Solder composition and electronic substrate

Abstract

To provide a solder composition that can sufficiently suppress voids and has excellent storage stability. [Solution] A solder composition comprising a flux composition containing (A) a rosin resin, (B) an activator, (C) an amine compound, and (D) a solvent, and (E) solder powder, wherein the (D) component contains (D1) a 1,2-alkanediol having 3 to 7 carbon atoms.

Description

Technical Field

[0001] The present invention relates to a solder composition and an electronic substrate.

Background Art

[0002] A solder composition is a mixture obtained by kneading a flux composition (such as a rosin-based resin, an activator, and a solvent) with solder powder into a paste form (for example, Patent Document 1). In this solder composition, solderability such as solder meltability and the property that solder easily wets and spreads (solder wetting and spreading), as well as suppression of voids and printability, are required. On the other hand, due to the diversification of functions of electronic devices, large electronic components such as LGA (Land Grid Array) are being mounted on electronic substrates. Among large electronic components, there are electronic components with a large electrode terminal area (for example, QFN (Quad Flatpack No Lead), power transistor). In such electronic components, since the printing area of the solder composition is large, voids tend to occur. Conventionally, in a solder composition, a combination of glycol ether solvents is usually used as a solvent. However, there is a problem that when only a combination of glycol ether solvents is used, void discharge is insufficient and it is difficult to reduce voids.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the other hand, when a glycol ether solvent and a diol solvent are used in combination, voids can be reduced, but in such a case, there is a problem that the storage stability of the solder composition decreases.

[0005] The present invention aims to provide a solder composition that can sufficiently suppress voids and has excellent storage stability, as well as an electronic substrate using the same. [Means for solving the problem]

[0006] According to the present invention, the following solder composition and electronic substrate are provided. [1] A solder composition comprising (A) a rosin resin, (B) an activator, (C) an amine compound, and (D) a solvent, and (E) solder powder, The aforementioned component (D) contains (D1) a 1,2-alkanediol having 3 to 7 carbon atoms. Solder composition. [2] In the solder composition described in [1], The (D1) component is at least one selected from the group consisting of 1,2-pentanediol and 1,2-butanediol. Solder composition. [3] In the solder composition described in [1] or [2], The (C) component is at least one selected from the group consisting of (C1) imidazole compounds and (C2) triazole compounds. Solder composition. [4] An electronic circuit board comprising a soldered portion using the solder composition described in any of [1] to [3]. [Effects of the Invention]

[0007] According to one aspect of the present invention, a solder composition that can sufficiently suppress voids and has excellent storage stability, as well as an electronic substrate using the same, can be provided. [Modes for carrying out the invention]

[0008] First, the solder composition according to this embodiment will be described. The solder composition according to this embodiment is a solder composition containing a flux composition containing (A) a rosin-based resin, (B) an activator, (C) an amine compound, and (D) a solvent, and (E) solder powder. The component (D) contains (D1) a 1,2-alkanediol having 3 to 7 carbon atoms.

[0009] According to this embodiment, a solder composition can be obtained that can sufficiently suppress voids and has excellent storage stability. The reason for this is not entirely clear, but the inventors speculate as follows. In other words, in the solder composition according to this embodiment, (D1) a 1,2-alkanediol having 3 to 7 carbon atoms is used as the (D) solvent. This (D1) component belongs to the diol-based solvents and has a high void suppression effect. Diol-based solvents generally tend to adversely affect the storage stability of solder compositions. However, surprisingly, 1,2-alkanediols having hydroxyl groups at positions 1 and 2 and having 3 to 7 carbon atoms do not adversely affect storage stability. Therefore, in this embodiment, this (D1) component improves the void suppression effect while maintaining storage stability. The inventors surmise that the effects of the present invention described above are achieved in this way.

[0010] [Flax composition] Next, the flux composition used in this embodiment will be described. The flux composition used in this embodiment is a component of the solder composition other than the solder powder, and contains (A) a rosin-based resin, (B) an activator, (C) an amine compound, and (D) a solvent, which will be described below.

