WO2022259630A1 - 銅粉 - Google Patents
銅粉 Download PDFInfo
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- WO2022259630A1 WO2022259630A1 PCT/JP2022/006770 JP2022006770W WO2022259630A1 WO 2022259630 A1 WO2022259630 A1 WO 2022259630A1 JP 2022006770 W JP2022006770 W JP 2022006770W WO 2022259630 A1 WO2022259630 A1 WO 2022259630A1
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- Prior art keywords
- copper powder
- copper
- temperature
- aqueous solution
- bulk density
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 title claims abstract description 102
- 239000002245 particle Substances 0.000 claims abstract description 57
- 239000010949 copper Substances 0.000 claims abstract description 43
- 229910052802 copper Inorganic materials 0.000 claims abstract description 39
- 238000002441 X-ray diffraction Methods 0.000 claims abstract description 4
- 230000001186 cumulative effect Effects 0.000 claims abstract description 4
- 238000000634 powder X-ray diffraction Methods 0.000 claims abstract description 4
- 238000000034 method Methods 0.000 claims description 18
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 8
- 229910052799 carbon Inorganic materials 0.000 claims description 8
- 229910052739 hydrogen Inorganic materials 0.000 claims description 8
- 239000001257 hydrogen Substances 0.000 claims description 8
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 7
- 230000004580 weight loss Effects 0.000 claims description 7
- 239000007787 solid Substances 0.000 claims description 2
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 48
- IKDUDTNKRLTJSI-UHFFFAOYSA-N hydrazine hydrate Chemical compound O.NN IKDUDTNKRLTJSI-UHFFFAOYSA-N 0.000 description 40
- 239000007864 aqueous solution Substances 0.000 description 36
- BERDEBHAJNAUOM-UHFFFAOYSA-N copper(I) oxide Inorganic materials [Cu]O[Cu] BERDEBHAJNAUOM-UHFFFAOYSA-N 0.000 description 25
- KRFJLUBVMFXRPN-UHFFFAOYSA-N cuprous oxide Chemical compound [O-2].[Cu+].[Cu+] KRFJLUBVMFXRPN-UHFFFAOYSA-N 0.000 description 25
- 229940112669 cuprous oxide Drugs 0.000 description 25
- 238000005245 sintering Methods 0.000 description 15
- 239000002002 slurry Substances 0.000 description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 12
- 239000003638 chemical reducing agent Substances 0.000 description 11
- OAKJQQAXSVQMHS-UHFFFAOYSA-N Hydrazine Chemical compound NN OAKJQQAXSVQMHS-UHFFFAOYSA-N 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 9
- 238000006722 reduction reaction Methods 0.000 description 8
- 230000000930 thermomechanical effect Effects 0.000 description 8
- 238000004458 analytical method Methods 0.000 description 7
- 239000000243 solution Substances 0.000 description 7
- 238000006243 chemical reaction Methods 0.000 description 6
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 6
- 230000007423 decrease Effects 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 239000000843 powder Substances 0.000 description 5
- 239000004065 semiconductor Substances 0.000 description 5
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 4
- 238000010521 absorption reaction Methods 0.000 description 4
- 229910000365 copper sulfate Inorganic materials 0.000 description 4
- ARUVKPQLZAKDPS-UHFFFAOYSA-L copper(II) sulfate Chemical compound [Cu+2].[O-][S+2]([O-])([O-])[O-] ARUVKPQLZAKDPS-UHFFFAOYSA-L 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 239000008188 pellet Substances 0.000 description 4
- 239000000758 substrate Substances 0.000 description 4
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 239000002612 dispersion medium Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- OFOBLEOULBTSOW-UHFFFAOYSA-N Malonic acid Chemical compound OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 description 2
- GQPLMRYTRLFLPF-UHFFFAOYSA-N Nitrous Oxide Chemical compound [O-][N+]#N GQPLMRYTRLFLPF-UHFFFAOYSA-N 0.000 description 2
- 229910021529 ammonia Inorganic materials 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 150000001879 copper Chemical class 0.000 description 2
- JZCCFEFSEZPSOG-UHFFFAOYSA-L copper(II) sulfate pentahydrate Chemical compound O.O.O.O.O.[Cu+2].[O-]S([O-])(=O)=O JZCCFEFSEZPSOG-UHFFFAOYSA-L 0.000 description 2
- 238000010908 decantation Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002105 nanoparticle Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- YVHUUEPYEDOELM-UHFFFAOYSA-N 2-ethylpropanedioic acid;piperidin-1-id-2-ylmethylazanide;platinum(2+) Chemical compound [Pt+2].[NH-]CC1CCCC[N-]1.CCC(C(O)=O)C(O)=O YVHUUEPYEDOELM-UHFFFAOYSA-N 0.000 description 1
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 108010010803 Gelatin Proteins 0.000 description 1
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 description 1
- 229920000084 Gum arabic Polymers 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- 241000978776 Senegalia senegal Species 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 235000010489 acacia gum Nutrition 0.000 description 1
