KR20240008021A - Low-temperature curable silicone conductive composition having excellent flexibility and resistance stability - Google Patents

Abstract

The present invention relates to a low-temperature curable silicone conductive composition with improved flexibility and resistance stability. Specifically, the present invention is capable of curing at a low temperature of 100°C or lower, while improving flexibility even after curing, improving resistance stability by maintaining resistance even during deformation such as bending, and further improving flexibility and resistance stability, which can reduce manufacturing costs. It relates to improved low-temperature curable silicone conductive compositions.

Description

Low-temperature curable silicone conductive composition having excellent flexibility and resistance stability}

The present invention relates to a low-temperature curable silicone conductive composition with improved flexibility and resistance stability. Specifically, the present invention is capable of curing at a low temperature of 100°C or lower, while improving flexibility even after curing, improving resistance stability by maintaining resistance even during deformation such as bending, and further improving flexibility and resistance stability, which can reduce manufacturing costs. It relates to improved low-temperature curable silicone conductive compositions.

Electrically conductive paste is used to mechanically bond components to each other while maintaining electrical conductivity in PCB boards and electronic devices. Unlike soldering, electrically conductive paste maintains mechanical strength with the polymer resin that makes up the paste and develops electrical conductivity through close contact with metal particles filled within it. Specifically, conductive particles dispersed in the paste come into contact during the curing step and develop electrical conductivity.

The use of electrically conductive paste as an alternative to soldering is not only for die bonding of semiconductor chips, flip chip bonding, assembly of electronic components such as crystal oscillators and sensors, and surface mounting of chip components, but also for parts that cannot be joined by soldering, such as various electrode materials. This is possible. In particular, electrically conductive paste is used as a substitute for materials that have restrictions on application at high temperatures or when direct soldering is not possible. Additionally, it has recently been in the spotlight for joining solar modules manufactured in a shingled structure.

Compared to soldering, electrically conductive paste can be processed at a relatively low temperature and has the advantage of significantly reducing the harmful side effects of the soldering process on the human body and the environment. Nevertheless, in order to satisfy the relatively excellent electrical conductivity, mechanical strength, heat resistance, and chemical resistance of soldering, further improvement in properties is required. In particular, since flexibility and resistance stability are dependent on each other and are always in conflict, a process of optimizing the composition ratio suitable for specifications and required characteristics is essential.

Electrically conductive pastes are made from a variety of materials and have different chemical, electrical, mechanical, and thermal properties due to their different compositions. One way to increase the electrical conductivity of an electrically conductive paste may be to increase the content of conductive filler, but the resulting decrease in the polymer resin content also causes a decrease in flexibility and adhesive strength. Therefore, it is very important that the electrically conductive paste has a sufficient level of flexibility and electrical conductivity at the same time, considering the manufacturing cost to suit the required characteristics.

In this regard, Korean Patent No. 10-1295801 discloses an electrically conductive adhesive composition containing a conductive metal filler containing particle-shaped metal powder and silver nanowires, a polymer resin, additives, a curing agent, and a curing accelerator. And Korean Patent No. 10-0888324 discloses a method of manufacturing a conductive adhesive using carbon nanotubes to improve the contact rate between conductive materials added inside the resin. However, this conventional patented technology has limitations in simultaneously realizing sufficient electrical conductivity and adhesion during low-temperature curing.

Therefore, there is an urgent need for a new conductive material that can be cured at low temperatures below 100℃, has improved flexibility even after curing, improves resistance stability by maintaining resistance even when deformed such as bending, and further reduces manufacturing costs. am.

Korean Patent No. 10-1295801 Korean Patent No. 10-0888324

The purpose of the present invention is to provide a silicone conductive composition that can be cured at a low temperature of 100°C or lower, has improved flexibility even after curing, improves resistance stability by maintaining resistance even when deformed such as bending, and further reduces manufacturing costs. Do it as

In order to solve the above problems, the present invention,

A low-temperature curable silicone conductive composition, comprising a polymer resin and electrically conductive particles, wherein the polymer resin is a polyorganosiloxane resin of the formula 1 below as a base resin, a polyorganosiloxane compound of the formula 2 below as a curing agent or chain extender, and a polyorganosiloxane compound of Formula 3 below as a plasticizer.

