TW202133976A - Solder paste, metal-coated particle for solder paste, and connection structure - Google Patents

Abstract

The present invention provides a solder paste which does not easily wet and expand in an unintended area at a time of connection, easily maintains a shape of a connection portion formed by the solder paste in a connection structure after the connection, and is capable of maintaining a high connection strength even if the connection structure after the connection is subjected to a thermal shock or a physical impact. A solder paste according to the present invention includes a plurality of solder particles and a plurality of metal-coated particles. The metal-coated particle has a specific gravity of 6.0 or less and includes a base material particle and a metal portion disposed on a surface of the base material particle. The metal portion includes metal capable of forming an intermetallic compound with solder, includes metal capable of performing melt-bonding with solder, or includes metal capable of diffusing with solder.

Description

Solder paste, metal coated particles for solder paste, and connection structure

The present invention relates to a solder paste containing a plurality of solder particles and a plurality of particles different from the solder particles. In addition, the present invention relates to a metal-coated particle used in solder paste. In addition, the present invention relates to a connected structure using the above-mentioned solder paste or metal-coated particles.

An anisotropic conductive material containing solder is known. The content of the solder particles in the anisotropic conductive material is, for example, 80% by weight or less.

On the other hand, a solder joint material containing a large amount of solder is known. The solder bonding material is, for example, solder paste. The content of the solder particles in the solder joint material exceeds 80% by weight, for example.

The above-mentioned solder bonding materials are used to obtain various connected structures. As the connection of the connection structure, for example, the connection between the flexible printed substrate and the glass substrate (FOG (Film on Glass)); the connection between the semiconductor chip and the flexible printed substrate (COF (Chip on Film, chip on film)) )); the connection between the semiconductor chip and the glass substrate (COG (Chip on Glass, chip on glass)); the connection between the flexible printed substrate and the glass epoxy substrate (FOB (Film on Board, coated board)); and electronic parts, molds The connection (SMT (Surface mount technology, surface mount technology)), etc. between the package or its package and the hard printed circuit board.

When the electrodes are electrically connected, the above-mentioned solder bonding material is selectively coated on the electrode as the soldering portion of the circuit board or the like by screen printing or the like. Next, semiconductor wafers and the like are laminated, and the solder is melted and then solidified. Through the solidified solder, the electrodes are electrically connected.

The following Patent Document 1 discloses a solder paste in which a plurality of solder particles are dispersed in a thermosetting resin composition. The solder paste may include high melting point metal particles having a higher melting point than the solder particles.

The following Patent Document 2 discloses a conductive paste containing tin-coated copper powder, resin and solvent. The copper powder coated with tin is coated with tin or tin alloy on the surface of the copper particles. The coating amount of the tin or tin alloy is 1% to 33% by mass of the entire tin-coated copper powder. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2013-220466 [Patent Document 2] Japanese Patent Laid-Open No. 2018-131666

[The problem to be solved by the invention]

The previous solder paste sometimes wets and spreads to unintended areas during connection.

In addition, in a solder paste containing high melting point metal particles as described in Patent Document 1, it may be difficult to uniformly disperse the high melting point metal particles in the solder paste. Therefore, in the connected structure after the connection, the shape of the connection portion formed by the solder paste may not be sufficiently maintained in some cases. As described in Patent Document 2, the tin-coated copper powder is sometimes difficult to be uniformly dispersed in the solder paste in the connected structure after the connection.

In addition, regarding the previous solder paste, when the connected structure after the connection is exposed to thermal shock or physical shock, the connection part formed by the solder paste may crack or peel off. Therefore, the connection strength may decrease.

The object of the present invention is to provide a solder paste and metal-coated particles for solder paste. The solder paste is difficult to wet and spread to unintended areas during connection, and it is easy to maintain the connection part formed by the solder paste in the connection structure after the connection. The shape of the connection structure after connection can maintain high connection strength even if exposed to thermal shock or physical shock. In addition, an object of the present invention is to provide a connected structure using the above-mentioned solder paste or the above-mentioned metal-coated particles for the solder paste. [Technical means to solve the problem]

According to a broad aspect of the present invention, there is provided a solder paste comprising a plurality of solder particles and a plurality of metal-coated particles, and the metal-coated particles have a specific gravity of 6.0 or less, and the metal-coated particles have base particles and are arranged on the base. The metal part on the surface of the material particle includes a metal capable of forming an intermetallic compound with solder, a metal capable of fusion bonding with solder, or a metal capable of diffusing together with solder.

According to a broad aspect of the present invention, there is provided a metal-coated particle for solder paste (hereinafter, sometimes referred to as "metal-coated particle"), which has a specific gravity of 6.0 or less, and has substrate particles and arranged on the surface of the substrate particles. The upper metal part includes a metal capable of forming an intermetallic compound with the solder, or a metal capable of fusion bonding with the solder, or a metal capable of diffusing together with the solder.

In a specific aspect of the solder paste and metal-coated particles of the present invention, the substrate particles are resin particles or organic-inorganic hybrid particles.

In a specific aspect of the solder paste and the metal-coated particles of the present invention, the metal portion includes the metal capable of forming an intermetallic compound with solder on the outer surface portion of the metal portion, or includes the aforementioned metal capable of fusion bonding with solder Metals, or include the above-mentioned metals that can diffuse with solder.

In a specific aspect of the solder paste and metal-coated particles of the present invention, the metal portion includes nickel, gold, tin, or an alloy containing tin on the outer surface portion of the metal portion.

In a specific aspect of the solder paste and metal-coated particles of the present invention, the metal part contains tin or an alloy containing tin on the outer surface portion of the metal part.

In a specific aspect of the solder paste and metal-coated particles of the present invention, the ratio of the average thickness of the metal portion to the particle size of the base particles is 0.005 or more.

In a specific aspect of the solder paste and the metal-coated particles of the present invention, the metal-coated particles have a rust inhibitor or flux on the outer surface of the metal part.

In a specific aspect of the solder paste of the present invention, the solder paste further includes at least one of an organic solvent and a flux.

In a specific aspect of the solder paste of the present invention, the content of the above-mentioned solder particles in 100% by weight of the solder paste is 50% by weight or more.

In a specific aspect of the solder paste of the present invention, the total content of the solder particles and the metal-coated particles in 100% by weight of the solder paste is 51% by weight or more.

According to a broad aspect of the present invention, there is provided a connection structure including: a first connection object member having a first connection region on the surface, a second connection object member having a second connection region on the surface, and the first connection The connection part of the connection target member and the second connection target member, and the connection part is formed of the solder paste, and the first connection region part and the second connection region part are electrically connected by solder formed from the solder particles Or physical connection.

According to a broad aspect of the present invention, there is provided a connection structure including: a first connection object member having a first connection region on the surface, a second connection object member having a second connection region on the surface, and the first connection The connection part of the connection target member and the second connection target member, and the connection part is formed of a solder paste containing a plurality of solder particles and a plurality of metal-coated particles. The metal-coated particles are the metal-coated particles as described above. 1 The connection area portion and the second connection area portion are electrically or physically connected by solder formed from the solder particles. [Effects of Invention]

The solder paste of the present invention has a plurality of solder particles and a plurality of metal-coated particles, the metal-coated particles have a specific gravity of 6.0 or less, and the metal-coated particles have base particles and metal parts arranged on the surfaces of the base particles. Regarding the solder paste of the present invention, the metal portion includes a metal capable of forming an intermetallic compound with solder, or a metal capable of fusion bonding with solder, or a metal capable of diffusing together with solder. Since the solder paste of the present invention has the above-mentioned structure, it is difficult to wet and spread to unintended areas during connection, and it is easy to maintain the shape of the connection portion formed by the solder paste in the connection structure after the connection, and the connection structure after the connection The body can maintain high connection strength even when exposed to thermal shock or physical shock.

The metal-coated particles for solder paste of the present invention have a specific gravity of 6.0 or less, and have substrate particles and metal parts arranged on the surface of the substrate particles. The metal portion of the metal-coated particles for solder paste of the present invention contains a metal capable of forming an intermetallic compound with solder, or contains a metal capable of fusion bonding with solder, or contains a metal capable of diffusing together with solder. Since the metal-coated particles for solder paste of the present invention have the above-mentioned structure, they can be suitably used for solder paste. The solder paste containing the metal-coated particles for solder paste of the present invention is difficult to wet and spread to unintended areas during connection, and it is easy to maintain the shape of the connection part formed by the solder paste in the connection structure after the connection, and after connection The connection structure can maintain high connection strength even when exposed to thermal shock or physical shock.

Hereinafter, the details of the present invention will be explained.

(Metal coated particles for solder paste) The metal-coated particles for solder paste of the present invention (hereinafter, sometimes referred to as "metal-coated particles") have a specific gravity of 6.0 or less. The metal-coated particle of the present invention has a substrate particle and a metal part arranged on the surface of the substrate particle. The metal part of the metal-coated particle of the present invention contains a metal capable of forming an intermetallic compound with solder, or contains a metal capable of fusion bonding with solder, or contains a metal capable of diffusing together with solder.

Since the metal-coated particles of the present invention have the above-mentioned structure, they can be suitably used for solder paste.

The solder paste containing the metal-coated particles of the present invention is difficult to wet and spread to unintended areas during connection. The reason is that the metal-coated particles have substrate particles and metal parts arranged on the surface of the substrate particles, and the specific gravity of the metal-coated particles is 6.0 or less. The metal-coated particles are easily uniformly dispersed in the solder paste, so the solder paste is difficult to wet and spread to unintended areas during connection.

