JP2019052330A - Method of producing low-temperature sinterable surface-treated copper particles - Google Patents

Abstract

To provide a method of surface treatment in an aqueous solution for producing novel surface-treated copper particles that can be used suitably for a paste usable in a low-temperature region.SOLUTION: A method of producing low-temperature sinterable surface-treated copper particles comprises a step of mixing copper particles having a BET specific surface area of 0.1 to 10.0 m/g with an aqueous solution of a compound selected from compounds represented by formulas (I)-(IV).SELECTED DRAWING: None

Description

  The present invention relates to a method for producing low-temperature sinterable surface-treated copper fine particles.

  In recent years, from the viewpoint of environmental protection, the growth of hybrid vehicles and electric vehicles is expected instead of gasoline vehicles. In these types, in order to secure a battery mounting space, adoption of next-generation power modules such as SiC and GaN is being considered in place of conventional power modules using Si. The next-generation power module has advantages over the conventional power module, such as high breakdown voltage, operation at high temperature, high current density, high switching speed, and low on-resistance.

  In the next-generation power module, it is said that the operating temperature exceeds 250 ° C. Therefore, if the chip is joined with Pb-free Sn-3Ag-0.5Cu solder having a melting point of 220 ° C, it will be joined during operation. The layer can melt. Therefore, the use of Au-based solder (Au—Sn, Au—Si, Au—Ge) has been studied as a Pb-free heat-resistant solder (Non-Patent Documents 1 to 3). However, while Au-based solder has heat resistance, Au is used, so that the material cost is high.

  Thus, in place of solder, a metal powder paste has been attracting attention in recent years. When the size of the metal powder is small, the surface energy is high, and sintering between the powders occurs at a temperature much lower than the melting point of the metal. Unlike solder, once sintered, it does not remelt unless it is heated to near the melting point of the metal. Taking advantage of such characteristics, development of Ag powder pastes and Cu powder pastes has been promoted (Patent Documents 1 to 3).

International Publication No. 2011/155055 JP2015-168878A JP, 2006-191084, A

P. Alexandrov, W .; Wright, M.C. Pan, M.C. Weiner, L .; Jiao and J.H. H. Zhao, Solid-State Electron. 47 (2003) p. 263. R. W. Johnson and L. Williams, Mater. Sci. Forum 483-485 (2005) p. 785. S. Tanimoto, K. et al. Matsui, Y. et al. Murakami, H .; Yamaguchi and H.K. Okumura, Proceedings of IMAPS HiTEC 2010 (May 11-13, 2010, Albuquerque, New Mexico, USA), p. 32-39.

  According to the study of the present inventor, the Ag powder paste as described in Patent Document 1 also requires a material cost, and migration measures are required depending on the use environment. Moreover, since the paste using Cu powder described in Patent Document 2 must be subjected to surface treatment of Cu powder using an organic solvent such as alcohol, there is a management limitation when the production amount increases. It can happen. Furthermore, since this Cu powder is made into a paste only in combination with an alcohol-based solvent, there are restrictions on the paste application method to the chip mounting portion. The Cu powder described in Patent Document 3 can be surface-treated in an aqueous solution, and even when a binder resin that causes sintering hindrance between powders is added to the paste in low-temperature firing, it is below the combustion temperature of the binder resin. Sintering between powders occurs even when baked at, and since it is possible to add a binder resin to the paste, it is easy to control the viscosity, and it is advantageous in that the range of paste coating methods on the chip mounting area is widened However, there is room for further improvement in the bonding capability at lower temperatures.

  Accordingly, an object of the present invention is to provide a method for producing novel surface-treated copper fine particles that can be suitably used for pastes that can be used in a low temperature region by surface treatment in an aqueous solution.

  As a result of intensive studies so far, the present inventor has made it possible to produce surface-treated fine particles by surface treatment in an aqueous solution by using a specific organic compound described later, and obtained surface-treated copper fine particles Has been found to be suitable for use in pastes that can be used in a low temperature range, and has reached the present invention.

