Nano-silver film with adjustable melting point and preparation method of nano-silver film

Abstract

The invention discloses a nano-silver film with an adjustable melting point and a preparation method of the nano-silver film. The method comprises the following steps: firstly, preparing a silver nanorod mother solution; mixing the obtained silver nanorod mother liquor with a detergent in proportion, and carrying out stirring washing and flocculation treatment; and the silver nanorod dispersion liquid obtained through final washing is transferred into a filter pressing device to be subjected to filter pressing and film forming, and the preliminarily-formed nano-silver film is obtained. And then, the prepared silver film is subjected to rolling treatment to achieve surface flattening, and then the silver film is placed in an environment with the temperature being 80-120 DEG C to be dried so that the silver film can be fully dehydrated. After drying is completed, the silver film can be directly stripped from the filter paper substrate, the stripped nano-silver film is subjected to cold pressing treatment, and the final nano-silver film is obtained. And the content of residual organic matters on the surface of the silver nanorod can be changed by regulating and controlling the washing times and the washing agent, so that the melting point of the nano-silver film is regulated and controlled.

Description

Technical Field

[0001] The invention relates to a silver film preparation process, in particular to a nano silver film with adjustable melting point and a preparation method thereof. Background Art

[0002] With the rapid development of high-power and highly integrated electronic devices, the performance requirements of packaging interconnect materials in device packaging are constantly increasing.

[0003] Silver, due to its excellent electrical and thermal conductivity and good oxidation resistance, has become a key interconnect material in the electronic packaging field. Among them, low-temperature sintering silver technology based on nanosilver can achieve high-density metal connections at relatively low temperatures, combining low-temperature processing with high-temperature service capabilities. It has been widely researched and initially applied in advanced packaging fields such as power devices and high-frequency communication devices.

[0004] Currently, the mainstream nano-silver sintering materials are mostly based on silver nanoparticles. They are prepared into stable slurries by mixing organic solvents, dispersants, binders and other additives, and then packaged and connected through screen printing, dispensing and other methods.

[0005] However, silver paste materials have the following major problems:

[0006] First, because it contains a large amount of organic components, the sintering process requires a complex degreasing stage, which easily produces organic residues at the material interface or within the film layer, reducing the final electrical and thermal conductivity and even affecting the reliability of the solder joints.

[0007] Secondly, the silver paste process is highly dependent on printing or dispensing equipment, and the film thickness and uniformity are limited, making it difficult to adapt to large-size packaging structures; in addition, the composition of organic additives is complex, making it difficult to achieve precise control of sintering behavior, especially the melting point. Summary of the Invention

[0008] In order to solve the problems of difficult-to-control melting point and high organic matter content of nano-silver films in the prior art, the present invention provides a nano-silver film with adjustable melting point and a preparation method thereof.

[0009] The present invention is achieved through the following technical solutions:

[0010] 1. A method for preparing a nanosilver film with a controllable melting point, comprising the following steps:

[0011] S1: Prepare silver nanorod mother solution, the silver nanorods have a length of 0.5-8 μm and a diameter of 20-120 nm;

[0012] S2: mixing the silver nanorod mother solution with a detergent in proportion, stirring and washing the mixture thoroughly and combining the washing with flocculation treatment, and repeatedly washing the mixture to obtain a silver nanorod dispersion;

[0013] S3: transferring the silver nanorod dispersion obtained in step S2 to a filter press apparatus for filter press formation to obtain a preliminarily formed nanosilver film;

[0014] S4: The nanosilver film initially formed in step S3 is subjected to roller pressing to achieve surface flatness, and then placed in a temperature environment of 80°C–120°C for drying for 20-120 minutes to fully dehydrate and shape the film; after drying, the silver film is directly peeled off from the filter paper substrate, and the peeled nanosilver film is cold-pressed to obtain the final nanosilver film.

[0015] The silver nanorods in step S1 have a length of 0.5-8 μm and a diameter of 20-120 nm.

[0016] The detergent in step S2 is one of deionized water, anhydrous ethanol, acetone, acetic acid, sodium chloride aqueous solution, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, and sodium borohydride aqueous solution;

[0017] The concentrations of the sodium chloride, sodium hydroxide, potassium hydroxide and sodium borohydride are between 0.5 and 10 g / L.

[0018] In step S2, the ratio of the silver nanorod mother solution to the detergent is 1:1-10, the stirring rate is 200-700 r / min, and the stirring time is 10-60 minutes.

[0019] In step S2, the filter membrane used in the flocculation treatment is a polypropylene (PP), polytetrafluoroethylene (PTFE) or organic nylon filter membrane, and the pore size of the filter membrane is 0.3-8 μm.

[0020] In step S3, the filter membrane used for the filter press is polypropylene (PP), polytetrafluoroethylene (PTFE) or organic nylon filter membrane, and the pore size of the filter membrane is 0.3-8 μm.

