JP6566248B2 - Flux for lead-free solder for clearance resist and lead-free solder paste for clearance resist - Google Patents

Description

  The present invention relates to a flux used for a lead-free solder paste applied to an electrode on a clearance resist structure substrate, and a lead-free solder paste using the flux.

  The soldering flux is a material used when surface mounting electronic parts such as ICs, capacitors and resistors on a printed circuit board. In surface mounting, solder paste is supplied to the electrode (land) on the printed circuit board by, for example, screen printing or a dispenser, an electronic component is placed thereon, and then the printed circuit board is reflowed to a temperature higher than the melting point of the solder metal. Thus, a mounting substrate is obtained.

  In recent years, as electrical appliances have become smaller and the electrode pattern on the printed circuit board has become finer, the printed circuit board has been improved from the conventional overresist structure (Figs. 2 and 3) from the viewpoint of suppressing chip standing of components and improving bonding strength. It is shifting to a resist structure (FIGS. 4 and 5). For example, Patent Document 1 details both structures.

  However, unlike the over resist structure substrate, the clearance resist structure substrate does not have a weir made of a solder resist on the periphery of the electrode on the substrate, as can be understood from FIG. Therefore, as shown in FIG. 6, the liquid flux easily flows out of the electrode from the solder paste applied on the electrode under reflow heating. As a result, more solder powder comes into contact with the outside air, and oxidation is promoted. As a result, the molten solder metal has poor wetting, and unmelted coarse solder particles remain mainly on the periphery of the electrode. Such a mechanism is described in detail in, for example, Patent Document 2.

  Such a problem of wetting failure occurs remarkably in lead-free solder metals (Sn—Ag—Cu type, Sn—Cu type, etc.). This is because the lead-free solder metal has a higher melting point than the conventional mainstream lead eutectic solder metal (Sn—Pb, etc.), so that the reflow temperature must be set high, resulting in strong oxidation. . For this reason, reflow is usually performed under nitrogen. However, in recent years, reflow has been performed in an air atmosphere in consideration of manufacturing costs, and the problem of poor wetting has become more serious.

  Therefore, the present inventor proposed in the prior application (Patent Document 3) a flux that can improve the wettability of the lead-free solder metal on the electrode on the clearance resist even in an air atmosphere. However, it was later found that the solder paste using this flux tends to thicken with time during storage and has a problem in storage stability.

JP 2003-249747 A JP 2010-212318 A JP 2014-195830 A

  The main problem of the present invention is to provide a flux that improves the storage stability of a lead-free solder paste and can improve the wettability of lead-free solder metal on a clearance resist substrate electrode even in an air atmosphere. It is in.

  Another object of the present invention is to provide a lead-free solder paste that has good storage stability and that hardly generates unmelted solder even when soldered on a clearance resist substrate electrode.

  As a result of intensive studies, the present inventors have found that the above problems can be solved by a flux containing a predetermined base resin, a solvent and an activator, and have completed the present invention.

  That is, the present invention is a flux for a lead-free solder paste for a clearance resist containing a base resin (A), a solvent (B) and an activator (C), wherein the component (A) contains a polymerized rosin (a1), B) component includes propylene glycol ether (b1) having a boiling point of 275 ° C. or less, and component (C) is represented by the general formula (1): HOOC-R—COOH (wherein R is a hydrocarbon group having 2 to 4 carbon atoms) And a lead-free solder paste for a clearance resist containing the flux and a lead-free solder powder.

  The lead-free solder paste obtained by using the flux of the present invention is excellent in viscosity stability even when stored for a long time (hereinafter also simply referred to as storage stability). Moreover, the paste is excellent in sufficient wettability (hereinafter also simply referred to as wettability) of the lead-free solder metal in the electrode on the clearance resist even in an air atmosphere.

  Furthermore, the flux of the present invention and the lead-free solder paste obtained using the same are excellent in heat resistance, and the wettability of the lead-free solder metal is good even if the preheating time of the reflow furnace is increased. Therefore, solderability is improved even when a large substrate is used that is generally difficult to transfer heat to the inside.

