JP4638825B2 - Multi-component metal particle slurry and conductive ink or conductive paste using the slurry - Google Patents

Description

  The invention according to the present application relates to a multi-component metal particle slurry. In particular, an object is to provide a multi-component metal particle slurry in which tin particles having a primary particle size of nm level are essential, and copper particles and silver particles having a primary particle size of nm level are combined.

  In order to achieve higher functionality at the same time as electronic devices are becoming smaller and lighter, circuit wiring for electronic devices and the like is also required to be smaller and lighter. As a result, new technologies such as fine circuit formation and high-density mounting are required. It has been sought. In particular, in recent years, it has become common to form a circuit and a conductive thin film by an inkjet method using a conductive ink as disclosed in Patent Document 1, and the conductivity of the conductive ink The quality improvement and application of metal nanoparticles (meaning metal particles having a primary particle size of nm level) as a filler are expected.

  On the other hand, there are problems of solder lead-free and solder plating waste associated with environmental measures. In order to solve this problem, there is a growing demand for conductive nanoparticle pastes and conductive inks having advantages such as lead-free, fluxless, and low-temperature mounting as disclosed in Patent Document 2.

  The metal nanoparticles are expected to exhibit a high surface activity that is not found in bulk materials due to the atomization effect due to the nano-sized particles, due to the effect of atomization. For example, a conductor formed using silver powder is required to have low electrical resistance and high connection reliability. Therefore, there has been an increasing demand for silver ink or silver paste that exhibits conductivity by sintering the silver powder itself as the filler as the resin component is cured. In view of lowering the firing temperature of silver particles, efforts have been made to refine the particles of silver powder, which is a conductive filler, to the nm level as disclosed in Patent Document 3.

JP 2002-324966 A JP-A-10-58190 JP 2002-324966 A

  However, in the case of conductive ink containing metal powder such as nano-sized silver powder and copper powder as a conductive filler, a large amount of dispersant is added as a protective colloid to ensure the dispersibility of the nanoparticles. Is common. As the dispersant used here, it is common to use a dispersant having a decomposition temperature higher than the firing temperature of the metal nanoparticles, and the low-temperature sintering characteristics inherent to the metal nanoparticles cannot be fully utilized. There is a drawback.

  In view of the above, there has been a demand in the market for conductive pastes and conductive inks having primary particle diameters on the order of nm showing good particle dispersibility and showing sufficient low-temperature sintering characteristics.

  In the conductive ink, in order to prevent re-aggregation of the metal nanoparticles as the conductive filler contained therein and ensure dispersibility, it is necessary to consider using a large amount of dispersant as a protective colloid. Therefore, the inventors of the present invention, as a result of diligent research, found that a certain amount of low-melting-point metal particles (tin nanoparticles) were contained as the metal nanoparticles that are conductive fillers. It was judged that sinterability could be secured. As a result, the inventors have conceived of using a multi-component metal particle slurry described below as a raw material for producing a conductive ink and a conductive paste excellent in sintering characteristics of a conductive filler.

Multi-component metal particle slurry according to the present invention: The multi-component metal particle slurry according to the present invention is a multi-component metal particle slurry containing metal particles having different nanoparticle size components in a solvent, the metal The particles include tin particles having a primary particle diameter of 30 nm to 300 nm, and any one or two of copper particles and silver particles having a primary particle diameter of 30 nm to 300 nm.

  In the multicomponent metal particle slurry according to the present invention, the metal particles preferably contain 20 vol% to 70 vol% of the total metal particles when the volume of the multicomponent metal particle slurry is 100 vol%.

  In the multi-component metal particle slurry according to the present invention, when the metal particles are composed of tin particles and copper particles or silver particles, when the total weight of the metal particles is 100 wt%, tin particles and copper particles or silver The weight content ratio with the particles is preferably [tin particles (wt%)] / [copper particles or silver particles (wt%)] = 0.2 to 0.8. Hereinafter, this is referred to as a two-component system.

  Further, in the multi-component metal particle slurry according to the present invention, when the metal particles are composed of tin particles, copper particles, and silver particles, when the total weight of the metal particles is 100 wt%, the tin particles and the copper particles The weight content ratio between the silver particles and the silver particles is [tin particles (wt%)]: [copper particles (wt%)]: [silver particles (wt%)], where the value of wt% of the tin particles is 1. It is preferable that it is 1: 0.05-0.30: 0.10-0.50. Hereinafter, this is referred to as a three-component system.

  The solvent used for the multi-component metal particle slurry according to the present invention contains 1 wt% to 30 wt% of a compound having a carboxyl group when the weight of the multi-component metal particle slurry is 100 wt%. It is preferable.

  In the multi-component metal particle slurry according to the present invention, the compound having a carboxyl group is preferably a carboxylic acid having a molecular weight of 200 or more.

Conductive ink using the multi-component metal particle slurry according to the present invention: The multi-component metal particle slurry can be used as it is, but the multi-component metal particle slurry according to the present invention is a solvent. It is also possible to use it as a basic material for adjusting the components after adjusting the conductive ink or conductive paste.

  That is, a certain amount of the solvent component of the multi-component metal particle slurry according to the present invention is removed, and a necessary component is added therein to adjust the conductive ink or conductive paste of any component. .

  The multi-component metal particle slurry according to the present invention uses tin nanoparticles as essential metal particles, combined with silver nanoparticles and copper nanoparticles. Suitable for formation. In particular, the multi-component metal particle slurry preferably contains a compound having a carboxyl group in order to improve low-temperature sinterability. By using a compound having a carboxyl group, an alloying reaction can be caused even when the firing temperature is around 200 ° C. Therefore, the conductive ink and conductive paste obtained by using these are suitable for low-temperature sintering applications. And by adjusting the content of tin nanoparticles, a product suitable as an alternative material such as solder paste can be provided.

