Metal nanofiller ink, conductive paste composition comprising same, and method for preparing same

Abstract

The present invention pertains to: a metal nanofiller ink comprising a dispersant, a diluent, and a complex compound formed by a coordination bonding between metal ions and a multidentate ligand; a conductive paste composition comprising the metal nanofiller ink and a base paste; and a method for preparing the metal nanofiller ink, and the present invention has the advantage of enabling low-temperature sintering while exhibiting excellent thermal and physical properties.

Description

Metal nanofiller ink, conductive paste composition containing the same, and method for manufacturing the same

[0001] The present invention relates to a metal nanofiller ink, a conductive paste composition containing the same, and a method for manufacturing the same. More specifically, the invention relates to a metal nanofiller ink capable of low-temperature sintering and having excellent thermal and physical properties, a conductive paste composition containing the same, and a method for manufacturing the same.

[0002] With the expansion of markets for electric vehicles, Energy Storage Systems (ESS), and renewable energy, the demand for semiconductors capable of operating at high temperatures is increasing, leading to active research on die-attach technology for attaching high-temperature operating semiconductor chips to substrates. Regarding die-attach, the conventional soldering process has been the most widely applied due to its fast process speed, which completes bonding within minutes, and its pressure-free nature; however, it is not suitable for high-temperature operating semiconductors due to the low melting temperature of lead (approximately 170°C).

[0003] Accordingly, sintering bonding technology using silver-based paste with silver (Ag) particles as fillers is considered a good alternative to conventional soldering processes. Silver has excellent thermal and electrical conductivity and a high melting point of approximately 960°C, making it suitable for the manufacture of high-temperature operating semiconductors.

[0004] However, when the sintering bonding process is performed at high temperatures, chip damage may occur due to the different thermal expansion coefficients of the various components integrated on the semiconductor chip. Therefore, in order to minimize damage to the semiconductor chip and improve productivity, the sintering bonding process is performed at a low temperature of 250°C or lower, and the sintered paste is required to have a high thermal conductivity of 100 W / m·K or higher.

[0005] Generally, micro-sized metal particles have high electrical and thermal properties because they have a small number of grain boundaries, but there is a problem that the sintering temperature must be raised above 500°C to form a dense structure. Consequently, if the sintering temperature is lowered to 250°C or lower, it is difficult to form a sintered body with high density, and if external mechanical or thermal shock is applied, serious damage such as cracking or delamination occurs.

[0006] Accordingly, there have been attempts to reduce porosity and induce low-temperature sintering by incorporating sub-micron sized metal powder into microfillers; however, when the particle size of the metal powder becomes sub-micrometer, inter-particle aggregation occurs. Consequently, when applied as a paste, these aggregates do not break down during the mixing and dispersion processes, making it difficult to observe the effects of low-temperature sintering and improved sintering density resulting from the application of sub-micrometer sized particles.

[0007] The present invention aims to produce a metal nanofiller ink capable of low-temperature sintering and having excellent thermal and physical properties, a conductive paste composition containing the same, and a method for manufacturing the same.

[0008] One embodiment of the present invention for achieving the above-described purpose relates to a metal nanofiller ink comprising: a complex formed by the coordination bonding of a metal ion and multiple ligands; a diluent; and a dispersant.

[0009] The above dispersant may include at least one of 1,2-diaminopropane (DAP), 2-amino-2-methyl-1-propanol (AMP), 2-methoxyethylamine (MEA), and ethylenediamine (EDA).

[0010] The above metal may include at least one of silver, copper, gold, platinum, palladium, ruthenium, copper, nickel, and zinc.

[0011] The multiple ligands forming the above complex may include two or more functional groups capable of forming a coordination bond with a metal ion.

[0012] The above functional group may include a carboxyl group.

[0013] The above multiple ligands may include at least one of oxalic acid, citric acid, propane-1,2,3-tricarboxylic acid, and agaric acid.

[0014] The multiple ligands forming the complex compound are oxalic acid, and the dispersant may be 1,2-diaminopropane (DAP).

[0015] The multiple ligands forming the complex compound are citric acid, and the dispersant may include at least one of 1,2-diaminopropane (DAP) and 2-amino-2-methyl-1-propanol (AMP).

[0016] Another embodiment of the present invention relates to a conductive paste composition comprising: the metal nanofiller ink; and a base paste comprising a metal powder, an epoxy resin, a curing agent, a curing accelerator, an additive, and an elastomer compound.

[0017] The above base paste and metal nanofiller ink may be included such that, for every 100 parts by weight of the base paste, the complex compound in the metal nanofiller ink is 0.1 to 0.4 parts by weight.

[0018] The above metal may include at least one of silver, copper, gold, platinum, palladium, ruthenium, copper, nickel, and zinc.

[0019] Another embodiment of the present invention relates to a method for manufacturing a metal nanofiller ink, comprising: a first step of preparing an aqueous solution of a metal precursor; a second step of preparing a ligand solution by mixing a multi-ligand containing two or more functional groups capable of forming a coordination bond with a metal ion of the metal precursor with a solvent; a third step of preparing a mixture containing a complex compound by mixing the aqueous solution of the metal precursor and the ligand solution; a fourth step of obtaining a complex compound by purifying the mixture; and a fifth step of preparing a metal nanofiller ink by mixing the complex compound with a diluent and a dispersant.

[0020] The above dispersant may include at least one of 1,2-diaminopropane (DAP), 2-amino-2-methyl-1-propanol (AMP), 2-methoxyethylamine (MEA), and ethylenediamine (EDA).

[0021] The above multiple ligands may include two or more functional groups capable of forming a coordination bond with the metal ion of the metal precursor.

