KR20240148569A - Bonding composition for low temperature sintering - Google Patents

Abstract

The present invention relates to a low-temperature sintering bonding composition. More specifically, the present invention relates to a low-temperature sintering bonding composition using silver powder coated with organic silver. According to one aspect of the present invention, a low-temperature sintering bonding composition is applied in the form of a composition containing a reducing agent to silver particles coated with organic silver, and then heated and pressurized to bond them, so that the organic silver component on the surface of the silver particles is reduced and melted at the same time, thereby promoting the melting of the silver adhesive layer as a whole, thereby melting at a relatively low melting temperature of 310°C or less, 250°C or less, 230°C or less, 210°C or less, 200°C or less, or 180°C or less, for example, 180 to 310°C, and capable of bonding a semiconductor to a substrate, an adhesive layer manufactured using the same, and a power semiconductor having the adhesive layer.

Description

{Bonding composition for low temperature sintering}

The present invention relates to a bonding composition for low-temperature sintering. More specifically, it relates to a bonding composition for low-temperature sintering using silver powder coated with organic silver.

As the eco-friendly electric vehicle and renewable energy markets grow, the demand for high-power and high-efficiency power semiconductors is increasing. Accordingly, the need for wide band gap (WBG) compound semiconductors based on silicon carbide (SiC) and gallium nitride (GaN) is increasing.

These power semiconductor devices must support higher power densities and switching frequencies while ensuring the reliability of high-performance electronic modules. However, there are limitations in achieving these goals when sintering with existing lead-free solders, as the bonding occurs at excessively high temperatures, which can damage the semiconductor devices.

In order to solve this problem, studies are being attempted to use conductive particle-based paste for bonding. However, conductive particle-based paste contains an organic binder, so residual carbon is generated after sintering, and there are cases where electrode spreading occurs due to the flowability of the organic binder during sintering. In particular, if such spreading and residual carbon occur during sintering below 350°C, it can cause interference with surrounding patterns or cause migration when power is applied, which can cause reliability problems.

Therefore, there is a demand for an adhesive that has excellent adhesive properties for heterojunction devices such as power semiconductors for electric vehicles without using an organic binder and can be sintered at low temperatures.

Korean Patent Publication No. 10-2016-0032613 (2016.03.24.)

The inventors of the present invention have a technical challenge in solving the problems of the prior art.

One object of the present invention is to provide a low-temperature sintering bonding composition that can bond at a low bonding temperature compared to conventional lead-free solder and adhesives using silver particles, has high bonding strength by melting even at low temperatures and low pressures, has no voids at the bonding surface, and can realize excellent thermal conductivity and a low coefficient of thermal expansion, thereby ensuring reliability (high durability) of electronic modules.

In addition, it is intended to provide a low-temperature sintering bonding composition that does not contain an organic binder such as epoxy resin or acrylic resin, thereby minimizing residual carbon during sintering, generating virtually no carbides, and improving the spreading phenomenon of electrodes.

In addition, it is possible to apply it to stencil or screen printing, etc., and after printing, heating, and bonding the semiconductor, the adhesive strength with the substrate increases, so that even when dropped from a height of 2 meters or more due to gravity or when hit on the floor with the force of a typical adult male, the bonding surface does not come off, and it is intended to provide a bonding composition for low-temperature sintering for power semiconductors.

In order to achieve the above task, research was conducted to develop an adhesive composition that does not generate carbides during sintering because it does not use a polymer binder, and also to develop an adhesive composition that can be sintered at low temperatures so that it can be applied to power semiconductors, etc., and that has excellent adhesive strength even when sintered at low temperatures.

As a result, the present invention was completed by discovering that the above-mentioned task can be achieved by coating the surface of silver particles with organic silver, which is a silver precursor compound, and manufacturing a silver paste composition by mixing it with a reducing agent and a solvent.

Specifically, when the composition is applied to an object to be bonded and the solvent is dried, the organic silver is reduced by a reducing agent, and silver nanoparticles are formed on the surface of the silver particles, and a silver adhesion layer is formed where the silver particles are in contact with each other even at a low firing temperature. Although this is not clear, it was found that the reduced silver nanoparticles on the surface of the silver particles promote melting of the silver adhesion layer, thereby providing a new type of low-temperature bonding silver paste composition capable of bonding at a relatively low melting temperature, 310°C or lower, preferably 300°C or lower.

One aspect of the present invention provides a low-temperature sintering bonding composition comprising surface-coated silver particles having a silver precursor compound coated on the surface of the silver particles; and a reducing agent.

In one embodiment, the low-temperature sintering bonding composition can be sintered at 310°C or lower, and may have an adhesive strength of 50 MPa or higher after sintering.

In one embodiment, the low-temperature sintering bonding composition may not contain an organic binder.

In one embodiment, the silver particles may be an aggregated powder having an average particle size of 0.5 to 2 ㎛ and a primary particle size of 45 to 500 nm.

