Soldering flux and preparation method of electronic component

Abstract

Provided is a flux capable of suppressing the occurrence of voids when continuous reflow soldering is performed using an indium alloy sheet under different temperature conditions. The flux contains a rosin ester, an organic acid (A), and a solvent (S). The organic acid (A) contains a dimer acid (A1) having a weight loss rate of 1 mass% or less when heated to 260 DEG C at a temperature increase rate of 10 DEG C / min in thermogravimetric measurement. The solvent (S) contains a solvent (S1) having a weight loss rate of 99 mass% or more when heated to 150 DEG C at a temperature increase rate of 6 DEG C / min in thermogravimetric measurement.

Description

Technical Field

[0001] The present invention relates to a method for preparing a soldering flux and an electronic component. This application claims priority based on Japanese Patent Application No. 2022-135236 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 TIM, a sheet having an increased indium content (hereinafter referred to as an indium alloy sheet) has been proposed. As an alloy used as a raw material of the indium alloy sheet, for example, an alloy containing 90 mass % In and 10 mass % Ag is used.

[0009] Indium has a lower hardness than other metal elements, and the indium alloy sheet has high followability and high adhesion to the surface of the bare chip and the cover. Therefore, the indium alloy sheet has high heat transfer efficiency from the bare chip to the cover with a heat sink. As a result, by using the indium alloy sheet, the heat discharge efficiency generated by the operation of the bare chip can be improved. In addition, since the indium alloy sheet containing Ag has a higher thermal conductivity than the indium sheet made of indium alone, the heat discharge efficiency can be further improved.

[0010] In the installation of the indium alloy sheet, the indium alloy sheet with flux applied on the surface is used to bond the lid with the heat sink and the bare chip by a single reflow soldering to obtain a semiconductor package. Since the melting point of indium is relatively low at 156°C, the bonding by a single reflow soldering is performed at a lower temperature than the normal bonding.

[0011] When a reflow soldering is performed at a temperature of, for example, 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 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 chip.

[0012] Then, after the primary reflow, a secondary reflow is performed to bond the solder balls to the back of the semiconductor package. In order to melt the solder balls, the secondary reflow is performed at a high temperature of, for example, 250° C. Since the secondary reflow is at a high temperature, the activator and the like are vaporized and voids are easily formed.

[0013] As described above, when the conventional soldering flux and indium alloy sheet are used to perform two reflow processes (primary reflow and secondary reflow), a large number of voids are easily generated on the bonding surface of the indium alloy sheet. Due to the voids, the efficiency of heat transfer from the chip to the cover with the heat sink via the indium alloy sheet is reduced, and the efficiency of discharging heat generated by the operation of the chip is reduced.

[0014] Therefore, an object of the present invention is to provide a flux capable of suppressing the generation of voids when continuous reflow soldering under different temperature conditions is performed using an indium alloy sheet.

[0015] Means of solving the problem

[0016] The present invention includes the following aspects.

[0017] [1] A soldering flux comprising a rosin ester, an organic acid (A) and a solvent (S), wherein the organic acid (A) comprises a dimer acid (A1), wherein the weight reduction rate of the dimer acid (A1) when heated to 260°C at a heating rate of 10°C / min in a thermogravimetric measurement is 1% by mass or less, and the solvent (S) comprises a solvent (S1), wherein the weight reduction rate of the solvent (S1) when heated to 150°C at a heating rate of 6°C / min in a thermogravimetric measurement is 99% by mass or more.

[0018] In the present invention, the "weight reduction rate" is measured, for example, as follows. Using a differential thermal-thermogravimetric simultaneous measuring apparatus (manufactured by Rigaku Corporation, TG-DTA8122), 10 mg of the sample to be measured is placed in an aluminum pan, and heating is started from room temperature of about 25°C, and the temperature is increased at a predetermined heating rate until a predetermined temperature is reached. Then, the weight reduction rate is calculated from the mass W0 (100% by mass) of the sample before heating and the mass W1 immediately after reaching the predetermined temperature by the following calculation formula.

[0019] Weight reduction rate (%) = 100 × {W0-W1} / W0

[0020] [2] The soldering flux according to [1], wherein the content of the dimer acid (A1) is 75% by mass or more based on the total mass of the organic acid (A).

[0021] [3] The soldering flux according to [1] or [2], wherein the content of the solvent (S1) is 80% by mass or more relative to the total mass of the solvent (S).

[0022] [4] The soldering flux according to any one of [1] to [3], wherein the dimer acid (A1) is at least one selected from dimers to which an unsaturated fatty acid having 18 carbon atoms is bonded.

[0023] [5] The soldering flux according to any one of [1] to [4], wherein the boiling point of the solvent (S1) is 200° C. or less.

[0024] [6] The soldering flux according to any one of [1] to [5], further comprising an azole.

[0025] [7] The soldering flux according to any one of [1] to [6], wherein the content of the dimer acid (A1) is 10% by mass or more and 60% by mass or less relative to the total mass of the soldering flux.

[0026] [8] The soldering flux according to any one of [1] to [7], wherein the content of the rosin ester is 15% by mass or more and 60% by mass or less relative to the total mass of the soldering flux.

[0027] [9] A method for preparing an electronic component, which is a method for preparing an electronic component containing a semiconductor package, the method comprising: a step (i) of obtaining a semiconductor package having a bonded body formed by bonding a bare chip and a cover via a thermal interface material (TIM); and a step (ii) of bonding solder balls to the back side of the semiconductor package to obtain the electronic component, wherein the TIM is a sheet made of an alloy of indium and silver, the step (i) comprising a heating operation (1), wherein the heating operation (1) causes the flux described in any one of [1] to [8] to be interposed between at least one of the TIM and the bare chip or between the TIM and the cover, and the bare chip and the cover are bonded by a reflow method, and the step (ii) comprising a heating operation (2), wherein the heating operation (2) bonds the solder balls to the semiconductor package by a reflow method.

[0028]

[10] The method for producing an electronic component according to [9], wherein the temperature conditions of the heating operation (1) are 150 to 250°C, and the temperature conditions of the heating operation (2) are 200 to 280°C.

[0029] Effects of the Invention

[0030] According to the present invention, it is possible to provide a flux capable of suppressing the generation of voids when continuous reflow soldering under different temperature conditions is performed using an indium alloy sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a cross-sectional view showing an embodiment of a method for manufacturing an electronic component, including a cover, a TIM, and a bare chip.

[0032] Figure 2 This is a cross-sectional view showing a step of applying flux on a TIM and a bare chip in accordance with one embodiment of a method for producing an electronic component.

[0033] Figure 3 This is one embodiment of a method for producing an electronic component, 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.

[0034] Figure 4 This is one embodiment of a method for manufacturing an electronic component, and shows a cross-sectional view of an electronic component obtained by bonding solder balls to the back surface of a semiconductor package. DETAILED DESCRIPTION

[0035] (Flux)

[0036] The soldering flux of the present embodiment contains rosin ester, an organic acid (A), and a solvent (S).

[0037] The organic acid (A) contains a dimer acid (A1) having a weight loss rate of 1 mass % or less when heated to 260° C. at a heating rate of 10° C. / min in a thermogravimetric measurement.

[0038] The solvent (S) contains a solvent (S1) having a weight reduction rate of 99% by mass or more when heated to 150° C. at a heating rate of 6° C. / min in a thermogravimetric measurement.

