JP7743380B2 - Solder composition and electronic substrate - Google Patents

Description

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

The solder composition is a paste-like mixture made by kneading a solder powder with a flux composition (rosin-based resin, activator, solvent, etc.) (see Patent Document 1). This solder composition is required to have viscosity stability (also called stability over time) in addition to printability and solderability.
As such, it is difficult to achieve both printability and resistance to sagging when heated.

Patent No. 5887330

However, when solder powder is made finer, its surface area increases, accelerating oxidation. This results in poor behavior during solder melting, leading to non-wetting and solder balls. To improve these issues, it is necessary to add large amounts of organic acids or halogen-based activators, which are activators in flux compositions, to promote the oxide film removal reaction on the solder powder surface. However, increasing the amount of activator in the flux composition accelerates the oxide film removal reaction caused by the reaction between the activator and the solder powder, reducing the stability of the solder composition over time and causing it to thicken. As such, it is difficult to achieve both finer solder powder and stability over time.

The present invention aims to provide a solder composition that exhibits excellent stability over time, even when using sufficiently fine solder powder, as well as an electronic substrate that uses the same.

According to the present invention, there are provided the following solder compositions and electronic substrates.
[1] A flux composition containing (A) a rosin-based resin, (B) an activator, (C) a thixotropic agent, and (D) a hindered phenol-based antioxidant, and (E) a solder powder,
The component (C) contains (C1) an amide compound whose DSC curve measured by differential scanning calorimetry (DSC) has a plurality of endothermic peaks, and at least one of the endothermic peaks is in the range of 130°C or higher and 220°C or lower;
The component (E) has a particle size distribution corresponding to any one of Type 5, Type 6, Type 7, and Type 8 or higher of IPC-J-STD-005A.
Solder composition.
[2] The solder composition according to [1],
The component (C1) contains (C11) an amide compound whose DSC curve has multiple endothermic peaks, with at least one of the endothermic peaks being in the range of 210°C or higher and 220°C or lower, and (C12) an amide compound whose DSC curve has multiple endothermic peaks, with at least one of the endothermic peaks being in the range of 140°C or higher and 160°C or lower.
Solder composition.
[3] The solder composition according to [1] or [2],
The component (B) contains an organic acid (B1) and an amine surfactant (B2),
The component (B2) is at least one selected from the group consisting of (B21) benzotriazoles and (B22) imidazolines.
Solder composition.
[4] The solder composition according to [3],
The component (B1) contains (B11) a dicarboxylic acid having 5 to 9 carbon atoms.
Solder composition.
[5] A soldered portion using the solder composition according to any one of [1] to [4].
Electronic board.

The present invention provides a solder composition that exhibits excellent stability over time, even when using sufficiently fine solder powder, as well as an electronic substrate that uses the same.

1 is a graph showing a DSC curve of the amide compound obtained in Preparation Example 1. 1 is a graph showing a DSC curve of the amide compound obtained in Preparation Example 2.

The solder composition according to this embodiment contains a flux composition containing (A) a rosin-based resin, (B) an activator, (C) a thixotropic agent, and (D) a hindered phenol-based antioxidant, and (E) a solder powder. The (C) thixotropic agent contains (C1) an amide compound whose DSC curve obtained by differential scanning calorimetry (DSC) has multiple endothermic peaks, with at least one of the endothermic peaks being in the range of 130°C to 220°C. Furthermore, the (E) solder powder has a particle size distribution corresponding to any one of Type 5, Type 6, Type 7, and Type 8 or higher of IPC-J-STD-005A.

According to this embodiment, even when a sufficiently fine solder powder such as component (E) is used, a solder composition having excellent stability over time can be obtained. The reason for this is not entirely clear, but the inventors speculate as follows.
That is, by using (C1) an amide compound whose DSC curve measured by differential scanning calorimetry (DSC) has a plurality of endothermic peaks, with at least one of the endothermic peaks being in the range of 130°C or higher and 220°C or lower, it is possible to improve sagging resistance during heating while maintaining printability and the like, and further, this component (C1) does not adversely affect stability over time.
Furthermore, component (D) can reduce the amount of Sn ions generated, thereby suppressing the reaction between component (A) or (B) and component (E). This improves the stability of the solder composition over time. This effect is particularly effective when component (B) is an activator that is likely to adversely affect stability over time, such as an organic acid or an amine-based activator. The inventors believe that the effects of the present invention are achieved in this manner.

