CN104708930A - Nanometer metal particle-containing conductive ink-based printing method - Google Patents

Abstract

The invention discloses a printing method of conductive ink containing nano metal particles, comprising: (1) providing conductive ink containing nano metal particles, and the solid content in the conductive ink is lower than 45wt%; (2) using airflow spraying the conductive ink onto the substrate to form a first metal pattern layer with a loose porous structure; (3) printing the conductive ink onto the first metal pattern layer by an inkjet printing method, Until a uniform metal layer with a thickness exceeding 1 μm is formed, the sheet resistance of the uniform metal layer after sintering is less than 1Ω/□. Preferably, step (2) further includes the operation of sintering the first metal pattern layer. The invention is simple in operation and low in cost, and can realize the printing and preparation of highly conductive metal patterns based on the existing metal ink, without additionally increasing the viscosity and metal solid content of the metal ink, and the obtained metal conductive pattern does not contain resin components, which is different from traditional silver paste The printed pattern has a higher conductivity than the printed pattern.

Description

Printing method of conductive ink containing nano metal particles

technical field

The invention relates to a printing method of conductive ink, in particular to a printing method of conductive ink containing nanometer metal particles realized by air jet printing and inkjet printing technology.

Background technique

Printed electronics (printed electronics) technology refers to the production process of manufacturing electronic products by directly printing electronic functional layers such as conductors, semiconductors, dielectric materials, and insulating materials on substrates. In the past few decades, reducing costs and improving cost performance has always been the driving force for the continuous development and growth of the electronics industry. Compared with the subtractive manufacturing method of etching and forming circuits in the traditional electronics industry, the additive manufacturing method represented by printing combines the two processes of film formation and patterning of electronic materials into one, which has the advantages of It has the advantages of saving raw materials, simple process, green and environmental protection (less industrial waste generated), and it is easy to cooperate with new materials to realize large-area flexible devices, which is more conducive to meeting the requirements of the electronics industry to reduce costs and expand the market. At present, the research on printed electronic devices has been extended to a wide range of fields, involving organic devices made of materials such as conductors, semiconductors, dielectric materials, and electrolytes. The use of printing methods to produce electronic products can effectively reduce production costs, and is currently the focus of research by academic institutions and companies around the world. In view of the fact that the traditional printing industry is very mature, once the bottleneck of the printed electronics industry is solved, it is expected to combine the electronics manufacturing industry and the printing industry in a relatively short period of time, which will bring about a significant reduction in the cost of electronic products and an extremely wide range of applications. Great expansion, and addressing the environmental and resource issues, as well as sustainability issues that currently plague the electronics industry.

In the research field of printed electronics, printing metal conductive patterns is the most mature subject, but how to use inkjet printing to obtain metal conductive patterns with a sheet resistance of less than 1 ohm is still a challenge. Theoretically, to improve the conductivity of the printed pattern, it is only necessary to increase the printing thickness. According to the conductivity of the existing printing ink after curing and sintering, the thickness of the metal pattern needs to be greater than 1 μm to obtain an ideal sheet resistance. However, the ink used in inkjet printing has the characteristics of low viscosity and low solid content. During the multi-layer printing process, the ink often dissolves and destroys the printed pattern, so that the effect of multiple printing is essentially similar to that of a single printing with more ink , so that the ink is prone to spontaneous flow on the substrate like "coffee rings" before drying. In this case, it is difficult to effectively obtain a uniform and thick metal layer only through multiple printings. On the contrary, it is easy to further aggravate the uneven thickness of large areas and affect the improvement of electrical conductivity. Sintering after each layer of printing can theoretically significantly improve the problem of uneven thickness in a large area, but since the amount of ink must be strictly controlled for each printing, repeated "printing-sintering" operations are time-consuming, laborious and costly .

Contents of the invention

Aiming at the deficiencies of the prior art, the object of the present invention is to provide a printing method of conductive ink containing nano metal particles, so as to obtain a high-quality metal conductive layer.

