TW202334367A - Conductive paste and multilayer substrate - Google Patents

Abstract

The present invention provides a conductive paste which is capable of forming a cured product that achieves high conductivity and long-term reliability at the same time. The present invention provides a conductive paste which contains, per 100 parts by mass of a liquid epoxy compound, 1,700 parts by mass to 3,300 parts by mass of metal particles that include high melting point metal particles (B1) which contain silver and/or copper and have a melting point of 800 DEG C or higher, low melting point metal particles (B2) which are formed of an alloy having a melting point of 130 DEG C to 150 DEG C, and low melting point metal particles (B3) which are formed of an alloy of two or more metals selected from the group consisting of tin, silver, copper, bismuth and indium, and have a melting point of 200 DEG C to 240 DEG C, 1 part by mass to 30 parts by mass of a curing agent, and 20 parts by mass to 200 parts by mass of a flux.

Description

Conductive paste and multilayer substrate

Field of invention The present invention relates to a conductive paste and a multilayer substrate using the conductive paste.

Background technology The conductive paste used for hole filling in substrates uses metal molten paste, which is added with flux, hardener, thermosetting resin and conductive filler. When heated under certain conditions, the resin will harden and the metal particles will Melt and metallize (that is, form an intermetallic compound between metal particles).

In order to achieve long-term connection stability in such a conductive paste, a known method is to use a combination of high-melting-point metal particles and low-melting-point metal particles as a conductive filler (Patent Documents 1 and 2).

However, in today's semiconductor devices that require high functionality and miniaturization, if the conductive paste prepared by these methods is used, the specific resistance when made into a cured product is high and the conductivity is insufficient.

In addition, in order to improve the conductivity, there is also an invention reported using a fluorine-based surfactant to improve the wettability of the conductive paste and enhance the connectivity (Patent Document 3).

Prior technical literature patent documents Patent Document 1: Japanese Patent Application Publication No. 2008-108629 Patent Document 2: International Publication No. 2016/136204 Patent Document 3: Japanese Patent Application Publication No. 2020-152778

Summary of the invention The problem to be solved by the invention However, although the adhesion of the conductive paste can be improved by using a fluorine-based surfactant, the specific resistance is not reduced when the hardened product is made, the conductivity is insufficient, and the long-term reliability has not been evaluated, and the effect is unknown.

Therefore, a conductive paste that can achieve both high conductivity and long-term reliability at a high level when forming a cured product has not yet been obtained.

The present invention is made to solve such problems, and its object is to provide a conductive paste that can form a cured product that has both high conductivity and long-term reliability.

means to solve problems The inventors of this case worked wholeheartedly to achieve the above goal, and found that cured products can have high conductivity and long-term reliability if the following conductive paste is used: a conductive paste containing a liquid epoxy resin , metal particles, hardener and flux, and, relative to 100 parts by mass of liquid epoxy resin, the metal particles are 1700 to 3300 parts by mass, the hardener is 1 to 30 parts by mass, and the flux is 20 parts by mass ~200 parts by mass; the aforementioned metal particles include: high-melting-point metal particles (B1), which contain silver and/or copper and have a melting point of 800°C or above; low-melting-point metal particles (B2), which are alloys with a melting point of 130°C~150°C. ; And, low melting point metal particles (B3), which are two or more alloys selected from the group consisting of tin, silver, copper, bismuth and indium, and have a melting point of 200°C to 240°C. The present invention was completed based on these findings.

That is, the present invention provides a conductive paste containing a liquid epoxy compound, metal particles, a hardener, and a flux, and the metal particles are 1,700 to 3,300 parts by mass relative to 100 parts by mass of the liquid epoxy compound. , the hardener is 1 to 30 parts by mass, and the flux is 20 to 200 parts by mass; the aforementioned metal particles include more than 3 types of metal particles: high melting point metal particles (B1), which contain silver and/or copper and have a melting point 800℃ or above; low-melting-point metal particles (B2), which are alloys with a melting point of 130℃~150℃; and, low-melting-point metal particles (B3), which are selected from the group consisting of tin, silver, copper, bismuth and indium Two or more alloys in the group, with a melting point of 200℃~240℃.

The above-mentioned conductive paste can be mixed with a large amount of metal particles by using the above-mentioned liquid epoxy compound, and as a result, the conductivity can be improved. By containing the high-melting-point metal particles (B1) and the low-melting-point metal particles (B2) in combination, a cured product has excellent electrical conductivity. By containing the above-mentioned low melting point metal particles (B3), the long-term reliability of the hardened product can be improved. Moreover, the metal particles including the above-mentioned high-melting-point metal particles (B1), the above-mentioned low-melting-point metal particles (B2), and the above-mentioned low-melting-point metal particles (B3) contain 1,700 to 3,300 parts by weight relative to 100 parts by mass of the above-mentioned liquid epoxy compound. parts by weight, thereby reducing the specific resistance of the hardened material of the conductive paste, improving the conductivity, and suppressing the occurrence of cracks, thereby improving long-term connection reliability. By containing 1 to 30 parts by mass of the hardener, cracks can be suppressed when making the hardened product and long-term reliability can be improved. By containing 20 parts by mass to 200 parts by mass of flux, the specific resistance can be reduced and the conductivity can be improved in the hardened material of the conductive paste.