Furthermore, regarding the solder paste containing the metal-coated particles of the present invention, it is easy to maintain the shape of the connecting portion formed of the solder paste in the connected structure after the connection. The reason is that the metal-coated particles have substrate particles and metal parts arranged on the surface of the substrate particles, and the specific gravity of the metal-coated particles is 6.0 or less. A further reason is that the metal portion of the metal-coated particles contains a metal capable of forming an intermetallic compound with solder, or contains a metal capable of fusion bonding with solder, or contains a metal capable of diffusing together with solder.

Furthermore, regarding the solder paste containing the metal-coated particles of the present invention, the connected structure after the connection can maintain high connection strength even if it is exposed to thermal shock or physical shock. The reason is that the aforementioned solder paste contains the aforementioned metal-coated particles. The connection part of the said connection structure contains the said metal-coated particle or the said base material particle. The metal-coated particles or the substrate particles effectively prevent cracks and peeling in the connection portion. As a result, even if the connected structure after the connection is exposed to thermal shock or physical shock, the high connection strength can be maintained.

Hereinafter, the present invention will be specifically explained with reference to the drawings. Furthermore, in Fig. 1 and the following figures, different parts can be replaced with each other.

Fig. 1 is a cross-sectional view showing a metal-coated particle according to the first embodiment of the present invention.

The metal-coated particle 1 shown in FIG. 1 has a base particle 2 and a metal part 3. The metal part 3 is arranged on the surface of the substrate particle 2. In the first embodiment, the metal portion 3 is in contact with the surface of the substrate particle 2, and the shape of the metal portion 3 is layered. The metal-coated particles 1 are coated particles obtained by coating the surface of a substrate particle 2 with a metal part 3. The entire surface of the substrate particle 2 is covered by the metal part 3.

In the metal-coated particle 1, the metal part 3 is a single-layer metal layer. The metal part of the metal-coated particle may cover the entire surface of the substrate particle, and the metal part may cover a part of the surface of the substrate particle. Furthermore, the metal part may or may not be in contact with the surface of the substrate particle. A layer other than the metal part may be arranged between the substrate particle and the metal part. From the viewpoint of further effectively exerting the effects of the present invention, the metal portion is preferably in contact with the surface of the substrate particle.

Fig. 2 is a cross-sectional view showing a metal-coated particle according to a second embodiment of the present invention.

The metal-coated particle 1A shown in FIG. 2 has a base particle 2A and a metal part 3A. The metal part 3A is arranged on the surface of the substrate particle 2A. In the second embodiment, the metal portion 3A is in contact with the surface of the substrate particle 2A, and the shape of the metal portion 3A is layered. The metal-coated particles 1A are coated particles obtained by coating the surface of a substrate particle 2A with a metal portion 3A. The entire surface of the substrate particle 2A is covered with the metal part 3A.

The metal part 3A has a first metal part 3AA as an inner layer and a second metal part 3AB as an outer layer. The first metal part 3AA is arranged on the surface of the substrate particle 2A. The second metal part 3AB is arranged on the outer surface of the first metal part 3AA.

The metal portion of the metal-coated particles may be a single-layer metal layer, or may be a multi-layer metal layer including two or more layers. The first metal part and the second metal part may be formed as metal parts with different compositions, or may be formed as metal parts with the same composition.

Fig. 3 is a cross-sectional view showing a metal-coated particle according to a third embodiment of the present invention.

The metal-coated particle 1B shown in FIG. 3 includes a base particle 2B and a metal part 3B arranged on the surface of the base particle 2B. The metal part 3B has a first metal part 3BA as an inner layer and a second metal part 3BB located on the outer side of the inner layer. In the third embodiment, the metal portion 3B is in contact with the surface of the substrate particle 2B, the shape of the first metal portion 3BA is layered, and the shape of the second metal portion 3BB is convex. The metal-coated particles 1B are coated particles obtained by coating the surface of the substrate particle 2B with a metal portion 3B. The entire surface of the substrate particle 2B is covered with the metal part 3B. The metal part 3BB is a convex part. The second metal part 3BB protrudes. The outer surface of the first metal part 3BA is partially covered by the second metal part 3BB.

The metal part of the metal-coated particle may include one metal part, or may include two or more metal parts. The first metal part and the second metal part may be formed as metal parts with different compositions, or may be formed as metal parts with the same composition.

The substrate particles in the metal-coated particles may be completely covered by the metal portion, or may not be completely covered. The said base material particle may have the part which is not covered with the said metal part. The metal part as the inner layer may be completely covered by the metal part on the outer side, or may be incompletely covered. The metal part as the inner layer may have a portion that is not covered by the metal part on the outer side.

The specific gravity of the metal-coated particles is 6.0 or less. The specific gravity of the metal-coated particles is preferably 5.5 or less, more preferably 5.0 or less, more preferably 4.5 or less, still more preferably 4.0 or less, and still more preferably 3.5 or less. If the specific gravity of the metal-coated particles is equal to or less than the above upper limit, the metal-coated particles are likely to be more uniformly dispersed in the solder paste. Therefore, it is easy to further maintain the shape of the connecting portion formed by the solder paste in the connected structure after the connection. The specific gravity of the metal-coated particles may be 1.1 or more, or 1.5 or more.

The specific gravity of the metal-coated particles can be measured using a pycnometer, an electronic hydrometer, or the like. The specific gravity of the metal-coated particles is particularly preferably measured using an electronic hydrometer. As the above electronic hydrometer, "EW-300SG" manufactured by Alfa Mirage, etc. may be mentioned.

Regarding the metal-coated particles, in 100% of the total surface area of the substrate particles, the area of the portion having the metal portion (the coverage rate of the metal portion) is preferably 5% or more, more preferably 10% or more, and more preferably 30 % Or more, more preferably 50% or more, particularly preferably 70% or more, most preferably 80% or more. In 100% of the total surface area of the substrate particles, the area of the portion having the metal portion is preferably 100% or less. If the area of the part having the metal part is greater than or equal to the above lower limit, the effect of the present invention can be more effectively exhibited.

In 100% of the total surface area of the substrate particles, the area of the part with the metal part can be calculated as follows, that is, using SEM-EDX (Scanning Electron Microscope-Energy Dispersive X-Ray spectrometer, scanning electron microscope-energy Dispersive X-ray spectrometer) analyzes the cross-section of conductive particles and then performs elemental mapping to perform image analysis.

The particle diameter of the metal-coated particles is preferably 1 μm or more, more preferably 3 μm or more, and is preferably 100 μm or less, and more preferably 30 μm or less. If the particle diameter of the metal-coated particles is greater than or equal to the aforementioned lower limit and less than or equal to the aforementioned upper limit, the effects of the present invention can be more effectively exhibited.

The particle diameter of the metal-coated particles is preferably an average particle diameter, and more preferably a number average particle diameter. The particle size of the metal-coated particles can be obtained, for example, by observing any 50 metal-coated particles with an electron microscope or an optical microscope, and calculating the average value of the particle size of each metal-coated particle, or using the particle size distribution Calculated by the measuring device. When observing with an electron microscope or an optical microscope, the particle diameter of each metal-coated particle is calculated as the diameter equivalent to a circle. When observed with an electron microscope or an optical microscope, the average particle diameter of any 50 metal-coated particles in terms of circle-equivalent diameter is almost equal to the average particle diameter of sphere-equivalent diameter. In the particle size distribution measuring device, the particle size of each metal-coated particle is determined as the particle size in terms of the equivalent diameter of the sphere. The average particle diameter of the metal-coated particles is preferably calculated using a particle size distribution measuring device.

The coefficient of variation (CV value) of the particle diameter of the metal-coated particles is preferably 10% or less, more preferably 5% or less. If the coefficient of variation of the particle diameter of the metal-coated particles is equal to or less than the above upper limit, the metal-coated particles are likely to be more uniformly dispersed in the solder paste.

The aforementioned coefficient of variation (CV value) can be measured as follows.

CV value (%)=(ρ/Dn)×100 ρ: The standard deviation of the particle size of the metal-coated particles Dn: the average value of the particle size of the metal-coated particles

The shape of the metal-coated particles is not particularly limited. The shape of the metal-coated particles may be a spherical shape, a shape other than a spherical shape, or a shape such as a flat shape.

The ratio of the average thickness of the metal portion to the particle size of the substrate particles (average thickness of the metal portion/particle size of the substrate particles) is preferably 0.0001 or more, more preferably 0.001 or more, and still more preferably 0.005 Above, 0.01 or more is particularly preferred. If the said ratio is more than the said lower limit, the effect of this invention will be exhibited more effectively. The ratio (average thickness of the metal portion/particle diameter of the substrate particle) is preferably 1 or less, and more preferably 0.5 or less. If the above-mentioned ratio is equal to or less than the above-mentioned upper limit, it is easy to reduce the specific gravity.

The average thickness of the metal part only considers the area where the metal part exists on the substrate particle, and does not consider the area where the metal part does not exist on the substrate particle. When the metal part is partially arranged on the surface of the substrate particle, the thickness of the region where the thickness of the metal part is zero (ie, zero) is not taken into consideration when calculating the average thickness of the metal part.

The average thickness of the metal part can be measured by observing the cross-section of the metal-coated particle, for example, using a transmission electron microscope (TEM). The average thickness of the metal part is preferably obtained by calculating the average value of the thickness of each metal part of any 50 metal-coated particles.

From the viewpoint of further effectively exerting the effects of the present invention, the metal-coated particles preferably contain a rust inhibitor or a flux on the outer surface of the metal portion. The metal-coated particles may contain a rust inhibitor or flux on the outer surface of the metal part.