Accordingly, the present invention includes the following (1).
(1)
A step of mixing copper fine particles having a BET specific surface area of 0.1 to 10.0 m ² / g and an aqueous solution of a compound selected from the compounds represented by the following formulas (I) to (IV):
Method for producing low-temperature sinterable surface-treated copper fine particles containing:
Formula (I):
(In the formula (I), R represents a C8 to C20 alkyl group or a C8 to C20 alkenyl group, x is an integer of 1 or more, y is an integer of 1 or more, and x + y is 2 to 2) (It is an integer of 45)
Formula (II):
(In the formula (II), R represents a C8-C20 alkyl group or a C8-C20 alkenyl group, x is an integer of 1 or more, y is an integer of 1 or more, and z is 1 or more.) And x + y + z is an integer of 3 to 45)
Formula (III):
(In the formula (III), R represents a C8-C20 alkyl group or a C8-C20 alkenyl group, n is an integer of 1 or more, m is an integer of 1 or more, and 2 ≦ n + m ≦ 45)
Formula (IV):
(In the formula (IV), R represents a C8 to C20 alkyl group or a C8 to C20 alkenyl group, x is an integer of 1 or more, y is an integer of 1 or more, and z is 1 or more.) W is an integer of 1 or more, x + y is an integer of 2 to 45, and z + w is an integer of 2 to 45).
(2)
The manufacturing method according to (1), wherein the copper fine particles are copper fine particles prepared by mixing copper fine particles prepared by a dry method with an acid.
(3)
A step of mixing the low-temperature sinterable surface-treated copper fine particles produced by the production method according to any one of (1) and (2) with a solvent and a binder resin;
The manufacturing method of the copper fine particle paste containing this.
(4)
A step of bonding the die and the support at a temperature of 300 ° C. or lower using the copper fine particle paste manufactured by the manufacturing method according to (3),
A method for manufacturing a power module, comprising:
(5)
A step of bonding the copper plate and the nitride substrate at a temperature of 300 ° C. or lower using the copper fine particle paste produced by the production method according to (3),
A method for manufacturing a power module, comprising:
(6)
The manufacturing method according to (4) or (5), wherein the joining step is performed in a nitrogen atmosphere containing formic acid or in a nitrogen atmosphere containing 5 vol% or less of hydrogen.
(7)
A low-temperature sintered surface treatment agent for copper fine particles, comprising a compound selected from compounds represented by the following formulas (I) to (IV):
Formula (I):
(In the formula (I), R represents a C8 to C20 alkyl group or a C8 to C20 alkenyl group, x is an integer of 1 or more, y is an integer of 1 or more, and x + y is 2 to 2) (It is an integer of 45)
Formula (II):
(In the formula (II), R represents a C8-C20 alkyl group or a C8-C20 alkenyl group, x is an integer of 1 or more, y is an integer of 1 or more, and z is 1 or more.) And x + y + z is an integer of 3 to 45)
Formula (III):
(In the formula (III), R represents a C8-C20 alkyl group or a C8-C20 alkenyl group, n is an integer of 1 or more, m is an integer of 1 or more, and 2 ≦ n + m ≦ 45)
Formula (IV):
(In the formula (IV), R represents a C8 to C20 alkyl group or a C8 to C20 alkenyl group, x is an integer of 1 or more, y is an integer of 1 or more, and z is 1 or more.) W is an integer of 1 or more, x + y is an integer of 2 to 45, and z + w is an integer of 2 to 45).
(8)
The copper fine particles are copper fine particles having a BET specific surface area of 0.1 to 10.0 m ² / g,
The low-temperature sintered surface treatment agent for copper fine particles according to (7), wherein the copper fine particles are prepared by mixing copper fine particles prepared by a dry method with an acid.

  According to the present invention, low-temperature sinterable surface-treated copper fine particles can be obtained by surface treatment in an aqueous solution. The low-temperature sinterable surface-treated copper fine particles obtained by the present invention can be suitably used for pastes that can be used in a low-temperature region. The paste obtained by the present invention can produce a joined body by suitably joining a semiconductor chip (die) and a support (substrate) under joining conditions in a low temperature region.

