JP2023132678A - flux and solder paste - Google Patents

Abstract

To provide a flux which can improve printability of a solder paste, and a solder paste which can improve printability.SOLUTION: A flux is used for soldering, contains a resin, an unsaturated aliphatic compound having 18 to 22 carbon atoms and having one unsaturated bond, a thixotropic agent, and a solvent, wherein the resin contains a rosin-based resin and a liquid resin having viscosity measured under conditions of a measurement temperature of 30°C and the number of rotation of 50 rpm by an E type viscometer of 300 mPa s or more and 55,000 mPa s or less, and the content of the unsaturated aliphatic compound is 3.0 mass% or more and 25.0 mass% or less with respect to the whole flux.SELECTED DRAWING: None

Description

The present invention relates to a flux used for soldering and a solder paste containing the flux.

Solder paste, which is a mixture of solder alloy and flux, is used in mounting technology for mounting electronic components such as chip components and package substrates on electronic circuit boards such as printed wiring boards. Specifically, the electronic components are bonded onto the electronic circuit board by screen printing solder paste on the pads on the surface of the electronic circuit board using a metal mask, then mounting the electronic components and heating (reflow) them. be done.

Conventionally, resin-based fluxes containing synthetic resins, rosin-based resins, and the like as resin components have been widely used as fluxes contained in solder pastes. It is widely known that when soldering is performed using a solder paste containing resin-based flux, a film called flux residue caused by the resin component remains on the electronic circuit board after soldering. There is.

There is a possibility that cracks may form in such flux residue due to temperature changes such as cooling/heating cycles. Therefore, if moisture infiltrates into the flux residue through the cracks, there is a risk of causing defects such as a decrease in the insulation between the leads. Therefore, in order to suppress the occurrence of cracks, it has been proposed to use a liquid resin with relatively high viscosity as a resin component in the flux. For example, Patent Document 1 discloses a flux containing a polybutadiene (meth)acrylate compound and a hydrogenated dimer acid.

Japanese Patent Application Publication No. 2013-188761

However, when a liquid resin with relatively high viscosity is used as the resin component in the flux as in Patent Document 1, the solder paste tends to adhere to the side surface of the opening of the metal mask, which may reduce the amount of solder supplied. . In particular, when using a metal mask with a low aspect ratio (the ratio of the opening area to the opening side area), the solder paste tends to adhere to the sides of the opening of the metal mask, so there is a risk of insufficient solder supply. be. Therefore, even when a liquid resin with relatively high viscosity is used as the resin component in the flux, it is desirable to suppress the decrease in the amount of solder supplied to the opening of the metal mask and improve the printability of the solder paste. It is rare.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a flux that can improve the printability of solder paste. Another object of the present invention is to provide a solder paste that can improve printability.

The flux according to the present invention is a flux used for soldering, which comprises a resin, an unsaturated aliphatic compound having 18 to 22 carbon atoms and one unsaturated bond, and a thixotropic agent. , a solvent, and the resin has a viscosity of 300 mPa·s or more and 55,000 mPa·s or less when measured with an E-type viscometer at a temperature of 30°C and a rotational speed of 50 rpm. a certain liquid resin, and the content of the unsaturated aliphatic compound is 3.0% by mass or more and 25.0% by mass or less based on the entire flux.

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

According to the present invention, it is possible to provide a flux that can improve the printability of solder paste. Furthermore, it is possible to provide a solder paste that can improve printability.

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

<Flux>
The flux according to this embodiment contains a resin, an unsaturated aliphatic compound, a thixotropic agent, and a solvent.

(resin)
The resin contains a rosin-based resin and a liquid resin whose viscosity is 300 mPa·s or more and 55,000 mPa·s or less when measured using an E-type viscometer at a temperature of 30° C. and a rotational speed of 50 rpm.

The rosin-based resin is not particularly limited, and includes, for example, one or more types selected from rosin and rosin derivatives (for example, hydrogenated rosin, polymerized rosin, disproportionated rosin, acrylic acid-modified rosin, etc.). Rosin resin can be used.

The content of the rosin resin should be 10.0% by mass or more based on the entire flux, from the viewpoint of increasing the dispersibility of the thixotropic agent to improve printability and stabilizing the viscosity of the solder paste. is preferable, and more preferably 20.0% by mass or more. Further, the content of the rosin resin is preferably 60.0% by mass or less, and preferably 35.0% by mass or less, based on the entire flux, from the viewpoint of maintaining the form as a solder paste. is more preferable. In addition, when two or more types of rosin-based resins are included, the content is the total content of the rosin-based resins.