[0022] The above functional group may include a carboxyl group.

[0023] The above multiple ligands may include at least one of oxalic acid, citric acid, propane-1,2,3-tricarboxylic acid, and agaric acid.

[0024] The multiple ligands forming the complex compound above may be oxalic acid, and the dispersant may be 1,2-diaminopropane (DAP).

[0025] The multiple ligands forming the complex compound are citric acid, and the dispersant may include at least one of 1,2-diaminopropane (DAP) and 2-amino-2-methyl-1-propanol (AMP).

[0026] The above metal may include at least one of silver, copper, gold, platinum, palladium, ruthenium, copper, nickel, and zinc.

[0027] The above ligand solution may contain a basic substance.

[0028] The metal nanofiller ink of the present invention is applied to a conductive paste composition, enabling low-temperature sintering while improving thermal and physical properties.

[0029] Figure 1 is the structural formula of the complex compound prepared in the preparation example.

[0030] Figure 2 is an SEM image of a film formed by sintering metal nanofiller ink.

[0031] Figure 3 shows the DSC analysis results of the metal nanofiller ink.

[0032] Figures 4 and 5 are photographs of the appearance of metal nanofiller ink according to the type of dispersant.

[0033] Figure 6 is an SEM image of a film formed by sintering a conductive paste composition.

[0034] Before describing the preferred embodiments of the present invention in detail below, it should be noted that the terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the present invention.

[0035] Throughout this specification, when a part is described as “comprising” a certain component, it means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0036] Throughout this specification, “%” used to indicate the concentration of a specific substance means (weight / weight)% for solid / solid, (weight / volume)% for solid / liquid, and (volume / volume)% for liquid / liquid, unless otherwise noted.

[0037] In each step, identification codes are used for convenience of explanation and do not describe the order of the steps; the steps may be performed differently from the specified order unless a specific order is clearly indicated in the context.

[0038] That is, each step may be carried out in the same order as specified, substantially simultaneously, or in the reverse order.

[0039] Hereinafter, embodiments of the present invention are examined. However, the scope of the present invention is not limited to the following preferred embodiments, and a person skilled in the art to which the present invention pertains may implement various modified forms from the contents described in the specification.

[0040] The present invention relates to a metal nanofiller ink, a conductive paste composition containing the same, and a method for manufacturing the same. The conductive paste composition containing the metal nanofiller ink of the present invention has the advantage of enabling low-temperature sintering while possessing excellent thermal and physical properties. Furthermore, since the metal nanofiller ink of the present invention is a liquid composition in which a metal complex compound acting as a metal nanofiller is uniformly dispersed, effective mixing and dispersion are possible when manufacturing the conductive paste composition.

[0041] The metal nanofiller ink of the present invention comprises a complex formed by the coordination bonding of multiple ligands and metal ions. Generally, complexes formed based on multiple ligands form coordination bonds with metal ions in proportion to the number of functional groups included in the ligands; therefore, the more functional groups of the multiple ligands there are, the closer the distance between the metal ions becomes. This enables rapid bonding between metal ions during the sintering of a conductive paste composition containing such a metal nanofiller ink, thereby enabling a sintering process at low temperatures. Furthermore, as the size of the sintered silver particles decreases, there is an advantage in that the porosity of the sintered body is reduced, and structural stability and properties such as thermal conductivity and electrical conductivity are improved through increased density.

[0042] One embodiment of the present invention relates to a metal nanofiller ink, wherein the metal nanofiller ink according to the present embodiment comprises a complex compound formed by the coordination bonding of a metal ion and multiple ligands; a diluent; and a dispersant.

[0043] The above complex is formed by the coordination bonding of a metal ion and multiple ligands and is a white powder-like substance. The above multiple ligands include two or more functional groups capable of forming a coordination bond with the metal ion, and thus can form a complex with a short distance between the metal ions, thereby enabling low-temperature sintering of the conductive paste composition containing it.

[0044] The above metal may include at least one of silver, copper, gold, platinum, palladium, ruthenium, copper, nickel, and zinc, and in particular, it is preferable to use silver, which has excellent thermal and electrical conductivity and a high melting temperature, making it suitable for manufacturing high-temperature operating semiconductors.

[0045] The above multiple ligand comprises two or more functional groups capable of forming a coordination bond with a metal ion, and the functional groups may include a carboxyl group. The above multiple ligand may include at least one of oxalic acid, citric acid, propane-1,2,3-tricarboxylic acid, and agaric acid, and it is more preferable to include at least one of oxalic acid and citric acid.

[0046] In the metal nanofiller ink according to the present embodiment, the complex compound may be included such that the metal atoms are 5 to 35 at% (atomic percent) based on the metal atoms in the complex compound. If included in an amount less than the above weight range, there is a problem in that effects such as low-temperature sintering and improved sintering density are not sufficiently obtained, and if included in an amount exceeding the above weight range, the complex compound is not uniformly dispersed and aggregates, acting as thermal resistance; therefore, it is preferable to include it within the above-described range.

[0047] The above diluent acts as a dispersion medium for metal nanofiller ink, and, for example, at least one of propylene glycol methyl ether (PGME), dipropylene glycol methyl ether (DPM), tripropylene glycol methyl ether (TPM), dipropylene glycol n-propyl ether (DPnP), dipropylene glycol n-butyl ether (DPnB), propylene glycol n-butyl ether (PnB), and propylene glycol n-propyl ether (PnP) may be used, but is not limited thereto.

[0048] The above-mentioned dispersant is added to uniformly disperse the complex compound within the diluent; by adding the dispersant, the complex compound is uniformly dispersed, allowing for the formation of a transparent metal nanofiller ink. Since the sintering characteristics of the conductive paste can only be improved if the complex compound is uniformly dispersed within the metal nanofiller ink, an appropriate dispersant must be used to ensure the metal nanofiller ink becomes transparent.

