IGBTs (Insulated Gate Bipolar Transistors), diodes, Schottky barrier diodes, MOS-FETs (Metal Oxide Semiconductor Field Effect Transistors), thyristors, logic circuits, sensors, analog integrated circuits, LEDs, semiconductor lasers, and oscillators.

[0029] (First component) The first member 20 may be made of copper, for example, but its material is not limited to copper and may be any material. As shown in Figure 2, the surface of the first member 20 on which the bonding paste 10 is applied is called surface 20A, and the surface opposite to surface 20A is called surface 20B. In this case, it is preferable that the developed area ratio Sdr of surface 20A of the first member 20 is 0.4 or more. Hereafter, when the developed area ratio Sdr is within these ranges, it will be described as "the developed area ratio Sdr is within the above range." By having the developed area ratio Sdr on the side to which the bonding paste 10 is applied be within the above range, the contact between the bonding paste 10 and the first member 20 is improved, and the bonding performance can be further improved. In this embodiment, it is preferable that the developed area ratio Sdr of the first member 20 is within the above range over the entire surface 20A, but it is not limited to that, and the developed area ratio Sdr of at least the area on the surface 20A to which the bonding paste 10 is applied may be within the above range. Furthermore, the developed area ratio Sdr of the surface 20B of the first member 20 may be arbitrary, but the developed area ratio Sdr of the surface 20B may also be within the above range. The Sdr (surface area ratio) can be measured in accordance with ISO 25178 by observing the sample within a 129 μm × 129 μm measurement range using a 100x objective lens on a laser microscope (Olympus OLS5000), processing to remove sample tilt and noise, and analyzing the resulting image.

[0030] In this embodiment, the first member 20 has a region formed by the roughened plating layer 22 in which the developed area ratio Sdr is within the above range. That is, in the example shown in Figure 2, the first member 20 has a roughened plating layer 22 formed on the surface 20A side, and the surface of the roughened plating layer 22 is the surface 20A (the region in which the developed area ratio Sdr is within the above range).

[0031] The method for forming the roughened plating layer 22 is arbitrary, but for example, by performing DC electroplating on the target surface of the first member 20, and then performing PR (Periodic Reverse) pulse electroplating, a roughened plating layer 22 with an expanded area ratio Sdr within the above range can be formed on the target surface of the first member 20. A more specific example of a method for forming the roughened plating layer 22 is described below.

[0032] When forming the roughened plating layer 22, electroplating is performed on the target surface of the first member 20. In this embodiment, it is preferable to use an electrolyte solution consisting of an aqueous solution of copper sulfate bath mainly composed of copper sulfate (CuSO4) and sulfuric acid (H2SO4), to which 3,3'-dithiobis(1-propanesulfonic acid) disodium has been added. Furthermore, it is preferable that the temperature of the plating bath be in the range of, for example, 25°C to 35°C.

[0033] The electroplating process is carried out first using the DC electroplating method, followed by the PR pulse electroplating method. In DC electroplating, the current density is 1 A / dm 2 More than 20A / dm 2 It is preferable that the application time be within the following range, from 10 seconds to 120 seconds. Here, as part of the electroplating process, first a DC electroplating method is performed, and then a PR pulse electroplating method is performed. This makes it possible to form fine irregularities dispersed on the surface of the large surface crystal grains, even when the surface crystal grains of the first component 20 are large.

[0034] The PR pulse electroplating method is an electroplating method that applies current while periodically reversing the direction of the current. For example, 1 A / dm 2 More than 30A / dm 2 The following positive electrolysis (anodic electrolysis with the first component 20 as the anode) is performed for a duration of 1 ms to 1000 ms and a current of 1 A / dm 2 More than 30A / dm 2The following negative electrolysis (negative electrode electrolysis with the first member 20 as the negative electrode) is repeated for a duration of 1 ms to 1000 ms. This repeatedly dissolves the surface of the first member 20 and deposits copper, thereby forming a roughened plating layer 22.

[0035] Here, the surface roughness of the roughened plating layer 22 can be adjusted by the surface properties of the first member 20 on which the roughened plating layer 22 is formed, and by various plating conditions (pulse application time, pulse waveform (deposition amount / dissolution amount ratio), pulse frequency). For example, increasing the pulse application time or adjusting the precipitate / dissolve ratio as a pulse waveform can increase the size of the protrusions. Adjusting the pulse frequency can increase the number of protrusions.