In order to realize the above-mentioned purpose of the invention, the present invention has adopted following technical scheme:

A printing method of conductive ink containing nano metal particles, comprising:

(1) Provide conductive ink containing nano-metal particles, and the solid content in the conductive ink is less than 45wt%;

(2) spraying the conductive ink onto the substrate by air jet printing to form a first metal pattern layer with a loose porous structure;

(3) Printing the conductive ink onto the first metal pattern layer by inkjet printing to form a uniform metal layer with a thickness exceeding 1 μm, and the sheet resistance of the uniform metal layer after sintering is less than 1Ω/□, especially is less than 50mΩ/□.

As one of the more preferred embodiments, step (2) includes: atomizing the conductive ink to produce ink droplets with a diameter of less than 10 μm, and then using the feeding airflow to send the ink droplets to the nozzle opening, and then using the focused airflow to The ink droplets are converged into a liquid stream with a diameter of less than 300 μm and sprayed onto the substrate.

Further, step (2) includes:

Adjusting the solvent content of the ink droplets by changing the atomization power, thereby controlling the concentration of the ejected conductive ink, wherein the smaller the atomization power, the higher the concentration of the ejected conductive ink;

And/or, adjust the solvent content of the ink droplets in the jetted liquid flow by changing the flow ratio of the feed air flow and the focused air flow, thereby controlling the concentration of the ejected conductive ink, wherein the lower the flow ratio of the feed air flow and the focused air flow, The higher the concentration of the conductive ink being ejected;

And/or, by changing the temperature of the nozzle opening to adjust the solvent content of the ink droplets in the jetted liquid flow, thereby controlling the concentration of the injected conductive ink, wherein the higher the temperature of the nozzle opening, the higher the concentration of the ejected conductive ink higher.

Further, the surface roughness of the first metal pattern layer is above 0.5 μm. The "difference" here refers to the difference between the height of the highest point and the height of the lowest point on the surface of the first metal pattern layer.

As one of the more preferred embodiments, the step (2) further includes: performing heating and sintering treatment on the first metal pattern layer, and the heating and sintering temperature is 80-300°C.

Further, the aforementioned heating and sintering methods include any one or a combination of two or more of heating tables, ovens, hot air, light waves or microwave heating and sintering methods, but are not limited thereto.

Further, the metal element contained in the conductive ink may include any one or a combination of two or more of gold, silver, copper, nickel, aluminum, platinum, but is not limited thereto.

As one of the more preferred embodiments, during the air jet printing and/or inkjet printing process, the substrate is also heated, and the heating temperature is 35-150°C.

Further, the base includes an insulating base.

Further, step (3) includes: printing the conductive ink on the first metal pattern layer for more than one time by inkjet printing method.

Compared with the prior art, the beneficial effects of the present invention at least include:

(1) By using the method of the present invention, the printing preparation of highly conductive metal patterns can be realized based on the existing metal ink, without additionally increasing the viscosity and metal solid content of the metal ink;

(2) The metal conductive pattern obtained by the method of the present invention does not contain resin components, and has higher conductivity than the pattern printed by traditional silver paste.

Description of drawings

1 is a schematic diagram of the principle of printing a loose porous metal pattern by an air jet printing device in the present invention, wherein 11 is a nozzle, 12 is a metal layer deposited on a substrate, and 13 is a substrate;

Fig. 2 is a microscope photo of the loose and porous silver pattern formed by air jet printing in Example 1 of the present invention.

Detailed ways

As mentioned earlier, due to the limitations of the inherent characteristics of inkjet printing inks, it is difficult for the industry to obtain a relatively uniform thick metal layer through inkjet printing methods, for example, metals with a sheet resistance of less than 1 ohm, especially less than 50 milliohms Conductive pattern layer.

In view of the deficiencies in the prior art, the inventor of this case proposed the technical solution of the present invention after long-term research and a lot of practice, which is mainly realized based on air jet printing technology and inkjet printing process.

Generally speaking, technical scheme of the present invention comprises:

(1) Provide conductive ink containing nano-metal particles, and the solid content in the conductive ink is less than 45wt%;

(2) Jetting the conductive ink onto the substrate by air jet printing to form a first metal pattern layer with a loose porous structure, and the roughness of the surface can exceed 0.5 μm;

(3) Print the conductive ink onto the first metal pattern layer by inkjet printing until a uniform metal layer with a thickness exceeding 1 μm is formed, and the sheet resistance of the uniform metal layer after sintering is less than 1Ω/□, especially is less than 50mΩ/□.

