Copper particles, paste composition, semiconductor device, electrical component, and electronic component

Abstract

The copper particles according to the present invention have a crystallite growth rate ratio k of more than 1.　k = (S200-S150) / (S300-S250) (S150 is the crystallite diameter (nm) of Cu (111) when the copper particles are heated to 150°C.　S200 is the crystallite diameter (nm) of Cu (111) when the copper particles are heated to 200°C.　S250 is the crystallite diameter (nm) of Cu (111) when the copper particles are heated to 250°C.　S300 is the crystallite diameter (nm) of Cu (111) when the copper particles are heated to 300°C.)

Description

Copper particles, paste composition, semiconductor device, electrical component and electronic component

[0001] The present disclosure relates to copper particles, and to paste compositions, semiconductor devices, electrical components, and electronic components using the same.

[0002] In semiconductor devices and various electric and electronic components, highly thermally conductive pastes are used as adhesives for joining components. Semiconductor devices generate more heat due to their higher integration and faster operation. To ensure stable operation, measures have been taken to dissipate heat, such as bonding heat-generating components such as semiconductor elements to heat-dissipating components with highly thermally conductive adhesives (pastes). Highly thermally conductive conductive pastes are also used for die-bonding bare chips, bonding LED chips, bonding electrodes to lead wires, and the like.

[0003] A paste composition containing copper particles has been proposed as one type of conductive paste with high thermal conductivity. The application of such a paste composition to printed electronics is also being considered. For the copper particles used in such a paste composition, copper particles that can be sintered at low temperatures are required from the viewpoints of applicability to organic substrates with low heat resistance, reduction of oxidation of the copper substrate, and reduction of thermal load on peripheral components. For example, Patent Document 1 discloses that when copper particles are heated from 30°C, the temperature at which the crystallite size ratio relative to the copper crystallite size at 30°C becomes 1.2 is 250°C or lower, and the amount of change in the crystallite size ratio per unit temperature in the temperature range of 250°C to 350°C is 2.0 × 10 －３ The copper particles described above are disclosed.

[0004] Japanese Patent Application Laid-Open No. 2019-2054

[0005] As a result of extensive research, the present inventors have found that a paste composition using specific copper particles can form a bonding layer of copper particles that has good low-temperature sintering properties and dimensional stability in high-temperature regions.

[0006] That is, the present disclosure relates to the following. [1] Copper particles having a crystallite growth rate ratio k of greater than 1: k=(S ２００ -S １５０ ) / (S３００ -S ２５０ ) [S １５０ is the crystallite diameter (nm) of Cu(111) when the copper particles are heated to 150°C. ２００ is the crystallite diameter (nm) of Cu(111) when the copper particles are heated to 200°C. ２５０ is the crystallite diameter (nm) of Cu(111) when the copper particles are heated to 250°C. ３００ is the crystallite diameter (nm) of Cu(111) when the copper particles are heated to 300°C.] [2] The following low temperature region crystallite growth rate V Ｌ The copper particles according to the above [1], wherein the surface roughness is more than 0.5 nm / °C. Ｌ = (S ２００ -S １５０ ) / (200-150) [3] The following high temperature region crystallite growth rate V Ｈ The copper particles according to the above [1] or [2], wherein the surface roughness is less than 0.2 nm / °C. Ｈ = (S ３００ -S ２５０ ) / (300-250) [4] BET specific surface area is 3.0 to 13.0 m ２ / g. [5] The copper particles according to any one of the above [1] to [4], which are plate-shaped. [6] A method for producing copper particles according to any one of the above [1] to [5], in which copper oxide and cuprous oxide are reduced using a reducing compound. [7] A method for producing copper particles according to the above [6], in which copper oxide and cuprous oxide are reduced using a reducing compound in the presence of an organic solvent. [8] Copper particles (A) according to any one of the above [1] to [5], in which the major axis (median diameter) is 0.3 to 5 μm and the crystallite size ratio S ２００ / S ３０ A paste composition comprising copper particles (B) having a bond strength of less than 1.2 and a solvent (C). [9] A semiconductor device having a bond formed using the paste composition according to [8] above.

[10] An electrical component having a bond formed using the paste composition according to [8] above.

[11] An electronic component having a bond formed using the paste composition according to [8] above.

[0007] The copper particles described in the examples of Patent Document 1 have a crystallite size ratio of 1.2 at 30°C in a high temperature range close to 250°C, and the crystallite size ratio in this high temperature range is only about 1.2, so further low-temperature sinterability is desired. Furthermore, the copper particles described in Patent Document 1 have a change in the crystallite size ratio per unit temperature of 2.0 × 10 in the temperature range of 250°C to 350°C. －３ For these reasons, sintering does not proceed sufficiently in the temperature range of 250° C. or less, and therefore sintering also proceeds in the high-temperature range of 250° C. or more and 350° C. or less. Therefore, when a bonded body of each member is formed by sintering the conductive paste containing the copper particles at about 250° C. and then exposed to a high-temperature range of 250° C. or more and 350° C. or less during actual use, sintering shrinkage of the copper particles proceeds, resulting in a problem of poor dimensional stability and reliability in the high-temperature range of 250° C. or more and 350° C. or less.

[0008] The present disclosure aims to provide copper particles that have good low-temperature sinterability and dimensional stability in high-temperature ranges, a method for producing the copper particles, a paste composition using the copper particles, and semiconductor devices, electrical components, and electronic components. The present disclosure provides copper particles that have good low-temperature sinterability and dimensional stability in high-temperature ranges, a method for producing the copper particles, a paste composition using the copper particles, and semiconductor devices, electrical components, and electronic components.