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

[Component (A)]
The rosin-based resin (A) used in this embodiment includes rosins and rosin-modified resins. Examples of rosins include gum rosin, wood rosin, and tall oil rosin. Examples of rosin-modified resins include disproportionated rosin, polymerized rosin, hydrogenated rosin, and derivatives thereof. Examples of hydrogenated rosins include fully hydrogenated rosin, partially hydrogenated rosin, and hydrogenated products of unsaturated organic acid-modified rosins (also referred to as "hydrogenated acid-modified rosin"), which are rosins modified with unsaturated organic acids (e.g., aliphatic unsaturated monobasic acids such as (meth)acrylic acid, aliphatic unsaturated dibasic acids such as α,β-unsaturated carboxylic acids such as fumaric acid and maleic acid, and unsaturated carboxylic acids having an aromatic ring such as cinnamic acid). These rosin-based 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, and more preferably 30% by mass or more and 60% by mass or less, based on 100% by mass of the flux composition. When the blending amount of component (A) is above the lower limit, oxidation of the copper foil surface of the soldering land is prevented, making the surface more easily wetted by molten solder, thereby improving solderability and sufficiently suppressing solder balls. Furthermore, when the blending amount of component (A) is below the upper limit, the amount of flux residue can be sufficiently suppressed.

[(B) Component]
Examples of the (B) activator used in this embodiment include organic acids, non-dissociative activators (halogen-based activators) made of non-dissociative halogenated compounds, and amine-based activators. These may be used alone or in combination of two or more. Among these, it is preferable to include an (B1) organic acid. It is also preferable that the (B) component further includes an (B2) amine-based activator.
Examples of the component (B1) include 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, pentadecylic acid, palmitic acid, margaric acid, stearic acid, tuberculostearic acid, arachidic acid, behenic acid, lignoceric acid, and glycolic acid.
Examples of 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. Among these, dicarboxylic acids having 5 to 9 carbon atoms are preferred from the viewpoint of activity.
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.

The blending amount of component (B1) is preferably 1% by mass or more and 10% by mass or less, more preferably 1.5% by mass or more and 7.5% by mass or less, and even more preferably 2% by mass or more and 5% by mass or less, based on 100% by mass of the flux composition. If the blending amount of component (B1) is above the lower limit, the activation effect tends to be improved, while if it is below the upper limit, the insulating properties of the flux composition tend to be maintained.

Examples of component (B2) include (B21) benzotriazoles (benzotriazole, 2-(2-hydroxy-5-methylphenyl), etc.), (B22) imidazolines (2-phenylimidazoline, 2-benzylimidazoline, etc.), amines (polyamines such as ethylenediamine, etc.), amine salts (organic acid salts or inorganic acid salts (hydrochloric acid, sulfuric acid, hydrobromic acid, etc.) of amines such as trimethylolamine, cyclohexylamine, diethylamine, and amino alcohols), amino acids (glycine, alanine, aspartic acid, glutamic acid, valine, etc.), and amide compounds. Among these, from the viewpoint of activity, (B21) benzotriazoles or (B22) imidazolines are preferred, and it is particularly preferred to use the components (B21) and (B22) in combination.
It is also preferable to use the component (B1) and the component (B2) in combination, and it is particularly preferable to use the component (B1), the component (B21), and the component (B22) in combination.

The blending amount of component (B2) is preferably 1% by mass or more and 10% by mass or less, and more preferably 2% by mass or more and 5% by mass or less, based on 100% by mass of the flux composition. If the blending amount of component (B2) is equal to or more than the lower limit, the activation action tends to be improved, while if it is equal to or less than the upper limit, the insulating properties of the flux composition tend to be maintained.
When the component (B21) and the component (B22) are used in combination, the mass ratio of the component (B21) to the component (B22) (component (B21)/component (B22)) is preferably 1/20 or more and 1/5 or less, and more preferably 1/15 or more and 1/8 or less.

