Method for manufacturing bonded body, and method for bonding bodies to be bonded

Abstract

Provided is a method for manufacturing a bonded body (16) in which a first body (11) to be bonded and a second body (12) to be bonded are bonded with a bonding layer (13c) therebetween. The manufacturing method comprises: a step for preparing a temporary fixing material-attached second body (14) to be bonded that has a temporary fixing material (20) disposed on one surface of the second body (12) to be bonded, and a first body (11) to be bonded on which a bonding layer precursor (13b) is formed; a step for obtaining a laminated body (15) by bringing the bonding layer precursor (13b) and the temporary fixing material-attached second body (14) to be bonded into abutment with each other such that the bonding layer precursor (13b) and the temporary fixing material (20) are in contact with each other; and a step for obtaining a bonded body (16) in which the first body (11) to be bonded and the second body (12) to be bonded are bonded by heating the laminated body (15) so as to turn the bonding layer precursor (13b) into a bonding layer (13c).

Description

Method for manufacturing joined body and method for joining bodies to be joined

[0001] The present invention relates to a method for producing a bonded body, and also to a method for bonding bodies to be bonded.

[0002] In recent years, semiconductor elements known as power devices have been widely used in power conversion and control devices such as inverters. Unlike integrated circuits such as memories and microprocessors, power devices are designed to control high currents, and therefore generate a great deal of heat during operation. For this reason, various technologies have been proposed for bonding semiconductor elements to substrates using metal pastes containing highly heat-resistant metal particles.

[0003] In a process of bonding a semiconductor element to a substrate, if the semiconductor element is placed on a coating layer of a metal paste and is transported in that state or is subjected to external vibrations, the semiconductor element may shift from its appropriate bonding position, resulting in a problem in bonding the semiconductor element to the substrate. For this reason, as in Patent Document 1, for example, a method for manufacturing a semiconductor device has been proposed, which includes the steps of applying a metal paste containing silver particles to a position on a substrate where a chip is to be mounted and then drying the paste to form an Ag layer on the position where the chip is to be mounted, supplying a temporary fixing material (temporary fixing material) so that the temporary fixing material is in contact with the position where the chip is to be mounted, and mounting the semiconductor chip on the Ag layer so that a portion of the back surface of the semiconductor chip is in contact with the temporary fixing material.

[0004] US Patent Application Publication No. 2018 / 0247884

[0005] The invention described in Patent Document 1 requires a step of applying a temporary fixing material onto the Ag layer made of a dried coating film of a metal paste, which may result in a decrease in productivity depending on the size, shape, etc. of the semiconductor chip used. There is also a demand for eliminating the step of applying a temporary fixing material onto the Ag layer itself.

[0006] Therefore, an object of the present invention is to provide a method for producing a bonded body and a method for bonding bodies to be bonded, which are highly productive.

[0007] The present invention provides a method for manufacturing a bonded body in which a first body to be bonded and a second body to be bonded are bonded via a bonding layer, the method comprising the steps of: preparing a second body to be bonded with a temporary fixing material, the second body to be bonded having a temporary fixing material arranged on one surface of the second body to be bonded, and the first body to be bonded having a bonding layer precursor formed thereon; obtaining a laminated body by bringing the bonding layer precursor and the second body to be bonded with the temporary fixing material into contact with each other; and heating the laminated body to turn the bonding layer precursor into a bonding layer, thereby obtaining the bonded body in which the first body to be bonded and the second body to be bonded are bonded.

[0008] The present invention also provides a method for bonding a first object to be bonded and a second object to be bonded via a bonding layer, the bonding method comprising the steps of: preparing a second object to be bonded with a temporary fixing material, the second object to be bonded having a temporary fixing material arranged on one surface of the second object to be bonded, and the first object to be bonded having a bonding layer precursor formed thereon; bringing the bonding layer precursor and the second object to be bonded with the temporary fixing material into contact with each other to obtain a laminate; and heating the laminate to turn the bonding layer precursor into a bonding layer, thereby obtaining a bonded body in which the first object to be bonded and the second object to be bonded are bonded together.

[0009] Fig. 1 is a process diagram showing one embodiment of a method for manufacturing a bonded body of the present invention. Fig. 2 is a plan view of one embodiment of a second bonded body with a temporary fixing material used in the manufacturing method shown in Fig. 1, seen from the side on which the temporary fixing material is arranged. Fig. 3 is a plan view of another embodiment of a second bonded body with a temporary fixing material used in the manufacturing method shown in Fig. 1, seen from the side on which the temporary fixing material is arranged. Fig. 4 is a perspective view showing one embodiment of a method for manufacturing the second bonded body with a temporary fixing material shown in Fig. 2.