[0009] The present disclosure will be described in detail below with reference to one embodiment. In this specification, the expression "XX to YY" means "XX or more and YY or less." In addition, in this specification, for a numerical range (for example, a range of content, etc.), lower and upper limits described in stages can be independently combined. In addition, in a numerical range described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in an example. In this specification, "solid content" means components excluding solvent.

[0010] [Copper Particles (Copper Particles (A))] The copper particles of the present disclosure are copper particles having a crystallite growth rate ratio k of greater than 1, as follows: k=(S ２００ -S １５０) / (S ３００ -S ２５０ ) where S １５０ is the crystallite size of Cu(111) when the copper particles are heated to 150°C. ２００ is the crystallite diameter (nm) of Cu(111) when the copper particles are heated to 200°C. ２５０ is the crystallite diameter (nm) of Cu(111) when the copper particles are heated to 250°C. ３００ is the crystallite diameter (nm) of Cu (111) when the copper particles are heated to 300° C. Hereinafter, the copper particles may be referred to as copper particles (A).

[0011] Above S Ｘ (X = 150, 200, 250, 300) can be measured as follows: In other words, copper particles are heated from 30 ° C. to X ° C. at a heating rate of 10 ° C. / min under a nitrogen gas atmosphere at atmospheric pressure, and XRD measurement is performed at X ° C. From the half width (full width at half maximum: FWHM) β of the Cu (111) peak in the XRD pattern and the Bragg angle θ (½ of the diffraction angle 2θ), the crystallite diameter S of Cu (111) can be calculated by the following Scherrer formula: Ｘ (nm) can be calculated. Ｘ = Kλ / βcosθ S Ｘ : crystallite diameter K: Scherrer constant (0.94) λ: wavelength of X-ray (nm) β: full width at half maximum (rad) θ: Bragg angle Specifically, it can be calculated by the method described in the examples. ３０ can also be measured in the same way.

[0012] Copper particles having a crystallite growth rate ratio k of greater than 1 have good low-temperature sinterability and dimensional stability in high-temperature regions. When copper particles have such good low-temperature sinterability, the bonding strength is high even when the copper particles are sintered at low temperatures to bond multiple components. Furthermore, when copper particles have such good dimensional stability in high-temperature regions, peeling and cracking of the bonded body are less likely to occur when a thermal cycle test in which cooling and heating are repeated is performed, and the rate of change in thermal resistance of the bonded portion is small. There is no particular upper limit for the crystallite growth rate ratio k, but it may be 20 or less from the viewpoints of ease of handling and ease of production. From this viewpoint, the crystallite growth rate ratio k may be greater than 1 and less than 20, may be 1.5 to 20, may be 2 to 20, may be 3 to 20, or may be 4 to 15.

[0013] In the copper particles of the present disclosure, the following low temperature region crystallite growth rate V Ｌ (nm / °C) may be greater than 0.5. Ｌ = (S ２００ -S １５０ ) / (200-150) Low temperature region crystallite growth rate V Ｌ Copper particles having a crystallite growth rate V (nm / °C) of more than 0.5 are sufficiently sintered in the low temperature range of 150 to 200°C, and have good low-temperature sinterability. Ｌ Although there is no particular restriction on the upper limit of the low temperature region crystallite growth rate V (nm / °C), it may be 10 or less from the viewpoint of ease of handling, ease of production, etc. Ｌ (nm / °C) may be greater than 0.5 and equal to or less than 10, may be 0.6 to 5, may be 0.6 to 1.5, may be 0.6 to 1, or may be 0.8 to 1.

[0014] In the copper particles of the present disclosure, the following high temperature region crystallite growth rate V Ｈ (nm / °C) may be less than 0.2. Ｈ = (S ３００ -S ２５０ ) / (300-250) High temperature range crystallite growth rate V ＨCopper particles having a crystallite growth rate V (nm / °C) of less than 0.2 are less likely to sinter in the high temperature range of 250 to 300°C, and therefore have good dimensional stability in the high temperature range. Ｈ (nm / °C) may be 0.18 or less, 0.17 or less, 0.16 or less, 0.15 or less, or 0.12 or less. There is no particular lower limit, but it may be greater than 0, as long as it is greater than 0.

[0015] In the copper particles of the present disclosure, the crystallite size ratio S ２００ / S ３０ The crystallite size ratio S may be 1.2 or more. ２００ / S ３０ Copper particles having a crystallite size ratio S of 1.2 or more have good low-temperature sinterability and good dimensional stability in the high-temperature range. ２００ / S ３０ There is no particular restriction on the upper limit of the crystallite size ratio S. However, from the viewpoint of ease of handling, ease of production, etc., it may be 5 or less. ２００ / S ３０ may be 1.2 to 5, may be 1.5 to 5, may be 2 to 5, may be 2.5 to 4, or may be 3 to 4. ３０ means the crystallite diameter of Cu (111) of the copper particles of the present disclosure at room temperature (30°C).

