Method for manufacturing electronic component mounting substrate, set of solder paste and flux, and flux

Abstract

The disclosed manufacturing method includes: a solder precoat formation step in which, after a solder paste is applied to a plurality of lands of a substrate, the solder paste is heated and melted so that a plurality of solder precoats in which the surfaces of the respective lands are covered by a coat layer are formed on the plurality of lands; a flux application step in which a flux is applied to the coat layers; an electronic component placement step in which terminals of a plurality of electronic components are placed on the plurality of solder precoats with the coat layers and the flux interposed therebetween; and a soldering step in which the plurality of electronic components are soldered to the plurality of lands by melting the plurality of solder precoats. The coat layers comprise residue of the solder paste. A first rosin-based resin in the solder paste and a second rosin-based resin in the flux are identical. A first solvent in the solder paste and a second solvent in the flux are identical.

Description

Manufacturing method of electronic component mounting board, set of solder paste and flux, and flux

[0001] The present disclosure relates to a method for manufacturing an electronic component mounting board, a set of solder paste and flux, and the flux.

[0002] The reflow soldering method is known as a method for soldering electronic components to a substrate. In the reflow soldering method, solder paste is first applied to lands on the substrate, and the electronic components are then mounted on the solder paste. The substrate is then heated to melt the solder paste, thereby soldering the electronic components to the substrate. In recent years, the miniaturization of electronic devices has led to an increasing demand for miniaturized electronic components and for multiple electronic components to be soldered to a substrate at close intervals (close-neighbor mounting). To meet these demands, the adoption of reflow soldering using a solder precoat for mass production has been considered (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2023-015554

[0004] Patent Document 1 (JP 2023-015554 A) discloses a "printed precoat method" as a method for forming a solder precoat at low cost, in which solder paste is supplied to a land on a substrate and reflowed. When mass-producing mounted substrates using solder precoats made by the printed precoat method, it is necessary to further reduce the rate of soldering defects and further increase yield. One of the purposes of this disclosure is to provide a method for manufacturing an electronic component mounted substrate that can suppress the occurrence of defects.

[0005] One aspect of the present disclosure is a first method for manufacturing an electronic component mounting board, the method comprising: a solder precoat forming step of applying solder paste to a plurality of lands of a board and then heating and melting the solder paste to form a plurality of solder precoats on the lands, each of whose surfaces is covered with a coating layer; a flux applying step of applying flux to the coating layer; an electronic component arranging step of arranging terminals of a plurality of electronic components on the plurality of solder precoats via the coating layer and the flux; and a soldering step of melting the plurality of solder precoats to solder the plurality of electronic components to the lands, wherein the coating layer is made of a residue of the solder paste; the solder paste includes a first rosin-based resin, a first solvent, a first activator, a first thixotropic agent, and solder particles; the flux includes a second rosin-based resin, a second solvent, a second activator, and a second thixotropic agent; The present invention relates to a first method for manufacturing an electronic component mounting substrate, wherein the first rosin resin and the second rosin resin are the same, and the first solvent and the second solvent are the same.

[0006] Another aspect of the present disclosure relates to a second manufacturing method for an electronic component mounting substrate, the second manufacturing method including: a solder precoat forming step of applying solder paste to a plurality of lands of a substrate and then heating and melting the solder paste to form a plurality of solder precoats on the lands, each of whose surfaces is covered with a coating layer; a flux application step of applying flux to the coating layer; an electronic component placement step of arranging terminals of a plurality of electronic components on the plurality of solder precoats via the coating layer and the flux; and a soldering step of melting the plurality of solder precoats to solder the plurality of electronic components to the lands, wherein the solder paste includes solder particles, the coating layer is made of a residue of the solder paste, and all of the constituent components of the solder paste except for the solder particles are the same as all of the constituent components of the flux.

[0007] Another aspect of the present disclosure relates to a set of solder paste and flux used in a first manufacturing method of an electronic component mounting board according to the present disclosure, wherein the solder paste includes a first rosin-based resin, a first solvent, a first activator, a first thixotropic agent, and solder particles; the flux includes a second rosin-based resin, a second solvent, a second activator, and a second thixotropic agent; the first rosin-based resin and the second rosin-based resin are the same; and the first solvent and the second solvent are the same.

[0008] Another aspect of the present disclosure relates to a set of a solder paste and a flux used in a second manufacturing method of an electronic component mounting board according to the present disclosure, wherein the solder paste contains solder particles, and all of the components of the solder paste except for the solder particles are the same as all of the components of the flux.

[0009] Another aspect of the present disclosure relates to a flux used in combination with a solder paste used in a first manufacturing method for an electronic component mounting board according to the present disclosure, wherein the solder paste includes a first rosin-based resin, a first solvent, a first activator, a first thixotropic agent, and solder particles; the flux includes a second rosin-based resin, a second solvent, a second activator, and a second thixotropic agent; the second rosin-based resin is the same as the first rosin-based resin contained in the solder paste; and the second solvent is the same as the first solvent contained in the solder paste.