  Hereinafter, embodiments of the multi-component metal particle slurry according to the present invention will be described. The multi-component metal particle slurry according to the present invention is a multi-component metal particle slurry containing metal particles having different nano particle size components in a solvent, and the metal particles have a primary particle size of 30 nm to 300 nm. It contains any one or two of tin particles and copper particles and silver particles having a primary particle diameter of 30 nm to 300 nm. That is, in the case of the multicomponent metal particle slurry according to the present invention, tin nanoparticles that are low melting point metals are essential as a constituent component. And as another component, a copper nanoparticle and a silver nanoparticle are selectively combined and used. Therefore, in order to avoid misunderstanding, the multi-component metal particle slurry according to the present invention will be described as being divided into a two-component system and a three-component system.

[Two-component multi-component metal particle slurry form according to the present invention]
Here, as the primary particle diameter of tin particles, copper particles, and silver particles, it is preferable to use nanoparticles in the range of 30 nm to 300 nm. Metal nanoparticles having a primary particle diameter of less than 30 nm are difficult to obtain as a product having a good particle size distribution. If a product with a good particle size distribution of less than 30 nm is obtained, it can be used. On the other hand, metal nanoparticles having a primary particle diameter exceeding 300 nm can be referred to as nanoparticles, but it is difficult to obtain sufficient low-temperature sinterability.

  Here, in order to make it easy to understand the explanation of the low-temperature sintering characteristics of the particles contained in the two-component multi-component metal particle slurry, the individual sintering characteristics of tin particles, silver particles, and copper particles will be described. In addition, the sintering characteristic of a metal particle is performed by observing the melting behavior of a metal particle, and is demonstrated with the measurement result using DSC (high temperature differential scanning calorimeter). The DSC is measured under the following conditions: a heating method in which a temperature rise rate is 10 ° C./min in a nitrogen atmosphere, a measurement range is room temperature to 800 ° C., constant temperature heating is performed at 80 ° C. for 30 minutes, and then the temperature is raised to 800 ° C. Adopted. Then, the degree of sintering was evaluated by an X-ray diffraction measurement device by looking at the crystallinity of the particles. And FE-SEM (field emission scanning electron microscope) was used for the state observation of particle | grains.

Thermal characteristics of tin particles: The melting characteristics and sintering characteristics of tin particles will be described. Here, FIG. 1 shows an FE-SEM observation image of tin particles of spherical nanoparticles having an average primary particle size of about 100 nm (hereinafter referred to as “sample A (tin)”). The D ₅₀ particle size distribution measurement by laser diffraction method of the tin particles with a nanoparticle size became large value of 0.3 [mu] m. As can be seen from the FE-SEM observation image of FIG. 1, this is an influence due to the presence of secondary particles due to particle aggregation, and it is considered that the adhesion force between particles is increased during aggregation due to atomization. However, this agglomerated state can be crushed to improve particle dispersibility in a particle dispersion treatment with a medium crusher such as a bead mill, a high-speed stirrer such as a homogenizer. Therefore, in the case of tin nanoparticles, it is preferable to perform wet particle dispersion treatment as described above to improve particle dispersibility, and it is preferable to obtain a uniform mixed state with copper particles or silver particles. The particle dispersion effect is preferably achieved by particle dispersion treatment until the value of [D ₅₀ (nm)] / [primary particle diameter (nm)] is 3.0 or less, more preferably 2.0 or less. . The tin particles having a nanoparticle size used in the following DSC analysis are also subjected to particle dispersion treatment by a fluid mill so that the value of [D ₅₀ (nm)] / [primary particle size (nm)] is 1.4. It was adjusted. On the other hand, FIG. 2 shows an FE-SEM observation image of spherical tin powder having an average primary particle size of about 2 μm (hereinafter referred to as “sample B (tin)”). As is apparent from FIG. 1, it can be understood that coarse powder having a primary particle diameter of about 5 μm and fine powder having a primary particle diameter of 1 μm or less are mixed, resulting in a considerably broad particle size distribution. However, judging from the FE-SEM observation image and the measurement result of the particle size distribution, it is considered that the particle aggregation is small.

  Next, using each of sample A (tin) and sample B (tin) having different particle sizes, measurement by DSC was performed in order to confirm the influence on the melting behavior due to the difference in particle size. As a result, in both sample A (tin) and sample B (tin), an endothermic peak derived from melting of tin was observed at around 230 ° C., and no difference due to the difference in particle diameter was observed. In addition, the exothermic peak by oxidation of organic substance was confirmed in 270 degreeC vicinity. The exothermic peak of this organic matter is that nanoparticles with a large specific surface area, especially nanoparticles of base metals such as tin, are very easy to oxidize, so we used a slurry in which metal particles were dispersed in an organic solvent so that they were not exposed to air This is due to Moreover, from the result of X-ray diffraction, the diffraction pattern peculiar to tin was confirmed for both sample A (tin) and sample B (tin), and it was confirmed that each was pure metallic tin.

  Then, in order to see the difference in sintering characteristics due to the difference in particle size, the following evaluation was performed. That is, first, metal particle slurries using tin particles of Sample A (tin) and Sample B (tin) were prepared. Here, a tin particle slurry was prepared by dispersing tin particles in an organic solvent (terpineol). Then, the tin content in the slurry at this time is adjusted so that the tin content is adjusted according to the particle size so that a good coating film can be formed. When the tin particle slurry is 100 wt%, sample A (tin) 68 wt% for the tin particles having a primary particle diameter of 100 nm, and 87 wt% for the tin particles having a primary particle diameter of 2 μm for sample B (tin). This tin particle slurry is printed on an aluminum substrate by screen printing, fired in a range of 130 ° C. to 300 ° C. in a nitrogen atmosphere, the state of the coating film after firing is observed by FE-SEM, and the particles are fired. The freezing state was observed. As a result, it was not possible to confirm that sintering occurred at 200 ° C. or lower when particles having a primary particle diameter of 2 μm were used for sample B (tin). On the other hand, when particles having a primary particle diameter of 100 nm of sample A (tin) were used, if fired at 150 ° C. or higher, particle growth by sintering was confirmed as shown in FIG. From the above results, it can be understood that although the melting behavior does not depend on the particle size, the sintering behavior between particles occurs at a lower temperature as the particle size is smaller.

