JP2009006337A - Ultrafine solder composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink-like solder composition which can be used for a soldering equivalent to that using an Sn-Ag based alloy solder by utilizing metal nano particles with the mean particle size being ≤100 nm suitable for the inkjet printing, blending the mixture of Sn nano particles and Ag nano particles, and using the melting of these metal nano particles at low temperature and the subsequent alloying thereof. <P>SOLUTION: In the ink-like solder composition, the mixing ratio W<SB>Sn</SB>:W<SB>Ag</SB>of Sn nano particles and Ag nano particles is selected in a range of (95:5) to (99.5:0.5) corresponding to the blending ratio of Sn to Ag in the Sn-Ag based alloy solder; the ratio d1:d2 is selected in a range of (4:1) to (10:1) while the mean particle size d1 of Sn nano particles and the mean particle size d2 of Ag nano particles being in a range of 2-100 nm. The flux component of 0.5-2 pts.mass is added per 10 pts.mass of Sn nano particles 10, and dispersed in a non-polar solvent of high boiling point. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ink-like solder composition containing ultrafine metal fine particles, which can be used for solder bonding between metals as a solder material. More specifically, it is a composition containing a mixture of metal nanoparticles composed mainly of tin nanoparticles and containing a small amount of silver nanoparticles, and the metal nanoparticles are fused together by heating. The present invention relates to an ink-like solder composition that can be used for soldering joining equivalent to Sn-Ag alloy solder. Solder bonding using a solder composition containing tin alloy-based solder fine particles, which is widely used as an electrical and physical bonding means between electronic components, mainly interlayer connection in printed wiring and semiconductor packages, printing The present invention relates to an ink-like solder composition that can be used for joining a wiring board and an electronic component, repairing wiring, and the like.

  As an electrical and physical joining means between electronic components, soldering joining using tin alloy solder is widely used. In particular, as a tin alloy solder material, use of a tin alloy solder not containing lead, so-called lead-free solder, has been advanced. As this lead-free solder, Sn—Ag alloy containing Sn as a main component and containing a small amount of Ag, Sn—Ag—Cu alloy containing Sn as a main component and a small amount of Ag and Cu, etc. Is being used.

  The solder composition is applied to a solder bonding pad of a printed wiring by a screen printing method using a paste solder composition obtained by mixing a tin alloy solder powder and a flux. . At that time, the particle diameter of the tin alloy solder powder is generally about 10 to 40 μm, and the film thickness and drawing accuracy (lower limit) of the coating film of the solder composition are limited by the particle diameter of the solder powder. Yes.

  Further, instead of screen printing, there is also an ink-like solder composition in which tin alloy solder fine particles having a particle diameter of about 0.5 to 2.0 μm, which can be used for ink jet printing, are uniformly dispersed in a dispersion solvent. It has been proposed (see Patent Document 1). In the ink-like solder composition, in order to uniformly disperse the tin alloy-based solder fine particles, a coating layer of a copolymer polymer type dispersant is formed on the surface of the fine particles. On the other hand, for example, an organic acid or an organic amine salt is added as an activator having a function of removing an oxide film formed on the surface of the tin alloy solder fine particles.

Instead of using the above-mentioned tin alloy-based solder particles, metal tin particles and a metal-containing organic complex containing silver ions and copper ions are blended, subjected to heat treatment, and reduced precipitation accompanying the thermal decomposition of the complex A method of forming Sn—Ag alloy and Sn—Ag—Cu alloy in the system from silver, copper and metal tin particles is also proposed (see Patent Document 2).
JP 2005-161341 A JP 2003-251494 A

  Compounding the metal-containing organic complex containing the metal tin particles and silver ions and copper ions, and applying heat treatment, from the silver, copper and the metal tin particles that are reduced and precipitated with the thermal decomposition of the complex, The technique (precipitation-type solder composition) for forming Sn—Ag alloy and Sn—Ag—Cu alloy in the system is a much simpler method than the technique of preparing tin alloy solder fine particles in advance.

  In the precipitation-type solder composition, in the process of selectively reducing and depositing silver and copper from the metal-containing organic complex containing silver ions and copper ions on the surface of the metal tin particles, the metal tin is replaced with silver ions. The mechanism of substitution reduction is used in which copper ions are reduced to silver atoms and copper atoms. When utilizing the mechanism of substitution reduction, it is necessary that clean metallic tin appears on the surface of the metallic tin particles. In the application method using screen printing or a dispenser, it is desirable that the solder composition to be applied is a paste with reduced fluidity. On the other hand, in application using the ink jet printing method, it is necessary to discharge as fine droplets, and it is necessary that the liquid composition has a low liquid viscosity and a high fluidity solder composition. Furthermore, since the opening diameter of the discharge port through which minute droplets are discharged is small, the particle diameter of the metal particles contained in the solder composition needs to be selected in a range not exceeding 2 μm. Further, the metal particles contained in the solder composition must be uniformly dispersed in the dispersion solvent. In other words, in order to maintain high dispersibility of the contained metal particles, it is necessary to provide a coating layer for the dispersant having an affinity for the dispersion solvent on the surface of the metal particles. Therefore, when forming a precipitation-type solder composition applicable to ink jet printing, for example, a coating layer of a copolymer polymer type dispersant is formed on the surface of metal tin particles having a particle diameter of about 0.5 to 2.0 μm. It is necessary to form. In that case, after applying the precipitation-type solder composition, before performing the substitution reduction, for example, it is necessary to remove in advance the coating layer made of a copolymer-type dispersant.

  On the other hand, as the chip-like electronic components mounted on the wiring board by solder bonding are miniaturized and the mounting density is increased, the size of pads used for solder bonding is further miniaturized. Accordingly, when the size of the pad to which the ink-like solder composition is applied is further miniaturized, the particle size of the metal particles contained in the ink used for the ink jet printing needs to be further miniaturized. At the same time, it is necessary to improve the uniformity and reproducibility of the coating film of the ink-like solder composition applied on the pad surface by ink jet printing. Specifically, an ink-like solder using metal nanoparticles having an average particle diameter of 100 nm or less as the metal fine particles contained in the ink-like solder composition so as to be compatible with fine pattern inkjet printing. Development of a composition is desired. In particular, when used for ink-jet printing of fine patterns, the contained metal nanoparticles do not form a lump, and the overall liquid viscosity is 50 mPa · s (20 ° C.) or less, which is a highly fluid ink-like. Development of a solder composition is desired. At that time, the solder composition itself is required to have a composition corresponding to so-called lead-free solder, for example, Sn—Ag alloy solder or Sn—Ag—Cu alloy solder.

  The present invention solves the aforementioned problems. That is, the object of the present invention is to use metal nanoparticles having an average particle diameter of 100 nm or less as the metal fine particles contained in the ink-like solder composition so as to be compatible with ink jet printing of fine patterns. An object of the present invention is to provide a highly fluid ink-like solder composition in which the metal nanoparticles do not form a lump and the total liquid viscosity is 50 mPa · s (20 ° C.) or less. In particular, so-called lead-free solder, for example, Sn-Ag alloy solder, Sn-Ag-Cu alloy solder having a composition corresponding to Sn-Ag alloy solder, Sn-Ag-Cu alloy solder. It is an object of the present invention to provide a highly fluid ink-like solder composition having a corresponding composition.

  In order to solve the above-mentioned problems, the present inventors first studied the use of alloy nanoparticles made of Sn—Ag alloy and Sn—Ag—Cu alloy having an average particle diameter of 100 nm or less. Generally, centrifugal spraying or gas atomization (gas spraying) is used to produce alloy fine particles. The size of droplets that can be sprayed is 0.1 μm at the lower limit, and the average particle size is 100 nm or less. It has proven difficult to form nanoparticles. In addition, it has also been confirmed that the alloy fine particles produced by these methods often have a plurality of fine particles fixed to each other to form a lump.

  On the other hand, metal nanoparticles with an average particle diameter of 1 to 100 nm composed of a single metal are coated with a coating molecule (such as amine) capable of coordinating with a metal element, and the coating molecule is dispersed. By using it as an agent, it can be stably dispersed in an organic solvent. In the state where the entire metal surface is covered with the coating agent molecular layer, no oxide film is formed on the surface of the metal nanoparticles having an average particle diameter of 1 to 100 nm. Then, when the coating molecular layer covering the entire metal surface is removed, the metal nanoparticles are fused to each other even at a relatively low temperature when the metal surfaces are brought into contact with each other. A sintered body can be constructed. Furthermore, when a metal nanoparticle is brought into contact with a bulk metal surface that exposes a clean metal surface, the interface between the bulk metal surface and the metal nanoparticle is caused by diffusion of metal atoms on the metal nanoparticle surface. It has already been verified that fusion occurs (see JP 2002-126869 A). Using the above phenomenon, it has also been verified that brazing bonding between metals can be achieved in which the bulk metal surfaces are bonded via a sintered body layer of metal nanoparticles.

  The above-described method exhibits a bonding strength comparable to that of solder bonding when the surfaces of the bulk metals to be bonded are both clean metal surfaces. On the other hand, when an oxide film with a very small thickness exists on the surface of the bulk metal to be bonded, the oxide film serves as a barrier, and the bulk metal surface caused by the diffusion of metal atoms on the surface of the metal nanoparticles Interfacial fusion with metal nanoparticles is inhibited. In that case, the ratio of the interface fusion between the bulk metal surface and the metal nanoparticles is actually small in the area of the apparent junction formation region. As a result, the bonding strength per area of the apparent bonding formation region is low according to the above ratio.

  The present inventors added a means for substantially avoiding the above-mentioned decrease in the “joint strength per area of the apparent joint formation region”, and thereby oxidized the surface of the bulk metal to be joined with a very small thickness. It was conceived that a good brazing joint can be achieved even in the presence of a coating.

In practice, in the brazing joint using interfacial fusion between the bulk metal surface and the metal nanoparticles, the area S _particle of each interfacial fusion site is approximately the square of the average particle diameter d of the metal nanoparticles (d ² ) In proportion to ( ² ), the area is fine. On the other hand, when no oxide film is present, the surface density of the interfacial fusion site that is originally generated on the entire surfaces to be joined: D _particle is the square of the average particle diameter d of the metal nanoparticles (d ² ). The density is inversely proportional. Therefore, the total area where interfacial fusion between the bulk metal surface and the metal nanoparticles is achieved per unit area: S _particle × D _particle is not significantly dependent on the average particle diameter d of the metal nanoparticles. It has become. Further, in detail, when the form of the interface fusion part between the bulk metal surface and the metal nanoparticle is examined, the area S _particle of each interface fusion site is S _particle ∝a (d) · d ^2, and the metal nanoparticle It depends on a factor a (d) that depends on the average particle diameter d. This factor a (d) decreases as the average particle diameter d of the metal nanoparticles increases, and increases as the average particle diameter decreases. Specifically, when interfacial fusion occurs, the area S _particle of the interfacial fusion site is determined by surface diffusion of metal atoms constituting the surface of the metal nanoparticles on the bulk metal surface. Due to this phenomenon, in the range of the average particle diameter of 2 nm to 100 nm, the factor a (d) is a (d) / a (d ′) ≈ (d) between the two average particle diameters d and d ′. There is a dependency that can be approximated by '/ d).

On the other hand, the interfacial fusion site between the bulk metal surface and the metal nanoparticles is reduced in the area S _particle of the effective interfacial fusion site that is actually joined by the intermetallic bond as the surface oxidation proceeds from the metal surface. Go. The effect of the reduction of the effective interface fusion site area S _particle resulting from the surface oxidation over time becomes more significant as the average particle diameter d of the metal nanoparticles is smaller.

  The present inventors once joined the bulk metal surfaces using interfacial fusion between the bulk metal surface and the metal nanoparticles via a sintered body layer of metal nanoparticles, and then the metal It was conceived that when the entire sintered body of nanoparticles was heated until it melted, the entire bulk metal surface was brazed and joined. In that case, the average composition of the whole sintered body layer of the metal nanoparticles corresponds to lead-free solder, for example, Sn—Ag alloy solder, Sn—Ag—Cu alloy solder used for solder bonding. It was conceived that the entire bulk metal surface was soldered with the composition.