The present invention will be described in detail below with reference to embodiments. The present invention is not limited to the specific embodiments described below.
[Production of low-temperature sinterable surface-treated copper fine particles]
The method for producing low-temperature sinterable surface-treated copper fine particles according to the present invention is represented by copper fine particles having a BET specific surface area of 0.1 to 10.0 m ² / g and the following formulas (I) to (IV). And a step of mixing an aqueous solution of a compound selected from the compounds.

[Surface treatment agent]
The compounds represented by the following formulas (I) to (IV) can be used for surface treatment for producing low-temperature sinterable surface-treated copper fine particles. The present invention also resides in a low-temperature sintered surface treatment agent for copper fine particles.

[Compound represented by formula (I)]
As the compound, a compound represented by the following formula (I) can be used.

Formula (I):

  In the formula (I), R is a C8 to C20 alkyl group or a C8 to C20 alkenyl group, preferably a C10 to C14 alkyl group or a C10 to C14 alkenyl group.

  In the formula (I), x is an integer of 1 or more, y is an integer of 1 or more, x + y is an integer of 2 to 45, preferably x + y is an integer of 8 to 16, more preferably x + y. Is an integer from 10 to 14.

  As the compound represented by the formula (I), a mixture of compounds satisfying the formula (I) can be used. For example, a mixture of a compound in which R is the above alkyl group and a compound in which R is the above alkenyl group can be used.

[Compound represented by formula (II)]
As the compound, a compound represented by the following formula (II) can be used.

Formula (II):

  In the formula (II), R is a C8 to C20 alkyl group or a C8 to C20 alkenyl group, preferably a C14 to C18 alkyl group or a C14 to C18 alkenyl group.

  In the formula (II), x is an integer of 1 or more, y is an integer of 1 or more, z is an integer of 1 or more, x + y + z is an integer of 3 to 45, and preferably x + y + z is 10 to 20 More preferably, x + y + z is an integer of 13-17.

  As the compound represented by the formula (II), a mixture of compounds satisfying the formula (II) can be used. For example, a mixture of a compound in which R is the above alkyl group and a compound in which R is the above alkenyl group can be used.

[Compound represented by Formula (III)]
As the compound, a compound represented by the following formula (III) can be used.

Formula (III):

  In the formula (III), R is a C8 to C20 alkyl group or a C8 to C20 alkenyl group, preferably a C8 to C18 alkyl group or a C8 to C18 alkenyl group.

  In the formula (III), n is an integer of 1 or more, m is an integer of 1 or more, satisfies 2 ≦ n + m ≦ 45, preferably satisfies 5 ≦ n + m ≦ 40, more preferably 10 ≦ n + m ≦ 30. Meet.

  As the compound represented by the formula (III), a mixture of compounds satisfying the formula (III) can be used. For example, a mixture of a compound in which R is the above alkyl group and a compound in which R is the above alkenyl group can be used.

[Compound represented by Formula (IV)]
As the compound, a compound represented by the following formula (IV) can be used.

Formula (IV):

  In the formula (IV), R is a C8 to C20 alkyl group or a C8 to C20 alkenyl group, preferably a C8 to C18 alkyl group or a C8 to C18 alkenyl group.

  In the formula (IV), x is an integer of 1 or more, y is an integer of 1 or more, z is an integer of 1 or more, w is an integer of 1 or more, and x + y is an integer of 2 to 45. Yes, z + w is an integer from 2 to 45. Preferably x + y is an integer of 2 to 20, more preferably x + y is an integer of 4 to 12, and more preferably x + y is an integer of 6 to 10. Preferably z + w is an integer of 2-20, more preferably z + w is an integer of 4-12, more preferably z + w is an integer of 6-10.

  As the compound represented by the formula (IV), a mixture of compounds satisfying the formula (IV) can be used. For example, a mixture of a compound in which R is the above alkyl group and a compound in which R is the above alkenyl group can be used.

[Surface treated copper fine particles and BET specific surface area]
As the copper fine particles to be surface-treated in the present invention, copper fine particles having a BET specific surface area of 0.1 to 10.0 m ² / g are used. In a preferred embodiment, the BET specific surface area of the copper fine particles can be 0.5 to 6.0 m ² / g. The BET specific surface area of the copper fine particles can be measured and calculated by, for example, Macsorb HM model-1201 (Mounttech Co., Ltd.).

