JP2014161890A - Solder powder, solder composition, and printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide solder powder for producing a solder composition excellent in heating sag resistance, fusibility and storage stability even in the case of using solder powder having a high solder melting point and a small average particle diameter.SOLUTION: Solder powder is characterized in that aliphatic monocarboxylic acid or aromatic monocarboxylic acid having one or more hydroxyl groups in one molecule is attached to, adsorbed by or bonded to the surface of the solder powder to be treated.

Description

  The present invention relates to a solder powder, a solder composition, and a printed wiring board.

2. Description of the Related Art In recent years, as electronic devices have become lighter, thinner, and smaller, printed wiring boards have been miniaturized, and mounting components mounted on printed boards have been downsized. For example, in an electronic device such as a smartphone, a small mounting component such as 0402 chip (a chip having a size of 0.4 mm × 0.2 mm) or 0603 chip (a chip having a size of 0.6 mm × 0.3 mm) is used. It is used. And since these minute mounting components are mounted on a board | substrate, the printing size and pitch (mounting component space | interval) of a solder composition (solder paste) also become small.
The mounting of minute parts such as 0402 chip and 0603 chip is particularly required for module parts, and it is predicted that many 0402 chips will be mounted in the near future. And the clearance gap between the parts is also 0.08-0.1 mm, and it is estimated that it will become the range of 0.05-0.06 mm finally.
In order to satisfy these requirements, it is required that the heat sagging property is excellent during the process of printing and heating the solder composition (preheat temperature region). However, since the heating temperature tends to increase due to the recent demand for lead-free, higher heating sag properties are required.

Further, in order to perform soldering at a minute pitch of minute parts, it is required to make the particle diameter of the solder powder fine. And the average particle diameter of the solder powder suitable for soldering such a fine part is desirably less than 20 μm, and in fact, a particle having a size of several μm is used.
Here, when the solder powder having a small average particle diameter is used, the specific surface area increases, and the amount of oxide generated on the surface of the solder powder increases accordingly. In order to melt and remove the oxide generated on the surface of the solder powder, use a solder composition having a flux component having a very high reducing power, or nitrogen reflow as a condition of the reflow apparatus in the mounting process. Has been implemented using.
However, when a flux component having a very high reducing power is used, there is a concern about storage stability and thickening in the paste printing process due to the high activity of the flux component. Also, the use of nitrogen reflow is a factor that increases running costs.

  On the other hand, surface treatment of solder powder has been studied for the purpose of improving various physical properties of the solder composition. For example, a solder powder that has been surface-treated with a treatment liquid comprising an organic acid and an organic solvent has been proposed (Patent Document 1). In addition, a solder powder formed by forming an organometallic compound of adipic acid and a metal on the surface of the solder powder has been proposed (Patent Document 2). Furthermore, a solder powder that has been surface-treated with a specific organosilicon compound has been proposed (Patent Document 3). In addition, a solder powder that has been surface-treated with a phosphoric acid-based anionic surfactant has been proposed (Patent Document 4).

JP 2005-66672 A JP-A-10-58190 Japanese Patent Laid-Open No. 9-19794 JP 2001-294901 A

  However, even when the solder powders described in Patent Documents 1 to 4 are used, if the solder melting point is high (for example, 200 ° C. or higher) and the average particle diameter is small (for example, 30 μm or less), All of the properties, meltability and storage stability could not be satisfied.

  Accordingly, the present invention provides a solder powder that can provide a solder composition having excellent heat sagging property, meltability and storage stability even when a solder powder having a high solder melting point and a small average particle size is used, and An object of the present invention is to provide a solder composition and a printed wiring board using the above.

  In order to solve the above problems, the solder powder of the present invention has an aliphatic monocarboxylic acid or aromatic monocarboxylic acid having one or more hydroxyl groups in one molecule attached to the surface of the solder powder to be treated. It is characterized by being adsorbed or bonded.