[0010] Another aspect of the present disclosure relates to a flux used in combination with a solder paste used in the second manufacturing method of an electronic component mounting board according to the present disclosure, wherein all of the components of the flux are the same as all of the components of the solder paste except for solder particles.

[0011] According to the present disclosure, defects can be reduced when manufacturing electronic component mounting boards. The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings.

[0012] 1B is a cross-sectional view schematically showing an example of a step of an example of a manufacturing method according to the present embodiment; FIG. 1C is a cross-sectional view schematically showing an example of a step following the step of FIG. 1D; FIG. 1D is a cross-sectional view schematically showing an example of a step following the step of FIG. 1A; FIG. 1B is a cross-sectional view schematically showing an example of a step following the step of FIG. 1C; and FIG. 1D is a cross-sectional view schematically showing an example of a step following the step of FIG.

[0013] The following describes embodiments of the present disclosure using examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values ​​and materials may be applied as long as the effects of the present disclosure are obtained. In this specification, the term "numerical value A to numerical value B" includes numerical value A and numerical value B and can be read as "numerical value A or greater and numerical value B or less." In the following description, when lower and upper limits for specific physical properties or conditions are exemplified, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not greater than the upper limit. In the following description, when examples of components or methods are listed, only one of the listed examples may be used, or multiple of the listed examples may be used in combination, unless otherwise specified.

[0014] (Method for manufacturing an electronic component mounting board) Hereinafter, the manufacturing method according to this embodiment may be referred to as "manufacturing method (M)." The manufacturing method (M) is a method for manufacturing an electronic component mounting board. The electronic component mounting board includes a substrate and electronic components mounted on the substrate. The substrate has a plurality of lands. In the electronic component mounting board, at least some of the electronic components are soldered to the lands.

[0015] The manufacturing method (M) includes a solder precoat forming step of applying solder paste to a plurality of lands of a substrate and then heating and melting the solder paste to form a plurality of solder precoats on the plurality of lands, each of whose surface is covered with a coating layer, a flux application step of applying flux to the coating layer, an electronic component placement step of arranging terminals of a plurality of electronic components on the plurality of solder precoats via the coating layer and the flux, and a soldering step of soldering the plurality of electronic components to the plurality of lands by melting the plurality of solder precoats. The flux applied in the flux application step will hereinafter be referred to as "flux (F)."

[0016] The coating layer is made of solder paste residue. The solder paste includes a first rosin-based resin, a first solvent, a first activator, a first thixotropic agent, and solder particles. The flux (F) includes a second rosin-based resin, a second solvent, a second activator, and a second thixotropic agent. The first rosin-based resin and the second rosin-based resin are the same. In other words, the rosin-based resin contained in the solder paste and the rosin-based resin contained in the flux (F) are the same. The first solvent and the second solvent are the same. In other words, the solvent contained in the solder paste and the solvent contained in the flux (F) are the same.

[0017] The first rosin-based resin, first solvent, first activator, first thixotropic agent, second rosin-based resin, second solvent, second activator, and second thixotropic agent may each be composed of only one type of compound or multiple types of compounds. When the first rosin-based resin is composed of multiple types of compounds, the second rosin-based resin is composed of those multiple types of compounds. When the first solvent is composed of multiple types of compounds, the second solvent is composed of those multiple types of compounds.

[0018] When the solder precoat is formed, a coating layer covering the solder precoat is formed. This coating layer is a residue of the solder paste. That is, the coating layer is formed by components of the solder paste used to form the solder precoat, other than the solder particles. Hereinafter, the components of the solder paste other than the solder particles may be referred to as "flux components of the solder paste." Usually, the layer of solder paste residue is removed by cleaning. However, in manufacturing method (M), the coating layer made of the residue is used as it is as an oxidation prevention film.

[0019] Electronic components are currently being miniaturized. As the miniaturization of electronic components reduces their mass, soldering using the reflow process becomes significantly more difficult than before. For example, if the flux does not function properly during reflow, soldering defects are more likely to occur.

[0020] In manufacturing method (M), flux is placed on the solder paste residue. After further investigation, the present inventors discovered that, as electronic components become increasingly miniaturized, conventional combinations of solder paste and flux can easily result in defects. For example, if the rosin-based resin in the solder paste is different from the rosin-based resin in the flux, and if the solvent in the solder paste is different from the solvent in the flux, the compatibility between the coating layer (solder paste residue) and the flux decreases. As a result, the consistency of the flux decreases during reflow, which tends to hinder the electronic component from approaching the solder. Furthermore, while flux residue needs to be cleaned after soldering the electronic component, insufficient cleaning of the flux residue can result in a problem of reduced quality of the substrate encapsulation by the encapsulation resin. Flux residue residue is particularly likely to occur as electronic components become increasingly miniaturized. The present disclosure is based on these new findings.