Substrate particles: The material of the aforementioned substrate particles is not particularly limited. The material of the aforementioned substrate particles may be organic materials or inorganic materials. As the substrate particles formed only of the above-mentioned organic material, resin particles and the like may be mentioned. As the substrate particles formed only of the above-mentioned inorganic materials, inorganic particles other than metals and the like can be mentioned. Examples of substrate particles formed of both the above-mentioned organic material and the above-mentioned inorganic material include organic-inorganic hybrid particles. From the viewpoint of making the specific gravity of the metal-coated particles easier to further decrease and further effectively exerting the effects of the present invention, the substrate particles are preferably resin particles or organic-inorganic hybrid particles, and more preferably resin particles.

Examples of the above-mentioned organic materials include polyolefin resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyisobutylene, and polybutadiene; polymethyl methacrylate and polyacrylic acid. Acrylic resins such as methyl esters; polycarbonate, polyamide, phenol-formaldehyde resin, melamine-formaldehyde resin, benzoguanamine-formaldehyde resin, urea-formaldehyde resin, phenolic resin, melamine resin, benzoguanamine resin, urea Resins, epoxy resins, unsaturated polyester resins, saturated polyester resins, polyethylene terephthalate, polycarbonate, polyphenylene ether, polyacetal, polyimide, polyimide imine, poly Ether ether ketone, polyether agglomerate, divinylbenzene polymer, and divinylbenzene copolymer, etc. As said divinylbenzene copolymer etc., a divinylbenzene-styrene copolymer, a divinylbenzene-(meth)acrylate copolymer, etc. are mentioned. From the viewpoint of further effectively exerting the effects of the present invention, the material of the substrate particles is preferably a polymer obtained by polymerizing one or more types of polymerizable monomers having ethylenic unsaturated groups.

In the case of polymerizing a polymerizable monomer having an ethylenically unsaturated group to obtain the substrate particles, examples of the polymerizable monomer having an ethylenically unsaturated group include non-crosslinking monomers and crosslinking Sexual monomer.

Examples of the above-mentioned non-crosslinkable monomers include: vinyl compounds, such as styrene monomers such as styrene, α-methylstyrene, and chlorostyrene; methyl vinyl ether, ethyl vinyl ether, and propyl ethylene Vinyl ether compounds such as ether; vinyl acetate, vinyl butyrate, vinyl laurate, vinyl stearate and other acid vinyl ester compounds; halogen-containing monomers such as vinyl chloride and vinyl fluoride; as (meth)acrylic acid Compounds of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (meth) Alkyl (meth)acrylate compounds such as lauryl acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, isopropyl (meth)acrylate, etc.; 2-hydroxyethyl (meth)acrylate, glycerol (meth)acrylate, polyoxyethylene (meth)acrylate, glycidyl (meth)acrylate and other oxygen atom-containing (meth)acrylate compounds; Nitrile-containing monomers such as (meth)acrylonitrile; halogen-containing (meth)acrylate compounds such as trifluoromethyl (meth)acrylate and pentafluoroethyl (meth)acrylate; as α-olefin compounds Olefin compounds such as diisobutylene, isobutylene, linealene, ethylene, and propylene; isoprene and butadiene as conjugated diene compounds.

Examples of the above-mentioned crosslinkable monomers include vinyl monomers such as divinylbenzene, 1,4-divinyloxybutane, and divinyl sulfonate as vinyl compounds; as (meth)acrylic compounds Of tetramethylolmethane tetra(meth)acrylate, polytetramethylene glycol diacrylate, tetramethylolmethane tri(meth)acrylate, tetramethylolmethane di(meth)acrylate , Trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, glycerol tri(meth)acrylate, glycerol di(meth)acrylate Ester, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, 1,4-butanediol bis(methyl) ) Polyfunctional (meth)acrylate compounds such as acrylate; triallyl (iso)cyanurate, triallyl trimellitate, diallyl phthalate, dienes as allyl compounds Propyl acrylamide, diallyl ether; tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyl Triethoxysilane, isopropyltrimethoxysilane, isobutyltrimethoxysilane, cyclohexyltrimethoxysilane, n-hexyltrimethoxysilane, n-octyltriethoxysilane, n-decyltrimethyl Oxysilane, phenyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diisopropyldimethoxysilane, trimethoxysilylstyrene, γ-( (Meth)acryloxypropyltrimethoxysilane, 1,3-divinyltetramethyldisiloxane, methylphenyldimethoxysilane, diphenyldimethoxysilane and other silanes Oxide compounds; vinyl trimethoxy silane, vinyl triethoxy silane, dimethoxy methyl vinyl silane, dimethoxy ethyl vinyl silane, diethoxy methyl vinyl silane, two Ethoxyethyl vinyl silane, ethyl methyl divinyl silane, methyl vinyl dimethoxy silane, ethyl vinyl dimethoxy silane, methyl vinyl diethoxy silane, ethyl Vinyl diethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, etc., containing polymerizable properties Silane alkoxides with double bonds; cyclic siloxanes such as decamethylcyclopentasiloxane; modified polysiloxane oils at one end, polysiloxane oils at both ends, side chain polysiloxane oils, etc. ( Reactivity) Polysiloxane oil; (meth)acrylic acid, maleic acid, maleic anhydride and other carboxyl-containing monomers.

Examples of the above-mentioned inorganic materials include silica, alumina, barium titanate, zirconia, carbon black, silicate glass, borosilicate glass, lead glass, soda lime glass, aluminosilicate glass, and the like.

The aforementioned substrate particles may be organic-inorganic hybrid particles. The aforementioned substrate particles may be core-shell particles. When the substrate particle is an organic-inorganic hybrid particle, the inorganic substance of the material of the substrate particle may, for example, be silica, alumina, barium titanate, zirconia, carbon black, and the like. The above-mentioned inorganic substance is preferably a non-metal. The substrate particles formed of the above-mentioned silicon dioxide are not particularly limited, and examples thereof include substrate particles obtained by hydrolyzing a silicon compound having two or more hydrolyzable alkoxysilyl groups to form crosslinks. After the polymer particles, they are fired as necessary. As the above-mentioned organic-inorganic hybrid particles, organic-inorganic hybrid particles formed of a crosslinked alkoxysilyl polymer and acrylic resin, etc. may be mentioned.

The organic-inorganic hybrid particles are preferably core-shell organic-inorganic hybrid particles having a core and a shell arranged on the surface of the core. The aforementioned core is preferably an organic core. The above-mentioned shell is preferably an inorganic shell. The substrate particle is preferably an organic-inorganic hybrid particle having an organic core and an inorganic shell arranged on the surface of the organic core.

As the material of the above-mentioned organic core, the above-mentioned organic material and the like can be mentioned.

As the material of the above-mentioned inorganic shell, the inorganic substances exemplified as the material of the above-mentioned base particle can be exemplified. The material of the above-mentioned inorganic shell is preferably silicon dioxide. The inorganic shell is preferably formed by forming a shell of metal alkoxide on the surface of the core by a sol-gel method, and then firing the shell. The above-mentioned metal alkoxide is preferably a silane alkoxide. The above-mentioned inorganic shell is preferably formed of silane alkoxide.

Metal Department: The metal part includes a metal capable of forming an intermetallic compound with the solder, or a metal capable of fusion bonding with the solder, or a metal capable of diffusing together with the solder. The metal part may include a metal capable of forming an intermetallic compound with the solder, may include a metal capable of fusion bonding with the solder, or may include a metal capable of diffusing together with the solder. The metal portion may further include metals other than metals capable of forming intermetallic compounds with solder, metals capable of fusion bonding with solder, and metals capable of diffusing together with solder.

From the viewpoint of further effectively exerting the effects of the present invention, the metal portion preferably contains a metal capable of forming an intermetallic compound with solder, or a metal capable of fusion bonding with solder, or contains a metal that can form an intermetallic compound with solder, or contains Metal that can diffuse with solder.

Furthermore, the metal capable of forming an intermetallic compound with solder is one that can form an intermetallic compound with tin in the equilibrium state diagram of the metal. A metal that can be melted and combined with solder can be melted by heating to bond with solder. The metal that can diffuse with the solder does not melt due to heating, but the metal diffuses in the solder when the solder melts.

From the viewpoint of further effectively exerting the effects of the present invention, the metal capable of forming an intermetallic compound with the solder is preferably nickel, gold, palladium, indium, silver, copper, tin or tin-containing alloys, more preferably nickel, Gold, tin or tin-containing alloy, more preferably tin or tin-containing alloy. From the viewpoint of further effectively exerting the effects of the present invention, the metal capable of fusion bonding with the solder is preferably indium, tin, or an alloy containing tin, more preferably tin or an alloy containing tin. From the viewpoint of further effectively exerting the effects of the present invention, the metal capable of diffusing together with the solder is preferably nickel, gold, palladium, silver, or copper, and more preferably nickel or gold.

From the viewpoint of further effectively exerting the effects of the present invention and further effectively improving the connection reliability, the metal part preferably contains nickel, gold, palladium, indium, silver, copper, tin or an alloy containing tin, and more Preferably it contains nickel, gold, tin, or an alloy containing tin, and more preferably contains tin or an alloy containing tin.

From the viewpoint of further effectively exerting the effects of the present invention and further effectively improving the connection reliability, the metal part preferably contains nickel, gold, palladium, silver, copper, tin or the outer surface of the metal part. The tin-containing alloy is more preferably nickel, gold, palladium, indium, tin or tin-containing alloy in the outer surface portion of the metal part. From the viewpoint of further effectively exerting the effects of the present invention and further effectively improving the connection reliability, the metal part further preferably contains nickel, gold, tin, or an alloy containing tin on the outer surface portion of the metal part.