[0039] The soldering flux of the present embodiment is suitable for use in performing continuous reflow for mounting an indium alloy sheet and bonding a solder ball.

[0040] In the primary reflow, reflow is performed at a low temperature (e.g., 170°C) close to the melting point of indium, and the indium alloy sheet is mounted. Next, in the secondary reflow, reflow is performed at a high temperature (e.g., 250°C) close to the melting point of the solder alloy, thereby bonding the solder balls to the substrate.

[0041] According to the soldering flux of this embodiment, the solvent (S1) is volatilized in one reflow process. As a result, when the indium alloy sheet is melted, no voids are generated due to the solvent (S1).

[0042] Furthermore, in the soldering flux of the present embodiment, the rosin ester and the dimer acid (A1) are unlikely to volatilize even at a high temperature during secondary reflow, and thus the generation of voids can be suppressed.

[0043] <Rosin Ester>

[0044] Rosin ester is an ester resin obtained by reacting a natural resin or a substance obtained by chemically modifying a natural resin (rosin derivative) with an alcohol. Rosin ester may have a hydroxyl group in addition to a carboxyl group.

[0045] Examples of the alcohol include glycerin and pentaerythritol.

[0046] Examples of the “natural resin” that can be a raw material for rosin ester include gum rosin, wood rosin, and tall oil rosin.

[0047] In this specification, "natural resin" includes a mixture of abietic acid and its isomers containing abietic acid as the main component. The total content of abietic acid and abietic acid isomers in the natural resin is, for example, 40% by mass or more and 80% by mass or less relative to the natural resin. In this specification, "main component" refers to a component whose content in the compound is 40% by mass or more among the components constituting the compound.

[0048] Representative examples of isomers of abietic acid include neoabietic acid, palustric acid, and levopimaric acid. The structure of abietic acid is shown below.

[0049] [Chemical formula 1]

[0050]

[0051] In the present invention, the "substances obtained by chemically modifying natural resins (rosin derivatives)" that can serve as the raw material of rosin esters include substances obtained by subjecting the "natural resins" to one or more treatments selected from hydrogenation, dehydrogenation, neutralization, alkylene oxide addition, amidation, dimerization, polymerization, and Diels-Alder cycloaddition.

[0052] Examples of the rosin derivative include purified rosin and modified rosin.

[0053] Examples of the modified rosin include hydrogenated rosin, polymerized rosin, polymerized hydrogenated rosin, disproportionated rosin, acid-modified rosin, 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 soap, hydrogenated rosin soap, and acid-modified rosin soap.

[0054] Among rosins, rosin esters are preferred due to their high heat resistance and low weight loss rate.

[0055] Rosin as a raw material of rosin ester is preferably hydrogenated rosin. Alcohol as a raw material of rosin ester is preferably glycerol. Rosin ester is preferably obtained by reacting hydrogenated rosin with glycerol.

[0056] The weight loss rate of rosin ester when heated to 260° C. at a heating rate of 10° C. / min in thermogravimetric measurement is preferably 15% by mass or less, more preferably 10% by mass or less, further preferably 8% by mass or less, and particularly preferably 7.5% by mass or less. The lower the value of the weight loss rate of rosin ester, the more preferred. The lower limit of the weight loss rate of rosin ester is not particularly limited as long as the effect of the present invention can be exerted, and for example, it may be 0.1% by mass, and may also be 0% by mass in measurement.

[0057] By setting the weight reduction rate of the rosin ester to be equal to or less than the above upper limit, it is easy to suppress the generation of voids when continuous reflow soldering is performed using the indium alloy sheet.

[0058] The acid value of the rosin ester is preferably 0.01 mgKOH / g to 50 mgKOH / g, more preferably 0.1 mgKOH / g to 30 mgKOH / g, further preferably 0.5 mgKOH / g to 20 mgKOH / g, particularly preferably 2 mgKOH / g to 10 mgKOH / g.

[0059] When the acid value of the rosin ester is equal to or greater than the lower limit in the above range, the activity of the flux can be easily improved. When the acid value of the rosin ester is equal to or less than the upper limit in the above range, the soldering meltability and wettability can be easily improved.

[0060] The acid value refers to the number of milligrams of potassium hydroxide required to neutralize the carboxyl groups in 1 g of the sample to be measured. The acid value of rosin ester can be measured, for example, according to the neutralization titration method 3.1 of JIS K0070 "Test methods for acid value, saponification value, ester value, iodine value, hydroxyl value and unsaponifiable matter of chemical products".

[0061] The acid value measured by this method is a weighted average value of the acid values ​​of all types of rosin esters contained in the flux.

[0062] The softening point of the rosin ester is preferably 85°C or higher and 110°C or lower, more preferably 90°C or higher and 105°C or lower, and even more preferably 90°C or higher and 100°C or lower.

[0063] When the softening point of the rosin ester is equal to or higher than the lower limit in the above range, the heat resistance of the rosin ester can be easily improved. When the softening point of the rosin ester is equal to or lower than the upper limit in the above range, the fluidity of the flux can be easily improved when the solder melts.

[0064] The softening point of rosin ester can be measured by the ring and ball method. As an example of the ring and ball method, there can be mentioned the method described in JIS K5902.

[0065] The rosin ester may be used alone or in combination of two or more.

[0066] The content of the rosin ester in the soldering flux is preferably 10% by mass or more and 70% by mass or less, and more preferably 15% by mass or more and 60% by mass or less, relative to the total mass (100% by mass) of the soldering flux.

[0067] <Organic acid (A)>

[0068] The organic acid (A) contained in the soldering flux of the present embodiment includes a dimer acid (A1). The organic acid (A) contained in the soldering flux of the present embodiment may include other organic acids in addition to the dimer acid (A1).

[0069] 《Dimer acid (A1)》

[0070] The weight loss rate of the dimer acid (A1) when heated to 260°C at a heating rate of 10°C / min in a thermogravimetric measurement is 1% by mass or less, preferably 0.8% by mass or less, more preferably 0.6% by mass or less, further preferably 0.4% by mass or less, particularly preferably 0.3% by mass or less, and most preferably 0.2% by mass or less.

[0071] The lower limit of the weight reduction rate of the dimer acid (A1) is not particularly limited as long as the effect of the present invention can be achieved, and may be, for example, 0.01% by mass or 0% by mass in measurement.

[0072] The dimer acid (A1) contains a dibasic acid obtained by dimerization of an unsaturated fatty acid as a main component. The dimer acid (A1) includes a hydrogenated dimer acid obtained by hydrogenating a dibasic acid obtained by dimerization of an unsaturated fatty acid.

[0073] The unsaturated fatty acid as a raw material of the dimer acid (A1) preferably has 18 carbon atoms. The dibasic acid as a main component of the dimer acid (A1) preferably has 36 carbon atoms, and more preferably is at least one selected from dimers of unsaturated fatty acids having 18 carbon atoms bonded thereto.

[0074] Examples of the unsaturated fatty acid as a raw material of the dimer acid (A1) include oleic acid, linoleic acid, vaccenic acid, elaidic acid, linolenic acid, acrylic acid, and methacrylic acid.

[0075] The unsaturated fatty acid as a raw material of the dimer acid (A1) is preferably at least one selected from oleic acid, linoleic acid, vaccenic acid and elaidic acid, and more preferably at least one selected from oleic acid and linoleic acid.

