KR102458238B1 - Catalyst Ink For 3D structure, And Manufacturing Methods of 3D Structure Using The Same - Google Patents

Abstract

A catalyst ink for plating and a method for manufacturing a three-dimensional electronic device by an electrochemical method using the same are disclosed. The present invention is a polymer binder; metal ions as catalysts; a coupling agent for coupling the polymer binder and metal ions; skeletal modeling powder; and a solvent, wherein the polymer has a lower critical temperature limit (Lower Critical Solution Temperature) on the temperature-composition phase equilibrium of the solvent-polymer binary system, and the lower critical temperature limit is 30°C or higher. provides According to the present invention, it is possible to provide a three-dimensional plating pattern having good conductivity.

Description

Catalyst ink for plating for forming a three-dimensional structure, and a method for manufacturing a three-dimensional structure using the same

The present invention relates to a catalyst ink for plating for forming a three-dimensional structure and a method for manufacturing an electronic device using the same, and more particularly, to a method for manufacturing a three-dimensional electronic device by an electrochemical method using the catalyst ink for plating. it's about

Printed electronics has advantages in that it simplifies a process by directly printing a desired shape, and enables fast and inexpensive circuit devices to be manufactured on various substrates, compared to conventional photolithography, which is complex and expensive.

In general, printed electronics technology manufactures electronic devices in the form of scanning, copying, and outputting a flat two-dimensional object, and there is a tendency to more highly integrate smaller devices on flexible substrates for electrical and electronic circuits. However, two-dimensional high integration has already encountered a physical and technological limit, and in order to further improve the degree of integration, it is required to manufacture three-dimensional electrical and electronic devices and circuits.

In this regard, conventional 3D printing is an additive manufacturing method for materials such as rubber, nylon, insulators such as plastics, and metals such as stainless steel, titanium, and silver based on 3D design data. It has the advantage of being able to shape types, tools and parts. However, in conventional 3D printing technologies such as FDM (Fused Deposit Modeling) and SLS (Selective Laser Printing), micro-patterns must be implemented with various functional materials due to process factors due to manufacturing techniques or limitations of raw materials used. It has limitations in being applied to printed electronic technology.

Recently, interest in 3D printed electronic technology that combines 3D printing technology and printed electronic technology is increasing. Printed electronic technology has been limitedly applied to some areas such as printed circuit board circuits, semiconductor photomasks, and display color filters in the past. It aims to reach manufacturing.

In order to implement this 3D printed electronic technology, a technology for forming a three-dimensional structure with various functional materials having conductivity, magnetic or electrical insulation is required, and the development of ink and printing technology suitable for 3D printing is also required.

US Patent No. 7922939 to Lewis et al. discloses a silver ink comprising a short-chain capping agent with a molecular weight of 10,000 or less and a long-chain capping agent with a molecular weight of 25,000 or more adsorbed on the surface of Ag particles, have. The ink in this patent exhibits shear thinning, which indicates a decrease in viscosity with increasing shear rate. Accordingly, the above patent forms a three-dimensional microstructure by direct ink writing using pressure extrusion.

However, an electronic device manufactured by such 3D printing technology has a problem in that it exhibits a high resistance value.

(1) US 7929939 B

An object of the present invention is to provide a catalyst ink for plating capable of forming a three-dimensional structure.

Another object of the present invention is to provide a catalyst ink for plating that maintains a thermodynamically stable structure in a plating solution.

Another object of the present invention is to provide a method of manufacturing a 3D structure that provides a three-dimensional structure having high conductivity.

The present invention in order to achieve the above technical problem, a polymer binder;

metal ions as catalysts; a coupling agent for coupling the polymer binder and metal ions; skeletal modeling powder; and a solvent, wherein the polymer has a lower critical temperature limit (Lower Critical Solution Temperature) on the temperature-composition phase equilibrium of the solvent-polymer binary system, and the lower critical temperature limit is 30°C or higher. provides

In the present invention, the lower limit of the critical temperature may be 50° C. or higher.

Also, in the present invention, the solvent may be water, alcohol, or acetone.