The blending amount of component (B) is preferably 1% by mass or more and 15% by mass or less, more preferably 1.5% by mass or more and 10% by mass or less, and particularly preferably 2% by mass or more and 7% by mass or less, relative to 100% by mass of the flux composition. If the blending amount of component (B) is above the lower limit, the activation effect tends to be improved, while if it is below the upper limit, the insulating properties of the flux composition tend to be maintained.

[(C) Component]
The thixotropic agent (C) used in this embodiment must contain an amide compound (C1) whose DSC curve obtained by differential scanning calorimetry (DSC) has multiple endothermic peaks, with at least one of the endothermic peaks being in the range of 130°C to 220°C. Such a component (C1) can improve sagging during heating while maintaining printability, and the component (C1) does not adversely affect stability over time. The DSC curve can be measured using a known differential scanning calorimeter, for example, a DSC6200 differential scanning calorimeter manufactured by Seiko Instruments Inc.

If the DSC curve does not have multiple endothermic peaks, it is not possible to achieve both printability and resistance to sagging during heating.
From the same viewpoint, the DSC curve preferably has three or more endothermic peaks, and from the viewpoint of the balance between sagging during printing and sagging during heating, it is particularly preferable that the DSC curve has three endothermic peaks.
If at least one of the endothermic peaks is not in the range of 130° C. or higher and 220° C. or lower, sagging during heating cannot be suppressed.

From a similar viewpoint, the component (C1) preferably contains (C11) an amide compound whose DSC curve has multiple endothermic peaks, at least one of which is in the range of 210°C or higher and 220°C or lower, and (C12) an amide compound whose DSC curve has multiple endothermic peaks, at least one of which is in the range of 140°C or higher and 160°C or lower.
When the component (C11) and the component (C12) are used in combination, the mass ratio of the component (C11) to the component (C12) (component (C11)/component (C12)) is preferably 1/10 or more and 10 or less, and more preferably 1/2 or more and 2 or less.

In component (C11), the endothermic peak at the lowest temperature is preferably in the range of 120°C or higher and 150°C or lower, more preferably in the range of 125°C or higher and 140°C or lower, and particularly preferably in the range of 125°C or higher and 135°C or lower, from the viewpoint of more reliably suppressing sagging during printing.

For component (C11), if the DSC curve has three endothermic peaks, the second endothermic peak from the low temperature side is preferably in the range of 150°C or higher and 190°C or lower. Having such an endothermic peak allows for a balance between sagging during printing and sagging during heating. From the same perspective, the second endothermic peak from the low temperature side is preferably in the range of 160°C or higher and 180°C or lower, and particularly preferably in the range of 165°C or higher and 175°C or lower.

For component (C11), a DSC curve that is particularly suitable from the perspective of improving sagging resistance during heating while maintaining printability preferably satisfies the following conditions: That is, the DSC curve preferably has three endothermic peaks, with the first endothermic peak from the low temperature side being in the range of 125°C to 135°C, the second endothermic peak from the low temperature side being in the range of 165°C to 175°C, and the third endothermic peak from the low temperature side being in the range of 210°C to 220°C.

This component (C1) can be prepared, for example, by condensing an aliphatic monocarboxylic acid having 2 to 22 carbon atoms, which may include a hydroxyaliphatic monocarboxylic acid, an aliphatic dicarboxylic acid having 2 to 12 carbon atoms, and a diamine having 2 to 16 carbon atoms.
Among aliphatic monocarboxylic acids having 2 to 22 carbon atoms, the use of one having fewer carbon atoms tends to result in a lower endothermic peak temperature in the DSC curve of component (C1).
Among aliphatic dicarboxylic acids having 2 to 12 carbon atoms, the use of one having fewer carbon atoms tends to result in a lower endothermic peak temperature in the DSC curve of component (C1).
Among diamines having 2 to 16 carbon atoms, the use of one having fewer carbon atoms tends to result in a lower endothermic peak temperature in the DSC curve of component (C1).

