Metal soldering paste and preparation method and application thereof

Abstract

The invention discloses metal soldering paste and a preparation method and application thereof. The preparation method comprises the following steps that A, metal particles are prepared; wherein the particle size of the metal particles is 5-5000 nm, and the sintering temperature of the metal particles is higher than 300 DEG C; b, uniformly mixing metal particles, a sintering aid and a solvent to obtain metal soldering paste; wherein the sintering temperature of the metal soldering paste ranges from 80 DEG C to 260 DEG C. According to the preparation method of the metal soldering paste, the preparation method is simple and high in operability, and the obtained metal soldering paste has high shear strength and conductivity on the premise of achieving low-temperature sintering by adding the sintering aid into the formula, so that the defects in the prior art are overcome.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic manufacturing, and in particular to a metal solder paste and a preparation method and application thereof. Background Art

[0002] In recent years, with the rapid development of integrated circuit technology, the internal structure of chips has become increasingly miniaturized and the functions have become more complex, and the requirements for interconnection materials have reached an unprecedented level. When traditional metal solder paste is used as an interconnection material, its sintering temperature is relatively high. Due to the different thermal expansion coefficients of the substrate, chip and solder paste, the high-temperature sintering process will cause the interconnection device formed by the substrate, chip and solder paste to produce large thermal stress, thereby reducing the mechanical properties of the interconnection device, especially the shear strength. In addition, during the high-temperature sintering process, the metal particles in the metal solder paste will undergo changes such as phase change, oxidation or grain coarsening, which will cause the conductive performance of the interconnection device to decrease.

[0003] In order to solve the problem of decreased shear strength and decreased electrical conductivity caused by the high sintering temperature of metal solder paste, the industry has adopted a solution of using thermally conductive adhesive as an interconnection material. Specifically, the curing temperature of thermally conductive adhesive is generally low (lower than 150°C), which can effectively prevent the chip from being affected by high temperature during the interconnection process. However, since the base resin of the thermally conductive adhesive is an insulator, its electrical conductivity is poor. Although its electrical conductivity can be improved by adding conductive fillers (such as metal particles and carbon black, etc.), the improvement in electrical conductivity achieved by the above means is often limited. At the same time, since the thermal expansion coefficient of the base resin is high and the thermal conductivity is relatively low, during the curing process, it is easy to cause the interconnection device formed by the substrate, chip and thermally conductive adhesive to produce greater thermal stress, which reduces the shear strength of the interconnection device. That is, although the conductive adhesive used as the interconnection material in the prior art can reduce the interconnection temperature, it still cannot meet the requirements of the interconnection device for shear strength and electrical conductivity. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a metal solder paste. The preparation method is simple and easy to operate. By adding a sintering aid to the formula, the obtained metal solder paste has high shear strength and conductive properties while achieving low-temperature sintering, thereby overcoming the shortcomings of the prior art.

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

[0006] The third object of the present invention is to provide an application of a metal solder paste, which is used in the preparation of interconnection devices to ensure that the obtained interconnection devices have good shear strength and conductive properties.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] A method for preparing a metal solder paste comprises the following steps:

[0009] A. preparing metal particles; wherein the particle size of the metal particles is 5 to 5000 nm, and the sintering temperature of the metal particles is greater than 300° C.;

[0010] B. The metal particles, sintering aid and solvent are mixed uniformly to obtain a metal solder paste; wherein the sintering temperature of the metal solder paste is 80 to 260°C.

[0011] Furthermore, in step B, the sintering aid is Bi, Bi2O3, Ga, Zn, Sn, Cs, Ce,

[0012] Any one or more combinations of La, Cd, TiO2, Sb, Rb, Al and Mg.

[0013] Furthermore, in step A, the particle size of the metal particles is 50 to 2000 nm.

[0014] Furthermore, in step A, the metal particles include any one or more combinations of elemental metal particles and alloy metal particles.

[0015] Further, in step A, the elemental metal particles include any one or more combinations of copper particles, silver particles, nickel particles, gold particles and aluminum particles;

[0016] The alloy metal particles include any one or more combinations of silver-coated copper, copper-silver alloy and copper-aluminum alloy.

