Film-coated copper sheet for chip front electrode connection and preparation method and application of film-coated copper sheet

Abstract

The invention provides a film-coated copper sheet for chip front electrode connection and a preparation method and application thereof. The preparation method of the film-coated copper sheet for chip front electrode connection comprises the following steps: A) carrying out pretreatment and single-side metallization treatment on a bare copper sheet to obtain a copper sheet with a single-side metallization layer; and B) uniformly coating metal soldering paste on the single-sided metallization layer of the copper sheet, and then drying in an inert atmosphere or a reducing atmosphere to obtain a film-coated copper sheet with a pre-sintered metal film formed on the surface. According to the film-coated copper sheet, a temporary fixing agent can be prevented from being used during hot pasting, the problems of organic matter pollution, bonding area reduction and the like caused by the adoption of the fixing agent when the front face of an existing chip is connected with a copper sheet are solved, the falling-off rate is low after hot pasting, the pasting strength is high, and the applicability of the film-coated copper sheet and the reliability of a power module are greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of high-performance power device packaging, and in particular to a coated copper sheet for connecting chip front electrodes, and a preparation method and application thereof. Background Art

[0002] The third generation wide bandgap semiconductor (SiC, GaN, etc.) devices have higher operating junction temperature, frequency and power density than Si-based devices. The conventional wire bonding method using aluminum wires is difficult to meet the packaging needs of the third generation semiconductor devices due to its inherent parasitic inductance, low current carrying capacity and reliability.

[0003] At present, many researchers have proposed to use copper wire instead of aluminum wire for wire bonding to improve the reliability of power modules, considering the high thermal conductivity, high yield strength and low thermal expansion coefficient of copper materials. However, copper wire can easily damage the coating on the front of the chip during ultrasonic bonding, thereby damaging the chip. When the copper sheet is connected to the front of the existing chip, the adhesion of the patch after the sintering paste is dried is insufficient, and the electronic components are easy to shift or fall off when transported from the assembly position to the sintering position. Therefore, it is often necessary to apply a fixing agent (such as a thermoplastic polymer), which increases the complexity of the process and the possibility of organic contamination, and also reduces the effective area of ​​wire bonding.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The purpose of the present invention is to provide a coated copper sheet for connecting the front electrode of a chip, and a preparation method and application thereof. The coated copper sheet can avoid the use of a temporary fixing agent during thermal bonding, solves the problems of organic pollution and reduced bonding area caused by the use of fixing agents when connecting the copper sheet on the front of the existing chip, reduces the shedding rate after thermal bonding, and improves the bonding strength.

[0006] The present invention provides a metal solder paste for connecting chip front electrodes, comprising the following components in parts by mass: 15-20 parts of coated metal particles and 80-85 parts of an auxiliary agent system; wherein the coated metal particles are obtained by coating metal particles with a coating agent, and the auxiliary agent system comprises the following components in parts by mass: 1.5-2.5 parts of a dispersant, 95.5-98 parts of a diluent and 0.5-2 parts of a thermosetting adhesive; preferably, the auxiliary agent system comprises the following components in parts by mass: 1.5-2.5 parts of a dispersant, 96.5-98 parts of a diluent and 0.5-1 parts of a thermosetting adhesive.

[0007] Specifically, the metal particles are selected from silver particles or copper particles, preferably silver particles. The morphology of the metal particles is flake or spherical; when the metal particles are spherical, the particle size of the metal particles is 100-800nm, preferably 300-500nm, for example, 300nm, 400nm, 500nm, 800nm; when the metal particles are flake, the size of the metal particles is 1000-2000nm, for example, 1000nm, 1500nm, 2000nm.

[0008] The coating agent is selected from at least one of polyvinyl pyrrolidone, polyvinyl alcohol and polyacrylic acid.

[0009] The thermosetting adhesive is selected from at least one of melamine formaldehyde resin, furan resin, polybutadiene resin and silicone resin, and is preferably at least one of furan resin, silicone resin and polybutadiene resin.

[0010] Preferably, the dispersant is selected from at least one of n-decanol, methanol, cyclohexanol and ethanol, preferably at least one of ethanol, cyclohexanol and n-decanol.