[0010] The present invention will be described below based on preferred embodiments. The present invention relates to a method for manufacturing a bonded body in which two bonded bodies, i.e., a first bonded body and a second bonded body, are bonded via a bonding layer. This manufacturing method can be broadly divided into the following steps: (1) a step of preparing a second bonded body with a temporary fixing material, in which a temporary fixing material is disposed on one surface of the second bonded body, and a first bonded body on which a bonding layer precursor is formed (preparation step); (2) a step of abutting the bonding layer precursor and the second bonded body with the temporary fixing material so that the bonding layer precursor and the temporary fixing material come into contact with each other, thereby obtaining a laminate (temporary fixing step); and (3) a step of heating the laminate to turn the bonding layer precursor into a bonding layer, thereby obtaining a bonded body in which the first bonded body and the second bonded body are bonded (bonding step). Each step will be described below with reference to FIGS. 1 to 4 .

[0011] (1) Preparation Step The preparation step can be roughly divided into a step of preparing a second body to be bonded 14 with a temporary fixing material, in which the temporary fixing material 20 is arranged on one surface of the second body to be bonded 12, and a step of preparing a first body to be bonded 11 on which the bonding layer precursor 13b is formed. There is no limitation on the order in which the two steps are performed, and one step may be performed after the other step, or both steps may be performed simultaneously in parallel.

[0012] First, a process for preparing the second bonded body 14 with a temporary fixing material (see FIGS. 2 and 3) will be described. The temporary fixing material 20 is used to temporarily fix the first bonded body 11 and the second bonded body 12 prior to bonding (i.e., permanently fixing) the two bodies. The temporarily fixed first bonded body 11 and second bonded body 12 are bonded in a bonding process to form a bonded body 16. Details of the temporary fixing material 20 will be described later.

[0013] There are no particular limitations on the arrangement pattern of the temporary fixing material 20 on the second object to be joined 12, and for example, the temporary fixing material 20 may be arranged on the entire surface of one surface of the second object to be joined 12, or may be arranged on only a part of one surface of the second object to be joined 12. From the viewpoint of reducing the amount of temporary fixing material 20 used while still exhibiting temporary fixing performance, it is preferable to arrange the temporary fixing material 20 so that areas 21 where the temporary fixing material 20 is arranged and areas 22 where the temporary fixing material 20 is not arranged are mixed on the second object to be joined 12, as shown in Figures 2 and 3. Reducing the amount of temporary fixing material 20 used here leads to cost reduction and also to suppression of voids and organic residues that may be generated when the laminate 15 is heat-treated in the joining step described below.

[0014] As an arrangement pattern of the temporary fixing material 20, for example, as shown in FIG. 2, the non-disposition portions 22 and the disposition portions 21 can be arranged in an island-in-sea pattern, in which island portions made of the disposition portions 21 are scattered in a sea portion made of the non-disposition portions 22. Alternatively, as shown in FIG. 3, the disposition portions 21 and the non-disposition portions 22 can be arranged in an island-in-sea pattern, in which island portions made of the non-disposition portions 22 are scattered in a sea portion made of the disposition portions 21. In these patterns, the size and shape of the island portions may be the same or different. Furthermore, the arrangement of the island portions may be regular or irregular. When the island portions are arranged regularly, the arrangement pattern of the island portions may be such that they are arranged at the intersections of vertical and horizontal grids or in a houndstooth check pattern. In addition to these patterns, the non-disposition portions 22 and the disposition portions 21 can also be arranged in a striped pattern, in which the non-disposition portions 22 and the disposition portions 21 are alternately arranged so as to extend in the same direction.

[0015] The ratio of the mass of the temporary fixing material 20 to the area of ​​the second object to be joined 12 is set to 0.00001 mg / mm from the viewpoint of reducing the amount of the temporary fixing material 20 used while still exhibiting temporary fixing performance. ２ 0.32mg / mm or more ２ It is preferable that the concentration is 0.0001 mg / mm or less. ２ 0.26mg / mm or more ２ It is more preferable to set the following:

[0016] From the viewpoint of being able to effectively prevent the generation of voids during bonding while exhibiting temporary bonding performance, the occupancy rate of the temporary fixing material 20 in the area of ​​the second object to be bonded 12 is preferably 1% or more and 90% or less, and more preferably 3% or more and 85% or less. Here, "the occupancy rate of the temporary fixing material 20 in the area of ​​the second object to be bonded 12" refers to the arithmetic mean value of the occupancy rate of the temporary fixing material 20 formed in each area portion, obtained by cutting out similar shapes that are 1 / 16 the size of the second object to be bonded 12 at any five positions on the second object to be bonded 12.

[0017] From a similar viewpoint, in the second bonded body 14 with temporary fixing material, when the mass of the second bonded body 12 is W1 and the mass of the temporary fixing material 20 is W2, it is preferable that the ratio W2 / W1 of W2 to W1 is 0.0001 or more and 0.50 or less.

