Preparation methods of flux and electronic components

Abstract

This invention provides a flux that can suppress the formation of voids during continuous reflow soldering of indium alloy sheets under varying temperature conditions. The flux comprises rosin ester, an organic acid (A), and a solvent (S). The organic acid (A) contains a dimer acid (Al), which exhibits a weight loss of less than 1% by mass when heated to 260°C at a heating rate of 10°C / min in a thermogravimetric analysis. The solvent (S) contains a solvent (S1), which exhibits a weight loss of more than 99% by mass when heated to 150°C at a heating rate of 6°C / min in a thermogravimetric analysis.

Description

Technical Field

[0001] This invention relates to a flux and a method for preparing electronic components. This application claims priority based on Japanese Patent Application No. 2022-135236, filed on August 26, 2022, the contents of which are incorporated herein by reference. Background Technology

[0002] In recent years, there has been a growing demand for higher capacity and higher speed in electronic devices. The highly integrated bare chips mounted on these devices generate a significant amount of heat during operation. Therefore, it is necessary to effectively dissipate this heat by installing heat sinks or similar devices on the bare chips.

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

[0004] Existing technical documents

[0005] Patent documents

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

[0007] The problem to be solved by the present invention

[0008] As a TIM (Transformer Indium Molding), a sheet material with an increased indium content is proposed (hereinafter referred to as indium alloy sheet). For example, an alloy with 90% by mass of In and 10% by mass of Ag is used as the raw material for the indium alloy sheet.

[0009] Indium has low hardness compared to other metallic elements, and indium alloy sheets exhibit high conformability and adhesion to the surfaces of bare chips and heat sinks. Therefore, indium alloy sheets offer high heat transfer efficiency from the bare chip to the heat sink cover. Consequently, the efficiency of heat dissipation generated by the operation of the bare chip can be improved by using indium alloy sheets. Furthermore, since indium alloy sheets containing Ag have higher thermal conductivity than indium sheets made solely of indium, heat dissipation efficiency can be further enhanced.

[0010] In the mounting of indium alloy sheets, indium alloy sheets coated with flux are used to bond a heat sink cover and a bare die through a single reflow soldering process, resulting in a semiconductor package. Because indium has a relatively low melting point of 156°C, the bonding is achieved through a single reflow soldering process at a lower temperature compared to typical bonding conditions.

[0011] When using conventional soldering flux for a single reflow soldering operation at, for example, 170°C, the flux does not wet and spread on the surface of the indium sheet but instead accumulates on the bonding surface. As a result, a large number of voids may be generated on the bonding surface. Due to these voids, the heat transfer efficiency from the chip through the indium sheet to the heat sink cover is reduced, thereby reducing the efficiency of heat dissipation generated by the chip's operation.

[0012] Then, after the first reflow soldering, a second reflow soldering is performed to bond the solder balls to the back side of the semiconductor package. This second reflow soldering is performed, for example, at a high temperature of 250°C to melt the solder balls. Because the second reflow soldering is at a high temperature, activators and the like vaporize, easily forming voids.

[0013] As described above, when using conventional soldering flux and indium alloy sheets for two reflow soldering processes (first reflow soldering and second reflow soldering), a large number of voids tend to form on the bonding surface of the indium alloy sheet. Due to these voids, the heat transfer efficiency from the chip through the indium alloy sheet to the heat sink cover is reduced, and the heat dissipation efficiency generated by the chip's operation is also reduced.

[0014] Therefore, the object of the present invention is to provide a flux that can suppress the generation of voids during continuous reflow soldering at different temperature conditions using indium alloy sheets.

[0015] Problem-solving methods

[0016] The present invention includes the following methods.

[0017] [1] A flux containing rosin ester, an organic acid (A) and a solvent (S), wherein the organic acid (A) contains a dimer acid (A1) and the dimer acid (A1) has a weight loss rate of less than 1% by mass when heated to 260°C at a heating rate of 10°C / min in a thermogravimetric assay, and the solvent (S) contains a solvent (S1) and the solvent (S1) has a weight loss rate of more than 99% by mass when heated to 150°C at a heating rate of 6°C / min in a thermogravimetric assay.

[0018] In this invention, the "weight reduction rate" is measured, for example, as follows. Using a differential thermal-thermogravimetric analyzer (Rigaku Corporation, TG-DTA8122), 10 mg of the test sample is placed in an aluminum pan and heated from room temperature (approximately 25°C) at a predetermined heating rate until a predetermined temperature is reached. Then, the weight reduction rate is calculated using the following formula from the mass W0 (100% by mass) of the test sample before heating and the mass W1 immediately after reaching the predetermined temperature.

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

[0020] [2] According to the flux described in [1], the content of the dimer acid (Al) is 75% by mass or more relative to the total mass of the organic acid (A).

[0021] [3] According to the flux described in [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 flux according to any one of [1] to [3], wherein the dimer acid (Al) is at least one selected from dimers of unsaturated fatty acids bonded with 18 carbon atoms.

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

[0024] [6] The flux according to any one of [1] to [5], wherein the flux further contains azoles.

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

[0026] [8] The 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 flux.

[0027] [9] A method for manufacturing an electronic component, which is a method for manufacturing an electronic component containing a semiconductor package, the method comprising: a step (i) of obtaining a semiconductor package having a bonding body formed by bonding a bare die and a cover via a thermal interface material (TIM); and a step (ii) of bonding solder balls on the back side 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) comprising a heating operation (1), the heating operation (1) wherein a flux described in any one of [1] to [8] is placed between the TIM and the bare die or between the TIM and the cover at least one, and the bare die is bonded to the cover by reflow soldering, the step (ii) comprising a heating operation (2), the heating operation (2) bonding the solder balls to the semiconductor package by reflow soldering.

[0028]

[10] According to the method for preparing electronic components described in [9], 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 present invention

[0030] According to the present invention, a flux can be provided that can suppress the generation of voids during continuous reflow soldering at different temperature conditions using indium alloy sheets. Attached Figure Description

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

[0032] Figure 2 This is a cross-sectional view of one embodiment of a method for manufacturing electronic components, showing the process of applying flux onto TIM and bare chips.

[0033] Figure 3 This is an embodiment of a method for manufacturing electronic components, showing a cross-sectional view of a joint obtained by fixing a cover to a substrate using a TIM after applying flux.

[0034] Figure 4 This is an embodiment of a method for manufacturing electronic components, showing a cross-sectional view of an electronic component obtained by bonding solder balls to the back side of a semiconductor package. Detailed Implementation

[0035] (Fluoride)

[0036] The flux in this embodiment contains rosin ester, organic acid (A), and solvent (S).

[0037] The organic acid (A) contains a dimer acid (A1), which has a weight loss of less than 1% by mass when heated to 260°C at a heating rate of 10°C / min in a thermogravimetric determination.

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

[0039] The flux of this embodiment is suitable for continuous reflow soldering applications used for mounting indium alloy sheets and joining solder balls.

[0040] In the first reflow soldering, reflow soldering is performed at a low temperature (e.g., 170°C) close to the melting point of indium, and an indium alloy sheet is mounted. Next, in the second reflow soldering, reflow soldering 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 flux of this embodiment, the solvent (S1) evaporates during a single reflow soldering operation. As a result, no voids from the solvent (S1) are generated when the indium alloy sheet melts.

[0042] Furthermore, in the flux of this embodiment, rosin ester and dimer acid (Al) are difficult to volatilize even at the high temperature of secondary reflow soldering, thus suppressing the generation of voids.

[0043] <Rosin Ester>

[0044] Rosin esters are ester resins obtained by reacting natural resins or substances obtained by chemically modifying natural resins (rosin derivatives) with alcohols. In addition to carboxyl groups, rosin esters may also contain hydroxyl groups.

