JP2023127903A - Solder composition and electronic substrate - Google Patents

Abstract

To provide a solder composition excellent in both printability and a dripping property during heating.SOLUTION: The solder composition contains: a flux composition containing (A) a rosin-based resin, (B) an activator and (C) a thixotropic agent; and (D) a solder powder. The (C) component contains (C1) an amide compound having a weight average molecular weight Mw from 500 to 2500 inclusive, a number average molecular weight Mn from 500 to 1500 inclusive, and a value of Mw/Mn from 1.2 to 2.5 inclusive.SELECTED DRAWING: None

Description

The present invention relates to a solder composition and an electronic board.

A solder composition is a paste-like mixture obtained by kneading solder powder with a flux composition (rosin resin, activator, solvent, etc.) (see Patent Document 1). In addition to printability and solderability, this solder composition is required to have the property of suppressing sag during preheating in the reflow process (the shape of the coating film of the solder composition collapses during preheating) (sagging resistance during heating). It will be done. In addition, in recent years, as mounting on micro lands has progressed, further improvement in sag resistance during heating is required. However, if the viscosity or thixotropy of the solder composition is increased in order to improve the sagging properties during heating, the printability of the solder composition tends to decrease. As described above, it is difficult to achieve both printability and sag resistance during heating.

Patent No. 5887330

An object of the present invention is to provide a solder composition that is excellent in both printability and sag resistance during heating, and an electronic board using the same.

According to one aspect of the present invention, the flux composition includes (A) a rosin-based resin, (B) an activator, and (C) a thixotropic agent, and (D) a solder powder, and the (C) The component contains (C1) an amide compound having a weight average molecular weight Mw of 500 or more and 2500 or less, a number average molecular weight Mn of 500 or more and 1500 or less, and a Mw/Mn value of 1.2 or more and 2.5 or less. A solder composition is provided.

According to one aspect of the present invention, an electronic board is provided that includes a soldering portion using the solder composition according to the one aspect of the present invention.

According to the present invention, it is possible to provide a solder composition that is excellent in both printability and sag resistance during heating, and an electronic board using the same.

These are graphs showing the results of molecular weight measurement of the amide compound obtained in Preparation Example 1. These are graphs showing the results of molecular weight measurement of the amide compound obtained in Preparation Example 2.

The solder composition of this embodiment contains (A) a rosin resin, (B) an activator, and (C) a flux composition containing a thixotropic agent, and (D) solder powder.

The reason why a solder composition that is excellent in both printability and sagging property during heating is obtained according to the present embodiment is not necessarily clear, but the present inventors speculate as follows.
That is, (C1) printing with an amide compound having a weight average molecular weight Mw of 500 to 2,500, a number average molecular weight Mn of 500 to 1,500, and a Mw/Mn value of 1.2 to 2.5. The present inventors conjecture that the mechanism by which the sagging property during heating can be improved while maintaining the properties is as follows.
First, the amide compound (C1) contributes to the thixotropy of the solder composition, but the degree of contribution to the thixotropy varies depending on the molecular weight of the amide compound. Furthermore, the degree of contribution to thixotropy also changes depending on the temperature of the solder composition. The component (C1) of this embodiment has an Mw/Mn value of 1.2 or more and 2.5 or less, and contains a predetermined amount or more of a relatively high molecular weight component. The contribution of the relatively high molecular weight component and the average molecular weight component to the thixotropic properties varies depending on the temperature of the solder composition. If the component (C1) of this embodiment is used, the thixotropic ratio can be adjusted to a range that provides excellent printability during printing, and the thixotropic ratio can be adjusted to a range that provides excellent heating sag during heating. The present inventors conjecture that the effects of the present invention described above are achieved in the manner described above.

[Flux composition]
First, the flux composition used in this embodiment will be explained. The flux composition used in this embodiment is a component other than the solder powder in the solder composition, and contains (A) a rosin resin, (B) an activator, and (C) a thixotropic agent, which will be described below. .

