Flux and solder paste

Abstract

To provide a flux and a solder paste containing the flux where the intermittent printability of the solder paste can be improved with good workability.SOLUTION: A flux used for soldering contains a solvent containing at least one kind selected from among tetraethylene glycol dimethyl ether and polyethylene glycol dimethyl ether. The total content of at least one kind selected from among tetraethylene glycol dimethyl ether and polyethylene glycol dimethyl ether is 35.0 mass% or more and 55.0 mass% or less to the total flux.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a flux used in soldering and a solder paste containing the flux. [Background technology]

[0002] A solder paste made from a mixture of solder alloy and flux is used in mounting electronic components such as chip components and package substrates onto electronic circuit boards such as printed wiring boards. Specifically, the solder paste is screen-printed onto the pads on the surface of the electronic circuit board using a metal mask, and then the electronic components are mounted and heated (reflowed) to join them to the electronic circuit board.

[0003] In recent years, electronic devices have become smaller and more powerful, leading to the miniaturization of electronic components. Patent Document 1, for example, discloses a flux that improves printability on such fine electronic components, including a solvent containing a higher alcohol having 12 to 22 carbon atoms and being liquid at room temperature. Patent Document 2 also discloses a flux that includes a solvent that is a mixture of a polyalkylene glycol monoalkyl ether and a polyalkylene glycol dialkyl ether. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2020-49539 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-87814 Summary of the Invention [Problem to be solved by the invention]

[0005] From the viewpoint of workability, screen printing is sometimes performed intermittently at regular intervals. However, after screen printing, a small amount of solder paste adheres to the openings of the metal mask. The adhered solder paste dries over time and adheres to the openings of the metal mask, which can even cause clogging. This reduces the amount of solder paste filled in the next screen printing run, which can lead to printing defects. While it is possible to wash off the solder paste that has adhered to the openings of the metal mask, this is not preferable due to poor workability.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a flux that is easy to work with and that can improve the intermittent printability of solder paste, and a solder paste that contains the flux. [Means for solving the problem]

[0007] The flux according to the present invention is used for soldering and contains a solvent containing at least one selected from tetraethylene glycol dimethyl ether and polyethylene glycol dimethyl ether, and the total content of the at least one selected from tetraethylene glycol dimethyl ether and polyethylene glycol dimethyl ether is 35.0 mass % or more and 55.0 mass % or less with respect to the entire flux.

[0008] This configuration of the flux makes it difficult for the flux to dry out even when left for a certain period of time, and also prevents an increase in adhesiveness, so that the solder paste is less likely to stick to the openings of the metal mask after screen printing, and furthermore, clogging is less likely to occur. As a result, the flux can improve the intermittent printability of the solder paste without the need for work such as washing off the solder paste.

[0009] In the flux according to the present invention, the total content of at least one selected from the group consisting of tetraethylene glycol dimethyl ether and polyethylene glycol dimethyl ether may be 40.0 mass % or more and 47.0 mass % or less with respect to the entire flux.

[0010] With this configuration, the solder paste is less likely to stick to the openings in the metal mask after screen printing, and clogging is less likely to occur. As a result, the flux can further improve the intermittent printability of the solder paste.

[0011] The flux according to the present invention may further contain a glycol ether solvent.

[0012] With this configuration, the solder paste is less likely to stick to the openings in the metal mask after screen printing, and clogging is less likely to occur. As a result, the flux can further improve the intermittent printability of the solder paste.

[0013] The solder paste according to the present invention contains the above-mentioned flux and a solder alloy powder.

[0014] The flux does not dry easily even when left for a certain period of time, and also suppresses an increase in adhesiveness, so that the solder paste is less likely to stick to the openings of the metal mask after screen printing, and furthermore, clogging is less likely to occur. As a result, the solder paste can improve intermittent printability without the need for operations such as washing it off.

[0015] In the solder paste according to the present invention, the particle diameter of the solder alloy powder may be 5 μm or more and 40 μm or less.

[0016] Since the particle size of the solder alloy powder is within the above-mentioned range, the solder paste can have good workability and improved intermittent printability in a wide range of applications, from solder pastes for general use to solder pastes for fine printing.

[0017] In the solder paste according to the present invention, the alloy of the solder alloy powder may be a Sn / Ag / Cu alloy.

