CN106001996B

CN106001996B - Solder composition and electronic substrate using the same

Info

Publication number: CN106001996B
Application number: CN201610183145.9A
Authority: CN
Inventors: 中路将一; 石垣幸一; 中村步美
Original assignee: Tamura Corp
Current assignee: Tamura Corp
Priority date: 2015-03-26
Filing date: 2016-03-28
Publication date: 2020-04-07
Anticipated expiration: 2036-03-28
Also published as: JP6138846B2; JP2016182633A; CN106001996A

Abstract

The present invention provides a solder composition comprising a flux composition and (E) a solder powder, wherein the flux composition comprises (A) a rosin resin, (B) an activator, (C) a thixotropic agent and (D) a solvent, and the component (B) contains (B1) a polycarboxylic acid having a melting point of 160-220 ℃ inclusive and 3 or more carboxyl groups in 1 molecule.

Description

Solder composition and electronic substrate using the same

Technical Field

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

Background

In recent years, as electronic devices have become thinner and smaller, printed wiring boards have become finer, and mounting components mounted on the printed wiring boards have become smaller. In order to bond such fine components at a fine pitch, it is required to make the solder powder into fine particles (for example, an average particle diameter of 20 μm or less).

However, if a solder powder having a small average particle diameter is produced, the specific surface area increases, and the amount of oxide generated on the surface of the solder powder increases accordingly. In order to remove oxides formed on the surface of solder powder by melting, a solder composition containing a flux component having a high reducing power is required, and for example, an activator or the like in the flux component has been studied (for example, document 1: japanese patent application laid-open No. 2006-110580).

However, when an activator such as an organic acid is added, although the wettability of the solder tends to be high, there is a problem that corrosion is likely to occur in the soldered portion. Further, there is a problem that solder balls and dripping due to heating are likely to occur due to the micronization of the solder powder. As described above, with the micronization of solder powder, there are various problems, and there is no solder composition that can satisfy all of these requirements.

Disclosure of Invention

Accordingly, an object of the present invention is to provide a solder composition which has excellent wettability with solder and can sufficiently suppress corrosion of a solder ball at a soldered portion, and dripping due to heating, even when solder powder having a small average particle diameter (for example, an average particle diameter of 20 μm or less) is used, and an electronic substrate using the same.

In order to solve the above problems, the present invention provides a solder composition and an electronic substrate as described below.

The solder composition of the present invention comprises a flux composition and (E) solder powder, wherein the flux composition comprises (A) a rosin resin, (B) an activator, (C) a thixotropic agent and (D) a solvent, and the component (B) contains (B1) a polycarboxylic acid having a melting point of 160-220 ℃ inclusive and 3 or more carboxyl groups in 1 molecule.

In the solder composition of the present invention, the amount of the component (B1) is preferably 0.01 mass% or more and 15 mass% or less with respect to 100 mass% of the flux composition.

In the solder composition of the present invention, the melting point of the component (B1) is preferably 180 ℃ or higher and 200 ℃ or lower.

In the solder composition of the present invention, it is preferable that the component (B1) has 1 or more aromatic rings.

In the solder composition of the present invention, the component (B1) is preferably a compound represented by the following general formula (1).

In the general formula (1), X is the same or different and each independently represents hydrogen, a hydroxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted acyl group. Further, X is optionally bonded to each other to form a ring structure.

In the solder composition of the present invention, it is preferable that the component (B) further contains (B2) a dicarboxylic acid having a melting point of 100 ℃ or higher and 200 ℃ or lower.

In the solder composition of the present invention, it is preferable that the melting point of the component (E) is 200 ℃ or higher and 250 ℃ or lower, and the average particle diameter of the component (E) is 20 μm or less.

The electronic substrate of the present invention is obtained by mounting an electronic component on a substrate using the solder composition.

