Low temperature sintered metal solder paste and method of making and use thereof

Abstract

The application discloses a low-temperature sintered metal solder paste and a preparation method and application thereof, and comprises the following steps: A. adding metal salt, sintering aids and reducing agent into a solvent, and obtaining a low-temperature sintered metal suspension after reaction; wherein the low-temperature sintered metal suspension contains metal nanoparticles, and the sintering temperature of the metal nanoparticles is greater than 300 DEG C; B. concentrating the low-temperature sintered metal suspension in a vacuum environment, and obtaining a low-temperature sintered metal solder paste; wherein the sintering temperature of the low-temperature sintered metal solder paste is 130-240 DEG C. The preparation method of the low-temperature sintered metal solder paste is simple, and the operability is strong; by adding sintering aids into the formula, the obtained metal solder paste has high shear strength and conductivity under the premise of realizing low-temperature sintering.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electronic manufacturing technology, in particular to a low-temperature sintering metal solder paste and a preparation method and application thereof. BACKGROUND

[0002] In recent years, with the rapid development of integrated circuit technology, the internal structure of the chip is increasingly miniaturized and complex, and the requirements for interconnection materials have reached an unprecedented level. When the traditional metal solder paste is used as an interconnection material, its sintering temperature is relatively high, and due to the difference in the thermal expansion coefficient of the substrate, chip and solder paste, a large thermal stress will be generated in the interconnection device formed by the substrate, chip and solder paste during high-temperature sintering, thereby reducing the mechanical properties of the interconnection device, especially the shear strength. In addition, during high-temperature sintering, the metal particles in the metal solder paste will undergo phase transition, oxidation or grain coarsening, etc., which will reduce the electrical conductivity of the interconnection device.

[0003] In order to solve the problems of shear strength reduction and electrical conductivity reduction caused by the high sintering temperature of the metal solder paste, the industry has adopted a solution of using a thermal conductive adhesive as an interconnection material. Specifically, the curing temperature of the thermal conductive adhesive is generally low (below 150℃), which can effectively avoid the influence of high temperature on the chip in the interconnection process, but due to the insulating property of the base resin of the thermal conductive adhesive, its electrical conductivity is poor, although it can be improved by adding conductive fillers (such as metal particles and carbon black, etc.), but the improvement of electrical conductivity achieved by the above means is often limited. At the same time, due to the high thermal expansion coefficient of the base resin and the relatively low thermal conductivity, a larger thermal stress will be generated in the interconnection device formed by the substrate, chip and thermal conductive adhesive during the curing process, which will reduce the shear strength of the interconnection device. That is, the use of conductive adhesive as an interconnection material in the prior art can reduce the interconnection temperature, but it still cannot meet the requirements of shear strength and electrical conductivity of the interconnection device. SUMMARY

[0004] The present application aims to provide a preparation method of a low-temperature sintering metal solder paste, which is simple and easy to operate. By adding a sintering aid to the formula, the obtained metal solder paste has high shear strength and electrical conductivity under the premise of low-temperature sintering, thereby overcoming the shortcomings of the prior art.

[0005] Another object of the present application is to provide a low-temperature sintering metal solder paste prepared by the above preparation method, which not only can be sintered at low temperature, but also has excellent shear strength and electrical conductivity.

[0006] The third object of the present application is to provide an application of a low-temperature sintering metal solder paste, which is applied to the preparation of an interconnection device to ensure that the obtained interconnection device has good shear strength and electrical conductivity.

[0007] To achieve the above object, the present application adopts the following technical solutions:

[0008] A method for preparing a low-temperature sintered metal solder paste, comprising the following steps:

[0009] A. adding a metal salt, a sintering aid and a reducing agent into a solvent to obtain a low-temperature sintered metal suspension after reaction; wherein the low-temperature sintered metal suspension contains metal nanoparticles, and the sintering temperature of the metal nanoparticles is > 300℃;

[0010] B. obtaining a low-temperature sintered metal solder paste after concentrating the low-temperature sintered metal suspension in a vacuum environment; wherein the sintering temperature of the low-temperature sintered metal solder paste is 130-240℃.

