Preparation and application of Ag-In composite soldering paste for inhibiting electrochemical migration of sintered silver

Abstract

The invention relates to preparation and application of Ag-In composite soldering paste for inhibiting electrochemical migration of sintered silver, and belongs to the field of packaging and interconnection of wide bandgap semiconductor devices. The Ag-In composite soldering paste is formed by mixing micro-nano silver particles, nano indium particles, an alcohol organic solvent and a silane coupling agent, the mass percent of the silver soldering paste is 85%-95%, and the mass percent of the indium paste is 5%-15%. The Ag-In composite soldering paste can effectively prolong the electrochemical migration life to more than 1000 hours under the harsh conditions of high temperature (400 DEG C) and high external voltage (400V), and compared with pure silver soldering paste, the Ag-In composite soldering paste has the advantages that the shear strength attenuation is within 10%, and the mechanical and electromigration resistance reliability of a wide bandgap semiconductor device can be remarkably improved.

Description

Technical Field

[0001] This invention relates to the preparation and application of an Ag-In composite solder paste that inhibits the electrochemical migration of sintered silver, belonging to the field of wide bandgap semiconductor device packaging technology. Background Technology

[0002] Wide-bandgap semiconductor devices, represented by silicon carbide (SiC) and gallium nitride (GaN), possess characteristics such as high breakdown field strength, high cutoff frequency, high thermal conductivity, and good thermal stability, which contribute to the high-temperature reliable operation of electronic components. This also places higher demands on the packaging and interconnect materials of electronic components. Nano-silver solder paste, as a packaging and interconnect material with high electrical conductivity, high thermal conductivity, and oxidation resistance, features low-temperature sintering and high-temperature operation, and has attracted widespread attention in the high-reliability packaging and interconnection of wide-bandgap semiconductor devices.

[0003] However, under high temperature and high electric field conditions, sintered silver is highly susceptible to electrochemical migration, forming dendritic crystals that conduct electricity, leading to short-circuit failure of the device. Typically, sintered silver first oxidizes at the anode, generating the intermediate product silver oxide. At high temperatures, silver oxide decomposes into silver ions and oxygen ions. Under the influence of an applied electric field, the silver ions migrate from the anode to the cathode, where they gain electrons to form metallic silver, which then deposits near the cathode to form silver bridges. Therefore, improving the resistance of sintered silver to electrochemical migration is crucial for achieving reliable high-temperature operation of wide-bandgap semiconductor devices. Summary of the Invention

[0004] The purpose of this invention is to suppress electrochemical migration short-circuit failure of sintered silver package interconnects in wide bandgap semiconductor devices. An Ag-In composite solder paste that suppresses electrochemical migration is prepared, which extends the electrochemical migration lifetime to more than 1000 hours under harsh conditions of high temperature (400℃) and high applied voltage (400V). Compared with pure silver solder paste, the shear strength of Ag-In composite solder paste is reduced by less than 10%.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides a silver solder paste comprising micro / nano silver particles, nano-indium particles, an alcohol-based organic solvent, and a silane coupling agent. The micro / nano silver particles and the alcohol-based organic solvent are mixed uniformly at a mass ratio of 4:1 to 5:1 to obtain the silver solder paste. The nano-indium particles and the silane coupling agent are mixed uniformly at a mass ratio of 2:1 to 3:1 to obtain an indium paste. The indium paste is then added to the silver solder paste, followed by ultrasonic vibration and high-speed stirring to ensure uniform mixing, resulting in Ag-In solder pastes with different doping ratios. As a preferred embodiment of the Ag-In composite solder paste of the present invention, the mass percentage of silver solder paste in the Ag-In composite solder paste is 85% to 95%, and the mass percentage of indium paste is 5% to 15%.

[0007] During the sintering process, the micro- and nano-silver particles in the Ag-In composite solder paste of the present invention react with the nano-indium particles to form Ag-In intermetallic compounds, thereby effectively inhibiting the oxidation of the micro- and nano-silver particles and improving the electrochemical migration lifetime of the sintered solder paste; in addition, the Ag-In intermetallic compounds have high bonding strength and can effectively suppress the decrease in shear strength caused by the introduction of nano-indium particles.