In the solder powder of this invention, it is preferable that carbon number of the hydrocarbon group in the said aliphatic monocarboxylic acid is 12-20.
In the solder powder of the present invention, it is preferable that the hydrocarbon group in the aromatic monocarboxylic acid has 6 or more carbon atoms.
In the solder powder of the present invention, it is preferable that an average particle diameter of the solder powder to be processed is 30 μm or less.
In the solder powder of the present invention, the solder powder to be processed preferably has a melting point of 200 ° C. or higher.

The solder composition of the present invention comprises the solder powder and a flux containing a rosin resin, an activator, a solvent, and a thixotropic agent.
The printed wiring board of the present invention is characterized in that an electronic component is mounted on a printed wiring board using the solder composition.

The reason why a solder composition having excellent heat sagging property and storage stability can be obtained even when a solder powder having a high solder melting point and a small average particle diameter is used by the solder powder of the present invention is not necessarily clear. The present inventors infer as follows.
That is, in the flux of the solder composition, there is an activity capable of reducing metal oxides such as rosin resin, carboxylic acid and inorganic acid salt in order to reduce the oxide compound on the surface of the solder powder and melt the solder. Agents, solvents such as alcohols, and thixotropic agents are contained, and those having a hydroxyl group as a functional group of these compounds are often used. Actually, there is a case where an interaction due to hydrogen bonding between amide bonds is suggested as a factor of thixotropy and viscosity characteristics of a compound (amides) having an amide bond as a thixotropic agent.
In the present invention, an aliphatic monocarboxylic acid or an aromatic monocarboxylic acid having one or more hydroxyl groups in one molecule is attached, adsorbed, or bonded to the surface of the solder powder to be treated. . In such a case, the surface of the solder powder is in a state like a bond between the metal and the carboxylic acid, and the surface of the solder powder has one or more hydroxyl groups in one molecule. It is covered with a film of carboxylic acid or aromatic monocarboxylic acid. Thereby, the characteristic deterioration by the oxidation of solder powder can be prevented, and the storage stability of a solder composition can be improved. In addition, the present inventors infer that the film on the surface of the solder powder has a hydroxyl group, whereby a hydroxyl group and a hydrogen bond of the compound contained in the flux can be generated, and good characteristics against heating sagging can be expressed.

According to the present invention, even when a solder powder having a high solder melting point and a small average particle size is used, a solder powder that can provide a solder composition excellent in heat sagging property, meltability and storage stability, and It becomes possible to provide a solder composition and a printed wiring board using the above.
Therefore, according to the present invention, it is possible to support mounting of minute parts and minute pitches without using a flux having a strong reducing power and without using reflow under a nitrogen atmosphere condition in the mounting process.

  First, the solder powder of the present invention will be described. The solder powder of the present invention is characterized in that an aliphatic monocarboxylic acid or an aromatic monocarboxylic acid described below is attached to, adsorbed on, or bonded to the surface of the solder powder to be treated. is there.

The aliphatic monocarboxylic acid or aromatic monocarboxylic acid used in the present invention needs to have one or more hydroxyl groups in one molecule.
The hydrocarbon group in the aliphatic monocarboxylic acid preferably has 12 or more and 20 or less carbon atoms. The hydrocarbon group in the aromatic monocarboxylic acid preferably has 6 or more carbon atoms, and more preferably 6 to 18 carbon atoms. If the carbon number is less than the lower limit, deterioration of physical properties due to oxidation of the solder powder tends not to be prevented.

Examples of the aliphatic monocarboxylic acid include hydroxyenanthic acid, hydroxycapric acid, hydroxylauric acid, hydroxymyristic acid, hydroxypentadecyl acid, hydroxypalmitic acid, hydroxymargaric acid, and hydroxystearic acid.
Examples of the aromatic monocarboxylic acid include hydroxybenzoic acid (such as 4-hydroxybenzoic acid and salicylic acid), dihydroxybenzoic acid (such as 2,4-hydroxybenzoic acid), hydroxynaphthalene acid, and dihydroxyhydroxynaphthalene acid.

