Silver colloid capable of being sintered at low temperature and application thereof

Abstract

The invention provides elargol capable of being sintered at low temperature and application thereof, and relates to the technical field of electronic product packaging materials, the elargol comprises the following raw material components: 14%-18% of epoxy resin, 4%-8% of an epoxy diluent, 0.3%-1.0% of a silane coupling agent, 1.5%-2.5% of a curing agent, 1.0%-2.0% of a solvent, 50%-70% of micron silver powder and 5%-20% of sinterable silver powder; the sum of the mass percentages of the components is 100%. The particle size range of the micron silver powder is 0.5-8 microns, and the particle size range of the sinterable silver powder is 0.3-2.2 microns. The silver colloid capable of being sintered at the low temperature, provided by the invention, can be subjected to pressureless sintering at 150-160 DEG C; the sinterable silver powder is added, so that the conductivity of the conductive adhesive is improved under the condition that the conductive adhesive is cured at 160 DEG C; and under the same curing condition, the high-temperature shearing force is obviously improved under the condition that the normal-temperature shearing force of the conductive adhesive is not influenced.

Description

Technical Field

[0001] This invention relates to the field of electronic product packaging materials, specifically to a low-temperature sintered silver paste and its applications, mainly used in the packaging of ICs, LEDs, passive components, automotive battery components and high-power devices. Background Technology

[0002] In recent years, high-power devices have been widely used in markets such as 5G and new energy vehicles. With the miniaturization, compactness, and increased power of these devices, the heat generated by semiconductors has also increased. To achieve good performance and long lifespan, it is necessary to ensure that each high-power device has sufficient heat dissipation performance and reliability.

[0003] Conventional conductive silver paste uses micron-sized silver powder and is typically cured at 100-175℃, with a thermal conductivity between 2-20 W / m·K. Because conventional conductive silver paste uses micron-sized silver powder, it can cure at low temperatures but cannot form a sintered structure, resulting in insufficient electrical and thermal conductivity and inadequate reliability.

[0004] Based on this, with the discovery of the low-temperature sintering properties of nano-silver, those skilled in the art have proposed replacing micron-sized silver with nano-silver. Representative foreign products of this type of low-temperature sintering silver paste include Kyocera CT2700, Heraeus mAgic DA295A, and F1510, all with sintering temperatures above 200℃. Domestically, Nanjing Xinxing Electronics Technology Co., Ltd. introduced a pressureless nano-silver paste prepared using their unique nano-silver ions, which can be sintered at temperatures above 200℃; their NF150 product can even be sintered as low as 150℃. Furthermore, Shanren New Materials' AS9300 product also uses nano-silver as a raw material component and can be sintered at 180℃. Xi'an Wisdom Valley Technology Research Institute Co., Ltd. reported the concept of mixed nano-silver. Using nano-silver powders of different sizes, 80nm and 20nm, mixed in a 1:9 ratio, it can be sintered without pressure at 150℃. However, the dispersant stabilizing the nano-silver did not decompose completely even at 400℃. The system requires a temperature of 230℃ to become dense, and it only achieves complete sintering density and high thermal conductivity at a temperature of 280℃.

[0005] Nano-silver has a small particle size and low surface energy, which enables it to achieve low-temperature sintering. However, the low surface energy causes rapid agglomeration, resulting in high internal stress and cracks. Furthermore, the preparation process of nano-silver is complex and produced in small quantities, making it much more expensive than conventional micron-sized silver powder. Consequently, the cost of low-temperature nano-sintered silver paste is high.

[0006] Therefore, there is an urgent need in this field for a new type of silver paste that can be sintered at low temperatures, achieving excellent electrical and thermal conductivity without the need for high temperature and pressure, and improving the bonding reliability of the silver paste. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the aforementioned background technology and provide a silver paste that can be sintered at low temperatures. By adding special micron-sized silver powder, it can be sintered without pressure at 150~160℃, ensuring excellent electrical and thermal conductivity without high temperature and pressure, and improving bonding reliability. In addition, this invention also protects the application of this silver paste in electronic product packaging processes.