[Surface treated copper fine particles and average particle size]
In a preferred embodiment, as the copper fine particles to be surface-treated in the present invention, copper fine particles having an average particle diameter in the range of, for example, 0.1 to 1.0 μm can be suitably surface-treated. The average particle diameter can be determined by image analysis from a SEM image, laser diffraction method, or dynamic light scattering method.

[Copper fine particles by dry method]
As the copper fine particles to be surface-treated in the present invention, copper fine particles obtained by performing a thermal plasma method can be suitably used. If the BET specific surface area exceeds 0.1 m ² / g, copper powder produced by a dry method other than the thermal plasma method may be applied. Examples of dry methods other than the thermal plasma method include a hydrogen reduction method of chloride by a CVD method and an oxygen combustion method of a metal oxide.

[Thermal plasma method]
The thermal plasma method can be performed by a known means, whereby fine copper particles, for example, submicron copper particles can be obtained.

[Acid treatment]
In a preferred embodiment, the copper fine particles obtained by the dry method can be used as copper fine particles to be surface-treated after mixing with an acid solution, preferably dilute sulfuric acid, to form dilute sulfuric acid-treated copper fine particles. it can. Mixing with dilute sulfuric acid can be performed, for example, by mixing dilute sulfuric acid in the range of 0.1N to 30N with copper fine particles while stirring or irradiating with ultrasonic waves. The copper fine particles treated with dilute sulfuric acid can be separated from the slurry containing dilute sulfuric acid by a known means and subjected to subsequent surface treatment. The copper fine particles may be subjected to a surface treatment after removing the acid remaining on the surface by means such as washing after separation from the slurry containing dilute sulfuric acid.

[Aqueous solutions of compounds represented by formulas (I) to (IV)]
The compounds represented by the above formulas (I) to (IV) can be used for surface treatment as an aqueous solution. The concentration of the compound (surface treatment agent) in the aqueous solution can be, for example, in the range of 0.1 to 30% by mass and 0.5 to 20% by mass. Or as for the density | concentration of the compound (surface treatment agent) in aqueous solution, the mass of a compound is 0.1-15 mass%, 0.1-12 mass%, 0.1-10 mass with respect to the mass of copper fine particles. % Can be prepared and used.

[Mixing step]
In the step of mixing copper fine particles having a BET specific surface area of 0.1 to 10.0 m ² / g and an aqueous solution of any one of the compounds of formulas (I) to (IV), the mixing is performed by known means. be able to. The mixing can be performed, for example, under atmospheric pressure, for example, at a temperature of 5 to 40 ° C., for example, 10 minutes to 3 hours. The copper fine particles mixed with the solution can be separated and recovered by a known means, and can be subjected to the subsequent treatment if desired.

[Low-temperature sinterable surface-treated copper fine particles]
The low-temperature sinterable surface-treated copper fine particles obtained by the present invention are obtained by a step of mixing with an aqueous solution, and then appropriately separated from the aqueous solution, followed by drying and crushing as necessary, and then a conductive paste ( The copper fine particle paste) can be made into a suitable form.

[Low temperature sintering]
The surface-treated copper fine particles obtained by the present invention are excellent in low-temperature sinterability. For example, when a copper fine particle paste is used, the firing temperature is, for example, 400 ° C. or lower, 350 ° C. or lower, 300 ° C. or lower, 250 ° C. or lower, for example 200 ° C. As described above, an excellent sintered body can be obtained at a firing temperature of 230 ° C. or higher and 250 ° C. or higher. That is, since the surface-treated copper fine particles obtained by the present invention are excellent in low-temperature sinterability, when a copper fine particle paste is used, a temperature condition equal to or lower than the decomposition temperature of the resin can be selected and sintered. it can.

[Copper fine particle paste]
By using the surface-treated copper fine particles, a conductive paste (copper fine particle paste) can be produced by a known means. In a preferred embodiment, for example, surface-treated copper fine particles can be mixed with a solvent to obtain a copper fine particle paste. Preferably, a binder resin is added to the paste to adjust the viscosity. If desired, additives, glass frit and the like may be added and used within a range that does not interfere with excellent low-temperature sinterability. Mixing can be carried out by known means, and may be carried out by one stage or two or more stages of kneading.