[0011] Preferably, the diluent is selected from at least one of ethylene glycol, propylene glycol, glycerol, n-butanol, diethylene glycol, acetone alcohol and polyethylene glycol, preferably at least one of ethylene glycol, propylene glycol and glycerol.

[0012] The present invention also provides a method for preparing the metal solder paste, comprising the following steps:

[0013] S1: pickling and drying the metal particles to obtain pretreated metal particles;

[0014] S2: mixing the pretreated metal particles with the coating agent and the organic solvent, ultrasonicating the mixture, and centrifuging the mixture to obtain coated metal particles;

[0015] S3: mixing a dispersant, a diluent and a thermosetting adhesive according to parts by mass and stirring to obtain an additive system;

[0016] S4: Mix the coated metal particles and the auxiliary agent system according to parts by mass and stir to obtain a metal solder paste.

[0017] In step S1, pickling is carried out with 3-5 mol / L sulfuric acid solution or 1-2 mol / L hypophosphorous acid solution, the concentration of the sulfuric acid solution is preferably 4-5 mol / L, and the concentration of the hypophosphorous acid solution is preferably 2 mol / L; the pickling temperature is room temperature, and the pickling time is 5-15 min, for example, 5-10 min; and drying is carried out under an inert atmosphere, the drying temperature is 50-60°C, and the drying time is 20-40 min.

[0018] In step S2, the organic solvent is anhydrous ethanol; the mass ratio of the pretreated metal particles, the coating agent and the anhydrous ethanol is (4-5): (3-4): (1-3); and the ultrasonic time is 10-40 min.

[0019] In step S3, the stirring is magnetic stirring; and the stirring time is 30-60 min.

[0020] In step S4, the stirring is magnetic stirring; and the stirring time is 20-40 minutes.

[0021] The present invention also provides a method for preparing a coated copper sheet for connecting a front electrode of a chip, comprising the following steps:

[0022] A) pre-treating and single-sided metallization treatment of the bare copper sheet to obtain a copper sheet with a single-sided metallization layer;

[0023] B) uniformly coating the metal solder paste according to any one of claims 1 to 5 on the single-sided metallization layer of the copper sheet, and then drying it in an inert atmosphere or a reducing atmosphere to obtain a coated copper sheet with a pre-sintered metal film formed on the surface.

[0024] In step A), the material of the bare copper sheet is oxygen-free copper, red copper, etc., the thickness of the bare copper sheet is 20-200 μm, for example, 70-100 μm; the hardness is 70-120 HV, for example, 90-120 HV.

[0025] The pretreatment includes: soaking the bare copper sheet in dilute sulfuric acid solution, anhydrous ethanol and deionized water in turn, repeating 2-3 times and then drying in an inert atmosphere; wherein the mass content of the dilute sulfuric acid solution is 2-5%, for example, 2-4%; the soaking time in the dilute sulfuric acid solution is 10-15 minutes; the soaking time in anhydrous ethanol is 3-5 minutes; the soaking time in deionized water is 3-5 minutes, for example, 4-5 minutes. The inert atmosphere is a nitrogen atmosphere, the drying temperature is 40-60°C, and the drying time is 20-40 minutes.

[0026] In step B), the single-sided metallization layer is Ag plating, Ni / Ag plating or Ni / Pd / Au plating; the thickness of the single-sided metallization layer is 1-3 μm; and the single-sided metallization layer is provided on the surface of the bare copper sheet, which is beneficial to improving the adhesion between the metal film and the copper sheet.

[0027] In step B), the inert atmosphere is nitrogen, argon and the like, and the reducing atmosphere is formic acid, platinum-catalyzed formic acid, nitrogen and hydrogen mixture and the like. The heating rate during drying is 2-50°C / min, preferably 10-40°C / min; the drying temperature is 100-180°C, preferably 120-140°C; the drying time is 2-60min, preferably 10-20min. The thickness of the pre-sintered metal film formed on the surface of the coated copper sheet is 25-150μm, for example 25-50μm. After preparation, the coated copper sheet of a specified shape can be processed by laser cutting or stamping, and the processed coated copper sheet is placed on the surface of the blue film for storage.