[0016] In the copper particles of the present disclosure, the crystallite growth rate difference ΔV (nm / °C) described below may be greater than 0. ΔV = (S ２００ -S １５０ ) / (200-150)-(S ３００ -S ２５０ ) / (300-250) Copper particles having a crystallite growth rate difference ΔV (nm / °C) of more than 0 have good low-temperature sinterability and dimensional stability in high-temperature regions. Furthermore, there is no particular upper limit to the crystallite growth rate difference ΔV (nm / °C), but from the viewpoints of ease of handling, ease of production, and the like, it may be 5 or less. From this viewpoint, the crystallite growth rate difference ΔV (nm / °C) may be more than 0 and 5 or less, may be 0.1 to 5, may be 0.2 to 3, may be 0.5 to 2, or may be 0.7 to 1.

[0017] In the copper particles of the present disclosure, the crystallite diameter of Cu(111) (S ３０ ) may be 5 to 100 nm, 5 to 50 nm, 10 to 40 nm, 15 to 35 nm, or 20 to 30 nm, from the viewpoint of obtaining copper particles having good low-temperature sintering properties and dimensional stability in high-temperature regions.

[0018] The copper particles of the present disclosure have a BET specific surface area of ​​3.0 to 13.0 m ２ The copper particles may have a specific surface area of ​​3.0 m / g. ２ / g or more, the sinterability of the copper particles can be ensured, and the specific surface area is 13.0 m ２ From this viewpoint, the specific surface area of ​​the copper particles is preferably 5.0 to 13.0 m / g or less, so that oxidation of the particle surface can be reduced. ２ / g, and 6.0 to 13.0 m ２ / g, and 7.0 to 13.0 m ２ / g, and 8.0 to 13.0 m ２ / g, and 9.0 to 13.0 m ２ The BET specific surface area can be measured by a BET single-point method using nitrogen adsorption with a specific surface area measuring device, and specifically, can be measured by the method described in the Examples.

[0019] The copper particles of the present disclosure may be plate-shaped. The copper particles have a larger contact area between particles than spherical particles because they are plate-shaped particles. It is estimated that a bonding layer formed from a paste composition using such plate-shaped particles has a high density, high bonding strength, and is likely to have high bonding reliability.

[0020] The copper particles may have a thickness of 5 to 50 nm, 8 to 40 nm, or 10 to 30 nm. The copper particles may have a major axis of 30 to 300 nm, 50 to 200 nm, or 110 to 180 nm, and the major axis may be greater than the thickness.

[0021] The aspect ratio (major axis / thickness) of the copper particles may be 1.5 to 15.0, 5.0 to 15.0, 7.5 to 14.0, 8.0 to 14.0, 9.0 to 14.0, or 10.0 to 14.0. When the copper particles have a major axis of 30 to 300 nm, the aspect ratio (major axis / thickness) may be 1.5 to 15.0, 5.0 to 15.0, 7.5 to 14.0, 8.0 to 14.0, 9.0 to 14.0, or 10.0 to 14.0. When the copper particles have a major axis of 50 to 200 nm, the aspect ratio (major axis / thickness) may be 1.5 to 15.0, 5.0 to 15.0, 7.5 to 14.0, 8.0 to 14.0, 9.0 to 14.0, or 10.0 to 14.0. When the copper particles have a major axis of 110 to 180 nm, the aspect ratio (major axis / thickness) may be 1.5 to 15.0, 5.0 to 15.0, 7.5 to 14.0, 8.0 to 14.0, 9.0 to 14.0, or 10.0 to 14.0. Copper particles having a major axis and aspect ratio within the above ranges tend to have better low-temperature sinterability and dimensional stability in high-temperature regions. The reasons for this are presumed to be as follows. Copper particles with major diameters and aspect ratios within the above ranges have a larger aspect ratio and therefore a larger amount of oxide on their surfaces than copper particles with smaller aspect ratios. Furthermore, copper particles with major diameters and aspect ratios within the above ranges have a larger number of contact points per unit weight between copper particles than copper particles with shorter major diameters. This balance is thought to reduce oxides on the particle surfaces, allowing the reduced metal surfaces to sinter rapidly and sufficiently at many points at low temperatures, resulting in improved low-temperature sinterability and dimensional stability at high temperatures.

[0022] The thickness and major axis of the copper particles are each the median (sum of the measured values / total number of measured particles) of the measured values ​​of at least 200 (e.g., 200) particles randomly extracted from an image taken during scanning electron microscope (SEM) observation. Specifically, the thickness and major axis of the copper particles can be measured by the method described in the Examples. The plate-like particles have a shape with a pair of substantially parallel flat surfaces, and the distance between the pair of flat surfaces is the "thickness," and the longest diameter on the flat surfaces is the "major axis" (median diameter).

[0023] [Method for producing copper particles] The method for producing copper particles of the present disclosure is not particularly limited. For example, a method of reducing a copper compound using a reducing compound may be used. The reduction may be carried out in the presence of a shape stabilizer. The copper compound, the shape stabilizer, and the reducing compound may be mixed in an organic solvent.

[0024] The method for producing copper particles of the present disclosure is directed to the production of copper oxide (copper oxide (II): CuO) and cuprous oxide (copper oxide (I): Cu ２ The method for producing copper particles may also be a method for producing copper particles in which copper oxide (copper oxide (II):CuO) and cuprous oxide (copper oxide (I):CuO) are reduced using a reducing compound. According to the method for producing copper particles, copper oxide serves as a crystal nucleus, and cuprous oxide is added to the nucleus to grow the crystal, which tends to easily produce copper particles with a large diameter and a large aspect ratio, and the above-mentioned crystallite growth rate ratio k exceeding 1. Furthermore, the method for producing copper particles of the present disclosure is also advantageous in that copper oxide (copper oxide (II):CuO) and cuprous oxide (copper oxide (I):CuO) are reduced using a reducing compound. ２ O) may be reduced using a reducing compound in the presence of an organic solvent.