[0011] [(A) component] Examples of (A) rosin-based resins used in this embodiment include 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 rosin include fully hydrogenated rosin, partially hydrogenated rosin, and hydrogenated unsaturated organic acid-modified rosin (also called "hydrogenated acid-modified rosin") which is a rosin modified with unsaturated organic acids (aliphatic unsaturated monobasic acids such as (meth)acrylic acid, aliphatic unsaturated dibasic acids such as fumaric acid and maleic acid, and unsaturated carboxylic acids having aromatic rings such as cinnamic acid). These rosin-based resins may be used individually or mixed in groups of two or more.

[0012] The amount of component (A) is preferably 20% to 60% by mass, and more preferably 30% to 50% by mass, based on 100% by mass of the flux composition. If the amount of component (A) is above the lower limit, oxidation of the copper foil surface of the soldering land can be prevented, making it easier for molten solder to wet the surface, thereby improving solderability and sufficiently suppressing solder balls. Furthermore, if the amount of component (A) is below the upper limit, the amount of flux residue can be sufficiently suppressed.

[0013] [(B) Component] The (B) activator used in this embodiment preferably contains an (B1) organic acid. This (B1) component can improve solder meltability.

[0014] (B1) Component examples include monocarboxylic acids, dicarboxylic acids, and other organic acids. These may be used individually or in combination of two or more. Examples of monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, capric acid, lauric acid, myristic acid, pentadecyl acid, palmitic acid, margaric acid, stearic acid, tubercurostearic 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, dodecanediic acid, fumaric acid, maleic acid, diglycolic acid, and tartaric acid. Other organic acids include 1,2,3-propanetricarboxylic acid, 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.

[0015] The amount of component (B1) is preferably 2% by mass or more and 15% by mass or less, and more preferably 4% by mass or more and 10% by mass or less, based on 100% by mass of the flux composition. If the amount of component (B1) is above the lower limit, the meltability tends to be improved, while if it is below the upper limit, the insulating properties of the flux composition tend to be maintained.

[0016] Component (B) may further contain other activators (such as halogenated activators and amine activators) in addition to component (B1), as long as they do not inhibit the effects of the present invention. The total amount of component (B1) is preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass or more, based on 100% by mass of component (B).

[0017] The amount of component (B) is preferably 2% by mass or more and 15% by mass or less, and more preferably 4% by mass or more and 10% by mass or less, based on 100% by mass of the flux composition. If the amount of component (B) is above the lower limit, the activity tends to be improved, while if it is below the upper limit, the insulating properties of the flux composition tend to be maintained.

[0018] [Component (C)] Examples of the amine compound (C) used in this embodiment include an imidazole compound (C1) and a triazole compound (C2). This component (C) can improve solderability or storage stability without adversely affecting voids. These may be used alone or in combination of two or more. In particular, it is preferable to use the component (C1) and the component (C2) in combination.

[0019] The component (C1) is preferably an imidazole compound having an alkyl group, and more preferably an imidazole compound having no phenyl group. Examples of the component (C1) include 2-ethyl-4-methylimidazole, 2,4-dimethylimidazole, 2-ethylimidazole, 2-pentylimidazole, and 2-undecyl-4-methylimidazole. Among these, it is preferable to use 2-ethyl-4-methylimidazole. When using the component (C1), its blending amount is preferably 1% by mass or more and 10% by mass or less, and more preferably 2% by mass or more and 7% by mass or less with respect to 100% by mass of the flux composition.

[0020] The component (C2) is preferably a triazole compound having a benzene ring. Examples of the component (C2) include benzotriazole, carboxybenzotriazole, methylbenzotriazole, 2-(2-hydroxy-5-methylphenyl)benzotriazole, and 1,2,4-triazole. Among these, it is preferable to use benzotriazole. When using the component (C2), its blending amount is preferably 0.1% by mass or more and 3% by mass or less, and more preferably 0.2% by mass or more and 1% by mass or less with respect to 100% by mass of the flux composition.

