Soldering flux and preparation method of joint body

Abstract

Provided is a flux which can be applied to the attachment of an indium sheet, has high wettability even in relatively low-temperature bonding, and has an improved ability to suppress the generation of voids. A flux containing rosin, an organic acid, and a solvent (S) is used. The organic acid contains a monocarboxylic acid (A1) having a melting point of 35-90 DEG C inclusive, and the solvent (S) contains a solvent (S1) having a boiling point of 100 DEG C or less.

Description

Technical Field

[0001] The present invention relates to a method for preparing a soldering flux and a joint body. This application claims priority based on Japanese Patent Application No. 2022-135185 filed in Japan on August 26, 2022, and the contents thereof are incorporated herein by reference. Background Art

[0002] In recent years, electronic devices have been required to have larger capacity and higher speed. The highly integrated bare chips mounted on such electronic devices generate a large amount of heat during operation. Therefore, it is necessary to effectively discharge the generated heat by installing a cover with a heat sink on the bare chip.

[0003] On the other hand, for example, Patent Document 1 proposes to sandwich a thermal interface material (TIM) containing a polymer between a bare chip and a cover provided with a heat sink in order to transfer heat generated by the operation of the bare chip to the heat sink more efficiently.

[0004] Prior art documents

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application No. 2010-539706 Summary of the invention

[0007] Problems to be solved by the present invention

[0008] As a TIM, a sheet consisting only of indium (hereinafter referred to as an indium sheet) is proposed. Indium has a lower hardness than other metal elements, and the indium sheet has high followability and high adhesion to the surface of the bare chip and the cover. Therefore, the indium sheet has high heat transfer efficiency from the bare chip to the cover with a heat sink. As a result, by using the indium sheet, the heat removal efficiency of the bare chip operation can be improved.

[0009] In mounting the indium sheet, the indium sheet with flux applied on the surface is used to bond the lid with the heat sink to the bare chip. Since the melting point of indium is relatively low at 156°C, the indium sheet is bonded by reflow soldering at a lower temperature than normal bonding.

[0010] When the indium sheet is mounted at 170°C using conventional soldering flux, the flux does not wet and spread on the surface of the indium sheet but gathers on the bonding surface, resulting in a large number of voids on the bonding surface. Due to the voids, the efficiency of heat transfer from the bare chip to the cover with the heat sink via the indium sheet is reduced, resulting in a reduction in the efficiency of dissipating heat generated by the operation of the bare chip.

[0011] Therefore, an object of the present invention is to provide a flux which can be suitably used for mounting of an indium sheet, has high wettability even in bonding under relatively low temperature conditions, and has an improved ability to suppress the generation of voids.

[0012] Means of solving the problem

[0013] The present invention includes the following aspects.

[0014] [1] A soldering flux comprising rosin, an organic acid and a solvent (S), wherein the organic acid comprises a monocarboxylic acid (A1) having a melting point of 35°C or higher and 90°C or lower, and the solvent (S) comprises a solvent (S1) having a boiling point of 100°C or lower.

[0015] [2] The soldering flux according to [1], wherein the molecular weight of the monocarboxylic acid (A1) is 180 or more and 350 or less.

[0016] [3] The soldering flux according to [1] or [2], wherein the content of the solvent (S1) is 50% by mass or more relative to the total mass of the solvent (S).

[0017] [4] The soldering flux according to any one of [1] to [3], further comprising an alkanolamine.

[0018] [5] The soldering flux according to any one of [1] to [4], wherein the content of the monocarboxylic acid (A1) is 0.5% by mass or more and 20% by mass or less relative to the total mass of the soldering flux.

[0019] [6] The soldering flux according to any one of [1] to [5], wherein the monocarboxylic acid (A1) contains palmitic acid, and the content of the palmitic acid is 60% by mass or more relative to the total mass of the monocarboxylic acid (A1).

[0020] [7] The soldering flux according to any one of [1] to [6], wherein the content of the rosin is 10% by mass or more and 50% by mass or less relative to the total mass of the soldering flux.

[0021] [8] A method for preparing a joint body, which is a method for preparing a joint body formed by bonding a bare chip and a cover via a thermal interface material (TIM), wherein the TIM is an indium sheet, and the flux described in any one of [1] to [7] is interposed between the TIM and the bare chip, or between the TIM and the cover, and the joint is performed by reflow soldering.

[0022] [9] The method for producing a bonded body according to [8], wherein the bonding by the reflow method is performed at a temperature lower than 200°C.

[0023] Effects of the Invention

[0024] According to the present invention, it is possible to provide a flux which can be suitably used for mounting of an indium sheet, has high wettability even in bonding under relatively low temperature conditions, and has an improved ability to suppress the generation of voids. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a cross-sectional view showing an embodiment of a method for producing a bonded body, and includes a cover, a TIM, and a bare chip.

[0026] Figure 2 This is a cross-sectional view showing a step of applying flux to a TIM and a bare chip according to one embodiment of a method for producing a bonded body.

[0027] Figure 3 This is one embodiment of a method for producing a bonded body, and shows a cross-sectional view of a bonded body obtained by applying flux and then fixing a cover to a substrate using a TIM. DETAILED DESCRIPTION

[0028] (Flux)

[0029] The soldering flux of this embodiment contains rosin, an organic acid, and a solvent (S). The organic acid contains a monocarboxylic acid (A1) having a melting point of 35° C. to 90° C. The solvent (S) contains a solvent (S1) having a boiling point of 100° C. or less.

[0030] In mounting the indium sheet, the lid with the heat sink and the bare chip are bonded using the indium sheet by reflow soldering at a low temperature (e.g., 170° C.). In conventional soldering flux, the soldering flux does not wet and spread on the surface of the indium sheet, but gathers on the bonding surface, resulting in a large number of voids on the bonding surface.

[0031] The flux according to this embodiment contains a monocarboxylic acid (A1) having a melting point of 35° C. to 90° C., so that the monocarboxylic acid (A1) can be melted to such an extent that gas is easily released even under low-temperature reflow and has sufficient wettability to the indium sheet.

[0032] Since the monocarboxylic acid (A1) contained in the flux of this embodiment has lower reactivity than a dicarboxylic acid, it is easy to suppress the generation of voids.

[0033] Furthermore, the solvent (S1) having a boiling point of 100°C or less contained in the flux of the present embodiment volatilizes before the indium sheet melts even in low-temperature reflow. As a result, when indium melts, no voids are generated from the solvent (S1).

[0034] Due to these synergistic effects, the flux of the present embodiment can suppress the generation of voids even during the mounting of the indium sheet.

[0035] <Rosin>

[0036] In the present invention, the term "rosin" includes natural resins containing abietic acid as a main component, mixtures of abietic acid and isomers thereof, and products obtained by chemically modifying natural resins (sometimes referred to as rosin derivatives).

[0037] The total content of abietic acid and isomers of abietic acid in the natural resin is, for example, 40% by mass or more and 80% by mass or less relative to the natural resin.

[0038] In the present specification, the term "main component" refers to a component whose content in the compound is 40% by mass or more among the components constituting the compound.

[0039] Representative examples of isomers of abietic acid include neoabietic acid, palustric acid, and levopimaric acid. The structure of abietic acid is shown below.

[0040] [Chemical formula 1]

[0041]

[0042] Examples of the “natural resin” include gum rosin, wood rosin, and tall oil rosin.

[0043] In the present invention, "substances obtained by chemically modifying natural resins (rosin derivatives)" include substances obtained by subjecting the "natural resins" to one or more treatments selected from hydrogenation, dehydrogenation, neutralization, alkylene oxide addition, amidation, dimerization and polymerization, esterification and Diels-Alder cycloaddition.