The solder composition of the present invention is excellent in wettability of solder even when solder powder having a small average particle diameter is used, and corrosion at a soldered portion, solder ball, and dripping due to heating can be sufficiently suppressed, and the reason for this is not clear, and the present inventors presume as follows.

That is, the present inventors speculate that the reason why the solder ball is generated when the solder powder having a small particle diameter (for example, the average particle diameter of the solder powder is 20 μm or less) is used is as follows. In short, during the preheating in the reflow step, the surface of the fine solder powder is oxidized to become foreign matter. This inhibits the solder powders from agglomerating during the main heating. Therefore, the present inventors speculate that the solder powder that cannot be agglomerated flows out between the pads together with the flux component to form a solder ball.

The flux composition of the present invention contains a (B1) component having 3 or more carboxyl groups in 1 molecule and having high activity, and the (B1) component can remove oxides on the surface of the solder powder. Since the melting point of the component (B1) is 160 ℃ or higher, the component (B1) becomes a component imparting thixotropy during preheating in the reflow step, and thus dripping due to heating can be suppressed. Further, since the melting point of the component (B1) is 160 ℃ or higher, the component imparts thixotropy even during the period from preheating to melting of the solder in the reflow step, and the outflow of the solder powder can be suppressed. Since the melting point of the component (B1) is 220 ℃ or lower, the component becomes liquid when the solder is melted in the reflow step, and thus unreacted materials are less likely to remain, and corrosion at the soldered portion is less likely to occur. The present inventors presume that the above-described effects of the present invention can be achieved as described above.

According to the present invention, it is possible to provide a solder composition which is excellent in wettability of solder even when solder powder having a small average particle diameter (for example, an average particle diameter of 20 μm or less) is used and which can suppress corrosion at a soldered portion, a solder ball, and dripping due to heating, and an electronic substrate using the solder composition.

Drawings

Fig. 1 is a graph showing a relationship between time and temperature at the time of reflow soldering in a test of wettability of solder.

Fig. 2 is an explanatory view for explaining a test method of corrosiveness.

Detailed Description

The solder composition of the present invention contains the flux composition described below and (E) solder powder described below.

[ flux composition ]

The flux composition used in the present invention is a component other than the above-mentioned component (E) in the solder composition, and contains (a) a rosin-based resin, (B) an activator, (C) a thixotropic agent, and (D) a solvent.

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 13% by mass or less, based on 100% by mass of the solder composition. When the amount of the flux composition to be mixed is less than 5% by mass (when the amount of the solder powder to be mixed exceeds 95% by mass), the flux composition as the binder is insufficient, and therefore the flux composition and the solder powder tend to be hardly mixed, whereas when the amount of the flux composition to be mixed exceeds 35% by mass (when the amount of the solder powder to be mixed is less than 65% by mass), sufficient soldering tends to be hardly formed when the obtained solder composition is used.

[ (A) component ]

The rosin-based resin (A) used in the present invention includes rosins and rosin-based modified resins, the rosins include gum rosin, wood rosin, tall oil rosin, disproportionated rosin, polymerized rosin, hydrogenated rosin, and derivatives thereof, the rosin-based modified resin includes unsaturated organic acid-modified resins of the rosins (modified resins of aliphatic unsaturated monobasic acids such as (meth) acrylic acid, aliphatic unsaturated dibasic acids such as α -unsaturated carboxylic acids such as fumaric acid and maleic acid, and unsaturated carboxylic acids having an aromatic ring such as cinnamic acid) which are reaction components of the Diels-Alder reaction, rosin acids such as these modified resins, and substances containing these modified substances as main components, and the rosin-based resins may be used alone in 1 kind or in a mixture of 2 or more kinds.

The amount of the component (a) is preferably 30 to 70 mass%, more preferably 35 to 60 mass%, based on 100 mass% of the flux composition. (A) When the amount of the component (a) is less than the lower limit, solderability, which is a property of preventing oxidation of the copper foil surface of the solder pad and the like and making the surface of the solder easily wet by molten solder, tends to be lowered and solder balls tend to be easily generated, while when the amount of the component (a) is more than the upper limit, the residual flux tends to be increased.