In addition, in the present invention, the polymer preferably includes an OH functional group. At this time, the polymer may include at least one selected from the group consisting of Hydroxypropyl cellulose , Methyl cellulose , Hydroxypropylmethyle cellulose, Ethyl(hydroxyethyl)cellulose , Poly(N-isopropylacrylamide-co-acrylic acid) and Poly(propylene glycol). have.

In the present invention, the metal of the metal ion may be at least one selected from the group consisting of Ag, Fe, Co, Ni, Cu, Pd, Pt, Sn, and Au.

In addition, in the present invention, the skeletal modeling powder may include at least one powder selected from the group consisting of CNT, graphite, graphene and graphene oxide, or may include a metal oxide powder or a metal nitride powder.

In order to achieve the other technical problem, the present invention provides a three-dimensional catalyst pattern by discharging a catalyst ink for plating including a polymer binder, a metal ion as a catalyst, and the polymer binder, a skeletal modeling powder and a solvent on a substrate. step; and electroless plating by immersing the substrate on which the precursor pattern is formed in a plating solution maintained at a temperature equal to or higher than the lower critical temperature limit (Lower Critical Solution Temperature) on the temperature-composition phase equilibrium of the solvent-polymer binary system to form a plating pattern It provides a method of manufacturing a three-dimensional structure comprising the steps.

In the present invention, in the step of forming the three-dimensional catalyst pattern, a method of pressure-discharging the catalyst ink for plating through a nozzle may be applied, and the catalyst ink for plating exhibits a behavior of transitioning from a solid-like behavior to a liquid-like behavior under shear stress. it is preferable

According to the present invention, it is possible to provide a catalyst ink capable of manufacturing a three-dimensional structure while having high adhesion. In addition, the catalyst ink of the present invention can provide a precursor pattern having thermodynamic stability in a plating bath environment. In addition, the present invention can further provide a three-dimensional plating pattern having good conductivity, and the pattern can be used for manufacturing wiring or a three-dimensional electronic device.

1 is a schematic phase diagram of an exemplary polymer-solvent system as a catalyst ink for plating of the present invention.
2 is a diagram schematically illustrating a pattern formation mechanism of the catalyst ink for plating of the present invention.
3 is a view for schematically explaining the printing technique of the present invention.
4 is a flowchart schematically illustrating a method of manufacturing a three-dimensional structure according to an embodiment of the present invention.
5 is a graph showing the flow characteristics of the catalyst ink for plating prepared according to an embodiment of the present invention.
6 is a photograph of a sample in which a three-dimensional catalyst pattern prepared according to an experimental example of the present invention is plated in a plating solution for different immersion times.
7 is a graph showing the results of measuring the electrical characteristics of the plating pattern obtained according to the plating time.
8 is an image of a three-dimensional pattern manufactured according to another embodiment of the present invention.

Hereinafter, the present invention will be described in detail by describing preferred embodiments of the present invention.

In the present invention, the catalyst ink for plating includes a metal as a catalyst, a polymer as a binder, a coupling agent for coupling the metal and the polymer, a skeleton modeling powder as a skeleton former, and a solvent.

In the present invention, the metal includes at least one metal selected from the group consisting of Ag, Fe, Co, Ni, Cu, Pd, Pt, Sn, and Au. In the ink composition of the present invention, since the catalyst is preferably present in an ionic form, the metal in the ink is preferably provided as a metal salt.

In addition, in the present invention, the polymer increases the viscosity of the ink and provides adhesion to the substrate. The polymer required in the present invention preferably includes an OH group at the terminal. In addition, in the present invention, the polymer is required to have certain thermodynamic properties, which will be separately described later.

In addition, in the present invention, the coupling agent couples the polymer and the metal salt. Illustratively, as the coupling agent, a silane coupling agent may be used, and 3-aminopropyl trimethoxysilane (APTMS). Examples are 3-Aminopropyl triethoxysilane (APTES) and 3-aminopropyldimethylethoxysilane (APDMES).