[0044] Examples of the rosin derivative include purified rosin and modified rosin.

[0045] Examples of the modified rosin include hydrogenated rosin, polymerized rosin, polymerized hydrogenated rosin, disproportionated rosin, acid-modified rosin, rosin ester, acid-modified hydrogenated rosin, acid-modified disproportionated rosin, acid-anhydride-modified disproportionated rosin, phenol-modified rosin, and α,β-unsaturated carboxylic acid-modified rosin (acrylic acid-modified rosin, maleic acid-modified rosin, fumaric acid-modified rosin, etc.), as well as purified products, hydrogenated products, and disproportionated products of the polymerized rosin, and purified products, hydrogenated products, and disproportionated products of the α,β-unsaturated carboxylic acid-modified products, abietol, abietamine, hydrogenated abietol, rosin ester, hydrogenated rosin ester, rosin soap, hydrogenated rosin soap, and acid-modified rosin soap.

[0046] Examples of rosin amines include a mixture of dehydroabietin amine, dihydroabietin amine, and tetrahydroabietin amine, which is referred to as a so-called disproportionated rosin amine. The structures of dehydroabietin amine, dihydroabietin amine, and tetrahydroabietin amine are shown below.

[0047] [Chemical formula 2]

[0048]

[0049] The rosin may be used alone or in combination of two or more.

[0050] The rosin preferably contains a rosin derivative, and more preferably contains at least one selected from the group consisting of acid-modified hydrogenated rosin and hydrogenated rosin.

[0051] The content of rosin in the soldering flux is preferably 5 mass % to 70 mass %, more preferably 10 mass % to 50 mass %, and further preferably 15 mass % to 45 mass %, relative to the total mass of the soldering flux (100 mass %).

[0052] When the content of rosin is equal to or greater than the lower limit in the above range, the wettability of the flux is easily improved and the generation of voids is easily suppressed. When the content of rosin is equal to or less than the upper limit in the above range, the generation of voids is easily suppressed.

[0053] <Organic acid>

[0054] The organic acid contained in the flux of the present embodiment includes a monocarboxylic acid (A1) having a melting point of 35° C. to 90° C. The organic acid contained in the flux of the present embodiment may include other organic acids in addition to the monocarboxylic acid (A1).

[0055] 《Monocarboxylic acid (A1)》

[0056] The melting point of the monocarboxylic acid (A1) is 35° C. to 90° C. The monocarboxylic acid is a carboxylic acid having one carboxyl group in the molecule.

[0057] The melting point of the monocarboxylic acid (A1) is preferably 40°C to 85°C, more preferably 45°C to 80°C, further preferably 50°C to 72°C, particularly preferably 55°C to 66°C, and most preferably 60°C to 66°C.

[0058] Since the melting point of indium is as low as 156° C., mounting of the indium sheet is performed by low-temperature reflow soldering (eg, 170° C.).

[0059] When the melting point of the monocarboxylic acid (A1) is at least the lower limit value within the above range, the reaction between the indium sheet and the monocarboxylic acid (A1) during reflow is easily suppressed, and thus the generation of voids during reflow is easily suppressed.

[0060] When the melting point of the monocarboxylic acid (A1) is below the upper limit of the above range, the monocarboxylic acid (A1) in the flux is easily melted during reflow, so that the voids generated during reflow are easily removed from the flux. In addition, the wettability of the flux is easily improved.

[0061] The molecular weight of the monocarboxylic acid (A1) is preferably 180 to 350, more preferably 190 to 310, further preferably 220 to 275, particularly preferably 240 to 265, and most preferably 250 to 260.

[0062] When the molecular weight of the monocarboxylic acid (A1) is at least the lower limit within the above range, the molar amount of the monocarboxylic acid (A1) contained in the flux at the same content (mass %) becomes smaller, and thus the generation of voids during reflow is easily suppressed.

[0063] When the molecular weight of the monocarboxylic acid (A1) is equal to or less than the upper limit value in the above range, the molar amount of the monocarboxylic acid (A1) contained in the flux at the same content (mass %) increases, and thus the wettability of the flux is easily improved.

[0064] Examples of the monocarboxylic acid (A1) include aliphatic monocarboxylic acids and aromatic monocarboxylic acids, and aliphatic monocarboxylic acids are preferred.

[0065] The aliphatic monocarboxylic acid may or may not contain a hydroxyl group.

[0066] The hydrocarbon group of the aliphatic monocarboxylic acid may be any of linear, branched or cyclic. The hydrocarbon group is preferably linear or branched, more preferably linear.

[0067] The hydrocarbon group may be a saturated hydrocarbon group or an unsaturated hydrocarbon group, and is preferably a saturated hydrocarbon group.

[0068] The aliphatic monocarboxylic acid preferably has 12 to 24 carbon atoms, more preferably 12 to 18 carbon atoms, further preferably 14 to 17 carbon atoms, particularly preferably 15 to 17 carbon atoms, and most preferably 16 carbon atoms.

[0069] When the monocarboxylic acid (A1) is a linear aliphatic monocarboxylic acid, examples of the monocarboxylic acid (A1) include lauric acid (C12, 45°C, 200), tridecanoic acid (C13, 41°C, 214), myristic acid (C14, 54°C, 228), pentadecanoic acid (C15, 52°C, 242), palmitic acid (C16, 63°C, 256), heptadecanoic acid (C17, 61°C, 270), stearic acid (C18, 70°C, 284), nonadecanoic acid (C19, 69°C, 299), arachidic acid (C20, 76°C, 313), heneicosanoic acid (C21, 75°C, 327), docosanoic acid (C22, 76°C, 341), tricosanoic acid (C23, 80°C, 355), and tetracosanoic acid (C24, 84°C, 369). The information in parentheses indicates the number of carbon atoms, melting point and molecular weight.

[0070] When the monocarboxylic acid (A1) is a linear aliphatic monocarboxylic acid, among the above, the monocarboxylic acid (A1) is preferably one or more selected from lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid and stearic acid, more preferably one or more selected from myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid and stearic acid, further preferably one or more selected from palmitic acid and stearic acid, and particularly preferably palmitic acid.

[0071] When the monocarboxylic acid (A1) is an aliphatic monocarboxylic acid containing a hydroxyl group, the monocarboxylic acid (A1) is preferably 12-hydroxystearic acid. 12-Hydroxystearic acid has a melting point of 76.5°C, a molecular weight of 300, and 18 carbon atoms.

[0072] The monocarboxylic acid (A1) may be used alone or in combination of two or more.

[0073] The content of the monocarboxylic acid (A1) relative to the total amount (100 mass%) of the flux is preferably 0.1 mass% to 30 mass%, more preferably 0.5 mass% to 20 mass%, further preferably 1 mass% to 20 mass%, particularly preferably 1 mass% to 15 mass%, and most preferably 3 mass% to 15 mass%.

[0074] When the content of the monocarboxylic acid (A1) is at least the lower limit in the above range, the wettability of the flux is easily improved and the generation of voids is easily suppressed. When the content of the monocarboxylic acid (A1) is at most the upper limit in the above range, the generation of voids is easily suppressed.

[0075] The content of palmitic acid is preferably 60% by mass or more and 100% by mass or less relative to the total mass of the monocarboxylic acid (A1).

[0076] When the content of palmitic acid is at least the lower limit value within the above range, the ability to suppress the generation of voids can be more easily improved.