[0017] Furthermore, in step B, the solvent is any one or more combinations of water, toluene, ether, ethyl acetate, ethanol, ethylene glycol, diethylene glycol, diethylene glycol, dipropylene glycol, glycerol, acetone, glycerin, terpineol and polyethylene glycol.

[0018] Furthermore, in step B, calculated by mass percentage, the content of metal particles in the metal solder paste is 20-85%, and the content of sintering aid in the metal solder paste is 0.001-20%.

[0019] A metal solder paste is prepared using the above-mentioned method for preparing the metal solder paste.

[0020] The invention discloses an application of a metal solder paste in preparing an interconnection device. The metal solder paste is used, and the steps include: coating the metal solder paste on a substrate, covering an interconnection chip on the coated surface of the metal solder paste, and sintering the substrate at a sintering temperature of 80 to 260° C. and a sintering pressure of 0 to 50 MPa to obtain an interconnection device.

[0021] Furthermore, the heating rate of the sintering temperature is 1 to 50° C. / min.

[0022] The technical solution provided by the present invention may include the following beneficial effects:

[0023] 1. This technical solution first limits the particle size of metal particles to 5-5000nm. Since the particle size of metal particles is extremely small, they have high surface energy and surface activity. The high surface energy and surface activity make it easier for metal particles to aggregate when they come into contact with each other, promote the sintering of metal particles, and make the metal particles have a lower sintering temperature. The sintering temperature of metal solder paste depends on the sintering temperature of metal particles. Therefore, the lower sintering temperature of metal particles makes the metal solder paste prepared using metal particles have a lower sintering temperature.

[0024] 2. In this technical solution, by adding a sintering aid, it is not only beneficial to reduce the sintering temperature of the metal solder paste, but also through the sintering aid's role in reducing the sintering temperature, providing additional surface active sites, and promoting diffusion, the shear strength and conductivity of the metal solder paste can be provided. DETAILED DESCRIPTION

[0025] The present technical solution provides a method for preparing a metal solder paste, comprising the following steps:

[0026] A. preparing metal particles; wherein the particle size of the metal particles is 5 to 5000 nm, and the sintering temperature of the metal particles is greater than 300° C.;

[0027] B. The metal particles, sintering aid and solvent are mixed uniformly to obtain a metal solder paste; wherein the sintering temperature of the metal solder paste is 80 to 260°C.

[0028] In order to solve the technical problem that the prior art is used as an interconnect material but cannot meet the shear strength and conductivity requirements of the interconnect device, the present technical solution proposes a method for preparing a metal solder paste, which simplifies the preparation steps, controls the particle size of the metal particles, and adds a sintering aid to the metal solder paste formula. Under the premise of achieving low-temperature sintering of the metal solder paste, the shear strength and conductivity after sintering are improved to meet actual use requirements.

[0029] Specifically, in order to solve the technical problems caused by the high sintering temperature of metal solder paste, the industry has adopted thermally conductive adhesive as the interconnection material. However, although the conductive adhesive used as the interconnection material in the prior art can reduce the interconnection temperature, it still cannot meet the shear strength and conductivity requirements of the interconnection device. The present technical solution first limits the particle size of the metal particles to 5 to 5000 nm. Since the particle size of the metal particles is extremely small, they have a higher surface energy and surface activity. The above high surface energy and surface activity make it easier for the metal particles to aggregate when they contact each other, promote the sintering of the metal particles, and make the metal particles have a lower sintering temperature. The sintering temperature of the metal solder paste depends on the sintering temperature of the metal particles. Therefore, the lower sintering temperature of the metal particles makes the metal solder paste prepared using the metal particles have a lower sintering temperature.

[0030] In addition, compared with the larger metal particles in the traditional metal solder paste, the diffusion distance between the metal particles of the above-mentioned particle size is shorter, which also enables the metal solder paste prepared with the metal particles to achieve sintering and densification at a lower temperature. That is, in the present technical solution, by limiting the particle size of the metal particles and utilizing the characteristics of the metal particles being easy to aggregate and having a short diffusion distance, the metal solder paste prepared with the metal particles of the above-mentioned particle size has a lower sintering temperature, which not only reduces the sintering energy consumption of the metal solder paste and realizes green sintering, but also helps to avoid the technical problem that the shear strength and conductivity of the metal solder paste are easily affected by the high sintering temperature, thereby ensuring its shear strength and conductivity.