[0036] As described above, in this embodiment, a region where the developed area ratio Sdr is within the above range is formed by forming the roughened plating layer 22. However, the region of the first member 20 where the developed area ratio Sdr is within the above range is not limited to the roughened plating layer 22, and the developed area ratio Sdr of the target region may be made to the above range by any treatment.

[0037] (Second component) The second member 30 may be, for example, a Si substrate with gold or silver plating formed on its surface, but is not limited to that and may be any member. The surface of the second member 30 on which the bonding paste 10 is applied is designated as surface 30A, and the surface opposite to surface 30A is designated as surface 30B. In this case, it is preferable that the developed area ratio Sdr of surface 30A of the second member 30 is 0.4 or more. When the area ratio Sdr on the side to which the bonding paste 10 is applied falls within the above range, the contact between the bonding paste 10 and the second member 30 is improved, thereby further improving the bonding performance. In this embodiment, it is preferable that the developed area ratio Sdr of the second member 30 is within the above range over the entire surface 30A, but it is not limited to that, and the developed area ratio Sdr of at least the area on the surface 30A to which the bonding paste 10 is applied may be within the above range. Furthermore, the developed area ratio Sdr of the surface 30B of the second member 30 may be arbitrary, but the developed area ratio Sdr of the surface 30B may also be within the above range.

[0038] In this embodiment, the second member 30 has a region formed by the roughened plating layer 32 in which the developed area ratio Sdr falls within the above range. That is, in the example shown in Figure 2, the roughened plating layer 32 is formed on the surface 30A side of the second member 30, and the surface of the roughened plating layer 32 is the surface 30A (the region in which the developed area ratio Sdr falls within the above range). The method for forming the roughened plating layer 32 is the same as that for the roughened plating layer 22 of the first member 20, so the explanation is omitted. Furthermore, the region of the second member 30 in which the developed area ratio Sdr falls within the above range is not limited to the roughened plating layer 32, and the developed area ratio Sdr of the target region may be made to fall within the above range by any treatment.

[0039] In the above description, the developed area ratio Sdr of the region to which the bonding paste 10 is applied is within the above range in both the first member 20 and the second member 30. However, it is not limited to this, and it is sufficient if the developed area ratio Sdr of the region to which the bonding paste 10 is applied in at least one of the first member 20 and the second member 30 is within the above range.

[0040] (Method of manufacturing the joint) Next, a method for manufacturing a bonded body 100 using a bonding paste 10 will be described. Figure 3 is a schematic diagram illustrating the method for manufacturing a bonded body. In this embodiment, a bonded body 100 (e.g., a semiconductor device) is manufactured by bonding a first member 20 (e.g., a circuit layer of an insulating circuit board) and a second member 30 (e.g., a semiconductor element) with a bonding layer 10A.

[0041] In this manufacturing method, a bonding paste 10, a first member 20, and a second member 30 are prepared.

[0042] (Paste placement process) Next, as shown in step S01 (paste placement step) in Figure 3, the bonding paste 10 is placed between the first member 20 and the second member 30 to form a laminate 100A with the bonding paste 10 placed between the first member 20 and the second member 30. Specifically, the bonding paste 10 is placed (applied) between the surface 20A of the first member 20 and the surface 30A of the second member 30. The bonding paste 10 can be said to be provided between the area on the first member 20 to which the bonding paste 10 is applied and the area on the second member 30 to which the bonding paste 10 is applied. In this embodiment, the bonding paste 10 is printed on the surface 20A of the first member 11 by metal mask printing, but the method of applying the bonding paste 10 is arbitrary. Furthermore, it is preferable that the thickness of the bonding paste 10 is within the range of 20 μm to 500 μm. Step S01 is carried out in an environment of 35°C or lower, preferably in an environment of 15°C to 35°C. By forming the laminate 100A at 35°C or lower, the bonding paste 10 can be used in a paste-like state, making it easy to form the laminate 100A. Furthermore, since the area ratio Sdr of the region to which the bonding paste 10 is applied is within the above range for at least one of the first member 20 and the second member 30, the bonding paste 10 and the liquid phase described later can spread appropriately over the surfaces of the first member 20 and the second member 30, enabling proper bonding.