[0021] Conventionally, solder paste and flux materials have been prepared from different materials to optimize their performance. However, if the solder paste material and the flux material are different, the above-mentioned problems may occur. Therefore, in manufacturing method (M), the same compound is used for the rosin-based resin of the solder paste and the rosin-based resin of the flux, and the same compound is used for the solvent of the solder paste and the solvent of the flux. By using the same materials, the above-mentioned problems can be prevented. As a result, the occurrence of defects in electronic component mounting boards can be significantly reduced.

[0022] (Solder Precoat Forming Process) In the solder precoat forming process, solder paste is applied to multiple lands on the substrate, and then the solder paste is heated and melted, thereby forming multiple solder precoats on the multiple lands, each of whose surfaces is covered with a coating layer. The solder precoat forming process may be performed in the following manner. In the solder precoat forming process, first, solder paste is applied to multiple lands on the substrate. The method for applying the solder paste is not limited, and a known method (e.g., screen printing) may be used. Next, the applied solder paste is heated to melt it, and then cooled and solidified. In this manner, the solder precoat is formed. The solder paste may be melted by heating the entire substrate to which the solder paste has been applied.

[0023] When the solder precoat is formed, a coating layer is also formed to cover the solder precoat. The coating layer is made of solder paste residue. That is, the coating layer is formed by components of the solder paste other than the solder particles. However, some of the components other than the solder particles may be denatured when the solder precoat is formed.

[0024] (Flux Application Step) In the flux application step, flux (solder flux) is applied to the coating layer. The flux (F) is used to ensure proper soldering in the subsequent reflow step. Furthermore, the flux (F) serves to hold the electronic component on the solder precoat until the reflow step is performed.

[0025] The method for applying the flux (F) is not limited, and known methods (e.g., screen printing) may be used. When the electronic components to be mounted are minute, the flux (F) may be applied only onto the solder precoat. This prevents the electronic components from moving from the solder precoat. In this case, the through-holes of the metal mask used for screen printing may be made smaller than the outer edge of the solder precoat. The flux (F) is applied through the through-holes.

[0026] In the manufacturing method (M), at least a part of the flux components of the solder paste and at least a part of the components of the flux (F) are the same. Each of the components will be described below.

[0027] The solder paste may contain additives other than the above-described components (first rosin resin, first solvent, first activator, first thixotropic agent, and solder particles), and the flux (F) may contain additives other than the above-described components (second rosin resin, second solvent, second activator, and second thixotropic agent).

[0028] The manufacturing method (M) satisfies the following condition (1). The manufacturing method (M) preferably satisfies the following conditions (2) and / or (3). The manufacturing method (M) may also satisfy all of the following conditions (1) to (4). (1) The first rosin resin and the second rosin resin are the same, and the first solvent and the second solvent are the same. (2) The first activator and the second activator are the same. In other words, the activator contained in the solder paste and the activator contained in the flux (F) are the same. (3) The first thixotropic agent and the second thixotropic agent are the same. In other words, the thixotropic agent contained in the solder paste and the thixotropic agent contained in the flux (F) are the same. (4) The other additives added to the solder paste (additives other than the rosin-based resin, activator, and thixotropic agent) are the same as the other additives added to the flux (F) (additives other than the rosin-based resin, activator, and thixotropic agent).

[0029] When the first rosin-based resin is composed of multiple compounds, the second rosin-based resin is composed of these multiple compounds. The same applies when condition (2) is satisfied and when condition (3) is satisfied. In an example solder paste, the first rosin-based resin, the first solvent, the first activator, and the first thixotropic agent each contain one corresponding compound. In an example flux (F), the second rosin-based resin, the second solvent, the second activator, and the second thixotropic agent each contain one corresponding compound.

[0030] Even if the first rosin-based resin and the second rosin-based resin are the same, if the first thixotropic agent and the second thixotropic agent are different and / or if the first activator and the second activator are different, unexpected reactions (e.g., polymerization reactions) are likely to occur during reflow. As a result, the consistency of the flux (F) may become too low, or cleaning of the residue may become difficult. These problems can be avoided by satisfying condition (2) and / or condition (3).

[0031] In the manufacturing method (M), all of the components of the solder paste except the solder particles may be the same as all of the components of the flux (F). That is, the compounds constituting the flux components of the solder paste may be exactly the same as the compounds constituting the flux (F).

[0032] In another aspect, the present disclosure provides a manufacturing method (M1) for manufacturing an electronic component mounting board. The manufacturing method (M1) includes a solder precoat forming step of applying solder paste to multiple lands on the board and then heating and melting the solder paste to form multiple solder precoats on the multiple lands, each of whose surfaces is covered with a coating layer; a flux application step of applying flux to the coating layer; an electronic component placement step of arranging terminals of multiple electronic components on the multiple solder precoats via the coating layer and the flux; and a soldering step of melting the multiple solder precoats to solder the multiple electronic components to the multiple lands. The solder paste includes solder particles. The coating layer is made of solder paste residue. All of the components of the solder paste, excluding the solder particles, are the same as those of the flux. The manufacturing method (M1) corresponds to an embodiment of the manufacturing method (M) in which all of the components of the solder paste, excluding the solder particles, are the same as those of the flux (F). The matters explained regarding the manufacturing method (M) are applicable to the manufacturing method (M1), so duplicated explanations will be omitted.