[0045] Examples of alcohols include glycerol and pentaerythritol.

[0046] The “natural resins” that can be used as raw materials for rosin esters include, for example, rosin resin, wood resin and rosin oil.

[0047] In this specification, "natural resin" includes a mixture of abrasive acid and its isomers, with abrasive acid as the main component. As an example, the total content of abrasive acid and its isomers in a natural resin is 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 that constitutes the compound and is present in a content of 40% by mass or more.

[0048] Representative examples of isomers of abietic acid include neorosinic acid, longleaf abietic acid, and L-piperidine. The structure of abietic acid is shown below.

[0049] [Chemical Formula 1]

[0050]

[0051] In this invention, the "substance obtained by chemically modifying natural resin (rosin derivative)" that can be used as a raw material for rosin esters includes a substance obtained by treating the "natural resin" with one or more of the following processes: hydrogenation, dehydrogenation, neutralization, alkyl epoxide addition, amidation, dimerization, polymerization, and Diels-Alder cyclization addition.

[0052] Examples of rosin derivatives include purified rosin and modified rosin.

[0053] Examples of modified rosin include, for example, hydrogenated rosin, polymerized rosin, polymerized hydrogenated rosin, disproportionated rosin, acid-modified rosin, acid-modified hydrogenated rosin, acid anhydride-modified hydrogenated rosin, acid-modified disproportionated rosin, acid anhydride-modified disproportionated rosin, phenol-modified rosin and α,β-unsaturated carboxylic acid modified products (acrylic acid modified rosin, maleic acid modified rosin, fumaric acid modified rosin, etc.), as well as purified products, hydrides and disproportions of the polymerized rosin, as well as purified products, hydrides and disproportions of the α,β-unsaturated carboxylic acid modified products, rosin alcohol, rosin amine, hydrogenated rosin alcohol, rosin soap, hydrogenated rosin soap, acid-modified rosin soap, etc.

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

[0055] Rosin used as a raw material for rosin esters is preferably hydrogenated rosin. Glycerol is preferably used as a raw material for rosin esters. Rosin esters are preferably substances 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 analysis 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. A lower weight loss rate of rosin ester is preferred. The lower limit of the weight loss rate of rosin ester is not particularly limited as long as the effects of the present invention are achieved; for example, it can be 0.1% by mass, or 0% by mass in the determination.

[0057] By keeping the weight reduction rate of rosin ester below the aforementioned upper limit, it is easy to suppress the generation of voids during continuous reflow soldering using indium alloy sheets.

[0058] The acid value of the rosin ester is preferably 0.01 mg KOH / g or more and 50 mg KOH / g or less, more preferably 0.1 mg KOH / g or more and 30 mg KOH / g or less, even more preferably 0.5 mg KOH / g or more and 20 mg KOH / g or less, and particularly preferably 2 mg KOH / g or more and 10 mg KOH / g or less.

[0059] When the acid value of rosin ester is above the lower limit of the above range, it easily improves the activity of the flux. When the acid value of rosin ester is below the upper limit of the above range, it easily improves the meltability and wettability of the solder.

[0060] Acid value refers to the number of milligrams of potassium hydroxide required to neutralize the carboxyl groups present in 1g of the sample being tested. The acid value of rosin esters can be determined, for example, according to the neutralization titration method in section 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 determined by this method is a weighted average of the acid values ​​of all types of rosin esters contained in the flux.

[0062] The softening point of 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] By setting the softening point of rosin ester above the lower limit of the aforementioned range, the heat resistance of rosin ester is easily improved. By setting the softening point of rosin ester below the upper limit of the aforementioned range, the fluidity of flux is easily improved when the solder melts.

[0064] The softening point of rosin esters can be determined by the ring and ball method. For example, the method described in JIS K5902 can be cited as an example of the ring and ball method.

[0065] Rosin esters can be used alone or in combination with two or more.

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

[0067] <Organic Acids (A)>

[0068] The organic acid (A) contained in the flux of this embodiment includes a dimer acid (A1). In addition to dimer acid (A1), the organic acid (A) contained in the flux of this embodiment may also contain other organic acids.

[0069] Dimeric acid (A1)

[0070] The weight loss rate of dimer acid (A1) when heated to 260°C at a heating rate of 10°C / min in a thermogravimetric determination 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 the weight reduction rate of the dimer acid (Al), the better. There is no particular limitation on the lower limit of the weight reduction rate of the dimer acid (Al) as long as the effects of the present invention are achieved; for example, it can be 0.01% by mass, or 0% by mass in measurement.

[0072] Dimer acids (A1) are mainly composed of dicarboxylic acids obtained through the dimerization of unsaturated fatty acids. Dimer acids (A1) include hydrogenated dimer acids, which are formed by the hydrogenation of dicarboxylic acids obtained through the dimerization of unsaturated fatty acids.

[0073] The unsaturated fatty acid used as a raw material for dimer acid (A1) is preferably 18 carbon atoms. The dicarboxylic acid, which is the main component of dimer acid (A1), is preferably 36 carbon atoms, and more preferably at least one selected from dimers formed by bonding unsaturated fatty acids with 18 carbon atoms.

[0074] Unsaturated fatty acids that can be used as raw materials for dimer acids (A1) include, for example, oleic acid, linoleic acid, isoleic acid, trans oleic acid, linolenic acid, acrylic acid, and methacrylic acid.

[0075] The unsaturated fatty acids used as raw materials for dimer acid (A1) are preferably selected from one or more of oleic acid, linoleic acid, isoleic acid and transoleic acid, and more preferably selected from one or more of oleic acid and linoleic acid.

[0076] Dimer acid (A1) can be used alone or in combination with two or more.

[0077] Dimeric acids (A1) can have unsaturated hydrocarbon groups, alicyclic hydrocarbon groups, aromatic hydrocarbon groups, etc. The degree of unsaturation of a dimer acid (A1) can be the value shown below. Here, the degree of unsaturation of a dimer acid (A1) is expressed as {(2m+2)-n} / 2, where m is the number of carbon atoms in the molecule of the dimer acid (A1), and n is the number of hydrogen atoms. The dicarboxylic acid, which is the main component of dimer acid (A1), has two carboxyl groups. The degree of unsaturation of this dicarboxylic acid is 2 or higher.

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

[0079] When the dimer acid (A1) contains two or more dimers with different degrees of unsaturation, the degree of unsaturation obtained by weighted averaging of these degrees of unsaturation is preferably 2 or more and 10 or less, more preferably 2 or more and 8 or less, even more 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] Dimer acid (A1) can be used alone or in combination with two or more.

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

[0082] By ensuring the content of dimer acid (Al) is within the specified range, the generation of voids during continuous reflow soldering using indium alloy sheets can be suppressed. Furthermore, when the content of dimer acid (Al) is above the lower limit of the specified range, the wettability of the indium alloy sheet is easily improved.

[0083] The total content of the dimer acid with 36 carbon atoms relative to the total mass (100% by mass) 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 most preferably 98% by mass or more and 100% by mass or less. It can also be measured as 100% by mass.

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

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

[0086] The proportion of peak area of ​​dimer acid with an unsaturation degree of 3 is preferably 10% or more and 70% or less, more preferably 20% or more and 60% or less, and even more preferably 30% or more and 50% or less.

[0087] The proportion of peak area of ​​dimer acid with an unsaturation degree of 4 is preferably 2% or more and 30% or less, more preferably 3% or more and 20% or less, and even more preferably 5% or more and 15% or less.

[0088] The proportion of peak area of ​​dimer acid with an unsaturation degree of 5 is preferably 0.1% or more and 15% or less, more preferably 0.5% or more and 10% or less, and even more preferably 1% or more and 5% or less.