[ (B) component ]

The activator (B) used in the present invention is required to contain the component (B1) described below.

The component (B) is a polycarboxylic acid having a melting point of 160 to 220 ℃ inclusive and 3 or more carboxyl groups in 1 molecule.

When the melting point of the component (B) is in the range of 160 ℃ to 220 ℃, corrosion of the soldered portion, solder ball, and dripping due to heating can be sufficiently suppressed. From the same viewpoint, the melting point of the component (B1) is more preferably 180 ℃ or higher and 200 ℃ or lower, and particularly preferably 190 ℃ or higher and 200 ℃ or lower.

When the number of carboxyl groups in 1 molecule of the component (B1) is 3 or more, the wettability of the solder can be sufficiently improved. From the same viewpoint, the number of carboxyl groups in 1 molecule is more preferably 3 or more and 6 or less, and particularly preferably 3.

The component (B1) may be an aliphatic polycarboxylic acid or an aromatic polycarboxylic acid, but is preferably an aromatic polycarboxylic acid having 1 or more aromatic rings from the viewpoint of activation. Further, examples of the aromatic ring in the component (B1) include: benzene rings, naphthalene rings, and the like. Among them, benzene rings are preferable from the viewpoint of lowering the melting point of the (B1) component.

Examples of the component (B1) include compounds represented by the following general formula (1).

In the above general formula (1), X's are the same or different. Each X independently represents hydrogen, a hydroxyl group, a substituted or unsubstituted alkyl group (e.g., methyl group or ethyl group), a substituted or unsubstituted aryl group (e.g., phenyl group), a substituted or unsubstituted alkenyl group (e.g., vinyl group), a substituted or unsubstituted alkoxy group (e.g., methoxy group or ethoxy group), or a substituted or unsubstituted acyl group (e.g., acetyl group). X are optionally bonded to each other to form a ring structure.

Specific examples of the component (B1) include trimellitic acid and the like.

The amount of the component (B1) is preferably 0.01 to 15 mass%, more preferably 0.1 to 8 mass%, still more preferably 0.5 to 4 mass%, and particularly preferably 0.8 to 2 mass% with respect to 100 mass% of the flux composition. (B1) When the amount of the component is less than the lower limit, solder balls tend to be easily generated and solder drops tend to be easily generated, while when the amount exceeds the upper limit, the insulating property of the flux composition tends to be lowered.

The component (B) preferably further contains (B2) a dicarboxylic acid having a melting point of 100 ℃ or higher and 200 ℃ or lower (more preferably 120 ℃ or higher and 200 ℃ or lower, and particularly preferably 160 ℃ or higher and 200 ℃ or lower). Since the fluidity of the activator in the flux composition can be adjusted to a more appropriate range by the component (B2), the action of the component (B1) can be synergistically enhanced.

Examples of the component (B2) include: malonic acid, succinic acid, adipic acid, suberic acid, sebacic acid, and the like. Among them, succinic acid and adipic acid are preferable, and succinic acid is more preferable from the viewpoint of activation. These (B2) components may be used alone in 1 kind, or may be used in combination of 2 or more kinds.

When the above-mentioned (B2) component is used, the amount of the component (B2) is preferably 0.1% by mass or more and 5% by mass or less, more preferably 0.2% by mass or more and 3% by mass or less, and particularly preferably 0.5% by mass or more and 2% by mass or less, relative to 100% by mass of the flux composition. When the amount of the component (B2) is less than the lower limit, solder tends to easily drip, while when it exceeds the upper limit, the insulating property of the flux composition tends to be lowered.

In the component (B), the component (B1), the component (B1), and an organic acid other than the component (B2) (hereinafter referred to as the component (B3)) may be used in combination.