[0049] The above dispersant may be an amine-based compound and may include, for example, at least one of 1,2-diaminopropane (DAP), 2-amino-2-methyl-1-propanol (AMP), 2-methoxyethylamine (MEA), and ethylenediamine (EDA).

[0050] The dispersant may be included in an amount of 5 to 28 moles per mole of the complex compound. If included in an amount less than the above weight range, the complex compound is not sufficiently uniformly dispersed, forming an opaque ink. When such metal nanofiller ink is applied to a conductive paste composition, there is a problem that it does not sinter, or even if it does sinter, the physical properties of the sintered body are poor. Therefore, it is preferable to include it within the above weight range.

[0051] The above-mentioned dispersant can be applied differently depending on the type of multiple ligands forming the complex, and in this case, due to the significantly effective dispersion effect, the sintering characteristics and thermal and electrical properties of the conductive paste composition containing the metal nanofiller ink can be significantly improved.

[0052] For example, when the multiple ligands forming the complex compound are oxalic acid, it is preferable to use 1,2-diaminopropane (DAP) as a dispersant. In this case, the dispersant may be included in an amount of 5 to 15 moles per mole of the complex compound. If included in an amount less than the above range, it is difficult to form a transparent ink, and if included in an amount exceeding the above range, the excess amine may induce a curing reaction of the resin when applying the metal nanofiller ink to the conductive paste, thereby causing serious changes in the paste over time; therefore, it is preferable to include it within the above-mentioned molar range.

[0053] As another example, when the multiple ligand forming the complex is citric acid, it is preferable to use at least one of 1,2-diaminopropane (DAP) and 2-amino-2-methyl-1-propanol (AMP) as a dispersant. When DAP is applied as a dispersant, it may be used in a ratio of 8 to 15 moles of DAP per mole of complex, and when AMP is applied as a dispersant, it is preferable to use 18 to 28 moles of AMP per mole of complex. Since the content of these dispersants is such that the complex forms a transparent ink in which it is uniformly dispersed, and does not induce a curing reaction of the resin when applied to a conductive paste, it is preferable to use the dispersants within the molar ranges described above.

[0054] As such, metal nanofiller ink containing a complex compound, a diluent, and a dispersant can enable low-temperature sintering of 250°C or lower when applied to a conductive paste composition, improve the density of the sintered body, reduce porosity, and improve the thermal, electrical, and physical properties of the sintered body.

[0055] Another embodiment of the present invention relates to a conductive paste composition comprising a metal nanofiller ink. The conductive paste composition comprises a metal nanofiller ink and a base paste.

[0056] The metal nanofiller ink described above comprises a complex, a diluent, and a dispersant. The complex is formed by the coordination bonding of a metal ion and a multiple ligand containing two or more functional groups capable of forming a coordination bond with the metal ion. When a conductive paste composition containing such a complex is sintered, thermal decomposition of the ligand within the complex occurs, causing the metal ion to be reduced, bond with surrounding metal atoms, and convert into a metal nanoparticle to form a sintered structure. In this process, using a multiple ligand-based metal complex with close proximity between metal ions allows for rapid bonding with surrounding metal ions during sintering to form metal nanofillers, thereby offering the advantage of enabling a sintering process at low temperatures. Since this metal nanofiller ink is identical to that described in the preceding embodiment of the present invention, a redundant description is omitted.

[0057] The metal nanofiller ink may be included in an amount of 0.1 to 0.4 parts by weight, preferably 0.1 to 0.3 parts by weight, per 100 parts by weight of base paste. If the amount falls outside this weight range, there is a problem that the effect of improving thermal conductivity is reduced, so it is desirable to include it within the weight range described above. In particular, if the amount exceeds the weight range described above, the volume of the complex compound particles becomes very large, and the complex compound is not completely dissolved during the manufacture of the metal nanofiller ink, making it impossible to manufacture a transparent ink. This causes uneven dispersion of the complex compound within the conductive paste composition, which may act as a factor that degrades the physical and thermal properties of the sintered body obtained by sintering the conductive paste composition.

[0058] The above base paste is a composition comprising metal powder, epoxy resin, a curing agent, a curing accelerator, an additive, and an elastomer compound. Specifically, with respect to 100 parts by weight of metal powder, it may comprise 1 to 8 parts by weight of epoxy resin, 1 to 12 parts by weight of curing agent, 0.005 to 0.6 parts by weight of curing accelerator, 3 to 15 parts by weight of additive, and 0.1 to 0.7 parts by weight of elastomer compound.

[0059] The metal powder is a material added to improve adhesion to a substrate and to achieve the required thermal and electrical conductivity by sintering the conductive paste composition when heated, thereby bonding the metal powders together and forming a thermal and electrical network. The metal powder may be a powder of a metal containing at least one of silver, copper, gold, platinum, palladium, ruthenium, nickel, and zinc, and specifically, a powder of the same metal as the metal contained in the metal nanofiller ink may be used.

[0060] It is preferable that the metal powder be in the form of flakes or plates, and metal powder having such a form has a large adhesion area between particles, which contributes to lowering the sintering temperature. The thickness of the shortest axis of such metal powder may be 10 to 100 nm, 15 to 80 nm, or 25 to 69 nm, and the length of the longest axis may be 50 to 600 nm, 100 to 500 nm, or 130 to 460 nm.

