Method for manufacturing bonded structure, method for manufacturing laminate, and bonding method

Abstract

A paste containing copper particles and an organic solvent is applied to the first bonded body (11) to form a coating film (13a); a portion of the organic solvent contained in the coating film (13a) is removed; a second bonded body (12) is pressed into the coating film (13a) in such a manner that a portion of the second bonded body (12) is buried in the coating film (13a) to obtain a laminate (14) sequentially provided with the first bonded body (11), the coating film (13a), and the second bonded body (12); and the laminate (14) is subjected to heating. When the average thickness of the coating film (13a) in a state after a drying process and before the second bonded body (12) is pressed into the coating film (13a) is set as X, and the average distance from the upper surface (11b) of the first bonded body (11) to the lower surface (12b) of the second bonded body (12) in a state where the laminate (14) is obtained is set as Y, the pressing rate P defined by 100 - (Y / X x 100) is 1.0 or greater and 50 or less.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a joined structure formed by joining two joined bodies. Furthermore, this invention relates to a method for manufacturing a laminated body for obtaining the joined structure and a method for joining two joined bodies. Background Technology

[0002] In recent years, semiconductor components known as power devices have been widely used in power conversion / control devices such as inverters. Unlike integrated circuits such as memory and microprocessors, power devices are used to control high currents, thus generating a great deal of heat during operation. Therefore, the solder used to mount power devices requires high heat resistance. However, currently used lead-free solders have the disadvantage of lower heat resistance compared to conventional lead-containing solders.

[0003] Therefore, various technologies have been proposed that use a paste containing metal particles, which restricts the use of harmful chemicals, instead of solder, and apply it to the object using various coating methods and then sinter it. For example, Patent Document 1 describes the following: a conductive paste containing metal particles is coated on an electrode pattern, a semiconductor element is placed on it, the semiconductor element is pressed down, and the conductive paste is heated while under pressure to form a sintered layer of metal particles.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-127219 Summary of the Invention

[0007] In the technology described in Patent Document 1, a semiconductor element is disposed on a conductive paste coating layer. When transported or subjected to external vibration in this state, the semiconductor element may shift from its proper bonding position, resulting in poor bonding between the semiconductor element and the electrode pattern. Therefore, the object of the present invention is to provide a method for manufacturing such a bonding structure that prevents misalignment or detachment of the bonded objects and enables smooth bonding of the bonded objects to each other.

[0008] This invention provides a method for manufacturing a joint structure, wherein the joint structure is formed by joining a first jointed body and a second jointed body using a joint layer, wherein...

[0009] The manufacturing method includes the following steps:

[0010] The process of applying a paste containing copper particles and organic solvent to the first substrate to form a coating film;

[0011] The drying process removes a portion of the organic solvent contained in the coating film;

[0012] A process is performed by pressing the second bonded body into the coating film in such a way that a portion of the second bonded body is embedded in the coating film, thereby obtaining a laminate comprising the first bonded body, the coating film, and the second bonded body in sequence; and

[0013] The process of heating the laminated body.

[0014] The average thickness of the coating film after the drying process and before the second bonded body is pressed into the coating film is defined as X (μm).

[0015] When the average distance from the upper surface of the first bonded body to the lower surface of the second bonded body in the state of obtaining the laminated body is defined as Y (μm),

[0016] The pressure ratio P, defined by 100-(Y / X×100), is greater than 1.0 and less than 50.

[0017] Furthermore, the present invention provides a method for manufacturing a laminate, which is used to join a first substrate to a second substrate, wherein,

[0018] The manufacturing method includes the following steps:

[0019] The process of applying a paste containing copper particles and organic solvent to the first substrate to form a coating film;

[0020] The drying process removes a portion of the organic solvent contained in the coating film; and

[0021] By pressing the second bonded body into the coating film in such a way that a portion of the second bonded body is embedded in the coating film, a laminate comprising the first bonded body, the coating film, and the second bonded body is obtained.

[0022] The average thickness of the coating film after the drying process and before the second bonded body is pressed into the coating film is defined as X (μm).

[0023] When the average distance from the upper surface of the first bonded body to the lower surface of the second bonded body in the state of obtaining the laminated body is defined as Y (μm),

[0024] The pressure ratio P, defined by 100-(Y / X×100), is greater than 1.0 and less than 50.

[0025] Furthermore, the present invention provides a joining method, which is a joining method between a first joined object and a second joined object, wherein,

[0026] The joining method includes the following steps:

[0027] The process of applying a paste containing copper particles and organic solvent to the first substrate to form a coating film;

[0028] The drying process removes a portion of the organic solvent contained in the coating film;

[0029] A process is performed by pressing the second bonded body into the coating film in such a way that a portion of the second bonded body is embedded in the coating film, thereby obtaining a laminate comprising the first bonded body, the coating film, and the second bonded body in sequence; and

[0030] The process of heating the laminated body.

[0031] The average thickness of the coating film after the drying process and before the second bonded body is pressed into the coating film is defined as X (μm).

[0032] When the average distance from the upper surface of the first bonded body to the lower surface of the second bonded body in the state of obtaining the laminated body is defined as Y (μm),

[0033] The pressure ratio P, defined by 100-(Y / X×100), is greater than 1.0 and less than 50. Attached Figure Description

[0034] Figure 1 This is a process diagram illustrating one embodiment of the manufacturing method of the joining structure of the present invention (process diagram up to the manufacturing of the laminate).

[0035] Figure 2 This is a magnified schematic diagram showing the main part of the laminate in which the second bonded body is pressed into the dried coating.

