JP2009289745A - Method of manufacturing heating sintered silver particle, paste-like silver particle composition, method of manufacturing solid silver, method of joining metal member, method of manufacturing printed wiring board, and method of manufacturing electrical circuit connection bump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paste-like silver particle composition to be a solid silver with excellent strength, electric conductivity and thermal conductivity by easily sintering silver particles if heated, and a method or the like of manufacturing a solid silver. <P>SOLUTION: The method of manufacturing silver particles in which higher fatty acid coating a surface or its derivative is substituted with a further inferior higher/middle fatty acid or its derivative, and the paste-like silver particle composition which is a paste matter made of the silver particles and volatile dispersion medium and is made to be a solid silver by volatilizing the volatile dispersion medium by heating and sintering the silver particles with each other, are provided. Moreover, the method of manufacturing the solid silver due to heating the paste-like silver particle composition, a method of joining a metal member using the paste-like silver particle composition, and a method of manufacturing a printed wiring board with silver wirings as well as a method of manufacturing an electric circuit connection bump, are provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a method for producing heat-sinterable silver particles coated with high / intermediate fatty acid or a derivative of high / intermediate fatty acid; heat-sinterable silver particles coated with a high / intermediate fatty acid or a derivative of high / intermediate fatty acid A paste-like silver particle composition comprising a volatile dispersion medium and sintered by heating to form solid silver having excellent strength, electrical conductivity and thermal conductivity; solid form from the paste-like silver particle composition A method for producing silver; a method for joining metal members using the paste-like silver particle composition; a method for producing a printed wiring board using the paste-like silver particle composition; and the paste-like silver particle composition The present invention relates to a method for manufacturing an electric circuit connecting bump using an object.

Conductive paste made by dispersing silver powder in thermosetting resin composition is cured by heating to form a conductive film, so that conductive circuit formation on printed circuit boards, resistors, capacitors, etc. Electrode formation of various electronic parts and display elements, formation of a conductive film for electromagnetic wave shielding, adhesion of chip parts such as capacitors, resistors, diodes, memories and arithmetic elements (CPUs) to substrates, solar cell electrodes, In particular, it is used for forming electrodes of solar cells that cannot be processed at high temperature using amorphous silicon semiconductors, forming external electrodes of chip-type ceramic electronic components such as multilayer ceramic capacitors, multilayer ceramic inductors, multilayer ceramic actuators, and the like.
In recent years, the amount of heat generated from chip parts has increased due to the high performance of chip parts, and it is required to improve the thermal conductivity as well as the electrical conductivity. When trying to improve the thermal conductivity, there is a problem that the viscosity of the paste increases and the workability is remarkably lowered.

In order to solve such a problem, the present inventors heated the paste-like silver particle composition composed of silver powder and a volatile dispersion medium, and the volatile dispersion medium volatilized and the silver powder was sintered. It became solid silver having extremely high electrical conductivity and thermal conductivity, and was found to be useful for joining metallic members and forming conductive circuits (WO2006 / 126614, WO2007 / 034833).
However, due to heat resistance limitations of electronic devices, electronic components, chip components, etc. and the materials constituting them, the paste-like composition is sintered at a low temperature, specifically at a temperature of 150 ° C. or less, and has adhesiveness. Increasingly, it is required to have
However, the development of adhesiveness is not sufficient especially in sintering at low temperatures, and this is caused by the coating agent of silver particles (for example, higher fatty acid salts, higher fatty acids) used for the purpose of preventing aggregation of silver particles. I realized there was a problem.

Since silver used in the paste-like silver particle composition is fine particles, the surface thereof is coated with an organic substance to prevent aggregation of the silver particles. In Japanese Patent Laid-Open No. 54-121270, silver powder coated with a higher fatty acid is produced by allowing a higher fatty acid to coexist in the silver powder production process in order to prevent aggregation of the silver powder. Specifically, a reducing agent such as formalin and sodium hydroxide and a higher fatty acid such as stearic acid and oleic acid are added to an aqueous silver nitrate solution and stirred, and then the silver powder coated with these higher fatty acids is separated.

JP-A-2001-49309 produces silver particles coated with higher fatty acid salts by coexisting with higher fatty acid salts (eg, sodium oleate, sodium stearate) when producing silver particles by reducing silver oxide. is doing. In JP-A-2001-49309, a higher fatty acid salt is added when flaking silver particles by a ball mill, and in JP-A-2003-55701, a surfactant and / or a higher grade are added when flaking silver particles by a ball mill. Fatty acids (eg, polyethylene glycol dioleate, oleic acid) are added.

WO2006 / 126614 WO2007 / 034833 JP 54-121270 A JP 2001-49309 A JP 2003-55701 A

The inventors of the present invention have a silver paste that does not have the above problem, that is, a paste that sinters at a relatively low temperature and becomes solid silver excellent in adhesive strength, hardness, electrical conductivity, and thermal conductivity. As a result of diligent research to develop a silver particle composition, the higher fatty acid or derivative thereof in silver particles coated with a higher fatty acid or derivative thereof is replaced with a lower high / intermediate fatty acid or a derivative of higher / intermediate fatty acid. It has been found that this is effective, and the present invention has been completed.

The object of the present invention is to heat-sinterable silver particles that, when heated, are easily sintered at a relatively low temperature and become solid silver having excellent adhesion strength, hardness, electrical conductivity and thermal conductivity. A paste-like silver particle composition, which, when heated, easily sinters silver particles at a relatively low temperature to form solid silver having excellent adhesion strength, hardness, electrical conductivity and thermal conductivity; paste Of producing solid silver excellent in strength, electrical conductivity and thermal conductivity from a silver particle composition; using the paste-like silver particle composition to strengthen a metal member with good electrical and thermal conductivity A method of manufacturing a printed wiring board having silver wiring excellent in wear resistance, adhesion to a substrate, electrical conductivity and thermal conductivity; and electricity excellent in electrical conductivity and thermal conductivity An object of the present invention is to provide a method for manufacturing a bump for circuit connection.

This purpose is
"[1] The higher fatty acid (a1) or higher fatty acid (a1) derivative (a2) of silver particles whose surface is coated with a higher fatty acid (a1) or a higher fatty acid (a1) derivative (a2) A method for producing heat-sinterable silver particles, characterized by substituting with a high / intermediate fatty acid (b1) lower than fatty acid (a1) or a derivative (b2) of high / intermediate fatty acid (b1).
[2] The heat sinterability according to [1], wherein the higher fatty acid (a1) has 17 or more carbon atoms and the higher / intermediate fatty acid (b1) has 16 or less carbon atoms. A method for producing silver particles.
[2-1] The heating according to [2], wherein the higher fatty acid (a1) has 17 to 24 carbon atoms and the higher / intermediate fatty acid (b1) has 8 to 14 carbon atoms. A method for producing sinterable silver particles. In addition,
“[2-2] The method for producing heat-sinterable silver particles according to [1], [2] or [2-1], wherein the silver particles are produced by a reduction method. Is achieved.

