TW201312595A - Metal nanoparticle paste, bonding method, bonded element and electronic substrate - Google Patents

Abstract

A metal nanoparticle paste includes: metal nanoparticles; a phosphate dispersant that has a hydrophilic portion; and a polar solvent, wherein the content of the metal nanoparticles is higher than or equal to 70 percent by weight and lower than 100 percent by weight.

Description

Metal nanoparticle paste, bonding method, bonded component and electronic substrate

The present invention relates to a metal nanoparticle paste, a bonding method using the metal nanoparticle paste, a bonded component bonded by the metal nanoparticle paste, and an electronic substrate having a wire formed of the metal nanoparticle paste .

In the prior art, solder is used as the bonding material; however, solder is difficult to use for power device components such as tantalum carbide and gallium nitride having a high operating temperature. Therefore, metal fine particle paste having high electrical resistance has been increasingly used as a bonding material. For example, Japanese Patent Application Publication No. 2009-279649 (JP 2009-279649 A) describes a bonding material containing silver nanoparticles (any of silver carbonate and silver oxide) and a carboxylic acid. In addition, Japanese Patent Application Publication No. 2011-21255 (JP 2011-21255 A) describes a composite nano-metal paste containing composite metal nanoparticles each having an organic layer, metal nano filler particles, and metal filler particles. Japanese Patent Application Publication No. 6-119808 (JP 6-119808 A) describes metal fine powders, organic binders, organic solvents, and phosphorus oxides.

When fine metal particles (especially metal nanoparticles) are used in the paste, the fine metal particles are flocculated, and the viscosity of the paste is excessively increased. Therefore, the handling is inconvenient, as it has been reported that the dispersing agent is used to prevent fine flocculation of metal fine particles (for example, Japanese Patent Application Laid-Open No. 2007-21475 (JP 2007-21475 A)).

As described above, when fine metal particles are used for the paste, the viscosity of the paste is gold It is a flocculation of fine particles and is improved. In this case, the viscosity can be lowered by increasing the amount of the organic solvent; however, on the other hand, the joint strength and the electrical conductivity/thermal conductivity are lowered. In order to prevent flocculation of fine metal particles, for example, a dispersant is used in JP 2007-21475 A; however, a large amount of organic solvent is also used, and the metal content in the paste is maintained at about 60% (example and Table 1).

Therefore, there is a need for a fine metal fine particle paste having excellent handleability, joint strength, and electrical conductivity/thermal conductivity, which has a low viscosity and a high ratio of fine metal fine particles.

The present inventors diligently studied and finally found that a low-viscosity metal nanoparticle paste containing a high ratio of metal nanoparticles can be produced using a phosphate-based dispersant.

A first aspect of the invention relates to (1) a metal nanoparticle paste comprising: metal nanoparticles; a phosphate-based dispersant having a hydrophilic portion; and a polar solvent, wherein the content of the metal nanoparticles is higher than or Equal to 70 weight percent and less than 100 weight percent.

(2) The metal nanoparticle paste of (1) above, wherein the content of the metal nanoparticles is higher than or equal to 90% by weight and less than 99% by weight.

(3) The metal nanoparticle paste of (2) above, wherein the content of the metal nanoparticles is higher than or equal to 95% by weight and less than 99% by weight.

(4) A metal nanoparticle according to any one of the above (1) to (3) a paste, wherein the metal nanoparticle paste has a viscosity lower than or equal to 100 Pa. s.

(5) The metal nanoparticle paste according to any one of the above (1) to (4), wherein the hydrophilic portion may be polyethylene glycol.

(6) The metal nanoparticle paste according to any one of the above (1) to (5), wherein the polar solvent is an alcohol solvent.

A second aspect of the invention relates to (7) a joining method comprising applying the metal nanoparticle paste according to any one of the above (1) to (6) to a joined member.

(8) In the joining method of (7) above, the joined member may be joined without pressure.

A third aspect of the invention relates to (9) a joined member obtained by the joining method as in (7) or (8) above.

