CN110640354B - Preformed solder and preparation method thereof - Google Patents
Preformed solder and preparation method thereof Download PDFInfo
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- CN110640354B CN110640354B CN201910797317.5A CN201910797317A CN110640354B CN 110640354 B CN110640354 B CN 110640354B CN 201910797317 A CN201910797317 A CN 201910797317A CN 110640354 B CN110640354 B CN 110640354B
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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
- B23K35/36—Selection of non-metallic compositions, e.g. coatings, fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest
- B23K35/3612—Selection of non-metallic compositions, e.g. coatings, fluxes; Selection of soldering or welding materials, conjoint with selection of non-metallic compositions, both selections being of interest with organic compounds as principal constituents
-
- 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
- B23K35/40—Making wire or rods for soldering or welding
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Manufacture Of Metal Powder And Suspensions Thereof (AREA)
- Powder Metallurgy (AREA)
Abstract
The invention relates to a preformed solder and a preparation method thereof. A preformed solder comprises a preformed metal matrix and a nanoparticle film coated on the outer surface of the matrix; the nanoparticle film contains mainly metal nanoparticles, and the melting point of the metal nanoparticles is lower than that of the metal matrix. The invention reduces the porosity formed by solvent volatilization in the solder sintering process, reduces the heat conduction loss and improves the welding reliability.
Description
Technical Field
The invention relates to the field of materials, in particular to a preformed solder and a preparation method thereof.
Background
The power semiconductor device IGBT is a core technology in applications such as rail transit, smart grid, aerospace, electric vehicle, new energy equipment, and industrial fields, and is called a "CPU" of a power electronic device. In recent years, with the progress of the IGBT towards intellectualization and miniaturization, the power density of the device is gradually increased, and the heat flux of the device during operation is also increased. If the heat cannot be rapidly discharged, the junction temperature of the semiconductor chip can rapidly rise, permanent damage can be caused to the power semiconductor device, and the power semiconductor device can fail.
The connection of the IGBT module chip is to realize the interconnection of the power semiconductor chip and the substrate through the connecting material, and the connecting layer of the chip and the substrate is the most important ring for providing necessary functions of heat dissipation, electric conduction, and mechanical support. At present, materials commonly used for the connecting layer comprise Sn-based soldering paste or soldering lug, and nano silver paste is required to be used for products with high temperature resistance requirements. Sn-based solders such as Sn-Ag and Sn-Ag-Cu have melting points of less than 300 ℃ and cannot be used in high-power devices and high-temperature environments. The volatilization of the solvent of the nano silver slurry in the sintering process can form pores in the sintering layer, thereby greatly reducing the heat conductivity of the sintering layer and causing hidden danger to the reliability of the product.
Disclosure of Invention
The first purpose of the invention is to provide a preformed solder, which reduces the porosity formed by solvent volatilization in the sintering process of the solder, reduces the heat conduction loss and improves the welding reliability.
The second purpose of the present invention is to provide a method for preparing the solder preform, which can modify the conventional metal solder through a simple process to achieve the effect of improving the thermal conductivity.
In order to achieve the above purpose of the present invention, the following technical solutions are adopted:
a preformed solder comprises a preformed metal matrix and a nanoparticle film coated on the outer surface of the matrix; the nanoparticulate membrane mainly contains nanoparticulate, and the melting point of the nanoparticulate is lower than the melting point of the preformed metal matrix.
The invention adds a layer of nano-particle film on the surface of the preformed metal matrix, and can achieve the following technical effects:
the nano-particle film is pre-baked and coated on the pre-formed surface, so that a compact particle film can be obtained, and compared with the existing nano-silver slurry, the porosity formed during welding (or sintering) is low, the heat conduction loss is less, and the welding reliability is higher.
The preformed metal matrix of the present invention may be any simple metal or alloy suitable for use in a solder. Since the metal matrix is mainly used as the core material of the preformed solder and is the main heat conducting medium, it is preferable to use a metal with a high melting point, such as (Ag, Ni, Cu), to meet the requirements of the IGBT for use in high power and high temperature environments. If the solder is used for other purposes, a suitable metal substrate is selected as required. The application of the solder preform is not limited, and the solder preform can be used not only as a connection layer in an IGBT, but also as an encapsulation layer, a heat conduction layer, and the like of other electronic devices or optical elements.
The preforming in the invention refers to the shape of the metal matrix which is preformed in advance, and refers to the shape of the solder for standby, namely the preformed metal matrix is coated by the nano-particle film and then is directly used without changing the size or the shape through the procedures of cutting and the like.
