KR20240025105A - Conductive bonding composition for electrohydrodynamic printing - Google Patents

Abstract

The present invention relates to conductive particles coated with conductive surface treatment agents; curable resin for bonding; Curing agents for curing curable resins; Solvent for dissolving curable resin and curing agent; and a conductive bonding composition for electrohydrodynamic printing containing an electric field reactivity regulator for EHD (electrohydrodynamic). According to the present invention, it can be usefully used as a conductive material for bonding microelectronic devices or semiconductors, and in particular, has a thickness of 30㎛ or less. It relates to a conductive bonding composition for EHD printing that enables effective bonding even at fine pitch and stable printing even at a viscosity of 100 cp or more.

Description

Conductive bonding composition for electrohydrodynamic printing

The present invention relates to a conductive bonding composition for electrohydrodynamic (EHD) printing, which can be usefully used as a conductive material for bonding microelectronic devices or semiconductors. In particular, effective bonding is possible even at a fine pitch of 30㎛ or less, It relates to a conductive bonding composition for EHD printing that allows stable printing even at a viscosity of 100 cp or more.

Conductive bonding compositions have a variety of applications in the fabrication and assembly of semiconductor packages and microelectronic devices. For example, it is used as a composition for adhering integrated circuit chips to a substrate (die bonding adhesive) or as a composition for adhering a circuit assembly to a printed circuit board (surface mount conductive adhesive).

More specifically, anisotropic conductive paste (ACP_anisotropic conductive paste) can be applied to COG assemblies (chip-onglass assemblies), flip chips on flex assemblies, non-contact smart card module assemblies, and flexible substrates or solid substrates. It has been used to form bonds for a variety of electronic hardware, including flip chip die attach to a rigid substrate.

Recently, micro LED (light-emitting diode), also called micro light-emitting diode, refers to an ultra-small LED with a side size of 100㎛ or less, and is one of the important technologies for implementing flat panel display technology. Micro LED has the advantage of superior energy efficiency and optical efficiency compared to existing LEDs, low heat generation per unit area, and the ability to implement very small pixels, so it has high potential for use in ultra-small displays and precision medical devices in addition to lighting.

A conductive film (ACF, anisotropic conductive film) is used to attach these micro LEDs to electrodes on a substrate. Since the size of the micro LED used in the 4K (3840 * 2160) flat panel display was at least 50 * 20㎛, a bonding process to attach electrodes using ACF was possible.

However, in order to realize high definition of 8K or higher, the size of the micro LED becomes smaller to 30*20㎛. Therefore, since the conductive particles currently used in ACF are very large, ranging from about 3 to 10㎛ in diameter, it is technically problematic to bond LED chips using conductive particles according to the existing method.

In particular, considering the fact that the gap between the electrodes of the LED chip is a fine pitch of 30㎛ or less, it is impossible to bond using existing conductive particles. Therefore, in order to overcome these shortcomings, the present invention provides a fine connection bonding composition for EHD that not only provides good conductivity, but also enables effective bonding even at a fine pitch of 30㎛ or less, and enables stable printing even at a viscosity of 100cp or more. there is.

In this regard, Korean Patent Publication No. 10-2018-0019346 (hereinafter referred to as Patent Document 1) discloses an electrohydrodynamic printing composition containing a conductive polymer and a nonionic surfactant, and Korean Patent Publication No. 10- No. 2010-0027842 (hereinafter referred to as Patent Document 2) is a nozzle 10 for spraying a solution 2 containing conductive particles by hydraulic pressure, the nozzle 10, and the sprayed product from the nozzle 10. It includes an intermediate electrode 20 located between the patterning object 1 on which the solution 2 is patterned, and a power supply 40 that supplies voltage with a potential difference to the nozzle 10 and the intermediate electrode 20. Disclosed is an electrohydrodynamic spray-type micro-conductive line patterning device characterized by the following configuration. However, Patent Documents 1 and 2 include conductive particles coated with a conductive surface treatment agent; Curable resin for bonding; A curing agent for curing the curable resin; Solvent for dissolving curable resin and curing agent; and an electric field reactivity regulator for EHD (electrohydrodynamic), which enables effective bonding even at a fine pitch of 30 ㎛ or less and enables stable printing even at a viscosity of 100 cp or more. A conductive bonding composition for EHD printing has not been disclosed.