The liquid resin has a viscosity of 300 mPa-s or more and 55,000 mPa-s or less, as measured by an E-type viscometer at a temperature of 30°C and a rotation speed of 50 rpm, according to JIS K 7117-2. - It is preferable that it is more than s and less than 50000 mPa*s. Examples of such liquid resins include GI-1000, GI-2000, and GI-3000 (manufactured by Nippon Soda Co., Ltd.), which are hydrogenated polybutadiene having hydroxyl groups at both ends (hydrogenated polybutadiene with hydroxyl groups at both ends). G-1000, G-2000, G-3000 (manufactured by Nippon Soda Co., Ltd.), Poly-bd R-15HT, Poly-bd R-45HT (manufactured by Nippon Soda Co., Ltd.), which are liquid polybutadiene having a hydroxyl group at the end (hydroxyl group-terminated liquid polybutadiene) , manufactured by Idemitsu Kosan Co., Ltd.), Poly-ip (manufactured by Idemitsu Kosan Co., Ltd.), which is a liquid polyisoprene having hydroxyl groups at both ends (hydroxyl group-terminated liquid polyisoprene), and liquid polyolefin having hydroxyl groups at both ends (hydroxyl group-terminated liquid polyolefin). A certain EPOL (manufactured by Idemitsu Kosan), polybutenes such as NOF Polybutene O-15N, NOF Polybutene 3N, NOF Polybutene 10N, NOF Polybutene 30N (all manufactured by NOF), Nippon Oil Polybutene Grate LV-7, Grade LV-50, Great LV-100, Grade HV-15, Grade 35, Grade HV-50, Grade HV-100, Grade HV-300 (manufactured by ENEOS), Acrylic resin Acrylic O (Arakawa Chemical Co., Ltd.) (manufactured by Nippon Steel Chemical & Materials), Outflow UMM-1001, UT-1001, CB-3060, CBB-3098 (manufactured by Soken Chemical Co., Ltd.), bisphenol A type epoxy resin YD-8125, YD-825GS (manufactured by Nippon Steel Chemical & Materials Co., Ltd.) ), EPICLON840, 840-S, 850, 850-S, EXA-850CRP, 850-LC (manufactured by DIC), bisphenol F type epoxy resin YDF-YDF-8170, YDF-870GS (manufactured by Nippon Steel Chemical & Materials) (manufactured by DIC), EPICLON830, 830-S, 835, EXA-830CRP, EXA-830LVP, EXA-835LV (manufactured by DIC). Among these, from the viewpoint of the effect of reducing cracks in flux residue and the ease of handling the resin, it is preferable that the liquid resin contains at least one selected from polybutadiene with hydrogenated hydroxyl groups at both ends and an acrylic resin. In addition, the said liquid resin may be used individually by 1 type, or may use 2 or more types together.

The content of the liquid resin is preferably 10.0% by mass or more, and preferably 20.0% by mass or more, based on the entire flux, from the viewpoint of suppressing the occurrence of cracks in the flux residue. is more preferable. Further, from the viewpoint of maintaining the form as a solder paste, the content of the liquid resin is preferably 60.0% by mass or less, and preferably 35.0% by mass or less, based on the entire flux. More preferred. In addition, when two or more types of liquid resins are included, the content is the total content of the liquid resins.

The resin may contain other resins than the rosin resin and the liquid resin. Examples of other resins include terpene phenol resin, phenol resin, polyvinyl acetate resin, ethylene-vinyl acetate copolymer, polylactic acid, and polystyrene. Note that the other resins may be used alone or in combination of two or more.

The content of the other resin is preferably 5.0% by mass or more, more preferably 10.0% by mass or more, based on the entire flux, from the viewpoint of influence on solder wettability. preferable. Further, the content of the other resin is preferably 30.0% by mass or less, and preferably 20.0% by mass or less, based on the entire flux, from the viewpoint of influence on solder wettability. is more preferable. In addition, when two or more types of other resins are included, the content is the total content of the other resins.

The total content of the resin is preferably 30.0% by mass or more, more preferably 40.0% by mass or more, based on the entire flux. Moreover, it is preferable that the total content of the said resin is 70.0 mass % or less with respect to the said whole flux, and it is more preferable that it is 60.0 mass % or less.