This purpose is
“[3] (A) The surface is composed of silver particles coated with high / intermediate fatty acid (b1) or high / intermediate fatty acid (b1) derivative (b2) and (B) a volatile dispersion medium. In the paste-like silver particle composition in which the volatile dispersion medium is volatilized and the silver particles are sintered together, the high / intermediate fatty acid (b1) or the derivative of the high / intermediate fatty acid (b1) covering the surface of the silver particles ( b2) is a higher fatty acid (a1) or a higher fatty acid (a1) derivative (a2) previously coated on the surface of the silver particles, and a higher, intermediate fatty acid (b1) or higher A paste-like silver particle composition characterized by being substituted with a derivative (b2) of intermediate fatty acid (b1).
[4] The pasty silver particles according to [3], wherein the higher fatty acid (a1) has 17 or more carbon atoms and the higher / intermediate fatty acid (b1) has 16 or less carbon atoms. Composition.
[4-1] The higher fatty acid (a1) has 17 to 24 carbon atoms, and the higher / intermediate fatty acid (b1) has 8 to 14 carbon atoms, according to [4] Paste silver particle composition.
[4-2] The average particle diameter (median diameter D50) of the silver particles (A) is larger than 0.1 μm and not larger than 20 μm, and the shape is spherical, granular or flaky, [3] Or the paste-like silver particle composition according to [4].
[4-3] The pasty silver particle composition according to [3] or [4], wherein the volatile dispersion medium (B) has a boiling point of 60 ° C. or higher and 300 ° C. or lower.
[5] The average particle diameter of the silver particles (A) is larger than 0.1 μm and not larger than 20 μm, the shape is spherical, granular or flaky, and the boiling point of the volatile dispersion medium (B) is 60 ° C. or higher and 300 ° C. The pasty silver particle composition according to [3] or [4], characterized in that: [4-2-1] The paste according to [3], [4] or [4-2], wherein the silver particles are produced by a reduction method -Like silver particle composition.
[5-1] The paste-like silver particle composition according to [5], which is characterized in that the silver particles are produced by a reduction method.

This purpose is
“By heating the paste-like silver particle composition according to [6] [3] or [4] at 70 ° C. or more and 400 ° C. or less, the volatile dispersion medium is volatilized to sinter the silver particles. A method for producing solid silver.
[6-1] The paste-like silver particle composition according to [5] is heated at 70 ° C. or more and 400 ° C. or less to volatilize the volatile dispersion medium and sinter the silver particles. A method for producing solid silver.
[7] The volume resistivity of the manufactured solid silver is 1 × 10 ⁻⁴ Ω · cm or less and the thermal conductivity is 10 W / m · K or more, [6] The manufacturing method of solid silver of description.
[7-1] The manufactured solid silver has a volume resistivity of 1 × 10 ⁻⁴ Ω · cm or less and a thermal conductivity of 10 W / m · K or more, [6 -1]. The method for producing solid silver according to [1]. Is achieved.

This purpose is
“The paste-like silver particle composition according to [8] [3] or [4] is interposed between a plurality of metal members, and the volatile dispersion medium is volatilized by heating at 70 ° C. or more and 400 ° C. or less. A method for joining metal members, comprising sintering silver particles and joining a plurality of metal members.
[8-1] The paste-like silver particle composition according to [5] is interposed between a plurality of metal members, and the volatile dispersion medium is volatilized by heating at 70 ° C. to 400 ° C. A method of joining metal members, comprising sintering metal members and joining a plurality of metal members together.
[9] The method for joining metal members according to [8], wherein the metal member is a metal substrate or a metal part of an electronic component.
[9-1] The method for joining metal members according to [8-1], wherein the metal member is a metal substrate or a metal part of an electronic component. Is achieved.

This purpose is
“The paste-like silver particle composition according to [10] [3] or [4] is applied onto a substrate coated with an adhesive, and heated at 70 ° C. or more and 400 ° C. or less to thereby produce the volatile dispersion. A method for producing a printed wiring board, comprising evaporating a medium and sintering the silver particles to form silver wiring on an adhesive.
[10-1] The volatile dispersion medium is volatilized by applying the paste-like silver particle composition according to [5] onto a substrate coated with an adhesive and heating at 70 ° C to 400 ° C. A method for producing a printed wiring board, comprising: sintering silver particles to form silver wiring on an adhesive. "

This purpose is
“The paste-like silver particle composition according to [11] [3] or [4] is applied in the form of dots to a pad portion for electric circuit connection on a semiconductor element or an electrode portion for electric circuit connection on a substrate, Electrical circuit connection, characterized by forming silver bumps on a semiconductor element or a substrate by volatilizing the volatile dispersion medium and sintering the silver particles by heating at a temperature of from ℃ to 400 ℃ Method of manufacturing bumps.
[11-1] The paste-like silver particle composition according to [5] is applied in the form of dots to an electric circuit connecting pad portion on a semiconductor element or an electric circuit connecting electrode portion on a substrate, and is applied at 70 ° C. or more and 400 A bump for electrical circuit connection, characterized in that by heating at ℃ or less, the volatile dispersion medium is volatilized to sinter the silver particles to form a silver bump on a semiconductor element or substrate. Production method. Is achieved.

According to the method for producing heat-sinterable silver particles of the present invention, the silver particles (A) are sintered together by heating, particularly by heating at 70 ° C. or more and 400 ° C. or less, and the adhesive strength, hardness, and electrical conductivity. Silver particles that become solid silver excellent in thermal conductivity can be easily produced.
In the paste-like silver particle composition of the present invention, the volatile dispersion medium (B) is volatilized by heating, and particularly when heated at 70 ° C. or more and 400 ° C. or less, the silver particles (A) sinter to bond strength. Solid silver with excellent hardness, electrical conductivity, and thermal conductivity.

According to the method for producing solid silver of the present invention, the volatile dispersion medium (B) is volatilized by heating, and the silver particles (A) are sintered together by heating at 70 ° C. or more and 400 ° C. or less. Solid silver excellent in adhesive strength, hardness, electrical conductivity and thermal conductivity can be produced.
According to the method for joining metal members of the present invention, the volatile dispersion medium (B) is volatilized by heating, and the silver particles (A) are sintered together, whereby a plurality of metal members are electrically and thermally conductive. It can be bonded well and well.

According to the method for producing a printed wiring board of the present invention, the volatile dispersion medium (B) is volatilized and the silver particles (A) are sintered together, resulting in wear resistance, adhesion to a substrate, electrical conductivity, and heat conduction. A printed wiring board having silver wiring with excellent properties can be manufactured. Moreover, a circuit board can be manufactured by mounting a chip or the like on the printed wiring board by the bonding method.

According to the method for manufacturing a bump for connecting an electric circuit of the present invention, a silver bump having excellent electrical conductivity and thermal conductivity can be efficiently and easily formed on a semiconductor element or a substrate.

2 is a differential thermal analysis (temperature increase rate: 5 ° C./min) chart in air for silver particles before and after substitution in Example 1. FIG. It is a differential thermal analysis (temperature rising rate 5 degree-C / min) chart in the atmosphere about the silver particle before substitution in Example 3 after substitution. It is a top view of the test body A for adhesive strength measurement in an Example. The paste-like silver particle composition 2 is printed and applied on a silver substrate 1 with a metal mask, and after mounting the silver chip 3, it is heated to bond the silver substrate 1 and the silver chip 3 and measure the adhesive strength. . It is a side view of the XX line direction in FIG.

The method for producing the heat-sinterable silver particles of the present invention comprises the surface of the silver particles coated with the higher fatty acid (a1) or the higher fatty acid (a1) derivative (a2). ) Derivative (a2) is substituted with higher fatty acid (b1) lower than higher fatty acid (a1) or derivative (b2) of higher fatty acid (b1). As a result of the replacement, heat-sinterable silver particles whose surface is coated with a higher / intermediate fatty acid (b1) lower than the higher fatty acid (a1) or a derivative (b2) of the higher / intermediate fatty acid (b1) are produced. .