[0021] (C) The amount of component (C) is preferably 2% to 12% by mass, and more preferably 3% to 7% by mass, based on 100% by mass of the flux composition. If the amount of component (B) is above the lower limit, solderability tends to be improved, while if it is below the upper limit, the insulating properties of the flux composition tend to be maintained.

[0022] [(D) component] The solvent (D) used in this embodiment must contain (D1) a 1,2-alkanediol having 3 to 7 carbon atoms. This (D1) component suppresses the generation of voids and maintains storage stability. The boiling point of component (D1) is preferably 220°C or lower. Furthermore, the number of carbon atoms in component (D1) is preferably 4 to 6, and particularly preferably 4 or 5. Examples of component (D1) include 1,2-pentanediol (boiling point: 210°C), 1,2-butanediol (boiling point: 194°C), 1,2-propanediol (boiling point: 188°C), 1,2-hexanediol (boiling point: 223°C), and 1,2-heptanediol (boiling point: 130°C). Among these, 1,2-pentanediol or 1,2-butanediol is preferred from the viewpoint of storage stability. In this specification, the boiling point refers to the boiling point at 1013 hPa.

[0023] The amount of component (D1) is preferably 10% by mass or more, more preferably 20% by mass or more, and particularly preferably 25% by mass or more, relative to 100% by mass of component (D). If the amount of component (D1) is above the lower limit, the generation of voids can be suppressed more reliably. The amount of component (D1) may be 80% by mass or less, 60% by mass or less, or 40% by mass or less, relative to 100% by mass of component (D).

[0024] Component (D) may contain solvents other than component (D1) (component (D2)) to the extent that the objectives of the present invention can be achieved. The boiling point of component (D2) is preferably 240°C or higher and 320°C or lower, and more preferably 270°C or higher and 310°C or lower. Examples of component (D2) include dibutyl adipate (boiling point: 305°C), diethylene glycol monohexyl ether, diethylene glycol monobutyl ether, α,β,γ-terpineol, benzyl glycol, diethylene glycol mono-2-ethylhexyl ether (EHDG, boiling point: 272°C), tripropylene glycol, diethylene glycol monobenzyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monobutyl ether, dipropylene glycol monobutyl ether, diethylene glycol monoethyl ether acetate, and 2,2-dimethyl-1,3-propanediol. These may be used individually or in combination of two or more. Among these, from the viewpoint of void suppression, it is preferable to use dibutyl adipate or diethylene glycol mono-2-ethylhexyl ether, and dibutyl adipate is particularly preferred.

[0025] The amount of component (D) is preferably 20% to 60% by mass, more preferably 25% to 50% by mass, and particularly preferably 30% to 40% by mass, based on 100% by mass of the flux composition. If the amount of solvent is within the above range, the viscosity of the resulting solder composition can be appropriately adjusted to an appropriate range.

[0026] [Sickling] The flux composition used in this embodiment may further contain a thixotropic agent from the viewpoint of printability and other factors. Any known thixotropic agent can be used as appropriate in this embodiment. Examples of thixotropic agents include hydrogenated castor oil, amides, kaolin, colloidal silica, organic bentonite, and glass frit. These may be used individually or in combination of two or more.

[0027] When using a thixotropic agent, the amount is preferably 1% to 12% by mass, more preferably 2% to 10% by mass, and particularly preferably 3% to 8% by mass, based on 100% by mass of the flux composition. If the amount of thixotropic agent is above the lower limit, thixotropy is achieved, and sagging during printing can be suppressed. If the amount of thixotropic agent is below the upper limit, the thixotropy will not be too high, and printing defects can be suppressed.