[0028] The present invention also provides a coated copper sheet for connecting the front electrodes of a chip, which is prepared according to the above preparation method.

[0029] The present invention also provides a method for connecting a coated copper sheet and a chip, comprising the following steps:

[0030] a) Place the chip on a heating platform and heat it to the thermal paste process temperature;

[0031] b) The suction head is heated to the thermal bonding process temperature, and the coated copper sheet is pressed and bonded to the front side of the chip using the heated suction head, and then placed in a sintering furnace for sintering to obtain a power device packaging structure.

[0032] In step a), the thermal bonding process temperature is 100-150°C, for example, 110-150°C.

[0033] In step b), the laminating pressure is 1-5MPa, such as 2-5MPa, and the laminating time is 0.1-2s, such as 1-2s; the coated copper sheet is pressed and laminated to the front of the chip, which can initially achieve the interface bonding between the two, so that the coated copper sheet is fixed to the front of the chip. The sintering temperature is 200-300°C, such as 250-270°C, the sintering pressure is 1-20MPa, such as 5-10MPa, and the sintering time is 1-30min, such as 3-15min. Sintering at the above temperature and pressure can achieve the interface metallurgical bonding between the coated copper sheet and the chip.

[0034] The metal solder paste of the present invention can avoid the use of temporary fixing agents during hot pasting, and solves the problems of organic pollution and reduced bonding area caused by the use of fixing agents when connecting the copper sheet on the front of the existing chip. Compared with the prior art, the use process of the coated copper sheet of the present invention is simple and convenient, and no additional temporary fixing agent is required. The residual organic matter during hot pasting can achieve the adhesion of the metal film and the chip. After sintering, the organic matter can be completely solidified in the sintering layer without escaping, avoiding the organic matter from escaping and polluting the surface of the workpiece, and the cured adhesive does not affect the subsequent sintering quality, achieving a good metallurgical combination of the metal film and the chip, with a low shedding rate and high bonding strength after hot pasting, greatly improving the applicability of the coated copper sheet and the reliability of the power module, and being able to well meet the packaging requirements of high-performance power devices. DETAILED DESCRIPTION

[0035] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0036] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form also includes the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this description, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0037] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] Example 1

[0039] The present embodiment provides a silver solder paste, comprising the following components in parts by mass: 15 parts of coated silver particles and 85 parts of an auxiliary agent system; wherein the coated silver particles are obtained by coating silver particles with a coating agent, polyvinyl pyrrolidone, and the silver particles are flaky in shape and have a size of 1500 nm; the auxiliary agent system comprises the following components in parts by mass: 1.5 parts of a dispersant cyclohexanol, 98 parts of a diluent ethylene glycol, and 0.5 parts of a thermosetting adhesive furan resin.

[0040] The preparation method of the silver solder paste of this embodiment comprises the following steps:

[0041] 1) Pickling and drying

[0042] The silver particles were pickled with a 5 mol / L sulfuric acid solution at room temperature for 5 min. After pickling, the particles were dried at 50° C. for 20 min in a nitrogen atmosphere to obtain pretreated silver particles.

[0043] 2) Coating

[0044] 40 parts of the above-mentioned pretreated silver particles, 30 parts of coating agent polyvinyl pyrrolidone and 30 parts of anhydrous ethanol were mixed, and after mixing, ultrasonication was performed for 10 minutes, and centrifugation was performed to obtain coated silver particles.

[0045] 3) Preparation of auxiliary agent system

[0046] 1.5 parts of cyclohexanol as a dispersant, 98 parts of ethylene glycol as a diluent, and 0.5 parts of furan resin as a thermosetting adhesive were mixed, and magnetically stirred at room temperature for 30 minutes to obtain an auxiliary agent system.

[0047] 4) Preparation of silver solder paste

[0048] 15 parts of the coated silver particles obtained in step 2) were mixed with 85 parts of the auxiliary agent system obtained in step 3), and magnetic stirring was performed for 20 minutes to obtain a silver solder paste.