[(A) Component]
Examples of the rosin resin (A) used in this embodiment include rosins and modified rosin resins. Examples of rosins include gum rosin, wood rosin, and tall oil rosin. Examples of the rosin-based modified resin include disproportionated rosin, polymerized rosin, hydrogenated rosin, and derivatives thereof. Hydrogenated rosins include fully hydrogenated rosins, partially hydrogenated rosins, unsaturated organic acids (alpha, β-, aliphatic unsaturated monobasic acids such as (meth)acrylic acid, fumaric acid, maleic acid, etc.) Unsaturated organic acid-modified rosin, which is a modified rosin of aliphatic unsaturated dibasic acids such as unsaturated carboxylic acids, unsaturated carboxylic acids with an aromatic ring such as cinnamic acid, etc.) (also called rosin). These rosin resins may be used alone or in combination of two or more.

The blending amount of component (A) is preferably 20% by mass or more and 70% by mass or less, more preferably 30% by mass or more and 60% by mass or less, based on 100% by mass of the flux composition. If the blending amount of component (A) is above the lower limit, it is possible to prevent oxidation of the copper foil surface of the soldering land and make it easier to wet the surface with molten solder, improving so-called solderability, and ensuring sufficient solder balls. can be suppressed to Moreover, if the blending amount of component (A) is below the above-mentioned upper limit, the amount of flux remaining can be sufficiently suppressed.

[(B) Component]
Examples of the activator (B) used in this embodiment include organic acids, non-dissociable activators (halogen-based activators) made of non-dissociable halogenated compounds, and amine-based activators. These may be used alone or in combination of two or more. Moreover, among these, it is preferable to contain (B1) an organic acid. Moreover, it is preferable that the component (B) further contains (B2) an amine-based activator.
Component (B1) includes monocarboxylic acids, dicarboxylic acids, and other organic acids. These may be used alone or in combination of two or more.
Monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, capric acid, lauric acid, myristic acid, pentadecyl acid, palmitic acid, margaric acid, stearic acid, tuberculostearic acid. , arachidic acid, behenic acid, lignoceric acid, and glycolic acid.
Dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, fumaric acid, maleic acid, tartaric acid, and diglycolic acid. Can be mentioned. Among these, succinic acid, glutaric acid, dodecanedioic acid and the like are preferred from the viewpoint of active action.
Other organic acids include 3-hydroxy-2-naphthoic acid, dimer acid, trimer acid, levulinic acid, lactic acid, acrylic acid, benzoic acid, salicylic acid, anisic acid, citric acid, and picolinic acid. Among these, from the viewpoint of active action, it is more preferable to use 3-hydroxy-2-naphthoic acid.
In addition, from the viewpoint of improving solder meltability in micro lands, it is preferable to use multiple organic acids in combination, and it is preferable to use succinic acid, glutaric acid, dodecanedioic acid, and 3-hydroxy-2-naphthoic acid in combination. is particularly preferred.

The blending amount of component (B1) is preferably 1% by mass or more and 12% by mass or less, more preferably 2% by mass or more and 10% by mass or less, based on 100% by mass of the flux composition. It is particularly preferable that the amount is 7% by mass or more. If the blending amount of component (B1) is at least the above-mentioned lower limit, there is a tendency that the active effect can be improved, while, on the other hand, when it is below the above-mentioned upper limit, the insulation properties of the flux composition tend to be maintained.

Components (B2) include imidazolines (such as 2-phenylimidazoline), amines (such as polyamines such as ethylenediamine), amine salts (amines such as trimethylolamine, cyclohexylamine, and diethylamine, and organic acid salts such as amino alcohols). Examples include inorganic acid salts (hydrochloric acid, sulfuric acid, hydrobromic acid, etc.), amino acids (glycine, alanine, aspartic acid, glutamic acid, valine, etc.), and amide compounds. Specifically, diphenylguanidine hydrobromide, cyclohexylamine hydrobromide, diethylamine salts (hydrochloride, succinate, adipate, sebacate, etc.), triethanolamine, monoethanolamine, these Examples include hydrobromide of amines. Among these, from the viewpoint of active action, imidazolines are preferred, and 2-phenylimidazoline is particularly preferred.
Further, from the viewpoint of improving solder meltability in micro lands, it is preferable to use the (B1) component and the (B2) component together, and it is particularly preferable to use the (B1) component and 2-phenylimidazoline together.