[0018] As shown in FIG. 2 , when the temporary fixing materials 20 are arranged at the intersections of a vertical and horizontal grid, the spacing between the temporary fixing materials 20 is preferably equal to or greater than the application diameter of the temporary fixing material 20 in both the vertical and horizontal directions, from the viewpoint of reducing the amount of temporary fixing material 20 used. Furthermore, from the viewpoint of achieving favorable temporary fixing performance, the spacing between the temporary fixing materials 20 is preferably equal to or less than the shorter of the vertical and horizontal lengths of the second object to be joined 12 (or, if both lengths are the same, that length). Note that the term "spacing" here refers to the distance from the center of one temporary fixing material 20 to the center of the other temporary fixing material 20 between adjacent temporary fixing materials 20. In the illustrated embodiment, the temporary fixing materials 20 are arranged at equal intervals in both the vertical and horizontal directions.

[0019] There are no particular limitations on the method for disposing the temporary fixing material 20 on one surface of the second object to be joined 12. For example, it can be performed by a transfer method, a screen printing method, a gravure printing method, a dispensing method, an inkjet printing method, a spray (atomization) method, a reverse coating method, a doctor blade method, or the like. Among these, it is preferable to dispose the temporary fixing material 20 on one surface of the second object to be joined 12 by a transfer method, because this method can be performed inexpensively and quickly. Note that the temporary fixing material 20 may or may not be heated when it is disposed on one surface of the second object to be joined 12.

[0020] 4 shows a preferred embodiment of the transfer method. First, a sheet 23 on which temporary fixing materials 20 are applied in a predetermined arrangement pattern is prepared, and the temporary fixing materials 20 arranged on the sheet 23 are brought into contact with the second object to be joined 12. Thereafter, the sheet 23 is peeled off, thereby transferring the temporary fixing materials 20 from the sheet 23 to the second object to be joined 12, thereby obtaining a second object to be joined 14 with the temporary fixing material. The temporary fixing materials 20 applied to the sheet 23 may be transferred in their entirety to the sheet 23, or only a portion of them may be transferred to the sheet 23. As a method for applying the temporary fixing materials 20 to the sheet 23, any of the methods exemplified above for arranging the temporary fixing materials 20 on one surface of the second object to be joined 12 can be used as appropriate.

[0021] There are no particular limitations on the material of the sheet 23, and it is possible to use, for example, organic materials, glass, metals, ceramics, etc. For the purpose of successful transfer, the surface of the sheet 23 on which the temporary fixing material 20 is placed may or may not be subjected to a release treatment using silicone or the like.

[0022] When transferring the temporary fixing material 20 to the second object to be joined 12, the sheet 23 and / or the second object to be joined 12 may or may not be heated. When the temporary fixing material 20 contains a solid component, it is preferable to heat the sheet 23 and / or the second object to be joined 12 in order to dissolve the solid component. The sheet 23 and the second object to be joined 12 may be heated before the temporary fixing material 20 and the second object to be joined 12 come into contact with each other, or may be heated after the temporary fixing material 20 and the second object to be joined 12 come into contact with each other. The heating temperature of the sheet 23 and / or the second object to be joined 12 may be, for example, 15°C or higher and 250°C or lower, particularly 20°C or higher and 200°C or lower.

[0023] From the viewpoint of arranging the temporary fixing materials 20 in a desired arrangement pattern on the second object to be joined 12, it is preferable that the arrangement pattern of the temporary fixing materials 20 on the sheet 23 be a mirror image of the desired arrangement pattern of the temporary fixing materials 20 on the second object to be joined 12. In the illustrated embodiment, the arrangement pattern of the temporary fixing materials 20 on the second object to be joined 12 is line-symmetric, and therefore the arrangement pattern of the temporary fixing materials 20 on the sheet 23 and the arrangement pattern of the temporary fixing materials 20 on the second object to be joined 12 are the same.

[0024] Next, a method for preparing the first bonded body 11 (see FIG. 1( a) ) on which the bonding layer precursor 13 b is formed will be described. The bonding layer precursor 13 b can be formed, for example, by applying a paste containing metal fine particles and an organic solvent (hereinafter also referred to as “metal paste”) to the one surface 11 a of the first bonded body 11. In this case, the coating film of the metal paste is the bonding layer precursor 13 b. Alternatively, the bonding layer precursor 13 b can be formed by forming a coating film of the metal paste on the one surface 11 a of the first bonded body 11 by the above-described method and then drying the coating film. In this case, the dried body of the coating film of the metal paste (dried coating film) is the bonding layer precursor 13 b. Furthermore, the bonding layer precursor 13 b may be formed by disposing a sheet containing metal fine particles dispersed in a resin on the one surface 11 a of the first bonded body 11.