In the present invention, due to the adoption of air jet printing technology, in the same case of using low-viscosity, low-solid-content metal conductive ink, what is ejected is not a single ink drop similar to inkjet printing, but a jet containing a large amount of waste. Airflow of liquid droplets at the liter (fL) level. Due to the larger specific surface area, these ultra-fine droplets can reduce the solvent content of the jetted ink through appropriate parameter control (such as changing the atomization power, the ratio of the feed air flow to the focus air flow, or the nozzle temperature), thereby obtaining a thicker ink. However, the loose and porous metal pattern layer, and when inkjet printing is performed on these metal patterns, the conductive ink will penetrate into the metal pattern, and its spontaneous flow will be strictly restricted due to the effect of surface tension. In this case, the phenomenon of large-area uneven thickness will be significantly curbed, which is conducive to obtaining a uniform metal layer with a thickness of more than 1 μm, thereby significantly improving the conductivity of the printed metal layer.

For example, as one of the preferred implementations, in the aforementioned air jet printing process, the conductive ink can be atomized first to produce ink droplets with a diameter of less than 10 μm, and then the ink droplets can be sent to the nozzle opening by the feeding air flow, and then The ink droplets are converged into a liquid stream with a diameter of less than 300 μm by using focused airflow, and sprayed onto the substrate.

Moreover, more preferably, the first metal pattern layer can also be heated and sintered at a heating and sintering temperature of 80-300° C., and then the inkjet printing operation is performed. The heating and sintering methods mentioned here can be implemented by various equipment or methods commonly used in the industry, for example, heating tables, ovens, hot air, light wave or microwave heating and sintering methods can be selected, and are not limited thereto.

Furthermore, the number of inkjet printing can be one pass or multiple passes, which depends on the requirements of practical applications.

And, according to the needs of practical applications, the metal elements contained in the aforementioned conductive ink can be selected from, but not limited to, any one or a combination of two or more of gold, silver, copper, nickel, aluminum, and platinum.

Furthermore, preferably, during the aforementioned air jet printing and/or inkjet printing process, the substrate can also be heated at the same time, and the heating temperature is 35-150°C.

The aforementioned substrates can be selected from various types of substrates that meet the application requirements, especially insulating substrates, such as polyimide films, silicon wafers with insulating layers, etc., but not limited thereto.

Obviously, the method of the present invention is simple to operate, low in cost, and can realize the printing preparation of highly conductive metal patterns based on the existing metal ink, without additionally increasing the viscosity and metal solid content of the metal ink, and the obtained metal conductive pattern does not contain resin components. And it has higher conductivity than the pattern printed by traditional silver paste.

In order to illustrate the technical solution of the present invention more clearly, the present invention will be further described in detail below in conjunction with the accompanying drawings and preferred embodiments. Obviously, the following descriptions are only some embodiments of the present invention. In other words, other inventions can also be obtained based on these embodiments without paying creative efforts.

Example 1

Soak a colorless transparent polyimide film cut to a length of 100 mm, a width of 40 mm, and a thickness of 0.12 mm in ethanol, isopropanol, and water, and ultrasonically clean it for 10-30 minutes, and blow dry it with high-purity nitrogen after taking it out. Then use air jet printing equipment to print commercial silver ink with ethylene glycol and water as solvents on the film. During the printing process, the actual power of the atomizer is 18-25 watts, the nozzle temperature range is 40-90 ℃, and the substrate heating temperature range is 50- 120 ℃, the flow ratio of feed air flow and focus air flow ranges from 1:5 to 1:15. The obtained pattern was then sintered on a heating table at 150-160° C. for 30 minutes. The obtained metal pattern has a thickness of 2-3 microns and an average roughness of over 0.8 microns.

Print again with an inkjet printing device on the sintered silver pattern, set the dot spacing to 10 microns, print a total of 3-6 times with inkjet printing, and the printed silver ink is subjected to the rough metal pattern of the first layer Restricted, the thickness remains flat over a large area after drying. After sintering again with a 150-160°C heating table for 30 minutes, the sheet resistance was lower than 0.05 Ω/□.