The blending amount of component (B2) is preferably 1% by mass or more and 12% by mass or less, more preferably 2% by mass or more and 10% by mass or less, based on 100% by mass of the flux composition. It is particularly preferable that the amount is 7% by mass or more. If the blending amount of component (B2) is at least the above-mentioned lower limit, there is a tendency that the active effect can be improved, while on the other hand, when it is below the above-mentioned upper limit, the insulation properties of the flux composition tend to be maintained.

The blending amount of component (B) is preferably 3% by mass or more and 25% by mass or less, more preferably 5% by mass or more and 20% by mass or less, based on 100% by mass of the flux composition. It is particularly preferable that the amount is 15% by mass or more. If the blending amount of component (B) is at least the above-mentioned lower limit, there is a tendency for the activation effect to be improved, whereas, on the other hand, when it is below the above-mentioned upper limit, the insulation properties of the flux composition tend to be maintained.

[(C) Component]
The (C) thixotropic agent used in this embodiment has (C1) a weight average molecular weight Mw of 500 or more and 2,500 or less, a number average molecular weight Mn of 500 or more and 1,500 or less, and a value of Mw/Mn of 1.2 or more and 2,500 or less. It is necessary to contain an amide compound that is .5 or less. With such a component (C1), it is possible to improve the sagging property during heating while maintaining printability.

If the weight average molecular weight Mw of the component (C1) is less than 500, sagging during heating cannot be suppressed. On the other hand, if the weight average molecular weight Mw of the component (C1) exceeds 2500, sagging during printing cannot be suppressed.
From the same viewpoint, the weight average molecular weight Mw of the component (C1) is preferably 700 or more and 2400 or less, more preferably 1000 or more and 2350 or less, and particularly preferably 1500 or more and 2300 or less.

If the number average molecular weight Mn of the component (C1) is less than 500, sagging during heating cannot be suppressed. On the other hand, if the number average molecular weight Mn of the component (C1) exceeds 1500, sagging during printing cannot be suppressed.
From the same viewpoint, the number average molecular weight Mn of the component (C1) is preferably 550 or more and 1400 or less, more preferably 600 or more and 1350 or less, and particularly preferably 700 or more and 1300 or less.

If the value of Mw/Mn of the component (C1) is less than 1.2 or more than 2.5, at least one of sag during heating and sag during printing cannot be suppressed.
From the same viewpoint, the value of Mw/Mn of the component (C1) is preferably 1.3 or more and 2.2 or less, particularly preferably 1.35 or more and 2 or less.

In this embodiment, it is preferable to use two or more of the components (C1) in combination. In this way, the properties of the solder composition can be made even more preferable.

This component (C1) includes, for example, an aliphatic monocarboxylic acid having 2 to 22 carbon atoms including a hydroxy aliphatic monocarboxylic acid, an aliphatic dicarboxylic acid having 2 to 12 carbon atoms, and a diamine having 2 to 16 carbon atoms. It can be produced by condensation.
Among aliphatic monocarboxylic acids having 2 to 22 carbon atoms, the number average molecular weight Mn of the component (C1) tends to be smaller as an aliphatic monocarboxylic acid having fewer carbon atoms is used.
Among aliphatic dicarboxylic acids having 2 to 12 carbon atoms, the number average molecular weight Mn of the component (C1) tends to be smaller as an aliphatic dicarboxylic acid having a smaller number of carbon atoms is used.
Among diamines having 2 to 16 carbon atoms, the number average molecular weight Mn of the component (C1) tends to be smaller as a diamine with a smaller number of carbon atoms is used.

