Pressureless sintering method of micron silver paste

Abstract

The invention provides a pressureless sintering method for micron silver paste. The pressureless sintering method comprises the following steps: preparing the micron silver paste; coating the micron silver paste between two to-be-connected connecting surfaces of a component; and the component is placed in a heating device, and the heating device emits infrared rays with a preset wavelength to heat the micron silver paste, so that a conductive silver layer is formed between the two connecting surfaces. The pressureless sintering method comprises the following steps: coating micron silver paste between two to-be-connected connecting surfaces of a component, placing the component coated with the micron silver paste in heating equipment, emitting infrared rays with a preset wavelength by the heating equipment to heat the micron silver paste, heating the micron silver paste before the component, and heating the micron silver paste after the component is heated. The solvent evaporated from the micron silver paste escapes through the gap between the two connecting surfaces, and a compact conductive silver layer can be formed between the two connecting surfaces of the component after sintering, so that the sintering cost is reduced, the sintering time is shortened, pressure is not required to be applied in the sintering process, and the quality of the component is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic packaging, and in particular to a pressureless sintering method of micron silver paste. Background Art

[0002] Third-generation semiconductor materials offer advantages such as wide bandgap widths, high breakdown electric field strength, and high electron saturation drift velocity. Power devices made from them exhibit low on-resistance, high voltage withstand, high switching frequency, and the ability to withstand high junction temperatures. These materials are more capable of meeting the electronics industry's demand for high-temperature, high-power, and high-frequency devices. To ensure the high performance and reliability of wide-bandgap semiconductor devices, the packaging process must adhere to stringent thermal, electrical, mechanical, and reliability constraints.

[0003] Chip attach is a critical step in the packaging process. Traditional interconnect materials, such as conductive adhesives and solder alloys, have melting temperatures below 250°C, making them incompatible with the application environment of wide-bandgap semiconductor devices. Silver sintering technology utilizes heating silver powder under a certain temperature and pressure to cause the particles to bond and sinter, forming a dense silver connection. Silver sintering is commonly used in electronic packaging, conductive connections, and microelectronic devices to achieve high-quality conductive connections.

[0004] Silver paste solders used for sintering are divided into nano silver paste solders and micro silver paste solders based on the size of the silver particles. Nano silver paste has a larger specific surface area and higher surface energy, and can be pressurelessly sintered at around 200 degrees Celsius, but the preparation cost of nano silver paste is relatively high. Micro silver paste is low-cost. The traditional sintering process involves sintering the micro silver paste and components in an oven. Due to the larger particle size and relatively small specific surface area of ​​micro silver paste, the sintering process requires higher temperatures and pressures. Summary of the Invention

[0005] In view of this, the present invention provides a pressureless sintering method for micron silver paste, which is used to solve the problem that the existing micron silver paste needs to be sintered under high temperature and high pressure during the sintering process, resulting in long sintering time and high sintering cost.

[0006] An embodiment of the present invention provides a pressureless sintering method for micron silver paste, comprising:

[0007] preparing micron silver paste;

[0008] Applying the micron silver paste between two connection surfaces of components to be connected;

[0009] The components are placed on a heating device, which emits infrared rays of a preset wavelength to heat the micron silver paste to form a conductive silver layer between the two connection surfaces.

[0010] According to an embodiment of the present invention, the step of the heating device emitting infrared rays of a preset wavelength to heat the micron silver paste includes:

[0011] In the first heating stage, the temperature is raised to a first preset temperature at a first preset heating rate;

[0012] In the first heat preservation stage, the temperature is kept at the first preset temperature for a first preset time;

[0013] In the second heating stage, the temperature is raised to a second preset temperature at a second preset heating rate;

[0014] In the second heat preservation stage, the second preset temperature is kept warm for a second preset time period.

[0015] According to an embodiment of the present invention, the first preset heating rate is 10-15°C / min;

[0016] The second preset heating rate is 25-30°C / min.