- 239000000205 acacia gum Substances 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000011088 calibration curve Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 239000008139 complexing agent Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
- 238000007323 disproportionation reaction Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 229920000159 gelatin Polymers 0.000 description 1
- 239000008273 gelatin Substances 0.000 description 1
- 235000019322 gelatine Nutrition 0.000 description 1
- 235000011852 gelatine desserts Nutrition 0.000 description 1
- 239000008103 glucose Substances 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 238000009766 low-temperature sintering Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000005374 membrane filtration Methods 0.000 description 1
- YQCIWBXEVYWRCW-UHFFFAOYSA-N methane;sulfane Chemical compound C.S YQCIWBXEVYWRCW-UHFFFAOYSA-N 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000001272 nitrous oxide Substances 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 238000007639 printing Methods 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 239000012279 sodium borohydride Substances 0.000 description 1
- 229910000033 sodium borohydride Inorganic materials 0.000 description 1
- GCLGEJMYGQKIIW-UHFFFAOYSA-H sodium hexametaphosphate Chemical compound [Na]OP1(=O)OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])OP(=O)(O[Na])O1 GCLGEJMYGQKIIW-UHFFFAOYSA-H 0.000 description 1
- 235000019982 sodium hexametaphosphate Nutrition 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 239000001577 tetrasodium phosphonato phosphate Substances 0.000 description 1
- 230000008646 thermal stress Effects 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
Images
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/05—Metallic powder characterised by the size or surface area of the particles
- B22F1/052—Metallic powder characterised by the size or surface area of the particles characterised by a mixture of particles of different sizes or by the particle size distribution
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/05—Metallic powder characterised by the size or surface area of the particles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/16—Making metallic powder or suspensions thereof using chemical processes
- B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
- B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/04—Making non-ferrous alloys by powder metallurgy
- C22C1/0425—Copper-based alloys
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C9/00—Alloys based on copper
Definitions
- This specification discloses a technology related to copper powder.
- the sintering type conductive paste is required to sinter the copper powder by heating at a relatively low temperature. This is because if the heating temperature is high, the heat may affect the base material and the semiconductor element. In addition, there is a concern that a large thermal stress is generated in the base material or the semiconductor element during cooling after being heated at a high temperature, and this may change the electrical characteristics of the circuit or the semiconductor element.
- Patent Document 1 discloses a method of "providing a conductive coating material capable of obtaining sufficient bonding strength even when bonding large-area members at a relatively low temperature.”
- a conductive coating material for bonding an element to a substrate comprising a metal powder, a non-heat-curable resin, and a dispersion medium, and having a shear rate of 0.01 to 100 [/s] at 25°C. is monotonically increasing with shear rate, and the bulk density of the metal powder is less than 3 [g/cm 3 ].
- Patent Document 2 contains a plurality of copper particles, and the particle diameter D50 when the cumulative frequency in the volume-based particle diameter histogram of the plurality of copper particles is 50% is 100 nm or more and 500 nm or less, and the D50 A copper powder in which the ratio D/D50 of the average crystallite diameter D of the plurality of copper particles is 0.10 or more and 0.50 or less.
- This specification discloses a copper powder with excellent low-temperature sinterability.
- the copper powder disclosed in this specification contains copper particles, has a compact bulk density of 1.30 g/cm 3 to 2.96 g/cm 3 , and has a volume-based particle size histogram of the copper particles. From the 50% particle diameter D50 when the frequency is 50% and the diffraction peak of the Cu (111) plane in the X-ray diffraction profile obtained by the powder X-ray diffraction method for the copper powder, it is obtained using Scherrer's formula. The crystallite diameter D satisfies D/D50 ⁇ 0.060.
- the copper powder described above has excellent low-temperature sinterability.
