WO2023109597A1 - 纳米铜焊膏及其在芯片封装互连结构中的应用 - Google Patents

纳米铜焊膏及其在芯片封装互连结构中的应用 Download PDF

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Publication number
WO2023109597A1
WO2023109597A1 PCT/CN2022/137056 CN2022137056W WO2023109597A1 WO 2023109597 A1 WO2023109597 A1 WO 2023109597A1 CN 2022137056 W CN2022137056 W CN 2022137056W WO 2023109597 A1 WO2023109597 A1 WO 2023109597A1
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Prior art keywords
nano
copper
solder paste
reducing agent
copper solder
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PCT/CN2022/137056
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English (en)
French (fr)
Inventor
朱朋莉
王春成
孙蓉
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深圳先进技术研究院
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Publication of WO2023109597A1 publication Critical patent/WO2023109597A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
    • B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
    • B23K35/24—Selection of soldering or welding materials proper
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
    • H01L24/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L24/26—Layer connectors, e.g. plate connectors, solder or adhesive layers; Manufacturing methods related thereto

Definitions

  • the invention belongs to the technical field of packaging of high-power electronic devices, and in particular relates to a nano-copper solder paste and its application in chip packaging and interconnection structures.
  • Metal copper has a very high melting point of 1083.4°C.
  • the high melting point of nano-copper after sintering endows it with very high stability, and nano-copper has a large specific surface area due to its small size, which can be sintered and diffused at a lower temperature.
  • nano-copper materials have the characteristics of low-temperature sintering and high melting point, and can be well applied in the packaging field of low-temperature soldering and high-temperature service. Therefore, nano-copper is considered to be a very potential high-temperature resistant chip interconnect material and the next generation of high-power devices. packaging material.
  • Nano-copper still has the following problems as a sintered solder paste material: nano-copper has high surface energy due to its small size, and high surface energy will cause the copper atoms on the surface to be very active, and then oxidize to form an oxide layer during the sintering process, and the dense oxide layer hinder the diffusion of atoms. In order to promote the diffusion of copper atoms, it is necessary to apply higher temperature and pressure during the sintering process, which will cause a certain degree of damage to the fragile chip. Therefore, some technical means are generally used in the application of copper nano solder paste to copper nano Oxidation of particles is inhibited. Usually, the way to prevent the oxidation of nano-copper materials is to place the sintering process in an inert atmosphere or a vacuum environment, but these special atmospheres and environments will greatly increase the cost in the production process.
  • the present invention provides a nano-copper solder paste and its application in the chip package interconnection structure to solve the problem of how to prevent the oxidation of the nano-copper solder paste during the sintering process with a small cost.
  • a nano-copper soldering paste comprises intermixed nano-copper particles, a reducing agent and an organic solvent carrier.
  • the mass ratio of the nano-copper particles, reducing agent and organic solvent carrier is (2-10):(0.1-1):1.
  • the mass ratio of the nano-copper particles, reducing agent and organic solvent carrier is (3-6):(0.2-0.5):1.
  • the nano-copper particles are spherical nano-copper particles.
  • the particle size of the nano-copper particles is 50nm-300nm.
  • the reducing agent is selected from any one of ascorbic acid, hydrazine hydrate, citrate, polyvinylpyrrolidone, sodium sulfite and sodium borohydride.
  • the organic solvent carrier is any one or two or more selected from ethylene glycol, glycerol, diethylene glycol, triethylene glycol, ⁇ -terpineol, ⁇ -terpineol and ⁇ -terpineol .
  • the mass ratio of the nano-copper particles, the reducing agent and the organic solvent carrier is (2 ⁇ 10):(0.1 ⁇ 1):1, and the particle size of the nano-copper particles is 50nm ⁇ 300nm spherical nano-copper particles
  • the reducing agent is selected from any one of ascorbic acid, hydrazine hydrate, citrate, polyvinylpyrrolidone, sodium sulfite and sodium borohydride
  • the organic solvent carrier is selected from ethylene glycol , glycerol, diethylene glycol, triethylene glycol, ⁇ -terpineol, ⁇ -terpineol and ⁇ -terpineol, any one or two or more.
  • the present invention also provides an application of the above-mentioned nano-copper solder paste in a chip package interconnection structure
  • the chip package interconnection structure includes a first mother sheet and a second mother sheet and is used for connecting all The connection layer of the first mother sheet and the second mother sheet, wherein the connection layer is formed by sintering the above-mentioned nano-copper solder paste through a sintering process of heating and applying pressure.
  • the heating temperature is 150°C ⁇ 300°C
  • the pressure is 1MPa ⁇ 20MPa.
  • the nano-copper solder paste provided in the embodiment of the present invention contains intermixed nano-copper particles, a reducing agent, and an organic solvent carrier. It has a low sintering temperature and a high melting point, and can be well applied to the field of electronic packaging for low-temperature soldering and high-temperature service .
  • the nano-copper solder paste by adding a reducing agent, the nano-copper solder paste has a certain self-reducing ability, and the sintering process does not require a protective atmosphere or a special environment, which can effectively prevent the oxidation of the nano-copper material and promote the sintering reaction to proceed completely. A uniform and dense connection layer is obtained, and the mechanical strength of the connection layer is improved.
  • the present invention can simplify the sintering process and reduce the production cost.
  • FIG. 1 is a schematic structural diagram of a packaging and interconnection structure in an embodiment of the present invention
  • Fig. 2 is the SEM picture of the nano-copper particle in the embodiment of the present invention.
  • FIG. 3 is a cross-sectional SEM diagram of the packaging and interconnection structure in Embodiment 1 of the present invention.
  • FIG. 4 is a cross-sectional SEM diagram of the packaging interconnection structure in Embodiment 2 of the present invention.
  • FIG. 5 is a cross-sectional SEM diagram of the package interconnection structure in Embodiment 3 of the present invention.
  • FIG. 6 is a cross-sectional SEM diagram of the packaging interconnection structure in Embodiment 4 of the present invention.
  • FIG. 7 is a cross-sectional SEM diagram of the package interconnection structure in Embodiment 5 of the present invention.
  • FIG. 8 is a cross-sectional SEM diagram of the packaging interconnection structure in Comparative Example 1 of the present invention.
  • FIG. 9 is a cross-sectional SEM diagram of the package interconnection structure in Comparative Example 2 of the present invention.
  • FIG. 10 is a cross-sectional SEM image of the package interconnection structure in Comparative Example 3 of the present invention.
  • nano-copper when nano-copper is used as a sintered solder paste material, nano-copper has high surface energy due to its small size, and high surface energy will cause the copper atoms on the surface to be very active, and then it is very easy to oxidize to form an oxide layer during the sintering process.