[0033] In this specification, the phrase "the components of the solder paste and the components of the flux (F) are the same" means that the compounds contained in these components are the same, but the content ratios of the compounds contained in the components may be different. That is, the constituent ratio of the flux components of the solder paste may be different from the constituent ratio of the components of the flux (F). For example, the proportion of the first rosin-based resin in the flux components of the solder paste may be different from the proportion of the second rosin-based resin in the flux (F).

[0034] (Electronic Component Placement Process) In the electronic component placement process, a plurality of electronic components are placed on a plurality of solder precoats via a coating layer and flux. The method for placing the electronic components is not particularly limited, and a known chip mounter may be used.

[0035] (Soldering Process) In the soldering process, multiple electronic components are soldered to multiple lands by melting multiple solder precoats. In this way, a substrate on which electronic components are mounted is manufactured. The method for performing the soldering process (reflow process) is not particularly limited, and a known reflow furnace may be used. Specifically, the substrate on which the electronic components are mounted is heated to a temperature equal to or higher than the temperature at which the solder precoats melt, thereby melting the solder precoats, and then the substrate is cooled to solidify the solder.

[0036] The size of the electronic component may be, for example, 0.4 mm long x 0.2 mm wide, 0.3 mm long x 0.15 mm wide, 0.25 mm long x 125 mm wide, 0.2 mm long x 0.1 mm wide, or 0.1 mm long x 0.5 mm wide. Here, the length and width of the electronic component refer to the length and width of the electronic component when viewed from above on the substrate. The electronic components mounted on the substrate may include electronic components of various sizes and types. The multiple electronic components mounted on the substrate may include electronic components such as JIS (Japanese Industrial Standards) 0402, 03015, 0201, and 01005. The smaller the size of the electronic component, the more likely it is that soldering defects will occur. Manufacturing method (M) is suitable for mounting fine electronic components because it can suppress soldering defects.

[0037] Manufacturing method (M) is particularly suitable for mounting multiple electronic components, including electronic components conforming to JIS (Japanese Industrial Standards) 0402 or below. JIS 0402 electronic components have a length of 0.4 mm and a width of 0.2 mm. That is, the multiple electronic components may include at least one electronic component having a length of 0.4 mm or less and a width of 0.2 mm or less. The at least one electronic component may be a chip-type electronic component having terminals on both ends in the longitudinal direction.

[0038] (Set of solder paste and flux) The set of solder paste and flux according to this embodiment may be referred to as "set (S)" below. The set (S) is used in a method for manufacturing an electronic component mounting board. Specifically, the set (S) is used in a series of steps for manufacturing one electronic component mounting board. The set (S) can be used in manufacturing method (M). The solder paste and flux (F) described in manufacturing method (M) can be used for the solder paste and flux of set (S). The matters described for the solder paste and flux (F) of manufacturing method (M) can also be applied to the solder paste and flux of set (S), so redundant explanations will be omitted. The matters described for set (S) may also be applied to manufacturing method (M).

[0039] The solder paste of set (S) includes a first rosin-based resin, a first solvent, a first activator, a first thixotropic agent, and solder particles. The flux of set (S) includes a second rosin-based resin, a second solvent, a second activator, and a second thixotropic agent. The first rosin-based resin and the second rosin-based resin are the same. The first solvent and the second solvent are the same.

[0040] As described above, set (S) satisfies the above condition (1). Set (S) preferably satisfies the above conditions (2) and / or (3). Set (S) may also satisfy all of the above conditions (1) to (4). The solder paste of set (S) can be prepared by mixing its components. The flux (flux (F)) of set (S) can be prepared by mixing its components.

[0041] All of the components of the solder paste, excluding the solder particles, may be the same as all of the components of the flux. In other words, the set (S) may be a set of the solder paste and the flux (F) used in the manufacturing method (M1).

[0042] The present disclosure provides a flux (flux (F)) to be used in combination with the solder paste used in manufacturing method (M). Furthermore, the present disclosure provides a flux (F1) to be used in combination with the solder paste used in manufacturing method (M1). Flux (F1) is a flux (F) in which all of the components of the flux are the same as all of the components of the solder paste except for the solder particles. Flux (F) has been described above, so a repeated explanation will be omitted.

[0043] The solder particles in the solder paste are not limited, and known solder particles (e.g., lead-free solder particles) can be used. The rosin-based resin, solvent, activator, and thixotropic agent used in the solder paste and flux (F) are described below.

[0044] (Rosin-based resin (first and second rosin-based resins)) Examples of rosin-based resins include natural rosins such as gum rosin and wood rosin, and derivatives thereof (polymerized rosin, hydrogenated rosin, disproportionated rosin, acid-modified rosin, rosin ester, etc.).