The conductive paste of the present invention is preferably such that the mass ratio of the low-melting-point metal particles (B2) to the low-melting-point metal particles (B3) is (B2)/(B3)=0.9~40. When the mass ratio of the low-melting-point metal particles (B2) and the low-melting-point metal particles (B3) is 0.9 or more, the specific resistance is reduced and the electrical conductivity becomes more excellent. In addition, when the mass ratio of the low-melting-point metal particles (B2) to the low-melting-point metal particles (B3) is 40 or less, the generation of cracks can be easily suppressed and long-term connection reliability can be achieved.

In addition, the above-mentioned hardener is preferably a hydroxyl-containing aromatic compound.

In addition, the above-mentioned hardener is preferably a phenol-based hardener and/or a naphthol-based hardener.

Furthermore, the present invention provides a multilayer substrate, which is composed of a plurality of conductive layers and an insulating layer interposed between the plurality of conductive layers, and the holes penetrating the insulating layer are filled with the hardened material of the conductive paste of the present invention, and penetrated therethrough. In the cured product of the conductive paste, the conductive layers connected to both sides of the insulating layer are electrically connected to each other.

Furthermore, in the above-mentioned conductive paste cured material, it is preferable that the above-mentioned high-melting-point metal particles (B1), low-melting-point metal particles (B2) and low-melting-point metal particles (B3) are melted and integrated with each other and alloyed.

Invention effect The conductive paste of the present invention can form a hardened product that has both high conductivity and long-term reliability.

Form used to implement the invention [Conductive paste] The conductive paste of the present invention contains at least a liquid epoxy compound, metal particles, a hardener and a flux. The above-mentioned conductive paste may contain components other than the above-mentioned components.

(liquid epoxy compound) The above-mentioned liquid epoxy compound is a compound having at least one epoxy group (oxirane group) in the molecule (in one molecule). The above-mentioned liquid epoxy compound means an epoxy compound that is liquid at normal temperature. In addition, "liquid at normal temperature" means a state that exhibits fluidity at 25° C. in a solvent-free state. The conductive paste of the present invention can contain a large amount of metal particles by containing the above-mentioned liquid epoxy compound with high fluidity, and as a result, the conductivity can be improved. Only one type of the above-mentioned liquid epoxy compound may be used, or two or more types may be used.

The liquid epoxy compound is not particularly limited, and examples thereof include bisphenol-type epoxy compounds, spirocyclic epoxy compounds, naphthalene-type epoxy compounds, biphenyl-type epoxy compounds, terpene-type epoxy compounds, and phenolic compounds. Varnish type epoxy compound, dimer acid modified epoxy compound, glycidylamine type epoxy compound, glycidyl ether type epoxy compound, rubber modified epoxy resin or chelate modified epoxy compound Resin etc. Among these, dimer acid-modified epoxy compounds are preferred because they can reduce the resistance value and have excellent storage stability.

Examples of the bisphenol type epoxy compound include a bisphenol A type epoxy compound, a bisphenol F type epoxy compound, a bisphenol S type epoxy compound, a tetrabromobisphenol A type epoxy compound, and the like.

Examples of the novolak-type epoxy compound include a cresol novolak-type epoxy compound, a phenol novolak-type epoxy compound, an α-naphthol novolak-type epoxy compound, or a brominated phenol novolac-type epoxy compound.

The above-mentioned dimer acid-modified epoxy compound refers to an epoxy compound modified by a dimer acid, that is, at least one carboxyl group in the dimer acid structure has reacted with a multifunctional epoxy compound. Here, the so-called dimer acid refers to a dimer of unsaturated fatty acid. The unsaturated fatty acid of the raw material is not particularly limited. For example, plant-derived oils and fats containing unsaturated fatty acids with 18 carbon atoms such as oleic acid or linoleic acid as the main component can be used. The structure of the dimer acid may be either cyclic or acyclic.

The epoxy compound used for acid-modifying the dimer is not particularly limited, and examples thereof include the epoxy compounds exemplified for the above-mentioned epoxy compounds. Only one type of epoxy compound contained in the above-mentioned dimer acid-modified epoxy compound may be used, or two or more types of epoxy compounds may be used. For example, a known dimer acid-modified ring modified with a dimer acid can be used to modify various epoxy compounds such as bisphenol type, ether ester type, novolak epoxy type, ester type, aliphatic type, aromatic type, etc. oxygen compounds.

Examples of the above-mentioned epoxypropylamine type epoxy compound include: tetraepoxypropyldiaminodiphenylmethane, N,N-bis(2,3-epoxypropyl)-4-(2,3- Aminophenol type epoxy compounds such as epoxypropoxy)aniline and so on.