The paste-like silver particle composition of the present invention comprises (A) silver particles whose surface is coated with a high / intermediate fatty acid (b1) or a high / intermediate fatty acid (b1) derivative (b2), and (B) a volatile dispersion. In the paste-like silver particle composition in which the volatile dispersion medium is volatilized by heating and the silver particles are sintered together by heating, the high / intermediate fatty acid (b1) or the high / intermediate fatty acid coating the silver particle surface The fatty acid (b1) derivative (b2) is a higher fatty acid (a1) or a higher fatty acid (a1) derivative (a2) that has been previously coated on the surface of silver particles, and is a higher / intermediate grade lower than the higher fatty acid (a1). It is characterized by being substituted with a fatty acid (b1) or a derivative (b2) of a high / intermediate fatty acid (b1).

The shape of the silver particles in the silver particles whose surface is coated with the higher fatty acid (a1) or the higher fatty acid (a1) derivative (a2) is not particularly limited, and is spherical, acicular, angular, dendritic, fibrous, Examples include flakes (pieces), granules, irregular shapes, and teardrops (see JIS Z2500: 2000). Further examples include oval, spongy, grape, spindle, substantially cubic, hexagonal plate, columnar, rod, porous, lump, square, round. From the viewpoint of ease of production and ease of procurement, the shape is preferably spherical, granular and flaky.

The spherical shape referred to here is a shape that is almost a sphere (see JIS Z2500: 2000). The spherical shape is not necessarily required, and the ratio of the major axis (DL) to the minor axis (DS) of the particle (DL) / (DS) (sometimes referred to as spherical coefficient or sphericity) is 1.0 to 1. Those in the range of .2 are preferred.
Granular is not an irregular shape but a shape with almost equal dimensions (see JIS Z2500: 2000).
The flake shape (strip shape) is a plate-like shape (see JIS Z2500: 2000) and is also called a scale shape because it is a thin plate shape like a scale.

The aspect ratio of the flaky silver particles mentioned here is preferably such that the value of [average major axis of particles (μm)] / [average minor axis of particles (μm)] is in the range of 1.0 to 8.0. . In calculating the aspect ratio, the average major axis and the average minor axis are observed with a scanning electron microscope at a magnification of about 1000 to 3000 times, and the major axis and minor axis of 20 or more silver particles in the observed image are measured. Then, it can be obtained as the average value. The aspect ratio may be a value of [average particle major axis (μm)] / [average particle thickness (μm)]. In this case, the aspect ratio is in the range of 2.0 to 20.0. preferable. Here, the average major axis can be obtained by the method described above, and the average thickness is obtained by preparing a sample in which flaky silver particles are solidified with a curable resin such as an epoxy resin. The cross section is observed with a scanning electron microscope at a magnification of about 5000 to 20000 times, and the thickness of 20 or more silver particles in the observed image is measured to obtain an average value thereof. No matter the shape, the particle size distribution is not limited.

The flake shape is usually processed into a flake shape by putting spherical or granular silver particles together with ceramic balls into a rotary drum device such as a ball mill and physically striking the silver particles with the balls. At this time, when the surface of the spherical or granular silver particles used as a raw material is not coated with higher fatty acids or higher fatty acid derivatives, etc., a small amount of higher fatty acids or higher fatty acid derivatives are added to reduce or prevent aggregation between silver particles. Is done. Therefore, the flaky silver particles are usually coated with a high fatty acid or a high fatty acid derivative.

The average particle diameter of the silver particles in the present invention is preferably larger than 0.1 μm and not larger than 20 μm from the viewpoint of heat sinterability. This average particle diameter is an average particle diameter (median diameter D50) of primary particles obtained by a laser diffraction / scattering particle size distribution measurement method. When the average particle diameter exceeds 20 μm, the sinterability between silver particles becomes low, and it is difficult to obtain excellent strength, electrical conductivity, thermal conductivity, and adhesion. Therefore, the average particle diameter is preferably 20 μm or less, and more preferably 10 μm or less. However, when the so-called nano-size is 0.1 μm or less, the surface activity of the silver particles is too strong, and the storage stability of the pasty silver particle composition may be lowered, so that it is larger than 0.1 μm. From such a viewpoint, the average particle diameter of the silver particles is preferably 0.2 to 10 μm. The median diameter D50 is also referred to as a laser diffraction method 50% particle size (see Japanese Patent Application Laid-Open No. 2003-55701) or a volume cumulative particle size D50 (see Japanese Patent Application Laid-Open No. 2007-84860).

The laser diffraction / scattering particle size distribution measurement method is a method of irradiating a metal beam with a laser beam and measuring the intensity of the diffracted light or scattered light emitted in various directions depending on the size of the metal particle. This is a general-purpose measurement method for determining the particle size of particles. Many measuring devices are commercially available (for example, a laser diffraction particle size distribution measuring device SALD manufactured by Shimadzu Corporation, a laser diffraction scattering particle size distribution measuring device Microtrac manufactured by Nikkiso Co., Ltd.), and using these, the average particle size can be easily obtained. The diameter (median diameter D50) can be measured. In the case where the aggregation of the metal particles is strong, it is preferably measured after being dispersed in a primary particle state by a homogenizer.

The production method of the silver particles is not particularly limited, and examples thereof include a reduction method, a pulverization method, an electrolysis method, an atomization method, a heat treatment method, and a combination method thereof, but high / intermediate fatty acid (b1) or high / intermediate fatty acid The reduction method is particularly preferable from the viewpoint of the substitution effect by the derivative (b2) of b1).

The higher fatty acid (a1) previously coated on the surface of the silver particles is a fatty acid having 15 or more carbon atoms, pentadecanoic acid, hexadecanoic acid (palmitic acid), heptadecanoic acid (margaric acid), octadecanoic acid (stearic acid). 12-hydroxyoctadecanoic acid (12-hydroxystearic acid), eicosanoic acid (arachinic acid), docosanoic acid (behenic acid), tetracosanoic acid (lignoceric acid), hexacosanoic acid (serotic acid), octacosanoic acid (montanic acid), etc. Linear saturated fatty acids; branched saturated fatty acids such as 2-pentylnonanoic acid, 2-hexyldecanoic acid, 2-heptyldodecanoic acid and isostearic acid; palmitoleic acid, oleic acid, isooleic acid, elaidic acid, linoleic acid, linolenic acid, ricinoleic acid , Gadrenic acid, erucic acid, ceracoleic acid, etc. Japanese fatty acids are exemplified.

The higher fatty acid (a1) in the higher fatty acid (a1) or the higher fatty acid (a1) derivative (a2) previously coated on the surface of the silver particles has a higher number of higher fatty acids having 17 or more carbon atoms, and the number of carbon atoms Is higher in 17 to 24 higher fatty acids. Examples of such higher fatty acids include margaric acid, stearic acid, oleic acid, linoleic acid, and linolenic acid.