[0045] The flux component of the solder paste and the flux (F) may contain a resin other than a rosin-based resin, such as an organic fatty acid ester, a polyalkylene oxide-based resin, a propylene glycol fatty acid ester, or an acetylene glycol. Specific examples thereof include organic fatty acid polyglycerol esters such as polyglycerol laurate, polyglycerol stearate, polyglycerol isostearate, polyglycerol sesquistearate, polyglycerol diisostearate, polyglycerol myristate, polyglycerol palmitate, polyglycerol oleate, polyglycerol behenate, and polyglycerol caprylate; polyethylene glycol, polyethylene glycol-polypropylene glycol copolymer, polyoxyethylene alkyl ester, polyoxyethylene tallow ester, polyglycerin, glycerin fatty acid ester, polyglycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid esters; and acetylene glycols such as 2,4,7,9-tetramethyl-5-decyne-4,7-diol-ethylene oxide adduct.

[0046] Other resins that can be used besides rosin-based resins include terpene resins, terpene phenolic resins, styrene resins, xylene resins, acrylic resins, polyester resins, polyolefin resins, polyamides, polyamines, phenolic resins, phenoxy resins, and epoxy resins. Examples of terpene resins include aromatic-modified terpene resins, hydrogenated terpene resins, and hydrogenated aromatic-modified terpene resins. Examples of terpene phenolic resins include hydrogenated terpene phenolic resins. Examples of styrene resins include styrene-acrylic acid copolymers and styrene-maleic acid copolymers. Examples of xylene resins include phenol-modified xylene resins, alkylphenol-modified xylene resins, phenol-modified resol-type xylene resins, polyol-modified xylene resins, and polyoxyethylene-added xylene resins. Examples of acrylic resins include acrylic acid, methacrylic acid, various esters of acrylic acid, various esters of methacrylic acid, crotonic acid, itaconic acid, maleic acid, maleic anhydride, esters of maleic acid, esters of maleic anhydride, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, and acrylic resins obtained by copolymerizing at least one monomer selected from vinyl chloride and vinyl acetate. Examples of polyolefin resins include polyethylene and polypropylene. Examples of epoxy resins include bisphenol A epoxy resin, bisphenol F epoxy resin, and bisphenol AD ​​epoxy resin.

[0047] (Thixotropic Agent (First and Second Thixotropic Agents)) The thixotropic agent imparts thixotropy to the flux. Examples of the thixotropic agent include wax-based thixotropic agents, amide-based thixotropic agents, and sorbitol-based thixotropic agents. Examples of the wax-based thixotropic agent include castor oil. Examples of the amide-based thixotropic agents include lauric amide, palmitic amide, stearic amide, behenic amide, hydroxystearic amide, saturated fatty acid amide, oleic amide, erucic amide, unsaturated fatty acid amide, p-toluenemethane amide, aromatic amide, methylene bisstearic amide, ethylene bislauric amide, ethylene bishydroxystearic amide, saturated fatty acid bisamide, methylene bisoleic amide, unsaturated fatty acid bisamide, m-xylylene bisstearic amide, aromatic bisamide, saturated fatty acid polyamide, unsaturated fatty acid polyamide, aromatic polyamide, substituted amide, methylolstearic amide, methylol amide, and fatty acid ester amide. Examples of sorbitol-based thixotropic agents include dibenzylidene-D-sorbitol, bis(4-methylbenzylidene)-D-sorbitol, etc. One type of thixotropic agent may be used alone, or two or more types may be used in combination.

[0048] (Activators (First and Second Activators)) The activators are compounds that reduce the oxide film that covers the surface of solder used in soldering electronic components. Examples of such solder include solder pre-coats and solder applied to the terminals (component electrodes) of electronic components. Note that resins such as rosin-based resins may also have some degree of activating effect. In this specification, the term "activator" refers to compounds other than rosin-based resins.

[0049] The activator reduces the oxide film and helps form a good bond. Examples of activators with a reducing effect include organic acids, amines, and halides. One activator may be used alone, or two or more activators may be used in combination.

[0050] Examples of organic acids used as activators include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dimer acid, propionic acid, 2,2-bishydroxymethylpropionic acid, tartaric acid, malic acid, glycolic acid, diglycolic acid, thioglycolic acid, dithioglycolic acid, stearic acid, 12-hydroxystearic acid, palmitic acid, and oleic acid.