  Further, the flux of the present invention is suitable for non-cleaning type mounting boards because it is not particularly necessary to clean and remove residues generated after soldering. Moreover, the lead-free solder paste obtained by using the flux of the present invention is excellent in screen printing suitability.

It is the graph which showed the reflow temperature profile in an Example and a comparative example. It is a schematic diagram (cross-sectional view) of an overresist structure substrate. A top view of the electrode on the actual over-resist structure substrate (left photo) and a state diagram (right photo) when the lead-free solder paste of Comparative Example 1 is melted on the electrode under the reflow temperature condition of the standard profile is there. In this case, since the flux outflow from the lead-free solder paste is suppressed by the over resist structure, unmelted solder does not occur. It is a schematic diagram (cross section) of a clearance resist structure substrate. The top view of the electrode on the actual clearance resist structure substrate (left photo) and the state diagram (right photo) when the lead-free solder paste of Comparative Example 1 is melted on such an electrode under the reflow temperature condition of the standard profile is there. Many unmelted particles are observed in the clearance resist structure. FIG. 5 is a schematic diagram illustrating a state in which when a solder paste placed on an electrode is reflow-heated, a liquid flux easily flows out of the electrode and leaves unmelted solder particles. FIG. 6 is a state diagram (photograph) when the lead-free solder paste according to Example 1 is melted on an electrode having an actual over resist structure. It can be confirmed that there is no unmelted solder in both the reflow temperature condition of the standard profile and the reflow temperature condition in which the preheating time is further increased by 20 seconds for the purpose of the heat resistance test. FIG. 6 is a state diagram (photograph) when the lead-free solder paste according to Example 1 is melted on an electrode having an actual clearance resist structure. It can be confirmed that there is no unmelted solder in both the reflow temperature condition of the standard profile and the reflow temperature condition in which the preheating time is further increased by 20 seconds for the purpose of the heat resistance test.

  The flux according to the present invention comprises a base resin (A) (hereinafter also referred to as component (A)), a solvent (B) (hereinafter also referred to as component (B)) and an activator (C) (hereinafter referred to as (C (Also referred to as a component)), and a flux for a lead-free solder paste for clearance resist (hereinafter also referred to simply as a flux), wherein the component (A) is also referred to as a polymerized rosin (a1) (hereinafter also referred to as a component (a1)). ), The component (B) includes a propylene glycol ether (b1) having a boiling point of 275 ° C. or less (hereinafter also referred to as the component (b1)), and the component (C) is represented by the general formula (1): HOOC-R— It is a composition containing dibasic acid (c1) (hereinafter also referred to as component (c1)) represented by COOH (wherein R represents a hydrocarbon group having 2 to 4 carbon atoms).

  As the component (a1), which is an essential requirement for the component (A), various known polymerized rosins can be used. Examples of the raw material rosin serving as the precursor include natural rosins such as gum rosin, wood rosin and tall oil rosin, and purified products thereof (hereinafter also referred to as purified rosin). The physical properties of the component (a1) are not particularly limited, but from the viewpoints of storage stability, wettability, and particularly heat resistance, the softening point is usually about 130 to 160 ° C., and the acid value is usually 130 to 160 mgKOH / g. What is about is preferable.

  In addition, from the viewpoint of improving the wettability, the component (A) is further provided as other rosin-based base resins, such as hydrogenated rosin (a2) (hereinafter also referred to as component (a2)), disproportionated rosin ( a3) (hereinafter also referred to as component (a3)) and α, β-unsaturated carboxylic acid-modified rosin (a4) (hereinafter also referred to as component (a4)) may be included. .