- the copper powder of one embodiment contains copper particles, has a compact bulk density of 1.30 g/cm 3 to 2.96 g/cm 3 , and has a cumulative frequency of 50% in the volume-based particle size histogram of the copper particles.
- Crystallite diameter D determined using the Scherrer formula from the diffraction peak of the Cu (111) plane in the X-ray diffraction profile obtained by the powder X-ray diffraction method for the copper powder and the 50% particle diameter D50 when it becomes satisfies D/D50 ⁇ 0.060.
- thermomechanical analysis As shown in the section of Examples, if the copper powder has a compacted bulk density of 1.30 g/cm 3 to 2.96 g/cm 3 and D/D50 ⁇ 0.060, thermomechanical analysis ( A new finding was obtained that the temperature is effectively lowered when the linear shrinkage rate by TMA becomes 5%.
- the temperature at 5% linear shrinkage in thermomechanical analysis means the temperature at which sintering of the copper powder progresses and the electrical resistance decreases to some extent. Therefore, a copper powder having a low 5% linear shrinkage temperature in thermomechanical analysis can be sufficiently sintered at such a low temperature and can be regarded as having excellent low-temperature sinterability.
- the hard bulk density is within the range of 1.30 g/cm 3 to 2.96 g/cm 3 , if the D/D50 is less than 0.060, or if the D/D50 is 0.060 or more, the hard bulk If the density is out of the range of 1.30 g/cm 3 to 2.96 g/cm 3 , the temperature of 5% linear shrinkage in thermomechanical analysis will increase to some extent, and the desired low temperature sinterability will be achieved. can't
- the copper powder of this embodiment has a compacted bulk density of 1.30 g/cm 3 to 2.96 g/cm 3 and D/D50 ⁇ 0.060, so it is believed to have excellent low-temperature sinterability. I can say.
- the copper powder has a compacted bulk density of 1.30 g/cm 3 to 2.96 g/cm 3 . If the ratio of the 50% particle diameter D50 to the crystallite diameter D (D/D50) is 0.060 or more and the bulk density is within this range, the linear shrinkage rate by thermomechanical analysis will be 5%. The temperature becomes sufficiently low as 290° C. or less.
- the firm bulk density is set to 1.30 g/cm 3 to 2.96 g/cm 3 , preferably 1.80 g/cm 3 to 2.80 g/cm 3 .
- a guide is attached to a 10 cc cup, copper powder is put in, and tapped 1000 times. After that, the guide is removed, the portion exceeding the 10 cc volume of the cup is scraped off, and the weight of the copper powder contained in the cup is measured. Using this weight, the firm bulk density can be determined.
- the ratio (D/D50) of the crystallite diameter D to the 50% particle diameter D50 of the copper powder is set to 0.060 or more.
- the sintering temperature is sufficiently low if D/D50 is 0.060 or more.
- D/D50 is preferably 0.065 or more.
- D/D50 may be between 0.065 and 0.095.
- the 50% particle size D50 is obtained by measuring the particle size of the copper particles in the copper powder using a laser diffraction/scattering particle size distribution analyzer. Means the particle diameter at which the volume-based frequency accumulation of 50%, and is measured based on JIS Z8825 (2013). More specifically, in the measurement of the 50% particle size D50, MASTERSIZER 3000 manufactured by Malvern can be used, dispersion medium: sodium hexametaphosphate aqueous solution, optical parameters: particle absorption rate 5.90, particle absorption rate (blue) 0 .92, particle refractive index 3.00, particle refractive index (blue) 0.52, scattering intensity: 6-8%.
- the crystallite diameter D means the average diameter of a crystallite that can be regarded as a single crystal. is obtained using In determining the crystallite size, RINT-2200 Ultima manufactured by Rigaku Co., Ltd. can be used under the conditions of CuK ⁇ rays, acceleration voltage of 45 KV, and 200 mA, and analysis software PDXL2 can be used.
- the BET specific surface area of the copper powder is preferably 0.5 m 2 /g to 10.0 m 2 /g. If the BET specific surface area exceeds 10.0 m 2 /g, it is difficult to ensure oxidation resistance, and there is concern that problems may arise in paste properties due to moisture absorption, aggregation, and the like. On the other hand, when the BET specific surface area is less than 0.5 m 2 /g, the particle size of the copper powder is large, and there is concern that the circuit printed with the paste and the bonding surface may not have sufficient smoothness. From this point of view, the BET specific surface area of the copper powder is preferably 0.5 m 2 /g to 10.0 m 2 /g, more preferably 2.0 m 2 /g to 7.0 m 2 /g. More preferred.