[0011] Further, in step A, the molar ratio of the metal salt to the reducing agent is 1:(1-10); and the molar ratio of the metal salt to the sintering aid is 1:(0.001-0.05).

[0012] Further, in step A, the particle size of the metal nanoparticles is 80-1200nm.

[0013] Further, in step A, the metal salt is any one of copper salt and silver salt;

[0014] The sintering aid includes any one or a combination of (BiO)2CO3, Bi(OH)3, Bi(C2H3O2)3, Bi2O3, Bi(NO3)3, Bi2(SO4)3, TiO2, Bi, Ce.

[0015] Further, in step A, the copper salt is any one of copper acetate, copper hydroxide, copper formate, copper carbonate, copper bicarbonate, copper acetylacetonate or copper oxalate;

[0016] The silver salt is any one of silver acetate, silver hydroxide, silver formate, silver carbonate, silver bicarbonate, silver acetylacetonate or silver oxalate;

[0017] The reducing agent is any one or a combination of hydrazine hydrate, ascorbic acid, glucose, phenylhydrazine and citric acid;

[0018] The solvent is any one or a combination of water, toluene, diethyl ether, ethyl acetate, ethanol, ethylene glycol, diethylene glycol, dipropylene glycol, glycerol, acetone, glycerol, terpineol and polyethylene glycol.

[0019] Further, in step A, the reaction temperature of the reaction is 15-100℃, and the reaction time is 5-180min.

[0020] Further, in step B, the content of the nano-metal particles in the low-temperature sintered metal solder paste is 20-99% by mass percentage.

[0021] Further, step A specifically comprises:

[0022] A1. adding a metal salt and a sintering aid into a partial amount of solvent, and stirring to obtain a first mixture;

[0023] A2. adding a reducing agent into the remaining amount of solvent, and stirring to obtain a second mixture;

[0024] A3. reacting the first mixture and the second mixture to obtain a low-temperature sintered metal suspension.

[0025] A low-temperature sintered metal solder paste is prepared by using the above-mentioned method for preparing a low-temperature sintered metal solder paste.

[0026] The application of a low-temperature sintered metal solder paste in preparing an interconnection device uses the above-mentioned low-temperature sintered metal solder paste, and comprises the following steps: coating the low-temperature sintered metal solder paste on a substrate; covering an interconnection chip on the surface of the coated low-temperature sintered metal solder paste; and sintering under the conditions of a sintering temperature of 130-240℃ and a sintering pressure of 0-50Mpa to obtain an interconnection device.

[0027] The technical solution provided by the application can have the following beneficial effects:

[0028] 1. In the technical solution, the metal salt is reduced into nano-metal particles by using a reducing agent, and the nano-metal particles have the characteristics of easy aggregation and short diffusion distance, so that the metal solder paste prepared by using the nano-metal particles has a low sintering temperature, which not only reduces the sintering energy consumption of the metal solder paste and realizes green sintering, but also avoids the technical problem that the high sintering temperature of the metal solder paste easily affects the shear strength and conductivity of the metal solder paste, thereby ensuring the shear strength and conductivity of the metal solder paste.

[0029] 2. In the technical solution, the sintering aid is added, which is beneficial to reducing the sintering temperature of the metal solder paste, and the sintering aid can provide the shear strength and conductivity of the metal solder paste through the mutual cooperation of the effects of reducing the sintering temperature, providing additional surface active sites, and promoting diffusion. DETAILED DESCRIPTION

[0030] The technical solution provides a method for preparing a low-temperature sintered metal solder paste, which comprises the following steps:

[0031] A. adding metal salt, sintering aid and reducing agent into solvent, and obtaining low-temperature sintered metal suspension after reaction; wherein the low-temperature sintered metal suspension contains metal nanoparticles, and the sintering temperature of the metal nanoparticles is > 300℃;

[0032] B. obtaining low-temperature sintered metal paste after concentrating the low-temperature sintered metal suspension in vacuum environment; wherein the sintering temperature of the low-temperature sintered metal paste is 130-240℃.