[0018] The solder paste has good workability and can improve intermittent printability even for the widely used Sn / Ag / Cu alloy.

[0019] In the solder paste according to the present invention, the Sn / Ag / Cu alloy may further contain at least one element selected from the group consisting of In, Bi, Sb, and Ni.

[0020] Even if these metal elements are added to the solder paste for the purpose of improving the thermal durability of the solder alloy, the solder paste can have good workability and improve intermittent printability. [Effects of the Invention]

[0021] According to the present invention, it is possible to provide a flux that is easy to work with and that can improve the intermittent printability of a solder paste, and a solder paste that includes the flux. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, a flux and a solder paste according to an embodiment of the present invention will be described.

[0023] <Flux>

[0024] (solvent) The flux according to this embodiment contains at least one solvent selected from tetraethylene glycol dimethyl ether and polyethylene glycol dimethyl ether. The total content of the at least one solvent selected from tetraethylene glycol dimethyl ether and polyethylene glycol dimethyl ether is 35.0 mass% or more and 55.0 mass% or less, preferably 40.0 mass% or more and 47.0 mass% or less, based on the total mass of the flux.

[0025] The flux according to this embodiment may contain a solvent other than tetraethylene glycol dimethyl ether and polyethylene glycol dimethyl ether. The flux according to this embodiment preferably further contains a glycol ether-based solvent as the other solvent. Examples of glycol ether-based solvents include diethylene glycol monohexyl ether (hexyl diglycol), diethylene glycol dibutyl ether (dibutyl diglycol), diethylene glycol mono-2-ethylhexyl ether (2-ethylhexyl diglycol), diethylene glycol monobutyl ether (butyl diglycol), triethylene glycol monobutyl ether (butyl triglycol), tripropylene glycol monobutyl ether ([2-(2-butoxymethylethoxy)methylethoxy]propanol), and triethylene glycol butyl methyl ether (1-[2-[2-(2-methoxyethoxy)ethoxy]ethoxy]butane). Among these, the glycol ether-based solvent is preferably at least one selected from diethylene glycol monohexyl ether (hexyl diglycol), diethylene glycol mono 2-ethylhexyl ether (2-ethylhexyl diglycol), triethylene glycol monobutyl ether (butyl triglycol), and tripropylene glycol monobutyl ether ([2-(2-butoxymethylethoxy)methylethoxy]propanol), and more preferably diethylene glycol monohexyl ether (hexyl diglycol) or tripropylene glycol monobutyl ether. In one aspect of the flux according to this embodiment, the solvent preferably consists of polyethylene glycol dimethyl ether and a glycol ether-based solvent.

[0026] The flux according to this embodiment may further use, as other solvents, known solvents such as aliphatic compounds such as n-hexane, isohexane, and n-heptane; esters such as isopropyl acetate, methyl propionate, and ethyl propionate; ketones such as methyl ethyl ketone, methyl-n-propyl ketone, and diethyl ketone; and alcohols such as ethanol, n-propanol, isopropanol, and isobutanol. The solvents may be used alone or in combination of two or more.

[0027] The content of the other solvents is preferably 5.0% by mass or more, more preferably 9.0% by mass or more, based on the total weight of the flux. The content of the other solvents is preferably 20.0% by mass or less, more preferably 15.0% by mass or less, based on the total weight of the flux. When two or more types of other solvents are contained, the above content is the total content of the other solvents.

[0028] (resin) The flux according to this embodiment may contain a resin. Examples of the resin include a rosin-based resin and a synthetic resin. The rosin-based resin is not particularly limited, and for example, one or more rosin-based resins selected from rosin and rosin derivatives (e.g., hydrogenated rosin, polymerized rosin, disproportionated rosin, acrylic acid-modified rosin, etc.) can be used. The synthetic resin is also not particularly limited, and known synthetic resins can be used. Note that one type of resin may be used alone, or two or more types may be used in combination.

[0029] The resin content is preferably 30.0% by mass or more, and more preferably 40.0% by mass or more, based on the total weight of the flux. The resin content is preferably 70.0% by mass or less, and more preferably 50.0% by mass or less, based on the total weight of the flux. When two or more types of resins are contained, the above content is the total resin content.