Thermal characteristics of silver particles: Next, melting behavior and sintering behavior regarding silver particles having a nano-level particle size will be described. Regarding these evaluation methods, the same evaluation as in the case of the tin particles was performed. As is apparent from the FE-SEM observation image of FIG. 4, one of the silver particles used here is a spherical silver nanoparticle having an average primary particle size of about 80 nm (hereinafter, “sample A (silver)”). In the same manner as in the case of nano-level tin particles, aggregation of the particles proceeds. As a result, the value of D _{50 in} the particle size distribution measurement is as large as 0.2 μm. Accordingly, the silver particles having the nanoparticle diameter used here are subjected to particle dispersion treatment by a fluid mill in the same manner as the tin particles having the nanoparticle diameter, and [D ₅₀ (nm)] / [primary particle diameter]. (Nm)] is adjusted to be 1.5. On the other hand, for comparison, the average primary particle size shown in the FE-SEM observation image of FIG. 5 is a spherical powder having a particle size distribution of 1 μm to 5 μm, including a coarse powder having a small particle aggregation. Broad silver particles (hereinafter referred to as “sample B (silver)”) were used.

  And although the melting characteristic by DSC was evaluated, from the measurement results, in the range of 800 ° C. or less for both sample A (silver) and sample B (silver), no endothermic peak derived from melting of silver was observed, There was no difference due to the difference in particle size. Further, from the results of X-ray diffraction of Sample A (silver) and Sample B (silver) after the melting test, only pure metal silver spectra were obtained for both samples.

  Next, a silver particle slurry was prepared in the same manner as in the case of the tin particles in order to see the sintering characteristics due to the difference in the particle diameter of the silver particles. And the silver content rate in the slurry at this time is adjusted such that the tin content is adjusted according to the particle size so that a good coating film can be formed, and when the silver particle slurry is 100 wt%, sample A (silver) The silver particle having a primary particle diameter of 80 nm was 72 wt%, and the silver particle having a primary particle diameter of 4 μm in Sample B (silver) was 91 wt%. Then, the sintering behavior was observed in the same manner as in the case of the tin particles. As a result, according to the observation result of FE-SEM, there was a sintering start point in the vicinity of 300 ° C. when particles having a primary particle diameter of 4 μm were used for sample B (silver). On the other hand, when a particle having a primary particle diameter of 80 nm was used for sample A (silver), a sintering start point was confirmed at around 150 ° C. FIG. 6 shows a fired film at a firing temperature of 150 ° C. From the above results, it can be understood that although the melting behavior does not depend on the particle size, the sintering behavior between particles occurs at a lower temperature as the particle size is smaller. These behaviors are the same as in the case of tin particles.

Thermal characteristics of copper particles: Next, the melting behavior and sintering behavior of copper particles having a nano-level particle size will be described. Regarding these evaluation methods, the same evaluation as in the case of the tin particles was performed. One of the copper particles used here is, as is apparent from the FE-SEM observation image of FIG. 7, a spherical copper particle having an average primary particle size of about 50 nm (hereinafter, “sample A (copper)”). In the same manner as in the case of nano-level tin particles, aggregation of the particles proceeds. As a result, the value of D _{50 in} the particle size distribution measurement is as large as 0.3 μm. Therefore, the copper particles having the nanoparticle diameter used here are subjected to particle dispersion treatment by a fluid mill in the same manner as the tin particles having the nanoparticle diameter, and [D ₅₀ (nm)] / [primary particle diameter]. (Nm)] is adjusted to be 1.4. On the other hand, for comparison, a copper powder having an angular portion with an average primary particle size of about 5 μm shown in the FE-SEM observation image of FIG. , Referred to as “Sample B (copper)”).

  And although the melting characteristic by DSC was evaluated, the endothermic peak derived from the melting of silver was not seen in the range of 800 ° C. or less for both sample A (copper) and sample B (copper) from the measurement results. There was no difference due to the difference in particle size. Furthermore, from the results of X-ray diffraction of Sample A (copper) and Sample B (copper) after the melting test, only pure metal copper spectra were obtained for both samples.

  Next, in order to see the sintering characteristics due to the difference in the particle size of the copper particles, a silver particle slurry was prepared in the same manner as in the case of the tin particles. And the silver content rate in the slurry at this time is adjusted such that the tin content is adjusted according to the particle size so that a good coating film can be formed, and when the silver particle slurry is 100 wt%, sample A (copper) The silver particle having a primary particle diameter of 50 nm was 88 wt%, and the silver particle having a primary particle diameter of 5 μm in Sample B (copper) was 88 wt%. Then, the sintering behavior was observed in the same manner as in the case of the tin particles. As a result, according to the observation result of FE-SEM, when particles having a primary particle diameter of 5 μm of sample B (copper) were used, sintering did not start even at 300 ° C. On the other hand, when particles having a primary particle diameter of 50 nm for sample A (copper) were used, it was confirmed that sintering started at 150 ° C. or higher. FIG. 9 shows a fired film at a firing temperature of 200 ° C. From the above results, it can be understood that although the melting behavior does not depend on the particle size, the sintering behavior between particles occurs at a lower temperature as the particle size is smaller. These behaviors are the same as in the case of tin particles.