[Paste solvent]
As the solvent, a solvent having a boiling point of 50 ° C. or higher and 250 ° C. or lower can be suitably used. Examples of such solvents include ethers, ketones, aromatic compounds, terpenes, alcohols, and glycols. As the solvent, terpineol, dihydroterpineol, polyethylene glycol, and propylene glycol are particularly preferable. The content of the solvent in the paste can be added and used in the range of, for example, 5 to 50% by weight, preferably 5 to 30% by weight.

[Binder resin for paste]
As the binder resin, any binder resin having a Tg of 50 to 200 ° C. can be used without particular limitation. Since the copper fine particles are fired in a non-oxidizing atmosphere or a reducing atmosphere, a binder resin having a low thermal decomposition temperature is preferable as the binder resin. Examples of suitable binder resins include cellulose resins, acrylic resins, and butyral resins. In particular, when TG measurement (thermogravimetry) is performed in a nitrogen atmosphere, a binder resin having a weight loss of 30% or more at 250 to 350 ° C. can be preferably used.

  In a preferred embodiment, since the surface-treated fine particles according to the present invention have excellent low-temperature sinterability, for example, even when a binder resin that may cause a sintering hindrance is added to the paste, the resin is treated with nitrogen. When TG measurement is performed in an atmosphere, sintering can be performed at a temperature equal to or lower than a temperature at which weight loss reaches 90%.

[Sintered body]
Using a copper fine particle paste, a sintered body (fired body) can be produced by performing coating and the like and firing by a known means. In a preferred embodiment, for example, a copper fine particle paste can be sintered (fired) at 300 ° C. or less in a non-oxidizing atmosphere to obtain a sintered body (fired body).

[Join]
The copper fine particle paste can be suitably used as a conductive bonding material for bonding by firing. In a preferred embodiment, the semiconductor chip (die) and the substrate (support) can be bonded by a known means using the copper fine particle paste. Such bonding is particularly called die bonding. Therefore, the bonding method according to the present invention is also in the die bonding method, and the manufacture of the bonded body according to the present invention is also in the method of manufacturing the power module. Furthermore, it can be suitably used for bonding a copper plate and a nitride substrate.

  For bonding, for example, the paste is applied to one of the bonding surfaces of the semiconductor chip (die) and the substrate (support), or both of the bonding surfaces, and the bonding surface of the semiconductor chip (die) and the substrate (support) is applied. It can be carried out by placing it in close contact with the applied paste and firing (sintering) it. When placing the paste in close contact with each other, pressure may be applied to the joint surface to ensure close contact. Alternatively, in order to ensure the close contact arrangement via the paste, the laminated body may be formed once by preliminary fixing by preliminary heating prior to sintering.

[Joint temperature]
The copper fine particle paste of the present invention can be suitably bonded by firing in a low temperature region. The firing temperature (joining temperature) can be, for example, 400 ° C. or lower, 350 ° C. or lower, and 300 ° C. or lower, for example, 200 to 300 ° C.

[atmosphere]
The above sintering (firing) can be performed, for example, in a non-oxidizing atmosphere or a reducing atmosphere. The non-oxidizing atmosphere refers to an atmosphere in which an oxidizing gas is not contained or reduced, for example, an atmosphere in which oxygen is completely or sufficiently removed. The reducing atmosphere contains 0.5 vol% or more, preferably 1.0 vol% or more of a reducing gas such as CO, H ₂ S, SO ₂ , H ₂ , HCHO, HCOOH, and H ₂ O in the atmosphere. Say the atmosphere. In a preferred embodiment, the bonding can be performed by sintering under a nitrogen atmosphere containing formic acid or a nitrogen atmosphere containing 5 vol% or less of hydrogen.

[Joint strength]
The copper fine particle paste according to the present invention reflects the excellent low-temperature sinterability of the surface-treated copper fine particles, and can produce a bonded body having excellent bonding strength even by firing at a low temperature. The joint strength of the joined body can be measured by the means described in the examples. In a preferred embodiment, for example, a bonding strength of 20 [MPa] or more and 20 to 50 [MPa] can be achieved.