[Formula 1]

In Formula 1, R ₁ and R ₂ are each independently hydrogen, C ₁ to C ₆ alkyl, or C ₂ to C ₆ alkenyl, provided that at least one of R ₁ is C ₂ to C ₆ alkenyl. and n is an integer from 79 to 1891,

[Formula 2]

In Formula 2, R ₃ and R ₅ are each independently C ₁ to C ₆ alkyl, and R ₄ are each independently hydrogen or C ₁ to C ₆ alkyl, provided that at least one of R ₄ is hydrogen, m and p are each independently integers from 0 to 400,

[Formula 3]

In Formula 3, R ₆ and R ₇ are each independently C ₁ to C ₆ alkyl, and q is 300 to 810.

Here, R ₁ is all vinyl, R ₂ is methyl, one of R ₄ is hydrogen, R ₃ and R ₅ are both methyl, and R ₆ and R ₇ are both methyl. A silicone conductive composition is provided.

In addition, the polyorganosiloxane resin of Formula 1 provides a low-temperature curable silicone conductive composition, characterized in that the weight average molecular weight is 6,000 g/mol or more and less than 140,000 g/mol.

And, based on 100 parts by weight of the base resin, the content of the polyorganosiloxane compound of Formula 2 is 10 to 100 parts by weight, and based on 100 parts by volume of the base resin, the content of the polyorganosiloxane compound of Formula 3 is 1. A low-temperature curable silicone conductive composition is provided, characterized in that from 10 to 10 parts by volume.

Meanwhile, the electrically conductive particles are low-temperature curable silicone conductive particles including micro spherical particles with an average particle diameter of 2 to 10 ㎛, micro plate-shaped particles with an average particle diameter of 2 to 50 ㎛, and nanoparticles with an average particle diameter of 10 to 500 ㎚. A composition is provided.

Here, a low-temperature curable silicone conductive composition is provided, characterized in that the particle size distribution ratio (γ) defined by Equation 1 below is 1.0 or less for the micro spherical particles and 2.0 or less for the micro plate-shaped particles.

[Equation 1]

γ=(D ₉₀ -D ₁₀ )/D ₅₀

In addition, based on 100 parts by weight of the micro plate-shaped particles, the content of the micro spherical particles is 25 to 83 parts by weight, and based on 100 parts by weight of the micro spherical particles, the content of the nanoparticles is 1 to 30 parts by weight. Provided is a low-temperature curable silicone conductive composition.

Furthermore, a low-temperature curable silicone conductive composition is provided, wherein the total weight of the electrically conductive particles is 300 to 600 parts by weight based on 100 parts by weight of the base resin.

In addition, the electrically conductive particles provide a low-temperature curable silicone conductive composition, characterized in that the overall density is 2.0 to 4.0 g/cc.

Meanwhile, a low-temperature curable silicone conductive composition is provided, characterized in that it further comprises one or more other additives selected from the group consisting of catalysts, retarders, non-conductive particles, and solvents.

The silicone conductive composition with improved flexibility and resistance stability according to the present invention can be cured at low temperatures below 100°C through a specific combination of polymer resins, and on the premise of this, it can be cured by precisely controlling the shape, particle size, and content of each type of electrically conductive particle. It shows an excellent effect of improving flexibility and improving resistance stability by maintaining resistance even during deformation such as bending.

1 is an electron micrograph of micro-plate-shaped particles among the electrically conductive particles included in the silicone conductive adhesive composition according to the present invention.
Figure 2 is an electron micrograph of micro-spherical particles among the electrically conductive particles contained in the silicone conductive adhesive composition according to the present invention.
Figure 3 is an electron micrograph of nanoparticles among the electrically conductive particles included in the silicone conductive adhesive composition according to the present invention.
Figure 4 is a schematic diagram schematically showing the efficient arrangement of electrically conductive particles in the silicone conductive adhesive composition according to the present invention.
Figure 5 is a photograph for measuring resistance according to bending deformation of a composition specimen in an example.
Figure 6 is a graph showing the resistance measured according to the bending strain and radius of curvature of the composition specimen in Examples.

Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosure will be thorough and complete, and so that the spirit of the invention can be sufficiently conveyed to those skilled in the art.

The low-temperature curable silicone conductive composition with improved flexibility and resistance stability according to the present invention may include a polymer resin and electrically conductive particles dispersed in the polymer resin.

Specifically, the polymer resin may include polyorganosiloxane of Formula 1 below as a base resin.

[Formula 1]

In Formula 1, R ₁ and R ₂ are each independently hydrogen, C ₁ to C ₆ alkyl, or C ₂ to C ₆ alkenyl, provided that at least one of R ₁ , preferably both R ₁ is C ₂ ~C ₆ alkenyl, more preferably vinyl, and n is an integer of 79 to 1891.

Here, the C ₁ to C ₆ alkyl may be, for example, methyl, ethyl, propyl, butyl, pentyl, or hexyl. In addition, alkenyl of C ₂ to C ₆ may be vinyl, allyl, 3-butenyl, or 5-hexenyl.

The polyorganosiloxane compound of Formula 1 may have a weight average molecular weight of 6,000 g/mol or more and less than 140,000 g/mol, for example, 15,000 to 30,000 g/mol. The kinematic viscosity (at 25°C) of the compound may be 100 to 100000 cSt.

Here, when the weight average molecular weight of the polyorganosiloxane compound of Formula 1 is less than 6,000 g/mol, the mechanical properties and heat resistance of the silicone conductive composition according to the present invention may be insufficient, while the weight average molecular weight is 140,000 g/mol. If it is more than this, the resistance stability of the composition after curing may decrease.

In particular, the polyorganosiloxane compound of Formula 1 may be polydimethylsiloxane (PDMS), in which all R ₁ is a vinyl group (CH ₂ =CH-) and R ₂ is a methyl group. Furthermore, at least one of R ₂ is an aromatic functional group, preferably a phenyl group, which can further improve the heat resistance, chemical resistance, etc. of the silicone conductive composition according to the present invention.

Meanwhile, the polymer resin may include polyorganosiloxane of Formula 2 below as a curing agent or chain extender.

[Formula 2]

In Formula 2, R ₃ and R ₅ are each independently C ₁ to C ₆ alkyl, and R ₄ are each independently hydrogen or C ₁ to C ₆ alkyl, provided that at least one of R ₄ is hydrogen, m and p are each independently integers from 0 to 400. Here, the C ₁ to C ₆ alkyl may be, for example, methyl, ethyl, propyl, butyl, pentyl, or hexyl. In particular, R ₃ and R ₅ are both methyl groups, and only one of R ₄ may be hydrogen.

Additionally, the polyorganosiloxane compound of Formula 2 may have a molecular weight of 300 to 20,000 g/mol, for example, 250 to 15,000 g/mol. Here, by adjusting the molecular weight of the polyorganosiloxane compound of Formula 2 to be relatively low, curing is possible at low temperatures and excellent electrical conductivity and improved resistance stability can be achieved after curing.

The content of the polyorganosiloxane compound of Formula 2 as a curing agent or chain extender may be 10 to 100 parts by weight based on 100 parts by weight of the polymer resin of Formula 1. Here, if the content of the polyorganosiloxane compound of Formula 2 is less than 10 parts by weight, low-temperature curing is difficult and mechanical properties and heat resistance after curing may be insufficient, whereas if it is more than 100 parts by weight, early curing occurs before application of the composition. This may occur and flexibility may decrease after curing.

Here, the molar ratio of the polymer resin containing the polyorganosiloxane of Formula 1 and the curing agent or chain extender containing the polyorganosiloxane of Formula 2 is 1:1 or more, for example, 1:5 to 1:10. may be included. Here, if the molar ratio is less than 1:1, low-temperature curing is difficult and mechanical properties, heat resistance, etc. may be insufficient after curing, while if it is more than 1:10, flexibility may be reduced after curing.

Additionally, the polymer resin may include a polyorganosiloxane compound of the following formula (3) as a plasticizer.

[Formula 3]

In Formula 3, R ₆ and R ₇ may each independently be C ₁ to C ₆ alkyl, for example, methyl, ethyl, propyl, butyl, pentyl, or hexyl, preferably methyl, and q is 300. It may be from 810 to 810.