The component (B3) may include, in addition to monocarboxylic acids and dicarboxylic acids other than the component (B2), organic acids other than the component (B1).

As monocarboxylic acids, there may be mentioned: formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, capric acid, lauric acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, stearic acid, methyl stearic acid, arachidic acid, behenic acid, lignoceric acid, glycolic acid, and the like.

Examples of the dicarboxylic acid other than the component (B2) include glutaric acid and the like.

As other organic acids, there may be mentioned: dimer acid, levulinic acid, lactic acid, acrylic acid, benzoic acid, salicylic acid, anisic acid, citric acid, picolinic acid, and the like.

These (B3) components may be used alone in 1 kind, or may be used in combination of 2 or more kinds. Among these components (B3), dimer acid is preferably used. Since the solder powder tends to be prevented from being re-oxidized by the dimer acid, the effect of the (B1) component can be synergistically enhanced.

The amount of the component (B3) is preferably 0.5% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 15% by mass or less, and particularly preferably 5% by mass or more and 15% by mass or less, based on 100% by mass of the flux composition. (B3) When the amount of the component is less than the lower limit, the activating action tends to be insufficient, while when it exceeds the upper limit, the insulating property of the flux composition tends to be lowered.

In the component (B), the component (B1) and the non-dissociative activator (B4) containing a non-dissociative halogenated compound may be used in combination. The component (B4) can impart an activating action as the component (B4) and hardly affects the activating actions of the components (B1) to (B3).

Examples of the component (B4) include non-salt organic compounds in which halogen atoms are covalently bonded. The halogenated compound may be a compound formed by covalent bonds of individual elements such as chlorine, bromine, iodine, and fluorine, for example, chloride, bromide, iodide, and fluoride, or a compound having covalent bonds of any 2 or all of chlorine, bromine, iodine, and fluorine. In order to improve the solubility of these compounds in an aqueous solvent, a substance having a polar group such as a hydroxyl group or a carboxyl group, for example, a halogenated alcohol or a halogenated carboxylic acid, is preferable. Examples of the halogenated alcohol include: 2, 3-dibromopropanol, 2, 3-dibromobutanediol, trans-2, 3-dibromo-2-butene-1, 4-diol, bromoalcohols such as 1, 4-dibromo-2-butanol and tribromoneopentanol, chlorohydrols such as 1, 3-dichloro-2-propanol and 1, 4-dichloro-2-butanol, fluoroalcohols such as 3-fluorocatechol, and other compounds similar to these. Examples of the halogenated carboxylic acid include: iodocarboxylic acids such as 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid and 5-iodoanthranilic acid, chlorocarboxylic acids such as 2-chlorobenzoic acid and 3-chloropropionic acid, bromocarboxylic acids such as 2, 3-dibromopropionic acid, 2, 3-dibromosuccinic acid and 2-bromobenzoic acid, and other compounds similar to these. Further, as these compounds, there can be mentioned: tris (2, 3-dibromopropyl) isocyanurate, and the like. These activators may be used alone in 1 kind, or may be used in combination of 2 or more kinds.

The amount of the component (B4) is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.2% by mass or more and 5% by mass or less, and particularly preferably 0.5% by mass or more and 2% by mass or less, based on 100% by mass of the flux composition. (B4) When the amount of the component is less than the lower limit, the spread of solder coating tends to be reduced, while when it exceeds the upper limit, the insulation property of the flux composition tends to be reduced.

The total amount of the component (B) 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 particularly preferably 5% by mass or more and 20% by mass or less, based on 100% by mass of the flux composition. (B) When the amount of the component is less than the lower limit, solder balls tend to be easily generated, while when the amount exceeds the upper limit, the insulating property of the flux composition tends to be lowered.