Examples of the higher fatty acid (a1) derivative (a2) include higher fatty acid metal salts, higher fatty acid esters, higher fatty acid amine salts, and higher fatty acid amides.
Examples of the metal salt of the higher fatty acid metal salt include alkali metal salts (for example, sodium salts and potassium salts), alkaline earth metal salts (for example, magnesium salts and calcium salts), aluminum salts, and transition metal salts. Examples of higher fatty acid esters include alkyl esters (for example, methyl esters and ethyl esters) and phenyl esters. Examples of amines of higher fatty acid amine salts include primary alkyl amines (eg, ethylamine, propylamine), primary phenylamines, secondary alkylamines (eg, diethylamine), and tertiary alkylamines. Examples of the amide of the higher fatty acid amide include N-alkylamide (for example, N-ethylamide), N, N′-dialkylamide (for example, N, N′-diethylamide), and N-phenylamide. The alkali metal salt of higher fatty acid (a1) and the amine salt of higher fatty acid (a1) are usually hydrophilic.
Silver particles whose silver surface is coated with higher fatty acid (a1) usually show water repellency.

The higher fatty acid (b1), which is lower than the higher fatty acid (a1), used to replace the higher fatty acid (a1) or the higher fatty acid (a1) derivative (a2) previously coated on the silver particle surface, High and intermediate fatty acids having 16 or less carbon atoms are preferable, and intermediate fatty acids having 8 to 14 carbon atoms are more preferable. Examples of such high and intermediate fatty acids include octanoic acid, capric acid, lauric acid, and myristic acid. In the present invention, “lower” means that the number of carbon atoms of the fatty acid is as small as one, and the number of carbon atoms is preferably 2 or more, more preferably 3 or less, in terms of the substitution effect.
Silver particles whose silver surface is coated with a high / intermediate fatty acid (b1) usually show water repellency.

Examples of the derivatives (b2) of lower and higher intermediate fatty acids (b1) include high / intermediate fatty acid metal salts, high / intermediate fatty acid esters, high / intermediate fatty acid amides, and high / intermediate fatty acid amine salts.
Examples of the metal salt of the high / intermediate fatty acid metal salt include alkali metal salts (for example, sodium salts and potassium salts), alkaline earth metal salts (for example, magnesium salts and calcium salts), aluminum salts, and transition metal salts. Examples of the esters of high / intermediate fatty acid esters include alkyl esters (for example, methyl esters and ethyl esters) and phenyl esters. Examples of the amides of high and intermediate fatty acid amides include N-alkylamides (for example, N-ethylamide), N, N′-dialkylamides (for example, N, N′-diethylamide), and N-phenylamide. The alkali metal salt of high / intermediate fatty acid and the amine salt of high / intermediate fatty acid are hydrophilic.

The heat-sinterable silver particles of the present invention have a higher fatty acid (a1) or higher fatty acid (a1) derivative of silver particles whose surface is coated with a higher fatty acid (a1) or a higher fatty acid (a1) derivative (a2). It is produced by replacing (a2) with a higher / intermediate fatty acid (b1) lower than the higher fatty acid (a1) or a derivative (b2) of the higher / intermediate fatty acid (b1). From the viewpoint of substitution ability, lower high / intermediate fatty acids (b1) are preferable, and then water-repellent derivatives of lower high / intermediate fatty acids (b1) are preferable.

The substitution method is not particularly limited, and for example, silver particles whose surface is coated with a higher fatty acid (a1) or a derivative (a2) of a higher fatty acid (a1) may be lower or higher than the higher fatty acid (a1). There is a method of immersing in a solution of the fatty acid (b1) or the derivative (b2) of the high / intermediate fatty acid (b1). At this time, the liquid may be stirred or shaken by a stirrer, a shaker, an ultrasonic vibrator, or the like.

If the lower high / medium fatty acid (b1) or the high / medium fatty acid (b1) derivative (b2) is solid at room temperature, the surface is dissolved in an organic solvent such as acetone or toluene, and then the surface is higher fatty acid. It is preferable to mix with silver particles coated with (a1) or a derivative (a2) of higher fatty acid (a1). The mixing ratio of the lower high / medium fatty acid (b1) or the derivative (b2) of the high / medium fatty acid (b1) and the organic solvent is not particularly limited as long as it can dissolve the former.

Although the temperature at the time of the said immersion is not specifically limited, In order to suppress aggregation of silver particles, it is preferable that it is below normal temperature. The dipping time is not particularly limited as long as it is sufficient to remove the higher fatty acid (a1) or the higher fatty acid (a1) derivative (a2) that has coated the surface of the silver particles.
Next, the silver particles are separated by filtering the immersion liquid or the mixture.

The silver particles thus separated are coated on the surface with a higher fatty acid (b1) lower than the higher fatty acid (a1) or a derivative of the higher fatty acid (b1) (b2). Since an excess of lower high / intermediate fatty acid (b1) or a derivative of high / medium fatty acid (b1) (b2) is attached, it is preferable to remove such excess. Further, since higher fatty acid (a1) or higher fatty acid (a1) derivative (a2) previously coated on the surface of silver particles may be adhered, it is preferable to remove these.

For that purpose, it is preferable to wash the separated silver particles with a volatile organic solvent, and examples of the organic solvent for this purpose include acetone, methanol, ethanol, isopropyl alcohol, methyl ethyl ketone, dimethyl sulfoxide, and tetrahydrofuran. This is because these organic solvents have a low boiling point and high volatility, and therefore can be easily removed by air drying or drying under reduced pressure at room temperature. Further, when the silver particles are produced by a reduction method, there is an advantage that the organic reducing agent adhering to the silver particles is also removed.

The amount of lower high / intermediate fatty acid (b1) or high / medium fatty acid (b1) derivative (b2) covering the surface of the silver particles thus obtained is determined by the sinterability of the silver particles and the sintering. From the viewpoint of the strength, electrical conductivity and thermal conductivity of the solid silver thus produced, it is preferably 0.01% or more, preferably 2.0% by weight or less, particularly 0.05% or more. It is preferably 1.0% by weight or less.

The amount of the high / intermediate fatty acid (b1) or the high / medium fatty acid (b1) derivative (b2) covering the silver particles can be measured by a usual method. The silver particles are heated to 500 ° C in an air stream and the high / intermediate fatty acid (b1) or high / medium fatty acid (b1) derivative (b2) adhering to the silver particles is oxidized, decomposed or volatilized or burned. A thermogravimetric analysis of removing and measuring weight loss is illustrated. Another method is to heat the silver particles in an oxygen stream and change the carbon in the high / intermediate fatty acid (b1) or high / medium fatty acid (b1) derivative (b2) attached to the silver particles to carbon dioxide. And a method of quantitative analysis by infrared absorption spectroscopy. In these cases, the total amount of the surface of the silver particles and the organic reducing agent in the silver particles is quantified, but the residual amount of the organic reducing agent is negligible and can be ignored.

Silver particles whose surface is coated with a higher fatty acid (a1) or a derivative of higher fatty acid (a1) (a2), higher / intermediate fatty acid (b1) or higher / intermediate fatty acid (b1) lower than the higher fatty acid (a1) In the silver particles coated with the derivative (b2), the surface of the silver particles may be oxidized. However, if the ratio of silver oxide is high, a large amount of oxygen is generated during heating, which may cause voids in the solid silver produced by sintering. 50% or less of the entire surface of the particles is preferable, 20% or less is more preferable, and 2% or less is more preferable. Especially in use cases such as die-bonding agents that become semi-sealed with a relatively large bonding area due to large chip connection such as memory and CPU, the presence of silver oxide causes a decrease in adhesive strength due to void generation. 10% or less is preferable.