[0049] Example 2

[0050] The present embodiment provides a silver solder paste, comprising the following components in parts by mass: 20 parts of coated silver particles and 80 parts of an auxiliary agent system; wherein the coated silver particles are obtained by coating silver particles with a coating agent, polyvinyl alcohol, and the silver particles are spherical with a particle size of 300 nm; the auxiliary agent system comprises the following components in parts by mass: 2.5 parts of dispersant ethanol, 96.5 parts of diluent glycerol and 1 part of thermosetting adhesive silicone resin.

[0051] The preparation method of the silver solder paste of this embodiment comprises the following steps:

[0052] 1) Pickling and drying

[0053] The silver particles were pickled with a 2 mol / L hypophosphorous acid solution at room temperature for 8 min. After pickling, the particles were dried at 60° C. for 40 min in a nitrogen atmosphere to obtain pretreated silver particles.

[0054] 2) Coating

[0055] 50 parts of the above-mentioned pretreated silver particles, 40 parts of coating agent polyvinyl alcohol and 10 parts of anhydrous ethanol were mixed, and after mixing, ultrasonication was performed for 40 minutes, and centrifugation was performed to obtain coated silver particles.

[0056] 3) Preparation of auxiliary agent system

[0057] 2.5 parts of dispersant ethanol, 96.5 parts of diluent glycerol and 1 part of thermosetting adhesive silicone resin were mixed, and magnetically stirred at room temperature for 60 minutes to obtain an additive system.

[0058] 4) Preparation of silver solder paste

[0059] 20 parts of the coated silver particles obtained in step 2) were mixed with 80 parts of the auxiliary agent system obtained in step 3), and magnetic stirring was performed for 40 minutes to obtain a silver solder paste.

[0060] Example 3

[0061] The present embodiment provides a copper solder paste, comprising the following components in parts by mass: 18 parts of coated copper particles and 82 parts of an auxiliary agent system; wherein the coated copper particles are obtained by coating copper particles with a coating agent, polyacrylic acid, and the copper particles are spherical with a particle size of 500 nm; the auxiliary agent system comprises the following components in parts by mass: 2 parts of a dispersant, n-decanol, 97 parts of a diluent, propylene glycol, and 1 part of a thermosetting adhesive, polybutadiene resin.

[0062] The preparation method of the silver solder paste of this embodiment comprises the following steps:

[0063] 1) Pickling and drying

[0064] The copper particles were pickled with a 4 mol / L sulfuric acid solution at room temperature for 10 min. After pickling, the copper particles were dried at 60° C. for 30 min in a nitrogen atmosphere to obtain pretreated silver particles.

[0065] 2) Coating

[0066] 45 parts of the pretreated copper particles, 40 parts of polyvinyl pyrrolidone as a coating agent and 15 parts of anhydrous ethanol were mixed, ultrasonicated for 10 minutes, and centrifuged to obtain coated silver particles.

[0067] 3) Preparation of auxiliary agent system

[0068] 2 parts of n-decanol as a dispersant, 97 parts of propylene glycol as a diluent and 1 part of polybutadiene resin as a thermosetting adhesive were mixed, and magnetically stirred at room temperature for 50 minutes to obtain an auxiliary agent system.

[0069] 4) Preparation of silver solder paste

[0070] 18 parts of the coated copper particles obtained in step 2) were mixed with 82 parts of the auxiliary agent system obtained in step 3), and magnetic stirring was performed for 20 minutes to obtain a copper solder paste.

[0071] Example 4

[0072] This embodiment provides a method for preparing a coated copper sheet for connecting the front electrode of a chip, and the steps are as follows:

[0073] S1: Preprocessing

[0074] The material of the bare copper sheet is red copper, with a thickness of 70μm and a hardness of 100HV.

[0075] First, soak the bare copper sheet in a 2% dilute sulfuric acid solution for 10 minutes, then soak it in anhydrous ethanol for 5 minutes, and then soak it in deionized water for 5 minutes; after repeating 3 times, dry it in a nitrogen atmosphere at 50°C for 40 minutes to obtain a clean, non-oxidized bare copper sheet.

[0076] S2: Single-sided metallization

[0077] The bare copper sheet pretreated in step S1 is subjected to single-sided metallization treatment to obtain a copper sheet with an Ag coating, wherein the thickness of the Ag coating is 1 μm.