[0043] (Liquid phase formation and volatilization process) Next, as shown in steps S02 and S03 of Figure 3, the laminate 100A is heated to a temperature above the liquid phase generation start temperature and below the liquid phase disappearance temperature, thereby generating a liquid phase between the first member 20 and the second member 30, and then the liquid phase is gradually evaporated. Specifically, the laminate 100A is heated to a first heating temperature that is above the liquid phase generation start temperature and below the liquid phase disappearance temperature. The liquid phase generation start temperature is the temperature at which the laminate 100A begins to generate a liquid phase, and is preferably in the range of over 35°C and under 100°C. The liquid phase disappearance temperature is the temperature at which the liquid phase generated from the laminate 100A completely disappears by evaporation, and is preferably in the range of over 100°C and under 200°C. At this time, during the heating process from the liquid phase generation start temperature, the copper complex formed by the copper salt and amine contained in the bonding paste 10 liquefies, and a liquid phase is generated between the first member 20 and the second member 30. As a result, as shown in step S02 of Figure 3, the relative positions of the first member 20 and the second member 30 are self-aligned by the surface tension of the liquid phase.

[0044] Then, as shown in step S03 (liquid phase volatilization step) of Figure 3, the laminate 100A in which the liquid phase has been generated is heated to a first heating temperature higher than the liquid phase generation start temperature and held therein, so that the liquid phase disappears (volatilizes) and the copper salt contained in the bonding paste 10 is reduced. That is, in step S03, after the relative positions of the first member 20 and the second member 30 are self-aligned, they are further heated to the first heating temperature and held therein. The first heating temperature is preferably in the range of 100°C to 200°C, and the holding time at the first heating temperature is preferably in the range of 5 minutes to 180 minutes. It is also preferable to set the temperature so that the liquid phase does not volatilize all at once. At this time, as shown in step S03 of Figure 3, the alcohol 18 reduces the copper complex to generate nano-sized copper particles, and the organic components (the acidic component of the copper salt 14, the amine 16, and the alcohol 18) volatilize, causing most of the liquid phase to disappear.

[0045] (Sintering process) In step S04 (sintering step) in Figure 3, the laminate 100A, which has been heated to a first heating temperature and whose liquid phase has disappeared, is heated to a second heating temperature to form a bonding layer 10A, which is a metal sintered body, from the bonding paste 10, thereby forming the bonded body 100. That is, in step S04, after the organic components have volatilized, it is further heated to a second heating temperature. The second heating temperature is higher than the liquid phase disappearance temperature, and is preferably higher than the first heating temperature. The second heating temperature is preferably 200°C or higher and 400°C or lower. The holding time at the second heating temperature is preferably within the range of 1 minute or more and 90 minutes or lower. At this time, the sintering of the metal powder proceeds, and as shown in step S04, a bonding layer 10A made of a sintered metal body is formed, and the first member 20 and the second member 30 are joined by the bonding layer 10A to form a bonded body 100.

[0046] (effect) As described above, the method for manufacturing the bonded body 100 according to this embodiment includes the step of placing a bonding paste 10, which contains metal powder 12, copper salt 14, amine 16, and alcohol 18, and has a ratio A / B of the weight A of Cu in the copper salt 14 to the weight B of the metal powder 12 of 0.02 or more and 0.25 or less, between a first member 20 and a second member 30 at 35°C or less to form a laminate 100A. The manufacturing method then includes the steps of raising the temperature of the laminate 100A to a temperature above the liquid phase generation start temperature of the bonding paste 10 and below the liquid phase disappearance temperature to generate a liquid phase between the first member 20 and the second member 30 and to volatilize the liquid phase, and raising the temperature of the laminate 100A to a heating temperature higher than the liquid phase generation start temperature to make the liquid phase disappear and form a metal sintered body, thereby forming a bonded body 100 in which the first member 20 and the second member 30 are joined. Here, at least one of the first member 20 and the second member 30 has a surface area ratio Sdr of 0.4 or more on the side that comes into contact with the bonding paste.