[0077] 《Other organic acids》

[0078] Examples of other organic acids include carboxylic acids and organic sulfonic acids. Examples of carboxylic acids include aliphatic carboxylic acids and aromatic carboxylic acids. Examples of aliphatic carboxylic acids include aliphatic monocarboxylic acids other than monocarboxylic acids (A1) and aliphatic dicarboxylic acids.

[0079] Examples of the aliphatic monocarboxylic acid include caproic acid, heptanoic acid, octanoic acid, nonanoic acid, isononanoic acid, decanoic acid, decenoic acid, undecanoic acid, lindolic acid, myristoleic acid, isopalmitic acid, palmitoleic acid, hexadecatrienoic acid, cyclopentenone undecanoic acid, isostearic acid, elaidic acid, parsleyic acid, stearatetraenoic acid, eleostearic acid, tarric acid, vaccenic acid, ricinoleic acid, vernolic acid, stearic acid oleic acid, linoleic acid, linolenic acid, and the like.

[0080] Examples of the aliphatic dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, eicosanedioic acid, tartaric acid, 2,4-diethylglutaric acid, diglycolic acid, 2-methylnonanedioic acid, 4-(methoxycarbonyl)-2,4-dimethylundecanedioic acid, 4,6-di(methoxycarbonyl)-2,4,6-trimethyltridecanedioic acid, and 8,9-di(methoxycarbonyl)-8,9-dimethylhexadecanedioic acid.

[0081] Examples of the aromatic carboxylic acid include salicylic acid, dibutylanilinoglycolic acid, terephthalic acid, p-hydroxyphenylacetic acid, phenylsuccinic acid, phthalic acid, benzoic acid, 2,3-dihydroxybenzoic acid, 2-quinolinecarboxylic acid, 3-hydroxybenzoic acid, p-anisic acid, picolinic acid, dipicolinic acid, and 3-hydroxypicolinic acid.

[0082] Examples of the carboxylic acid include tris(2-carboxyethyl)isocyanurate and 1,3-cyclohexanedicarboxylic acid.

[0083] In addition, as other organic acids, hydroxycarboxylic acids can be mentioned.

[0084] Examples of the hydroxycarboxylic acid include 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butyric acid, citric acid, isocitric acid, malic acid, and tartaric acid.

[0085] Examples of other organic acids include dimer acid, trimer acid, hydrogenated dimer acid which is a hydrogenated product of dimer acid, and hydrogenated trimer acid which is a hydrogenated product of trimer acid.

[0086] Examples of the organic sulfonic acid include aliphatic sulfonic acid, aromatic sulfonic acid, etc. Examples of the aliphatic sulfonic acid include alkanesulfonic acid, alkanolsulfonic acid, etc.

[0087] The soldering flux of the present embodiment may or may not contain other organic acids.

[0088] The other organic acids may be used alone or in combination of two or more.

[0089] In the case where the flux of the present embodiment contains other organic acids, the content of other organic acids, relative to the total amount (100 mass%) of the flux, may be greater than 0 mass% and less than 10 mass%, or may be greater than 0 mass% and less than 7 mass%, or may be greater than 0 mass% and less than 5 mass%, or may be greater than 0 mass% and less than 3 mass%, or may be greater than 0 mass% and less than 2 mass%, or may be greater than 0 mass% and less than 1 mass%, or may be greater than 0 mass% and less than 0.5 mass%, or may be greater than 0 mass% and less than 0.3 mass%, or may be greater than 0 mass% and less than 0.1 mass%.

[0090] <Solvent (S)>

[0091] The solvent (S) contains a solvent (S1) having a boiling point of 100° C. or less. Examples of the solvent (S1) include 2-propanol and ethanol.

[0092] The solvent (S1) may be used alone or in combination of two or more.

[0093] The boiling point of the solvent (S1) is preferably 50°C or higher and 100°C or lower, more preferably 60°C or higher and 90°C or lower, and further preferably 70°C or higher and 85°C or lower.

[0094] In this specification, the boiling point refers to the temperature of a liquid at which the saturated vapor pressure of the liquid is equal to one atmospheric pressure (ie, 1013 hPa).

[0095] The solvent (S) may contain other solvents (S2) in addition to the solvent (S1).

[0096] The other solvents (S2) may be used alone or in combination of two or more.

[0097] The boiling point of the other solvent (S2) exceeds 100° C. The boiling point of the other solvent (S2) is preferably higher than 100° C. and 350° C. or lower, more preferably 150° C. or higher and 300° C. or lower, and further preferably 200° C. or higher and 280° C. or lower.

[0098] Examples of the other solvent (S2) include alcohol solvents, glycol ether solvents, and terpineols.

[0099] Examples of the alcohol solvent include 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, isobornylcyclohexanol, 2,4-diethyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexyne-2,5-diol, 2,3-dimethyl-2,3-butanediol, 2-methylpentane-2,4-diol, 1,1,1-tris(hydroxymethyl)propane, 2- Ethyl-2-hydroxymethyl-1,3-propanediol, 2,2'-oxybis(methylene)bis(2-ethyl-1,3-propanediol), 2,2-bis(hydroxymethyl)-1,3-propanediol, 1,2,6-trihydroxyhexane, 1-ethynyl-1-cyclohexanol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 2-hexyl-1-decanol, 2-methyl-2,4-pentanediol (hexanediol), octanediol, etc.

[0100] Examples of the glycol ether solvents include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, ethylene glycol monobutyl ether (ethylene glycol butyl ether), ethylene glycol monohexyl ether (ethylene glycol hexyl ether), diethylene glycol monohexyl ether (hexyldiglycol), diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, methyl glycerol, triethylene glycol butyl methyl ether, tetraethylene glycol, tetraethylene glycol dimethyl ether, and tripropylene glycol n-butyl ether.

[0101] Examples of the terpineols include α-terpineol, β-terpineol, γ-terpineol, and a terpineol mixture (ie, a mixture whose main component is α-terpineol and contains β-terpineol or γ-terpineol).

[0102] Examples of other solvents include dioctyl sebacate (DOS) and liquid paraffin.

[0103] The other solvents may be used alone or in combination of two or more.

[0104] The content of the solvent (S) in the soldering flux is preferably 10% by mass or more and 95% by mass or less, and more preferably 25% by mass or more and 90% by mass or less, relative to the total amount (100% by mass) of the soldering flux.

[0105] The content of the solvent (S1) in the flux is preferably 10% by mass or more and 95% by mass or less, more preferably 25% by mass or more and 90% by mass or less, and further preferably 29.5% by mass or more and 88.5% by mass or less, relative to the total amount of the flux (100% by mass).

[0106] Relative to the total mass of the solvent (S), the content of the solvent (S1) is preferably 50% by mass or more and 100% by mass or less, more preferably 55% by mass or more and 100% by mass or less, further preferably 60% by mass or more and 100% by mass or less, particularly preferably 65% ​​by mass or more and 100% by mass or less, and may be 70% by mass or more and 100% by mass or less, 80% by mass or more and 100% by mass or less, 90% by mass or more and 100% by mass or less, 95% by mass or more and 100% by mass or less, or 100% by mass.

[0107] When the content of the solvent (S1) is equal to or greater than the lower limit in the above range, the ability to suppress the generation of voids can be further enhanced. In addition, the flux can be easily sprayed.

[0108] <Other ingredients>

[0109] The soldering flux of the present embodiment may contain other components as necessary in addition to the rosin, the organic acid, and the solvent (S).