In 100% by weight of the metal part, the content of tin is preferably 0.1% by weight or more, more preferably 1% by weight or more, and is preferably 100% by weight or less, and more preferably 90% by weight or less. The content of the tin may be 80% by weight or less, 60% by weight or less, 40% by weight or less, 20% by weight or less, or 10% by weight or less. If the content of tin is at least the above lower limit and below the above upper limit, the effects of the present invention will be more effectively exhibited.

When the metal part is multilayered, the content of tin in 100% by weight of the tin-containing layer is preferably 0.1% by weight or more, more preferably 1% by weight or more, and preferably 100% by weight or less, more preferably It is 90% by weight or less. The content of the tin may be 80% by weight or less, 60% by weight or less, 40% by weight or less, 20% by weight or less, or 10% by weight or less. If the content of tin is at least the above lower limit and below the above upper limit, the effects of the present invention will be more effectively exhibited.

Preferably, the metal part is formed of solder. More preferably, the outer surface portion of the metal portion is formed of solder.

The above-mentioned solder is preferably a metal (low melting point metal) with a melting point of 450°C or less based on JIS Z3001: welding term. The low melting point metal refers to a metal with a melting point of 450°C or less. The melting point of the low melting point metal is preferably 300°C or less. In addition, the above-mentioned solder contains tin. In 100% by weight of the metal contained in the solder, the content of tin is preferably 30% by weight or more, more preferably 40% by weight or more, still more preferably 70% by weight or more, particularly preferably 90% by weight or more. If the content of tin in the solder is greater than or equal to the above lower limit, the effects of the present invention will be more effectively exhibited.

In addition, the content of various metals in the metal part or the metal-containing layer can be analyzed by a high-frequency inductively coupled plasma emission spectrometer ("ICP-AES" manufactured by Horiba Manufacturing Co., Ltd.) or a fluorescent X-ray analysis device (Shimadzu Manufacturing Co., Ltd.) "EDX-800HS" manufactured by the company), etc. for measurement.

The low melting point metal constituting the aforementioned solder is not particularly limited. The low melting point metal is preferably tin or an alloy containing tin. The alloy may be exemplified by tin-silver alloy, tin-copper alloy, tin-silver-copper alloy, tin-bismuth alloy, tin-zinc alloy, tin-indium alloy, and the like. In terms of excellent wettability of the connection target member, the low melting point metal is preferably tin, tin-silver alloy, tin-silver-copper alloy, tin-bismuth alloy, and tin-indium alloy. More preferred are tin-bismuth alloys and tin-indium alloys.

In order to further improve the connection strength, the aforementioned solder may contain metals such as nickel, copper, antimony, aluminum, zinc, iron, gold, titanium, phosphorus, germanium, tellurium, cobalt, bismuth, manganese, chromium, molybdenum, and palladium. In addition, from the viewpoint of further improving the connection strength, the solder preferably contains nickel, copper, antimony, aluminum, or zinc. From the viewpoint of further improving the connection strength, the content of the metals used to increase the connection strength in 100% by weight of the solder is preferably 0.0001% by weight or more, and preferably 1% by weight or less.

The metal part may be formed in one layer. The above-mentioned metal part may be formed of a plurality of layers. That is, the above-mentioned metal part may have a laminated structure of two or more layers. From the viewpoint of further effectively improving the conduction reliability, it is preferable that the metal part has a laminated structure of two or more layers.

The method of forming a metal part on the surface of the said base material particle is not specifically limited. Examples of methods for forming the above-mentioned metal parts include: electroless plating methods, electroplating methods, physical collision methods, mechanochemical reaction methods, physical vapor deposition or physical adsorption methods, and metal powder or a combination of metal powder and a binder. A method of applying paste on the surface of substrate particles. The method of forming the above-mentioned metal part is preferably an electroless plating, electroplating, or a physical collision method. As the above-mentioned physical vapor deposition method, methods such as vacuum vapor deposition, ion plating, and ion sputtering may be mentioned. In addition, the above-mentioned physical collision method uses Theta Composer (manufactured by Tokusu Works Co., Ltd.) or the like.

Rust inhibitor: The outer surface of the metal part can be treated with an anti-rust agent. The metal-coated particles may have an anti-rust film formed of an anti-rust agent on the outer surface of the metal part.

As the above-mentioned rust inhibitor, a compound having an alkyl group having 6 to 22 carbon atoms (hereinafter may be referred to as compound A) and the like may be mentioned. The aforementioned rust inhibitor may be a compound that does not contain phosphorus. The rust inhibitor may, for example, be an alkyl phosphate compound or an alkyl mercaptan. As for the said rust inhibitor, only 1 type may be used, and 2 or more types may be used together.

If the alkyl carbon number of the compound A is 6 or more, the metal part is more difficult to rust. When the number of carbon atoms in the alkyl group of the compound A is 22 or less, the conductivity becomes higher. The number of carbon atoms in the alkyl group of the compound A is preferably 16 or less. The above-mentioned alkyl group may have a linear structure or a branched structure. The above-mentioned alkyl group preferably has a linear structure.

The compound A is not particularly limited as long as it has an alkyl group having 6 to 22 carbon atoms. The above-mentioned compound A is preferably a phosphoric acid ester or a salt thereof having an alkyl group having 6 to 22 carbons, a phosphite ester or a salt thereof having an alkyl group having 6 to 22 carbons, or an alkyl group having 6 to 22 carbons. Alkoxysilane. The above-mentioned compound A is preferably an alkyl mercaptan having an alkyl group having 6 to 22 carbons or a dialkyl disulfide having an alkyl group having 6 to 22 carbons. The compound A having an alkyl group having 6 to 22 carbon atoms is preferably a phosphoric acid ester or a salt thereof, a phosphite ester or a salt thereof, an alkoxysilane, an alkyl mercaptan, or a dialkyl disulfide. By using these suitable compounds A, the metal parts can be made more difficult to rust. From the viewpoint of being more difficult to rust, the above-mentioned compound A is preferably the above-mentioned phosphate or its salt, phosphite or its salt, or alkyl mercaptan, and more preferably the above-mentioned phosphate or its salt, or phosphite Or its salt. The above-mentioned compound A may use only 1 type, and may use 2 or more types together.

The above-mentioned compound A preferably has a reactive functional group capable of reacting with the outer surface of the metal part. The rust inhibitor is preferably chemically bonded to the metal part. The presence of the above-mentioned reactive functional group and the above-mentioned chemical bonding make it difficult for the above-mentioned rust inhibitor to peel off. As a result, the metal part is harder to rust.

Examples of the above-mentioned phosphoric acid ester or its salt having an alkyl group having 6 to 22 carbon atoms include: hexyl phosphate, heptyl phosphate, monooctyl phosphate, monononyl phosphate, monodecyl phosphate, monoundecyl phosphate Alkyl ester, monododecyl phosphate, monotridecyl phosphate, monotetradecyl phosphate, monopentadecyl phosphate, monohexyl phosphate monosodium salt, monoheptyl monosodium phosphate Salt, monooctyl phosphate monosodium salt, monononyl phosphate monosodium salt, monodecyl phosphate monosodium salt, monoundecyl phosphate monosodium salt, monododecyl phosphate monosodium salt, monophosphate monosodium salt Tridecyl monosodium salt, monotetradecyl phosphate monosodium salt and monopentadecyl phosphate monosodium salt, etc. Potassium salts of the above-mentioned phosphoric esters can also be used.

Examples of the phosphite or salt thereof having an alkyl group having 6 to 22 carbon atoms include hexyl phosphite, heptyl phosphite, monooctyl phosphite, monononyl phosphite, and monodecyl phosphite. Ester, monoundecyl phosphite, monododecyl phosphite, monotridecyl phosphite, monotetradecyl phosphite, monopentadecyl phosphite, monopentadecyl phosphite Hexyl ester monosodium salt, monoheptyl phosphite monosodium salt, monooctyl phosphite monosodium salt, monononyl phosphite monosodium salt, monodecyl phosphite monosodium salt, monoundecyl phosphite Monosodium salt, monododecyl phosphite monosodium salt, monotridecyl phosphite monosodium salt, monotetradecyl phosphite monosodium salt and monopentadecyl phosphite monosodium Salt etc. Potassium salts of the above-mentioned phosphites can also be used.

As the above-mentioned alkoxysilane having an alkyl group having 6 to 22 carbon atoms, for example, hexyltrimethoxysilane, hexyltriethoxysilane, heptyltrimethoxysilane, heptyltriethoxysilane, Octyltrimethoxysilane, octyltriethoxysilane, nonyltrimethoxysilane, nonyltriethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, undecyltrimethoxysilane Oxysilane, undecyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, tridecyltrimethoxysilane, tridecyltriethoxysilane Silane, tetradecyltrimethoxysilane, tetradecyltriethoxysilane, pentadecyltrimethoxysilane and pentadecyltriethoxysilane, etc.

As the alkyl mercaptan having an alkyl group having 6 to 22 carbon atoms, for example, hexyl mercaptan, heptyl mercaptan, octyl mercaptan, nonyl mercaptan, decyl mercaptan, undecyl mercaptan, and decyl mercaptan may be mentioned. Dialkyl mercaptan, tridecyl mercaptan, tetradecyl mercaptan, pentadecyl mercaptan and hexadecyl mercaptan, etc. The above-mentioned alkyl mercaptan preferably has a thiol group at the end of the alkyl chain.