  • a dense oxide layer hinders the diffusion of atoms, which in turn hinders sintering.
  • the existing solution is to place the sintering process in an inert atmosphere or a vacuum environment to prevent oxidation, but these special atmospheres and environments will greatly increase the cost in the production process.
  • an embodiment of the present invention provides a nano-copper solder paste, which includes nano-copper particles mixed with each other, a reducing agent, and an organic solvent carrier.
  • a reducing agent By adding a reducing agent, the nano-copper solder paste has a certain self-reducing ability, and the sintering process does not require a protective atmosphere or a special environment, which can effectively prevent the oxidation of the nano-copper material, promote the sintering reaction to complete and obtain a uniform and dense
  • the connection layer improves the mechanical strength of the connection layer.
  • the present invention can simplify the sintering process and reduce the production cost.
  • the mass ratio of the nano-copper particles, the reducing agent and the organic solvent carrier is (2-10):(0.1-1):1.
  • the mass parts of the nano-copper particles are, for example, 2 parts, 2.5 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts or 10 parts
  • the mass part of the reducing agent is, for example, 0.1 part, 0.2 part, 0.3 part, 0.4 part, 0.5 part, 0.6 part, 0.7 part, 0.8 part, 0.9 part or 1 part.
  • the mass parts of the copper nanoparticles are preferably 3-6 parts, and the mass parts of the reducing agent are preferably 0.2-0.5 parts.
  • the nano-copper particles are spherical nano-copper particles.
  • the particle size of the nano-copper particles is 50nm-300nm, such as 50nm, 80nm, 100nm, 120nm, 150nm, 180nm, 200nm, 250nm or 300nm.
  • the reducing agent is selected from any one of ascorbic acid, hydrazine hydrate, citrate, polyvinylpyrrolidone, sodium sulfite and sodium borohydride.
  • the organic solvent carrier is any one or more than two selected from ethylene glycol, glycerin, diethylene glycol, triethylene glycol, ⁇ -terpineol, ⁇ -terpineol and ⁇ -terpineol.
  • the organic solvent carrier is selected from two kinds of ethylene glycol, glycerol, diethylene glycol, triethylene glycol, ⁇ -terpineol, ⁇ -terpineol and ⁇ -terpineol Mixed solvents can be mixed in any proportion, and the preferred mixing ratio is 1:1 ⁇ 1:2.
  • an embodiment of the present invention also provides an application of the above-mentioned nano-copper solder paste in a chip package interconnection structure
  • the chip package interconnection structure includes a first mother sheet and a second mother sheet, and is used for The connection layer connecting the first mother sheet and the second mother sheet, wherein the connection layer is formed by sintering the above-mentioned nano-copper solder paste through a sintering process of heating and applying pressure.
  • the first mother sheet and the second mother sheet are, for example, DBC substrates (copper-clad ceramic substrates).
  • a DBC substrate includes a ceramic substrate, a copper layer, a nickel layer, and a gold layer arranged in sequence.
  • connection surface of the first mother sheet and/or the second mother sheet Coating the nano-copper solder paste provided by the embodiment of the present invention to the connection surface of the first mother sheet and/or the second mother sheet to form a solder paste coating, and then facing the first mother sheet and the second mother sheet according to the connection surface Stacking is performed so that the solder paste coating is located between the first mother chip and the second mother chip, followed by a sintering process so that the solder paste coating is sintered to form a connection layer.
  • the first mother chip 10 and the second mother chip 20 are all selected as DBC substrates, and the solder paste coating is sintered to form a connection layer 30 located between the first mother chip 10 and the second mother chip 20. Between the second mother sheets 20 , the connecting layer 30 connects the first mother sheet 10 and the second mother sheet 20 to each other.
  • pulse thermocompression welding or ultrasonic thermocompression welding can be used to heat and apply pressure to the stacked structure to sinter the nano-copper solder paste to complete the interconnection.
  • the heating temperature can be 150°C ⁇ 300°C, such as 150°C, 160°C, 180°C, 200°C, 230°C, 250°C, 280°C, 290°C or 300°C;
  • the pressure can be 1MPa ⁇ 20MPa, For example, it is 1 MPa, 2 MPa, 5 MPa, 8 MPa, 10 MPa, 13 MPa, 15 MPa, 16 MPa, 18 MPa or 20 MPa.
  • nano-copper solder paste and its application will be described below in conjunction with specific examples. Those skilled in the art will understand that the following examples are only specific examples of the nano-copper solder paste of the present invention and its application. It is not intended to limit all of them.
  • An embodiment of the present invention provides a nano-copper solder paste, which includes nano-copper particles mixed with each other, a reducing agent and an organic solvent carrier.
  • the nano-copper particle selection particle diameter is the spherical nano-copper particle of 50nm ⁇ 300nm, the SEM figure of the spherical nano-copper particle in the present embodiment is shown in Figure 2;
  • the described reducing agent is selected as ascorbic acid;
  • the organic solvent carrier is selected It is a mixture of glycerin and ⁇ -terpineol with a mass ratio of 1:1.
  • the mass ratio of the copper nanoparticles, reducing agent and organic solvent carrier is 6:0.5:1. According to the above mass ratio, the nano-copper particles, the reducing agent and the organic solvent carrier are stirred and mixed to obtain the nano-copper solder paste.
  • the nano-copper solder paste prepared above is applied to packaging and interconnection of electronic devices. Specifically, referring to FIG. 1 , both the first mother chip and the second mother chip in the package interconnection structure are selected as DBC substrates.
  • the mother sheets are processed: the DBC substrates (the first mother sheet and the second mother sheet) are ultrasonically washed in ethanol to remove impurities on the surface and dried.
  • the nano-copper solder paste prepared in this embodiment is evenly coated on the connecting surface of the DBC substrate and then stacked on each other to obtain a "sandwich" structure of DBC substrate/nano-copper solder paste coating/DBC substrate.
  • the stacked structure of the above DBC substrate/nano copper solder paste coating/DBC substrate was heated at a pressure of 5 MPa and a temperature of 260 Low temperature sintering and welding at °C, the pressure holding time is 20 min, the nano-copper paste coating is sintered to form the connection layer. After cooling, the package interconnection structure shown in Figure 1 is obtained.
  • FIG. 3 is a SEM image of a section of the packaging interconnection structure in this embodiment. It can be seen from the figure that the sintering necks between the particles are tight and thick, and the connection of the connection layer is uniform and dense.
  • the connection layer of this embodiment was subjected to a shear fracture test, and the connection layer formed by sintering the nano-copper solder paste of this embodiment was cooled and the shear force was measured to be 38.15 MPa (wherein, 5 test samples were prepared according to this embodiment, and the test data is the average value of 5 test samples).