The silver particles coated with lower high / intermediate fatty acid (b1) or high / medium fatty acid (b1) derivative (b2) have high heat sinterability, so until a paste-like silver composition is obtained. It is better not to heat as much as possible.

The paste-like silver particle composition of the present invention comprises a silver particle (A) coated with a high / intermediate fatty acid (b1) or a high / medium fatty acid (b1) derivative (b2) and a volatile dispersion medium (B). It is a mixture, and powdery silver particles are made into a paste by the action of the volatile dispersion medium (B). By making a paste, it can be discharged in a thin line form from a cylinder or nozzle, and it can be easily applied with a metal mask, and can be easily applied to the shape of an electrode. The paste form includes a cream form and a slurry form.

The volatile dispersion medium is used instead of the non-volatile dispersion medium because the silver particles easily sinter when the dispersion medium volatilizes in advance when the silver particles are sintered by heating. This is because electrical conductivity and thermal conductivity are likely to increase. The volatile dispersion medium does not alter the surface of the silver particles and has a boiling point of 60 ° C. or higher and preferably 300 ° C. or lower. When the boiling point is less than 60 ° C., the solvent easily evaporates during the operation of preparing the paste-like silver particle composition, and when the boiling point is greater than 300 ° C., the volatile dispersion medium remains after the silver particles are sintered. Because it might be.

As such a volatile dispersion medium (B), water; volatile monohydric alcohols such as ethyl alcohol, propyl alcohol, butyl alcohol, pentyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, and benzyl alcohol Volatile polyhydric alcohols such as ethylene glycol and propylene glycol; volatile aliphatic hydrocarbons such as lower n-paraffins and lower isoparaffins; volatile aromatic hydrocarbons such as toluene and xylene; acetone, methyl ethyl ketone, methyl isobutyl ketone , Cyclohexanone, diacetone alcohol (4-hydroxy-4-methyl-2-pentanone), 2-octanone, isophorone (3,5,5-trimethyl-2-cyclohexen-1-one), dibutylketone Volatile ketones such as ethyl (2,6-dimethyl-4-heptanone); volatile acetates such as ethyl acetate (ethyl acetate) and butyl acetate; methyl butyrate, methyl hexanoate, methyl octanoate, methyl decanoate Volatile aliphatic carboxylic acid esters such as: volatile ethers such as tetrahydrofuran, methyl cellosolve, propylene bricol monomethyl ether, methylmethoxybutanol, butyl carbitol; low molecular weight volatile silicone oils and volatile organic modified silicone oils Is done.

Two or more volatile dispersion media (B) may be used in combination. When water is used as the volatile dispersion medium (B), the silver particles (A) coated with the high / intermediate fatty acid (b1) or the high / medium fatty acid (b1) derivative exhibit water repellency. It is preferable to use together with a water-soluble volatile dispersion medium (B).

The amount of the volatile dispersion medium (B) is sufficient to make the silver particles (A) coated with the high / intermediate fatty acid (b1) or the high / medium fatty acid (b1) derivative (b2) into a paste. The amount may be 5 to 20 parts by weight, preferably 6 to 14 parts by weight per 100 parts by weight of the heat-sinterable silver particles (A). The paste-like silver particle composition of the present invention includes reduced silver, atomized silver, silver colloid, silver alloy, surface silver-coated powder, and other metals other than the heat-sinterable silver particles (A) unless they are contrary to the object of the present invention. You may contain additives, such as a system and a nonmetallic powder, a metal compound, a metal complex, a thixotropic agent, a stabilizer, and a coloring agent.

In the paste-like silver particle composition of the present invention, the volatile dispersion medium (B) is volatilized by heating, and the heat-sinterable silver particles (A) are sintered to each other so that strength, electrical conductivity, and heat conduction are obtained. It becomes solid silver having excellent properties and exhibits adhesiveness. At this time, the volatile dispersion medium (B) may be volatilized, and then the heat-sinterable silver particles (A) may be sintered together, or the silver particles may be sintered together with the volatilization of the volatile dispersion medium. Since silver inherently has high strength and extremely high electrical and thermal conductivity, the sintered product of the silver particles of the present invention also has high strength and extremely high electrical and thermal conductivity. The heating temperature at this time should just be the temperature which a volatile dispersion medium volatilizes and silver particle can sinter, and is 70 degreeC or more normally. However, if the temperature exceeds 400 ° C., the volatile dispersion medium (B) may suddenly evaporate and adversely affect the shape of the solid silver. Therefore, the temperature must be 400 ° C. or less, preferably 220 ° C. It is below, More preferably, it is 180 degrees C or less, More preferably, it is 150 degrees C or less.

The electrical conductivity of solid silver formed by sintering silver particles (A) coated with high / intermediate fatty acid (b1) or high / medium fatty acid (b1) derivative (b2) is 1 in volume resistivity. It is preferably × 10 ⁻⁴ Ω · cm or less, and more preferably 1 × 10 ⁻⁵ Ω · cm or less. The thermal conductivity is preferably 10 W / m · K or more, and more preferably 30 W / m · K or more. The shape of the solid silver formed by sintering the heat-sinterable silver particles (A) is not particularly limited, and is a sheet shape, a film shape, a tape shape, a linear shape, a disk shape, a block shape, a spot shape, an indefinite shape. Is exemplified.

When the paste-like silver particle composition of the present invention is heated, the volatile dispersion medium (B) is volatilized and the heat-sinterable silver particles (A) are sintered, so that the strength, electrical conductivity, and thermal conductivity are excellent. , Metal parts that were in contact, such as gold substrate, gold-plated substrate, silver substrate, silver-plated metal substrate, copper substrate, palladium substrate, palladium-plated metal substrate, platinum substrate, platinum-plated metal substrate, aluminum substrate, nickel-plated substrate, Since it becomes solid silver having adhesiveness to metal parts such as metal substrates such as tin-plated metal substrates or metal substrates, electrodes on electrically insulating substrates, electronic components, electronic devices having metal substrates and metal parts, Useful for joining electrical components, electrical devices, etc. Such bonding includes bonding of chip components such as capacitors and resistors and circuit boards; bonding of semiconductor chips such as diodes, transistors, memories, ICs, and CPUs to lead frames or circuit boards; cooling semiconductor chips having high heat generation and cooling. The joining with a board is illustrated.

Although washing of the silver particle (A) sintered product produced by heating the paste-like silver particle composition of the present invention is unnecessary, it may be washed with water or an organic solvent. In particular, when the volatile dispersion medium (B) is a hydrophilic solvent, it can be washed with water, and there is no problem of VOC generation as in the case of washing with an organic solvent such as alcohol. Since each component of the paste-like silver particle composition of the present invention has few impurities, it can be easily washed.

When the paste-like silver particle composition of the present invention is heated, the volatile dispersion medium (B) is volatilized, and the heat-sinterable silver particles (A) are sintered together, resulting in high strength, extremely high electrical conductivity and heat. It becomes solid silver having conductivity. Therefore, a curable adhesive such as an epoxy resin adhesive, a silicone resin adhesive, a printed wiring board coated with a polyimide resin adhesive, or a primer composition was applied, and then a curable adhesive was applied. Before the adhesive is cured on the printed wiring board, the paste-like silver particle composition is applied and heated to form a silver wiring having excellent wear resistance and adhesion to the board. it can. The method for applying the paste-like silver particle composition of the present invention is not particularly limited, and includes dispensing, printing (for example, screen printing), metal mask coating, spraying, brushing, and the like. Moreover, a circuit board can be manufactured by mounting a chip or the like on the printed wiring board.