[0025] As described above, the bonding layer precursor is a metal paste containing metal fine particles and an organic solvent or a dried form thereof, or a sheet in which metal fine particles are dispersed in a resin.

[0026] When obtaining a dried body from the metal paste coating, it is not necessary to remove all of the organic solvent; it is sufficient to remove the organic solvent to the extent that the metal paste coating loses fluidity. Therefore, the organic solvent may remain in the bonding layer precursor 13b. In this case, from the viewpoint of suppressing the generation of voids and organic residues and suppressing a decrease in bonding strength due to an inability to ensure the thickness after sintering, it is preferable that the proportion of the organic solvent contained in the bonding layer precursor 13b be 10 mass% or less.

[0027] From the viewpoint of sufficiently reducing the amount of organic solvent contained in the bonding layer precursor 13b, the drying temperature of the metal paste coating film can be, for example, from 60° C. to 150° C. Furthermore, the drying temperature of the metal paste coating film can be, for example, from 5 minutes to 120 minutes.

[0028] The formation of the bonding layer precursor 13b by drying the coating film of the metal paste can be performed in an inert gas atmosphere such as nitrogen gas or argon gas, or in the air. Heating may be performed under reduced pressure. There are no particular limitations on the heating means. For example, heating means such as blowing hot air, irradiating with infrared rays, or heating in a heating furnace can be used.

[0029] 1(a) and 1(b), the bonding layer precursor 13b and the second bonded body 14 with the temporary fixing material are brought into contact with each other so that the bonding layer precursor 13b and the temporary fixing material 20 come into contact with each other, thereby obtaining a laminate 15. In the laminate 15, the temporary fixing material 20 is interposed between the first bonded body 11 and the second bonded body 12, and the first bonded body 11 and the second bonded body 12 are temporarily fixed together due to this. Note that, to facilitate understanding, the temporary fixing material 20, which is normally not visible, is shown in FIG. 1(b). "Temporary fixation" refers to a state in which the first bonded object 11 and the second bonded object 12 are temporarily fixed together, and although the fixed state changes when a large external force is applied, the fixed state does not change when a small external force is applied (for example, when a stack 15 of the first bonded object 11 and the second bonded object 12 is placed so that the bonding surfaces of both bonded objects 11 and 12 face vertically, a force that would cause either the first bonded object 11 or the second bonded object 12 to fall under its own weight).

[0030] In the prior art, temporary fixing was typically performed by applying a temporary fixing material to the bonding layer precursor and then laminating the second bonded body 12 on it. However, this temporary fixing method, which requires a temporary fixing material application step, is not desirable from the perspective of productivity. Furthermore, applying the temporary fixing material requires forming a pattern corresponding to the shapes of the bonded body and the bonding layer precursor, which also reduces productivity. Furthermore, voids may occur in the bonding layer 13c during the subsequent bonding process, reducing the bonding strength between the bonded bodies 11 and 12. In contrast, the manufacturing method of the present invention allows the temporary fixing material 20 to be easily formed on one side of the second bonded body 12 in advance, thereby not impairing productivity. Furthermore, forming the temporary fixing material 20 on one side of the second bonded body 12 in a pattern optimized for increasing bonding strength reduces the likelihood of voids occurring in the bonding layer 13c during the subsequent bonding process, thereby improving the bonding strength of the resulting bonded body 16.

[0031] When the bonding layer precursor 13b and the second bonded body 14 with the temporary fixing material are brought into contact with each other, the bonding layer precursor 13b and the second bonded body 14 with the temporary fixing material may be brought into contact at room temperature without being heated, or either or both of the bonding layer precursor 13b and the second bonded body 14 with the temporary fixing material may be heated in advance before being brought into contact with each other.

[0032] (3) Bonding Step Next, the laminate 15 shown in FIG. 1(b) is heated (FIG. 1(c)). The metal microparticles contained in the bonding layer precursor 13b are sintered by the heating to form a bonding layer 13c that bonds the two bonded bodies 11 and 12. In this manner, a bonded body 16 is obtained in which the two bonded bodies 11 and 12 are bonded by the bonding layer 13c. Since heating is typically performed in a heating furnace (not shown), the temporarily fixed bonded bodies 11 and 12 shown in FIG. 1(b) are transported to the heating furnace by a transport means (not shown). Since the bonded bodies 11 and 12 are temporarily fixed in a short time by the temporary fixing material 20, positional deviation between the bonded bodies 11 and 12 during transport is effectively prevented. As a result, the bonded bodies 11 and 12 are bonded in the heating furnace at the originally intended bonding positions.