[0089] The proportion of peak area of ​​dimer acid with an unsaturation degree of 6 is preferably 1% or more and 30% or less, more preferably 2% or more and 20% or less, and even more preferably 3% or more and 15% or less.

[0090] The proportion of peak area of ​​dimer acid with an unsaturation degree of 7 is preferably 2% or more and 30% or less, more preferably 3% or more and 20% or less, and even more preferably 5% or more and 15% or less.

[0091] The proportion of peak area of ​​dimer acid with an unsaturation degree of 8 is preferably 0.1% or more and 15% or less, more preferably 0.5% or more and 10% or less, and even more preferably 1% or more and 5% or less.

[0092] Alternatively, when the dimer acid (A1) contains a variety of dimers with 36 carbon atoms, the content of dimers with 36 carbon atoms relative to the total mass (100% by mass) of the dimer acid (A1) is preferably within the following range.

[0093] The content of dimer acid with 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 even more preferably 20% by weight or more and 30% by weight or less.

[0094] The content of dimer acid with 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 even more preferably 30% by weight or more and 50% by weight or less.

[0095] The content of dimer acid with 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 even more preferably 5% by mass or more and 15% by mass or less.

[0096] The content of dimer acid with 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 even more preferably 1% by mass or more and 5% by mass or less.

[0097] The content of dimer acid with 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 even more preferably 3% by mass or more and 15% by mass or less.

[0098] The content of dimer acid with 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 even more preferably 5% by mass or more and 15% by mass or less.

[0099] The content of dimer acid with 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 even more 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 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 and aliphatic dicarboxylic acids.

[0102] Examples of aliphatic monocarboxylic acids include, for example, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, isononanoic acid, decanoic acid, decenoic acid, lauric acid (dodecanoic acid), undecanoic acid, 5-dodecenoic acid, tridecanoic acid, myristicinic acid, pentadecanoic acid, palmitic acid, isopalmitic acid, palmitoleic acid, hexadecanetrienoic acid, cyclopentene undecanoic acid, heptadecanic acid, isostearic acid, transoleic acid, parsleyic acid, stearatetraenoic acid, tung acid, tarric acid, isoleic acid, ricinoleic acid, piperidinic acid, styracidin, styracidin, tarric acid, isoleic acid, ricinoleic acid, piperidinic acid, styracidin, nonadecanic acid, eicosanoic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, linolenic acid, myristic acid, etc.

[0103] Examples of aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, dodecanoic acid, eicosanoic acid, tartaric acid, 2,4-diethylglutaric acid, diethylene glycol acid, 2-methylazelaic acid, 4-(methoxycarbonyl)-2,4-dimethylundecanoic acid, 4,6-di(methoxycarbonyl)-2,4,6-trimethyltetrazoic acid, and 8,9-di(methoxycarbonyl)-8,9-dimethylhexadecanoic acid.

[0104] Examples of aromatic carboxylic acids include, for example, salicylic acid, dibutylaniline diethanolic acid, terephthalic acid, p-hydroxyphenylacetic acid, phenylsuccinic acid, phthalic acid, benzoic acid, 2,3-dihydroxybenzoic acid, 2-quinoline carboxylic acid, 3-hydroxybenzoic acid, p-anestic acid, pyridinecarboxylic acid, pyridinedicarboxylic acid, and 3-hydroxypyridinecarboxylic acid.

[0105] In addition, examples of carboxylic acids include tris(2-carboxyethyl) isocyanurate and 1,3-cyclohexanedicarboxylic acid.

[0106] In addition, hydroxycarboxylic acids can be cited as other organic acids. Examples of hydroxycarboxylic acids include 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butyric acid, citric acid, isocitric acid, malic acid, tartaric acid, etc., with 2,2-bis(hydroxymethyl)propionic acid being preferred.

[0107] Furthermore, other dimer acids (excluding dimer acid (A1)) can be cited as carboxylic acids. These other dimer acids (excluding dimer acid (A1)) include hydrogenated dimer acids (excluding dimer acid (A1)). These other dimer acids exhibit a weight loss rate exceeding 1% by mass when heated to 260°C at a heating rate of 10°C / min in a thermogravimetric determination. The aforementioned dimer acid (A1) can be cited as a raw material for these other dimer acids.

[0108] Furthermore, trimeric acids can be cited as examples of carboxylic acids. Trimeric acids are mainly composed of tribasic acids obtained through the trimerization of unsaturated fatty acids. Trimeric acids include hydrogenated trimeric acids. As raw materials for trimeric acids, the aforementioned raw materials in dimer acids (Al) can be cited as examples.

[0109] Examples of organic sulfonic acids include, for example, aliphatic sulfonic acids and aromatic sulfonic acids. Examples of aliphatic sulfonic acids include, for example, alkyl sulfonic acids and alkanol sulfonic acids.

[0110] Other organic acids can be used alone or in combination of two or more.

[0111] As other organic acids, carboxylic acids are preferred, and preferably selected from one or more aliphatic monocarboxylic acids and aliphatic dicarboxylic acids.

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

[0113] By keeping the content of other organic acids below the upper limit of the above range, it is easy to suppress the generation of voids during continuous reflow soldering using indium alloy sheets.

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

[0115] By ensuring that the content of dimer acid (Al) is above the lower limit of the above range, it is easy to suppress the generation of voids during continuous reflow soldering using indium alloy sheets.

[0116] Solvent (S)

[0117] The flux in this embodiment contains solvent (S1) as the solvent. In addition to solvent (S1), solvent (S) may also contain solvent (S2).

[0118] Solvent (S1)

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

[0120] The upper limit of the weight reduction rate of the solvent (S1) is not particularly limited as long as the effect of the present invention can be achieved; for example, it can be 100% by mass.

[0121] Examples of solvents (S1) include 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 below 200°C, more preferably above 150°C and below 200°C, and even more preferably above 170°C and below 200°C.

[0123] In this specification, boiling point refers to the temperature of a liquid when its saturated vapor pressure is equal to 1 atmosphere (i.e., 1013 hPa).

[0124] Solvent (S1) can be used alone or in combination with two or more solvents.

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

[0126] Solvent (S2)

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

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

[0129] The boiling point of the solvent (S2) is preferably above 200°C and below 350°C, more preferably above 250°C and below 350°C, and even more preferably above 250°C and below 330°C.

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

[0131] Examples of alcohol-based solvents 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-hexyn-2,5-diol, 1,1,1-tris(hydroxymethyl)propane, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 2,2'-oxobis(methylene)bis(2-ethyl-1,3-propanediol), 2,2-bis(hydroxymethyl)-1,3-propanediol, 1,2,6-trihydroxyhexane, 1,4-cyclohexanediol, 2,4,7,9-tetramethyl-5-decyn-4,7-diol, and 2-hexyl-1-decyl octanediol.

[0132] Examples of glycol ether solvents include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, ethylene glycol monohexyl ether (ethylene glycol hexyl ether), diethylene glycol monohexyl ether (hexyl diethylene glycol), 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 terpineols include α-terpineol, β-terpineol, γ-terpineol, and mixtures of terpineols (i.e., mixtures whose main component is α-terpineol and which contain β-terpineol or γ-terpineol).

[0134] In addition, examples of solvents include dioctyl sebacate (DOS) and liquid paraffin.

[0135] Solvent (S2) can be used alone or in combination with two or more solvents.

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

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

[0138] By ensuring that the solvent (S1) content is above the lower limit of the above range, it is easy to suppress the generation of voids during continuous reflow soldering using indium alloy sheets.