Examples of the dialkyl disulfide having an alkyl group having 6 to 22 carbon atoms include dihexyl disulfide, diheptyl disulfide, dioctyl disulfide, and dinonyl disulfide. , Didecyl disulfide, di-undecyl disulfide, di-dodecyl disulfide, di-tridecyl disulfide, di-tetradecyl disulfide, di- Pentadecyl disulfide and dihexadecyl disulfide, etc.

Flux: The outer surface of the metal part can be treated with flux. By using flux, the oxidation of the metal in the metal part can be prevented, or foreign matter or oxide film can be removed. The above-mentioned flux is not particularly limited. As the above-mentioned flux, fluxes commonly used in solder bonding and the like can be used.

Examples of the above-mentioned flux include: zinc chloride, a mixture of zinc chloride and inorganic halides, a mixture of zinc chloride and inorganic acids, molten salts, phosphoric acid, phosphoric acid derivatives, organic halides, hydrazine, and amine compounds , Organic acids and rosin, etc. Only one type of the above-mentioned flux may be used, or two or more types may be used in combination.

As said molten salt, ammonium chloride etc. are mentioned. As said organic acid, lactic acid, citric acid, stearic acid, glutamic acid, glutaric acid, etc. are mentioned. As said rosin, activated rosin and non-activated rosin, etc. are mentioned. The above-mentioned flux is preferably an organic acid or rosin having two or more carboxyl groups. The above-mentioned flux may be an organic acid having two or more carboxyl groups, or may be rosin. By using organic acids and rosin with two or more carboxyl groups, the connection strength and conduction reliability are further improved.

Examples of the organic acid having two or more carboxyl groups include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid.

Examples of the above-mentioned amine compounds include: cyclohexylamine, dicyclohexylamine, benzylamine, benzhydrylamine, imidazole, benzimidazole, phenylimidazole, carboxybenzimidazole, benzotriazole, and carboxybenzo Triazole and so on.

The rosin mentioned above is a rosin with rosin acid as the main component. As said rosin, abietic acid, acrylic modified rosin, etc. are mentioned. The flux is preferably rosin, more preferably rosin acid. By using these suitable fluxes, the flux effect is further improved.

The activation temperature (melting point) of the above-mentioned flux is preferably 50°C or higher, more preferably 70°C or higher, still more preferably 80°C or higher, and preferably 200°C or lower, more preferably 190°C or lower, more preferably 160°C or lower, more preferably 150°C or lower, and still more preferably 140°C or lower. If the activation temperature of the flux is above the above lower limit and below the above upper limit, the effect of the flux is further improved.

The melting point of the above-mentioned flux can be determined by differential scanning calorimetry (DSC). As a differential scanning calorimetry (DSC) device, "EXSTAR DSC7020" manufactured by SII Corporation can be mentioned.

Moreover, it is preferable that the boiling point of the said flux is 200 degrees C or less.

The above-mentioned flux is preferably a flux that releases cations by heating. By using a flux that releases cations by heating, the connection strength and conduction reliability are further improved.

As the above-mentioned flux that releases cations by heating, the above-mentioned thermal cationic initiator (thermal cation hardener) can be mentioned.

From the viewpoint of further enhancing the effect of the flux, the flux is preferably a salt of an acid compound and an alkali compound.

The above-mentioned acid compound is preferably an organic compound having a carboxyl group. Examples of the above-mentioned acid compounds include: aliphatic carboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, citric acid, Malic acid; cyclohexyl carboxylic acid, 1,4-cyclohexyl dicarboxylic acid as cyclic aliphatic carboxylic acid; phthalic acid, terephthalic acid, trimellitic acid and ethylene diamine as aromatic carboxylic acid Tetraacetic acid and so on. From the viewpoint of further effectively improving the connection strength and further effectively improving the conduction reliability, the above-mentioned acid compound is preferably glutaric acid, cyclohexyl carboxylic acid or adipic acid.

The above-mentioned base compound is preferably an organic compound having an amino group. As the above-mentioned base compound, diethanolamine, triethanolamine, methyldiethanolamine, ethyldiethanolamine, cyclohexylamine, dicyclohexylamine, benzylamine, benzhydrylamine, 2-methylbenzylamine, 3-methylbenzylamine, 4-tert-butylbenzylamine, N-methylbenzylamine, N-ethylbenzylamine, N-phenylbenzylamine, N-tert-butylbenzylamine, N-isopropyl Benzylamine, N,N-dimethylbenzylamine, imidazole compounds and triazole compounds. From the viewpoint of further effectively improving the connection strength and further effectively improving the conduction reliability, the above-mentioned alkali compound is preferably benzylamine.

(Solder paste) The solder paste of the present invention includes a plurality of solder particles and a plurality of metal-coated particles. The solder paste of the present invention contains metal-coated particles. The above-mentioned metal-coated particles can be used for the solder paste of the present invention. The specific gravity of the metal-coated particles contained in the solder paste of the present invention is 6.0 or less. The metal-coated particles contained in the solder paste of the present invention have a base particle and a metal part arranged on the surface of the base particle. The metal portion of the metal-coated particles contained in the solder paste of the present invention includes a metal capable of forming an intermetallic compound with solder, or a metal capable of fusion bonding with solder, or a metal capable of diffusing together with solder.

The term "solder paste" includes a paste-like solder bonding material that is melted by heating to connect the connection object members.

The ratio of the particle diameter of the solder particles to the particle diameter of the substrate particles (the particle diameter of the solder particles/the particle diameter of the substrate particles) is preferably 0.1 or more, more preferably 0.5 or more, and still more preferably 1 Above, 1.5 or more is particularly preferred. The above-mentioned ratio (the particle diameter of the solder particles/the particle diameter of the substrate particles) is preferably 20 or less, more preferably 15 or less, still more preferably 10 or less, and particularly preferably 8 or less. If the said ratio is more than the said lower limit and the said upper limit, the effect of this invention will be exhibited more effectively.

In the solder paste, the content of the solder particles is preferably 20% by weight or more, more preferably 30% by weight or more, still more preferably 50% by weight or more, and particularly preferably 70% by weight or more. In the solder paste, the content of the solder particles is preferably 99.99% by weight or less, more preferably 99.90% by weight or less, still more preferably 99.00% by weight or less, and particularly preferably 98.00% by weight or less. If the content of the solder particles is greater than or equal to the aforementioned lower limit and less than or equal to the aforementioned upper limit, the effects of the present invention can be more effectively exhibited.

In the solder paste, the content of the metal-coated particles is preferably 0.01% by weight or more, more preferably 0.10% by weight or more, still more preferably 0.50% by weight or more, and particularly preferably 1.00% by weight or more. In the solder paste, the content of the metal-coated particles is preferably 70% by weight or less, more preferably 50% by weight or less, still more preferably 30% by weight or less, and particularly preferably 20% by weight or less. If the content of the metal-coated particles is greater than or equal to the aforementioned lower limit and less than or equal to the aforementioned upper limit, the effects of the present invention can be more effectively exhibited.

In the solder paste, the total content of the solder particles and the metal-coated particles is preferably 21% by weight or more, more preferably 31% by weight or more, still more preferably 51% by weight or more, and particularly preferably 71% by weight or more. In the solder paste, the total content of the solder particles and the metal-coated particles is preferably 100% by weight or less, more preferably 99.9% by weight or less, still more preferably 99.0% by weight or less, and particularly preferably 98.0% by weight or less. If the total content of the solder particles and the metal-coated particles is greater than or equal to the aforementioned lower limit and less than or equal to the aforementioned upper limit, the effects of the present invention can be more effectively exhibited.

The solder paste of the present invention may include at least one of an organic solvent and a flux. The solder paste of the present invention may include an organic solvent, and may also include a flux. In addition, the solder paste of the present invention may optionally contain additives such as a thixotropic agent or a surfactant.

Solder particles: The particle size of the solder particles is preferably 0.1 μm or more, more preferably 1 μm or more, and is preferably 100 μm or less, and more preferably 50 μm or less. If the particle diameter of the solder particles is greater than or equal to the aforementioned lower limit and less than or equal to the aforementioned upper limit, the effects of the present invention can be more effectively exhibited.

The particle diameter of the solder particles is preferably an average particle diameter, and more preferably a number average particle diameter. The particle size of the solder particles can be determined, for example, by observing any 50 solder particles with an electron microscope or an optical microscope and calculating the average value of the particle sizes of each solder particle, or by using a particle size distribution measuring device. When observing with an electron microscope or an optical microscope, the particle diameter of each solder particle is calculated as the diameter equivalent to a circle. When observing with an electron microscope or an optical microscope, the average diameter of any 50 solder particles in terms of circle equivalent diameter is almost equal to the average diameter of sphere equivalent diameter. In the particle size distribution measuring device, the particle size of each solder particle is calculated as the particle size in terms of the equivalent diameter of the sphere. The average particle size of the solder particles is preferably calculated using a particle size distribution measuring device.

The coefficient of variation (CV value) of the particle diameter of the solder particles is preferably 15% or less, more preferably 10% or less. If the coefficient of variation of the particle diameter of the solder particles is equal to or less than the upper limit, it is easy to disperse the solder particles more uniformly in the solder paste.

The aforementioned coefficient of variation (CV value) can be measured as follows.

CV value (%)=(ρ/Dn)×100 ρ: Standard deviation of the size of solder particles Dn: the average value of the diameter of the solder particles

The shape of the aforementioned solder particles is not particularly limited. The shape of the above-mentioned solder particles may be a spherical shape, a shape other than a spherical shape, or a shape such as a flat shape.