[0033] In order to solve the technical problem that the existing technology has low curing temperature, but poor shear strength and conductivity, the technical solution provides a preparation method of low-temperature sintered metal paste. By simplifying the preparation steps, controlling the preparation conditions, using reducing agent to reduce metal salt into nano metal particles, and adding sintering aid to the metal paste formula, the obtained metal paste has high shear strength and conductivity under the premise of low-temperature sintering, so as to meet the actual use requirement.

[0034] Specifically, in order to solve the technical problem of high sintering temperature of metal paste, the industry uses thermal conductive adhesive as interconnection material. However, the existing technology uses conductive adhesive as interconnection material, which can reduce the interconnection temperature, but still cannot meet the demand of interconnection device for shear strength and conductivity. The technical solution first uses reducing agent to reduce metal salt into nano metal particles. The particle size of nano metal particles is extremely small, and has high surface energy and surface activity. The above high surface energy and surface activity makes nano metal particles more easily aggregate when they contact each other, promotes the sintering of nano metal particles, and makes nano metal particles have lower sintering temperature. The sintering temperature of metal paste depends on the sintering temperature of nano metal particles, so the lower sintering temperature of nano metal particles makes the metal paste prepared by using nano metal particles have lower sintering temperature. In addition, compared with the larger metal particles in traditional metal paste, the diffusion distance between nano metal particles is shorter, which also makes the metal paste prepared by using nano metal particles sinter and densify at lower temperature. That is, in the technical solution, by using reducing agent to reduce metal salt into nano metal particles, and using the characteristics of easy aggregation and short diffusion distance of nano metal particles, the metal paste prepared by using nano metal particles has lower sintering temperature, which not only reduces the sintering energy consumption of metal paste and realizes green sintering, but also avoids the technical problem that high sintering temperature of metal paste easily affects its shear strength and conductivity, so as to ensure its shear strength and conductivity.

[0035] Secondly, although the nano metal particles have a lower sintering temperature due to the characteristics of easy aggregation and short diffusion distance, the sintering temperature of the metal nano particles is generally higher than 300°C, so the sintering temperature of the metal solder paste is also > 300°C. The above sintering temperature range still has a risk of oxidation of the nano metal particles. When the nano metal particles are oxidized to metal oxides, the metal oxides will hinder sintering because the metal oxides have a higher melting point than the nano metal particles, so that the metal oxides and the nano metal particles themselves are not easy to sinter together, resulting in a relatively loose solder sintered body formed after sintering of the metal solder paste, thereby reducing the shear strength and conductivity, and still failing to meet the requirements of high shear strength and conductivity in application sites.

[0036] In order to further reduce the sintering temperature of the metal solder paste, a sintering aid is added to the metal solder paste formula in the technical solution, which reduces the energy threshold required for sintering of the nano metal particles by using the activation of the sintering aid, greatly reduces the sintering temperature of the metal solder paste, and realizes sintering in the temperature range of 130-240°C. Not only does it greatly reduce the sintering energy consumption of the metal solder paste and realize green sintering, but it also effectively avoids the oxidation of the nano metal particles at high sintering temperatures, which hinders sintering and affects the shear strength and conductivity. Further, the sintering aid can provide additional surface active sites for the nano metal particles during sintering, promote the interaction and combination between the nano metal particles, and effectively improve the density of the solder sintered body formed after sintering of the metal solder paste, thereby improving the shear strength and conductivity of the metal solder paste. In addition, the sintering aid also helps the uniform dispersion of the metal nano particles in the metal solder paste, avoids the agglomeration of the metal nano particles, and makes it easier for the metal nano particles to form a dense solder sintered body during sintering, which is also beneficial to improving the shear strength and conductivity of the metal solder paste. That is, by adding the sintering aid in the technical solution, it is not only beneficial to reducing the sintering temperature of the metal solder paste, but also through the multiple functions of reducing the sintering temperature by the sintering aid, providing additional surface active sites and promoting diffusion, to provide the shear strength and conductivity of the metal solder paste.