(10) In the joined element according to (10) above, the joined member has a shear strength of 80 to 110 MPa.

A fourth aspect of the invention is directed to (11) an electronic substrate having a wire formed of the metal nanoparticle paste of any one of the above (1) to (6).

As with these aspects of the invention, it is possible to provide low viscosity metal nanoparticle pastes containing high ratios of metal nanoparticles.

The features, advantages, and technical and industrial advantages of the exemplary embodiments of the present invention will be described below with reference to the accompanying drawings.

Detailed description of the invention Metal nanoparticle paste

A first specific embodiment of the present invention relates to a metal nanoparticle paste comprising: metal nanoparticles, a phosphate dispersant having a hydrophilic portion, and a polar solvent, wherein the content of the metal nanoparticles is higher than or equal to 70 Weight percent and less than 100 weight percent. The metal nanoparticle paste according to the first embodiment of the present invention may contain a high ratio of metal nanoparticles, but it has a low viscosity, and thus the metal nanoparticle paste has excellent handleability, joint strength, and electrical conductivity/thermal conductivity.

The metal type used as the metal nanoparticle is not particularly limited and may be any precious metal or any base metal. The noble metal may be, for example, gold, silver, rhodium, ruthenium, palladium, iridium, platinum or the like. The base metal may be, for example, copper, aluminum, iron, nickel, or the like. The number of metal types used may be one or may be used in combination of two or more. The metal nanoparticles may be in the form of a metal oxide or a metal salt as long as the metal nanoparticles maintain conductivity/thermal conductivity. In the first embodiment of the present invention, although not particularly limited, silver is preferably used in terms of conductivity and thermal conductivity.

The particle diameter of the metal nanoparticle is not particularly limited as long as it has a diameter of a nanometer. However, when the particle diameter becomes small, the contact area between the particles increases and the joint strength and the electrical conductivity/thermal conductivity are improved, so that the particle diameter is desirably small. For example, metal nanoparticles having a particle diameter of 1 to 500 nm, more desirably 5 to 300 nm, more desirably 10 to 200 nm, and particularly desirably 20 to 100 nm are used. Metal nanoparticles having a specific particle size range may be used alone or metal nanoparticles having different particle size ranges may be used in combination.

The content of the metal nanoparticle in the metal nanoparticle paste is higher than or equal to 70% by weight and less than 100% by weight (for example, less than 99% by weight), more desirably higher than or equal to 80% by weight, more desirably high At or equal to 85 weight percent, more desirably greater than or equal to 90 weight percent, it is particularly desirable, particularly desirable to be greater than or equal to 93 weight percent, and particularly desirably greater than or equal to 95 weight percent.

The phosphate dispersant has a phosphate group and a hydrophilic portion. Typically, the metal nanoparticles are each coated with an organic protective film (such as a fatty acid) to prevent flocculation. The organic protective film can be replaced by a phosphate having a strong coordinating power to the metal. Further, the dispersibility of the metal nanoparticles in a polar solvent is improved by the hydrophilic portion. Thereby, it is possible to prevent the metal nanoparticles from flocculation.

The phosphate-based dispersant has no particular limitation as long as it has a phosphate group and a hydrophilic portion. For example, the phosphoric acid dispersant may be a phosphate dispersant, a polyoxyalkylene alkyl ether phosphate dispersant, a polyoxyalkylene alkyl phenyl ether phosphate dispersant, or the like. The phosphate can be in the form of a salt. The hydrophilic portion may be, for example, a polyalkylene glycol (polyethylene glycol, polytetraethylene glycol, polypropylene glycol, etc.), polyglycerin or the like. Although not particularly limited, the phosphate-based dispersant preferably has polyethylene glycol as a hydrophilic portion.

Further, the phosphoric acid-based dispersant has the following structure represented by Structural Formula 1:

In the formula, x is an integer from 6 to 20 (more than 6 to 14 is desired) Number), y is an integer from 0 to 5 (more desirable to be an integer from 0 to 2), z is an integer from 0 to 5 (more desirable to be an integer from 0 to 2), and x + y + z is 6 to 30 Integer (more than 6 to 18 integers).

