Preparation method of self-reducing hybrid conductive silver ink for aerosol micro-scale printing

Abstract

The invention discloses a method for preparing a self-reducing hybrid conductive silver ink for aerosol microscale printing, comprising: dissolving a complexing agent and an additive in a solvent to obtain a mixed solution A; then dissolving a silver precursor in the mixed solution A to obtain a silver-ammine complex solution; then dissolving a volatile compound that is non-reducible at room temperature and can release a strong reducing substance after heating in the silver-ammine complex solution to obtain a mixed solution B; finally, adding a volatile weak reducing substance dropwise to the mixed solution B, reacting while adding, until the volatile weak reducing substance is added dropwise, to obtain a self-reducing hybrid conductive silver ink for aerosol microscale printing. The invention prepares a hybrid conductive silver ink, which adopts two different types of reducing agents to cooperate with each other, has the advantages of both particle-type ink and particle-free ink, improves the film-forming property of the ink, realizes high-precision printing, and can meet the printing requirements of various printed circuits and special-shaped circuits.

Description

Technical Field

[0001] The invention belongs to the field of silver-based conductive inks, and in particular is a method for preparing aerosol micro-scale printing self-reducing mixed conductive silver ink. Background Art

[0002] In recent years, with the continuous development of printing technology and 3D printing technology, the application of printing technology to prepare electronic circuits has become more and more common. Compared with traditional technologies such as photolithography and magnetron sputtering, printed electronics technology has the advantages of thinness, flexibility, low cost, easy manufacturing, high-speed manufacturing response time, green environmental protection, and high energy efficiency. It can realize the mass and high-speed production of traditional electronic products and effectively reduce production costs. It is the main development direction of the transformation and upgrading of the traditional printing industry and the modern microelectronics manufacturing industry.

[0003] As an emerging non-contact printed electronics technology, aerosol jet printing technology has broad application prospects. Compared with inkjet printing technology, the printing resolution of aerosol jet printing technology does not depend on the size of the nozzle, and can realize the preparation of high-precision electronic devices. Compared with screen printing technology, aerosol jet printing technology does not require template preparation, which greatly simplifies the process flow of device preparation. In addition, traditional electronic printing technology is relatively expensive and only supports two-dimensional printing, while aerosol jet printing technology can achieve three-dimensional printing, prepare special-shaped circuits and micro-scale three-dimensional structure design.

[0004] As we all know, the performance of a device depends mainly on the material and preparation process of the device, so ink plays a vital role in aerosol jet printing technology. Traditional conductive inks, whether particle-based or particle-free, have disadvantages such as poor atomization performance, high price, and poor adhesion. For example, the particle-free silver ink mentioned in the document "Reactive Silver Inks for Patterning High-Conductivity Features at Mild Temperatures" is unstable when printing finer lines (less than 50 microns) due to its large surface tension, and is prone to breakpoints. The particle-based silver ink mentioned in the document "Synthesis of silver nano particles and fabrication of aqueous Ag inks for inkjet printing" requires a sintering temperature of 350°C, making it difficult to apply to most flexible substrates. Summary of the invention

[0005] In view of the deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a method for preparing aerosol micro-scale printing self-reducing hybrid conductive silver ink.

[0006] The technical solution of the present invention to solve the technical problem is to provide a method for preparing aerosol micro-scale printing self-reducing hybrid conductive silver ink, characterized in that the method comprises the following steps:

[0007] Step 1, dissolving the complexing agent and the additive in a solvent to obtain a homogeneous mixed solution A;

[0008] Step 2, dissolving the silver precursor in the mixed solution A obtained in step 1 to obtain a homogeneous silver-ammine complex solution;

[0009] Step 3, dissolving a volatile compound that has no reducing properties at room temperature and can release strong reducing substances after heating in the silver-ammine complex solution obtained in step 2 to obtain a homogeneous mixed solution B;

[0010] Step 4: Add the volatile weak reducing substance dropwise to the mixed solution B obtained in step 3, reacting while adding until the addition of the volatile weak reducing substance is completed, at which time the solution changes from colorless and transparent to reddish brown, and an aerosol microscale printing self-reducing hybrid conductive silver ink is obtained.