  It is ideal if alloy nanoparticles having a composition corresponding to lead-free solder, for example, Sn-Ag alloy solder, Sn-Ag-Cu alloy solder, can be adopted as the metal nanoparticles. As such, the production of such alloy nanoparticles is difficult. Therefore, after forming a sintered body layer of metal nanoparticles that are uniformly mixed using a mixture of metal nanoparticles composed of constituent metals at a ratio corresponding to the composition of the target alloy, the metal nanoparticles are formed. It was found that when the entire sintered body of particles was heated until it melted, the whole could be made into a uniform alloyed state. At that time, the composition corresponding to the intended Sn-Ag alloy solder and Sn-Ag-Cu alloy solder is 95 wt% to 99.5 wt% Sn and 5 wt% to 0.5 wt% Ag. It has been found that when the average particle diameter of the metal nanoparticles composed of each constituent metal is selected equally, the average composition is in a non-uniform state. In order to avoid the microscopic compositional non-uniformity, the ratio of the average particle diameter d1 of the tin nanoparticles to the average particle diameter d2 of the silver nanoparticles; d1: d2 is 4: 1 to 10: 1. By selecting the range, it is effective that the ratio of the number N1 of tin nanoparticles and the number N2 of silver nanoparticles satisfies a relationship of N1 ≦ N2 in the mixture of metal nanoparticles made of constituent metals. I found it. That is, when the said conditions were satisfy | filled, it discovered that the condition where a silver nanoparticle contact | connects the circumference | surroundings of a tin nanoparticle was achieved. In this situation, when the entire sintered body layer of metal nanoparticles having been uniformly mixed is heated until it is melted, the entire structure can be quickly made into a uniform alloyed state.

  At that time, in the composition corresponding to the Sn—Ag—Cu based alloy solder, Cu is 0.7 wt% to 0.1 wt%, and when using Cu nanoparticles, the number of tin nanoparticles N1 and the number of copper nanoparticles In order that the ratio of N3 satisfies the relationship of N1 ≦ N3, the ratio of the average particle diameter d1 of the tin nanoparticles and the average particle diameter d3 of the copper nanoparticles; d1: d3 is a range of 10: 1 or less Will be selected. In doing so, it was taken into account that copper nanoparticles were much more susceptible to surface oxidation than silver nanoparticles. Regarding copper, it is preferable to blend as an organic acid copper salt, to form metallic copper from the organic acid copper salt in the course of the heat treatment, and to form a coating layer of the generated copper on the surface of the tin nanoparticles. I found out.

  After forming a sintered body layer of metal nanoparticles having a uniform mixed composition using a mixture of metal nanoparticles, the surface of the molten metal is oxidized during the process of melting the entire sintered body layer of metal nanoparticles. In order to avoid receiving, it is necessary that the entire sintered body layer is immersed in a non-polar solvent having a high boiling point. Utilizing this situation, the entire sintered body layer of the metal nanoparticles is melted and wetted on the entire metal surface to be joined, so that the flux agent is dissolved in a high-polarity nonpolar solvent and I found it desirable.

  Of course, the dispersion is made by dissolving the fluxing agent in a high-polarity nonpolar solvent, and if necessary, dissolving a small amount of organic acid copper salt and uniformly dispersing tin nanoparticles and silver nanoparticles. It was also confirmed that a highly fluid ink-like solder composition having a liquid viscosity of 100 mPa · s (20 ° C.) or less can be obtained. Therefore, it was confirmed that it can be applied to inkjet printing.

  Based on these series of findings, the present inventors have completed the present invention.

That is, the ink-like solder composition according to the first embodiment of the present invention is
Ink-like solder comprising tin nanoparticles having an average particle diameter of 2 to 100 nm, silver nanoparticles, and a flux component, and the tin nanoparticles and silver nanoparticles are uniformly dispersed in a non-polar solvent having a high boiling point A composition comprising:
The mixing ratio W _Sn : W _Ag (provided that W _Sn + W _Ag = 100) of the tin nanoparticles and silver nanoparticles is selected in the range of 95: 5 to 99.5: 0.5;
A ratio d1: d2 between the average particle diameter d1 of the tin nanoparticles and the average particle diameter d2 of the silver nanoparticles is selected in the range of 4: 1 to 10: 1;
The addition amount of the flux component per 10 parts by mass of the tin nanoparticles is selected in the range of 0.5 to 2 parts by mass;
A hydrocarbon solvent having a boiling point in the range of 200 ° C. to 320 ° C. is selected as the high boiling nonpolar solvent.

Further, the ink-like solder composition according to the second aspect of the present invention,
Including tin nanoparticles having an average particle diameter of 2 to 100 nm, silver nanoparticles, organic acid copper salt, and a flux component, the tin nanoparticles and silver nanoparticles are uniformly dispersed in a high-polarity nonpolar solvent. An ink-like solder composition comprising:
The compounding ratio W _Sn : W _Ag : W _Cu (provided that W _Sn + W _Ag + W _Cu = 100) of the copper contained in the tin nanoparticles, silver nanoparticles and organic acid copper salt is as follows:
W _Sn in the range of 95-99.5,
W _Ag in the range of 5-0.5,
Select W _Cu in the range of 0.7-0.1,
A ratio d1: d2 between the average particle diameter d1 of the tin nanoparticles and the average particle diameter d2 of the silver nanoparticles is selected in the range of 4: 1 to 10: 1;
The addition amount of the flux component per 10 parts by mass of the tin nanoparticles is selected in the range of 0.5 to 2 parts by mass;
A hydrocarbon solvent having a boiling point in the range of 200 ° C. to 320 ° C. is selected as the high boiling nonpolar solvent. At that time, copper rosinate can be suitably used as the organic acid copper salt.

  In any of the above-described first and second ink-like solder compositions of the present invention, it is preferable to select the following embodiment.

  First, the liquid viscosity of the ink-like solder composition is preferably selected in the range of 5 mPa · s to 30 mPa · s (20 ° C.).

further,
When the ratio d1: d2 of the average particle diameter d1 of the tin nanoparticles and the average particle diameter d2 of the silver nanoparticles is selected in the range of 4: 1 to 10: 1, the range satisfying the above ratio,
The average particle diameter d1 of the tin nanoparticles is selected in the range of 10 to 100 nm,
More preferably, the average particle diameter d2 of the silver nanoparticles is selected in the range of 2 to 20 nm.

  On the other hand, the silver nanoparticles are coated with an alkylamine capable of coordinative bonding using a lone electron pair on the nitrogen atom of the amino group with respect to silver atoms on the surface, It is preferably dispersed in a high-polarity nonpolar solvent.

  In that case, it is desirable that the compounding amount of the alkylamine is selected in the range of 1 to 6 parts by mass per 10 parts by mass of the silver nanoparticles.

  In particular, the alkylamine is preferably a primary alkylamine having 8 to 14 carbon atoms.

In any of the above-described first form of the present invention and the ink-like solder composition of the second form,
It is preferable to select a form in which rosin or hydrogenated rosin is added as the flux component.

  The ink-like solder composition according to the present invention dissolves a fluxing agent in a non-polar solvent having a high boiling point, and if necessary, dissolves a small amount of an organic acid copper salt to uniformly disperse tin nanoparticles and silver nanoparticles. The dispersion obtained by dispersing in the above is a highly fluid ink-like solder composition having an overall liquid viscosity of 100 mPa · s (20 ° C.) or less. Therefore, this highly fluid ink-like solder composition can be applied with a uniform coating thickness in a target fine pattern shape by applying, for example, an ink jet printing method. Furthermore, although it is lower than the melting point of metal tin, low temperature sintering of tin nanoparticles and silver nanoparticles, interfacial fusion between the metal surface to be joined and tin nanoparticles, silver nanoparticles, and mixed organic acid copper salt By heating to a temperature at which copper atoms can be precipitated, tin nanoparticles, silver nanoparticles, and the deposited layer of deposited copper metal are uniformly mixed to form a sintered layer of metal nanoparticles Thus, the metal surfaces having symmetry of bonding can be bonded via the sintered body layer of the metal nanoparticles. Finally, the sintered body layer of the metal nanoparticles is heated to a temperature equal to or higher than the melting point of the target tin alloy, and in the presence of the flux agent dissolved in the high-polarity nonpolar solvent, the metal The sintered body layer of nanoparticles can be melted to perform solder bonding with good bonding strength.

  Hereinafter, the ink-like solder composition according to the present invention and the solder bonding method using the same will be described in more detail.

  First, an ink-like solder composition according to the present invention is a so-called lead-free solder, which uses Sn—Ag alloy solder, Sn—Ag—Cu alloy solder as a solder material. It is intended for use in solder bonding.

  The ink-like solder composition according to the first aspect of the present invention is intended for use in solder bonding between metals using Sn—Ag alloy solder as a solder material. Accordingly, an ink-like product comprising tin nanoparticles having a mean particle diameter of 2 to 100 nm, silver nanoparticles, and a flux component, and uniformly dispersing the tin nanoparticles and silver nanoparticles in a high-polarity nonpolar solvent. The solder composition.

The mixing ratio (mass ratio) of tin nanoparticles and silver nanoparticles contained, so as to correspond to the composition of the intended Sn—Ag alloy solder, W _Sn : W _Ag ( _WSN + W _Ag = 100 ) Is selected in the range of 95: 5 to 99.5: 0.5. At that time, the ratio d1: d2 of the average particle diameter d1 of the tin nanoparticles and the average particle diameter d2 of the silver nanoparticles is selected in the range of 4: 1 to 10: 1. When the density of tin (20 ° C.): 7.265 g · cm ⁻³ and the density of silver (20 ° C.): 10.49 g · cm ⁻³ are considered, the ratio d1: d2 is in the range of 4: 1 to 10: 1. Is selected, the ratio W1: W2 of the mass W1 of one tin nanoparticle to the mass W2 of one silver nanoparticle is in the range of 44.3: 1 to 693: 1.

For example, in the case of W _Sn : W _Ag = 95: 5, when the ratio d1: d2 is selected to be 4: 1, the ratio N1 of the number N1 of tin nanoparticles and the number N2 of silver nanoparticles is the mixing ratio described above. / N2 is 43/100. In the case of W _Sn : W _Ag = 99.5: 0.5, when the ratio d1: d2 is selected in the range of 10: 1, the number of tin nanoparticles N1 and the number of silver nanoparticles are the above-mentioned mixing ratio. The ratio N1 / N2 of N2 is 29/100. The ratio N1 / N2 of the number N1 of tin nanoparticles and the number N2 of silver nanoparticles is at least 1/50 <N1 / N2 <5, preferably 1/20 ≦ N1 / N2 ≦ 2, more preferably According to the mixing ratio (mass ratio) W _Sn : W _Ag so that 1/10 ≦ N1 / N2 ≦ 1, the ratio d1: between the average particle diameter d1 of tin nanoparticles and the average particle diameter d2 of silver nanoparticles d2 is selected in the range of 4: 1 to 10: 1.

Assuming that N1 / N2 = 4, there is at least one silver nanoparticle per 2 × 2 × 2 = 8 tin nanoparticles stacked in a cubic lattice. That is, as described above, according to the mixing ratio (mass ratio) W _Sn : W _Ag , the ratio d1: d2 of the average particle diameter d1 of the tin nanoparticles and the average particle diameter d2 of the silver nanoparticles is set to 4: 1 to 4: 1. When selected in the range of 10: 1, in the mixture of tin nanoparticles and silver nanoparticles that are uniformly mixed, the composition ratio is locally determined from the target mixing ratio (mass ratio) W _Sn : W _Ag , Extremely misaligned situations are avoided.

  Furthermore, when the ratio d1: d2 of the average particle diameter d1 of the tin nanoparticles and the average particle diameter d2 of the silver nanoparticles is selected in the range of 4: 1 to 10: 1, the tin nanoparticle is within a range that satisfies the above ratio. More preferably, the average particle diameter d1 of the particles is selected in the range of 10 to 100 nm, and the average particle diameter d2 of the silver nanoparticles is selected in the range of 2 to 20 nm. In particular, when the ratio d1: d2 is selected in the range of 4: 1 to 10: 1, the average particle diameter d1 of the tin nanoparticles is selected in the range of 20 to 50 nm in a range that satisfies the above ratio, More preferably, the average particle diameter d2 of the silver nanoparticles is selected in the range of 2 to 10 nm.

  On the other hand, in order to obtain a state in which the tin nanoparticles and silver nanoparticles are uniformly dispersed in the non-polar solvent having a high boiling point of the dispersion solvent, the surface of the tin nanoparticles and silver nanoparticles is arranged with respect to the metal element. A coating molecule layer with coating molecules capable of coordinate bonding is provided. Specifically, for silver nanoparticles, a coating agent molecular layer is provided using an amine compound having a terminal amino group. In addition, a coating agent molecular layer is provided for tin nanoparticles using a compound having an amino group or a hydroxyl group.

  An amine compound having a terminal amino group utilized for this coating agent molecule, for example, an alkylamine, is coordinated to the surface of the silver nanoparticle by utilizing a lone pair on the nitrogen atom of the amino group. To form a dense coating agent molecular layer. On the other hand, an amine compound having a terminal amino group, for example, an alkylamine, has an affinity derived from the hydrocarbon skeleton for a non-polar solvent having a high boiling point as a dispersion solvent. Accordingly, silver nanoparticles having a coating molecular layer with an amine compound having a terminal amino group, for example, an alkylamine, utilize the affinity for a non-polar solvent having a high boiling point due to the coating molecular layer, It is in a state having dispersibility. Further, in the state where the surfaces are coated with the coating agent molecular layer, since the metal surfaces are prevented from contacting each other directly, the situation of forming a mass fused to each other is also avoided. As a coating agent molecule for silver nanoparticles, an alkylamine is preferably used as an amine compound having a terminal amino group. For example, as an alkylamine, the alkyl group is preferably selected in the range of C8 to C14, and has an amino group at the terminal of the alkyl chain. For example, the alkylamine in the range of C8 to C14 has thermal stability and its vapor pressure is not so high, and when it is stored at room temperature or the like, the content rate is maintained and controlled within a desired range. It is preferably used from the viewpoint of handling properties.