[0110] Examples of other components include resin components other than rosin, activators other than organic acids, thixotropic agents, metal deactivators, surfactants, silane coupling agents, antioxidants, and colorants.

[0111] 《Resin ingredients other than rosin》

[0112] Examples of resins other than rosin include terpene resins, modified terpene resins, terpene phenol resins, modified terpene phenol resins, styrene resins, modified styrene resins, xylene resins, modified xylene resins, acrylic resins, polyethylene resins, acrylic-polyethylene copolymer resins, ethylene-vinyl acetate copolymer resins, and other thermosetting resins.

[0113] Examples of modified terpene resins include aromatic modified terpene resins, hydrogenated terpene resins, hydrogenated aromatic modified terpene resins, etc. Examples of modified terpene phenol resins include hydrogenated terpene phenol resins, etc. Examples of modified styrene resins include styrene acrylic resins, styrene maleic acid resins, etc. Examples of modified xylene resins include phenol modified xylene resins, alkylphenol modified xylene resins, phenol modified resol type xylene resins, polyol modified xylene resins, polyoxyethylene added xylene resins, etc.

[0114] As other thermosetting resins, epoxy resins can be mentioned, for example.

[0115] Examples of epoxy resins include bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, glycidylamine type resins, alicyclic epoxy resins, aminopropane type epoxy resins, biphenyl type epoxy resins, naphthalene type epoxy resins, anthracene type epoxy resins, triazine type epoxy resins, dicyclopentadiene type epoxy resins, triphenylmethane type epoxy resins, fluorene type epoxy resins, phenol aralkyl type epoxy resins, and novolac type epoxy resins.

[0116] The soldering flux of the present embodiment does not need to contain any resin component other than rosin.

[0117] When the soldering flux of the present embodiment contains a resin component other than rosin, the content of the resin component other than rosin, relative to the total amount (100 mass%) of the soldering flux, may be greater than 0 mass% and less than 10 mass%, may be greater than 0 mass% and less than 7 mass%, may be greater than 0 mass% and less than 5 mass%, may be greater than 0 mass% and less than 3 mass%, may be greater than 0 mass% and less than 2 mass%, may be greater than 0 mass% and less than 1 mass%, may be greater than 0 mass% and less than 0.5 mass%, may be greater than 0 mass% and less than 0.3 mass%, or may be greater than 0 mass% and less than 0.1 mass%.

[0118] 《Surfactants other than organic acids》

[0119] Examples of the activator other than the organic acid include amines, halogen compounds, and organic phosphorus compounds.

[0120] [amine]

[0121] Examples of the amine include azoles, guanidines, alkanolamines, alkylamine compounds, and amine polyoxyalkylene adducts.

[0122] Examples of the azoles include 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole trimellitate, 1-cyanoethyl-2-phenylimidazole trimellitate, 2,4-diamino-6-[2′-methylimidazolyl-(1′)]-ethyl tris-imidazolyl 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazole chloride, 2-methylimidazoline, 2-phenylimidazoline, 2,4-diamino-6-vinyl-s-triazine, 2,4-Diamino-6-vinyl-s-triazine isocyanuric acid adduct, 2,4-diamino-6-methacryloyloxyethyl-s-triazine, epoxy-imidazole adduct, 2-methylbenzimidazole, 2-octylbenzimidazole, 2-pentylbenzimidazole, 2-(1-ethylpentyl)benzimidazole, 2-nonylbenzimidazole, 2-(4-thiazolyl)benzimidazole, benzimidazole, 1,2,4-triazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-pentylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2, 2'-Methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol], 6-(2-benzotriazolyl)-4-tert-octyl-6'-tert-butyl-4'-methyl-2,2'-methylenebisphenol, 1,2,3-benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]benzotriazole, carboxybenzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole, 2,2'-[[(methyl-1H-benzotriazol-1-yl)methyl]imino]bisethanol, 1-(1',2'-dicarboxyethyl)benzotriazole, 1-(2,3-dicarboxypropyl)benzotriazole, 1-[(2-ethylhexylamino)methyl]benzotriazole, 2,6-Bis[(1H-benzotriazol-1-yl]methyl]-4-methylphenol, 5-methylbenzotriazole, 5-phenyltetrazolyl, etc.

[0123] Examples of the guanidines include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylguanidine, 1,3-di-o-isopropylphenylguanidine, and 1,3-di-o-isopropylphenyl-2-propionylguanidine.

[0124] Examples of the alkanolamine include N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine, N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine, monoethanolamine, diethanolamine, triethanolamine, 1-amino-2-propanol, bis(2-hydroxypropyl)amine, and tris(2-hydroxypropyl)amine.

[0125] Examples of the alkylamine compound include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, cyclohexylamine, hexadecylamine, and stearylamine.

[0126] Examples of the amine polyoxyalkylene adduct include terminal diamine polyalkylene glycol, aliphatic amine polyoxyalkylene adduct, aromatic amine polyoxyalkylene adduct, and polyamine polyoxyalkylene adduct.

[0127] Examples of the alkylene oxide added to the amine polyoxyalkylene adduct include ethylene oxide, propylene oxide, and butylene oxide.

[0128] The terminal diamine polyalkylene glycol is a compound in which both ends of a polyalkylene glycol are aminated.

[0129] Examples of the terminal diamine polyalkylene glycol include terminal diamine polyethylene glycol, terminal diamine polypropylene glycol, and terminal diamine polyethylene glycol-polypropylene glycol copolymers.

[0130] Examples of the terminal diamine polyethylene glycol-polypropylene glycol copolymer include polyethylene glycol-polypropylene glycol copolymer bis(2-aminopropyl) ether and polyethylene glycol-polypropylene glycol copolymer bis(2-aminoethyl) ether.

[0131] Aliphatic amine polyoxyalkylene adducts, aromatic amine polyoxyalkylene adducts and polyamine polyoxyalkylene adducts are adducts in which a polyoxyalkylene group is bonded to the nitrogen atom of the amine. Examples of the amine include ethylenediamine, 1,3-propylenediamine, 1,4-butylenediamine, hexamethylenediamine, diethylenetriamine, laurylamine, stearylamine, oleylamine, tallowamine, cured tallowamine, tallowpropyldiamine, m-xylenediamine, toluenediamine, p-xylidine, phenylenediamine, isophoronediamine, 1,10-decanediamine, 1,12-dodecanediamine, 4,4-diaminodicyclohexylmethane, 4,4-diaminodiphenylmethane, butane-1,1,4,4-tetraamine, and pyrimidine-2,4,5,6-tetraamine.

[0132] The amines may be used alone or in combination of two or more.

[0133] The amine is preferably an alkanolamine, more preferably at least one selected from monoethanolamine, diethanolamine, triethanolamine and 1-amino-2-propanol, and still more preferably diethanolamine.

[0134] The content of the amine is preferably 0.1% by mass to 5% by mass, more preferably 0.2% by mass to 3% by mass, and even more preferably 0.2% by mass to 1% by mass, relative to the total mass of the flux.

[0135] The soldering flux of the present embodiment contains an amine, preferably an alkanolamine, so that wettability can be easily improved and the ability to suppress the generation of voids can be easily further improved.

[0136] [Halogen compounds]

[0137] Examples of the halogen compound include amine hydrohalide salts and organic halogen compounds other than amine hydrohalide salts.

[0138] Amine hydrohalides are compounds formed by reacting amines with hydrogen halides.

[0139] Examples of the amines herein include the amines described above in "Amines".