[0139] <Other Ingredients>

[0140] In this embodiment, the flux may contain other components as needed, in addition to rosin esters, organic acids (A), and solvents (S). Examples of other components include rosin esters other than rosin esters, activators other than organic acids (A), thixotropic agents, metal passivators, surfactants, silane coupling agents, antioxidants, and colorants.

[0141] Other Rosin

[0142] Other examples of rosin include the aforementioned natural resins and rosin derivatives obtained by chemically modifying these natural resins (excluding rosin esters).

[0143] In this specification, "rosin derivatives (excluding rosin esters) obtained by chemically modifying natural resins" includes resins obtained by treating the "natural resins" with one or more of the following processes: hydrogenation, dehydrogenation, neutralization, epoxide addition, amidation, dimerization and polymerization, and Diels-Alder cyclization addition.

[0144] Examples of rosin derivatives include purified rosin and modified rosin.

[0145] Examples of modified rosin include, for example, hydrogenated rosin, polymerized rosin, polymerized hydrogenated rosin, disproportionated rosin, acid-modified hydrogenated rosin, acid anhydride-modified hydrogenated rosin, acid-modified disproportionated rosin, acid anhydride-modified disproportionated rosin, phenol-modified rosin, and α,β-unsaturated carboxylic acid modified products (acrylic acid-modified rosin, maleic acid-modified rosin, fumaric acid-modified rosin, etc.), as well as purified products, hydrides and disproportions of the polymerized rosin, and purified products, hydrides and disproportions of the α,β-unsaturated carboxylic acid modified products, rosin alcohol, rosin amine, hydrogenated rosin alcohol, rosin soap, hydrogenated rosin soap, acid-modified rosin soap, etc.

[0146] As a rosin amine, such as a mixture of dehydrorosin amine, dihydrorosin amine, and tetrahydrorosin amine, it refers to the so-called disproportionated rosin amine. The structures of dehydrorosin amine, dihydrorosin amine, and tetrahydrorosin amine are shown below.

[0147] [Chemical Formula 2]

[0148]

[0149] Other rosins can be used alone or in combination with two or more.

[0150] The content of rosin esters relative to the total mass of rosin (100% by mass) 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, even more 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 also be 100% by mass.

[0151] By keeping the rosin ester content below the lower limit of the above range, it is easy to suppress the generation of voids during continuous reflow soldering using indium alloy sheets.

[0152] Other active agents

[0153] Other active agents include, for example, amines, halogen compounds, and organophosphorus compounds.

[0154] [amine]

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

[0156] Examples of azoles include, for instance, 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-heptadecanylimidazole, 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, and 2,4-diamino-6-[2'-methylimidazole-(1')]-ethyltrimethylimidazole. Azine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyltriazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyltriazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyltriazine isocyanuric acid adduct, 2-phenylimidazolyl isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazolium, 2-phenyl-4-methyl-5-hydroxymethylimidazolium, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazoline, 2,4-diamino-6-vinyltriazine, 2,4-Diamino-6-vinyltriazine isocyanuric acid adduct, 2,4-diamino-6-methacryloyloxyethyltriazine, epoxy-imidazolium 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]diethanol, 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-phenyltetrazole, etc.

[0157] Examples of guanidines include, for example, 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 alkanolamines include, for example, N,N,N',N'-tetra(2-hydroxypropyl)ethylenediamine, N,N,N',N'-tetra(2-hydroxyethyl)ethylenediamine, monoethanolamine, diethanolamine, triethanolamine, 1-amino-2-propanol, bis(2-hydroxypropyl)amine, tri(2-hydroxypropyl)amine, etc.

[0159] Examples of alkylamine compounds include, for example, ethylamine, triethylamine, ethylenediamine, triethylenetetramine, cyclohexylamine, hexadecylamine, stearylamine, etc.

[0160] Examples of amine polyoxyethylene adducts include terminal diamine polyalkylene glycols, aliphatic amine polyoxyethylene adducts, aromatic amine polyoxyethylene adducts, and polyamine polyoxyethylene adducts.

[0161] Examples of epoxides that are added to amine polyoxyethylene adducts include ethylene oxide, propylene oxide, and butane oxide.

[0162] Terminal diamine polyalkylene glycols are compounds formed by amylating both ends of polyalkylene glycols.

[0163] Examples of terminal diamine polyalkylene glycols include, for example, terminal diamine polyethylene glycol, terminal diamine polypropylene glycol, and terminal diamine polyethylene glycol-polypropylene glycol copolymer.

[0164] Examples of terminal diamine polyethylene glycol-polypropylene glycol copolymers 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 an amine. Examples of such amines include ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, hexamethylenediamine, diethylenetriamine, laurylamine, stearylamine, oleylamine, tallow amine, cured tallow amine, tallow propyl diamine, m-xylenediamine, toluenediamine, p-xyleneamine, phenylenediamine, isophoronediamine, 1,10-decanediamine, 1,12-dodecanediamine, 4,4-diaminodicyclohexylmethane, 4,4-diaminodiphenylmethane, butane-1,1,4,4-tetramine, and pyrimidine-2,4,5,6-tetramine.

[0166] Amines can be used alone or in combination with two or more.

[0167] As an amine, azoles are preferred, and 2-phenylimidazole is more preferred.

[0168] When the flux contains an amine, the content of the amine relative to the total mass of the flux is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 5% by mass or less.

[0169] The presence of amines in the flux enhances its wettability. A amine content above the lower limit of the aforementioned range further enhances wettability. A amine content below the upper limit of the aforementioned range improves the ability to suppress void formation.

[0170] [Halogen compounds]

[0171] Examples of halogen compounds include, for example, hydrohalates and other organic halogen compounds.

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

[0173] As an amine here, one can cite the amines mentioned above in "Amines".

[0174] Alternatively, halogen compounds other than amine hydrohalides can be used, for example, salts formed by reacting an amine with tetrafluoroboric acid (HBF4) or complexes formed by reacting an amine with boron trifluoride (BF3). Examples of such complexes include boron trifluoride piperidine.

[0175] Other halogenated compounds besides amine hydrohalates include, for example, halogenated aliphatic compounds. A halogenated aliphatic hydrocarbon group is a group in which some or all of the hydrogen atoms constituting the aliphatic hydrocarbon group are replaced by halogen atoms.

[0176] Halogenated aliphatic compounds include halogenated aliphatic alcohols and halogenated heterocyclic compounds.

[0177] Examples of halogenated aliphatic alcohols include, for example, 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-buten-1,4-diol.

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

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

[0180] [In the formula, R] h11 Represents an n-valent heterocyclic group. R h12 This indicates a halogenated aliphatic hydrocarbon group.

[0181] As R h11 The heterocycle with an n-valent heterocyclic group can be exemplified by a ring structure in which a portion of the carbon atom constituting an aliphatic or aromatic hydrocarbon ring is replaced by a heteroatom. Examples of heteroatoms in this heterocycle include oxygen, sulfur, and nitrogen atoms. This heterocycle is preferably a 3- to 10-membered ring, more preferably a 5- to 7-membered ring. Examples of such heterocycles include isocyanurate rings.

[0182] R h12 The halogenated aliphatic hydrocarbon group in the compound preferably has 1 to 10 carbon atoms, more preferably 2 to 6 carbon atoms, and even more preferably 3 to 5 carbon atoms. Additionally, R... h12 Preferably, it is a brominated aliphatic hydrocarbon group or a chlorinated aliphatic hydrocarbon group, more preferably a brominated aliphatic hydrocarbon group, and even more preferably a brominated saturated aliphatic hydrocarbon group.

[0183] Examples of halogenated heterocyclic compounds include tri-(2,3-dibromopropyl)isocyanurate.