  A tin particle having a nano-level particle diameter as described above is an essential component, and silver particles or copper particles having a nano-level particle diameter are combined with this to form a two-component multi-component metal particle slurry. It is used as a conductive filler. Hereinafter, in consideration of the combination, melting characteristics and sintering characteristics in the case of a two-component multi-component metal particle slurry will be described.

Thermal characteristics of the two-component system (tin particles and silver particles): First, in order to examine the reactivity of the alloying reaction between different metals due to the difference in particle size, the above-mentioned sample A (tin) having a primary particle size of 100 nm And the sample A (silver) having a primary particle size of 80 nm and the sample B (tin) having a primary particle size of 2 μm and a sample A (silver) having a primary particle size of 80 nm are compared. went. At this time, the above-mentioned tin particle slurry and silver particle slurry are mixed and kneaded so that tin particles (wt%) and silver particles (wt%) are in a ratio of 1: 1. A multi-component metal particle slurry (hereinafter simply referred to as “tin / silver slurry”) containing the two-component nanoparticles. Next, this multi-component metal particle slurry was printed on an aluminum substrate by a screen printing method, and baked in a range of 150 ° C. to 300 ° C. in a nitrogen atmosphere to prepare a fired film.

  As a result, when the sample A (tin) with a primary particle diameter of 100 nm and the sample A (silver) with a primary particle diameter of 80 nm are combined, the result of FE-SEM observation of the fired film is 150 ° C. or higher. It was confirmed that the particles were sintered to grow particles. Further, when the X-ray diffraction pattern of the fired film was measured, the diffraction pattern of tin and silver was observed separately in the fired film at 150 ° C. However, in the fired film at 200 ° C., although the diffraction pattern of single tin and silver is slightly observed, the diffraction pattern of the silver-tin alloy becomes strong and the progress of alloying is considered to be remarkable. Furthermore, in the fired film at 300 ° C., the diffraction pattern of single tin and silver completely disappears, and only the diffraction pattern of the silver-tin alloy is observed. Next, the melting characteristics were measured by DSC. When measured using a tin / silver slurry before firing, an endothermic peak derived from melting of tin at 227 ° C. and an endothermic peak specific to the silver-tin alloy at 484 ° C. were confirmed. On the other hand, the measurement by DSC was performed on the fired film after firing the tin / silver slurry here at 300 ° C. As a result, the endothermic peak derived from tin disappeared, and the endothermic peak peculiar to the silver-tin alloy at 484 ° C. appeared more strongly. That is, when DSC measurement is performed using a tin / silver slurry before firing, alloying proceeds in the middle of the measurement, but in the case of a fired film fired once at 300 ° C., alloying has already proceeded. The endothermic peak peculiar to the silver-tin alloy appeared more strongly, which is evidence that the alloying by firing is performed well.

  On the other hand, when sample B (tin) having a primary particle diameter of 2 μm and sample A (silver) having a primary particle diameter of 80 nm are combined, the following results are obtained. Here, the above-mentioned tin nanoparticles with a primary particle size of 100 nm are merely replaced with tin particles with a primary particle size of 2 μm. In the same manner as described above, tin particles (wt%) and silver particles (wt%) Is a multi-component metal particle slurry (hereinafter simply referred to as “tin / silver slurry”) containing two-component nanoparticles of tin particles and silver particles in a ratio of 1: 1. Next, this tin / silver slurry was printed on an aluminum substrate by a screen printing method, and baked in a range of 150 to 300 ° C. in a nitrogen atmosphere to prepare a baked film.

  As a result, when X-ray diffraction of the fired film is performed, a diffraction pattern peculiar to the silver-tin alloy is observed in the fired film at 200 ° C., but a unique diffraction pattern of tin is also strongly observed. This is the same for both the 300 ° C. and the fired film, and it can be determined that the silver-tin alloy and the independent tin component are mixed. Next, melting characteristics were measured by DSC. When measured using a tin / silver slurry before firing, an endothermic peak derived from melting of tin at 227 ° C. and an endothermic peak specific to the silver-tin alloy at 484 ° C. were confirmed. On the other hand, the measurement by DSC was performed on the fired film after firing the tin / silver slurry here at 300 ° C. As a result, an endothermic peak peculiar to single tin is confirmed, and an endothermic peak peculiar to a silver-tin alloy at 484 ° C. appears. Thus, if single tin remains after firing, the electrical resistance of the fired film increases, which is not preferable. As can be seen from these results, the difference in the alloying reaction depending on the particle size of the tin particles becomes clear. And if it is going to perform sufficient alloying in the low-temperature baking area | region at 300 degrees C or less, it can be understood that it is necessary to use in combination particle | grains with a particle size of nano level. Moreover, if complete alloying has occurred, tin (232 ° C.) having a low melting point will not be present in the fired film. It becomes a fired film having excellent characteristics.

Thermal characteristics of two-component system (tin particles and copper particles): Next, a fired film was prepared using a multi-component slurry in which tin nanoparticles and copper nanoparticles were combined. The copper particles used here are the nano-level copper particles (sample A (copper)) having a spherical shape and an average primary particle size of about 50 nm shown in FIG. Moreover, the tin particle used here is a tin particle (sample A (tin)) of spherical nanoparticles having an average primary particle diameter of about 100 nm shown in FIG. That is, the evaluation was performed when the sample A (tin) having a primary particle diameter of 100 nm and the sample A (copper) having a primary particle diameter of 50 nm were combined.