[ (C) ingredient ]

As the thixotropic agent (C) used in the present invention, there may be mentioned: solidified castor oil, amides, kaolin, colloidal silicon dioxide, organic bentonite, glass powder and the like. These thixotropic agents may be used alone in 1 kind, or may be used in combination of 2 or more kinds.

The amount of the component (C) is preferably 1 mass% or more and 15 mass% or less, and more preferably 2 mass% or more and 10 mass% or less, based on 100 mass% of the flux composition. When the amount is less than the lower limit, thixotropy is not obtained and dripping tends to occur easily, while when it exceeds the upper limit, thixotropy becomes too high and printing failure tends to occur easily.

[ (D) component ]

As the solvent (D) used in the present invention, a known solvent can be suitably used. As such a solvent, a water-soluble solvent having a boiling point of 170 ℃ or higher is preferably used.

Examples of such solvents include: diethylene glycol, dipropylene glycol, triethylene glycol, hexylene glycol, diethylene glycol hexylether, 1, 5-pentanediol, diethylene glycol methyl ether, diethylene glycol butyl ether, diethylene glycol-2-ethylhexyl Ether (EHDG), octanediol, ethylene glycol phenyl ether, diethylene glycol monohexylether, tetraethylene glycol dimethyl ether (MTEM). These solvents may be used alone in 1 kind, or may be used in combination of 2 or more kinds.

The amount of the component (D) is preferably 20 to 60 mass%, more preferably 30 to 50 mass%, based on 100 mass% of the flux composition. If the amount of the solvent is within the above range, the viscosity of the obtained solder composition can be appropriately adjusted to an appropriate range.

[ other ingredients ]

The flux composition used in the present invention may contain, in addition to the component (a), the component (B), the component (C), and the component (D), other additives, and further other resins, as required. As other additives, there may be mentioned: defoaming agent, antioxidant, modifier, delustering agent, foaming agent and the like. Examples of the other resin include acrylic resins.

[ (E) ingredient ]

The solder powder (E) used in the present invention is preferably composed of only a lead-free solder powder, but may be a lead-containing solder powder. As the solder alloy in the solder powder, an alloy containing tin (Sn) as a main component is preferable. Further, as the second element of the alloy, there can be mentioned: silver (Ag), copper (Cu), zinc (Zn), bismuth (Bi), antimony (Sb), and the like. Further, other elements (third and above elements) may be added to the alloy as necessary. As other elements, there may be mentioned: copper, silver, bismuth, antimony, aluminum (Al), indium (In), and the like.

In addition, the solder powder is preferably a lead-free solder powder from the viewpoint of influence on the environment. Here, the lead-free solder powder refers to a powder of a solder metal or alloy to which lead is not added. Among them, the presence of lead as an inevitable impurity in the lead-free solder powder is allowed, but in this case, the amount of lead is preferably 100 mass ppm or less.

Specific examples of the lead-free solder powder include: Sn-Ag, Sn-Ag-Cu, Sn-Ag-Bi, Sn-Ag-Cu-Bi, Sn-Sb, Sn-Zn-Bi, Sn-Zn-Al, Sn-Ag-Bi-In, Sn-Ag-Cu-Bi-In-Sb, In-Ag and the like. Among them, from the viewpoint of soldering strength, Sn — Ag — Cu based solder alloys are preferably used. The melting point of the Sn-Ag-Cu based solder is usually 200 ℃ or higher and 250 ℃ or lower. In the Sn — Ag — Cu based solder, the solder having a low silver content has a melting point of 210 ℃ to 250 ℃.

The average particle size of the component (E) is usually 1 μm or more and 40 μm or less, and from the viewpoint of coping with an electronic substrate having a narrow pitch of lands, the upper limit of the average particle size is preferably 25 μm or less, more preferably 20 μm or less, still more preferably 15 μm or less, and particularly preferably 12 μm or less. On the other hand, the lower limit of the average particle size is not particularly limited, and may be, for example, 2 μm or more, or 3 μm or more. The average particle diameter can be measured by a dynamic light scattering particle diameter measuring apparatus.