In the present invention, the skeletal modeling powder forms a skeleton of a three-dimensional structure and performs a function of supporting the three-dimensional structure after pattern formation. The skeletal modeling powder is insoluble in solvents such as carbon material powders such as graphite, graphene, and CNT, metal oxide powders such as alumina and zirconia, metal nitride powders, metal oxynitride powders, polymer powders, etc., and is maintained in a solid phase in the solvent A powdered material may be used. In the present invention, the shape of the skeletal modeling powder may have any shape such as a plate shape, a square shape, a needle shape, or a spherical shape, and there is no particular limitation on the particle size. However, the average particle diameter may affect the resolution of a three-dimensional structure such as an electronic circuit, and there is a limitation in that a nozzle diameter smaller than the average particle diameter cannot be used. In the present invention, it is preferable that the average particle diameter of the skeleton-shaped powder is 10 nm to 500 μm.

2 is a diagram schematically illustrating a pattern formation mechanism of the catalyst ink for three-dimensional plating of the present invention.

As shown, for example, a silanization reaction in which a silane coupling agent is coupled to a terminal OH group to a polymer such as HPC (Hydroxypropyl cellulose) is performed, and a metal salt is coupled to an amino group of the formed surface to form a metal ion complex (metal ion). complex) is formed.

1 is a phase diagram of a polymer-solvent system for explaining the thermodynamic properties required for the catalyst ink for plating of the present invention.

In the present invention, the mixtures (mixtures) of the polymer and solvent constituting the catalyst ink for plating exhibit a phase change according to the composition-temperature. Preferably, the mixture is stable to form a complete solid solution state in a liquid phase below a predetermined temperature, and this temperature is called a Lower Critical Solution Temperature (LCST). On the other hand, if the composition-temperature coordinate of the mixture on the phase equilibrium diagram is located inside the spinodal curve passing the critical temperature lower limit, the mixture is separated into two phases, that is, the polymer or a phase derived therefrom is precipitated from the solvent. When the composition-temperature coordinates of the mixture are located between the spinodal curve and the coexistence curve on the phase equilibrium diagram, partial phase separation occurs, which can be called a metastable state.

The properties of such a polymer-solvent mixture can provide the following desirable advantages in the present invention. At the temperature of the ink preparation and storage conditions (eg, room temperature), the mixture is stabilized into a liquid solid solution phase, so that the polymer can be uniformly dispersed in the solvent.

On the other hand, if the plating condition of a higher temperature, for example, a relatively high temperature above the LCST temperature is maintained, the printed precursor pattern immersed in the plating bath does not deteriorate even when exposed to a plating solution (eg, a solvent such as water). In this case, it is because the polymer constituting the precursor pattern is thermodynamically stable to be separated from the solvent.

Such ink properties do not dissolve or decompose the precursor pattern in the plating solution, so the precursor pattern allows the plating film to firmly bond the substrate. In addition, the line width of the precursor pattern formed with the plating ink may be maintained as it is in the plating solution, and the uniformly printed line width may be maintained throughout the plating process.

The polymer and solvent constituting the plating ink of the present invention have a relationship on the phase equilibrium shown by the above-described polymer-solvent. Preferably, the polymer and the solvent used in the plating ink have a lower critical temperature limit (LCST) in the temperature-composition phase equilibrium of the polymer-solvent system, and the lower critical temperature limit is 30° C. or more, 35° C. or more, 40° C. or more, 45°C or higher, or 50°C or higher.

Table 1 shows the preferred polymer-solvent systems and LCST values in the present invention.

division polymer menstruum LCST One Hydroxypropyl cellulose Water 45℃ 2 Methyl cellulose Water 50℃ 3 Hydroxypropylmethyle cellulose Water 70℃ 4 Ethyl(hydroxyethyl)cellulose Water 65℃ 5 Poly(N-isopropylacrylamide-co-acrylic acid) Water 32~36℃ 6 Poly(propylene glycol) Water 50℃

In the present invention, the plating operation conditions related to the polymer, solvent content and composition of the plating ink may be designed by reflecting the following matters.

For example, when using HPC (Hydroxypropyl cellulose) of Table 1 as a polymer, the LCST is approximately 45°C. However, the spinodal curve corresponding to the polymer-solvent composition is convex downward, and the corresponding temperature value increases when the composition is changed based on the LCST as the bottom point. Therefore, in the polymer-solvent composition in the actual ink, the polymer can be maintained in a covalent state in the solvent even at a temperature higher than the LCST. Therefore, in order to suppress dissolution of the printed precursor pattern, it is preferable to perform plating at a temperature equal to or higher than the spinodal curve corresponding to the composition, for example, at a temperature of 60°C or higher.