  At this time, the above-described tin particle slurry and copper particle slurry are mixed and kneaded so that the ratio of the tin particles (wt%) and the copper particles (wt%) is 1: 1, and the tin particles and the copper particles A multi-component metal particle slurry (hereinafter simply referred to as “tin / copper slurry”) containing the two-component nanoparticles. Next, this multi-component metal particle slurry was printed on an aluminum substrate by a screen printing method, and baked in a range of 150 to 300 ° C. in a nitrogen atmosphere to prepare a baked film.

As a result, when the sample A (tin) having a primary particle size of 100 nm and the sample A (copper) having a primary particle size of 50 nm are combined, if the sintered film is 150 ° C. or higher from the observation result by FE-SEM It was confirmed that the particles were sintered to grow particles. However, the result of X-ray diffraction was different from that of the tin / silver slurry. That is, when the firing temperature is 150 ° C., the point that a single diffraction pattern of tin and copper can be obtained is the same as in the case of using a tin / silver slurry. On the other hand, when the firing temperature is 200 ° C., a single diffraction pattern of tin and copper is slightly observed even if the progress of firing is observed in the appearance of FE-SEM observation. A certain Cu ₃ Sn diffraction pattern begins to be observed. Then, when the firing temperature and 300 ° C., the diffraction pattern of a single tin and copper disappeared, the diffraction pattern of the Cu 3 _Sn becomes remarkable. It can be seen that the combination of tin and copper, even between nanoparticles, is difficult to cause mutual diffusion and cannot be alloyed unless a firing temperature around 300 ° C. is adopted.

  Next, melting characteristics based on the results of DSC measurement will be described. The measurement conditions are the same as described above. As a result of DSC measurement of tin nanoparticles before firing, a characteristic endothermic peak of tin was observed at 225 ° C and an exothermic peak believed to be due to oxidation of organic substances at 300 to 400 ° C. The peak disappears and only the exothermic peak is present. As a result of the DSC measurement, it was confirmed that, in the case of the copper-tin combination, the melting temperature was increased by alloying after firing, as in the case of the silver-tin combination. In the case of the sintered film at 200 ° C. in the case of the silver-tin combination, the diffraction pattern of the silver-tin alloy is strongly confirmed, whereas the sintered film at 200 ° C. in the case of the copper-tin combination is copper. -The diffraction pattern of the tin alloy is very weak. This confirms that the copper-tin combination requires higher temperature heating for alloying than the silver-tin combination. This is probably because the copper nanoparticle surface is more easily oxidized than the silver nanoparticle surface, and the alloying temperature has increased due to the oxidation of the copper nanoparticle surface.

  Through experiments and research as described above, the present inventors have used a combination of metal nanoparticles having a primary particle diameter of more than 300 nm, so that the firing temperature is 300 ° C. or lower, more preferably 200 ° C. or lower. It was concluded that alloyable sintering of tin particles and copper particles or silver particles is possible. Therefore, even if nanoparticles exceeding 300 nm are combined and sintered, a temperature exceeding 300 ° C. is necessary for the firing temperature, which is not preferable. In particular, when used as a substitute material for solder powder, sintering with melting and alloying at around 200 ° C. is required, which is not preferable.

Content of metal particles in a two-component multi-component metal particle slurry: In the two-component multi-component metal particle slurry according to the present invention, the metal particles have a volume of 100 vol as the multi-component metal particle slurry. %, It is preferably 20 vol% to 70 vol%. Here, it should be clearly stated that the total metal particles means the sum of tin particles and copper particles or silver particles. The multicomponent metal particle slurry is obtained by dispersing metal nanoparticles in a solvent, and the total amount of metal particles is determined according to the use of the multicomponent metal particle slurry. For example, 15 vol% to 25 vol% when used as a conductive ink, 80 vol% to 92 vol% when used as a conductive paste, and various methods such as a screen printing method and a gravure printing method which are methods for forming a conductive film In accordance with the method and equipment characteristics, an organic solvent is added as appropriate and adjustments are made. Therefore, if this multicomponent metal particle slurry is considered as a basic material for preparing a conductive ink and a conductive paste, it is preferably supplied as a metal particle slurry of 18 vol% to 97 vol%. However, when the metal particles are contained at a high concentration as the metal particle slurry, reaggregation of the particles may occur in the slurry. When the particle dispersibility is always kept stable, 18 vol% to 50 vol. %, More preferably about 18 vol% to 35 vol%, from the viewpoint of ensuring the long-term stability of the quality.

  In the two-component multi-component metal particle slurry according to the present invention, when the total weight of the tin particles and the copper particles or silver particles is 100 wt%, the weight content of the tin particles and the copper particles or silver particles is contained. The ratio is preferably [tin particles (wt%)] / [copper particles or silver particles (wt%)] = 0.2 to 0.8. If the value of [tin particles (wt%)] / [copper particles or silver particles (wt%)] is less than 0.2 and the amount of tin particles is too small, low-temperature sinterability of the fired film is obtained. Since it disappears, it is not preferable. On the other hand, if the value of [tin particles (wt%)] / [copper particles or silver particles (wt%)] exceeds 0.8, the amount of tin particles present is larger than the amount of copper particles or silver particles present Even if sufficient alloying occurs by sintering, a tin component that is not alloyed remains alone, and the melting temperature after sintering is lowered, which is not preferable. In addition, when the value of [tin particles (wt%)] / [copper particles or silver particles (wt%)] is 0.3, more preferably more than 0.4, it is preferable for use as a substitute material for solder paste, When the value of [tin particle (wt%)] / [copper particle or silver particle (wt%)] is less than 0.3, it is suitable for low-temperature sintering processing of electrical conductors that do not make electrical resistance a particular problem. is there.