[0076] The dimer acid (A1) may be used alone or in combination of two or more.

[0077] Dimer acid (A1) can have unsaturated hydrocarbon group, alicyclic hydrocarbon group, aromatic hydrocarbon group etc. The unsaturation of dimer acid (A1) can be the value shown below. Here, the unsaturation of dimer acid (A1) is represented by {(2m+2)-n} / 2, wherein m is the number of carbon atoms in the molecule of dimer acid (A1), and n is the number of hydrogen atoms. The dibasic acid as the main component of dimer acid (A1) has 2 carboxyl groups. The unsaturation of the dibasic acid is more than 2.

[0078] The unsaturation degree of the dimer acid (A1) is preferably 2 or more and 20 or less, more preferably 2 or more and 15 or less, further preferably 2 or more and 10 or less, particularly preferably 2 or more and 8 or less.

[0079] When the dimer acid (A1) contains two or more dimer acids having different degrees of unsaturation, the unsaturation degree obtained by weighted average of these unsaturations is preferably 2 or more and 10 or less, more preferably 2 or more and 8 or less, further preferably 2 or more and 6 or less, particularly preferably 2.5 or more and 4.5 or less, and most preferably 3 or more and 4 or less.

[0080] The dimer acid (A1) may be used alone or in combination of two or more.

[0081] The content of the dimer acid (A1) is preferably 5 mass % to 70 mass %, more preferably 10 mass % to 60 mass %, and further preferably 15 mass % to 60 mass %, relative to the total mass (100 mass %) of the flux.

[0082] When the content of the dimer acid (A1) is within the above range, the generation of voids during continuous reflow soldering using the indium alloy sheet can be suppressed. In addition, when the content of the dimer acid (A1) is greater than the lower limit of the above range, wettability to the indium alloy sheet can be easily improved.

[0083] The total content of the dimer acid having 36 carbon atoms is preferably 70% by mass or more and 100% by mass or less, more preferably 80% by mass or more and 100% by mass or less, further preferably 90% by mass or more and 100% by mass or less, particularly preferably 95% by mass or more and 100% by mass or less, most preferably 98% by mass or more and 100% by mass or less, and may be 100% by mass in measurement.

[0084] When the dimer acid (A1) contains a plurality of dimer acids, each dimer acid can be analyzed using a liquid chromatography-Fourier transform mass spectrometer. In the prepared ion chromatogram, the ratio of the peak area derived from each dimer acid having 36 carbon atoms to the total peak area (100%) derived from all molecules contained in the dimer acid (A1) is preferably within the following range.

[0085] The peak area derived from the dimer acid having an unsaturation degree of 2 is preferably 5% or more and 50% or less, more preferably 15% or more and 40% or less, and further preferably 20% or more and 30% or less.

[0086] The ratio of the peak area of ​​the dimer acid having an unsaturation degree of 3 is preferably 10% to 70%, more preferably 20% to 60%, further preferably 30% to 50%.

[0087] The ratio of the peak area of ​​the dimer acid having an unsaturation degree of 4 is preferably 2% to 30%, more preferably 3% to 20%, further preferably 5% to 15%.

[0088] The ratio of the peak area of ​​the dimer acid having an unsaturation degree of 5 is preferably 0.1% to 15%, more preferably 0.5% to 10%, and even more preferably 1% to 5%.

[0089] The ratio of the peak area of ​​the dimer acid having an unsaturation degree of 6 is preferably 1% to 30%, more preferably 2% to 20%, and further preferably 3% to 15%.

[0090] The ratio of the peak area of ​​the dimer acid having an unsaturation degree of 7 is preferably 2% to 30%, more preferably 3% to 20%, further preferably 5% to 15%.

[0091] The ratio of the peak area of ​​the dimer acid having an unsaturation degree of 8 is preferably 0.1% to 15%, more preferably 0.5% to 10%, and even more preferably 1% to 5%.

[0092] Alternatively, when the dimer acid (A1) contains a plurality of types of dimer acids having 36 carbon atoms, the content of the dimer acid having 36 carbon atoms is preferably within the following range relative to the total mass (100 mass%) of the dimer acid (A1).

[0093] The content of the dimer acid having an unsaturation degree of 2 is preferably 5% by weight or more and 50% by weight or less, more preferably 15% by weight or more and 40% by weight or less, and further preferably 20% by weight or more and 30% by weight or less.

[0094] The content of the dimer acid having an unsaturation degree of 3 is preferably 10% by weight or more and 70% by weight or less, more preferably 20% by weight or more and 60% by weight or less, and further preferably 30% by weight or more and 50% by weight or less.

[0095] The content of the dimer acid having an unsaturation degree of 4 is preferably 2% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 20% by mass or less, and further preferably 5% by mass or more and 15% by mass or less.

[0096] The content of the dimer acid having an unsaturation degree of 5 is preferably 0.1% by mass or more and 15% by mass or less, more preferably 0.5% by mass or more and 10% by mass or less, and further preferably 1% by mass or more and 5% by mass or less.

[0097] The content of the dimer acid having an unsaturation degree of 6 is preferably 1% by mass or more and 30% by mass or less, more preferably 2% by mass or more and 20% by mass or less, and further preferably 3% by mass or more and 15% by mass or less.

[0098] The content of the dimer acid having an unsaturation degree of 7 is preferably 2% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 20% by mass or less, and further preferably 5% by mass or more and 15% by mass or less.

[0099] The content of the dimer acid having an unsaturation degree of 8 is preferably 0.1% by mass or more and 15% by mass or less, more preferably 0.5% by mass or more and 10% by mass or less, and further preferably 1% by mass or more and 5% by mass or less.

[0100] 《Other organic acids》

[0101] Examples of other organic acids include carboxylic acids, organic sulfonic acids, etc. Examples of carboxylic acids include aliphatic carboxylic acids, aromatic carboxylic acids, etc. Examples of aliphatic carboxylic acids include aliphatic monocarboxylic acids, aliphatic dicarboxylic acids, etc.

[0102] Examples of the aliphatic monocarboxylic acid include caproic acid, heptanoic acid, octanoic acid, nonanoic acid, isononanoic acid, decanoic acid, decenoic acid, lauric acid (dodecanoic acid), undecanoic acid, 5-dodecenoic acid, tridecanoic acid, myristoleic acid, pentadecanoic acid, palmitic acid, isopalmitic acid, palmitoleic acid, hexadecatrienoic acid, cyclopentenonedecanoic acid, heptadecanoic acid, isostearic acid, elaidic acid, parsleyic acid, stearatetraenoic acid, eleostearic acid, tarric acid, vaccenic acid, ricinoleic acid, vernolic acid, sterculic acid, nonadecanoic acid, eicosanoic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, linolenic acid, myristic acid, and the like.

[0103] 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-methylzelaic 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.

[0104] Examples of the aromatic carboxylic acid include salicylic acid, dibutylanilinodiglycolic 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.

[0105] Examples of the carboxylic acid include tris(2-carboxyethyl)isocyanurate and 1,3-cyclohexanedicarboxylic acid.

[0106] In addition, other organic acids include hydroxycarboxylic acids, such as 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butyric acid, citric acid, isocitric acid, malic acid, tartaric acid, etc., and 2,2-bis(hydroxymethyl)propionic acid is preferred.