The larger the amount of the aliphatic dicarboxylic acid having 2 to 12 carbon atoms to the aliphatic monocarboxylic acid having 2 to 22 carbon atoms, the larger the number average molecular weight Mn of the component (C1) tends to be.
The total amount of carboxyl groups in the aliphatic monocarboxylic acid having 2 to 22 carbon atoms and the aliphatic dicarboxylic acid having 2 to 12 carbon atoms is preferably equal to the amount of amino groups in the diamine having 2 to 16 carbon atoms. . When these amounts are equal, the condensation reaction tends to proceed.

The temperature during the condensation reaction is preferably 100°C or more and 250°C or less, more preferably 120°C or more and 210°C or less, particularly preferably 150°C or more and 190°C or less. The higher this temperature is, the higher the weight average molecular weight Mw of the component (C1) tends to be.
The time for the condensation reaction is preferably 1 hour or more and 15 hours or less, more preferably 3 hours or more and 11 hours or less, particularly preferably 5 hours or more and 8 hours or less. The longer this time, the greater the weight average molecular weight Mw of component (C1) tends to be.
That is, the values of weight average molecular weight Mw, number average molecular weight Mn, and Mw/Mn of component (C1) can be determined by (i) adjusting the type and amount of raw materials for component (C1), and (ii) condensation reaction. It can be adjusted as appropriate by adjusting the temperature at the time of the reaction and (iii) adjusting the time for the condensation reaction.

The blending amount of component (C1) is preferably 0.1% by mass or more and 25% by mass or less, more preferably 1% by mass or more and 20% by mass or less, based on 100% by mass of the flux composition. It is more preferably 2% by mass or more and 16% by mass or less, and particularly preferably 3% by mass or more and 10% by mass or less. If the blending amount of component (C) is at least the above-mentioned lower limit, sagging during printing and sagging during heating can be suppressed. If the blending amount of component (C) is below the above-mentioned upper limit, the thixotropy will not be too high and printing defects can be suppressed.

Component (C) may contain a thixotropic agent other than component (C1) (hereinafter referred to as component (C2)). Examples of the component (C2) include hydrogenated castor oil, amides other than the component (C1), kaolin, colloidal silica, organic bentonite, and glass frit. These may be used alone or in combination of two or more.

The blending amount of component (C) is preferably 1% by mass or more and 25% by mass or less, more preferably 3% by mass or more and 20% by mass or less, and 5% by mass or less, based on 100% by mass of the flux composition. % or more and 16% by mass or less, and particularly preferably 6% by mass or more and 10% by mass or less. If the blending amount of component (C) is at least the above-mentioned lower limit, thixotropic properties can be obtained and sag during printing can be suppressed. If the blending amount of component (C) is below the above-mentioned upper limit, the thixotropy will not be too high and printing defects can be suppressed.

[solvent]
The flux composition of this embodiment preferably further contains a solvent from the viewpoint of printability and the like. As the solvent used here, any known solvent can be used as appropriate. As such a solvent, it is preferable to use a solvent having a boiling point of 170° C. or higher. Moreover, glycol solvents are preferred.
Examples of such solvents include diethylene glycol, dipropylene glycol, triethylene glycol, hexylene glycol, hexyl diglycol, 1,5-pentanediol, methyl carbitol, butyl carbitol, and 2-ethylhexyl diglycol (EHDG). , octanediol, phenyl glycol, diethylene glycol monohexyl ether, tetraethylene glycol dimethyl ether, and dibutyl maleic acid. These solvents may be used alone or in combination of two or more.

When a solvent is used, the amount thereof is preferably 10% by mass or more and 60% by mass or less, and more preferably 20% by mass or more and 40% by mass or less, based on 100% by mass of the flux composition. If the blending amount of the solvent is within the above range, the viscosity of the resulting solder composition can be adjusted to an appropriate range.