Solvent in two-component multi-component metal particle slurry: The metal nanoparticles used in the multi-component metal particle slurry according to the present invention can be collected by filtration, washing, dehydration and drying. However, it is very fine and is preferably stored in a slurry state in order to prevent oxidation of the excess particle surface. When stored in a slurry state, there is no particular limitation, but it is preferable to use the following solvent. The solvent used here is preferably one containing 1 wt% to 30 wt% of a compound having a carboxyl group when the weight of the multicomponent metal particle slurry is 100 wt%. The solvent here refers to one or more organic solvents such as terpineol, methanol, ethanol, propyl alcohol, acetone, methyl ethyl ketone, butyl carbitol, ethylene glycol, which can be easily processed into a conductive paste or conductive ink after the fact. It is preferable to use as a main agent in combination. And 1 wt%-30 wt% of compounds which have a carboxyl group are contained here. This compound having a carboxyl group adheres to the surface of the metal particles in the slurry and functions in the same manner as the surface treatment agent, but as an auxiliary agent for further enhancing the low-temperature sintering performance when forming a fired film. Function. If the compound having a carboxyl group is included in the multi-component metal particle slurry according to the present invention in advance, even if it is processed into a conductive paste or conductive ink by, for example, solvent substitution, the metal The adhesion of the compound having a carboxyl group to the surface of the nanoparticle occurs, and the low-temperature sintering performance is effectively enhanced. When the content of the compound having a carboxyl group is less than 1 wt% when the weight of the multi-component metal particle slurry is 100 wt%, an auxiliary agent for further improving the low-temperature sintering performance when forming a fired film Cannot function as. On the other hand, even if the content of the compound having a carboxyl group exceeds 30 wt% when the weight of the multi-component metal particle slurry is 100 wt%, the low-temperature sintering performance cannot be further improved, and rather it is fired. This is not preferable because the residual amount of organic matter in the film (which can be dissolved and analyzed as a carbon amount later) increases and causes an increase in electrical resistance.

  In addition, it is preferable to add ethyl cellulose, an acrylic resin, a polyester resin, an epoxy resin, a urethane resin, or the like as a resin component in the solvent from the viewpoint of further improving the low-temperature sintering performance. The amount of these resins added is preferably in the range of 1 wt% to 15 wt% when the weight of the metal particles in the multicomponent metal particle slurry is 100 wt%. When the content of these resin components is less than 1 wt%, the effect of improving the low temperature sinterability cannot be obtained. On the other hand, if the content of these resin components exceeds 15 wt%, the multicomponent metal particle slurry tends to be thickened and difficult to handle, and at the same time, carbon components as impurities in the fired film Is liable to remain and increases the conductor resistance, which is not preferable.

  The compound having a carboxyl group is particularly preferably a carboxylic acid having a molecular weight of 200 or more. The carboxylic acid having a molecular weight of less than 200 is less effective in improving the low-temperature sintering characteristics, but carboxylic acids having a molecular weight of 200 or more can remarkably improve the low-temperature sintering characteristics. Specific examples of the carboxylic acid having a molecular weight of 200 or more are stearic acid, oleic acid, behenic acid and the like.

  Here, in order to evaluate the change in the low-temperature sintering characteristics, judgment was made using an FE-SEM observation image and a crystallite diameter calculated by X-ray diffraction. When the compound having a carboxyl group referred to herein (hereinafter referred to as “carboxylic acid” in the description with reference to the drawings) is included in the multicomponent metal particle slurry, the effect of remarkably improving the low temperature sinterability is shown by FE−. This will be described with an SEM observation image. FIG. 10 shows an observation image 30000 times as large as that of a fired film obtained using a metal particle slurry (sample A (tin)) not containing carboxylic acids at a firing temperature of 200 ° C. in a nitrogen atmosphere. FIG. 11 shows an observation image of 30000 times the fired film obtained under the same conditions using the same metal particle slurry containing carboxylic acids (content of carboxylic acids 8 wt%). Then, the crystallite diameter of the fired film was measured. Initially, the crystallite diameter of the sintered film when carboxylic acids were not included was 435 mm. On the other hand, when stearic acid was used as the carboxylic acid, the crystallite diameter of the fired film was 775 mm, the crystallite diameter of oleic acid was 592 mm, and the crystallite diameter of acrylic acid was 576 mm. As can be seen from this result, it can be said that if a carboxylic acid having a molecular weight of 200 or more is used, the sintering characteristics are improved, the particles are easily diffused or melt-bonded, and particles having a large crystallite diameter are generated. On the other hand, the crystallite diameter when using decanoic acid having a molecular weight of less than 200 is 418 mm, indicating that the sintering performance is inferior to that when the carboxylic acids are not added. That is, carboxylic acids having a molecular weight of less than 200 work to inhibit the sintering of the particles.

  Next, in order to confirm the influence of carboxylic acids on the low-temperature sintering characteristics in the two-component system, determination was made using an FE-SEM observation image in the same manner as described above. When the carboxylic acids mentioned here are included in the multi-component metal particle slurry, the effect of significantly improving the low-temperature sinterability will be described with an FE-SEM observation image as compared with the case of single metal nanoparticles. FIG. 12 shows a tin / silver particle slurry (sample A (tin) and sample A (silver) not containing carboxylic acids, [tin nanoparticles (wt%)] / [silver nanoparticles (wt%). )] = 1), and a 100,000 times observed image of a portion where the firing state of the fired film obtained at a firing temperature of 200 ° C. is most easily captured. FIG. 13 shows the same conditions using the same metal particle slurry (stearic acid content 8 wt%, ethyl cellulose content 5 wt%) containing stearic acid as the carboxylic acid and ethyl cellulose as the resin component. The observation image of 30000 times of the site where the fired state of the obtained fired film is most easily captured is shown. As can be seen from FIG. 12, even if the sintering is in progress, the presence of particles connected by sintering can be clearly confirmed when enlarged. On the other hand, in FIG. 13, although observed at a lower magnification than in FIG. 12, there are fewer sites where the sintered and connected particles can be observed, completely melted, alloyed, and flattened. Is observed. Therefore, it can be understood that the tin / silver metal particle slurry containing stearic acid as the carboxylic acid sinters more easily without looking at the difference in crystallite diameter. This result is the same for the ternary multi-component metal particle slurry described later.