[0025] (Copper Compound) Examples of copper compounds include copper oxides, copper hydroxides, copper nitrides, and copper carboxylates. From the viewpoint of obtaining the copper particles of the present disclosure in high yield, the copper compound may be copper oxides. The copper compound may be used alone or in combination of two or more.

[0026] Copper oxides include copper oxide (I) (cuprous oxide: Cu ２Examples of copper carboxylates include copper(I) formate, copper(I) acetate, copper(I) propionate, copper(I) butyrate, copper(I) valerate, copper(I) hexanoate, copper(I) octanoate, and copper(I) decanoate, as well as copper carboxylate anhydrides or hydrates such as copper(II) formate, copper(II) acetate, copper(II) propionate, copper(II) butyrate, copper(II) valerate, copper(II) hexanoate, copper(II) octanoate, and copper(II) citrate. Commercially available copper carboxylates may be used. Copper carboxylates synthesized by known methods may also be used. The copper carboxylate may be copper (II) acetate monohydrate from the viewpoints of availability and production efficiency of the copper particles of the present disclosure.

[0027] Copper oxides include copper oxide (I) (cuprous oxide: Cu ２ When copper(I) oxide and copper(II) oxide (CuO) are used in combination, the mass ratio of copper(I) oxide to copper(II) oxide (copper(I) oxide:copper(II) oxide) may be 1-40:60-99, 5-30:70-95, or 5-25:75-95.

[0028] The BET specific surface area of ​​copper (I) oxide is 10 to 40 m ２ / g, and 15 to 35m ２ / g, and 20 to 30m ２ The BET specific surface area of ​​copper (II) oxide may be 0.1 to 10 m ２ / g, and 0.1 to 5.0 m ２ / g, and 0.1 to 1.2 m ２ The BET specific surface area can be measured by the above-mentioned method.

[0029] The average particle size of copper(I) oxide may be 0.1 to 10 μm, 0.5 to 5.0 μm, or 0.5 to 1.2 μm. The average particle size of copper(II) oxide may be 1.0 to 15 μm, 1.3 to 12 μm, or 1.5 to 10 μm. Unless otherwise specified, the average particle size (particle size at 50% cumulative volume: D50) refers to the particle size at which the cumulative volume from the small particle size side reaches 50% in a volume-based particle size distribution measured using a laser diffraction / scattering particle size distribution analyzer. For example, the average particle size can be measured using a laser diffraction / scattering particle size distribution analyzer (LA-920, manufactured by Horiba, Ltd.).

[0030] (Reducing Compound) The reducing compound is not particularly limited as long as it has the reducing power to reduce the copper compound and liberate metallic copper. Examples of the reducing compound include hydrazine derivatives. The reducing compound may be used alone or in combination of two or more. Examples of hydrazine derivatives include hydrazine monohydrate, methylhydrazine, ethylhydrazine, n-propylhydrazine, isopropylhydrazine, n-butylhydrazine, isobutylhydrazine, sec-butylhydrazine, tert-butylhydrazine, n-pentylhydrazine, isopentylhydrazine, neopentylhydrazine, tert-pentylhydrazine, n-hexylhydrazine, isohexylhydrazine, n-heptylhydrazine, n-octylhydrazine, n-nonylhydrazine, n-decylhydrazine, n-undecylhydrazine, n-dodecylhydrazine, cyclohexylhydrazine, phenylhydrazine, 4-methylphenylhydrazine, benzylhydrazine, 2-phenylethylhydrazine, 2-hydrazinoethanol, and acetohydrazine.

[0031] The amount of the reducing compound used may be 0.1 to 10 mol, 0.5 to 5 mol, or 0.8 to 3 mol per mol of the copper compound.

[0032] (Organic Solvent) The organic solvent is not particularly limited as long as it is capable of carrying out a uniform reaction without inhibiting the properties of the complex formed by mixing the copper compound, shape stabilizer, and reducing compound. The organic solvent may be compatible with the reducing compound. Examples of the organic solvent include alcohols such as 1-propanol, 2-propanol, butanol, pentanol, hexanol, heptanol, octanol, ethylene glycol, 1,3-propanediol, 1,2-propanediol, butyl cellosolve, ethyl carbitol, and butyl carbitol; butyl carbitol acetate, ethyl carbitol acetate, and diethylene glycol diethyl ether. One type of organic solvent may be used alone, or two or more types may be used in combination.

[0033] When an organic solvent is used, the amount used may be such that the copper compound, the shape stabilizer, and the reducing compound can be uniformly mixed. The amount of the organic solvent used may be, for example, 0.1 to 500 times by volume the volume of the shape stabilizer.

[0034] (Shape Stabilizer) The shape stabilizer may be, for example, at least one selected from the group consisting of an amine compound such as 3-amino-1-propanol, a carboxylic acid such as hexanoic acid, and a phosphate ester, or a combination of an amine compound and a carboxylic acid. The shape stabilizer coats at least a portion of the copper particles of the present disclosure, thereby reducing oxidation of the particle surface and reducing inter-particle aggregation. Furthermore, the fluidity of a paste composition using the copper particles is improved.

[0035] The amount of the shape stabilizer used may be 0.1 to 10 mol, 0.5 to 5.0 mol, or 1.0 to 5.0 mol per mol of the copper compound.