[0033] From the viewpoint of sufficiently sintering the metal fine particles to increase the bonding strength between the bodies 11 and 12 and from the viewpoint of removing the temporary fixing material 20 by heat, the heating temperature of the laminate 15 is preferably 180° C. or higher, and more preferably 200° C. or higher. Furthermore, from the viewpoint of preventing the bodies 11 and 12 from being damaged by heat, the heating temperature of the laminate 15 is preferably 350° C. or lower, and more preferably 330° C. or lower. The atmosphere in which the laminate 15 is heated can be any of an oxygen-containing atmosphere such as air, an inert gas atmosphere such as nitrogen, and a reducing gas atmosphere containing hydrogen, formic acid, or the like.

[0034] The heating of both the bodies to be bonded 11 and 12 may be performed without applying pressure (a state in which only the weight of both the bodies to be bonded 11 and 12 is applied), or may be performed under pressure in order to further improve bonding reliability. When heating under pressure, the pressure to be applied is preferably 1 MPa or more and 40 MPa or less, and more preferably 5 MPa or more and 30 MPa or less.

[0035] Next, the temporary fixing material 20, the metal paste, the resin, the first object to be joined 11, and the second object to be joined 12 used in the above-mentioned joining method by temporary fixing will be described.

[0036] The temporary fixing material 20 preferably contains a substance that is solid at 25°C (hereinafter also referred to as the "first component"), from the viewpoint of making it easier to retain its sheet shape. Note that "solid" refers to a rigid body that undergoes no or very little deformation or volume change, and that does not flow to fit the internal shape of a container when the temporary fixing material 20 is placed in the container, nor does it diffuse to fill the entire container. Examples of such a substance include stone-like, rock-like, wax-like, and wax-like substances.

[0037] Examples of the first component include monoalcohols, polyhydric alcohols, polyhydric alcohol alkyl ethers, polyhydric alcohol aryl ethers, esters, heterocyclic compounds, amides, amines, saturated hydrocarbons, cyclic terpene alcohols and their derivatives, ketones, and carboxylic acids. These first components can be used alone or in combination of two or more. Among these, saturated aliphatic monoalcohols, saturated aliphatic polyhydric alcohols, saturated fatty acid esters, cyclic terpene alcohol derivatives, oxygen-containing heterocyclic compounds, and saturated aliphatic monocarboxylic acids are preferred. Preferably, these have 6 to 21 carbon atoms. Among these, myristyl alcohol, palmityl alcohol, stearyl alcohol, 1,6-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, trimethylolpropane, methyl stearate, borneol, 2,4,6-triisopropyl-1,3,5-trioxane, capric acid, lauric acid, myristic acid, palmitic acid, and the like are particularly preferred.

[0038] The temporary fixing material 20 preferably contains, in addition to the first component, an organic solvent (hereinafter also referred to as the "second component") having a boiling point of 150°C or higher. The second component is preferably liquid at 25°C. By including the second component having a boiling point of 150°C or higher in the temporary fixing material 20, excessive volatilization of the solvent component in the temporary fixing material 20 can be prevented, and the temporary fixing effect is more stably exhibited between the temporary fixing step and the subsequent joining step. From the viewpoint of more reliably obtaining such an effect, the boiling point of the second component is preferably 150°C or higher and 400°C or lower, and more preferably 160°C or higher and 350°C or lower. In this specification, the boiling point refers to the boiling point under an atmospheric pressure of 1 atmosphere.

[0039] The temporary fixing material 20 preferably contains 5% by mass or more, and more preferably 10% by mass or more, of the second component in order to increase the fluidity of the temporary fixing material 20. Furthermore, the temporary fixing material 20 preferably contains 58% by mass or less, and more preferably 45% by mass or less, of the second component in order to shorten the curing time after temporary fixing and to increase the strength of the temporary fixing.

[0040] As described above, the second component can be suitably selected from those that do not change the state of the bonding layer precursor 13b and have the necessary fluidity for placement on one surface of the second object to be bonded 12. Examples of such second components include monoalcohols, 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, and the like, which are similar to the organic solvents listed above. These organic components can be used alone or in combination of two or more. Among these, saturated aliphatic polyhydric alcohols, unsaturated aliphatic monoalcohols, unsaturated fatty acid esters, tertiary amines, cyclic terpene alcohol derivatives, unsaturated aliphatic monocarboxylic acids, and saturated aliphatic hydrocarbons are preferred. Preferably, these organic components have 3 to 21 carbon atoms. Among these, particularly preferred are glycerin, 1,2,4-butanetriol, oleyl alcohol, methyl oleate, triethanolamine, 4-(1'-acetoxy-1'-methylethyl)-cyclohexanol acetate, isobornylcyclohexanol, oleic acid, normal decane, and the like. The above phrase "does not change the state of the bonding layer precursor 13b" refers to the fact that, when 1 μL of the second component is dropped onto the bonding layer precursor 13b and the sintered precursor is dried at 110°C or less, no change is observed in the bonding layer precursor 13b before and after the dropping when observed under a microscope at a magnification of 140x. Furthermore, this "no change is observed" also includes not only the fact that no change is observed in the bonding layer precursor 13b before and after the dropping, but also the fact that no traces of the dropping are observed in the ultrasonic flaw detection image after bonding.