[Resistivity]
The copper fine particle paste according to the present invention reflects the excellent low-temperature sinterability of the surface-treated copper fine particles, and can produce a fired body (sintered body) excellent in specific resistance even by firing at a low temperature. The specific resistance [μΩ · cm] of the fired body can be measured by the means described in the examples. In a preferred embodiment, the specific resistance can be 20 μΩ · cm or less at a firing temperature of 300 ° C., 20 μΩ · cm or less at a firing temperature of 250 ° C., and 25 μΩ · cm or less at 200 ° C.

[Manufacture of power modules]
The copper fine particle paste according to the present invention reflects the excellent low-temperature sinterability of the surface-treated copper fine particles, and can achieve excellent bonding strength and specific resistance as described above even by firing at a low temperature. That is, it is particularly suitable for die bonding for manufacturing a power module.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the following examples.

[Example 1: Preparation of copper fine particles by thermal plasma method]
20 g of copper fine particles having a BET specific surface area of 3.0 m ² / g produced by a thermal plasma method were transferred to a plasma torch (MODEL PL-50, TEKNA Plasma Systems Inc.), a 2 MHz high frequency power source (Japan High Frequency), a water-cooled reaction vessel, The plasma powder apparatus composed of a stainless steel filter was used for the production according to the following procedure. Ar—H ₂ plasma was generated in a torch connected to a high frequency power source. Ar gas was supplied as a central gas from the vertical direction to the induction coil, and an Ar—H ₂ mixed gas was supplied as a sheath gas around the central gas. Electrolytic copper powder (JX metal, 52-H (average particle size 25 μm)) as a raw material powder was injected into the plasma from the top of the torch through a powder introduction nozzle together with a carrier gas. The electrolytic copper powder supply rate at this time was 1.9 g / min (“Powder and Powder Metallurgy” Vol. 54 No. 1, p39-). By changing the supply rate of the electrolytic copper powder, copper fine particles having different specific surface areas were produced.

[BET specific surface area]
Each BET specific surface area was measured by the following procedure. The obtained results are shown in Table 1.
Measurement was performed by a one-point method using a Macsorb HM model-1201 (Mounttech Co., Ltd.). The measurement was performed with 10 g of copper fine particles, a degassing temperature of 150 ° C., and a degassing time of 15 minutes.

[Example 2: Evaluation of Examples 1-8, 11-17, 20-26, 29-35]
[Surface treatment of copper fine particles]
After stirring the copper fine particle 20g obtained by the procedure of Example 1 and 100 ml of 25 vol% dilute sulfuric acid for 10 minutes, the copper fine particle was recovered by suction filtration. After 40 mL of an aqueous solution containing a predetermined amount of an organic compound (surface treatment agent) with respect to copper fine particles on the filter paper and copper fine particles were mixed at 300 rpm for 1 hour using a stirrer, copper fine powder was recovered. Then, after drying at 70 degreeC in nitrogen for 1 hour, it was crushed and the surface-treated copper fine particle was obtained.

  The structure of each surface treating agent used in each example will be described later. The ratio of the mass of the surface treatment agent to the copper fine particles used in each example is summarized in Table 1.

[Preparation of paste]
The obtained surface-treated copper fine particles had a metal ratio of 80%, an acrylic resin vehicle (Kohaku Chemistry, KFA-2000, solid content of 32 to 35% by mass) with a resin content of 1%, and the balance of dihydroterpineol (used as a solvent). The paste was prepared using three rolls after stirring with a mixer.

[Measurement of bonding strength]
Each paste obtained was coated on a copper plate with a metal mask to a thickness of 50 μm, a 5 mm square copper plate was placed on the coated paste, and heated in air at 120 ° C. for 1 minute to obtain a laminate. It was.
The obtained laminate was joined by applying a pressure of 0.4 MPa at 250 ° C. or 200 ° C. for 10 minutes while flowing nitrogen formate bubbling at room temperature to obtain a joined body.
The bonding strength of the obtained bonded body was measured by the following procedure. The obtained results are shown in Table 1.
A tool was applied from the side of the joining portion, and a load was applied until the 5 mm square copper plate was peeled off. The value obtained by dividing the load when the 5 mm square copper plate was peeled off by 25 mm ² was obtained as the bonding strength.