  • the shear fracture test of the connecting layer is specifically: fixing the sample on the fixture of the shear force tester, and controlling the tester to push and compress the sample at a speed of 100 microns per second to perform shearing.
  • the corresponding shear force is read from the shear force tester when the sample breaks.
  • An embodiment of the present invention provides a nano-copper solder paste, which includes nano-copper particles mixed with each other, a reducing agent and an organic solvent carrier.
  • the nano-copper particle is selected as a spherical nano-copper particle with a particle size of 50nm ⁇ 300nm, and the reducing agent is selected as citrate; the organic solvent carrier is selected as ethylene glycol and ⁇ -terpineol with a mass ratio of 1:1. mixture.
  • the mass ratio of the copper nanoparticles, reducing agent and organic solvent carrier is 5:0.3:1. According to the above mass ratio, the nano-copper particles, the reducing agent and the organic solvent carrier are stirred and mixed to obtain the nano-copper solder paste.
  • the nano-copper solder paste prepared above is applied to packaging and interconnection of electronic devices. Specifically, referring to FIG. 1 , both the first mother chip and the second mother chip in the package interconnection structure are selected as DBC substrates.
  • the mother sheets are processed: the DBC substrates (the first mother sheet and the second mother sheet) are ultrasonically washed in ethanol to remove impurities on the surface and dried.
  • the nano-copper solder paste prepared in this embodiment is evenly coated on the connecting surface of the DBC substrate and then stacked on each other to obtain a "sandwich" structure of DBC substrate/nano-copper solder paste coating/DBC substrate.
  • the stacked structure of the above DBC substrate/nano copper solder paste coating/DBC substrate is sintered and welded at a pressure of 15MPa and a temperature of 250°C.
  • the pressure holding time is 20min, and the nano copper solder paste coating is sintered to form a connection. layer.
  • the package interconnection structure shown in Figure 1 is obtained.
  • FIG. 4 is a SEM image of a section of the packaging interconnection structure in this embodiment. It can be seen from the figure that the connection of the connection layer is uniform and dense.
  • the connection layer of this embodiment is subjected to a shear fracture test, and the connection layer formed by sintering the nano-copper solder paste of this embodiment is cooled and the shear force measured is 43.52 MPa (wherein, 5 test samples were prepared according to this embodiment, and the test data is the average value of 5 test samples).
  • An embodiment of the present invention provides a nano-copper solder paste, which includes nano-copper particles mixed with each other, a reducing agent and an organic solvent carrier.
  • the nano-copper particles are spherical nano-copper particles with a particle size of 50nm ⁇ 300nm;
  • the reducing agent is selected to be sodium borohydride;
  • the organic solvent carrier is selected to be a mixture of ethylene glycol and diethylene glycol at a mass ratio of 1:1.
  • the mass ratio of the copper nanoparticles, reducing agent and organic solvent carrier is 4:0.2:1. According to the above mass ratio, the nano-copper particles, the reducing agent and the organic solvent carrier are stirred and mixed to obtain the nano-copper solder paste.
  • the nano-copper solder paste prepared above is applied to packaging and interconnection of electronic devices. Specifically, referring to FIG. 1 , both the first mother chip and the second mother chip in the package interconnection structure are selected as DBC substrates.
  • the mother sheets are processed: the DBC substrates (the first mother sheet and the second mother sheet) are ultrasonically washed in ethanol to remove impurities on the surface and dried.
  • the nano-copper solder paste prepared in this embodiment is evenly coated on the connecting surface of the DBC substrate and then stacked on each other to obtain a "sandwich" structure of DBC substrate/nano-copper solder paste coating/DBC substrate.
  • the stacked structure of the above DBC substrate/nano-copper paste coating/DBC substrate was heated at a pressure of 3 MPa and a temperature of 200 Low-temperature sintering welding is carried out at °C, and the pressure holding time is 20 minutes.
  • the nano-copper solder paste coating is sintered to form a connection layer. After cooling, the package interconnection structure shown in Figure 1 is obtained.
  • FIG. 5 is a SEM image of a section of the packaging interconnection structure in this embodiment. It can be seen from the figure that the connection of the connection layer is uniform and dense.
  • the shear fracture test was carried out on the connection layer of this embodiment, and the shear force measured after cooling the connection layer formed by sintering the nano-copper solder paste of this embodiment was 46.37MPa (wherein, 5 test samples were prepared according to this embodiment, and the test The data is the average value of 5 test samples).
  • An embodiment of the present invention provides a nano-copper solder paste, which includes nano-copper particles mixed with each other, a reducing agent and an organic solvent carrier.
  • the nano-copper particles are spherical nano-copper particles with a particle diameter of 50nm-300nm; the reducing agent is selected to be sodium sulfite; the organic solvent carrier is selected to be ethylene glycol.
  • the mass ratio of the copper nanoparticles, reducing agent and organic solvent carrier is 7:0.6:1. According to the above mass ratio, the nano-copper particles, the reducing agent and the organic solvent carrier are stirred and mixed to obtain the nano-copper solder paste.
  • the nano-copper solder paste prepared above is applied to packaging and interconnection of electronic devices. Specifically, referring to FIG. 1 , both the first mother chip and the second mother chip in the package interconnection structure are selected as DBC substrates.
  • the mother sheets are processed: the DBC substrates (the first mother sheet and the second mother sheet) are ultrasonically washed in ethanol to remove impurities on the surface and dried.
  • the nano-copper solder paste prepared in this embodiment is evenly coated on the connecting surface of the DBC substrate and then stacked on each other to obtain a "sandwich" structure of DBC substrate/nano-copper solder paste coating/DBC substrate.
  • the stacked structure of the above DBC substrate/nano-copper paste coating/DBC substrate is sintered and welded at a pressure of 8 MPa and a temperature of 230°C.
  • the pressure holding time is 20 minutes, and the nano-copper paste coating is sintered to form a connection. layer.
  • the package interconnection structure shown in Figure 1 is obtained.
  • FIG. 6 is a SEM image of a section of the packaging and interconnection structure in this embodiment. It can be seen from the figure that there are many gaps in the connection layer.
  • the shear fracture test was carried out on the connection layer of this embodiment. After the connection layer formed by sintering the nano-copper solder paste of this embodiment was cooled, the measured shear force was 25.23MPa (wherein, 5 test samples were prepared according to this embodiment, and the test The data is the average value of 5 test samples).
  • the organic solvent carrier of Examples 1-3 uses a mixture of two solvents, and the connection layer has better mechanical properties after encapsulation. This may be due to the fact that a single solvent system (such as Example 4) is easy to volatilize a large amount at a certain temperature point quickly, which will lead to too many internal voids in the connection layer formed by sintering, and the density is relatively poor.