In one embodiment, the silver precursor compound is silver maleate, silver fumarate, silver glyoxylate, silver pyruvate, silver succinate, silver glutalate, silver gluconate, silver picrate, silver citrate, silver iminodiacetate, silver nitrilotriacetate, silver ethylenediaminetetraacetate, silver benzoate, silver neodecanoate, silver laurate, silver stearate. The compound may be any one or a mixture of two or more selected from the group consisting of silver stearate, silver oleate, silver linolate, silver abietate, silver alkylammonium carbamates, and silver alkylammonium carbonates, but is not limited thereto.

In one embodiment, the reducing agent is selected from the group consisting of methylamine, ethylamine, propylamine, butylamine, pentylamine, aniline, 1,4-phenyldiamine, 4-bromoaniline, 3-amino-1-propanol, alkanolamine, hydrogen peroxide, formic acid, ammonium formate, sodium formate, glyoxal, hydroquinone, hydrazine, pyrogallol, glucose, gallic acid, formalin, anhydrous sodium bisulfite, sodium sulfoxylate (rongalit), formaldehyde, amine compounds, glycol compounds, glycerol, dimethylformamide, tannic acid, citrate, glucose, ascorbic acid, L(+)-ascorbic acid, isoascorbic acid, ascorbic acid derivatives, oxalic acid, formic acid, ethylene glycol, propylene glycol, polyethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, It may be any one selected from the group consisting of 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2-butene-1,4-diol, 2,3-butanediol, pentanediol, hexanediol, octanediol, decanol, glycerol, 1,1,1-trihydroxymethylethane, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 1,2,6-hexanetriol, 1,2,3-hexanetriol, 1,2,4-butanetriol, threitol, erythritol, pentaerythritol, phenoxyethanol, hexitol, and iminodiethanol, but is not limited thereto.

Another aspect of the present invention comprises the steps of applying a low-temperature sintering bonding composition according to the above aspect on a power semiconductor substrate, drying the same, and forming an adhesive coating layer having a silver adhesive layer formed by the silver particles and silver nanoparticles coming into contact with each other while reducing silver nanoparticles on the surface of the silver particles; and

A step of forming an adhesive layer by stacking semiconductor chips on the adhesive coating layer and sintering them;

A method for manufacturing a power semiconductor including:

In one aspect, the silver nanoparticles may also be formed on the substrate to contribute to adhesion between the substrate and the silver particles.

In one embodiment, the sintering may be performed at 310° C. or lower.

In one embodiment, the silver particles may be melted and bonded by the sintering.

In one embodiment, the reduction may be reduction by heating.

In one embodiment, the heating may be performed at 200°C or lower.

In one embodiment, pressurization may be performed simultaneously at a pressure of 20 MPa or less during the sintering.

In one embodiment, the adhesive strength of the adhesive layer may be 50 MPa or more.

According to one aspect of the present invention, a low-temperature sintering bonding composition promotes melting of a silver bonding layer by reducing organic silver applied to the surface of silver particles, thereby melting at a relatively low melting temperature, for example, 310°C or less, 250°C or less, 230°C or less, 210°C or less, 200°C or less, or 180°C or less, and capable of bonding a semiconductor to a substrate, an adhesive layer manufactured using the same, and a power semiconductor having the adhesive layer can be provided.

That is, it is thought that the organic silver coated on the surface of the silver particles is reduced to form silver nanoparticles, and at the same time, the reduced silver nanoparticles promote the melting of the silver particles, which are the base material constituting the core. That is, the silver particles generated by the reduction of the organic source applied to the surface promote the sintering of the silver powder, which is the base material, in the sintering step during pressurized heating, and thus act as a sintering aid, so that the sintering temperature of the silver powder, which is the base material, can be lowered, and accordingly, a bonding composition capable of low-temperature sintering can be provided.

In addition, by using silver powder coated with organic silver, the organic silver acts as a binder replacing organic binders such as ethyl cellulose and acrylic resin, which are generally used in paste manufacturing at room temperature or in printing such as stencil or screen printing, and after completing the drying step after printing, the adhesive strength with the substrate is increased, so that a bonding composition can be provided in which the electrode does not fall off even when dropped from a height of 2 meters or more due to gravitational acceleration or when hit on the floor with the force of a normal adult.

In addition, since there is no organic binder during sintering, residual carbon after sintering can be minimized, and the spreadability of the electrode due to the flowability of the organic binder during sintering can be minimized.

In addition, by using solvents having an obtuse contact angle with the substrate without damaging wettability with the silver powder, it is possible to form an electrode in which the bonding composition and the electrode formed therefrom do not spread or surface diffusion does not occur at each step during the printing step, drying step, and firing step.