[0037] Again, in step A of the technical solution, the metal salt, sintering aid and reducing agent are added into the solvent, that is, the metal nanoparticles generated in the process of reducing the metal salt into metal nanoparticles are surrounded by the solvent, which reduces the possibility of the metal nanoparticles contacting with the external air and being oxidized, and is conducive to ensuring the performance of the metal solder paste. In addition, in step B of the technical solution, the low-temperature sintering metal suspension is concentrated in a vacuum environment, which also reduces the possibility of the metal nanoparticles in the low-temperature sintering metal suspension being oxidized in the concentration process, and is also conducive to ensuring the performance of the metal solder paste.

[0038] Finally, the preparation method of the metal solder paste in the prior art is generally a liquid phase reduction method. The preparation method of the metal solder paste prepared by the liquid phase reduction method generally comprises the following steps: (1) mixing a precursor metal salt, a reducing agent, a dispersing agent or a protective agent and the like in a liquid phase to obtain a nano metal particle liquid phase; (2) separating the liquid phase and the nano metal particle liquid phase; and (3) preparing a metal solder paste. However, the above step (2) comprises multiple washing and separation of the nano metal particles, which not only leads to a very complicated preparation process, but also causes the nano metal particles to be exposed to the air multiple times, thereby aggravating the agglomeration and oxidation of the nano metal particles. In the technical solution, the preparation of the metal solder paste is realized by two steps of step A (reduction reaction) and step B (vacuum concentration), and the nano metal particles do not need to be separately subjected to centrifugation, washing and drying and the like, which not only greatly simplifies the preparation process of the metal solder paste, but also reduces the possibility of the nano metal particles being exposed to the air and easily agglomerated and oxidized, thereby ensuring the performance of the metal solder paste.

[0039] Preferably, in step B, the concentration method comprises any one of centrifugal separation, evaporation concentration and drying concentration.

[0040] The technical solution limits the concentration method to multiple methods, which is conducive to selecting a suitable centrifugal method according to actual needs and improving the flexibility of the concentration method.

[0041] Preferably, in step B, the concentration method is centrifugal separation, the speed of the centrifugal separation is 8000-12000 rpm, and the centrifugal time is 1-30 min.

[0042] The technical solution preferably limits the concentration method to centrifugal separation and limits the speed and time of the centrifugal separation, which is conducive to improving the concentration effect and thereby ensuring the performance of the metal solder paste.

[0043] Further, in step A, the molar ratio of the metal salt to the reducing agent is 1:(1-10), and the molar ratio of the metal salt to the sintering aid is 1:(0.001-0.05).

[0044] When the molar ratio of the metal salt to the reducing agent is too low, the metal salt cannot be completely reduced into nano-metal particles, which is not conducive to ensuring the performance of the metal solder paste; when the molar ratio of the metal salt to the reducing agent is too high, the production cost is too high, causing unnecessary waste. Therefore, by limiting the molar ratio of the metal salt to the reducing agent, the performance of the metal solder paste is ensured at a lower cost.

[0045] When the molar ratio of the metal salt to the sintering aid is too low, the content of the sintering aid is too high, which easily affects the conductivity of the metal solder paste; when the content of the sintering aid is too low, the effect of reducing the sintering temperature of the metal solder paste is limited. Therefore, by limiting the molar ratio of the metal salt to the sintering aid, the performance of the metal solder paste is ensured under the premise of reducing the sintering temperature of the metal solder paste.

[0046] Preferably, the molar ratio of the metal salt to the reducing agent is 1:(2-8).

[0047] By further limiting the molar ratio of the metal salt to the reducing agent, not only can the metal salt be completely reduced into nano-metal particles, but even if the nano-metal particles are oxidized into metal oxides during the preparation process, the metal oxides can also be reduced as much as possible, thereby more favorably ensuring the performance of the metal solder paste.

[0048] Further, in step A, the particle size of the metal nanoparticles is 80-1200 nm.

[0049] The smaller the particle size of the metal nanoparticles, the smaller the sintering energy required, but when the particle size of the metal nanoparticles is too small, the metal nanoparticles are easily oxidized and agglomerated, resulting in an increase in the sintering temperature of the metal solder paste and a decrease in the performance of the metal solder paste; when the particle size of the metal nanoparticles is too large, the sintering temperature of the metal solder paste is easily increased. Therefore, by limiting the particle size of the metal nanoparticles to 80-1200 nm in the present technical solution, the performance and sintering temperature of the metal solder paste are favorably ensured.