[0061] The above epoxy resin is a binder resin and is a material added to realize the basic adhesive strength and physical properties of the conductive paste composition. As the epoxy resin, it is preferable to use a glycidyl ether type epoxy resin produced by the condensation reaction of diphenylmethane and epichlorohydrin. The glycidyl ether type epoxy resin has low viscosity, excellent compatibility with other resins, excellent mechanical and chemical resistance, and improves the dispersibility of metal powder to enable smooth sintering, thereby enabling high thermal and electrical conductivity.

[0062] Examples of such glycidyl ether-type epoxy resins include triglycidyl aminophenol (TGAP), 4-[2-(4-hydroxyphenyl)propan-2-yl]phenol, triglycidyl p-aminophenol (TGPAP), tetraglycidyl diaminodiphenylmethane (TGDDM), bis(4-glycidyloxyphenyl)methane (BFDGE), triglycidyl m-aminophenol (TGMAP), tetraglycidyl diaminodiphenylsulfone (TGDDS), diglycidyl aniline, and At least one selected from the group consisting of diglycidyl-o-toluidine may be included, but is not limited thereto.

[0063] The epoxy resin in the conductive paste composition may be included in an amount of 1 to 8 parts by weight per 100 parts by weight of metal powder. If the content of the epoxy resin is less than the above range, the film properties such as heat resistance, chemical resistance, and adhesion are reduced due to a decrease in the flowability and crosslinking density of the conductive paste composition. If the content of the epoxy resin is excessive, organic materials hinder contact with the metal powder, thereby reducing the sintering density and consequently reducing thermal conductivity and electrical conductivity. Therefore, it is preferable to include it within the weight range described above.

[0064] The above-mentioned curing agent is added to control the curing speed of the epoxy resin and to improve workability and storage stability, and the addition of the curing agent enables the achievement of a high curing density of the epoxy resin.

[0065] Furthermore, the addition of a curing agent contributes to the formation of a continuous welding phase of the metal powder. Specifically, since the sintering of the metal powder is carried out in combination by externally applied heat and the reaction heat generated during the curing reaction of the epoxy resin, welding between the metal powders proceeds effectively at low temperatures. Consequently, the formation of a continuous welding phase of the metal powder results in increased electrical and thermal conductivity, and offers the advantages of shortening process time and lowering process temperature.

[0066] Acid anhydride-based curing agents may be used as such curing agents, for example, at least one selected from the group consisting of nadic maleic anhydride, dodecyl succin anhydride, maleic anhydride, succin anhydride, hexahydrophthalic anhydride (HHPA), tetrahydrophthalic anhydride, pyromellitic dihydride, cyclohexanedicarbonyl anhydride, methyltetrahydrophthalic anhydride (MeTHPA), methylhexahydrophthalic anhydride (MeHHPA), nadic methyl anhydride (NMA), hydrolyzed methyl nadic anhydride, phthalic anhydride, and nadic anhydride may be used.

[0067] The above curing agent may be included in an amount of 1 to 12 parts by weight per 100 parts by weight of metal powder. If the content of the curing agent is insufficient, problems such as reduced electrical conductivity, thermal conductivity, and adhesion may occur due to the incomplete curing of the epoxy resin. If the curing agent is included in excess, process problems may occur due to low viscosity and high flowability, and the presence of uncured material and the presence of a substrate that hinders welding of the metal powder may degrade physical properties. Therefore, it is preferable to include it within the weight range described above.

[0068] The above-mentioned curing accelerator is a catalytic material that induces a curing reaction between the epoxy resin and the curing agent, and an imidazole-based compound may be used as the curing accelerator. Imidazole compounds include 2-methylimidazole (2MZ), 2-undecylimidazole (C11-Z), 2-heptadecylimidazole (C17Z), 1,2-dimethylimidazole (1,2DMZ), 2-ethyl-4-methylimidazole (2E4MZ), 2-phenylimidazole (2PZ), 2-phenyl-4-methylimidazole (2P4MZ), and 1-benzyl-2-methylimidazole (1B2MZ). 1-benzyl-2-phenylimidazole (1B2PZ), 1-cyanoethyl-2-methylimidazole (2MZ-CN), 1-cyanoethyl-2-ethyl-4-methylimidazole (2E4MZ-CN), 1-cyanoethyl-2-undecylimidazole (C11Z-CN), 1-cyanoethyl-2-phenylimidazolium trimellitate (2PZCNS-PW), 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine (2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine; 2MZ-A), 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine (2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine;C11Z-A), 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine (2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine; 2E4MZ-A), 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct (2,4-diamino-6-[2'-methyllimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct (2MA-OK), 2-phenyl-4,5-dihydroxymethylimidazole (2-phenyl-4,5-dihydroxymethylimidazole; 2PHZ-PW) and It may include at least one selected from the group consisting of 2-phenyl-4-methyl-5-hydroxymethylimidazole (2-phenyl-4-methyl-5-hydroxymethylimidazole; 2P4MHZ-PW).

[0069] The above curing accelerator may be included in an amount of 0.005 to 0.6 parts by weight per 100 parts by weight of metal powder, and when included within this weight range, the activity of the curing agent is smoothly carried out and the curing reaction of the epoxy resin proceeds well, and the stability of the conductive paste composition is improved, thereby preventing problems that may occur during storage or processes utilizing it.

[0070] The above additive is added to improve the physical properties and various characteristics of the conductive paste composition. For example, a glycidyl ether-based diluent may be used as an additive. The glycidyl ether-based diluent is inserted between the main chains of the epoxy cured product through a chemical reaction, thereby providing the effect of loosening the three-dimensional network structure throughout the composition, which increases the flexibility of the conductive paste composition, lowers the viscosity, and lowers the modulus after curing.