[Measurement of resistivity]
The paste prepared by the above procedure was printed on a slide glass with a width of 5 mm and a length of 20 mm, and baked at 250 ° C. for 10 minutes while flowing nitrogen formate bubbled at room temperature, and the specific resistance was measured.
The specific resistance was measured by the following procedure. The obtained results are shown in Table 1.
First, the resistance of the fired body was measured with a Lorester GX. Thereafter, the thickness of the fired body was calculated with a three-dimensional measuring device, and the specific resistance was determined from the resistance value, the fired body cross-sectional area, and the length of the fired body.

[Surface treatment agent]
The structure of the organic compound (surface treatment agent) used above is shown below.
Surface treatment agent A: (Aoki Yushi, product name: blaunon L207) (in the following, x + y = 12, R is an alkyl group having 12 carbon atoms)

Surface treatment agent B: (manufactured by Lion, product name: Liponol DA-T / 25) (in the following, x + y + z = 15, R is an alkyl group having 14 to 18 carbon atoms or an alkenyl group having 14 to 18 carbon atoms) is there)

Surface treatment agent C: (Sanyo Chemicals, product name: Sannix NP) (in the following, 2 ≦ n + m ≦ 45, R is an alkyl group having 8 to 20 carbon atoms or an alkenyl group having 8 to 20 carbon atoms) is there)

Surface treatment agent D: (manufactured by Lion, product name: Liponol C / 18-18) (in the following, x + y = 8, z + w = 8, R is an alkyl group having 8 to 18 carbon atoms or 8 to 18 carbon atoms) Is an alkenyl group of

[Example 3: Evaluation of Examples 10, 19, 28, and 37]
Various surface-treated copper fine particles obtained by the procedures of Examples 1 and 2 were pasted by the procedure of Example 2, and the firing atmosphere was the same as that of Example 2 except that the formic acid bubbled nitrogen was changed to nitrogen containing 2% H ₂ . The bonding strength and specific resistance were measured by the procedure.

[Example 4: Evaluation of Examples 9, 18, 27, and 36]
40 mL of an aqueous solution containing a predetermined amount of an organic compound (surface treatment agent) and 20 μg of copper fine particles obtained by the procedure of Example 1 were mixed for 1 hour at 300 rpm using a stirrer, and then copper fine powder was recovered. did. Then, after drying at 70 degreeC in nitrogen for 1 hour, it was crushed and the surface-treated copper fine particle was obtained. Each of these surface-treated copper fine particles was made into a paste by the procedure of Example 2, and the bonding strength and specific resistance were measured by the procedure of Example 2.

[Example 5: Evaluation of Comparative Examples 1 and 2]
[Preparation of copper fine particles]
In the same procedure as in Example 1, copper fine particles were obtained.

[Synthesis of organic compounds]
An amine compound was synthesized as a nitrogen-containing organic substance (organic substance) by the following procedure. Epoxy compound (Denacol EX-521 (manufactured by Nakase ChemteX Corp.)) 10.0 g and 5.72 g of diethanolamine or 2.45 g of dimethylamine are put into a three-necked flask, and a cooling tube using dry ice-methanol as a cooling medium is provided. Prepared and reacted at 60 ° C. for 3 hours to obtain a compound modified with diethanolamine or dimethylamine.

[Surface treatment of copper fine particles]
Using the obtained modified compound (organic compound) as a surface treating agent for a comparative example, surface treatment was performed on the obtained copper fine particles by the same procedure as in Example 2 to obtain surface-treated copper fine particles. Obtained. Table 1 summarizes the types of surface treatment agents used as comparative examples and the amounts used.

[Preparation of paste, measurement of bonding strength, measurement of specific resistance]
Using the obtained surface-treated copper fine particles, a paste was prepared by the same procedure as in Example 1, the bonding strength was measured, and the specific resistance was measured and evaluated. The obtained results are shown in Table 1.