[0184] In addition, examples of halogenated compounds other than aminohydrohalides include, for example, iodinated carboxyl compounds such as 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, and 5-iodoaminoanisic 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] In addition, halogen compounds other than aminohydrohalides can be cited as examples of organochlorine compounds. Examples of organochlorine compounds include chlorinated alkanes, chlorinated fatty acid esters, chlorinated bactericidal acid, and chlorinated bactericidal anhydride.

[0186] Halogen compounds can be used alone or in combination of two or more.

[0187] Organophosphorus compounds

[0188] Examples of organophosphorus compounds include, for example, acidic phosphate esters, acidic phosphonates, and acidic hypophosphonates.

[0189] Organophosphorus compounds can be used alone or in combination of two or more.

[0190] Thixotropic agents

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

[0192] Examples of ester-based thixotropic agents include, for example, ester compounds, specifically hydrogenated castor oil and ethyl myristate.

[0193] Examples of amide-based thixotropic agents include monoamides, diamides, and polyamides.

[0194] Examples of monoamides include laurylamide, palmitamide, stearamide, behenamide, hydroxystearamide, saturated fatty acid amide, oleamide, erucamide, unsaturated fatty acid amide, 4-methylbenzamide (p-toluamide), p-toluenemethaneamide, aromatic amide, hexamethylene hydroxystearamide, substituted amide, hydroxymethylstearamide, hydroxymethylamide, fatty acid ester amide, etc.

[0195] Examples of diamides include ethylenedicarboxylic acid (C6-24 carbon atoms in fatty acids) amides, ethylenedihydroxycarboxylic acid (C6-24 carbon atoms in fatty acids) amides, hexamethylenedicarboxylic acid (C6-24 carbon atoms in fatty acids) amides, hexamethylenedihydroxycarboxylic acid (C6-24 carbon atoms in fatty acids) amides, and aromatic diamides. Examples of fatty acids used as raw materials for these diamides include stearic acid (C18 carbon atoms), oleic acid (C18 carbon atoms), and lauric acid (C12 carbon atoms).

[0196] Examples of polyamides include saturated fatty acid polyamides, unsaturated fatty acid polyamides, aromatic polyamides, 1,2,3-propanetricarboxylic acid tris(2-methylcyclohexylamide), cyclic amide oligomers, and non-cyclic amide oligomers.

[0197] Examples of cyclic amide oligomers include amide oligomers obtained by condensing dicarboxylic acids and diamines into a cyclic form, amide oligomers obtained by condensing tricarboxylic acids and diamines into a cyclic form, amide oligomers obtained by condensing dicarboxylic acids and triamines into a cyclic form, amide oligomers obtained by condensing tricarboxylic acids and triamines into a cyclic form, amide oligomers obtained by condensing dicarboxylic acids and tricarboxylic acids and diamines into a cyclic form, amide oligomers obtained by condensing dicarboxylic acids and tricarboxylic acids and triamines into a cyclic form, amide oligomers obtained by condensing dicarboxylic acids and diamines and triamines into a cyclic form, and amide oligomers obtained by condensing dicarboxylic acids and tricarboxylic acids and diamines and triamines into a cyclic form.

[0198] Furthermore, examples of acyclic amide oligomers include those obtained by the condensation polymerization of monocarboxylic acids with diamines and / or triamines to form acyclic amide oligomers, and those obtained by the condensation polymerization of dicarboxylic acids and / or tricarboxylic acids with monoamines to form acyclic amide oligomers. When the amide oligomer contains a monocarboxylic acid or a monoamine, the monocarboxylic acid or monoamine functions as terminal molecules, resulting in acyclic amide oligomers with reduced molecular weight. Additionally, in the case of amide compounds obtained by the condensation polymerization of dicarboxylic acids and / or tricarboxylic acids with diamines and / or triamines to form acyclic amide compounds, the acyclic amide oligomer becomes an acyclic polymeric amide polymer. Furthermore, acyclic amide oligomers also include those obtained by the condensation polymerization of monocarboxylic acids and monoamines to form acyclic amide oligomers.

[0199] Examples of sorbitol-based thixotropic agents include, for example, dibenzylidene-D-sorbitol, di(4-methylbenzylidene)-D-sorbitol, (D-)sorbitol, monobenzylidene(-D-)sorbitol, and mono(4-methylbenzylidene)-(D-)sorbitol.

[0200] The flux of this embodiment may or may not contain a thixotropic agent. When the flux of this embodiment contains a thixotropic agent, a single thixotropic agent may be used, or two or more thixotropic agents may be used in combination.

[0201] Metal passivating agents

[0202] Examples of metal passivating agents include hindered phenolic compounds and nitrogen compounds.

[0203] The "metal passivating agent" mentioned here refers to a compound that has the property of preventing metals from deteriorating due to contact with a certain compound.

[0204] Hindered phenolic compounds are phenolic compounds that have a large substituent (such as a branched chain or cyclic alkyl group such as tert-butyl) at at least one ortho position of phenol.

[0205] Hindered phenolic compounds are not particularly limited; examples include bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylene bis(oxyethylene)], N,N'-hexamethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide], 1,6-hexanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and 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 tetratetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2-thiodiethylidene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, N,N'-hexamethylene Compounds such as bis(3,5-di-tert-butyl-4-hydroxy-hydrogenated cinnamamide), 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, and compounds represented by the following chemical formulas.

[0206] [Chemical Formula 3]

[0207]

[0208] (where Z represents a substituted alkylene group. R) 81 and R 82 Each can be independently a substituted alkyl, aralkyl, aryl, heteroaryl, cycloalkyl, or heterocycloalkyl group. 83 and R 84 Each is an alkyl group that can be substituted independently.

[0209] Nitrogen compounds used as metal passivating agents include, for example, hydrazide nitrogen compounds, amide nitrogen compounds, triazole nitrogen compounds, and melamine nitrogen compounds.

[0210] As nitrogen compounds in the acylhydrazine system, any nitrogen compound with an acylhydrazine skeleton is acceptable. Examples include dodecanoic acid bis[N2-(2-hydroxybenzoyl)hydrazine], N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, decanedicarboxylic acid disalicylic acid hydrazine, N-salicyl-N'-salicylic acid hydrazine, m-nitrobenzoyl hydrazine, 3-aminophthalic acid hydrazine, phthalic acid dihydrazine, adipic acid hydrazine, oxaloyl di(2-hydroxy-5-octylphenylmethylene hydrazine), N'-benzoylpyrrolidone carboxylic acid hydrazine, and N,N'-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hydrazine.

[0211] As an amide-based nitrogen compound, any nitrogen compound with an amide skeleton is acceptable, such as N,N'-bis{2-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxy]ethyl}oxalamide.

[0212] As a triazole nitrogen compound, any nitrogen compound with a triazole skeleton is acceptable, such as N-(2H-1,2,4-triazol-5-yl)salicylic acid amide, 3-amino-1,2,4-triazole, 3-(N-salicylic acid)amino-1,2,4-triazole, etc.

[0213] As a melamine-based nitrogen compound, any nitrogen compound with a melamine skeleton is acceptable, including melamine and melamine derivatives. More specifically, examples include triaminotriazine, alkylated triaminotriazine, alkoxyalkylated triaminotriazine, melamine, alkylated melamine, alkoxyalkylated melamine, N2-butylmelamine, N2,N2-diethylmelamine, and N,N,N',N',N",N"-hexa(methoxymethyl)melamine.

[0214] Metal passivating agents can be used alone or in combination of two or more.

[0215] Surfactants

[0216] Examples of surfactants include, for instance, nonionic surfactants.

[0217] Examples of nonionic surfactants include, for instance, polyoxyethylene adducts.