[0041] In addition to the first and second components described above, the temporary fixing material 20 may contain other components within a range that does not impair the effects of the present invention.

[0042] It is preferable that the temporary fixing material 20 is substantially free of organic polymer compounds and inorganic compounds. By not including organic polymer compounds and inorganic compounds in the temporary fixing material 20, for example, it is possible to shorten the solidification time and suppress the permeation of the temporary fixing material 20 over time. This ensures the strength of the temporary fixing of both the objects to be joined 11 and the second object to be joined 12 even when the process time for joining the first object to be joined 11 and the second object to be joined 12 is relatively long. Note that the term "substantially free" allows for the inevitable mixing of organic polymer compounds or inorganic compounds.

[0043] Examples of the organic polymer compound include polyolefins such as polyethylene, polypropylene, and ethylene-α-olefin copolymers; polyesters such as polyethylene terephthalate and polybutylene terephthalate; vinyl polymers such as polyvinyl chloride and polystyrene; (meth)acrylic acid polymers such as poly(meth)acrylic acid and polyalkyl(meth)acrylate; terpene polymers such as polyethylene glycol, terpene polymers, and terpene phenol polymers; polycarbonate, polyethersulfone, and the like.

[0044] The temporary fixing material 20 can be prepared, for example, by mixing the first component and the second component in a heated state at 30°C or higher and 70°C or lower, or by mixing the first component and the second component and then heating the mixture to 30°C or higher and 70°C or lower.

[0045] The temporary fixing material 20 preferably has a 95% mass loss temperature in a nitrogen atmosphere of 300°C or lower, and more preferably 280°C or lower. Since the temporary fixing material 20 has such properties, it is easily removed in the joining step, and residue is less likely to be left between the first and second objects to be joined 11 and 12. This increases the joining strength between the first and second objects to be joined 11 and 12. Meanwhile, the temporary fixing material 20 preferably has a 10% mass loss temperature in a nitrogen atmosphere of 120°C or higher, and more preferably 150°C or higher. Because of these properties, the temporary fixing material 20 can stably exert its temporary fixing effect during the period from temporary fixing to the next step, the joining step. The above-mentioned 95% mass loss temperature and 10% mass loss temperature are the 95% mass loss temperature and 10% mass loss temperature when a sample is heated from 25°C to 40°C at a heating rate of 2°C / min in a nitrogen flow, maintained at this temperature for 15 minutes, and then subjected to thermogravimetric differential thermal analysis under the following conditions: a heating rate of 10°C / min in a nitrogen atmosphere (e.g., in a nitrogen flow), and a sample mass of 30 mg.

[0046] Next, the metal paste used in the manufacturing method of the present invention will be described. The metal paste contains metal fine particles and an organic solvent. While there are no particular limitations on the type of metal used for the metal fine particles, it is advantageous to use a metal with a relatively high melting point in order to enhance the heat resistance of the bonded body 16. Examples of such metals include copper, silver, gold, aluminum, titanium, nickel, or alloys of two or more of these. Copper, silver, or alloys of these are particularly preferred, with copper or copper alloys being particularly preferred. When the metal fine particles contain these metal components, the electrical conductivity and thermal conductivity of the bonding layer formed from the bonding layer precursor are improved. In particular, when the metal fine particles contain copper, the heat resistance of the bonding layer is also improved, making copper an advantageous metal from an economical perspective. The metal fine particles may contain the various metal components described above, and a portion of the particle surface may be modified.

[0047] Volume cumulative particle size D of metal fine particles ＳＥＭ５０ The volume cumulative particle diameter D is preferably 0.01 μm or more and 30 μm or less in order to maintain good bonding between the first and second objects to be bonded.ＳＥＭ５０ can be determined, for example, by the following measurement method. Metal fine particles with clear contours are photographed using a scanning electron microscope (SEM) at a magnification of 10,000 times or more and 150,000 times or less. After the SEM image of the metal fine particles is read using Mac-View manufactured by Mountech Co., Ltd., 50 or more metal fine particles on the SEM image are randomly selected and the particle diameters (Heywood diameters) of the particles are measured. Next, the volume of the particles is calculated from the obtained Heywood diameter assuming that the particles are spherical, and the particle diameter at 50% by volume of the cumulative volume is determined as the volume cumulative particle diameter D ＳＥＭ５０ Let's say.