[0031] Secondly, although metal particles with a particle size of 5 to 5000 nm have a lower sintering temperature due to their easy aggregation and short diffusion distance, thus making the metal solder paste have a lower sintering temperature, the sintering temperature of metal particles with a particle size of 5 to 5000 nm is also relatively high, generally greater than 300°C, making the sintering temperature of the metal solder paste also greater than 300°C, and the above sintering temperature range still leaves the metal particles at risk of being oxidized. And when the metal particles are oxidized to metal oxides, since the metal oxides have a higher melting point than the metal particles, the metal oxides will hinder sintering, making it difficult for the metal oxides and the metal particles themselves to sinter together, making the solder paste sintered body formed after the metal solder paste is sintered relatively loose, thereby reducing its shear strength and conductivity, and still cannot meet the requirements of places with high shear strength and conductivity.

[0032] In order to further reduce the sintering temperature of the metal solder paste, the technical solution specifically adds a sintering aid to the metal solder paste formula, and utilizes the activation effect of the sintering aid to reduce the energy threshold required for the sintering of metal particles, so that the sintering temperature of the metal solder paste is greatly reduced, and sintering is achieved within a temperature range of 80 to 260°C, which not only greatly reduces the sintering energy consumption of the metal solder paste and achieves green sintering, but also effectively avoids the metal particles being easily oxidized when the sintering temperature is high, thereby hindering sintering, thereby affecting its shear strength and conductivity. Further, the sintering aid can provide additional surface active sites for nano-metal particles during the sintering process, promote the interaction and bonding between nano-metal particles, and effectively improve the density of the solder paste sintered body formed after the metal solder paste is sintered, thereby improving the shear strength and conductivity of the metal solder paste. In addition, the sintering aid also helps the uniform dispersion of metal particles in the metal solder paste, avoids the agglomeration of metal particles, and makes it easier for metal particles to form a dense solder paste sintered body during the sintering process, which is also beneficial to improve the shear strength and conductivity of the metal solder paste. That is, the addition of sintering aids in the present technical solution is not only beneficial for lowering the sintering temperature of the metal solder paste, but also can provide the shear strength and conductivity of the metal solder paste through the interaction of the sintering aids in lowering the sintering temperature, providing additional surface active sites, and promoting diffusion.

[0033] Again, in the present technical solution, the metal solder paste can be prepared through two steps, step A (preparing metal particles) and step B (mixing raw materials), and in step B, the addition amount of each raw material can be limited according to actual needs. The metal solder paste can be obtained without the need for a concentration process, which not only greatly simplifies the preparation process of the metal solder paste, but also reduces the possibility of metal particles being easily agglomerated and oxidized when exposed to the air, thereby ensuring the performance of the metal solder paste.

[0034] It should be noted that the method for preparing metal particles in the present technical solution can adopt conventional liquid phase reduction method, electrodeposition method, microemulsion method, pyrolysis method, spark discharge method, ball milling method and pulsed laser ablation in the prior art, which is not limited here.

[0035] Further description, in step B, the sintering aid is any one or more combinations of Bi, Bi2O3, Ga, Zn, Sn, Cs, Ce, La, Cd, TiO2, Sb, Rb, Al and Mg.

[0036] Because Bi, Bi2O3, Ga, Zn, Sn, Cs, Ce, La, Cd, TiO2, Sb, Rb, Al and Mg can all promote low temperature sintering, therefore, the preferred sintering aid of the present technical solution is any one or more combinations of Bi, Bi2O3, Ga, Zn, Sn, Cs, Ce, La, Cd, TiO2, Sb, Rb, Al and Mg. In addition, low melting point metal elements such as Bi and Sn can not only reduce the sintering temperature, but also form liquid phase during sintering, accelerating the rearrangement and densification of metal particles. TiO2 and Bi2O3 can not only reduce the sintering temperature, but also because both have good sintering activity and wettability, help promote the combination between nano metal particles, thereby improve the shear strength and conductivity of metal solder paste. In addition, elements such as Ga and Zn can also not only reduce the sintering temperature, but also can improve the performance of solder paste sintered body by solid solution strengthening or forming intermetallic compounds. Rare earth elements such as Ce and La can not only reduce the sintering temperature, but also improve the performance of the solder paste sintered body by purifying the grain boundaries and inhibiting the segregation of impurities.