Examples of the above-mentioned glycidyl ether type epoxy compound include: (glycidoxyphenyl)methane, glycidoxyphenyl)ethane, glycidyl alkyl ether, and the like.

The above-mentioned rubber-modified epoxy resin contains a rubber component in the epoxy resin. Examples of the rubber component include butadiene rubber, acrylic rubber, silicone rubber, butyl rubber, isoprene rubber, styrene rubber, chloroprene rubber, NBR, SBR, IR, EPR, and the like. Only one type of the above-mentioned rubber component may be used, or two or more types may be used.

(metal particles) The conductive paste of the present invention contains metal particles: high-melting-point metal particles (B1), which contain silver and/or copper and have a melting point of 800°C or above; low-melting-point metal particles (B2), which have a melting point of 130°C to 150°C. Alloy; and low melting point metal particles (B3), which are two or more alloys selected from the group consisting of tin, silver, copper, bismuth and indium, and have a melting point of 200°C to 240°C.

＜High melting point metal particles (B1)＞ The high melting point metal particles (B1) are metal particles containing copper (melting point: 1083°C) and/or silver (melting point: 961°C). The conductive paste of the present invention can exhibit sufficient conductivity by combining the high-melting-point metal particles (B1) and the low-melting-point metal particles (B2). In addition, the above-mentioned high-melting-point metal particles (B1) may contain metals other than copper and silver. Examples include the following: gold (melting point: 1064°C), nickel (melting point: 1455°C), zinc (melting point: 420°C) , or those containing one or more of these alloys and having a melting point of 800°C or above. In addition, only one type of the above-mentioned high melting point metal particles (B1) may be used, or two or more types may be used.

Furthermore, the high melting point metal particles (B1) may be metal-coated metal particles, and examples include silver-coated copper particles, gold-coated copper particles, silver-coated nickel particles, or silver-coated alloy particles. Examples of the silver-coated alloy particles include silver-coated copper alloy particles in which a copper-containing alloy (for example, a copper alloy composed of an alloy of copper, nickel, and zinc) is coated with silver.

The melting point of the high-melting-point metal particles (B1) is 800°C or higher, preferably 900°C or higher, and preferably 1000°C or higher. Since the melting point of the high-melting-point metal particles (B1) is 800° C. or higher, a large amount of highly conductive metal can be contained in the metal particles, and the conductivity of the cured product becomes even more excellent. Furthermore, the melting point of the high-melting-point metal particles (B1) is preferably 1300°C or lower, more preferably 1200°C or lower. Since the melting point of the high-melting-point metal particles (B1) is 1300° C. or lower, alloying becomes easier when the conductive paste is made into a hardened product.

The content of the above-mentioned high melting point metal particles (B1) is preferably 400 to 1800 parts by mass, preferably 500 to 1500 parts by mass, and more preferably 600 to 1400 parts by mass relative to 100 parts by mass of the liquid epoxy compound. Parts by mass, especially 700 parts by mass to 1300 parts by mass. By containing 400 parts by mass or more of the high-melting-point metal particles (B1) with respect to 100 parts by mass of the liquid epoxy compound, the specific resistance can be easily reduced and sufficient electrical conductivity can be exerted when forming a hardened product. In addition, when the content of the high-melting-point metal particles (B1) is 1800 parts by mass or less, it is possible to achieve excellent hole burial properties, suppress the occurrence of cracks when forming a hardened product, and improve long-term reliability.

＜Low melting point metal particles (B2)＞ The above-mentioned low melting point metal particles (B2) are metal particles of an alloy with a melting point of 130°C to 150°C. The conductive paste of the present invention can exhibit sufficient conductivity by combining the high-melting-point metal particles (B1) and the low-melting-point metal particles (B2). Only one type of low melting point metal particles (B2) may be used, or two or more types may be used.

The above-mentioned low melting point metal particles (B2) are preferably an alloy containing tin (melting point: 232°C) and bismuth (melting point: 271°C). In addition to tin and bismuth, other metals are also acceptable as long as their melting points can be 130°C to 150°C. contain. Furthermore, the mass ratio of tin:bismuth in the low-melting-point metal particles (B2) is preferably 80:20 to 40:60. By having the above mass ratio of tin:bismuth, it is easy to make the melting point of the above melting point metal particles (B2) within the range of 130°C to 150°C.

The melting point of the low-melting-point metal particles (B2) is 130°C to 150°C, and preferably 135°C to 145°C. When the melting point is within the above range, metallization can be easily performed during the hardening reaction of the conductive paste.

