Preparation method of low-temperature high-thermal-conductivity nano-silver adhesive

Abstract

The invention discloses a preparation method of a low-temperature high-thermal-conductivity nano-silver adhesive, which comprises the following steps: dissolving a dispersing agent in a solvent, and uniformly stirring to form a stable dispersion liquid; high-purity silver powder is added into the dispersion liquid, a high-speed stirrer or an ultrasonic disperser is used for mixing to obtain the low-temperature high-thermal-conductivity nano-silver adhesive, and the average particle size of the high-purity silver powder is 20-150 nm. Compared with a traditional welding material, the low-temperature high-thermal-conductivity nano-silver adhesive has the advantages of being low in stress, low in thermal expansion coefficient, high in thermal conductivity, high in electric conductivity, large in bonding strength, low in halogen heteroion content, free of lead metal content and environmentally friendly in packaging application.

Description

Technical Field

[0001] The invention relates to the technical field of electronic power device packaging interface materials, in particular to a method for preparing a low-temperature and high-thermal-conductivity nano silver adhesive. Background Art

[0002] The third generation semiconductors represented by silicon carbide and gallium nitride have excellent electrical properties and are widely used in new energy vehicles, high-speed railways, deep space exploration and other fields. Silicon carbide and gallium nitride are usually used in relatively harsh high temperature or high radiation conditions, and during service, the bonding materials of semiconductor chips will be affected by mechanical vibration, thermomechanical stress, high-density current, etc., so there are very high requirements for the bonding strength, thermal conductivity and even thermal resistance of their packaging materials. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention provides a preparation method and application of a low-temperature and high-thermal-conductivity nano-silver adhesive.

[0004] In a first aspect, a method for preparing a low-temperature and high-thermal-conductivity nanosilver adhesive is provided, the preparation method comprising the following steps:

[0005] The dispersant is dissolved in a solvent and stirred evenly to form a stable dispersion; high-purity silver powder is added to the dispersion and mixed using a high-speed stirrer or an ultrasonic disperser to obtain the low-temperature and high-thermal-conductivity nano-silver adhesive, wherein the average particle size of the high-purity silver powder is 20nm-150nm.

[0006] In combination with the first aspect, in some embodiments of the first aspect, the ratio of the solvent, the dispersant, and the high-purity silver powder is 5:1:94.

[0007] In combination with the first aspect, in some embodiments of the first aspect, the dispersant is polyvinyl alcohol and / or acrylate, and the solvent is ethylene glycol and / or propylene glycol.

[0008] In combination with the first aspect, in some embodiments of the first aspect, the low-temperature and high-thermal-conductivity nanosilver adhesive is stored in an environment below -40°C, preferably, stored in an environment below -60°C.

[0009] In combination with the first aspect, in some embodiments of the first aspect, the average particle size of the high-purity silver powder is 50nm-100nm.

[0010] In the second aspect, an application of the low-temperature, high-thermal-conductivity nanosilver adhesive described in any one of the first aspects is provided, comprising: warming the low-temperature, high-thermal-conductivity nanosilver adhesive at room temperature; pre-treating the chip and the substrate; coating and positioning the low-temperature, high-thermal-conductivity nanosilver adhesive, comprising uniformly coating the low-temperature, high-thermal-conductivity nanosilver adhesive on the connection surface of the chip or the substrate, and setting the position of the chip and the substrate by a crystal bonding machine to ensure accurate alignment of the chip and the substrate; attaching the chip to the substrate, placing it in a high-temperature pressure sintering furnace, and sintering it at a sintering temperature of 280°C-350°C, so that the low-temperature, high-thermal-conductivity nanosilver adhesive forms a dense silver layer, thereby realizing metallurgical bonding between the chip and the substrate.

[0011] In combination with the second aspect, in some embodiments of the second aspect, the low-temperature and high-thermal-conductivity nano-silver adhesive has a temperature recovery time of greater than or equal to 60 minutes at room temperature.

[0012] In combination with the second aspect, in some embodiments of the second aspect, the pretreatment includes cleaning, degreasing, and roughening the surfaces of the chip and the substrate.

[0013] In combination with the second aspect, in some embodiments of the second aspect, the sintering temperature is 300°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic diagram of a low-temperature and high-thermal-conductivity nanosilver adhesive provided in an embodiment of the present application. DETAILED DESCRIPTION

[0015] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not 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.