[0036] Figure 3 (a) ~ Figure 3 (c) is a schematic diagram showing the method of measuring the values ​​of X and Y in order to calculate the pressure ratio P defined by 100-(Y / X×100). Detailed Implementation

[0037] The present invention will now be described based on preferred embodiments. The present invention relates to a method for manufacturing a joined structure formed by joining two joined bodies, namely a first joined body and a second joined body, by means of a joining layer. This manufacturing method generally comprises the following steps.

[0038] (1) A process of applying a paste containing copper particles and organic solvent to the first substrate to form a coating film.

[0039] (2) A drying process to remove a portion of the organic solvent contained in the coating.

[0040] (3) A process of pressing the second substrate into the coating film in such a way that a portion of the second substrate is embedded in the coating film to obtain a laminate having the first substrate, the coating film and the second substrate.

[0041] (4) The process of heating the laminate.

[0042] The following is for reference Figure 1 Each process step is explained.

[0043] Figure 1 This is a process diagram illustrating one embodiment of the manufacturing method of the joining structure of the present invention.

[0044] First, such as Figure 1 As shown in (a), a first substrate 11 is prepared, and a paste is applied to one surface of the first substrate 11 to form a wet coating film 13a. The paste contains copper particles and an organic solvent.

[0045] There are no particular limitations on the application method of the paste. For example, a wet coating film can be formed by screen printing, gravure printing, dot printing, reverse coating, and doctor blade application.

[0046] From the viewpoint of ensuring sufficient bonding strength, the average thickness of the wet coating 13a is preferably 18 μm or more, more preferably 20 μm or more, and even more preferably 25 μm or more.

[0047] Furthermore, from the viewpoint of making the coating film smoother and preventing the coating film from cracking after drying, the average thickness of the wet coating film 13a is preferably 1000 μm or less, more preferably 800 μm or less, and even more preferably 500 μm or less.

[0048] For example, a non-contact surface profilometer utilizing white interference can be used to calculate the average thickness of the wet coating 13a. An example of a non-contact surface profilometer is the AMETEK ZeGage Pro. In this case, the software uses ZYGO Mx version 8.0.0, with a 1.0x zoom lens and a 1.4x objective lens. In the software's MEASUREMENT tab, under Basic Settings - Options tab, select Extended for Scan Length, and input a value at least 100 μm larger than the thickness of the wet coating 13a being measured. Set the scan start position to Bottom. The measurement field of view is set to include a portion of the reference surface 11 that forms the thickness during image recognition of the wet coating 13a being measured. Specifically, the measurement field of view is set to extend at least 1 mm beyond the periphery of the wet coating 13a. By setting the measurement field of view to include a portion of the reference surface 11, the quadrilateral R described later can be configured within an appropriate range.

[0049] After setting up and performing the measurement, open the Level / Step item in the Investigation Tools under the ANALYSIS tab of the software. When you select Add Shapes (One Reference and One test Default rectangles), the quadrilateral R for selecting the reference plane and the quadrilateral T for measuring the height from the reference plane will be displayed.

[0050] The quadrilateral R is configured such that each side has a size of 500 μm × 500 μm or more, at the location where the first bonded object 11 is present and excluding the wetted coating 13a. If the quadrilateral R includes portions other than the first bonded object 11, the reference cannot be accurately determined. Since the quadrilateral R is the reference for calculating the thickness of the measured object, it cannot include portions other than the first bonded object 11. Furthermore, by configuring the quadrilateral R to a size of 500 μm × 500 μm or more, an average value taking into account the surface roughness, etc., of the first bonded object 11 is used as the reference, thus enabling a more accurate calculation of the thickness of the wetted coating 13a.

[0051] Next, quadrilateral T is positioned such that its longitudinal and transverse sides are located 500 μm inward from the longitudinal and transverse sides of the wetted coating 13a of the object being measured, respectively. Then, when the "Apply" button for the item labeled "Level / Step" is clicked, a value is recorded inside quadrilateral T. This value is taken as the average thickness of the wetted coating 13a.

[0052] The paste can be applied only to one side of the first bonded body 11, at a position further inward than the periphery. Figure 1(a) shows the state in which a paste is applied to one side of the first bonded body 11 at a position inside the periphery 11a to form a coating (wet coating 13a).

[0053] From the viewpoint of reliable bonding between the first bonded body 11 and the second bonded body 12, it is preferable that the coating area of ​​the paste is the area of ​​the wet coating film 13a formed by the coating extending from the periphery of the second bonded body 12 (described later).

[0054] Next, as Figure 1 As shown in (b), the wet coating 13a is dried to remove a portion of the organic solvent contained in the wet coating 13a, resulting in a dried coating 13b. By removing a portion of the organic solvent from the wet coating 13a, the conformability of the dried coating 13b is improved. From this point of view, in Figure 1 In the drying process shown in (b), the wet coating 13a is dried such that the mass of the wet coating 13a is preferably reduced by 3.0% or more by mass, more preferably by 3.2% or more by mass, particularly preferably by 5.0% or more by mass, and especially preferably by 7.0% or more by mass.

[0055] On the other hand, if excessive removal of organic solvent from the wet coating 13a is carried out, the dried coating 13b becomes hard, sometimes making it difficult to smoothly press the second bonded body into the dried coating 13b (described later). From this point of view, in the drying process, the wet coating 13a is dried in a manner that preferably reduces the mass of the wet coating 13a by 30.0% or less by mass, and particularly preferably by 28.0% or less by mass.

[0056] The method for measuring the percentage reduction in mass of the wetted coating 13a is described in the examples described later.