[0140] In addition, as halogen compounds other than amine hydrohalide salts, for example, salts formed by reacting amines with tetrafluoroboric acid (HBF4) or complexes formed by reacting amines with boron trifluoride (BF3) can also be used. As such complexes, for example, boron trifluoride piperidine and the like can be cited.

[0141] Examples of halogen compounds other than amine hydrohalides include halogenated aliphatic compounds. The halogenated aliphatic hydrocarbon group refers to a group in which a part or all of the hydrogen atoms constituting the aliphatic hydrocarbon group are substituted with halogen atoms.

[0142] Examples of the halogenated aliphatic compounds include halogenated aliphatic alcohols and halogenated heterocyclic compounds.

[0143] Examples of the halogenated aliphatic alcohol include 1-bromo-2-propanol, 3-bromo-1-propanol, 3-bromo-1,2-propanediol, 1-bromo-2-butanol, 1,3-dibromo-2-propanol, 2,3-dibromo-1-propanol, 1,4-dibromo-2-butanol, and trans-2,3-dibromo-2-butene-1,4-diol.

[0144] Examples of the halogenated heterocyclic compound include compounds represented by the following general formula (h1).

[0145] R h11 -(R h12 ) n (h1)

[0146] [Where R h11 represents an n-valent heterocyclic group. h12 represents a halogenated aliphatic hydrocarbon group.]

[0147] As R h11 The heterocyclic ring of the n-valent heterocyclic group in the ring may be a ring structure in which a part of the carbon atoms constituting the aliphatic hydrocarbon or aromatic hydrocarbon ring is substituted with a heteroatom. Examples of the heteroatom in the heterocyclic ring include an oxygen atom, a sulfur atom, a nitrogen atom, etc. The heterocyclic ring is preferably a 3- to 10-membered ring, and more preferably a 5- to 7-membered ring. Examples of the heterocyclic ring include an isocyanurate ring, etc.

[0148] R h12 The halogenated aliphatic hydrocarbon group in preferably has 1 to 10 carbon atoms, more preferably 2 to 6 carbon atoms, and still more preferably 3 to 5 carbon atoms. h12 Preferred are brominated aliphatic hydrocarbon groups and chlorinated aliphatic hydrocarbon groups, more preferred are brominated aliphatic hydrocarbon groups, and still more preferred are brominated saturated aliphatic hydrocarbon groups.

[0149] Examples of the halogenated heterocyclic compound include tris-(2,3-dibromopropyl)isocyanurate and the like.

[0150] In addition, as halogen compounds other than amine hydrohalides, for example, iodinated carboxyl compounds such as 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, and 5-iodoanthranilic acid; chlorinated carboxyl compounds such as 2-chlorobenzoic acid and 3-chloropropionic acid; and halogenated carboxyl compounds such as brominated carboxyl compounds such as 2,3-dibromopropionic acid, 2,3-dibromosuccinic acid, and 2-bromobenzoic acid.

[0151] Examples of halogen compounds other than amine hydrohalides include organic chlorine compounds, such as chlorinated alkanes, chlorinated fatty acid esters, chlorendic acid, and chlorendic anhydride.

[0152] The halogen compounds may be used alone or in combination of two or more.

[0153] Organophosphorus compounds

[0154] Examples of the organic phosphorus compound include acidic phosphoric acid esters, acidic phosphonic acid esters, and acidic phosphinates.

[0155] The organic phosphorus compound may be used alone or in combination of two or more.

[0156] 《Thixotropic Agent》

[0157] Examples of the thixotropic agent include ester-based thixotropic agents, amide-based thixotropic agents, and sorbitol-based thixotropic agents.

[0158] Examples of the ester-based thixotropic agent include ester compounds, and specific examples include hydrogenated castor oil and ethyl myristate.

[0159] Examples of the amide-based thixotropic agent include monoamide, bisamide, and polyamide.

[0160] Examples of the monoamide include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide, saturated fatty acid amide, oleic acid amide, erucic acid amide, unsaturated fatty acid amide, 4-methylbenzamide (p-toluamide), p-toluene methane amide, aromatic amide, hexamethylene hydroxystearic acid amide, substituted amides, hydroxymethyl stearic acid amide, hydroxymethyl amide, and fatty acid ester amides.

[0161] Examples of the bisamides include ethylenebis fatty acid (the carbon number of fatty acid is C6-24) amide, ethylenebishydroxy fatty acid (the carbon number of fatty acid is C6-24) amide, hexamethylenebis fatty acid (the carbon number of fatty acid is C6-24) amide, hexamethylenebishydroxy fatty acid (the carbon number of fatty acid is C6-24) amide, aromatic bisamides, etc. Examples of fatty acids as raw materials of the bisamides include stearic acid (the carbon number is C18), oleic acid (the carbon number is C18), lauric acid (the carbon number is C12), etc.

[0162] Examples of the polyamide include polyamides such as saturated fatty acid polyamide, unsaturated fatty acid polyamide, aromatic polyamide, 1,2,3-propanetricarboxylic acid tris(2-methylcyclohexylamide), cyclic amide oligomers, and non-cyclic amide oligomers.

[0163] Examples of the cyclic amide oligomer include amide oligomers obtained by polycondensation of dicarboxylic acid and diamine into a ring, amide oligomers obtained by polycondensation of tricarboxylic acid and diamine into a ring, amide oligomers obtained by polycondensation of dicarboxylic acid and triamine into a ring, amide oligomers obtained by polycondensation of tricarboxylic acid and triamine into a ring, amide oligomers obtained by polycondensation of dicarboxylic acid, tricarboxylic acid and diamine into a ring, amide oligomers obtained by polycondensation of dicarboxylic acid, tricarboxylic acid and triamine into a ring, amide oligomers obtained by polycondensation of dicarboxylic acid, diamine and triamine into a ring, amide oligomers obtained by polycondensation of tricarboxylic acid, diamine and triamine into a ring, and amide oligomers obtained by polycondensation of dicarboxylic acid, tricarboxylic acid, diamine and triamine into a ring.

[0164] In addition, the non-cyclic amide oligomer can include the situation that monocarboxylic acid and diamine and / or triamine are polycondensed into non-cyclic and the amide oligomer obtained, the situation that dicarboxylic acid and / or tricarboxylic acid and monoamine are polycondensed into non-cyclic and the amide oligomer obtained, etc. In the case of the amide oligomer containing monocarboxylic acid or monoamine, monocarboxylic acid and monoamine function as terminal molecules (terminal molecules) to become the non-cyclic amide oligomer with reduced molecular weight. In addition, in the case of the amide compound obtained by polycondensing dicarboxylic acid and / or tricarboxylic acid with diamine and / or triamine into non-cyclic, the non-cyclic amide oligomer becomes a non-cyclic high molecular system amide polymer. In addition, the non-cyclic amide oligomer also includes the amide oligomer obtained by condensing monocarboxylic acid and monoamine into non-cyclic.

[0165] Examples of the sorbitol-based thixotropic agent include dibenzylidene-D-sorbitol, di(4-methylbenzylidene)-D-sorbitol, (D-)sorbitol, monobenzylidene (-D-)sorbitol, and mono(4-methylbenzylidene)-(D-)sorbitol.

[0166] The soldering flux of the present embodiment may not contain a thixotropic agent, or may contain a thixotropic agent. When the soldering flux of the present embodiment contains a thixotropic agent, the thixotropic agent may be used alone or in combination of two or more.

[0167] 《Metal passivator》

[0168] Examples of the metal deactivator include hindered phenol compounds and nitrogen compounds.

[0169] The "metal deactivator" mentioned here refers to a compound having the ability to prevent metal from deteriorating due to contact with a certain compound.