[0028] [Antioxidant] The flux composition used in this embodiment may further contain an antioxidant from the viewpoint of solder meltability and other factors. Any known antioxidant can be used as the antioxidant in this embodiment. Examples of antioxidants include sulfur compounds, hindered phenol compounds, and phosphite compounds. Among these, hindered phenol compounds are preferred.

[0029] Examples of hindered phenol compounds include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylenebis(oxyethylene)], N,N'-bis[2-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl]oxamide, and N,N'-bis{3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl}hydrazine. Among these, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] is particularly preferred from the viewpoint of solder meltability. Furthermore, these compounds may be used individually or in combination of two or more, but it is preferable to use them in combination of two or more. Specifically, it is preferable to use pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] in combination with other hindered phenol compounds.

[0030] When an antioxidant is used, the amount it is added is preferably 1% to 10% by mass, and more preferably 2% to 6% by mass, based on 100% by mass of the flux composition. The amount of antioxidant added is preferably within the above range from the viewpoint of balancing solder fusion properties and other physical properties.

[0031] [Other ingredients] In addition to components (A), (B), (C), and (D), a thixotropic agent, and an antioxidant, the flux composition used in this embodiment may optionally contain other additives and other resins. Examples of other additives include defoamers, modifiers, matting agents, and foaming agents. The amount of these additives is preferably 0.01% by mass or more and 5% by mass or less based on 100% by mass of the flux composition. Examples of other resins include acrylic resins.

[0032] [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 the above-mentioned embodiment and the solder powder (E) described below. The amount of flux composition is preferably 5% to 35% by mass, more preferably 7% to 18% by mass, and particularly preferably 8% to 15% by mass, based on 100% by mass of the solder composition. If the amount of flux composition is less than 5% by mass (when the amount of solder powder exceeds 95% by mass), there is insufficient flux composition as a binder, making it difficult to mix the flux composition with the solder powder. On the other hand, if the amount of flux composition exceeds 35% by mass (when the amount of 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.

[0033] [(E) component] The solder powder (E) used in this embodiment is preferably a solder powder with a melting point of 200°C or higher and 250°C or lower. In this embodiment, assuming that solder powder with a melting point of 200°C or higher and 250°C or lower is used, a component (D) with an appropriate boiling point is used. In this solder powder, a solder alloy mainly composed of tin (Sn) is preferred. The second element of this alloy may include silver (Ag), copper (Cu), zinc (Zn), bismuth (Bi), indium (In), and antimony (Sb). Furthermore, other elements (third and subsequent elements) may be added to this alloy as needed. Other elements may include copper, silver, bismuth, indium, antimony, and aluminum (Al). Here, lead-free solder powder refers to powder of solder metal or alloy without the addition of lead. However, the presence of lead as an unavoidable impurity in lead-free solder powder is permissible, but in this case, the amount of lead is preferably 300 ppm by mass or less.

[0034] Examples of solder alloys used in lead-free solder powder include Sn-Ag and Sn-Ag-Cu alloys. Among these, Sn-Ag-Cu solder alloys are preferred from the viewpoint of solder joint strength. The melting point of Sn-Ag-Cu solder is usually between 200°C and 250°C (preferably between 200°C and 240°C). Among Sn-Ag-Cu solders, those with a low silver content have a melting point of 210°C to 250°C (preferably between 220°C and 240°C).

[0035] Component (E) preferably consists of powder with a particle size of 10 μm to 25 μm, which accounts for 90% or more by mass. Meeting these conditions makes it possible to use electronic circuit boards with narrow solder pad pitches. The average particle size of component (E) is more preferably 1 μm to 25 μm, even more preferably 2 μm to 22 μm, and particularly preferably 3 μm to 20 μm, from the viewpoint of being compatible with electronic substrates with narrow solder pad pitches. The average particle size can be measured using a dynamic light scattering particle size analyzer.

[0036] [Method for manufacturing solder composition] The solder composition according to this embodiment can be manufactured by blending the flux composition described above and the solder powder (E) described above in the predetermined proportions and stirring them together.