The content of the above-mentioned low melting point metal particles (B2) is preferably 300 to 2400 parts by mass, preferably 400 to 2300 parts by mass, and more preferably 500 to 2200 parts by mass relative to 100 parts by mass of the liquid epoxy compound. Parts by mass, especially 600 parts by mass to 2000 parts by mass. When the content of the low-melting-point metal particles (B2) is 300 parts by mass or more relative to 100 parts by mass of the liquid epoxy compound, sufficient electrical conductivity can be exerted when the cured product is formed. In addition, when the content of the low-melting-point metal particles (B2) is 2,400 parts by mass or less, it is possible to achieve excellent hole-burying properties, suppress the occurrence of cracks when forming a hardened product, and improve long-term reliability.

＜Low melting point metal particles (B3)＞ The above-mentioned low melting point metal particles (B3) are two or more alloys selected from the group consisting of tin, silver, copper, bismuth and indium, and have a melting point of 200°C to 240°C. The conductive paste of the present invention can improve the long-term reliability of the conductive paste by containing the above-mentioned low melting point metal particles (B3). Only one type of low melting point metal particles (B3) may be used, or two or more types may be used.

The low melting point metal particles (B3) are preferably an alloy containing tin as a main component. In addition, as long as the melting point is within the range of 200°C to 240°C, metals other than the above-mentioned metals may be included. In the total amount of the above-mentioned alloy (100% by mass), the content ratio of tin is preferably 80% by mass or more, preferably 85% by mass or more, and particularly preferably 90% by mass or more. Since the low-melting-point metal particles (B3) contain tin as a main component, the melting point can be easily adjusted to 200°C to 240°C.

The melting point of the above-mentioned low-melting-point metal particles (B3) is 200°C to 240°C, and preferably 205°C to 235°C. When the melting point of the low-melting-point metal particles (B3) is within the above range, long-term reliability can be easily improved.

The content of the above-mentioned low melting point metal particles (B3) is preferably 40 to 700 parts by mass, preferably 50 to 600 parts by mass, and especially 60 to 500 parts by mass relative to 100 parts by mass of the liquid epoxy compound. share. When the content of the low-melting-point metal particles (B3) is 40 parts by mass or more relative to 100 parts by mass of the liquid epoxy compound, long-term connection reliability can be improved when a hardened product is formed. In addition, when the content of the low-melting-point metal particles (B3) is 700 parts by mass or less, appropriate filling properties can be exerted.

Furthermore, the conductive paste of the present invention may contain metal particles other than the above-described high-melting-point metal particles (B1), the above-described low-melting-point metal particles (B2), and the above-described low-melting point metal particles (B3).

From the viewpoint of making the conductive paste of the present invention exhibit conductivity and long-term reliability, the above-mentioned high melting point metal particles (B1), the above-mentioned low melting point metal particles (B2), and the above-mentioned low melting point metal particles contained in the above-mentioned conductive paste The total amount of (B3) is preferably 90 mass% or more of the total amount of metal particles (100 mass%), preferably 95 mass% or more, especially 99 mass% or more.

The shapes of the above-mentioned metal particles include: spherical, flake-like (scale-like), dendritic, fibrous, amorphous (polyhedral), etc. The particle shapes of the high melting point metal particles (B1), the low melting point metal particles (B2), and the low melting point metal particles (B3) may be different or the same. Among them, the spherical shape is more preferable from the viewpoint of higher hole-burying properties, filling properties, higher coating stability, and better conductivity of the conductive paste. Moreover, regarding the average particle diameter (D50) of the above-mentioned metal particles, the above-mentioned high-melting-point metal particles (B1), the above-mentioned low-melting-point metal particles (B2), and the above-mentioned low-melting point metal particles (B3) are each preferably 0.5 μm to 30 μm, preferably It is 1μm~10μm.

The total amount of metal particles used in the conductive paste of the present invention is 1700 to 3300 parts by mass, preferably 1800 to 3200 parts by mass, and preferably 1900 parts by mass based on 100 parts by mass of the liquid epoxy compound. parts ~3000 parts by mass. When the content of the metal particles is 1700 parts by mass or more relative to 100 parts by mass of the liquid epoxy compound, the specific resistance can be reduced and the conductivity can be improved when the cured product is formed. In addition, when the content of the above-mentioned metal particles is 3300 parts by mass or less, filling properties and long-term reliability can be improved.

In addition, the mass ratio of the above-mentioned low-melting-point metal particles (B2) and the above-mentioned low-melting-point metal particles (B3) is preferably (B2)/(B3)=0.9~40, preferably 1.3~35. When the mass ratio of the low-melting-point metal particles (B2) to the low-melting-point metal particles (B3) is 0.9 or more, the specific resistance of the conductive paste when it is made into a hardened product is reduced, the conductivity is excellent, and the long-term reliability is improved. sex. In addition, when the mass ratio of the low-melting-point metal particles (B2) to the low-melting-point metal particles (B3) is 40 or less, the cured product will have sufficient reflow resistance and thermal cycle resistance, and will have excellent long-term reliability.

(hardener) The above-mentioned hardening agent is preferably one that hardens the liquid epoxy compound contained in the conductive paste of the present invention. Therefore, the above-mentioned hardener preferably has a functional group reactive with the epoxy group. Only one type of the above-mentioned hardener may be used, or two or more types may be used.