[0036] The reduction reaction of the copper compound may be heated from the viewpoint of sufficient reaction progress. The reaction temperature may be −20 to 140° C., 25 to 120° C., or 40 to 100° C. The reaction time may be 20 to 360 minutes, 30 to 300 minutes, or 40 to 240 minutes from the viewpoint of sufficient reaction progress.

[0037] When the content of the vessel in which the reduction reaction was carried out is a liquid (liquid mixture), the solid matter may be separated, for example, by centrifugation or the like. The obtained solid matter may be washed with an organic solvent, and further, by centrifugation or the like, the solid matter may be obtained as a cake of copper particles. The washing method is not particularly limited as long as the shape stabilizer, reducing compound, etc. are sufficiently removed. The organic solvent for washing may be alcohol. Examples of alcohol include ethanol, 1-propanol, 2-propanol, butanol, pentanol, hexanol, heptanol, octanol, ethylene glycol, 1,3-propanediol, 1,2-propanediol, diethylene glycol, butyl cellosolve, ethyl carbitol, butyl carbitol, etc. The organic solvent for washing may be used alone, or two or more types may be used in combination.

[0038] [Paste Composition] The paste composition of the present disclosure contains the copper particles (copper particles (A)) of the present disclosure described above, which have a major axis (median diameter) of 0.3 to 5 μm and a crystallite diameter ratio S ２００ / S ３０ The paste composition contains copper particles (B) having a viscosity of less than 1.2, and a solvent (C). The paste composition is diluted with the solvent (C) from the viewpoints of handleability and viscosity during use.

[0039] (Copper Particles (A)) The copper particles (A) are as described above. From the viewpoint of obtaining a paste composition having good low-temperature sinterability and dimensional stability in the high-temperature range, the content of the copper particles (A) in 100% by mass of the solid content of the paste composition may be 10 to 90% by mass, 40 to 90% by mass, 50 to 90% by mass, or 60 to 80% by mass.

[0040] (Copper Particles (B)) The copper particles (B) are not particularly limited as long as they are those used in ordinary copper pastes. The major axis (median diameter) of the copper particles (B) may be 0.3 to 5 μm. When the major axis (median diameter) of the copper particles (B) is relatively large, such as 0.3 to 5 μm, the sinterability is low and shrinkage during sintering is unlikely to occur, so that a paste composition containing the copper particles (B) can reduce the effect of volumetric shrinkage during sintering. Furthermore, a paste composition containing the copper particles (B) has high fluidity and improved workability. From the above viewpoints, the major axis (median diameter) of the copper particles (B) may be 0.5 to 4 μm, 0.5 to 3.5 μm, 0.5 to 3 μm, 0.5 to 2.5 μm, or 0.8 to 1.5 μm. The aspect ratio (major axis / thickness) of the copper particles (B) may be 1.0 to 15.0, 1.0 to 10.0, 1.0 to 8.0, 2.0 to 8.0, 2.0 to 6.0, or 3.0 to 5.0. The major axis (median diameter) of the copper particles (B) can be measured by the same method as for the copper particles (A), specifically, by the method described in the Examples.

[0041] Crystallite size ratio S of copper particles (B) ２００ / S ３０ may be less than 1.2, may be 1.1 or less, or may be 1.05 or less. The copper particles (B) have low sinterability and are less likely to shrink during sintering, so that a paste composition containing the copper particles (B) can suppress the effect of volumetric shrinkage during sintering. From the same viewpoint, the crystallite growth rate ratio k of the copper particles (B) may be 1 or less.

[0042] The crystallite growth rate V of the copper particles (B) in the low temperature range is as follows: ３０－２００ (nm / °C) may be 0.1 or less. ３０－２００ = (S ２００ -S ３０ ) / (200-30) Low temperature region crystallite growth rate V ３０－２００ Copper particles (B) having a crystallite growth rate V (nm / °C) of 0.1 or less have a small rate of change per unit temperature of crystallites and are less likely to undergo sintering.３０－２００ (nm / °C) may be 0.07 or less, 0.05 or less, or 0.03 or less.

[0043] The following high temperature region crystallite growth rate V of copper particles (B) Ｈ (nm / °C) may be 0.1 or less. Ｈ = (S ３００ -S ２５０ ) / (300-250) High temperature range crystallite growth rate V Ｈ Copper particles (B) having a crystallite growth rate V (nm / °C) of 0.1 or less have a small rate of change of crystallites per unit temperature and are less likely to undergo sintering. Ｈ (nm / °C) may be 0.07 or less, 0.05 or less, or 0.03 or less.

[0044] The crystallite growth rate difference ΔV of copper particles (B) is as follows: Ｂ (nm / °C) may be between -0.1 and 0.1. Ｂ =V ３０－２００ -V Ｈ Crystallite growth rate difference ΔV Ｂ Copper particles (B) having a crystallite growth rate difference ΔV (nm / °C) of -0.1 to 0.1 have a small rate of change of crystallites per unit temperature and are less likely to sinter. Ｂ (nm / °C) may be from -0.07 to 0.07, from -0.05 to 0.05, or from -0.03 to 0.03.

[0045] The copper particles (B) of the present disclosure have a BET specific surface area of ​​3.0 m ２ The copper particles (B) may have a BET specific surface area of ​​3.0 m / g or less. ２ When the BET specific surface area of ​​the copper particles (B) is less than 2.0 m / g, the surface activity of the particles can be suppressed, making sintering less likely to occur, thereby reducing the effect of sintering shrinkage. ２ / g, and may be less than 1.0 m ２ / g, and may be less than 0.8m ２ / g.