[0047] The bonding paste 10 according to this embodiment contains metal powder 12, copper salt 14, amine 16, and alcohol 18, and is in paste form within a temperature range of 15°C to 35°C. Since a liquid phase is generated during the heating process from 35°C, when this bonding paste 10 is placed between the first member 20 and the second member 30 for bonding, a liquid phase is generated between the first member 20 and the second member 30 during the heating process, and the surface tension of this liquid phase allows the relative positions of the first member 20 and the second member 30 to self-align. Furthermore, since it contains metal powder 12, even when a liquid phase is generated, a distance can be maintained between the first member 20 and the second member 30, and a bonding layer 10A can be sufficiently formed. Furthermore, in this embodiment, the temperature is raised above the liquid phase generation start temperature to eliminate the liquid phase, and then the temperature is raised further above the liquid phase disappearance temperature to form a metal sintered body. As a result, even if the material is placed in a high-temperature environment again after firing, no liquid phase will be generated, and a bonding layer with excellent heat resistance and bonding strength can be formed. Furthermore, in this embodiment, the ratio A / B of the weight of Cu in the copper salt to the weight of the metal powder is set to a range of 0.02 or more, ensuring sufficient copper salt content, allowing for adequate formation of a liquid phase during the heating process at the time of joining, and enabling self-alignment. Moreover, since the ratio A / B of the weight of Cu in the copper salt to the weight of the metal powder is set to a range of 0.25 or less, the amount of liquid phase generated is not excessive, and the amount of volatile organic matter is suppressed, resulting in a sufficiently high density of the metal sintered body after firing, and achieving strong bonding strength. Furthermore, in this embodiment, since alcohol is included, nano-sized copper particles can be generated by reducing the copper ions of the copper salt that have become liquid phase during the heating process during bonding. This causes the organic components that had formed complexes with the copper ions to volatilize, making it possible to reliably eliminate the liquid phase. Furthermore, in this embodiment, by increasing the surface roughness of at least one of the first member 20 and the second member 30 on the side that comes into contact with the bonding paste, the bonding paste 10 and the liquid phase can be properly spread across the surfaces of the first member 20 and the second member 30, thereby properly bonding them and improving self-alignment and bonding strength.

[0048] In this manufacturing method, the step of volatilizing the liquid phase involves raising the laminate 100A to a first heating temperature higher than the liquid phase generation start temperature and holding it there, thereby eliminating the liquid phase and reducing the copper salt 14 to form the bonded body 100. In the next step, it is preferable to raise the laminate 100A, from which the liquid phase has disappeared, to a second heating temperature higher than the first heating temperature to form a metal sintered body (bonding layer 10A) and thus form the bonded body 100. According to this manufacturing method, by performing heating in two stages, heating at the first heating temperature and heating at the second heating temperature, the liquid phase can be properly eliminated and sintering can be properly carried out.

[0049] This manufacturing method further includes the step of performing DC electroplating on at least one of the first member 20 and the second member 30, and then performing PR pulse electroplating, thereby forming a roughened plating layer on the surface of at least one of the first member 20 and the second member 30 that comes into contact with the bonding paste 10, with a developed area ratio Sdr of 0.4 or more. By performing this roughening plating treatment, the surface on the side that comes into contact with the bonding paste 10 is appropriately roughened, allowing the bonding paste 10 and liquid phase to spread evenly across the surfaces of the first member 20 and the second member 30, thereby improving self-alignment and bonding strength.

[0050] The bonding paste 10 preferably further contains silver salt. Further inclusion of silver salt can further improve bonding strength.

[0051] (Examples) Figure 4 is a table showing a sample of the embodiment, Figure 5 is an explanatory diagram of the mounting position of the second member and the method for confirming self-alignment in the embodiment, Figure 6 is an explanatory diagram of the evaluation method for liquid phase generation temperature in the embodiment, and Figure 7 is a table showing the evaluation results for each example.

[0052] In each example and comparative example, the copper salt and amine shown in Figure 4 were mixed in the ratio shown in Figure 4 to obtain a copper salt-amine mixture. Then, the copper salt-amine mixture was mixed with the metal powder, alcohol, and in some cases silver salt shown in Figure 4 to obtain various mixtures.

[0053] Next, the above-mentioned mixture was placed on a first member, which had a thickness of 2 mm and whose material and developed area ratio Sdr were as shown in Figure 4 (thickness: 50 μm, area: 3 mm square). A second member, which had a thickness of 0.4 mm and whose material and developed area ratio Sdr were as shown in Figure 4, was mounted on top of the placed mixture. This process was carried out at room temperature between 15°C and 35°C. Here, the developed area ratio Sdr refers to the roughness of the area where the mixture is placed, and is a value measured by the method described in the embodiments above. The mixture mounting position of the second component was adjusted so that two sides of the mixture mounting surface and the element surface coincided, as shown in Figure 5(a). This was heated to form a bonding layer, and the first component and the second component were joined together. The heating conditions were as shown in Figure 4. For example, in Example 1, the mixture was heated from room temperature to the first heating temperature shown in Figure 7 and held for the holding time (first heating time) shown in Figure 7. Then, the temperature was further increased to the second heating temperature shown in Figure 7 and held for the holding time (second heating time) shown in Figure 7. After that, the temperature was lowered to room temperature. The heating rate and cooling rate were set to 2°C / min. In Example 29, where SnAgCu was used as the metal powder, the phase formation temperature was defined as the melting temperature of SnAgCu, and the liquid phase disappearance temperature was defined as the volatilization temperature of the flux. In Example 30, where Cu core Sn shell was used as the metal powder, the liquid phase formation temperature was defined as the melting point of Sn, and the liquid phase disappearance temperature was defined as the flux volatilization temperature. The following items were evaluated regarding the obtained mixture and bonding status.