Example 2

Soak the silicon wafer with a silicon dioxide insulating layer cut into 20 mm square and 0.12 mm thick in ethanol, isopropanol and water for 10-30 minutes, and blow dry with high-purity nitrogen after taking it out. Then use air jet printing equipment to print commercial gold ink with ether as the main component of the solvent on the film. During the printing process, the actual power of the atomizer is 15-20 watts, the nozzle temperature range is 40-60 ℃, and the substrate heating temperature range is 50- 75 ℃, the flow ratio of feed air flow and focus air flow ranges from 1:3 to 1:12. The obtained pattern is then sintered on a heating table at 150-160° C. for 15-30 minutes. The obtained metal pattern has a thickness of 1-2 microns and an average roughness of over 0.5 microns.

Print again with an inkjet printing device on the sintered gold pattern, set the dot spacing to 20 microns, print a total of 5-8 times with inkjet printing, and the printed silver ink is subjected to the rough metal pattern of the first layer Restricted, the thickness remains flat over a large area after drying. After sintering again with a heating table at 150-160°C for 15-30 minutes, the sheet resistance is lower than 0.2 Ω/□.

The foregoing is only a specific embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, some improvements and modifications can also be made without departing from the principle of the present invention. It should be regarded as the protection scope of the present invention.

Claims (10)

1. a Method of printing for the conductive ink containing nano-metal particle, is characterized in that, comprising:

(1) conductive ink containing nano-metal particle is provided, and in described conductive ink the content of solid lower than 45wt%;

(2) with air-flow spray printing method, described conductive ink is ejected on base material, forms first metal pattern layer with loose and porous structure;

(3) with ink-jet printing process by described printing of conductive inks in described first metal pattern layer, to forming the homogenous metal layer of thickness more than 1 μm, described homogenous metal layer after sintering square resistance is less than 1 Ω/.

2. the Method of printing of the conductive ink containing nano-metal particle according to claim 1, it is characterized in that, step (2) comprising: described conductive ink atomization is produced the ink droplet that diameter is less than 10 μm, described ink droplet is delivered to jet hole by recycling feeding air-flow, the liquid stream then utilizing focused gas flow ink droplet to be converged to diameter to be less than 300 μm, and be ejected in substrate.

3. the Method of printing of the conductive ink containing nano-metal particle according to claim 2, it is characterized in that, step (2) comprising:

By changing the solvent of ink droplet described in atomization power adjusting, thus control the concentration of injected conductive ink, wherein, atomization power is less, and the conductive ink concentration be ejected is higher;

And/or, regulated the solvent of injected liquid stream ink inside droplet by the flow proportional changing feeding air-flow and focused gas flow, thus control the concentration of injected conductive ink, wherein, the flow proportional of feeding air-flow and focused gas flow is lower, and the conductive ink concentration be ejected is higher;

And/or regulated the solvent of injected liquid stream ink inside droplet by the temperature changing jet hole, thus control the concentration of injected conductive ink, wherein, the temperature of jet hole is higher, and the conductive ink concentration be ejected is higher.

4. the Method of printing of the conductive ink containing nano-metal particle according to claim 1, it is characterized in that, described first metal pattern layer rough surface waviness is more than 0.5 μm.

5. the Method of printing of the conductive ink containing nano-metal particle according to claim 1, it is characterized in that, step (2) also comprises: carry out heat-agglomerating process to described first metal pattern layer, heat-agglomerating temperature is at 80-300 DEG C.

6. the Method of printing of the conductive ink containing nano-metal particle according to claim 5, it is characterized in that, the mode of heat-agglomerating process comprises any one or two or more combinations in warm table, baking oven, hot blast, light wave or heating using microwave sintering processing.

7. the Method of printing of the conductive ink containing nano-metal particle according to claim 1, is characterized in that, in described conductive ink, contained metallic element comprises any one or the two or more combinations in gold, silver, copper, nickel, aluminium, platinum.

8. the Method of printing of the conductive ink containing nano-metal particle according to claim 1, it is characterized in that, in air-flow spray printing and/or ink jet printing process, also heat substrate, heating-up temperature is 35-150 DEG C.

9. the Method of printing of the conductive ink containing nano-metal particle according to claim 1 or 8, it is characterized in that, described substrate comprises dielectric base.

10. the Method of printing of the conductive ink containing nano-metal particle according to claim 1, it is characterized in that, step (3) comprising: printed more than one time in the first metal pattern layer with inkjet printing methods by described conductive ink.