[0046] The copper particles (B) of the present disclosure may be plate-shaped or spherical.

[0047] The major axis (median diameter) of the copper particles (B) is the median (sum of the measured values / total number of measured particles) of at least 200 (e.g., 200) particles extracted from an image taken in scanning electron microscope (SEM) observation. In the case of plate-like particles, the particles have a shape having a pair of substantially parallel flat surfaces, and the distance between the pair of flat surfaces is defined as the "thickness," and the longest diameter on the flat surfaces is defined as the "major axis" (median diameter).

[0048] The content of the copper particles (B) in 100% by mass of the solid content of the paste composition may be 10 to 90% by mass, 12 to 60% by mass, 15 to 50% by mass, or 20 to 40% by mass, from the viewpoint of obtaining a paste composition having good low-temperature sinterability and dimensional stability in a high-temperature range.

[0049] (Solvent (C)) The paste composition is diluted with a solvent (C) from the viewpoints of handleability during use, viscosity, and the like. Examples of the solvent (C) include 1-propanol, 2-propanol, ethylene glycol, 1,3-propanediol, 1,2-propanediol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 3-methyl-1,5-pentanediol, glycerin, and polyethylene glycol from the viewpoints of dispersibility of copper particles and volatility during sintering of the paste composition. The solvent (C) may be one type alone, or two or more types may be used in combination. The solvent (C) for dilution may be the same as the solvent (C) for washing the copper particles.

[0050] (Additives) In addition to the copper particles (A), copper particles (B), solvent (C), and components derived from the production of the copper particles, the paste composition of the present disclosure may also contain, as necessary, known additives commonly used in conductive pastes. Examples of additives include thermoplastic resins, thermosetting resins, curing accelerators, stress-reducing agents such as rubber and silicone, coupling agents, antifoaming agents, surfactants, colorants such as pigments and dyes, polymerization inhibitors, and antioxidants. One type of additive may be used alone, or two or more types may be used in combination. The total content of the copper particles (A) and copper particles (B) in the paste composition, based on 100% by mass of the total amount of copper-containing particles, may be 80 to 100% by mass, 80 to 100% by mass, 95 to 100% by mass, 99 to 100% by mass, or even 100% by mass. The total content of the copper particles (A) and the copper particles (B) in the solid content of the paste composition may be 80 to 100 mass%, 80 to 100 mass%, 95 to 100 mass%, 99 to 100 mass%, or 100 mass%. The total content of the copper particles (A), the copper particles (B), and the solvent (C) in the paste composition may be 80 to 100 mass%, 80 to 100 mass%, 95 to 100 mass%, 99 to 100 mass%, or 100 mass%.

[0051] (Preparation of Paste Composition) The paste composition of the present disclosure can be prepared by kneading a mixture of copper particles (A), copper particles (B), a solvent (C), and additives used as needed, using a kneading machine such as a disperse, a kneader, a three-roll mill, or a planetary mixer, followed by degassing.

[0052] A cured product of the paste composition of the present disclosure contains a sintered body of the copper particles of the present disclosure and has high thermal conductivity and excellent heat dissipation. Therefore, when the paste composition of the present disclosure is used as a bonding material for substrates of elements or heat dissipation components, the thermal conductivity of the device is improved and the ability to dissipate heat from inside the device to the outside is improved. Therefore, the use of the paste composition of the present disclosure can stabilize the operation of various products such as semiconductor devices, electrical components, and electronic components.

[0053] The paste composition is usually sintered by heating to 100 to 250°C in an inert gas atmosphere. Examples of inert gases include nitrogen, argon, and helium. Nitrogen is preferred from the viewpoints of availability and cost. The heating temperature may be 120 to 230°C or 150 to 200°C from the viewpoint of good sinterability. Sintering may be performed under normal pressure or under pressure. The heating time is set appropriately depending on the heating temperature, the shape of the sintered body, and the like. From the viewpoint of sufficient sintering progress, the heating time may be, for example, 5 to 180 minutes, 10 to 120 minutes, or 30 to 90 minutes.

[0054] [Semiconductor Device] The semiconductor device of the present disclosure has a bonded portion formed using a paste composition. Examples of the semiconductor device include a semiconductor element and a substrate serving as an element support member bonded using the paste composition. The paste composition may be used as a die bond.

[0055] By using the paste composition of the present disclosure for bonding, a bonding layer with high density and high bonding strength is formed. The bonding layer has a low rate of change in thermal resistance even when subjected to repeated temperature changes, and high bonding reliability, resulting in a semiconductor device with stable operation.

[0056] The semiconductor element may be a known semiconductor element, for example, a transistor, a diode, etc., or a wide band gap semiconductor element using SiC, GaN, etc., or a light emitting element such as an LED. Examples of the element support member include a copper plate, a silver-plated copper plate, a lead frame (PPF; Pre Plated Leadframe) plated with Ni / Pd, Ti / Pd / Au, Ni / Pd / Au, etc., a glass epoxy plate, a ceramic member, etc.

[0057] The bonding strength of the bonding layer formed using the paste composition for bonding varies depending on the purpose and object of bonding, but from the viewpoint of sufficient bonding strength, it may be 20 MPa or more, 30 MPa or more, or 40 MPa or more. The bonding strength is a die shear strength, and specifically, it can be measured by the method described in the examples.