[0078] S3: Apply silver solder paste

[0079] The silver solder paste of Example 1 is coated on the Ag coating of the copper sheet after the single-sided metallization treatment in step S2 by printing. The thickness of the silver solder paste is controlled to be about 100 μm and the thickness is uniform. After coating, it is placed in a drying furnace.

[0080] S4: Drying

[0081] The copper sheet coated with silver solder paste in step S3 is heated and dried in a nitrogen atmosphere, and the heating rate during heating and drying is 10°C / min, the drying temperature is 120°C, and the drying time is 20min, so as to obtain a coated copper sheet, the surface of which is a pre-sintered silver film, the thickness of the pre-sintered silver film is 50μm, and there is no temporary fixing agent. The coated copper sheet of the specified shape is processed by laser cutting, and the processed coated copper sheet is placed on the surface of the blue film for storage.

[0082] Example 5

[0083] This embodiment provides a method for preparing a coated copper sheet for connecting the front electrode of a chip, and the steps are as follows:

[0084] S1: Preprocessing

[0085] The material of the bare copper sheet is oxygen-free copper, with a thickness of 100μm and a hardness of 120HV.

[0086] First, soak the bare copper sheet in a 4% dilute sulfuric acid solution for 15 minutes, then soak it in anhydrous ethanol for 3 minutes, and then soak it in deionized water for 5 minutes; after repeating 3 times, dry it in a nitrogen atmosphere at 50°C for 40 minutes to obtain a clean, oxidation-free bare copper sheet.

[0087] S2: Single-sided metallization

[0088] The bare copper sheet pretreated in step S1 is subjected to single-sided metallization treatment to sequentially form a Ni coating and an Ag coating (collectively referred to as a Ni / Ag coating) on ​​the surface of the bare copper sheet; wherein the thickness of the Ni coating is 2 μm, the thickness of the Ag coating is 1 μm, and the total thickness of the Ni / Ag coating is 3 μm.

[0089] S3: Apply silver solder paste

[0090] The silver solder paste of Example 2 is coated on the Ni / Ag coating of the copper sheet after single-sided metallization in step S2 by printing. The thickness of the silver solder paste is controlled to be about 50 μm and the thickness is uniform. After coating, the paste is placed in a drying oven.

[0091] S4: Drying

[0092] The copper sheet coated with silver solder paste in step S3 is heated and dried in a formic acid atmosphere, and the heating rate during heating and drying is 10°C / min, the drying temperature is 140°C, and the drying time is 20min, so as to obtain a coated copper sheet, the surface of which is a pre-sintered silver film, the thickness of the pre-sintered silver film is 25μm, and there is no temporary fixing agent. The coated copper sheet of the specified shape is processed by laser cutting, and the processed coated copper sheet is placed on the surface of the blue film for storage.

[0093] Example 6

[0094] This embodiment provides a method for preparing a coated copper sheet for connecting the front electrode of a chip, and the steps are as follows:

[0095] S1: Preprocessing

[0096] The bare copper sheet is made of oxygen-free copper, with a thickness of 75μm and a hardness of 90HV.

[0097] First, soak the bare copper sheet in a 4% dilute sulfuric acid solution for 15 minutes, then soak the bare copper sheet in anhydrous ethanol for 4 minutes, and then soak the bare copper sheet in deionized water for 4 minutes; after repeating 3 times, dry it in a nitrogen atmosphere at 50°C for 30 minutes to obtain a clean, oxidation-free bare copper sheet.

[0098] S2: Single-sided metallization

[0099] The bare copper sheet pretreated in step S1 is subjected to single-sided metallization treatment to sequentially form a Ni plating layer, a Pd plating layer and an Au plating layer (collectively referred to as a Ni / Pd / Au plating layer) on the surface of the bare copper sheet; wherein the thickness of the Ni plating layer is 1.8 μm, the thickness of the Pd plating layer is 0.2 μm, the thickness of the Au plating layer is 1 μm, and the total thickness of the Ni / Pd / Au plating layer is 3 μm.