Examples of the curing agent include isocyanate curing agents, phenol curing agents, naphthol curing agents, imidazole curing agents, and amine curing agents. Furthermore, from the viewpoint of reactivity with an epoxy compound, the hardener is preferably a hydroxyl-containing aromatic compound. The above-mentioned hydroxyl-containing aromatic compound is preferably a phenol-based hardener, a naphthol-based hardener, or the like.

Examples of the above-mentioned phenol-based hardener include phenol-based hardeners having a novolak structure, nitrogen-containing phenol-based hardeners, and phenol-based hardeners containing a trisulfide skeleton.

Examples of the naphthol-based hardener include naphthol-based hardeners having a novolak structure, nitrogen-containing naphthol-based hardeners, and naphthol-based hardeners containing a triskeleton skeleton.

The content of the above-mentioned hardener is 1-30 parts by mass relative to 100 parts by mass of the above-mentioned liquid epoxy compound, and is preferably 2-27 parts by mass, preferably 3-25 parts by mass. If the content is 1 part by mass or more, the curable compound in the conductive paste will be sufficiently hardened to achieve better long-term reliability. If the content is 30 parts by mass or less, the curing agent will not hinder conduction when forming a cured product, and the conductivity will be better.

(flux) The above-mentioned flux has the effect of promoting the metallization of the above-mentioned metal particles. Examples of the flux include polycarboxylic acid compounds and compounds other than these. Only one type of flux may be used, or two or more types may be used.

As the above-mentioned polycarboxylic acid compound, taking dicarboxylic acid as an example, examples include: oxalic acid, glutaric acid, adipic acid, succinic acid, sebacic acid, malonic acid, maleic acid, fumaric acid, phthalic acid, and pimelic acid. , suberic acid, azelaic acid, terephthalic acid, citraconic acid, α-ketoglutaric acid, diglycolic acid, thiodiglycolic acid, dithiodiglycolic acid , 4-cyclohexene-1,2-dicarboxylic acid, dodecanedioic acid, diphenyl ether-4,4'-dicarboxylic acid, pyridine-2,6-dicarboxylic acid, tetrahydrocarboxylic acid, Hexahydrocarboxylic acid, tetrahydrophthalic acid, hexahydrophthalic acid, etc.; examples of tricarboxylic acids include: trimellitic acid, citric acid, isocitric acid, butane-1,2,4-tricarboxylic acid, cyclohexane Alkane-1,2,4-tricarboxylic acid, benzene-1,2,4-tricarboxylic acid, 1,2,3-propanetricarboxylic acid, etc.; examples of tetracarboxylic acids include: ethylenetetracarboxylic acid , 1,2,3,4-butanetetracarboxylic acid, cyclobutane-1,2,3,4-tetracarboxylic acid, benzene-1,2,4,5-tetracarboxylic acid, etc.

Examples of compounds other than the above include zinc chloride, lactic acid, oleic acid, stearic acid, glutamic acid, benzoic acid, glutamine hydrochloride, aniline hydrochloride, cetylpyridine bromide, urea, Triethanolamine, glycerol, hydrazine and rosin, etc.

The content of the above-mentioned flux is 20-200 parts by mass relative to 100 parts by mass of the above-mentioned liquid epoxy compound, and is preferably 30-180 parts by mass, preferably 40-160 parts by mass. If the content of the above-mentioned flux is 20 parts by mass or more, the metallization of the above-mentioned metal particles can be sufficiently promoted when forming a hardened product. If the content is 200 parts by mass or less, the flux will not interfere with electrical conduction when the cured product is formed, and the electrical conductivity will be better.

(other ingredients) The conductive paste of the present invention may also contain other components than the above components within a range that does not impair the effects of the present invention. Examples of the above-mentioned other components include components that may be contained in known or customary compositions. Examples of the above-mentioned other components include other adhesive components other than the above-mentioned liquid epoxy compound, solvents, defoaming agents, leveling agents, thickeners, adhesives, fillers, flame retardants, colorants, and the like. Only one type of the above-mentioned other components may be used, or two or more types may be used.

Examples of the other adhesive components include thermosetting compounds other than the above-mentioned liquid epoxy compounds. Examples of the thermosetting compound include epoxy compounds, acrylate compounds, phenol resins, urethane resins, melamine resins, and alkyd resins that are solid at room temperature. In addition, the term "solid at normal temperature" means a state that does not exhibit fluidity at 25° C. in a solvent-free state. Only one type of the above-mentioned other binder components may be used, or two or more types may be used.

The conductive paste of the present invention may or may not contain the other binder components mentioned above. In addition, when the above-mentioned other adhesive components are contained, from the viewpoint of reducing the viscosity of the conductive paste and improving the handleability, the content is preferably 50 parts by mass or less based on 100 parts by mass of the above-mentioned liquid epoxy compound, preferably 30 parts by mass or less, preferably 10 parts by mass or less.