[0030] (thixotropic agent) The flux according to the present embodiment may further contain a thixotropic agent to further enhance the thixotropy of the flux. Examples of thixotropic agents include castor oil, fatty acid amides, fatty acid bisamides, polyamide compounds, kaolin, colloidal silica, organic bentonite, and glass frit. Among these, fatty acid bisamides or polyamide compounds are preferred from the viewpoint of heat resistance. Examples of fatty acid amides include stearic acid amide, lauric acid amide, palmitic acid amide, oleic acid amide, erucic acid amide, behenic acid amide, myristic acid amide, and N-hydroxyethyl-12-stearyl amide. Examples of fatty acid bisamides include methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene bis-12-hydroxystearic acid amide, N,N'-distearyl adipic acid amide, and N,N'-xylylene bis-12-hydroxystearyl amide. Examples of polyamide compounds include aliphatic polyamide compounds such as VA-79, AMX-6096A, WH-215, and WH-255 (all manufactured by Kyoeisha Chemical Co., Ltd.), SP-10 and SP-500 (all manufactured by Toray Industries, Inc.), Grilamid L20G and Grilamid TR55 (all manufactured by MSC Japan), and aromatic polyamide compounds (semi-aromatic polyamide compounds or fully aromatic polyamide compounds) containing cyclic compounds such as benzene rings and naphthalene rings in the main chain, such as JH-180 (manufactured by Ito Oil Mills). Thixotropic agents may be used singly or in combination of two or more.

[0031] The content of the thixotropic agent is preferably 1.0 mass% or more, more preferably 3.0 mass% or more, based on the total mass of the flux. Furthermore, the content of the thixotropic agent is preferably 7.0 mass% or less, more preferably 5.0 mass% or less, based on the total mass of the flux. When two or more thixotropic agents are contained, the above content is the total content of the thixotropic agents.

[0032] (activator) The flux according to this embodiment may contain an activator. The activator is not particularly limited, and examples thereof include organic acid activators, amine compounds, amino acid compounds, and halogen-based activators such as amine halogen salts and halogen compounds. The activators may be used alone or in combination of two or more.

[0033] The organic acid surfactant is not particularly limited, and examples thereof include monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, capric acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, tuberculostearic acid, arachidic acid, behenic acid, lignoceric acid, and glycolic acid; dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, methylsuccinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, tartaric acid, and diglycolic acid; and other organic acids such as dimer acid, levulinic acid, lactic acid, acrylic acid, benzoic acid, salicylic acid, anisic acid, citric acid, picolinic acid, tris(2-carboxyethyl)isocyanuric acid, and tris(2-carboxypropyl)isocyanuric acid.

[0034] The amine compound is not particularly limited, and examples thereof include tetraacetylethylenediamine (N,N,N',N'-tetraacetylethylenediamine), N-acetylimidazole, N-acetylphthalimide, acetamidobenzoic acid (3-acetamidobenzoic acid, 4-acetamidobenzoic acid), N-acetylanthranilic acid, acetamidonitrobenzoic acid (2-acetamido-6-nitrobenzoic acid, 3-acetamido-4-nitrobenzoic acid, 3-acetamido-2-nitrobenzoic acid, 5-acetamido-2-nitrobenzoic acid), and the like.

[0035] The amino acid compound is not particularly limited, and examples thereof include N-acetylphenylalanine (N-acetyl-L-phenylalanine, N-acetyl-DL-phenylalanine, N-acetyl-D-phenylalanine), N-acetylglutamic acid (N-acetyl-L-glutamic acid), N-acetylglycine, N-acetylleucine (N-acetyl-L-leucine, N-acetyl-DL-leucine, N-acetyl-D-leucine), and N-acetylphenylglycine (N-acetyl-N-phenylglycine, N-acetyl-L-phenylglycine, N-acetyl-DL-phenylglycine).

[0036] Examples of amines in the amine halogen salts include diethylamine, dibutylamine, tributylamine, diphenylguanidine, and cyclohexylamine. Examples of halogens in the amine halogen salts include fluorine, chlorine, bromine, and iodine. Examples of halogen compounds include tris(2,3-dibromopropyl)isocyanuric acid, 2,3-dibromo-2-butene-1,4-diol, 2-bromo-3-iodo-2-butene-1,4-diol, and TBA-bis(2,3-dibromopropyl ether).