  • An embodiment of the present invention provides a nano-copper solder paste, which includes nano-copper particles mixed with each other, a reducing agent and an organic solvent carrier.
  • nano-copper particles with a diameter of 50nm-300nm are selected as the nano-copper particles; polyvinylpyrrolidone is selected as the reducing agent; triethylene glycol is selected as the organic solvent carrier.
  • the mass ratio of the copper nanoparticles, reducing agent and organic solvent carrier is 8:0.1:1. According to the above mass ratio, the nano-copper particles, the reducing agent and the organic solvent carrier are stirred and mixed to obtain the nano-copper solder paste.
  • the nano-copper solder paste prepared above is applied to packaging and interconnection of electronic devices. Specifically, referring to FIG. 1 , both the first mother chip and the second mother chip in the package interconnection structure are selected as DBC substrates.
  • the mother sheets are processed: the DBC substrates (the first mother sheet and the second mother sheet) are ultrasonically washed in ethanol to remove impurities on the surface and dried.
  • the nano-copper solder paste prepared in this embodiment is evenly coated on the connecting surface of the DBC substrate and then stacked on each other to obtain a "sandwich" structure of DBC substrate/nano-copper solder paste coating/DBC substrate.
  • the stacked structure of the above DBC substrate/nano copper solder paste coating/DBC substrate was sintered and welded at a pressure of 15MPa and a temperature of 300°C, and the pressure holding time was 20 min, the nano-copper paste coating is sintered to form the connection layer. After cooling, the package interconnection structure shown in Figure 1 is obtained.
  • Fig. 7 is a SEM image of the cross-section of the packaging interconnection structure in this embodiment. It can be seen from the figure that the sintering of the connection layer is not sufficient, resulting in many voids. The possible reason is that the polymer reducing agent is difficult to decompose and hinders the sintering.
  • the connection layer of this embodiment was subjected to a shear fracture test, and the connection layer formed by sintering the nano-copper solder paste of this embodiment was cooled and the shear force was measured to be 15.47 MPa (wherein, 5 test samples were prepared according to this embodiment, and the test data is the average value of 5 test samples).
  • Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the nano-copper solder paste in Comparative Example 1 only contains nano-copper particles and an organic solvent carrier, that is, the nano-copper particles and the organic solvent carrier are mixed according to a mass ratio of 6:1 Mix to prepare the nano-copper solder paste of Comparative Example 1.
  • Fig. 8 is a SEM image of a cross-section of the packaging interconnection structure in this comparative example. It can be seen from the figure that the connection layer formed by sintering has high porosity and roughness, which may be due to oxidation that hinders sintering.
  • connection layer of Comparative Example 1 was subjected to a shear fracture test, and the connection layer formed by sintering the nano-copper solder paste of Comparative Example 1 was cooled and the shear force measured was 14.38 MPa (wherein, 5 test samples are prepared, and the test data is the average value of 5 test samples).
  • Example 1 Comparing the test results of Comparative Example 1 with Example 1, it can be seen that the nano-copper solder paste in Example 1 has a higher mechanical strength due to the addition of a reducing agent, so the connection layer formed by final sintering has higher mechanical strength, and the shear force is greatly increased. improvement.
  • Comparative Example 2 provided the same nano copper solder paste as Comparative Example 1.
  • the difference between Comparative Example 2 and Comparative Example 1 is that the sintering process is different when the nano-copper solder paste is applied to the packaging and interconnection of electronic devices.
  • the specific difference is that the sintering process of Comparative Example 2 is carried out in an argon atmosphere .
  • FIG. 9 is an SEM image of a section of the package interconnection structure in this comparative example.
  • connection layer of comparative example 2 was subjected to a shear fracture test, and the connection layer formed by sintering the nano-copper solder paste of comparative example 2 was cooled and the shear force measured was 40.63 MPa (wherein, 5 test samples are prepared, and the test data is the average value of 5 test samples).
  • Comparative Example 3 provided the same nano copper solder paste as Comparative Example 1.
  • the difference between Comparative Example 3 and Comparative Example 1 is that the sintering process is different when the nano-copper solder paste is applied to the packaging and interconnection of electronic devices.
  • the specific difference is that the sintering process of Comparative Example 3 is at a higher temperature and more performed under high pressure.
  • FIG. 10 is a SEM image of a section of the package interconnection structure in this comparative example.
  • connection layer of comparative example 3 was subjected to a shear fracture test, and the connection layer formed by sintering the nano-copper solder paste of comparative example 3 was cooled and the shear force measured was 58.72 MPa (wherein, 5 test samples are prepared, and the test data is the average value of 5 test samples).
  • the nano-copper solder paste provided in the above examples contains intermixed nano-copper particles, a reducing agent, and an organic solvent carrier. It has a low sintering temperature and a high melting point, and can be well applied to low-temperature soldering and high-temperature service. Electronic packaging field.
  • the nano-copper solder paste by adding a reducing agent, the nano-copper solder paste has a certain self-reducing ability, and the sintering process does not require a protective atmosphere or a special environment, which can effectively prevent the oxidation of the nano-copper material and promote the sintering reaction to proceed completely. A uniform and dense connection layer is obtained, and the mechanical strength of the connection layer is improved.
  • the present invention can simplify the sintering process and reduce the production cost.