As a plasticizer, the polyorganosiloxane compound of Formula 3 can be inserted between the base resins to weaken the attractive force and expand the distance, thereby improving the flexibility of the composition. Here, the content of the plasticizer may be 1 to 10 parts by volume based on 100 parts by volume of the base resin.

Meanwhile, the electrically conductive particles may be silver, copper, gold, aluminum, molybdenum, zinc, tungsten, nickel, iron, palladium, platinum, tin, lead, titanium, etc., and may be used alone or in a mixture of two or more types. there is. Although not limited thereto, silver or silver-plated copper may be preferably used.

The electrically conductive particles have a total density of 2.0 to 4.0 g/cc and include micro-sized plate-shaped particles shown in FIG. 1, micro-sized spherical particles shown in FIG. 2, and nano-sized particles shown in FIG. 3. can do. As a result, as shown in Figure 4, the total content can be minimized through efficient arrangement of the electrically conductive particles by shape, thereby ensuring sufficient adhesive strength and mechanical properties of the composition, and at the same time increasing the contact area between the conductive particles to reduce contact resistance. By reducing it, a sufficient electrical network can be formed within the polymer resin.

Specifically, the total content of the electrically conductive particles may be 300 to 600 parts by weight based on 100 parts by weight of the polymer resin. Here, if the content of the electrically conductive particles is less than 300 parts by weight, a sufficient electrical network cannot be formed within the polymer resin, whereas if it is more than 600 parts by weight, the flexibility of the adhesive composition decreases and efficient arrangement of the conductive particles is difficult. There is a problem that the specific resistance of the composition increases and the resistance stability decreases.

Furthermore, among the electrically conductive particles, the content of micro spherical particles is 25 to 83 parts by weight based on 100 parts by weight of micro plate-shaped particles, and the content of nanoparticles is 1 to 30 parts by weight based on 100 parts by weight of micro spherical particles.

In particular, among the electrically conductive particles, the average particle diameter of micro-spherical particles may be 2 to 10 ㎛, the average particle diameter of micro plate-shaped particles may be 2 to 50 ㎛, the average particle diameter of nanoparticles may be 10 to 500 ㎚, and the D of the nanoparticles ₅₀ may be 40 to 60 nm. If the shortest axis is more than 30% of the longest axis in any cross section, it may be a micro spherical particle, and if it is less than 30%, it may be a micro plate-shaped particle.

Furthermore, the particle size distribution ratio (γ) defined by Equation 1 below may be 1.0 or less, for example, 0.1 to 1.0 for micro-spherical particles, and 2.0 or less, for example, 1.1 to 2.0 for micro-plate-shaped particles.

[Equation 1]

γ=(D ₉₀ -D ₁₀ )/D ₅₀

The smaller the value of the particle size distribution ratio (γ) defined by Equation 1 above, the more uniform the particle size distribution is based on 50% of the cumulative weight of the particles, and the larger the value of the particle size distribution ratio (γ), the more uniform the particle size distribution is. means that it is non-uniform, and if the particle size distribution ratio (γ) of each micro-spherical particle and micro-plate-shaped particle satisfies the range described above, efficient arrangement of electrically conductive particles is possible within the polymer resin, thereby increasing the content of conductive particles. Despite minimizing , a sufficient electrical network can be formed and at the same time, the silicone conductive composition according to the present invention can maintain high adhesive strength.

Meanwhile, among the electrically conductive particles, nanoparticles can improve the adhesive strength of the silicone conductive composition according to the present invention. The nanoparticles may have a hydrophobic surface to improve compatibility with the polymer resin, and if necessary, the hydrophobic film may be removed through pretreatment.

The nanoparticles have a high specific surface area and can increase the contact effect with other particles and the surface to be adhered through secondary bonding through the surface. These nanoparticles can effectively stick to the surface of the adherend, generate strong mechanical bonding, and secure adhesion. At this time, the adhesive strength can be improved as the adhesion between the surface to be adhered and the composition becomes stronger than the cohesion between the compositions.

In addition, the nanoparticles have a small nano-sized particle size and can penetrate into the fine bends of the rough surface to be adhered, thereby increasing the contact surface with the adhered surface and improving adhesive strength.