The above-mentioned solder is preferably a metal (low melting point metal) with a melting point of 450°C or less based on JIS Z3001: welding term. The low melting point metal refers to a metal with a melting point of 450°C or less. The melting point of the low melting point metal is preferably 300°C or less. In addition, the above-mentioned solder contains tin. In 100% by weight of the metal contained in the solder, the content of tin is preferably 30% by weight or more, more preferably 40% by weight or more, still more preferably 70% by weight or more, particularly preferably 90% by weight or more. If the tin content in the solder is more than or equal to the above lower limit, the effects of the present invention will be more effectively exhibited.

Furthermore, the content of various metals in the solder particles can be analyzed by a high-frequency inductively coupled plasma emission spectrometer ("ICP-AES" manufactured by Horiba) or a fluorescent X-ray analyzer ("EDX" manufactured by Shimadzu) -800HS”) and so on.

The low melting point metal constituting the aforementioned solder is not particularly limited. The low melting point metal is preferably tin or an alloy containing tin. The alloy may be exemplified by tin-silver alloy, tin-copper alloy, tin-silver-copper alloy, tin-bismuth alloy, tin-zinc alloy, tin-indium alloy, and the like. From the viewpoint of further effectively improving the connection strength and further effectively improving the conduction reliability, the above-mentioned low melting point metal is preferably tin, tin-silver alloy, tin-silver-copper alloy, tin-gold alloy, tin-antimony Alloy, tin-lead alloy, tin-bismuth alloy, tin-indium alloy.

In order to further improve the connection strength, the aforementioned solder may contain metals such as nickel, copper, antimony, aluminum, zinc, iron, gold, titanium, phosphorus, germanium, tellurium, cobalt, bismuth, manganese, chromium, molybdenum, and palladium. In addition, from the viewpoint of further improving the connection strength, the solder preferably contains nickel, copper, antimony, aluminum, or zinc. From the viewpoint of further improving the connection strength, the content of the metals used to increase the connection strength in 100% by weight of the solder is preferably 0.0001% by weight or more, and more preferably 1% by weight or less.

From the viewpoint of further effectively exerting the effects of the present invention, the above-mentioned solder particles are preferably Sn-Ag-Cu particles (SAC particles), Sn-Bi particles or Pb-Sn particles, and more preferably Sn-Ag-Cu particles (SAC particles) or Sn-Bi particles, more preferably Sn-Ag-Cu particles (SAC particles). The above-mentioned solder particles may be Sn-Ag-Cu particles (SAC particles), Sn-Bi particles, or Pb-Sn particles.

Flux: By using the above-mentioned flux, it is possible to prevent the oxidation of solder particles, metal-coated particles and the metal in the electrode, or to remove foreign matter or oxide film. As the above-mentioned flux in the above-mentioned solder paste, the flux described in the description column of the above-mentioned metal-coated particles can be exemplified.

When the solder paste contains the flux, the content of the flux in 100% by weight of the solder paste is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, and still more preferably 0.5% by weight or more, In addition, it is preferably 30% by weight or less, and more preferably 25% by weight or less. If the content of the flux is above the above lower limit and below the above upper limit, it is more difficult to form an oxide film on the surface of the solder and the electrode, and furthermore, the oxide film formed on the surface of the solder and the electrode can be removed more effectively.

Organic solvents: By using the above-mentioned organic solvent, the operability of the solder paste can be improved, or the viscosity of the solder paste can be adjusted. Examples of the organic solvent in the solder paste include: alcohol compounds such as ethanol; ketone compounds such as acetone, methyl ethyl ketone, and cyclohexanone; aromatic hydrocarbon compounds such as toluene, xylene, and tetramethylbenzene; Cellosolve, methyl cellosolve, butyl cellosolve, carbitol, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol diethyl ether, tripropylene glycol monomethyl ether Glycol ether compounds; ethyl acetate, butyl acetate, butyl lactate, cellosolve acetate, butyl cellosolve acetate, carbitol acetate, butyl carbitol acetate, propylene glycol monomethyl ether Ester compounds such as acetate, dipropylene glycol monomethyl ether acetate, and propylene carbonate; aliphatic hydrocarbon compounds such as octane and decane; and petroleum solvents such as petroleum ether and naphtha.

When the solder paste contains the organic solvent, the content of the organic solvent in 100% by weight of the solder paste is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, and even more preferably 0.5% by weight or more, In addition, it is preferably 30% by weight or less, and more preferably 25% by weight or less. If the content of the organic solvent is greater than or equal to the aforementioned lower limit and less than or equal to the aforementioned upper limit, the workability of the solder paste can be improved, and it is difficult to generate voids in the connected portion after the connection.

Other ingredients: The aforementioned solder paste may contain vinyl resins, thermoplastic resins, curable resins, thermoplastic block copolymers, elastomers, and the like as other components.

As said vinyl resin, vinyl acetate resin, acrylic resin, styrene resin, etc. are mentioned. As said thermoplastic resin, a polyolefin resin, an ethylene-vinyl acetate copolymer, a polyamide resin, etc. are mentioned. As said curable resin, epoxy resin, polyurethane resin, polyimide resin, unsaturated polyester resin, etc. are mentioned. Furthermore, the above-mentioned curable resin may be a room temperature curable resin, a thermosetting resin, a light curable resin, or a moisture curable resin. The above-mentioned curable resin may be used in combination with a curing agent. Examples of the above-mentioned thermoplastic block copolymers include styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, and styrene-butadiene-styrene block copolymers. The hydrogenated product of block copolymer, and the hydrogenated product of styrene-isoprene-styrene block copolymer, etc. As said elastomer, a styrene-butadiene copolymer rubber, an acrylonitrile-styrene block copolymer rubber, etc. are mentioned.

(Connection structure) The connection structure of the present invention includes: a first connection object member having a first connection region portion on the surface, a second connection object member having a second connection region portion on the surface, and connecting the first connection object member and the second connection object The connecting part of the component. In the connection structure of the present invention, the connection portion is formed of the solder paste. The connection portion includes solder formed from the solder particles, and the metal-coated particles or particles formed from the metal-coated particles. In the connection structure of the present invention, the first connection region portion and the second connection region portion are electrically connected by solder formed from the solder particles.

In the connection portion, the metal portion in the metal-coated particles preferably forms an intermetallic compound with solder, is combined with solder, or diffuses together with solder.

In the above-mentioned connection structure, the metal-coated particles or particles formed from the metal-coated particles may not be in contact with both the first connection region portion and the second connection region portion, or may only be connected to the first connection region. The area part and one of the above-mentioned second connection area parts are in contact with each other.

The average thickness of the connection portion is preferably larger than the particle diameter of the metal-coated particles or particles formed from the metal-coated particles.

Fig. 4 is a cross-sectional view schematically showing a connection structure using a solder paste containing the metal-coated particles shown in Fig. 1.

The connection structure 21 shown in FIG. 4 includes a first connection object member 22, a second connection object member 23, and a connection portion 24 that connects the first connection object member 22 and the second connection object member 23. The connecting portion 24 is formed of a solder paste including a plurality of solder particles and metal-coated particles 1.

The connecting portion 24 includes solder 24a formed from a plurality of solder particles. The connecting portion 24 includes particles 24 b formed from the metal-coated particles 1.

The surface (upper surface) of the first connection object member 22 has plural or single first connection region portions 22a. The surface (lower surface) of the second connection object member 23 has a plurality of or a single second connection region portion 23a. The first connection region portion 22a and the second connection region portion 23a are electrically or physically connected by solder 24a formed from solder particles. Therefore, the first connection object member 22 and the second connection object member 23 are electrically or physically connected by the solder 24a.

The manufacturing method of the said connection structure is not specifically limited. As an example of the method of manufacturing the above-mentioned connected structure, the following method may be mentioned: the above-mentioned solder paste is placed between the above-mentioned first connection object member and the above-mentioned second connection object member to obtain a layered body, and then the layered body is heated And pressurization. The solder particles contained in the solder paste are melted by heating and pressing, and the connection regions are electrically or physically connected by the solder formed from the solder particles. The above-mentioned pressurization pressure is 9.8×10 ⁴ Pa to 4.9×10 ⁶ Pa. The above heating temperature is 120°C to 220°C.

The above-mentioned first connection target member and second connection target member are not particularly limited. As the above-mentioned first connection object member and second connection object member, specifically, a semiconductor chip, a semiconductor package, an LED (Light Emitting Diode) chip, an LED package, a capacitor, and a diode may be mentioned. Electronic parts such as body; and electronic parts such as resin film, printed circuit board, flexible printed circuit board, flexible flat cable, rigid-flex board, glass epoxy substrate and circuit board such as glass substrate. The first connection target member and the second connection target member are preferably electronic components.

The above-mentioned connection region part may be an electrode.

Examples of electrodes provided on the above-mentioned connection object member include: gold electrodes, nickel electrodes, tin electrodes, aluminum electrodes, copper electrodes, molybdenum electrodes, silver electrodes, SUS (Steel Use Stainless, Japanese stainless steel standards) electrodes, tungsten electrodes, etc. Metal electrode. When the connection object member is a flexible printed circuit board, the electrode is preferably a gold electrode, a nickel electrode, a tin electrode, a silver electrode, or a copper electrode. When the connection object member is a glass substrate, the electrode is preferably an aluminum electrode, a copper electrode, a molybdenum electrode, a silver electrode, or a tungsten electrode. Furthermore, when the above-mentioned electrode is an aluminum electrode, it may be an electrode formed only of aluminum, or an electrode with an aluminum layer on the surface area of the metal oxide layer. As the material of the metal oxide layer, indium oxide doped with trivalent metal element and zinc oxide doped with trivalent metal element can be mentioned. As the above-mentioned trivalent metal element, Sn, Al, Ga, etc. may be mentioned.