[0017] According to an embodiment of the present invention, the first preset temperature ranges from 125 to 150° C.;

[0018] The second preset temperature ranges from 210 to 250°C.

[0019] According to an embodiment of the present invention, the first preset duration is 13 to 18 minutes;

[0020] The second preset time length is 40 to 50 minutes.

[0021] According to an embodiment of the present invention, the step of preparing the micron silver paste includes:

[0022] obtaining silver particles of a preset particle size;

[0023] mixing the silver particles, dispersant, binder and solvent to form a mixed material;

[0024] The mixed material is stirred to obtain the micron silver paste.

[0025] According to an embodiment of the present invention, the silver particles are spherical in shape.

[0026] According to an embodiment of the present invention, the preset particle size is 1-6 μm.

[0027] According to an embodiment of the present invention, the infrared device emits multiple infrared rays of preset wavelengths to heat the micron silver paste.

[0028] According to an embodiment of the present invention, the preset wavelength ranges from 0.8 to 1.4 μm.

[0029] The pressureless sintering method of micron silver paste provided in an embodiment of the present invention can at least achieve the following technical effects: micron silver paste is coated between two connection surfaces of a component to be connected, the component coated with the micron silver paste is placed in a heating device, and the heating device emits infrared rays of a preset wavelength to heat the micron silver paste. The micron silver paste is heated before the component, and the solvent evaporated from the micron silver paste escapes through the gap between the two connection surfaces. After sintering, a dense conductive silver layer can be formed between the two connection surfaces of the component, which reduces the sintering cost, shortens the sintering time, and can achieve reliable connection of the components. No pressure needs to be applied during the sintering process, which is beneficial to ensuring the quality of the components. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0031] Figure 1 A flow chart schematically illustrates a method for pressureless sintering of a micron silver paste according to an embodiment of the present invention;

[0032] Figure 2 The figure schematically shows a temperature rise diagram of the sintering process according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to specific embodiments and the accompanying drawings. It is apparent that the embodiments described are only a portion of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are intended to fall within the scope of protection of the present invention.

[0034] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the presence of the features, steps, operations and / or components, but do not exclude the presence or addition of one or more other features, steps, operations or components.

[0035] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0036] Silver sintering is commonly used in electronic packaging, conductive connections, and microelectronic devices to achieve high-quality conductive connections. Silver sintering has the following advantages: high conductivity. Silver has excellent conductive properties. Silver sintering can achieve connections with low resistance and high current transmission capacity, which is suitable for high-frequency and high-frequency applications; low-temperature connection. Compared with other metal sintering technologies, silver sintering can achieve connections at relatively low temperatures, which helps to protect sensitive substrate materials or devices; excellent reliability. The connections formed by silver sintering have good mechanical strength and heat resistance, and can withstand temperature cycles and mechanical stress, ensuring the stability and reliability of the connection; wide applicability. The silver sintering process can be used for a variety of substrate materials, such as ceramics, semiconductors, glass, and plastics, and is suitable for various types of packaging and connection requirements; environmental protection. Compared with other connection methods, silver sintering does not contain toxic solder paste or chemicals, can meet the requirements of lead-free packaging, and is environmentally friendly.

[0037] Silver paste solders used for sintering are mainly divided into nano-silver paste and micron-silver paste. Nano-silver paste has a large specific surface area and high surface energy, and can be sintered without pressure at around 200°C. However, the preparation cost of nano-silver paste is relatively high. Due to the large particle size and relatively small specific surface area of ​​micron-silver paste, the traditional sintering process in an oven is used. This requires high sintering temperatures and long sintering times under certain pressure to ensure the bonding strength of components.

[0038] The present invention provides a pressureless sintering method for micron silver paste, which can realize sintering under low temperature and pressureless conditions, effectively shorten the sintering time, and reduce the sintering cost.

[0039] The following combination Figure 1 The pressureless sintering method of the micron silver paste according to the embodiment of the present invention is described.