[0071] Glycidyl ether-based diluents have monofunctional or difunctional groups and may include at least one selected from the group consisting of Lauryl Alcohol Glycidyl Ether (LGE), Butyl Glycidyl Ether (BGE), 2-Ethylhexyl Glycidyl Ether, Allyl Glycidyl Ether (AGE), Polypropylene Glycol Diglycidyl Ether, 1,4-Butanediol Glycidyl Ether, Neopentyl Glycol Diglycidyl Ethers, and 1,6-Hexanediol Diglycidyl Ether, but are not limited thereto.

[0072] The above additive may be included in an amount of 3 to 15 parts by weight per 100 parts by weight of metal powder.

[0073] The above-mentioned elastomer compound is uniformly distributed within the matrix of the conductive paste composition, thereby providing the effect of reducing the modulus. Additionally, it occupies a large volume fraction relative to its weight, which has the effect of reducing the distance between metal powders. In other words, by reducing the volume of the matrix excluding the metal powders, the sintering density of the metal powders is improved; this increases the sintering density, enabling the sintering of the metal powders even at low temperatures. Furthermore, it can absorb thermal shock to prevent cracking or delamination.

[0074] For example, at least one selected from the group consisting of polysilsesquioxane, polypropylenesilsesquioxane, polyphenylsilsesquioxane, and polymethylenesilsesquioxane may be used as such an elastomer compound.

[0075] When the content of the above elastomer compound is low, the modulus of the conductive paste composition is high, and when the conductive paste composition is applied to a die bonding process, problems such as interlayer delamination occur. When the content of the elastomer compound is excessive, the viscosity increases significantly, the thermal conductivity decreases, and there are problems that hinder the sintering of the metal powder due to void phenomena. Therefore, it is preferable that the elastomer compound be included in an amount of 0.1 to 0.7 parts by weight per 100 parts by weight of metal particles.

[0076] This conductive paste composition can be applied as a conductive adhesive paste in the semiconductor manufacturing process and exhibits high thermal and electrical conductivity even when processed at a low sintering temperature of 250°C or lower, thus improving workability and productivity, and has the advantage of improving the electrical and thermal properties of the semiconductor to which it is applied.

[0077] Meanwhile, another embodiment of the present invention relates to a method for manufacturing a metal nanofiller ink. Since a metal nanofiller ink according to one embodiment of the present invention can be manufactured according to this embodiment, some redundant descriptions are omitted.

[0078] A method for manufacturing a metal nanofiller ink according to the present embodiment comprises: a first step of preparing an aqueous solution of a metal precursor; a second step of preparing a ligand solution by mixing a multi-ligand containing two or more functional groups capable of forming a coordination bond with a metal ion of the metal precursor with a solvent; a third step of preparing a mixture containing a complex compound by mixing the aqueous solution of the metal precursor and the ligand solution; a fourth step of preparing a complex compound by purifying the mixture; and a fifth step of preparing a metal nanofiller ink by mixing the complex compound with a diluent and a dispersant.

[0079] First, a first step of preparing an aqueous metal precursor solution, which is a raw material solution, and a second step of preparing a ligand solution containing multiple ligands are performed, but the order of performing the first step and the second step is not particularly limited. For example, it is possible for the first step to precede and the second step to be performed sequentially, or in the reverse order, or to be performed simultaneously.

[0080] The first step is to prepare an aqueous solution of a metal precursor, and the metal may include at least one of silver, copper, gold, platinum, palladium, ruthenium, copper, nickel, and zinc. For example, if silver is used as the metal, the metal precursor may be silver nitrate (AgNO3).

[0081] The second step is to prepare a ligand solution by mixing a metal ion of the metal precursor with a multi-ligand comprising two or more functional groups capable of forming a coordination bond with the metal ion, using a solvent. The functional groups may include carboxyl groups, and the multi-ligand may include at least one of oxalic acid, citric acid, propane-1,2,3-tricarboxylic acid, and agaric acid. The ligand solution may be prepared by dissolving and dispersing the multi-ligand in an organic solvent, and the organic solvent may be, for example, one or more of ethanol and isopropanol, but is not limited thereto.

[0082] At this stage, a basic substance may be mixed together to activate the functional groups of multiple ligands, and the basic substance may include, for example, at least one selected from the group consisting of sodium hydroxide (NaOH), ethanolamine (H2NC2H4OH), and triethanolamine (C6H15NO3), but the usable basic substances are not limited thereto.

[0083] The basic substance included in the ligand solution may be included such that the molar ratio of the basic substance to 1 mole of multiple ligand is equal to or less than the number of functional groups in one molecule of multiple ligand. This is because if the ratio of the basic substance is too low, the reactivity of the ligand decreases, and if the ratio of the basic substance is too high, metal oxides may be formed due to side reactions between OH- and metal ions.

[0084] The third step above is a step of preparing a mixture containing a complex compound by mixing the aqueous metal precursor solution and the ligand solution. Specifically, the aqueous metal precursor solution and the ligand solution can be mixed and stirred to induce a coordination reaction, and the formation of a complex compound can be determined through the formation of a white precipitate.

[0085] At this stage, the aqueous metal precursor solution and the ligand solution can be mixed such that the molar ratio of metal ions to 1 mole of multiple ligands is equal to the number of functional groups in one mole of multiple ligands.

[0086] The fourth step above is a step of purifying the mixture to prepare a complex compound. The method of purifying the mixture is not particularly limited, but can be carried out using a vacuum purification method, and water, ethanol, acetone, etc., may be used as a solvent during purification, but is not limited thereto. When using a vacuum purification method, purification may be performed one or more times, preferably three times, and additional purification may be carried out depending on the physical properties of the final product.