Hereinafter, examples and comparative examples are given to specifically explain the present invention. The present invention is not limited to the following examples.

As the substrate particles, the following particles were prepared.

Resin particle 1: "Micropearl SP-220" manufactured by Sekisui Chemical Industry Co., Ltd. (resin particles made of divinylbenzene copolymer, particle size 20 μm)

Resin particles 2: "Micropearl SP-210" manufactured by Sekisui Chemical Industry Co., Ltd. (resin particles made of divinylbenzene copolymer, particle size 10 μm)

Resin particles 3: "Micropearl SP-295" manufactured by Sekisui Chemical Industry Co., Ltd. (resin particles made of divinylbenzene copolymer, particle size 5 μm)

Organic-inorganic hybrid particles 1: Organic-inorganic hybrid particles having an organic core formed of acrylic resin and an inorganic shell formed of a cross-linked alkoxysilyl polymer (produced according to Synthesis Example 1 below, particle size 20 μm)

<Synthesis Example 1> In a 500 mL reaction vessel equipped with a stirrer and a thermometer, 300 g of 0.13% by weight ammonia solution was added. Next, slowly add 4.1 g of methyltrimethoxysilane, 19.2 g of vinyltrimethoxysilane, and polysiloxane alkoxy oligomer (X-41 manufactured by Shin-Etsu Chemical Co., Ltd.) to the ammonia solution in the reaction vessel. -1053") 0.7 g mixture. While stirring, the hydrolysis reaction and the condensation reaction were carried out, and then 2.4 mL of a 25% by weight aqueous ammonia solution was added. The particles are separated from the aqueous ammonia solution, and the resulting particles ^{are calcined at an oxygen partial pressure of 10 -17} atm and 350° C. for 2 hours to obtain organic-inorganic mixed particles.

Nickel particles 1: particle size 20 μm

Copper particles 1: Particle size 10 μm

(Example 1) Production of metal coated particles: On the outer surface of the resin particles 1, a metal layer with an inner layer of nickel and an outer layer of tin is formed by electroless plating to obtain metal coated particles. In the obtained metal-coated particles, the metal portion is layered.

Preparation of solder paste containing metal coated particles: The prepared metal coated particles 2.0 parts by weight and SAC paste (solder paste containing SAC particles, "M705-RGS800" manufactured by Senju Metal Industry Co., Ltd., the particle size of SAC particles 20 μm) 98.0 parts by weight, using a planetary mixer, Stir under the conditions of 1200 rpm, 120 seconds and 0.2 kPa to obtain a solder paste containing metal-coated particles.

(Examples 2 and 3) Except for setting the type of substrate particles as shown in Table 1 below, the same procedure as in Example 1 was carried out to obtain metal-coated particles. Except for using the obtained metal-coated particles, a solder paste containing metal-coated particles was obtained in the same manner as in Example 1.

(Example 4) On the outer surface of the resin particle 1, a metal part with a nickel layer as the inner layer and tin protrusions on the outer side is formed by electroless plating to obtain metal-coated particles. In the obtained metal-coated particles, the outer surface of the metal portion is protrusion-like, and tin protrusions are locally formed on the nickel layer. Except for using the obtained metal-coated particles, a solder paste containing metal-coated particles was obtained in the same manner as in Example 1.

(Example 5) The metal-coated particles of Example 1 were prepared. The outer surface of the particles is treated with flux (rosin) to obtain metal-coated particles. Except for using the obtained metal-coated particles, a solder paste containing metal-coated particles was obtained in the same manner as in Example 1.

(Example 6) On the outer surface of the resin particles 1, a metal layer with an inner layer of nickel and an outer layer of an alloy layer of tin and silver is formed by electroless plating to obtain metal coated particles. Except for using the obtained metal-coated particles, a solder paste containing metal-coated particles was obtained in the same manner as in Example 1.

(Example 7) On the outer surface of the resin particle 1, a metal layer with an inner layer of nickel and an outer layer of gold is formed by electroless plating to obtain metal coated particles. Except for using the obtained metal-coated particles, a solder paste containing metal-coated particles was obtained in the same manner as in Example 1.

(Example 8) Except for changing the thickness of the metal layer, metal-coated particles were obtained in the same manner as in Example 1. Except for using the obtained metal-coated particles, a solder paste containing metal-coated particles was obtained in the same manner as in Example 1.

(Example 9) On the outer surface of the resin particles 1, a metal layer of nickel is formed by electroless plating to obtain metal-coated particles. Except for using the obtained metal-coated particles, a solder paste containing metal-coated particles was obtained in the same manner as in Example 1.

(Examples 10 and 11) The metal-coated particles of Example 1 were prepared. Except changing the content of the metal-coated particles as shown in Table 1 below, in the same manner as in Example 1, a solder paste containing metal-coated particles was obtained.

(Example 12) The metal-coated particles of Example 1 were prepared. Change the type of solder paste from SAC paste to SnBi paste (solder paste containing Sn-Bi particles, "L20-BLT-T7F" manufactured by Senju Metal Industry Co., Ltd., Sn-Bi particle size 20 μm), except for this In the same manner as in Example 1, a solder paste containing metal-coated particles was obtained.

(Example 13) On the outer surface of the resin particle 1, a metal layer with an inner layer of nickel and an outer layer of gold is formed by electroless plating to obtain metal coated particles. Use the obtained metal-coated particles, and change the type of solder paste from SAC paste to SnBi paste (solder paste containing Sn-Bi particles, "L20-BLT-T7F" manufactured by Senju Metal Industry Co., Ltd., particles of Sn-Bi particles Diameter 20 μm), except for that, in the same manner as in Example 1, a solder paste containing metal-coated particles was obtained.

(Example 14) The metal-coated particles of Example 1 were prepared. Change the type of solder paste from SAC paste to Pb-Sn paste (solder paste containing Pb-Sn particles, "OZ 295-162F-50-8" manufactured by Senju Metal Industry Co., Ltd., Pb-Sn particle size 20 μm ) Except for this, in the same manner as in Example 1, a solder paste containing metal-coated particles was obtained.

(Example 15) Except for setting the type of substrate particles as shown in Table 1 below, the same procedure as in Example 1 was carried out to obtain metal-coated particles. Except for using the obtained metal-coated particles, a solder paste containing metal-coated particles was obtained in the same manner as in Example 1.

(Comparative example 1) Prepare SAC paste (solder paste containing SAC particles, "M705-RGS800" manufactured by Senju Metal Industry Co., Ltd., with a particle size of SAC particles of 20 μm) itself as the solder paste.

(Comparative example 2) Prepare resin particles 1. Except for changing the metal-coated particles to resin particles 1, the same procedure as in Example 1 was carried out to obtain a resin particle-containing solder paste.

(Comparative example 3) Prepare nickel particles 1. Except for changing the metal-coated particles to nickel particles 1, the same procedure as in Example 1 was carried out to obtain a metal particle-containing solder paste.

(Comparative Example 4) Except for setting the types of substrate particles as shown in Table 2 below, in the same manner as in Example 1, metal-coated particles provided with a metal layer in which the inner layer is a nickel layer and the outer layer is a tin layer were obtained. Except having used the obtained metal-coated particles, the same procedure as in Example 1 was carried out to obtain a metal particle-containing solder paste.

(Comparative Example 5) Prepare copper particles 1. Except for changing the metal-coated particles to copper particles 1, the same procedure as in Example 1 was carried out to obtain a metal particle-containing solder paste.

(Evaluate) The connected structure A was obtained in the following manner.

Prepare a copper plate (approximately square with 10.0 mm on one side and 0.1 mm in height) as the first connection object member. A silicon wafer (approximately square with a side of 2.0 mm and a height of 0.1 mm) was prepared as the second connection target member. Use a metal mask with a length of 2.5 mm, a width of 2.5 mm, and a height of 100 μm to print the solder paste on the first connection object component on the screen. After printing, the second connection object member is laminated to obtain a laminated body. Under the conditions of average heating temperature: 1.2°C/sec, peak temperature: melting point of solder particles + 8°C, the resulting laminate was reflowed to obtain a connected structure A.

The connected structure B was obtained in the following manner.

Prepare a copper plate (approximately square with a side of 50.0 mm and a height of 0.1 mm) as the member to be connected. A metal mask with a length of 2000 μm, a width of 500 μm, and a height of 120 μm is used for the solder paste obtained by printing on the connecting target component. Under the conditions of average heating temperature: 1.2°C/sec, peak temperature: melting point of solder particles + 8°C, the printed copper plate was reflowed to obtain the connection structure B.

(1) Initial shear strength The shear strength of the connected structure A obtained immediately after the reflow treatment was measured. The shear strength uses "Dage4000" manufactured by Nordson to measure the strength at break.

(2) Shear strength after time The connection structure A is prepared after the initial shear strength has been measured. Perform 1000 cycles of the TCT (Temperature Cycling Test) test as follows to obtain the connected structure after time. The above-mentioned 1 cycle of the TCT test refers to the conditions of -45°C and 30 minutes as the low temperature side. 125°C and 30 minutes are regarded as the thermal fluctuation of the conditions on the high temperature side. The shear strength after time was measured in the same manner as in (1) the measurement of the initial shear strength.