[0040] like Figure 1 As shown, the pressureless sintering method of micron silver paste provided by the embodiment of the present invention includes:

[0041] Step 101: preparing micron silver paste;

[0042] Step 102: Applying micron silver paste between two connection surfaces of the component to be connected;

[0043] Step 103: Place the component on a heating device, which emits infrared light of a preset wavelength to heat the micron silver paste to form a conductive silver layer between the two connection surfaces.

[0044] The process of preparing micron silver paste includes obtaining silver particles of a preset particle size, mixing the silver particles, a dispersant, a binder and a solvent in a certain weight ratio to form a mixed material, and stirring the mixed material to prepare the micron silver paste.

[0045] The preparation process of silver particles is to mix silver nitrate, hydrazine carbonate, concentrated ammonia water and deionized water in a certain weight ratio. Because hydrazine carbonate is unstable, it decomposes to produce carbon dioxide and hydrazine. Hydrazine reacts with silver ammonia ions under strong alkaline conditions to reduce silver.

[0046] A 0.2 mol / L silver nitrate solution is prepared with deionized water, followed by the addition of 3 times the amount of concentrated ammonia. NaOH is then added to adjust the pH to 12-13, and a certain amount of polyvinyl pyrrolidone dispersant is added. A water bath is adjusted to a certain temperature, and hydrazine carbonate is added and mixed according to a predetermined addition time. The mixture is stirred at 300 rpm for 5 minutes to allow the reaction to proceed. After the reaction is complete, the mixture is centrifuged, and the filtered silver powder is then dried in a vacuum drying oven at 50 degrees Celsius for 5-8 hours to obtain ultrafine silver powder of a predetermined particle size, with the silver particles ranging from 1 to 6 microns.

[0047] The preparation process of micron silver paste is as follows: add 15 parts by weight of acetone to a container, then add 45 parts by weight of epoxy resin, stir until completely dissolved to obtain organic carrier A for standby use. Add 1 part by weight of polysilicone, 0.4 parts by weight of silane coupling agent, and 0.4 parts by weight of succinic acid to 10 parts by weight of acetone, stir and mix evenly to obtain mixture B for standby use. Add 28 parts by weight of micron silver powder to mixture B in multiple times, set the stirring speed to 500 revolutions per minute, and stir and disperse evenly to obtain mixture C; add organic carrier A to mixture C in multiple times, set the stirring speed to 1500 revolutions per minute, stir for 1 hour, and mix evenly to prepare micron silver paste.

[0048] After preparing the micron silver paste, it is applied to the components to be connected. For example, if the components include a substrate and a chip, the two connecting surfaces to be connected include the first connecting surface of the substrate and the second connecting surface of the chip. The micron silver paste is printed on the first connecting surface of the substrate using a screen or applied using a dispensing device. The chip is then bonded to the micron silver paste on the substrate, with the second connecting surface of the chip aligned with the first connecting surface of the substrate, ensuring a tight fit between the chip and the micron silver paste, with the micron silver paste adhering between the chip and the substrate.

[0049] The components are then placed in a heating device for sintering. The heating device can emit short-wave infrared rays of a preset wavelength, and use short-wave infrared rays to sinter the micron silver paste. Semiconductor materials have a high transmittance to short-wave infrared rays. Short-wave infrared rays penetrate the chip and directly heat the micron silver paste. The heating efficiency is high, and low-temperature sintering of micron silver paste solder can be achieved under pressureless conditions.

[0050] Infrared heating equipment and oven heating operate on different principles. Infrared lamp heating converts electrical energy into infrared radiation, directly causing molecular vibrations on the surface of the material being heated. This heats the surface of the material being heated, allowing for faster, localized heating and high efficiency. Oven heating heats the air through conduction and convection, requiring a longer time to fully heat the material and resulting in lower heating efficiency.