[0057] exist Figure 1 In the drying process shown in (b), from the viewpoint of smoothly pressing the second bonded body 12 into the dried coating 13b as described later, it is preferable to remove the organic solvent in such a way that the average thickness X of the dried coating 13b is 15 μm or more, more preferably 18 μm or more, and even more preferably 20 μm or more.

[0058] On the other hand, from the viewpoint of easily obtaining a smooth coating film and preventing the coating film from cracking after drying, in the drying process, it is preferable to remove the organic solvent in such a way that the average thickness X of the dried coating film 13b is 800 μm or less, more preferably 500 μm or less, and even more preferably 400 μm or less.

[0059] The method for measuring the average thickness X of the dried coating 13b is described later.

[0060] exist Figure 1 In the drying process shown in (b), from the viewpoint of adjusting the evaporation rate of the organic solvent contained in the wet coating 13a to achieve an appropriate hardness of the dried coating 13b, it is preferable to set the heating temperature of the wet coating 13a within an appropriate range. From this viewpoint, when the drying process is carried out under atmospheric pressure, when the boiling point of the organic solvent contained in the wet coating 13a is set to M (°C), the heating temperature of the wet coating 13a is preferably set to 20°C or higher and M°C or lower, more preferably 25°C or higher and [M-10]°C or lower, and even more preferably 30°C or higher and [M-20]°C or lower. When the wet coating 13a contains two or more organic solvents, the boiling point of the organic solvent with the highest boiling point is defined as M.

[0061] In relation to the heating temperature, the heating time of the wet coating 13a is set such that a dry coating 13b with a hardness sufficient to allow for the smooth pressing of the second substrate 12 into the dry coating 13b, as described later. When the drying process is performed under atmospheric pressure, it is preferable to perform heating for at least 1 minute and approximately 120 minutes.

[0062] Furthermore, the formation of the dried coating 13b, achieved by heating the wet coating 13a, can be carried out in an inert gas atmosphere or at atmospheric level. Alternatively, it can be carried out under reduced pressure. There are no particular limitations on the heating method. For example, heating methods such as hot air blowing, infrared irradiation, or heating in a furnace can be used.

[0063] After the dried coating 13b is formed, then as follows Figure 1 As shown in (c), the second adherend 12 is placed on the dried coating 13b. Preferably, the second adherend 12 is placed on the dried coating 13b such that the dried coating 13b extends from the periphery of the second adherend 12.

[0064] In this embodiment, before placing the second adherend 12 on the dried coating 13b, it is not necessary to apply a fixing agent between the dried coating 13b and the second adherend 12. As will be described later, in this embodiment, since the second adherend 12 is pressed into the dried coating 13b such that a portion of the second adherend 12 is embedded in the dried coating 13b, it is not necessary to use a fixing agent to fix the dried coating 13b and the second adherend 12. Thus, according to the manufacturing method of this embodiment, the step of applying a fixing agent can be omitted, thereby simplifying the manufacturing process and shortening the manufacturing time. Furthermore, in this invention, the aforementioned fixing agent may not be used, but its use is also acceptable. Examples of fixing agents include monohydric alcohols, polyhydric alcohols, polyhydric alcohol alkyl ethers, polyhydric alcohol aryl ethers, esters, heterocyclic compounds, amides, amines, saturated hydrocarbons, cyclic terpene alcohols and their derivatives, ketones, carboxylic acids, etc.

[0065] As described above, since a portion of the solvent remains in the dried coating film 13b, it possesses shape retention and deformability. Therefore, by applying pressure to the second adherend 12 placed on the dried coating film 13b, the dried coating film 13b is deformed, and the second adherend 12 is pressed into the dried coating film 13b in such a way that a portion of the second adherend 12 is embedded in the dried coating film 13b. Thus, a laminate 14 is formed, consisting of the first adherend 11, the dried coating film 13b, and the second adherend 12 in sequence. Furthermore, the pressing of the second adherend 12 can, for example, be performed as follows: Figure 1 As shown in (d), a plate-shaped pressing fixture 15 is used. Alternatively, the second substrate 12 can be directly pressed into the dry coating 13b using a fixture (not shown) used when placing the second substrate 12. Alternatively, a suitable weight can be gripped using a fixture used when placing the second substrate 12, and the weight can be brought into contact with the second substrate 12 to press it into the dry coating 13b.

[0066] exist Figure 2 The figure shows a magnified view of the main portion representing the state in which the second bonded body 12 is pressed into the dried coating film 13b. As shown in the figure, when the second bonded body 12 is pressed into the dried coating film 13b, the lower region of the second bonded body 12 in the thickness direction Z is embedded in the dried coating film 13b, and the side surface 12a of this lower region is surrounded by the dried coating film 13b. As a result, the second bonded body 12 is fixed by the dried coating film 13b. The fixing of the second bonded body 12 by the dried coating film 13b is achieved through the interlocking between the dried coating film 13b and the side surface 12a of the lower region of the second bonded body 12. Alternatively, the adhesiveness of the dried coating film 13b can also be utilized.

[0067] The inventors have discovered that, in order to reliably fix the second bonded body 12 to the dry coating 13b and subsequently bond the first bonded body 11 to the second bonded body 12, the following predetermined relationship needs to be satisfied as a condition for pressing in the second bonded body 12. Specifically, it is advantageous to press in the second bonded body 12 with a pressing rate P defined by the following formula (1) of 1.0 or more, preferably 1.5 or more, more preferably 2.0 or more, and even more preferably 2.5 or more.

[0068] On the other hand, in the bonded structure obtained by sintering the laminate 14, from the viewpoint of sufficiently improving the bonding strength between the first bonded body 11 and the second bonded body 12, it is preferable that the thickness of the dried coating 13b located between the first bonded body 11 and the second bonded body 12 in the laminate 14 does not become excessively thin. From this viewpoint, the value of the indentation rate P is 50 or less, preferably 30 or less, and more preferably 25 or less.