  Similarly, for tin nanoparticles, a compound having an amino group or a hydroxyl group uses a lone electron pair on the nitrogen atom of the amino group or a lone electron pair on the oxygen atom of the hydroxyl group, Coordinate bonding is performed to form a dense coating molecule layer. On the other hand, an amine compound having an amino group, for example, an alkylamine, or a compound having a hydroxyl group, for example, an alkyl alcohol, has an affinity derived from the hydrocarbon skeleton for a non-polar solvent having a high boiling point as a dispersion solvent. have. Therefore, an amine compound having an amino group, for example, an alkylamine, or a compound having a hydroxyl group, for example, a tin nanoparticle having a coating molecular layer with an alkyl alcohol has a high boiling point due to the coating molecular layer. By using the affinity for nonpolar solvents, it is in a state having dispersibility. Further, in the state where the surfaces are coated with the coating agent molecular layer, since the metal surfaces are prevented from contacting each other directly, the situation of forming a mass fused to each other is also avoided.

  It is preferable to use an alkylamine as an amine compound having a terminal amino group as a coating agent molecule for tin nanoparticles. For example, as an alkylamine, the alkyl group is preferably selected in the range of C8 to C14, and has an amino group at the terminal of the alkyl chain. For example, the alkylamine in the range of C8 to C14 has thermal stability and its vapor pressure is not so high, and when it is stored at room temperature or the like, the content rate is maintained and controlled within a desired range. It is preferably used from the viewpoint of handling properties.

  In addition, as a method for producing metal nanoparticles that can be stably dispersed in the organic solvent and having a coating molecular layer on the surface, Japanese Patent Application Laid-Open No. 3-34211 is prepared by using a gas evaporation method. In addition, a colloidal dispersion of metal fine particles of 10 nm or less and a method for producing the same are disclosed. Japanese Patent Application Laid-Open No. 11-319538 discloses a colloidal dispersion of metal fine particles having an average particle diameter of several nanometers to several tens of nanometers using a reduction precipitation method using an amine compound for reduction, and its production. A method is disclosed.

  On the other hand, a hydrocarbon solvent having a boiling point in the range of 200 ° C. to 320 ° C. is selected as the high boiling nonpolar solvent used as the dispersion solvent. In the ink-like solder composition according to the first aspect of the present invention, the coating molecule that coats the surface of the tin nanoparticles and the coating molecule that coats the surface of the silver nanoparticles are mixed with the melting point of tin (232 ° C.). ), The tin nanoparticles and the silver nanoparticles were precipitated by elution in the non-polar solvent having a high boiling point by heating at a temperature T1 that is significantly lower than that on the metal surfaces to be joined. Form a structure. Moreover, in the process of this heat treatment, the oxide film remaining on the metal surfaces to be joined is removed by using a flux agent. In order to carry out these liquid phase reactions, it is necessary that the tin nanoparticles and the silver nanoparticles are immersed in a high-polarity nonpolar solvent at the stage of the heat treatment. By making the above selection, it is avoided that the dispersion solvent completely evaporates prior to the heat treatment process. As the hydrocarbon solvent having a boiling point in the range of 200 ° C. to 320 ° C., a linear alkane having a carbon number in the range of 12 to 18 and an alkane having a branch having a carbon number in the range of 11 to 16 can be suitably used. . The temperature T1 of the first heat treatment for releasing the coating agent molecules is at least significantly lower than the melting point of tin (232 ° C.), and more than the melting point of the target Sn—Ag alloy. Also, the temperature can be lowered. For example, the temperature T1 of the first heat treatment is preferably selected in the range of 180 ° C to 225 ° C.

  On the other hand, the flux component contained in the non-polar solvent having a high boiling point is used for removing the oxide film remaining on the metal surface. Moreover, a flux component is contained in the state melt | dissolved in the nonpolar solvent of a high boiling point. Of course, in the stage of heating at a temperature T1 that is significantly lower than the melting point of tin (232 ° C.), most of it should not evaporate. An organic acid satisfying the conditions, generally a monocarboxylic acid having a boiling point of 200 ° C. or higher, for example, a monocarboxylic acid having 8 or more carbon atoms (R—COOH) can be suitably used. The oxide film remaining on the metal surface is generally composed of a metal oxide in the form of M (II) O. When a monocarboxylic acid (R—COOH) acts on the metal oxide M (II) O, a basic metal salt of a carboxylic acid is first generated by the following reaction.

M (II) O + R—COOH → R—COO ⁻ [M ²⁺ · OH ⁻ ]

At that time, in a non-polar solvent having a high boiling point, a compound having an amino group, for example, an amine compound such as an alkylamine (R′—NH ₂ ), which is used as a coating molecule for silver nanoparticles or tin nanoparticles. Is dissolved. This alkylamine (R′—NH ₂ ) is much easier to cause coordination with the metal ion M ²⁺ than with the metal atom M. Accordingly, alkylamine (R′—NH ₂ ) acts on the basic metal salt of the carboxylic acid to produce an amine complex as described below, for example.

^{R-COO - [M 2+ ·} OH -] + 4R'-NH 2 → R-COO - [M 2+ (R'-NH 2) 4] OH -
When the above-mentioned amine complex is constituted, dissolution in a high-polarity nonpolar solvent becomes easier. At that time, since the concentration of the alkylamine (R′—NH ₂ ) itself dissolved in the non-polar solvent having a high boiling point is lowered, it is coordinated to the metal atom on the metal surface of the silver nanoparticle or tin nanoparticle. Dissociation of the alkylamine (R′—NH ₂ ) bonded to is promoted.

R′—NH ₂ : Ag → R′—NH ₂ + Ag
R′—NH ₂ : Sn → R′—NH ₂ + Sn

For example, when the metal surface to be bonded is a copper pad surface, the natural oxide film is removed by washing the surface of the copper pad with 2.5 N sulfuric acid in advance, and the surface is almost oxidized. The film is not present. A tin oxide SnO type oxide film is present on the surface of the tin plating film applied to the soldering terminal electrode surface of the electronic component, which is one of the bonding objects. Further, when a copper plating film or a silver / palladium plating film is formed on the terminal electrode surface, only an oxide film of about one molecular layer exists. Therefore, the use of a monocarboxylic acid having a boiling point of 200 ° C. or higher, such as rosin (abietic acid) or hydrogenated rosin, as the flux component can sufficiently achieve the effect of removing the oxide film. The content of the flux component is selected so that the concentration in the non-polar solvent having a high boiling point is within a range in which the above-described flux treatment properly proceeds. For example, when rosin (abietic acid) or hydrogenated rosin is used, it is preferably selected within the range of 1 to 2 parts by mass per 100 parts by mass of the high boiling nonpolar solvent.

  The blending ratio of the total of silver nanoparticles and tin nanoparticles and the high-polarity nonpolar solvent determines the liquid viscosity of the solder composition to be produced. Of course, depending on the liquid viscosity of the non-polar solvent having a high boiling point, the volume ratio of the tin nanoparticles to the silver nanoparticles and the dispersion solvent in the ink-like solder composition is 1:70 to 1: 140. It is preferable to select the range. In that case, in the ink-like solder composition according to the first embodiment of the present invention, the liquid viscosity of the ink-like solder composition is at least 50 mPa · s (20 ° C.) or less, usually 5 mPa · s to It is preferably selected in the range of 30 mPa · s (20 ° C.). Actually, the blending ratio of the non-polar solvent having a high boiling point is adjusted within the above range so that the liquid viscosity is within the above range.

  In using the ink-like solder composition according to the first aspect of the present invention, in the first heat treatment step in which heating is performed at a temperature T1 that is significantly lower than the melting point (232 ° C.) of tin, By elution of the coating molecules into the non-polar solvent with a high boiling point by using the accelerating process, the tin nanoparticles and the silver nanoparticles are precipitated to form a layered structure on the metal surfaces to be joined. To do. As a result, the tin nanoparticles and the silver nanoparticles stacked on the metal surfaces to be bonded are bonded to each other on the clean metal surface by causing interfacial fusion. In addition, the tin nanoparticles and silver nanoparticles forming the laminated structure are in a state where the metal surfaces are in contact with each other, causing mutual fusion, and the low-temperature sintered body layer composed of metal nanoparticles as a whole. And once configured. Further, even with the other metal surface in contact with the upper surface of the laminated structure, interfacial fusion is caused between the metal surface and partial adhesion is achieved. Since the blending ratio with the non-polar solvent having a high boiling point is relatively high, the low-temperature sintered body layer formed at this stage remains relatively low in density indicated by the metal component.

  When the ink-like solder composition according to the first embodiment of the present invention is used, as a second heat treatment step, it is subsequently heated to a temperature T2 higher than the melting point of tin (232 ° C.). In addition, when the tin nanoparticles contained in the low-temperature sintered body layer composed of metal nanoparticles are melted, alloying proceeds between the tin nanoparticles and the fused silver nanoparticles. Thus, the Sn—Ag alloy having the intended composition is melted. At that time, in the state in which the remaining flux agent is present, both the lower and upper clean metal surfaces wet and spread, and both are soldered with an Sn-Ag alloy. It becomes a state. As the temperature T2 in the second heat treatment step, a temperature at which solder bonding with a conventional Sn-Ag alloy is performed is selected. Therefore, it is preferable to select the temperature T2 of the second heat treatment in the range of 240 ° C to 280 ° C. When the second heat treatment step is completed, the first thickness of the present invention is such that the layer thickness of the solder joint portion of the Sn-Ag alloy is in the range of 3 μm to 20 μm, preferably in the range of 5 μm to 15 μm. It is desirable to select the coating thickness of the ink-like solder composition according to the embodiment in the range of 30 μm to 200 μm, preferably in the range of 50 μm to 150 μm.

  In addition, by using the ink-like solder composition according to the first embodiment of the present invention, solder bonding is performed by solder bonding pads provided on a wiring board and solder bonding on the pads. A terminal for solder joining of electronic components to be mounted can be mentioned. As a solder bonding pad, either a copper pad or a copper pad surface on which a tin plating film is formed or a nickel / gold plating film is formed for the purpose of improving solder wettability. Is also applicable. On the other hand, as a terminal for soldering of electronic parts, for the purpose of improving solder wettability, a tin plating film, a copper plating film, or silver / palladium plating is applied. It can be applied to any of these.

  Next, the ink-like solder composition according to the second aspect of the present invention is intended for use in solder bonding between metals using Sn—Ag—Cu alloy solder as a solder material. Therefore, it contains tin nanoparticles, silver nanoparticles, organic acid copper salts, and flux components with an average particle diameter of 2 to 100 nm, and the tin nanoparticles and silver nanoparticles are uniformly dispersed in a high boiling nonpolar solvent. An ink-like solder composition is obtained.

The compounding ratio W _Sn : W _Ag : W of the copper contained in the tin nanoparticles, silver nanoparticles, and organic acid copper salt contained so as to correspond to the composition of the target Sn—Ag—Cu alloy solder. _Cu (however, W _Sn + W _Ag + W _Cu = 100) is
W _Sn in the range of 95-99.5,
W _Ag in the range of 5-0.5,
W _Cu is selected in the range of 0.7 to 0.1. At that time, the ratio d1: d2 of the average particle diameter d1 of the tin nanoparticles and the average particle diameter d2 of the silver nanoparticles is selected in the range of 4: 1 to 10: 1.

  Actually, except for the organic acid copper salt added as a copper component, the tin nanoparticle, the silver nanoparticle, the flux component, and the high-polarity nonpolar solvent are in the first form of the present invention. Such an ink-like solder composition has substantially the same configuration. Accordingly, in the ink-like solder composition according to the first aspect of the present invention, the preferred form is the same as the preferred form in the ink-like solder composition according to the second aspect of the invention. It has become.