[0051] The heating device used in the present invention includes a housing, infrared lamps, and a control system. The housing comprises an internal cabin and an external housing. The cabin can be made of stainless steel, and the external housing can be made of stainless steel. The overall structure of the infrared heating device is compact, making it suitable for mounting small chips. For example, the dimensions of the heating device can be 850*850*426mm.

[0052] Multiple infrared lamps are distributed within the chamber. For example, three infrared lamps are spaced apart and emit infrared light with a wavelength range of 0.78 to 1.4 microns. The infrared lamps have a power of 1 kW and can reach a maximum heating temperature of 500°C. The control system includes a human-machine interface module, a temperature control module, and a controller. Both the human-machine interface module and the temperature control module are connected to the controller. The human-machine interface module facilitates setting various heating parameters of the heating equipment, while the temperature control module facilitates temperature control during the sintering process.

[0053] Infrared light can be divided into short-wave infrared, medium-wave infrared, and long-wave infrared based on its wavelength. Most semiconductor chips are nearly transparent to short-wave infrared, while micronized silver paste primarily absorbs short-wave infrared. Therefore, during the infrared sintering process, short-wave infrared light can penetrate the chip and directly heat the micronized silver paste, heating it before the chip and substrate, achieving higher heating efficiency. Furthermore, since the micronized silver paste is heated first, its temperature is higher than that of the external atmosphere, allowing the evaporated solvent to easily escape through the gap between the chip and substrate. As a result, the conductive silver layer formed between the chip and substrate after sintering has low porosity and high shear strength.

[0054] Gallium nitride and silicon have high transmittance for visible light (wavelengths of approximately 400-700nm), but their transmittance gradually decreases when the wavelength exceeds 700nm. Silver, on the other hand, has very low transmittance for short-wave infrared light (wavelengths of approximately 1-2.5μm), primarily exhibiting absorption characteristics. Taking both into consideration, short-wave infrared light with a wavelength of 1μm can be selected as the heating source.

[0055] After setting the heating parameters, turn on the heating equipment. The chip has a high transmittance to short-wave infrared rays. Short-wave infrared rays pass through the chip and directly heat the micron silver paste. During the sintering process, as the temperature rises, the organic solvent in the micron silver paste solder evaporates, the silver particles diffuse, migrate to and contact adjacent silver particles, and then the holes between the silver particles gradually close and shrink. Finally, the grains grow to form a dense conductive silver layer, realizing a reliable connection between the chip and the substrate.

[0056] The diffusion coefficient of silver particles during sintering follows the Arrhenius equation: Where Q is the activation energy and D0 is a coefficient determined by the atomic vibration frequency and jump distance.

[0057] Infrared radiation directly heats the micron silver paste through the chip, making the temperature of the micron silver paste higher than the temperature of the surrounding air, promoting the volatilization of organic solvents and moisture inside the micron silver paste, which is beneficial to reducing the porosity inside the conductive silver layer, thereby improving the bonding strength and conductivity of the conductive silver layer.

[0058] Shear strength testing showed that, at the same sintering temperature, the conductive silver layer obtained using infrared heating increased shear strength by 16.84% and conductivity by 28.43% compared to the traditional oven-fired silver sintering process. Furthermore, due to the higher heating efficiency of infrared radiation, the infrared sintering process only required approximately 90 minutes to achieve a conductive silver layer of the same bonding strength, resulting in a 33.3% improvement in sintering efficiency compared to the traditional oven-fired silver sintering process.

[0059] Compared with nano silver paste, micron silver paste has a lower preparation cost. The heating equipment sintered the nano silver paste coated between the chip and the substrate. The short-wave infrared rays passed through the chip to heat the micron silver paste. The organic solvent in the micron silver paste was fully volatilized, which effectively shortened the sintering time, reduced the sintering cost, reduced the porosity of the conductive silver layer, and achieved reliable connection of components.

[0060] Compared with the traditional sintering process that requires additional auxiliary pressure, the chip, substrate and micron silver paste are sintered by short-wave infrared rays. During the sintering process, no pressure is required and the chip will not be damaged, which is conducive to ensuring the quality of components.