[0170] The hindered phenol compound refers to a phenol compound having a bulky substituent (for example, a branched or cyclic alkyl group such as a tert-butyl group) at at least one ortho position of phenol.

[0171] The hindered phenol compound is not particularly limited, and examples thereof include bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylenebis(oxyethylene)], N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide], 1,6-hexanediolbis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2'-dihydroxy-3,3 '-Bis(α-methylcyclohexyl)-5,5'-dimethyldiphenylmethane, 2,2'-methylenebis(6-tert-butyl-p-cresol), 2,2'-methylenebis(6-tert-butyl-4-ethylphenol), triethylene glycol bis[3-(3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,4- Bis(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylimino)-1,3,5-triazine, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2-dithiodiethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, N,N'-hexamethylene Bis(3,5-di-tert-butyl-4-hydroxy-hydrocinnamic acid amide), 3,5-di-tert-butyl-4-hydroxybenzylphosphonate-diethyl ester, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, N,N'-bis[2-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl]oxalamide, compounds represented by the following chemical formulas, and the like.

[0172] [Chemical formula 3]

[0173]

[0174] (wherein Z is an alkylene group which may be substituted. 81 and R 82 Each is independently an alkyl group, an aralkyl group, an aryl group, a heteroaryl group, a cycloalkyl group or a heterocycloalkyl group which may be substituted. 83 and R 84 Each is independently an alkyl group which may be substituted.)

[0175] Examples of the nitrogen compound in the metal deactivator include hydrazide nitrogen compounds, amide nitrogen compounds, triazole nitrogen compounds, and melamine nitrogen compounds.

[0176] As the hydrazide nitrogen compound, any nitrogen compound having a hydrazide skeleton may be used, and examples thereof include dodecanedioic acid bis[N2-(2-hydroxybenzoyl)hydrazide], N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazide, decanedicarboxylic acid disalicylic hydrazide, N-salicylic-N'-salicylic hydrazide, m-nitrophenyl hydrazide, 3-aminophthalhydrazide, phthalic acid dihydrazide, adipic acid hydrazide, oxalyl di(2-hydroxy-5-octylbenzylidene hydrazide), N'-benzoylpyrrolidonecarboxylic acid hydrazide, and N,N'-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hydrazide.

[0177] The amide nitrogen compound may be any nitrogen compound having an amide skeleton, and examples thereof include N,N′-bis{2-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxy]ethyl}oxalamide.

[0178] The triazole nitrogen compound may be any nitrogen compound having a triazole skeleton, and examples thereof include N-(2H-1,2,4-triazol-5-yl)salicylamide, 3-amino-1,2,4-triazole, and 3-(N-salicyloyl)amino-1,2,4-triazole.

[0179] As the melamine-based nitrogen compound, any nitrogen compound having a melamine skeleton may be used, and examples thereof include melamine, melamine derivatives, etc. More specifically, examples thereof include triaminotriazine, alkylated triaminotriazine, alkoxyalkylated triaminotriazine, melamine, alkylated melamine, alkoxyalkylated melamine, N2-butylmelamine, N2,N2-diethylmelamine, N,N,N',N',N",N"-hexa(methoxymethyl)melamine, etc.

[0180] The metal deactivators may be used alone or in combination of two or more.

[0181] Surfactants

[0182] Examples of the surfactant include nonionic surfactants.

[0183] Examples of the nonionic surfactant include polyoxyalkylene adducts.

[0184] Examples of the alkylene oxide derived from the polyoxyalkylene adduct include ethylene oxide, propylene oxide, and butylene oxide.

[0185] Examples of the polyoxyalkylene adducts include polyethylene glycol, polypropylene glycol, polyethylene glycol-polypropylene glycol copolymers, ethylene oxide-resorcinol copolymers, polyoxyalkylene acetylene glycols, polyoxyalkylene glycerol ethers, polyoxyalkylene alkyl ethers, polyoxyalkylene esters, polyoxyalkylene alkyl amides and the like.

[0186] Alternatively, examples of the nonionic surfactant include polyoxyalkylene adducts of alcohols. Examples of the alcohol include aliphatic alcohols, aromatic alcohols, and polyols.

[0187] The surfactant may be used alone or in combination of two or more.

[0188] Antioxidants

[0189] Examples of the antioxidant include hindered phenol-based antioxidants such as 2,2′-dihydroxy-3,3′-bis(α-methylcyclohexyl)-5,5′-dimethyldiphenylmethane.

[0190] The "antioxidant" referred to herein refers to a compound having a capability of inhibiting oxidation of the solder alloy.

[0191] The antioxidants may be used alone or in combination of two or more.

[0192] In mounting the indium sheet, since the melting point of indium constituting the sheet is as low as 156° C., reflow soldering is performed under low temperature conditions.

[0193] The flux of this embodiment has high wettability even in relatively low-temperature bonding and can improve the ability to suppress the generation of voids. Although the reason for such an effect is not clear, it is speculated as follows.

[0194] Monocarboxylic acids (A1) such as palmitic acid have lower melting points than dicarboxylic acids such as adipic acid. The flux of the present embodiment can exhibit sufficient wettability even in relatively low temperature reflow soldering by containing monocarboxylic acids (A1) having a relatively low melting point.

[0195] Since the monocarboxylic acid (A1) has lower reactivity due to the carboxyl group than the dicarboxylic acid, the amount of voids resulting from the reaction between the carboxylic acid and the metal oxide can also be reduced.

[0196] The solvent (S1) having a boiling point of 100°C or less will volatilize before the indium sheet melts even in low-temperature reflow. As a result, when the indium melts, no voids are generated from the solvent (S1).

[0197] Due to these synergistic effects, the flux of the present embodiment can suppress the generation of voids even during the mounting of the indium sheet.

[0198] Since the flux of this embodiment has the above-mentioned effects, it can be suitably used for mounting of indium sheets.

[0199] (Method for preparing a conjugate)

[0200] The method for producing a bonded body in this embodiment is a method for obtaining a bonded body by bonding a bare chip and a lid together via a thermal interface material (TIM) using the flux of the above-described embodiment.

[0201] The method for producing the bonded body of the present embodiment will be described by taking as an example a method having a flux applying step, a lid attaching step, and a reflow step.

[0202] use Figures 1 to 3 A preferred embodiment of the method for preparing a conjugate of this embodiment is described below. In the method for preparing a conjugate of this embodiment, Figure 1 As shown, a substrate 40 on which the lid 10 , the TIM 20 , and the bare chip 41 are mounted is prepared.

[0203] A metallization layer 42 is provided on the surface of the bare chip 41. The metallization layer 42 may be, for example, a Ni-plated layer, a Ni / Au-plated layer, etc. The metallization layer 42 may also have a plurality of layers of different compositions. The metallization layer 42 may be formed, for example, by a method such as sputtering.

[0204] The cover 10 is provided with a metallization layer 11 on the surface facing the TIM 20. As the metallization layer 11, the same layer as the metallization layer 42 of the bare chip 41 can be cited. The cover 10 is provided with a heat sink 12 on the surface opposite to the surface facing the TIM 20. As the material of the heat sink 12, for example, metals such as aluminum, iron, and copper can be cited.

[0205] The TIM 20 is an indium sheet made of only indium. The TIM 20 is in a plate shape. The size of the TIM 20 is equal to or smaller than the size of the metallization layer 11 of the cover 10 and the metallization layer 42 of the bare chip 41 .