[0054] (Properties at 15°C-35°C) Each obtained mixture was visually inspected, and if a powdery residue was observed (i.e., a crumbly state), it was classified as "powdered." For each mixture other than those classified as "powdered," viscosity was measured using a rheometer (TA Instruments DHR-3) at temperatures of 15°C and 35°C, with a shear rate of 10¹ / s. Mixtures with a viscosity of 10 Pa·s or higher at both 15°C and 35°C were classified as "paste-like," while those with a viscosity of less than 10 Pa·s at either temperature were classified as "liquid."

[0055] (Presence or absence of liquid phase formation / Temperature at which liquid phase formation begins) Measurements were performed using thermogravimetric differential thermal analysis (TG-DTA) (NETZSCH, STA-2500 Regulus). Differential thermal analysis was conducted in a nitrogen atmosphere at a heating rate of 10°C / min from 25°C to 500°C. Liquid phase formation was determined when no weight loss was observed in the TG curve and an endothermic peak was observed in the DTA curve. The liquid phase formation initiation temperature was defined as the temperature at which a tangent line drawn from the peak of the DTA curve toward the low-temperature region (low-temperature side), as shown in Figure 6, intersects with the extension of the flat portion of the DTA curve. The liquid phase formation initiation temperatures for each example are shown in Figure 7.

[0056] (Disappearance of the liquid phase / Disappearance temperature of the liquid phase) The liquid phase disappearance temperature was defined as the temperature at which the tangent line during weight reduction intersects the extension of the straight line representing the steady state after weight reduction has ended in the TG curve described above. The liquid phase disappearance temperatures for each example are shown in Figure 7.

[0057] (Self-alignment) After firing, the distance between adjacent edges of the joining material and the second member was measured. As shown in Figure 5(b), if the distance was 0.2 mm or more on all four edges, it was marked as having self-alignment properties ("○"). As shown in Figure 5(c), if the distance was less than 0.2 mm on even one edge, it was marked as not having self-alignment properties ("×"). The evaluation results of the self-alignment for each example are shown in Figure 7.

[0058] (Market share strength) The joint strength was measured using a shear strength evaluation tester (MFM 1500HF, manufactured by TRY PRESICION). Specifically, the joint strength was measured by fixing the first member of the joint horizontally and using a shear tool to press horizontally from the side onto the second member of the joint at a position 50 μm above the surface (top surface) of the joint layer, and measuring the strength at which the second member fractured. The shear tool was moved at a speed of 0.1 mm / second. Three strength tests were performed for each condition, and the arithmetic mean of these tests was used as the measured joint strength. Shear strengths of less than 20 MPa were marked with "×", and those of 20 MPa or more were marked with "〇". The evaluation results of the shear strength for each example are shown in Figure 7.

[0059] (Heat resistance evaluation) For the fired samples, a thermal shock test was performed 100 times using a thermal shock tester (TSE-11-A, manufactured by ESPEC). This test consisted of heating to 175°C for 15 minutes, then cooling to -40°C for 15 minutes, and finally heating back up to 175°C. An ultrasonic imaging device (FSP8V, Hitachi Power Solutions Co., Ltd.) was used to image the area where the second and first components were joined by a bonding layer. The transducer (probe) used had a frequency of 140 MHz. The area of ​​delamination was determined from the captured images, and areas where the delamination area was less than 10% of the chip area were marked with "○", and areas where it was 10% or more were marked with "×". In the images from the ultrasonic imaging device, the areas where the second and first components are delaminate appear white, and the areas where they are joined appear gray. The results of the heat resistance evaluation for each example are shown in Figure 7.