[0008] The technical solution of this invention is: a silver paste that can be sintered at low temperatures, comprising the following components by mass percentage: Epoxy resin 14%~18%, Epoxy diluent 4%~8%, Silane coupling agent 0.3%~1.0%, Hardener 1.5%~2.5%, Solvent 1.0%~2.0%, 50%~70% micron silver powder 5%~20% silver powder can be sintered. The sum of the mass percentages of the above components is 100%; the micron-sized silver powder has a particle size range of 0.5~8 μm, and the sinterable silver powder has a particle size range of 0.3~2.2 μm. All particle sizes mentioned in this invention refer to the median particle size D50.

[0009] The preferred silver paste is capable of low-temperature sintering, wherein the micron-sized silver powder has a specific surface area of ​​0.3~2.2 m². 2 / g is a combination of one or more silver powder products with different particle sizes, and the tap density of the micron-sized silver powder is between 2 and 6 g / cm³. 3 between.

[0010] The preferred low-temperature sinterable silver paste includes silver powder 1 with a particle size of 5.0 μm; it also includes any one of silver powder 2 with a particle size of 6.0 μm, silver powder 3 with a particle size of 7.0 μm, and silver powder 4 with a particle size of 0.8 μm; the mass ratio of any one of silver powder 2, silver powder 3, and silver powder 4 to silver powder 1 is 1:4.6~6.3. The micron-sized silver powder is obtained by combining silver powder products with different particle sizes to reduce porosity and improve compactness.

[0011] The preferred low-temperature sinterable silver paste, wherein the epoxy resin is one or more of bisphenol A epoxy resin, bisphenol F epoxy resin and epoxidized polybutadiene; The epoxy diluent is an alicyclic glycidyl ether and / or a phenyl glycidyl ether.

[0012] The preferred low-temperature sinterable silver paste uses a curing agent that is one or more of aliphatic amines, alicyclic amines, adipic acid, sulfone, and methylimidazole. More preferably, the curing agent is a combination of alicyclic amines, adipic acid, and methylimidazole in a mass ratio of 4:9:7.

[0013] The preferred silver paste is one or more of ethylene glycol butyl ether, diethylene glycol, heptanol, and terpineol.

[0014] The preferred silver paste is one that can be sintered at low temperatures, wherein the sinterable silver powder has a specific surface area of ​​2.5~4.0 m². 2 / g, peak sintering temperature 150~155℃, tap density 1~2 g / cm³ 3 between.

[0015] The preferred low-temperature sinterable silver paste comprises the following raw material components by mass percentage: Epoxy resin 15%~16.5%, Epoxy diluent 5%~6%, Silane coupling agent 0.4%~0.6%, Hardener 1.8%~2.2%, Solvent 1.5%~2.0%, 54%~60% micron silver powder It can sinter 15%~20% silver powder.

[0016] The preferred low-temperature sinterable silver paste has the following properties: Resistivity ≤250 μΩ·cm; At room temperature, the shear force on a 0.65×0.65mm chip is ≥2.7 kg·f; at 200±2℃, the shear force on a 0.65×0.65mm chip is ≥520 g·f. 200±2℃ is equivalent to 198~202℃.

[0017] The present invention also provides a method for preparing the above-mentioned low-temperature sinterable silver paste, comprising the steps of: mixing epoxy resin, epoxy diluent, silane coupling agent, curing agent and solvent, then adding micron-sized silver powder and sinterable silver powder and stirring evenly, and finally placing the mixture in a vacuum homogenizer for homogenization to obtain low-temperature sinterable silver paste.

[0018] According to another aspect of the present invention, the application of the above-described low-temperature sinterable silver paste in electronic product packaging processes is protected.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. The silver paste that can be sintered at low temperatures provided by this invention can be sintered without pressure at 150~160℃; by adding special silver powder, the conductivity of the conductive paste is improved while maintaining a curing temperature of 160℃; and under the same curing conditions, the high-temperature shear force of the conductive paste is significantly improved without affecting the room temperature shear force of the conductive paste, thus improving the bonding reliability.

[0020] 2. By compounding conventional micron-sized silver powder with sinterable silver powder in a specific ratio, the silver paste of the present invention can be effectively sintered at 150~160℃ without pressure. After curing, the resistivity can be as low as 58 μΩ·cm, which is significantly lower than the resistivity of silver paste made only from conventional micron-sized silver powder.

