Soldering flux composition, solder composition, and method for manufacturing electronic substrate

Abstract

The flux composition of the present application is a flux composition containing (A) a rosin-based resin, (B) an activator, (C) a solvent, and (D) an antioxidant, characterized in that the (D) component contains (D1) a compound represented by the following structural formula (D1), and the blending amount of the (D) component is 4 mass% or more relative to 100 mass% of the flux composition.

Description

TECHNICAL FIELD

[0001] The present application relates to a flux composition, a solder composition, and a method for manufacturing an electronic substrate. BACKGROUND

[0002] A solder composition is a mixture obtained by kneading a flux composition (a composition containing a rosin-based resin, an activator, a solvent, and the like) with a solder powder into a paste. In the solder composition, soldering properties such as solder meltability, a property that a solder easily wets and spreads (solder wet and spread), and the like are required. Also, in order to satisfy these requirements, the activator and the like in the flux composition have been studied (for example, Document 1 (Japanese Patent Application Publication No. 2013-169557)).

[0003] On the other hand, mobile terminals such as smartphones are advancing toward miniaturization and multifunctionalization. Electronic components used in them are also being made finer. It is necessary to join the pads of such fine-area electronic components with a small amount of solder composition. In addition, solder compositions are also used for large substrates. In the case where a solder composition is used in a large substrate, it is necessary to extend the preheating time in a reflow process. In addition, in the case of a large substrate, the heat capacity is large, and it takes time to reach the preheating temperature, as a result of which there is a tendency for the time for which the substrate is heated in a reflow furnace to become long. In such a case, an activator such as a low-molecular-weight organic acid easily becomes inactivated, and the meltability in a fine area decreases. On the other hand, in the case where the amount of the activator is increased, problems such as copper corrosion easily occur. As described above, there is a demand for a solder composition that can cope with the fining of electronic components, and also cope with large substrates. SUMMARY

[0004] PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] An object of the present application is to provide a flux composition, a solder composition, and a method for manufacturing an electronic substrate, in which the meltability in a fine area is excellent, and copper corrosion can be inhibited.

[0006] MEANS OF SOLVING THE PROBLEM

[0007] According to one embodiment of the present application, a flux composition is provided, which is a flux composition containing (A) a rosin-based resin, (B) an activator, (C) a solvent, and (D) an antioxidant, the (D) component containing a compound represented by the following structural formula (D1),

[0008]

[0009] In the flux composition of one embodiment of the present application, it is preferable that the (D) component further contain (D2) an antioxidant having a hindered phenol structure (excluding the (D1) component).

[0010] In the flux composition of one embodiment of the present application, it is preferable that the (B) component contain (B1) an organic acid having a carbon number of 10 or more, and the blending amount of the (B1) be 8 mass% or more and 20 mass% or less with respect to 100 mass% of the flux composition.

[0011] In the flux composition of one embodiment of the present application, the blending amount of the (A) is preferably 30 mass% or more and 70 mass% or less with respect to 100 mass% of the flux composition.

[0012] With one embodiment of the present application, a solder composition containing the flux composition of one embodiment of the present application and (E) a solder powder is provided.

[0013] In the solder composition of one embodiment of the present application, it is preferable that the solder alloy in the (E) component contain at least one kind selected from tin, copper, zinc, silver, antimony, lead, indium, bismuth, nickel, gold, cobalt, and germanium.

[0014] With one embodiment of the present application, a method for manufacturing an electronic substrate, which is a method for manufacturing an electronic substrate in which soldering is performed using the solder composition of one embodiment of the present application, is provided, and the method includes: a reflow step of disposing an electronic component on the solder composition and heating by a reflow furnace, in which the arrival time of the melting temperature is 330 seconds or more.