The heating temperature may be a temperature at which the volatile dispersion medium (B) can be volatilized and the silver particles can be sintered, and is usually 70 ° C. or higher. However, if the temperature exceeds 400 ° C., the volatile dispersion medium (B) may suddenly evaporate and adversely affect the shape of the solid silver. Therefore, the temperature must be 400 ° C. or less, preferably 220 ° C. It is below, More preferably, it is 180 degrees C or less, More preferably, it is 150 degrees C or less.

When the paste-like silver particle composition of the present invention is heated, the volatile dispersion medium (B) is volatilized, and the silver particles (A) are sintered together, thereby having high strength, extremely high electrical conductivity, and thermal conductivity. It becomes solid silver. Accordingly, the volatile dispersion medium is volatilized by applying the paste-like silver particle composition in a dot shape to the electric circuit connecting pad part on the semiconductor element or the electric circuit connecting end part on the substrate and heating. Then, the silver particles can be sintered to produce a silver bump on the semiconductor element or the substrate.

Here, examples of the semiconductor element include a diode, a transistor, a memory, and a CPU.
Examples of the method for applying the paste-like silver particle composition in the form of dots include dripping, dispensing, printing (for example, screen printing), and metal mask application.
The heating temperature may be a temperature at which the volatile dispersion medium (B) can be volatilized and the silver particles can be sintered, and is usually 70 ° C. or higher. However, if the temperature exceeds 400 ° C., the volatile dispersion medium (B) may suddenly evaporate and adversely affect the shape of the solid silver. Therefore, the temperature must be 400 ° C. or less, preferably 220 ° C. It is below, More preferably, it is 180 degrees C or less, More preferably, it is 150 degrees C or less.

Since the pasty silver particle composition of the present invention contains a volatile dispersion medium (B), it is preferably stored in a sealed container. When used after long-term storage, it is preferable to use the container after shaking or stirring the container. Refrigerated storage may be performed for the purpose of improving storage stability, and the storage temperature is 10 ° C. or lower, but it is preferably a temperature at which the volatile dispersion medium (B) does not solidify particularly in a sealed container. When a syringe is used for the sealed container, a small amount can be discharged using a dispenser.

Examples and comparative examples of the present invention will be given. In Examples and Comparative Examples, “part” means “part by weight” and “%” means “% by weight”. The aspect ratio of flaky silver particles, the hardness, adhesive strength, volume resistivity and thermal conductivity of solid silver produced by heating and sintering a paste-like silver particle composition are as follows. Measured at 25 ° C.

[Aspect ratio of flaky silver particles]
The flaky silver particles are observed with a scanning electron microscope at a magnification of 2000 times, the major axis and minor axis of the 20 silver particles in the observed image are measured, and the average value of each is determined as the average major axis and the average minor axis. The aspect ratio A was calculated from [average particle major axis (μm)] / [average particle minor axis (μm)].
The flaky silver particles are observed with a scanning electron microscope at a magnification of 10,000 times, and the major axis and thickness of 20 silver particles in the observed image are measured. Then, the aspect ratio B was calculated by [average major particle diameter (μm)] / [average particle thickness (μm)].

[Differential thermal analysis in air for silver particles before and after substitution]
Using a differential thermothermal gravimetric simultaneous measurement device (DTG-60AH type manufactured by Shimadzu Corporation), the temperature of the silver particles before and after substitution is increased from 23 ° C. to 400 ° C. at a rate of temperature increase of 5 ° C./min. A DTA curve was taken.

A paste-like silver particle composition was applied on a polytetrafluoroethylene resin plate having a width of 50 mm, a length of 50 mm, and a thickness of 1.0 mm, using a 500 μm-thick metal mask having an opening of a width of 10 mm and a length of 10 mm. Then, it was heated in a forced circulation oven at 150 ° C. for 2 hours to form film-like silver. The hardness of the film-like silver was measured by a method according to JIS Z 2244.

[Adhesive strength]
On a silver substrate (silver purity 99.99%) 1 having a width of 25 mm, a length of 70 mm, and a thickness of 1.0 mm, four openings having a width of 2.5 mm and a length of 2.5 mm are provided at an interval of 10 mm. The paste-like silver particle composition 2 is applied using a metal mask having a thickness of 100 μm, and a silver chip (silver purity 99.99%) having a width of 2.5 mm × a length of 2.5 mm × a thickness of 0.5 mm is formed thereon 3 After mounting, the film was joined by heating in a forced circulation oven at 150 ° C. for 2 hours. The side surface of the silver chip 3 having a width of 2.5 mm, a length of 2.5 mm, and a thickness of 0.5 mm of the test specimen for measuring the adhesive strength thus obtained was pressed at a pressing speed of 23 mm / min by an adhesive strength tester. The bond strength {unit; N (kgf)} was defined as the load when the joint was sheared and broken. The number of adhesion strength measurements was four, and the average value of four times was defined as the adhesion strength.

[Volume resistivity]
A paste-like silver particle composition was applied on a polytetrafluoroethylene resin plate having a width of 50 mm, a length of 50 mm, and a thickness of 1.0 mm, using a 500 μm-thick metal mask having an opening of a width of 10 mm and a length of 10 mm. Then, it was heated in a forced circulation oven at 150 ° C. for 2 hours to form film-like silver. The volume resistivity (unit: Ω · cm) of the film-like silver was measured by a method according to JIS K 7194.

[Thermal conductivity]
A paste-like silver particle composition is applied onto a polytetrafluoroethylene resin plate having a width of 50 mm, a length of 50 mm, and a thickness of 1.0 mm using a 2 mm thick metal mask having an opening of a width of 10 mm and a length of 10 mm. Then, it was heated in a forced circulation oven at 150 ° C. for 2 hours to obtain plate-like silver. The plate-shaped silver was measured for thermal conductivity (unit: W / mK) by a laser flash method using a thermal constant measuring device.

[Reference example]
The method for producing silver particles (A) in which the higher fatty acid (a1) covering the surface is replaced with lower higher / intermediate fatty acid (b1) is as follows.
In a beaker, 100 parts of silver particles coated with a higher fatty acid (a1) and lower higher / intermediate fatty acid (b1) {if liquid at 25 ° C. were used as they were. In the case of a solid at 25 ° C., 100 parts of acetone (used as a 30% solution with Wako Pure Chemical Industries, Ltd., reagent grade 1) were added, and stirred at 25 ° C. for 5 hours using a magnetic stirrer. . Let stand for 10 minutes to remove as much of the supernatant liquid as possible (higher and intermediate fatty acids (b1) lower than higher fatty acid (a1) or their acetone solution), then acetone (Wako Pure Chemical Industries, Ltd., reagent grade 1) ) 100 parts were added and similarly stirred at 25 ° C. for 10 minutes using a magnetic stirrer. In the same manner, the supernatant was removed as much as possible, then acetone was added again to wash the silver particles in the same manner. After repeating this five times, the silver particles were taken out and air-dried at 25 ° C. for 16 hours.