[0008] Secondly, the present invention provides a method for preparing the above-mentioned silver solder paste, comprising the following steps:

[0009] (1) Nano silver particles (100-500 nm) and micro silver particles (1000-1500 nm) are uniformly mixed to obtain micro-nano silver particles, wherein the mass fraction of nano silver particles is 70-85% and the mass fraction of micro silver particles is 15-30%.

[0010] (2) Mix the micro-nano silver particles and terpineol (α-terpineol, β-terpineol, γ-terpineol) evenly, wherein the mass ratio of micro-nano silver particles to alcohol organic solvent is 4:1 to 5:1, to obtain silver solder paste.

[0011] (3) Mix the nano-indium particles and methylsilane coupling agent evenly, wherein the mass ratio of nano-indium particles to silane coupling agent is 2:1 to 3:1, to obtain indium paste;

[0012] (4) At room temperature, indium paste is added to silver solder paste, followed by ultrasonic vibration and high-speed stirring to mix the two evenly, so as to obtain Ag-In solder paste with different doping ratios.

[0013] (5) In the obtained Ag-In composite solder paste, the mass percentage of silver solder paste is 85% to 95%, and the mass percentage of indium paste is 5% to 15%.

[0014] Thirdly, this invention provides the application of the above-mentioned Ag-In composite solder paste in wide-bandgap semiconductor device package interconnect structures, including the following steps:

[0015] (1) Place the chip and substrate in alcohol and ultrasonically clean for 3-5 minutes to remove surface dirt. Then use a vacuum drying oven to dry at 30-60℃ for 20 minutes to allow the alcohol on the substrate surface to fully evaporate.

[0016] (2) Coat the cleaned substrate surface with Ag-In composite solder paste with a thickness of 50-80 μm;

[0017] (3) Place the cleaned chip on a substrate coated with Ag-In composite solder paste and attach it to the solder paste coating surface to form a sandwich structure;

[0018] (4) Place the sandwich structure obtained in step (3) in a sintering furnace, sinter at a temperature of 250-300°C, hold for 30-60 minutes, and allow to cool naturally to room temperature after sintering to obtain the encapsulated interconnect sample.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: the Ag-In composite solder paste of the present invention extends the electrochemical migration life to more than 1000 hours under harsh conditions of high temperature (400℃) and high applied voltage (400V), and the shear strength of the Ag-In composite solder paste decreases by less than 10% compared with pure silver solder paste. Attached Figure Description

[0020] Figure 1 This is a silver bridge diagram of the electromigration of the Ag-In composite solder paste of the present invention;

[0021] Figure 2 This is a scanning electron microscope image of the Ag-In composite solder paste sintered body of the present invention. Detailed Implementation

[0022] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments and comparative examples. The purpose of this description is to provide a detailed understanding of the invention, not to limit its scope. All other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention. Unless otherwise specified, the experimental reagents and instruments involved in the implementation of this invention are commonly used reagents and instruments.

[0023] Example 1

[0024] (1) The nano silver particles and the micro silver particles are uniformly mixed to obtain micro-nano silver particles, wherein the mass fraction of the nano silver particles is 70% and the mass fraction of the micro silver particles is 30%.

[0025] (2) Mix the micro-nano silver particles and α-terpineol evenly, wherein the mass ratio of micro-nano silver particles to alcohol organic solvent is 4:1, to obtain silver solder paste.

[0026] (3) Mix the nano-indium particles and methylsilane coupling agent evenly, wherein the mass ratio of nano-indium particles to silane coupling agent is 2:1, to obtain indium paste;

[0027] (4) At room temperature, indium paste is added to silver solder paste, followed by ultrasonic vibration and high-speed stirring to mix the two evenly. The mass percentage of silver solder paste is 85% and the mass percentage of indium paste is 15%.

[0028] (5) Place the chip and substrate in alcohol and ultrasonically clean for 3-5 minutes to remove surface dirt, and then use a vacuum drying oven to dry them so that the alcohol on the substrate surface can be fully evaporated.

[0029] (6) Coat the cleaned substrate with silver solder paste and Ag-In composite solder paste with a thickness of 80μm, and place the cleaned chip on the substrate coated with solder paste to form a sandwich structure.

[0030] (7) The sandwich structure obtained in step (6) is placed in a sintering furnace. The sintering temperature is 300℃ and the sintering time is 60min. After sintering, it is naturally cooled to room temperature to obtain the encapsulated interconnect sample. The shear strength of the silver solder paste and Ag-In composite solder paste encapsulated interconnect sample is 35±2MPa and 31±2MPa, respectively.