[0050] Further, in step A, the metal salt is any one of a copper salt and a silver salt;

[0051] The sintering aid includes any one or a combination of multiple of (BiO)2CO3, Bi(OH)3, Bi(C2H3O2)3, Bi2O3, Bi(NO3)3, Bi2(SO4)3, TiO2, Bi, and Ce.

[0052] Since both the copper salt and the silver salt are low in price, and the nano-copper particles obtained by reducing the copper salt and the nano-silver particles obtained by reducing the silver salt both have good conductivity. Therefore, the metal salt is limited to be any one of a copper salt and a silver salt in the present technical solution.

[0053] Further, since (BiO)2CO3, Bi(OH)3, Bi(C2H3O2)3, Bi2O3, Bi(NO3)3, Bi2(SO4)3, TiO2, Bi, Ce can promote low-temperature sintering, the sintering aid is preferably any one or a combination of (BiO)2CO3, Bi(OH)3, Bi(C2H3O2)3, Bi2O3, Bi(NO3)3, Bi2(SO4)3, TiO2, Bi, and Ce. In addition, (BiO)2CO3, Bi(OH)3, Bi(C2H3O2)3, Bi(NO3)3, and Bi2(SO4)3 are all generated after sintering, and TiO2 and Bi2O3 both have good sintering activity and wettability, which helps to promote the combination between nano metal particles, thereby improving the shear strength and conductivity of the metal solder paste after sintering. Bi not only can reduce the sintering temperature, but also is beneficial to fill the voids between nano metal particles, and is beneficial to improve the shear strength and conductivity of the metal solder paste. In addition, Bi can also form an alloy with other nano metal particles to improve the corrosion resistance of the metal solder paste after sintering. Ce not only can reduce the sintering temperature, but also plays a catalytic role in the sintering process, thereby reducing the activation energy of the sintering reaction and accelerating the sintering process.

[0054] Further, in step A, the copper salt is any one of copper acetate, copper hydroxide, copper formate, copper carbonate, copper bicarbonate, copper acetylacetone, or copper oxalate;

[0055] The silver salt is any one of silver acetate, silver hydroxide, silver formate, silver carbonate, silver bicarbonate, silver acetylacetone, or silver oxalate;

[0056] The reducing agent is any one or a combination of hydrazine hydrate, ascorbic acid, glucose, phenylhydrazine, and citric acid;

[0057] The solvent is any one or a combination of water, toluene, diethyl ether, ethyl acetate, ethanol, ethylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, glycerol, acetone, glycerol, terpineol, and polyethylene glycol.

[0058] By optimizing the types of copper salt, silver salt, reducing agent, and solvent, the performance of the metal solder paste can be ensured, and the selection of suitable raw materials according to actual needs provides more possibilities and flexibility for its application in different fields.

[0059] Further, in step A, the reaction temperature is 15-100℃, and the reaction time is 5-180min.

[0060] By optimizing the reaction temperature and reaction time of the reaction, the metal salt is reduced as much as possible, and the sintering aid fully plays its role, under the premise of ensuring the performance of the metal solder paste, the production cost is reduced, and the production efficiency is improved.

[0061] Further, in step B, the content of the nano metal particles in the low-temperature sintered metal solder paste is 20-99% by mass percentage.

[0062] The content of the nano metal particles in the low-temperature sintered metal solder paste is 20-99% by mass percentage, so that metal solder pastes with different nano metal particle contents can be selected according to actual application requirements, improving its practicability.

[0063] Further, step A specifically includes:

[0064] A1. The metal salt and the sintering aid are added to part of the formula amount of the solvent, and after stirring, a first mixture is obtained;

[0065] A2. The reducing agent is added to the remaining formula amount of the solvent, and after stirring, a second mixture is obtained;

[0066] A3. The first mixture and the second mixture are reacted to obtain a low-temperature sintered metal suspension.

[0067] By optimizing step A, the metal salt, the sintering aid and the reducing agent are fully dissolved and dispersed, thereby facilitating the performance of the metal solder paste.