[0015] Effects of the Invention

[0016] With the present application, a flux composition in which the melting property in a small area is excellent and in which copper corrosion can be inhibited, a solder composition, and a method for manufacturing an electronic substrate can be provided. DETAILED DESCRIPTION

[0017] [Flux composition]

[0018] First, the flux composition used in the present embodiment will be described. The flux composition used in the present embodiment is a component other than a solder powder in a solder composition, and the flux composition contains the (A) rosin-based resin, the (B) activator, the (C) solvent, and the (D) antioxidant described below.

[0019] [(A) component]

[0020] As the (A) rosin-based resin used in the present embodiment, rosin-based and rosin-based modified resins can be given. As the rosin-based, gum rosin, wood rosin, tall oil rosin, and the like can be given. As the rosin-based modified resin, disproportionated rosin, polymerized rosin, hydrogenated rosin, and derivatives thereof, and the like can be given. As the hydrogenated rosin, fully hydrogenated rosin, partially hydrogenated rosin, and hydrogenates of unsaturated organic acid-modified rosin (also referred to as "hydrogenated acid-modified rosin") of unsaturated organic acid (aliphatic unsaturated monobasic acid such as (meth)acrylic acid, aliphatic unsaturated dibasic acid such as fumaric acid, maleic acid, and α,β-unsaturated carboxylic acid having an aromatic ring such as cinnamic acid, and the like) of modified rosin, and the like can be given. These rosin-based resins can be used singly or in combination of two or more.

[0021] The blending amount of the (A) component is preferably 30% by mass or more and 70% by mass or less, more preferably 34% by mass or more and 60% by mass or less, and particularly preferably 35% by mass or more and 50% by mass or less, relative to 100% by mass of the flux composition. When the blending amount of the (A) component is the lower limit or more, the solderability can be improved, and the solder balls can be sufficiently suppressed. The solderability refers to a property of preventing oxidation of the copper foil surface of the solder pad, so that the molten solder easily wets the surface thereof. Further, when the blending amount of the (A) component is the upper limit or less, the flux residue amount can be sufficiently suppressed.

[0022] [(B) component]

[0023] The (B) activator used in the present embodiment preferably contains a (B1) organic acid having 10 or more (more preferably 11 or more) carbon atoms. This (B1) component is not easily deactivated even in the case of a long preheating time, and the melting in a small area can be improved. Further, there is a tendency that this (B1) component does not easily cause copper corrosion.

[0024] As the (B1) component, dodecanedioic acid, icosanedioic acid, dimer acid, trimer acid, 1-hydroxy-2-naphthoic acid, 3-hydroxy-2-naphthoic acid, 1,4-dihydroxy-2-naphthoic acid, and the like can be given. These can be used singly or in combination of two or more.

[0025] The blending amount of the (B1) component is preferably 8% by mass or more and 20% by mass or less, and more preferably 10% by mass or more and 18% by mass or less, relative to 100% by mass of the flux composition. When the blending amount of the (B1) component is the lower limit or more, there is a tendency that the melting in a small area can be improved, and on the other hand, when it is the upper limit or less, there is a tendency that the insulation of the flux composition can be maintained.

[0026] Within the scope of achieving the effects of the present invention, component (B) may contain an organic acid with fewer than 10 carbon atoms (B2). However, such low molecular weight organic acids with fewer than 10 carbon atoms are prone to deactivation and copper corrosion when the preheating time is long. Therefore, it is preferable that the activator (B) used in this embodiment does not contain this component (B2).

[0027] As components of (B2), examples include monocarboxylic acids, dicarboxylic acids, and other organic acids with fewer than 10 carbon atoms.

[0028] Examples of monocarboxylic acids with fewer than 10 carbon atoms include formic acid, acetic acid, propionic acid, and butyric acid.

[0029] Examples of dicarboxylic acids with fewer than 10 carbon atoms include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, and azelaic acid.

[0030] Other organic acids with fewer than 10 carbon atoms include lactic acid, benzoic acid, salicylic acid, and citric acid.