The low-temperature sintering bonding composition according to one embodiment of the present invention can be applied to bonding of electronic devices required in the fields of power semiconductors for electric vehicles, aerospace, wind power, space exploration, and deep oil and gas exploration. In addition, it can be applied to substrates such as high-power LED bonding materials and polyethylene terephthalate films, and can be sintered at 310°C or lower, specifically, sintered at 200 to 300°C in air, and can be applied to low-resistance sintered bodies. In addition, it can sufficiently melt and bond without pressure during sintering or under a pressure of 15 MPa or lower, preferably 10 MPa or lower.

Figure 1 is a cross-sectional view showing one embodiment of the surface-coated silver particles of the present invention.

Hereinafter, the present invention will be described in more detail. However, the following specific examples or examples are only a reference for describing the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

Also, unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of this invention is only for the purpose of effectively describing particular embodiments and is not intended to be limiting of the invention.

Additionally, the singular forms used in the specification and the appended claims are intended to include the plural forms as well, unless the context clearly dictates otherwise.

Additionally, when a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

Additionally, unless otherwise specifically defined in the present invention, when a layer or member is said to be located “on” another layer or member, this includes not only cases where a layer or member is in contact with another layer or member, but also cases where another layer or member exists between the two layers or two members.

In addition, the terms “about,” “substantially,” etc. used in this specification are used in a meaning that is at or close to the numerical value when manufacturing and material tolerances inherent in the meanings mentioned are presented, and are used to prevent unscrupulous infringers from unfairly utilizing the disclosure contents in which exact or absolute numerical values are mentioned to aid understanding of the present invention.

One aspect of the present invention provides a low-temperature sintering bonding composition, i.e., a low-temperature sintering silver paste composition, comprising surface-coated silver particles in which a silver precursor (also referred to as ‘organic silver’) compound is coated on the surface of the silver particles; and a reducing agent.

Another aspect of the present invention provides a low-temperature sintering bonding composition, i.e., a low-temperature sintering silver paste composition, comprising: surface-coated silver particles having a silver precursor (also referred to as ‘organic silver’) compound coated on the surface of the silver particles; a reducing agent; and a solvent.

In one aspect, the silver particles may be used without limitation as long as they are commonly used in the relevant field, and their shapes, such as spherical or flake-shaped, are also not limited. In addition, the silver particles may be manufactured by a common manufacturing method, such as a wet method or a dry method.

The above silver particles may be primary particles or secondary particles formed by agglomeration of primary particles, and although not limited thereto, may be an agglomerated powder having an average particle diameter of 0.5 to 2 ㎛ and a primary particle diameter of 45 to 500 nm. Although it is preferable in the above range because it is advantageous for exhibiting low-temperature sintering and adhesive strength, it is not limited thereto. In addition, the shape of the above silver particles is not limited thereto, and may be, for example, a sphere, a flake, an agglomerated shape, etc., and may be a mixture of silver particles having one or more of these shapes, and a plurality of silver particles including agglomerated secondary particles may be used.

In one embodiment, the silver precursor compound may be used without limitation as long as it is a substance that is coated on the surface of the silver particle and then reduced to silver metal by a reducing agent during the heating process to dry the solvent of the bonding composition.

The above silver precursor compound can be an organic silver, and by using the organic silver, it can contribute to low-temperature sintering and expression of adhesive strength of the adhesive layer without using a separate polymer binder.

Specific examples of the organic silver include silver maleate, silver fumarate, silver glyoxylate, silver pyruvate, silver succinate, silver glutalate, silver gluconate, silver picrate, silver citrate, silver iminodiacetate, silver nitrilotriacetate, silver ethylenediaminetetraacetate, silver benzoate, silver neodecanoate, silver laurate, and silver stearate. The compound may be any one or a mixture of two or more selected from the group consisting of silver stearate, silver oleate, silver linolate, silver abietate, silver alkylammonium carbamates, and silver alkylammonium carbonates, but is not limited thereto.

More preferably, silver neodecanoate, silver laurate, silver stearate, silver oleate, silver linolate, etc. may be used, and by using these, dispersion stability is good, reactivity with a reducing agent at the drying temperature of the solvent is good, and long-term storage stability in the solvent of the bonding composition is excellent, so it may be preferable, but is not limited thereto.

The above silver precursor compound may be coated on the surface of the silver particle with a thickness of 1 nm to 60 nm, and may be preferable because it has excellent long-term storage stability and excellent adhesive strength within the above range, but is not limited thereto. The presence or absence of the coating may be confirmed using GC-MS, etc.

The content of the above silver precursor may be 0.01 to 10.0 parts by weight, 0.05 to 5.0 parts by weight, 0.1 to 3.0 parts by weight, or 0.5 to 2.0 parts by weight, relative to 100 parts by weight of the surface-coating silver particles, but is not limited thereto.