When composing the composition of the Sn—Ag—Cu-based alloy solder, regarding the copper, an organic acid copper salt is added instead of the copper nanoparticles. In the first heat treatment step, a material in which copper atoms are selectively precipitated from an organic acid copper salt on the surface of the Sn nanoparticles by the following substitution deposition process is used. For example, when a copper salt of a monocarboxylic acid: (R ″ COO) ₂ Cu is used as the organic acid copper salt, the dimeric copper salt of the monocarboxylic acid: [(R "COO) ₂ Cu: Cu (R" COO) ₂ ]. When heated, the monocarboxylic acid copper salt dissociated from the dimer: (R "COO) ₂ Cu has the following process: Then, it precipitates on the Sn nanoparticle surface.
_{[(R "COO) 2 Cu} : Cu (R" COO) 2] → 2 (R "COO -) 2 Cu 2+
(R ″ COO ⁻ ) ₂ Cu ²⁺ + Sn → Cu + (R ″ COO ⁻ ) ₂ Sn ^{2+
_{(R "COO -) 2 Sn}} 2+ + 4R'-NH 2 → (R" COO -) 2 [Sn 2+ (R'-NH 2) 4]

As a result of the copper atoms precipitated on the surface of the Sn nanoparticles being aggregated by surface diffusion, a copper coating layer is formed on the surface of the Sn nanoparticles. At the same time, interdiffusion also proceeds with heating, and a copper coating layer having a partial diffusion region is formed on the Sn nanoparticle surface.

The organic acid copper salt utilized in the above process is preferably a monocarboxylic acid copper salt: (R ″ COO) ₂ Cu having sufficient solubility in a high-polarity nonpolar solvent, for example, It is preferable to use a copper salt of a monocarboxylic acid having 7 to 14 carbon atoms, in particular, a tin salt of a monocarboxylic acid: (R ″ COO) ₂ Sn produced as a by-product in the substitution precipitation process is a non-polarity having a high boiling point. It is preferable that it can be quickly eluted in a solvent. From this point of view, it is preferable to use a copper salt of rosin, a copper salt of naphthenic acid, or the like.

The organic acid copper salt contained in the ink-like solder composition according to the second embodiment of the present invention is dissociated from the dimer type by heating and becomes a monomer, but in a nonpolar solvent, Since the solubility of the monomer is not high, it selectively adsorbs in the form of (R ″ COO) ₂ Cu: Sn to the tin atoms on the surface of the tin nanoparticles from which the coating agent molecular layer has been removed. In addition, substitution deposition is performed through the above-described process, although the same substitution deposition proceeds on the surface of the tin plating film, but the total surface area exposed to the tin metal is the same as that of the tin nanoparticles. Since the total surface area is orders of magnitude larger, the amount of precipitation on the surface of the tin plating film is negligible.

  In particular, since tin nanoparticles whose surface is protected by the coating agent molecular layer are used, when the coating agent molecular layer is removed, the surface is in a state where no oxide film exists. Therefore, substitution precipitation of the organic acid copper salt proceeds effectively, and it is possible to substitute and deposit almost the entire amount of the mixed organic acid copper salt on the surface of the tin nanoparticles.

Therefore, in the first heat treatment step, the metal surfaces to be joined are fixed through a low-temperature sintered body layer formed of tin nanoparticles having a copper coating layer formed on the surface and silver nanoparticles. It will be in the state. Furthermore, as a second heat treatment step, the tin nanoparticles contained in the low-temperature sintered body layer composed of metal nanoparticles are subsequently heated to a temperature T2 higher than the melting point of tin (232 ° C.). As the melting of the alloy proceeds, alloying proceeds between the tin nanoparticles having a copper coating layer formed on the surface thereof and the fused silver nanoparticles, and Sn-Ag having a target composition as a whole. -Cu alloy is melted. At that time, in the state where the remaining flux agent is present, both the lower clean metal surface and the upper clean metal surface wet and spread, and both are joined by soldering with an Sn—Ag—Cu alloy. It is done. The temperature T2 in the second heat treatment step is selected as a temperature at which solder bonding with a conventional Sn—Ag—Cu alloy is performed. Therefore, it is preferable to select the temperature T2 of the second heat treatment in the range of 240 ° C to 280 ° C. When the second heat treatment step is completed, the layer thickness of the solder joint portion of the Sn—Ag—Cu-based alloy is in the range of 3 μm to 20 μm, preferably in the range of 5 μm to 15 μm. The coating thickness of the ink-like solder composition according to the second embodiment is preferably selected in the range of 30 μm to 200 μm, and preferably in the range of 50 μm to 150 μm.

As described above, the ink-like solder composition of the present invention is applied on the metal surface with a uniform coating thickness, and then the first heating is performed with the other metal surface in contact with the upper surface. By performing the treatment, the space between the two metal surfaces is once fixed through a low-temperature sintered body layer formed of tin nanoparticles and silver nanoparticles. Furthermore, after the second heat treatment step is performed, when the melting of the tin nanoparticles in the low-temperature sintered body layer formed of the tin nanoparticles and the silver nanoparticles is promoted, the entire target composition The alloy is rapidly alloyed into the Sn—Ag-based alloy and the Sn—Ag—Cu-based alloy, and good solder bonding is achieved on the entire bonding surface. In particular, the metal surface that comes into contact with the ink-like solder composition at the stage of the first heat treatment step has a clean surface because the blended flux component acts. As a result, when solder bonding is formed by the second heat treatment, no oxide film remains at the interface, and extremely high bonding strength is achieved.

  Hereinafter, the present invention will be described more specifically with reference to examples. These examples are examples of the best mode according to the present invention, but the present invention is not limited by these examples.

Example 1
Hydrogenated rosin is added as a tin nanoparticle, silver nanoparticle, rosin copper salt, and flux component, and an ink-like solder composition is prepared by the following procedure.

As a raw material for tin nanoparticles, a commercially available tin nanoparticle dispersion, specifically, 10 parts by mass of tin nanoparticles having an average particle size of 42 nm, was added to toluene (boiling point 110.6 ° C., specific gravity d ₄ ^20). = 0.867) Tin nanocolloid (Shinko Chemical Industry Co., Ltd.) dispersed in 90 parts by mass is used. As a raw material for silver nanoparticles, in a dispersion solvent in which 7 parts by mass of dodecylamine (molecular weight 185.36, melting point 28.3 ° C., boiling point 248 ° C., specific gravity d ₄ ⁴⁰ = 0.7841) was dissolved in 58 parts by mass of toluene. A commercially available silver nanoparticle dispersion (trade name: Independently Dispersed Ultrafine Particles Ag1T manufactured by Vacuum Metallurgy) in which 35 parts by mass of silver nanoparticles having an average particle diameter of 3 nm are dispersed is used. In the silver nanoparticle dispersion liquid, the surface of the silver nanoparticle is formed via a coordinated bond to the silver atom using a lone electron pair in which dodecylamine, which is an alkylamine, is present on the nitrogen atom of the amino group. A covering molecular layer is formed on the substrate. Therefore, the silver nanoparticles are uniformly dispersed in the dispersion solvent using dodecylamine forming a coating molecular layer on the surface as a dispersant. As a raw material of rosin copper salt (copper (II) salt of abietic acid), a toluene solution of rosin copper salt (concentration 20 wt%, copper content 1.91 wt%) is used.

  Further, as a raw material for hydrogenated rosin (molecular weight 304) added as a fluxing agent, a 22.9% by mass hydrogenated rosin toluene solution is used.

  First, in a 100 ml eggplant-shaped flask, 30 parts by mass of tin nanocolloid (containing Sn 10 wt%), 0.22 parts by mass of silver ultrafine particle dispersion Ag1T (containing Ag40.2 wt%), a toluene solution of rosin copper salt (concentration 20 wt%) %, Copper content 1.91 wt%) 0.80 parts by mass, toluene solution of hydrogenated rosin (concentration 22.9 wt%) 1.67 parts by mass, mixed and stirred at 40 ° C. for 1 hour. After completion of the stirring, the dispersion solvent toluene is removed by concentration under reduced pressure. The mixture after the solvent removal contains 0.09 parts by mass of silver nanoparticles, 0.016 parts by mass of dodecylamine, and 0.38 parts by mass of hydrogenated rosin per 3 parts by mass of tin nanoparticles.

As a dispersion solvent, 3.14 parts by mass of the mixture after desolvation, N14 (tetradecane, viscosity 2.0 to 2.3 mPa · s (20 ° C.), melting point 5.86 ° C., boiling point 253.57 ° C., specific gravity d ₄ ²⁰ = 0.7924, manufactured by Nippon Mining Petrochemical Co., Ltd.) is added in an amount of 27.3 parts by mass. Thereafter, the mixture is stirred at room temperature (25 ° C.) to obtain a uniform dispersion. After the stirring, the dispersion was filtered with a 0.2 μm membrane filter.

The resulting dispersion is a highly fluid composition having a liquid viscosity (B-type rotational viscometer, measurement temperature 20 ° C.) of 10 mPa · s, and is a uniform black ink-like solder composition. In the solder composition, the mixing ratio of tin nanoparticles, silver nanoparticles, copper in the rosin copper salt: W _Sn : W _Ag : W _Cu is 96.5: 3: 0.5, Sn—Ag -The ratio is suitable for Cu alloy solder. The melting point of the Sn—Ag—Cu alloy at this ratio is 219 ° C. with respect to the melting point of metal tin 232 ° C. Tin density (20 ° C.): 7.265 g · cm ⁻³ , Silver density (20 ° C.): 10.49 g · cm ⁻³ , average particle diameter of tin nanoparticles d1 = 42 nm and average particle diameter of silver nanoparticles Considering the ratio d1: d2 = 42: 3 of d2 = 3 nm, the ratio N1: N2 of the number N1 of tin nanoparticles to the number N2 of silver nanoparticles is estimated to be 18: 1060. In the ink-like solder composition, the volume ratio of the tin nanoparticles, the silver nanoparticles, and the dispersion solvent is 0.4: 35.

Using the produced ink-like solder composition, a 3216 chip component having a Sn plating electrode was soldered onto a copper pad on the substrate. The copper pad on the substrate is previously washed with 2.5N sulfuric acid, washed with water and then dried. By the pickling treatment, the oxide film on the surface of the copper pad is removed. An ink-like solder composition is inkjet printed on the copper pad surface using an inkjet apparatus. The coating thickness of the printed ink-like solder composition was about 100 μm.

  On the coating film of the ink-like solder composition on the copper pad, the 3216 chip component is placed in a shape in which the Sn plating electrode is in close contact. Heat treatment is performed at 220 ° C. for 5 minutes, and then at 270 ° C. for 3 minutes. During heating to 220 ° C., the oxide film on the metal surface is removed by the flux agent. At the same time, with this heat treatment, dodecylamine constituting the coating molecular layer on the surface of the silver nanoparticles is released. In addition, the dissolved rosin copper salt (copper (II) salt of abietic acid) deposits copper atoms on the surface of tin metal by the following substitutional reduction reaction on the surface of tin nanoparticles without surface oxide film. Let The copper atoms deposited on the metal tin surface of the tin nanoparticles once constitute a coating layer covering the surface of the tin nanoparticles.

[(C ₁₉ H ₂₉ COO) ₂ Cu: Cu (OOCH ₂₉ C ₁₉ ) ₂ ] → 2 (C ₁₉ H ₂₉ COO ⁻ ) ₂ Cu ²⁺
(C ₁₉ H ₂₉ COO ⁻ ) ₂ Cu ²⁺ + Sn → Cu + (C ₁₉ H ₂₉ COO ⁻ ) ₂ Sn ²⁺

As a result, tin nanoparticles having no surface oxide film and silver nanoparticles are deposited on a copper pad showing a clean surface, resulting in a densely laminated state. At the site where the tin nanoparticles and silver nanoparticles are in contact with each other on the metal surface, the fusion proceeds. Also, the tin nanoparticles and silver nanoparticles that are in contact with the copper pad surface are also fused at the site of contact with the copper surface. proceed. In particular, denser fusion proceeds at a contact portion between the surface of the copper nanoparticles and a tin nanoparticle formed with a copper atom coating layer on the surface. On the other hand, the surface of the Sn plating electrode of the 3216 chip component placed on the coating film of the ink-like solder composition is also in a state where a clean metal surface is exposed. When tetradecane as a dispersion solvent evaporates, the surface of the Sn plating electrode comes into close contact with the upper surface of the mixture layer of tin nanoparticles and silver nanoparticles in a densely stacked state. The fusion of the tin nanoparticles and silver nanoparticles in contact with the surface of the Sn plating electrode similarly proceeds at the contact site with the tin plating surface.

  Next, in a heating (reflow) treatment at 270 ° C. for 3 minutes, in the mixture layer of the tin nanoparticles that have already been mutually fused, the tin nanoparticles that the copper atom coating layer has, and the silver nanoparticles, As a result of exceeding the melting point, melting progresses as a whole and alloying progresses. Therefore, a state in which the surface of the copper pad and the surface of the Sn plating electrode are wetted by the Sn—Ag—Cu alloy to be generated is achieved, and solder bonding is performed. At this stage, the layer thickness of the Sn—Ag—Cu alloy layer at the solder joint portion corresponds to 10 μm.

When the die shear strength of the 3216 chip component was measured under the condition that the area size of the solder joint portion was 0.8 mm ² , it showed a high strength of 50 N at room temperature. Furthermore, when the die shear strength is measured at 200 ° C., it is 38 N, and a sufficiently high bonding strength is maintained.