The solder powder to be treated used in the present invention is preferably composed only of lead-free solder powder (lead-free solder powder), but may be leaded solder powder. The melting point of the solder powder to be treated is preferably 200 ° C. or higher and 240 ° C. or lower, and more preferably 210 ° C. or higher and 230 ° C. or lower. Even in the case where the melting point is within the above range, according to the present invention, a solder composition having excellent heat sagging property, meltability and storage stability can be obtained. Moreover, when melting | fusing point exceeds the said upper limit, it exists in the tendency for reflow temperature to become high too much.
As the solder alloy in the solder powder to be treated, an alloy containing tin as a main component is preferable. Examples of the second element of the alloy include silver, copper, zinc, bismuth, and antimony. Furthermore, you may add another element (after 3rd element) to this alloy as needed. Examples of other elements include copper, silver, bismuth, antimony, aluminum, indium, nickel, cobalt, phosphorus, germanium, gallium, and zinc.
Although it does not specifically limit as an alloy composition of lead-free solder powder, Sn / Ag / Cu, Sn / Cu, Sn / Bi, Sn / Ag, Sn / Zn, Sn / Bi / Zn, etc. are mentioned. Here, the lead-free solder powder refers to a solder metal or alloy powder to which lead is not added. However, it is allowed that lead is present as an inevitable impurity in the lead-free solder powder. In this case, the amount of lead is preferably 500 ppm by mass or less.

  The average particle diameter of the solder powder to be treated is preferably 30 μm or less, more preferably 1 μm or more and 20 μm or less, and particularly preferably 2 μm or more and 10 μm or less. If the average particle diameter is within the above range, it is preferable in that it can be applied to recent mounting where the pitch is narrow. The average particle size can be measured with a laser diffraction / scattering particle size distribution analyzer.

As a method for adhering, adsorbing, or bonding the aliphatic monocarboxylic acid or the aromatic monocarboxylic acid to the surface of the solder powder to be treated, for example, the following method can be employed.
For example, the solder of the present invention is prepared by preparing a solution containing the aliphatic monocarboxylic acid or the aromatic monocarboxylic acid, immersing the solder powder to be treated in the solution, and then washing and drying. A powder can be produced. In addition, the manufacturing method of the solder powder of this invention is not limited to this method.

The solvent used for the solution is not particularly limited as long as it can dissolve the aliphatic monocarboxylic acid or the aromatic monocarboxylic acid. Examples of such a solvent include alcohols.
The processing conditions for the solder powder can be set as appropriate and are not particularly limited. For example, the concentration of the solution is preferably 5% by mass or more and 30% by mass or less. Moreover, it is preferable that the temperature of the said solution is 20 degreeC or more and 80 degrees C or less. The immersion time in the solution is preferably 10 minutes or more and 5 hours or less.

Next, the solder composition of the present invention will be described. The solder composition of the present invention is characterized by containing the above-described solder powder and a flux containing a rosin resin, an activator, a solvent and a thixotropic agent.
The blending amount of the solder powder is preferably 80% by mass or more and 95% by mass or less with respect to 100% by mass of the solder composition. When the amount of the solder powder is less than 80% by mass (when the amount of the flux exceeds 20% by mass), it tends to be difficult to form a sufficient solder joint when the obtained solder composition is used. On the other hand, when the blending amount of the solder powder exceeds 95% by mass (when the blending amount of the flux is less than 5% by mass), the flux as the binder is insufficient, and it is difficult to mix the flux and the solder powder. Tend to be.

The flux used in the present invention contains a rosin resin, an activator, a solvent and a thixotropic agent.
Examples of the rosin resin used in the present invention include natural rosin (unmodified rosin) and modified rosin. Examples of natural rosin include gum rosin, tall oil rosin, and wood rosin. Examples of the modified rosin include polymerized rosin, hydrogenated rosin, rosin ester, and rosin modified resin. These rosin resins may be used alone or in combination of two or more.

  The blending amount of the rosin resin is preferably 35% by mass or more and 60% by mass or less with respect to 100% by mass of the flux. If the blending amount is less than the lower limit, so-called solderability tends to be lowered. On the other hand, if the blending amount exceeds the upper limit, the flux residual amount tends to increase.