[0031] Without impairing the effects of the present invention, in addition to component (B1), component (B) may further contain other activators (such as (B3) halogen activators and (B4) amine activators). However, component (B3) is prone to causing copper corrosion, therefore component (B) preferably contains only component (B1). Furthermore, the total amount of component (B1) relative to 100% by mass of component (B) is preferably 85% by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

[0032] The amount of component (B) relative to 100% by mass of the flux composition is preferably 8% by mass or more and 25% by mass or less, more preferably 10% by mass or more and 20% by mass or less, and particularly preferably 12% by mass or more and 18% by mass or less. When the amount of component (B) is above the lower limit, there is a tendency to improve the activity; on the other hand, when it is below the upper limit, there is a tendency to maintain the insulation properties of the flux composition.

[0033] [(C) Component]

[0034] As the solvent (C) used in this embodiment, a known solvent may be used. As such a solvent, a solvent with a boiling point of 170°C or higher is preferred.

[0035] Examples of such solvents include: diethylene glycol, dipropylene glycol, triethylene glycol, hexanediol, 1,5-pentanediol, methyl carbitol, butyl carbitol, 2-ethylhexyl diethylene glycol, octanediol, phenyl glycol, diethylene glycol monohexyl ether (DEH), tetraethylene glycol dimethyl ether (MTEM), and dibutylmaleic acid. These solvents can be used individually or in combination of two or more.

[0036] The amount of component (C) is preferably 10% to 60% by mass, more preferably 20% to 50% by mass, relative to 100% by mass of the flux composition. When the amount of solvent is within the aforementioned range, the viscosity of the resulting solder composition can be appropriately adjusted to an appropriate range.

[0037] [(D) component]

[0038] The antioxidant (D) used in this embodiment needs to contain a compound represented by the following structural formula (D1). This (D1) component improves meltability in small areas and inhibits copper corrosion caused by component (B). This (D1) component is N,N'-bis{3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl}hydrazine.

[0039]

[0040] The amount of component (D1) relative to 100% by mass of the flux composition is preferably 0.1% by mass to 10% by mass, more preferably 0.2% by mass to 5% by mass, and particularly preferably 0.5% by mass to 2% by mass. When the amount of component (D1) is within the range described above, the meltability in small areas can be improved, and copper corrosion can be suppressed.

[0041] From the viewpoint of meltability in a small area and inhibition of copper corrosion, it is preferable that component (D) further contains (D2) an antioxidant with a hindered phenolic structure (except for component (D1)).

[0042] Examples of (D2) components include: pentaerythritol tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate][ethylenebis(oxyethylene)] and N,N'-bis[2-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl]oxalamide, etc.

[0043] When using component (D2), from the viewpoint of balancing solder meltability with other physical properties, the mass ratio of component (D2) to component (D1) ((D2) / (D1)) is preferably 1 to 10, more preferably 2 to 9, and particularly preferably 4 to 8.

[0044] To the extent that it does not impair the effects of the present invention, in addition to components (D1) and (D2), component (D) may further contain other antioxidants (hereinafter referred to as component (D3)). However, component (D) preferably contains only component (D1) or only components (D1) and (D2). Furthermore, the total amount of components (D1) and (D2) relative to 100% by mass of component (D) is preferably 85% by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

[0045] Examples of (D3) components include: sulfur compounds (such as 3,3'-dithiodipropionate dodecyl ester), benzotriazole compounds (such as 1,2,3-benzotriazole), and phosphite compounds.

[0046] The amount of component (D) relative to 100% by mass of the flux composition needs to be 4% by mass or more. When the amount of component (D) is less than 4% by mass, the solubility in small areas becomes insufficient or copper corrosion occurs. Furthermore, from the viewpoint of balancing solder solubility with other physical properties, the amount of component (D) is preferably 4% by mass or more and 15% by mass or less, more preferably 4.5% by mass or more and 10% by mass or less, and particularly preferably 5% by mass or more and 8% by mass or less.