[0037] Further, in step A, the particle size of the metal particles is 50 to 2000 nm.

[0038] This technical solution is beneficial to further improve the performance of metal solder paste by further optimizing the particle size of metal particles.

[0039] To further illustrate, in step A, the metal particles include any one or more combinations of elemental metal particles and alloy metal particles.

[0040] Since both single-element metal particles and alloy metal particles have excellent electrical conductivity and thermal conductivity, the present technical solution preferably uses metal particles that include any one or more combinations of single-element metal particles and alloy metal particles to ensure the performance of the metal solder paste.

[0041] In addition, since the metal particles can be selected from any one or more combinations of elemental metal particles and alloy metal particles, it not only increases the diversity of metal solder paste preparation methods and material selection, but also provides more possibilities and flexibility for its application in different fields.

[0042] Further, in step A, the elemental metal particles include any one or more combinations of copper particles, silver particles, nickel particles, gold particles and aluminum particles;

[0043] The alloy metal particles include any one or more combinations of silver-coated copper, copper-silver alloy and copper-aluminum alloy.

[0044] In the present technical solution, further optimization of the types of elemental metal particles and alloy metal particles is beneficial to ensuring the performance of the metal solder paste.

[0045] Further, in step B, the solvent is any one or more of water, toluene, ether, ethyl acetate, ethanol, ethylene glycol, diethylene glycol, diethylene glycol, dipropylene glycol, glycerol, acetone, glycerin, terpineol and polyethylene glycol.

[0046] By preferably including a plurality of types of solvents, not only the performance of the metal solder paste can be ensured, but also a suitable solvent can be selected according to actual needs, thereby providing more possibilities and flexibility for the preparation process.

[0047] Further, in step B, calculated by mass percentage, the content of metal particles in the metal solder paste is 20-85%, and the content of sintering aid in the metal solder paste is 0.001-20%.

[0048] Calculated by mass percentage, the content of metal particles in the metal solder paste is 20-85%, so that metal solder pastes with different metal particle contents can be selected according to actual application requirements to improve their practicality. In addition, when the content of the sintering aid is too high, it is easy to affect the conductive properties of the metal solder paste; when the content of the sintering aid is too low, its effect on reducing the sintering temperature of the metal solder paste is limited. Therefore, the technical solution optimizes the content of the sintering aid in the metal solder paste to 0.001-20%, so as to ensure the performance of the metal solder paste while reducing the sintering temperature of the metal solder paste.

[0049] A metal solder paste is prepared using the above-mentioned method for preparing the metal solder paste.

[0050] The present invention also provides a method for preparing a metal solder paste. The prepared metal solder paste can not only be sintered at ultra-low temperature, but also has excellent shear strength and electrical conductivity.

[0051] The invention discloses an application of a metal solder paste in preparing an interconnection device. The metal solder paste is used, and the steps include: coating the metal solder paste on a substrate, covering an interconnection chip on the coated surface of the metal solder paste, and sintering the substrate at a sintering temperature of 80 to 260° C. and a sintering pressure of 0 to 50 MPa to obtain an interconnection device.

[0052] The technical solution also proposes an application of a metal solder paste in the preparation of an interconnection device, comprising the following steps: coating the metal solder paste on a substrate to obtain the coated metal solder paste, covering the surface of the coated metal solder paste with an interconnection chip, and sintering at a sintering temperature of 80 to 260°C and a sintering pressure of 0 to 50 MPa to obtain an interconnection device, thereby ensuring that the obtained interconnection device has good shear strength and conductivity.

[0053] It is further explained that the heating rate of the sintering temperature is 1 to 50° C. / min.