[0100] S3: Apply silver solder paste

[0101] The copper solder paste of Example 3 is coated on the Ni / Pd / Au coating of the copper sheet after single-sided metallization in step S2 by printing. The thickness of the copper solder paste is controlled to be about 50 μm and the thickness is uniform. After coating, the copper solder paste is placed in a drying oven.

[0102] S4: Drying

[0103] The copper sheet coated with silver solder paste in step S3 is heated and dried in a formic acid atmosphere, and the heating rate during heating and drying is 40°C / min, the drying temperature is 140°C, and the drying time is 10min, so as to obtain a coated copper sheet, the surface of which is a pre-sintered copper film, the thickness of the pre-sintered copper film is 25μm, and there is no temporary fixing agent. The coated copper sheet of the specified shape is processed by laser cutting, and the processed coated copper sheet is placed on the surface of the blue film for storage.

[0104] Example 7

[0105] This embodiment provides a method for connecting a coated copper sheet to a chip, comprising the following steps:

[0106] S1: Place the chip on a heating platform and heat it to the thermal paste process temperature of 130°C.

[0107] S2: The suction head is heated to the hot-sticking process temperature of 130°C, and the coated copper sheet of the predetermined shape of Example 4 is removed from the blue film by the heated suction head, and then pressed and bonded to the front side of the chip. The bonding pressure is 3 MPa, and the bonding time is 1 s, so as to preliminarily achieve the interface bonding between the coated copper sheet and the chip, and fix the coated copper sheet to the front side of the chip.

[0108] S3: placing the chip with the coated copper sheet in step S2 in a sintering furnace, and sintering for 3 minutes at a sintering temperature of 250° C. and a sintering pressure of 10 MPa to achieve interface metallurgical bonding between the coated copper sheet and the chip, thereby obtaining a power device packaging structure.

[0109] Example 8

[0110] This embodiment provides a method for connecting a coated copper sheet to a chip, comprising the following steps:

[0111] S1: Place the chip on a heating platform and heat it to the thermal paste process temperature of 110°C.

[0112] S2: Heat the suction head to the hot-sticking process temperature of 110°C, and use the heated suction head to remove the coated copper sheet of the predetermined shape of Example 5 from the blue film, and then pressurize and bond it to the front side of the chip. The bonding pressure is 5 MPa and the bonding time is 2 s. The interface bonding between the coated copper sheet and the chip is initially achieved, and the coated copper sheet is fixed to the front side of the chip.

[0113] S3: placing the chip with the coated copper sheet in step S2 in a sintering furnace, and sintering for 15 minutes at a sintering temperature of 270° C. and a sintering pressure of 5 MPa to achieve interface metallurgical bonding between the coated copper sheet and the chip, and obtain a power device packaging structure.

[0114] Example 9

[0115] This embodiment provides a method for connecting a coated copper sheet to a chip, comprising the following steps:

[0116] S1: Place the chip on a heating platform and heat it to the thermal paste process temperature of 150°C.

[0117] S2: Heat the suction head to the hot-sticking process temperature of 150°C, and use the heated suction head to remove the coated copper sheet of the predetermined shape of Example 6 from the blue film, and then pressurize and bond it to the front side of the chip. The bonding pressure is 2 MPa and the bonding time is 1 s. The interface bonding between the coated copper sheet and the chip is initially achieved, so that the coated copper sheet is fixed to the front side of the chip.

[0118] S3: placing the chip with the coated copper sheet in step S2 in a sintering furnace, and sintering for 3 minutes at a sintering temperature of 260° C. and a sintering pressure of 10 MPa to achieve interface metallurgical bonding between the coated copper sheet and the chip, and obtain a power device packaging structure.

[0119] Comparative Example 1

[0120] Except that the auxiliary agent system in the silver solder paste does not add a thermosetting binder, the rest is the same as Example 7; the auxiliary agent system of the silver solder paste in this comparative example is composed of 2 parts of dispersant cyclohexanol and 98 parts of diluent ethylene glycol.