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Abstract

本发明公开了一种纳米铜焊膏，所述纳米铜焊膏包括相互混合的纳米铜颗粒、还原剂和有机溶剂载体。本发明提供的纳米铜焊膏，包含了相互混合的纳米铜颗粒、还原剂和有机溶剂载体，其烧结温度低且熔点高，能够很好地应用于低温焊接高温服役的电子封装领域。本发明中通过添加还原剂，使得所述纳米铜焊膏具有一定的自还原能力，在烧结过程不需要保护气氛或特殊的环境，就可以有效地防止纳米铜材料发生氧化，促进烧结反应完全进行而获得均匀致密的连接层，提升连接层机械强度。

Description

纳米铜焊膏及其在芯片封装互连结构中的应用 技术领域
本发明属于高功率电子器件封装技术领域，具体涉及一种纳米铜焊膏及其芯片封装互连结构中的应用。
 背景技术
自动驾驶、航空航天、高速铁路和油气勘探等领域所需要的工作环境越来越恶劣，相应的对于芯片的要求也越来越高。传统的硅基芯片已经不能满足这些领域中特定环境下的需求。为此，研究人员把目光投向了宽禁隙半导体（例如SiC 和GaN），它们能很好地满足现阶段人们对高性能芯片的需求。宽禁隙半导体（例如SiC 和GaN）在高功率电器中有非常广泛的应用前景，它们能够在高于250℃的情况下进行正常的工作而且还具有非常高的击穿电压和工作频率。传统的锡铅焊料的熔点比较的低（230℃左右），因此在超过的250℃的情况下，传统的焊料已经不能够胜任。
金属铜具有很高的熔点1083.4℃，纳米铜烧结完成后具有高熔点的特性赋予其非常高的稳定性，并且纳米铜由于尺寸小而比表面积大，在较低的温度下就能实现烧结扩散，即，纳米铜材料具有低温烧结和高熔点的特性，能够很好地应用于低温焊接高温服役的封装领域，因此，纳米铜被认为是非常潜力的耐高温芯片互联材料和下一代高功率器件封装材料。
纳米铜作为烧结焊膏材料仍然存在以下问题：纳米铜由于其尺寸小而表面能高，高表面能会导致表面的铜原子非常活泼，进而在烧结过程中发生氧化形成氧化层，致密的氧化层会阻碍原子的扩散。为了促进铜原子的扩散，需要在烧结过程中施加更高的温度和压力，会对脆弱的芯片造成一定程度的损坏，因此在铜纳米焊膏的应用过程中一般会采用一些技术手段对铜纳米颗粒的氧化进行抑制。通常防止纳米铜材料发生氧化的方法是将烧结工艺置于惰性气氛或真空环境中进行，但是这些特殊的气氛和环境会极大增加生产过程中的成本。
 技术问题
有鉴于此，本发明提供了一种纳米铜焊膏及其芯片封装互连结构中的应用，以解决如何通过较小的成本来防止纳米铜焊膏在烧结过程中发生氧化的问题。
 技术解决方案
为了实现上述目的，本发明采用了如下的技术方案：
一种纳米铜焊膏，所述纳米铜焊膏包括相互混合的纳米铜颗粒、还原剂和有机溶剂载体。
优选地，所述纳米铜焊膏中，所述纳米铜颗粒、还原剂以及有机溶剂载体的质量比为(2~10)：(0.1~1)：1。
优选地，所述纳米铜焊膏中，所述纳米铜颗粒、还原剂以及有机溶剂载体的质量比为(3~6)：(0.2~0.5)：1。
优选地，所述纳米铜颗粒为球形纳米铜颗粒。
优选地，所述纳米铜颗粒的粒径为50nm~300nm。
优选地，所述还原剂选自抗坏血酸、水合肼、柠檬酸盐、聚乙烯吡咯烷酮、亚硫酸钠和硼氢化钠中的任意一种。
优选地，所述有机溶剂载体为选自乙二醇、甘油、二甘醇、三甘醇、β-萜品醇、γ-萜品醇和δ-萜品醇中的任意一种或两种以上。
优选地，所述纳米铜焊膏中，所述纳米铜颗粒、还原剂以及有机溶剂载体的质量比为(2~10)：(0.1~1)：1，所述纳米铜颗粒为粒径为50nm~300nm的球形纳米铜颗粒，所述还原剂选自抗坏血酸、水合肼、柠檬酸盐、聚乙烯吡咯烷酮、亚硫酸钠和硼氢化钠中的任意一种，所述有机溶剂载体为选自乙二醇、甘油、二甘醇、三甘醇、β-萜品醇、γ-萜品醇和δ-萜品醇中的任意一种或两种以上。
进一步地，本发明还提供了一种如上所述的纳米铜焊膏在芯片封装互连结构中的应用，所述芯片封装互连结构包括第一母片和第二母片以及用于连接所述第一母片和第二母片的连接层，其中，所述连接层是采用如上所述的纳米铜焊膏通过加热并施压的烧结工艺烧结形成。
具体地，所述烧结工艺中，加热温度为150℃~300℃，施压压力为1MPa ~20MPa。
 有益效果
本发明实施例中提供的纳米铜焊膏，包含了相互混合的纳米铜颗粒、还原剂和有机溶剂载体，其烧结温度低且熔点高，能够很好地应用于低温焊接高温服役的电子封装领域。本发明中通过添加还原剂，使得所述纳米铜焊膏具有一定的自还原能力，在烧结过程不需要保护气氛或特殊的环境，就可以有效地防止纳米铜材料发生氧化，促进烧结反应完全进行而获得均匀致密的连接层，提升连接层的机械强度。相比于现有的将烧结工艺置于惰性气氛或真空环境中进行的方式，本发明可以简化烧结工艺而降低生产成本。
 附图说明
图1是本发明实施例中的封装互连结构的结构示意图；
图2是本发明实施例中的纳米铜颗粒的SEM图；
图3是本发明实施例1中的封装互连结构的切面SEM图；
图4是本发明实施例2中的封装互连结构的切面SEM图；
图5是本发明实施例3中的封装互连结构的切面SEM图；
图6是本发明实施例4中的封装互连结构的切面SEM图；
图7是本发明实施例5中的封装互连结构的切面SEM图；
图8是本发明对比例1中的封装互连结构的切面SEM图；
图9是本发明对比例2中的封装互连结构的切面SEM图；
图10是本发明对比例3中的封装互连结构的切面SEM图。
 本发明的实施方式
为使本发明的目的、技术方案和优点更加清楚，下面结合附图对本发明的具体实施方式进行详细说明。这些优选实施方式的示例在附图中进行了例示。附图中所示和根据附图描述的本发明的实施方式仅仅是示例性的，并且本发明并不限于这些实施方式。
在此，还需要说明的是，为了避免因不必要的细节而模糊了本发明，在附图中仅仅示出了与根据本发明的方案密切相关的结构和/或处理步骤，而省略了与本发明关系不大的其他细节。