[0037] The content of the activator is preferably 0.5% by mass or more, more preferably 3.0% by mass or more, based on the total weight of the flux. The content of the activator is preferably 20.0% by mass or less, more preferably 10.0% by mass or less, based on the total weight of the flux. When a halogen-based activator is included as the activator, its content is preferably 0.1% by mass or less, from the viewpoint of environmental load. When two or more activators are included, the above content is the total content of the activators.

[0038] The flux according to the present embodiment may contain at least one other additive selected from the group consisting of a stabilizer, a surfactant, an antifoaming agent, and a corrosion inhibitor. The total content of the other additives is not particularly limited and may be, for example, 5.0 mass % or less with respect to the total amount of the flux.

[0039] The flux according to this embodiment contains a solvent containing at least one selected from tetraethylene glycol dimethyl ether and polyethylene glycol dimethyl ether, and the content of this solvent is 35.0% by mass or more and 55.0% by mass or less of the total flux. This makes the flux resistant to drying even when left for a certain period of time, and also suppresses an increase in adhesiveness, making it less likely for the solder paste to adhere to the openings of the metal mask after screen printing, and furthermore, less likely to cause clogging. As a result, the flux can improve the intermittent printability of the solder paste without the need for operations such as washing off the solder paste.

[0040] In the flux according to this embodiment, the content of at least one selected from tetraethylene glycol dimethyl ether and polyethylene glycol dimethyl ether is 40.0% by mass to 47.0% by mass of the entire flux, so that the solder paste is less likely to adhere to the openings of the metal mask after screen printing and is less likely to clog, thereby improving the intermittent printability of the solder paste.

[0041] <Solder paste> The solder paste according to this embodiment contains the above-mentioned flux and solder alloy powder. The solder paste is obtained by mixing the flux and the solder alloy powder. The content of the flux is preferably 5 to 20 mass % of the entire solder paste. Furthermore, the content of the solder alloy powder is preferably 80 to 95 mass % of the entire solder paste.

[0042] The particle size of the solder alloy powder is preferably 5 μm or more and 40 μm or less, and more preferably 15 μm or more and 28 μm or less.

[0043] Examples of the alloy of the solder alloy powder include lead-free solder alloys and lead-containing eutectic solder alloys. However, from the viewpoint of reducing environmental impact, lead-free solder alloys are preferred. Examples of lead-free solder alloys include alloys containing tin, silver, copper, indium, zinc, bismuth, antimony, etc. More specifically, examples include alloys such as Sn / Ag, Sn / Ag / Cu, Sn / Cu, Sn / Ag / Bi, Sn / Bi, Sn / Ag / Cu / Bi, Sn / Sb, Sn / Zn / Bi, Sn / Zn, Sn / Zn / Al, Sn / Ag / Bi / In, Sn / Ag / Cu / Bi / In / Sb, and In / Ag. Among these, the alloy of the solder alloy powder is preferably a Sn / Ag / Cu alloy. Furthermore, it is more preferable that the Sn / Ag / Cu alloy further contains at least one element selected from In, Bi, Sb, and Ni. The alloy also contains unavoidable impurities, which are components that are inevitably mixed in during the manufacturing process and are acceptable to the extent that they do not affect the effects of the present invention.

[0044] The solder paste according to this embodiment contains the above-described flux and a solder alloy powder. The flux is resistant to drying even when left for a certain period of time and also suppresses an increase in adhesiveness, so that the solder paste is less likely to adhere to the openings of the metal mask after screen printing and is less likely to clog. As a result, the solder paste can improve intermittent printability without the need for washing off or other operations.

[0045] The solder paste according to this embodiment has a particle diameter of the solder alloy powder of 5 μm or more and 40 μm or less, and therefore has good workability and improved intermittent printability in a wide range of applications, from solder pastes for general use to solder pastes for fine printing.

[0046] In the solder paste according to this embodiment, the alloy of the solder alloy powder may be a Sn / Ag / Cu alloy, which can provide good workability and improved intermittent printability even for the widely used Sn / Ag / Cu alloy.