[0061] In an embodiment of the present invention, micron silver paste is coated between two connecting surfaces of a component to be connected, and the component coated with the micron silver paste is placed in a heating device. The heating device emits infrared rays of a preset wavelength to heat the micron silver paste. The micron silver paste is heated before the component, and the solvent evaporated from the micron silver paste escapes through the gap between the two connecting surfaces. After sintering, a dense conductive silver layer can be formed between the two connecting surfaces of the component, which reduces the sintering cost, shortens the sintering time, and can achieve reliable connection of the components. No pressure needs to be applied during the sintering process, which is beneficial to ensuring the quality of the components.

[0062] like Figure 2 As shown, in an optional embodiment, the step of emitting infrared rays of a preset wavelength by an infrared device to heat the micron silver paste includes:

[0063] In the first heating stage, the temperature is raised to a first preset temperature at a first preset heating rate;

[0064] In the first heat preservation stage, the temperature is kept at a first preset temperature for a first preset time;

[0065] In the second heating stage, the temperature is raised to a second preset temperature at a second preset heating rate;

[0066] The second heat preservation stage is to keep the temperature at a second preset temperature for a second preset time.

[0067] Specifically, the process of heating the micron silver paste includes four stages: a first heating stage, a first heat preservation stage, a second heating stage, and a second heat preservation stage.

[0068] During the first heating stage, components coated with micronized silver paste are heated from room temperature to a first preset temperature at a first preset heating rate. During this first heating stage, the temperature is raised at a slower rate to ensure that the organic solvent in the micronized silver paste can fully evaporate. If the heating rate is too fast during this stage, some of the solvent in the micronized silver paste will not have enough time to evaporate, resulting in numerous pores in the sintered conductive silver layer and affecting the component's conductivity. The first preset heating rate range is 10-15°C / min.

[0069] The first preset temperature range is 125-150°C, for example, 130°C. The first preset temperature is maintained for a period of time to further volatilize the organic solvent in the micron silver paste, ensuring that all the organic solvent in the micron silver paste is volatilized. The first preset time range is 13-18 minutes.

[0070] In the second heating stage, the temperature in the cabin is raised from the first preset temperature to the second preset temperature at a second preset heating rate. In the second heating stage, the temperature is raised at a faster heating rate, and the second preset heating rate ranges from 25 to 30°C / min.

[0071] The second preset temperature range is 210-250°C, for example, 220°C. The second preset temperature is maintained for a period of time, preferably 40-50 minutes. During the second heating and holding stages, the silver particles diffuse, migrate toward and contact adjacent silver particles, and the pores between the silver particles gradually close and shrink, while the grains grow to form a dense conductive silver layer.

[0072] Compared with traditional sintering in an oven, the use of infrared equipment to sinter the micron silver paste has a low sintering temperature and a short sintering time. The connection between the chip and the substrate can be achieved at a lower temperature, which helps to protect sensitive base materials and components.

[0073] Pressure sintering subjects the material to simultaneous high temperature and pressure, using the heat and stress to promote the bonding of powder particles and densification of the material. Because infrared light can penetrate the chip to heat the micronized silver paste, the present sintering method eliminates the need for applying pressure to the chamber during the entire sintering process, resulting in low-temperature, pressureless sintering.

[0074] Furthermore, the heating device is provided with an air filling port, through which a protective gas is filled into the cabin. The protective gas may be nitrogen, and the nitrogen in the cabin plays a role in protecting the sintering environment in the cabin.

[0075] In an alternative embodiment, the silver particles are spherical in shape.

[0076] Specifically, to further enhance the bonding strength and conductivity of the conductive silver layer, spherical silver particles are used in the preparation of the micron silver paste. Spherical silver particles have a larger specific surface area and higher surface energy, making it easier to form interconnections between particles.