[0218] Examples of epoxides derived from polyoxyethylene adducts include ethylene oxide, propylene oxide, and butane oxide.

[0219] Examples of polyoxyethylene adducts include, for example, polyethylene glycol, polypropylene glycol, polyethylene glycol-polypropylene glycol copolymer, ethylene oxide-resorcinol copolymer, polyoxyethylene acetylene glycol, polyoxyethylene glycerol ether, polyoxyethylene alkyl ether, polyoxyethylene ester, polyoxyethylene alkylamide, etc.

[0220] Alternatively, polyoxyethylene adducts of alcohols can be cited as nonionic surfactants. Examples of alcohols include, for instance, aliphatic alcohols, aromatic alcohols, and polyols.

[0221] Surfactants can be used alone or in combination of two or more.

[0222] Antioxidants

[0223] Examples of antioxidants include hindered phenolic antioxidants such as 2,2'-dihydroxy-3,3'-bis(α-methylcyclohexyl)-5,5'-dimethyldiphenylmethane. Here, "antioxidant" refers to a compound that has the property of inhibiting the oxidation of solder alloys.

[0224] Antioxidants can be used alone or in combination of two or more.

[0225] The flux described above is suitable for continuous reflow soldering for mounting indium alloy sheets and joining solder balls.

[0226] In the first reflow soldering, 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 an indium alloy sheet to obtain a semiconductor package. Then, in the second reflow soldering, 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 side of the semiconductor package.

[0227] In conventional reflow soldering, flux does not diffuse on the surface of the indium sheet but accumulates on the bonding surface, resulting in numerous voids on the bonding surface of the indium alloy sheet. The flux of this embodiment contains a solvent (S1) that readily evaporates even at low temperatures. During a single reflow soldering operation at low temperatures, the solvent (S1) evaporates. As a result, no voids from the solvent (S1) are generated when the indium alloy sheet melts.

[0228] Because the secondary reflow soldering process involves high temperatures, activators and other components can easily vaporize, forming voids. However, the flux, rosin ester, and dimer acid (Al) in this embodiment are difficult to vaporize even at high temperatures. Therefore, void formation can be suppressed in both primary and secondary reflow soldering under different temperature conditions.

[0229] (Preparation method of the conjugate)

[0230] In the method for manufacturing an electronic component containing a semiconductor package of this manner, the flux described in the above embodiment is used to perform a first reflow soldering process to bond the chip and cover via a thermal interface material (TIM), thereby obtaining a semiconductor package. Then, a second reflow soldering process is performed to fix solder balls onto the obtained semiconductor package, thereby obtaining an electronic component.

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

[0232] Process (i):

[0233] The process of obtaining a semiconductor package having a bonding assembly formed by bonding a chip and a cover via a TIM (Technical Insulation Model).

[0234] Process (ii):

[0235] The process of bonding solder balls to the back of the semiconductor package to obtain electronic components.

[0236] use Figures 1-4 A preferred embodiment of a method for fabricating an electronic component comprising a semiconductor package of this manner will be described. In the method for fabricating the bonding body of this embodiment, as... Figure 1 As shown, a substrate 40 is prepared to be equipped with a cover 10, a TIM 20 and a bare chip 41.

[0237] A metallization layer 42 is provided on the surface of the bare chip 41. The metallization layer 42 can be, for example, a Ni-plated layer, a Ni / Au-plated layer, etc. The metallization layer 42 can also have multiple layers with different compositions. The metallization layer 42 can be formed, for example, by sputtering or other methods.

[0238] The cover 10 has a metallization layer 11 on the surface opposite to the TIM 20. The metallization layer 11 can be the same as the metallization layer 42 of the bare chip 41. The cover 10 has a heat sink 12 on the surface opposite to the surface opposite to the TIM 20. Materials for the heat sink include, for example, metals such as aluminum, iron, and copper.

[0239] TIM20 is a sheet material made of an alloy of indium and silver. TIM20 is plate-shaped. The size of TIM20 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 used as the raw material for the sheet made of the alloy is preferably 75% by mass or more and 99% by mass or less, and more preferably 85% by mass or more and 95% by mass or less, relative to the total amount of the alloy (100% by mass).

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

[0242] <Process (i)>

[0243] In process (i), a semiconductor package is obtained having a bonding assembly formed by attaching a chip and a cover via a thermal interface material (TIM).

[0244] Regarding process (i), an example is given of a method that includes flux application, cap installation, and heating operation (1).

[0245] Flux Application Process

[0246] As flux 50, the flux 50 described in the above embodiment is preferably used. (See also...) Figure 2 The flux application process is explained. Figure 2 This is a cross-sectional view showing the TIM20 and the bare die 41 coated with flux 50. In the flux coating process, the flux 50 is placed between the TIM20 and the bare die 41 or between the TIM20 and the cap 10, at least one of them.

[0247] In the flux application process, flux 50 is applied to the bonding surfaces (42a, 20b) of the bare chip 41 and TIM20 or the bonding surfaces (11a, 20a) of the cover 10 and TIM20.

[0248] Flux 50 is applied to the bonding surface as described below. Flux 50 is applied to the surface 42a of the metallization layer 42 of the bare die 41. Next, a TIM 20 is placed on the metallization layer 42 of the bare die 41 with flux 50 applied. Flux 50 is applied to the surface 20a of the TIM 20 stacked on the bare die 41, opposite to the surface 20b that contacts the bare die 41.

[0249] Examples of flux 50 application devices include spray flux applicators and foam flux applicators. Among these, spray flux applicators are preferred from the viewpoint of coating amount stability.

[0250] Cover Installation Procedure

[0251] In the cover mounting process, after applying flux 50 to the bonding surface, the cover 10 is fixed to the substrate 40 on which the TIM 20 and bare chip 41 are stacked. (Refer to...) Figure 3 The installation process for the cover is explained. Figure 3 This diagram shows a laminate 60 in which the cover 10 and the substrate 40 are bonded together by adhesive resin 43 after the flux 50 is applied.

[0252] In the cover mounting process, after applying flux 50, adhesive resin 43 is applied to one side of the substrate 40. Next, the cover 10 is heat-pressed onto the substrate 40, on which the TIM 20 and bare chip 41 are stacked, and the adhesive resin 43 is cured. Thus, the cover 10 is fixed relative to the substrate 40. Through the cover mounting process, a laminate 60 is obtained in which the cover 10 and the substrate 40 are bonded together by the adhesive resin 43.

[0253] Heating Operation (1)

[0254] In the heating operation (1), the laminate 60 is heated by reflow soldering. Through the heating operation (1), the cover 10 and the bare chip 41 are bonded via TIM 20 to obtain a semiconductor package 60'.

[0255] Since indium, which constitutes the indium alloy sheet used as TIM, has a melting point of 156°C, bonding can be achieved even at temperatures lower than typical reflow soldering temperatures. The reflow soldering temperature is preferably 150–250°C, and more preferably 150–200°C.

[0256] <Process (ii)>

[0257] In step (ii), solder balls 70 are bonded to the back surface 60a of the semiconductor package 60' by heating operation (2), thereby obtaining electronic component 100. (Refer to...) Figure 4 The process (ii) will be described. The back surface 60a of the semiconductor package 60' refers to the surface of the semiconductor package 60' opposite to the surface with the cover fixed on it.

[0258] In step (ii), firstly, solder balls 70 are placed on the back surface 60a of the semiconductor package 60'. Next, the semiconductor package 60' with solder balls 70 is heated (2). Through the heating operation (2), the solder balls 70 melt and bond to the semiconductor package 60'.

[0259] The heating operation (2) involves heating the semiconductor package 60' using a reflow soldering method. The reflow soldering temperature is preferably above 200°C and below 280°C.

