Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
  • B23K35/02—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape
  • B23K35/0222—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by mechanical features, e.g. shape for use in soldering or brazing
  • B23K35/0244—Powders, particles or spheres; Preforms made therefrom
  • B23K35/025—Pastes, creams or slurries
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
  • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
  • B23K35/24—Selection of soldering or welding materials proper
  • B23K35/26—Selection of soldering or welding materials proper with the principal constituent melting at less than 400°C
  • B23K35/262—Sn as the principal constituent
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
  • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
  • B23K35/24—Selection of soldering or welding materials proper
  • B23K35/26—Selection of soldering or welding materials proper with the principal constituent melting at less than 400°C
  • B23K35/264—Bi as the principal constituent
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
  • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
  • B23K35/36—Selection of non-metallic compositions, e.g. coatings or fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest
  • B23K35/3612—Selection of non-metallic compositions, e.g. coatings or fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest with organic compounds as principal constituents
  • B23K35/3615—N-compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
  • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
  • B23K35/36—Selection of non-metallic compositions, e.g. coatings or fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest
  • B23K35/3612—Selection of non-metallic compositions, e.g. coatings or fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest with organic compounds as principal constituents
  • B23K35/3618—Carboxylic acids or salts
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
  • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
  • B23K35/36—Selection of non-metallic compositions, e.g. coatings or fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest
  • B23K35/362—Selection of compositions of fluxes
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C12/00—Alloys based on antimony or bismuth
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C13/00—Alloys based on tin
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C13/00—Alloys based on tin
  • C22C13/02—Alloys based on tin with antimony or bismuth as the next major constituent
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C28/00—Alloys based on a metal not provided for in groups C22C5/00 - C22C27/00

Definitions

• the present invention relates to a solder paste containing a lead-free solder alloy with a solidus temperature of 150°C or less and a specific flux.
• lead-free solder is widely used for soldering electronic components.
• Typical compositions of lead-free solder include Sn--Ag--Cu, Sn--Cu--Ni, and Sn--Sb solder alloys. Solder alloys of these systems have higher melting points than those of the Sn--Pb system.
• the melting point of Sn--Pb-based eutectic solder alloys that have been used in the past is 183.degree.
• the melting point of -0.05Ni is 227°C
• the melting point of Sn-5.0Sb is 238°C, both of which are high melting points. Therefore, in order to use the above-mentioned lead-free solder alloy, design changes are made so that the heat resistance temperature of the parts is increased, and electronic circuit boards are mounted using the parts.
• Sn--Bi-based and Sn--In-based lead-free solder alloys which have a lower melting point by containing a predetermined amount of Bi or In, are suitable for substrates that use electronic components with low heat resistance, shock, vibration, and environmental temperature. It is used for products where the operating environment is not severe (e.g., LED lights, notebook computers, etc.). Furthermore, in recent years, from the viewpoint of cost, solder alloys with a low melting point such as those described above have been developed for personal computers, which are substrates that are not high in heat resistance but are excellent in terms of cost, and do not require high impact resistance. (low-melting point solder alloys) have come to be used, and with this as a trigger, the movement to use low-melting point solders for general-purpose home appliances is spreading.
• solder alloys which are one of the low melting point solder alloys
• solder alloys with an In content of 50 to 52% by mass are known. °C (ISO standard), it is considerably lower than the melting point of general lead-free solder alloys, and is said to be suitable for joining electronic parts with low heat resistance.
• low-melting-point Sn—In solder alloys contain a large amount of In, which is a scarce resource also known as a rare metal, and In is a more expensive material than other metals. Concerned.
• solder alloys with a Bi content of 32 to 40% by mass and 35 to 59% by mass are known, among which 42Sn-58Bi
• the eutectic composition has a melting point of 139° C., and is said to be suitable for bonding electronic parts with low heat resistance.
• a Sn—Bi solder alloy with a low melting point tends to become hard and brittle when it contains a large amount of Bi, resulting in poor elongation of the alloy and reduced bonding properties such as drop impact resistance.
• Sn—Bi-based solder alloys contain specific components in specific amounts.
• a cream solder paste containing solder paste flux and solder powder is supplied to the electrodes on the circuit board by contact printing, dispenser discharge, or the like, and a capacitor is mounted on the top of the solder paste.