In one embodiment, the method for manufacturing the surface-coated silver particles includes a method of adding silver particles to a solution in which a silver precursor compound is dispersed and coating the particles through drying, or a method of dispersing silver particles in a solvent, adding a solution containing silver ions to the dispersed silver particles, and mixing a fatty acid and a pH regulator to synthesize a silver precursor compound, thereby coating the surface of the silver particles. The silver precursor compound solution may be an aqueous dispersion containing a silver precursor compound.

Another method is to physically mix a silver precursor compound with silver particles to obtain surface-treated silver particles. Examples of the mixing device include a planetary mixer, a tumbler mixer, a Henschel mixer, an intensive mixer, etc., and any other device that can physically adsorb the silver precursor compound onto the surface of the silver particles is not particularly limited. In order to adsorb a solid silver precursor compound, it is advantageous to liquefy so that all particles are evenly treated. However, in the case of a silver precursor, it can be reduced and precipitated as silver particles when liquefying, and therefore it can be adsorbed onto the surface in a wax-like state using a surface treatment device without liquefying. In addition, any method capable of adsorbing the silver precursor onto the surface of the particles can be appropriately employed excluding the above-mentioned characteristic process.

In one embodiment, the reducing agent may be used without limitation as long as it is a substance that reduces a silver precursor compound by heating during the process of applying the composition and then drying it to form a thin film.

Specifically, examples of the reducing agent include methylamine, ethylamine, propylamine, butylamine, pentylamine, aniline, 1,4-phenyldiamine, 4-bromoaniline, 3-amino-1-propanol, alkanolamine, hydrogen peroxide, formic acid, ammonium formate, sodium formate, glyoxal, hydroquinone, hydrazine, pyrogallol, glucose, gallic acid, formalin, sodium bisulfite anhydrous, sodium sulfoxylate (rongalit), formaldehyde, amine compounds, glycol compounds, glycerol, dimethylformamide, tannic acid, citrate, glucose, ascorbic acid, L(+)-ascorbic acid, isoascorbic acid, ascorbic acid derivatives, oxalic acid, formic acid, ethylene glycol, propylene glycol, polyethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, It may be any one selected from, or a mixture of two or more selected from, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2-butene-1,4-diol, 2,3-butanediol, pentanediol, hexanediol, octanediol, decanol, glycerol, 1,1,1-trihydroxymethylethane, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 1,2,6-hexanetriol, 1,2,3-hexanetriol, 1,2,4-butanetriol, threitol, erythritol, pentaerythritol, phenoxyethanol, hexitol, and iminodiethanol, but is not limited thereto.

Specifically, the reducing agent may be an alcohol compound selected from decanol, ethylene glycol, propylene glycol, 1,3-propanediol, diethylene glycol, and triethylene glycol.

The reducing agent is preferably used in an amount of 1 part by weight or more per 100 parts by weight of silver particles in terms of the yield of the precipitated silver powder. When using a reducing agent having a relatively weak reducing power, such as the alcohol-based compound, it is better to further increase the amount of the reducing agent used. For example, the reducing agent can be used by adjusting the content depending on the type used. Specifically, for example, when using an alcohol-based compound as the reducing agent, it can be used in an amount of 2 parts by weight to 100 parts by weight, 10 parts by weight to 70 parts by weight, or 20 parts by weight to 60 parts by weight, per 100 parts by weight of silver particles.

In addition, it may be advantageous during drying to include a solvent having a boiling point of 100 to 200°C as a reducing agent, and its content may include 10 to 50 parts by weight.

In one embodiment, the low-temperature sintering bonding composition of the present invention may use an alcohol-based compound, such as decanol, ethylene glycol, propylene glycol, 1,3-propanediol, diethylene glycol, and triethylene glycol, as the reducing agent, and when such an alcohol-based compound is used as the reducing agent, a separate solvent may not be required. However, a separate solvent may be further added in order to further improve the coatability and drying property, if necessary. In addition, when a different substance is used instead of an alcohol-based compound as the reducing agent, an alcohol-based solvent may be used as the solvent.

In one embodiment, the solvent may be used without limitation as long as it has excellent wettability with silver particles, an obtuse contact angle with a substrate, and can form an electrode in which the electrode paste does not spread or surface diffusion does not occur at each stage during the application, drying, and sintering stages of the composition. Specifically, the solvent may be used without limitation as long as it has a boiling point of 100 to 290° C.

The type of the solvent is not limited as long as it is a solvent having a boiling point of 100 to 290° C. Specifically, for example, ether solvents such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monobutyl ether, diethylene glycol dimethyl ether, and dipropylene glycol dimethyl ether; terpene solvents such as terpineol, terpineol acetate, dihydroterpineol, and dihydroterpineyl acetate; A solvent selected from the group consisting of alcohol solvents such as ethylene glycol, propylene glycol, polyethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2-butene-1,4-diol, 2,3-butanediol, pentanediol, hexanediol, octanediol, decanol, glycerol, 1,1,1-trihydroxymethylethane, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 1,2,6-hexanetriol, 1,2,3-hexanetriol, 1,2,4-butanetriol, threitol, erythritol, pentaerythritol, phenoxyethanol, hexitol and iminodiethanol; may be used, but is not limited to:

In one embodiment, the low-temperature sintering bonding composition may have a solid content of 30 to 90 wt%, and the viscosity of the composition may be 30 to 150 Pa.s (Brookfield DVII, SCR 14 spindle @ 25°C, 10 rpm), and although it is preferable and not limited thereto, mass production is possible because stencil or screen printing is possible within the above range.