[0031] (8) The prepared silver solder paste and Ag-In composite solder paste were sintered at 300℃ for 60 min to obtain electrochemical migration lifetime test samples. Under the high temperature condition of 400℃, a voltage of 400V was applied to conduct electromigration experiments. The failure lifetime of the silver solder paste was 370±20 min and the failure lifetime of the Ag-In composite solder paste was 1139±20 min.

[0032] Example 2

[0033] (1) The nano silver particles and the micro silver particles are uniformly mixed to obtain micro-nano silver particles, wherein the mass fraction of the nano silver particles is 85% and the mass fraction of the micro silver particles is 15%.

[0034] (2) Mix the micro-nano silver particles and α-terpineol evenly, wherein the mass ratio of micro-nano silver particles to alcohol organic solvent is 5:1, to obtain silver solder paste.

[0035] (3) Mix the nano-indium particles and methylsilane coupling agent evenly, wherein the mass ratio of nano-indium particles to silane coupling agent is 3:1, to obtain indium paste;

[0036] (4) At room temperature, indium paste is added to silver solder paste, followed by ultrasonic vibration and high-speed stirring to mix the two evenly. The mass percentage of silver solder paste is 95% and the mass percentage of indium paste is 5%.

[0037] (5) Place the chip and substrate in alcohol and ultrasonically clean for 3-5 minutes to remove surface dirt, and then use a vacuum drying oven to dry them so that the alcohol on the substrate surface can be fully evaporated.

[0038] (6) Coat the cleaned substrate with silver solder paste and Ag-In composite solder paste with a thickness of 80μm, and place the cleaned chip on the substrate coated with solder paste to form a sandwich structure.

[0039] (7) The sandwich structure obtained in step (6) is placed in a sintering furnace. The sintering temperature is 250℃ and the sintering time is 60min. After sintering, it is naturally cooled to room temperature to obtain the encapsulated interconnect sample. The shear strength of the silver solder paste and Ag-In composite solder paste encapsulated interconnect sample is 39±2MPa and 36±2MPa, respectively.

[0040] (8) The prepared silver solder paste and Ag-In composite solder paste were sintered at 250℃ for 60 min to obtain electrochemical migration lifetime test samples. Under the high temperature of 400℃, a voltage of 400V was applied to conduct electromigration experiments. The failure lifetime of the silver solder paste was 420±20 min and the failure lifetime of the Ag-In composite solder paste was 1276±20 min.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. An Ag-In composite solder paste to inhibit sintered silver electrochemical migration, characterized in that, The silver soldering paste is mixed by micro-nano silver particles with an average particle size of 100-1500 nm, nano-indium particles with an average particle size of 50-150 nm, an alcohol organic solvent, and a silane coupling agent.

2. The Ag-In composite solder paste of claim 1, wherein, The micro-nano silver particles are mixed by 70-85% nano silver particles (100-500 nm) and 15-30% micro silver particles (1000-1500 nm) in mass fraction.

3. The Ag-In composite solder paste of claim 1, wherein, The alcohol organic solvent is a pine oil alcohol, including alpha-pine oil alcohol, beta-pine oil alcohol, and gamma-pine oil alcohol.

4. The Ag-In composite solder paste of claim 1, wherein, The silane coupling agent is a methyl silane coupling agent.

5. The Ag-In composite solder paste of claim 1, wherein, The method comprises the following steps: S1: uniformly mixing micro-nano silver particles and an alcohol organic solvent at room temperature to obtain a silver soldering paste; S2: uniformly mixing nano-indium particles and a silane coupling agent at room temperature to obtain an indium paste body; S3: adding the indium paste body obtained in step S2 into the silver soldering paste obtained in step S1, and then ultrasonically oscillating and high-speed stirring to uniformly mix the two to obtain an Ag-In soldering paste with different doping ratios.

6. The Ag-In composite solder paste of claim 1, wherein, The mass ratio of the micro-nano silver particles to the alcohol organic solvent is 4:1-5:1, and the mass ratio of the nano-indium particles to the silane coupling agent is 2:1-3:

1.

7. The Ag-In composite solder paste of claim 1, wherein, The mass percentage of the silver soldering paste in the Ag-In composite soldering paste is 85%-95%, and the mass percentage of the indium paste body is 5%-15%.

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