3 is a view for schematically explaining a 3D printing (meniscus-guided printing) method of the present invention.

Referring to FIG. 3 , the catalyst ink 20 for plating of the present invention is maintained in a printing pen 110 having a nozzle. The ink 20 may include dispersed particles 22 including the aforementioned metal ions, polymers, skeletal modeling powder, and the like, and a solvent 24 .

The printing pen 110 comes into contact with the substrate 10, and the pen 110 moves from the contact point in a specific direction, for example, in a direction parallel to the substrate, by a predetermined distance to pressurize ink from the nozzle (FIG. 3 (a)). . Any method such as pneumatic or hydraulic pressure may be used as the method of pressurizing the ink. When the pen moves at a predetermined speed in a direction parallel to the substrate, a pattern 12 corresponding to the movement trajectory of the nozzle is printed on the substrate as a result. Then, the nozzle returns to a predetermined position on the substrate and ejects ink in the same manner to laminate a new pattern 12B on the pattern 12A. A desired three-dimensional pattern may be formed by such a lamination method. Although it has been described that the nozzle moves in a horizontal direction with the substrate to form a three-dimensional structure pattern, the present invention is not limited thereto, and the nozzle discharges ink while moving in a vertical direction with respect to the substrate to form a columnar or wire-shaped structure pattern. may form.

In the present invention, it is necessary to control the flow characteristics of the ink for seamless printing of the three-dimensional structure pattern. In order to provide sufficient bonding force between the printed precursor pattern and the substrate (substrate), a significant amount of binder and coupling agent may be used, and since a significant amount of modeling powder is used to maintain the shape of the structure, the ink may have a viscosity of the ink depending on an external force. shows the changing viscoelastic behavior. In this case, the plating ink of the present invention exhibits a flow characteristic that changes from a liquid-like behavior to a solid-like behavior according to the magnitude of the stress. That is, the ink of the present invention exhibits a liquid-like behavior under the shear stress experienced while passing through the nozzle by pressurization, and exhibits a solid-like behavior after passing through the nozzle and patterned on the substrate to form a shape as a part of a three-dimensional structure. be able to keep

For example, looking at the flow characteristics of the plating ink, there is a point where the storage modulus = loss modulus relationship with respect to a specific stress value in the shear stress section of 10 ¹ to 10 ⁴ Pa, and a stress smaller than this At values, the storage modulus is greater than the loss modulus, and at higher stress values, the storage modulus is less than the loss modulus.

In the present invention, the catalyst ink for plating preferably has a viscosity of 10 ⁰ to 10 ⁵ Pa·s, more preferably 10 ¹ to 10 ⁴ Pa·s. Ink of low viscosity shows good flow characteristics, but has high flowability, making it difficult to maintain the shape of the three-dimensional structure, and excessive viscosity makes it difficult to discharge the ink without interruption.

In the present invention, the flow characteristics of the plating ink may be controlled by the concentration of the modeling powder, the concentration of metal ions, the concentration of the binder, and the concentration of the coupling agent. Preferably, in the present invention, the concentration of the modeling powder is 100 to 500 g/L, the concentration of metal ions is 10 to 100 g/L, the concentration of the binder is 50 to 200 g/L, and the concentration of the coupling agent is 10 to 100 g It is preferably /L.

Hereinafter, a method of forming a wiring pattern using the aforementioned plating ink will be described.

4 is a view for schematically explaining a method of forming a three-dimensional structure according to an embodiment of the present invention.

Referring to FIG. 4 , a predetermined three-dimensional catalyst pattern is formed on a substrate using the above-described catalyst ink for plating ( S100 ).

The printing technique of the pressurized ejection method as described with reference to FIG. 3 may be applied to the printing of the three-dimensional catalyst pattern.