Patent Document 1: Korean Patent Publication No. 10-2018-0019346

Patent Document 2: Korean Patent Publication No. 10-2010-0027842

The purpose of the present invention is to solve the above-described conventional problems, and provides an electrohydraulic device that not only provides good conductivity, but also enables stable electrical connection even at a fine pitch of 30㎛ or less, and enables stable printing even at a viscosity of 100cp or more. An object is to provide a conductive bonding composition for (electrohydrodynamic, EHD) printing.

However, the object of the present invention is not limited to the object mentioned above, and other objects not mentioned will be clearly understood by those skilled in the art from the description below.

To achieve the above object, the present invention provides conductive particles coated with conductive surface treatment agents; curable resin for bonding; Curing agents for curing curable resins; Solvent for dissolving curable resin and curing agent; and an electric field responsiveness modifier for electrohydrodynamic (EHD).

According to the conductive bonding composition for electrohydrodynamic (EHD) printing of the present invention, it can be usefully used as a conductive material for bonding microelectronic devices or semiconductors, and in particular, effective bonding is possible even at a fine pitch of 30㎛ or less, and 100cp It provides a special effect that enables stable printing even at the above viscosity.

Figure 1 is an example showing a process for bonding a micro LED chip using the conductive bonding composition for EHD printing of the present invention.
Figure 2 is a diagram showing the comparison of printability evaluation results of the conductive bonding composition for EHD printing obtained in Example 1 and Comparative Example 1 of the present invention.
Figure 3 is a diagram showing the printability evaluation results of the conductive bonding composition for EHD printing obtained in Example 1 of the present invention.
Figure 4 is a diagram showing the results of electrical resistance measurement of the conductive bonding composition for EHD printing obtained in Example 1 of the present invention.
Figure 5 is a diagram showing the results of micro LED chip bonding evaluation of the conductive bonding composition for EHD printing obtained in Example 1 of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings attached to the present invention.

Figure 1 shows a process for attaching a micro LED chip to a substrate electrode using a conductive bonding composition for EHD printing according to the present invention.

In a preferred embodiment of the present invention, the conductive bonding composition for EHD printing includes conductive particles coated with conductive surface treatment agents; curable resin for bonding; Curing agents for curing curable resins; Solvent for dissolving curable resin and curing agent; and an electric field responsiveness regulator for electrohydrodynamic (EHD).

In a preferred embodiment of the present invention, the conductive bonding composition for EHD printing preferably contains 20 to 40 wt% of conductive particles coated with conductive surface treatment agents. If it is less than 20wt%, it is difficult to exhibit sufficient conductivity to drive or light a micro LED chip, and if it is more than 40wt%, the content of nanoparticles with a large surface area increases, making the overall viscosity of the composition very high, making printing difficult. There is a difficult problem.

In a preferred embodiment of the present invention, the conductive bonding composition for EHD printing preferably contains 20 to 40 wt% of curable resin. If it is less than 20wt%, it is difficult to secure sufficient adhesion between micro LED chips, making it difficult to secure sufficient reliability, and if it is more than 40wt%, it is difficult to secure sufficient electrical conductivity by interfering with the electrical connection of the conductive particles.

In a preferred embodiment of the present invention, the conductive bonding composition for EHD printing preferably uses 5 to 20 wt% of a curing agent. If it is less than 5wt%, it is difficult for the curable resin to sufficiently harden, making it impossible to obtain sufficient adhesion between micro LED chips. If it is more than 20wt%, curing progresses too quickly, which causes a problem in that the lifespan of the conductive bonding composition is shortened. From this point of view, the ratio of the curable resin of the present invention to the curing agent is preferably 4:1 (curable resin:curing agent ratio) to 1:1.