(Example 2)
Hydrogenated rosin is added as a tin nanoparticle, silver nanoparticle, rosin copper salt and a flux component, and an ink-like solder composition is prepared by the following procedure.

As a raw material for tin nanoparticles, a commercially available tin nanoparticle dispersion, specifically, 10 parts by mass of tin nanoparticles having an average particle size of 42 nm, was added to toluene (boiling point 110.6 ° C., specific gravity d ₄ ^20). = 0.867) Tin nanocolloid (Shinko Chemical Industry Co., Ltd.) dispersed in 90 parts by mass is used. Dispersing solvent in which 7 parts by mass of dodecylamine (molecular weight: 185.36, melting point: 28.3 ° C., boiling point: 248 ° C., specific gravity d ₄ ⁴⁰ = 0.7841) was dissolved in 52.8 parts by mass of toluene as a raw material for silver nanoparticles A commercially available silver nanoparticle dispersion (trade name: independently dispersed ultrafine particles Ag1T manufactured by vacuum metallurgy) in which 40.2 parts by mass of silver nanoparticles having an average particle diameter of 10 nm are dispersed is used. In the silver nanoparticle dispersion liquid, the surface of the silver nanoparticle is formed via a coordinated bond to the silver atom using a lone electron pair in which dodecylamine, which is an alkylamine, is present on the nitrogen atom of the amino group. A covering molecular layer is formed on the substrate. Therefore, the silver nanoparticles are uniformly dispersed in the dispersion solvent using dodecylamine forming a coating molecular layer on the surface as a dispersant. As a raw material of rosin copper salt (copper (II) salt of abietic acid), a toluene solution of rosin copper salt (concentration 20 wt%, copper content 1.91 wt%) is used.

  Further, as a raw material for hydrogenated rosin (molecular weight 304) added as a fluxing agent, a 22.9% by mass hydrogenated rosin toluene solution is used.

  First, in a 100 ml eggplant-shaped flask, 100 parts by mass of tin nanocolloid (containing Sn 10 wt%), 0.773 parts by mass of silver ultrafine particle dispersion Ag1T (containing Ag40.2 wt%), a toluene solution of rosin copper salt (concentration 20 wt%) %, Copper content 1.91 wt%) 2.71 parts by mass, hydrogenated rosin in toluene solution (concentration 22.9 wt%) 5.59 parts by mass, mixed and stirred at 40 ° C. for 1 hour. After completion of the stirring, the dispersion solvent toluene is removed by concentration under reduced pressure. The solvent-removed mixture is 0.311 parts by mass of silver nanoparticles, 0.0518 parts by mass of rosin copper salt (in terms of copper content), 0.054 parts by mass of dodecylamine, hydrogenated per 10 parts by mass of tin nanoparticles. 1.28 parts by mass of rosin are included.

As a dispersion solvent, 3.14 parts by mass of the mixture after desolvation, N14 (tetradecane, viscosity 2.0 to 2.3 mPa · s (20 ° C.), melting point 5.86 ° C., boiling point 253.57 ° C., specific gravity d ₄ ²⁰ = 0.7924, manufactured by Nippon Mining Petrochemical Co., Ltd.) is added in an amount of 27.3 parts by mass. Thereafter, the mixture is stirred at room temperature (25 ° C.) to obtain a uniform dispersion. After the stirring, the dispersion was filtered with a 0.2 μm membrane filter.

The resulting dispersion is a highly fluid composition having a liquid viscosity (B-type rotational viscometer, measurement temperature 20 ° C.) of 15 mPa · s, and is a uniform black ink-like solder composition. In the solder composition, the mixing ratio of tin nanoparticles, silver nanoparticles, copper in the rosin copper salt: W _Sn : W _Ag : W _Cu is 96.5: 3: 0.5, Sn—Ag -The ratio is suitable for Cu alloy solder. The melting point of the Sn—Ag—Cu alloy at this ratio is 219 ° C. with respect to the melting point of metal tin 232 ° C. Tin density (20 ° C.): 7.265 g · cm ⁻³ , Silver density (20 ° C.): 10.49 g · cm ⁻³ , average particle diameter of tin nanoparticles d1 = 42 nm and average particle diameter of silver nanoparticles Considering the ratio d1: d2 = 42: 10 of d2 = 10 nm, the ratio N1: N2 of the number N1 of tin nanoparticles and the number N2 of silver nanoparticles is estimated to be 18:29. In the ink-like solder composition, the volume ratio of the total of tin nanoparticles, silver nanoparticles, and copper derived from the rosin copper salt to the dispersion solvent is 0.4: 35.

  Using the produced ink-like solder composition, a 3216 chip component having a Sn plating electrode was soldered onto a copper pad on the substrate. The copper pad on the substrate is previously washed with 2.5N sulfuric acid, washed with water and then dried. By the pickling treatment, the oxide film on the surface of the copper pad is removed. An ink-like solder composition is inkjet printed on the copper pad surface using an inkjet apparatus. The coating thickness of the printed ink-like solder composition was about 100 μm.

  On the coating film of the ink-like solder composition on the copper pad, the 3216 chip component is placed in a shape in which the Sn plating electrode is in close contact. Heat treatment is performed at 220 ° C. for 10 minutes, and then at 270 ° C. for 3 minutes. During heating to 220 ° C., the oxide film on the metal surface is removed by the flux agent. At the same time, with this heat treatment, dodecylamine constituting the coating molecular layer on the surface of the silver nanoparticles is released. In addition, the dissolved rosin copper salt (copper (II) salt of abietic acid) deposits copper atoms on the surface of tin metal by the following substitutional reduction reaction on the surface of tin nanoparticles without surface oxide film. Let The copper atoms deposited on the metal tin surface of the tin nanoparticles once constitute a coating layer covering the surface of the tin nanoparticles.

[(C ₁₉ H ₂₉ COO) ₂ Cu: Cu (OOCH ₂₉ C ₁₉ )] → 2 (C ₁₉ H ₂₉ COO ⁻ ) ₂ Cu ²⁺
(C ₁₉ H ₂₉ COO ⁻ ) ₂ Cu ²⁺ + Sn → Cu + (C ₁₉ H ₂₉ COO ⁻ ) ₂ Sn ²⁺

As a result, tin nanoparticles having no surface oxide film and silver nanoparticles are deposited on a copper pad showing a clean surface, resulting in a densely laminated state. At the site where the tin nanoparticles and silver nanoparticles are in contact with each other on the metal surface, the fusion proceeds. Also, the tin nanoparticles and silver nanoparticles that are in contact with the copper pad surface are also fused at the site of contact with the copper surface. proceed. In particular, a denser fusion proceeds at a contact portion between the tin nanoparticle in which the coating layer of copper atoms on the surface is formed and the copper surface. On the other hand, the surface of the Sn plating electrode of the 3216 chip component placed on the coating film of the ink-like solder composition is also in a state where a clean metal surface is exposed. When tetradecane as a dispersion solvent evaporates, the surface of the Sn plating electrode comes into close contact with the upper surface of the mixture layer of tin nanoparticles and silver nanoparticles in a densely stacked state. The fusion of the tin nanoparticles and silver nanoparticles in contact with the surface of the Sn plating electrode similarly proceeds at the contact site with the tin plating surface.

  Next, in a heating (reflow) treatment at 270 ° C. for 3 minutes, in the mixture layer of the tin nanoparticles that have already been mutually fused, the tin nanoparticles that the copper atom coating layer has, and the silver nanoparticles, As a result of exceeding the melting point, melting progresses as a whole and alloying progresses. Therefore, a state in which the surface of the copper pad and the surface of the Sn plating electrode are wetted by the Sn—Ag—Cu alloy to be generated is achieved, and solder bonding is performed. At this stage, the layer thickness of the Sn—Ag—Cu alloy layer at the solder joint portion corresponds to 10 μm.

When the die shear strength of the 3216 chip component was measured under the condition that the area size of the solder joint portion was 0.8 mm ² , it showed a high strength of 40 N at room temperature. Furthermore, when the die shear strength is measured at 200 ° C., it is 35 N, and a sufficiently high bonding strength is maintained.

(Example 3)
Hydrogenated rosin is added as tin nanoparticles, silver nanoparticles, and a flux component, and an ink-like solder composition is prepared by the following procedure.

As a raw material for tin nanoparticles, a commercially available tin nanoparticle dispersion, specifically, 10 parts by mass of tin nanoparticles having an average particle size of 42 nm, was added to toluene (boiling point 110.6 ° C., specific gravity d ₄ ^20). = 0.867) Tin nanocolloid (Shinko Chemical Industry Co., Ltd.) dispersed in 90 parts by mass is used. Dispersing solvent in which 7 parts by mass of dodecylamine (molecular weight: 185.36, melting point: 28.3 ° C., boiling point: 248 ° C., specific gravity d ₄ ⁴⁰ = 0.7841) was dissolved in 52.8 parts by mass of toluene as a raw material for silver nanoparticles A commercially available silver nanoparticle dispersion (trade name: independently dispersed ultrafine particles Ag1T manufactured by vacuum metallurgy) in which 40.2 parts by mass of silver nanoparticles having an average particle diameter of 10 nm are dispersed is used. In the silver nanoparticle dispersion liquid, the surface of the silver nanoparticle is formed via a coordinated bond to the silver atom using a lone electron pair in which dodecylamine, which is an alkylamine, is present on the nitrogen atom of the amino group. A covering molecular layer is formed on the substrate. Therefore, the silver nanoparticles are uniformly dispersed in the dispersion solvent using dodecylamine forming a coating molecular layer on the surface as a dispersant.

  Moreover, a 22.9 mass% toluene solution is used for the raw material of hydrogenated rosin (molecular weight 304) added as a flux agent.

  First, in a 100 ml eggplant-shaped flask, 100 parts by mass of tin nanocolloid (containing Sn 10 wt%), 0.77 parts by mass of silver ultrafine particle dispersion Ag1T (containing Ag 40.2 wt%), a toluene solution of hydrogenated rosin (concentration 22) .9 wt%) 5.56 parts by mass is added, mixed, and stirred at 40 ° C. for 1 hour. After completion of the stirring, the dispersion solvent toluene is removed by concentration under reduced pressure. The mixture after solvent removal contains 0.31 part by mass of silver nanoparticles, 0.054 parts by mass of dodecylamine, and 1.27 parts by mass of hydrogenated rosin per 10 parts by mass of tin nanoparticles.

As a dispersion solvent, 3.14 parts by mass of the mixture after desolvation, N14 (tetradecane, viscosity 2.0 to 2.3 mPa · s (20 ° C.), melting point 5.86 ° C., boiling point 253.57 ° C., specific gravity d ₄ ²⁰ = 0.7924, manufactured by Nippon Mining Petrochemical Co., Ltd.) is added in an amount of 27.3 parts by mass. Thereafter, the mixture is stirred at room temperature (25 ° C.) to obtain a uniform dispersion. After the stirring, the dispersion was filtered with a 0.2 μm membrane filter.

The resulting dispersion is a highly fluid composition having a liquid viscosity (B-type rotational viscometer, measurement temperature 20 ° C.) of 13 mPa · s, and is a uniform black ink-like solder composition. The mixing ratio of tin nanoparticles and silver nanoparticles: W _Sn : W _Ag in the solder composition is 97: 3, which is a ratio suitable for Sn—Ag alloy solder. The melting point of this ratio of Sn—Ag alloy is 221 ° C. relative to the melting point of metal tin 232 ° C. Tin density (20 ° C.): 7.265 g · cm ⁻³ , Silver density (20 ° C.): 10.49 g · cm ⁻³ , average particle diameter of tin nanoparticles d1 = 42 nm and average particle diameter of silver nanoparticles Considering the ratio d1: d2 = 42: 10 of d2 = 10 nm, the ratio N1: N2 of the number N1 of tin nanoparticles and the number N2 of silver nanoparticles is estimated to be 18:29. In the ink-like solder composition, the volume ratio of tin nanoparticles, silver nanoparticles, and the dispersion solvent is 0.4: 35.

  Using the produced ink-like solder composition, a 3216 chip component having a Sn plating electrode was soldered onto a copper pad on the substrate. The copper pad on the substrate is previously washed with 2.5N sulfuric acid, washed with water and then dried. By the pickling treatment, the oxide film on the surface of the copper pad is removed. An ink-like solder composition is inkjet printed on the copper pad surface using an inkjet apparatus. The coating thickness of the printed ink-like solder composition was about 100 μm.

  On the coating film of the ink-like solder composition on the copper pad, the 3216 chip component is placed in a shape in which the Sn plating electrode is in close contact. Heat treatment is performed at 220 ° C. for 10 minutes, and then at 270 ° C. for 3 minutes. During heating to 220 ° C., the oxide film on the metal surface is removed by the flux agent. At the same time, with this heat treatment, dodecylamine constituting the coating molecular layer on the surface of the silver nanoparticles is released.