Examples of the activator used in the present invention include organic acids, organic halogen compounds, and amine activators. These activators may be used individually by 1 type, and may mix and use 2 or more types.
Examples of the organic acid include other organic acids in addition to monocarboxylic acid and dicarboxylic acid.
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, glycolic acid and the like.
Examples of the dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, tartaric acid, diglycolic acid and the like.
Examples of other organic acids include dimer acid, levulinic acid, lactic acid, acrylic acid, benzoic acid, salicylic acid, anisic acid, citric acid, and picolinic acid.

Examples of the organic halogen compound include dibromobutenediol, dibromosuccinic acid, 5-bromobenzoic acid, 5-bromonicotinic acid, and 5-bromophthalic acid.
Examples of the amine activator include amines (polyamines such as ethylenediamine), amine salts (amines such as trimethylolamine, cyclohexylamine, diethylamine, and organic acid salts such as amino alcohols and inorganic acid salts (hydrochloric acid, sulfuric acid, odors). Hydroacid, etc.)), amino acids (glycine, alanine, aspartic acid, glutamic acid, valine, etc.), amide compounds and the like.

  The blending amount of the activator is preferably 0.5% by mass or more and 20% by mass or less with respect to 100% by mass of the flux. If the blending amount is less than the lower limit, solder balls tend to be easily formed. On the other hand, if the blending amount exceeds the upper limit, the insulating property tends to decrease.

  Examples of the solvent used in the present invention include diethylene glycol, dipropylene glycol, triethylene glycol, hexylene glycol, hexyl diglycol, 1,5-pentanediol, methyl carbitol, butyl carbitol, 2-ethylhexyl diglycol, octane diol, Phenyl glycol is mentioned. These solvents may be used alone or in combination of two or more.

  The amount of the solvent is preferably 25% by mass or more and 60% by mass or less with respect to 100% by mass of the flux. If the blending amount is within the above range, the viscosity of the obtained solder composition can be appropriately adjusted to an appropriate range.

  Examples of the thixotropic agent used in the present invention include hardened castor oil, amides, kaolin, colloidal silica, organic bentonite, and glass frit. Among these, amides are preferable from the viewpoint of interaction with the surface of the solder powder of the present invention. These thixotropic agents may be used alone or in combination of two or more.

  The amount of the thixotropic agent is preferably 1% by mass or more and 10% by mass or less with respect to 100% by mass of the flux. If the blending amount is less than the lower limit, thixotropy cannot be obtained and the sagging tends to occur. On the other hand, if the amount exceeds the upper limit, the thixotropy tends to be too high and the coating tends to be poor.

  In addition to the rosin resin, the activator, the solvent, and the thixotropic agent, an additive may be added to the flux used in the present invention as necessary. Examples of the additive include a matting agent, a foaming agent, and an antifoaming agent. The blending amount of these additives is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 0.5% by mass or more and 5% by mass or less with respect to 100% by mass of the flux.

  Next, the printed wiring board of the present invention will be described. The printed wiring board of the present invention is characterized in that an electronic component is mounted on a printed wiring board using the solder composition described above. Therefore, the printed wiring board of the present invention can also be used for mounting of minute parts and minute pitches.

Examples of the coating apparatus used here include a metal mask printing machine, a screen printing machine, a dispenser, and a jet dispenser.
As a soldering method, a method using a laser light source may be adopted in addition to a method using a reflow furnace.
About the solder composition of this invention, you may leave the residue film | membrane covered with the wiring board carrying an electronic component, without wash | cleaning.

It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements and the like within a scope that can achieve the object of the present invention are included in the present invention.
For example, in the above embodiment, the solder composition flux using a rosin resin as a base resin is not limited to this. For example, an acrylic resin or an epoxy resin may be used as the base resin for the flux. In this case, the composition of the flux may be adjusted as appropriate in accordance with the base resin.
.

EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these examples.
<Preparation of solder powder>
[Example 1-1]
A surface treatment solution is prepared by adding 150 g of 12-hydroxystearic acid and 1000 mL of industrial ethanol to a flask, heating to 50 ° C., stirring at a rotation speed of 150 rpm under nitrogen atmosphere conditions, and dissolving 12-hydroxystearic acid. Got. 1000 g of solder powder (alloy composition: Sn-3.0Ag-0.5Cu, average particle size: 20.5 μm, particle size distribution: 14 to 27 μm, solder melting point: 217 to 220 ° C.) is introduced into this surface treatment solution. And stirred for 3 hours. The solder powder after stirring was suction filtered while being washed with isopropyl alcohol, and then dried in an air drying oven at 70 ° C. to obtain a surface-treated solder powder.

[Example 1-2]
A surface-treated solder powder was obtained in the same manner as in Example 1-1 except that 4-hydroxybenzoic acid was used in place of 12-hydroxystearic acid.
[Example 1-3]
A surface-treated solder powder was obtained in the same manner as in Example 1-1 except that 2,4-dihydroxybenzoic acid was used in place of 12-hydroxystearic acid.

[Comparative Example 1-1]
A surface-treated solder powder was obtained in the same manner as in Example 1-1 except that stearic acid was used instead of 12-hydroxystearic acid.
[Comparative Example 1-2]
A surface-treated solder powder was obtained in the same manner as Example 1-1 except that benzoic acid was used instead of 12-hydroxystearic acid.
[Comparative Example 1-3]
A surface-treated solder powder was obtained in the same manner as in Example 1-1 except that adipic acid was used in place of 12-hydroxystearic acid.

[Comparative Example 1-4]
5 g of octadecyltrimethoxysilane, 450 g of ethanol and 0.5 g of water were taken and stirred at room temperature for 30 minutes to hydrolyze the silane compound. Thereafter, 1000 g of solder powder (alloy composition: Sn-3.0Ag-0.5Cu, average particle size: 20.5 μm, particle size distribution: 14 to 27 μm, solder melting point: 217 to 220 ° C.) is added, and 3 at 45 ° C. Reaction was performed for a time, and after completion of the reaction, the pressure was reduced and ethanol and water were removed to obtain a surface-treated solder powder.
[Comparative Example 1-5]
DDP2 (manufactured by Nikko Chemicals) as a phosphate anionic surfactant 10 mL, heptane 1000 mL, solder powder (alloy composition: Sn-3.0Ag-0.5Cu, average particle size: 20.5 μm, particle size distribution: 14 (-27 μm, solder melting point: 217-220 ° C.) is put in a beaker and stirred with a magnetic stirrer at about 800 rpm for 15 minutes. Furthermore, the solution and the solder powder were separated, the solder powder was washed with heptane for 15 minutes, and dried in a furnace kept at 60 ° C. for 30 minutes, thereby obtaining a surface-treated solder powder.

<Preparation of solder composition>
[Example 2-1]
45 parts by mass of rosin resin (trade name “KE-604”, manufactured by Arakawa Chemical Industries), 10 parts by mass of activator A (trade name “SL-12”, manufactured by Okamura Oil Co., Ltd.), activator B (trade name “ UNIDYME14 "(manufactured by Maruzen Oil Chemicals Co., Ltd.) 5 parts by mass, solvent (2-ethylhexyl diglycol, manufactured by Nippon Emulsifier Co., Ltd.) 35 parts by mass, and thixotropic agent (trade name" Sripacs ZHH ", manufactured by Nippon Kasei Co., Ltd.) Was put into a container and mixed using a rough machine to obtain a flux.
Thereafter, 12% by mass of the obtained flux and 88% by mass of the surface-treated solder powder obtained in Example 1-1 were put into a container and mixed for 2 hours with a kneader to obtain a solder composition.

[Example 2-2]
Instead of the surface-treated solder powder obtained in Example 1-1, the surface-treated solder powder obtained in Example 1-2 (alloy composition: Sn-3.0Ag-0.5Cu, average particle size: 20. A solder composition was obtained in the same manner as in Example 2-1, except that 5 μm, particle size distribution: 14 to 27 μm, solder melting point: 217 to 220 ° C. were used.
[Example 2-3]
A solder composition was obtained in the same manner as in Example 2-1, except that the surface-treated solder powder obtained in Example 1-3 was used instead of the surface-treated solder powder obtained in Example 1-1. It was.