[0121] Comparative Example 2

[0122] Except for the different auxiliary agent system in the silver solder paste, the rest is the same as Example 7; the auxiliary agent system of the silver solder paste in this comparative example is composed of 1.8 parts of dispersant cyclohexanol, 98 parts of diluent ethylene glycol and 0.2 parts of thermosetting adhesive furan resin.

[0123] Comparative Example 3

[0124] Except for the different auxiliary agent system in the silver solder paste, the rest is the same as Example 7; the auxiliary agent system of the silver solder paste in this comparative example is composed of 1 part of dispersant cyclohexanol, 94.5 parts of diluent ethylene glycol and 4.5 parts of thermosetting adhesive furan resin.

[0125] Comparative Example 4

[0126] The process is the same as that of Example 7 except that the single-sided metallization treatment is not performed, that is, the Ag plating layer is not provided, but the silver solder paste is directly coated on the pre-treated bare copper sheet.

[0127] Comparative Example 5

[0128] Except for using phenolic resin to replace the thermosetting adhesive furan resin, the rest is the same as Example 7.

[0129] Comparative Example 6

[0130] This comparative example provides a silver solder paste, comprising the following components in parts by mass: 6 parts of silver particles and 85 parts of an auxiliary agent system; wherein the silver particles are flaky in shape and have a size of 1500 nm; the auxiliary agent system comprises the following components in parts by mass: 1.5 parts of dispersant cyclohexanol, 5.3 parts of binder polyvinyl pyrrolidone, 92.7 parts of diluent ethylene glycol and 0.5 parts of thermosetting adhesive furan resin.

[0131] Comparative Example 7

[0132] The present comparative example provides a silver solder paste, comprising the following components in parts by mass: 15 parts of coated silver particles and 85 parts of an auxiliary agent system; wherein the coated silver particles are obtained by coating silver particles with a corrosion inhibitor, succinic acid, and the silver particles are flaky in shape and 1500 nm in size; the auxiliary agent system comprises the following components in parts by mass: 1.5 parts of a dispersant cyclohexanol, 5.3 parts of a binder polyvinyl pyrrolidone, 92.7 parts of a diluent ethylene glycol and 0.5 parts of a thermosetting adhesive furan resin.

[0133] The preparation method of the silver solder paste of this comparative example comprises the following steps:

[0134] 1) Pickling and drying

[0135] The silver particles were pickled with a 5 mol / L sulfuric acid solution at room temperature for 5 min. After pickling, the particles were dried at 50° C. for 20 min in a nitrogen atmosphere to obtain pretreated silver particles.

[0136] 2) Coating

[0137] 40 parts of the above-mentioned pretreated silver particles, 1.2 parts of corrosion inhibitor succinic acid and 58.8 parts of anhydrous ethanol were mixed, and after mixing, ultrasonication was performed for 10 minutes, and centrifugation was performed to obtain coated silver particles.

[0138] 3) Preparation of auxiliary agent system

[0139] 1.5 parts of cyclohexanol as a dispersant, 5.3 parts of polyvinyl pyrrolidone as a binder, 92.7 parts of ethylene glycol as a diluent and 0.5 parts of furan resin as a thermosetting adhesive were mixed, and magnetically stirred at room temperature for 30 minutes to obtain an additive system.

[0140] 4) Preparation of silver solder paste

[0141] 15 parts of the coated silver particles obtained in step 2) were mixed with 85 parts of the auxiliary agent system obtained in step 3), and magnetic stirring was performed for 20 minutes to obtain a silver solder paste.

[0142] Test Example 1

[0143] The following method was used to test the coated copper sheets after thermal bonding and the coated copper sheets after sintering in each embodiment and comparative example:

[0144] Thermal paste shedding rate: the probability of natural falling of the coated copper sheet after testing 100 thermal pastes;

[0145] Average thrust of thermal paste: the average thrust when the coated copper sheets after 30 thermal pastes are pushed horizontally until they fall off;

[0146] Sintering average shear strength: Test the ratio of the average thrust when 30 sintered coated copper sheets are pushed horizontally until they fall off to the force-bearing area.

[0147] The results are shown in Table 1.