(3) Dispersibility Observe the cross-section of the connected structure A obtained immediately after reflow. At this time, the half height line of the solder connection part is divided into upper and lower parts, and the number of particles present in each part is calculated. Calculate the ratio using the ten-point system and use it as an indicator of dispersion (e.g. up 6/down 4). The closer the upper and lower ratios are, the higher the dispersibility is judged to be.

(4) Exudation In the production stage of the connection structure A, the area of the solder paste printed part is measured before reflow. Thereafter, immediately after the reflow treatment, the resulting connection structure A was evaluated for the planar area of the connection portion. Evaluate the increase ratio of the area of the connection after reflow to the area of the plane before reflow. Set the plane area before reflow as 100%, and set the increase area (%) as the exudation value. The plane area is measured using "VHX" manufactured by KEYENCE.

(5) Short circuit For the connection structure B (5 in total) obtained immediately after the reflow treatment, evaluate whether there is a short circuit between the electrodes.

The details and results are shown in Tables 1 to 3 below.

[Table 1] Metal coated particles Solder paste Substrate particles Outer metal part Rust inhibitor or flux proportion Solder particles Metal coated particles type Particle size (μm) form Type of metal type Content (wt%) Content (wt%) Example 1 Resin particles 1 20 Floor Sn - 2.3 SAC 86.3 2.0 Example 2 Resin particles 2 10 Floor Sn - 3.0 SAC 86.3 2.0 Example 3 Resin particles 3 5 Floor Sn - 4.1 SAC 86.3 2.0 Example 4 Resin particles 1 20 Protruding Sn - 2.3 SAC 86.3 2.0 Example 5 Resin particles 1 20 Floor Sn Have 2.3 SAC 86.3 2.0 Example 6 Resin particles 1 20 Floor SnAg alloy - 2.3 SAC 86.3 2.0 Example 7 Resin particles 1 20 Floor Au - 1.7 SAC 86.3 2.0 Example 8 Resin particles 1 20 Floor Sn - 4.5 SAC 86.3 2.0 Example 9 Resin particles 1 20 Floor Ni - 2.1 SAC 86.3 2.0 Example 10 Resin particles 1 20 Floor Sn - 2.3 SAC 83.8 5.0 Example 11 Resin particles 1 20 Floor Sn - 2.3 SAC 87.5 0.5 Example 12 Resin particles 1 20 Floor Sn - 2.3 SnBi 88.2 2.0 Example 13 Resin particles 1 20 Floor Au - 1.7 SnBi 88.2 2.0 Example 14 Resin particles 1 20 Floor Sn - 2.3 PbSn 90.1 2.0 Example 15 Organic-inorganic hybrid particles 1 20 Floor Sn - 2.6 SAC 86.3 2.0

[Table 2] Metal coated particles Solder paste Substrate particles Outer metal part Rust inhibitor or flux proportion Solder particles Metal coated particles type Particle size (μm) form Type of metal type Content (wt%) Content (wt%) Comparative example 1 - - - - - - SAC - - Comparative example 2* Resin particles 1 20 - - - 1.1 SAC 86.3 2.0 Comparative example 3* Nickel particles 1 20 - - - 8.9 SAC 86.3 2.0 Comparative example 4 Nickel particles 1 20 Floor Sn - 9.0 SAC 86.3 2.0 Comparative example 5* Copper particles 1 10 - - - 9.1 SAC 86.3 2.0 *Use base particles themselves instead of metal coated particles

[table 3] Evaluate Initial shear strength (MPa) Shear strength after time (MPa) Decrease rate of shear strength after time Dispersibility (up/down) Ooze Short circuit (number of occurrences/total number) Example 1 70.7 69.3 2% (5/5) 104% 0/5 Example 2 69.5 68.8 1% (5/5) 102% 0/5 Example 3 66.3 65.6 1% (5/5) 103% 0/5 Example 4 67.0 65.7 2% (5/5) 103% 0/5 Example 5 65.2 63.9 2% (5/5) 103% 0/5 Example 6 59.9 57.5 4% (5/5) 102% 0/5 Example 7 70.6 65.3 7% (5/5) 103% 0/5 Example 8 78.5 78.3 0% (5/5) 101% 0/5 Example 9 62.4 58.6 6% (6/4) 102% 0/5 Example 10 62.0 60.5 2% (5/5) 100% 0/5 Example 11 63.0 59.2 6% (5/5) 105% 0/5 Example 12 57.0 55.6 3% (5/5) 103% 0/5 Example 13 53.0 49.2 7% (5/5) 103% 0/5 Example 14 61.8 59.0 4% (7/3) 102% 0/5 Example 15 64.8 63.5 2% (5/5) 104% 0/5 Comparative example 1 60.0 46.2 twenty three% - 117% 4/5 Comparative example 2* 20.5 9.6 53% (9/1) 101% 0/5 Comparative example 3* 57.0 49.6 13% (2/8) 103% 0/5 Comparative example 4 61.3 53.9 12% (2/8) 103% 0/5 Comparative example 5* 62.3 55.4 11% (2/8) 104% 0/5 *Use base particles themselves instead of metal coated particles

1, 1A, 1B: metal coated particles 2, 2A, 2B: substrate particles 3, 3A, 3B: Metal Department 3AA: Part 1 Metal 3AB: The second metal part 3BA: Part 1 Metal 3BB: The second metal part 21: Connection structure 22: The first connection object member 22a: The first connection area 23: The second connection object member 23a: The second connection area 24: Connection part 24a: Solder 24b: particles

Fig. 1 is a cross-sectional view showing a metal-coated particle according to the first embodiment of the present invention. Fig. 2 is a cross-sectional view showing a metal-coated particle according to a second embodiment of the present invention. Fig. 3 is a cross-sectional view showing a metal-coated particle according to a third embodiment of the present invention. Fig. 4 is a cross-sectional view schematically showing a connection structure using a solder paste containing the metal-coated particles shown in Fig. 1.

Claims (19)

A solder paste comprising a plurality of solder particles and a plurality of metal-coated particles, and The specific gravity of the metal-coated particles is 6.0 or less, and The metal-coated particles have a substrate particle and a metal part arranged on the surface of the substrate particle, The metal part includes a metal capable of forming an intermetallic compound with the solder, or a metal capable of fusion bonding with the solder, or a metal capable of diffusing together with the solder. The solder paste according to claim 1, wherein the substrate particles are resin particles or organic-inorganic hybrid particles. The solder paste of claim 1 or 2, wherein the metal portion contains the metal capable of forming an intermetallic compound with solder on the outer surface portion of the metal portion, or contains the metal that can be fused with solder, or contains the metal that can be combined with solder. The above metals diffused together. The solder paste of claim 1 or 2, wherein the metal part contains nickel, gold, tin, or an alloy containing tin on the outer surface portion of the metal part. The solder paste of claim 1 or 2, wherein the metal part contains tin or an alloy containing tin on the outer surface portion of the metal part. The solder paste according to claim 1 or 2, wherein the ratio of the average thickness of the metal portion to the particle diameter of the substrate particle is 0.005 or more. The solder paste of claim 1 or 2, wherein the metal-coated particles have an anti-rust agent or flux on the outer surface of the metal part. Such as the solder paste of claim 1 or 2, which further includes at least one of an organic solvent and a flux. Such as the solder paste of claim 1 or 2, wherein in 100% by weight of the solder paste, the content of the above-mentioned solder particles is 50% by weight or more. The solder paste of claim 1 or 2, wherein the total content of the solder particles and the metal-coated particles in 100% by weight of the solder paste is 51% by weight or more. A metal-coated particle for solder paste with a specific gravity of 6.0 or less, and Having a substrate particle and a metal part arranged on the surface of the substrate particle, The metal part includes a metal capable of forming an intermetallic compound with the solder, or a metal capable of fusion bonding with the solder, or a metal capable of diffusing together with the solder. The metal-coated particles for solder paste according to claim 11, wherein the substrate particles are resin particles or organic-inorganic hybrid particles. The metal-coated particles for solder paste according to claim 11 or 12, wherein the metal portion contains the metal capable of forming an intermetallic compound with solder on the outer surface portion of the metal portion, or contains the metal capable of fusion bonding with solder, or Contains the above-mentioned metals that can diffuse with solder. The metal-coated particle for solder paste according to claim 11 or 12, wherein the metal portion contains nickel, gold, tin, or an alloy containing tin on the outer surface portion of the metal portion. The metal-coated particle for solder paste according to claim 11 or 12, wherein the metal part contains tin or an alloy containing tin on the outer surface portion of the metal part. The metal-coated particle for solder paste according to claim 11 or 12, wherein the ratio of the average thickness of the metal portion to the particle diameter of the base particle is 0.005 or more. For example, the metal-coated particles for solder paste of claim 11 or 12 have an anti-rust agent or flux on the outer surface of the metal part. A connection structure comprising: a first connection object member having a first connection region portion on the surface, A second connection target member having a second connection area portion on the surface, and The connecting portion connecting the first connection object member and the second connection object member, and The above-mentioned connecting portion is formed of a solder paste as in any one of claims 1 to 10, The first connection region portion and the second connection region portion are electrically or physically connected by solder formed from the solder particles. A connection structure comprising: a first connection object member having a first connection region portion on the surface, A second connection target member having a second connection area portion on the surface, and The connecting portion connecting the first connection object member and the second connection object member, and The above-mentioned connecting portion is formed of a solder paste containing a plurality of solder particles and a plurality of metal-coated particles, The above-mentioned metal-coated particles are metal-coated particles according to any one of claims 11 to 17, and The first connection region portion and the second connection region portion are electrically or physically connected by solder formed from the solder particles.

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