[0011] Compared with the prior art, the present invention has the following beneficial effects:

[0012] (1) The present invention prepares a hybrid conductive silver ink, which adopts two different types of reducing agents to cooperate with each other, and has the advantages of both particle-type ink (good printing boundary and easy storage) and particle-free ink (low sintering temperature, good adhesion and conductivity), improves the film-forming property of the ink, and realizes high-precision printing with a maximum precision of 15 microns, which can meet the printing needs of various printed circuits and special-shaped circuits.

[0013] (2) The present invention uses two different types of reducing substances. The concentration of the volatile weak reducing substance increases rapidly during the subsequent post-sintering treatment due to the volatilization of the solvent, and it begins to react with the silver precursor to precipitate silver nanoparticles, which significantly reduces the temperature of the post-sintering treatment (within 140°C), thereby meeting the printing conditions of most flexible substrates; the volatile compounds that are non-reducing at room temperature and can release strong reducing substances after heating will release strong reducing substances such as formaldehyde and acetaldehyde when decomposed by heat, so that the silver precursor that has not been reduced by the volatile weak reducing substance is reduced more thoroughly, and finally the silver conductive lines are purer and the conductivity is improved.

[0014] (3) The present invention uses silver nanoparticles obtained by reduction of volatile weak reducing substances. When the liquid line printing is completed, the nanoparticles in the solution are used to transform the evaporation mode of the liquid line from volume reduction evaporation to thickness reduction evaporation. The coffee ring effect is used to pin the droplets. When the liquid line printing is completed, the droplets are immediately pinned in place to prevent the liquid line from shrinking due to solvent evaporation, thereby preventing breakpoints, bad points, etc. from being caused.

[0015] (4) The silver nanoparticles required for silver ink are spontaneously generated during the reaction process and do not require additional addition, which simplifies the preparation process. They are also specially developed for aerosol jet printing technology and have better adaptability.

[0016] (5) The conductive silver ink of the present invention has excellent aerosolization performance, low cost, green and environmentally friendly, good conductivity and can be printed with high precision. It can meet the printing and production of various precision circuits and precision electronic devices. It has high practical application value and is suitable for application scenarios such as printed circuits, temperature sensors, strain sensors, flexible electrodes, and membrane switches, and is particularly suitable for aerosol jet printing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is an optical microscope photograph of the silver conductive line with a resolution of 50 μm prepared in Example 1 of the present invention;

[0018] Figure 2 This is an optical microscope photograph of a silver conductive line with a resolution of 60 μm prepared in Example 1 of the present invention;

[0019] Figure 3 This is an optical microscope photograph of the silver conductive line with a resolution of 70 μm prepared in Example 1 of the present invention;

[0020] Figure 4 This is an optical microscope photograph of the silver conductive line with a resolution of 110 μm prepared in Example 1 of the present invention;

[0021] Figure 5 This is a scanning electron microscope photo of the conductive silver ink prepared in Example 1 of the present invention after printing and sintering;

[0022] Figure 6 This is an optical microscope photograph of silver microcolumns printed with the conductive silver ink prepared in Example 2 of the present invention;

[0023] Figure 7 An optical microscope photograph of the silver conductive lines with the highest precision printed by the conductive silver ink prepared in Example 3 of the present invention;

[0024] Figure 8 This is an optical microscope photograph of a microcircuit array printed with conductive silver ink prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0025] The specific embodiments of the present invention are given below. The specific embodiments are only used to further illustrate the present invention in detail and do not limit the protection scope of the claims of the present invention.

[0026] The present invention provides a method for preparing aerosol micro-scale printing self-reducing hybrid conductive silver ink (hereinafter referred to as the method), characterized in that the method comprises the following steps:

[0027] Step 1, dissolving the complexing agent and the additive in a solvent to obtain a homogeneous mixed solution A;

[0028] Preferably, in step 1, in the mixed solution A, the mass fraction of the complexing agent is 5-20wt%, and the mass fraction of the additive is 2-5wt%.