[Example 6: Comparative Example 3]
The copper fine particles obtained by the procedure of Example 1 were made into a paste by the procedure of Example 2, and the bonding strength and specific resistance were measured.

[Results of Examples 2 to 6]
As shown in Table 1, the specific resistance and bonding strength were good in the examples. In the comparative example, the specific resistance or bonding strength was inferior to that of the example.

[Table 1]

[Continuation of Table 1]

  According to the present invention, surface-treated copper fine particles having excellent low-temperature sinterability can be obtained by a simple process of mixing in an aqueous solution. The present invention is industrially useful.

Claims (8)

A step of mixing copper fine particles having a BET specific surface area of 0.1 to 10.0 m ² / g and an aqueous solution of a compound selected from the compounds represented by the following formulas (I) to (IV):
Method for producing low-temperature sinterable surface-treated copper fine particles containing:
Formula (I):
(In the formula (I), R represents a C8 to C20 alkyl group or a C8 to C20 alkenyl group, x is an integer of 1 or more, y is an integer of 1 or more, and x + y is 2 to 2) (It is an integer of 45)
Formula (II):
(In the formula (II), R represents a C8-C20 alkyl group or a C8-C20 alkenyl group, x is an integer of 1 or more, y is an integer of 1 or more, and z is 1 or more.) And x + y + z is an integer of 3 to 45)
Formula (III):
(In the formula (III), R represents a C8-C20 alkyl group or a C8-C20 alkenyl group, n is an integer of 1 or more, m is an integer of 1 or more, and 2 ≦ n + m ≦ 45)
Formula (IV):
(In the formula (IV), R represents a C8 to C20 alkyl group or a C8 to C20 alkenyl group, x is an integer of 1 or more, y is an integer of 1 or more, and z is 1 or more.) W is an integer of 1 or more, x + y is an integer of 2 to 45, and z + w is an integer of 2 to 45).   The manufacturing method according to claim 1, wherein the copper fine particles are copper fine particles prepared by mixing copper fine particles prepared by a dry method with an acid. A step of mixing the low-temperature sinterable surface-treated copper fine particles produced by the production method according to claim 1 with a solvent and a binder resin;
The manufacturing method of the copper fine particle paste containing this. A step of bonding the die and the support at a temperature of 300 ° C. or lower using the copper fine particle paste manufactured by the manufacturing method according to claim 3;
A method for manufacturing a power module, comprising: A step of bonding the copper plate and the nitride substrate at a temperature of 300 ° C. or lower using the copper fine particle paste produced by the production method according to claim 3;
A method for manufacturing a power module, comprising:   The manufacturing method according to claim 4 or 5, wherein the bonding step is performed in a nitrogen atmosphere containing formic acid or in a nitrogen atmosphere containing 5 vol% or less of hydrogen. A low-temperature sintered surface treatment agent for copper fine particles, comprising a compound selected from compounds represented by the following formulas (I) to (IV):
Formula (I):
(In the formula (I), R represents a C8 to C20 alkyl group or a C8 to C20 alkenyl group, x is an integer of 1 or more, y is an integer of 1 or more, and x + y is 2 to 2) (It is an integer of 45)
Formula (II):
(In the formula (II), R represents a C8-C20 alkyl group or a C8-C20 alkenyl group, x is an integer of 1 or more, y is an integer of 1 or more, and z is 1 or more.) And x + y + z is an integer of 3 to 45)
Formula (III):
(In the formula (III), R represents a C8-C20 alkyl group or a C8-C20 alkenyl group, n is an integer of 1 or more, m is an integer of 1 or more, and 2 ≦ n + m ≦ 45)
Formula (IV):
(In the formula (IV), R represents a C8 to C20 alkyl group or a C8 to C20 alkenyl group, x is an integer of 1 or more, y is an integer of 1 or more, and z is 1 or more.) W is an integer of 1 or more, x + y is an integer of 2 to 45, and z + w is an integer of 2 to 45). The copper fine particles are copper fine particles having a BET specific surface area of 0.1 to 10.0 m ² / g,
The low-temperature-sintered surface treating agent for copper fine particles according to claim 7, which is a copper fine particle prepared by mixing copper fine particles prepared by a dry method with an acid.