[0087] The fifth step above is a step of preparing a metal nanofiller ink by mixing the complex obtained in the fourth step with a diluent and a dispersant.

[0088] The above diluent acts as a dispersion medium for metal nanofiller ink, and, for example, at least one of propylene glycol methyl ether (PGME), dipropylene glycol methyl ether (DPM), tripropylene glycol methyl ether (TPM), dipropylene glycol n-propyl ether (DPnP), dipropylene glycol n-butyl ether (DPnB), propylene glycol n-butyl ether (PnB), and propylene glycol n-propyl ether (PnP) may be used, but is not limited thereto.

[0089] At least one of the above 1,2-diaminopropane (DAP), 2-amino-2-methyl-1-propanol (AMP), 2-methoxyethylamine (MEA), and ethylenediamine (EDA) may be used.

[0090] The dispersant may be applied differently depending on the type of multiple ligands forming the complex, for example, when oxalic acid is used, it is preferable to use 1,2-diaminopropane (DAP) as the dispersant, and when citric acid is used, it is preferable to use at least one of 1,2-diaminopropane (DAP) and 2-amino-2-methyl-1-propanol (AMP) as the dispersant.

[0091]

[0092] Hereinafter, the specific operation and effects of the present invention will be explained through an embodiment of the present invention. However, this is presented as a preferred example of the present invention, and the scope of the rights of the present invention is not limited according to the embodiment.

[0093] [Preparation Example 1]

[0094] A ligand solution was prepared by dissolving the ligand in ethanol, mixing it with a 1M aqueous NaOH solution, and stirring for 10 minutes. The ligand solution was mixed with an aqueous silver nitrate solution and reacted by stirring in a dark room at room temperature for 1 hour. The mixture was then purified using a vacuum filter, redispersed in a purification solvent, and purified again using a vacuum filter. This process was repeated three times to obtain a white powder-form complex (silver nanofiller). Water, ethanol, and acetone were used once each as the purification solvents, in that order.

[0095] A diluent, DPnB (di(propylene glycol) butyl ether), was prepared, and the silver nanofiller was mixed into it to a concentration of 16.7 at% based on silver atoms, and a dispersant was added and stirred to prepare a silver nanofiller ink.

[0096] The type of ligand, the molar ratio of ligand to NaOH when preparing the ligand solution, the molar ratio of ligand to silver nitrate when mixing the ligand solution with the silver nitrate aqueous solution, and the type and content of the dispersant used are listed in Table 1. Among the dispersants in Table 1, DAP is 1,2-diaminopropane and AMP is 2-amino-2-methyl-1-propanol, and the content of the dispersant refers to the molar ratio per 1 mole of the complex compound. In addition, the structural formulas of each complex compound are shown in Figure 1, and in Figure 1, (a), (b), (c), and (d) are the structural formulas of the complex compounds of Example 1, Example 2, Comparative Example 1, and Comparative Example 2, respectively.

[0097] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Type of Ligand Citric Acid Oxalic Acid Benzoic Acid Acetic Acid Number of Reactive Functional Groups 3 2 11 NaOH:Ligand (Molar) 3:12:11:11:1 Silver Ion:Ligand (Water) 3:12:11:11:1 Dispersant AAMP DAP AAMP AAMP Dispersant Content (Molar) 18.5 5.16.7 4.5

[0098]

[0099] [Experimental Example 1]

[0100] A metal nanofiller ink film prepared in Preparation Example 1 was formed on a polyimide substrate using an applicator, and after sintering in a 160°C convection oven for 1 hour, an SEM image of the sintered body (film) was taken and is shown in FIG. 2. In FIG. 2, (a), (b), (c), and (d) are SEM images of Example 1, Example 2, Comparative Example 1, and Comparative Example 2, respectively.

[0101] In addition, the particle size and resistivity of the silver nanoparticles of each sintered body were measured and listed in Table 2.

[0102] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Particle Size (nm) 30~40 70~80 100~150~100 Resistivity (μΩ·cm) 12.8 7.35 Unmeasurable 53.2

[0103] Looking at the sintering morphology, it was confirmed that the size of the silver nanoparticles decreased and sintering proceeded smoothly in the order of Example 1, Example 2, Comparative Example 2, and Comparative Example 1. This is believed to be because the greater the number of reactive functional groups within a single ligand molecule, the closer the distance between coordinately bonded silver ions becomes, leading to the rapid formation of silver nanoparticles and facilitating necking and sintering between particles. Additionally, while Example 1 and Example 2 exhibited electrical characteristics similar to those of bulk silver as a result of resistivity measurements, Comparative Example 1 and Comparative Example 2 showed poor or significantly reduced electrical characteristics.

[0104] Therefore, through the results of this experiment, it was confirmed that using a multi-ligand-based complex is desirable to induce low-temperature sintering of metal nanofiller ink.

[0105] [Experimental Example 2]

[0106] Differential scanning calorimetry (DSC) analysis was performed on each metal nanofiller ink prepared in Preparation Example 1, and the results are shown in FIG. 3. In FIG. 3, (a), (b), (c), and (d) are thermogravimetric graphs of Example 1, Example 2, Comparative Example 1, and Comparative Example 2, respectively.

[0107] As a result of the experiment, the total melting point of the silver nanofiller was measured to be 178.3°C for Example 1, 184.2°C for Example 2, 204°C for Comparative Example 1, and 206.1°C for Comparative Example 2.

[0108] Although the number of carbon atoms of the ligands used in these metal nanofiller inks is similar, it was confirmed that the melting point of multi-ligand-based silver nanofillers is 20–30°C lower than that of single-ligand due to the difference in the number of functional groups, and through this, it was confirmed that it is desirable to use multi-ligand-based complexes for low-temperature sintering.