[0047] [Thixotropic agent]

[0048] From the viewpoint of printability, the flux composition of this embodiment preferably further contains a thixotropic agent. Examples of thixotropic agents used herein include: cured castor oil, amides, kaolin, colloidal silica, organobentonite, and glass powder. These can be used individually or in combination of two or more.

[0049] The amount of thixotropic agent incorporated relative to 100% by mass of the flux composition is preferably 1% by mass or more and 20% by mass or less, more preferably 2% by mass or more and 12% by mass or less. When the amount is less than the lower limit, thixotropy cannot be obtained, and there is a tendency for it to sag easily. On the other hand, when the amount exceeds the upper limit, the thixotropy is too high, and there is a tendency for it to be poorly printed.

[0050] [Other ingredients]

[0051] In addition to components (A), (B), (C), (D), and the thixotropic agent, the flux composition used in this embodiment may also contain other additives and resins as needed. Examples of other additives include defoamers, modifiers, matting agents, and foaming agents. The amount of these additives is preferably 0.01% to 5% by mass relative to 100% by mass of the flux composition. Examples of other resins include acrylic resins and polybutadiene.

[0052] [Solder Composition]

[0053] Next, the solder composition of this embodiment will be described. The solder composition of this embodiment contains the flux composition of this embodiment and the solder powder (E) described below.

[0054] The amount of flux composition relative to 100% by mass of the solder composition is preferably 5% by mass or more and 35% by mass or less, more preferably 7% by mass or more and 15% by mass or less, and particularly preferably 8% by mass or more and 12% by mass or less. When the amount of flux composition is less than 5% by mass (when the amount of solder powder is more than 95% by mass), the flux composition as a binder is insufficient, and therefore there is a tendency to make it difficult to mix the flux composition and the solder powder. On the other hand, when the amount of flux composition is more than 35% by mass (when the amount of solder powder is less than 65% by mass), when using the obtained solder composition, there is a tendency to make it difficult to form a sufficient solder bond.

[0055] [(E) component]

[0056] The solder powder used in this invention preferably contains only lead-free solder powder, but it can also contain leaded solder powder. Furthermore, the solder alloy in the solder powder preferably contains at least one element selected from tin (Sn), copper (Cu), zinc (Zn), silver (Ag), antimony (Sb), lead (Pb), indium (In), bismuth (Bi), nickel (Ni), gold (Au), cobalt (Co), and germanium (Ge).

[0057] The solder alloy in this solder powder is preferably an alloy with tin as the main component. Furthermore, the solder alloy more preferably contains tin, silver, and copper. Additionally, as an additive element, the solder alloy may contain at least one of antimony, bismuth, and nickel. With the flux composition of this embodiment, even when using a solder alloy containing easily oxidizable additive elements such as antimony, bismuth, and nickel, the formation of voids can be suppressed.

[0058] Here, lead-free solder powder refers to powder of solder metal or alloy without added lead. However, lead is permitted as an unavoidable impurity in lead-free solder powder, in which case the amount of lead is preferably less than 300 ppm by mass.

[0059] As alloy systems for lead-free solder powder, examples include: Sn-Ag-Cu system, Sn-Cu system, Sn-Ag system, Sn-Bi system, Sn-Ag-Bi system, Sn-Ag-Cu-Bi system, Sn-Ag-Cu-Ni system, Sn-Ag-Cu-Bi-Sb system, Sn-Ag-Bi-In system, Sn-Ag-Cu-Bi-In-Sb system, etc.

[0060] (E) The average particle size of the component is typically 1 μm to 40 μm, but from the viewpoint that it can also handle electronic substrates with narrow pad spacing, it is more preferably 1 μm to 35 μm, further preferably 2 μm to 35 μm, and particularly preferably 3 μm to 32 μm. It should be noted that the average particle size can be measured by a dynamic light scattering particle size measuring device.

[0061] [Method for manufacturing solder composition]

[0062] The solder composition of this embodiment can be manufactured by mixing the flux composition described above and the solder powder (E) described above in the given ratio and stirring the mixture.