• a mounting method in which, after mounting an electronic component such as the like, it is heated in a reflow furnace to melt the solder paste and join the electronic component and the electrode.
• solder paste containing a Sn—Bi solder alloy as solder powder has the problem that solder balls are often generated due to the surface oxide film of the solder powder. It is known that the occurrence of a large number of solder balls is one of the causes of a decrease in insulation resistance and the occurrence of short circuits.
• Patent Document 2 describes a solder paste that can suppress the occurrence of solder balls by incorporating a combination of three types of dicarboxylic acids with different carbon numbers into the flux. , a solder paste containing a solder alloy containing highly oxidizing alloying elements has been proposed.
• a flux containing rosin, a solvent, a thixotropic agent, and an activator uses organic acids and imidazoles as the activator, and particularly carbon
• the present inventors have found that the above problems can be solved by using a dicarboxylic acid having 4 to 6 carbon atoms and an imidazole compound having 3 to 6 carbon atoms or a derivative thereof in combination.
• the combination of the dicarboxylic acid and the imidazole can stabilize the dicarboxylic acid contained in the solder paste, thereby suppressing the reaction with the solder alloy, Furthermore, it becomes possible to suppress the change in the viscosity of the solder paste. Since the imidazoles having 3 to 6 carbon atoms have a high reaction rate, they can be activated at an early stage during heating, and are considered to be very effective in suppressing the formation of solder balls.
• a first form of the present invention is a solder paste containing solder powder and flux
• the solder powder is a lead-free solder alloy having a solidus temperature of 150 ° C. or less
• the flux contains rosin, solvent, thixotropic agent, and organic acids and imidazoles as activators,
• the organic acids include one or more dicarboxylic acids having 4 to 6 carbon atoms
• the imidazoles are solder pastes containing one or more imidazole compounds having 3 to 6 carbon atoms or derivatives thereof.
• the lead-free solder alloy having a solidus temperature of 150° C. or less may be the following (i) or (ii). (i) Bi 32% by mass or more and 40% by mass or less, Sb 0.1% by mass or more and 1.0% by mass or less, Cu 0.1% by mass or more and 1.0% by mass or less, Ni 0.001% by mass or more and 0.1% by mass or less , Ag0 mass% or more and 0.3 mass% or less, Fe0 mass% or more and 0.1 mass% or less, Co0 mass% or more and 0.1 mass% or less, Ga0 mass% or more and 0.01 mass% or less, Mn0 mass% 0.01 mass% or less, V0 mass% or more and 0.01 mass% or less, P0 mass% or more and 0.1 mass% or less, Ge 0 mass% or more and 0.1 mass% or less, and the balance is Sn and inevitable impurities
• a certain lead-free solder alloy hereinafter also referred to as lead-free solder alloy 1).
• the content of Sb in the lead-free solder alloy 1 is preferably 0.1% by mass or more and 1.0% by mass or less, and 0.1% by mass or more and 0.1% by mass or more, from the viewpoint of improving the ductility of the solder alloy. 0.9% by mass or less is more preferable.
• the content of Cu in the lead-free solder alloy 1 is preferably 0.1% by mass or more and 1.0% by mass or less from the viewpoint of ductility of the solder alloy and suppression of copper erosion. It is more preferably 0.3% by mass or more and 0.7% by mass or less.
• the intermetallic compound particles of Cu and Sn are refined (suppression of growth or coarsening), and the strength of the alloy and the solder joint body
• the Ni content is preferably 0.001% by mass or more and 0.1% by mass or less, and the Ni content is preferably 0.005% by mass or more and 0.07% by mass or less. It is more preferably 0.01% by mass or more and 0.05% by mass or less.
• the Ag can improve the wettability of the solder alloy.
• the Ag content is preferably 0.001% by mass or more and 0.3% by mass or less in the lead-free solder alloy having a solidus temperature of 150° C. or less.
• the content of each of these metals is preferably 0.001% by mass or more and 0.1% by mass or less in the lead-free solder alloy having a solidus temperature of 150° C. or less.
• Ga, Mn, V, P, and Ge have the effect of preventing oxidation of the surface of the solder alloy.
• Ga, Mn, V, and Ge are preferable.
• Each content of Ga, Mn, and V is preferably 0.001% by mass or more and 0.01% by mass or less in the lead-free solder alloy having a solidus temperature of 150° C. or less.