如前所述，纳米铜作为烧结焊膏材料时，纳米铜由于其尺寸小而表面能高，高表面能会导致表面的铜原子非常活泼，进而在烧结过程中极易发生氧化形成氧化层，致密的氧化层会阻碍原子的扩散，进而阻碍烧结的进行。为了促进铜原子的扩散，需要在烧结过程中施加更高的温度和压力，会对脆弱的芯片造成一定程度的损坏，因此在铜纳米焊膏的应用过程中一般会采用一些技术手段对铜纳米颗粒的氧化进行抑制。现有的解决方式是将烧结工艺置于惰性气氛或真空环境中进行以防止氧化，但是这些特殊的气氛和环境会极大增加生产过程中的成本。
为了解决以上问题，本发明实施例提供了一种纳米铜焊膏，所述纳米铜焊膏包括相互混合的纳米铜颗粒、还原剂和有机溶剂载体。通过添加还原剂，使得纳米铜焊膏具有一定的自还原能力，在烧结过程不需要保护气氛或特殊的环境，就可以有效地防止纳米铜材料发生氧化，促进烧结反应完全进行而获得均匀致密的连接层，提升连接层的机械强度。相比于现有的将烧结工艺置于惰性气氛或真空环境中进行的方式，本发明可以简化烧结工艺而降低生产成本。
在优选的方案中，所述纳米铜焊膏中，所述纳米铜颗粒、还原剂以及有机溶剂载体的质量比为(2~10)：(0.1~1)：1。具体地，以1质量份的有机溶剂载体为基准，所述纳米铜颗粒的质量份例如是2份、2.5份、3份、4份、5份、6份、7份、8份、9份或10份，所述还原剂的质量份例如是0.1份、0.2份、0.3份、0.4份、0.5份、0.6份、0.7份、0.8份、0.9份或1份。更为优选的方案中，以1质量份的有机溶剂载体为基准，所述纳米铜颗粒的质量份优选为3~6份，所述还原剂的质量份优选为0.2~0.5份。
在优选的方案中，所述纳米铜颗粒为球形纳米铜颗粒。所述纳米铜颗粒的粒径为50nm~300nm，例如是50nm、80nm、100nm、120nm、150nm、180nm、200nm、250nm或300nm。
在优选的方案中，所述还原剂选自抗坏血酸、水合肼、柠檬酸盐、聚乙烯吡咯烷酮、亚硫酸钠和硼氢化钠中的任意一种。所述有机溶剂载体为选自乙二醇、甘油、二甘醇、三甘醇、β-萜品醇、γ-萜品醇和δ-萜品醇中的任意一种或两种以上。
更为优选的方案中，所述有机溶剂载体为选自乙二醇、甘油、二甘醇、三甘醇、β-萜品醇、γ-萜品醇和δ-萜品醇中的两种的混合溶剂，可按任意比例混合，优选的混合比例是1:1~1:2。
进一步地，本发明实施例还提供了一种如上所述的纳米铜焊膏在芯片封装互连结构中的应用，所述芯片封装互连结构包括第一母片和第二母片以及用于连接所述第一母片和第二母片的连接层，其中，所述连接层是采用如上所述的纳米铜焊膏通过加热并施压的烧结工艺烧结形成。
具体地，所述第一母片和第二母片例如是DBC基板（覆铜陶瓷基板），通常地，DBC基板包括依次设置的陶瓷基底、铜层、镍层和金层。
将本发明实施例提供的纳米铜焊膏涂覆到第一母片和/或第二母片的连接面上形成焊膏涂层，然后将第一母片和第二母片按照连接面相对进行堆叠，使得焊膏涂层位于第一母片和第二母片之间，接着进行烧结工艺使得焊膏涂层烧结形成连接层。作为一个具体的例子，参阅图1所示的封装互连结构，第一母片10和第二母片20均选择为DBC基板，焊膏涂层烧结形成连接层30位于第一母片10和第二母片20之间，连接层30将第一母片10和第二母片20相互连接。
具体地方案中，可以使用脉冲热压焊或超声热压焊对堆叠后的结构加热、施压，使纳米铜焊膏烧结完成互连。其中，加热温度可以为150℃~300℃，例如是150℃、160℃、180℃、200℃、230℃、250℃、280℃、290℃或300℃；施压压力可以为1MPa ~20MPa，例如是1MPa、2MPa、5MPa、8MPa、10MPa、13MPa、15MPa、16MPa、18MPa或20MPa。
以下将结合具体的实施例来说明以上所述的纳米铜焊膏及其应用，本领域技术人员所理解的是，下述实施例仅是本发明的纳米铜焊膏及其应用的具体示例，而不用于限制其全部。
实施例1
本发明实施例提供了一种纳米铜焊膏，所述纳米铜焊膏包括相互混合的纳米铜颗粒、还原剂和有机溶剂载体。
其中，纳米铜颗粒选择粒径为50nm~300nm的球形纳米铜颗粒，本实施例中的球形纳米铜颗粒的SEM图如图2所示；所述还原剂选择为抗坏血酸；所述有机溶剂载体选择为甘油和β-萜品醇质量比为1:1的混合物。
其中，本实施例中，所述纳米铜颗粒、还原剂以及有机溶剂载体的质量比为6：0.5：1。按照以上质量比例，将纳米铜颗粒、还原剂以及有机溶剂载体搅拌混合，获得所述纳米铜焊膏。
将以上制备得到的纳米铜焊膏应用于电子器件的封装互连。具体地，参阅图1，封装互连结构中的第一母片和第二母片均选择为DBC基板。
首先，对母片进行处理：将DBC基板（第一母片和第二母片）在乙醇中超声洗涤除去其表面的杂质并晾干。
接着，将本实施例制得的纳米铜焊膏均匀涂覆在DBC基板的连接面上再相互堆叠，得到DBC基板/纳米铜焊膏涂层/DBC基板的 “三明治”结构。
然后，将以上DBC基板/纳米铜焊膏涂层/DBC基板的堆叠结构在压力为5 MPa ，温度为260 ℃下进行低温烧结焊接，压力保持时间为20 min，纳米铜焊膏涂层被烧结形成连接层。冷却后获得如图1所示的封装互连结构。
图3是本实施例中的封装互连结构的切面的SEM图，从图中可以获知，颗粒间的烧结颈紧密粗大，连接层的连接均匀致密。对本实施例的连接层进行剪切断裂测试，本实施例的纳米铜焊膏烧结形成的连接层冷却后测得剪切力为38.15 MPa（其中，按照本实施例制备获得5个测试样品，测试数据取5个测试样品的平均值）。
需要说明的是，所述对连接层进行剪切断裂测试具体是：将样品固定于剪切力测试仪的固定夹具上，控制测试仪以100微米每秒的速度推动压缩所述样品进行剪切断裂测试，在样品断裂时从剪切力测试仪中读取获得对应的剪切力。
实施例2
本发明实施例提供了一种纳米铜焊膏，所述纳米铜焊膏包括相互混合的纳米铜颗粒、还原剂和有机溶剂载体。