- the copper powder is degassed in a vacuum at a temperature of 70° C. for 5 hours, and then measured according to JIS Z8830: 2013, for example, BELSORP-mini manufactured by Microtrack Bell. II.
- the copper powder preferably has a carbon content of 0.50% by mass or less, more preferably 0.30% by mass or less, particularly 0.15% by mass or less. This is because if the carbon content is high, solid carbon remaining during firing may interfere with sintering.
- the carbon content is measured by high-frequency induction heating furnace combustion-infrared absorption method. Specifically, using a carbon sulfur analyzer such as LECO's CS844 model, LECO's LECOCEL II and Fe chips, etc. are used as combustion improvers, and a steel pin is used for the calibration curve to measure the carbon content of the copper powder. can do.
- a carbon sulfur analyzer such as LECO's CS844 model, LECO's LECOCEL II and Fe chips, etc. are used as combustion improvers, and a steel pin is used for the calibration curve to measure the carbon content of the copper powder. can do.
- the hydrogen reduction weight loss of the copper powder can be measured as the weight loss when the copper powder is heated at 800° C. for 10 minutes or longer in an atmosphere containing 2% to 100% by volume of hydrogen. If the hydrogen reduction weight loss is large, it is considered that the oxidation of the copper particles in the copper powder has progressed, and there is concern that sintering will become difficult to proceed. For this reason, the hydrogen reduction weight loss of the copper powder is preferably 1.5% or less, particularly 1.0% or less.
- the above copper powder can sinter the copper particles contained therein at a relatively low temperature.
- Such low-temperature sinterability can be confirmed as follows. About 0.3 g of copper powder is filled in a cylindrical mold with a diameter of 5 mm and then uniaxially pressed to obtain a cylindrical shape with a height of about 3 mm and a density of 4.7 ⁇ 0.1 g / cc. A green compact pellet is produced. After that, using a thermomechanical analyzer (TMA), the compact pellets were heated at 25°C to 10°C in an atmosphere containing 2% by volume of hydrogen (H 2 ) and the balance being nitrogen (N 2 ). /min.
- TMA thermomechanical analyzer
- the copper particles forming the compact pellet are sintered, and the volume of the compact decreases, approaching the density of metallic copper (approximately 8.9 g/cm 3 ).
- the linear shrinkage rate the rate of change in the columnar height in the shrinking direction of such compact pellets.
- the temperature at which the linear shrinkage rate becomes 5% is 350° C. or lower.
- the copper powder as described above can be produced by using, for example, a chemical reduction method or a disproportionation method.
- the details of the chemical reduction method are as follows, although the production of copper powder is not limited thereto.
- a step of washing the copper particles, a step of performing solid-liquid separation, a step of drying, and a step of pulverizing as necessary are performed in this order.
- an aqueous solution of copper sulfate after raising the temperature of an aqueous solution of copper sulfate to an appropriate reaction temperature, the pH is adjusted with an aqueous solution of sodium hydroxide or an aqueous solution of ammonia, and then an aqueous solution of hydrazine is added at once for reaction to produce copper sulfate. It is reduced to cuprous oxide particles having a particle size of about 100 nm.
- an aqueous solution containing sodium hydroxide and hydrazine is added dropwise, and then an aqueous hydrazine solution is added dropwise to reduce the cuprous oxide particles to copper particles.
- the resulting slurry is filtered, washed with pure water and methanol, and dried. Copper powder is thus obtained.
- the reducing agent such as hydrazine added to the copper sulfate aqueous solution is for reducing bivalent copper to monovalent copper (cuprous oxide).
- the reducing agent can be added in portions.
- the first reducing agent is mainly used for the generation of metallic copper nuclei, and the second reducing agent is used for the growth of the metallic copper nuclei. .
- the compacted bulk density of the copper powder and the ratio of the 50% particle size to the crystallite size tend to be controlled favorably.
- an aqueous solution of copper sulfate or nitrate can be used as the aqueous copper salt solution.
- the alkaline aqueous solution may specifically be an aqueous solution of NaOH, KOH, NH 4 OH, or the like.
- the reducing agent for the aqueous reducing agent solution include hydrazine and organic substances such as sodium borohydride and glucose.