[0077] After shear strength testing, at the same sintering temperature, the conductive silver layer obtained using spherical micron silver paste solder had a shear strength increase of 23.62% and a conductivity increase of 26.38% compared with the triangular-shaped micron silver paste solder.

[0078] In an optional embodiment, the infrared device emits multiple beams of infrared rays with preset wavelengths to heat the micron silver paste.

[0079] Specifically, there are multiple infrared lamp tubes distributed in the cabin of the heating equipment. For example, there are three infrared lamp tubes distributed in the cabin, and the three infrared lamp tubes are arranged at intervals. During the sintering process, the three infrared lamp tubes emit three beams of infrared light with a wavelength of 1 micron to heat the components, which is beneficial to uniformly heat the micron silver paste between the chip and the substrate, and thus helps to improve the density of the conductive silver layer.

[0080] The sintering process of the micron silver paste is described in detail below using a specific embodiment.

[0081] The silver particles are prepared as follows: a 0.2 mol / L silver nitrate solution is prepared in deionized water, 3 times the amount of concentrated ammonia is added, and then NaOH is added to adjust the pH to 12-13. A certain amount of polyvinyl pyrrolidone dispersant is then added. A water bath is set to a certain temperature, and hydrazine carbonate is added and mixed according to a certain addition time. The mixture is stirred at 300 rpm for 5 minutes to allow for sufficient reaction. After the reaction is complete, the solution is centrifuged, and the filtered silver powder is then dried in a vacuum drying oven at 50 degrees Celsius for 5-8 hours to produce silver particles with a particle size of 1-6 microns.

[0082] The process for preparing the micron silver paste is as follows: 15 parts by weight of acetone is added to a container, and then 45 parts by weight of epoxy resin is added and stirred until completely dissolved to obtain an organic vehicle A for later use; 1 part by weight of polysilicone, 0.4 parts by weight of a silane coupling agent, and 0.4 parts by weight of succinic acid are added to 10 parts by weight of acetone, and stirred to mix evenly to obtain a mixture B for later use.

[0083] 28 parts by weight of micron silver powder was added to mixture B in three times, the stirring speed was set to 500 revolutions per minute, and the mixture was stirred and dispersed evenly to obtain mixture C; organic carrier A was added to mixture C in small amounts in five times, the stirring speed was set to 1500 revolutions per minute, the stirring time was 1 hour, and the mixture was mixed evenly to prepare micron silver paste.

[0084] The process for applying micron silver paste is as follows: The components to be connected include a substrate and a chip. The substrate and chip are cleaned. A dispensing device is used to apply micron silver paste to the first connection surface of the substrate. A scraper is then used to evenly apply the paste. The second connection surface of the chip is then bonded to the micron silver paste, forming a thick layer of micron silver paste between the substrate and chip.

[0085] The sintering process is as follows: Components coated with micron silver paste are placed in a heating device. The heating device is turned on, and multiple infrared lamps within the chamber emit 1-micron infrared rays, which penetrate the chip and heat the micron silver paste. A temperature control module controls heating parameters such as the first preset heating rate, the second preset heating rate, the first preset temperature, the second preset temperature, the first preset duration, and the second preset duration.

[0086] The temperature inside the chamber is raised from room temperature to a first preset temperature, which may be 130°C, at a heating rate of 13°C / min. The chamber is then maintained at this first preset temperature for a first preset time, which may be 15 minutes. During the first heating stage, the heating rate is slow, allowing the organic solvent in the micron silver paste to fully evaporate. The remaining organic solvent in the micron silver paste is further evaporated by maintaining the temperature at 130°C for 15 minutes, effectively removing the organic solvent from the micron silver paste.

[0087] After the first heat preservation stage, the temperature inside the chamber is raised from the first preset temperature to a second preset temperature, which may be 220°C, at a heating rate of 26°C / min. The chamber is then held at the second preset temperature for a second preset time, which may be 45 minutes. During the second heat preservation stage and the second heat preservation stage, the silver particles diffuse, migrate toward and contact adjacent silver particles, and the pores between the silver particles gradually close and shrink.