As a result, the silicone conductive composition according to the present invention can be cured at a low temperature of 100°C or lower, has improved flexibility even after curing, improves resistance stability by maintaining resistance even when deformed such as bending, and further reduces manufacturing costs. Shows effect.

The low-temperature curable silicone conductive composition according to the present invention may further include catalysts, retarders, non-conductive particles, solvents, etc. as other additives.

Specifically, the catalyst functions to accelerate the curing reaction of the adhesive composition at low temperatures, and a platinum group metal atom compound, for example, a Karstedt or Speier series platinum compound, may be used. Platinum group metals include platinum, rhodium, and palladium, and platinum group metal atomic compounds include chloroplatinic acid, reaction products of chloroplatinic acid and alcohol, platinum-olefin complex, platinum-vinylsiloxane complex, platinum-ketone complex, and platinum-phosphine complex. There are platinum compounds such as rhodium-phosphine complexes, rhodium compounds such as rhodium-sulfide complexes, and palladium compounds such as palladium-phosphine complexes.

The content of the catalyst may be 10 to 1000 ppm, preferably 50 to 500 ppm. If the catalyst content is below the standard, the curing reaction at low temperature may be insufficient, whereas if the catalyst content is above the standard, the curing reaction may be insufficient before application of the composition. Hardening problems may occur.

Meanwhile, the retardant is an additive to achieve storage stability by suppressing natural hardening when stored at room temperature before applying the adhesive composition, and is a fumarate, maleate, and tetravinylcyclotetrasiloxane-based Heat, etc. can be used.

To improve the storage stability of the adhesive composition at room temperature, a retarder having a boiling point of at least 60°C, preferably 100 to 220°C, may be used. Additionally, the content of the retardant may be 200 to 1,000 parts by volume based on 100 parts by volume of the catalyst. Here, if the content of the retardant is less than 200 parts by volume, storage stability at room temperature may be reduced, while if it is more than 1,000 parts by volume, the curing reaction may be insufficient when curing at low temperature after application.

The non-conductive particles may be silicon dioxide (SiO ₂ ), alumina (Al ₂ O ₃ ), calcium carbonate (CaCO ₃ ), boron nitride (BN), etc., and, for example, have an average particle diameter of 10 to 1,000 nm. It may be, and the content may be 1 to 20 parts by weight based on 100 parts by weight of the polymer resin.

The non-conductive particles form secondary bonds with the siloxane bonds of the polymer resin, which can help improve the rheological properties of the polymer resin depending on time or shear force. After curing the composition, it maintains the shape of the border of the adhesive and changes its size. It can help maintain uniformity.

The solvent may be an organic solvent, and one having excellent chemical compatibility with the polymer resin may be used. The boiling point is preferably 100°C or higher, which can improve final working viscosity and delay curing, which can help ensure storage stability during storage.

The silicone conductive composition according to the present invention can be uniformly mixed with the polymer resin, electrically conductive particles, and other additives by methods such as milling, blending, stirring, and planetary mixing. You can.

Additionally, the mixed silicone conductive composition may be cured at 80 to 200°C, preferably 80 to 100°C. Additionally, although not limited thereto, the curing time may be 0.5 to 3 hours.

[Example]

1. Manufacturing example

A 1 mm thick silicone conductive composition according to the present invention was applied to a fluorine release film, cured at 80°C, and the peeled composition specimen was bent with wires for resistance measurement connected to both ends of the specimen as shown in Figure 5. While doing so, the resistance according to the bending radius was measured.

The measurement results are as shown in Figure 6 and Table 1 below.

Curvature radius (mm) bending strain Resistance [mΩ] 3.175 0.15748 41.4 3.05 0.163934 41.4 2.305 0.21692 41.4 2.15 0.232558 41.4 2 0.25 41.4 1.88 0.265957 41.4 1.715 0.291545 41.4 1.65 0.30303 41.4 1.6 0.3125 41.4 1.55 0.322581 41.4 1.45 0.344828 41.4 1.335 0.374532 41.4 1.24 0.403226 41.4 1.135 0.440529 41.4 1.02 0.490196 41.4 0.75 0.666667 41.4 0.45 1.111111 41.4 0.18 2.777778 41.4 0.09 5.555556 41.4 0.06 8.333333 41.4

As shown in Table 1 and Figure 6, it was confirmed that the resistance was maintained uniformly even though the radius of curvature of the composition specimen gradually decreased and the bending strain increased. Accordingly, it was confirmed that the silicone conductive composition according to the present invention had improved flexibility after curing and improved resistance stability in which the resistance was maintained uniformly even when bent.