[0206] <Flux Coating Process>

[0207] As the soldering flux 50, the soldering flux 50 of the above-mentioned embodiment is preferably used. Figure 2 The flux application process will be described. Figure 2 1 is a cross-sectional view showing the TIM 20 and the bare chip 41 to which the flux 50 is applied. In the flux application step, the flux 50 is interposed between the TIM 20 and the bare chip 41 and between the TIM 20 and the lid 10 .

[0208] In the flux application step, the flux 50 is applied to the bonding surfaces ( 42 a , 20 b ) of the bare chip 41 and the TIM 20 and the bonding surfaces ( 11 a , 20 a ) of the lid 10 and the TIM 20 .

[0209] The flux 50 is applied to the bonding surface as follows. The flux 50 is applied to the surface 42a of the metallization layer 42 of the bare chip 41. Next, the TIM 20 is placed on the metallization layer 42 of the bare chip 41 to which the flux 50 is applied. The flux 50 is applied to the surface 20a of the TIM 20 stacked on the bare chip 41, which is opposite to the surface 20b in contact with the bare chip 41.

[0210] As the coating apparatus of the flux 50, a spray flux coater, a foaming flux coater, etc. are mentioned. Among them, a spray flux coater is preferable from the viewpoint of the stability of the coating amount.

[0211] <Cover installation process>

[0212] In the cover mounting process, after applying the flux 50 on the bonding surface, the cover 10 is fixed on the substrate 40 on which the TIM 20 and the bare chip 41 are stacked. Figure 3 The cover mounting process will be described. Figure 3 The figure shows a laminated body 60 in which the cover 10 and the substrate 40 are bonded together by the adhesive resin 43 after the flux 50 is applied.

[0213] In the cover mounting process, after applying the flux 50, the adhesive resin 43 is applied to one surface of the substrate 40. Then, the cover 10 and the substrate 40 stacked with the TIM 20 and the bare chip 41 are bonded by thermocompression, and the adhesive resin 43 is cured. Thus, the cover 10 is fixed to the substrate 40. Through the cover mounting process, a laminated body 60 in which the cover 10 and the substrate 40 are bonded by the adhesive resin 43 is obtained.

[0214] <Reflow process>

[0215] In the reflow process, the laminated body 60 is reflowed. The lid 10 and the bare chip 41 are bonded to each other via the TIM 20 by the reflow process.

[0216] The reflow temperature is preferably lower than 200° C. Since indium constituting the indium sheet as TIM has a melting point of 156° C., the indium sheet can be joined even at a lower temperature than normal reflow. The reflow temperature is preferably 160 to 200° C., more preferably 170 to 190° C.

[0217] According to the bonding method of the joint body of the embodiment described above, the soldering flux of the embodiment described above has excellent wettability even at low temperatures, so it is easy to improve the adhesion of the TIM to the cover and the bare chip. As a result, the bare chip and the cover can be well bonded through the TIM (i.e., the indium sheet). In addition, since the amount of voids on the bonding surface of the indium sheet is reduced, the joint body bonded in the above manner can efficiently release the heat generated from the bare chip.

[0218] (Other embodiments)

[0219] As described above, in the method for manufacturing a bonded body of the present embodiment, the flux 50 is interposed between at least one of the TIM 20 and the bare chip 41 or between the TIM 20 and the lid 10 .

[0220] In the above embodiment, the flux 50 is applied to the bonding surface 42 a of the bare chip 41 with the TIM 20 and the bonding surface 11 a of the TIM 20 with the lid 10 , but the surface to which the flux 50 is applied is not limited thereto.

[0221] For example, to interpose the flux 50 between the TIM 20 and the bare chip 41 , the flux 50 may be applied to the bonding surface 20 b of the TIM 20 to the bare chip 41 or to the bonding surface 11 a of the lid 10 to the TIM 20 .

[0222] Example

[0223] Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to the following examples.

[0224] <Preparation of flux>

[0225] (Examples 1 to 45, Comparative Examples 1 to 4)

[0226] The fluxes of Examples and Comparative Examples were prepared according to the compositions shown in Tables 1 to 6. The components of the raw materials used are shown below. The composition ratios in Tables 1 to 6 are based on the mass % when the total mass of the flux is 100 mass %, and blanks refer to 0 mass %.

[0227] Rosin: Acrylic acid modified hydrogenated rosin, hydrogenated rosin

[0228] As the organic acid, monocarboxylic acid (A1) and dicarboxylic acid are used.

[0229] Monocarboxylic acid (A1): lauric acid (melting point 45°C, molecular weight 200), palmitic acid (melting point 63°C, molecular weight 256), stearic acid (melting point 70°C, molecular weight 284), 12-hydroxystearic acid (melting point 76.5°C, molecular weight 300)

[0230] Dicarboxylic acids: eicosanedioic acid, adipic acid, sebacic acid

[0231] Amine: Diethanolamine

[0232] As the solvent (S), a solvent (S1) and a solvent (S2) were used.

[0233] Solvent (S1): 2-propanol (boiling point 82°C)

[0234] Solvent (S2): Diethylene glycol monohexyl ether (boiling point 259°C)

[0235] According to the evaluation method described in <Evaluation 1> below, a bonded body was prepared, and "Evaluation of the ability to suppress void generation" and "Evaluation of wettability" were performed. The results of these evaluations are shown in Tables 1 to 5.

[0236] <Evaluation 1>

[0237] 《Evaluation of the ability to suppress void generation》

[0238] Preparation method of the conjugate:

[0239] A cover having an Au / Ni plated portion (size: 8 mm×8 mm) on the surface and a substrate having an Au / Ni plated portion (size: 8 mm×8 mm) on the surface were prepared.

[0240] As a solder sheet, an indium sheet (size: 7 mm×7 mm×400 μm) consisting of only indium was prepared, and 2 mg of the flux of each example was sprayed on the front and back surfaces of the indium sheet.

[0241] A copper plate with a thickness of 300 μm was placed as a spacer around the Au / Ni plated portion of the substrate. Next, the indium sheet coated with flux was sandwiched between the cover and the Au / Ni plated portion of the substrate and fixed with a jig.

[0242] Next, the lid and the substrate sandwiching the solder sheet were subjected to reflow soldering to obtain a joint body. The reflow soldering was performed in the atmosphere at a temperature increase rate of 10°C / min until the temperature reached 170°C.

[0243] Verification method:

[0244] The obtained bonded body is irradiated with X-rays from the vertical direction of the substrate, and the void area is measured by analyzing the transmitted X-rays. The measurement is performed using XD7600NT (manufactured by Nordson). In the measurement of the void area, when the X-rays pass through at least one void, it is measured as the presence of a void. The void detection diameter is a void of 0.1 μm or more. Next, the ratio of the total area of ​​the voids to the total area of ​​the indium sheet is calculated as the void area ratio (%).

[0245] Judgment criteria:

[0246] A: The void area ratio is less than 10%.

[0247] B: The void area ratio is 10% or more and less than 15%.

[0248] C: The void area ratio is 15% or more.

[0249] The flux with an evaluation result of A or B is acceptable, and the flux with an evaluation result of C is unacceptable.

[0250] 《Evaluation of Wettability》

[0251] Verification method:

[0252] As the solder sheet, an indium sheet (size: 2 mm×2 mm×100 μm) consisting of only indium was prepared.

[0253] 0.5 mg of the flux of each example was applied to the front and back surfaces of the indium sheet, respectively. The solder sheet coated with the flux was placed on the Au / Ni electrode.