[Three-component multi-component metal particle slurry form according to the present invention]
The three-component multi-component metal particle slurry according to the present invention is a multi-component metal particle slurry containing metal particles having different nano-particle size components in a solvent, and the metal particles have a primary particle size. It is a three-component metal particle comprising tin particles of 30 nm to 300 nm, copper particles having a primary particle diameter of 30 nm to 300 nm, and silver particles having a primary particle diameter of 30 nm to 300 nm. That is, it is a slurry containing three kinds of nanoparticles.

Thermal properties of ternary system (tin particles, silver particles, copper particles): Here, each nanoparticle of tin (sample A (tin)), silver (sample A (silver)), copper (sample A (copper)) The slurry was kneaded at a weight ratio of 1: 1: 1 to prepare a tin / silver / copper multicomponent slurry. And after screen printing like the above-mentioned, it baked in the range of 150-300 degreeC in nitrogen atmosphere, and obtained the baked film.

Judging from the FE-SEM observation image of the fired film, it was confirmed that the nanoparticles were connected and grown by firing at 150 ° C. or higher. From the results of X-ray diffraction, when the firing temperature was 200 ° C., a slight diffraction pattern of Cu ₃ Sn was confirmed in addition to the individual diffraction patterns of tin, silver, and copper. When the firing temperature is 300 ° C., the single diffraction patterns of tin and copper disappear, but the diffraction pattern of Cu ₃ Sn and the single diffraction pattern of silver can be strongly confirmed.

Considering the above results, it can be said that it is different from the reaction behavior of the ternary system based on the behavior that can be confirmed simply by the two-component system. That is, in the case of the two-component system, when the combination of copper and tin is compared with the combination of silver and tin, in order to cause alloying, the former combination of copper and tin has a higher temperature. It was thought that heating of was necessary. However, in the case of a three-component system of a combination of tin-silver-copper, the alloying reaction between copper and tin takes precedence over the alloying reaction between silver and tin, and Cu ₃ Sn is generated early. . At this stage, the clear mechanism of this phenomenon has not been specified, but by adopting a ternary mixed nanoparticle composition, sintering characteristics that cannot occur with single nanoparticles or two-component nanoparticles are not possible. I foresee what will be obtained.

  Also here, it is preferable to use nanoparticles having a primary particle diameter of tin particles, copper particles, and silver particles in the range of 30 nm to 300 nm. Hereinafter, the meaning of the upper and lower limits will be described just in case, but it is substantially the same as described above. Metal nanoparticles having a primary particle diameter of less than 30 nm are difficult to obtain as a product having a good particle size distribution. If a product with a good particle size distribution of less than 30 nm is obtained, it can be used. On the other hand, metal nanoparticles having a primary particle diameter exceeding 300 nm can be referred to as nanoparticles, but it is difficult to obtain sufficient low-temperature sinterability. That is, through experiments and research as described above, the present inventors have used a combination of metal nanoparticles having a primary particle diameter of more than 300 nm, and a firing temperature of 300 ° C. or less, more preferably 200 ° C. or less. It was concluded that sintering that enables alloying between metal particles was possible. Therefore, even if it is going to combine and sinter the nanoparticle exceeding 300 nm, since the temperature exceeding 300 degreeC is necessarily required for baking temperature, it is unpreferable. This is because, in particular, when used as a substitute material for solder powder, sintering with melting and alloying at around 200 ° C. is required.

Content of metal particles in ternary multi-component metal particle slurry: In the ternary multi-component metal particle slurry according to the present invention, the metal particles have a volume of 100 vol as the multi-component metal particle slurry. %, The total metal particle amount of tin particles, copper particles, and silver particles is preferably 20 vol% to 70 vol%. The total amount of metal particles is determined according to the use of the multi-component metal particle slurry. In addition, since the view when using as a conductive ink and a conductive paste is as above-mentioned, and the more preferable range is also as above-mentioned, the overlapping description here is abbreviate | omitted.

  In the ternary multi-component metal particle slurry according to the present invention, when the total weight of the tin particles, the copper particles and the silver particles is 100 wt%, the weight content ratio of the tin particles, the copper particles and the silver particles is tin. When the value of wt% of the particles is 1, [tin particles (wt%)]: [copper particles (wt%)]: [silver particles (wt%)] = 1: 0.05-0.30: 0 .10 to 0.50 is preferable. As long as the balance of the weight content ratio is maintained, mutual diffusion by heating between the metal nanoparticles can be performed well, and a sintered film having good strength and heat resistance can be obtained. That is, in this weight content ratio, when the amount of tin resulting from tin particles is smaller than that of copper particles and silver particles, the low-temperature sinterability of the fired film cannot be obtained. On the other hand, when the amount of tin due to tin particles increases with respect to copper particles and silver particles, the abundance of tin particles decreases with respect to the abundance of copper particles and silver particles, and sufficient alloying by sintering Even if it raise | generates, the tin component which is not alloyed remains independently, and the melting temperature after sintering becomes low, and is unpreferable. In addition, when considered as the weight content ratio of the silver particles and the copper particles, there is no particular limitation because the copper and silver have a region that is widely dissolved. Depending on the use of the finally obtained fired film, the weight content ratio can be arbitrarily determined in consideration of the electrical resistance of the fired film, the strength of the fired film, and the like.