The nano metal particles described in the present invention may be any metal as long as it satisfies a melting point lower than that of the metal matrix. The metal type of the metal matrix is the same as or different from that of the nano metal particles, and when the metal type of the metal matrix is the same as that of the nano metal particles, the melting point of the nano metal particles is lower than that of the metal matrix inevitably due to the nano effect. In terms of material availability, cost, and the like, the nano metal particles are preferably nano Cu particles or nano Ag particles.
The preformed metal matrix is in a sheet shape, a strip shape, a column shape or other irregular shapes, so that the nano metal particles can be coated and attached conveniently.
The particle size of the nano metal particles is preferably less than or equal to 300 nm.
The nanoparticle film preferably further contains at least one of a dispersant, a resin, and an organic acid. The dispersing agent can uniformly disperse the nano metal particles and avoid agglomeration. The resin can be uniformly coated on the surface of the nano-particles, so that the nano-particles can be dispersed and protected, and the long-term storage of the solder at normal temperature can be ensured. The organic acid can remove oxide layers on the surfaces of the nano particles and the substrate in the process of sintering the solder.
The dispersant is preferably at least one of hydrogenated castor oil and polyamide.
The resin is preferably at least one of rosin and modified rosin, and is preferably at least one of hydrogenated rosin and polymerized rosin.
The organic acid is preferably a solid organic acid, preferably at least one of succinic acid, adipic acid, glutaric acid, salicylic acid and pimelic acid, such as succinic acid, adipic acid, glutaric acid, salicylic acid or pimelic acid, or a mixture of adipic acid and glutaric acid, or a mixture of succinic acid and glutaric acid, or the like.
Preferably, the weight ratio of the dispersant, the resin and the organic acid is 1-5: 5-15: 2 to 6.
The invention also provides a preparation method of the preformed solder, which comprises the following steps:
coating slurry containing nano metal particles on the surface of a preformed metal matrix, and then drying to form a nano particle film; when the nanoparticle film contains a modifier, it is added in its entirety to the slurry.
The method mainly relates to two procedures of coating and drying, and does not need complex or expensive equipment.
The slurry for coating of the invention at least contains an organic solvent to dilute the nanoparticles; if the organic vehicle contains a modifier, the organic solvent also serves to dissolve the modifier.
The organic solvent is preferably at least one of alcohol, ketone and ester, mainly lower alcohol, ketone and ester, more preferably at least one of ethanol, isopropanol, acetone and ethyl acetate, such as ethanol, isopropanol, acetone or ethyl acetate, or a mixture of ethanol and acetone, or a mixture of isopropanol and ethyl acetate, or a mixture of ethanol and ethyl acetate; the above mixing refers to mixing in any proportion.
The concentration of the nano-metal particles in the slurry according to the present invention is determined according to the requirements of fluidity, film compactness, cost, etc., and considering the above, any value in the range of 40-90wt.% is preferred, such as 40 wt.%, 45 wt.%, 50 wt.%, 55 wt.%, 60 wt.%, 65 wt.%, 70 wt.%, 75 wt.%, 80 wt.%, 85 wt.%, 90wt.%, etc.
Preferably, when the slurry contains a dispersant, a resin and an organic acid, the weight ratio of the organic solvent, the dispersant, the resin and the organic acid is preferably 74-92: 1-5: 5-15: 2-6, preferably 82-92: 1-4: 5-10: 2-4, for example 74:5:15:6, 76:3:15:6, 80:5:9:6, 89:2.5:5:1.5, 92:1:5:2, 80:4:10:4, and the like.
The metal substrate may also be cleaned prior to the coating.
Preferably, the drying is drying until the organic solvent is removed. For ethanol, isopropanol, acetone and ethyl acetate, the temperatures typically required are: 50-80 ℃.
Preferably, the slurry is obtained by: all raw materials of the slurry are sheared and mixed, and the shearing speed is more than 6000 rpm.
In summary, compared with the prior art, the invention achieves the following technical effects:
(1) the solder of the invention takes a metal matrix as a core and nano metal particles as a film, and simultaneously realizes the purposes of sintering at low melting point and stable connection at high temperature: the characteristic of low melting point of the nano particles is utilized, sintering interconnection at low temperature can be realized, and the formed sintering layer has high melting point of metal and can meet the use requirements of an IGBT (insulated gate bipolar translator) in high-power and high-temperature environments;
(2) the nano-particle film is pre-baked and coated on the pre-formed surface, so that a compact particle film can be obtained, and compared with the existing nano-silver slurry, the porosity formed during welding (or sintering) is low, the heat conduction loss is less, and the welding reliability is higher.