In a preferred embodiment of the present invention, the conductive bonding composition for EHD printing preferably uses 1 to 3 wt% of an electric field reactivity regulator for EHD. If it is less than 1 wt%, it is difficult to secure sufficient electrical resistance of the conductive bonding composition itself, and if it is more than 3 wt%, the electrical resistance of the conductive bonding composition itself becomes too low, making it difficult to secure good EHD printability. .

In a preferred embodiment of the present invention, the conductive particles may be selected from the group consisting of silver (Ag), gold (Au), indium (In), and indium tin oxide (ITO).

The conductive particles may have a size ranging from 0.01 to 5.0 ㎛, and the use of conductive particles in this range is most appropriate for a fine pitch of 30 ㎛ or less.

In a preferred embodiment of the present invention, it is important that the conductive particles are used with their surfaces coated with a conductive surface treatment agent. To increase the reactivity of EHD, which is a feature of the present invention, a conductive surface treatment agent that is a water-soluble polymer or single molecule compound can be used.

To be more specific, the biggest advantage of electrohydrodynamic (EHD) printing is that it can print high-viscosity ink. In the case of inkjet, printing can be done using ink in the range of approximately 10-50 cP, and in the case of gravure printing, ink in the range of approximately 100-1000 cP. Among these, there are not many non-contact printing techniques that can print high-viscosity ink. Electrohydrodynamic printing can print inks with a very wide range of viscosity, from 10 to 10000 cP. Therefore, from an application perspective, there is an advantage in being able to apply various inks.

However, despite these advantages, in EHD inkjet printing technology, various parameters such as voltage, distance from the substrate, flow rate, and nozzle thickness directly affect printability. In particular, printing high-viscosity ink with a viscosity of 100 cp or more requires a high voltage of 1 KV or more. However, if a high voltage is applied, a spray-shaped meniscus is formed due to a short circuit, and if a voltage that is too low is applied, the surface tension of the ink is stronger than the applied voltage, forming a cone-jet-shaped meniscus. There is a problem in that printing is unstable or the ink itself cannot be printed because the ink is not formed.

To solve this problem, printing is possible if the distance to the substrate (micro LED electrode) is shortened, but if it is too close, an electrical short may occur, and if it is too far, a certain shape (dotting) is realized due to the whipping phenomenon. You won't be able to do it.

In order to solve this problem, the present invention provides a technology that enables stable printing even at a viscosity of 100 cp or more by coating the surface of conductive particles with a conductive surface treatment agent.

In a preferred embodiment of the present invention, the conductive surface treatment agent refers to a polymer or monomolecular compound that has polarity in an aqueous solution, and the polymer includes a hydroxyl group (-OH), an amide group (-CONH ₂ ), and an ether group ( -COC), primary amine (-NH2), secondary amine (-NHR), tertiary amine (--RNR), carboxylic group (-COO-M ⁺ ), sulfonic group (-SOOM), phosphate group (-OPOOM) It is a water-soluble polymer with a sulfate group (-OSOOOM).

More specifically, examples of water-soluble polymers that can be used in the present invention include starch, gums, polysaccharide, cellulose with a hydroxyl group, acrylicpolyol (APO), and polyethylene oxide (PEO). , PVA (polyvinyl alcohol), PAAM (polyacrylamide), PVP (Polyvinylpyrrolidone), PAA (polyacrylic acid), PSSA (polystrensulfonic acid), PPA (polyphosphoric acid), PESA (polyethylenesulfonic acid), PEI (polyethyleneimide), PA (polyamines) , PAMAM (polyamideamine), poly(2-vinylpiperidine salt), and Poly(vinylamine salt).

In addition, single molecular compounds that can be used in the present invention include caprylic acid, pelargonic acid, caproic acid, undecanic acid, and lauric acid. ), myristic acid, behenic acid, palmitic acid, lignoceric acid, stearic acid, Eicosanoic acid, and A fatty acid selected from the group consisting of oleic acid may be used.