Further, according to the solder composition of the present invention, even when the average particle size of the solder powder is small, the solder has excellent wettability, and corrosion at the soldered portion, solder ball, and dripping due to heating can be sufficiently suppressed.

[ method for producing solder composition ]

The solder composition of the present invention can be produced by mixing the flux composition described above and the solder powder (E) described above in the above-mentioned predetermined ratio and then stirring and mixing them.

[ electronic substrate ]

Next, the electronic substrate of the present invention will be explained. The electronic substrate (such as a printed circuit board) of the present invention is obtained by mounting an electronic component on a substrate (such as a printed wiring board) using the solder composition described above. Therefore, the electronic substrate of the present invention can sufficiently suppress corrosion at the soldered portion, solder balls, and dripping due to heating.

As the coating apparatus used here, there are exemplified: screen printers, metal mask printers, dispensers, jetting dispensers, etc.

In addition, the electronic component can be mounted on the substrate by a reflow step of mounting the electronic component on the printed wiring board by providing the electronic component on the solder composition applied by the application device and heating the electronic component in a reflow furnace under a predetermined condition.

In the reflow step, the electronic component is placed on the solder composition and heated in a reflow furnace under a predetermined condition. In this reflow step, the electronic component and the printed wiring board can be sufficiently soldered to each other. As a result, the electronic component can be mounted on the printed wiring board.

The reflow conditions may be set as appropriate according to the melting point of the solder. For example, when a Sn-Ag-Cu based solder alloy is used, preheating is performed at a temperature of 150 to 200 ℃ for 60 to 120 seconds, and the peak temperature may be set to 230 to 270 ℃.

The solder composition and the electronic board of the present invention are not limited to the above embodiments, and the present invention includes modifications, improvements, and the like within a range that can achieve the object of the present invention.

For example, the electronic board is not limited to the above-described electronic board, but the printed wiring board and the electronic component are bonded by a reflow process. For example, the printed wiring board and the electronic component may be bonded by a step of heating the solder composition with a laser (laser heating step) instead of the reflow step. In this case, the laser light source is not particularly limited, and can be appropriately used according to the wavelength corresponding to the metal absorption band. Examples of the laser light source include: solid-state laser (ruby, glass, YAG, etc.), semiconductor laser (GaAs, InGaAsP, etc.), liquid laser (dye, etc.), gas laser (He-Ne, Ar, CO)₂Quasi-molecule, etc.).

Examples

The present invention will 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 as follows.

(component (A))

Rosin resin: hydrogenated acid-modified rosin available under the trade name "Pine crystal KE-604", available from Mitsuwa chemical industries, Ltd

((B1) component)

An activator A: trimellitic acid (see the following structural formula (S1)) has a melting point of 195 DEG C

(other Components)

An activator B: trimellitic acid (see the following structural formula (S2)) has a melting point of 229-231 DEG C

An activator C: trimesic acid (see the following structural formula (S3)) has a melting point of more than 300 DEG C

((B2) component)

An activator D: succinic acid, melting point of 185-187 DEG C

((B3) component)

An activator E: pyridinecarboxylic acid

An activator F: dimer acid, trade name "UNIDYME 14", manufactured by Arizona Chemical Co

An activator G: glutaric acid, melting point of 95-98 DEG C

((B4) component)

An activator H: trans-2, 3-dibromo-2-butene-1, 4-diol (TDBD)

(component (C))

Thixotropic agent: cured castor oil, trade name "HIMAKO (ヒマ hard)", manufactured by KF writing Co

(component (D))

Solvent A: diethylene glycol-2-ethylhexyl Ether (EHDG)

Solvent B: tetraethylene glycol dimethyl ether (MTEM)

((E) component)

Solder powder: a particle size of 5 to 15 μm (average particle size of 10 μm), a solder melting point of 220 ℃, and a solder composition Sn/Ag3.0/Cu0.5