[0021] 3. Due to the introduction of sinterable silver powder, a stronger bond is formed during the low-temperature curing process. The chip shear force of the silver paste at a high temperature of 200℃ is as high as 825.8 g·f, which is more than 175% higher than that of silver paste made only from conventional micron silver powder, greatly enhancing the long-term reliability of power devices in high-temperature operating environments.

[0022] 4. This invention uses 50-70% conventional micron-sized silver powder as the main component, with only a small amount (5-20%) of specially treated sinterable silver powder added. By introducing sintering into conventional conductive adhesives with limited raw material costs, it achieves low-temperature sintering and high reliability while possessing excellent cost-effectiveness and promising industrialization prospects. Attached Figure Description

[0023] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 The image shows the electron microscope (SEM) scan results of the conductive adhesive prepared in Comparative Example 1 after curing. Figure 2 The image shows the electron microscope (SEM) scan results of the conductive adhesive prepared in Example 1 after curing. Figure 3 This is a SEM image of the conductive adhesive prepared in Example 6 after curing. Figure 4 The DSC curve analysis diagram of silver powder 4; Figure 5 This is the DSC curve analysis chart of silver powder 5. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0025] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0026] According to one aspect of the present invention, a low-temperature sinterable silver paste is provided, comprising the following raw material components: epoxy resin, epoxy diluent, silane coupling agent, curing agent, solvent, micron-sized silver powder, and sinterable silver powder. The sinterable silver powder is a special micron-sized silver powder whose surface has been activated and coated with an organic coating layer, and has a specific surface area of ​​2.5~4.0 μm². 2 / g, peak sintering temperature 150~155℃; micron-sized silver powder, which is conventional ordinary micron-sized silver powder, with a median particle size between 0.5~8 μm and a specific surface area of ​​0.3~2.2 m². 2 / g, tap density is between 2 and 6 g / cm³ 3 The silver powder, which is between micrometers, can be in the form of flakes, spheres, dendrites or other shapes.

[0027] It should be noted that the micron silver powder can be a single type of micron silver powder or a mixture of micron silver powders that meet the requirements. For example, silver powder 1, silver powder 2, silver powder 3 and silver powder 4 mentioned in the following embodiments are all micron silver powders. In the process of preparing silver paste, one or more of them can be selected as micron silver powders.

[0028] In addition, the epoxy resin can be any one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, and LEPB in epoxy butadiene; the epoxy diluent can be any alicyclic glycidyl ether or phenyl glycidyl ether or a mixture thereof; the curing agent can be any one or more of aliphatic amine, alicyclic amine, adipic acid, sulfone, and methylimidazole; the silane coupling agent can be KH550 or KH560; and the solvent can be any one or more of ethylene glycol butyl ether, diethylene glycol, heptanol, and terpineol.

[0029] Regarding the content of each component, it can be expressed as a percentage by mass: epoxy resin 14%~18%, epoxy diluent 4%~8%, silane coupling agent 0.3%~1.0%, curing agent 1.5%~2.5%, solvent 1.0%~2.0%, micron-sized silver powder 50%~70%, and sinterable silver powder 5%~20%, with the sum of the mass percentages of the above components being 100%. According to another aspect of the present invention, the application of the above-described low-temperature sinterable silver paste in electronic product packaging processes is protected. Specifically, this silver paste is mainly used in the packaging of ICs, LEDs, passive components, automotive battery components, and high-power devices.

[0030] The following uses specific experimental data to illustrate the beneficial effects of the embodiments of the present invention compared to the prior art.

[0031] Unless otherwise specified, all materials and reagents used in the following examples are commercially available; and unless otherwise specified, all implementation methods used in the following examples are conventional methods.

[0032] In the examples below, silver powder 1, silver powder 2, silver powder 3, and silver powder 4 are all conventional micron-sized silver powders, with silver powder 1, silver powder 2, and silver powder 3 being large-sized micron-sized silver powders, and silver powder 4 being a small-sized micron-sized silver powder. Silver powder 5 is a special micron-sized silver powder with an active organic layer coated on its surface—a sinterable micron-sized silver powder. It is a small-sized micron-sized silver powder. The initial sintering temperature of silver powder 5 is 135.2℃, the peak sintering temperature is 150.1℃, and the final sintering temperature is 169.3℃. The specific models and specifications of silver powders 1-5 are shown in Table 1 below.