[0054] A faster heating rate can shorten the sintering cycle, but it may also lead to uneven internal temperature distribution of the solder paste sintered body formed after the metal solder paste is sintered, resulting in thermal stress and other problems, which is not conducive to improving the performance of the interconnection device. A slower heating rate helps the components in the metal solder paste to melt evenly and reduce the generation of defects, but the production efficiency is too low. Therefore, the preferred heating rate of the sintering temperature in this technical solution is 1 to 50°C / min, which improves the production efficiency while ensuring the performance of the interconnection device.

[0055] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0056] Performance Testing:

[0057] (1) Shear strength: A low-temperature sintered metal solder paste is coated on a substrate, and an interconnection chip is placed on the surface of the coated low-temperature sintered metal solder paste. The interconnection device is sintered to obtain an interconnection device. The shear strength of the interconnection device is tested using an IC packaging welding strength tester (SERIES-4000-DONDESTER). When the shear strength is greater than 40 MPa, it is qualified.

[0058] (2) Conductivity: A low-temperature sintered metal solder paste is coated on a substrate, and an interconnection chip is placed on the surface of the coated low-temperature sintered metal solder paste. The interconnection device is sintered to obtain an interconnection device. The surface resistivity of the interconnection device is tested using an ST-2258C four-probe tester. When the resistivity is <15×10-8Ω.m, it is qualified.

[0059] Example 1

[0060] A. preparing copper particles; wherein the particle size of the copper particles is 500 nm, and the sintering temperature of the copper particles is 320° C.;

[0061] B. The copper particles, Bi2O3 and ethanol are uniformly mixed to obtain a metal solder paste with a sintering temperature of 130° C., wherein the content of the copper particles in the metal solder paste is 50%; and the content of Bi2O3 in the metal solder paste is 0.1%.

[0062] Example 2

[0063] A. preparing silver-coated copper particles; wherein the particle size of the silver-coated copper particles is 1000 nm, and the sintering temperature of the silver-coated copper particles is 350° C.;

[0064] B. The silver-coated copper particles, Sn and propylene glycol are uniformly mixed to obtain a metal solder paste with a sintering temperature of 80 to 260° C., wherein the content of the silver-coated copper particles in the metal solder paste is 35%; and the content of Sn in the metal solder paste is 10%.

[0065] Example 3

[0066] A. preparing silver particles; wherein the particle size of the silver particles is 3000 nm, and the sintering temperature of the metal particles is 380° C.;

[0067] B. The silver particles, Zn and diethylene glycol are uniformly mixed to obtain a metal solder paste with a sintering temperature of 80 to 260° C., wherein the content of the silver particles in the metal solder paste is 60%; and the content of the Zn in the metal solder paste is 5%.

[0068] Comparative Example 1

[0069] The preparation method and raw materials of Comparative Example 1 are the same as those of Example 1, except that no sintering aid is added in Comparative Example 1.

[0070] The metal solder 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. When other conditions were the same, the interconnection devices were compared with those prepared by traditional conductive adhesives and traditional metal solder pastes. The test results are shown in Table 1:

[0071] Table 1 Performance test results of different interconnect devices

[0072] Performance test items Shear strength(MPa) Conductivity(Ω.m) Example 1 67.62 <![CDATA[6.13×10 -8 ]]> Example 2 60.13 <![CDATA[8.74×10 -8 ]]> Example 3 58.05 <![CDATA[11.62×10 -8 ]]> Comparative Example 1 43.38 <![CDATA[15.48×10 -8 ]]> Traditional conductive adhesive 38.26 <![CDATA[19.14×10 -8 ]]> Traditional metal solder paste 38.48 <![CDATA[17.03×10 -8 ]]>

[0073] From the test results in Table 1, it can be seen that the shear strength of the interconnection device prepared by the ultra-low temperature sintered metal solder paste of the present technical solution is greater than 50MPa, and the resistivity is less than 13×10 -8 Ω.m, and its various performances are better than those of the interconnection devices prepared by the traditional conductive adhesive and the traditional metal solder paste, that is, the existing interconnection device has high shear strength and conductivity, and when 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 solution has high shear strength and guidance, which can break through the functional limitations of the traditional conductive adhesive and the traditional metal solder paste, and solve the technical problem that the traditional conductive adhesive and the traditional metal solder paste have poor shear strength and guidance and cannot meet the actual use requirements.