In a preferred embodiment of the present invention, the water-soluble polymer preferably has a molecular weight (Mw) in the range of 500 to 1,000,000. If it is less than 500, there is a problem in that the electric field reactivity of the EHD and adhesion to the substrate are poor. On the other hand, if it exceeds 1,000,000, the viscosity becomes very high, making printing difficult.

In a preferred embodiment of the present invention, the conductive surface treatment agent, which is a water-soluble polymer or monomolecular compound, has a melting point in the range of 0 to 120°C. In the case of exceeding 120°C, there is a problem in that the melting point is high, the resin exclusion ability of the curable resin is reduced, and the electric path between the metal layers is not established. Conversely, when using a surface treatment agent with a melting point below 0°C, there is a disadvantage in that it is difficult to uniformly disperse the conductive particles at room temperature.

In a preferred embodiment of the present invention, the curable resin and the curing agent for curing the curable resin are not particularly limited, but it is most preferable to use an epoxy resin from the viewpoint of long-term reliability after bonding. The preferred epoxy curable resin in the present invention may be a dicyclopentadiene type epoxy resin or a naphthalene type epoxy resin.

More specifically, the dicyclopentadiene type epoxy resin may be dicyclopentadienoxide or a phenol novolak epoxy resin having a dicyclopentadiene skeleton. In addition, the naphthalene-type epoxy resin includes 1-glycidylnaphthalene, 2-glycidylnaphthalene, 1,2-diglycidylnaphthalene, 1,5-diglycidylnaphthalene, 1,6-diglycidylnaphthalene, 1,7-diglycidylnaphthalene , 2,7-diglycidylnaphthalene, or triglycidylnaphthalene, 1,2,5,6-tetraglycidylnaphthalene (1,2,5,6-tetraglycidylnaphthalene) ), etc. may be used.

In the present invention, the dicyclopentadiene type epoxy resin and naphthalene type epoxy resin may be used individually, or both may be used together.

In a preferred embodiment of the present invention, the curing agent is a material that can cause a curing reaction with a curing binder. Its components are not limited, but any compound that can be cured by reacting with a curing binder contained in the composition can be used by those skilled in the art. A range of compounds can be selected, for example compounds containing one or more amines or carboxylic anhydrides in the molecule. In a preferred embodiment, the curing agent may be a 4,4-diaminodiphenylmethane (DDM) compound.

In a preferred embodiment of the present invention, an electrolyte, conductive particle, or conductive polymer may be used as the electric field reactivity control agent for EHD. The electrolyte refers to a substance that is split into ions in an aqueous solution and carries electric current. Examples of such electrolytes include sodium chloride (NaCl), sulfuric acid, hydrochloric acid, sodium hydroxide (NaOH), and potassium hydroxide (KOH). The conductive particles refer to nanoparticles having metal or non-metal conductivity, and representative examples include silver (Ag) nanoparticles, gold (Au) nanoparticles, and conductive carbon nanoparticles. In addition, the conductive polymer may be, for example, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS).

In a preferred embodiment of the present invention, the solvent included in the conductive bonding composition for EHD printing can be any solvent commonly used in the art, without limitation, as long as it can dissolve the curable resin and the curing agent, and is preferably an alcohol. , ethers, acetals, ketones, esters, alcohol esters, ketones, alcohols, ether alcohols, ketone ethers, ketone esters, ester ethers, aromatic solvents, etc. can be used.