- an organic substance such as a complexing agent or a dispersing agent may be added during the process of producing the copper powder.
- a complexing agent or a dispersing agent may be added during the process of producing the copper powder.
- gelatin, ammonia, gum arabic, etc. can be added once or more between the step of preparing a raw material solution and the step of obtaining a slurry containing copper particles.
- the copper powder thus produced is, for example, mixed with a resin material and a dispersion medium to form a paste, and is particularly suitable for use as a conductive paste that can be used for bonding a semiconductor element and a substrate or forming wiring. Are suitable.
- Invention Example 8 The procedure was the same as in Invention Example 1 until the slurry containing cuprous oxide was synthesized. Next, after dropping 4.5 L of a mixed aqueous solution of 101 g of hydrazine monohydrate and 409 g of sodium hydroxide, the pH is adjusted, and 1.3 L of an aqueous solution of 43 g of hydrazine monohydrate is dropped to form cuprous oxide. It was reduced to metallic copper, washed with water, dried and pulverized in the same manner.
- Comparative example 2 The procedure was the same as in Comparative Example 1 until the slurry containing cuprous oxide was synthesized. Next, after dropping 4.5 L of a mixed aqueous solution of 14.4 g of hydrazine monohydrate and 409 g of sodium hydroxide, the pH was adjusted, and 1.3 L of an aqueous solution of 129.6 g of hydrazine monohydrate was added dropwise. Cuprous oxide was reduced to metallic copper, and washed with water, dried and pulverized in the same manner.
- invention examples 1 to 13 having a compacted bulk density of 1.30 g/cm 3 to 2.96 g/cm 3 and D/D50 ⁇ 0.060 satisfy any of these conditions. It can be seen that the TMA 5% shrinkage temperature is 290° C. or less, which is sufficiently low as compared with Comparative Examples 1 to 4, which do not have the TMA.
- the sintering temperature becomes the lowest when the hard bulk density is around 2.00 g/cm 3 .
- the hardened bulk density is in the range of 1.30 g/cm 3 to 2.96 g/cm 3
- the sintering temperature gradually increases as the hardened bulk density increases or decreases from around 2.00 g/cm 3 . It tends to be secondary functional.