  Examples of the component (a2) include those obtained by hydrogenating the raw material rosin by various known methods. The hydrogenation method is not limited, and various known methods can be employed. Usually, the raw material rosin may be hydrogenated at about 0.1 to 30 MPa using a hydrogenation catalyst as necessary in the presence of various hydrogen sources. Examples of the hydrogen source include hydrogen gas and lithium aluminum hydride. Moreover, Raney nickel, palladium carbon, etc. are mentioned as this hydrogenation catalyst. The physical properties of the component (a2) are not particularly limited, but from the viewpoints of storage stability, wettability, heat resistance, etc., the softening point is usually about 80 to 120 ° C., and the acid value is usually about 150 to 190 mgKOH / g. It is.

  Examples of the component (a3) include those obtained by disproportionating the raw material rosin by various known methods. Various known methods can be adopted for disproportionation. Usually, the reaction can be carried out at normal pressure using a disproportionation catalyst in the presence of various hydrogen sources. Examples of the disproportionation catalyst include palladium, rhodium and platinum. The physical properties of the component (a3) are not particularly limited, but from the viewpoints of storage stability, wettability, heat resistance, etc., the softening point is usually about 80 to 120 ° C., and the acid value is usually about 150 to 190 mgKOH / g. It is.

  As the component (a4), a Diels-Alder reaction product of the raw material rosin and various known α, β unsaturated carboxylic acids ((meth) acrylic acid, (anhydrous) maleic acid, fumaric acid, etc.), and purified products thereof , Hydrides and disproportionates, and various known ones can be used. Further, the physical properties of the component (a4) are not particularly limited, but from the viewpoints of storage stability, wettability, heat resistance, etc., the softening point is usually about 120 to 140 ° C., and the acid value is usually about 230 to 250 mgKOH / g. It is.

  When other rosin-based base resins are included in the component (A), the content of each component is not particularly limited, but from the viewpoint of storage stability, wettability, heat resistance, etc., the component (a1) is usually 10 to 10. About 90% by weight, preferably about 20 to 85% by weight, more preferably about 30 to 80% by weight, and other rosin base resins are usually 90 to 10% by weight, preferably 15 to 80% by weight, more preferably Is 20 to 70% by weight.

  The flux of the present invention can also contain rosin base resins other than the components (a1) to (a4). Specifically, for example, an esterified product of at least one selected from the group consisting of the raw material rosin, the component (a1), the component (a2), the component (a3) and the component (a4) and various known polyhydric alcohols; Examples include purified products, hydrides, and disproportionates of the esterified product. Examples of the polyhydric alcohol include trivalent alcohols such as glycerin, trimethylolethane and trimethylolpropane, and tetravalent alcohols such as pentaerythritol and diglycerin. The amount of these rosin base resins used is not particularly limited, but is usually less than 15% by weight when the component (A) is 100% by weight.

  In addition, the flux of the present invention includes, as non-rosin base resin, for example, epoxy resin, acrylic resin, polyimide resin, nylon resin, polyacrylonitrile resin, vinyl chloride resin, vinyl acetate resin, polyolefin resin, fluorine resin, and ABS. Synthetic resins such as resins, and elastomers such as isoprene rubber, styrene butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber, nylon rubber, nylon elastomer, and polyester elastomer can be included. The amount of these non-rosin base resins used is not particularly limited, but is usually less than 5% by weight when component (A) is 100% by weight.

  As the component (b1), which is an essential requirement for the component (B), various known compounds can be used without particular limitation as long as they are propylene glycol ethers having a boiling point of 275 ° C. or lower. In place of the component (b1), a solder paste obtained by using a propylene glycol ether having a boiling point exceeding 275 ° C. or an ethylene glycol ether having a boiling point less than 275 ° C. has a wet solder metal wettability. Insufficient solder is likely to be generated. From this viewpoint, the boiling point of the component (b1) is preferably about 200 to 275 ° C, more preferably about 200 to 250 ° C.

  Specific examples of the component (b1) include, for example, butylpropylene triglycol (boiling point 274 ° C), methylpropylene triglycol (boiling point 242 ° C), phenylpropylene glycol (boiling point 243 ° C), butylpropylene diglycol (boiling point 231 ° C). And propylpropylene diglycol (boiling point 212 ° C.). Among these, from the viewpoint of wettability, at least one selected from the group consisting of butylpropylene triglycol, methylpropylene triglycol, phenylpropylene glycol and butylpropylene diglycol is preferable. In particular, at least one selected from the group consisting of butylpropylene triglycol, methylpropylene triglycol and phenylpropylene glycol is preferable.