(other Components)

Antioxidant: hindered phenol antioxidant under the trade name "IRGANOX 245" manufactured by Ciba Japan

[ example 1]

A flux composition was obtained by charging 36 mass% of a rosin-based resin, 6 mass% of a thixotropic agent, 30 mass% of a solvent a, 14.9 mass% of a solvent B, 0.1 mass% of an activator a, 0.5 mass% of an activator D, 0.5 mass% of an activator E, 6 mass% of an activator F, 3 mass% of an activator G, 1 mass% of an activator H, and 2 mass% of an antioxidant into a container and mixing them using a planetary mixer.

Then, the obtained flux composition 11 mass% and solder powder 89 mass% (total 100 mass%) were put into a container and mixed using a planetary mixer, thereby preparing a solder composition.

[ examples 2 to 5]

Solder compositions were obtained in the same manner as in example 1, except that various materials were blended in accordance with the compositions shown in table 1.

[ comparative examples 1 to 7]

Solder compositions were obtained in the same manner as in example 1, except that various materials were blended in accordance with the compositions shown in table 2.

< evaluation of solder composition >

The solder composition was evaluated by the following methods (solder ball, solder wettability, corrosiveness, and heat dripping). The obtained results are shown in tables 1 and 2.

(1) Solder ball

The test of the solder ball (solder ball) was carried out according to the method described in appendix 11 of JIS Z3284-1994. That is, a ceramic plate (size: 50 mm. times.50 mm, thickness: 0.5mm) was prepared, and a solder composition was printed on the ceramic plate using a metal mask having a circular pattern hole with a diameter of 6.5mm and a thickness of 0.2mm to obtain a test piece. The test piece was placed on a hot plate adjusted to 260 ℃ and kept for 5 seconds after the solder melted. The test piece was observed with a microscope, and the solder ball was evaluated according to the following criteria.

◎ the solder (powder) melts and the solder becomes a larger ball with no solder balls around it.

○ the solder (powder) melts, the solder becomes a large ball, and there are 3 or less solder balls with a diameter of 75 μm or less around the ball.

X: the solder (powder) melts, and the solder becomes a large ball, and 4 or more solder balls having a diameter of 75 μm or less or a plurality of fine balls are arranged in a semi-continuous ring shape around the solder.

X: there is a portion where the solder (powder) is not melted, and a plurality of fine balls are arranged in a semi-continuous ring shape around the larger balls of the solder.

(2) Wettability of solder

The solder wettability (dewetting) test was carried out according to the method described in appendix 10 of JIS Z3284-1994. That is, a phosphorus deoxidized copper plate (size: 50 mm. times.50 mm, thickness: 0.5mm) was prepared and polished with a polishing agent. A test piece was obtained by printing a solder composition on the phosphorus deoxidized copper plate using a metal mask having a circular pattern hole with a diameter of 6.5mm and a thickness of 0.2 mm. The test piece was subjected to reflow treatment under the reflow conditions shown in fig. 1 in a nitrogen atmosphere. The test piece was observed with a microscope, and the wettability of the solder was evaluated according to the following criteria.

○ the solder composition-coated portions are all in a state of being wetted by the solder.

△ the majority of the solder composition coated is in a state of being wetted by the solder (dewetting is also included).