Another aspect of the present invention comprises the steps of applying a low-temperature sintering bonding composition according to the above aspect on a power semiconductor substrate, drying the same, and forming an adhesive coating layer having a silver adhesive layer formed by the silver particles and silver nanoparticles coming into contact with each other while reducing silver nanoparticles on the surface of the silver particles; and

The present invention provides a method for manufacturing a power semiconductor without using an organic binder, including the step of forming an adhesive layer by stacking a semiconductor chip on the adhesive coating layer and then sintering the semiconductor chip.

The low-temperature sintering bonding composition used in the above manufacturing method is the same as that described above, so a duplicate description is omitted.

In one embodiment, the step of applying the low-temperature sintering bonding composition onto the power semiconductor substrate is not limited to roller, brush, spray application, etc., and stencil or screen printing is possible.

In one embodiment, the drying is preferably performed at a temperature at which the rearrangement of silver particles occurs along with drying of the solvent used in the low-temperature sintering bonding composition, and at the same time, the reducing agent reacts with the silver precursor compound to cause reduction. That is, the reduction may be performed by heating at the drying temperature. Specifically, the heating may be performed at 70° C. or higher, and may be from 70 to 200° C. Or, it may be from 100 to 150° C.

As the reduction occurs through the drying, a silver adhesion layer is formed by the silver particles and silver nanoparticles coming into contact with each other due to the silver nanoparticles that are reduced and generated on the surface of the silver particles.

In one embodiment, the silver particles may be melted and bonded by the sintering. The sintering may be performed at a temperature for sintering the silver particles, and according to the manufacturing method of the present invention, the sintering of the silver powder can be promoted in the sintering step by the silver nanoparticles formed on the surface of the silver particles and between the substrate and the silver particles by the reduction, thereby lowering the sintering temperature compared to the original sintering temperature of the silver powder. In addition, since a separate polymer binder is not used, carbides are not generated.

Specifically, for example, the sintering may be performed at 310°C or lower, and more specifically, at 300°C or lower, 250°C or lower, 230°C or lower, 200°C or lower, or 180°C or lower, for example, 180 to 310°C. In addition, during the sintering, sufficient melting and bonding are possible even under no pressure or under a pressure of 15 MPa or lower, preferably 10 MPa or lower.

The adhesive layer manufactured according to one embodiment of the present invention has excellent adhesive strength, so that the electrode does not fall off even when dropped from a height of 2 meters or more due to gravitational acceleration or when struck on the floor with the force of a typical adult male. More specifically, the adhesive strength may be 50 MPa or more, or 50 to 150 MPa, but is not limited thereto.

The present invention will be described in more detail based on the following examples and comparative examples. However, the following examples and comparative examples are only examples for describing the present invention in more detail, and the present invention is not limited by the following examples and comparative examples.

The following physical properties were evaluated as follows.

1) Application

The bonding compositions manufactured in the examples and comparative examples were printed on a metal stencil mask and applied to a silver-plated copper substrate in patterns of 10 each of 0.6×0.6 mm, 10 each of 1.0×1.0 mm, 10 each of 3.0×3.0 mm, and 10 each of 5.0×5.0 mm at a printing thickness of 200 μm, and then the number of printing defects was evaluated.

Excellent is when there are two or fewer defects, and defective is when there are three or more defects.

2) Dry adhesion

The bonding compositions manufactured in the examples and comparative examples were applied to a silver-plated copper substrate with a printing thickness of 200 μm in the same manner as in the applicability evaluation, and the substrate was dried for 30 minutes with hot air at 130° C., and then dropped from a height of 1 m, to evaluate the number of patterns that were broken or removed.

Here, if any part of each pattern is missing, the pattern is considered to be missing. As for the evaluation criteria, if the number of patterns without damage is 39 to 40, the adhesion is considered excellent (PASS), and if the number is less than that, the adhesion is considered poor (NG).

3) Sinterability

The bonding compositions manufactured in the Examples and Comparative Examples were applied to six patterns each measuring 2.8 × 2.8 mm on a silver-plated copper substrate, and then dried with hot air at 130°C for 30 minutes to obtain electrode patterns. A silver-plated copper block measuring 3 × 3 × 2 mm was placed on the applied and dried electrode patterns, and sintered at a heating rate of 95°C/min for about 180 seconds from room temperature to the actual temperature of 310°C (set temperature 300°C) while applying a pressure of 10 MPa. The sintering performance was observed on the sintered surface using a field emission scanning electron microscope (FE-SEM), and was judged as very good when the porosity was 19% or less, excellent when the porosity was 25% or less, and good when the porosity was 30% or less.