The content of the phosphoric acid dispersant in the metal nanoparticle paste is not particularly limited, however, in order to increase the content of the metal nanoparticle, the content of the phosphate dispersant is preferably as low as possible. For example, the content of the phosphoric acid-based dispersing agent is desirably 0.1 to 10% by weight, more desirably 0.3 to 5% by weight, and particularly desirably 0.5 to 2% by weight.

The polar solvent is not particularly limited as long as the polar solvent has an affinity for the hydrophilic portion of the phosphate-based dispersant. For example, the polar solvent can be a protic polar solvent such as water and an alcohol, an aprotic polar solvent such as a guanamine, such as dimethylacetamide, a nitrile such as acetonitrile, a ketone such as acetone, and a cyclic ether ( For example, tetrahydrofuran)). Although not particularly limited, the polar solvent is preferably an alcohol (for example, a C1 to C18 alcohol or the like). More specifically, the alcohol may be butanol, pentanol, hexanol, heptanol, octanol, isodecylcyclohexanol, terpineol, octanediol, decyl alcohol, decyl alcohol, undecyl alcohol or the like.

The content of the polar solvent in the metal nanoparticle paste is not particularly limited, however, in order to increase the content of the metal nanoparticle, the lower the content of the polar solvent, the better. For example, the content of the polar solvent is desirably from 0.5 to 10% by weight, more desirably from 1 to 7% by weight, and particularly desirably from 3 to 5% by weight.

The metal nanoparticle paste can be prepared by mixing metal nanoparticles, a phosphoric acid dispersant, and a polar solvent with each other. The metal nanoparticles are easily flocculated, so each of the metal nanoparticles is preferably coated with an organic protective film such as a grease. Fatty acid. The order of mixing is not particularly limited, however, it is desirable to mix a phosphate dispersant and a polar solvent, and then add metal nanoparticles.

The metal nanoparticle paste according to the first embodiment of the present invention can maintain a low viscosity while containing a high ratio of metal nanoparticles. For example, the metal nanoparticle paste has a viscosity lower than or equal to 300 Pa. s, more desirable is less than or equal to 200 Pa. s, and especially hope to be less than or equal to 100 Pa. s (for example, 1 to 100 Pa.s). It should be noted that, unless otherwise specified in the specification, the viscosity value means a value measured using a plate cone viscometer at a rotation speed of 10 rpm and a temperature of 20 ° C as in the case of the examples described later.

Further, it is preferable to maintain the relationship between the content X (% by weight) of the metal nanoparticles and the viscosity Y (Pa.s) represented by the inequality (1), and it is preferable to maintain the inequality (2). The relational expression is expressed, and it is preferable to maintain the relational expression represented by inequality (3).

2. Joining method

The second and third embodiments of the present invention are respectively directed to a method of joining a joined member using a metal nanoparticle paste and a joined member obtained by the method. The metal nanoparticle paste according to the first embodiment of the present invention contains a high ratio of metal nanoparticles, and thus a joined member having excellent shear strength can be produced.

The joined member is not particularly limited. The joined member may be a metal material Materials, plastic materials, ceramic materials, etc. The metal material may be, for example, a copper substrate, a gold substrate, an aluminum substrate, or the like. The plastic material may be, for example, polyimide, polyethylene, polypropylene, polyethylene terephthalate, polycarbonate, polyethylene naphthalate or the like. The ceramic material may be, for example, glass, ruthenium or the like.

Further, the bonded member may be an electronic component. In particular, when a metal having high heat resistance is used as the metal nanoparticle, power device elements such as tantalum carbide and gallium nitride can be used as the joined member. The self-cooling can be performed using the power device components, so no cooler is required and the cost can be significantly reduced.

