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 for soldering and a solder paste containing the flux.

Background Art

[0002] In the mounting technology of mounting electronic components such as chip components and package substrates on an electronic circuit board such as a printed wiring board, a solder paste in which a solder alloy and a flux are mixed is used. Specifically, after screen-printing a solder paste using a metal mask on pads on the surface of an electronic circuit board, an electronic component is mounted and heated (reflowed), whereby the electronic component is joined to the electronic circuit board.

[0003] In recent years, with the miniaturization and high performance of electronic devices, electronic components have also been miniaturized. As a flux for improving the printability for such fine electronic components, for example, Patent Document 1 discloses a flux containing a solvent containing a higher alcohol having 12 or more and 22 or less carbon atoms and being liquid at normal temperature. Further, Patent Document 2 discloses a flux containing 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

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Screen printing may be intermittently performed at regular intervals from the perspective of workability. 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, and may even cause clogging. Therefore, when performing the next screen printing, the filling amount of the solder paste decreases, and there is a problem that printing defects are likely to occur. Although it is conceivable to wash off the solder paste adhering to the openings of the metal mask, it is not preferable because of poor workability.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a flux that is excellent in workability and can improve the intermittent printability of solder paste, and a solder paste containing the flux.

Means for Solving the Problems

[0007] The flux according to the present invention is a flux 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 at least one selected from tetraethylene glycol dimethyl ether and polyethylene glycol dimethyl ether is 35.0% by mass or more and 55.0% by mass or less with respect to the entire flux.

[0008] Due to such a configuration, the flux is difficult to dry even when left for a certain period of time, and also suppresses an increase in adhesiveness. Therefore, after screen printing, the solder paste is less likely to adhere to the openings of the metal mask, and further, clogging is less likely to occur. As a result, the flux can improve the intermittent printability of the solder paste without performing operations such as washing off the solder paste.

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

[0010] With such a configuration, after screen printing, the solder paste is less likely to adhere to the openings of the metal mask, and further, 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-based solvent.

[0012] With such a configuration, after screen printing, the solder paste is less likely to adhere to the openings of the metal mask, and further, 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-described flux and solder alloy powder.

[0014] The flux is difficult to dry even when left for a certain period of time, and in order to suppress an increase in adhesiveness, after screen printing, the solder paste is less likely to adhere to the openings of the metal mask, and further, clogging is less likely to occur. As a result, the solder paste can improve the intermittent printability without performing 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 diameter of the solder alloy powder in the solder paste is within the above range, in a wide range of applications from a generally used solder paste to a solder paste for fine printing, the workability is good and the intermittent printability can be improved.

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

[0018] The solder paste can improve the intermittent printability with good workability 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 selected from In, Bi, Sb, and Ni.

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

[0021] According to the present invention, it is possible to provide a flux that can improve the intermittent printability of the solder paste with good workability, and a solder paste containing the flux. [Embodiments for Carrying Out the Invention]

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

[0023] [Flux]

[0024] [Solvent] The flux according to the present embodiment contains at least one selected from tetraethylene glycol dimethyl ether and polyethylene glycol dimethyl ether as a solvent. The total content of at least one selected from tetraethylene glycol dimethyl ether and polyethylene glycol dimethyl ether is 35.0% by mass or more and 55.0% by mass or less, preferably 40.0% by mass or more, and preferably 47.0% by mass or less with respect to the entire flux.

[0025] The flux according to this embodiment may contain tetraethylene glycol dimethyl ether and other solvents other than polyethylene glycol dimethyl ether. The flux according to this embodiment preferably further contains a glycol ether solvent as the other solvent. Examples of the glycol ether solvent 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), triethylene glycol butyl methyl ether (1-[2-[2-(2-methoxyethoxy)ethoxy]ethoxy]butane), and the like. Among these, the glycol ether 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, the flux according to this embodiment preferably consists of polyethylene glycol dimethyl ether and a glycol ether solvent.

[0026] The flux according to this embodiment may further contain, as other solvents, 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 known solvents such as alcohols such as ethanol, n-propanol, isopropanol, and isobutanol. The solvent may be used alone or in combination of two or more.

[0027] The content of other solvents is preferably 5.0% by mass or more, more preferably 9.0% by mass or more, based on the total flux. Also, the content of other solvents is preferably 20.0% by mass or less, more preferably 15.0% by mass or less, based on the total flux. When two or more other solvents are included, the 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 rosin-based resins and synthetic resins. 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. Also, as the synthetic resin, known synthetic resins can be used without particular limitation. The resin may be used alone or in combination of two or more.

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

[0030] (Thixotropic agent) The flux according to this embodiment may further contain a thixotropic agent from the viewpoint of further enhancing the thixotropy of the flux. Examples of the thixotropic agent include castor hardened oil, fatty acid amide, fatty acid bisamide, polyamide compound, kaolin, colloidal silica, organic bentonite, glass frit, and the like. Among these, from the viewpoint of heat resistance, the thixotropic agent is preferably a fatty acid bisamide or a polyamide compound. Examples of the fatty acid amide include stearic acid amide, lauric acid amide, palmitic acid amide, oleic acid amide, erucic acid amide, behenic acid amide, myristic acid amide, N-hydroxyethyl-12-stearyl amide, and the like. Examples of the fatty acid bisamide 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, N,N'-xylylene bis-12-hydroxystearyl amide, and the like. Examples of the polyamide compound include VA-79, AMX-6096A, WH-215, WH-255 (manufactured by Kyoeisha Chemical Co., Ltd.), SP-10, SP-500 (manufactured by Toray Industries, Inc.), Grillamid L20G, Grillamid TR55 (manufactured by EMS Chemie Japan Co., Ltd.), etc., which are aliphatic polyamide compounds, and JH-180 (manufactured by Ito Oil Co., Ltd.), etc., which are aromatic polyamide compounds (semi-aromatic polyamide compounds or wholly aromatic polyamide compounds) containing cyclic compounds such as benzene rings and naphthalene rings in the main chain. The thixotropic agent may be used alone or in combination of two or more.