- the compacted bulk density is out of the above range, the sintering temperature increases remarkably.
- Comparative Example 2 in which D/D50 is less than 0.060, has a sintering temperature of getting higher.
- the copper powder described above has excellent low-temperature sinterability.
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- General Chemical & Material Sciences (AREA)
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Abstract
Description
一の実施形態の銅粉は、銅粒子を含み、固めかさ密度が1.30g/cm3~2.96g/cm3であり、銅粒子の体積基準の粒子径ヒストグラムで累積頻度が50%になるときの50%粒子径D50と、当該銅粉に対する粉末X線回折法で得られるX線回折プロファイル中のCu(111)面の回折ピークから、シェラーの式を用いて求めた結晶子径Dとが、D/D50≧0.060を満たすものである。
銅粉の固めかさ密度は、1.30g/cm3~2.96g/cm3である。50%粒子径D50と結晶子径Dとの比(D/D50)が0.060以上で、固めかさ密度がこの範囲内であれば、熱機械分析による線収縮率が5%になるときの温度が、290℃以下と十分に低くなる。
銅粉の50%粒子径D50に対する結晶子径Dの比(D/D50)は、0.060以上とする。固めかさ密度が上述した所定の範囲内である場合は、D/D50が0.060以上であれば、焼結温度が十分に低くなる。
銅粉のBET比表面積は、0.5m2/g~10.0m2/gであることが好ましい。BET比表面積が10.0m2/gを超える場合は、耐酸化性を担保することが難しく、また吸湿や凝集などにより、ペースト特性に問題が生じることが懸念される。一方、BET比表面積が0.5m2/g未満である場合は、銅粉の粒径が大きく、ペーストを印刷した回路や接合面の平滑性が充分ではないことが懸念される。この観点から、銅粉のBET比表面積は、0.5m2/g~10.0m2/gであることが好ましく、さらに2.0m2/g~7.0m2/gであることがより一層好ましい。
銅粉は、炭素含有量が0.50質量%以下であること、さらに0.30質量%以下、特に0.15質量%以下であることが好適である。炭素分が多いと、焼成時に残留する固形炭素が焼結を妨げるおそれがあるからである。
銅粉の水素還元減量は、水素を2体積%~100体積%含有する雰囲気の下、銅粉を800℃で10分以上加熱したときの重量の減少分として測定することができる。水素還元減量が多い場合は、銅粉中の銅粒子の酸化が進んでいると考えられ、それにより焼結が進みにくくなることが懸念される。このことから、銅粉の水素還元減量は、1.5%以下、特に1.0%以下であることが好ましい。
また、上記の銅粉は、それに含まれる銅粒子どうしが比較的低い温度で焼結することが可能なものである。かかる低温焼結性は、次のようにして確認することができる。約0.3gの銅粉を直径5mmの円柱状の型に充填してから一軸加圧を行い、高さが約3mmの円柱状であって密度が4.7±0.1g/ccである圧粉体ペレットを作製する。その後、熱機械分析装置(TMA)を用いて、水素(H2)を2体積%で含むとともに残部が窒素(N2)である雰囲気の下、上記の圧粉体ペレットを25℃から10℃/minの速度で昇温する。このとき、温度の上昇に伴い、圧粉体ペレットを構成する銅粒子が焼結し、圧粉体の体積は減少して、金属銅の密度(約8.9g/cm3)に近づく。そのような圧粉体ペレットの収縮方向の円柱高さの変化率を線収縮率と称すると、この線収縮率が5%になるときの温度が低い方が、優れた低温焼結性を有する銅粉であると評価することができる。特に、上記の線収縮率が5%になるときの温度が350℃以下であることが好ましい。
以上に述べたような銅粉は、たとえば、化学還元法または不均化法を用いること等により製造することができる。銅粉の製造はそれらに限らないが、化学還元法の詳細については次のとおりである。
より具体的な一例では、硫酸銅水溶液を、適切な反応温度に昇温した後、水酸化ナトリウム水溶液やアンモニア水溶液でpHを調整した後、ヒドラジン水溶液を一気に添加して反応を行い、硫酸銅を粒径100nm程度の亜酸化銅粒子へ還元する。亜酸化銅粒子を含むスラリーを反応温度に昇温した後、水酸化ナトリウムとヒドラジンとを含む水溶液を滴下し、さらにその後にヒドラジン水溶液を滴下することで亜酸化銅粒子を銅粒子へ還元させる。反応終了後、得られたスラリーを濾過し、次いで純水及びメタノールで洗浄し、更に乾燥させる。これにより、銅粉が得られる。
このようにして製造された銅粉は、たとえば、樹脂材料及び分散媒等と混合してペースト状にし、半導体素子と基板との接合や配線形成に使用され得る導電性ペースト等に用いることに特に適している。