[0109] [Experimental Example 3]

[0110] Metal nanofiller inks were prepared using citric acid with three functional groups as a ligand, in the same manner as in Example 1, but samples were prepared by varying the type and content of the dispersant. 1,2-diaminopropane (DAP), 2-amino-2-methyl-1-propanol (AMP), 2-methoxyethylamine (MEA), and ethylenediamine (EDA) were used as dispersants. Subsequently, the appearance of each sample was photographed and is shown in Fig. 4. In Fig. 4, (a) to (f) are photographs of the appearance of samples 1 to 6, in order.

[0111] In addition, a coating was formed on a substrate and sintered at 160°C for 1 hour, and the presence or absence of sintering was evaluated and recorded in Table 3. The resistivity of the film formed after sintering was measured and recorded in Table 3.

[0112] Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Dispersant DAPAMPMEAEDA Nanofiller : Dispersant (Molar) 1:4.5 1:8.3 1:9.5 1:18.5 1:14.8 1:20 Ink Appearance Opaque Suspension Transparent Ink Opaque Suspension Transparent Ink Transparent Ink Opaque Suspension Sintering Presence XOXOXX Resistivity (μΩ·cm) Unmeasurable 23.7 Unmeasurable 12.3 5.3×10 7 Unmeasurable

[0113] As a result of the experiment, it was confirmed that when citric acid was used as the ligand, transparent ink was produced and sintering was successfully achieved only when DAP or AMP was used as the dispersant. In the case of samples 5 and 6, there were problems where transparent ink was not produced or sintering did not occur even though an excessive amount of dispersant was included. Additionally, it was found that even when DAP or AMP was used as the dispersant, if the content was insufficient (samples 1 and 3), transparent ink was not produced and sintering did not occur.

[0114] Therefore, through this experiment, it was found that when citric acid is used as a multiple ligand, it is desirable to use DAP or AMP as a dispersant to prepare an ink in which silver nanofillers are uniformly dispersed; when using DAP, it is desirable to use at least 8 moles of dispersant, preferably at least 8.3 moles, per mole of complex (silver nanofiller); and when using AMP as a dispersant, it is desirable to use at least 18 moles, preferably at least 18.5 moles, per mole of complex.

[0115] [Experimental Example 4]

[0116] Metal nanofiller inks were prepared using oxalic acid with two functional groups as a ligand in the same manner as in Example 2, but samples were prepared with varying types and amounts of dispersants, and experiments identical to those in Experimental Example 3 were performed. The appearance photographs are shown in FIG. 5, and the results regarding sintering and resistivity measurements are shown in Table 4. In FIG. 5, (a) to (e) are appearance photographs of samples 7 to 11, in order.

[0117] Sample 7 Sample 8 Sample 9 Sample 10 Sample 11 Dispersant DAPAMPMEAEDA is Nanofiller:Dispersant (Molar) 1:3.5 1:5.11:40 1:7 1:46 Ink Appearance Opaque Suspension Transparent Ink Opaque Suspension Transparent Ink Opaque Suspension Sintering Presence XOXXX Resistivity (μΩ·cm) Unmeasurable 7.35 Unmeasurable Unmeasurable Unmeasurable

[0118] As a result of the experiment, it was confirmed that when oxalic acid is used as a ligand, a transparent ink is formed and sintering occurs well only when DAP is used as a dispersant. However, even when DAP is used as a dispersant, if its content is insufficient as in Sample 7, a transparent ink is not formed and sintering does not occur. Therefore, through the results of this experiment, it was confirmed that it is desirable to use DAP as a dispersant when using an oxalic acid-based complex compound when manufacturing metal nanofiller ink. In this case, it was confirmed that it is desirable to include at least 5 moles, preferably at least 5.1 moles, of DAP per mole of the complex compound (silver nanofiller).

[0119]

[0120] [Preparation Example 2]

[0121] A base paste was prepared comprising 80 wt% micro silver powder, 3.28 wt% epoxy resin, 4.35 wt% curing agent (methyltetrahydrophthalic anhydride), 0.06 wt% curing accelerator (2-ethyl-4-methylimidazole), 11.65 wt% additive (polypropylene glycol diglycidyl ether), and 0.66 wt% elastomer compound (polysilsesquioxane), and a conductive paste composition was prepared by adding the silver nanofiller ink prepared in the preparation example.

[0122] Metal nanofiller ink was added such that the content of silver nanofillers in the metal nanofiller ink was 0.1 to 0.5 wt% with respect to 100 parts by weight of the base paste, and the amount added is listed in Table 5. Sample 12 was a base paste without silver nanofiller ink added and was used as a control.

[0123] Sample 12 Sample 13 Sample 14 Sample 15 Sample 16 Ligand Type Citric Acid Citric Acid Citric Acid Acetic Acid is the nanofiller content (wt%) 0.10.30.50.3

[0124] [Experimental Example 5]

[0125] Each sample prepared in Preparation Example 2 was molded into a circular pellet shape of the same size and heat-treated at 190°C for 1 hour to sinter, thereby preparing specimens. The thermal conductivity of each specimen was measured, and the results are listed in Table 6. SEM images were taken and are shown in Figure 6. In Figure 6, (a), (b), (c), and (d) are SEM images of Sample 12, Sample 13, Sample 14, and Sample 16, respectively.