Examples of the above-mentioned solvents include the following well-known or commonly used organic solvents: ketones such as methyl ethyl ketone, acetone, and acetophenone; ethers such as methylcellulose, methylcarbitol, diethylene glycol dimethyl ether, and tetrahydrofuran. ; Methylcellulose acetate, butyl acetate, methyl acetate and other esters.

The content ratio of the solvent in the conductive paste of the present invention is not particularly limited, but it is preferably 10 mass % or less, preferably 5 mass % or less, based on 100 mass % of the total amount of the conductive paste of the present invention.

The viscosity of the conductive paste of the present invention measured at 25°C using BH type viscometer spindle No. 7 (rotation speed: 10 rpm) is preferably 300 dPa. s~2500dPa. s, preferably 500dPa. s~2000dPa. s. If the viscosity is within the above range, the filling property will be more excellent.

The conductive paste of the present invention can be used for filling holes such as through-holes or through-holes in semiconductor packages. Especially from the viewpoint of excellent electrical conductivity and long-term reliability, it can be used as hole filling in multilayer substrates.

When the conductive paste of the present invention is used to fill through-holes in a multilayer substrate, thermosetting compounds such as liquid epoxy compounds are cured by thermal hardening, and at the same time, the above-mentioned high-melting-point metal particles (B1) and the above-mentioned low-melting point metal particles are hardened. The metal particles (B2) and the low-melting-point metal particles (B3) are melted and metallized, and the metal particles are integrated with the contact portions of the conductive layers provided at the upper and lower ends of the through holes. In this case, compared with the case where the metal particles and the conductive layer are simply in contact, higher conductivity can be obtained, and the bonding reliability between the conductive paste and the conductive layer is significantly improved. In addition, the above-mentioned conductive paste also has excellent adhesion to the insulating layer of the multilayer substrate, so that a multilayer substrate with high long-term reliability can be produced.

[Method for manufacturing conductive paste] The conductive paste of the present invention is not particularly limited and can be produced by known or customary methods. For example, the above-mentioned components can be mixed and stirred using a three-roller mill, a planetary stirring device, a planetary mixer, a homogenizer, a paddle mixer, or the like, and can be produced.

[Multilayer substrate] The multilayer substrate of the present invention is preferably a multilayer substrate composed of a plurality of conductive layers and an insulating layer between the plurality of conductive layers, and the holes penetrating the insulating layer are filled with a conductive paste cured material, and the conductive paste passes through the conductive paste. In the hardened material, the conductive layers connected to both sides of the above-mentioned insulating layer are electrically connected to each other.

The conductive layer is not particularly limited as long as it can exhibit conductivity. Examples include gold, silver, copper, palladium, nickel, aluminum, or alloys containing one or more of these metals. In addition, the conductive layer may be a single layer or a laminate of the same type or different types.

The thickness of the above-mentioned conductive layer is preferably 5nm~10μm. In addition, when the conductive layer has a multi-layer structure, the thickness of the conductive layer is the total thickness of all layers.

The above-mentioned insulating layer is not particularly limited as long as it can exert insulating properties. Examples include: plastic substrate (especially plastic film), glass plate, etc. The above-mentioned insulating layer may be a single layer or a laminate of the same type or different types.

The thickness of the above-mentioned insulating layer is preferably 1 μm ~ 1000 μm. In addition, when the insulating layer has a multi-layer structure, the thickness of the above-mentioned insulating layer is the total thickness of all layers.

The above-mentioned multi-layer substrate is preferably a structure in which the above-mentioned conductive layer is formed on both sides of the above-mentioned insulating layer, and has a structure of laminated with more than 2 layers, and preferably has a laminated structure with 2 to 10 layers.

Furthermore, in the above-mentioned conductive paste cured material used in the above-mentioned multilayer substrate, it is preferable that the above-mentioned high-melting-point metal particles (B1), the above-mentioned low-melting-point metal particles (B2), and the above-mentioned low-melting point metal particles (B3) are melted and integrated with each other and alloyed. change. In addition, the above-mentioned alloying means that when used for filling holes in a multilayer substrate, adjacent metal particles are connected and integrated with each other, and at the same time, the metal particles are also connected and integrated with the conductive layer in contact with the upper end and lower end of the hole. change.

[Manufacturing method of multilayer substrate] FIG. 1 is a schematic cross-sectional view showing an example of manufacturing a multilayer substrate using the conductive paste of the present invention. In FIG. 1, symbol 1 represents an insulating layer, symbol 2 represents a conductive paste filled in the through holes of the insulating layer 1, symbol 3 represents a conductive layer, symbol 2' represents a hardened product of the conductive paste 2, and symbol 3' represents Patterned conductive layer. In addition, this figure shows an example in which the filler directly contacts the inner wall of the through hole when the through hole of the substrate is not plated.