[0029] Preferably, in step 1, the complexing agent is ammonia water, 1,2-propylenediamine or butanediamine; the additive is polyvinyl alcohol (PVA), carboxymethyl cellulose or polyurethane (PU); and the solvent is at least one of anhydrous ethanol, water, isopropanol and n-butanol.

[0030] Preferably, in step 1, the dissolution process is: stirring at a rotation speed of 50-200 rpm at room temperature for 10-20 min.

[0031] Step 2, dissolving the silver precursor in the mixed solution A obtained in step 1 to obtain a homogeneous silver-ammine complex solution;

[0032] Preferably, in step 2, the mass fraction of the silver precursor in the silver ammonia complex solution is 5-20wt%.

[0033] Preferably, in step 2, the silver precursor is weak acid silver or silver oxide; the weak acid silver is silver acetate, silver propionate or silver formate.

[0034] Preferably, in step 2, the dissolution process is: stirring at a rotation speed of 50-200 rpm at room temperature for 10-20 min.

[0035] Step 3, dissolving a volatile compound that has no reducing properties at room temperature and can release strong reducing substances after heating in the silver-ammine complex solution obtained in step 2 to obtain a homogeneous mixed solution B;

[0036] Preferably, in step 3, in the mixed solution B, the mass fraction of the volatile compound that has no reducing property at room temperature and can release strong reducing substances after heating is 1-1.5wt%.

[0037] Preferably, in step 3, the volatile compound that has no reducing properties at room temperature and can release strong reducing substances after heating is at least one of diethanolamine, ethylene glycol and glycerol, preferably diethanolamine.

[0038] Preferably, in step 3, the dissolution process is: stirring at a rotation speed of 50-200 rpm at room temperature for 10-20 min.

[0039] Step 4: Add the volatile weak reducing substance dropwise into the mixed solution B obtained in step 3, reacting while adding until the addition of the volatile weak reducing substance is completed, at which time the solution changes from colorless and transparent to reddish brown, and an aerosol microscale printing self-reducing hybrid conductive silver ink (referred to as conductive silver ink) is obtained.

[0040] Preferably, in step 4, the mass fraction of the volatile weakly reducing substance in the conductive silver ink is 3-5%.

[0041] Preferably, in step 4, the volatile weak reducing substance is at least one of formic acid, ammonium formate, methyl formate and N,N-dimethylformamide, preferably formic acid or ammonium formate.

[0042] Preferably, in step 4, the reaction process is: stirring at a rotation speed of 50-200 rpm at room temperature for 10-20 min.

[0043] Preferably, in step 4, the solution changes from colorless and transparent to reddish brown, which is due to the precipitation of silver nanoparticles, and the mass fraction of the silver nanoparticles in the conductive silver ink is 0.5-1.5%.

[0044] Preferably, the method further comprises step 5: performing post-processing on the conductive silver ink obtained in step 4.

[0045] Preferably, in step 5, the post-processing of the finished product is: diluting the conductive silver ink into different concentrations using the solvent in step 1 according to needs, and then sealing and storing in a dark place and refrigeration.

[0046] Embodiment 1:

[0047] Step 1. Under stirring at room temperature, 0.6 mL of 1,2-propylenediamine and 0.05 g of PVA were dissolved in 4 mL of a mixed solvent (the mixed solvent consisted of water and anhydrous ethanol, and the mass ratio of water to anhydrous ethanol was 11:20), and stirred at 100 rpm for 15 min to fully mix them to obtain a mixed solution A;

[0048] Step 2, adding 1 g of silver acetate to the mixed solution A of step 1, stirring at 100 rpm for 15 min at room temperature to completely dissolve it, to obtain a silver ammonia complex solution;

[0049] Step 3, adding 0.05 mL of diethanolamine to the silver ammonia complex solution of step 2, stirring at 100 rpm for 15 min at room temperature to completely dissolve it, to obtain a mixed solution B;

[0050] Step 4: Under the condition of stirring at room temperature and 100 rpm, 0.3 mL of formic acid was added dropwise to the mixed solution B of step 3. The solution was observed to change from colorless and transparent to reddish brown. At this time, silver nanoparticles with a mass fraction of 1% were precipitated to obtain conductive silver ink.