The greater the amount of aliphatic dicarboxylic acid having 2 to 12 carbon atoms relative to the aliphatic monocarboxylic acid having 2 to 22 carbon atoms, the higher the temperature range of the lowest endothermic peak in the DSC curve of component (C1).
It is preferable that 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 equal to the amount of amino groups in the diamine having 2 to 16 carbon atoms. When these amounts are equal, the condensation reaction proceeds easily.

The temperature during the condensation reaction is preferably from 100° C. to 250° C., more preferably from 120° C. to 210° C., and particularly preferably from 150° C. to 190° C. The higher this temperature, the higher the temperature range of the lowest endothermic peak in the DSC curve of component (C1) tends to be.
The time required for the condensation reaction is preferably from 1 to 15 hours, more preferably from 3 to 11 hours, and particularly preferably from 5 to 8 hours. The longer this time, the higher the temperature range of the lowest endothermic peak in the DSC curve of component (C1) tends to be.
In other words, the number of endothermic peaks in the DSC curve of component (C1), the temperature range of the highest endothermic peak, and the temperature range of the lowest endothermic peak can be appropriately adjusted by (i) adjusting the types and amounts of raw materials for component (C1), (ii) adjusting the temperature during the condensation reaction, and (iii) adjusting the time spent on 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, even more preferably 2% by mass or more and 16% by mass or less, and particularly preferably 3% by mass or more and 12% by mass or less, based on 100% by mass of the flux composition. When the blending amount of component (C1) is above the lower limit, sagging during printing and sagging during heating can be suppressed. When the blending amount of component (C1) is below the upper limit, thixotropy is not 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 component (C2) include hydrogenated castor oil, amides other than component (C1), kaolin, colloidal silica, organic bentonite, and glass frit. These may be used alone or in combination of two or more.
However, from the viewpoint of not adversely affecting stability over time, it is particularly preferable that component (C) consists solely of component (C1). From the same viewpoint, the blending amount of component (C1) is preferably 70% by mass or more, and more preferably 90% by mass or more, based on 100% by mass of component (C).

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, even more preferably 5% by mass or more and 16% by mass or less, and particularly preferably 6% by mass or more and 12% by mass or less, relative to 100% by mass of the flux composition. When the blending amount of component (C) is above the lower limit, thixotropy is achieved and sagging during printing can be suppressed. When the blending amount of component (C) is below the upper limit, thixotropy is not too high and printing defects can be suppressed.

[(D) Component]
The hindered phenol-based antioxidant (D) used in this embodiment is a hindered phenol compound that acts as an antioxidant. This component (D) can improve the stability over time of the solder composition. However, antioxidants other than hindered phenol-based antioxidants cannot improve the stability over time of the solder composition.
Examples of the component (D) include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylenebis(oxyethylene)], N,N'-bis[2-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl]oxamide, N,N '-Bis{3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl}hydrazine, 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol], 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate, N,N'-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide], 1,6-hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide], xanediol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2'-methylenebis(6-tert-butyl-p-cresol), 2,2'-methylenebis(6-tert-butyl-4-ethylphenol), 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-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 3,5-di-tert-butyl-4-hydroxybenzylphosphonate-diethyl ester, and 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene.

The blending amount of component (D) is preferably 0.5% by mass or more and 15% by mass or less, more preferably 1% by mass or more and 12% by mass or less, even more preferably 1.5% by mass or more and 9% by mass or less, and particularly preferably 2% by mass or more and 6% by mass or less, based on 100% by mass of the flux composition. If the blending amount of component (D) is above the lower limit, sufficient stability over time can be ensured. If the blending amount of component (C) is below the upper limit, 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, etc. As the solvent used here, a known solvent can be appropriately used. As such a solvent, it is preferable to use a solvent with a boiling point of 170°C or higher. In addition, a glycol-based solvent is preferable.
Examples of such solvents include diethylene glycol, dipropylene glycol, triethylene glycol, hexylene glycol, hexyl diglycol, 1,5-pentanediol, methyl carbitol, butyl carbitol, 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, its amount is preferably 10% by mass or more and 60% by mass or less, and more preferably 20% by mass or more and 50% by mass or less, relative to 100% by mass of the flux composition. If the amount of solvent is within this range, the viscosity of the resulting solder composition can be adjusted appropriately within an appropriate range.