In order to prepare the multilayer substrate of the present invention, for example, as shown in FIG. 1(a) , a drill or a laser is used to form a through hole in the preheated insulating layer 1 , and then the conductive paste 2 is filled into the through hole, and As shown in (b), conductive layers 3 are arranged on the upper and lower sides of the insulating layer 1, pressed and integrated, and heated under predetermined conditions. This heating hardens the liquid epoxy compound and melts the metal particles, thereby metallizing the adjacent metal particles to connect each other, and at the same time, the end surfaces of the conductive layer and the metal particles are firmly bonded. After hardening, for example, as shown in (c), the conductive layer can be patterned if necessary.

The heating conditions for the conductive paste are those suitable for both the hardening of the liquid epoxy compound and the metallization of the metal particles. Therefore, the specific conditions will vary depending on the composition of the paste, but the general standard is a temperature range of about 150°C to 180°C. Reheat for about 30 to 120 minutes. In addition, this figure shows a case where there are two conductive layers and one insulating layer. However, a multilayer substrate in which three or more conductive layers and two or more insulating layers are alternately laminated can also be manufactured as described above.

Example Hereinafter, one embodiment of the present invention will be described in more detail based on examples.

＜Preparation of conductive paste＞ Each component described in Table 1 and Table 2 was blended and mixed to prepare each conductive paste of an Example and a Comparative Example (the numerical values in the table represent parts by mass). Details of each ingredient used are as follows.

Liquid epoxy compound: Trade name "jER871", manufactured by Mitsubishi Chemical Corporation High melting point metal particles (B1) 1: Silver-coated copper powder (melting point 990°C, average particle diameter 3 μm), manufactured by DOWA ELECTRONICS High melting point metal particles (B1) 2: Silver powder (melting point 961°C, average particle diameter 3 μm), manufactured by DOWA ELECTRONICS High melting point metal particles (B1) 3: copper powder (melting point 1083°C, average particle diameter 3 μm), manufactured by Fukuda Metal Particle Foil Powder Industry Co., Ltd. Low melting point metal particles (B2): Sn-Bi alloy metal particles (Sn: Bi=42:58, melting point 138°C, average particle size 6 μm) Low melting point metal particles (B3): Sn96.5-Ag3.0-Cu0.5 metal particles (Sn:Ag:Cu=96.5:3.0:0.5, melting point 217°C, average particle size 6μm) Hardener: Phenol-based hardener, trade name "TAMANOL758", manufactured by Arakawa Chemical Industry Co., Ltd. Fluxing agent: 8-Ethyloctadecanedioic acid, manufactured by Okamura Oil Co., Ltd.

＜Preparation of evaluation substrate＞ Using a CO ₂ laser, a 169-hole connection pattern of φ100 μm was formed on an insulating layer with a thickness of about 100 μm (manufactured by Panasonic, trade name "R-1551"), and printed using a printing method. After the above-mentioned conductive paste is filled in the holes, it is pressed using a vacuum press under the following pressure conditions and temperature conditions, thereby producing an evaluation substrate. Pressure: It takes 17 minutes to increase the pressure from 0kg/ ^cm2 to a surface pressure of 10.2kg/ ^cm2 , and maintain it in this state for 10 minutes. Next, the pressure was raised to a surface pressure of 30.6 kg/cm ² over 24 minutes, and after maintaining this state for 46 minutes, the pressure was reduced to 0 kg/cm ² over 23 minutes. Temperature: Raise the temperature from 30°C to 130°C in 17 minutes and maintain it in this state for 10 minutes. Next, the temperature was raised to 180°C over 24 minutes, maintained in this state for 46 minutes, and then cooled to 30°C over 23 minutes.

[evaluation] Using the above-mentioned conductive paste or the above-mentioned evaluation substrate, various physical property values were evaluated.

(1) Specific resistance Use a metal printing plate to linearly print the above-mentioned conductive paste prepared in the Examples and Comparative Examples (length 60 mm, width 1 mm, thickness approximately 100 μm) on a glass epoxy substrate, and heat it at 180°C for 60 minutes, thereby allowing it to be formally cured, and an evaluation substrate on which a conductive pattern was formed was produced. Next, a tester was used to measure the resistance value between both ends of the conductive pattern, and the specific resistance was calculated from the cross-sectional area (S, cm ² ) and length (L, cm) using the following formula (1). In addition, five lines of linear printing were applied to three glass epoxy substrates each to form a total of 15 conductive patterns, and the average value of the specific resistances was calculated and evaluated as follows. Specific resistance = (S/L)×R (1) ○: Specific resistance is less than 5×10 ^-5 Ω. cm ×: Specific resistance is 5×10 ^-5 Ω. cm or more

(2) Filling property Using an X-ray penetrating device (trade name "Y.Cheetah μHD", manufactured by Yxlon International), the via portion of the above evaluation substrate was observed under the following measurement conditions, and the filling was evaluated. sex. <Measurement conditions> Voltage: 50kV, current: 80μA, power: 4W ○: Good printability ×: Unfilled paste or cracks occurred during hardening