• the Ge content is preferably 0.001% by mass or more and 0.1% by mass or less in the lead-free solder alloy having a solidus temperature of 150° C. or less.
• Si, Ca, and Ti also have the effect of preventing oxidation of the surface of the solder alloy.
• the content of each of these metals is preferably 0.001% by mass or more and 0.01% by mass or less in the lead-free solder alloy having a solidus temperature of 150° C. or less.
• the flux used in the solder paste of the present invention preferably contains 4 to 12% by mass of the dicarboxylic acid having 4 to 6 carbon atoms with respect to the total mass of the flux.
• the dicarboxylic acid having 4 to 6 carbon atoms includes a dicarboxylic acid having a linear (saturated) structure, and preferably contains at least one selected from the group consisting of succinic acid, glutaric acid and adipic acid. .
• the imidazole compound having 3 to 6 carbon atoms or its derivative is preferably contained in an amount of 2 to 8% by mass with respect to the total mass of the flux.
• the imidazole compound having 3 to 6 carbon atoms or a derivative thereof may be one or two selected from the group consisting of imidazole, 2-methylimidazole, 2-ethylimidazole and 2-ethyl-4-methylimidazole. The above may be combined.
• the flux preferably does not contain halogens, halides, and halogen-based activators from the viewpoint of reducing environmental impact.
• the flux may contain a monocarboxylic acid.
• the ratio of the content of the dicarboxylic acid having 4 to 6 carbon atoms/the monocarboxylic acid (hereinafter referred to as dicarboxylic acid/monocarboxylic acid, the ratio of the mass blended as a raw material) Adjustment within the range of 0.8 to 10 is preferable from the viewpoint of the effect of suppressing the occurrence of solder balls.
• the ratio of the content of the dicarboxylic acid having 4 to 6 carbon atoms/the imidazole compound having 3 to 6 carbon atoms or a derivative thereof (hereinafter referred to as dicarboxylic acid/imidazole, the ratio of the mass blended as a raw material) It is preferable to adjust it within the range of 0.5 to 5 from the viewpoint of the effect of suppressing the occurrence of solder balls.
• the flux may contain an antioxidant.
• the content ratio of the antioxidant/the imidazole compound having 3 to 6 carbon atoms or a derivative thereof (hereinafter referred to as the antioxidant/imidazoles, the mass blended as a raw material ratio) is preferably adjusted within the range of 1 or less from the viewpoint of the effect of suppressing the occurrence of solder balls.
• the dicarboxylic acid/monocarboxylic acid is in the range of 0.8 to 10
• the dicarboxylic acid/imidazole is in the range of 0.5 to 5
• the antioxidant/imidazole is in the range of 1 or less. is more preferable than satisfying each ratio alone because the effect of suppressing the occurrence of solder balls is particularly excellent.
• a second form of the present invention is a solder joint formed using the solder paste described above.
• a third aspect of the present invention is an electronic component or electronic device having the solder joint.
• the solder paste of the present invention contains a lead-free solder alloy with a solidus temperature of 150° C. or less, maintains the conventional effects of the solder alloy, and utilizes the characteristics of the solder alloy, and furthermore, the generation of solder balls during joining. can be effectively suppressed, the reliability of bonding can be improved not only for normal electronic components or electronic devices, but also for electronic components or electronic devices with low heat resistance.
• solder paste The solder paste of the present invention contains solder powder and flux.
• solder powder used in the present invention is composed of a lead-free solder alloy having a solidus temperature of 150° C. or less.
• lead-free solder alloys having a solidus temperature as described above include Sn--Bi series, Sn--In series, and the like.
• Examples of the Sn-Bi system include 43Sn-57Bi, 42Sn-58Bi, 42Sn-57Bi-1Ag, and the Sn-Bi system proposed by the present applicant described in Patent Document 1.
• the Sn--In system includes 50Sn-50In, 48Sn-52In, and the like. Among them, the Sn—Bi system is preferable from the viewpoint of being excellent in cost.
• solder alloy 2 which is 0% by mass or more and 0.1% by mass or less of Ge, and the balance is Sn and inevitable impurities, and the alloy composition is 32% by mass to 40% by mass of Bi, and 0.1% by mass or more of Sb 1.0% by mass or less, Cu 0.1% by mass or more and 1.0% by mass or less, Ni 0.001% by mass or more and 0.1% by mass or less, the balance being Sn and inevitable impurities Lead-free solder alloy 1, It can be suitably used as solder powder.