[0107] In addition, as carboxylic acid, other dimer acids (except dimer acid (A1)) can be mentioned. Other dimer acids (except dimer acid (A1)) include hydrogenated dimer acids (except dimer acid (A1)). When other dimer acids are heated to 260° C. at a heating rate of 10° C. / min in thermogravimetric measurement, the weight reduction rate exceeds 1% by mass. As raw materials of other dimer acids, the above raw materials for dimer acid (A1) can be mentioned.

[0108] In addition, as carboxylic acid, trimer acid can be mentioned. Trimer acid has a tribasic acid obtained by trimerization of unsaturated fatty acid as a main component. Trimer acid includes hydrogenated trimer acid. As raw materials of trimer acid, the raw materials mentioned above in dimer acid (A1) can be mentioned.

[0109] 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.

[0110] The other organic acids may be used alone or in combination of two or more.

[0111] As other organic acids, carboxylic acids are preferred, and at least one selected from aliphatic monocarboxylic acids and aliphatic dicarboxylic acids is preferred.

[0112] When the soldering flux contains other organic acids, the content of other organic acids is preferably greater than 0 mass % and less than 10 mass % relative to the total mass of the soldering flux, more preferably greater than 0 mass % and less than 5 mass %, further preferably greater than 0 mass % and less than 1.5 mass %, particularly preferably greater than 0 mass % and less than 1 mass %.

[0113] When the content of other organic acids is equal to or less than the upper limit value within the above range, the generation of voids during continuous reflow soldering using the indium alloy sheet can be easily suppressed.

[0114] The content of the dimer acid (A1) is preferably 75% by mass or more, more preferably 75% by mass or more and 100% by mass or less, further preferably 85% by mass or more and 100% by mass or less, particularly preferably 90% by mass or more and 100% by mass or less, relative to the total mass of the organic acid (A).

[0115] When the content of the dimer acid (A1) is at least the lower limit value within the above range, it is easy to suppress the generation of voids during continuous reflow using the indium alloy sheet.

[0116] <Solvent (S)>

[0117] The solvent (S) contained in the flux of the present embodiment includes a solvent (S1). The solvent (S) may include a solvent (S2) in addition to the solvent (S1).

[0118] Solvent (S1)

[0119] The weight reduction rate of the solvent (S1) when heated to 150° C. at a heating rate of 6° C. / min in thermogravimetric measurement is 99% by mass or more.

[0120] The upper limit of the weight reduction rate of the solvent (S1) is not particularly limited as long as the effects of the present invention can be exhibited, and may be, for example, 100 mass %.

[0121] As the solvent (S1), for example, 3-methoxybutyl acetate, 2-methyl-2,4-pentanediol (hexanediol), 2-propanol, 1,2-butanediol, 2,3-butanediol, 2,3-dimethyl-2,3-butanediol, 2-methylpentane-2,4-diol, 1-ethynyl-1-cyclohexanol, 1,4-cyclohexanediol, ethylene glycol monobutyl ether (butyl glycol), etc., preferably one or more selected from 3-methoxybutyl acetate and 2-methyl-2,4-pentanediol (hexanediol).

[0122] The boiling point of the solvent (S1) is preferably 200°C or lower, more preferably 150°C or higher and 200°C or lower, and further preferably 170°C or higher and 200°C or lower.

[0123] 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 1 atmospheric pressure (ie, 1013 hPa).

[0124] The solvent (S1) may be used alone or in combination of two or more.

[0125] The total content of the solvent (S1) relative to the total mass of the flux (100 mass%) is preferably 10 mass% to 90 mass%, more preferably 15 mass% to 85 mass%, further preferably 20 mass% to 75 mass%.

[0126] Solvent (S2)

[0127] The weight loss rate of the solvent (S2) when heated to 150° C. at a heating rate of 6° C. / min in thermogravimetric measurement is less than 99% by mass.

[0128] The lower limit of the weight reduction rate of the solvent (S2) is not particularly limited as long as the effects of the present invention can be exhibited, and may be, for example, 10% by mass.

[0129] The boiling point of the solvent (S2) is preferably higher than 200°C and lower than 350°C, more preferably higher than 250°C and lower than 350°C, and further preferably higher than 250°C and lower than 330°C.

[0130] Examples of the solvent (S2) include alcohol solvents, glycol ether solvents, and terpineols.

[0131] Examples of the alcohol solvent include 1,3-butanediol, 1,4-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, 1,1,1-tri(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, 1,4-cyclohexanedimethanol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, and 2-hexyl-1-decanol octanediol.

[0132] Examples of the glycol ether solvent include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, ethylene glycol monohexyl ether (ethylene glycol hexyl ether), diethylene glycol monohexyl ether (hexyl diglycol), 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.

[0133] 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).

[0134] Moreover, as a solvent, dioctyl sebacate (DOS), liquid paraffin, etc. are mentioned, for example.

[0135] The solvent (S2) may be used alone or in combination of two or more.

[0136] The total content of the solvent (S) is preferably 10% by mass or more and 90% by mass or less, and more preferably 20% by mass or more and 75% by mass or less, relative to the total mass (100% by mass) of the flux.

[0137] Relative to the total mass of the solvent (S), the content of the solvent (S1) is preferably 70 mass % or more, more preferably 70 mass % or more and 100 mass % or less, further preferably 80 mass % or more and 100 mass % or less, particularly preferably 85 mass % or more and 100 mass % or less, and most preferably 90 mass % or more and 100 mass % or less.

[0138] When the content of the solvent (S1) is equal to or more than the lower limit value in the above range, it is easy to suppress the generation of voids when continuous reflow soldering is performed using the indium alloy sheet.

[0139] <Other ingredients>

[0140] The soldering flux in this embodiment may contain other components as required in addition to rosin ester, organic acid (A) and solvent (S). Other components include other rosins other than rosin ester, other activators other than organic acid (A), thixotropic agents, metal deactivators, surfactants, silane coupling agents, antioxidants, colorants, etc.

[0141] Other rosin

[0142] Examples of other rosins include the above-mentioned natural resins and rosin derivatives obtained by chemically modifying the natural resins (except rosin esters).

[0143] In the present specification, "rosin derivatives obtained by chemically modifying natural resins (excluding rosin esters)" include resins obtained by subjecting the "natural resins" to one or more treatments selected from hydrogenation, dehydrogenation, neutralization, alkylene oxide addition, amidation, dimerization and polymerization, and Diels-Alder cycloaddition.

[0144] Examples of the rosin derivative include purified rosin and modified rosin.

[0145] Examples of the modified rosin include hydrogenated rosin, polymerized rosin, polymerized hydrogenated rosin, disproportionated rosin, acid-modified hydrogenated rosin, acid-modified disproportionated rosin, acid-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, as well as purified products, hydrogenated products, and disproportionated products of the α,β-unsaturated carboxylic acid-modified products, abietol, abietamine, hydrogenated abietol, rosin soap, hydrogenated rosin soap, and acid-modified rosin soap.

[0146] 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.

[0147] [Chemical formula 2]

[0148]

[0149] The other rosins may be used alone or in combination of two or more.

[0150] The content of the rosin ester is preferably 70% by mass or more and 100% by mass or less, more preferably 80% by mass or more and 100% by mass or less, further preferably 90% by mass or more and 100% by mass or less, particularly preferably 95% by mass or more and 100% by mass or less, and may be 100% by mass, relative to the total mass of the rosin (100% by mass).