[0033] Table 1. Specifications of Silver Powder

[0034] In the following examples, the epoxy resin used is bisphenol A epoxy resin, the epoxy diluent is aliphatic glycidyl ether epoxy resin (butyl glycidyl ether BGE), the curing agent is a mixture of alicyclic amine IPDA, adipic acid and methylimidazole, and the solvent is a homogeneous mixture of diethylene glycol and terpineol in a mass ratio of 1:1.

[0035] Example 1 Referring to the raw material composition in Table 2, weigh 100g of the raw material components. Mix the organic components (15.8g of bisphenol A epoxy resin, 5.9g of aliphatic glycidyl ether epoxy resin, 0.5g of silane coupling agent, 0.4g of cycloaliphatic amine, 0.9g of adipic acid, 0.7g of methylimidazole, and 1.6g of solvent) evenly. Then add 59.6g of silver powder 1, 9.6g of silver powder 2, and 5g of silver powder 5, and stir evenly. Subsequently, use a vacuum homogenizer "ZYMC-700VS" to stir and degas for 3 minutes to obtain the conductive adhesive of Example 1. Store the conductive adhesive at -40℃ and allow it to warm to room temperature for at least 2 hours before use.

[0036] Example 2 Example 2 uses the same organic composition as Example 1, but with a different silver powder composition. Specifically, referring to Table 2, in Example 2, the silver powder composition is 59.6g of silver powder 1, 9.6g of silver powder 3, and 5g of silver powder 5.

[0037] Example 2 uses the same method as Example 1 to prepare conductive adhesive, which will not be described again here.

[0038] Example 3 Example 3 uses the same organic composition as Example 1, but with a different silver powder composition. Specifically, referring to Table 2, in Example 3, the silver powder composition is 59.6g of silver powder 1, 9.6g of silver powder 4, and 5g of silver powder 5.

[0039] Example 3 uses the same method as Example 1 to prepare conductive adhesive, which will not be described again here.

[0040] Example 4 Example 4 uses the same organic composition as Example 1, but with a different silver powder composition. Specifically, referring to Table 2, in Example 4, the silver powder composition is 54.6g of silver powder 1, 9.6g of silver powder 2, and 10g of silver powder 5.

[0041] Example 4 uses the same method as Example 1 to prepare conductive adhesive, which will not be described again here.

[0042] Example 5 Example 5 uses the same organic composition as Example 1, but with a different silver powder composition. Specifically, referring to Table 2, in Example 5, the silver powder composition is 49.6g of silver powder 1, 9.6g of silver powder 2, and 15g of silver powder 5.

[0043] Example 5 uses the same method as Example 1 to prepare conductive adhesive, which will not be described again here.

[0044] Example 6 Example 6 uses the same organic composition as Example 1, but with a different silver powder composition. Specifically, referring to Table 2, in Example 6, the silver powder composition is 44.6g of silver powder 1, 9.6g of silver powder 2, and 20g of silver powder 5.

[0045] Example 6 uses the same method as Example 1 to prepare conductive adhesive, which will not be described again here.

[0046] Comparative Example 1 Referring to the raw material composition in Table 2, Comparative Example 1 also uses the same organic composition as Examples 1-6 and the same preparation method. The difference lies in the composition of the silver powder. The silver powder composition of Examples 1-6 all contains sinterable silver powder, namely silver powder 5, while Comparative Example 1 does not contain silver powder 5.

[0047] Specifically, 100g of the raw material components were weighed, and the organic components, namely 15.8g of bisphenol A epoxy resin, 5.9g of aliphatic glycidyl ether epoxy resin, 0.5g of silane coupling agent, 0.4g of cycloaliphatic amine, 0.9g of adipic acid, 0.7g of methylimidazole, and 1.6g of diluent, were mixed evenly. Then, 64.6g of silver powder 1 and 9.6g of silver powder 2 were added and stirred evenly. Subsequently, the mixture was stirred and degassed using a vacuum homogenizer "ZYMC-700VS" for 3 minutes to obtain the conductive adhesive of Comparative Example 1. The conductive adhesive was stored at -40℃ and allowed to warm to room temperature for at least 2 hours before use.