始めに硫酸銅五水和物2400gとクエン酸30gを8.7Lの純水に溶かした水溶液に、水酸化ナトリウム540gとヒドラジン一水和物144gの混合水溶液6.7Lを一気に混合し、亜酸化銅のナノ粒子(平均粒径が約100nm)を含むスラリーを合成した。次いで、この亜酸化銅粒子が懸濁したスラリーを50℃以上に加熱してから、ヒドラジン一水和物43gと水酸化ナトリウム409gの混合水溶液4.5Lを滴下し、水酸化ナトリウム水溶液を添加して、pHを調整してから、ヒドラジン一水和物101gの水溶液1.3Lを滴下した。反応終了後、デカンテーションを繰り返し水洗し、乾燥・粉砕を行って、銅粉を得た。
亜酸化銅を含むスラリーを合成するまでは発明例1と同様とした。次いで、ヒドラジン一水和物29gと水酸化ナトリウム409gの混合水溶液4.5Lを滴下してから、pHを調整し、さらにヒドラジン一水和物115gの水溶液1.3Lを滴下して亜酸化銅を金属銅へ還元し、同様に水洗・乾燥・粉砕を行った。
亜酸化銅を含むスラリーを合成するまでは発明例1と同様とした。次いで、ヒドラジン一水和物43gと水酸化ナトリウム409gの混合水溶液4.5Lを滴下してから、pHを調整し、さらにヒドラジン一水和物101gの水溶液1.3Lを滴下して亜酸化銅を金属銅へ還元し、同様に水洗・乾燥・粉砕を行った。
亜酸化銅を含むスラリーを合成するまでは発明例1と同様とした。次いで、ヒドラジン一水和物72gと水酸化ナトリウム409gの混合水溶液4.5Lを滴下してから、pHを調整し、さらにヒドラジン一水和物72gの水溶液1.3Lを滴下して亜酸化銅を金属銅へ還元し、同様に水洗・乾燥・粉砕を行った。
亜酸化銅を金属銅へ還元した後、膜ろ過で固液分離を繰り返して洗浄したことを除いて、発明例2と実質的に同様にして、銅粉を得た。
亜酸化銅を含むスラリーを合成するまでは発明例1と同様とした。次いで、ヒドラジン一水和物101gと水酸化ナトリウム409gの混合水溶液4.5Lを滴下してから、pHを調整し、さらにヒドラジン一水和物43gの水溶液1.3Lを滴下して亜酸化銅を金属銅へ還元し、同様に水洗・乾燥・粉砕を行った。
亜酸化銅を含むスラリーを合成するまでは発明例1と同様とした。次いで、ヒドラジン一水和物72gと水酸化ナトリウム409gの混合水溶液4.5Lを滴下してから、pHを調整し、さらにヒドラジン一水和物72gの水溶液1.3Lを滴下して亜酸化銅を金属銅へ還元し、同様に水洗・乾燥・粉砕を行った。
亜酸化銅を含むスラリーを合成するまでは発明例1と同様とした。次いで、ヒドラジン一水和物72gと水酸化ナトリウム409gの混合水溶液4.5Lを滴下してから、pHを調整し、さらにヒドラジン一水和物72gの水溶液1.3Lを滴下して亜酸化銅を金属銅へ還元し、同様に水洗・乾燥・粉砕を行った。
始めに硫酸銅五水和物500gとクエン酸6gを1.8Lの純水に溶かした水溶液に、水酸化ナトリウム113gとヒドラジン一水和物30gの混合水溶液1.3Lを一気に混合し、亜酸化銅のナノ粒子(平均粒径が約100nm)を含むスラリーを合成した。次いで、この亜酸化銅粒子が懸濁したスラリーを50℃以上に加熱してから、ヒドラジン一水和物3gと水酸化ナトリウム55gの混合水溶液0.5Lを滴下し、水酸化ナトリウム水溶液を添加して、pHを調整してから、ヒドラジン一水和物27gの水溶液0.28Lを滴下した。反応終了後、デカンテーションを繰り返し水洗し、乾燥・粉砕を行って、銅粉を得た。
亜酸化銅を含むスラリーを合成するまでは比較例1と同様とした。次いで、ヒドラジン一水和物14.4gと水酸化ナトリウム409gの混合水溶液4.5Lを滴下してから、pHを調整し、さらにヒドラジン一水和物129.6gの水溶液1.3Lを滴下して亜酸化銅を金属銅へ還元し、同様に水洗・乾燥・粉砕を行った。
比較例2と同じ条件で亜酸化銅を金属銅へ還元した後、該銅粒子600gに、マロン酸0.3gを含有する水溶液2Lを加え、室温下にて350rpmで60分攪拌して、洗浄・乾燥を行って銅粉を作製した。
上記の発明例1~13及び比較例1~4のそれぞれの銅粉について、先述した方法に従い、固めかさ密度、50%粒子径、結晶子径、BET比表面積、水素還元減量、炭素含有量及び、熱機械分析(TMA)による線収縮率が5%になるときの温度をそれぞれ測定した。その結果を表1に示す。なお、比較例3の銅粉の結晶子径は測定していなかったので不明である。また、各銅粉の固めかさ密度とTMA5%収縮温度との関係及び、D/D50とTMA5%収縮温度との関係をそれぞれ、図1及び2にグラフで示す。
Claims (4)
- 銅粒子を含む銅粉であって、
固めかさ密度が1.30g/cm3~2.96g/cm3であり、
銅粒子の体積基準の粒子径ヒストグラムで累積頻度が50%になるときの50%粒子径D50と、当該銅粉に対する粉末X線回折法で得られるX線回折プロファイル中のCu(111)面の回折ピークから、シェラーの式を用いて求めた結晶子径Dとが、D/D50≧0.060を満たす銅粉。 - BET比表面積が0.5m2/g~10.0m2/gである請求項1に記載の銅粉。
- 炭素含有量が0.50質量%以下である請求項1または2に記載の銅粉。
- 水素還元減量が1.5%以下である請求項1~3のいずれか一項に記載の銅粉。
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