[0151] When the content of the rosin ester is equal to or less than the lower limit in the above range, it is easy to suppress the generation of voids when continuous reflow soldering is performed using the indium alloy sheet.

[0152] Other active agents

[0153] Examples of other activators include amines, halogen compounds, and organic phosphorus compounds.

[0154] [amine]

[0155] Examples of the amine include azoles, guanidines, alkanolamines, alkylamine compounds, and amine polyoxyalkylene adducts.

[0156] 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.

[0157] 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.

[0158] 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.

[0159] Examples of the alkylamine compound include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, cyclohexylamine, hexadecylamine, and stearylamine.

[0160] Examples of the amine polyoxyalkylene adduct include terminal diamine polyalkylene glycol, aliphatic amine polyoxyalkylene adduct, aromatic amine polyoxyalkylene adduct, and polyamine polyoxyalkylene adduct.

[0161] Examples of the alkylene oxide added to the amine polyoxyalkylene adduct include ethylene oxide, propylene oxide, and butylene oxide.

[0162] The terminal diamine polyalkylene glycol is a compound in which both ends of a polyalkylene glycol are amino-modified.

[0163] Examples of the terminal diamine polyalkylene glycol include terminal diamine polyethylene glycol, terminal diamine polypropylene glycol, and terminal diamine polyethylene glycol-polypropylene glycol copolymers.

[0164] 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.

[0165] 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.

[0166] The amines may be used alone or in combination of two or more.

[0167] The amine is preferably an azole, and more preferably 2-phenylimidazole.

[0168] When the soldering flux contains an amine, the content of the amine is preferably 0.1 mass % to 10 mass % inclusive, and more preferably 0.1 mass % to 5 mass % inclusive, based on the total mass of the soldering flux.

[0169] When the soldering flux contains amine, the wettability of the soldering flux can be improved more easily. When the content of the amine is greater than the lower limit of the above range, the wettability of the soldering flux can be improved more easily. When the content of the amine is less than the upper limit of the above range, the ability to suppress the generation of voids can be improved more easily.

[0170] [Halogen compounds]

[0171] Examples of the halogen compound include amine hydrohalide salts and organic halogen compounds other than amine hydrohalide salts.

[0172] Amine hydrohalides are compounds formed by reacting amines with hydrogen halides.

[0173] Examples of the amines herein include the amines described above in "Amines".

[0174] 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. Examples of the complexes include boron trifluoride piperidine and the like.

[0175] 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.

[0176] Examples of the halogenated aliphatic compounds include halogenated aliphatic alcohols and halogenated heterocyclic compounds.

[0177] 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.

[0178] Examples of the halogenated heterocyclic compound include compounds represented by the following general formula (h1).

[0179] R h11 -(R h12 ) n (h1)

[0180] [Where R h11 represents an n-valent heterocyclic group. h12 represents a halogenated aliphatic hydrocarbon group.]

[0181] 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.

[0182] 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.

[0183] Examples of the halogenated heterocyclic compound include tris-(2,3-dibromopropyl)isocyanurate and the like.

[0184] 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.

[0185] 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.

[0186] The halogen compounds may be used alone or in combination of two or more.

[0187] Organophosphorus compounds

[0188] Examples of the organic phosphorus compound include acidic phosphoric acid esters, acidic phosphonic acid esters, and acidic phosphinates.

[0189] The organic phosphorus compound may be used alone or in combination of two or more.

[0190] 《Thixotropic Agent》

[0191] Examples of the thixotropic agent include ester-based thixotropic agents, amide-based thixotropic agents, and sorbitol-based thixotropic agents.

[0192] Examples of the ester-based thixotropic agent include ester compounds, and specific examples include hydrogenated castor oil and ethyl myristate.

[0193] Examples of the amide-based thixotropic agent include monoamide, bisamide, and polyamide.

[0194] 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.

[0195] 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.

[0196] 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.

[0197] 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.

[0198] 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.

[0199] 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.

[0200] 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.

[0201] 《Metal passivator》

[0202] Examples of the metal deactivator include hindered phenol compounds and nitrogen compounds.

[0203] The "metal deactivator" mentioned here refers to a compound having the ability to prevent metal from deteriorating due to contact with a certain compound.

[0204] 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.

[0205] 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.

[0206] [Chemical formula 3]

[0207]

[0208] (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.)

[0209] Examples of the nitrogen compound in the metal deactivator include hydrazide nitrogen compounds, amide nitrogen compounds, triazole nitrogen compounds, and melamine nitrogen compounds.

[0210] As the hydrazide-based 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.

[0211] 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.

[0212] 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.

[0213] 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.

[0214] The metal deactivators may be used alone or in combination of two or more.

[0215] Surfactants

[0216] Examples of the surfactant include nonionic surfactants.

[0217] Examples of the nonionic surfactant include polyoxyalkylene adducts.

[0218] Examples of the alkylene oxide derived from the polyoxyalkylene adduct include ethylene oxide, propylene oxide, and butylene oxide.

[0219] 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.

[0220] Alternatively, examples of the nonionic surfactant include polyoxyalkylene adducts of alcohols. Examples of the alcohol include aliphatic alcohols, aromatic alcohols, and polyols.

[0221] The surfactant may be used alone or in combination of two or more.

[0222] Antioxidants

[0223] Examples of the antioxidant include hindered phenol antioxidants such as 2,2'-dihydroxy-3,3'-bis(α-methylcyclohexyl)-5,5'-dimethyldiphenylmethane, etc. The "antioxidant" herein refers to a compound having a function of inhibiting oxidation of the solder alloy.

[0224] The antioxidant may be used alone or in combination of two or more.

[0225] The flux according to the embodiment described above is suitable for continuous reflow for mounting an indium alloy sheet and bonding a solder ball.

[0226] In the primary reflow, reflow is performed at a low temperature (e.g., 170°C) near the melting point of indium, thereby bonding the heat sink and the chip with the indium alloy sheet to obtain a semiconductor package. Next, in the secondary reflow, reflow is performed at a high temperature (e.g., 250°C) close to the melting point of the solder alloy, thereby bonding the solder balls to the back of the semiconductor package.

[0227] In a single reflow, the conventional soldering flux does not diffuse on the surface of the indium sheet, but gathers on the bonding surface, and as a result, a large number of voids are easily generated on the bonding surface of the indium alloy sheet. The soldering flux of this embodiment contains a solvent (S1) that is easily volatilized even at low temperatures. In a single reflow under low temperature conditions, the solvent (S1) volatilizes. As a result, when the indium alloy sheet is melted, no voids from the solvent (S1) are generated.

[0228] Since the secondary reflow is at a high temperature, the activator and the like are easily vaporized to form voids. The flux, rosin ester and dimer acid (A1) of this embodiment are difficult to vaporize even at high temperatures. Therefore, the generation of voids can be suppressed in the primary reflow and the secondary reflow under different temperature conditions.

[0229] (Method for preparing a conjugate)

[0230] In the method for preparing an electronic component including a semiconductor package of the present embodiment, the flux of the above embodiment is used to perform a primary reflow soldering, and the chip and the cover are bonded via a thermal interface material (TIM), thereby obtaining a semiconductor package. Then, a secondary reflow soldering is performed to fix the solder balls on the obtained semiconductor package, thereby obtaining an electronic component.

[0231] The production method of this embodiment includes the following steps (i) and (ii).