[Example 1]
In the production method of the reference example, flaky silver particles produced by a commercially available reduction method and coated with stearic acid on the surface (average particle size (median diameter D50) of primary particles obtained by laser diffraction method is 1.2 μm). The aspect ratio A is 1.6, the aspect ratio B is 2.4, and the amount of organic substances (note: the total amount of stearic acid and a small amount of organic reducing agent) is 0.3% by weight. And stearic acid (18 carbon atoms) covering the surface of the silver particles using octanoic acid (made by Wako Pure Chemical Industries, Ltd., special grade reagent) as a lower and higher intermediate fatty acid (b1). , Molecular weight 284) was substituted with octanoic acid (8 carbon atoms, molecular weight 144) to obtain silver particles (A).

In order to confirm that the stearic acid was replaced with octanoic acid, differential thermal analysis (at a heating rate of 5 ° C./min) in the atmosphere was performed on the silver particles before and after the substitution, and the results are shown in FIG. According to FIG. 1, the oxidative decomposition peak temperature of stearic acid before substitution is 210 ° C. The oxidative decomposition peak temperature after substitution is 199 ° C., and no exothermic peak is detected at 210 ° C. of the oxidative decomposition peak temperature of stearic acid. Therefore, it was found that stearic acid was replaced with octanoic acid.

A paste-like silver particle composition is prepared by adding 3.5 parts of 1-hexanol (Wako Pure Chemical Industries, Ltd., reagent grade) to 50 parts of the silver particles (A) and mixing with a spatula until uniform. Prepared. This paste-like silver particle composition could be applied in a good shape without sagging or flowing during application with a metal mask. With respect to this paste-like silver particle composition, the hardness, adhesion strength, volume resistivity, and thermal conductivity of solid silver as a heat-sintered product were measured, and the results are summarized in Table 1. The film-like silver used for the hardness measurement had sufficient hardness to be solid. From the above results, this paste-like silver particle composition is useful for producing solid solid silver, useful for joining metal members firmly with good electrical conductivity and thermal conductivity, Useful for forming silver wiring with excellent wear resistance, adhesion to substrates, electrical and thermal conductivity, and useful for forming silver bumps on semiconductor devices or substrates all right.

[Example 2]
In Example 1, paste was used in the same manner as in Example 1 except that lower isoparaffin (manufactured by Nippon Petrochemical Co., Ltd., trade name Isosol 300) having a distillation range of 106 ° C. to 202 ° C. was used instead of 1-hexanol. A silver particle composition was prepared. This paste-like silver particle composition could be applied in a good shape without sagging or flowing during application with a metal mask. With respect to this paste-like silver particle composition, the hardness, adhesion strength, volume resistivity, and thermal conductivity of solid silver as a heat-sintered product were measured, and the results are summarized in Table 1. The film-like silver used for the hardness measurement had sufficient hardness to be solid. From the above results, this paste-like silver particle composition is useful for producing solid solid silver, useful for joining metal members firmly with good electrical conductivity and thermal conductivity, Useful for forming silver wiring with excellent wear resistance, adhesion to substrates, electrical and thermal conductivity, and useful for forming silver bumps on semiconductor devices or substrates all right.

[Example 3]
In the production method of the reference example, granular silver particles (without a coating agent) produced by a commercially available reduction method were put into a ball mill, and oleic acid was added to flake and the surface was made of oleic acid. Coated flaky silver particles {average particle diameter (median diameter D50) of primary particles obtained by laser diffraction method is 3.0 µm, aspect ratio A is 3.3, aspect ratio B is 15.3 30% of lauric acid (manufactured by Wako Pure Chemical Industries, Ltd., special grade of reagent) and the amount of organic substances (note: the total amount of oleic acid and a small amount of organic reducing agent is 0.3% by weight). A flaky silver particle (A) in which oleic acid (18 carbon atoms, molecular weight 282) covering the surface of silver particles was replaced with lauric acid (12 carbon atoms, 200 molecular weight) using a% acetone solution. Obtained.

In order to confirm that oleic acid was replaced with lauric acid, differential thermal analysis (at a temperature rising rate of 5 ° C./min) in air was performed on the silver particles before and after the substitution, and the results are shown in FIG. According to FIG. 2, the oxidative decomposition peak temperature of oleic acid before substitution is 227 ° C. The oxidative decomposition peak temperature after substitution is 212 ° C., and no exothermic peak is detected in the vicinity of 227 ° C. of the oleic acid oxidative decomposition peak temperature. Therefore, it was found that oleic acid was replaced with lauric acid.

To 50 parts of the silver particles (A), 4 parts of lower isoparaffin having a distillation range of 106 ° C. to 202 ° C. (trade name Isosol 300, manufactured by Nippon Petrochemical Co., Ltd.) is added and mixed uniformly using a spatula. A pasty silver particle composition was prepared by mixing up to. This paste-like silver particle composition could be applied in a good shape without sagging or flowing when applied with a metal mask. With respect to this paste-like silver particle composition, the hardness, adhesion strength, volume resistivity, and thermal conductivity of solid silver as a heat-sintered product were measured, and the results are summarized in Table 1. The film-like silver used for the hardness measurement had sufficient hardness to be solid. From the above results, this paste-like silver particle composition is useful for producing solid solid silver, useful for joining metal members firmly with good electrical conductivity and thermal conductivity, Useful for forming silver wiring with excellent wear resistance, adhesion to substrates, electrical and thermal conductivity, and useful for forming silver bumps on semiconductor devices or substrates all right.

[Comparative Example 1]
Instead of silver particles (A) in which stearic acid (18 carbon atoms, molecular weight 284) covering the surface of silver particles was replaced with octanoic acid (8 carbon atoms, molecular weight 144) in Example 2, commercially available The flaky silver particles produced by the above reduction method and coated on the surface with stearic acid (the average particle diameter (median diameter D50) of primary particles obtained by the laser diffraction method is 1.2 μm, and the aspect ratio A is 1. 6, silver particles coated with an aspect ratio B of 2.4 and an organic substance amount (note: the total amount of stearic acid and a small amount of organic reducing agent) is 0.3% by weight. A pasty silver particle composition was prepared in the same manner as in Example 2 except that it was used. This paste-like silver particle composition could be applied in a good shape without sagging or flowing during application with a metal mask. With respect to this paste-like silver particle composition, the hardness, adhesion strength, volume resistivity, and thermal conductivity of solid silver as a heat-sintered product were measured, and the results are summarized in Table 1. In particular, the adhesive strength was insufficient.

[Comparative Example 2]
In Example 3, instead of the flaky silver particles (A) in which the oleic acid (18 carbon atoms, molecular weight 282) covering the surface of the silver particles was replaced with lauric acid (12 carbon atoms, 200 molecular weight). A granular silver particle produced by a commercially available reduction method is put into a ball mill, and oleic acid is added to make a flake. The flaky silver particle whose surface is coated with oleic acid {laser diffraction method The average particle diameter (median diameter D50) of the primary particles obtained by the above is 3.0 μm, the aspect ratio A is 3.3, the aspect ratio B is 15.3, the amount of organic matter (note: oleic acid and A paste-like silver particle composition was prepared in the same manner as in Example 3 except that the total amount of the trace amount of the organic reducing agent was 0.3% by weight.
This paste-like silver particle composition could be applied in a good shape without sagging or flowing during application with a metal mask. With respect to this paste-like silver particle composition, the hardness, adhesion strength, volume resistivity, and thermal conductivity of solid silver as a heat-sintered product were measured, and the results are summarized in Table 1. In particular, the adhesive strength was insufficient.