  As a result, tin nanoparticles having no surface oxide film and silver nanoparticles are deposited on a copper pad showing a clean surface, resulting in a densely laminated state. At the site where the tin nanoparticles and silver nanoparticles are in contact with each other on the metal surface, the fusion proceeds. Also, the tin nanoparticles and silver nanoparticles that are in contact with the copper pad surface are also fused at the site of contact with the copper surface. proceed. On the other hand, the surface of the Sn plating electrode of the 3216 chip component placed on the coating film of the ink-like solder composition is also in a state where a clean metal surface is exposed. When tetradecane as a dispersion solvent evaporates, the surface of the Sn plating electrode comes into close contact with the upper surface of the mixture layer of tin nanoparticles and silver nanoparticles in a densely stacked state. The fusion of the tin nanoparticles and silver nanoparticles in contact with the surface of the Sn plating electrode similarly proceeds at the contact site with the tin plating surface.

  Next, in the heating (reflow) treatment at 270 ° C. for 3 minutes, in the mixture layer of tin nanoparticles and silver nanoparticles that have already been mutually fused, as a result of exceeding the melting point of metallic tin, the melting proceeds overall, Alloying proceeds. Therefore, a state in which the surface of the copper pad and the surface of the Sn plating electrode are wet is achieved by the Sn—Ag alloy to be formed, and solder bonding is performed. At this stage, the thickness of the Sn—Ag alloy layer at the solder joint portion corresponds to 13 μm.

When the die shear strength of the 3216 chip component was measured under the condition that the area size of the solder joint portion was 0.8 mm ² , it showed a high strength of 50 N at room temperature. Furthermore, when the die shear strength is measured at 200 ° C., it is 36 N, and a sufficiently high bonding strength is maintained.

Example 4
Hydrogenated rosin is added as a tin nanoparticle, two types of silver nanoparticles, and a flux component, and an ink-like solder composition is prepared by the following procedure.

As a raw material for tin nanoparticles, a commercially available tin nanoparticle dispersion, specifically, 10 parts by mass of tin nanoparticles having an average particle size of 42 nm, was added to toluene (boiling point 110.6 ° C., specific gravity d ₄ ^20). = 0.867) Tin nanocolloid (Shinko Chemical Industry Co., Ltd.) dispersed in 90 parts by mass is used. As a raw material for silver nanoparticles, a silver nanoparticle dispersion containing two kinds of silver nanoparticles having an average particle diameter of 5 nm and different from 30 nm is used.

In a dispersion of silver nanoparticles having an average particle diameter of 5 nm, 7 parts by mass of dodecylamine (molecular weight 185.36, melting point 28.3 ° C., boiling point 248 ° C., specific gravity d ₄ ⁴⁰ = 0.7841) is 52.8 masses of toluene. 40.2 parts by mass of silver nanoparticles having an average particle diameter of 5 nm are dispersed in a dispersion solvent dissolved in the part, and a commercially available silver nanoparticle dispersion (trade name: Independently Dispersed Ultrafine Particles Ag1T manufactured by Vacuum Metallurgy ) Is used. In the silver nanoparticle dispersion liquid, the surface of the silver nanoparticle is formed via a coordinated bond to the silver atom using a lone electron pair in which dodecylamine, which is an alkylamine, is present on the nitrogen atom of the amino group. A covering molecular layer is formed on the substrate. Therefore, the silver nanoparticles are uniformly dispersed in the dispersion solvent using dodecylamine forming a coating molecular layer on the surface as a dispersant.

  On the other hand, a dispersion of silver nanoparticles having an average particle diameter of 30 nm is prepared by the following method. Silver nanoparticles having an average particle diameter of 5 nm are used as core particles, and silver is deposited on the surface by wet reduction to obtain silver nanoparticles having an average particle diameter of 30 nm. At that time, silver oleate of an organic acid silver (II) salt is used as a silver raw material, hydrazine is used as a reducing agent, reduction is performed in a solvent ethanol, and the silver nanoparticles added to the reaction liquid are reduced. A deposited layer of silver atoms is formed using the surface as a nucleus. In the solvent, dodecylamine covering the surface of silver nanoparticles having an average particle diameter of 5 nm is released, and silver atoms are selectively deposited on the exposed surface. Although the film thickness of the silver deposit layer has a wide distribution, silver nanoparticles having an average particle diameter of 30 nm are formed. Moreover, the surface of the silver nanoparticle with an average particle diameter of 30 nm produced is the state coat | covered with the ethanolamine which functions as a dispersing agent. After separating from the reaction liquid, a dispersion liquid is prepared by dispersing 40 parts by mass of silver nanoparticles having an average particle diameter of 30 nm in 60 parts by mass of toluene as a dispersion solvent.

  Further, as a raw material for hydrogenated rosin (molecular weight 304) added as a fluxing agent, a 22.9% by mass hydrogenated rosin toluene solution is used.

  First, in a 100 ml eggplant-shaped flask, 100 parts by mass of tin nanocolloid (containing Sn 10 wt%), silver ultrafine particle dispersion Ag1T (containing Ag 40.2 wt%) 0.0769 parts by mass, silver nanoparticles dispersed with an average particle diameter of 30 nm Add 0.696 parts by mass of liquid (containing 40 wt% Ag) and 5.56 parts by mass of a toluene solution of hydrogenated rosin (concentration 22.9 wt%), mix and stir at 40 ° C. for 1 hour. After completion of the stirring, the dispersion solvent toluene is removed by concentration under reduced pressure. The mixture after solvent removal contains 0.31 part by mass of silver nanoparticles, 0.054 parts by mass of dodecylamine, and 1.27 parts by mass of hydrogenated rosin per 10 parts by mass of tin nanoparticles.

As a dispersion solvent, 3.14 parts by mass of the mixture after desolvation, N14 (tetradecane, viscosity 2.0 to 2.3 mPa · s (20 ° C.), melting point 5.86 ° C., boiling point 253.57 ° C., specific gravity d ₄ ²⁰ = 0.7924, manufactured by Nippon Mining Petrochemical Co., Ltd.) is added in an amount of 27.3 parts by mass. Thereafter, the mixture is stirred at room temperature (25 ° C.) to obtain a uniform dispersion. After the stirring, the dispersion was filtered with a 0.2 μm membrane filter.

The resulting dispersion is a highly fluid composition having a liquid viscosity (B-type rotational viscometer, measurement temperature 20 ° C.) of 11 mPa · s, and is a uniform black ink-like solder composition. The total blending ratio of tin nanoparticles and two types of silver nanoparticles: W _Sn : W _Ag in the solder composition is 97: 3, which is a ratio suitable for Sn—Ag alloy solder. The melting point of the Sn—Ag alloy at this ratio is 221 ° C. with respect to the melting point of metal tin 232 ° C. Tin density (20 ° C.): 7.265 g · cm ⁻³ , silver density (20 ° C.): 10.49 g · cm ⁻³ , average particle diameter d1 of tin nanoparticles = 42 nm, and silver having an average particle diameter of 5 nm Considering the ratio d1: d2 = 42: 5 of the average particle diameter d2 = 5 nm of nanoparticles, the ratio of the number N1 of tin nanoparticles and the number N2 of silver nanoparticles having an average particle diameter of 5 nm: N1: N2 is 18: It is estimated to be 33. The ratio N1: N3 of the number N1 of tin nanoparticles and the number N3 of silver nanoparticles having an average particle diameter of 30 nm is estimated to be 18: 1.3. The ratio of the number N2 of silver nanoparticles having an average particle diameter of 5 nm and the number N3 of silver nanoparticles having an average particle diameter of 30 nm: N2: N3 is estimated to be 33: 1.3. 95% is occupied by silver nanoparticles having an average particle diameter of 5 nm. In other words, the majority corresponds to a state in which a small number of silver nanoparticles having an average particle diameter of 30 nm are further added to silver nanoparticles having an average particle diameter of 5 nm.

  In the ink-like solder composition, the volume ratio of the tin nanoparticles, the silver nanoparticles, and the dispersion solvent is 0.4: 35.

  Using the produced ink-like solder composition, a 3216 chip component having a Sn plating electrode was soldered onto a copper pad on the substrate. The copper pad on the substrate is previously washed with 2.5N sulfuric acid, washed with water and then dried. By the pickling treatment, the oxide film on the surface of the copper pad is removed. An ink-like solder composition is inkjet printed on the copper pad surface using an inkjet apparatus. The coating thickness of the printed ink-like solder composition was about 100 μm.

  On the coating film of the ink-like solder composition on the copper pad, the 3216 chip component is placed in a shape in which the Sn plating electrode is in close contact. Heat treatment is performed at 220 ° C. for 10 minutes, and then at 270 ° C. for 3 minutes. During heating to 220 ° C., the oxide film on the metal surface is removed by the flux agent. At the same time, with this heat treatment, dodecylamine constituting the coating molecular layer on the surface of the silver nanoparticles having an average particle diameter of 5 nm is released. Moreover, the ethanolamine which comprises the dispersing agent layer which coat | covers the silver nanoparticle surface with an average particle diameter of 30 nm is also made | formed.

  As a result, tin nanoparticles without a surface oxide film, silver nanoparticles with an average particle diameter of 5 nm, and silver nanoparticles with an average particle diameter of 30 nm were deposited on a copper pad showing a clean surface and densely stacked. It becomes a state. At that time, since the number of silver nanoparticles having an average particle diameter of 30 nm is small, the probability of contact with the copper pad surface is small. At the site where the tin nanoparticle and silver nanoparticle are in contact with the metal surface, the fusion proceeds, and the tin nanoparticle in contact with the copper pad surface and the silver nanoparticle having an average particle diameter of 5 nm are in contact with the copper surface. Similarly, fusion proceeds. On the other hand, the surface of the Sn plating electrode of the 3216 chip component placed on the coating film of the ink-like solder composition is also in a state where a clean metal surface is exposed. When tetradecane as a dispersion solvent evaporates, the surface of the Sn plating electrode comes into close contact with the upper surface of the mixture layer of tin nanoparticles and silver nanoparticles in a densely stacked state. The tin nanoparticles in contact with the surface of the Sn plating electrode and the silver nanoparticles having an average particle diameter of 5 nm are similarly fused at the contact site with the tin plating surface.

  Next, in the heating (reflow) treatment at 270 ° C. for 3 minutes, in the mixture layer of tin nanoparticles and silver nanoparticles that have already been mutually fused, as a result of exceeding the melting point of metallic tin, the melting proceeds overall, Alloying proceeds. Therefore, a state in which the surface of the copper pad and the surface of the Sn plating electrode are wet is achieved by the Sn—Ag alloy to be formed, and solder bonding is performed. At this stage, the thickness of the Sn—Ag alloy layer at the solder joint portion corresponds to 15 μm.

When the die shear strength of the 3216 chip component was measured under the condition of an area size of 0.8 mm ^{2 at} the solder joint portion, it showed a high strength of 45 N at room temperature. Furthermore, when the die shear strength is measured at 200 ° C., it is 30 N, and a sufficiently high bonding strength is maintained.

(Reference Example 1)
A hydrogenated rosin is added as tin nanoparticles, silver 2-ethylhexanoate (II), and a flux component, and a paste solder composition is prepared by the following procedure.

As a raw material for tin nanoparticles, a commercially available tin nanoparticle dispersion, specifically, 10 parts by mass of tin nanoparticles having an average particle size of 42 nm, was added to toluene (boiling point 110.6 ° C., specific gravity d ₄ ^20). = 0.867) Tin nanocolloid (Shinko Chemical Industry Co., Ltd.) dispersed in 90 parts by mass is used. As a raw material of silver 2-ethylhexanoate (II), silver 2-ethylhexanoate (II) ((CH ₃ —CH ₂ —CH ₂ —CH ₂ —CH (C ₂ H ₅ ) —COO) ₂ Ag) is used. , A solution (containing 2.1 wt% Ag) dissolved in dibutylaminopropylamine (boiling point 205 ° C., specific gravity d ₄ ²⁰ = 0.827) at a concentration of 4.89 wt% is used.

  Moreover, a 22.9 mass% toluene solution is used for the raw material of hydrogenated rosin (molecular weight 304) added as a flux agent.

  First, in a 100 ml eggplant-shaped flask, 100 parts by mass of tin nanocolloid (containing Sn 10 wt%), dibutylaminopropylamine solution of silver 2-ethylhexanoate (II) (containing Ag 2.1 wt%), 14.71 parts by mass, Add 5.56 parts by mass of hydrogenated rosin in toluene (concentration 22.9 wt%), mix and stir at 40 ° C. for 1 hour. After completion of the stirring, the dispersion solvent toluene is removed by concentration under reduced pressure. The solvent-removed mixture contains 0.31 part by mass of silver (II) 2-ethylhexanoate, 14.4 parts by mass of dibutylaminopropylamine, and 1.27 parts by mass of hydrogenated rosin per 10 parts by mass of tin nanoparticles. include.