[0063] [Manufacturing Method of Electronic Substrates]

[0064] Next, the method for manufacturing the electronic substrate according to this embodiment will be described. The method for manufacturing the electronic substrate according to this embodiment is characterized by using the solder composition described above. According to the method for manufacturing the electronic substrate according to this embodiment, an electronic substrate can be manufactured by mounting electronic components onto an electronic substrate (printed circuit board, etc.) using the solder composition.

[0065] The solder composition of this embodiment exhibits excellent meltability in small areas and can suppress copper corrosion. Therefore, it can handle both miniaturized electronic components and large substrates.

[0066] Examples of coating devices used here include: screen printing machines, metal mask printing machines, distributors, and jet distributors.

[0067] Furthermore, by placing electronic components on a solder composition coated by the coating apparatus and heating the electronic components on a printed circuit board under given conditions in a reflow oven, it is possible to mount electronic components onto an electronic substrate.

[0068] In the reflow process, the electronic components are placed on the solder composition and heated in a reflow oven under given conditions. This reflow process enables a full solder bond between the electronic components and the printed circuit board. As a result, the electronic components can be mounted on printed circuit boards, etc.

[0069] The reflow conditions can be set appropriately based on the melting point of the solder. For example, the preheating temperature is preferably 140°C to 200°C. From the viewpoint of dealing with large substrates, the preheating time is preferably 100 seconds to 250 seconds, more preferably 120 seconds to 200 seconds. The peak temperature is preferably 230°C to 270°C, more preferably 240°C to 255°C. Furthermore, from the viewpoint of dealing with large substrates, the holding time at a temperature of 220°C or higher is preferably 40 seconds to 160 seconds, more preferably 100 seconds to 150 seconds.

[0070] Furthermore, from the viewpoint of dealing with large substrates, the time to reach the preheating temperature (e.g., 140°C) is preferably 180 seconds or more, more preferably 200 seconds or more, and particularly preferably 220 seconds or more and 500 seconds or less. From the viewpoint of dealing with large substrates, the time to reach the melting temperature (e.g., 220°C) is preferably 330 seconds or more, more preferably 350 seconds or more, and particularly preferably 360 seconds or more and 700 seconds or less.

[0071] It should be noted that, as with the reflow conditions described, the longer the solder powder is exposed in the reflow oven, the more it oxidizes, and the solder's melt properties tend to deteriorate. In contrast, the solder composition of this embodiment can withstand such reflow conditions.

[0072] Furthermore, the solder composition and electronic substrate of this embodiment are not limited to the embodiment described herein, and variations and improvements within the scope of achieving the purpose of this invention are also included in this invention.

[0073] For example, in the electronic substrate, the printed circuit board and electronic components are bonded by a reflow process, but this is not limited to this. For example, instead of a reflow process, the printed circuit board and electronic components can be bonded by a process of heating the solder composition using a laser (laser heating process). In this case, there is no particular limitation on the laser light source, and a laser light source can be appropriately used according to the wavelength that matches the absorption band of the metal. Examples of laser light sources include: solid-state lasers (ruby, glass, YAG, etc.), semiconductor lasers (GaAs and InGaAsP, etc.), liquid lasers (pigment, etc.), and gas lasers (He-Ne, Ar, CO2, and excimer, etc.).

[0074] Example

[0075] The present invention will now be described in more detail with reference to embodiments and comparative examples, but the invention is not limited to these examples. It should be noted that the materials used in the embodiments and comparative examples are shown below.

[0076] ((A) ingredient)

[0077] Rosin-based resins: Hydrogenated acid modified rosin, trade name "PINECRYSTALKE-604", manufactured by Arakawa Chemical Industry Co., Ltd.

[0078] ((B1) component)

[0079] Organic acid A: 3-hydroxy-2-naphthoic acid

[0080] Organic acid B: Dodecanoic acid

[0081] Organic acid C: dimer acid, trade name "UNIDYME14", manufactured by ARIZONA CHEMICAL.