[Comparative Example 2-1]
Instead of the surface-treated solder powder obtained in Example 1-1, a solder composition was obtained in the same manner as in Example 2-1, except that a solder powder not subjected to surface treatment was used.
[Comparative Example 2-2]
A solder composition was obtained in the same manner as in Example 2-1, except that the surface-treated solder powder obtained in Comparative Example 1-1 was used instead of the surface-treated solder powder obtained in Example 1-1. It was.
[Comparative Example 2-3]
A solder composition was obtained in the same manner as in Example 2-1, except that the surface-treated solder powder obtained in Comparative Example 1-2 was used instead of the surface-treated solder powder obtained in Example 1-1. It was.
[Comparative Example 2-4]
A solder composition was obtained in the same manner as in Example 2-1, except that the surface-treated solder powder obtained in Comparative Example 1-3 was used instead of the surface-treated solder powder obtained in Example 1-1. It was.
[Comparative Example 2-5]
A solder composition was obtained in the same manner as in Example 2-1, except that the surface-treated solder powder obtained in Comparative Example 1-4 was used instead of the surface-treated solder powder obtained in Example 1-1. It was.
[Comparative Example 2-6]
A solder composition was obtained in the same manner as in Example 2-1, except that the surface-treated solder powder obtained in Comparative Example 1-5 was used instead of the surface-treated solder powder obtained in Example 1-1. It was.

[Comparative Example 2-7]
To the flux obtained in Example 2-1, 2 parts by mass of 4-hydroxybenzoic acid was further added and mixed to obtain a flux.
Thereafter, 12 mass% of the obtained flux and solder powder not subjected to surface treatment (alloy composition: Sn-3.0Ag-0.5Cu, average particle size: 20.5 μm, particle size distribution: 14 to 27 μm, Solder melting point: 217 to 220 ° C.) 88% by mass was put into a container and mixed for 2 hours in a kneader to obtain a solder composition.
[Comparative Example 2-8]
To the flux obtained in Example 2-1, 10 parts by mass of 4-hydroxybenzoic acid was further added and mixed to obtain a flux.
Thereafter, the obtained flux of 12% by mass and solder powder not subjected to surface treatment (alloy composition: Sn-3.0Ag-0.5Cu, average particle size: 20.5 μm, particle size distribution: 14 to 27 μm, solder (Melting point: 217-220 ° C.) 88% by mass was put into a container and mixed for 2 hours in a kneader to obtain a solder composition.

<Evaluation of solder powder and solder composition>
The solder powder and solder composition were evaluated (melting property and heat sagging property) by the following methods. The obtained results are shown in Table 1. Table 1 shows the substances used for the surface treatment in each example and the components added to the flux.
(1) Meltability (meltability test after solder powder deterioration)
Dispose 30 g of solder powder in a 50 mL container, cover the open mouth of the container with non-woven paper so that impurities such as dust do not enter, and leave it in a constant temperature and humidity chamber maintained at 40 ° C. and 90 RH% for 72 hours. Thereafter, a solder composition was prepared according to the operations of the examples and comparative examples, and the solder composition to be tested was printed on a ceramic plate using a circular pattern metal mask having a diameter of 6.5 mm, and a hot temperature set at 270 ° C. Heat on the plate for 10 seconds to melt the solder composition. After cooling, the solder powder balls (solder balls) that did not melt in the printing range are observed. When there is no solder ball, it is determined that the meltability is “good”. When the solder ball remains, it is determined that the meltability is “bad”.

(2) Heat sagging property JIS Z 3284 The same printed pattern as the method of Annex 7 (having a pattern hole of 3.0 mm x 0.7 mm, and arranging it in steps of 0.1 mm from 0.2 mm to 1.2 mm. A printed pattern having a pattern hole) is used to print a solder composition on a ceramic substrate to obtain a test plate. Then, the test plate is placed in a furnace heated to 170 ° C. and heated for 1 minute. The test plate after heating is observed, and the minimum interval at which the printed solder composition is not integrated is measured among the pattern holes.
Depending on the application of the solder composition, the particle size of the solder powder, the amount of the thixotropic agent in the flux, the amount of the flux in the solder composition, etc. can be adjusted as appropriate, and the range of heat sagability used in actual products Can be appropriately adjusted within the range that can be used in actual products. In this test, in order to clarify the effect of the surface treatment of the solder powder, the blending amount of the flux was made the same in both the examples and comparative examples, and the superiority or inferiority compared to the case of using the solder powder not subjected to the surface treatment was evaluated. ing.