[0021] In step S2, the flocculant used in the flocculation treatment is at least one of dodecylbenzenesulfonic acid, lauryl aluminum sulfate, aluminum chloride, citric acid, sodium citrate, polyaluminum chloride, ferrous sulfate, ferric chloride, potassium aluminum sulfate, and polyacrylamide.

[0022] The concentration of the flocculant is 10-300 g / L, and the ratio of the added amount to the reaction solution is 1:5-60.

[0023] In step S3, the filter press pressure is 0.1-0.4 MPa;

[0024] In step S4, the rolling pressure of the rolling treatment is 10-100 Kg, the thickness of the silver film is 50-400 μm; the drying temperature is 80-120° C., the drying time is 20-120 min, the cold pressing pressure is 30-400 MPa, and the cold pressing time is 1-12 h.

[0025] Compared with the prior art, the present invention has the following advantages and effects:

[0026] The present invention purifies silver nanorods by multiple washings, significantly improving their purity and resulting in a nanosilver film with a low organic matter content. Furthermore, increasing the number of washes effectively reduces the amount of organic matter remaining on the surface of the silver nanorods, thereby enabling controllable adjustment of the melting point of the nanosilver film. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a macroscopic photograph of the nanosilver film obtained in Example 1;

[0028] Figure 2 This is a scanning electron microscope (SEM) photograph of the nanosilver film prepared in Example 1;

[0029] Figure 3 is the differential thermal-thermogravimetric analysis curve of the silver nanorods prepared in Example 1;

[0030] Figure 4 The SEM images of the nanosilver film prepared in Example 1 after being kept at different temperatures for 30 minutes;

[0031] Figure 5 This is a SEM photo of the nanosilver film prepared in Example 2;

[0032] Figure 6 The differential thermal analysis-thermogravimetric analysis curve of the silver nanorods prepared in Example 2;

[0033] Figure 7 The SEM images of the nanosilver film prepared in Example 2 after being kept at different temperatures for 30 minutes;

[0034] Figure 8 This is a SEM photo of the nanosilver film prepared in Example 3;

[0035] Figure 9 The differential thermal analysis-thermogravimetric analysis curve of the silver nanorods prepared in Example 3;

[0036] Figure 10 The nanosilver film prepared in Example 3 was kept at different temperatures for 30 minutes. DETAILED DESCRIPTION

[0037] The preparation process of the nanosilver film with adjustable melting point of the present invention is further described in detail below with reference to specific examples.

[0038] Example 1:

[0039] The silver nanorod solution was mixed with anhydrous ethanol at a volume ratio of 1:2 and washed at a stirring rate of 600 rpm for 20 minutes. After washing, 30 g / L of aluminum dodecyl sulfate flocculant was added to the mixture, mixed thoroughly, and allowed to settle completely. The solution was then filtered through an 8 μm pore size polypropylene (PP) membrane to collect the silver nanorod precipitate. The resulting precipitate was washed again using the same process, for a total of two rounds of washing. The washed and purified silver nanorod dispersion was transferred to a filter press and filtered at 0.2 MPa. After filtration, the resulting filter cake was flattened by applying a 50 kg roller pressure. The treated silver film was then dried at 80°C for 60 minutes to fully dehydrate it. After drying, the silver film could be directly separated from the filter paper. Finally, the separated silver nanorod film was cold-pressed at 40 MPa for 8 hours.

[0040] Figure 1 This is a macroscopic photograph of the nanosilver film obtained in this example;

[0041] Figure 2 is a scanning electron microscope (SEM) photograph of the nanosilver film prepared in this example;

[0042] Figure 3 is the differential thermal-thermogravimetric analysis curve of the silver nanorods prepared in this example;

[0043] Figure 4 These are SEM images of the nanosilver film prepared in this example after being kept at different temperatures for 30 minutes.

[0044] Example 2

[0045] The silver nanorod solution was mixed with deionized water at a volume ratio of 1:9 and washed for 60 minutes at a stirring rate of 300 rpm. After washing, a 40 g / L aluminum chloride flocculant was added to the mixture, stirred thoroughly, and allowed to settle completely. The solution was then filtered through a 5 μm pore size polytetrafluoroethylene (PTFE) filter to collect the silver nanorod precipitate. The washing and filtration process was repeated for three rounds to effectively remove impurities and surface residues. The resulting silver nanorod dispersion was transferred to a filter press and filtered at 0.3 MPa. After complete dehydration, the filter cake was flattened by applying a 20 kg roller pressure. The resulting filter cake was dried at 120°C for 20 minutes. After drying, the nanosilver film was directly peeled from the filter paper. Finally, the separated silver film was cold-pressed at 200 MPa for 4 hours.

[0046] Figure 5 is a SEM photo of the nanosilver film prepared in this example;

[0047] Figure 6 is the differential thermal-thermogravimetric analysis curve of the silver nanorods prepared in this embodiment;

[0048] Figure 7 These are SEM images of the nanosilver film prepared in this example after being kept at different temperatures for 30 minutes.