[0037] [Electronic circuit board] Next, the electronic circuit board according to this embodiment will be described. The electronic circuit board according to this embodiment is characterized by having a soldered portion using the solder composition described above. The electronic circuit board according to this embodiment can be manufactured by mounting electronic components on an electronic circuit board (such as a printed circuit board) using the solder composition. The solder composition according to this embodiment, as described above, can sufficiently suppress large-diameter voids even when the printed area of ​​the solder composition is large. Therefore, it can be used particularly suitably when QFN is used as an electronic component. The coating equipment used here includes screen printing machines, metal mask printing machines, dispensers, and jet dispensers. Furthermore, electronic components can be mounted on an electronic circuit board by a reflow process, in which electronic components are placed on a solder composition applied by the coating apparatus, and the solder is heated under predetermined conditions in a reflow oven to mount the electronic components onto a printed circuit board.

[0038] In the reflow process, the electronic components are placed on the solder composition and heated in a reflow oven under predetermined conditions. This reflow process enables sufficient solder bonding between the electronic components and the printed circuit board. As a result, the electronic components can be mounted on the printed circuit board. The reflow conditions should be set appropriately according to the melting point of the solder. For example, the preheat temperature is preferably 140°C to 200°C, and more preferably 150°C to 160°C. The preheat time is preferably 60 seconds to 120 seconds. The peak temperature is preferably 230°C to 270°C, and more preferably 240°C to 255°C. Furthermore, the holding time at a temperature of 220°C or higher is preferably 20 seconds to 80 seconds.

[0039] Furthermore, the solder composition and electronic substrate according to this embodiment are not limited to the above-described embodiment, and any modifications, improvements, etc., within the scope that can achieve the objectives of the present invention are included in the present invention. For example, in the aforementioned electronic substrate, the printed circuit board and electronic components are bonded by a reflow process, but this is not the only method. For example, instead of the reflow process, the printed circuit board and electronic components 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 according to the wavelength matched to the absorption band of the metal. Examples of laser light sources include solid-state lasers (ruby, glass, YAG, etc.), semiconductor lasers (GaAs, and InGaAsP, etc.), liquid lasers (dyes, etc.), and gaseous lasers (He-Ne, Ar, CO2, and excimers, etc.). [Examples]

[0040] Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited in any way by these examples. The materials used in the examples and comparative examples are listed below. (Component A) Rosin-based resin A: Hydrogenated acid-modified rosin, product name "Pine Crystal KE-604", manufactured by Arakawa Chemical Industries, Ltd. Rosin-based resin B: Special modified rosin, product name "Haritack F-85", manufactured by Harima Chemicals Co., Ltd. ((B1) component) Organic acid: Adipic acid ((C1) component) Amine compound A: 2-ethyl-4-methylimidazole ((C2) component) Amine compound B: 1,2,3-benzotriazole (Component D1) Solvent A: 1,2-pentanediol (boiling point: 210°C) Solvent B: 1,2-butanediol (boiling point: 194°C) ((D2) component) Solvent C: 1,5-pentanediol (boiling point: 239°C) Solvent D: 1,4-butanediol (boiling point: 228°C) Solvent E: Dibutyl adipate (boiling point: 305°C) Solvent F: Diethylene glycol mono-2-ethylhexyl ether (2-ethylhexyl diglycol (EHDG), boiling point: 272°C), manufactured by Nippon Emulsifier Co., Ltd. (Other ingredients) Thixolytic agent: High-grade fatty acid polyamide, product name "Talen VA-79", manufactured by Kyoeisha Chemical Co., Ltd. Antioxidant A: Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], trade name "ANOX20", manufactured by Shiraishi Calcium Co., Ltd. Antioxidant B:N,N'-bis{3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl}hydrazine, trade name "Irganox MD1024", manufactured by BASF. ((E) component) Solder powder: Alloy composition is Sn-3.0Ag-0.5Cu, particle size distribution is 15-25 μm (corresponding to IPC-J-STD-005A Type 5), solder melting point is 217-220°C.