(unsaturated aliphatic compound)
The flux according to this embodiment contains an unsaturated aliphatic compound having 18 to 22 carbon atoms and one unsaturated bond. The unsaturated aliphatic compound preferably contains at least one selected from unsaturated aliphatic alcohols, unsaturated fatty acids, and unsaturated fatty acid esters, and more preferably contains unsaturated aliphatic alcohols.

From the viewpoint of improving the slipperiness of the solder paste, the content of the unsaturated aliphatic compound is preferably 3.0% by mass or more, and preferably 5.0% by mass or more, based on the entire flux. Further, the content of the unsaturated aliphatic compound is 25.0% by mass or less, and preferably 15.0% by mass or less, based on the entire flux, from the viewpoint of maintaining the form as a solder paste. preferable. In addition, when two or more types of unsaturated aliphatic compounds are included, the content is the total content of the unsaturated aliphatic compounds.

The unsaturated aliphatic alcohol has 18 or more and 22 or less carbon atoms, and has one unsaturated bond. Examples of the unsaturated aliphatic alcohol include oleyl alcohol, elaidyl alcohol, ricinoleyl alcohol, and erucyl alcohol. Among these, from the viewpoint of improving the slipperiness of the solder paste, the unsaturated aliphatic alcohol preferably contains oleyl alcohol, and more preferably consists of oleyl alcohol. In addition, the said unsaturated aliphatic alcohol may be used individually by 1 type, or may use 2 or more types together.

The content of the unsaturated aliphatic alcohol is preferably 3.0% by mass or more, and preferably 5.0% by mass or more, based on the entire flux, from the viewpoint of improving the slipperiness of the solder paste. is more preferable. Further, from the viewpoint of maintaining the form as a solder paste, the content of the unsaturated aliphatic alcohol is preferably 25.0% by mass or less, and 15.0% by mass or less, based on the entire flux. It is more preferable that there be. In addition, when two or more types of unsaturated aliphatic alcohols are included, the content is the total content of unsaturated aliphatic alcohols.

The unsaturated fatty acid has 18 or more and 22 or less carbon atoms, and has one unsaturated bond. Examples of the unsaturated fatty acids include oleic acid, elaidic acid, vaccenic acid, gadoleic acid, eicosenoic acid, and erucic acid. Among these, from the viewpoint of improving the slipperiness of the solder paste, it is preferable that the unsaturated fatty acid contains oleic acid. In addition, the said unsaturated fatty acid may be used individually by 1 type, or may use 2 or more types together.

From the viewpoint of improving the slipperiness of the solder paste, the content of the unsaturated fatty acid is preferably 3.0% by mass or more, more preferably 5.0% by mass or more, based on the entire flux. preferable. Further, from the viewpoint of maintaining the form as a solder paste, the content of the unsaturated fatty acid is preferably 25.0% by mass or less, and 15.0% by mass or less, based on the entire flux. is more preferable. In addition, when two or more types of unsaturated fatty acids are included, the content is the total content of unsaturated fatty acids.

The unsaturated fatty acid ester has 18 or more and 22 or less carbon atoms, and has one unsaturated bond. The unsaturated fatty acid esters include methyl oleate, ethyl oleate, butyl oleate, pentyl oleate, hexyl oleate, heptyl oleate, octyl oleate, nonyl oleate, dosyl oleate, undecyl oleate, Dodecyl oleate, isopropyl oleate, isobutyl oleate, 2-ethylhexyl oleate, octyldodecyl oleate, methyl erucate, ethyl erucate, butyl erucate, hexyl erucate, heptyl erucate, octyl erucate, Nonyl erucate, dosyl erucate, undecyl erucate, dodecyl erucate, isopropyl erucate, isobutyl erucate, 2-ethylhexyl erucate, octyldodecyl erucate, and the like. Among these, from the viewpoint of improving the slipperiness of the solder paste, it is preferable that the unsaturated fatty acid ester contains methyl oleate. In addition, the said unsaturated fatty acid ester may be used individually by 1 type, or may use 2 or more types together.

From the viewpoint of improving the slipperiness of the solder paste, the content of the unsaturated fatty acid ester is preferably 3.0% by mass or more, and preferably 5.0% by mass or more, based on the entire flux. More preferred. Further, from the viewpoint of maintaining the form as a solder paste, the content of the unsaturated fatty acid ester is preferably 25.0% by mass or less, and 15.0% by mass or less, based on the entire flux. It is more preferable. In addition, when two or more types of unsaturated fatty acid esters are included, the content is the total content of the unsaturated fatty acid esters.