[0069] P = 100 - (Y / X × 100) (1)

[0070] In Equation (1), X (μm) is the average thickness of the dried coating 13b in the state after the drying process of the wet coating 13a and before the second bonded body 12 is pressed into the dried coating 13b.

[0071] Y (μm) is the average distance from the upper surface 11b of the first bonded body 11 to the lower surface 12b of the second bonded body in the state of obtaining the laminate 14 (refer to...). Figure 2 ).

[0072] X and Y are measured by the methods described below.

[0073] After the drying process of the wet coating 13a, such as Figure 3 As shown in (a), the second substrate 12 is mounted on the center of the dried coating 13b using a chip mounter at a low pressure of 0.004 MPa. The time from the second substrate 12 contacting the dried coating 13b to the pressure reaching 0.004 MPa is, for example, less than 1 second, and the holding time of the pressure from reaching 0.004 MPa is set to 0.4 seconds. The average thickness A of the dried coating 13b and the second substrate 12 bonded together from the upper surface 11b of the first substrate 11 is calculated using the same method as for the wet coating 13a. Then, the average thickness B of only the second substrate 12 is subtracted from the average thickness A (refer to...). Figure 2 The obtained value is taken as the average thickness X (μm) of the dried coating 13b. The average thickness B of the second bonded body 12 is measured in advance.

[0074] For example, after placing the second substrate 12 on a reference surface with a smooth SiC substrate (with a surface roughness of 0.03 μm or less based on JIS B 0601:1994) that is more than 200% larger than the second substrate 12, the average thickness B of the second substrate 12 can be calculated using a non-contact surface profilometer and in the same way as the wet coating 13a.

[0075] Next, as Figure 3 As shown in (b), a plate-shaped weight 20 with an area smaller than the second bonded object 12 is mounted on the second bonded object 12 using a chip mounter with a pressure of 0.8 MPa. The time from the moment the weight 20 contacts the second bonded object 12 until the applied pressure reaches 0.8 MPa is less than 5 seconds from the moment of contact, and the time from the moment the pressure reaches 0.8 MPa is set to 2 seconds.

[0076] Next, as Figure 3 As shown in (c), the laminate 14 is obtained by removing only the mounted weight 20 using suction tweezers. Then, the average distance D of the laminate 14 from the upper surface 11b of the first bonded body 11 to the upper surface 12c of the second bonded body 12 is measured (refer to...). Figure 2 Furthermore, the average distance D can be calculated using the same method as the method for calculating the average thickness of the wet coating 13a described above. Specifically, except that the quadrilateral T is arranged such that its longitudinal and transverse sides are located at the positions where the second bonded body 12 exists, and at positions 500 μm inward from the longitudinal and transverse sides of the second bonded body 12 being measured, the calculation is performed in the same manner as the method for calculating the average thickness of the wet coating 13a, thereby calculating the average distance D from the upper surface 12c of the second bonded body 12 to the upper surface 11b of the first bonded body 11 (refer to...). Figure 2 ).

[0077] The value obtained by subtracting the average thickness B of the second bonded body 12 from the average distance D is set as the average distance Y from the upper surface 11b of the first bonded body 11 to the lower surface 12b of the second bonded body.

[0078] The value of the indentation rate P needs to be as described above. From the viewpoint of reliably fixing the second bonded body 12 by the dried coating film 13b and from the viewpoint of sufficiently improving the bonding strength between the first bonded body 11 and the second bonded body 12, the value of the average distance Y in the formula (1) that defines the indentation rate P is preferably 5 μm or more and 500 μm or less, more preferably 10 μm or more and 300 μm or less.

[0079] From the viewpoint of properly fixing the second substrate 12 to the dry coating film 13b and from the viewpoint of sufficiently improving the bonding strength between the first substrate 11 and the second substrate 12, the pressure at which the second substrate 12 is pressed into the dry coating film 13b is preferably 0.004 MPa or more and 5 MPa or less, more preferably 0.01 MPa or more and 4.5 MPa or less, and even more preferably 0.05 MPa or more and 4 MPa or less.

[0080] From the viewpoint of properly fixing the second bonded body 12 to the dry coating 13b and from the viewpoint of sufficiently improving the bonding strength between the first bonded body 11 and the second bonded body 12 in the heating process that becomes the next process, the holding time from the point of reaching the target pressure of the second bonded body 12 is preferably 0.01 seconds or more, more preferably 0.05 seconds or more.

[0081] Furthermore, the duration of maintenance from the time the target pressure of the second coupled body 12 is reached is not particularly limited, as long as it does not significantly reduce productivity; for example, it can be set to 7 seconds or less.

[0082] like Figure 2 As shown, if the second bonded body 12 is fixed, the position of the second bonded body 12 relative to the first bonded body 11 will not easily shift even if an external force is applied to the laminate 14. Therefore, when the laminate 14 is transported to the firing furnace for the next process, such as the heating process described below, the positional relationship between the first bonded body 11 and the second bonded body 12 can be stably maintained.

[0083] The laminate 14, formed by fixing the second bonded body 12 to the dried coating 13b, is then subjected to a heating process. Since the heating process is performed in a different location than the process for obtaining the laminate described above, it is moved to the apparatus that heats the laminate 14. During this movement, external forces such as vibration may be applied to the laminate 14, but since the second bonded body 12 is properly fixed to the dried coating 13b through the aforementioned process for obtaining the laminate, misalignment of the second bonded body 12 can be suppressed. Alternatively, the heating apparatus may also function as a device for holding the second bonded body 12, heating the laminate 14 on-site without moving it.

