CN105462366A - Preparation method of low-temperature sintering non-granular silver conductive ink - Google Patents

Abstract

The invention relates to the technical field of conductive ink, in particular to a method for preparing low-temperature sintered particle-free silver conductive ink. A method for preparing a low-temperature sintered particle-free silver conductive ink, characterized in that the specific steps are as follows: (1) dissolving silver nitrate and sodium salt in deionized water, and then adding the sodium salt solution into the silver nitrate solution to obtain silver salt ; (2) dissolving alcohols and amines in a solvent; (3) adding the silver salt obtained in step (1) to the mixed solution system obtained in step (2) in turn to obtain a clear and transparent solution; (4) adding The viscosity regulator and the surface tension regulator are added to the solution prepared in step (3), and the particle-free silver conductive ink that can be used in inkjet printing technology is obtained. Compared with the prior art, it provides a particle-free conductive ink with good stability and low-temperature sintering and a preparation method thereof. The conductive ink can ensure good conductivity at a relatively low silver content, thereby reducing costs.

Description

A kind of preparation method of low-temperature sintering particle-free silver conductive ink

technical field

The invention relates to the technical field of conductive ink, in particular to a method for preparing low-temperature sintered particle-free silver conductive ink.

Background technique

Due to the development of various electronic devices in the direction of high precision, high density, high stability and micro technology, conductive inks are widely used in solar cells, printed circuit boards (PCB), thin film transistors (TFT), organic light emitting diodes (OLED), radio frequency The application of identification technology (RFID) and other aspects is becoming more and more extensive. Compared with mask printing technology, the use of conductive ink printing technology has the characteristics of convenient operation, high speed, high resolution, and reduced waste of raw materials, which has attracted the attention of people from all walks of life. Especially in recent years, wearable devices have gradually entered the market, and people's demand for flexible products is also increasing. Inkjet printing technology can be used for the preparation of flexible electronic products. Compared with screen printing technology, it has higher accuracy and saves raw materials, so it is a promising technology.

The key to inkjet printing technology is the ink. For the printed electronics industry, the performance of conductive ink determines the performance of the product to a large extent. Commonly used conductive inks can be roughly divided into metal-based conductive inks, carbon-based conductive inks, and polymer-based conductive inks, among which metal-based conductive inks are the most widely used. The metals in metal-based conductive inks are generally nano-scale gold, silver, copper, etc., because as the particle size decreases, the sintering temperature will gradually decrease, which will allow more materials to be used as substrates for inkjet printing . Nano-gold has good conductivity but is expensive; nano-copper is cheap and has similar conductivity to silver, but it is easily oxidized. In contrast, nano-silver has good chemical stability. Even with a small amount of oxidation, the obtained silver oxide can still conduct electricity, so there are no strict requirements for the application environment. Moreover, silver has the best conductivity and moderate price, which makes great progress in the research work related to silver-based conductive ink.

In recent years, commercialized products have gradually increased. These nano-silver conductive inks are mainly composed of nano-silver, linkers, solvents and additives. Usually, the preparation method of nano-silver conductive ink is to prepare nano-silver sol, directly add humectants, pH regulators, binders, surfactants, etc., and obtain evenly dispersed conductive ink by stirring and filtering. This method is simple and convenient, but the silver content is low and may contain impurities such as reducing agents. In addition, some people also centrifugally wash the nano-silver sol, vacuum-dry it to obtain nano-silver powder, then disperse it in a solvent, add tackifiers, curing accelerators, leveling agents and other additives, and stir evenly to obtain conductive ink. This method does not guarantee the stability of the conductive ink. For particle-type nano-silver conductive ink, its stability is a key issue. With the extension of time, a certain degree of agglomeration will occur between the particles, which will easily lead to the clogging of the printer nozzle. The particle-free silver conductive ink does not have the phenomenon of clogging the nozzle due to the absence of particles, so it has broad application prospects.