(3) The dispersant added in the nano-particle film is beneficial to the uniformity of the quality and performance of the solder;
(4) the resin added in the nano-particle film plays a role in protecting and fixing the nano-metal particles;
(5) the organic acid added into the nano-particle film can assist in removing an oxide layer of a welded interface;
(6) the slurry coated on the surface of the metal matrix is dried before application, which is beneficial to improving the density of the nano-particles on the matrix.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to examples, but it will be understood by those skilled in the art that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
Example 1
The organic carrier comprises the following components in percentage by weight: 89 wt% of isopropanol; 2 wt% of polyamide; 5 wt% of polymerized rosin; succinic acid 2.5 wt%; 1.5 wt% of salicylic acid;
nano-particles: 50nm-100nm nano silver particles;
preforming a copper sheet: a copper sheet of 2mm × 2mm × 0.1 mm;
preparation of organic vehicle: adding the components of the organic carrier into a container in proportion, processing for 45min at a shearing speed of 6000rpm by using high-speed shearing equipment, controlling the temperature to be 60-100 ℃, and cooling to obtain the organic carrier.
Preparing nano slurry: uniformly mixing 80 wt% of nano silver particles with an organic carrier, and vacuumizing to obtain nano slurry;
preparing preformed solder: cleaning a preformed copper sheet to remove oil stains on the surface, coating nano silver slurry with the thickness of 0.2mm on the surface of the preformed copper sheet, drying for 1h in an oven at the temperature of 80 ℃, and cooling to obtain a preformed solder.
Example 2
The organic carrier comprises the following components in percentage by weight: 70 wt% of isopropanol; 12 wt% of ethyl acetate; hydrogenated castor oil 2 wt%; 2 wt% of polyamide; 10 wt% of modified rosin; 4 wt% of pimelic acid;
nano-particles: 5nm-50nm nano silver particles;
pre-forming a nickel sheet: a nickel sheet of 10mm × 15mm × 0.2 mm;
preparation of organic vehicle: adding the components of the organic carrier into a container in proportion, processing for 45min at a shearing speed of 6000rpm by using high-speed shearing equipment, controlling the temperature to be 60-100 ℃, and cooling to obtain the organic carrier.
Preparing nano slurry: uniformly mixing the nano silver particles with an organic carrier according to 60 wt%, and vacuumizing to obtain nano slurry;
preparing preformed solder: cleaning a preformed nickel sheet to remove surface oil stains, coating nano silver slurry with the thickness of 0.12mm on the preformed surface, drying in a 60 ℃ drying oven for 1h, and cooling to obtain the preformed solder.
Example 3
The organic carrier comprises the following components in percentage by weight: 74 wt% of ethyl acetate; hydrogenated castor oil 5 wt%; 7 wt% of polymerized rosin; 8 wt% of hydrogenated rosin; 1 wt% of glutaric acid; 5 wt% of adipic acid;
nano-particles: 30nm-80nm nano-copper particles;
preforming a copper sheet: a circular copper sheet with the diameter of 10mm and the thickness of 0.1 mm;
preparation of organic vehicle: adding the components of the organic carrier into a container in proportion, processing for 45min at a shearing speed of 6000rpm by using high-speed shearing equipment, controlling the temperature to be 60-100 ℃, and cooling to obtain the organic carrier.
Preparing nano slurry: uniformly mixing 40 wt% of nano copper particles with an organic carrier, and vacuumizing to obtain nano slurry;
preparing preformed solder: cleaning a preformed copper sheet to remove oil stains on the surface, coating nano copper slurry with the thickness of 0.12mm on the surface of the preformed copper sheet, drying for 1h in a 50 ℃ drying oven, and cooling to obtain a preformed solder.
Example 4
The organic carrier comprises the following components in percentage by weight: 60 wt% of absolute ethyl alcohol; 32 wt% of acetone; 1 wt% of hydrogenated castor oil; 2 wt% of modified rosin; 3 wt% of hydrogenated rosin; 1 wt% of succinic acid; 1 wt% of glutaric acid;
nano-particles: 200nm-300nm of nano silver particles;
preforming a copper sheet: a copper sheet block of 10mm × 10mm × 2 mm;
preparation of organic vehicle: adding the components of the organic carrier into a container in proportion, processing for 45min at a shearing speed of 6000rpm by using high-speed shearing equipment, controlling the temperature to be 60-100 ℃, and cooling to obtain the organic carrier.
Preparing nano slurry: uniformly mixing 90 wt% of nano silver particles with an organic carrier, and vacuumizing to obtain nano slurry;
preparing preformed solder: cleaning a preformed copper sheet to remove surface oil stains, coating nano silver slurry with the thickness of 0.1mm on two 10mm multiplied by 10mm surfaces of the preformed sheet block body, drying for 1h in a 50 ℃ oven, and cooling to obtain the preformed solder.