(thixotropic agent)
The flux according to this embodiment includes a thixotropic agent. Examples of the thixotropic agent include hydrogenated castor oil, fatty acid amide, fatty acid bisamide, polyamide compound, kaolin, colloidal silica, organic bentonite, glass frit, and the like. Among these, the thixotropic agent is preferably a fatty acid bisamide or a polyamide compound from the viewpoint of heat resistance. Examples of fatty acid bisamides include methylene bisstearamide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, and hexamethylene bis stearic acid amide. , hexamethylenebisbehenic acid amide, hexamethylenebis-12-hydroxystearic acid amide, N,N'-distearyladipic acid amide, N,N'-xylylenebis-12-hydroxystearylamide, and the like. Examples of polyamide compounds include aliphatic polyamide compounds such as Talen VA-79, AMX-6096A, WH-215, and WH-255 (all manufactured by Kyoeisha Chemical Co., Ltd.), SP-10, and SP-500 (all manufactured by Toray Industries, Inc.). Aromatic polyamide compounds (semi-aromatic polyamide compounds or fully aromatic polyamide compounds) containing a cyclic compound such as a benzene ring or a naphthalene ring in the main chain, such as Grilamid L20G, Grilamid TR55 (manufactured by M Chemie Japan), etc. ), such as JH-180 (manufactured by Ito Oil Co., Ltd.). In addition, the thixotropic agents may be used alone or in combination of two or more.

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 entire flux. Further, 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 entire flux. In addition, when two or more types of thixotropic agents are included, the content is the total content of the thixotropic agents.

(solvent)
The flux according to this embodiment contains a solvent. Examples of the 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), and triethylene. Glycol ethers such as glycol monobutyl ether (butyl triglycol), polyethylene glycol dimethyl ether, tripropylene glycol n-butyl ether; aliphatic compounds such as n-hexane, isohexane, n-heptane; isopropyl acetate, methyl propionate, propionic acid Known solvents such as esters such as ethyl; ketones such as methyl ethyl ketone, methyl-n-propyl ketone and diethyl ketone; and alcohols such as ethanol, n-propanol, isopropanol and isobutanol can be used. In addition, the said solvent may be used individually by 1 type, or may use 2 or more types together.

The content of the solvent is preferably 15.0% by mass or more, more preferably 23.0% by mass or more, based on the entire flux. Further, the content of the solvent is preferably 40.0% by mass or less, more preferably 30.0% by mass or less, based on the entire flux. In addition, when two or more kinds of the above-mentioned solvents are included, the above-mentioned content is the total content of the solvents.

(Saturated aliphatic alcohol)
The flux according to this embodiment may contain saturated aliphatic alcohol. The saturated aliphatic alcohol is not particularly limited, and examples thereof include 1-tridecanol, cetanol, 1-heptadecanol, stearyl alcohol, isostearyl alcohol, and the like. The content of the saturated aliphatic alcohol is preferably 8.0% by mass or less, and 5.0% by mass or less based on the entire flux, from the viewpoint of improving the slipperiness of the solder paste on the side surface of the opening of the metal mask. It is more preferable that it is less than % by mass, and even more preferable that it does not contain saturated aliphatic alcohol. In addition, the said saturated aliphatic alcohol may be used individually by 1 type, or may use 2 or more types together.

(activator)
The flux according to this embodiment may contain an activator. The activator is not particularly limited, and examples thereof include organic acid activators, amine compounds, amino acid compounds, halogen activators such as amine halogen salts and halogen compounds, and the like. In addition, the said activator may be used individually by 1 type, or may use 2 or more types together.

The organic acid activator is not particularly limited, and includes, for example, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, capric acid, lauric acid, myristic acid, pentadecylic acid, and palmitic acid. monocarboxylic acids such as margaric acid, stearic acid, tuberculostearic acid, arachidic acid, behenic acid, lignoceric acid, glycolic acid; oxalic acid, malonic acid, succinic acid, methylsuccinic acid, glutaric acid, adipic acid, pimelic acid Dicarboxylic acids such as , suberic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, tartaric acid, diglycolic acid; 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, and other organic acids.

Examples of the halogen compound include tris(2,3-dibromopropyl)isocyanuric acid, 2,3-dibromo-2-butene-1,4-diol, and 2-bromo-3-iodo-2-butene-1,4- Examples include diol, TBA-bis(2,3-dibromopropyl ether), and the like.

The content of the activator is preferably 0.5% by mass or more, more preferably 3.0% by mass or more, based on the entire flux. Further, the content of the activator is preferably 20.0% by mass or less, more preferably 10.0% by mass or less, based on the entire flux. In addition, when two or more types of the above-mentioned activators are contained, the above-mentioned content is the total content of the activators.