[0068] A low-temperature sintered metal solder paste prepared by the above-mentioned preparation method of a low-temperature sintered metal solder paste.

[0069] The present application also provides a low-temperature sintered metal solder paste prepared by the above-mentioned preparation method of a low-temperature sintered metal solder paste, which not only can be sintered at low temperature, but also has excellent shear strength and conductivity.

[0070] The application of a low-temperature sintered metal solder paste in preparing an interconnection device uses the above-mentioned low-temperature sintered metal solder paste, which includes the following steps: coating the low-temperature sintered metal solder paste on a substrate; covering an interconnection chip on the surface of the coated low-temperature sintered metal solder paste, and sintering under the conditions of a sintering temperature of 130-240℃ and a sintering pressure of 0-50Mpa to obtain an interconnection device.

[0071] The technical scheme further provides an application of the low-temperature sintered metal solder paste in preparation of an interconnection device, and comprises the following steps: coating the low-temperature sintered metal solder paste on a substrate, covering an interconnection chip on the surface of the coated low-temperature sintered metal solder paste, and sintering under the conditions of a sintering temperature of 130-240 DEG C and a sintering pressure of 0-50 Mpa to obtain the interconnection device, so that the obtained interconnection device has good shear strength and conductivity.

[0072] The technical scheme of the present application is further illustrated by a specific embodiment.

[0073] Performance test:

[0074] (1) Shear strength: the low-temperature sintered metal solder paste is coated on a substrate, an interconnection chip is covered on the surface of the coated low-temperature sintered metal solder paste, and sintering is performed to obtain an interconnection device, and an IC package welding strength tester (SERIES-4000-DONDESTER) is used to test the shear strength of the interconnection device, and when the shear strength is greater than 40 MPa, it is qualified.

[0075] (2) Conductivity: the low-temperature sintered metal solder paste is coated on a substrate, an interconnection chip is covered on the surface of the coated low-temperature sintered metal solder paste, and sintering is performed to obtain an interconnection device, and an ST-2258C four-probe tester is used to test the surface resistivity of the interconnection device, and when the surface resistivity is less than 15 x 10 -8 Ω.m, it is qualified.

[0076] Example 1

[0077] A. Copper carbonate and Bi(OH)3 are added into 100 mL of ethanol, and after stirring, a first mixture is obtained; hydrazine hydrate is added into 100 mL of ethanol, and after stirring, a second mixture is obtained; the first mixture and the second mixture are reacted at 80 DEG C for 30 min to obtain a low-temperature sintered metal suspension; wherein the low-temperature sintered metal suspension contains copper nanoparticles with a particle size of 800 nm, and the sintering temperature of the copper nanoparticles is 330 DEG C; the molar ratio of copper carbonate to hydrazine hydrate is 1:5; the molar ratio of copper carbonate to Bi(OH)3 is 1:0.02; and the content of the nano metal particles in the low-temperature sintered metal solder paste is 30%.

[0078] B. The low-temperature sintered metal suspension is centrifuged in a vacuum environment to obtain a low-temperature sintered metal solder paste; wherein the sintering temperature of the metal solder paste is 180 DEG C; the centrifugation speed is 10000 rpm, and the centrifugation time is 20 min.

[0079] Example 2

[0080] A. silver acetate, Bi2O3 were added into 120 mL glycerol, after stirring, a first mixture was obtained; ascorbic acid was added into 80 mL glycerol, after stirring, a second mixture was obtained; the first mixture and the second mixture were reacted at 100℃ for 20 min to obtain a low-temperature sintering metal suspension; wherein the low-temperature sintering metal suspension contains silver nanoparticles with a particle size of 500 nm, and the sintering temperature of the silver nanoparticles is 310℃; the molar ratio of silver acetate to ascorbic acid is 1:4; the molar ratio of silver acetate to Bi2O3 is 1:0.001; the content of silver nanoparticles in the low-temperature sintering metal paste is 50%;

[0081] B. the low-temperature sintering metal suspension was centrifuged under vacuum to obtain a low-temperature sintering metal paste; wherein the sintering temperature of the metal paste is 220℃; the centrifugation speed is 8000 rpm, and the centrifugation time is 10 min.