其中，纳米铜颗粒选择粒径为50nm~300nm的球形纳米铜颗粒，所述还原剂选择为柠檬酸盐；所述有机溶剂载体选择为乙二醇和γ-萜品醇质量比为1:1的的混合物。
其中，本实施例中，所述纳米铜颗粒、还原剂以及有机溶剂载体的质量比为5：0.3：1。按照以上质量比例，将纳米铜颗粒、还原剂以及有机溶剂载体搅拌混合，获得所述纳米铜焊膏。
将以上制备得到的纳米铜焊膏应用于电子器件的封装互连。具体地，参阅图1，封装互连结构中的第一母片和第二母片均选择为DBC基板。
首先，对母片进行处理：将DBC基板（第一母片和第二母片）在乙醇中超声洗涤除去其表面的杂质并晾干。
接着，将本实施例制得的纳米铜焊膏均匀涂覆在DBC基板的连接面上再相互堆叠，得到DBC基板/纳米铜焊膏涂层/DBC基板的 “三明治”结构。
然后，将以上DBC基板/纳米铜焊膏涂层/DBC基板的堆叠结构在压力为15MPa ，温度为250℃下进行低温烧结焊接，压力保持时间为20min，纳米铜焊膏涂层被烧结形成连接层。冷却后获得如图1所示的封装互连结构。
图4是本实施例中的封装互连结构的切面的SEM图，从图中可以获知，连接层的连接均匀致密。对本实施例的连接层进行剪切断裂测试，本实施例的纳米铜焊膏烧结形成的连接层冷却后测得剪切力为43.52 MPa（其中，按照本实施例制备获得5个测试样品，测试数据取5个测试样品的平均值）。
实施例3
本发明实施例提供了一种纳米铜焊膏，所述纳米铜焊膏包括相互混合的纳米铜颗粒、还原剂和有机溶剂载体。
其中，纳米铜颗粒选择粒径为50nm~300nm的球形纳米铜颗粒；所述还原剂选择为硼氢化钠；所述有机溶剂载体选择为乙二醇和二甘醇按质量比1:1的混合物。
其中，本实施例中，所述纳米铜颗粒、还原剂以及有机溶剂载体的质量比为4：0.2：1。按照以上质量比例，将纳米铜颗粒、还原剂以及有机溶剂载体搅拌混合，获得所述纳米铜焊膏。
将以上制备得到的纳米铜焊膏应用于电子器件的封装互连。具体地，参阅图1，封装互连结构中的第一母片和第二母片均选择为DBC基板。
首先，对母片进行处理：将DBC基板（第一母片和第二母片）在乙醇中超声洗涤除去其表面的杂质并晾干。
接着，将本实施例制得的纳米铜焊膏均匀涂覆在DBC基板的连接面上再相互堆叠，得到DBC基板/纳米铜焊膏涂层/DBC基板的 “三明治”结构。
然后，将以上DBC基板/纳米铜焊膏涂层/DBC基板的堆叠结构在压力为3 MPa ，温度为200 ℃下进行低温烧结焊接，压力保持时间为20min，纳米铜焊膏涂层被烧结形成连接层。冷却后获得如图1所示的封装互连结构。
图5是本实施例中的封装互连结构的切面的SEM图，从图中可以获知，连接层的连接均匀致密。对本实施例的连接层进行剪切断裂测试，本实施例的纳米铜焊膏烧结形成的连接层冷却后测得剪切力为46.37MPa（其中，按照本实施例制备获得5个测试样品，测试数据取5个测试样品的平均值）。
实施例4
本发明实施例提供了一种纳米铜焊膏，所述纳米铜焊膏包括相互混合的纳米铜颗粒、还原剂和有机溶剂载体。
其中，纳米铜颗粒选择粒径为50nm~300nm的球形纳米铜颗粒；所述还原剂选择为亚硫酸钠；所述有机溶剂载体选择为乙二醇。
其中，本实施例中，所述纳米铜颗粒、还原剂以及有机溶剂载体的质量比为7：0.6：1。按照以上质量比例，将纳米铜颗粒、还原剂以及有机溶剂载体搅拌混合，获得所述纳米铜焊膏。
将以上制备得到的纳米铜焊膏应用于电子器件的封装互连。具体地，参阅图1，封装互连结构中的第一母片和第二母片均选择为DBC基板。
首先，对母片进行处理：将DBC基板（第一母片和第二母片）在乙醇中超声洗涤除去其表面的杂质并晾干。
接着，将本实施例制得的纳米铜焊膏均匀涂覆在DBC基板的连接面上再相互堆叠，得到DBC基板/纳米铜焊膏涂层/DBC基板的 “三明治”结构。
然后，将以上DBC基板/纳米铜焊膏涂层/DBC基板的堆叠结构在压力为8MPa ，温度为230℃下进行低温烧结焊接，压力保持时间为20min，纳米铜焊膏涂层被烧结形成连接层。冷却后获得如图1所示的封装互连结构。
图6是本实施例中的封装互连结构的切面的SEM图，从图中可以获知，连接层的具有较多的空隙。对本实施例的连接层进行剪切断裂测试，本实施例的纳米铜焊膏烧结形成的连接层冷却后测得剪切力为25.23MPa（其中，按照本实施例制备获得5个测试样品，测试数据取5个测试样品的平均值）。
将实施例1-3和实施例4进行对比，实施例1-3的有机溶剂载体选择使用两种溶剂的混合物，封装后连接层具有更好地机械性能。这可能是采用单溶剂体系（例如实施例4）容易在某个温度点大量快速的挥发，这种情况会导致烧结形成的连接层的内部空洞过多，致密性相对较差。
实施例5
本发明实施例提供了一种纳米铜焊膏，所述纳米铜焊膏包括相互混合的纳米铜颗粒、还原剂和有机溶剂载体。
其中，纳米铜颗粒选择粒径为50nm~300nm的球形纳米铜颗粒；所述还原剂选择为聚乙烯吡咯烷酮；所述有机溶剂载体选择为三甘醇。
其中，本实施例中，所述纳米铜颗粒、还原剂以及有机溶剂载体的质量比为8：0.1：1。按照以上质量比例，将纳米铜颗粒、还原剂以及有机溶剂载体搅拌混合，获得所述纳米铜焊膏。
将以上制备得到的纳米铜焊膏应用于电子器件的封装互连。具体地，参阅图1，封装互连结构中的第一母片和第二母片均选择为DBC基板。
首先，对母片进行处理：将DBC基板（第一母片和第二母片）在乙醇中超声洗涤除去其表面的杂质并晾干。
接着，将本实施例制得的纳米铜焊膏均匀涂覆在DBC基板的连接面上再相互堆叠，得到DBC基板/纳米铜焊膏涂层/DBC基板的 “三明治”结构。
然后，将以上DBC基板/纳米铜焊膏涂层/DBC基板的堆叠结构在压力为15MPa ，温度为300℃下进行低温烧结焊接，压力保持时间为20 min，纳米铜焊膏涂层被烧结形成连接层。冷却后获得如图1所示的封装互连结构。
图7是本实施例中的封装互连结构的切面的SEM图，从图中可以获知，连接层的烧结不够充分，导致很多空隙，可能原因是高分子还原剂难分解阻碍了烧结的进行。对本实施例的连接层进行剪切断裂测试，本实施例的纳米铜焊膏烧结形成的连接层冷却后测得剪切力为15.47 MPa（其中，按照本实施例制备获得5个测试样品，测试数据取5个测试样品的平均值）。