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

[Solder Composition]
Next, the solder composition according to this embodiment will be described. The solder composition according to this embodiment contains the flux composition used in this embodiment described above and the solder powder (E) described below.
The 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 particularly preferably 8% by mass or more and 12% by mass or less, relative to 100% by mass of the solder composition. If the amount of the flux composition is less than 5% by mass (if the amount of the solder powder exceeds 95% by mass), there is insufficient flux composition as a binder, making it difficult to mix the flux composition and the solder powder. On the other hand, if the amount of the flux composition is more than 35% by mass (if the amount of the solder powder is less than 65% by mass), it tends to be difficult to form a sufficient solder joint when using the resulting solder composition.

[(E) component]
The solder powder (E) used in this embodiment is a solder powder having a particle size distribution corresponding to any one of IPC-J-STD-005A Type 5, Type 6, Type 7, and Type 8 or higher. When this component (E) is used, stability tends to decrease, but by using the above-mentioned flux composition, a solder composition with excellent stability over time can be obtained.
The solder powder is preferably made of lead-free solder powder alone, but may be lead-containing solder powder. The solder alloy in the solder powder preferably contains at least one element selected from the group consisting of tin (Sn), copper (Cu), zinc (Zn), silver (Ag), antimony (Sb), lead (Pb), indium (In), bismuth (Bi), nickel (Ni), cobalt (Co), and germanium (Ge).
The solder alloy in this solder powder is preferably an alloy containing tin as a main component. Furthermore, this solder alloy more preferably 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 this embodiment, even when using a solder alloy containing easily oxidized additive elements such as antimony, bismuth, and nickel, the generation of voids can be suppressed.
Here, lead-free solder powder refers to a powder of solder metal or alloy to which no lead is added. However, although the presence of lead as an unavoidable impurity in the lead-free solder powder is permitted, in this case, the amount of lead is preferably 300 mass ppm or less.

Specific alloy systems for lead-free solder powder include Sn-Ag-Cu, Sn-Cu, Sn-Ag, Sn-Bi, Sn-Ag-Bi, Sn-Ag-Cu-Bi, Sn-Ag-Cu-Ni, Sn-Ag-Cu-Bi-Sb, Sn-Ag-Bi-In, and Sn-Ag-Cu-Bi-In-Sb systems.

From the perspective of compatibility with electronic boards with narrow solder pad pitches, the average particle diameter of component (E) is preferably 1 μm or more and 20 μm or less, and even more preferably 2 μm or more and 15 μm or less. The average particle diameter can be measured using a dynamic light scattering particle size analyzer.

[Method for producing solder composition]
The solder composition according to this embodiment can be produced by blending the above-described flux composition and the above-described (E) solder powder in the predetermined ratio, and stirring and mixing them.

[Electronic board]
Next, the electronic substrate according to this embodiment will be described. The electronic substrate according to this embodiment is characterized by having a soldered portion using the solder composition described above. The electronic substrate of the present invention can be produced by mounting electronic components on an electronic substrate (such as a printed wiring board) using the solder composition.
Examples of the coating device used here include a screen printer, a metal mask printer, a dispenser, and a jet dispenser.
Furthermore, an electronic component can be mounted on an electronic board by a reflow process in which an electronic component is placed on the solder composition applied by the application device, and heated under predetermined conditions in a reflow furnace to mount the electronic component on a printed wiring board.