With the development of electronic products in the direction of flexibility, printing substrates have also changed from traditional hard substrates such as glass to plastic substrates such as PET and PI. For plastic substrates, the maximum temperature it can withstand is relatively lower than that of glass. Therefore, only conductive inks capable of low-temperature sintering can meet the requirements for use. It is extremely urgent to develop inks that can be sintered at low temperature and have good conductivity.

Contents of the invention

In order to overcome the deficiencies of the prior art, the present invention provides a kind of good stability, low-temperature sinterable particle-free conductive ink and its preparation method. The conductive ink can ensure good conductivity at a relatively low silver content, thereby reducing the cost.

In order to achieve the above object, a method for preparing a low-temperature sintering particle-free silver conductive ink is designed, which is characterized in that: the specific steps are as follows:

(1) Weigh silver nitrate and one or two sodium salts according to the coefficient ratio in the chemical reaction equation, respectively dissolve them in deionized water until they are completely dissolved, then add the sodium salt solution dropwise to the silver nitrate solution, and stir Until the reaction is complete, the precipitate obtained by the reaction is filtered and dried in the dark to obtain different insoluble silver salts;

(2) Dissolve alcohols and amines in a solvent with a volume ratio of 1:2~2:1, and stir evenly at room temperature;

(3) Add one or two silver salts obtained in step (1) into the mixed solution system obtained in step (2) in sequence, and continue to stir until the silver salt is completely dissolved to obtain a clear and transparent solution, and then pass through 0.22~0.45 um membrane filtration;

(4) Add an appropriate amount of viscosity regulator and surface tension regulator into the solution prepared in step (3), and stir evenly to obtain a particle-free silver conductive ink that can be used in inkjet printing technology.

The sodium salt is one or a combination of sodium carbonate, sodium acetate and sodium citrate.

The alcohols are alcohols with less than 4 carbon atoms, including one or more combinations of methanol, ethanol, ethylene glycol, glycerol, 1,2-propanediol, isopropanol, and butanol.

The amines are one or more of methylamine, diethylamine, butylamine, ammonia water, isopropylamine, ethylenediamine, propylenediamine, 1,3-propylenediamine, ethanolamine, diethanolamine, triethanolamine kind of combination.

The solvent is one or a combination of deionized water, ethanol, isopropanol, and ethylene glycol.

Described viscosity modifier is polyethylene glycol 200, polyethylene glycol 300, polyethylene glycol 400, ethylene glycol, glycerol, diethylene glycol, 1,2-propylene glycol, terpineol one or more combinations of .

The surface tension modifier is one or more of polyvinylpyrrolidone, sodium dodecylsulfonate, polyacrylamide, cetyltrimethylammonium bromide, sodium dodecylbenzenesulfonate combination.

The particle-free silver conductive ink is a stable transparent clear solution; the silver content of the particle-free silver conductive ink is 5%-20%; the particle-free silver conductive ink has a viscosity of 2cP-20cP.

The sintering temperature of the particle-free silver conductive ink can be as low as 90°C, preferably 100°C-140°C.

The particle-free silver conductive ink is formed into a film on a variety of printing substrates by inkjet printing, and then processed by heating and sintering to obtain a conductive pattern with good conductivity and excellent adhesion. The printing substrate is glass. Silicon wafers, paper, plastics, ceramics, the plastics are polyethylene terephthalate plastics, polyurethane, polyacrylonitrile, polyimide and the like.

Compared with the prior art, the present invention provides a particle-free conductive ink with good stability and low-temperature sintering and its preparation method. The conductive ink can ensure good conductivity at a relatively low silver content, thereby reducing costs .

The method is obtained by adding a certain amount of silver salt into a mixed solution of alcohols and amines, stirring until completely dissolved, and then filtering. The operation method is simple; the particle-free nano-silver conductive ink that can be sintered at low temperature is very suitable for inkjet printing technology.

The preparation method is simple and the cost is low; it can be sintered at low temperature, has good conductivity, and the sheet resistance can be as low as 0.01Ω/□; the ink is a clear and transparent solution without particles, and has good stability; it is suitable for inkjet printing electronic technology.