(3) Corrosiveness of

The corrosion test was carried out according to the method described in appendix 4 of JIS Z3284-1994. That is, 2 copper plates (size: 50 mm. times.50 mm, thickness: 0.5mm) were prepared, polished with a polishing agent, and subjected to ultrasonic cleaning. Then, as shown in fig. 2, a copper plate having 5mm portions at both ends thereof bent in コ -shapes was used as a first substrate a, and a copper plate having 6mm portions at both ends thereof bent in コ -shapes was used as a second substrate B. The solder composition P was printed on the second substrate B using a metal mask having a circular pattern hole with a diameter of Φ 6.5mm and a thickness of 0.2 mm. The second substrate B was covered with the first substrate A to prepare a test piece. The test piece was placed on a hot plate adjusted to a temperature of 270 ℃ and kept for 5 seconds after the solder was melted. The test piece was placed in a constant temperature and humidity chamber set at 40 ℃ and a relative humidity of 90% and allowed to stand for 96 hours to obtain a test piece after the test. The test piece after the test was visually observed to confirm the presence or absence of discoloration of the residue on the first substrate a and the second substrate B, and further, the residue was washed with IPA to visually confirm the presence or absence of discoloration of copper, and the discoloration of the copper foil was evaluated according to the following criteria.

○ No discoloration of the residue and of the copper.

△ No discoloration of the residue, but discoloration of the copper surface.

X: there was discoloration of the residue and discoloration of the copper surface.

(4) Heated to drip

The heat dripping test was carried out according to the method described in appendix 8 of JIS Z3284-1994. That is, a copper-clad laminate (size: 80 mm. times.60 mm, thickness: 1.6mm) was prepared, polished with a polishing agent, and the surface was wiped with IPA. Then, a test piece was obtained by printing a solder composition on the copper-clad laminate using a metal mask having 2 kinds of pattern holes (i) of 3.0 × 0.7mm or (ii) of 3.0 × 1.5mm and having a thickness of 0.2mm, the pattern holes being arranged at a pitch of 0.1 mm. The test piece was heated in an oven set at 150 ℃ for 1 minute. The test piece was visually observed, and the dropping by heating was evaluated at a minimum interval at which all the printed solder compositions were not integrated in 5 columns of 2 patterns. It should be noted that the smaller the minimum interval, the better the heat dropping.

TABLE 1

TABLE 2

From the results shown in tables 1 and 2, it was confirmed that the solder balls of the solder compositions of the present invention (examples 1 to 5) were excellent in solder wettability, corrosiveness and thermal dripping. Therefore, it was confirmed that the solder composition of the present invention has excellent wettability with solder and can sufficiently suppress corrosion at a soldered portion, solder ball, and dripping due to heating even when solder powder having a small average particle diameter (solder composition is tin-silver-copper, and melting point of solder is 200 ℃ or higher and 250 ℃ or lower) is used.

In contrast, it is found that when the solder composition containing no component (B1) is used (comparative examples 1 to 7), the solder ball and solder are insufficient in wettability, corrosiveness, and thermal dripping.

Claims

1. A solder composition comprising a flux composition and a solder powder having a melting point E of 200 ℃ or higher and 250 ℃ or lower, the flux composition comprising A a rosin-based resin, B an activator, C a thixotropic agent and D a solvent, wherein,

the component B contains an aromatic polycarboxylic acid having a melting point of B1 of 180 to 220 ℃ and 3 or more carboxyl groups in 1 molecule and 1 or more aromatic rings, and B3 dimer acid.

2. The solder composition according to claim 1, wherein the amount of the component B1 is 0.01 to 15 mass% based on 100 mass% of the flux composition.

3. The solder composition according to claim 1, wherein the melting point of the component B1 is 180 ℃ or more and 200 ℃ or less.

4. The solder composition according to claim 1, wherein the component B1 is a compound represented by the following general formula (1),

in the general formula (1), X is the same or different and each independently represents hydrogen, a hydroxyl group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted acyl group, and X is optionally bonded to each other to form a ring structure.

5. The solder composition according to claim 1, wherein the component B further contains a dicarboxylic acid having a melting point of B2 of 100 ℃ or higher and 200 ℃ or lower.

6. The solder composition according to claim 1, wherein an average particle diameter of the E component is 20 μm or less.

7. An electronic substrate, wherein an electronic component is mounted on a substrate using the solder composition according to any one of claims 1 to 6.