[0082] Organic acid D: Trimeric acid (90% or more by mass), trade name "Floradyme 6500", manufactured by Florachem.

[0083] ((B2) component)

[0084] Organic acid E: Succinic acid

[0085] Organic acid F: glutaric acid

[0086] Organic acid G: Adipic acid

[0087] Organic acid H: octanoic acid

[0088] ((C) component)

[0089] Solvent A: Diethylene glycol monohexyl ether (DEH, hexyl diethylene glycol) Solvent B: Tetraethylene glycol dimethyl ether, trade name "HAISORUBU MTEM", manufactured by Toho Chemical Co., Ltd.

[0090] ((D1) ingredient)

[0091] Antioxidant A: N,N'-bis{3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl}hydrazine, trade name "IRGANOXMD 1024", manufactured by BASF JAPAN.

[0092] ((D2) component)

[0093] Antioxidant B: Bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylenebis(oxyethylene)], trade name "IRGANOX 245", manufactured by BASF.

[0094] Antioxidant C: Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], trade name "ANOX20"

[0095] Antioxidant D: N,N'-bis[2-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl]oxalamide, trade name "NAUGARD XL-1", manufactured by SHIRAISHI CALCIUM Co., Ltd.

[0096] ((D3) ingredient)

[0097] Antioxidant E: 1,2,3-benzotriazole, trade name "VERZONE Crysta", manufactured by Yamato Chemical Co., Ltd.

[0098] (Other ingredients)

[0099] Thixotropic agent: Trade name "SLIPACKS H", manufactured by Nippon Chemical Co., Ltd.

[0100] (E) component)

[0101] Solder powder: The alloy composition is Sn-3.0Ag-0.5Cu, the particle size distribution is 15-25μm, and the solder melting point is 217-220℃.

[0102] [Example 1]

[0103] 35% by mass of rosin resin, 4% by mass of organic acid A, 4% by mass of organic acid B, 4% by mass of organic acid C, 32.5% by mass of solvent A, 8% by mass of solvent B, 0.5% by mass of antioxidant A, 4% by mass of antioxidant B, and 8% by mass of thixotropic agent were added to a container and mixed using a planetary mixer to obtain a flux composition.

[0104] Then, 11.8% by mass of the obtained flux composition and 88.2% by mass of solder powder (totaling 100% by mass) are added to a container and mixed by a planetary mixer to prepare the solder composition.

[0105] [Examples 2-6]

[0106] The solder composition was obtained by combining the materials according to the composition shown in Table 1, except that the solder composition was obtained in the same manner as in Example 1.

[0107] [Comparative Examples 1-11]

[0108] The solder composition was obtained by combining the materials according to the composition shown in Table 1, except that the solder composition was obtained in the same manner as in Example 1.

[0109] <Evaluation of Solder Compositions>

[0110] Solder compositions were evaluated using the following methods (fusibility of micropads, copper corrosion, solder balls, and voids). The results are shown in Table 1. It should be noted that evaluations of viscosity stability and wettability were omitted for solder compositions exhibiting problematic properties.

[0111] (1) Melting properties of micro pads

[0112] Solder compositions were printed onto a substrate using a 0.08 mm thick metal mask. It should be noted that 100 test patterns of copper foil pads with diameters of 0.28 mm, 0.26 mm, 0.24 mm, 0.22 mm, and 0.20 mm were printed. Test substrates were then prepared by reflowing the substrate under the following conditions: a preheating temperature of 140–200 °C for 160 seconds (reaching 140 °C in 235 seconds), a holding time above 220 °C for 120 seconds (reaching 220 °C (melting temperature) in 413 seconds), and a peak temperature of 250 °C. The diameter of the smallest molten pad (in mmφ) was measured by microscopic observation of the test substrate. A smaller diameter indicates better meltability. It should be noted that, from the viewpoint of excellent meltability in a small area, the diameter of the smallest molten pad is preferably 0.20 mm.