  As can be seen from the above, when the silver particles and the copper particles are combined and regarded as “mixed second component particles”, as in the case of the two-component system, [tin particles (wt%)] / [mixed second component particles]. Component particles (wt%)] = 0.2 to 0.8 is preferable. If the value of [tin particles (wt%)] / [mixed second component particles (wt%)] is less than 0.2 and the amount of tin particles is too small, low-temperature sinterability of the fired film is obtained. Disappear. On the other hand, when the value of [tin particles (wt%)] / [mixed second component particles (wt%)] exceeds 0.8, the amount of tin particles increases relative to the amount of mixed second components. Even if sufficient alloying by sintering occurs, a tin component that does not alloy remains alone, which is not preferable because the melting temperature after sintering becomes low. In addition, when the value of [tin particles (wt%)] / [mixed second component particles (wt%)] is 0.3, more preferably more than 0.4, it is preferable for use as a substitute material for solder paste, When the value of [tin particles (wt%)] / [mixed second component particles (wt%)] is less than 0.3, it is suitable for low-temperature sintering processing of conductors where electrical resistance is not a particular problem. is there.

Solvent in ternary multi-component metal particle slurry: The solvent used in the ternary multi-component metal particle slurry according to the present invention is as described above when the weight of the multi-component metal particle slurry is 100 wt%. Similarly, it is preferable to contain 1 wt% to 30 wt% of a compound having a carboxyl group. The compound having a carboxyl group is preferably a carboxylic acid having a molecular weight of 200 or more. Since these are the same as described above, description thereof is omitted here.

  The multi-component metal particle slurry according to the present invention is a combination of tin nanoparticles, silver nanoparticles, and copper nanoparticles, and is suitable for forming a fired film alloyed at a firing temperature of 300 ° C. or lower. Therefore, if the content of the tin nanoparticles is appropriately adjusted, it becomes suitable as a basic material for preparing a conductive paste or conductive ink that can be sintered or melted at around 200 ° C. as a solder substitute material. . In particular, when the multi-component metal particle slurry contains a compound having a carboxyl group for improving low-temperature sinterability, it is fired and melted in a lower temperature region than a general low-temperature solder material. Therefore, it can be expected to be applied in the field of printed wiring board circuit wiring and surface mounting.

  In addition, the multi-component metal particle slurry according to the present invention can easily replace the constituent solvent with a solvent of another component, and can prepare a conductive ink or conductive paste having a necessary composition. It is easy and suitable for manufacturing products of various compositions.

It is an FE-SEM observation image of a tin nanoparticle. It is an FE-SEM observation image of a tin particle. It is a FE-SEM observation image of the baking film | membrane (baking temperature 150 degreeC) comprised with the tin nanoparticle. It is a FE-SEM observation image of a silver nanoparticle. It is an FE-SEM observation image of silver particles. It is a FE-SEM observation image of the baking film | membrane (baking temperature of 150 degreeC) comprised with the silver nanoparticle. It is an FE-SEM observation image of a copper nanoparticle. It is an FE-SEM observation image of a copper particle. It is a FE-SEM observation image of the baking film | membrane (baking temperature of 200 degreeC) comprised with the copper nanoparticle. It is a 30000 times as many observed image of the baking film | membrane obtained by the nitrogen atmosphere and the baking temperature of 200 degreeC using the tin nanoparticle slurry which does not contain carboxylic acids. It is a 30000 times observed image of the baking film | membrane obtained by nitrogen atmosphere and baking temperature 200 degreeC using the same tin nanoparticle slurry containing carboxylic acid. It is a 30000 times as many observed image of the typical site | parts of the baking state of the baking film | membrane obtained by nitrogen atmosphere and the baking temperature of 200 degreeC using the tin / silver particle slurry which does not contain carboxylic acids. It is a 30000 times as many observation image of the typical site | part of the baking state of the baking film | membrane obtained by using the tin / silver particle slurry which contained stearic acid etc. as carboxylic acids at a nitrogen atmosphere and the baking temperature of 200 degreeC.

Claims (8)

A multi-component metal particle slurry containing metal particles having different nanoparticle size components in a solvent,
The metal particles are tin particles having a primary particle diameter of 30 nm to 300 nm,
A multi-component metal particle slurry containing one or two of copper particles and silver particles having a primary particle size of 30 nm to 300 nm. The multi-component metal particle slurry according to claim 1, wherein the metal particles contain 20 vol% to 70 vol% of total metal particles when the volume of the multi-component metal particle slurry is 100 vol%. In the case where the metal particles are composed of tin particles and copper particles or silver particles,
When the total weight of the metal particles is 100 wt%, the weight content ratio of tin particles to copper particles or silver particles is [tin particles (wt%)] / [copper particles or silver particles (wt%)] = 0. The multicomponent metal particle slurry according to claim 1 or 2, which is from 2 to 0.8. In the case where the metal particles are composed of tin particles, copper particles, and silver particles,
When the total weight of the metal particles is 100 wt%, the weight content ratio of the tin particles, the copper particles, and the silver particles when the wt% value of the tin particles is 1, [tin particles (wt%)]: [Copper particles (wt%)]: [silver particles (wt%)] = 1: 0.05 to 0.30: 0.10 to 0.50 The multicomponent system according to claim 1 or claim 2 Metal particle slurry. The multicomponent metal particles according to any one of claims 1 to 4, wherein the solvent contains 1 wt% to 30 wt% of a compound having a carboxyl group when the weight of the multicomponent metal particle slurry is 100 wt%. slurry. The multi-component metal particle slurry according to claim 5, wherein the compound having a carboxyl group is a carboxylic acid having a molecular weight of 200 or more. The electroconductive ink obtained using the multicomponent-type metal particle slurry in any one of Claims 1-6. The electroconductive paste obtained using the multicomponent-type metal particle slurry in any one of Claims 1-6.