• the alloy composition of the lead-free solder alloy 1 may be composed only of Sn, Bi, Sb, Cu, Ni and inevitable impurities.
• the alloy composition of the lead-free solder alloy 2 may be composed only of Sn, Bi and unavoidable impurities.
• the lead-free solder alloys 1 and 2 further contain, as other metals, one or more selected from the group consisting of Ag, Fe, Co, Ga, Mn, V, P and Ge. may
• Examples of the lead-free solder alloy 1 include 32% by mass to 40% by mass of Bi, 0.1% by mass to 1.0% by mass of Sb, 0.1% by mass to 1.0% by mass of Cu, and 0.001% by mass of Ni. % or more and 0.1% by mass or less as a basic composition, In addition to the basic composition, a solder alloy containing 0.001 to 0.3% by mass of Ag, the balance being Sn and unavoidable impurities; In addition to the basic composition, a solder alloy containing 0.001 to 0.1% by mass of Fe, the balance being Sn and inevitable impurities; In addition to the basic composition, a solder alloy containing 0.001 to 0.1% by mass of Co, the balance being Sn and inevitable impurities; In addition to the basic composition, a solder alloy containing 0.001 to 0.01% by mass of Ga and the balance being Sn and unavoidable impurities; In addition to the basic composition, a solder alloy containing 0.001 to 0.01% by mass of Mn, the balance being
• the particle size of the solder powder used in the solder paste of the present invention is not particularly limited as long as it is adjusted so that the effects of the present invention can be achieved. Moreover, the particle size is preferably Type 3 to 6 of IPC standard.
• the flux used in the present invention contains rosin, solvent, thixotropic agent, and organic acids and imidazoles as activators.
• the content of each component in the flux indicates the ratio by mass of the components mixed as raw materials in the total mass of the flux.
• rosin examples include natural rosins such as gum rosin, wood rosin and tall oil rosin, disproportionated rosins, hydrogenated rosins, formylated rosins, fumarated rosins, maleated rosins, and acrylated rosins. modified rosins such as rosins, rosin esters, and the like. These rosins may be used alone or in combination of two or more.
• the content of rosin in the total mass of the flux is preferably 20 to 60% by mass from the viewpoint of the meltability of the solder paste of the present invention, the effect of suppressing the formation of solder balls, and the properties of the solder paste. , 30 to 55 mass % is more preferred.
• rosin In addition to the rosin, other resins such as acrylic resins, rosin-based resins, styrene-maleic acid resins, epoxy resins, urethane resins, polyester resins, phenoxy resins, terpene resins, and polyalkylene carbonates may be added singly or in combination. may be mixed and used. When using these other resins, the total content of rosin and other resins should be adjusted to 60% by mass or less.
• solvent known solvents applicable to solder paste or flux can be used.
• Hydrocarbons such as terpineol, 1,8-terpine monoacetate, 1,8-terpine diacetate, dihydroterpineol and the like. Only one kind of the solvent may be used, or two or more kinds thereof may be used in combination.
• the content of the solvent in the total mass of the flux may be determined based on the viscosity and printability of the solder paste, and is preferably 20-50% by mass, for example.
• the thixotropic agent is not particularly limited as long as it can adjust the viscosity of the solder paste of the present invention to a desired value, but known agents applicable to solder paste or flux can be used. Hydrogenated castor oil, beeswax, carnauba wax, fatty acid amide wax, stearic acid amide, ethylenebisstearic acid amide, ethylenebishydroxystearic acid amide, hexamethylenebishydroxystearic acid amide and the like.
• the thixotropic agent may be used alone or in combination of two or more.
• the content of the thixotropic agent in the total mass of the flux is 2 to 10% by mass from various viewpoints such as prevention of separation between the alloy powder and the flux, heat resistance to maintain the shape after printing, and compatibility with other raw materials. Preferably.
• the organic acids used as activators in the present invention contain one or more of dicarboxylic acids having 4 to 6 carbon atoms.
• the activity can be effectively exhibited even at low temperatures, and during bonding
• the occurrence of solder balls can be suppressed.
• the effect of suppressing the generation of solder balls during bonding is the effect seen when the organic acid is a combination of the C4-C6 dicarboxylic acid and the C3-C6 imidazole compound or derivative thereof. .