[0113] (2) Copper corrosion

[0114] Based on the method described in IPC TM650 2.6.15C, a copper foil corrosion test was performed to evaluate copper corrosion. The result of the copper foil corrosion test was graded as "A" for passing and "C" for other results.

[0115] (3) Solder ball

[0116] Solder composition was printed onto a substrate using a 0.08 mm thick metal mask, and 0.8 mm pitch Quad Flat Packages (QFPs) were mounted. An evaluation substrate was prepared by reflowing the substrate under the same conditions as for evaluating the meltability of the micro-pads. The slit portions of the QFP were observed using a magnifying glass, and the number of solder balls generated between the slits was counted. The solder balls were then evaluated according to the following criteria.

[0117] A: The number of balls generated per pin is less than 10.

[0118] B: The number of balls generated per pin is more than 10 but less than 30.

[0119] C: More than 30 balls are generated per pin.

[0120] (4) Gaps

[0121] Solder composition was printed onto a substrate using a 0.08 mm thick metal mask, and 0.5 mm pitch Quad Flat Non-leaded Packages (QFNs) were mounted. Under the same conditions as the evaluation of the meltability of the micro-pads, a reflow process was performed to prepare an evaluation substrate. Furthermore, using an X-ray inspection device manufactured by Nagoya Electric Industry Co., Ltd., the voids were measured, and the void area ratio in the pad portion of the QFN was calculated using the device's standard application [(total void area / total pad area) × 100]. The voids were evaluated according to the following criteria.

[0122] A: The void area ratio is less than 20%.

[0123] B: The void area ratio exceeds 20% but is below 25%.

[0124] C: The porosity exceeds 25%.

[0125]

[0126] As shown in Table 1, the results confirm that the solder compositions of the present invention (Examples 1-6) exhibit good results in terms of the meltability of the micro pads, copper corrosion, solder balls, and voids.

[0127] Therefore, it has been confirmed that the solder composition of the present invention exhibits excellent meltability in small areas and is able to suppress copper corrosion.

Claims

1. A flux composition comprising rosin resin A, activator B, solvent C, and antioxidant D. The amount of rosin resin A is 30% to 70% by mass relative to 100% by mass of the flux composition. The activator B contains an organic acid B1 with 10 or more carbon atoms. The amount of the organic acid B1 with 10 or more carbon atoms is 8% to 20% by mass relative to 100% by mass of the flux composition. The total amount of the organic acid B1 with 10 or more carbon atoms is 85% or more, relative to 100% by mass of the activator B. The amount of activator B relative to 100% by mass of the flux composition is 8% by mass or more and 25% by mass or less. The amount of solvent C is 10% to 60% by mass relative to 100% by mass of the flux composition. The antioxidant D contains compound D1 represented by the following structural formula D1, and antioxidant D2 having a hindered phenolic structure, in addition to compound D1. The mass ratio of antioxidant D2 to compound D1, i.e., D2 / D1, is more than 1 and less than 10. The total amount of compound D1 and antioxidant D2 is 85% by mass or more relative to 100% by mass of antioxidant D1. The amount of antioxidant D relative to 100% by mass of the flux composition is 4.5% by mass or more and 15% by mass or less. 。 2. A solder composition comprising: The flux composition of claim 1, and Solder powder E.

3. The solder composition according to claim 2, wherein, The solder alloy in the solder powder E contains at least one of the following: tin, copper, zinc, silver, antimony, lead, indium, bismuth, nickel, gold, cobalt, and germanium.

4. A method for manufacturing an electronic substrate, comprising a method for manufacturing an electronic substrate soldered using the solder composition according to claim 2 or claim 3, the method comprising: The reflow process involves placing electronic components onto the solder composition and heating them in a reflow oven. The melting temperature in the reflow process is reached in more than 330 seconds.

Images