[0232] Step (i):

[0233] Process for obtaining a semiconductor package having a bonded body formed by bonding a chip and a lid via a TIM

[0234] Step (ii):

[0235] A step of bonding solder balls to the back surface of the semiconductor package to obtain an electronic component.

[0236] use Figures 1 to 4 , a preferred embodiment of a method for preparing an electronic component containing a semiconductor package of the present embodiment is described. In the method for preparing a bonded body of the present embodiment, as Figure 1 As shown in FIG. 1 , a substrate 40 on which the lid 10 , the TIM 20 , and the bare chip 41 are mounted is prepared.

[0237] 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.

[0238] 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, for example, metals such as aluminum, iron, and copper can be cited.

[0239] The TIM 20 is a sheet made of an alloy of indium and silver. 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 .

[0240] The indium content in the alloy as a raw material of the alloy sheet is preferably 75 mass % or more and 99 mass % or less, and more preferably 85 mass % or more and 95 mass % or less, based on the total amount of the alloy (100 mass %).

[0241] The content of silver in the alloy is preferably 1 mass % or more and 25 mass % or less, and more preferably 5 mass % or more and 15 mass % or less, relative to the total amount of the alloy (100 mass %).

[0242] <Step (i)>

[0243] In step (i), a semiconductor package including a bonded body in which a chip and a lid are bonded together via a thermal interface material (TIM) is obtained.

[0244] Regarding the step (i), a method including a flux applying step, a lid attaching step, and a heating operation (1) will be described as an example.

[0245] 《Flux coating process》

[0246] 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 at least one of the TIM 20 and the bare chip 41 or between the TIM 20 and the lid 10 .

[0247] In the flux coating step, the flux 50 is coated on the bonding surfaces ( 42 a , 20 b ) of the bare chip 41 and the TIM 20 or the bonding surfaces ( 11 a , 20 a ) of the lid 10 and the TIM 20 .

[0248] 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.

[0249] As the coating apparatus of the flux 50, a spray flux coater, a foam flux coater, etc. are mentioned. Among them, a spray flux coater is preferable from the viewpoint of the stability of the coating amount.

[0250] 《Cover installation process》

[0251] 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.

[0252] 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.

[0253] 《Heating operation (1)》

[0254] In the heating operation (1), the stacked body 60 is heated by a reflow method. By the heating operation (1), the lid 10 and the bare chip 41 are bonded via the TIM 20, and a semiconductor package 60' is obtained.

[0255] Since the melting point of indium constituting the indium alloy sheet as TIM is 156° C., bonding is possible even at a temperature lower than that of ordinary reflow soldering. The reflow soldering temperature is preferably 150 to 250° C., and more preferably 150 to 200° C.

[0256] <Step (ii)>

[0257] In step (ii), the solder ball 70 is bonded to the back surface 60a of the semiconductor package 60' by the heating operation (2), thereby obtaining the electronic component 100. Figure 4 Step (ii) will be described. The back surface 60a of the semiconductor package 60' is a surface of the semiconductor package 60' that is opposite to the surface to which the cover is fixed.

[0258] In step (ii), first, solder balls 70 are placed on the back surface 60a of the semiconductor package 60'. Next, the semiconductor package 60' with the solder balls 70 placed thereon is subjected to heating operation (2). By heating operation (2), the solder balls 70 are melted and bonded to the semiconductor package 60'.

[0259] The heating operation (2) is to heat the semiconductor package 60' by reflow soldering. The reflow soldering temperature is preferably 200°C or more and 280°C or less.

[0260] According to the method for manufacturing an electronic component including a semiconductor package of the embodiment described above, even in the heating operation (2) performed at a high temperature, the amount of voids in the bonding surface of the sheet (i.e., the surface containing the flux) can be reduced. As a result, the heat generated from the chip can be efficiently released.

[0261] (Other embodiments)

[0262] 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 .

[0263] 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.

[0264] 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 .

[0265] Example

[0266] Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to the following examples.

[0267] <Preparation of flux>

[0268] (Examples 1 to 25, Comparative Examples 1 to 4)

[0269] The fluxes of Examples and Comparative Examples were prepared according to the compositions shown in Tables 1 to 4. The components of the raw materials used are shown below. The composition ratios in Tables 1 to 4 are based on the mass % when the total mass of the flux is 100 mass %, and blanks refer to 0 mass %.

[0270] As the rosin, rosin ester, acrylic acid-modified hydrogenated rosin, and hydrogenated rosin are used.

[0271] Rosin ester:

[0272] As the rosin ester, what is obtained by reacting hydrogenated rosin with glycerin is used.

[0273] As the organic acid, a dimer acid (A1) and other organic acids are used.

[0274] Dimer acid (A1): hydrogenated dimer acid

[0275] As the hydrogenated dimer acid, a hydrogenated dimer acid obtained by partially hydrogenating a reaction product of oleic acid and linoleic acid is used. The hydrogenated dimer acid is a hydrogenated dimer acid containing a dimer acid having 36 carbon atoms and a trimer acid having 54 carbon atoms.

[0276] The dimer acid having 36 carbon atoms is a plurality of dimer acids having different degrees of unsaturation. Here, the degree of unsaturation of the dimer acid is a value represented by {(2m+2)-n} / 2, wherein m is the number of carbon atoms in the dimer acid molecule and n is the number of hydrogen atoms in the dimer acid molecule.

[0277] The dimer acid having 36 carbon atoms includes a dimer acid having a degree of unsaturation of 2, a dimer acid having a degree of unsaturation of 3, a dimer acid having a degree of unsaturation of 4, a dimer acid having a degree of unsaturation of 5, a dimer acid having a degree of unsaturation of 6, a dimer acid having a degree of unsaturation of 7, and a dimer acid having a degree of unsaturation of 8.

[0278] Other organic acids: adipic acid, palmitic acid, sebacic acid, 12-hydroxystearic acid

[0279] Amine: 2-phenylimidazole

[0280] As the solvent (S), a solvent (S1) and a solvent (S2) were used.

[0281] Solvent (S1): 3-methoxybutyl acetate (boiling point 172°C), hexanediol (boiling point 197°C)

[0282] Solvent (S2): Diethylene glycol monohexyl ether (boiling point 260°C)

[0283] Here, the boiling point refers to the temperature of the target liquid when the saturated vapor pressure of the liquid is equal to one atmospheric pressure (ie, 1013 hPa).

[0284] [Measurement of weight reduction rate]

[0285] The weight reduction rates of rosin ester, acrylic acid-modified hydrogenated rosin, dimer acid (A1), other organic acids, solvent (S1), and solvent (S2) were measured as follows.

[0286] Using a differential thermal-thermogravimetric simultaneous measuring apparatus (TG-DTA8122 manufactured by Rigaku Corporation), 10 mg of the sample to be measured was placed in an aluminum pan, and heating was started from room temperature of about 25°C, and the temperature was increased at a predetermined heating rate until a predetermined temperature was reached. Then, the weight loss rate was calculated from the mass W0 (100% by mass) of the sample before heating and the mass W1 immediately after reaching the predetermined temperature using the following calculation formula.

[0287] Weight reduction rate (%) = 100 × {W0-W1} / W0

[0288] The weight reduction rates of rosin ester, acrylic acid-modified hydrogenated rosin, dimer acid (A1) and other organic acids are measured at a specified temperature of 260°C and 10°C / min and a specified heating rate. The values ​​in parentheses represent the weight reduction rates.