The flux according to the present embodiment may contain, as other additives, at least one selected from, for example, stabilizers, surfactants, antifoaming agents, and antioxidants. The total content of other additives is not particularly limited, and can be, for example, 5.0% by mass or less based on the entire flux.

The flux according to the present embodiment is a flux used for soldering, and includes a resin, an unsaturated aliphatic compound having 18 to 22 carbon atoms and one unsaturated bond, and a thixotropic agent. and a solvent, the resin has a viscosity of 300 mPa·s or more and 55,000 mPa·s or less when measured with an E-type viscometer at a temperature of 30°C and a rotational speed of 50 rpm. , and the content of the unsaturated aliphatic compound is 3.0% by mass or more and 25.0% by mass or less based on the entire flux, so that The slipperiness of the solder paste is improved, making it difficult for the solder paste to adhere to the side surfaces of the opening of the metal mask. As a result, the flux can improve the printability of solder paste.

In the flux according to the present embodiment, the unsaturated aliphatic compound includes at least one selected from unsaturated aliphatic alcohol, unsaturated fatty acid, and unsaturated fatty acid ester, so that This improves the slipperiness of the solder paste against the metal mask, making it difficult for the solder paste to adhere to the side surfaces of the opening of the metal mask. As a result, the flux can improve the printability of solder paste.

The flux according to the present embodiment has a content of the unsaturated aliphatic compound of 5.0% by mass or more and 15.0% by mass or less based on the entire flux, so that the flux can be soldered to the side surface of the opening of the metal mask. The slipperiness of the paste is improved, making it difficult for solder paste to adhere to the side surfaces of the metal mask opening. As a result, the printability of the solder paste can be improved.

<Solder paste>
The solder paste according to this embodiment contains the above-mentioned flux and solder alloy powder. The solder paste is obtained by mixing the flux and the solder alloy powder. The content of the flux is preferably 5.0% by mass or more and 20.0% by mass or less based on the entire solder paste. Further, the content of the solder alloy powder is preferably 80.0% by mass or more and 95.0% by mass or less based on the entire solder paste.

Examples of the alloy of the solder alloy powder include lead-free solder alloys and lead-containing eutectic solder alloys, but from the viewpoint of reducing environmental load, lead-free solder alloys are preferable. Examples of lead-free solder alloys include alloys containing tin, silver, copper, indium, zinc, bismuth, antimony, and the like. More specifically, Sn/Ag, Sn/Ag/Cu, Sn/Cu, Sn/Ag/Bi, Sn/Bi, Sn/Ag/Cu/Bi, Sn/Sb, Sn/Zn/Bi, Sn/ Examples include alloys such as 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. Moreover, it is more preferable that the Sn/Ag/Cu alloy further contains at least one selected from In, Bi, Sb, and Ni. Further, the alloy contains inevitable impurities. Unavoidable impurities refer to components that are unavoidably mixed in during the manufacturing process and are allowed within a range that does not affect the effects of the present invention.

The particle size of the solder alloy powder is preferably 5 μm or more and 45 μm or less, more preferably 15 μm or more and 39 μm or less.

The solder paste according to this embodiment contains the above-mentioned flux and solder alloy powder. The flux improves the slipperiness of the solder paste on the side surface of the opening of the metal mask, and makes it difficult for the solder paste to adhere to the side surface of the opening of the metal mask. As a result, the solder paste can improve printability.

In the solder paste according to the present embodiment, the alloy of the solder alloy powder may be a Sn/Ag/Cu alloy. The solder paste can also improve the printability of Sn/Ag/Cu alloys, which are widely used.

In the solder paste according to the present embodiment, the Sn/Ag/Cu alloy may further contain at least one selected from In, Bi, Sb, and Ni. Even if these metal elements are added to the solder paste for the purpose of improving the cold and heat durability of the solder alloy, the printability can be improved.

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

<Preparation of solder paste>
Each of the raw materials in the amounts shown in Tables 1 to 4 was placed in a heating container and heated to dissolve all the raw materials. Thereafter, by cooling to room temperature, a uniformly dispersed flux was obtained. Note that each blending amount shown in Tables 1 to 4 is equal to the content of each component contained in the flux. Next, 11.8% by mass of each flux and 88.2% by mass of the solder alloy powder shown in Tables 1 to 4 were mixed to obtain solder pastes for each Example and Comparative Example.