[Antioxidant]
The flux composition of this embodiment preferably further contains an antioxidant from the viewpoint of solder meltability. As the antioxidant used here, any known antioxidant can be used as appropriate. Examples of antioxidants include sulfur compounds, hindered phenol compounds, and phosphite compounds. Among these, hindered phenol compounds are preferred.

Examples of hindered phenol compounds include pentaerythritol tetrakis [3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], bis[3-(3-tert-butyl-4-hydroxy-5-methyl) phenyl)propionic acid][ethylenebis(oxyethylene)], N,N'-bis[2-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl]oxamide, and N,N'-bis{3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl}hydrazine.

[Other ingredients]
In addition to the (A) component, (B) component, (C) component, solvent, and antioxidant, the flux composition used in this embodiment may contain other additives as necessary. of resin can be added. Other additives include antifoaming agents, modifiers, matting agents, foaming agents, and the like. The blending amount of these additives is preferably 0.01% by mass or more and 5% by mass or less based on 100% by mass of the flux composition. Other resins include acrylic resins.

[Solder composition]
Next, the solder composition of this embodiment will be explained. The solder composition of this embodiment contains the above-described flux composition of this embodiment and (D) solder powder described below.
The blending amount of the flux composition is preferably 5% by mass or more and 35% by mass or less, more preferably 7% by mass or more and 15% by mass or less, and 8% by mass based on 100% by mass of the solder composition. It is particularly preferable that the amount is 12% by mass or less. If the amount of flux composition is less than 5% by mass (if the amount of solder powder is more than 95% by mass), there is not enough flux composition as a binder, so the flux composition and solder powder are mixed. On the other hand, when the blending amount of the flux composition exceeds 35% by mass (when the blending amount of the solder powder is less than 65% by mass), when the resulting solder composition is used, It tends to be difficult to form a sufficient solder joint.

[(D) Component]
The solder powder (D) used in this embodiment is preferably composed of only lead-free solder powder, but may be leaded solder powder. The solder alloys in this solder powder include tin (Sn), copper (Cu), zinc (Zn), silver (Ag), antimony (Sb), lead (Pb), indium (In), bismuth (Bi), It is preferable to contain at least one member selected from the group consisting of nickel (Ni), cobalt (Co), and germanium (Ge).
The solder alloy in this solder powder is preferably an alloy containing tin as a main component. Moreover, it is more preferable that this solder alloy contains tin, silver, and copper. Furthermore, this solder alloy may contain at least one of antimony, bismuth, and nickel as an additive element. According to the flux composition of the present embodiment, the generation of voids can be suppressed even when a solder alloy containing easily oxidizable additive elements such as antimony, bismuth, and nickel is used.
Here, the lead-free solder powder refers to a solder metal or alloy powder that does not contain lead. However, although it is permissible for lead to exist as an unavoidable impurity in the lead-free solder powder, in this case, the amount of lead is preferably 300 mass ppm or less.

Specifically, lead-free solder powder alloys include Sn-Ag-Cu, Sn-Cu, Sn-Ag, Sn-Bi, Sn-Ag-Bi, and Sn-Ag-Cu. -Bi system, Sn-Ag-Cu-Ni system, Sn-Ag-Cu-Bi-Sb system, Sn-Ag-Bi-In system, Sn-Ag-Cu-Bi-In-Sb system, etc.

The average particle diameter of component (D) is usually 1 μm or more and 40 μm or less, but from the viewpoint of being compatible with electronic boards with narrow soldering pad pitches, it is more preferably 1 μm or more and 35 μm or less, and 2 μm or more and 35 μm or less. It is even more preferable that it is below, and it is especially preferable that it is 3 μm or more and 32 μm or less. Note that the average particle diameter can be measured using a dynamic light scattering type particle diameter measuring device.