[0260] According to the above-described method for manufacturing electronic components containing semiconductor packages, even during the heating operation (2) performed at high temperatures, the amount of voids in the bonding surfaces of the sheet (i.e., the surfaces containing flux) can be reduced. As a result, heat generated from the chip can be released efficiently.

[0261] (Other implementation methods)

[0262] As described above, the method for preparing the bonding body in this manner is to place flux 50 between TIM20 and bare chip 41, or between TIM20 and cap 10, at least one of these.

[0263] In the above embodiment, flux 50 is applied to the bonding surface 42a of the bare chip 41 with the TIM20 and the bonding surface 11a of the TIM20 with the cover 10, but the surfaces on which flux 50 is applied are not limited to these.

[0264] For example, in order to place the flux 50 between the TIM20 and the bare chip 41, the flux 50 can be applied to the bonding surface 20b of the TIM20 and the bare chip 41, or the flux 50 can be applied to the bonding surface 11a of the cover 10 and the TIM20.

[0265] Example

[0266] The present invention will be described below through embodiments, but the present invention is not limited to the following embodiments.

[0267] <Preparation of Flux>

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

[0269] The fluxes of the formulation examples and comparative examples are shown in Tables 1-4. The composition of the raw materials used is shown below. The composition percentages in Tables 1-4 are based on the total mass of the flux as 100% by mass, with blank columns indicating 0% by mass.

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

[0271] Rosin esters:

[0272] As a rosin ester, it uses a substance formed by reacting hydrogenated rosin with glycerol.

[0273] Dimer acids (A1) and other organic acids are used as organic acids.

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

[0275] As a hydrogenated dimer acid, it is used to obtain a hydrogenated dimer acid by partial hydrogenation of the reactants of oleic acid and linoleic acid. The hydrogenated dimer acid is a hydrogenated dimer acid containing a dimer acid with 36 carbon atoms and a trimer acid with 54 carbon atoms.

[0276] Dimeric acids with 36 carbon atoms are of various types containing different degrees of unsaturation. Here, the degree of unsaturation of a dimer acid is represented by the value of {(2m+2)-n} / 2, where 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] Dimeric acids with 36 carbon atoms are those containing dimeric acids with an unsaturation degree of 2, 3, 4, 5, 6, 7, and 8.

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

[0279] Amine: 2-Phenylidene

[0280] As solvent (S), solvent (S1) and solvent (S2) are used.

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

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

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

[0284] [Determination of weight loss rate]

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

[0286] Using a differential thermal-thermogravimetric analyzer (Rigaku Corporation, TG-DTA8122), 10 mg of the test sample is placed in an aluminum pan and heated from room temperature (approximately 25°C) at a specified heating rate until the specified temperature is reached. Then, the weight loss rate is calculated using the following formula from the mass W0 (100% by mass) of the test sample before heating and the mass W1 immediately after reaching the specified temperature.

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

[0288] The weight loss rates of rosin esters, acrylic acid-modified hydrogenated rosin, dimer acids (Al), and other organic acids were measured at specified temperatures of 260°C and heating rates of 10°C / min. The values ​​in parentheses represent the weight loss rate.

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

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

[0291] The weight reduction rates of solvent (S1) and solvent (S2) were determined by setting the specified temperature and the specified heating rate to 150°C and 6°C / min, respectively.

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

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

[0294] [Analysis of hydrogenated dimer acids]

[0295] Prepare a 5000 ppm solution of hydrogenated dimer acid dissolved in 2-propanol. Analyze the solution using liquid chromatography-Fourier transform mass spectrometry.

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

[0297] The Orbitrap ID-X (Thermo Fisher Scientific) was used as the Fourier transform mass spectrometer. The analytical conditions were negative mode electrospray ionization. The m / z measurement range was 200–2000.

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

[0299] Hydrogenated dimer acids are hydrogenated dimer acids containing various types of 36-carbon dimer acids and 54-carbon trimer acids. The total peak area from the various 36-carbon dimer acids accounts for more than 99% of the total area (100%) from all molecules.

[0300] The area ratio of each dimer acid with 36 carbon atoms to the total area (100%) from all molecules is shown below.

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

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

[0303] [Determination of softening point]

[0304] The softening point of rosin was determined using the ring and ball method as described in JIS K5902. Rosin with a softening point below 80°C was tested in a water bath. Rosin with a softening point above 80°C was tested in a glycerol bath. Each rosin was tested twice. The softening point below is the average of the two measurements.

[0305] Rosin ester (softening point 95℃), acrylic acid-modified hydrogenated rosin (softening point 130℃), hydrogenated rosin (softening point 72℃).

[0306] [Determination of acid value]

[0307] The acid value of rosin esters was determined according to the neutralization titration method in section 3.1 of JISK0070 "Test methods for acid value, saponification value, ester value, iodine value and hydroxyl value of mixed unsaponifiables of chemical products".

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

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

[0310] The evaluation methods described in <Evaluation 1> were used to evaluate the ability to suppress void formation and the wettability. The results of these evaluations are shown in Tables 1-4.

[0311] <Evaluation 1>

[0312] Evaluation of the ability to suppress void generation

[0313] Method for preparing the conjugate:

[0314] Prepare a cover with an Au / Ni plating portion (8mm×8mm) on its surface, and a substrate with an Au / Ni plating portion (8mm×8mm) on its surface.

[0315] As solder sheet material, an indium alloy sheet (size: 7mm × 7mm × 400μm) composed of an alloy of 90% by mass of In and 10% by mass of Ag is prepared. 2mg of flux is applied to both the front and back sides of the indium alloy sheet, respectively.

[0316] A 300μm thick copper plate is placed around the Au / Ni plating area of ​​the substrate as a spacer. Next, an indium alloy sheet coated with flux is clamped between the cover and the Au / Ni plating area of ​​the substrate and fixed with a clamp.

[0317] Next, the cover and substrate holding the indium alloy sheet are reflow soldered once to obtain the joint. A second reflow soldering is then performed in atmospheric conditions at a heating rate of 10°C / min until the temperature reaches 170°C.

[0318] Next, the joint that had undergone one reflow soldering was subjected to a second reflow soldering. In the second reflow soldering, the temperature was raised from room temperature to 250°C in 450 seconds at a heating rate of 0.5°C / second.

[0319] Verification method:

[0320] The void area was measured by irradiating the bonded assembly, which had undergone secondary reflow soldering, with X-rays applied perpendicular to the substrate and analyzing the transmitted X-rays. The measurement was performed using an XD7600NT (manufactured by Nordson). In the void area measurement, the presence of a void was considered confirmed when X-rays passed through at least one void. Voids with a diameter of 0.1 μm or larger were detected. The ratio of the total void area to the total area of ​​the indium alloy sheet was then calculated as the void area percentage (%).

[0321] Judgment criteria:

[0322] A: The porosity is less than 10%.

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

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

[0325] Fluxes with an evaluation result of A or B are considered qualified, while fluxes with an evaluation result of C are considered unqualified.

[0326] Evaluation of wettability

[0327] Verification method:

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

[0329] 0.5 mg of flux was applied to both the front and back sides of the indium alloy sheet. The flux-coated indium alloy sheet was then placed on the Au / Ni electrode.

[0330] Next, the electrodes with indium alloy sheets were reflow soldered under the following conditions: the temperature was increased to 180°C at a rate of 6°C / min, and held at 180°C for 3 minutes.

[0331] Next, after removing the flux, the area of ​​wetting spread is measured.

[0332] Judgment criteria:

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

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

[0335] Fluxes with an evaluation result of A or B are considered qualified.

[0336] Evaluation of the coating properties

[0337] Verification method:

[0338] Using a spraying device (TG-SS2 (full cone type), manufactured by a spray system company), with the air pressure set to 0.3 MPa, it was verified whether flux could be applied to the metal plates in various cases.