In a preferred embodiment of the present invention, a curing accelerator may be additionally used to promote the curing reaction between the epoxy resin and the curing agent. Such curing accelerators include, for example, 2-methylimidazole, 2,4-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, and 2-phenyl-4-methyl. Imidazole compounds selected from midazole (2-Phenyl-4-methylimidazole); Triethylamine, benzyldimethylamine, methylbenzyldimethylamine, 2-(dimethylaminomethyl)phenol, 2,4,6-tris(dimethylaminomethyl)phenol (2,4,6-Tris(dimethylaminomethyl)phenol), tri tertiary amine compounds selected from ethylphosphine, tributylphosphine, and 1,8-diazabicyclo(5,4,0)undecene-7; and an organic phosphine selected from triphenylphosphine, trimethylphosphine, triethylphosphine, tributylphosphine, tris(4-methoxyphenyl)phosphine, and tri(nonylphenyl)phosphine. Any compound may be used, and among them, it is preferable to use an organic phosphine compound having excellent moisture resistance and heat hardness. Two or more types of these curing accelerators can be used in combination, and these curing accelerators are preferably used in an amount of 0.1 to 10% by weight based on the total amount of the epoxy resin composition. If the content of the curing accelerator is less than 0.1% by weight, problems with poor adhesion may occur due to insufficient curing of the epoxy resin composition, and if it exceeds 10% by weight, the curing speed of the epoxy resin composition becomes too fast, making it difficult to secure sufficient electrical conductivity. There is.

Additionally, in the present invention, a conductive filler may be optionally included. Examples of the conductive filler include film-forming thermoplastic solid resin, or nano size filler. The nano-sized filler, which is optionally included in the present invention, can improve adhesive strength and reduce the total heat of reaction in the system by reducing mismatch in thermal expansion coefficient.

Hereinafter, the manufacturing process of the silver-coated activated carbon electrode for the desalting process of the present invention will be described with reference to specific examples.

Manufacturing Example 1

<Conductive particle surface treatment>

A dispersion solution was prepared by dispersing 50 g of Ag nanoparticles with an average particle diameter of 40 nm (new nano material) in 500 g of ethanol using a homogenizer. In the dispersion solution prepared in this way, 10 g of PVP (Polyvinylpyrrolidone) with a molecular weight of 10,000 (Aldrich) was added as a conductive surface treatment agent and completely dissolved, thereby preparing a coating solution using a homogenizer. Sludge was prepared by precipitating the metal-coated nanoparticles from the coating solution thus prepared using a centrifuge. The prepared sludge was completely dried using a freeze dryer to prepare conductive particles coated with PVP.

Example 1

<Preparation of conductive bonding composition>

30 wt% of the conductive particles coated with PVP obtained in Preparation Example 1 were subjected to ultrasonic waves on 30 wt% of a DCPD-containing epoxy compound (KDCP-130EK80, Kukdo Chemical), a dicyclopentadiene (DCPD) type curable resin. It was dispersed using. The dispersed solution contains 10 wt% of 4,4-diaminodiphenylmethane (DDM), an amine-based curing agent, as a curing agent, and 2-phenyl-4-methylimidazole (2) as a curing accelerator. A conductive bonding composition was prepared using 2wt% of -Phenyl-4-methylimidazole). A conductive bonding composition for EHD was prepared by adding 2 wt% of Heraeus' conductive polymer (product name Clevios) to the prepared composition. The viscosity of the composition prepared in this way was 450 cp.

Comparative Example 1

A conductive bonding composition for EHD was prepared in the same manner as in Example 1, except that 30 wt% of Ag nanoparticles, which were conductive particles, were used as is, without coating with PVP, a conductive surface treatment agent. The viscosity of the composition prepared in this way was 430 cp.

Experiment example

1. EHD printability evaluation (1)

The conductive bonding compositions obtained in Example 1 and Comparative Example 1 were printed at the same printing voltage of 1.5KV using EHD printing equipment (eNanojet (product name)), and the results of Example 1 and Comparative Example 1 were It is shown in Figure 2. As shown in Figure 2, the composition obtained in Example 1 uniformly forms a certain shape (dotting), but on the contrary, the composition of Comparative Example 1 does not form a certain shape (dotting) and the composition sprays. ), you can see that there is a problem.

2. EHD printability evaluation (2)

The conductive bonding composition for EHD obtained in Example 1 was printed on the glass surface deposited with Mo/Al/Mo using EHD printing equipment (eNanojet (product name)), and the results are shown in Figure 3. indicated. Referring to Figure 3, the size of the dot is 15㎛, the height is about 1.5㎛, and it can be confirmed that it is printed uniformly using EHD printing equipment.