[Method for manufacturing solder composition]
The solder composition of the present embodiment can be manufactured by blending the above-described flux composition and the above-described solder powder (D) in the above-described predetermined ratio and stirring and mixing.

[Electronic substrate]
Next, the electronic board of this embodiment will be explained. The electronic board of this embodiment is characterized by having a soldered portion using the solder composition described above. The electronic board of the present invention can be manufactured by mounting electronic components on an electronic board (printed wiring board, etc.) using the solder composition.
Examples of the coating device used here include a screen printer, a metal mask printer, a dispenser, a jet dispenser, and the like.
In addition, electronic components are placed on the solder composition coated by the coating device, heated under predetermined conditions in a reflow oven, and mounted on the printed wiring board through a reflow process. It can be implemented in

In the reflow process, the electronic component is placed on the solder composition and heated under predetermined conditions in a reflow oven. Through this reflow process, sufficient solder bonding can be achieved between the electronic component and the printed wiring board. As a result, the electronic component can be mounted on the printed wiring board.
Reflow conditions may be appropriately set depending on the melting point of the solder. For example, the preheat temperature is preferably 140°C or more and 200°C or less, more preferably 150°C or more and 160°C or less. Preheating time is preferably 60 seconds or more and 120 seconds or less. The peak temperature is preferably 230°C or more and 270°C or less, more preferably 240°C or more and 255°C or less. Further, the holding time at a temperature of 220° C. or higher is preferably 20 seconds or more and 60 seconds or less.

Further, the solder composition and the electronic board of the present embodiment are not limited to the above-described embodiments, and modifications and improvements within the range that can achieve the object of the present invention are included in the present invention.
For example, in the electronic board, the printed wiring board and the electronic component are bonded together by a reflow process, but the present invention is not limited to this. For example, instead of the reflow process, the printed wiring board and the electronic component may be bonded by a process of heating the solder composition using laser light (laser heating process). In this case, the laser light source is not particularly limited, and can be appropriately employed depending on the wavelength matched to the absorption band of the metal. Examples of laser light sources include solid lasers (ruby, glass, YAG, etc.), semiconductor lasers (GaAs, InGaAsP, etc.), liquid lasers (dye, etc.), and gas lasers (He-Ne, Ar, CO ₂ , etc.). excimer, etc.).

Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples in any way. The materials used in the Examples and Comparative Examples are shown below.
((A) component)
Rosin resin A: Hydrogenated acid-modified rosin (softening point: 124-134°C, acid value: 230-245 mgKOH/g), trade name "Pine Crystal KE-604", manufactured by Arakawa Chemical Co., Ltd. Rosin resin B: Complete Hydrogenated rosin (softening point: 79-88°C, acid value: 158-173mgKOH/g), trade name "Foral AX", manufactured by Rika Finetech (component (B1))
Organic acid A: succinic acid Organic acid B: glutaric acid Organic acid C: dodecanedioic acid Organic acid D: 3-hydroxy-2-naphthoic acid (component (B2))
Amine activator: 2-phenylimidazoline ((C1) component)
Amide compound A: amide compound obtained in Preparation Example 1 below (weight average molecular weight Mw is 2000, number average molecular weight Mn is 1139, Mw/Mn is 1.755)
Amide compound B: amide compound obtained in Preparation Example 2 below (weight average molecular weight Mw is 1030, number average molecular weight Mn is 746, Mw/Mn is 1.381)
((C2) component)
Thixotropic agent A: Hexamethylene hydroxystearic acid amide, trade name "Slipax ZHH", manufactured by Mitsubishi Chemical Corporation, Mw/Mn is less than 1.2 Thixotropic agent B: ethylene bishydroxystearic acid amide, trade name "Slipax H", Mitsubishi Manufactured by Chemical Co., Ltd., Mw/Mn is less than 1.2 Thixotropic agent C: Trade name "Himakou", manufactured by KF Trading Co., Ltd. (other ingredients)
Amine compound: 2-phenylimidazoline Antioxidant: Trade name "Irganox 245", manufactured by BASF Solvent: diethylene glycol mono-2-ethylhexyl ether (2-ethylhexyl diglycol (EHDG), boiling point: 272°C), Nippon Nyukazai Co., Ltd. ((D) component)
Solder powder: Alloy composition is Sn-3.0Ag-0.5Cu, particle size distribution is 15-25μm (corresponding to type 5 of IPC-J-STD-005A), solder melting point is 217-220℃