Although this specification has been described with reference to preferred embodiments of the present invention, those skilled in the art may modify and modify the present invention in various ways without departing from the spirit and scope of the present invention as set forth in the claims described below. Changes may be made. Therefore, if the modified implementation basically includes the elements of the claims of the present invention, it should be considered to be included in the technical scope of the present invention.

Claims (10)

A low-temperature curable silicone conductive composition, comprising:
Contains polymer resin and electrically conductive particles,
The polymer resin includes a polyorganosiloxane resin of Formula 1 below as a base resin, a polyorganosiloxane compound of Formula 2 below as a curing agent or chain extender, and a polyorganosiloxane compound of Formula 3 below as a plasticizer. Curable silicone conductive composition.
[Formula 1]

In Formula 1, R ₁ and R ₂ are each independently hydrogen, C ₁ to C ₆ alkyl, or C ₂ to C ₆ alkenyl, provided that at least one of R ₁ is C ₂ to C ₆ alkenyl. and n is an integer from 79 to 1891,
[Formula 2]

In Formula 2, R ₃ and R ₅ are each independently C ₁ to C ₆ alkyl, and R ₄ are each independently hydrogen or C ₁ to C ₆ alkyl, provided that at least one of R ₄ is hydrogen, m and p are each independently integers from 0 to 400,
[Formula 3]

In Formula 3, R ₆ and R ₇ are each independently C ₁ to C ₆ alkyl, and q is 300 to 810. According to paragraph 1,
R ₁ is all vinyl, R ₂ is methyl,
One of R ₄ is hydrogen, R ₃ and R ₅ are both methyl,
A low-temperature curable silicone conductive composition, wherein R ₆ and R ₇ are both methyl. According to paragraph 2,
A low-temperature curable silicone conductive composition, characterized in that the polyorganosiloxane resin of Formula 1 has a weight average molecular weight of 6,000 g/mol or more and less than 140,000 g/mol. According to paragraph 2,
The content of the polyorganosiloxane compound of Formula 2 is 10 to 100 parts by weight based on 100 parts by weight of the base resin,
A low-temperature curable silicone conductive composition, characterized in that the content of the polyorganosiloxane compound of Formula 3 is 1 to 10 parts by volume based on 100 parts by volume of the base resin. According to any one of claims 1 to 4,
The electrically conductive particles include micro spherical particles with an average particle diameter of 2 to 10 μm, micro plate-shaped particles with an average particle diameter of 2 to 50 μm, and nanoparticles with an average particle diameter of 10 to 500 nm. A low-temperature curable silicone conductive composition. According to clause 5,
A low-temperature curable silicone conductive composition, characterized in that the particle size distribution ratio (γ) defined by Equation 1 below is 1.0 or less for the micro spherical particles and 2.0 or less for the micro plate-shaped particles.
[Equation 1]
γ=(D ₉₀ -D ₁₀ )/D ₅₀ According to clause 6,
Based on 100 parts by weight of the micro plate-shaped particles, the content of the micro spherical particles is 25 to 83 parts by weight, and based on 100 parts by weight of the micro spherical particles, the content of the nanoparticles is 1 to 30 parts by weight, Low-temperature curable silicone conductive composition. In clause 7,
A low-temperature curable silicone conductive composition, characterized in that, based on 100 parts by weight of the base resin, the total weight of the electrically conductive particles is 300 to 600 parts by weight. According to clause 5,
A low-temperature curable silicone conductive composition, wherein the electrically conductive particles have a total density of 2.0 to 4.0 g/cc. According to any one of claims 1 to 4,
A low-temperature curable silicone conductive composition, characterized in that it further comprises one or more other additives selected from the group consisting of catalysts, retarders, non-conductive particles, and solvents.