[Comparative Example 3]
In Example 3, instead of the flaky silver particles (A) in which the oleic acid (18 carbon atoms, molecular weight 282) covering the surface of the silver particles was replaced with lauric acid (12 carbon atoms, 200 molecular weight). A flaky silver particle having a surface coated with lauric acid, which is produced by putting granular silver particles without a coating agent produced by a commercially available reduction method into a ball mill and adding lauric acid to form flakes. {The average particle diameter of the primary particles obtained by the laser diffraction method is 3.0 μm, the aspect ratio A is 2.9, the aspect ratio B is 9.0, and the amount of organic substances (note: lauric acid and trace amount The total amount of the organic reducing agent was 0.3 wt%} was used in the same manner as in Example 3 except that the pasty silver particle composition was prepared. This paste-like silver particle composition could be applied in a good shape without sagging or flowing during application with a metal mask. With respect to this paste-like silver particle composition, the hardness, adhesion strength, volume resistivity, and thermal conductivity of solid silver as a heat-sintered product were measured, and the results are summarized in Table 1. In particular, the adhesive strength was insufficient.

[Example 4]
An epoxy resin adhesive (trade name SW2214, manufactured by Sumitomo 3M Limited) is applied onto a 1.2 mm thick FRP plate using a 50 μm thick metal mask having an opening of 1 mm width × 50 mm length. The pasty silver particle composition of Example 2 was printed and applied in the same manner, over the applied epoxy resin adhesive. This ERP plate was heated in a forced circulation oven at 150 ° C. for 2 hours to cure the epoxy resin adhesive and sinter silver particles.
When the volume resistivity in the length direction of a silver wiring circuit having a width of 1 mm, a length of 50 mm and a thickness of 50 μm on this printed wiring board was measured, it was 9 × 10 ⁻⁶ Ω · cm, which was practically sufficient conductivity. Had.

[Comparative Example 4]
An epoxy resin wiring circuit having a width of 1 mm, a length of 50 mm, and a thickness of 50 μm was produced in the same manner as in Example 4 except that the paste-like silver particle composition of Example 2 was not used. As in Example 4, when the volume resistivity in the length direction was measured for an epoxy resin wiring circuit having a width of 1 mm, a length of 50 mm, and a thickness of 50 μm, it was 1 × 10 ⁺¹ Ω · cm or more, and the conductivity was It was very low.

[Example 5]
A copper wiring circuit (width 1 mm, length 50 mm, thickness 30 μm) formed on a 1.2 mm thick FRP plate is gold-plated on both ends of the electric circuit, 1 mm long, 1 mm wide, 100 μm thick The paste-like silver particle composition of Example 2 was printed and applied in the form of dots using a metal mask having the following openings. The FRP plate was heated in a forced circulation oven at 150 ° C. for 2 hours to sinter the silver particles, thereby producing electric circuit connecting bumps.
When the electric resistance between the electric circuit connecting bumps formed at both ends of the electric circuit was measured, it was less than 0.05Ω, and the electric conductivity was sufficiently practical.

The heat-sinterable silver particles produced by the production method of the present invention are useful as a main raw material for a paste-like silver particle composition.
The paste-like silver particle composition, solid silver production method and metal member joining method of the present invention include the formation of electrodes for various electronic components such as resistors and capacitors, and electrodes for various display elements, and conductive film for electromagnetic wave shielding. Chip-type ceramic electronic components such as formation, bonding of chip components such as capacitors, resistors, diodes, memories, arithmetic elements (CPUs) to substrates, formation of solar cell electrodes, multilayer ceramic capacitors, multilayer ceramic inductors, multilayer ceramic actuators, etc. It is useful for forming external electrodes, and forming conductive circuits on a printed circuit board.
The method for producing a wiring board of the present invention is useful for efficiently producing a printed wiring board having silver wiring.
The method for producing a bump for connecting an electric circuit of the present invention is useful for efficiently producing a silver bump on a semiconductor element or a substrate.

A Test specimen for measuring adhesive strength 1 Silver substrate 2 Pasty silver particle composition (solid silver after heating and sintering)
3 Silver chip

Claims (11)

Higher fatty acid (a1) or higher fatty acid (a1) or higher fatty acid (a1) derivative (a2) of silver particle coated with higher fatty acid (a1) or higher fatty acid (a1) derivative (a2) A method for producing heat-sinterable silver particles, characterized by substituting with a lower high / intermediate fatty acid (b1) or a derivative (b2) of a high / intermediate fatty acid (b1). 2. The heat-sinterable silver particles according to claim 1, wherein the higher fatty acid (a1) has 17 or more carbon atoms and the higher / intermediate fatty acid (b1) has 16 or less carbon atoms. Method. (A) The surface is composed of silver particles coated with high / intermediate fatty acid (b1) or a derivative (b2) of high / intermediate fatty acid (b1), and (B) a volatile dispersion medium. In the paste-like silver particle composition in which the medium is volatilized and the silver particles are sintered, the high / intermediate fatty acid (b1) or the high / intermediate fatty acid (b1) derivative (b2) covering the surface of the silver particles, The higher fatty acid (a1) or the higher fatty acid (a1) derivative (a2) previously coated on the surface of the silver particles is converted to a higher / intermediate fatty acid (b1) or higher / intermediate fatty acid (b1) lower than the higher fatty acid (a1). A paste-like silver particle composition, which is substituted with a derivative (b2) of 4. The paste-like silver particle composition according to claim 3, wherein the higher fatty acid (a1) has 17 or more carbon atoms and the higher / intermediate fatty acid (b1) has 16 or less carbon atoms. The average particle diameter (median diameter D50) of the silver particles (A) is larger than 0.1 μm and not larger than 20 μm, the shape is spherical, granular or flaky, and the boiling point of the volatile dispersion medium (B) is 60 ° C. or higher. The paste-like silver particle composition according to claim 3 or 4, wherein the composition is 300 ° C or lower. The paste-like silver particle composition according to claim 3, claim 4 or claim 5 is heated at 70 ° C or higher and 400 ° C or lower to volatilize the volatile dispersion medium and sinter the silver particles. A method for producing solid silver. 7. The solid state according to claim 6, wherein the produced solid silver has a volume resistivity of 1 × 10 ⁻⁴ Ω · cm or less and a thermal conductivity of 10 W / m · K or more. Silver production method. The paste-like silver particle composition according to claim 3, 4 or 5 is interposed between a plurality of metal members, and the volatile dispersion medium is volatilized by heating at 70 ° C to 400 ° C. A method for joining metal members, comprising sintering silver particles and joining a plurality of metal members. The metal member joining method according to claim 8, wherein the metal member is a metal substrate or a metal portion of an electronic component. The volatile dispersion medium is obtained by applying the paste-like silver particle composition according to claim 3, 4 or 5 on a substrate coated with an adhesive and heating at 70 ° C to 400 ° C. The method for producing a printed wiring board is characterized in that the silver particles are sintered to form silver wiring on the adhesive. The paste-like silver particle composition according to claim 3, 4 or 5 is applied in a dot shape to an electric circuit connecting pad portion on a semiconductor element or an electric circuit connecting electrode portion on a substrate. By heating at 400 ° C. or lower, the volatile dispersion medium is volatilized to sinter the silver particles to form silver bumps on a semiconductor element or on a substrate. Bump manufacturing method.

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