[Preparation example 1]
A predetermined amount of 12-hydroxystearic acid derived from hydrogenated castor oil fatty acid and an aliphatic dicarboxylic acid having 2 to 12 carbon atoms were added to a reaction apparatus equipped with a stirrer, a thermometer, and a water separator. It was heated to 100°C and melted. Thereafter, a predetermined amount of hexamethylene diamine is added, and a condensation reaction is carried out at a temperature of 150°C to 190°C under a nitrogen atmosphere for 5 to 8 hours while dehydrating, resulting in amidation, resulting in an amide compound with an acid value of 5 mgKOH/g or less. I got an A.

[Preparation example 2]
A preparation with an acid value of 5 mgKOH/g or less was carried out in the same manner as in Preparation Example 1, except that the type and amount of the aliphatic dicarboxylic acid having 2 to 12 carbon atoms used and the temperature and time during the condensation reaction were changed. Amide compound B was obtained.

[Molecular weight measurement of amide compounds]
The molecular weights (weight average molecular weight Mw, number average molecular weight Mn) of the amide compounds obtained in Preparation Examples 1 and 2 were measured by gel permeation chromatography (GPC) analysis. The conditions for analysis are as follows. The results obtained are shown in FIGS. 1 and 2.
・GPC device: HLC-8420GPC (manufactured by Tosoh Corporation)
・Column: TSKgel Super AWM-H (6.0mm I.D. x 15cm) x 2 (manufactured by Tosoh Corporation)
・Detector: Differential refractometer (RI detector), polarity=(+)
・Eluent: HFIP (1,1,1,3,3,3-hexafluoro-2-propanol) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) + 10mM-CF ₃ COONa (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. 1st grade)
・Flow rate: 0.3mL/min
・Column temperature: 40℃
・Sample concentration: 1mg/mL
・Sample injection volume: 20μL
- Sample pretreatment: The sample was weighed, a predetermined amount of eluent was added, and the sample was allowed to dissolve overnight at room temperature. After gently shaking and mixing, the mixture was filtered using a 0.45 μm PTFE cartridge filter. In addition, when the sample solution was visually observed, no insoluble matter was observed in the sample.
- Calibration curve: A cubic approximated curve using standard polymethyl methacrylate (PMMA) (manufactured by Agilent Technologies). That is, the obtained value is the PMMA equivalent molecular weight.

[Example 1]
Rosin resin A 31% by mass, rosin resin B 9% by mass, organic acid A 0.5% by mass, organic acid B 0.5% by mass, organic acid C 1% by mass, organic acid D 2.5% by mass, amine activator 5% by mass %, 32.5% by mass of solvent, 2% by mass of antioxidant, and 16% by mass of amide compound A were charged into a container and mixed using a planetary mixer to obtain a flux composition.
Thereafter, 11% by mass of the obtained flux composition, 1.2% by mass of the solvent, and 87.8% by mass of the solder powder (100% by mass in total) were put into a container and mixed in a planetary mixer to form a solder composition. I prepared something.

[Examples 2 to 9]
A solder composition was obtained in the same manner as in Example 1 except that each material was blended according to the composition shown in Table 1.
[Comparative Examples 1 to 3]
A solder composition was obtained in the same manner as in Example 1 except that each material was blended according to the composition shown in Table 1.