[0254] Next, the electrode on which the indium sheet was placed was subjected to reflow soldering under the following conditions: The reflow soldering was performed by heating the electrode to 180° C. at a heating rate of 6° C. / min and maintaining the temperature at 180° C. for 3 minutes.

[0255] Next, after removing the flux, the area of ​​wetting extension was measured.

[0256] Judgment criteria:

[0257] A: The area of ​​infiltration extension is 2.5 mm 2 above.

[0258] B: The area of ​​infiltration extension is 2.0 mm 2 Above and less than 2.5mm 2 .

[0259] The flux with an evaluation result of A or B is considered acceptable.

[0260] The evaluation results are shown in Table 6.

[0261] <Evaluation 2>

[0262] 《Evaluation of the ability to suppress void generation》

[0263] As the solder sheet, a SAC alloy sheet (size: 7 mm×7 mm×400 μm) composed of a solder alloy containing 3 mass % of Ag, 0.5 mass % of Cu, and the balance of Sn was prepared.

[0264] The same method as in <Evaluation 1> "Evaluation of void generation suppression capability" was used to verify the SAC alloy sheet and the flux of Example 5 and Comparative Example 3. The reflow was performed in the atmosphere at a heating rate of 30°C / min until the temperature reached 250°C.

[0265] 《Evaluation of Wettability》

[0266] As the solder sheet, a SAC alloy sheet (size: 2 mm×2 mm×100 μm) composed of a solder alloy containing 3 mass % of Ag, 0.5 mass % of Cu, and the balance of Sn was prepared.

[0267] The same method as in "Evaluation of Wettability" in <Evaluation 1> was used to verify the SAC alloy sheet and the flux of Example 5 and Comparative Example 3. The reflow process was performed by heating the temperature to 250°C at a heating rate of 6°C / min and maintaining the temperature at 250°C for 3 minutes.

[0268] [Table 1]

[0269]

[0270] The fluxes of Examples 1 to 9 containing the monocarboxylic acid (A1) having a melting point of 35° C. or higher and 90° C. or lower were evaluated as A or B in terms of void generation suppressing ability.

[0271] The fluxes of Comparative Examples 1 to 4 not containing the monocarboxylic acid (A1) were evaluated as C in terms of void generation suppressive ability.

[0272] The soldering flux of Example 5 containing palmitic acid was evaluated as A in terms of void generation suppression capability. The soldering fluxes of Examples 7 to 9 containing lauric acid, stearic acid or 12-hydroxystearic acid were evaluated as B in terms of void generation suppression capability.

[0273] The soldering flux of Example 5 containing alkanolamine was rated A in the evaluation of void generation suppression capability and wettability.

[0274] The soldering flux of Example 6 containing no alkanolamine was rated B in the evaluation of void generation suppression capability and wettability.

[0275] [Table 2]

[0276]

[0277] The flux of Example 10 in which the content of palmitic acid was 60% by mass or more based on the total mass of the monocarboxylic acid (A1) was evaluated as A in terms of void generation suppressing capability.

[0278] The flux of Example 11, in which the content of palmitic acid was less than 60% by mass based on the total mass of the monocarboxylic acid (A1), was evaluated as B in terms of void generation suppressing ability.

[0279] The flux of Example 12 in which the content of the solvent (S1) was 65% by mass or more based on the total mass of the solvent (S) was evaluated as A in terms of void generation suppressing capability.

[0280] The soldering flux of Example 13, in which the content of the solvent (S1) was less than 65% by mass based on the total mass of the solvent (S), was evaluated as B in terms of void generation suppressing capability.

[0281] [Table 3]

[0282]

[0283] [Table 4]

[0284]

[0285] [Table 5]

[0286]

[0287] The fluxes of Examples 15, 17 to 19, 22 to 25, 27, and 29 to 31, in which the total content of rosin was 15% to 45% by mass relative to the total mass of the flux and the content of palmitic acid was 3% to 15% by mass relative to the total mass of the flux, were rated A in terms of void generation suppression capability and wettability.

[0288] The fluxes of Examples 34 and 38, in which the total content of rosin was 10% by mass based on the total mass of the flux, were rated B in terms of void generation suppression capability and wettability.

[0289] The fluxes of Examples 37, 41, and 45, in which the total content of rosin was 50% by mass based on the total mass of the flux, were evaluated as B in terms of void generation suppressing capability.

[0290] The fluxes of Examples 26 and 38, in which the content of palmitic acid was 1% by mass based on the total mass of the flux, were rated B in the void generation suppressing ability and the wettability.

[0291] The fluxes of Examples 20 to 21, 32 to 33, and 44 to 45, in which the content of palmitic acid was 20% by mass based on the total mass of the flux, were evaluated as B in terms of void generation suppressing ability.

[0292] [Table 6]

[0293]

[0294] In "Evaluation 2", when the SAC alloy sheet and the flux of Example 5 were used, the void generation suppression capability and wettability were evaluated as A. In addition, when the SAC alloy sheet and the flux of Comparative Example 3 were used, the void generation suppression capability and wettability were evaluated as A.

[0295] The soldering flux of Comparative Example 3 containing no monocarboxylic acid (A1) had a void suppression capability of A when using a SAC alloy sheet and a void suppression capability of C when using an indium sheet. That is, voids were more likely to occur in the indium sheet than in the SAC alloy sheet.

[0296] The soldering flux of Example 5 containing the monocarboxylic acid (A1) can sufficiently suppress voids even when an indium sheet is used.

[0297] Industrial Applicability

[0298] The soldering flux of the present invention is suitable for preparing a bonded body having high heat dissipation efficiency, in which a lid provided with a heat sink and a bare chip are bonded via an indium sheet.

[0299] Explanation of symbols

[0300] 10 cover, 11 metallization layer, 11a bonding surface, 12 heat sink, 20 thermal interface material (TIM), 20a, 20b bonding surface, 40 substrate, 41 bare chip, 42 metallization layer, 42a bonding surface, 43 adhesive resin, 50 flux, 60 laminate

Claims

1. A soldering flux comprising rosin, an organic acid and a solvent (S), The organic acid contains a monocarboxylic acid (A1) having a melting point of 35° C. or higher and 90° C. or lower, The solvent (S) contains a solvent (S1) having a boiling point of 100° C. or less.

2. The soldering flux according to claim 1, wherein The molecular weight of the monocarboxylic acid (A1) is 180 or more and 350 or less.

3. The soldering flux according to claim 1 or 2, wherein The content of the solvent (S1) is 65% by mass or more relative to the total mass of the solvent (S).

4. The soldering flux according to any one of claims 1 to 3, wherein The soldering flux also contains an alkanolamine.

5. The soldering flux according to any one of claims 1 to 4, wherein The content of the monocarboxylic acid (A1) is 0.5 mass % or more and 20 mass % or less relative to the total mass of the soldering flux.

6. The soldering flux according to any one of claims 1 to 5, wherein The monocarboxylic acid (A1) contains palmitic acid, The content of palmitic acid is 60% by mass or more relative to the total mass of the monocarboxylic acid (A1).

7. The soldering flux according to any one of claims 1 to 6, wherein The content of the rosin is 10 mass % or more and 50 mass % or less relative to the total mass of the soldering flux.

8. A method for preparing a bonded body, wherein a bare chip and a cover are bonded together via a thermal interface material (TIM). in, The TIM is an indium sheet, The flux according to any one of claims 1 to 7 is interposed between at least one of the TIM and the bare chip or between the TIM and the cover, and bonding is performed by a reflow method.

9. The method for preparing a conjugate according to claim 8, wherein: The bonding by the reflow method is performed at a temperature lower than 200°C.

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