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

Furthermore, the solder composition and electronic substrate of the present embodiment are not limited to the above-described embodiment, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention.
For example, in the electronic substrate, the printed wiring board and the electronic component are bonded by a reflow process, but this is not limiting. 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 selected depending on the wavelength that matches the absorption band of the metal. Examples of laser light sources include solid-state lasers (ruby, glass, YAG, etc.), semiconductor lasers (GaAs, InGaAsP, etc.), liquid lasers (dye, etc.), and gas lasers (He—Ne, Ar, CO ₂ , excimer, etc.).

The present invention will now be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. The materials used in the examples and comparative examples are listed below.
(Component (A))
Rosin-based resin A: hydrogenated acid-modified rosin (softening point: 124 to 134°C, acid value: 230 to 245 mgKOH/g), trade name "Pine Crystal KE-604", manufactured by Arakawa Chemical Industries, Ltd. Rosin-based resin B: fully hydrogenated rosin (softening point: 79 to 88°C, acid value: 158 to 173 mgKOH/g), trade name "Foral AX", manufactured by Rika Finetech Co., Ltd. (component (B1)).
Organic acid A: glutaric acid Organic acid B: suberic acid Organic acid C: azelaic acid (component (B21))
Benzotriazoles: Benzotriazole (component (B22))
Imidazolines: 2-phenylimidazoline ((C11) component)
Amide compound A: an amide compound obtained in Preparation Example 1 below (having a hydroxy group; in a DSC curve, the first endothermic peak temperature, from the low temperature side, is 128°C, the second endothermic peak temperature is 170°C, and the third endothermic peak temperature is 216°C).
((C12) component)
Amide compound B: an amide compound obtained in Preparation Example 2 below (having no hydroxy group, and having a first endothermic peak temperature of 86°C, a second endothermic peak temperature of 123°C, and a third endothermic peak temperature of 147°C from the low temperature side in a DSC curve).
((D) component)
Hindered phenolic antioxidant A: bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylenebis(oxyethylene)], trade name "Irganox 245", manufactured by BASF. Hindered phenolic antioxidant B: N,N'-bis{3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl}hydrazine, trade name "Irganox MD1024", manufactured by BASF. Phenolic antioxidant C: pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], trade name "ANOX20", manufactured by Shiraishi Calcium Co., Ltd. Hindered phenolic antioxidant D: N,N'-bis[2-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl]oxamide, trade name "Nauguard XL-1", manufactured by Shiraishi Calcium Co., Ltd. (Other ingredients)
Solvent: Diethylene glycol mono-2-ethylhexyl ether (2-ethylhexyl diglycol (EHDG), boiling point: 272°C), manufactured by Nippon Nyukazai Co., Ltd. (component (E))
Solder powder A: Alloy composition is Sn-3.0Ag-0.5Cu, particle size distribution is 15 to 25 μm (equivalent to Type 5 of IPC-J-STD-005A), solder melting point is 217 to 220°C
Solder powder B: alloy composition Sn-3.0Ag-0.5Cu, particle size distribution 5-20 μm (equivalent to Type 6 of IPC-J-STD-005A), solder melting point 217-220°C
(Other ingredients)
Solder powder C: Alloy composition is Sn-3.0Ag-0.5Cu, particle size distribution is 20 to 38 μm (equivalent to Type 4 of IPC-J-STD-005A), solder melting point is 217 to 220°C

[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 each added to a reaction apparatus equipped with a stirrer, a thermometer, and a water divider, and the mixture was melted by heating to 80 to 100° C. Thereafter, a predetermined amount of hexamethylenediamine was added, and a condensation reaction was carried out while dehydrating at a temperature of 150 to 190° C. under a nitrogen atmosphere for 5 to 8 hours to effect amidation, yielding an amide compound A having an acid value of 5 mgKOH/g or less.

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

[Differential scanning calorimetry (DSC) of amide compounds]
The DSC curves of the amide compounds obtained in Preparation Examples 1 and 2 were measured using a differential scanning calorimeter under the following measurement conditions. The results are shown in Figures 1 and 2, respectively.
Differential scanning calorimeter: DSC6200 (Seiko Instruments Inc.)
Sample: 10 mg Measurement atmosphere: nitrogen atmosphere Measurement temperature: 30°C to 250°C Temperature rise rate: 20°C/min

[Example 1]
35 mass % of rosin-based resin A, 10 mass % of rosin-based resin B, 2.4 mass % of organic acid A, 39.6 mass % of solvent, 3 mass % of hindered phenol-based antioxidant A, 4 mass % of amide compound A, and 6 mass % of amide compound B 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 and 89% by mass of solder powder (total of 100% by mass) were placed in a container and mixed with a planetary mixer to prepare a solder composition.