[0047] In the solder paste according to this embodiment, the Sn / Ag / Cu alloy may further contain at least one element selected from the group consisting of In, Bi, Sb, and Ni. Even if these metal elements are added to improve the thermal durability of the solder alloy, the solder paste can still have good workability and improve intermittent printability. [Example]

[0048] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0049] <Preparing solder paste> The resin, solvent, thixotropic agent, activator, and antioxidant in the amounts shown in Table 1 were placed in a heating container and heated to 180°C to obtain a varnish component. The varnish component and other components were then mixed at room temperature to obtain a uniformly dispersed flux. The amounts shown in Table 1 are equal to the contents of the respective components in the flux. Next, 11.8 mass% of each flux and 88.2 mass% of the solder alloy powder shown in Table 1 were mixed to obtain a solder paste for each Example and Comparative Example.

[0050] [Table 1]

[0051] Details of each raw material contained in the flux shown in Table 1 are shown in Table 2. Details of the solder alloys shown in Table 1 are shown in Table 3.

[0052] [Table 2]

[0053] [Table 3]

[0054] <Evaluation of intermittent printing> fruit Example 14~17, Reference examples 1~13 300 g of the solder paste of each comparative example was placed on a metal mask set in a printing machine (YVP-Xg, manufactured by Yamaha Motor Co.), and rolling was performed four times to allow the solder paste to blend into the metal mask. The back of the metal mask was then dry cleaned, and the first printing was performed under the printing conditions described below. The mask was then left to stand for 60 minutes in an environment with a temperature of 24 to 26°C and a humidity of 50 to 60% RH, and the back of the metal mask was then dry cleaned, and the second printing was performed under the printing conditions described below. The first printing was performed on two sheets, and the transfer rate was evaluated for the first sheet.

[0055] (Printing conditions) Printing squeegee: Metal squeegee Squeegee angle: 60° Metal mask thickness: 120 μm Printing speed: 40mm / sec Pad shape: Circle (0.25mmφ) or Square (0.25mm x 0.25mm) Number of pads: 50 Pad material: OSP treated copper

[0056] (Evaluation of transcription rate) The solder transfer rate was calculated by detecting the solder on the copper pads of each printed board using a KOHYOUNG aSPIer and determining the volume percentage. The average volume percentage for 50 pads is shown in Table 1.

[0057] Furthermore, if even one pad was judged to have a volume percentage of less than 10%, it was deemed to have a removal defect. The results are shown in Table 1.

[0058] Based on the average volume % and the results of removal failure, a rating of A to E was given according to the criteria in Table 4. The results are shown in Table 1. Solder pastes rated A to C were considered to be passable, and solder pastes rated D and E were considered to be failable.

[0059] [Table 4]

[0060] As can be seen from the results in Table 1, all the requirements of the present invention are met. Sumi Example 14~17 The solder paste of Example 1 has an average volume percentage of 65% or more after 60 minutes of printing, and there are no defects in the printing, showing excellent intermittent printing properties.

[0061] On the other hand, the solder pastes of Comparative Examples 1, 3, and 4, which do not contain tetraethylene glycol dimethyl ether or polyethylene glycol dimethyl ether, and Comparative Example 2, which has a polyethylene glycol dimethyl ether content of less than 35.0 mass%, have an average volume percentage of less than 65% after 60 minutes of printing for pad shapes of ○ and □, and also have poor printability, indicating that they have poor intermittent printability.

Claims

1. A flux used in soldering, A solvent containing polyethylene glycol dimethyl ether and not containing tetraethylene glycol dimethyl ether, the content of the polyethylene glycol dimethyl ether is 35.0 mass% or more and 55.0 mass% or less with respect to the entire flux, the solvent further contains a glycol ether solvent other than tetraethylene glycol dimethyl ether and other than polyethylene glycol dimethyl ether, A flux, wherein the content of the glycol ether solvent other than tetraethylene glycol dimethyl ether and other than polyethylene glycol dimethyl ether is 9.0 mass % or more and 20.0 mass % or less with respect to the entire flux.

2. A solder paste comprising the flux according to claim 1 and a solder alloy powder.

3. 3. The solder paste according to claim 2, wherein the particle diameter of the solder alloy powder is 5 μm or more and 40 μm or less.

4. 4. The solder paste according to claim 2, wherein the alloy of the solder alloy powder is a Sn / Ag / Cu alloy.

5. 5. The solder paste according to claim 4, wherein the Sn / Ag / Cu alloy further contains at least one element selected from the group consisting of In, Bi, Sb, and Ni.

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