Description of drawings

Fig. 1 is the XRD spectrum of the silver citrate prepared in the embodiment 1 of the present invention.

Fig. 2 is an SEM image of sintering at 100°C in Example 1 of the present invention.

Fig. 3 is a SEM image of the viscosity-adjusted ink in Example 4 of the present invention printed by an inkjet printer and sintered at 140°C.

Fig. 4 is the sheet resistance value of the ink in Example 4 of the present invention at different sintering temperatures.

detailed description

Example 1

Dissolve 8.823g of sodium citrate in 40ml of deionized water, dissolve 15.288g of silver nitrate in 40ml of deionized water, then add the sodium citrate solution dropwise into the aqueous solution of silver nitrate, stir at room temperature for 2 hours, and place on a cloth filter in a dark funnel, wash twice with deionized water, and continue to filter until a dry white powder is obtained, which is characterized by XRD, as shown in Figure 1, which is completely consistent with PDF#01-0030, and it is proved to be lemon acid silver.

Mix 5ml of methanol, 2ml of isopropylamine and 3ml of isopropanol evenly, keep the temperature to room temperature, then add 2.0g of silver citrate, and stir at room temperature for 1 hour to obtain a light yellow transparent solution, which is filtered through a 0.45um filter membrane to obtain Silver citrate conductive ink.

The ink was dropped on the glass sheet by the method of drip coating, and treated at 100°C for 30 minutes, and the square resistance was measured by the RTS-8 four-probe tester to reach 0.06Ω/□, and the obtained silver film was characterized by SEM, as shown in Figure 2 Show. After the conductive ink was placed at room temperature for 3 months, the solution had no obvious precipitation and had good stability.

Example 2

The preparation method of silver citrate solid powder is identical with embodiment 1, and the preparation method of silver carbonate solid powder is as the preparation method of silver citrate among the embodiment 1.

2g of silver citrate and 0.16g of silver carbonate were successively dissolved in a mixed solution consisting of 5ml of methanol, 3ml of isopropanol and 4.3ml of isopropylamine, and stirred at room temperature for 1 hour to obtain a light yellow transparent solution, which was filtered through a 0.45um filter membrane. A particle-free silver conductive ink with a silver content of about 13% was obtained.

Drop the ink on the glass sheet by drip coating, and treat it at 120°C for 2 minutes. The sheet resistance measured by a four-probe tester can be as low as 0.06Ω/□.

The resulting ink was adjusted to a viscosity of 5-15mPa·s with diethylene glycol, printed by an inkjet printer, and sintered at 100°C. After sintering at 100°C for 20min, the sheet resistance of the film layer was 0.1Ω/□.

Example 3

The preparation method of silver acetate solid powder is as the preparation method of silver citrate among the embodiment 1.

Dissolve 1.6g of silver acetate in a mixed solution consisting of 3ml of methanol, 1.5ml of ethanol and 2ml of ethanolamine, and stir at room temperature for 1 hour to obtain a light yellow transparent solution. After filtering through a 0.45um filter membrane, a particle-free silver conductive ink is obtained.

Drop the ink on the glass plate by drip coating, and treat it at 140°C for 2 minutes. The sheet resistance measured by a four-probe tester can be as low as 0.06Ω/□.

Example 4

16g of silver citrate and 2.5g of silver carbonate were successively dissolved in a mixed solution composed of 40ml of methanol, 24ml of isopropanol and 37ml of isopropylamine, stirred at room temperature for 1 hour to obtain a light yellow transparent solution, which was filtered through a 0.45um filter membrane to obtain Particle-free silver conductive ink.

The above ink was directly used in an A4 flatbed printer to form a film on PET, and after sintering at 140° C. for 20 minutes, the sheet resistance of the obtained film layer was 0.41Ω/□.