[0339] Judgment criteria:

[0340] A: Flux can be applied to the metal plate using a spraying device.

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

[0342] Flux with an evaluation result of A is qualified, and flux with an evaluation result of B is unqualified.

[0343] The evaluation methods described in <Evaluation 2> below were used to evaluate the ability to suppress void formation and the wettability. The results of these evaluations are shown in Table 4.

[0344] <Evaluation 2>

[0345] Evaluation of the ability to suppress void generation

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

[0347] Using SAC alloy sheets and the fluxes of Example 1 and Comparative Example 4, the verification was conducted using the same method as in Evaluation 1, "Evaluation of the Ability to Inhibit Void Generation".

[0348] The conditions for single and double reflow soldering are as follows. For single reflow soldering, perform a heating rate of 10°C / min at atmospheric pressure until the temperature rises from room temperature (25°C) to 250°C. For double reflow soldering, heat the temperature from room temperature (25°C) to 250°C over 450 seconds at a heating rate of 0.5°C / sec.

[0349] Evaluation of wettability

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

[0351] Using SAC alloy sheets and the fluxes of Example 1 and Comparative Example 4, the wettability was verified using the same method as in Evaluation 1.

[0352] Reflow soldering involves heating from room temperature (25°C) to 250°C at a rate of 6°C / minute and holding at 250°C for 3 minutes.

[0353] [Table 1]

[0354]

[0355] The fluxes of Examples 1 and 2, which contain rosin ester, dimer acid (A1), and solvent (S1), were rated as A for their ability to suppress void formation.

[0356] The flux of Comparative Example 1, which does not contain solvent (S1), was rated as C in terms of its ability to suppress void formation.

[0357] The fluxes of Comparative Examples 2-3, which do not contain dimer acid (Al), were rated as C in terms of their ability to suppress void formation.

[0358] The flux of Comparative Example 4, which does not contain rosin ester, was rated as C in terms of its ability to suppress void formation.

[0359] The flux of Example 1, in which the content of solvent (S1) is 100% by mass relative to the total mass of solvent (S), is rated as A for its ability to suppress void formation.

[0360] The flux of Example 3, in which the content of solvent (S1) is 83% by mass relative to the total mass of the stretchable solvent (S), has an evaluation of B for its ability to suppress void formation.

[0361] The flux of Example 1, which contains dimer acid (Al), was rated A for its coatability.

[0362] The flux of Comparative Example 1, which does not contain dimer acid (Al), was rated as B in terms of coatability.

[0363] The fluxes of Comparative Examples 2-3, whose content of other organic acids was 15% by mass relative to the total mass of the flux, were rated as B in terms of coatability.

[0364] [Table 2]

[0365]

[0366] The fluxes of Examples 4, 7 to 11, in which the content of dimer acid (A1) is 90% by mass or more relative to the total mass of organic acid (A), are evaluated as having an A-level ability to suppress void formation.

[0367] The fluxes of Examples 5-6 and 12-13, in which the content of dimer acid (A1) is less than 90% by mass relative to the total mass of organic acid (A), were evaluated as having a void generation suppression ability of B.

[0368] [Table 3]

[0369]

[0370] The fluxes of Examples 15-20, 22-23, and 25, in which the content of dimer acid (Al) is 15% by mass or more relative to the total mass of the flux, are rated as A in terms of wettability.

[0371] The fluxes of Examples 14, 21, and 24, in which the content of dimer acid (Al) is 10% by mass relative to the total mass of the flux, were rated as B for wettability.

[0372] [Table 4]

[0373]

[0374] In Evaluation 2, the evaluation of void formation suppression ability and wettability when using SAC alloy sheet and flux of Example 1 was A. Furthermore, the evaluation of void formation suppression ability and wettability when using SAC alloy sheet and flux of Comparative Example 4 was also A.

[0375] For the flux of Comparative Example 4, which does not contain rosin ester, the void suppression capability is A when using SAC alloy sheet and C when using indium alloy sheet. That is, voids are more likely to occur when using indium alloy sheet compared to using SAC alloy sheet.

[0376] The flux of Example 1, which contains rosin ester, is able to adequately suppress voids even when using indium alloy sheets.

[0377] The flux of the present invention, by containing rosin ester, dimer acid (Al) and solvent (S1), can suppress the generation of voids in the resulting joint even when using solder sheets with high indium content.

[0378] Industrial applicability

[0379] The flux of the present invention is applicable to the manufacturing process of electronic components using indium alloy sheets with improved heat dissipation efficiency.

[0380] Explanation of symbols

[0381] 10. Cover, 11. Metallization layer, 11a. Bonding surface, 12. Heat sink, 20. Thermal interface material (TIM), 20a, 20b. Bonding surfaces, 40. Substrate, 41. Bare chip, 42. Metallization layer, 42a. Bonding surface, 43. Adhesive resin, 50. Flux, 60. Semiconductor package, 60a. Back side, 70. Solder ball, 100. Electronic component.

Claims

1. A flux comprising rosin ester, an organic acid (A), and a solvent (S), The organic acid (A) contains a dimer acid (A1), and the dimer acid (A1) exhibits a weight loss of less than 1% by mass when heated to 260°C at a heating rate of 10°C / min in a thermogravimetric determination. The solvent (S) contains solvent (S1), which, when heated to 150°C at a heating rate of 6°C / min in a thermogravimetric determination, exhibits a weight reduction rate of ≥99% by mass. The content of the dimer acid (Al) relative to the total mass of the flux (100% by mass) is 5% by mass or more and 70% by mass or less. The content of the dimer acid (Al) is 75% by mass or more relative to the total mass of the organic acid (A). The content of the solvent (S1) relative to the total mass of the flux (100% by mass) is 10% by mass or more and 90% by mass or less. The content of solvent (S1) is 70% by mass or more relative to the total mass of solvent (S).

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

3. The flux according to claim 1, wherein, The dimer acid (A1) is selected from at least one dimer of an unsaturated fatty acid bonded with 18 carbon atoms.

4. The flux according to claim 1, wherein, The solvent (S1) has a boiling point below 200°C.

5. The flux according to claim 1, wherein, The flux also contains azoles.

6. The flux according to claim 1, wherein, The content of the solvent (S1) relative to the total mass of the flux (100% by mass) is 10% by mass or more and 75% by mass or less. The content of the dimer acid (Al) relative to the total mass of the flux is 10% by mass or more and 60% by mass or less.

7. The flux according to claim 1, wherein, The content of the solvent (S1) relative to the total mass of the flux (100% by mass) is 10% by mass or more and 75% by mass or less. The content of the rosin ester relative to the total mass of the flux is 15% by mass or more and 60% by mass or less.

8. A method for fabricating an electronic component, which is a method for fabricating an electronic component containing a semiconductor package, the method comprising: Step (i) to obtain a semiconductor package having a bonding assembly formed by bonding a bare die to a cover via a thermal interface material (TIM); as well as, Step (ii) of obtaining electronic components by bonding solder balls to the back side of the semiconductor package. The TIM is a sheet material made of an alloy of indium and silver. The process (i) includes a heating operation (1), which involves applying the flux according to any one of claims 1 to 7 between the TIM and the bare die, or between the TIM and the cover, to at least one of these conditions, and then bonding the bare die to the cover via reflow soldering. The process (ii) includes a heating operation (2) that bonds the solder balls to the semiconductor package via reflow soldering.

9. The method for manufacturing an electronic component according to claim 8, wherein, The temperature conditions for the heating operation (1) are 150–250°C. The temperature conditions for the heating operation (2) are 200-280°C.

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