[0051] Examples of amines used as activators include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2-methylimidazole. Phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')] ]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4, 5-Dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazoline, 2,4-diamino-6-vinyl-s-triazine, 2,4-diamino-6-vinyl-s-triazine isocyanuric acid adduct, 2,4-Diamino-6-methacryloyloxyethyl-s-triazine, epoxy-imidazole adduct, 2-methylbenzimidazole, 2-octylbenzimidazole, 2-pentylbenzimidazole, 2-(1-ethylpentyl)benzimidazole, 2-nonylbenzimidazole, 2-(4-thiazolyl)benzimidazole, benzimidazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol], 6 -(2-benzotriazolyl)-4-tert-octyl-6'-tert-butyl-4'-methyl-2,2'-methylenebisphenol, 1,2,3-benzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]benzotriazole, carboxybenzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole, 2,2'-[[(methyl-1H-benzotriazol-1-yl)methyl]imino]bisethanol, 1-(1',2'-dicarboxyethyl)benzotriazole, 1-(2,3-dicarboxypropyl)benzotriazole, 1-[(2-ethylhexylamino)methyl]benzotriazole, 2,6-bis[(1H-benzotriazol-1-yl)methyl]-4-methylphenol, 5-methylbenzotriazole, 5-phenyltetrazole, and the like.

[0052] Examples of the halide used as an activator include amine hydrohalides, organic halogen compounds, etc. Examples of the amine constituting the amine hydrohalide include ethylamine, ethylenediamine, triethylamine, diphenylguanidine, ditolylguanidine, methylimidazole, 2-ethyl-4-methylimidazole, etc. Examples of the hydrogen halide include hydrogen chloride, hydrogen bromide, hydrogen iodide, etc. Examples of the organic halogen compound include trans-2,3-dibromo-2-butene-1,4-diol, triallyl isocyanurate hexabromide, 1-bromo-2-butanol, 1-bromo-2-propanol, 3-bromo-1-propanol, 3-bromo-1,2-propanediol, 1,4-dibromo-2-butanol, 1,3-dibromo-2-propanol, 2,3-dibromo-1-propanol, 2,3-dibromo-1,4-butanediol, and 2,3-dibromo-2-butene-1,4-diol.

[0053] (Solvent (First and Second Solvents)) Examples of the solvent include water, alcohol-based solvents, glycol-based solvents, ketone-based solvents, hydrocarbon-based solvents, ester-based solvents, glycol ether-based solvents, terpineols, etc. One type of solvent may be used alone, or two or more types may be used in combination.

[0054] Examples of alcohol-based solvents include isopropyl alcohol, 1,2-butanediol, isobornylcyclohexanol, 2,4-diethyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexyne-2,5-diol, 2,3-dimethyl-2,3-butanediol, 1,1,1-tris(hydroxymethyl)ethane, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 2,2'-oxybis(methylene)bis(2-ethoxymethyl)ethane, and 2,2'-oxybis(methylene)bis(2-ethoxymethyl)ethane. ethyl-1,3-propanediol), 2,2-bis(hydroxymethyl)-1,3-propanediol, 1,2,6-trihydroxyhexane, bis[2,2,2-tris(hydroxymethyl)ethyl]ether, 1-ethynyl-1-cyclohexanol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, erythritol, threitol, guaiacol glycerol ether, 3,6-dimethyl-4-octyne-3,6-diol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, and the like.

[0055] Examples of glycol solvents include ethylene glycol monomethyl ether, triethylene glycol monomethyl ether, polyethylene glycol monomethyl ether (295°C), triethylene glycol monobutyl ether, diethylene glycol monohexyl ether (hexyl carbitol), diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, diethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, diethylene glycol monobenzyl ether, diethylene glycol dibutyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monobutyl ether, propylene glycol monophenyl ether, diethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether, 2-methylpentane-2,4-diol, and triethylene glycol monobutyl ether.

[0056] Examples of ketone solvents include methyl ethyl ketone, methyl-n-propyl ketone, diethyl ketone, and cyclohexanone.

[0057] Examples of hydrocarbon solvents include normal hexane, isohexane, cyclohexane, methylcyclohexane, ethylcyclohexane, normal heptane, isoheptane, normal octane, isooctane, limonene, 2-methyl-2-butene, 2-methyl-1-pentene, 2-methyl-2-pentene, 3-ethyl-2-butene, 2,3-dimethyl-2-butene, 2,4,4-trimethyl-1-pentene, and 2,4,4-trimethyl-2-pentene.

[0058] Examples of ester-based solvents include butyl stearate, 2-ethylhexyl stearate, isotridecyl stearate, methyl oleate, isobutyl oleate, coconut fatty acid methyl ester, methyl laurate, isopropyl myristate, isopropyl palmitate, 2-ethylhexyl palmitate, and octyldodecyl myristate.

[0059] In the flux components of the solder paste, the mass ratio of the first rosin resin, the first solvent, the first activator, and the first thixotropic agent may be first rosin resin:first solvent:first activator:first thixotropic agent=0.2-0.6:0.3-0.7:0.02-0.08:0.02-0.08. In the flux (F), the mass ratio of the second rosin resin, the second solvent, the second activator, and the second thixotropic agent may be second rosin resin:second solvent:second activator:second thixotropic agent=0.5-0.7:0.2-0.4:0.02-0.08:0.02-0.08.

[0060] Examples of embodiments according to the present disclosure will be specifically described below with reference to the drawings. The embodiments described below can be modified based on the above description. The matters described below may also be applied to the above embodiments. Matters that are not essential to the embodiments according to the present disclosure may be omitted. For ease of understanding, the following figures may show components at different scales. Hatching of some components may be omitted in the following figures.