[0058] [Electrical and Electronic Components] The electrical or electronic components of the present disclosure have a joint formed using the paste composition of the present disclosure. Examples of the electrical or electronic component include a heat-generating component and a heat-dissipating component joined using the paste composition. The paste composition may be used as a bonding agent for heat-dissipating components.

[0059] By using the paste composition of the present disclosure for bonding, a bonding layer with high density and high bonding strength is formed. The bonding layer has a low rate of change in thermal resistance and high bonding reliability even when subjected to repeated thermal cycles (heat cycles), resulting in high heat dissipation and reduced temperature rise in heat-generating components, resulting in an electric or electronic component with stable operation.

[0060] Examples of heat-generating components include optical pickups and power transistors. The heat-generating component may be the semiconductor element or a component having the semiconductor element. Examples of heat-dissipating components include heat sinks and heat spreaders. The heat-generating component and the heat-dissipating component may be directly bonded via the paste composition, or may be indirectly bonded via another component with high thermal conductivity sandwiched therebetween.

[0061] Next, the present disclosure will be specifically described using examples, but the present disclosure is not limited to these examples in any way.

[0062] [Production of Copper Particles] The compounds used in the production of copper particles in each of the Examples and Comparative Examples are as follows: <Copper Compound> FCO-M6B: Copper oxide; manufactured by Furukawa Chemicals Corporation; specific surface area: 26 m ２ / g, D50: 0.9 μm FRC-D70: Cuprous oxide; manufactured by Furukawa Chemicals Corporation; specific surface area: 0.2 m ２ / g, D50: 7.8 μm FRC-10A: Cuprous oxide; manufactured by Furukawa Chemicals Corporation; specific surface area: 0.9 m ２ / g, D50: 2.0 μm 1200YP: copper particles; Mitsui Mining & Smelting Co., Ltd.; specific surface area: 0.67 m ２ / g, D50: 3.0 μm 1100YP: copper particles; Mitsui Mining & Smelting Co., Ltd.; specific surface area: 1.3 m ２ / g, D50: 1.3 μm <Amine compounds> 3-amino-1-propanol; manufactured by Tokyo Chemical Industry Co., Ltd. <Carboxylic acid> Hexanoic acid; manufactured by Tokyo Chemical Industry Co., Ltd. <Reducing compounds> Hydrazine monohydrate; manufactured by Fujifilm Wako Pure Chemical Industries Co., Ltd. <Organic solvents> 1-propanol; manufactured by Tokyo Chemical Industry Co., Ltd. Ethanol; manufactured by Tokyo Chemical Industry Co., Ltd. Diethylene glycol; manufactured by Tokyo Chemical Industry Co., Ltd.

[0063] Example 1: A 2000 mL round-bottom flask was charged with 2 mmol of copper oxide (FCO-M6B), 8 mmol of cuprous oxide (FRC-D70), 20 mmol of 3-amino-1-propanol, 20 mmol of hexanoic acid, 10 mmol of hydrazine monohydrate, and 30 mmol of 1-propanol. The mixture was heated in an 80°C oil bath while stirring at 250 rpm and mixed for 180 minutes. The resulting mixture was centrifuged (25°C, 10,000 rpm, 15 minutes; the same conditions apply hereinafter), and the supernatant was removed. Ethanol was added to the residue, and the mixture was washed by stirring for 10 minutes in a vacuum planetary centrifugal mixer (25°C, 1,000 rpm). The supernatant was then removed. This procedure was repeated four times. Furthermore, the ethanol was replaced with diethylene glycol, and the same procedure of washing, centrifugation, and removal of the supernatant was repeated twice to obtain a copper particle cake.

[0064] Example 2 and Comparative Example 1 Each copper particle cake was obtained by carrying out the same operation as in Example 1 except that the raw material components shown in Table 1 were used.

[0065] [Measurement and Evaluation of Copper Particles] The copper particles (cakes) produced in the Examples and Comparative Examples were subjected to the following measurement and evaluation. The evaluation results are shown in Table 1. The following measurement and evaluation were also carried out on the copper particles 1200YP and copper particles 1100YP. The evaluation results are shown in Table 2.

[0066] (X-ray Diffraction (XRD) Measurement) A cake of copper particles was applied to a glass plate to a thickness of 200 μm to obtain a measurement sample. XRD measurement was performed on the measurement sample. The following devices were used: X-ray diffractometer: "SmartLab SE" (manufactured by Rigaku Corporation); Corrosion-resistant infrared heating sample high-temperature device for X-ray diffractometer: "Reactor X" (manufactured by the same company). Specifically, the temperature was raised from 30°C to 400°C at a heating rate of 10°C / min in a nitrogen atmosphere, and the crystallite diameter S at the measurement temperature X (30°C, 150°C, 200°C, 250°C, 300°C) was measured. Ｘ (S ３０ , S １５０ , S ２００ , S ２５０ , S ３００ At each measurement temperature X, the time required for one XRD measurement was 15 seconds, and the temperature of the measurement atmosphere was maintained without increasing during the XRD measurement.