In this mixture after solvent removal, as a dispersion solvent, N14 (tetradecane, viscosity 2.0 to 2.3 mPa · s (20 ° C.), melting point 5.86 ° C. per 3.11 parts by weight of the portion excluding decalin, 27.3 parts by mass of boiling point 253.57 ° C., specific gravity d ₄ ²⁰ = 0.7924, manufactured by Nippon Mining Petrochemical Co., Ltd. is added. Thereafter, the mixture is stirred at room temperature (25 ° C.) to obtain a uniform dispersion. After the stirring, the dispersion was filtered with a 0.2 μm membrane filter.

The resulting dispersion is a highly fluid composition having a liquid viscosity (B-type rotational viscometer, measurement temperature 20 ° C.) of 20 mPa · s, and is a uniform black ink-like solder composition. The mixing ratio of tin nanoparticles and silver derived from silver 2-ethylhexanoate (II) in the solder composition: W _Sn : W _Ag is 97: 3, which is a ratio suitable for Sn—Ag alloy solder. ing. The melting point of the Sn—Ag alloy at this ratio is 221 ° C. with respect to the melting point of metal tin 232 ° C.

  In the ink-like solder composition, the volume ratio of tin nanoparticles to the dispersion solvent is 0.4: 35.

  Using the produced ink-like solder composition, a 3216 chip component having a Sn plating electrode was soldered onto a copper pad on the substrate. The copper pad on the substrate is previously washed with 2.5N sulfuric acid, washed with water and then dried. By the pickling treatment, the oxide film on the surface of the copper pad is removed. An ink-like solder composition is applied to the surface of the copper pad using an inkjet apparatus. The coating thickness of the ink-like solder composition was about 120 μm.

On the coating film of the ink-like solder composition on the copper pad, the 3216 chip component is placed in a shape in which the Sn plating electrode is in close contact. Heat treatment is performed at 220 ° C. for 30 minutes and then at 270 ° C. for 3 minutes. During heating to 220 ° C., the oxide film on the metal surface is removed by the flux agent. At the same time, with this heat treatment, from silver 2-ethylhexanoate (II), for example, on the surface of tin nanoparticles having no surface oxide film, silver atoms are formed on the surface of metal tin by the following substitutional reduction reaction. Precipitate. Silver atoms deposited on the metal tin surface of the tin nanoparticles once constitute a coating layer covering the surface of the tin nanoparticles.

(C ₇ H ₁₅ COO ⁻ ) ₂ Ag ²⁺ + Sn → Ag + (C ₇ H ₁₅ COO ⁻ ) ₂ Sn ²⁺

In addition, partly due to the thermal decomposition of silver 2-ethylhexanoate (II), silver atoms are liberated and agglomerate with each other to form silver nanoparticles in the system.

  As a result, on the copper pad showing a clean surface, tin nanoparticles having no surface oxide film, tin nanoparticles having a silver coating layer formed on the surface, and silver nanoparticles generated in the system are deposited, It will be in the state where it was densely laminated. At the site where the tin nanoparticles and silver nanoparticles are in contact with each other on the metal surface, the fusion proceeds. Also, the tin nanoparticles and silver nanoparticles that are in contact with the copper pad surface are also fused at the site of contact with the copper surface. proceed. On the other hand, the surface of the Sn plating electrode of the 3216 chip component placed on the coating film of the paste solder composition is also in a state where a clean metal surface is exposed. When tetradecane as a dispersion solvent evaporates, the surface of the Sn plating electrode comes into close contact with the upper surface of the mixture layer of tin nanoparticles and silver nanoparticles in a densely stacked state. The fusion of the tin nanoparticles and silver nanoparticles in contact with the surface of the Sn plating electrode similarly proceeds at the contact site with the tin plating surface.

  Next, in the heating (reflow) treatment at 270 ° C. for 3 minutes, in the mixture layer of tin nanoparticles and silver nanoparticles that have already been mutually fused, as a result of exceeding the melting point of metallic tin, the melting proceeds overall, Alloying proceeds. Therefore, a state in which the surface of the copper pad and the surface of the Sn plating electrode are wet is achieved by the Sn—Ag alloy to be formed, and solder bonding is performed. At this stage, the thickness of the Sn—Ag alloy layer at the solder joint portion corresponds to 13 μm.

When the die shear strength of the 3216 chip component was measured under the condition that the area size of the solder joint portion was 0.8 mm ² , it showed a high strength of 48 N at room temperature. Furthermore, when the die shear strength is measured at 200 ° C., it is 31 N, and a sufficiently high bonding strength is maintained.

(Reference Example 2)
A hydrogenated rosin is added as tin nanoparticles, silver 2-ethylhexanoate (II), and a flux component, and a paste solder composition is prepared by the following procedure.

As a raw material for tin nanoparticles, a commercially available tin nanoparticle dispersion, specifically, 10 parts by mass of tin nanoparticles having an average particle size of 42 nm, was added to toluene (boiling point 110.6 ° C., specific gravity d ₄ ^20). = 0.867) Tin nanocolloid (Shinko Chemical Industry Co., Ltd.) dispersed in 90 parts by mass is used. As a raw material of silver 2-ethylhexanoate (II), silver 2-ethylhexanoate (II) ((CH ₃ —CH ₂ —CH ₂ —CH ₂ —CH (C ₂ H ₅ ) —COO) ₂ Ag) is used. A solution (containing 2.1 wt% of Ag) dissolved in a concentration of 4.89 wt% in decalin (cis-form: boiling point 195.7 ° C., specific gravity d ₄ ²⁰ = 0.8963) of an organic solvent is used.

  Further, as a raw material for hydrogenated rosin (molecular weight 304) added as a fluxing agent, a 22.9% by mass hydrogenated rosin toluene solution is used.

  First, in a 100 ml eggplant-shaped flask, 100 parts by mass of tin nanocolloid (containing Sn 10 wt%), decalin solution of silver 2-ethylhexanoate (II) (containing 2.1 wt% of Ag) 14.71 parts by mass, hydrogenated rosin Of toluene solution (concentration 22.9 wt%) is added, mixed, and stirred at 40 ° C. for 1 hour. After completion of the stirring, the dispersion solvent toluene is removed by concentration under reduced pressure. The mixture after the solvent removal contains 0.31 part by mass of silver (II) 2-ethylhexanoate, 14.4 parts by mass of decalin, and 1.27 parts by mass of hydrogenated rosin per 10 parts by mass of tin nanoparticles. Yes.

In this mixture after solvent removal, as a dispersion solvent, N14 (tetradecane, viscosity 2.0 to 2.3 mPa · s (20 ° C.), melting point 5.86 ° C. per 3.11 parts by weight of the portion excluding decalin, 27.3 parts by mass of boiling point 253.57 ° C., specific gravity d ₄ ²⁰ = 0.7924, manufactured by Nippon Mining Petrochemical Co., Ltd. is added. Thereafter, the mixture is stirred at room temperature (25 ° C.) to obtain a uniform dispersion. After the stirring, the dispersion was filtered with a 0.2 μm membrane filter.

The resulting dispersion is a low fluid composition having a liquid viscosity (B-type rotational viscometer, measurement temperature 20 ° C.) of 500 mPa · s, and is a uniform black paste solder composition. The mixing ratio of tin nanoparticles and silver derived from silver 2-ethylhexanoate (II) in the solder composition: W _Sn : W _Ag is 97: 3, which is a ratio suitable for Sn—Ag alloy solder. ing. The melting point of the Sn—Ag alloy at this ratio is 221 ° C. with respect to the melting point of metal tin 232 ° C.

  In the paste-like solder composition, the volume ratio of tin nanoparticles to the dispersion solvent is 0.4: 35.

  Using the prepared paste-like solder composition, a 3216 chip component having an Sn plating electrode was soldered onto a copper pad on the substrate. The copper pad on the substrate is previously washed with 2.5N sulfuric acid, washed with water and then dried. By the pickling treatment, the oxide film on the surface of the copper pad is removed. A paste solder composition is applied to the surface of the copper pad using a dispenser. The coating thickness of the paste solder composition was about 120 μm.

On the coating film of the paste solder composition on the copper pad, a 3216 chip component is placed in a shape in which the Sn plating electrode is in close contact. Heat treatment is performed at 220 ° C. for 30 minutes and then at 270 ° C. for 3 minutes. During heating to 220 ° C., the oxide film on the metal surface is removed by the flux agent. At the same time, with this heat treatment, from silver 2-ethylhexanoate (II), for example, on the surface of tin nanoparticles having no surface oxide film, silver atoms are formed on the surface of metal tin by the following substitutional reduction reaction. Precipitate. Silver atoms deposited on the metal tin surface of the tin nanoparticles once constitute a coating layer covering the surface of the tin nanoparticles.

(C ₇ H ₁₅ COO ⁻ ) ₂ Ag ²⁺ + Sn → Ag + (C ₇ H ₁₅ COO ⁻ ) ₂ Sn ²⁺

In addition, due to the thermal decomposition of silver (II) 2-ethylhexanoate, silver atoms are liberated and agglomerate with each other to form silver nanoparticles in the system.

  As a result, on the copper pad showing a clean surface, tin nanoparticles having no surface oxide film, tin nanoparticles having a silver coating layer formed on the surface, and silver nanoparticles generated in the system are deposited, It will be in the state where it was densely laminated. At the site where the tin nanoparticles and silver nanoparticles are in contact with each other on the metal surface, the fusion proceeds. Also, the tin nanoparticles and silver nanoparticles that are in contact with the copper pad surface are also fused at the site of contact with the copper surface. proceed. On the other hand, the surface of the Sn plating electrode of the 3216 chip component placed on the coating film of the paste solder composition is also in a state where a clean metal surface is exposed. When tetradecane as a dispersion solvent evaporates, the surface of the Sn plating electrode comes into close contact with the upper surface of the mixture layer of tin nanoparticles and silver nanoparticles in a densely stacked state. The fusion of the tin nanoparticles and silver nanoparticles in contact with the surface of the Sn plating electrode similarly proceeds at the contact site with the tin plating surface.

  Next, in the heating (reflow) treatment at 270 ° C. for 3 minutes, in the mixture layer of tin nanoparticles and silver nanoparticles that have already been mutually fused, as a result of exceeding the melting point of metallic tin, the melting proceeds overall, Alloying proceeds. Therefore, a state in which the surface of the copper pad and the surface of the Sn plating electrode are wet is achieved by the Sn—Ag alloy to be formed, and solder bonding is performed. At this stage, the thickness of the Sn—Ag alloy layer at the solder joint portion corresponds to 15 μm.

When the die shear strength of the 3216 chip component was measured under the condition that the area size of the solder joint portion was 0.8 mm ² , it showed a high strength of 48 N at room temperature. Furthermore, when the die shear strength is measured at 200 ° C., it is 32 N, and a sufficiently high bonding strength is maintained.

(Comparative Example 1)
Hydrogenated rosin is added as a tin nanoparticle, silver particle, rosin copper salt, and flux component, and an ink-like solder composition is prepared by the following procedure.

As a raw material for tin nanoparticles, a commercially available tin nanoparticle dispersion, specifically, 10 parts by mass of tin nanoparticles having an average particle size of 42 nm, was added to toluene (boiling point 110.6 ° C., specific gravity d ₄ ^20). = 0.867) Tin nanocolloid (Shinko Chemical Industry Co., Ltd.) dispersed in 90 parts by mass is used. As a raw material for silver particles, a silver particle dispersion liquid in which 40 parts by mass of silver particles having an average particle diameter of 1 μm are dispersed in 90 parts by mass of toluene is used. As a raw material of rosin copper salt (copper (II) salt of abietic acid), a toluene solution of rosin copper salt (concentration 20 wt%, copper content 1.91 wt%) is used.

  Further, as a raw material for hydrogenated rosin (molecular weight 304) added as a fluxing agent, a 22.9% by mass hydrogenated rosin toluene solution is used.

  First, in a 100 ml eggplant-shaped flask, 100 parts by mass of tin nanocolloid (containing Sn 10 wt%), 0.773 parts by mass of silver particle dispersion (containing 40 wt% Ag), rosin copper salt (toluene solution, 20%, for containing copper) 2.91 parts by weight of 1.91%) and 5.59 parts by weight of a toluene solution of hydrogenated rosin (concentration 22.9 wt%) are added, mixed, and stirred at 40 ° C. for 1 hour. After completion of the stirring, the dispersion solvent toluene is removed by concentration under reduced pressure. The mixture after solvent removal contains 0.311 parts by mass of silver particles, 0.0518 parts by mass of rosin copper salt (in terms of copper content), and 1.28 parts by mass of hydrogenated rosin per 10 parts by mass of tin nanoparticles. ing.

As a dispersion solvent, N14 (tetradecane, viscosity 2.0 to 2.3 mPa · s (20 ° C.), melting point 5.86 ° C., boiling point 253.57 ° C., specific gravity per 3.11 parts by mass of the mixture after desolvation. d ₄ ²⁰ = 0.7924, manufactured by Nippon Mining Petrochemical Co., Ltd.) is added in an amount of 27.3 parts by mass. Thereafter, the mixture is stirred at room temperature (25 ° C.) to obtain a uniform dispersion.