[0060] Figure 7 shows that in each example, using the bonding paste shown in this embodiment, in the embodiment where the developed area ratio Sdr of at least one of the first and second members is 0.4 or more, the evaluations of self-alignment, shear strength, and heat resistance all passed. This shows that the relative positions of the members can be adjusted by self-alignment, and that heat resistance and bonding strength can be improved. On the other hand, in comparative examples that do not satisfy at least one of the conditions of using the bonding paste shown in this embodiment and having an unfolded area ratio Sdr of at least one of the first and second members of 0.4 or more, at least one of the evaluations of self-alignment, shear strength, and heat resistance fails, indicating that self-alignment, heat resistance, and bonding strength cannot be improved. For example, in Comparative Example 1, the ratio A / B of the weight of Cu A to the weight of metal powder B was lower than 0.02, resulting in insufficient liquid phase volume and inadequate self-alignment. In Comparative Example 2, the ratio A / B was higher than 0.25, resulting in an excess of liquid phase and a high amount of organic matter. Consequently, the sintered body density was low, and the bonding strength was insufficient. In Comparative Examples 3 and 4, solder materials that form hard and brittle intermetallic compounds were used for joining, and since a joining paste containing metal powder and copper salt was not used, the heat resistance was insufficient. In Comparative Example 5, the bonding paste did not contain copper salts, and no liquid phase was generated during the heating process, resulting in insufficient self-alignment. In Comparative Example 6, the step of forming a bonded body by raising the heating temperature to a temperature higher than the liquid phase disappearance temperature to form a metal sintered body was not included, resulting in residual organic components and insufficient bonding strength. In Comparative Example 7, the step of raising the temperature to above the liquid phase generation start temperature and below the liquid phase disappearance temperature to generate and volatilize the liquid phase was not included. As a result, gas leakage marks remained due to the rapid volatilization of the liquid phase, and the bonding strength was insufficient. In comparative examples 8 and 9, the joint strength was insufficient because the Sdr of both the first and second members was less than 0.4.

[0061] Although embodiments of the present invention have been described above, the embodiments are not limited to those described herein. Furthermore, the aforementioned components include those that can be easily conceived by those skilled in the art, those that are substantially the same, and those that fall within the so-called equivalent range. Moreover, the aforementioned components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the embodiments described above. [Explanation of Symbols]

[0062] 10 Bonding paste 12 Metal powder 14 Copper salts 16 Amine 18 Alcohol 20 First Member 30 Second Member 100 zygote 100A laminate

Claims

1. A bonding paste comprising a metal powder containing at least one of silver and copper, a copper salt containing an organic copper carboxylate, an amine capable of forming a copper complex when added together with the copper salt, and an alcohol, wherein the content of the metal powder is 25 mass% or more and 75 mass% or less, the content of the alcohol is 1 mass% or more and 10 mass% or less, and the ratio A / B of the weight A of Cu in the copper salt to the weight B of the metal powder is 0.02 or more and 0.25 or less, is placed between a first member and a second member at 35°C or below to form a laminate; The laminate is heated to a temperature above the liquid phase generation start temperature of the bonding paste and below the liquid phase disappearance temperature, thereby generating a liquid phase between the first member and the second member and volatilizing the liquid phase. The step of forming a joint in which the first member and the second member are joined by raising the temperature of the laminate to a heating temperature higher than the liquid phase disappearance temperature to form a metal sintered body, Includes, At least one of the first member and the second member has a surface area ratio Sdr of 0.4 or more on the side that comes into contact with the bonding paste. A method for manufacturing a composite body.

2. In the step of volatilizing the liquid phase, the laminate is heated to a first heating temperature higher than the liquid phase generation start temperature and held therein, thereby eliminating the liquid phase and reducing the copper salt. The method for manufacturing a bonded body according to claim 1, wherein in the step of forming the bonded body, the laminate from which the liquid phase has disappeared is heated to a second heating temperature higher than the first heating temperature to form the metal sintered body and thus form the bonded body.

3. A method for manufacturing a bonded body according to claim 1 or 2, further comprising the step of performing DC electroplating on at least one of the first member and the second member, and then performing PR pulse electroplating, to form a roughened plating layer on the surface of at least one of the first member and the second member that is in contact with the bonding paste, wherein the developed area ratio Sdr is 0.4 or more.

4. The method for manufacturing a bonded body according to claim 1 or claim 2, wherein the bonding paste further comprises a silver salt.

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