[0061] Embodiment 1 An example of the manufacturing method (M) will be described in Embodiment 1. The steps in the manufacturing method of Embodiment 1 are schematically shown in the cross-sectional views of Figures 1A to 1E.

[0062] First, as shown in Fig. 1A, a substrate 1 having a plurality of lands 2 formed on its surface is prepared. Next, as shown in Fig. 1B, a solder precoat 3 is formed on the lands 2. The solder precoat 3 can be formed using the solder paste described above. When the solder precoat 3 is formed, a coating layer 4 is formed to cover the solder precoat 3. As described above, the coating layer 4 is a residue of the solder paste.

[0063] Next, as shown in Fig. 1C, flux 5 is applied to the solder precoat 3 (more specifically, the coating layer 4). Next, as shown in Fig. 1D, a plurality of electronic components 11 are placed on the plurality of solder precoats 3 with the coating layer 4 and flux 5 interposed therebetween. The example electronic component 11 shown in Fig. 1D has terminals on both ends. The terminals are soldered to the lands 2.

[0064] Next, the solder precoat 3 is melted and then cooled (reflow process). As a result, as shown in FIG. 1E, the electronic component 11 is soldered to the land 2 by the solder 3x. In this manner, an electronic component mounting board 100 on which the electronic component 11 is mounted is manufactured. In the reflow process, the coating layer 4 and the flux 5 become residue 6. Because manufacturing method (M) suppresses unexpected reactions, the performance of the flux 5 is fully exhibited, and soldering defects are suppressed. Furthermore, because manufacturing method (M) suppresses unexpected reactions, the residue 6 can be easily removed by cleaning.

[0065] (Additional Note) The above description discloses the following techniques. (Technology 1) A method for manufacturing an electronic component mounting board, comprising: a solder precoat forming step of applying solder paste to a plurality of lands of a board and then heating and melting the solder paste to form a plurality of solder precoats on the lands, each of whose surface is covered with a coating layer; a flux applying step of applying flux to the coating layer; an electronic component arranging step of arranging terminals of a plurality of electronic components on the plurality of solder precoats via the coating layer and the flux; and a soldering step of melting the plurality of solder precoats to solder the plurality of electronic components to the lands, wherein the coating layer is made of a residue of the solder paste; the solder paste includes a first rosin-based resin, a first solvent, a first activator, a first thixotropic agent, and solder particles; the flux includes a second rosin-based resin, a second solvent, a second activator, and a second thixotropic agent; the first rosin-based resin and the second rosin-based resin are the same; A method for manufacturing an electronic component mounting substrate, wherein the first solvent and the second solvent are the same. (Technology 2) The manufacturing method according to Technology 1, wherein the first activator and the second activator are the same. (Technology 3) The manufacturing method according to Technology 1 or 2, wherein the first thixotropic agent and the second thixotropic agent are the same.(Technology 4) A method for manufacturing an electronic component mounting board, comprising: a solder precoat forming step of applying solder paste to a plurality of lands of a board and then heating and melting the solder paste to form a plurality of solder precoats on the lands, each of whose surface is covered with a coating layer; a flux application step of applying flux to the coating layer; an electronic component placement step of arranging terminals of a plurality of electronic components on the plurality of solder precoats via the coating layer and the flux; and a soldering step of melting the plurality of solder precoats to solder the plurality of electronic components to the lands, wherein the solder paste contains solder particles, the coating layer is made of residue of the solder paste, and all of the constituent components of the solder paste except for the solder particles are the same as all of the constituent components of the flux. (Technology 5) The manufacturing method according to any one of Technologies 1 to 4, wherein the plurality of electronic components includes at least one electronic component having a length of 0.4 mm or less and a width of 0.2 mm or less, and the at least one electronic component is a chip-type electronic component having terminals on both longitudinal ends. (Technology 6) A set of solder paste and flux used in the manufacturing method of an electronic component mounting board according to Technology 1, wherein the solder paste includes a first rosin-based resin, a first solvent, a first activator, a first thixotropic agent, and solder particles, and the flux includes a second rosin-based resin, a second solvent, a second activator, and a second thixotropic agent, and the first rosin-based resin and the second rosin-based resin are the same, and the first solvent and the second solvent are the same. (Technology 7) The set according to Technology 6, wherein the first activator and the second activator are the same. (Technology 8) The set according to Technology 6 or 7, wherein the first thixotropic agent and the second thixotropic agent are the same. (Technology 9) A set of solder paste and flux used in the method for manufacturing an electronic component mounting board according to Technology 4, wherein the solder paste contains solder particles, and all of the constituent components of the solder paste excluding the solder particles are the same as all of the constituent components of the flux.(Technology 10) A flux used in combination with a solder paste used in the manufacturing method of an electronic component mounting board according to Technology 1, wherein the solder paste includes a first rosin resin, a first solvent, a first activator, a first thixotropic agent, and solder particles, and the flux includes a second rosin resin, a second solvent, a second activator, and a second thixotropic agent, wherein the second rosin resin is the same as the first rosin resin contained in the solder paste, and the second solvent is the same as the first solvent contained in the solder paste. (Technology 11) The flux according to Technology 10, wherein the second activator is the same as the first activator contained in the solder paste. (Technology 12) The flux according to Technology 10 or 11, wherein the second thixotropic agent is the same as the first thixotropic agent contained in the solder paste. (Technology 13) A flux used in combination with a solder paste used in the manufacturing method of an electronic component mounting board according to Technology 4, wherein all of the components of the flux are the same as all of the components of the solder paste except for solder particles.