The resulting dispersion is a highly fluid composition having a liquid viscosity (B-type rotational viscometer, measurement temperature 20 ° C.) of 12 mPa · s, and is a uniform ink-like solder composition. In the solder composition, the mixing ratio of tin nanoparticles, silver nanoparticles, copper in the rosin copper salt: W _Sn : W _Ag : W _Cu is 96.5: 3: 0.5, Sn—Ag -The ratio is suitable for Cu alloy solder. The melting point of the Sn—Ag—Cu alloy at this ratio is 221 ° C. with respect to the melting point of metal tin 232 ° C. Tin density (20 ° C.): 7.265 g · cm ⁻³ , silver density (20 ° C.): 10.49 g · cm ⁻³ , average particle diameter of tin nanoparticles d1 = 42 nm, and average particle diameter of silver particles Considering the ratio d1: d2 = 42: 1000 of d2 = 1 μm, the ratio N1: N2 of the number N1 of tin nanoparticles and the number N2 of silver particles having an average particle diameter of 1 μm is estimated to be 1800000: 3.

  In the ink-like solder composition, the volume ratio of the total amount of tin nanoparticles, silver particles, and copper derived from the rosin copper salt to the dispersion solvent is 0.4: 35.

  Using the produced ink-like solder composition, soldering of a 3216 chip part having an Sn plating electrode was attempted on a copper pad on a substrate. The copper pad on the substrate is previously washed with 2.5N sulfuric acid, washed with water and then dried. By the pickling treatment, the oxide film on the surface of the copper pad is removed. An ink-like solder composition is applied to the copper pad surface using a dispenser. The coating thickness of the ink-like solder composition was about 140 μm.

  On the coating film of the ink-like solder composition on the copper pad, the 3216 chip component is placed in a shape in which the Sn plating electrode is in close contact. Heat treatment is performed at 220 ° C. for 10 minutes, and then at 270 ° C. for 3 minutes. During heating to 220 ° C., the oxide film on the metal surface is removed by the flux agent. In addition, the dissolved rosin copper salt (copper (II) salt of abietic acid) deposits copper atoms on the surface of tin metal by the following substitutional reduction reaction on the surface of tin nanoparticles without surface oxide film. Let The copper atoms deposited on the metal tin surface of the tin nanoparticles once constitute a coating layer covering the surface of the tin nanoparticles.

[(C ₁₉ H ₂₉ COO) ₂ Cu: Cu (OOCH ₂₉ C ₁₉ )] → 2 (C ₁₉ H ₂₉ COO ⁻ ) ₂ Cu ²⁺
(C ₁₉ H ₂₉ COO ⁻ ) ₂ Cu ²⁺ + Sn → Cu + (C ₁₉ H ₂₉ COO ⁻ ) ₂ Sn ²⁺

Next, in the heating (reflow) treatment at 270 ° C. for 3 minutes, the melting point of metallic tin is in a state where a limited number of silver particles are mixed in the layer of tin nanoparticles that have already been mutually fused. As a result, melting of the tin nanoparticles proceeds, but alloying having a uniform composition as a whole has not been achieved. Therefore, in most of the portions, the surface of the copper pad and the surface of the Sn plating electrode are wetted by the molten metal tin, and the bonding using simple tin is performed. At this stage, the apparent thickness of the alloy layer at the solder joint portion corresponds to 17 μm.

When the die shear strength of the 3216 chip component was measured under the condition that the area size of the joined portion was 0.8 mm ² , the strength was only 7 N at room temperature.

(Comparative Example 2)
Tin nanoparticles, silver particles, and rosin copper salt are added, and an ink-like solder composition is prepared by the following procedure.

As a raw material for tin nanoparticles, a commercially available tin nanoparticle dispersion, specifically, 10 parts by mass of tin nanoparticles having an average particle size of 42 nm, was added to toluene (boiling point 110.6 ° C., specific gravity d ₄ ^20). = 0.867) Tin nanocolloid (Shinko Chemical Industry Co., Ltd.) dispersed in 90 parts by mass is used. As a raw material for silver particles, a silver particle dispersion liquid in which 40 parts by mass of silver particles having an average particle diameter of 1 μm are dispersed in 90 parts by mass of toluene is used. As a raw material of rosin copper salt (copper (II) salt of abietic acid), a toluene solution of rosin copper salt (concentration 20 wt%, copper content 1.91 wt%) is used.

  First, in a 100 ml eggplant-shaped flask, 100 parts by mass of tin nanocolloid (containing Sn 10 wt%), 0.773 parts by mass of silver particle dispersion (containing 40 wt% Ag), rosin copper salt (toluene solution, 20%, for containing copper) 1.91%) is added to 2.71 parts by weight, mixed and stirred at 40 ° C. for 1 hour. After completion of the stirring, the dispersion solvent toluene is removed by concentration under reduced pressure. The mixture after solvent removal contains 0.311 parts by mass of silver particles and 0.0518 parts by mass of rosin copper salt (in terms of copper content) per 10 parts by mass of tin nanoparticles.

As a dispersion solvent, N14 (tetradecane, viscosity 2.0 to 2.3 mPa · s (20 ° C.), melting point 5.86 ° C., boiling point 253.57 ° C., specific gravity per 3.11 parts by mass of the mixture after desolvation. d ₄ ²⁰ = 0.7924, manufactured by Nippon Mining Petrochemical Co., Ltd.) is added in an amount of 27.3 parts by mass. Thereafter, the mixture is stirred at room temperature (25 ° C.) to obtain a uniform dispersion.

The resulting dispersion is a highly fluid composition having a liquid viscosity (B-type rotational viscometer, measurement temperature 20 ° C.) of 20 mPa · s, and is a uniform ink-like solder composition. In the solder composition, the mixing ratio of tin nanoparticles, silver nanoparticles, copper in the rosin copper salt: W _Sn : W _Ag : W _Cu is 96.5: 3: 0.5, Sn—Ag -The ratio is suitable for Cu alloy solder. The melting point of the Sn—Ag—Cu alloy at this ratio is 219 ° C. with respect to the melting point of metal tin 232 ° C. Tin density (20 ° C.): 7.265 g · cm ⁻³ , silver density (20 ° C.): 10.49 g · cm ⁻³ , average particle diameter of tin nanoparticles d1 = 42 nm, and average particle diameter of silver particles Considering the ratio d1: d2 = 42: 1000 of d2 = 1 μm, the ratio N1: N2 of the number N1 of tin nanoparticles and the number N2 of silver particles having an average particle diameter of 1 μm is estimated to be 1800000: 3.

  In the ink-like solder composition, the volume ratio of the total amount of tin nanoparticles, silver particles, and copper derived from the rosin copper salt to the dispersion solvent is 0.4: 35.

  Using the produced ink-like solder composition, soldering of a 3216 chip part having an Sn plating electrode on a copper pad on a substrate was attempted. The copper pad on the substrate is previously washed with 2.5N sulfuric acid, washed with water and then dried. By the pickling treatment, the oxide film on the surface of the copper pad is removed. An ink-like solder composition is applied to the copper pad surface using a dispenser. The coating thickness of the ink-like solder composition was about 90 μm.

  On the coating film of the ink-like solder composition on the copper pad, the 3216 chip component is placed in a shape in which the Sn plating electrode is in close contact. Heat treatment is performed at 220 ° C. for 10 minutes, and then at 270 ° C. for 3 minutes. Since the flux agent is not contained, the oxide film on the metal surface is not removed during heating to 220 ° C. Therefore, it is difficult for the dissolved rosin copper salt (copper (II) salt of abietic acid) to perform the following substitutional reduction reaction on the surface of tin nanoparticles having no surface oxide film.

[(C ₁₉ H ₂₉ COO) ₂ Cu: Cu (OOCH ₂₉ C ₁₉ )] → 2 (C ₁₉ H ₂₉ COO ⁻ ) ₂ Cu ²⁺
(C ₁₉ H ₂₉ COO ⁻ ) ₂ Cu ²⁺ + Sn → Cu + (C ₁₉ H ₂₉ COO ⁻ ) ₂ Sn ²⁺

Next, in the heating (reflow) treatment at 270 ° C. for 3 minutes, the melting point of metallic tin in a state where a limited number of silver particles are mixed in the layer of tin nanoparticles in which the surface oxide film remains. As a result, melting of the tin nanoparticles proceeds, but alloying having a uniform composition as a whole has not been achieved. Therefore, for the most part, the molten metal tin comes into contact with the surface of the copper pad and the surface of the Sn plating electrode, but is not subjected to flux treatment and is in a state of attempting to join using tin alone.

An attempt was made to measure the die shear strength of the 3216 chip component under the condition that the area size of the joined portion was 0.8 mm ² , but the strength could not be measured at room temperature. That is, as a result of the oxide film layer remaining on the bonding surface, solder bonding was not performed.

  The fine solder composition of the present invention can be used for solder bonding in which the area of the bonding portion is small, including the case where the electrode of the electronic component chip is solder bonded onto the solder bonding pad surface on the wiring board. In particular, since it can be applied in a fine pattern shape by applying the ink-jet printing method, when mounting electronic component chips on a wiring board with high density by solder bonding using lead-free solder Furthermore, it can be suitably used as a solder composition on ink.

Claims (9)

Ink-like solder comprising tin nanoparticles having an average particle diameter of 2 to 100 nm, silver nanoparticles, and a flux component, and the tin nanoparticles and silver nanoparticles are uniformly dispersed in a non-polar solvent having a high boiling point A composition comprising:
The mixing ratio W _Sn : W _Ag (provided that W _Sn + W _Ag = 100) of the tin nanoparticles and silver nanoparticles is selected in the range of 95: 5 to 99.5: 0,5;
A ratio d1: d2 between the average particle diameter d1 of the tin nanoparticles and the average particle diameter d2 of the silver nanoparticles is selected in the range of 4: 1 to 10: 1;
The addition amount of the flux component per 10 parts by mass of the tin nanoparticles is selected in the range of 0.5 to 2 parts by mass;
An ink-like solder composition, wherein a hydrocarbon solvent having a boiling point in the range of 200 ° C to 320 ° C is selected as the non-polar solvent having a high boiling point. Including tin nanoparticles having an average particle diameter of 2 to 100 nm, silver nanoparticles, organic acid copper salt, and a flux component, the tin nanoparticles and silver nanoparticles are uniformly dispersed in a high-polarity nonpolar solvent. An ink-like solder composition comprising:
The compounding ratio W _Sn : W _Ag : W _Cu (provided that W _Sn + W _Ag + W _Cu = 100) of the copper contained in the tin nanoparticles, silver nanoparticles and organic acid copper salt is as follows:
W _Sn in the range of 95-99.5,
W _Ag in the range of 5-0.5,
Select W _Cu in the range of 0.7-0.1,
A ratio d1: d2 between the average particle diameter d1 of the tin nanoparticles and the average particle diameter d2 of the silver nanoparticles is selected in the range of 4: 1 to 10: 1;
The addition amount of the flux component per 10 parts by mass of the tin nanoparticles is selected in the range of 0.5 to 2 parts by mass;
An ink-like solder composition, wherein a hydrocarbon solvent having a boiling point in the range of 200 ° C to 320 ° C is selected as the non-polar solvent having a high boiling point. The ink-like solder composition according to claim 2, wherein rosin acid copper is used as the organic acid copper salt. The liquid viscosity of the ink-like solder composition is selected in a range of 5 mPa · s to 30 mPa · s (20 ° C.), according to any one of claims 1 to 3. Ink-like solder composition. When the ratio d1: d2 of the average particle diameter d1 of the tin nanoparticles and the average particle diameter d2 of the silver nanoparticles is selected in the range of 4: 1 to 10: 1, the range satisfying the above ratio,
The average particle diameter d1 of the tin nanoparticles is selected in the range of 10 to 100 nm,
The ink-like solder composition according to any one of claims 1 to 4, wherein an average particle diameter d2 of the silver nanoparticles is selected in a range of 2 to 20 nm. The silver nanoparticles are coated with an alkylamine capable of coordinative bonding using a lone electron pair on a nitrogen atom of an amino group with respect to silver atoms on the surface, and the high boiling point is formed. The ink-like solder composition according to any one of claims 1 to 5, wherein the ink-like solder composition is dispersed in a nonpolar solvent. The ink-like solder composition according to claim 6, wherein the compounding amount of the alkylamine is selected in a range of 1 to 6 parts by mass per 10 parts by mass of the silver nanoparticles. The ink-like solder composition according to claim 6 or 7, wherein the alkylamine is a primary alkylamine having 8 to 14 carbon atoms. The ink-like solder composition according to any one of claims 1 to 8, wherein rosin or hydrogenated rosin is added as the flux component.