[0082] Example 3

[0083] A. copper hydroxide, TiO2 were added into 140 mL diethylene glycol, after stirring, a first mixture was obtained; citric acid was added into 60 mL diethylene glycol, after stirring, a second mixture was obtained; the first mixture and the second mixture were reacted at 60℃ for 90 min to obtain a low-temperature sintering metal suspension; wherein the low-temperature sintering metal suspension contains copper nanoparticles with a particle size of 1200 nm, and the sintering temperature of the copper nanoparticles is 360℃; the molar ratio of copper hydroxide to citric acid is 1:6; the molar ratio of copper hydroxide to TiO2 is 1:0.05; the content of metal nanoparticles in the low-temperature sintering metal paste is 80%;

[0084] B. the low-temperature sintering metal suspension was centrifuged under vacuum to obtain a low-temperature sintering metal paste; wherein the sintering temperature of the metal paste is 240℃; the centrifugation speed is 12000 rpm, and the centrifugation time is 30 min.

[0085] Comparative Example 1

[0086] Comparative Example 1 and Example 1 have the same preparation method and raw materials, except that no sintering aid is added in Comparative Example 1.

[0087] The metal pastes prepared by the preparation methods of Examples 1-3 and Comparative Example 1 were used to prepare interconnection devices, and the performance of the prepared interconnection devices was tested. Under the condition that other conditions are the same, the prepared interconnection devices were compared with the interconnection devices prepared by traditional conductive adhesive and traditional metal paste, and the specific test results are shown in Table 1:

[0088] Table 1 Performance test results of different interconnection devices

[0089] Performance test items Shear strength (MPa) Electrical conductivity (Ω.m) Example 1 60.98 13.64 x 10 -8 ]]> Example 2 58.63 13.91 x 10 -8 ]] Example 3 54.32 14.18 x 10 -8 ]] Comparative Example 1 38.17 18.48 x 10 -8 ]] Conventional conductive adhesive 37.49 19.7 x 10 -8 ]] Conventional metal solder paste 39.75 17.04 x 10 -8 ]]

[0090] From the test results of Table 1, it can be seen that the interconnection device prepared by the low-temperature sintering metal solder paste has a shear strength > 40 MPa and a resistivity < 15 x 10 -8 Ω.m, and the performance of the interconnection device is better than that of the conventional conductive adhesive and the conventional metal solder paste, that is, the existing interconnection device has higher shear strength and conductivity, and in the case that other conditions are the same, the shear strength and conductivity of the interconnection device depend on the shear strength and conductivity of the metal solder paste. Therefore, the metal solder paste obtained by the technical scheme has higher shear strength and conductivity, can break through the functional limitations of the conventional conductive adhesive and the conventional metal solder paste, and solves the technical problems that the conventional conductive adhesive and the conventional metal solder paste have poor shear strength and conductivity and cannot meet the actual use requirements.

[0091] In the comparative example 1, the shear strength and conductivity are reduced due to the absence of the sintering aid, and the sintering is not complete at low temperature due to the absence of the sintering aid, which further affects the shear strength and conductivity, so that the shear strength and conductivity of the obtained interconnection device are poor and cannot meet the use requirements.

[0092] It should be noted that the conventional conductive adhesive includes silver powder 50-80 parts, coupling agent 1-2 parts, graphene 10-20 parts, dodecylamine aminopropionic acid sodium 3-5 parts, dimethyl dichlorosilane 3-5 parts, curing agent 2-3 parts, accelerator 2-3 parts, release agent 2-3 parts, preservative 1-2 parts, polymeric cellulose 20-35 parts and conductive fiber 10-35 parts, calculated in mass parts.

[0093] The conventional metal solder paste includes 80-92% brazing powder and 8-20% binder, calculated in mass percentage; the brazing powder includes nano-silver powder 10-30%, silver-copper alloy powder 60-80%, aluminum-silicon alloy powder / titanium-aluminum alloy powder 5-10% and titanium hydride powder 2-5%, calculated in mass percentage; the binder includes solvent 75-90%, thickening agent 5-10%, surfactant 2-4%, dispersant 1-2% and thixotropic agent 2-5%, calculated in mass percentage.