[0048] There is no particular limitation on the shape of the metal fine particles, and examples thereof include spherical, polyhedral, flat, amorphous, and combinations thereof. The metal fine particles may have two or more peaks in their particle size distribution.

[0049] The metal fine particles may have a surface treatment agent attached to their surfaces. By attaching a surface treatment agent to the surfaces of the metal fine particles, excessive aggregation and oxidation of the metal fine particles can be suppressed. Examples of the surface treatment agent include fatty acids, aliphatic amines, silane coupling agents, titanate coupling agents, aluminate coupling agents, etc.

[0050] The type of organic solvent contained in the metal paste is not particularly limited as long as it can disperse the metal fine particles into a paste. Examples of organic solvents include monoalcohols, polyhydric alcohols, polyhydric alcohol alkyl ethers, polyhydric alcohol aryl ethers, polyethers, esters, nitrogen-containing heterocyclic compounds, amides, amines, terpene alcohols, ketones, and saturated hydrocarbons.

[0051] The metal paste may contain an appropriate adjuster to adjust various properties of the paste. Examples of the adjuster include a reducing agent, a viscosity adjuster, and a surface tension adjuster. The reducing agent is preferably one that promotes sintering of the metal particles, such as monoalcohols, polyhydric alcohols, amino alcohols, citric acid, oxalic acid, formic acid, ascorbic acid, aldehydes, hydrazine and its derivatives, hydroxylamine and its derivatives, dithiothreitol, phosphite, hydrophosphite, phosphorous acid and its derivatives, etc.

[0052] When the bonding layer precursor 13b is a sheet in which metal particles are dispersed in a resin, the metal particles may be any of those described above as metal particles contained in a metal paste. Examples of the resin contained in the sheet include various polyolefin resins such as polyethylene, polypropylene, polymethylpentene, and copolymers thereof; various polyamide resins such as nylon 6, nylon 66, nylon 12, nylon 11, metaxylylene adipamide (mXD6), hexamethylene terephthalamide (6T), and copolymers thereof; polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene-2,6-naphthalate (PEN), polymethylene terephthalate (PMT), polypropylene terephthalate (PPT), polyethylene-p-oxybenzoate (PEOB), poly-1,4 Examples of suitable resins include various polyester resins such as polyesters copolymerized with cyclohexylene dimethylene terephthalate (PCT) and copolymer components such as diol components (e.g., diethylene glycol, neopentyl glycol, polyalkylene glycol) and dicarboxylic acid components (e.g., adipic acid, sebacic acid, phthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid); and thermoplastic resins such as acrylic resin, methacrylic resin, polyacetal (POM) resin, polyphenylene sulfide (PPS) resin, polycarbonate resin, and chlorine-containing resins (e.g., polyvinyl chloride (PVC) and polyvinylidene chloride (PVdC). Thermosetting resins such as phenolic resin, epoxy resin, urea resin, melamine resin, and silicone resin may also be used.

[0053] There are no particular limitations on the type of the first bonded body 11 and the second bonded body 12. In general, it is preferable that both the first bonded body 11 and the second bonded body 12 contain a metal on their bonding target surfaces. For example, a member having a surface made of metal can be used as at least one of the first bonded body 11 and the second bonded body 12. The term "metal" refers to a metal itself that does not form 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 an alloy made of a combination of two or more of these metals.

[0054] When at least one of the first bonded body 11 and the second bonded body 12 is a member having a surface made of metal, it is generally preferable that the surface made of metal is flat, but in some cases it may be curved.

[0055] Specific examples of the first bonded body 11 and the second bonded body 12 include, independently of one another, spacers or heat sinks made of the above-mentioned metals, semiconductor elements, and substrates having at least one of the above-mentioned metals on their surfaces. Examples of the substrate include an insulating substrate having a metal layer such as copper on the surface of a ceramic or aluminum nitride plate. When semiconductor elements are used as the first bonded body 11 and / or the second bonded body 12, the semiconductor elements contain one or more elements such as Si, Ga, Ge, C, N, and As.

[0056] The first object to be bonded 11 is preferably a substrate. The second object to be bonded 12 is preferably either a spacer or a semiconductor element. When bonding a substrate and a heat sink, the first object to be bonded 11 is preferably a heat sink and the second object to be bonded 12 is preferably a substrate.

[0057] The bonded body 16 obtained by this manufacturing method is suitable for use in devices that handle large currents, such as electronic circuits for automobiles and electronic circuits equipped with power devices.