[0084] In the heating process, heat is applied to the laminate 14 after it has been pressurized, or while it is under pressure, or without pressure. From the viewpoint of reliably sintering the copper particles in the dried coating 13b and reliably improving the bonding strength between the first bonded body 11 and the second bonded body 12, the heating temperature is preferably 180°C or higher and 350°C or lower, more preferably 200°C or higher and 300°C or lower.

[0085] When the laminate 14 is heated after pressurization or under pressurized conditions, from the viewpoint of properly fixing the dried coating 13b to the second bonded body 12, it is preferable to set the pressure to 0.1 MPa or more and 35 MPa or less, more preferably to 1 MPa or more and 30 MPa or less, and even more preferably to 2 MPa or more and 28 MPa or less.

[0086] The atmosphere used in the heating process can be, for example, atmospheric atmosphere, inactive gas atmosphere, or reducing atmosphere.

[0087] By employing this fixing method, a target joint structure (not shown) can be obtained. In this joint structure, the first and second jointed bodies are joined together by means of a joint layer composed of sintered copper particles.

[0088] Next, the paste, the first bonded body, and the second bonded body used in the above-described bonding method by fixation will be described.

[0089] The paste used in this invention is composed of copper particles and an organic solvent. The paste may also contain various modifiers.

[0090] There are no particular restrictions on the shape of the copper particles contained in the paste; either spherical or non-spherical shapes can be used.

[0091] Spherical copper particles are defined as having a sphericity coefficient of 0.85 or higher. When taking scanning electron microscope images of copper particles, and setting the area of ​​the two-dimensional projection image of a primary particle as S and the perimeter as L, the formula is 4πS / L. 2 The circularity coefficient is calculated using the formula.

[0092] The copper particles are non-spherical, meaning that the roundness coefficient is less than 0.85.

[0093] Specific examples of non-spherical shapes include flattened, hexahedral, octahedral, spindle-shaped, and irregular shapes. Flattened refers to a shape having a pair of plate-like surfaces that form the main face of the particle and lateral surfaces orthogonal to these plate-like surfaces. The plate-like surfaces and lateral surfaces can each be independently planar, curved, or concave-convex.

[0094] Copper particles can also have two or more different shapes. From the viewpoint of obtaining a bonded structure with high bonding strength, it is particularly preferred that the copper particles include flat copper particles and spherical copper particles. Alternatively, it is also possible to have multiple copper particles with the same shape but different particle sizes, or copper particles with different shapes and particle sizes.

[0095] The particle size of the copper particles in the case of spherical shape is determined by the following method: The Heywood diameter of each of 50 or more clearly defined primary copper particles is measured using images obtained with a scanning electron microscope within a magnification range of 10,000x to 150,000x. Then, the volume assuming the particles are perfectly spherical is calculated based on the obtained Heywood diameter, and the cumulative volumetric diameter (50% of the volumetric capacity) is taken as the particle size of the copper particle.

[0096] The copper particles preferably have a particle size greater than 0.1 μm, more preferably 0.11 μm or more, and even more preferably 0.12 μm or more. On the other hand, the copper particle size is preferably 0.55 μm or less, more preferably 0.5 μm or less. Since the copper particle size is greater than 0.1 μm, shrinkage cracking is less likely to occur when the dried coating 13b is fired to form a sintered body (bonding layer). On the other hand, by setting the copper particle size to 0.55 μm or less, the sintering of the copper particles present in the dried coating 13b can be sufficient.

[0097] The particle size of flattened copper particles is determined using the following method: Images of clearly defined copper particles are acquired using a scanning electron microscope at magnifications of 500x to 50,000x, and these images are then analyzed. Specifically, when the flattened copper particle's surface is rotated 360 degrees horizontally and an imaginary circumscribed rectangle is considered in each two-dimensional projection image, the longest side of the rectangle with the largest circumscribed rectangle is taken as the major axis. The major axes of at least 50 randomly selected particles are measured, and their arithmetic mean is calculated and taken as the particle size. For example, Mounttech's Mac-view image analysis software for particle size distribution is used in the image analysis.

[0098] When the copper particles are flat, the particle size is preferably 0.3 μm or more and 50 μm or less, more preferably 0.5 μm or more and 40 μm or less, and even more preferably 1 μm or more and 20 μm or less. By keeping the particle size within this range, cracking of the sintered body caused by excessive volume shrinkage of the dried coating 13b is prevented when combined with spherical copper particles, and the sinterability of the dried coating 13b is excellent.

[0099] From the viewpoint of improving the filling properties of copper particles to exhibit sufficient bonding strength, the content of copper particles in the paste is preferably 50% by mass or more and 95% by mass or less, more preferably 60% by mass or more and 95% by mass or less.

[0100] Copper particles can also have a surface treatment agent attached to their surface. By attaching the surface treatment agent to the surface of the copper particles, it is possible to inhibit the excessive aggregation of the copper particles.

[0101] The organic solvent contained in the paste preferably has a boiling point M of 150°C or higher and 300°C or lower, particularly 160°C or higher and 290°C or lower, and especially 170°C or higher and 280°C or lower. Specifically, examples include monohydric alcohols, polyhydric alcohols, polyhydric alcohol alkyl ethers, polyhydric alcohol aryl ethers, esters, nitrogen-containing heterocyclic compounds, amides, amines, saturated hydrocarbons, etc. These organic solvents can be used alone or in combination of two or more. By containing an organic solvent with a boiling point within the aforementioned temperature range in the paste, it is easier to adjust the evaporation rate of the organic solvent contained in the wet coating 13a, and it is easier to achieve the appropriate hardness of the dried coating 13b.