[0016] Compared with traditional welding materials, silver has many characteristics such as high electrical and thermal conductivity, high melting point and high mechanical strength, while nano silver paste is regarded as the most promising new connection material due to its unique low-temperature sintering and high-temperature service performance. The use of nano silver particles can not only achieve low-temperature sintering, but also avoid the problem of intermetallic compound growth caused by excessively high temperatures, and has a good application prospect.

[0017] This application provides a method for preparing a low-temperature and high-thermal-conductivity nanosilver adhesive:

[0018] Dissolve the dispersant in the solvent and stir evenly to form a stable dispersion;

[0019] Add silver powder with a purity of more than 99% to the dispersion, and mix with a high-speed stirrer or an ultrasonic disperser to obtain the low-temperature and high-thermal-conductivity nanosilver adhesive.

[0020] Wherein, the average particle size of the high-purity silver powder is 20nm-150nm.

[0021] Compared with traditional welding materials, the low-temperature and high-thermal-conductivity nano-silver adhesive of the present application has the advantages of low stress, low thermal expansion coefficient, high thermal conductivity, high electrical conductivity, high bonding strength, low halogen impurity ion content, and lead-free metal content in packaging applications, which is green and environmentally friendly.

[0022] According to application requirements, during the mixing process using a high-speed stirrer or an ultrasonic disperser, the concentration of the silver nanoparticles in the solvent can be adjusted by adding an appropriate amount of solvent and dispersant, wherein the ratio of solvent: dispersant: high-purity silver powder is 3:1:96-7:1:92, with 5:1:94 being the optimal ratio.

[0023] The dispersant is used to ensure the dispersion stability of the silver nanoparticles in the solvent, prevent the nanoparticles from agglomerating, and ensure uniform sintering during the sintering process to achieve good thermal conductivity and bonding properties.

[0024] In some embodiments, the dispersant may be polyvinyl alcohol, acrylate, or the like.

[0025] In some embodiments, the solvent may be ethylene glycol, propylene glycol, or the like.

[0026] Preferably, the average particle size of the high-purity silver powder is 50nm-100nm.

[0027] Specifically, the low-temperature and high-thermal-conductivity nano-silver adhesive is a nano-silver paste with certain fluidity and viscosity.

[0028] It is understandable that the proportions and mixing conditions of the ingredients need to be precisely controlled during the preparation process, where the mixing conditions include the mixing order, mixing temperature, stirring speed, etc. At the same time, care must be taken to avoid the mixing of impurities so as not to affect the properties of the silver paste, such as thermal conductivity and bonding strength.

[0029] In some embodiments, the low-temperature and high-thermal-conductivity nanosilver adhesive is stored in an environment below -40°C, preferably, stored in an environment below -60°C.

[0030] Among them, low-temperature storage is mainly to maintain its performance, avoid component decomposition and extend shelf life. Low-temperature storage can ensure that the adhesive can provide optimal electrical and thermal conductivity when used, meeting the demanding requirements of high-precision electronic devices.

[0031] Specifically, the above-mentioned low-temperature and high-thermal-conductivity nano-silver adhesive can be applied to the scenario of fully sealed electronic component packaging.

[0032] The present application also provides an application of the low-temperature and high-thermal-conductivity nanosilver adhesive described in any one of the above items, including:

[0033] Returning the low-temperature and high-thermal-conductivity nanosilver adhesive to room temperature;

[0034] Pre-process the chip and substrate;

[0035] Applying and positioning the low-temperature and high-thermal-conductivity nanosilver adhesive, including uniformly applying the low-temperature and high-thermal-conductivity nanosilver adhesive on the connection surface of the chip or the substrate, and setting the position of the chip and the substrate by a die bonding machine to ensure accurate alignment of the chip and the substrate;

[0036] The chip is attached to the substrate, placed in a high-temperature pressure sintering furnace, and sintered at 280°C-350°C and a pressure of >20MPa, so that the low-temperature and high-thermal-conductivity nanosilver adhesive forms a dense silver layer to achieve metallurgical bonding between the chip and the substrate.

[0037] Among them, the purpose of temperature regeneration is to improve its operability, increase bonding strength and promote the sintering process. Through proper temperature regeneration treatment, the optimal performance of the adhesive can be ensured to meet the strict thermal management and electrical interconnection requirements in electronic devices.

[0038] Among them, pre-treatment of the chip and the substrate can improve the wettability and bonding strength between the silver paste and the connection surface.

[0039] In some embodiments, the low-temperature and high-thermal-conductivity nanosilver adhesive is warmed up at room temperature for more than 60 minutes.

[0040] In some embodiments, the pretreatment includes cleaning, degreasing, and roughening the surface of the chip and the substrate.