[0148] Table 1

[0149]

[0150] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A metal solder paste for connecting the front electrodes of a chip, characterized in that: The invention comprises the following components in parts by mass: 15-20 parts of coated metal particles and 80-85 parts of an auxiliary agent system; wherein the coated metal particles are obtained by coating metal particles with a coating agent, and the auxiliary agent system comprises the following components in parts by mass: 1.5-2.5 parts of a dispersant, 95.5-98 parts of a diluent and 0.5-2 parts of a thermosetting adhesive.

2. The metal solder paste according to claim 1, characterized in that: The metal particles are selected from silver particles or copper particles; Preferably, the coating agent is selected from at least one of polyvinyl pyrrolidone, polyvinyl alcohol and polyacrylic acid; Preferably, the thermosetting adhesive is selected from at least one of melamine formaldehyde resin, furan resin, polybutadiene resin and silicone resin; Preferably, the dispersant is selected from at least one of n-decanol, methanol, cyclohexanol and ethanol; Preferably, the diluent is selected from at least one of ethylene glycol, propylene glycol, glycerol, n-butanol, diethylene glycol, acetol and polyethylene glycol.

3. The method for preparing the metal solder paste according to claim 1 or 2, characterized in that: The steps include: S1: pickling and drying the metal particles to obtain pretreated metal particles; S2: mixing the pretreated metal particles with the coating agent and the organic solvent, ultrasonicating the mixture, and centrifuging the mixture to obtain coated metal particles; S3: mixing a dispersant, a diluent and a thermosetting adhesive according to parts by mass and stirring to obtain an additive system; S4: Mix the coated metal particles and the auxiliary agent system according to parts by mass and stir to obtain a metal solder paste.

4. The preparation method according to claim 3, characterized in that: In step S1, pickling is performed using a 3-5 mol / L sulfuric acid solution or a 1-2 mol / L hypophosphorous acid solution, and the pickling time is 5-15 min; drying is performed under an inert atmosphere, the drying temperature is 50-60° C., and the drying time is 20-40 min.

5. The preparation method according to claim 3, characterized in that: In step S2, the organic solvent is anhydrous ethanol; the mass ratio of the pretreated metal particles, the coating agent and the anhydrous ethanol is (4-5): (3-4): (1-3); and the ultrasonic time is 10-40 min.

6. A method for preparing a coated copper sheet for connecting the front electrode of a chip, characterized in that: The steps include: A) pre-treating and single-sided metallization treatment of the bare copper sheet to obtain a copper sheet with a single-sided metallization layer; B) uniformly coating the metal solder paste according to any one of claims 1 to 5 on the single-sided metallization layer of the copper sheet, and then drying it in an inert atmosphere or a reducing atmosphere to obtain a coated copper sheet with a pre-sintered metal film formed on the surface.

7. The preparation method according to claim 6, characterized in that: The pretreatment includes: soaking the bare copper sheet in dilute sulfuric acid solution, anhydrous ethanol and deionized water in sequence, repeating 2-3 times and then drying in an inert atmosphere; Preferably, the single-sided metallization layer is an Ag plating layer, a Ni / Ag plating layer or a Ni / Pd / Au plating layer; the thickness of the single-sided metallization layer is 1-3 μm; Preferably, the thickness of the pre-sintered metal film is 25-150 μm; Preferably, the heating rate during drying is 2-50° C. / min, the drying temperature is 100-180° C., and the drying time is 2-60 min.

8. A coated copper sheet for connecting the front electrode of a chip, characterized in that: Prepared according to the preparation method according to claim 6 or 7.

9. The method for connecting the coated copper sheet and the chip according to claim 8, characterized in that: The steps include: a) Place the chip on a heating platform and heat it to the thermal paste process temperature; b) The suction head is heated to the thermal bonding process temperature, and the coated copper sheet is pressed and bonded to the front side of the chip using the heated suction head, and then placed in a sintering furnace for sintering to obtain a power device packaging structure.

10. The connection method according to claim 9, characterized in that: In step a), the thermal bonding process temperature is 100-150°C; Preferably, in step b), the laminating pressure is 1-5 MPa, and the laminating time is 0.1-2 s; the sintering temperature is 200-300° C., the sintering pressure is 1-20 MPa, and the sintering time is 1-30 min.

Images