  In addition, (B) component can contain another solvent as needed. Specifically, non-ether alcohol solvents such as 2-propanol, octanediol, benzyl alcohol, 1,3-butanediol, 1,4-butanediol, 2- (2-n-butoxyethoxy) ethanol and terpineol Ester solvents such as isopropyl acetate, ethyl propionate, butyl benzoate and diethyl adipate; hydrocarbon solvents such as n-hexane, dodecane and tetradecene; and pyrrolidone solvents such as N-methyl-2-pyrrolidone; Propylene glycol ethers having a temperature exceeding 275 ° C .; ethylene glycol ethers having a temperature less than 275 ° C. The amount used is not particularly limited, but is usually less than 5% by weight when the component (B) is 100% by weight.

  The component (c1), which is an essential component of the component (C), is represented by the general formula (1): HOOC-R-COOH (wherein R represents a hydrocarbon group having 2 to 4 carbon atoms). Any known compound can be used without particular limitation. Specific examples include alkylene aliphatic dibasic acids such as succinic acid, glutaric acid and adipic acid, and alkenylene aliphatic dibasic acids such as fumaric acid, maleic acid and maleic anhydride. Among these, from the viewpoint of wettability, at least one selected from the group consisting of succinic acid, glutaric acid, adipic acid, fumaric acid and maleic acid is preferable.

  In addition, (C) component can contain another active agent as needed. Specifically, for example, oxalic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, dimer acid, itaconic acid and other saturated or unsaturated aliphatic dibasic acids (except for those corresponding to (c1)) Trans) -2,3-dibromo-1,4-butenediol, cis-2,3-dibromo-1,4-butenediol, 1-bromo-2-butanol, 1-bromo-2-propanol, 3) -Bromo such as bromo-1-propanol, 3-bromo-1,2-propanediol, 1,4-dibromo-2-butanol, 1,3-dibromo-2-propanol and 2,3-dibromo-1-propanol Alcohol; 3-bromopropionic acid, 2-bromovaleric acid, 5-bromo-n-valeric acid, 2-bromoisovaleric acid, 2,3-dibromosuccinic acid, 2-bromosuccinic acid And bromodicarboxylic acids such as 2,2-dibromoadipic acid; saturated or unsaturated aliphatic monobasic acids such as capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, stearic acid, oleic acid and linoleic acid; Monobasic acids having aromatic or heterocyclic rings such as benzoylbenzoic acid, benzoic acid, hydroxybenzoic acid, picolinic acid and furancarboxylic acid; bromohydroxycarboxylic acids such as dibromosalicylic acid; ethylamine bromate, diethylamine bromate, diethylamine Amine-based bromo compounds such as hydrochloride and methylamine bromate; 1-bromo-3-methyl-1-butene, 1,4-dibromobutene, 1-bromo-1-propene, 2,3-dibromopropene 1,2-dibromo-1-phenylethane, 1,2-dibromostyrene, 4-s Aroyloxybenzyl bromide, 4-stearyloxybenzyl bromide, 4-stearylbenzyl bromide, 4-bromomethylbenzyl stearate, 4-stearoylaminobenzyl bromide, 2,4-bisbromomethylbenzyl stearate, 4-palmitoyl Active hydrogen-free bromo compounds such as oxybenzyl bromide, 4-myristoyloxybenzyl bromide, 4-lauroyloxybenzyl bromide and 4-undecanoyloxybenzyl bromide; halogen atoms such as stearylamine, distearylamine and dibutylamine Non-containing amines can be exemplified, and these can be used singly or in combination of two or more. Moreover, although the usage-amount of these is not specifically limited, Usually, when (C) component is 100 weight%, it is less than 5 weight%.