[0031] The content of the thixotropic agent is preferably 1.0% by mass or more, more preferably 3.0% by mass or more, based on the total amount of the flux. Also, the content of the thixotropic agent is preferably 7.0% by mass or less, more preferably 5.0% by mass or less, based on the total amount of the flux. When two or more thixotropic agents are contained, the 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-based activators, amine compounds, amino acid compounds, halogen-based activators such as amine halide salts and halogen compounds, and the like. Note that the activator may be used alone or in combination of two or more kinds.

[0033] The organic acid-based activator 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, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, tuberculostearic acid, arachidic acid, behenic acid, lignoceric acid, glycolic acid; dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, methyl succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, tartaric acid, 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, 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. For example, 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), or N-acetylphenylglycine (N-acetyl-N-phenylglycine, N-acetyl-L-phenylglycine, N-acetyl-DL-phenylglycine), etc. may be mentioned.

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

[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 amount of the flux. Also, 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 amount of the flux. Further, when the activator contains a halogen-based activator, its content is preferably 0.1% by mass or less from the viewpoint of environmental load. In addition, when two or more activators are contained, the above content is the total content of the activators.

[0038] The flux according to this embodiment may contain at least one selected from, for example, a stabilizer, a surfactant, an antifoaming agent, and a corrosion inhibitor as other additives. The total content of the other additives is not particularly limited, and for example, it can be 5.0% by mass or less based on the total amount of the flux.

[0039] The flux according to this embodiment contains a solvent including at least one selected from tetraethylene glycol dimethyl ether and polyethylene glycol dimethyl ether, and the content thereof is 35.0% by mass or more and 55.0% by mass or less with respect to the whole flux. As a result, it is difficult to dry even when left for a certain period of time, and in order to suppress an increase in adhesiveness, after screen printing, it is difficult for the solder paste to adhere to the openings of the metal mask, and furthermore, it is difficult to cause clogging. As a result, the flux can improve the intermittent printability of the solder paste without performing operations such as washing off the solder paste.

[0040] The flux according to this embodiment has a content of at least one selected from the tetraethylene glycol dimethyl ether and the polyethylene glycol dimethyl ether of 40.0% by mass or more and 47.0% by mass or less with respect to the whole flux. As a result, after screen printing, it is more difficult for the solder paste to adhere to the openings of the metal mask, and furthermore, it is more difficult to cause clogging. As a result, the flux can further improve the intermittent printability of the solder paste.

[0041] <Solder paste> The solder paste according to this embodiment contains the above-described 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% by mass with respect to the whole solder paste. Also, the content of the solder alloy powder is preferably 80 to 95% by mass with respect to the whole solder paste.

[0042] The particle diameter 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 improve workability and intermittent printability even for the widely used Sn / Ag / Cu alloy.

[0047] The solder paste according to this embodiment may further contain at least one selected from In, Bi, Sb, and Ni in the Sn / Ag / Cu alloy. Even if these metal elements are added for the purpose of improving the thermal and cold durability of the solder alloy, the solder paste can have good workability and improved intermittent printability.

Example

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

[0049] <Production of solder paste> The resin, solvent, thixotropic agent, activator, and antioxidant in the blending amounts shown in Table 1 were put into a heating container and heated to 180 °C to obtain a varnish component. Thereafter, the varnish component and other components were mixed at room temperature to obtain a flux uniformly dispersed. Note that each blending amount shown in Table 1 is equal to the content of each component contained in the flux. Next, each flux was mixed so that it became 11.8 mass% and the solder alloy powder shown in Table 1 became 88.2 mass% to obtain the solder pastes of each example and each comparative example.

[0050]

Table 1

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

[0052]

Table 2

[0053]

Table 3

[0054] <Evaluation of intermittent printing> 300 g of the solder paste of Examples 2 to 7, 9 to 13, each comparative example, and Reference Examples 1, 8, and 14 to 17 was placed on a metal mask set in a printing machine (YVP-Xg, manufactured by Yamaha Motor Co., Ltd.), and rolling was performed four times to ensure that the solder paste was applied to 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. 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 defect in removal. 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 pass, and solder pastes rated D and E were considered to be fail.

[0059] [Table 4]

[0060] As can be seen from the results in Table 1, the solder pastes of Examples 2 to 7 and 9 to 13 that satisfy all the requirements of the present invention have an average volume % in printing after 60 minutes of 65% or more and have no missing defects, indicating excellent intermittent printability.

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

Claims

Claim 1 A flux used for soldering, containing a solvent containing polyethylene glycol dimethyl ether, wherein the content of polyethylene glycol dimethyl ether is 40.0% by mass or more and 47.0% by mass or less based on the total flux. Claim 2 A solder paste containing the flux according to Claim 1 and solder alloy powder. Claim 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. Claim 4 The solder paste according to Claim 2 or 3, wherein the alloy of the solder alloy powder is a Sn / Ag / Cu alloy. Claim 5 The solder paste according to Claim 4, wherein the Sn / Ag / Cu alloy further contains at least one selected from In, Bi, Sb, and Ni.

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