[0094] The technical principles of the present application are described above in combination with specific embodiments. These descriptions are only for the purpose of explaining the principles of the present application and cannot be interpreted in any way as a limitation on the scope of protection of the present application. Based on the explanations herein, those skilled in the art can conceive other specific embodiments of the present application without creative labor, and these embodiments will fall within the scope of protection of the present application.

Claims

1. A method for preparing a low-temperature sintering metal solder paste, characterized in that, Includes the following steps: A. A metal salt, sintering aid, and reducing agent are added to a solvent, and a low-temperature sintering metal suspension is obtained after the reaction; wherein the low-temperature sintering metal suspension contains metal nanoparticles, and the sintering temperature of the metal nanoparticles is >300℃; the sintering aid includes any one or more combinations of (BiO)2CO3, Bi(OH)3, Bi(C2H3O2)3, Bi2O3, Bi(NO3)3, Bi2(SO4)3, TiO2, Bi, and Ce; B. The low-temperature sintered metal suspension is concentrated under vacuum to obtain a low-temperature sintered metal solder paste; wherein the sintering temperature of the low-temperature sintered metal solder paste is 130-240℃.

2. The method for preparing a low-temperature sintering metal solder paste according to claim 1, characterized in that, In step A, the molar ratio of the metal salt to the reducing agent is 1:(1-10); the molar ratio of the metal salt to the sintering aid is 1:(0.001-0.05).

3. The method for preparing a low-temperature sintering metal solder paste according to claim 1, characterized in that, In step A, the particle size of the metal nanoparticles is 80–1200 nm.

4. The method for preparing a low-temperature sintering metal solder paste according to claim 1, characterized in that, In step A, the metal salt is either a copper salt or a silver salt.

5. The method for preparing a low-temperature sintering metal solder paste according to claim 4, characterized in that, In step A, the copper salt is any one of copper acetate, copper hydroxide, copper formate, copper carbonate, copper bicarbonate, copper acetylacetonate, or copper oxalate. The silver salt is any one of silver acetate, silver hydroxide, silver formate, silver carbonate, silver bicarbonate, silver acetylacetone, or silver oxalate. The reducing agent is any one or a combination of hydrazine hydrate, ascorbic acid, glucose, phenylhydrazine and citric acid; The solvent is any one or a combination of water, toluene, diethyl ether, ethyl acetate, ethanol, ethylene glycol, diethylene glycol, diethylene glycol, dipropylene glycol, glycerol, acetone, glycerol, terpineol, and polyethylene glycol.

6. The method for preparing a low-temperature sintering metal solder paste according to claim 1, characterized in that, In step A, the reaction temperature is 15–100°C and the reaction time is 5–180 min.

7. The method for preparing a low-temperature sintering metal solder paste according to claim 1, characterized in that, In step B, the content of nano-metal particles in the low-temperature sintered metal solder paste is 20-99% by mass percentage.

8. The method for preparing a low-temperature sintering metal solder paste according to claim 1, characterized in that, Step A specifically includes: A1. Add the metal salt and sintering aid to a portion of the solvent in the formula, and stir to obtain the first mixture; A2. Add the reducing agent to the remaining solvent in the formula, stir, and obtain the second mixture; A3. The first mixture and the second mixture are reacted to obtain a low-temperature sintered metal suspension.

9. A low-temperature sintering metal solder paste, characterized in that, It is prepared using the method for preparing low-temperature sintering metal solder paste as described in any one of claims 1 to 8.

10. The application of a low-temperature sintering metal solder paste in the fabrication of interconnect devices, characterized in that, Using the low-temperature sintering metal solder paste as described in claim 9, the method includes the following steps: coating the low-temperature sintering metal solder paste onto a substrate; covering the surface of the coated low-temperature sintering metal solder paste with an interconnect chip; and sintering the solder paste at a sintering temperature of 130–240°C and a sintering pressure of 0–50 MPa to obtain an interconnect device.