The joined members can be joined as follows. A metal nanoparticle paste is placed (eg, applied) onto the joined member and fired. The metal paste of the prior art has a low metal content. Therefore, unless the existing metal paste is fired under pressure, voids are formed in the metal paste, and it is difficult to firmly bond the joined members. On the other hand, the metal nanoparticle paste according to the first embodiment of the present invention has an extremely high content of metal nanoparticles. Therefore, the joined member can be firmly joined without pressure. Here, the "no pressure" condition means that high pressure is not required to be applied using a machine or the like, and the pressure applied by the joint member by hand is not excluded. Since the joined members can be joined without pressure, the manufacturing cost of the joined components can be significantly reduced.

The joined element joined using the metal nanoparticle paste according to the first embodiment of the present invention has high shear strength. The shear strength in this specification means the shear strength obtained in the shear strength test described in the examples. For example, the joined member according to the third embodiment of the present invention has a shear strength of 20 to 120 MPa, more preferably 60 to 115 MPa, and particularly preferably 80. Up to 110 MPa.

In the joined component according to the third embodiment of the present invention, the composition of the composition of the metal nanoparticle paste is changed. The polar solvent which is a component of the paste is reduced by natural evaporation and firing at the time of bonding, and thus the content of the metal nanoparticle is relatively increased. Further, the phosphate-based dispersant may also be decomposed by firing at the time of bonding. This can affect the content of metal nanoparticles.

In the joined component according to the third embodiment of the present invention, phosphorus generated in the phosphoric acid-based dispersant is easily separated in the vicinity of the interface between the fired metal nanoparticle paste and the joined member (Fig. 5A and Fig. 5B). . Thus, in the joined element according to the third embodiment of the present invention, the concentration of phosphorus in the vicinity of the joint interface is relatively high, and the concentration of phosphorus in other portions is relatively low.

The metal nanoparticle paste according to the first embodiment of the present invention can be used to form a wire of an electronic substrate. Therefore, a fourth specific example of the present invention relates to an electronic substrate having a line formed of a metal nanoparticle paste. The metal nanoparticle paste according to the first embodiment of the present invention has a low viscosity and contains a large amount of metal nanoparticles having a small particle diameter. Therefore, a subtle line may be formed.

Example

Specific examples of the present invention will be described in more detail below using examples and comparative examples, however, the technical scope of the present invention is not limited to the embodiments.

1. Preparation of metal nanoparticle paste

Will be used as silver nanoparticles for metal nanoparticles (up to 50 nm), Silver nanofiller (100 to 200 nm) and silver filler (300 nm), DISPER-BYK111 (made by BYK) used as a phosphate dispersant, and isodecylcyclohexanol (product name: Terusolve MTPH, by Nippon Terpene) Manufactured in accordance with the ratio shown in the following table, which is used as a polar solvent, to prepare 90% by weight, 91% by weight, 92% by weight, 93% by weight, 94% by weight, and 95% by weight, respectively. Silver content of silver nanoparticle paste.

2. Measurement of viscosity

The silver cones were measured at various rotation speeds (rpm) and temperatures of 20 ° C using a plate cone viscometer (cone rotor: 3° x R9.7) (TV-25 viscometer, manufactured by Toki Sangyo Co., Ltd.). The viscosity of each of the rice particles paste. The results are shown in Figure 1.

3. Shear strength test

Each of the above silver nanoparticle pastes was applied to a copper plate of 3 mm × 3 mm and adhered to a copper plate of 50 mm × 10 mm (Fig. 2A). Thereafter, a 50 mm x 10 mm copper plate having the adhered 3 mm × 3 mm copper plate was fired at 250 ° C for 1 hour under no pressure to join the 3 mm × 3 mm copper plate. Thus, a sample was prepared. Subsequently, the shear strength of each sample was measured using a push-pull gauge RX-100 (manufactured by Aikoh Engineering, Co., Ltd.) (Fig. 2B). The test was carried out 5 times for each silver content. The results are shown in Figure 3.

For comparison, measurements were also made by using silver nanoparticles (32.7 weight percent), silver nanofiller (42.1 weight percent), silver filler (14 weight percent), isodecylcyclohexanol (4.7 weight percent) and Shear strength of a sample obtained from an octanol (6.5 weight percent) metal nanoparticle paste which was fired at 350 ° C for 1 hour without pressure. The viscosity of the paste and the bonding strength of the sample are shown in Fig. 4.