[0051] The conductive silver ink prepared in Example 1 was used as a raw material, and ultrasonic atomization was used. A nozzle with a 300-μm caliber was selected, the carrier gas flow rate was 60 sccm, the sheath gas flow rate was 120 sccm, the nozzle moved at a speed of 5 mm / s, and liquid lines were printed when the substrate was 70° C., and then the substrate with the liquid lines was sintered at 120° C. for 20 min to obtain silver conductive lines.

[0052] Depend on Figure 1-4 It can be seen that the silver conductive lines prepared using the conductive silver ink prepared in Example 1 as a raw material have neat edges, small splashes, and excellent printing performance.

[0053] Depend on Figure 5 It can be seen that the conductive silver ink prepared in Example 1 has fine and uniform particles after printing and sintering, and has few surface pores, which explains why it has low resistivity and good adhesion.

[0054] Embodiment 2:

[0055] Step 1, under stirring at room temperature, dissolve 0.5 mL of concentrated ammonia and 0.1 g of PVA in 4 mL of anhydrous ethanol, and stir at 50 rpm for 15 min to fully mix, to obtain a mixed solution A;

[0056] Step 2, adding 1 g of silver propionate to the mixed solution A of step 1, stirring at 50 rpm for 15 min at room temperature to completely dissolve it, to obtain a silver ammonia complex solution;

[0057] Step 3, adding 0.05 mL of ethylene glycol to the silver ammonia complex solution of step 2, stirring at 50 rpm for 15 min at room temperature to completely dissolve it, to obtain a mixed solution B;

[0058] Step 4: Add 0.3 mL of ammonium formate dropwise into the mixed solution B of step 3 under stirring at room temperature and 50 rpm. The solution is observed to change from colorless and transparent to reddish brown. At this time, silver nanoparticles with a mass fraction of 0.5% are precipitated to obtain conductive silver ink.

[0059] The conductive silver ink prepared in Example 2 was used as a raw material, and ultrasonic atomization was used. A nozzle with a 300-micron caliber was selected, the carrier gas flow rate was 50 sccm, the sheath gas flow rate was 130 sccm, the nozzle moved at a speed of 5 mm / s, and stayed at the location where the silver microcolumns were required for 5 s. When the substrate was at 90° C., a shaped electrode with silver microcolumns was printed, and then the substrate with the shaped electrode with silver microcolumns was sintered at 120° C. for 20 min to completely silverize the shaped electrode with silver microcolumns.

[0060] Depend on Figure 6 It can be seen that the conductive silver ink prepared in Example 2 can be used to print special-shaped electrodes such as columnar electrodes.

[0061] Embodiment 3:

[0062] Step 1, under stirring at room temperature, dissolve 1 g of diaminobutane and 0.1 g of carboxymethyl cellulose in 4 mL of a mixed solvent (the mixed solvent consists of water and anhydrous ethanol, and the mass ratio of water to anhydrous ethanol is 11:20), stir at 200 rpm for 15 min to fully mix, and obtain a mixed solution A;

[0063] Step 2, adding 1.5 g of silver oxide to the mixed solution A of step 1, stirring at 200 rpm for 15 min at room temperature to completely dissolve it, to obtain a silver ammonia complex solution;

[0064] Step 3, adding 1 g of ethylene glycol to the silver ammonia complex solution of step 2, stirring at 200 rpm for 15 min at room temperature to completely dissolve it, to obtain a mixed solution B;

[0065] Step 4: Under the condition of stirring at room temperature and 200 rpm, 0.5 mL of formic acid was added dropwise to the mixed solution B of step 3. The solution was observed to change from colorless and transparent to reddish brown. At this time, silver nanoparticles with a mass fraction of 1% were precipitated to obtain conductive silver ink.