As is apparent from the results shown in Table 1, the solder composition using the solder powder of the present invention (Examples 2-1 to 2-3) has a high solder melting point of 217 to 220 ° C. and an average particle diameter. Even when a solder powder as small as 20.5 μm was used, it was confirmed that the heat sagging property and the meltability were excellent. These solder compositions are also excellent in storage stability because the amount of reducing component in the flux is appropriate.
On the other hand, when solder powder that has not been subjected to surface treatment is used (Comparative Example 2-1), there is no resistance to oxidative degradation. As a result, it was found that the meltability test after deterioration of the solder powder was “bad”, and the heat sagging property was also bad at 0.5 mm.

  Also, when using solder powder with stearic acid, benzoic acid, adipic acid, octadecyltrimethoxysilane, or phosphate anionic surfactant attached or adsorbed or bonded to the surface of the solder powder (comparison) In Examples 2-2 to 2-6), it was found that the heat sagging property was as bad as 0.5 mm to 0.7 mm as in the case of using the solder powder not subjected to the surface treatment. In addition, the result of the meltability test after the solder powder deterioration is “good”, and it can be seen that the surface treatment is effective for the deterioration of the solder powder. In addition, this inventor presumes that the reason why heating sag does not improve depending on the type of surface treatment is as follows. In other words, even if a surface treatment film made of hydrocarbon organic compounds is formed on the surface of the solder powder, the interaction between hydrogen bonds and hydroxyl groups and amino groups such as carboxylic acid, alcohol solvent and thixotropic agent in the flux component The present inventors infer that it is in the same situation as the solder powder that is not processed at all.

  Further, even when solder powder not subjected to surface treatment is used and 4-hydroxybenzoic acid is added to the flux (Comparative Examples 2-7 and 2-8), it is “bad” in the meltability test after deterioration of the solder powder. Thus, it was found that the heat sagging property was also as bad as 0.5 mm. The inventor infers that the reason for this result is as follows. That is, 4-hydroxybenzoic acid is not attached to, or adsorbed to, or bonded to the surface of the solder powder, so it does not suppress the oxidative deterioration of the solder powder in advance, and reduces the oxidatively deteriorated solder powder surface. The ability to do is not high. Therefore, it becomes “defective” in the meltability test after solder powder deterioration. Moreover, since there is no interaction between the surface of the solder powder and the flux component, the inventor infers that the heat sag does not improve.

  The solder powder and the solder composition of the present invention can be suitably used as a technique for mounting a component on a printed wiring board of an electronic device.

Claims (7)

  It is characterized in that an aliphatic monocarboxylic acid or an aromatic monocarboxylic acid having one or more hydroxyl groups in one molecule is attached, adsorbed or bonded to the surface of the solder powder to be treated. Solder powder. The solder powder according to claim 1,
The solder powder, wherein the hydrocarbon group in the aliphatic monocarboxylic acid has 12 to 20 carbon atoms. In the solder powder according to claim 1 or 2,
The solder powder, wherein the hydrocarbon group in the aromatic monocarboxylic acid has 6 or more carbon atoms. In the solder powder according to any one of claims 1 to 3,
The solder powder, wherein the solder powder to be treated has an average particle size of 30 μm or less. In the solder powder according to any one of claims 1 to 4,
Solder powder, wherein the solder powder to be treated has a melting point of 200 ° C. or higher.   A solder composition comprising the solder powder according to any one of claims 1 to 5 and a flux containing a rosin resin, an activator, a solvent, and a thixotropic agent.   An electronic component is mounted on a printed wiring board using the solder composition according to claim 6.