[0102] When the paste contains multiple types of organic solvents, it is preferable that at least one organic solvent has a boiling point within the stated temperature range, and it is particularly preferable that all organic solvents have a boiling point within the stated temperature range.

[0103] From the viewpoint of adjusting the evaporation rate of the organic solvent contained in the wet coating 13a to achieve an appropriate hardness of the dried coating 13b, the content of organic solvent in the paste is preferably 3.0% by mass or more and 30.0% by mass or less, more preferably 5.0% by mass or more and 29.0% by mass or less, and even more preferably 7.0% by mass or more and 28.0% by mass or less.

[0104] The paste may also contain appropriate modifiers to adjust various properties. Examples of modifiers include reducing agents, viscosity modifiers, and surface tension modifiers.

[0105] As a reducing agent, a good reducing agent to promote the sintering of copper particles is a combination of various reducing agents, such as monohydric alcohols, polyhydric alcohols, amino alcohols, citric acid, oxalic acid, formic acid, ascorbic acid, aldehydes, hydrazine and its derivatives, hydroxylamine and its derivatives, dithiothreitol, phosphite, hydrogen phosphite, phosphorous acid and its derivatives, etc.

[0106] As a viscosity modifier, it is preferable to use a viscosity modifier that can adjust the viscosity of the paste and is preferably set within the viscosity range mentioned above. Examples of such modifiers include ketones, esters, alcohols, glycols, hydrocarbons, and polymers.

[0107] As a surface tension modifier, a surface tension modifier that can adjust the surface tension of the wet coating 13a is preferred. Examples include acrylic surfactants, silicone surfactants, alkyl polyoxyethylene ethers, fatty acid glycerides and other polymers, alcohols, hydrocarbons, esters and glycols and other monomers.

[0108] From the perspective of improving the coatability or printability of the paste, the viscosity of the paste at a shear rate of 10s is important. -1The lower limit is preferably 10 Pa·s or more and 200 Pa·s or less, more preferably 15 Pa·s or more and 200 Pa·s or less.

[0109] The viscosity of the paste can be measured using a MARS III rheometer manufactured by Thermo Scientific. The measurement conditions for the paste viscosity are as follows.

[0110] Measurement mode: Shear rate dependent measurement

[0111] Sensor: Parallel type (Φ20mm)

[0112] Temperature measured: 25℃

[0113] Gap: 0.300mm

[0114] Shearing rate: 0.05~120.01s -1

[0115] Measurement time: two minutes

[0116] There are no particular limitations on the types of the first joint 11 and the second joint 12. Generally, it is preferred that both the first joint 11 and the second joint 12 contain metal on their joint surfaces. For example, as at least one of the first joint 11 and the second joint 12, a component having a surface made of metal can be used. "Metal" refers to a metal itself that has not formed a compound with other elements or an alloy of two or more metals. Examples of such metals include copper, silver, gold, aluminum, palladium, or nickel, or alloys composed of two or more of these elements.

[0117] When at least one of the first joined body 11 and the second joined body 12 is a member having a surface made of metal, the surface made of metal is generally preferably planar, but may also be curved depending on the circumstances.

[0118] Specific examples of the first bonded body 11 and the second bonded body 12 include, independently, spacers made of the aforementioned metals, heat sinks, semiconductor elements, and substrates having at least one of the aforementioned metals on their surfaces.

[0119] As a substrate, for example, an insulating substrate with a metal layer such as copper on the surface of a ceramic or aluminum nitride plate can be used.

[0120] When a semiconductor element is used as the first bonded object 11 and / or the second bonded object 12, the semiconductor element contains one or more elements such as Si, Ga, Ge, C, N, and As.

[0121] The first substrate 11 is preferably a substrate. The second substrate 12 is preferably any one of a spacer, a heat sink, or a semiconductor element.

[0122] At least one of the first bonded body 11 and the second bonded body 12 can be a dried body containing a paste comprising metal particles and an organic solvent. Specifically, the first bonded body 11 can be a component having a surface made of metal, and the second bonded body 12 can be a dried body containing a paste comprising metal particles and an organic solvent. Furthermore, when using a dried body containing a paste, it is preferable to form the dried body by applying the paste to a support substrate made of a metal such as copper and then drying it.

[0123] The bonding structure obtained by this manufacturing method is suitable for devices that handle high currents, such as automotive electronic circuits and electronic circuits with power devices installed.

[0124] Regarding the above-described embodiments, the present invention also discloses the following methods for manufacturing joint structures, manufacturing laminates, and joining methods.

[0125] [1]

[0126] A method for manufacturing a joint structure, wherein the joint structure is formed by joining a first jointed body and a second jointed body using a joint layer, wherein...

[0127] The manufacturing method includes the following steps:

[0128] The process of applying a paste containing copper particles and organic solvent to the first substrate to form a coating film;

[0129] The drying process removes a portion of the organic solvent contained in the coating film;

[0130] A process is performed by pressing the second bonded body into the coating film in such a way that a portion of the second bonded body is embedded in the coating film, thereby obtaining a laminate comprising the first bonded body, the coating film, and the second bonded body in sequence; and

[0131] The process of heating the laminated body.

[0132] The average thickness of the coating film after the drying process and before the second bonded body is pressed into the coating film is defined as X (μm).

[0133] When the average distance from the upper surface of the first bonded body to the lower surface of the second bonded body in the state of obtaining the laminated body is defined as Y (μm),

[0134] The pressure ratio P, defined by 100-(Y / X×100), is greater than 1.0 and less than 50.