4. Component analysis

The element ratio in the vicinity of the joint interface between the silver portion and the copper portion in each of the samples produced by the silver nanoparticle paste according to the specific example of the present invention was analyzed by TEM-EDS. As shown in Fig. 5B, it was revealed that the phosphorus generated in the phosphoric acid-based dispersant was separated around the joint interface.

1‧‧‧ copper plate, 3mm × 3mm (thickness 0.5mm)

2‧‧‧ joint, 3mm × 3mm

3‧‧‧ copper plate (thickness 1.0mm)

4‧‧‧Cutting tools

5‧‧‧ copper plate

6‧‧‧Joint Department (Silver)

7‧‧‧ copper plate

8‧‧‧ joint interface

9‧‧‧Silver part

10‧‧‧ copper part

Figure 1 shows the results of the viscosity of a silver nanoparticle paste according to a specific example of the present invention; 2A is a schematic view showing a sample used in a shear strength test, wherein the left side view is a side view of the sample, the right side view is a plan view of the sample; FIG. 2B is a schematic view showing a shear strength test; The results of the shear strength test; FIG. 4 shows the viscosity of the metal nanoparticle paste in the comparative example and the joint strength of the sample; FIG. 5A shows the TEM image of the joint interface of the sample; and FIG. 5B shows the element of the joint interface of the sample. Analysis results.

Claims (17)

A metal nanoparticle paste characterized by comprising: metal nanoparticle; a phosphate dispersant having a hydrophilic portion; and a polar solvent, wherein the content of the metal nanoparticle is higher than or equal to 70 weight percent and less than 100 weight percentage. The metal nanoparticle paste of claim 1, wherein the content of the metal nanoparticles is higher than or equal to 90% by weight and less than 99% by weight. The metal nanoparticle paste of claim 2, wherein the content of the metal nanoparticles is higher than or equal to 95% by weight and less than 99% by weight. The metal nanoparticle paste according to any one of claims 1 to 3, wherein the metal nanoparticles are selected from the group consisting of gold, silver, ruthenium, rhodium, palladium, iridium, platinum, copper, aluminum, iron. And at least one of the group consisting of nickel. The metal nanoparticle paste according to any one of claims 1 to 4, wherein the metal nanoparticles are made of at least one of a metal oxide having a conductivity/thermal conductivity and a metal salt. The metal nanoparticle paste according to any one of claims 1 to 5, wherein the metal nanoparticle paste has a viscosity lower than or equal to 100 Pa. s. Metal nanoparticles according to any one of claims 1 to 6 The sub-paste, wherein the hydrophilic portion is selected from one of the group consisting of polyalkylene glycol and polyglycerol. The metal nanoparticle paste of claim 7, wherein the hydrophilic portion is selected from the group consisting of polyethylene glycol, polytetraethylene glycol, and polypropylene glycol. The metal nanoparticle paste according to any one of claims 1 to 8, wherein the polar solvent has an affinity for a hydrophilic portion of the phosphate dispersant. The metal nanoparticle paste of claim 9, wherein the polar solvent is any one of a protic polar solvent and an aprotic polar solvent. The metal nanoparticle paste of claim 10, wherein the protic polar solvent is selected from the group consisting of water and alcohol. The metal nanoparticle paste of claim 10, wherein the aprotic polar solvent is selected from the group consisting of guanamine, nitrile, ketone and cyclic ether. A joining method, characterized in that the metal nanoparticle paste according to any one of claims 1 to 12 is applied to the joined member. The joining method of claim 13, which additionally comprises joining the joined member without pressure. A joined component obtained by the joining method of claim 13 or 14 of the patent application. Such as the joined component of claim 15 of the patent scope, wherein the The joint element has a shear strength of 80 to 110 MPa. An electronic substrate characterized by comprising a wire formed of a metal nanoparticle paste according to any one of claims 1 to 12.