• the organic acid consists only of a dicarboxylic acid having 10 or more carbon atoms
• an imidazole compound having 3 to 6 carbon atoms or a derivative thereof is used, solder balls are not generated.
• the inventors have confirmed that it cannot be suppressed sufficiently. If the number of carbon atoms in the organic acid is 3 or less, it is not effective because the heat resistance of the resulting solder paste is low.
• the dicarboxylic acid having 4 to 6 carbon atoms is preferably represented by the formula HOOC-R-COOH, where R is an aliphatic hydrocarbon group having 2 to 4 carbon atoms.
• the bonding position of the carboxyl group is not particularly limited, but in the case of a straight chain, both ends are suitable.
• the aliphatic hydrocarbon group may be linear or branched, but a linear saturated aliphatic hydrocarbon group is preferred. Moreover, the number of carbon atoms in the branched chain is 2 to 3.
• succinic acid, glutaric acid, and adipic acid are preferable because they are excellent in the effect as an activator.
• the dicarboxylic acids having 4 to 6 carbon atoms may be used alone or in combination of two or more.
• the content of the dicarboxylic acid having 4 to 6 carbon atoms is preferably 4 to 12% by mass, more preferably 4 to 10% by mass, based on the total mass of the flux.
• a dicarboxylic acid having 10 or more carbon atoms and a monocarboxylic acid may be added as an organic acid that is an activator.
• the dicarboxylic acid having 10 or more carbon atoms is not particularly limited, and examples thereof include sebacic acid, dodecanedioic acid, and eicosadioic acid.
• the monocarboxylic acid is not particularly limited, but stearic acid, palmitic acid, oleic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, nonadecanoic acid, eicosanoic acid, heneicosanoic acid, docosanoic acid, 2 - monovalent carboxylic acids in which aliphatic hydrocarbons such as decyltetradecanoic acid are substituted with carboxy groups, 12-hydroxydodecanoic acid, 12-hydroxyoctadecanoic acid, 13-hydroxytridecanoic acid, 14-hydroxytetradecanoic acid, 9,16 -Hydroxy fatty acids such as dihydroxyoctadecanoic acid and polyhydroxy fatty acids such as dihydroxyhexadecanoic acid, dihydroxyoctadecanoic acid and dihydroxy
• the aliphatic hydrocarbon may be linear/branched or saturated/unsaturated. Moreover, you may have a substituent.
• the dicarboxylic acid having 10 or more carbon atoms and the monocarboxylic acid may be used alone, or two or more of them may be used in combination.
• the ratio of the content of the dicarboxylic acid having 4 to 6 carbon atoms/monocarboxylic acid (based on mass) to the dicarboxylic acid having 4 to 6 carbon atoms is 0.8 to 10. is preferably adjusted to
• the imidazoles used as active agents in the present invention contain one or more imidazole compounds having 3 to 6 carbon atoms or derivatives thereof.
• Examples of the imidazole compound having 3 to 6 carbon atoms or a derivative thereof include imidazole, a derivative of an imidazole compound having one or two aliphatic hydrocarbon groups having 1 to 3 carbon atoms in the imidazole skeleton, and the like.
• the aliphatic hydrocarbon group may be linear, branched, or alicyclic, and is preferably an aliphatic hydrocarbon group.
• Examples of the imidazole compound derivatives include 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole and the like.
• imidazole, 2-ethylimidazole, and 2-ethyl-4-methylimidazole are preferable from the viewpoints of high reaction rate and excellent viscosity stability by suppressing the viscosity change of the solder paste.
• the imidazole compounds having 3 to 6 carbon atoms or derivatives thereof may be used singly or in combination of two or more.
• the imidazoles are preferably contained in an amount of 2 to 8% by mass with respect to the total mass of the flux.
• the combined use of the dicarboxylic acid having 4 to 6 carbon atoms and the imidazole can stabilize the dicarboxylic acid contained in the solder paste, thereby preventing the reaction with the solder alloy. It is possible to suppress the viscosity change of the solder paste. Furthermore, since the imidazole contained in the solder paste of the present invention has a high reaction rate, it can exhibit its active effect at an early stage during heating, which is also very effective in suppressing the formation of solder balls. It is thought that there is
• the ratio of the content of the dicarboxylic acid having 4 to 6 carbon atoms to the imidazole is adjusted within the range of 0.5 to 5. , there is a tendency that the effects of the present invention are likely to be exhibited.