[0048] Comparative Example 2 Comparative Example 2 used the same organic composition as Comparative Example 1, but with a different silver powder composition. Specifically, referring to Table 2, in Comparative Example 2, the silver powder composition consisted of 64.6 g of silver powder 1 and 9.6 g of silver powder 3.

[0049] Comparative Example 2 uses the same method as Comparative Example 1 to prepare conductive adhesive, which will not be described in detail here.

[0050] Comparative Example 3 Comparative Example 3 used the same organic composition as Comparative Example 1, but with a different silver powder composition. Specifically, referring to Table 2, in Comparative Example 3, the silver powder composition consisted of 64.6 g of silver powder 1 and 9.6 g of silver powder 4.

[0051] Comparative Example 3 uses the same method as Comparative Example 1 to prepare conductive adhesive, which will not be described in detail here.

[0052] Table 2 shows the raw material composition of the conductive adhesives in the above embodiments and comparative examples. A horizontal comparison clearly shows that Comparative Examples 1-3 and Examples 1-6 use the same mass of epoxy resin, epoxy diluent, curing agent, silane coupling agent, and solvent. The difference lies in the specific selection of silver powder. For Comparative Examples 1-3, sinterable silver powder was not used; instead, two types of conventional micron-sized silver powder were included. The first type of micron-sized silver powder consisted of 64.6g of silver powder 1, while the second type consisted of 9.6g each of silver powder 2, silver powder 3, and silver powder 4. In Examples 1-6, all of them contain both conventional sinterable silver powder and micronized silver powder. In Examples 1-3, the sinterable silver powder is 5g of silver powder 5, and there are two types of micronized silver powder. The first type is 59.6g of silver powder 1, and the second type is 9.6g of silver powder 2, silver powder 3, and silver powder 4 respectively. In Examples 1, 4-6, the sinterable silver powder is silver powder 5, but the mass is 5g, 10g, 15g, and 20g respectively. The micronized silver powder has two particle size specifications. The first type is silver powder 1, and the second type is silver powder 2.

[0053] Table 2. Formulation of silver paste for examples and comparative examples.

[0054] Performance testing The conductive adhesives prepared in each embodiment and comparative example were subjected to performance tests.

[0055] 1. Conductivity test (1) Sample preparation Take the conductive adhesives obtained in Examples 1 to 6 and Comparative Examples 1 to 3, prepare long strips with a thickness of 0.005 cm and a width of 0.3 cm, place them in an oven, set the temperature to rise from room temperature to 160°C in 0.5 h, and then keep the temperature constant for 1.5 h to complete the curing. After curing, place the samples to room temperature.

[0056] (2) Resistivity test Using a digital multimeter "VICTOR 86B", the resistance of each sample was tested using the two-point probe method, and then the resistivity was calculated using the following formula: ρ=RS / L Where: ρ is resistivity, in Ω·cm; R is resistance, and the unit is Ω; S represents the test cross-sectional area, in cm². 2 ; L represents the length of the material, in cm.

[0057] (3) Results Analysis The electrical properties of the conductive adhesives in the examples and comparative examples are shown in Table 3. As can be seen from Table 3, the change in the composition of the micron-sized silver powder in comparative examples 1-3 had little effect on the conductivity; the resistivity of examples 1-3 was slightly lower than that of comparative examples 1-3; and the resistivity of examples 4-6 was significantly lower than that of comparative examples 1-3.

[0058] This indicates that in Comparative Examples 2 and 3, the addition of silver powder 3 and silver powder 4 with different particle sizes did not result in a significant difference in conductivity compared to Comparative Example 1. Examples 1-3, after adding 5% by mass of sinterable silver powder (silver powder 5), exhibited conductivity comparable to Comparative Examples 1-3 without the addition of this silver powder. Furthermore, a comparison of Examples 1, 4-6 revealed that the conductivity significantly increased after adding 5%, 10%, 15%, and 20% by mass of sinterable silver powder (silver powder 5), respectively. This result demonstrates that by adding sinterable silver powder (silver powder 5) and gradually increasing its proportion, the resulting conductive adhesive becomes denser after curing, indirectly confirming the existence of a sintering process at 160°C.