[0041] Preferably, the sintering temperature is 280°C-350°C. Preferably, the sintering temperature is 300°C.

[0042] In the following examples, the reagent information is shown in Table 1, and the experimental instruments used are commercially available unless otherwise stated.

[0043] Example 1

[0044] 0.5 g of dispersant polyvinyl alcohol was dissolved in 0.1 g of solvent ethylene glycol, and stirred evenly to form a stable dispersion. 9.4 g of high-purity silver powder with an average particle size of 20 nm-150 nm was added to the dispersion, and mixed using a high-speed stirrer or an ultrasonic disperser to obtain the low-temperature and high-thermal-conductivity nanosilver adhesive of Example 1.

[0045] Embodiment 2-5

[0046] The preparation methods of Examples 2-5 refer to Example 1, and the particle size of the nano silver powder and the mass of each component refer to Table 1.

[0047] Comparative Example 1-2

[0048] The preparation method of Comparative Example 1-2 is as shown in Example 1, and the particle size of the nano silver powder and the mass of each component are specifically shown in Table 1.

[0049] The test of thermal conductivity refers to GB / T 10294-2008 "Thermal conductivity test method - Determination of thermal conductivity". The average thermal resistance of the sintered interface layer is 3.3-5.1mm2 K / W. The larger the thermal resistance value, the worse the thermal conductivity.

[0050] The bonding strength test method is as follows: clean, degrease and roughen the surface of the chip and substrate, evenly coat the low-temperature and high-thermal conductivity nanosilver adhesive that has been warmed up at room temperature for 60 minutes on the connection surface of the chip, and set the position of the chip and the substrate through a crystal bonding machine to ensure the accurate alignment of the chip and the substrate; stick the chip coated with the low-temperature and high-thermal conductivity nanosilver adhesive on the substrate, place it in a sintering furnace, and sinter it at a certain temperature of 300°C. Among them, the connection area is 2.9mm×2.9mm. The shear strength of the joint interconnected by the low-temperature and high-thermal conductivity nanosilver adhesive is obtained by thrust machine (100kg) test, and the test process is based on the thrust test standard JESD22-B117A.

[0051] Table 1

[0052]

[0053] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0054] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a low-temperature and high-thermal-conductivity nanosilver adhesive, characterized in that: include: Dissolve the dispersant in the solvent and stir evenly to form a stable dispersion; Add high-purity silver powder to the dispersion and mix with a high-speed stirrer or an ultrasonic disperser to obtain the low-temperature and high-thermal-conductivity nanosilver adhesive. Wherein, the average particle size of the high-purity silver powder is 20nm-150nm.

2. The preparation method according to claim 1, characterized in that: The ratio of the solvent, the dispersant and the high-purity silver powder is 5:1:

94.

3. The preparation method according to claim 1, characterized in that: The dispersant is polyvinyl alcohol and / or acrylate.

4. The preparation method according to claim 1, characterized in that: The solvent is ethylene glycol and / or propylene glycol.

5. The preparation method according to claim 1, characterized in that: The low-temperature and high-thermal-conductivity nano-silver adhesive is stored in an environment below -40°C.

6. The preparation method according to claim 1, characterized in that: The average particle size of the high-purity silver powder is 50nm-100nm.

7. An application of the low-temperature and high-thermal-conductivity nanosilver adhesive according to any one of claims 1 to 6, comprising: Returning the low-temperature and high-thermal-conductivity nanosilver adhesive to room temperature; Pre-process the chip and substrate; Applying and positioning the low-temperature and high-thermal-conductivity nanosilver adhesive, including uniformly applying the low-temperature and high-thermal-conductivity nanosilver adhesive on the connection surface of the chip or the substrate, and setting the position of the chip and the substrate by a die bonding machine to ensure accurate alignment of the chip and the substrate; The chip is attached to the substrate, placed in a high-temperature pressure sintering furnace, and sintered at a sintering temperature of 280°C-350°C, so that the low-temperature and high-thermal-conductivity nanosilver adhesive forms a dense silver layer to achieve metallurgical bonding between the chip and the substrate.

8. The use according to claim 7, characterized in that: The low-temperature and high-thermal-conductivity nano-silver adhesive has a temperature recovery time of greater than or equal to 60 minutes at room temperature.

9. The use according to claim 7, characterized in that: The pretreatment includes cleaning, degreasing and roughening the surface of the chip and substrate.

10. The use according to claim 7, characterized in that: The sintering temperature is 300°C.

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