3. Electrical resistance evaluation

The conductive bonding composition for EHD obtained in Example 1 was printed using EHD printing equipment (Enjet Co., Ltd., eNanojet (product name)) on a specimen for electrical resistance evaluation, as shown in FIG. 4. The size of the Au electrode was 30㎛*30㎛, and the dot size of the conductive bonding composition was 30㎛. A specimen for evaluation was placed on the printed conductive bonding composition, and cured at 150°C/13 seconds while applying 40N using bonding equipment (Cube NT Co., Ltd., Conventional thermo-compression (TC) bonding). The electrical resistance of the bonded sample was measured using an electrical resistance meter, a 2-point probe, as shown in FIG. 4.

4. Micro LED bonding evaluation

As shown in Figure 5, the conductive bonding composition obtained in Example 1 was printed on a Mo/Al/Mo-deposited substrate with a size of 35x25㎛. It was printed using EHD printing equipment (Enjet Co., Ltd., eNanojet (product name)), and the size of the printed dots was 10㎛. A 25*35㎛ micro LED chip (Red chip) was placed on the printed conductive bonding composition using transfer equipment (Enjet Co., Ltd. 1BY1), and heat curing was performed at 150°C for 30 minutes. . Afterwards, it was turned on using a voltage application device, and the results of Example 1 are shown in FIG. 5. As shown in Figure 5, it was confirmed that the micro LED chip lights up normally.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications and changes are possible without departing from the technical spirit of the present invention as is known in the technical field to which the present invention pertains. It will be clear to those who have the knowledge.

Claims (8)

Conductive particles coated with conductive surface treatment agents;
curable resin for bonding;
Curing agents for curing curable resins;
Solvent for dissolving the curable resin and curing agent; and
Conductive bonding composition for electrohydrodynamic printing comprising an electric field responsiveness modifier for EHD (electrohydrodynamic). The method of claim 1, comprising 20 to 40 wt% of conductive particles coated with a conductive surface treatment agent, 20 to 40 wt% of curable resin, 5 to 20 wt% of curing agent, 1 to 3 wt% of electric field reactivity modifier for EHD, and the remaining amount of solvent. A conductive bonding composition for electrohydrodynamic printing characterized by: The conductive bonding composition for electrohydrodynamic printing according to claim 1, wherein the conductive particles are selected from the group consisting of silver (Ag), gold (Au), indium (In), and ITO (indium tin oxide). The method of claim 1, wherein the conductive surface treatment agent,
Starch, gums, polysaccharide, cellulose with hydroxyl group, acrylic polyol (APO), polyethylene oxide (PEO), polyvinyl alcohol (PVA), polyacrylamide (PAAM), polyvinylpyrrolidone (PVP) ), polyacrylic acid (PAA), polystrensulfonic acid (PSSA), polyphosphoric acid (PPA), polyethylenesulfonic acid (PESA), polyethyleneimide (PEI), polyamines (PA), polyamideamine (PAMAM), poly(2-vinylpiperidine salt), and A water-soluble polymer selected from the group consisting of poly(vinylamine salt); or
Caprylic acid, pelargonic acid, caproic acid, undecanic acid, lauric acid, myristic acid, behenic acid ( A fatty acid selected from the group consisting of behenic acid, palmitic acid, lignoceric acid, stearic acid, eicosanoic acid, and oleic acid. A conductive bonding composition for electrohydrodynamic printing. The conductive bonding composition for electrohydrodynamic printing according to claim 4, wherein the water-soluble polymer has a molecular weight (Mw) in the range of 500 to 1,000,000. The conductive bonding composition for electrohydrodynamic printing according to claim 1, wherein the conductive surface treatment agent has a melting point in the range of 0 to 120°C. The conductive bonding composition for electrohydrodynamic printing according to claim 1, wherein the curable resin for bonding is a dicyclopentadiene epoxy resin or a naphthalene epoxy resin. The conductive bonding composition for electrohydrodynamic printing according to claim 1, wherein the electric field reactivity regulator for EHD is an electrolyte, a conductive particle, or a conductive polymer.