In the present invention, the three-dimensional catalyst pattern may constitute a part of the three-dimensional structure. For example, a portion of the three-dimensional structure may be implemented as a three-dimensional catalyst pattern, and the remaining portion may be implemented as a non-catalytic pattern. In addition, the three-dimensional catalyst pattern may be formed to contact the substrate, but alternatively, it may be formed on another three-dimensional pattern on the substrate.

Next, the metal is electroless-plated by immersing the substrate on which the three-dimensional catalyst pattern is printed in a plating solution. The plating metal is selectively plated on the catalyst pattern surface (S110).

In the present invention, the plating solution may be a solution containing various metals and metal alloys such as Cu, Ni, Ni-P, Ni-W-P, and Ni-W-Cu-P.

In the present invention, the polymer binder of the catalyst ink for plating exhibits LCST behavior in the plating solution. Therefore, the temperature of the plating solution is maintained above the LCST. Preferably, the temperature of the plating solution is adjusted so as to be located above the spinodal curve on the composition-temperature phase diagram of the polymer-solvent system. Accordingly, the polymer binder is not dissolved in the plating solution, and the plating film can be firmly bonded to the substrate. In addition, the shape of the catalyst pattern may be directly transferred to the pattern after plating.

The plating speed in electroless plating depends on the temperature of the plating solution. Specifically, the plating rate may increase exponentially in proportion to the plating temperature. Therefore, the plating method using the catalyst ink for plating of the present invention enables plating at a high temperature, thereby greatly improving the growth rate of the plating film.

<Experimental Example 1: Preparation of Plating Ink>

100 g/L of silver nitrate (Daejeong Hwageum), 100 g/L of 3-aminopropyltriethoxysilane (Sigma-Aldrich), 200 g/L of hydroxicpropyl cellulose (Sigma-Aldrich), 250 g/L of graphite powder in water Ink was prepared by sequentially dissolving in water at room temperature.

The viscosity of the catalyst ink for plating was measured with a cone-and-plate rheometer (MCR102, Anton Paar) in a shear rate range of 100 ~ ^{10 2} s ^-1 . In order to obtain the storage modulus and the loss modulus as a function of stress, the stress was continuously changed at a constant frequency of 1 Hz.

5 is a graph showing flow characteristics of the prepared catalyst ink for plating. As can be seen from the upper right graph of FIG. 5 , the catalyst ink exhibits a shear thinning phenomenon in which the viscosity decreases according to the shear rate.

In addition, as shown in FIG. 5 , the catalyst ink exhibits a solid-like behavior of storage modulus > loss modulus in a low shear stress section, but exhibits a storage modulus in a high shear stress section. modulus) < loss modulus (storage modulus) shows liquid-like behavior. Therefore, by appropriately controlling the ejection pressure of the nozzle, the ink of the present invention exhibits a liquid-like behavior when passing through the nozzle so that it is discharged without interruption, and exhibits a solid-like behavior after passing through the nozzle and is laminated on the substrate, resulting in a three-dimensional structure It is possible to maintain its shape as a part of

<Experimental Example 2: Preparation of precursor pattern>

With the ink prepared in Experimental Example 1, 50 mm * 50 mm * 100 on a polyimide substrate using a micronozzle having an opening diameter of 200 μm at the nozzle tip. A three-dimensional catalyst pattern having a grid structure of mm (L*W*H) was formed. The prepared three-dimensional precursor pattern was observed with Hitachi's S-4800 FE-SEM.

<Experimental Example 3: Electroless Plating>

The precursor pattern prepared in Experimental Example 1 was subjected to a Cu electroless plating solution maintained at a temperature of about 60 ° C. (Copper sulfate pentahydrate (Daejeong Hwageum) 6.78 g/L, Potassium hydrogen tartrate (Daejeong Hwageum) 20.04 g/L (Daejeong Hwageum), sodium hydroxide (Daejeong Hwageum) 8g/L) was immersed for 3 to 30 minutes for plating. The prepared plating pattern was observed with Hitachi's S-4800 FE-SEM. In addition, electrical conductivity was measured at room temperature using a Keisley 2612A instrument using a two-point probe method.

6 is a photograph of a sample in which a three-dimensional catalyst pattern prepared according to an experimental example was plated in a plating solution for different immersion times.