[0289] Rosin: rosin ester (7.1 mass%), acrylic acid-modified hydrogenated rosin (11.9 mass%), hydrogenated rosin (25.6 mass%)

[0290] Organic acid: hydrogenated dimer acid (0.1 mass%), adipic acid (99.5 mass%), palmitic acid (97.0 mass%), sebacic acid (52.9 mass%), 12-hydroxystearic acid (11.9 mass%)

[0291] The weight reduction rates of the solvent (S1) and the solvent (S2) were measured at a predetermined temperature of 150° C. and a predetermined temperature increase rate of 6° C. / min., respectively.

[0292] Solvent (S1): 3-methoxybutyl acetate (99.0 mass%), hexylene glycol (99.0 mass%)

[0293] Solvent (S2): diethylene glycol monohexyl ether (21.0 mass %)

[0294] [Analysis of hydrogenated dimer acid]

[0295] 5000 ppm of hydrogenated dimer acid dissolved in 2-propanol was prepared and the solution was analyzed using liquid chromatography-Fourier transform mass spectrometry.

[0296] As a liquid chromatography apparatus, UltiMate 3000 (manufactured by Thermo Fisher) was used. A mixture of 5 mM ammonium formate aqueous solution and methanol was used as the mobile phase for gradient analysis. As a column, Aquity UPLC BEH C18 (1.7 μm, 2.1×100 mm) was used. The column temperature was set to 50° C., the flow rate was set to 0.35 mL / min, and the injection volume was 1 μL.

[0297] As a Fourier transform mass spectrometer, orbitrap ID-X (manufactured by Thermo Fisher Scientific) was used. The analysis conditions were the negative mode of the electrospray ionization method. The measurement range of m / z was 200 to 2000.

[0298] It was confirmed that the hydrogenated dimer acid used contained a plurality of molecules. Based on the prepared ion chromatogram, the ratio of the peak area derived from each molecule to the total peak area derived from all detected molecules (100%) was calculated.

[0299] The hydrogenated dimer acid is a hydrogenated dimer acid containing a plurality of dimer acids having 36 carbon atoms and a trimer acid having 54 carbon atoms. The total area of ​​the peaks derived from the plurality of dimer acids having 36 carbon atoms is 99% or more relative to the total area derived from all molecules (100%).

[0300] The area ratios of the dimer acids having 36 carbon atoms relative to the total area (100%) derived from all molecules are shown below.

[0301] Dimer acid with an unsaturation degree of 2 (26.7%), dimer acid with an unsaturation degree of 3 (40.6%), dimer acid with an unsaturation degree of 4 (10.6%), dimer acid with an unsaturation degree of 5 (2.6%), dimer acid with an unsaturation degree of 6 (7.5%), dimer acid with an unsaturation degree of 7 (10.1%), and dimer acid with an unsaturation degree of 8 (1.9%).

[0302] It is estimated that the content of each dimer acid having different unsaturation degrees relative to the total amount of hydrogenated dimer acid (100% by mass) is substantially consistent with the above-mentioned area ratio.

[0303] [Determination of softening point]

[0304] The softening point of rosin is measured by the ring and ball method described in JIS K5902. Rosin with a softening point of 80°C or less is measured in a water bath. Rosin with a softening point exceeding 80°C is measured in a glycerin bath. Each rosin is measured twice. The softening point below is the average of the two measured values.

[0305] Rosin ester (softening point 95°C), acrylic acid modified hydrogenated rosin (softening point 130°C), hydrogenated rosin (softening point 72°C)

[0306] [Determination of acid value]

[0307] The acid value of the rosin ester is measured by the neutralization titration method in accordance with 3.1 of JIS K0070 "Test methods for acid value, saponification value, ester value, iodine value and hydroxyl value of chemical products - mixed unsaponifiable matter".

[0308] Dissolve 3 g of rosin ester in ethanol / diethyl ether (mixing ratio 1:1). Use phenolphthalein as an indicator and titrate with 0.1 mol / L KOH ethanol solution. The point where the solution turns slightly red is taken as the endpoint.

[0309] The acid value of rosin ester is 6 mgKOH / g.

[0310] The evaluation of the void generation suppressing ability and the evaluation of the wettability were performed according to the evaluation method described in <Evaluation 1> below. The evaluation results are shown in Tables 1 to 4.

[0311] <Evaluation 1>

[0312] 《Evaluation of the ability to suppress void generation》

[0313] Preparation method of the conjugate:

[0314] 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.

[0315] As a solder sheet, an indium alloy sheet (size: 7 mm×7 mm×400 μm) composed of an alloy of 90 mass % In and 10 mass % Ag was prepared, and 2 mg of the flux of each example was applied to the front and back surfaces of the indium alloy sheet.

[0316] 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 alloy sheet coated with flux was sandwiched between the cover and the Au / Ni plated portion of the substrate and fixed with a jig.

[0317] Next, the lid and the substrate sandwiching the indium alloy sheet were subjected to primary reflow to obtain a bonded body. The primary reflow was performed in the atmosphere at a heating rate of 10°C / min until the temperature reached 170°C.

[0318] Next, the bonded body subjected to the primary reflow was subjected to secondary reflow. In the secondary reflow, the temperature was increased from room temperature to 250° C. at a heating rate of 0.5° C. / sec for 450 seconds.

[0319] Verification method:

[0320] The bonded body that has been reflowed twice is irradiated with X-rays from the vertical direction of the substrate, and the transmitted X-rays are analyzed to measure the void area. 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 0.1 μm or more. Next, the ratio of the total area of ​​the voids to the total area of ​​the indium alloy sheet is calculated as the void area ratio (%).

[0321] Judgment criteria:

[0322] A: The void area ratio is less than 10%.

[0323] B: The void area ratio is 10% or more and less than 15%.

[0324] C: The void area ratio is 15% or more.

[0325] The flux with an evaluation result of A or B is acceptable, and the flux with an evaluation result of C is unacceptable.

[0326] 《Evaluation of Wettability》

[0327] Verification method:

[0328] As the solder sheet, an indium alloy sheet (size: 2 mm×2 mm×100 μm) composed of an alloy of 90 mass % In and 10 mass % Ag was prepared.

[0329] 0.5 mg of the flux of each example was applied to the front and back surfaces of the indium alloy sheet, respectively. The indium alloy sheet coated with the flux was placed on the Au / Ni electrode.

[0330] Next, the electrode on which the indium alloy 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.

[0331] Next, after removing the flux, the area of ​​wetting extension was measured.

[0332] Judgment criteria:

[0333] A: The area of ​​infiltration extension is 2.5 mm 2 above.

[0334] B: The area of ​​infiltration extension is 2.0 mm 2 Above and less than 2.5mm 2 .

[0335] The flux with an evaluation result of A or B is considered acceptable.

[0336] 《Evaluation of coating properties》

[0337] Verification method:

[0338] Using a spray coating apparatus (TG-SS2 (full cone type), manufactured by Spray Systems Co.), the gas pressure was set to 0.3 MPa, and it was verified whether the flux of each example could be applied to a metal plate.

[0339] Judgment criteria:

[0340] A: You can use a spray device to apply flux to the metal plate.

[0341] B: Do not use a spray device to apply flux to metal plates.

[0342] The flux with an evaluation result of A was acceptable, and the flux with an evaluation result of B was unacceptable.