  The flux of the present invention may further contain various known thixotropic agents (D) (hereinafter also referred to as (D) component). Specifically, polyamide thixotropic agents and / or animal and plant thixotropic agents are preferable from the viewpoint of screen-printing suitability of the lead-free solder paste. Examples of the polyamide thixotropic agent include stearic acid amide and 12-hydroxystearic acid ethylene bisamide, and examples of the animal and plant type thixotropic agent component include hardened castor oil, beeswax, carnauba wax, and the like. Or in combination of two or more.

  The flux of the present invention may further contain various known antioxidants (E) (hereinafter also referred to as the component (E)). Specifically, for example, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3- (3-t-butyl-5 -Methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n -Octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-t- Butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, N, N′-hexamethylenebis 3,5-di-tert-butyl-4-hydroxy-hydrocinamide), 3,5-di-tert-butyl-4-hydroxybenzylphosphonate-diethyl ester, 1,3,5-trimethyl-2, Hindered phenolic antioxidant of 4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene; 2,6-di-t-butyl-p-cresol, 2,4-dimethyl Other phenolic antioxidants such as -6-tert-butyl-phenol, styrenate phenol, 2,4-bis [(octylthio) methyl] -o-cresol; triphenyl phosphite, triethyl phosphite, trilauryl triti Phosphorus antioxidants such as phosphaeto, tris (tridecyl) phosphite; dilauryl thiodipropionate, dilauryl sa Fido, 2-mercaptobenzimidazole, can be exemplified a sulfur-based antioxidant such as lauryl stearyl thiodipropionate, it alone type, or may be used in combination of two or more. Among these, a hindered phenol antioxidant is preferable from the viewpoint of wettability and color tone of the flux residue. When the color tone of the flux residue is good, visual inspection (confirmation of wetting spread, etc.) of the solder joint becomes easy, and cleaning is not necessary.

The flux of the present invention is a mixture of the components (A) to (E), and the mixing means, mixing order and conditions are not particularly limited. Moreover, although content of (A) component-(E) component is not specifically limited, Usually, it is as follows.
(A) Component: Usually about 25 to 50% by weight, preferably about 35 to 45% by weight (B) Component: Usually about 20 to 70% by weight, preferably about 25 to 55% by weight (C) Component: Usually 3 to 3% About 15% by weight, preferably about 5 to 7% by weight (D) Component: Usually about 0 to 20% by weight, preferably about 2 to 10% by weight (E) Component: Usually about 0 to 10% by weight, preferably 2 ~ 8% by weight

  The lead-free solder paste of the present invention is a composition containing the flux of the present invention and lead-free solder powder. Moreover, although the usage-amount of each is not specifically limited, Usually, the former is about 5 to 30 weight% and the latter is about 70 to 95 weight%.

  As the lead-free solder powder, various known ones can be used without particular limitation as long as they do not contain lead. Specifically, Sn-based lead-free solder powders such as Sn-Ag, Sn-Cu, Sn-Sb, Sn-Zn, and Sn-Bi lead-free solder powders are preferable. The lead-free solder powder is doped with one or more elements of Ag, Al, Au, Bi, Co, Cu, Fe, Ga, Ge, In, Ni, P, Pt, Sb, and Zn. It may be. Specific examples of the lead-free solder powder include Sn95Sb5, Sn99.3Cu0.7, Sn97Cu3, Sn92Cu6Ag2, Sn99Cu0.7Ag0.3, Sn95Cu4Ag1, Sn97Ag3, Sn96.3Ag3.7, Sn42-Bi58 and the like. Moreover, although the average particle diameter of lead-free solder powder is not specifically limited, Usually, it is about 1-50 micrometers, Preferably it is about 15-40 micrometers. Further, the shape of the powder is not particularly limited, and may be spherical or irregular. The spherical shape preferably means that the aspect ratio of the powder is within 1.2. Also, the mixing means, mixing order and conditions of the flux of the present invention and the lead-free solder powder are not particularly limited.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the technical scope of the present invention is not limited to these examples. In the examples, “%” and “part” mean “% by weight” and “part by weight” unless otherwise specified.