4) Adhesive strength

After sintering, the adhesive strength was measured in the same manner as the sinterability evaluation of item 3) above.

The bonding strength of the adhesive layer was measured using a DAGE4000 DS200Kg equipment according to the Die Shear value of AMIL-STD-883 Method No. 2019 Die Shear Strength.

As for the evaluation criteria, if the bonding strength is 60 MPa or higher, it is evaluated as very good (PASS), if it is 50 MPa or higher, it is evaluated as good (PASS), and if it is less than 50 MPa, it is evaluated as poor (NG).

5) BLT Evaluation

After sintering, BLT (Bonded Line Thickness, [㎛]) was measured in the same manner as the sinterability evaluation of item 3) above.

The BLT was measured by observing the cross-section of the sintered sample using an SEM to measure the BLT thickness. As an evaluation criterion, a BLT of 50 ㎛ or less was evaluated as BLT Good (PASS), and a BLT of more than that was evaluated as BLT Bad (NG).

6) Presence or absence of residual carbon

A thermogravimetric differential thermal analyzer (TA Instruments Ltd., model number SDT Q600) was used to measure the temperature-dependent weight loss of the composition by heating from room temperature (approximately 25°C) to 600°C at a heating rate of 10°C/min. It showed complete evaporation of the solvent and decomposition of the metal-organic precursor below 250°C. Furthermore, since the exothermic peak of the differential thermal analysis occurred below 250°C, it was confirmed that most of the organic compounds were completely oxidized below 250°C. The total weight loss at 250°C means that in the metallic gel at 250°C when heated, the organic fraction is completely separated from elemental silver and evaporated, leaving only bulk silver metal without carbon residue. Therefore, the thermal decomposition of the silver precursor deposits only pure silver metal without carbon residue. The residue percentage in TGA at temperatures above 250°C is close to the theoretical silver weight percentage of the silver particles. This clearly indicates that the thermal decomposition of the particles has occurred completely. The value of the residual carbon content of each sample after sintering was measured using a CS analyzer (LECO, Model Number CS744) and was compared relative to the value of Example 1.

[Example 1]

1) Preparation of silver particles coated with organic silver

The average particle size of the agglomerated powder was 1.7 ㎛, and the average particle size of the primary silver particles was 70 nm.

The above silver particles were placed in an intensive mixer, and 0.5 weight part of silver laurate as organic silver was sequentially added to 100 weight parts of the silver particles, and stirring was performed at 1500 rpm for 180 minutes to produce coated silver particles (referred to as ‘organic silver-coated silver particles (1)’ in Table 1 below).

2) Preparation of silver paste composition

A low-temperature sintering bonding composition was prepared by mixing 10 parts by weight of propylene glycol as a reducing agent, 30 parts by weight of 1,3-propanediol, and 30 parts by weight of terpineol as a solvent with respect to 100 parts by weight of the surface-coated silver particles manufactured above. The properties of the low-temperature sintering bonding composition were evaluated and are shown in Tables 1 and 2.

3) Manufacture and evaluation of power semiconductor sintered specimens

The manufactured low-temperature sintering bonding composition was applied in eight patterns on a DBC (silver-plated copper) substrate and dried with hot air at 130°C for 30 minutes. Then, 3x3 mm copper blocks (silver-plated copper) were placed on each of the printed and dried electrode patterns, and pressure firing was performed at 310°C while applying a pressure of 10 MPa. The adhesive strength of each of the pressure-fired specimens was measured, and the average of the values excluding the maximum and minimum was used as the adhesive strength value of each sample. As a result, it was confirmed that the adhesive strength was 63.9 MPa, indicating excellent adhesion. The evaluation results are shown in Fig. 1.

[Example 2]

In the above Example 1, the same procedure as Example 1 was carried out except that the content of the reducing agent was changed as shown in Table 1 below. The evaluation results are shown in Figure 1.

[Example 3]

In the above Example 2, the same procedure as Example 2 was performed except that the coated silver particles were changed.

Silver particles coated in the same manner as in Example 1 were manufactured using surface-coated silver particles, except that the content of organic silver, silver lauric acid, was changed to 2 parts by weight, and silver particles coated in the same manner as in Example 1 (referred to as ‘organic silver-coated silver particles (2)’ in Table 1 below) were manufactured. The evaluation results are shown in Fig. 1.