<Evaluation of solder composition>
The solder composition was evaluated (properties, heating sag, printability) by the following method. The results obtained are shown in Table 1.
(1) Properties Visually check whether the solder composition has gloss. Then, use a spatula to stir the solder composition in the center and sides of the container to check for smoothness. Then, the properties were evaluated according to the following criteria.
◎: No problem with gloss and smoothness.
○: There is no problem with gloss, but there is some problem with smoothness.
Δ: There is a problem in at least one of gloss and smoothness.
×: There are problems in both gloss and smoothness.
(2) Heating sag Print the solder composition on the test board (double-sided copper-clad laminate) using a metal mask with patterned holes arranged at a pitch of 0.1 mm from 0.1 mm to 1.2 mm. Then, the mixture was heated at a temperature of 150° C. for 1 minute. The test board after heating is observed, and the minimum interval among the pattern holes at which the printed solder composition does not become integrated is determined. This measurement is performed for a plurality of pattern holes and the average thereof is taken. Then, heating sag was evaluated according to the following criteria.
◎: The average minimum interval is 0.2 mm or less.
○: The average minimum interval is more than 0.2 mm and less than 0.3 mm.
Δ: The average minimum distance is more than 0.3 mm and less than 0.4 mm.
×: The average minimum interval is 0.4 mm or more.
(3) Printability A test board (FR4 base material, solder resist opening diameter 75 μm) and a metal mask (thickness 30 μm, metal mask opening diameter 95 μm, pitch size 130 μm) having a pattern corresponding to this test board were used. The solder composition was printed on the test board using a printing device (product name: SP-0601, manufactured by Panasonic Factory Solutions Co., Ltd.) using a urethane squeegee with a metal hardness of 90 and a printing angle of 60°C.
The test board after printing was observed using a metallurgical microscope, and the ratio (non-transfer rate) in which the solder composition was not transferred to the Cu land (9,800 locations) and the presence or absence of parts where the Cu land was visible were determined. was observed, and the printability was evaluated according to the following criteria.
◎: 100% of the solder composition was transferred.
○: Untransfer rate is less than 0.1%.
Δ: Untransfer rate is 0.1% or more and less than 0.5%.
×: The untransfer rate is 0.5% or more, or the solder composition is not transferred onto the substrate and there are parts where the Cu land is visible.

As is clear from the results shown in Table 1, the solder compositions of the present invention (Examples 1 to 9) have good results in terms of QFN end surface wetting and viscosity stability during storage. confirmed. Note that the solder compositions of Examples 1 to 4 do not contain a halogen-based activator, so they are non-halogen type solder compositions.
Therefore, it was confirmed that the solder composition of the present invention is excellent in both wettability and viscosity stability during storage, despite being halogen-free or non-halogen type.

The solder composition of the present invention can be suitably used as a technique for mounting electronic components on electronic substrates such as printed wiring boards of electronic devices.

Claims (5)

A flux composition containing (A) a rosin resin, (B) an activator, and (C) a thixotropic agent, and (D) a solder powder,
The component (C) has (C1) a weight average molecular weight Mw of 500 or more and 2500 or less, a number average molecular weight Mn of 500 or more and 1500 or less, and a value of Mw/Mn of 1.2 or more and 2.5 or less. containing an amide compound,
Solder composition. The solder composition according to claim 1,
The weight average molecular weight Mw of the component (C1) is 1500 or more and 2300 or less, the number average molecular weight Mn is 700 or more and 1300 or less, and the value of Mw/Mn is 1.35 or more and 2 or less,
Solder composition. The solder composition according to claim 1 or 2,
The component (C1) is obtained by condensing an aliphatic monocarboxylic acid having 2 to 22 carbon atoms including a hydroxy aliphatic monocarboxylic acid, an aliphatic dicarboxylic acid having 2 to 12 carbon atoms, and a diamine having 2 to 16 carbon atoms. It is an amide compound consisting of
Solder composition. The solder composition according to any one of claims 1 to 3,
Using two or more of the components (C1) in combination;
Solder composition. A soldered part using the solder composition according to any one of claims 1 to 4,
Electronic substrate.

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