[0049] Example 3

[0050] The silver nanorod solution was mixed with a sodium chloride aqueous solution at a volume ratio of 1:3 and washed at a stirring rate of 200 rpm for 40 minutes. After washing, 80 g / L of citric acid flocculant was added to the mixture, stirred thoroughly, and allowed to settle completely. The solution was then filtered through a 5 μm organic nylon filter membrane to collect the silver nanorod precipitate. The washing and filtration steps were repeated for a total of five rounds. The washed silver nanorod dispersion was transferred to a filter press and filtered under a pressure of 0.4 MPa to form a filter cake. After filtration, the resulting filter cake was flattened by applying a roller pressure of 80 kg. The filter cake was then dried at 100°C for 40 minutes to completely dehydrate it. After drying, the silver film could be directly peeled from the filter paper to obtain a pre-formed silver nanofilm. Finally, the separated silver nanofilm was cold-pressed at a pressure of 80 MPa for 3 hours.

[0051] Figure 8 is a SEM photo of the nanosilver film prepared in this example;

[0052] Figure 9 is the differential thermal-thermogravimetric analysis curve of the silver nanorods prepared in this embodiment;

[0053] Figure 10 These are SEM images of the nanosilver film prepared in this example after being kept at different temperatures for 30 minutes.

[0054] As described above, the present invention can be implemented better.

[0055] The implementation methods of the present invention are not limited to the above-mentioned embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a nanosilver film with adjustable melting point, characterized in that The following steps are involved: S1: Prepare silver nanorod mother solution, the silver nanorods have a length of 0.5-8 μm and a diameter of 20-120 nm; S2: mixing the silver nanorod mother solution with a detergent in proportion, stirring and washing the mixture thoroughly and combining the washing with flocculation treatment, and repeatedly washing the mixture to obtain a silver nanorod dispersion; S3: transferring the silver nanorod dispersion obtained in step S2 to a filter press apparatus for filter press formation to obtain a preliminarily formed nanosilver film; S4: The nanosilver film initially formed in step S3 is subjected to roller pressing to achieve surface flatness, and then placed in a temperature environment of 80°C–120°C for drying for 20-120 minutes to fully dehydrate and shape the film; after drying, the silver film is directly peeled off from the filter paper substrate, and the peeled nanosilver film is cold-pressed to obtain the final nanosilver film.

2. The method for preparing a nanosilver film with adjustable melting point according to claim 1, wherein: The detergent in step S2 is one of deionized water, anhydrous ethanol, acetone, acetic acid, sodium chloride aqueous solution, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, and sodium borohydride aqueous solution.

3. The method for preparing a nanosilver film with adjustable melting point according to claim 2, wherein: The concentrations of the sodium chloride, sodium hydroxide, potassium hydroxide and sodium borohydride are between 0.5 and 10 g / L.

4. The method for preparing a nanosilver film with adjustable melting point according to claim 1, wherein: In step S2, the ratio of the silver nanorod mother solution to the detergent is 1:1-10, the stirring rate is 200-700 r / min, and the stirring time is 10-60 minutes.

5. The method for preparing a nanosilver film with adjustable melting point according to claim 1, wherein: In step S2, the filter membrane used in the flocculation treatment is a polypropylene (PP), polytetrafluoroethylene (PTFE) or organic nylon filter membrane, and the pore size of the filter membrane is 0.3-8 μm.

6. The method for preparing a nanosilver film with adjustable melting point according to claim 1, wherein: In step S3, the filter membrane used for the filter press is polypropylene (PP), polytetrafluoroethylene (PTFE) or organic nylon filter membrane, and the pore size of the filter membrane is 0.3-8 μm.

7. The method for preparing a nanosilver film with adjustable melting point according to claim 1, wherein: In step S2, the flocculant used in the flocculation treatment is at least one of dodecylbenzenesulfonic acid, lauryl aluminum sulfate, aluminum chloride, citric acid, sodium citrate, polyaluminum chloride, ferrous sulfate, ferric chloride, potassium aluminum sulfate, and polyacrylamide.

8. The method for preparing a nanosilver film with adjustable melting point according to claim 7, wherein: The concentration of the flocculant is 10-300 g / L, and the ratio of the added amount to the reaction solution is 1:5-60.

9. The method for preparing a nanosilver film with adjustable melting point according to claim 1, wherein: In step S3, the filter press pressure is 0.1-0.4 MPa; In step S4, the rolling pressure of the rolling treatment is 10-100 Kg, the thickness of the silver film is 50-400 μm; the drying temperature is 80-120° C., the drying time is 20-120 min, the cold pressing pressure is 30-400 MPa, and the cold pressing time is 1-12 h.

10. A nanosilver film with adjustable melting point, characterized in that Obtained by the preparation method according to any one of claims 1 to 9.

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