• the solder paste of the present invention may contain an antioxidant.
• the antioxidant include at least one of phenol antioxidants and triazole antioxidants.
• phenolic antioxidant a less hindered phenolic antioxidant in which the ortho positions on both sides of the phenol hydroxyl group are not substituted with a methyl group or a t-butyl group (tertiary butyl group), only one ortho position is Partially hindered phenolic antioxidants substituted with methyl groups and the other ortho position with t-butyl groups, and fully hindered phenolic antioxidants with both ortho positions substituted with t-butyl groups. Inhibitors are included.
• Phenolic antioxidants include hindered phenol antioxidants as well as 2,2′-hydroxy-3,3-di( ⁇ -cyclohexyl)-5,5′-dimethylphenylmethane.
• triazole antioxidant examples include 3-amino-1,2,4-triazole, 3-(N-salicyloyl)amino-1,2,4-triazole, 3-(N-salicyloyl)amino-1 , 2,4-triazole, benzotriazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5 -chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2, 2′-methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol], 6-(2-benzotriazolyl)-4-tert-octyl-6′-tert-butyl-4
• the antioxidant is preferably contained in an amount of 0.1 to 2.5% by mass with respect to the total mass of the flux.
• the content ratio (by mass) of the dicarboxylic acid having 4 to 6 carbon atoms/monocarboxylic acid is within the range of 0.8 to 10, and the content ratio of the dicarboxylic acid/imidazole ( by adjusting the content ratio (based on mass) of the antioxidant/imidazole to 1 or less, regardless of the alloy composition, the occurrence of solder balls is greatly reduced. can be effectively suppressed. Further, when adjusting so as to satisfy all of the above three ratio ranges, the lower limit of the content ratio of the antioxidant/imidazole is adjusted to 0.01 or more, further 0.02 or more. , the occurrence of solder balls can be more effectively suppressed regardless of the alloy composition.
• the flux preferably does not contain halogens, halides and halogen-based activators from the viewpoint of reducing environmental load.
• "does not contain” specifically means that the flux is 0% by mass in the total mass of the flux.
• the halogen and halogen-based activators include amines, amine hydrohalides, and organic halogen compounds.
• Halides include carboxylic acid chlorides and bromides.
• the content of the flux is 8.0 to 12.0% by weight with respect to the total weight of the solder paste of the present invention so that the solder paste maintains a creamy form and enables proper printing. is preferred, and 9.0 to 11.0% by mass is more preferred.
• the solder paste of the present invention can be produced by preparing powder of a lead-free solder alloy having a solidus temperature of 150° C. or less and flux, and then kneading the obtained flux and solder powder.
• solder alloy powder having a solidus temperature of 150° C. or lower commercially available powdered Sn—Bi-based, Sn—In-based solder alloys, etc. may be used as they are.
• lead-free solder alloys 1 and 2 each metal can be mixed according to a standard method to produce a solder alloy.
• the particle size of the solder powder may be adjusted to a desired particle size by a known method.
• the shape of the powder is generally preferably spherical in consideration of paste viscosity variations and printability.
• the raw materials of the flux, rosin, solvent, thixotropic agent, organic acids and imidazoles, and optional components, if necessary, are weighed in predetermined amounts, mixed, heated and dissolved.
• means for mixing various components and the means for heating and melting means known in the manufacture of solder paste may be used.
• solder paste In the process of kneading and manufacturing the solder paste, a predetermined amount of the solder powder and the flux are weighed, put into a kneader, and kneaded to manufacture the solder paste.
• solder joint The solder joints of this embodiment can be formed by a known method using the solder paste of the present invention.
• solder joints At the formed solder joints, the occurrence of solder balls can be effectively suppressed, so that highly reliable joints can be achieved in electronic components or electronic devices having the solder joints.
• solder joint As the known method, there is a reflow method, but there is no particular limitation as long as it can form a solder joint, such as heating with a laser.
• an electronic circuit mounting board on which electronic components are mounted for example, electrodes and an insulating layer are formed at predetermined positions on the board, and the solder paste of the present invention is printed using a mask having a predetermined pattern. Then, an electronic component conforming to the pattern is mounted at a predetermined position and reflowed to produce an electronic circuit mounting board.