[0135] [2]

[0136] According to the manufacturing method of the joint structure described in [1], wherein,

[0137] The average thickness X of the coating after the drying process is 15 μm or more.

[0138] [3]

[0139] According to the manufacturing method described in [1] or [2], wherein,

[0140] The paste contains 3.0% by mass and less than 30.0% by mass of the organic solvent.

[0141] In the drying process, the coating film is dried such that the mass of the coating film is reduced by more than 3.0% by mass and less than 30.0% by mass.

[0142] [4]

[0143] The manufacturing method according to any one of [1] to [3], wherein,

[0144] The boiling point M of the organic solvent is above 150°C and below 300°C.

[0145] The heating temperature in the drying process is above 20°C and below M°C.

[0146] [5]

[0147] The manufacturing method according to any one of [1] to [4], wherein,

[0148] In the process of obtaining the laminate, a pressure of 0.004 MPa or more and 5 MPa or less is applied to the second substrate to press the second substrate into the coating film.

[0149] [6]

[0150] A method for manufacturing a laminated body, comprising joining a first substrate and a second substrate, wherein,

[0151] The manufacturing method includes the following steps:

[0152] The process of applying a paste containing copper particles and organic solvent to the first substrate to form a coating film;

[0153] The drying process removes a portion of the organic solvent contained in the coating film;

[0154] By pressing the second bonded body into the coating film in such a way that a portion of the second bonded body is embedded in the coating film, a laminate comprising the first bonded body, the coating film, and the second bonded body is obtained.

[0155] The average thickness of the coating film after the drying process and before the second bonded body is pressed into the coating film is defined as X (μm).

[0156] When the average distance from the upper surface of the first bonded body to the lower surface of the second bonded body in the state of obtaining the laminated body is defined as Y (μm),

[0157] The pressure ratio P, defined by 100-(Y / X×100), is greater than 1.0 and less than 50.

[0158] [7]

[0159] A joining method, wherein a first joined body and a second joined body are joined, wherein,

[0160] The joining method includes the following steps:

[0161] The process of applying a paste containing copper particles and organic solvent to the first substrate to form a coating film;

[0162] The drying process removes a portion of the organic solvent contained in the coating film;

[0163] A process is performed by pressing the second bonded body into the coating film in such a way that a portion of the second bonded body is embedded in the coating film, thereby obtaining a laminate comprising the first bonded body, the coating film, and the second bonded body in sequence; and

[0164] The process of heating the laminated body.

[0165] The average thickness of the coating film after the drying process and before the second bonded body is pressed into the coating film is defined as X (μm).

[0166] When the average distance from the upper surface of the first bonded body to the lower surface of the second bonded body in the state of obtaining the laminated body is defined as Y (μm),

[0167] The pressure ratio P, defined by 100-(Y / X×100), is greater than 1.0 and less than 50.

[0168] Example 1

[0169] The present invention will now be described in more detail with reference to embodiments. However, the scope of the present invention is not limited to these embodiments. Furthermore, unless otherwise specified, "%" refers to "mass %".

[0170] [Examples 1 and 2, and Comparative Examples 1 and 2]

[0171] (1) Preparation of paste

[0172] The following ingredients are used as components of the paste.

[0173] Copper powder 1: 53% spherical copper particles with a particle size of 0.1–0.2 μm.

[0174] • Copper powder 2: 23% flat copper particles with a particle size of 4.5μm

[0175] Organic solvent 1: Hexanediol (boiling point 198℃) 18.9%

[0176] Organic solvent 2: Diethylene glycol (boiling point 244.3℃) 2.4%

[0177] Organic solvent 3: Polyethylene glycol 300 (boiling point 250℃) 0.76%

[0178] • Reducing agent: 1.9% bis(2-hydroxyethyl)iminotris(hydroxymethyl)methane

[0179] (2) Application of paste to the first bonded body

[0180] A copper substrate (20mm × 20mm, 2mm thick) was used as the first substrate to be bonded. On this substrate, a paste was printed using a metal mask (6mm × 6mm, 100μm thick) to form a rectangular wet coating.

[0181] The wet coating was dried in atmospheric air at 40°C for the times shown in Table 1 to remove the organic solvent, resulting in a dried coating. The percentage reduction in coating mass due to the removal of the organic solvent is also shown in the table. The thickness of the dried coating is also shown in the table.

[0182] The percentage reduction in the mass of the wetted coating is measured using the following methods.

[0183] After measuring the mass of a copper substrate using an electronic balance, the mass of the substrate containing the wet coating after paste printing is measured using the same electronic balance. The mass of the wet coating obtained by subtracting the mass of the substrate before printing from the mass of the substrate containing the wet coating is taken as the mass of the wet coating obtained by printing. Then, after drying the substrate containing the wet coating for a predetermined time, the mass of the substrate containing the dried coating is measured using an electronic balance. The mass of the wet coating reduced due to drying is taken as the mass of the wet coating reduced by drying by subtracting the mass of the substrate containing the dried coating from the mass of the copper-only substrate. The mass reduction percentage (%) of the wet coating is calculated by dividing the mass of the wet coating reduced by drying by the mass of the wet coating obtained by printing and multiplying by 100.

[0184] (3) Place the second substrate onto the dried coating film.

[0185] As the second substrate, a model component for a semiconductor power device is envisioned, and an Ag-plated SiC chip (5mm × 5mm) is prepared. The Ag-plated surface of the SiC chip is placed on the center of the dried coating using a chip mounter at a pressure of 0.004 MPa. The average thickness B of the second substrate is shown in Table 1.