[Examples 2 to 12]
A solder composition was obtained in the same manner as in Example 1, except that the materials were mixed according to the composition shown in Table 1.
[Comparative Examples 1 to 5]
A solder composition was obtained in the same manner as in Example 1, except that the materials were mixed according to the composition shown in Table 1.

<Evaluation of Solder Composition>
The solder compositions were evaluated (viscosity changes during storage and use) by the following methods. The results are shown in Table 1.
(1) Viscosity Change During Storage First, the viscosity of a solder composition sample is measured. The sample is then placed in a sealed container, placed in a thermostatic bath at 30°C, and stored for 30 days, and the viscosity of the stored sample is measured. The difference (η2 - η1) between the initial viscosity value (η1) and the viscosity value (η2) after 30 days of storage at 30°C is calculated, and the viscosity increase rate [{(η2 - η1)/η1} x 100] (unit: %) is calculated. The viscosity measurement is performed using a spiral viscosity measurement device (PCU-II model, manufactured by Malcom, measurement temperature: 25°C, rotation speed: 10 rpm).
(2) Viscosity Change During Use First, the viscosity of a solder composition sample was measured. The sample was then placed in a viscometer, and the rotor was rotated at 10 rpm and 25°C for 24 hours to measure the viscosity of the sample. The difference (η3-η1) between the initial viscosity value (η1) and the viscosity value (η3) after 24 hours was calculated, and the viscosity increase rate [{(η3-η1)/η1} x 100] (unit: %) was calculated. The viscosity was measured using a spiral viscosity meter (PCU-II model, manufactured by Malcom, measurement temperature: 25°C, rotation speed: 10 rpm). If the viscosity value (η3) could not be measured, the result was recorded as "impossible."

As is clear from the results shown in Table 1, it was confirmed that the solder compositions of the present invention (Examples 1 to 12) showed good results in all of the viscosity changes during storage and during use.
Therefore, it was confirmed that the solder composition of the present invention has excellent stability over time even when a sufficiently fine solder powder is used.

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 for electronic devices.

Claims (4)

A flux composition containing (A) a rosin-based resin, (B) an activator, (C) a thixotropic agent, and (D) a hindered phenol-based antioxidant, and (E) a solder powder,
The component (C) contains (C1) an amide compound whose DSC curve measured by differential scanning calorimetry (DSC) has a plurality of endothermic peaks, and at least one of the endothermic peaks is in the range of 130°C or higher and 220°C or lower;
The component (C1) comprises: (C11) an amide compound whose DSC curve has three endothermic peaks, the first endothermic peak from the low temperature side being in the range of 125°C or higher and 135°C or lower, the second endothermic peak from the low temperature side being in the range of 165°C or higher and 175°C or lower, and the third endothermic peak from the low temperature side being in the range of 210°C or higher and 220°C or lower; and (C12) an amide compound whose DSC curve has multiple endothermic peaks, at least one of the endothermic peaks being in the range of 140°C or higher and 160°C or lower;
The component (E) has a particle size distribution corresponding to any one of Type 5, Type 6, Type 7, and Type 8 or higher of IPC-J-STD-005A.
Solder composition. The solder composition according to claim 1 ,
The component (B) contains an organic acid (B1) and an amine surfactant (B2),
The component (B2) is at least one selected from the group consisting of (B21) benzotriazoles and (B22) imidazolines.
Solder composition. The solder composition according to claim 2 ,
The component (B1) contains (B11) a dicarboxylic acid having 5 to 9 carbon atoms.
Solder composition. A soldered portion using the solder composition according to claim 1 or 2.
Electronic board.