Comparative example 1
The nanosilver paste of example 1.
Comparative example 2
The nanosilver paste of example 2.
Comparative example 3
Nano-copper slurry in example 3.
Comparative example 4
The nanosilver paste of example 4.
The preformed solder of the above example and the nanometal paste of the comparative example were placed in two flat copper sheets at 30% H at 280 deg.C2The sintering was performed in a nitrogen atmosphere, and the thermal conductivity of the connection layer was measured after sintering, and the results are shown in table 1. It can be seen that the heat-conducting property of the preformed sintering layer of the invention is better than that of the corresponding nano-slurry sintering layer.
TABLE 1 thermal conductivity of the connecting layer
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (10)
1. A preformed solder is characterized by comprising a preformed metal matrix and a nanoparticle film coated on the outer surface of the matrix; the nanoparticle film is composed of nanoparticles and a modifier, and the melting point of the nanoparticles is lower than the melting point of the preformed metal matrix; the modifier consists of a dispersant, resin and organic acid; the dispersant is at least one of hydrogenated castor oil and polyamide; the resin is at least one of rosin and modified rosin, the organic acid is solid organic acid, and the organic acid is at least one of succinic acid, adipic acid, glutaric acid, salicylic acid and pimelic acid; the weight ratio of the dispersant, the resin and the organic acid is 1-5: 5-15: 2 to 6.
2. The solder preform of claim 1, wherein the nano-metal particles are nano-copper particles or nano-silver particles.
3. The solder preform of claim 1, wherein the material of the pre-formed metal matrix is silver, nickel, or copper-based metal.
4. The pre-formed solder of claim 1, in which the pre-formed metal matrix is in the form of a sheet, strip or cylinder.
5. The solder preform of claim 1, wherein the nano-metal particles have a particle size of 300nm or less.
6. A method of making a solder preform according to any one of claims 1 to 5, characterised in that it comprises the steps of:
coating slurry containing nano metal particles on the surface of a preformed metal matrix, and then drying to form a nano particle film;
the nanoparticle film contains a modifier, all of which is added to the slurry.
7. The method according to claim 6, wherein the slurry further contains an organic solvent, and the organic solvent is at least one of ethanol, isopropanol, acetone, and ethyl acetate.
8. The method of claim 7, wherein the concentration of the nano-metal particles in the slurry is 40-90 wt.%.
9. The method according to claim 7, wherein the weight ratio of the organic solvent to the dispersant to the resin to the organic acid is 74 to 92: 1-5: 5-15: 2 to 6.
10. The method for preparing according to claim 7, wherein the slurry is obtained by: all raw materials of the slurry are sheared and mixed, and the shearing speed is more than 6000 rpm.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| JP2005205696A (en) * | 2004-01-21 | 2005-08-04 | Ebara Corp | Joining article |
| US7422141B2 (en) * | 2004-01-22 | 2008-09-09 | Hrl Laboratories, Llc | Microparticle loaded solder preform allowing bond site control of device spacing at micron, submicron, and nanostructure scale |
| JP2007136503A (en) * | 2005-11-17 | 2007-06-07 | Toda Kogyo Corp | Clad solder for joining |
| JP5810553B2 (en) * | 2011-02-28 | 2015-11-11 | 三菱マテリアル株式会社 | Laminate for bonding and bonded body |
| CH705321A1 (en) * | 2011-07-19 | 2013-01-31 | Alstom Technology Ltd | Solder foil for high-temperature soldering and method of repairing or manufacturing components using this solder film. |
| CN102922071B (en) * | 2012-10-25 | 2014-10-08 | 哈尔滨工业大学 | Method for preparing low-temperature interconnection/high-temperature serving joints by using nano intermetallic compound particles |
| CN106373954A (en) * | 2016-10-14 | 2017-02-01 | 天津大学 | Sintered IGBT (Insulated Gate Bipolar Transistor) module applying nanometer silver soldering paste and fabrication method of sintered IGBT module |
| CN106751277B (en) * | 2016-12-29 | 2019-06-21 | 广州汉源新材料股份有限公司 | A kind of welding preparation process of nano particle composite material film |
| CN106783768B (en) * | 2016-12-29 | 2019-04-02 | 广州汉源新材料股份有限公司 | A kind of preforming nanometer silverskin |
| CN107845617B (en) * | 2017-09-19 | 2020-12-15 | 全球能源互联网研究院有限公司 | Chip sintered product, subunit, IGBT packaging module and preparation method |
| CN108847395B (en) * | 2018-06-25 | 2020-01-07 | 深圳市先进连接科技有限公司 | Preparation and packaging method of presintered nano-network silver film for low-temperature quick connection |
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