[0074] Since no sintering aid is added to comparative example 1, the shear strength and conductivity are reduced; at the same time, since no sintering aid is added, it cannot be completely sintered at low temperature, which further affects the shear strength and conductivity, so that the shear strength and conductivity of the obtained interconnect device are poor and cannot meet the use requirements.

[0075] It should be noted that, calculated by mass, the traditional conductive adhesive includes 50-80 parts of silver powder, 1-2 parts of coupling agent, 10-20 parts of graphene, 3-5 parts of sodium dodecylaminopropionate, 3-5 parts of dimethyldichlorosilane, 2-3 parts of curing agent, 2-3 parts of accelerator, 2-3 parts of bail agent, 1-2 parts of preservative, 20-35 parts of polymer cellulose and 10-35 parts of conductive fiber.

[0076] Calculated by mass percentage, traditional metal solder paste includes 80-92% brazing powder and 8-20% binder; calculated by mass percentage, brazing powder includes 10-30% nano silver powder, 60-80% silver-copper alloy powder, 5-10% aluminum-silicon alloy powder / titanium-aluminum alloy powder and 2-5% titanium hydride powder; calculated by mass percentage, the binder includes 75-90% solvent, 5-10% thickener, 2-4% surfactant, 1-2% dispersant and 2-5% thixotropic agent.

[0077] The technical principle of the present invention is described above in conjunction with specific embodiments. These descriptions are only for explaining the principle of the present invention and cannot be interpreted as limiting the scope of protection of the present invention in any way. Based on the explanations herein, those skilled in the art can associate other specific implementations of the present invention without paying creative labor, and these methods will fall within the scope of protection of the present invention.

Claims

1. A method for preparing a metal solder paste, characterized in that: The following steps are involved: A. preparing metal particles; wherein the particle size of the metal particles is 5 to 5000 nm, and the sintering temperature of the metal particles is greater than 300° C.; B. The metal particles, sintering aid and solvent are mixed uniformly to obtain a metal solder paste; wherein the sintering temperature of the metal solder paste is 80 to 260°C.

2. The method for preparing a metal solder paste according to claim 1, characterized in that: In step B, the sintering aid is Bi, Bi2O3, Ga, Zn, Sn, Cs, Ce, La, Cd, TiO2, Sb, Any one or more combinations of Rb, Al and Mg.

3. The method for preparing a metal solder paste according to claim 1, characterized in that: In step A, the particle size of the metal particles is 50 to 2000 nm.

4. The method for preparing a metal solder paste according to claim 1, characterized in that: In step A, the metal particles include any one or more combinations of elemental metal particles and alloy metal particles.

5. The method for preparing a metal solder paste according to claim 4, characterized in that: In step A, the elemental metal particles include any one or more combinations of copper particles, silver particles, nickel particles, gold particles and aluminum particles; The alloy metal particles include any one or more combinations of silver-coated copper, copper-silver alloy and copper-aluminum alloy.

6. The method for preparing a metal solder paste according to claim 1, characterized in that: In step B, the solvent is any one or more of water, toluene, ether, ethyl acetate, ethanol, ethylene glycol, diethylene glycol, diethylene glycol, dipropylene glycol, glycerol, acetone, glycerin, terpineol and polyethylene glycol.

7. The method for preparing a metal solder paste according to claim 1, characterized in that: In step B, calculated by mass percentage, the content of metal particles in the metal solder paste is 20-85%, and the content of sintering aid in the metal solder paste is 0.001-20%.

8. A metal solder paste, characterized in that: The metal solder paste is prepared using the method for preparing the metal solder paste as described in any one of claims 1 to 7.

9. Application of a metal solder paste in preparing an interconnect device, characterized in that: The use of the metal solder paste as claimed in the claim comprises the following steps: coating the metal solder paste on a substrate, covering an interconnection chip on the surface of the coated metal solder paste, and sintering at a sintering temperature of 80 to 260° C. and a sintering pressure of 0 to 50 MPa to obtain an interconnection device.

10. Use of a metal solder paste in preparing interconnection devices according to claim 9, characterized in that: The heating rate of the sintering temperature is 1-50°C / min.