[0058] The above-described embodiments of the present invention encompass the following technical concepts. [1] A method for manufacturing a bonded body in which a first body to be bonded and a second body to be bonded are bonded via a bonding layer, the method comprising the steps of: preparing a second body to be bonded with a temporary fixing material, the second body having a temporary fixing material disposed on one surface of the second body to be bonded, and the first body to be bonded with a bonding layer precursor; bringing the bonding layer precursor and the second body to be bonded with the temporary fixing material into contact with each other to obtain a laminate; and heating the laminate to turn the bonding layer precursor into a bonding layer, thereby obtaining the bonded body in which the first body to be bonded and the second body to be bonded are bonded. [2] The manufacturing method according to [1], in which the second body to be bonded with the temporary fixing material is prepared by disposing the temporary fixing material on the second body to have a mixture of disposed and undisposed portions. [3] The manufacturing method according to [1] or [2], in which the temporary fixing material includes a substance that is solid at 25°C. [4] The manufacturing method according to any one of [1] to [3], wherein the temporary fixing material has a 95% mass loss temperature in a nitrogen atmosphere of 300° C. or less. [5] The manufacturing method according to any one of [1] to [4], wherein in the second body to be joined with the temporary fixing material, a ratio W2 / W1 of a mass W2 of the temporary fixing material to a mass W1 of the second body to be joined is 0.0001 or more and 0.50 or less. [6] The manufacturing method according to any one of [1] to [5], wherein the temporary fixing material contains 5 mass % or more of an organic solvent having a boiling point of 150° C. or more. [7] A method for bonding a first body to be bonded and a second body to be bonded via a bonding layer, the method comprising: preparing a second body to be bonded with a temporary fixing material, the second body having a temporary fixing material arranged on one surface of the second body to be bonded, and the first body to be bonded with a bonding layer precursor; obtaining a laminate by bringing the bonding layer precursor and the second body to be bonded with the temporary fixing material into contact with each other; and obtaining a bonded body in which the first body to be bonded and the second body to be bonded are bonded together by heating the laminate and turning the bonding layer precursor into a bonding layer.[8] The manufacturing method according to any one of [1] to [6], wherein the bonding layer precursor is a metal paste containing metal fine particles and an organic solvent or a dried product thereof, or a sheet in which metal fine particles are dispersed in a resin. [9] The bonding method according to [7], wherein the bonding layer precursor is a metal paste containing metal fine particles and an organic solvent or a dried product thereof, or a sheet in which metal fine particles are dispersed in a resin.

[0059] According to the present invention, a highly productive method for producing a bonded body and a highly productive method for bonding objects to be bonded are provided.

Claims

1. A method for manufacturing a bonded body in which a first object to be bonded and a second object to be bonded are bonded via a bonding layer, the method comprising the steps of: preparing a second object to be bonded with a temporary fixing material, the second object to be bonded having a temporary fixing material disposed on one surface of the second object to be bonded, and the first object to be bonded having a bonding layer precursor formed thereon; obtaining a laminate by bringing the bonding layer precursor and the second object to be bonded with the temporary fixing material into contact with each other; and heating the laminate to turn the bonding layer precursor into a bonding layer, thereby obtaining the bonded body in which the first object to be bonded and the second object to be bonded are bonded.

2. A manufacturing method according to claim 1, wherein the temporary fixing material is arranged on the second object to be joined so that there is a mixture of arranged and non-arranged areas, thereby preparing the second object to be joined with the temporary fixing material.

3. The manufacturing method according to claim 1 or 2, wherein the temporary fixing material contains a substance that is solid at 25°C.

4. The manufacturing method according to claim 1 or 2, wherein the temporary fixing material has a mass reduction temperature of 300°C or less in a nitrogen atmosphere at which the mass of the temporary fixing material decreases by 95%.

5. A manufacturing method according to claim 1 or 2, wherein in the second bonded body with the temporary fixing material, the ratio W2 / W1 of the mass W2 of the temporary fixing material to the mass W1 of the second bonded body is 0.0001 or more and 0.50 or less.

6. The manufacturing method according to claim 1 or 2, wherein the temporary fixing material contains 5% by mass or more of an organic solvent having a boiling point of 150°C or higher.

7. The manufacturing method according to claim 1 or 2, wherein the bonding layer precursor is a metal paste containing metal particles and an organic solvent or a dried version thereof, or a sheet in which metal particles are dispersed in a resin.

8. A method for bonding a first object to be bonded and a second object to be bonded via a bonding layer, comprising the steps of: preparing a second object to be bonded with a temporary fixing material, the second object having a temporary fixing material disposed on one surface thereof, and the first object to be bonded with a bonding layer precursor; obtaining a laminate by bringing the bonding layer precursor and the second object to be bonded with the temporary fixing material into contact with each other; and heating the laminate to turn the bonding layer precursor into a bonding layer, thereby obtaining a bonded object in which the first object to be bonded and the second object to be bonded are bonded together.

9. The bonding method according to claim 8, wherein the bonding layer precursor is a metal paste containing fine metal particles and an organic solvent or a dried version thereof, or a sheet in which fine metal particles are dispersed in a resin.

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