(3) Initial via (Via) resistance value The initial through-hole resistance value of the above-mentioned evaluation substrate is measured by measuring the resistance value between both ends of the above-mentioned connection pattern, and dividing the resistance value by the number of each hole, obtaining the resistance value of each hole and calculating the average value, press Evaluate as described. ○: Less than 4.0mΩ/Via ×: 4.0mΩ/Via or more

(4) Long-term reliability 1 (reflow resistance) The above-mentioned evaluation substrate was repeatedly subjected to a reflow oven treatment at 260°C for 10 seconds five times, and then the through-hole resistance value was measured, and the change rate of the through-hole resistance value was evaluated based on the evaluation substrate before the test. In addition, the measurement method of the through hole resistance value is the same as the measurement method of the initial through hole resistance value mentioned above. In addition, the following long-term reliability aspects 2 to 4 are also evaluated in the same way. ○: When the resistance value change rate is within ±10% ×: When the resistance value change rate is greater than ±10%

(5) Long-term reliability 2 (thermal cycle resistance) After the above-mentioned evaluation substrate was subjected to a thermal cycle test of -60°C for 30 minutes and 125°C for 30 minutes for 1,000 cycles, the resistance value of the conductive paste was measured, and the through-hole resistance was calculated based on the evaluation substrate before the test. The value change rate is evaluated as above.

(6) Long-term reliability 3 (heat resistance test) The resistance value of the conductive paste was measured after the evaluation substrate was left standing at 100° C. for 1000 hours, and the change rate of the through-hole resistance value was calculated based on the evaluation substrate before the test, and the evaluation was performed as described above.

(7) Long-term reliability 4 (humidity resistance test) Measure the resistance value of the conductive paste after the above-mentioned evaluation substrate is left standing for 1000 hours in an environment with a temperature of 85°C and a humidity of 85%, and calculate the change rate of the through-hole resistance value based on the evaluation substrate before the test. , evaluate as above.

[Table 1]

[Table 2]

Examples 1 to 7 confirmed excellent conductivity and long-term reliability. Comparative Example 1, which does not contain low-melting-point metal particles (B3), has insufficient long-term reliability. Comparative Example 3 in which the metal particle content is less than 1,700 parts by mass has insufficient conductivity and long-term reliability. Comparative Examples 2 and 4 in which the metal particle content exceeds 3300 parts by mass lack filling properties and reflow resistance, resulting in insufficient long-term reliability. In addition, Comparative Example 5 in which the hardener is less than 1 part by mass has poor long-term reliability, and Comparative Example 6 in which the hardener is more than 30 parts by mass has insufficient electrical conductivity. Furthermore, Comparative Example 7 with a flux of less than 20 parts by mass is a result of lack of long-term reliability, and Comparative Example 8 with a flux of more than 200 parts by mass is a result of insufficient electrical conductivity.

1: Insulation layer 2: Conductive paste 2’: Hardened material of conductive paste 3: Conductive layer 3’: Patterned conductive layer

FIG. 1 is a schematic cross-sectional view showing an example of manufacturing a multilayer substrate using the conductive paste of the present invention.

(without)

Claims (6)

A conductive paste containing a liquid epoxy compound, metal particles, a hardener and a flux, and, relative to 100 parts by mass of the liquid epoxy compound, the metal particles are 1,700 to 3,300 parts by mass, and the hardener is 1 mass part ~30 parts by mass, flux is 20 parts by mass ~200 parts by mass; The aforementioned metal particles include: High melting point metal particles (B1), which contain silver and/or copper and have a melting point of 800°C or above; Low melting point metal particles (B2), which are alloys with a melting point of 130°C~150°C; and Low melting point metal particles (B3) are two or more alloys selected from the group consisting of tin, silver, copper, bismuth and indium, and have a melting point of 200°C to 240°C. Such as the conductive paste of claim 1, wherein the mass ratio of the aforementioned low melting point metal particles (B2) and the aforementioned low melting point metal particles (B3) is (B2)/(B3)=0.9~40. The conductive paste of claim 1 or 2, wherein the hardener is a hydroxyl-containing aromatic compound. The conductive paste according to any one of claims 1 to 3, wherein the hardener is a phenol-based hardener and/or a naphthol-based hardener. A multilayer substrate is composed of a plurality of conductive layers and an insulating layer between the plurality of conductive layers, and the holes penetrating the insulating layer are filled with a conductive paste, and the conductive paste is connected through the conductive paste. The conductive layers on both sides of the insulating layer are electrically connected to each other; the aforementioned cured conductive paste is a cured product of the conductive paste according to any one of claims 1 to 4. The multilayer substrate of claim 5, wherein in the conductive paste cured material, the high melting point metal particles (B1), the low melting point metal particles (B2) and the low melting point metal particles (B3) are melted and integrated with each other. and alloyed.