Adjust the viscosity of the above ink to 11mPa s with terpineol, and print it through the DimatixQS-256/10 nozzle. After sintering at 140°C for 20min, a silver film with a sheet resistance of 0.02Ω/□ was obtained. The surface morphology is shown in Figure 3 shown. After printing twice, heat treatment at different temperatures, the relationship between sheet resistance and temperature is shown in Figure 4.

Claims (10)

1. a kind of preparation method of low-temperature sintering particle-free silver conductive ink, is characterized in that: concrete steps are as follows: (1) Weigh silver nitrate and one or two sodium salts according to the coefficient ratio in the chemical reaction equation, respectively dissolve them in deionized water until they are completely dissolved, then add the sodium salt solution dropwise to the silver nitrate solution, and stir Until the reaction is complete, the precipitate obtained by the reaction is filtered and dried in the dark to obtain different insoluble silver salts; (2) Dissolve alcohols and amines in a solvent with a volume ratio of 1:2~2:1, and stir evenly at room temperature; (3) Add one or two silver salts obtained in step (1) into the mixed solution system obtained in step (2) in sequence, and continue to stir until the silver salt is completely dissolved to obtain a clear and transparent solution, and then pass through 0.22~0.45 um membrane filtration; (4) Add an appropriate amount of viscosity regulator and surface tension regulator into the solution prepared in step (3), and stir evenly to obtain a particle-free silver conductive ink that can be used in inkjet printing technology. 2. The preparation method of a kind of low-temperature sintering particle-free silver conductive ink according to claim 1, characterized in that: the sodium salt is one or a combination of sodium carbonate, sodium acetate, and sodium citrate. 3. the preparation method of a kind of low-temperature sintering particle-free silver conductive ink according to claim 1, is characterized in that: described alcohols is the alcohols that carbon number is less than 4, comprises methyl alcohol, ethanol, ethylene glycol, One or more combinations of glycerol, 1,2-propanediol, isopropanol, butanol. 4. the preparation method of a kind of low-temperature sintering particle-free silver conductive ink according to claim 1 is characterized in that: described amines are methylamine, diethylamine, butylamine, ammoniacal liquor, isopropylamine, ethylenediamine , propylenediamine, 1,3-propylenediamine, ethanolamine, diethanolamine, triethanolamine in one or more combinations. 5. the preparation method of a kind of low-temperature sintering particle-free silver conductive ink according to claim 1, is characterized in that: described solvent is one or both in deionized water, ethanol, isopropanol, ethylene glycol kind of combination. 6. the preparation method of a kind of low-temperature sintering particle-free silver conductive ink according to claim 1, is characterized in that: described viscosity modifier is polyethylene glycol 200, polyethylene glycol 300, polyethylene glycol 400 , ethylene glycol, glycerol, diethylene glycol, 1,2-propylene glycol, terpineol, or one or more combinations. 7. the preparation method of a kind of low-temperature sintering particle-free silver conductive ink according to claim 1 is characterized in that: described surface tension regulator is polyvinylpyrrolidone, sodium dodecylsulfonate, polyacrylamide, One or more combinations of cetyltrimethylammonium bromide and sodium dodecylbenzenesulfonate. 8. the preparation method of a kind of low-temperature sintering particle-free silver conductive ink according to claim 1 is characterized in that: described particle-free silver conductive ink is a stable transparent clear solution; the silver content of particle-free silver conductive ink is 5%~20%; the viscosity of particle-free silver conductive ink is 2cP~20cP. 9. The preparation method of a low-temperature sintering particle-free silver conductive ink according to claim 1, characterized in that: the sintering temperature of the particle-free silver conductive ink can be as low as 90°C, preferably 100°C~140°C . 10. the preparation method of a kind of low-temperature sintering particle-free silver conductive ink according to claim 1, is characterized in that: described particle-free silver conductive ink forms a film on a variety of printing substrates by inkjet printing, and then After heating and sintering, a conductive pattern with good conductivity and excellent adhesion is obtained, and the printing substrate is glass, silicon wafer, paper, plastic, and ceramics.