[0088] After the second heat preservation stage, it is naturally cooled from the second preset temperature of 220°C to room temperature, forming a dense conductive silver layer between the chip and the substrate, thereby achieving a reliable connection between the chip and the substrate.

[0089] The pressureless sintering method of micron silver paste provided by the present invention is to apply micron silver paste between the two connection surfaces of the component to be connected, and place the component coated with micron silver paste in a heating device. The heating device emits infrared rays of a preset wavelength to heat the micron silver paste. The infrared rays penetrate the chip and directly heat the micron silver paste, thereby realizing low-temperature, pressureless sintering and packaging connection of semiconductor components. The sintering process includes a first heating stage, a second heating stage, a third heating stage and a fourth heating stage. In the first heating stage, the heating rate is slow, and the organic solvent in the micron silver paste can be fully volatilized. The first heat preservation stage allows the residual organic solvent in the micron silver paste to be further volatilized. In the second heating stage and the second heat preservation stage, the silver particles diffuse, migrate to and contact adjacent silver particles, and the pores between the silver particles gradually close and shrink. After natural cooling, a dense conductive silver layer is obtained. The sintering method of the present invention reduces the sintering cost, shortens the sintering time, and reduces the porosity of the conductive silver layer. No pressure is required during the sintering process, which is conducive to ensuring the quality of the components.

[0090] The foregoing is merely a specific embodiment of the present invention, but the scope of protection of this application is not limited thereto. Any changes or substitutions made within the spirit and principles of the present invention shall be included within the scope of protection of this application. Therefore, the scope of protection of this application shall be subject to the scope of protection of the claims.

Claims

1. A pressureless sintering method for micron silver paste, characterized in that: include: preparing micron silver paste; Applying the micron silver paste between two connection surfaces of components to be connected; The components are placed on a heating device, which emits infrared rays of a preset wavelength to heat the micron silver paste to form a conductive silver layer between the two connection surfaces.

2. The pressureless sintering method of micron silver paste according to claim 1, characterized in that: The step of the heating device emitting infrared rays of a preset wavelength to heat the micron silver paste comprises: In the first heating stage, the temperature is raised to a first preset temperature at a first preset heating rate; In the first heat preservation stage, the temperature is kept at the first preset temperature for a first preset time; In the second heating stage, the temperature is raised to a second preset temperature at a second preset heating rate; In the second heat preservation stage, the second preset temperature is kept warm for a second preset time period.

3. The pressureless sintering method of micron silver paste according to claim 2, characterized in that: The first preset heating rate is 10-15°C / min; The second preset heating rate is 25-30°C / min.

4. The pressureless sintering method of micron silver paste according to claim 2, characterized in that: The first preset temperature ranges from 125 to 150°C; The second preset temperature ranges from 210 to 250°C.

5. The pressureless sintering method of micron silver paste according to claim 2, characterized in that: The first preset duration is 13 to 18 minutes; The second preset time length is 40 to 50 minutes.

6. The pressureless sintering method of micron silver paste according to claim 1, characterized in that: The steps of preparing the micron silver paste include: obtaining silver particles of a preset particle size; mixing the silver particles, dispersant, binder and solvent to form a mixed material; The mixed material is stirred to obtain the micron silver paste.

7. The pressureless sintering method of micron silver paste according to claim 6, characterized in that: The silver particles are spherical in shape.

8. The pressureless sintering method of micron silver paste according to claim 6, characterized in that: The preset particle size is 1 to 6 μm.

9. The pressureless sintering method of micron silver paste according to any one of claims 1 to 8, characterized in that: The infrared device emits multiple beams of infrared rays with preset wavelengths to heat the micron silver paste.

10. The pressureless sintering method of micron silver paste according to any one of claims 1 to 8, characterized in that: The preset wavelength ranges from 0.8 to 1.4 μm.

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