对比例1
对比例1与实施例1的区别在于：对比例1中的纳米铜焊膏仅包含有纳米铜颗粒和有机溶剂载体，即，将纳米铜颗粒和有机溶剂载体按照质量比为6：1的比例混合，制备获得对比例1的纳米铜焊膏。
参照实施例1的方式将对比例1的纳米铜焊膏应用于电子器件的封装互连，烧结工艺的具体参数与实施例1的完全相同。图8是本对比例中的封装互连结构的切面的SEM图，从图可以看出来烧结形成的连接层孔隙率高且粗糙，这可能是因为氧化导致了烧结受阻。
对对比例1的连接层进行剪切断裂测试，对比例1的纳米铜焊膏烧结形成的连接层冷却后测得剪切力为14.38 MPa（其中，制备获得5个测试样品，测试数据取5个测试样品的平均值）。
将对比例1与实施例1的测试结果进行对比可知，实施例1中的纳米铜焊膏由于添加了还原剂，因此最终烧结形成的连接层具有更高的机械强度，剪切力得到很大的提升。
对比例2
对比例2提供了与对比例1完全相同的纳米铜焊膏。对比例2与对比例1不同在于，将纳米铜焊膏应用于电子器件的封装互连时的烧结工艺有所不同，具体的区别在于：对比例2的烧结工艺是在氩气的气氛中进行。图9是本对比例中的封装互连结构的切面的SEM图。
对对比例2的连接层进行剪切断裂测试，对比例2的纳米铜焊膏烧结形成的连接层冷却后测得剪切力为40.63 MPa（其中，制备获得5个测试样品，测试数据取5个测试样品的平均值）。
将对比例1、对比例2与实施例1的测试结果进行对比可知，实施例1中的纳米铜焊膏通过添加还原剂，最终烧结形成的连接层具有更高的机械强度，与现有的不添加还原剂而在惰性气体的气氛中进行烧结的结果大致相当。然而，相比于现有的将烧结工艺置于惰性气氛或真空环境中进行的方式，本发明添加还原剂的方式可以简化烧结工艺而降低生产成本。
对比例3
对比例3提供了与对比例1完全相同的纳米铜焊膏。对比例3与对比例1不同在于，将纳米铜焊膏应用于电子器件的封装互连时的烧结工艺有所不同，具体的区别在于：对比例3的烧结工艺是在更高的温度和更高的压力下进行。
具体地，对比例3中的烧结温度为300℃，烧结压力为20MPa。图10是本对比例中的封装互连结构的切面的SEM图。
对对比例3的连接层进行剪切断裂测试，对比例3的纳米铜焊膏烧结形成的连接层冷却后测得剪切力为58.72 MPa（其中，制备获得5个测试样品，测试数据取5个测试样品的平均值）。
将对比例1、对比例3与实施例1的测试结果进行对比可知：通过提高烧结温度和烧结压力，可以降低铜纳米颗粒氧化带来的负面影响，烧结形成的连接层也具有较好地机械强度。但是高温高压常常会带来非常严重的后果，比如损坏芯片，设备负荷大，生产工艺不兼容。因此，相比于通过提高烧结温度和烧结压力的方式，本发明添加还原剂的方式可以简化烧结工艺而降低生产成本。
综上所述，以上实施例提供的纳米铜焊膏，包含了相互混合的纳米铜颗粒、还原剂和有机溶剂载体，其烧结温度低且熔点高，能够很好地应用于低温焊接高温服役的电子封装领域。本发明中通过添加还原剂，使得所述纳米铜焊膏具有一定的自还原能力，在烧结过程不需要保护气氛或特殊的环境，就可以有效地防止纳米铜材料发生氧化，促进烧结反应完全进行而获得均匀致密的连接层，提升连接层的机械强度。相比于现有的将烧结工艺置于惰性气氛或真空环境中进行的方式，本发明可以简化烧结工艺而降低生产成本。
以上所述仅是本申请的具体实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本申请原理的前提下，还可以做出若干改进和润饰，这些改进和润饰也应视为本申请的保护范围。

Claims (10)

  1. 一种纳米铜焊膏，其特征在于，所述纳米铜焊膏包括相互混合的纳米铜颗粒、还原剂和有机溶剂载体。
  2. 根据权利要求1所述的纳米铜焊膏，其特征在于，所述纳米铜焊膏中，所述纳米铜颗粒、还原剂以及有机溶剂载体的质量比为(2~10)：(0.1~1)：1。
  3. 根据权利要求2所述的纳米铜焊膏，其特征在于，所述纳米铜焊膏中，所述纳米铜颗粒、还原剂以及有机溶剂载体的质量比为(3~6)：(0.2~0.5)：1。
  4. 根据权利要求1所述的纳米铜焊膏，其特征在于，所述纳米铜颗粒为球形纳米铜颗粒。
  5. 根据权利要求4所述的纳米铜焊膏，其特征在于，所述纳米铜颗粒的粒径为50nm~300nm。
  6. 根据权利要求1所述的纳米铜焊膏，其特征在于，所述还原剂选自抗坏血酸、水合肼、柠檬酸盐、聚乙烯吡咯烷酮、亚硫酸钠和硼氢化钠中的任意一种。
  7. 根据权利要求1所述的纳米铜焊膏，其特征在于，所述有机溶剂载体为选自乙二醇、甘油、二甘醇、三甘醇、β-萜品醇、γ-萜品醇和δ-萜品醇中的任意一种或两种以上。
  8. 根据权利要求1所述的纳米铜焊膏，其特征在于，所述纳米铜焊膏中，所述纳米铜颗粒、还原剂以及有机溶剂载体的质量比为(2~10)：(0.1~1)：1，所述纳米铜颗粒为粒径为50nm~300nm的球形纳米铜颗粒，所述还原剂选自抗坏血酸、水合肼、柠檬酸盐、聚乙烯吡咯烷酮、亚硫酸钠和硼氢化钠中的任意一种，所述有机溶剂载体为选自乙二醇、甘油、二甘醇、三甘醇、β-萜品醇、γ-萜品醇和δ-萜品醇中的任意一种或两种以上。
  9. 一种如权利要求1-8任一项所述的纳米铜焊膏在芯片封装互连结构中的应用，所述芯片封装互连结构包括第一母片和第二母片以及用于连接所述第一母片和第二母片的连接层，其特征在于，所述连接层是采用权利要求1-8任一项所述的纳米铜焊膏通过加热并施压的烧结工艺烧结形成。
  10. 根据权利要求9所述的应用，其特征在于，所述烧结工艺中，加热温度为150℃~300℃，施压压力为1MPa ~20MPa。
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