Referring to FIG. 6 , it can be seen that the shape of the three-dimensional pattern is maintained during the plating process, and the size of the plating particles increases as the plating time elapses.

7 is a graph showing the results of measuring the electrical characteristics of the plating pattern obtained according to the plating time. 7 shows that the resistance decreases as the plating time elapses.

<Experimental Example 4>

A catalyst pattern was formed along the surface of a substrate having a surface slope and plated.

As for the surface inclination, a substrate having an inclination of 140° and 90° was used. Fig. 8 (a) is an image of a pattern printed on each substrate, and Fig. 8 (b) is an image of a pattern that has undergone plating. Conventional printing equipment, such as inkjet or aerojet, can print a pattern at a gentle inclination, but in the present invention, it is possible to print a pattern on a substrate inclined at 90°.

As mentioned above, although the present invention has been described above through the embodiments of the present invention, the above description is by way of illustration of the present invention, and the present invention is not limited thereto. Without departing from the scope of the appended claims and the scope of the present invention, it should be regarded as belonging to the scope of the present invention to the extent that various modifications can be made by any person skilled in the art to which the present invention pertains.

Claims (14)

polymer binder;
metal ions as catalysts;
a coupling agent coupling the polymer binder and metal ions;
skeletal modeling powder; and
contains a solvent
The polymer has a lower critical temperature limit (Lower Critical Solution Temperature) on the temperature-composition phase equilibrium of the solvent-polymer binary system, and the lower critical temperature limit is 30°C or higher. According to claim 1,
The lower limit of the critical temperature is a catalyst ink for plating, characterized in that 50 ℃ or more. According to claim 1,
The solvent is a catalyst ink for plating, characterized in that water, alcohol, or acetone. 4. The method of claim 3,
The polymer is a catalyst ink for plating, characterized in that it comprises an OH functional group. 4. The method of claim 3,
The polymer comprises at least one selected from the group consisting of Hydroxypropyl cellulose , Methyl cellulose , Hydroxypropylmethyle cellulose, Ethyl (hydroxyethyl) cellulose , Poly (N-isopropylacrylamide-co-acrylic acid) and Poly (propylene glycol) Catalyst ink for plating. According to claim 1,
The metal of the metal ion is at least one selected from the group consisting of Ag, Fe, Co, Ni, Cu, Pd, Pt, Sn, and Au. According to claim 1,
The skeletal modeling powder comprises at least one powder selected from the group consisting of CNT, graphite, graphene and graphene oxide. According to claim 1,
The skeletal modeling powder is a catalyst ink for plating, characterized in that it comprises a metal oxide powder or a metal nitride powder. forming a three-dimensional catalyst pattern by discharging a catalyst ink for plating including a polymer binder, a metal ion as a catalyst, a coupling agent for coupling the polymer binder and the metal ion, a skeletal modeling powder, and a solvent on a substrate; and
The substrate on which the three-dimensional catalyst pattern is formed is immersed in a plating solution maintained at a temperature above the lower critical solution temperature on the temperature-composition phase equilibrium of the solvent-polymer binary system and electroless plating to form a plating pattern. comprising the steps of forming
The lower limit of the critical temperature is a manufacturing method of a three-dimensional structure, characterized in that 30 ℃ or more. 10. The method of claim 9,
the solvent is water,
The polymer comprises at least one selected from the group consisting of Hydroxypropyl cellulose , Methyl cellulose , Hydroxypropylmethyle cellulose, Ethyl (hydroxyethyl) cellulose , Poly (N-isopropylacrylamide-co-acrylic acid) and Poly (propylene glycol) A method for manufacturing a three-dimensional structure. delete 10. The method of claim 9,
The lower limit of the critical temperature is a method of manufacturing a three-dimensional structure, characterized in that 50 ℃ or more. 10. The method of claim 9,
The three-dimensional catalyst pattern forming step,
A method of manufacturing a three-dimensional structure, characterized in that the catalyst ink for plating is discharged under pressure through a nozzle. 14. The method of claim 13,
The catalyst ink for plating is a method of manufacturing a three-dimensional structure, characterized in that the transition from a solid-like behavior to a liquid-like behavior under shear stress.

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