[0126] Sample 12 Sample 13 Sample 14 Sample 15 Sample 16 Thermal Conductivity (W / m·K) 788 4.383 35.45 9.3

[0127] Looking at the experimental results, samples 13 and 14, which used multi-ligand-based complexes, showed the highest thermal conductivity, while sample 16, which used single-ligand-based complexes, was found to have a thermal conductivity approximately 28% lower than this. In the case of sample 15, it was impossible to manufacture a transparent ink because the concentration of silver nanofiller particles that can be dissolved during the preparation of the silver nanofiller ink exceeded the limit. This is interpreted to be because the silver nanofillers did not achieve uniform dispersion within the paste, resulting in the specimen itself not being properly prepared for thermal conductivity measurement.

[0128] As a result of SEM imaging, it was confirmed that the acetic acid-based sample 16 hardly underwent sintering at a low temperature (190℃), and among the citric acid-based samples, samples 13 and 14 underwent sintering well, and in particular, sample 14 underwent the best sintering.

[0129] Therefore, it was confirmed through this experiment that when preparing a conductive paste composition, it is preferable to include a complex compound (metal nanofiller) in the metal nanofiller ink in an amount of 0.1 to 0.4 parts by weight per 100 parts by weight of base paste, and particularly most preferable to include an amount of 0.1 to 0.3 parts by weight.

[0130] The present invention is not limited to the specific embodiments and descriptions described above, and various modifications can be made by anyone with ordinary knowledge in the technical field to which the invention pertains without departing from the essence of the invention as claimed in the claims, and such modifications fall within the scope of protection of the present invention.

[0131]

[0132] The present invention relates to a metal nanofiller ink capable of low-temperature sintering and having excellent thermal and physical properties, and a conductive paste composition containing the same. The metal nanofiller ink comprising a complex compound formed by the coordination bonding of a metal ion and multiple ligands; a diluent; and a dispersant is applied to a conductive paste composition, and since it enables low-temperature sintering and improves thermal and physical properties, it has industrial applicability.

Claims

A complex formed by the coordination bonding of a metal ion and multiple ligands; Diluent; and Metal nanofiller ink containing a dispersant. In paragraph 1, The above-mentioned dispersant comprises at least one of 1,2-diaminopropane (DAP), 2-amino-2-methyl-1-propanol (AMP), 2-methoxyethylamine (MEA), and ethylenediamine (EDA), in a metal nanofiller ink. In paragraph 1, The metal nanofiller ink comprising at least one of silver, copper, gold, platinum, palladium, ruthenium, copper, nickel, and zinc. In paragraph 1, A metal nanofiller ink in which the multiple ligands forming the above complex compound comprise two or more functional groups capable of forming a coordination bond with a metal ion. In paragraph 4, The above functional group is a metal nanofiller ink comprising a carboxyl group. In paragraph 5, The above multiple ligands comprise at least one of oxalic acid, citric acid, propane-1,2,3-tricarboxylic acid, and agaric acid, metal nanofiller ink. In paragraph 5, The multiple ligands forming the above complex are oxalic acid, and A metal nanofiller ink in which the dispersant is 1,2-diaminopropane (DAP). In paragraph 5, The multiple ligands forming the above complex are citric acid, and The above-mentioned dispersant comprises at least one of 1,2-diaminopropane (DAP) and 2-amino-2-methyl-1-propanol (AMP), a metal nanofiller ink. A metal nanofiller ink according to any one of claims 1 to 8; and A conductive paste composition comprising a base paste comprising metal powder, epoxy resin, curing agent, curing accelerator, additive, and elastomer compound. In Paragraph 9, A conductive paste composition comprising 0.1 to 0.4 parts by weight of a complex compound in a metal nanofiller ink per 100 parts by weight of the base paste. In Paragraph 9, The above metal powder is a conductive paste composition comprising at least one metal powder selected from silver, copper, gold, platinum, palladium, ruthenium, copper, nickel, and zinc. First step of preparing an aqueous solution of a metal precursor; A second step of preparing a ligand solution by mixing a multi-ligand comprising two or more functional groups capable of forming a coordination bond with the metal ion of the metal precursor with a solvent; A third step of preparing a mixture containing a complex compound by mixing the above-mentioned aqueous metal precursor solution and ligand solution; A fourth step of purifying the above mixture to obtain a complex compound; and A method for manufacturing a metal nanofiller ink, comprising: a fifth step of mixing the above complex compound with a diluent and a dispersant to manufacture a metal nanofiller ink. In Paragraph 12, A method for preparing a metal nanofiller ink, wherein the above-mentioned dispersant comprises at least one of 1,2-diaminopropane (DAP), 2-amino-2-methyl-1-propanol (AMP), 2-methoxydetylamine (MEA), and ethylenediamine (EDA). In Paragraph 12, A method for manufacturing a metal nanofiller ink, wherein the above-mentioned multiple ligands comprise two or more functional groups capable of forming a coordination bond with a metal ion. In Paragraph 14, A method for manufacturing a metal nanofiller ink in which the functional group comprises a carboxyl group. In paragraph 15, A method for preparing a metal nanofiller ink, wherein the above multiple ligands comprise at least one of oxalic acid, citric acid, propane-1,2,3-tricarboxylic acid, and agaric acid. In paragraph 15, The multiple ligands forming the above complex are oxalic acid, and A method for manufacturing a metal nanofiller ink, wherein the dispersant is 1,2-diaminopropane (DAP). In paragraph 15, The multiple ligands forming the above complex are citric acid, and A method for preparing a metal nanofiller ink, wherein the above-mentioned dispersant comprises at least one of 1,2-diaminopropane (DAP) and 2-amino-2-methyl-1-propanol (AMP). In Paragraph 12, A method for manufacturing a metal nanofiller ink, wherein the metal comprises at least one of silver, copper, gold, platinum, palladium, ruthenium, copper, nickel, and zinc. In Paragraph 12, The above ligand solution is a method for manufacturing a metal nanofiller ink comprising a basic substance.

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