[0066] The present disclosure can be used for a method for manufacturing an electronic component mounting board, a solder paste and flux set, and the flux. Although the present invention has been described with reference to presently preferred embodiments, such disclosure should not be interpreted as limiting. Various modifications and alterations will undoubtedly become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. Therefore, the appended claims should be construed to cover all modifications and alterations without departing from the true spirit and scope of the present invention.

[0067] 1: Substrate 2: Land 3: Solder precoat 3x: Solder 4: Coating layer 5: Flux 6: Residue 11: Electronic component

Claims

1. A method for manufacturing an electronic component mounting board, comprising: a solder precoat forming step of applying solder paste to a plurality of lands of a board and then heating and melting the solder paste to form a plurality of solder precoats on the lands, each of whose surface is covered with a coating layer; a flux application step of applying flux to the coating layer; an electronic component placement step of arranging terminals of a plurality of electronic components on the plurality of solder precoats via the coating layer and the flux; and a soldering step of melting the plurality of solder precoats to solder the plurality of electronic components to the lands, wherein the coating layer is made of a residue of the solder paste; the solder paste includes a first rosin-based resin, a first solvent, a first activator, a first thixotropic agent, and solder particles; the flux includes a second rosin-based resin, a second solvent, a second activator, and a second thixotropic agent; the first rosin-based resin and the second rosin-based resin are the same; The method for manufacturing an electronic component mounting substrate, wherein the first solvent and the second solvent are the same.

2. The method of claim 1, wherein the first activator and the second activator are the same.

3. The manufacturing method according to claim 1 or 2, wherein the first thixotropic agent and the second thixotropic agent are the same.

4. A method for manufacturing an electronic component mounting board, comprising: a solder precoat forming step of applying solder paste to a plurality of lands of a board and then heating and melting the solder paste to form a plurality of solder precoats on the lands, each of whose surface is covered with a coating layer; a flux application step of applying flux to the coating layer; an electronic component placement step of arranging terminals of a plurality of electronic components on the plurality of solder precoats via the coating layer and the flux; and a soldering step of melting the plurality of solder precoats to solder the plurality of electronic components to the lands, wherein the solder paste contains solder particles, the coating layer is made of residue of the solder paste, and all of the constituent components of the solder paste except for the solder particles are the same as all of the constituent components of the flux.

5. The manufacturing method according to claim 1 or 4, wherein the plurality of electronic components includes at least one electronic component having a length of 0.4 mm or less and a width of 0.2 mm or less, and the at least one electronic component is a chip-type electronic component having terminals on both ends in the longitudinal direction.

6. A set of solder paste and flux used in the method for manufacturing an electronic component mounting board according to claim 1, wherein the solder paste comprises a first rosin resin, a first solvent, a first activator, a first thixotropic agent, and solder particles; the flux comprises a second rosin resin, a second solvent, a second activator, and a second thixotropic agent; the first rosin resin and the second rosin resin are the same; and the first solvent and the second solvent are the same.

7. The set of claim 6, wherein the first active agent and the second active agent are the same.

8. The set according to claim 6 or 7, wherein the first thixotropic agent and the second thixotropic agent are the same.

9. A set of solder paste and flux used in the manufacturing method of an electronic component mounting board according to claim 4, wherein the solder paste contains solder particles, and all of the constituent components of the solder paste, excluding the solder particles, are the same as all of the constituent components of the flux.

10. A flux used in combination with a solder paste used in the method for manufacturing an electronic component mounting board described in claim 1, wherein the solder paste contains a first rosin resin, a first solvent, a first activator, a first thixotropic agent, and solder particles; the flux contains a second rosin resin, a second solvent, a second activator, and a second thixotropic agent; the second rosin resin is the same as the first rosin resin contained in the solder paste; and the second solvent is the same as the first solvent contained in the solder paste.

11. The flux of claim 10, wherein the second activator is the same as the first activator contained in the solder paste.

12. The flux according to claim 10 or 11, wherein the second thixotropic agent is the same as the first thixotropic agent contained in the solder paste.

13. A flux used in combination with the solder paste used in the manufacturing method of an electronic component mounting board according to claim 4, wherein all of the constituent components of the flux are the same as all of the constituent components of the solder paste except for the solder particles.

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