[0041] [Example 1] Rosin resin A (32.5% by mass), rosin resin B (9.5% by mass), organic acid (7% by mass), solvent A (10% by mass), solvent B (26.5% by mass), antioxidant A (2% by mass), antioxidant B (1% by mass), amine compound A (5% by mass), amine compound B (0.5% by mass), and thixotropic agent (6% by mass) were placed in a container and mixed using a planetary mixer to obtain a flux composition. Subsequently, 12% by mass of the obtained flux composition and 88% by mass of solder powder (100% by mass in total) were placed in a container and mixed in a planetary mixer to prepare the solder composition.

[0042] [Examples 2-8] A solder composition was obtained in the same manner as in Example 1, except that each material was blended according to the composition shown in Table 1. [Comparative Examples 1-8] A solder composition was obtained in the same manner as in Example 1, except that each material was blended according to the composition shown in Table 1.

[0043] <Evaluation of solder composition> The solder composition was evaluated (QFN voids, storage stability) using the following method. The results are shown in Table 1. (1) QFN void An evaluation substrate was fabricated by printing a solder composition onto a substrate using a metal mask, mounting QFN components (size: 8mm x 8mm, thickness: 0.75mm), and then performing a reflow process with a preheat temperature of 150-180°C for 80 seconds, a holding time of 220°C or higher for 50 seconds, and a peak temperature of 245°C. The substrate was then observed using an X-ray inspection device ("NLX-5000", manufactured by NAGOYA ELECTRIC WORKS). From the obtained observation images, the void ratio [(void area / electrode area) x 100] was calculated, and the average value (n=4) was taken. Based on the void ratio, QFN voids were evaluated according to the following criteria. ◎: The void ratio is less than 15%. ○: The void ratio is 15% or more but less than 20%. △: The void ratio is 20% or more but less than 25%. ×: The void fraction is 25% or higher. (2) Storage stability The viscosity stability during storage was evaluated in accordance with the description in JIS Z 3284-3 (2014). Specifically, first, the viscosity of the solder composition was measured as a sample. Then, the sample was placed in a sealed container and placed in a constant temperature bath at 30°C for 14 days, and the viscosity of the stored sample was measured. The viscosity change rate [{(η2-η1) / (η1)}×100] between the viscosity value before storage (η1) and the viscosity value after 14 days of storage at 30°C (η2) was calculated. Based on the viscosity change rate results, the viscosity stability during storage was evaluated according to the following criteria. ○: The viscosity change rate is between -5% and 5%. ×: The viscosity change rate is -15% or more but less than -5%, or greater than 5% but 15% or less. ××: The viscosity change rate is less than -15% or greater than 15%.

[0044] [Table 1]

[0045] As is clear from the results shown in Table 1, the solder compositions of the present invention (Examples 1-8) were confirmed to have good results in all aspects, including QFN voids and storage stability. Therefore, it has been confirmed that the solder composition of the present invention can sufficiently suppress voids and has excellent storage stability. [Industrial applicability]

[0046] The solder composition of the present invention can be suitably used as a technique for mounting electronic components on electronic circuit boards such as printed circuit boards of electronic devices.

Claims

1. A solder composition comprising (A) a rosin-based resin, (B) an activator, (C) an amine compound, and (D) a solvent, and (E) solder powder, The above component (D) contains (D1) a 1,2-alkanediol having 3 to 7 carbon atoms. Solder composition.

2. In the solder composition according to claim 1, The (D1) component is at least one selected from the group consisting of 1,2-pentanediol and 1,2-butanediol. Solder composition.

3. In the solder composition according to claim 1 or claim 2, The (C) component is at least one selected from the group consisting of (C1) imidazole compounds and (C2) triazole compounds. Solder composition.

4. An electronic circuit board comprising a soldering portion using the solder composition described in claim 1 or claim 2.

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