<Preparation of flux>
Example 1
44.5 parts of commercially available polymerized rosin (product name “Aradim R140”, softening point 140 ° C., acid value 145 mg KOH / g; manufactured by Arakawa Chemical Industries, Ltd.), commercially available methylpropylene triglycol (trade name “MFTG”, 44 parts of Nippon Emulsifier Co., Ltd., 5 parts of succinic acid (SA), 6 parts of polyamide thixotropic agent (trade name “MA-WAX-O”, manufactured by Kawaken Fine Chemical Co., Ltd.), And 0.5 part of an antioxidant (trade name “Irganox 1010”, manufactured by Ciba Japan Co., Ltd.) were mixed well under heating to prepare a flux.

Examples 2-14, Comparative Examples 1-10
In accordance with Example 1, the raw materials shown in Tables 1 and 2 were mixed well under heating in their parts to prepare each flux.

<Confirmation of wettability: Aspect of solder paste>
Commercially available lead-free solder powder (96.5Sn / 3Ag / 0.5Cu, manufactured by Mitsui Kinzoku Co., Ltd., particle size 20-38 μm, normal product) and the flux of Example 1 are 89% by weight and 11% by weight, respectively. A solder paste was prepared by kneading with a softener. Next, this solder paste was printed on a pattern having a clearance resist structure using a stencil mask having a thickness of 100 μm, and then a 0603 capacitor was mounted on a mounter, and the conditions of the standard profile shown in FIG. After reflowing under a profile condition (heat resistance condition) in which the time was increased by 20 seconds, the wettability of solder metal (presence of unmelted solder) at the joint was visually judged according to the following criteria. Moreover, the wettability was similarly judged visually about the flux of Examples 2-14 and Comparative Examples 1-10.

(Degree of wettability)
A: There is no unmelted solder at the part joint.
○: Unmelted solder can be confirmed in a part of the component joint.
X: Unmelted solder can be confirmed at all component joints.

<Storage stability: Solder paste mode>
For each of the solder pastes of Examples and Comparative Examples, both the viscosity immediately after preparation and the viscosity after being kept in a constant temperature bath at 40 ° C. for 24 hours are both commercially available spiral viscometers (product name “PCU-205”). The thickness of the solder paste was calculated based on the following formula.

Thickening rate = [(Viscosity at 10 rpm after holding at 40 ° C. for 24 hours−Viscosity at 10 rpm immediately after solder paste preparation) ÷ (Viscosity at 10 rpm immediately after solder paste preparation)] × 100

  In addition, the said heat retention condition intends the temperature acceleration test, and the thickening rate in this test substantially reproduces the thickening rate after storing for 6 months or more at 0 ° C to 10 ° C. When the thickening rate was less than 10%, the storage stability was considered good considering the measurement error.

* 1 Commercially available acrylated rosin (trade name “KE-604”, manufactured by Arakawa Chemical Industries, Ltd.)
* 2 ... Commercial hydrogenated rosin (trade name “CRW-300”, softening point 84 ° C., acid value 170 mgKOH / g; manufactured by Arakawa Chemical Industries, Ltd.)
* 3 ... Commercially disproportionated rosin (trade name “KR-614”, softening point 87 ° C., acid value 175 mgKOH / g; manufactured by Arakawa Chemical Industries, Ltd.)
* 4: Methylpropylene triglycol (trade name “MPTG”, manufactured by Nippon Emulsifier Co., Ltd., boiling point 242 ° C.)
* 5 ... Butylpropylene diglycol (Brand name "BPDG", Nippon Emulsifier Co., Ltd., boiling point 231 ° C)
* 6 ・ ・ ・ Phenylpropylene glycol (trade name “PPG”, Nippon Emulsifier Co., Ltd., boiling point 243 ° C.)
* 7 ... Butylpropylene triglycol (trade name “BPTG”, Nippon Emulsifier Co., Ltd., boiling point 274 ° C.)
* 8: Succinic acid (carbon number of R = 2, manufactured by Tokyo Chemical Industry Co., Ltd.)
* 9: Glutaric acid (carbon number of R = 3, manufactured by Tokyo Chemical Industry Co., Ltd.)
* 10 ... Adipic acid (carbon number of R = 4, manufactured by Tokyo Chemical Industry Co., Ltd.)
* 11 ... Fumaric acid (R carbon number = 2, manufactured by Tokyo Chemical Industry Co., Ltd.)