[0066] The conductive silver ink prepared in Example 1 was used as a raw material, and ultrasonic atomization was used. A nozzle with a 200-μm caliber was selected, the carrier gas flow rate was 30 sccm, the sheath gas flow rate was 100 sccm, the nozzle moved at a speed of 5 mm / s, and liquid lines were printed when the substrate was 70° C., and then the substrate with the liquid lines was sintered at 120° C. for 20 min to obtain silver conductive lines.

[0067] Depend on Figure 7 It can be seen that the highest printing accuracy of the conductive silver ink prepared in Example 3 is close to the printing accuracy limit of the aerosol jet printing technology.

[0068] Depend on Figure 8 It can be seen that the conductive silver ink prepared in Example 3 has the ability to continuously print micro devices.

[0069] The properties of the conductive silver inks prepared in Examples 1-3 are shown in Table 1.

[0070]

[0071] Any matters not described in the present invention are applicable to the prior art.

Claims

1. A method for preparing aerosol micro-scale printing self-reducing hybrid conductive silver ink, characterized in that: The method comprises the following steps: Step 1, dissolving the complexing agent and the additive in a solvent to obtain a homogeneous mixed solution A; The complexing agent is ammonia water, 1,2-propylenediamine or butanediamine; the additive is polyvinyl alcohol, carboxymethyl cellulose or polyurethane; Step 2, dissolving the silver precursor in the mixed solution A obtained in step 1 to obtain a homogeneous silver-ammine complex solution; Step 3, dissolving a volatile compound that has no reducing properties at room temperature and can release strong reducing substances after heating in the silver-ammine complex solution obtained in step 2 to obtain a homogeneous mixed solution B; The volatile compound that has no reducing property at room temperature and can release strong reducing substances after heating is at least one of diethanolamine, ethylene glycol and glycerol; Step 4, adding the volatile weak reducing substance dropwise into the mixed solution B obtained in step 3, reacting while adding, until the addition of the volatile weak reducing substance is completed, at which time the solution changes from colorless and transparent to reddish brown, to obtain an aerosol microscale printing self-reducing hybrid conductive silver ink; The volatile weak reducing substance is at least one of formic acid, ammonium formate, methyl formate and N,N-dimethylformamide.

2. The method for preparing aerosol micro-scale printing self-reducing hybrid conductive silver ink according to claim 1, characterized in that: In step 1, in the mixed solution A, the mass fraction of the complexing agent is 5 to 20 wt %, and the mass fraction of the additive is 2 to 5 wt %.

3. The method for preparing aerosol micro-scale printing self-reducing hybrid conductive silver ink according to claim 1, characterized in that: In step 1, the solvent is at least one of anhydrous ethanol, water, isopropanol and n-butanol.

4. The method for preparing aerosol micro-scale printing self-reducing hybrid conductive silver ink according to claim 1, characterized in that: In step 2, in the silver-ammine complex solution, the mass fraction of the silver precursor is 5 to 20 wt %.

5. The method for preparing aerosol micro-scale printing self-reducing hybrid conductive silver ink according to claim 1, characterized in that: In step 2, the silver precursor is weak acid silver or silver oxide; the weak acid silver is silver acetate, silver propionate or silver formate.

6. The method for preparing aerosol micro-scale printing self-reducing hybrid conductive silver ink according to claim 1, characterized in that: In step 3, in the mixed solution B, the mass fraction of the volatile compound that has no reducing property at room temperature and can release strong reducing substances after heating is 1 to 1.5 wt %.

7. The method for preparing aerosol micro-scale printing self-reducing hybrid conductive silver ink according to claim 1, characterized in that: In step 4, in the conductive silver ink, the mass fraction of the volatile weak reducing substance is 3-5%.

8. The method for preparing aerosol micro-scale printing self-reducing hybrid conductive silver ink according to claim 1, characterized in that: In step 1, step 2 and step 3, the dissolution process is: stirring at a speed of 50 to 200 rpm at room temperature for 10 to 20 minutes; In step 4, the reaction process is: stirring at a rotation speed of 50 to 200 rpm at room temperature for 10 to 20 minutes.

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