[Comparative Example 1]

In the above Example 1, instead of using surface-coated silver particles, silver particles in the form of aggregated powder having an average particle diameter of 200 nm, in which silver particles having a primary particle diameter of 45 nm are aggregated, were used. That is, a composition was prepared by mixing non-surface-coated silver particles having an average particle diameter of 200 nm (referred to as “non-coated silver particles (3)” in Table 1 below) with a reducing agent and a solvent in the contents described in Table 1 below. The prepared composition was applied on a power semiconductor substrate and dried with hot air at 130° C. for 30 minutes, and then copper blocks measuring 3 × 3 mm were each placed on the printed and dried electrode patterns, and pressure firing was performed at 310° C. while applying a pressure of 10 MPa. The adhesive strength of each of the evaluated specimens was measured, and the average of the values excluding the maximum and minimum was used as the adhesive strength value of each sample. As a result, it was confirmed that the adhesive strength was 49.2 MPa, which was lower than that of Example 1. In addition, it was confirmed that sintering was performed at a high temperature of 300℃ or higher. The evaluation results are shown in Fig. 1.

[Comparative Example 2]

Surface-coated silver particles were manufactured in the same manner as in Example 1, except that particles coated with fatty acids were used as the surface-coated silver particles as shown below.

In addition, a low-temperature sintering bonding composition was manufactured using the manufactured surface-coated silver particles in the same manner as in Example 1, and an adhesive layer was formed on a power semiconductor. As a result, it was confirmed that the adhesive strength was 10.2 MPa, which was lower than that of Example 1. In fact, one out of six adhesives fell off from the substrate.

Silver particles were used as agglomerated powder with a primary particle size of 45 nm and an average particle size of 200 nm.

For 100 parts by weight of the above silver particles, 0.5 parts by weight of lauric acid as a fatty acid was sequentially weighed and added to an intensive mixer, and the silver particles and lauric acid were stirred at 1500 rpm for 180 minutes to produce coated silver particles (referred to as ‘fatty acid-coated silver particles (4)’ in Table 1 below). The evaluation results are shown in Fig. 1.

[Comparative Example 3]

A composition was prepared in the same manner as in Example 1, but further including a binder resin.

Using the same surface-coated silver particles as in Example 1, and with respect to 100 parts by weight of the organic silver-coated silver particles (1), 10 parts by weight of propylene glycol as a reducing agent, 30 parts by weight of 1,3-propanediol, 30 parts by weight of terpineol as a solvent, and 0.4 parts by weight of ethyl cellulose resin (DOW ETHOCEL STD 4) as a binder resin were mixed to prepare a low-temperature sintering bonding composition. When the prepared low-temperature sintering bonding composition was applied onto a power semiconductor substrate, a phenomenon in which the applied material was dragged occurred.

As a result of the performance evaluation using the same method as Example 1, the adhesive strength was found to be good at 50.3 MPa, but it was confirmed that the adhesive strength was lower than that of Example 1. This is because, as a result of the measurement using a differential gravimetric analyzer, the DT exothermic peak occurred above 250°C and the carbon content was detected as 206 ppm, so it is estimated that carbides, which are residual carbon, remained after sintering and interfered with the interfacial bonding strength of silver. The evaluation results are shown in Fig. 1.

[Comparative Example 4]

Instead of using surface-modified silver particles, a silver precursor and a reducing agent were mixed into the composition and used.

Silver particles having a primary particle size of 45 nm were used as agglomerated powder having an average particle size of 200 nm. That is, for 100 parts by weight of uncoated silver particles having an average particle size of 200 nm (‘uncoated silver particles (3)’ in Table 1 below), 0.5 parts by weight of silver lauric acid as organic silver and a reducing agent and solvent were mixed in the contents described in Table 1 below to prepare a bonding composition for low-temperature sintering.

The manufactured low-temperature sintering bonding composition was applied onto a power semiconductor substrate and dried with hot air at 130°C for 30 minutes. Then, 3x3 mm copper blocks (silver-plated copper) were placed on each of the printed and dried electrode patterns, and pressure firing was performed at 310°C while applying a pressure of 10 MPa. The adhesive strength of each of the evaluated specimens was measured, and the average of the values excluding the maximum and minimum was used as the adhesive strength value of each sample.

As a result, it was confirmed that the adhesive strength was 38.4 MPa, which was lower than that of Example 1. In addition, when organic silver was mixed into the composition and applied, it was found that the wettability was lower and the sintering adhesion was lower than when the coated particles were used as in the present invention. The evaluation results are shown in Fig. 1.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Silver particle type/content (weight part) Organic silver coated silver particles (1)/
100 Organic silver coated silver particles (1)/
100 Organic silver coated silver particles (2)/
100 Uncoated silver particles (3)/
100 Fatty acid coated silver particles (4)/
100 Organic silver coated silver particles (1)/
100 Uncoated silver particles (3)/
100 Propylene glycol
(weight) 10 20 20 10 10 10 10 1,3-propanediol
(weight) 30 20 20 30 30 30 30 Terpineol
(weight) 30 30 30 30 30 30 30 bookbinder
(weight) - - - - - 0.4 - Organic silver
(weight) - - - - - - 0.5 Application excellence excellence excellence error error error excellence Dry adhesion excellence excellence excellence error error Good excellence Sinterability Very good Very good Very good Good error error excellence Adhesive strength Very good excellence excellence excellence error excellence error Residual carbon
(ppm) 0 0 0 256 0 206 193 BLT Good
(48.7㎛) Good
(48.7㎛) Good
(48.3㎛) Good
(48.7㎛) error
(60.4㎛) error
(50.4㎛) Good
(46.4㎛)