* 12 ... Hexyl diglycol (trade name “HeDG”, ethylene glycol ether having a boiling point of 259 ° C., Nippon Emulsifier Co., Ltd., boiling point 259 ° C.)
* 13 ... 2-ethylhexyl diglycol (trade name “EHDG”, ethylene glycol ether having a boiling point of 272 ° C., manufactured by Nippon Emulsifier Co., Ltd., boiling point 272 ° C.)
* 14 ... 2-hexyldecanol (trade name “Engecol 160BR”, manufactured by Shin Nippon Rika Co., Ltd., boiling point 195-215 ° C.)
* 15 ... Oxalic acid (carbon number of R = 1, manufactured by Tokyo Chemical Industry Co., Ltd.)
* 16: Suberic acid (carbon number of R = 6, manufactured by Tokyo Chemical Industry Co., Ltd.)
* 17 ... Dodecanedioic acid (carbon number of R = 10, manufactured by Tokyo Chemical Industry Co., Ltd.)
* 18: Precipitation of CRW-300 was remarkable in the flux of Comparative Example 2, and preparation of a homogeneous solder paste was difficult, so wettability and storage stability were not evaluated.
* 19: In the flux of Comparative Example 9, precipitates derived from KR-614 were prominently generated, and it was difficult to prepare a homogeneous solder paste, so wetting and storage stability were evaluated. There wasn't.

1 Over resist structure substrate 2 Electrode (land)
3 Solder resist 4 Substrate 5 Clearance structure substrate 6 Lead-free solder paste 7 Flowed flux 8 Unmelted solder

Claims (9)

A flux for a lead-free solder paste for a clearance resist containing a base resin (A), a solvent (B) and an activator (C),
(A) component contains polymerization rosin (a1),
The component (B) includes a propylene glycol ether (b1) having a boiling point of 275 ° C. or less,
Component (C) is the general formula (1): (wherein, R represents a hydrocarbon group having 2 to 4 carbon atoms.) HOOC-R-COOH viewed contains a dibasic acid (c1) represented by,
(B1) component is at least one selected from the group consisting of methylpropylene triglycol, butylpropylene diglycol, phenylpropylene glycol and butylpropylene triglycol,
(C) Component content is 3 to 15% by weight,
Flux characterized by that. The flux according to claim 1, wherein the component (A) further contains at least one selected from the group consisting of hydrogenated rosin (a2), disproportionated rosin (a3), and α, β-unsaturated carboxylic acid-modified rosin (a3). . The flux according to claim 1 or 2 , wherein the component (c1) is at least one selected from the group consisting of succinic acid, glutaric acid, adipic acid, fumaric acid and maleic acid. Furthermore, the flux in any one of Claims 1-3 containing a thixotropic agent (D). The flux according to claim 4 , wherein the component (D) is a polyamide thixotropic agent and / or an animal or plant type thixotropic agent. Furthermore, the flux in any one of Claims 1-5 containing antioxidant (E). (E) The flux in any one of Claims 1-6 whose component is a hindered phenolic antioxidant. (A), (B), the parallel beauty component (D) and (E) content of Ingredients are as follows, one of the flux of claims 1-7.
(A) component: 25-50 weight%
(B) component: 20 to 70 % by weight
( D) Component: 0 to 20% by weight
(E) component: 0 to 10% by weight A lead-free solder paste for a clearance resist containing the flux according to any one of claims 1 to 8 and a lead-free solder powder.