[0059] Table 3 Resistivity Data

[0060] 2. Characterization by scanning electron microscopy (SEM) (1) Sample preparation Take 1g of the conductive adhesive prepared in Comparative Example 1, Example 1 and Example 6 and weigh it onto a glass slide, controlling the thickness between 0.5 and 1.0 cm. Place it in an oven and set it to heat from room temperature to 160°C for 0.5 hours, then keep it at a constant temperature for 1.5 hours to complete the curing. After curing, grind and polish the surface.

[0061] (2) SEM characterization The polished surface of the sample was observed using a scanning electron microscope “TESCAN MIRA LMS”.

[0062] (3) Results Analysis SEM results are attached to the instruction manual. Figure 1 , 2And 3. The conductive adhesives prepared in Comparative Example 1, Example 1, and Example 6 all contained the same total amount of silver powder, with the mass percentages of silver powder 5 being 0%, 5%, and 20%, respectively. From Figures 1-3 It can be seen that, after curing under the same conditions, the cross-sectional structure of Example 1, with 5% silver powder, is more compact than that of Comparative Example 1. In Example 6, with 20% silver powder, the cross-section is even denser, and the silver powder can be clearly observed to emanate from within. Figure 1 The particle dispersion, to Figure 3 The middle part tends to be blocky, and the number of interconnected block structures increases. It can be seen that with the addition and increase of sinterable silver powder, namely silver powder 5, the density of the solidified structure increases, and the sintering of silver paste is more obvious.

[0063] 3. Adhesion test (1) Sample preparation A 0.65×0.65mm Si chip and an SOP-8L copper-plated silver frame were selected. After bonding with the conductive adhesives prepared in Examples 1-6 and Comparative Examples 1-3, the chips were placed in an oven and heated from room temperature to 160°C for 0.5 hours, and then kept at a constant temperature for 1.5 hours to complete the curing process.

[0064] (2) Shear force test Its shear force was tested using a wire bonding push-pull force tester "HAWK-8200S". The room temperature shear force was tested at room temperature (25±1℃), and the high temperature shear force was tested at 200±2℃.

[0065] (3) Results Analysis The room temperature shear force data of the conductive adhesives prepared in each embodiment and comparative example are shown in Table 4 (Note: the unit of shear force data is g·f). Ten sets of shear force data were tested for each conductive adhesive model, and their average values ​​were calculated. As can be seen from the average room temperature shear force data in Table 4, after curing at 160℃, the difference in room temperature shear force between comparative examples 1-3 and examples 1-6 is not significant, indicating that the introduction of sinterable silver powder, i.e., silver powder 5, did not affect the room temperature shear force of the conductive adhesive.

[0066] Table 4. Shear Force Data at Room Temperature

[0067] The high-temperature shear force data of the conductive adhesives prepared in each embodiment and comparative example are shown in Table 5 (Note: the unit of shear force data is g·f). Ten sets of shear force data were tested for each conductive adhesive model, and their average values ​​were calculated. As shown in Table 4, all conductive adhesives were cured at 160℃. After adjusting the composition of different conventional micron-sized silver powders, the average high-temperature shear force of comparative examples 1-3 was between 296-308 g·f, with no significant difference. Among them, comparative examples 2 and 3, which added conventional micron-sized silver powders 3 and 4 with different particle sizes, respectively, failed to improve the high-temperature shear force of the conductive adhesives. In contrast, examples 1-3 all added 5% by mass of sinterable silver powder, i.e., silver powder 5, and their average high-temperature shear force was between 530-547 g·f. Between these examples, the values ​​were all more than 75% higher than those of the comparative examples. Examples 1, 4, 5, and 6 added sinterable silver powder (silver powder 5) at mass ratios of 5%, 10%, 15%, and 20%, respectively, and only the ratio of silver powder 1 to silver powder 5 was adjusted while keeping other components consistent. The average high-temperature shear forces were 546, 625, 722, and 826 g·f, respectively, which were 82.6%, 108.7%, 141.2%, and 175.8% higher than the average value of 299 g·f of comparative examples 1 to 3.