Details of each raw material contained in the flux shown in Tables 1 to 4 are shown in Table 5. Further, details of the solder alloys shown in Tables 1 to 4 are shown in Table 6. Further, details of the unsaturated aliphatic alcohols shown in Tables 1 to 4 are shown in Table 7. "Components other than oleyl alcohol" in Table 7 includes stearyl alcohol, palmitole alcohol, and cetanol. Note that the effective ratios of oleyl alcohol in Tables 1 to 4 were calculated from the content of oleyl alcohol contained in each unsaturated aliphatic alcohol shown in Table 7. The effective proportions of oleyl alcohol shown in Tables 1 to 4 are equal to the content of oleyl alcohol in the specification.

<Measurement of viscosity of liquid resin>
The viscosity (Pa·s) of the liquid resin was measured using an E-type viscometer (RE-100U, manufactured by Toki Sangyo Co., Ltd.) by a measuring method according to JIS K 7117-2 under the following measurement conditions. Note that the liquid resin "TEAI-1000" used in Comparative Example 4 could not be measured because it exceeded the upper limit (60,000 mPa·s) of the measurable range with the above-mentioned E-type viscometer. The measurement results are shown in Table 5.

(Measurement condition)
Rotation speed during measurement: 50 rpm
Measurement temperature: 30℃
Viscosity value: Read the value 2 minutes after starting measurement

<Evaluation of printability>
300g of the solder paste of each example and each comparative example was placed on a metal mask set on a printing machine (YVP-Xg, manufactured by YAMAHA Motor), and rolling was performed 4 times to blend the solder paste onto the metal mask. Ta. After dry cleaning the back side of the metal mask, printing was performed twice under the following printing conditions.

(Printing conditions)
Printing environment: temperature 24-26℃, humidity 50-60%RH
Printing squeegee: Metal squeegee Squeegee angle: 60°
Metal mask thickness: 150μm
Printing speed: 40mm/sec
Pad shape and size: □ shape, 0.30mm x 0.30mm
Number of pads: 100 (50 pads x n = 2)
Pad material: OSP treated copper Metal mask aspect ratio (metal mask opening area (0.09 mm ² )/metal mask opening side area (0.18 mm ² )): 0.50

The solder transfer rate was calculated by detecting the solder on the copper pad of each printed board using a KOHYONG aSPIer (manufactured by KOH YOUNG TECHNOLOGY) and calculating its volume %. Ratio of pads with a volume% of 105% or more (filling rate of 105% or more) to the entire pad (100 pieces), a ratio of pads with a volume% of 75% or more and less than 105% (filling rate of 75% or more and less than 105%), Tables 1 to 4 show the percentage of pads with a volume % of less than 75% (filling rate of less than 75%).

The evaluation of the transfer rate is judged as "1 (excellent)" when the proportion of the filling rate of 75% or more and less than 105% is 90% or more, and is judged as "2 (excellent)" when the proportion of the filling rate of 105% or more is 10% or more. otherwise, it was determined as "3 (poor)". The determination results are shown in Tables 1 to 4.

As can be seen from the results in Tables 1 to 4, the solder pastes of each example that meet all the requirements of the present invention have excellent printability because the proportion of filling ratios of 75% or more and less than 105% is 90% or more. shows.

Claims (6)

A flux used for soldering,
Contains a resin, an unsaturated aliphatic compound having 18 or more and 22 or less carbon atoms and having one unsaturated bond, a thixotropic agent, and a solvent,
The resin includes a rosin resin and a liquid resin whose viscosity is 300 mPa·s or more and 55,000 mPa·s or less when measured with an E-type viscometer at a temperature of 30° C. and a rotation speed of 50 rpm.
A flux in which the content of the unsaturated aliphatic compound is 3.0% by mass or more and 25.0% by mass or less based on the entire flux. The flux according to claim 1, wherein the unsaturated aliphatic compound contains at least one selected from unsaturated aliphatic alcohols, unsaturated fatty acids, and unsaturated fatty acid esters. The flux according to claim 1 or 2, wherein the content of the unsaturated aliphatic compound is 5.0% by mass or more and 15.0% by mass or less based on the entire flux. A solder paste containing the flux according to any one of claims 1 to 3 and a solder alloy powder. The solder paste according to claim 4, wherein the alloy of the solder alloy powder is a Sn/Ag/Cu alloy. The solder paste according to claim 5, wherein the Sn/Ag/Cu alloy further contains at least one selected from In, Bi, Sb, and Ni.