Although the present invention has been described through specific matters and limited examples as described above, these have been provided only to help a more general understanding of the present invention, and the present invention is not limited to the above examples, and those skilled in the art to which the present invention pertains can make various modifications and variations from this description.

Therefore, the idea of the present invention should not be limited to the described embodiments, and all things that are equivalent or equivalent to the claims described below as well as the same are included in the scope of the idea of the present invention.

10 : Silver particles
20: Silver precursor compound coating layer
100: Surface coating silver particles

Claims (14)

A low-temperature sintering bonding composition comprising surface-coated silver particles, wherein a silver precursor compound is coated on the surface of the silver particles; and a reducing agent. In paragraph 1,
The above low-temperature sintering bonding composition can be sintered at 310°C or lower, and has an adhesive strength of 50 MPa or higher after sintering. In paragraph 1,
A low-temperature sintering bonding composition, wherein the low-temperature sintering bonding composition does not contain an organic binder. In paragraph 1,
A low-temperature sintering bonding composition comprising an aggregated powder having an average particle size of 0.5 to 2 ㎛ and a primary particle size of 45 to 500 nm. In paragraph 1,
The above silver precursor compounds are silver maleate, silver fumarate, silver glyoxylate, silver pyruvate, silver succinate, silver glutalate, silver gluconate, silver picrate, silver citrate, silver iminodiacetate, silver nitrilotriacetate, silver ethylenediaminetetraacetate, silver benzoate, silver neodecanoate, silver laurate, silver stearate, and oleic acid. A low-temperature sintering bonding composition, wherein the bonding composition comprises one or a mixture of two or more selected from the group consisting of silver oleate, silver linolate, silver abietate, silver alkylammonium carbamates and silver alkylammonium carbonates. In paragraph 1,
The above reducing agent is methylamine, ethylamine, propylamine, butylamine, pentylamine, aniline, 1,4-phenyldiamine, 4-bromoaniline, 3-amino-1-propanol, alkanolamine, hydrogen peroxide, formic acid, ammonium formate, sodium formate, glyoxal, hydroquinone, hydrazine, pyrogallol, glucose, gallic acid, formalin, anhydrous sodium bisulfite, sodium sulfoxylate (rongalit), formaldehyde, amine compounds, glycol compounds, glycerol, dimethylformamide, tannic acid, citrate, glucose, ascorbic acid, L(+)-ascorbic acid, isoascorbic acid, ascorbic acid derivatives, oxalic acid, formic acid, ethylene glycol, propylene glycol, polyethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, A low-temperature sintering bonding composition, wherein the composition is one or a mixture of two or more selected from the group consisting of 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2-butene-1,4-diol, 2,3-butanediol, pentanediol, hexanediol, octanediol, decanol, glycerol, 1,1,1-trihydroxymethylethane, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 1,2,6-hexanetriol, 1,2,3-hexanetriol, 1,2,4-butanetriol, threitol, erythritol, pentaerythritol, phenoxyethanol, hexitol, and iminodiethanol. A step of applying a low-temperature sintering bonding composition selected from any one of claims 1 to 6 onto a power semiconductor substrate and drying the same to form a reduced silver nanoparticle on the surface of the silver particle, thereby forming an adhesive coating layer having a silver adhesive layer formed by the silver particles and silver nanoparticles coming into contact with each other; and
A step of forming an adhesive layer by stacking semiconductor chips on the adhesive coating layer and sintering them;
A method for manufacturing a power semiconductor including: In Article 7,
A method for manufacturing a power semiconductor, wherein the silver nanoparticles are also formed on the substrate and contribute to adhesion between the substrate and the silver particles. In Article 7,
A method for manufacturing a power semiconductor, wherein the above sintering is performed at 310°C or lower. In Article 7,
A method for manufacturing a power semiconductor, wherein the silver particles are melted and bonded by the above sintering. In Article 7,
A method for manufacturing a power semiconductor, wherein the above reduction is performed by heating. In Article 11,
A method for manufacturing a power semiconductor, wherein the above heating is performed at a temperature of 200°C or less. In Article 9,
A method for manufacturing a power semiconductor, wherein pressurization is simultaneously performed at a pressure of 20 MPa or less during the above sintering. In Article 7,
A method for manufacturing a power semiconductor, wherein the adhesive strength of the adhesive layer is 50 MPa or more.