• solder joints are formed on the electrodes. Moreover, it becomes possible to join the electrode and the electronic component at the solder joint.
• the electronic device is not particularly limited as long as it is an electronic device incorporating the electronic component, and examples thereof include a personal computer, a home appliance, and an audio device.
• a personal computer a home appliance
• an audio device for example, by using the electronic circuit mounting board manufactured as described above, a highly reliable electronic control device is manufactured.
• solder paste of the present invention can suppress the generation of solder balls in low-temperature soldering, so that even electronic components or electronic devices with low heat resistance can maintain high bonding reliability. becomes possible.
• solder alloy was produced by blending each metal according to a standard method so as to have the composition shown in Table 1. Using the obtained solder alloys, solder powders (alloy compositions 1 to 19) were prepared according to a conventional method. The particle size of the powder corresponds to IPC standard type 4 (20 to 38 ⁇ m). All of the obtained solder powders were lead-free solder alloys with a solidus temperature of 150° C. or less. Each solder alloy had the composition shown in Table 1 and contained unavoidable impurities originating from the raw materials.
• solder paste was prepared by combining solder powder of a lead-free solder alloy and flux according to a prescribed formula.
• solder paste was evaluated for solder ball suppression according to the following procedure.
• Table 5 shows the results.
• solder ball test method specified in JIS Z 3284 was used. Specifically, a solder paste was printed (6.5 mm ⁇ ) on a ceramic plate, and the solder paste was heated and melted on a hot plate at 209° C. (alloy compositions 1 to 18) or 174° C. (alloy composition 19). After melting, the melted solder is in the shape of a single large ball on the ceramic plate, but the solder particles (solder balls) around it that have not been aggregated into one are observed, and the solder balls are removed by the method described in JIS. It was counted and evaluated according to the following evaluation criteria. It should be noted that the smaller the number of solder balls, the better.
• the solder pastes using the fluxes of Production Examples 1, 15, and 20 were evaluated as ⁇ for suppression of solder ball formation in all combinations of alloy compositions 1 to 19 of the solder powder composition. , the effect of suppressing the occurrence of solder balls was exhibited remarkably regardless of the alloy composition.
• the solder paste using the flux of Production Example 10 was also evaluated as ⁇ for suppression of solder ball formation in all combinations of alloy compositions 1 to 19 of the composition of the solder powder. The effect of suppressing ball generation was sufficiently exhibited.
• the fluxes of Production Examples 1, 15, and 20 all had a dicarboxylic acid/imidazole content of 0.5 to 5, a dicarboxylic acid/monocarboxylic acid content of 0.8 to 10, and an antioxidant/imidazole content of 1 or less. It was adjusted to the range.
• the solder pastes combined with the fluxes of Comparative Production Examples 1, 5, and 8 were evaluated as ⁇ or ⁇ in terms of suppression of solder ball formation, and compared with the flux used in the above production examples, solder ball formation was suppressed. The inhibitory effect was inferior.
• the content ratio of the flux obtained in Production Example 1 and the solder powder having the alloy composition 1 was changed to 9.0% by mass and 11.0% by mass.
• the solder ball suppressing effect was confirmed in the case where the solder ball was suppressed, all the evaluations were ⁇ .
• the dicarboxylic acid having 4 to 6 carbon atoms / the above The content ratio of the monocarboxylic acid (by mass) is in the range of 0.8 to 10, and the content ratio of the dicarboxylic acid having 4 to 6 carbon atoms/the imidazole (by mass) is 0.5 to 5. Within the range of, the ratio of the content of the antioxidant / imidazole (based on mass) is within the range of 1 or less, and it can be seen that all three ratios are satisfied (Examples 1, 4, 5, 8, 15-20).
• the solder paste of the present invention contains a lead-free solder alloy with a low melting point and a solidus temperature of 150 ° C. or less, and can effectively suppress the generation of solder balls during bonding, so that it can be used for electronic components with low heat resistance. It is expected to be applied to the mounting of substrates of electronic devices that require bonding, for example, substrates of personal computers and the like.

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• 2021
  • 2021-12-28 EP EP21939878.1A patent/EP4335941A4/en active Pending
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  • 2021-12-28 US US18/289,495 patent/US20240238915A1/en active Pending
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