[0067] (Scanning Electron Microscope (SEM) Observation) A cake of copper particles was applied to a brass sample stage with carbon tape attached, and dried at 90°C for 3 hours in a nitrogen atmosphere to prepare a sample. This sample was observed with an SEM (Schottky field emission scanning electron microscope "JSM-F100", manufactured by JEOL Ltd.; acceleration voltage 15 kV, magnification 100,000 times; the same applies hereinafter). The length of 200 randomly selected particles in the SEM image was measured, and the thickness and major axis (median diameter) of the particles were determined. In Tables 1 and 2, the thickness and major axis indicate the respective median values ​​(sum of measured values / total number of particles measured).

[0068] (BET Specific Surface Area) A sample was prepared by applying a cake of copper particles and drying it in a nitrogen atmosphere at 70°C for 12 hours. The specific surface area of ​​the sample was measured by the BET single-point method using nitrogen adsorption using a specific surface area measuring device (Macsorb (registered trademark) HM Model-1220, manufactured by Mountec Co., Ltd.).

[0069]

[0070]

[0071] (Examples 3 to 6 and Comparative Examples 2 to 3) The copper particles (A) (cake) and copper particles (B) produced in Examples 1 and 2 and Comparative Example 1 were diluted with diethylene glycol in the proportions shown in Table 3 to prepare paste compositions with a nonvolatile content of 83 mass%.

[0072] [Evaluation of Sintered Body Properties] Each paste composition was subjected to the following measurements and evaluations. The evaluation results are shown in Table 3.

[0073] (Bonding strength) Using the prepared paste composition, a Ti / Pd / Au-plated aluminum nitride piece (3 mm × 3 mm, thickness 200 μm) was bonded to a Ni / Pd-plated copper substrate, and heated at 200 ° C. for 60 minutes in a nitrogen atmosphere (containing 3% by volume of hydrogen) to sinter the copper particles to prepare a bonded test piece (a test piece without a sealing resin). The die shear strength (bonding strength) of the bonded test piece was measured using a bond strength tester ("4000Plus Bond Tester", manufactured by Nordon DAGE; room temperature (25 ° C.), distance from substrate to loading jig 0.15 mm, loading speed 30 mm / min).

[0074] (Cold-Heat Cycle Test) Using the paste composition, a Ti / Au-plated silicon chip (3 mm x 3 mm, 200 μm thick) was bonded to a Ni / Pd / Au-plated die pad (4 mm x 4 mm) of a QFP (Quad Flat Package) frame. The resulting mixture was heated at 200°C for 60 minutes in a nitrogen atmosphere (containing 3% by volume of hydrogen) to sinter the copper particles. This was then mold-sealed with an encapsulating epoxy resin ("KE-G3000D" manufactured by Kyocera Corporation) to prepare a bonded test specimen (a test specimen with encapsulating resin). A cold-heat cycle test (1 cycle: -40°C to 120°C / 30 minutes, 2000 cycles) was performed on the test specimens without encapsulating resin and with encapsulating resin. The rate of change in thermal resistance of the junction before and after the test was measured using a transient thermal resistance measurement device ("Simcenter T3Ster" manufactured by Siemens). The rate of change of this thermal resistance is shown in Table 3. The lower the rate of change, the higher the joint reliability.

[0075]

[0076] The bonding layers formed using the paste compositions of Examples 3 to 6 containing the copper particles (A) of Examples 1 and 2 were found to be excellent in low-temperature sinterability (bonding strength) and dimensional stability in the high-temperature range (heat-and-cool cycle test). On the other hand, the bonding layers formed using the paste compositions of Comparative Examples 2 and 3 not containing the copper particles (A) of Examples 1 and 2 were found to be inferior in low-temperature sinterability (bonding strength) and dimensional stability in the high-temperature range (heat-and-cool cycle test).

Claims

1. Copper particles having a crystallite growth rate ratio k of greater than 1. k = (S ２００ -S １５０ ) / (S ３００ -S ２５０ ) [S １５０ is the crystallite diameter (nm) of Cu(111) when the copper particles are heated to 150°C. ２００ is the crystallite diameter (nm) of Cu(111) when the copper particles are heated to 200°C. ２５０ is the crystallite diameter (nm) of Cu(111) when the copper particles are heated to 250°C. ３００ is the crystallite diameter (nm) of Cu(111) when the copper particles are heated to 300°C.] 2. Crystallite growth rate V in the low temperature range Ｌ 2. The copper particles according to claim 1, wherein V is greater than 0.5 nm / °C. Ｌ = (S ２００ -S １５０ ) / (200-150) 3. Crystallite growth rate V in the high temperature range Ｈ 3. The copper particles according to claim 1, wherein V is less than 0.2 nm / °C. Ｈ = (S ３００ -S ２５０ ) / (300-250) 4. BET specific surface area: 3.0 to 13.0 m ２ The copper particles according to any one of claims 1 to 3, wherein the copper content is 1 / g.

5. Copper particles according to any one of claims 1 to 4, which are plate-shaped.

6. A method for producing copper particles according to any one of claims 1 to 5, in which copper oxide and cuprous oxide are reduced using a reducing compound.

7. A method for producing copper particles as described in claim 6, in which copper oxide and cuprous oxide are reduced using a reducing compound in the presence of an organic solvent.

8. Copper particles (A) according to any one of claims 1 to 5, having a major axis (median diameter) of 0.3 to 5 μm and a crystallite diameter ratio S ２００ / S ３０ A paste composition comprising copper particles (B) having a viscosity of less than 1.2, and a solvent (C).

9. A semiconductor device having a joint formed using the paste composition according to claim 8.

10. An electrical component having a joint formed using the paste composition of claim 8.

11. An electronic component having a joint formed using the paste composition according to claim 8.

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