[0186] (4) Formation of stacked bodies

[0187] By applying the pressure shown in Table 1 to the SiC chip for two seconds from the side opposite to the Ag-plated side, the SiC chip is pressed into the dry coating to form a laminate. The indentation rate P is calculated using the method described above. The results are shown in Table 1.

[0188] Regarding Comparative Example 1, the mass reduction of the wet coating was as small as 3.1%, therefore the dried coating was in a deformable state, and a portion of the dried coating bulged towards the upper part of the second bonded body when pressure was applied. The thicknesses under this condition were measured, and the indentation rate P was calculated.

[0189] (5) Firing of laminated bodies

[0190] The laminate is moved to a firing furnace, pressurized to 9 MPa in a nitrogen atmosphere, heated to 280°C, and held for 5 minutes to fire the coating to form a bonding layer, thus obtaining a bonded structure.

[0191] [Evaluation 1]

[0192] In the embodiments and comparative examples, the stack obtained in “(4) Formation of the stack” was flipped over for 1 second, and the SiC chip was visually observed for misalignment and detachment. The results are shown in Table 1.

[0193] [Evaluation 2]

[0194] In the examples and comparative examples, to confirm the bonding strength of the bonded structure obtained in "(5) Firing of the laminate", the shear strength was measured by the following method. Shear strength (MPa) is calculated as the fracture pressure (N) / the bottom area of ​​the SiC chip (mm²). 2 The values ​​are defined as follows. The results are shown in Table 1. In addition, for Comparative Example 2, since the SiC chip fell off during the evaluation of SiC chip misalignment and detachment, this evaluation was not performed and is marked as "-" in Table 1.

[0195] • Measuring device name: Condor Sigma (manufactured by XYZTEC)

[0196] Force sensor: 200 kgf

[0197] • Cutting tool: 6.0mm width, 2.0mm thickness, 1 / 4-inch shaft (Model: T0S 663060)

[0198] • Shear rate: 50 μm / s

[0199] • Shear height: 0.02mm (zero point is the top of the coating printed in 6mm square sections)

[0200]

[0201] As shown in Table 1, if the method of the embodiment is used, misalignment and detachment of the SiC chip will not occur. It can also be seen that sufficient bonding strength can be obtained.

[0202] Industrial availability

[0203] According to the present invention, a method for manufacturing a joint structure is provided, which enables the jointing of the jointed bodies to be performed using a jointing material without causing misalignment or detachment.

Claims

1. A method for manufacturing a joint structure, wherein the joint structure is formed by joining a first jointed body and a second jointed body using a joint layer, wherein, The manufacturing method includes the following steps: The process of applying a paste containing copper particles and organic solvent to the first substrate to form a coating film; The drying process removes a portion of the organic solvent contained in the coating film; The process involves pressing the second bonded body into the coating film in such a way that a portion of the second bonded body is embedded in the coating film, thereby obtaining a laminate comprising the first bonded body, the coating film, and the second bonded body in sequence; as well as The process of heating the laminated body. The average thickness of the coating film after the drying process and before the second bonded body is pressed into the coating film is defined as X (μm). When the average distance from the upper surface of the first bonded body to the lower surface of the second bonded body in the state of obtaining the laminated body is defined as Y (μm), The pressure ratio P, defined by 100-(Y / X×100), is greater than 1.0 and less than 50.

2. The method for manufacturing the joint structure according to claim 1, wherein, The average thickness X of the coating after the drying process is 15 μm or more.

3. The manufacturing method according to claim 1 or 2, wherein, The paste contains 3.0% by mass and less than 30.0% by mass of the organic solvent. In the drying process, the coating film is dried such that the mass of the coating film is reduced by more than 3.0% by mass and less than 30.0% by mass.

4. The manufacturing method according to claim 1 or 2, wherein, The boiling point M of the organic solvent is above 150°C and below 300°C. The heating temperature in the drying process is above 20°C and below M°C.

5. The manufacturing method according to claim 1 or 2, wherein, In the process of obtaining the laminate, a pressure of 0.004 MPa or more and 5 MPa or less is applied to the second substrate to press the second substrate into the coating film.

6. A method for manufacturing a laminate, used to join a first substrate and a second substrate, wherein, The manufacturing method includes the following steps: The process of applying a paste containing copper particles and organic solvent to the first substrate to form a coating film; The drying process removes a portion of the organic solvent contained in the coating film; By pressing the second bonded body into the coating film in such a way that a portion of the second bonded body is embedded in the coating film, a laminate comprising the first bonded body, the coating film, and the second bonded body is obtained. The average thickness of the coating film after the drying process and before the second bonded body is pressed into the coating film is defined as X (μm). When the average distance from the upper surface of the first bonded body to the lower surface of the second bonded body in the state of obtaining the laminated body is defined as Y (μm), The pressure ratio P, defined by 100-(Y / X×100), is greater than 1.0 and less than 50.

7. A joining method, wherein a first joined body and a second joined body are joined, wherein, The joining method includes the following steps: The process of applying a paste containing copper particles and organic solvent to the first substrate to form a coating film; The drying process removes a portion of the organic solvent contained in the coating film; The process involves pressing the second bonded body into the coating film in such a way that a portion of the second bonded body is embedded in the coating film, thereby obtaining a laminate comprising the first bonded body, the coating film, and the second bonded body in sequence; as well as The process of heating the laminated body. The average thickness of the coating film after the drying process and before the second bonded body is pressed into the coating film is defined as X (μm). When the average distance from the upper surface of the first bonded body to the lower surface of the second bonded body in the state of obtaining the laminated body is defined as Y (μm), The pressure ratio P, defined by 100-(Y / X×100), is greater than 1.0 and less than 50.

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