[0343] The evaluation results are shown in Table 4.

[0344] <Evaluation 2>

[0345] 《Evaluation of the ability to suppress void generation》

[0346] As a solder sheet, a SAC alloy sheet (size: 7 mm×7 mm×400 μm) composed of an alloy containing 3 mass % of Ag, 0.5 mass % of Cu, and the balance of Sn was prepared.

[0347] Using the SAC alloy sheet and the fluxes of Example 1 and Comparative Example 4, verification was performed by the same method as in "Evaluation of the ability to suppress void generation" in <Evaluation 1>.

[0348] The primary reflow and secondary reflow conditions are as follows. The primary reflow was performed in the atmosphere at a heating rate of 10°C / min until the temperature was raised from room temperature (25°C) to 250°C. In the secondary reflow, the temperature was raised from room temperature (25°C) to 250°C at a heating rate of 0.5°C / sec for 450 seconds.

[0349] 《Evaluation of Wettability》

[0350] As a solder sheet, a SAC alloy sheet (size: 2 mm×2 mm×100 μm) composed of an alloy of 3 mass % Ag, 0.5 mass % Cu, and the balance Sn was prepared.

[0351] Using the SAC alloy sheet and the fluxes of Example 1 and Comparative Example 4, verification was performed by the same method as in "Evaluation of Wettability" in <Evaluation 1>.

[0352] The reflow process was performed by heating the temperature from room temperature (25°C) to 250°C at a heating rate of 6°C / min and maintaining the temperature at 250°C for 3 minutes.

[0353] [Table 1]

[0354]

[0355] The fluxes of Examples 1 and 2 containing rosin ester, dimer acid (A1) and solvent (S1) were evaluated as A in terms of void generation suppressing capability.

[0356] The flux of Comparative Example 1 not containing the solvent (S1) was evaluated as C in terms of void generation suppressing capability.

[0357] The fluxes of Comparative Examples 2 and 3 not containing the dimer acid (A1) were evaluated as C in terms of void generation suppressing ability.

[0358] The flux of Comparative Example 4 containing no rosin ester was evaluated as C in terms of void generation suppressing capability.

[0359] The soldering flux of Example 1, in which the content of the solvent (S1) was 100% by mass based on the total mass of the solvent (S), was evaluated as A in terms of void generation suppression capability.

[0360] The soldering flux of Example 3, in which the content of the solvent (S1) was 83% by mass based on the total mass of the telescopic solvent (S), was evaluated as B in terms of void generation suppression capability.

[0361] The soldering flux of Example 1 containing the dimer acid (A1) was evaluated as A in terms of coating properties.

[0362] The soldering flux of Comparative Example 1 not containing the dimer acid (A1) was evaluated as B in terms of coating properties.

[0363] The soldering fluxes of Comparative Examples 2 and 3, in which the content of other organic acids was 15% by mass based on the total mass of the soldering flux, were evaluated as B in terms of coating properties.

[0364] [Table 2]

[0365]

[0366] The fluxes of Examples 4 and 7 to 11, in which the content of the dimer acid (A1) was 90% by mass or more based on the total mass of the organic acid (A), were evaluated as A in terms of void generation suppressing ability.

[0367] The fluxes of Examples 5 to 6 and 12 to 13, in which the content of the dimer acid (A1) was less than 90% by mass based on the total mass of the organic acid (A), were evaluated as B in terms of void generation suppressing ability.

[0368] [Table 3]

[0369]

[0370] The soldering fluxes of Examples 15 to 20, 22 to 23, and 25, in which the content of the dimer acid (A1) was 15% by mass or more based on the total mass of the soldering flux, were evaluated as A in terms of wettability.

[0371] The soldering fluxes of Examples 14, 21, and 24, in which the content of the dimer acid (A1) was 10% by mass based on the total mass of the soldering flux, were evaluated as B in terms of wettability.

[0372] [Table 4]

[0373]

[0374] In <Evaluation 2>, when the SAC alloy sheet and the soldering flux of Example 1 were used, the void generation suppression capability and wettability were evaluated as A. Also, when the SAC alloy sheet and the soldering flux of Comparative Example 4 were used, the void generation suppression capability and wettability were evaluated as A.

[0375] The soldering flux of Comparative Example 4 containing no rosin ester had a void suppression capability of A when using a SAC alloy sheet and a void suppression capability of C when using an indium alloy sheet. That is, voids were more likely to occur when using an indium alloy sheet than when using a SAC alloy sheet.

[0376] The soldering flux of Example 1 containing rosin ester can sufficiently suppress voids even when an indium alloy sheet is used.

[0377] The soldering flux of the present invention contains rosin ester, dimer acid (A1) and solvent (S1), and can suppress the generation of voids in the obtained joint body even when a solder sheet having a high indium content is used.

[0378] Industrial Applicability

[0379] The soldering flux of the present invention is suitable for a process of producing electronic components with improved heat dissipation efficiency using an indium alloy sheet.

[0380] Explanation of symbols

[0381] 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 semiconductor package, 60a back side, 70 solder balls, 100 electronic components.

Claims

1. A soldering flux comprising rosin ester, an organic acid (A) and a solvent (S), The organic acid (A) contains a dimer acid (A1), wherein the weight loss rate of the dimer acid (A1) when heated to 260° C. at a heating rate of 10° C. / min in a thermogravimetric measurement is 1% by mass or less, The solvent (S) contains a solvent (S1) having a weight reduction rate of 99% by mass or more when heated to 150° C. at a heating rate of 6° C. / min in a thermogravimetric measurement.

2. The soldering flux according to claim 1, wherein The content of the dimer acid (A1) is 75% by mass or more relative to the total mass of the organic acid (A).

3. The soldering flux according to claim 1 or 2, wherein The content of the solvent (S1) is 80% 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 dimer acid (A1) is at least one selected from dimers to which an unsaturated fatty acid having 18 carbon atoms is bonded.

5. The soldering flux according to any one of claims 1 to 4, wherein The boiling point of the solvent (S1) is 200° C. or lower.

6. The soldering flux according to any one of claims 1 to 5, wherein The soldering flux further contains azoles.

7. The soldering flux according to any one of claims 1 to 6, wherein The content of the dimer acid (A1) is 10% by mass or more and 60% by mass or less relative to the total mass of the flux.

8. The soldering flux according to any one of claims 1 to 7, wherein The content of the rosin ester is 15 mass % or more and 60 mass % or less relative to the total mass of the soldering flux.

9. A method for preparing an electronic component, which is a method for preparing an electronic component containing a semiconductor package, the method comprising: Step (i) of obtaining a semiconductor package having a bonded body formed by bonding a bare chip and a cover via a thermal interface material (TIM); as well as, step (ii) of bonding solder balls to the back surface of the semiconductor package to obtain an electronic component, Wherein, the TIM is a sheet made of an alloy of indium and silver, The step (i) includes a heating operation (1), wherein the heating operation (1) causes the flux according to any one of claims 1 to 8 to be interposed between at least one of the TIM and the bare chip or between the TIM and the cover, and the bare chip and the cover are bonded together by reflow soldering, The step (ii) includes a heating operation (2), wherein the heating operation (2) bonds the solder balls to the semiconductor package by a reflow process.

10. The method for preparing an electronic component according to claim 9, wherein: The temperature condition of the heating operation (1) is 150-250°C, The temperature condition of the heating operation (2) is 200-280°C.

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