[0068] The results show that when the composition of the micron-sized silver powder is changed without adding sinterable silver powder (silver powder 5), there is no significant difference in the high-temperature shear force of the conductive adhesive regardless of whether silver powder 3 or silver powder 4 is added. After adding 5% of sinterable silver powder (silver powder 5), the high-temperature shear force of the conductive adhesive increases synchronously, while there is no significant difference between the different compositions of the micron-sized silver powder. However, keeping other compositions consistent and only adjusting the ratio of micron-sized silver powder to sinterable silver powder (silver powder 5), the high-temperature shear force gradually increases with the increase of the mass ratio of silver powder 5.

[0069] Table 5 High-Temperature Shear Force Data

[0070] Based on the above experiments, the DSC curves of silver powder 4 and silver powder 5 were analyzed, such as... Figure 4 , 5 Compared to silver powder 4, silver powder 5 exhibits a violent exothermic phenomenon around 150℃, indicating that the silver powder is active around 150℃ and reacts with each other.

[0071] The above combined results demonstrate that the addition of sinterable silver powder (silver powder 5) improves the conductivity of the conductive adhesive while maintaining a curing temperature of 160℃. Furthermore, under the same curing conditions, it significantly increases the high-temperature shear force of the conductive adhesive without affecting its room-temperature shear force. These results indicate that the introduction of silver powder 5 induces sintering in the conductive adhesive during curing at 160℃.

[0072] The specific embodiments of the present invention have been described above. Based on the above description, those skilled in the art can make various changes and modifications without departing from the technical concept of the present invention.

Claims

1. A silver paste capable of low-temperature sintering, characterized in that, Contains components by mass percentage: Epoxy resin 14%~18%, Epoxy diluent 4%~8%, Silane coupling agent 0.3%~1.0%, Hardener 1.5%~2.5%, Solvent 1.0%~2.0%, 50%~70% micron silver powder 5%~20% silver powder can be sintered. The sum of the mass percentages of the above components is 100%; the micron-sized silver powder has a particle size range of 0.5~8 μm, and the sinterable silver powder has a particle size range of 0.3~2.2 μm.

2. The low-temperature sinterable silver paste according to claim 1, characterized in that, The specific surface area of ​​the micron-sized silver powder is 0.3~2.2 m². 2 / g is a combination of one or more silver powder products with different particle sizes.

3. The low-temperature sinterable silver paste according to claim 1, characterized in that, The epoxy resin is one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, and epoxidized polybutadiene. The epoxy diluent is an alicyclic glycidyl ether and / or a phenyl glycidyl ether.

4. The low-temperature sinterable silver paste according to claim 1, characterized in that, The curing agent is one or more of the following: aliphatic amines, cycloaliphatic amines, adipic acid, sulfone, and methylimidazole.

5. The low-temperature sinterable silver paste according to claim 1, characterized in that, The solvent is one or more of ethylene glycol butyl ether, diethylene glycol, heptanol, and terpineol.

6. The low-temperature sinterable silver paste according to claim 1, characterized in that, The sinterable silver powder has a specific surface area of ​​2.5~4.0 m². 2 / g, sintering peak temperature 150~155℃.

7. The low-temperature sinterable silver paste according to claim 1, characterized in that, It contains the following raw material components by mass percentage: Epoxy resin 15%~16.5%, Epoxy diluent 5%~6%, Silane coupling agent 0.4%~0.6%, Hardener 1.8%~2.2%, Solvent 1.5%~2.0%, 54%~60% micron silver powder It can sinter 15%~20% silver powder.

8. The low-temperature sinterable silver paste according to claim 1, characterized in that, The properties of the silver paste that can be sintered at low temperatures include: Resistivity ≤250 μΩ·cm; At room temperature, the shear force on a 0.65×0.65mm chip is ≥2.7 kg·f; at 200±2℃, the shear force on a 0.65×0.65mm chip is ≥520 g·f.

9. A method for preparing a low-temperature sinterable silver paste as described in any one of claims 1 to 8, characterized in that, The process includes the following steps: mixing epoxy resin, epoxy diluent, silane coupling agent, curing agent, and solvent; adding micron-sized silver powder and sinterable silver powder and stirring until homogeneous; and finally homogenizing the mixture in a vacuum homogenizer to obtain silver paste that can be sintered at low temperatures.

10. The application of a low-temperature sinterable silver paste as described in any one of claims 1 to 8 in electronic product packaging processes.

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