KR20150080377A - Thermal adhesive - Google Patents

Abstract

The present invention relates to a thermal conductive adhesive. The present invention comprises a polysiloxane resin matrix and a metal nanorod filler. According to the present invention, it is possible to provide a thermal conductive adhesive composition wherein a thermal conductivity is excellent even with a charge capacity of a small amount of filler; and production process properties, stability of a cured product after the processing such as coating, spreading, etc., and mechanical properties thereof such as hardness, adhesive strength, tensile strength, etc. are excellent.

Description

Thermal adhesive

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermally conductive adhesive, and more particularly, to an adhesive paste applied between a heat source and a component to perform bonding and thermal conduction of components.

Various types of semiconductor packages have been proposed along with high performance and high functionality of electronic parts. The LED package using LED (Light Emitting Diode), which is a semiconductor device that emits light when a forward voltage is applied, has advantages such as low power consumption and low environmental load. Therefore, a small display such as a mobile phone, Liquid crystal televisions, and the like, and various electric and electronic products such as automobile console panels and automobile lighting, household lighting, signboards and displays, alarms, and other household appliances.

In general, adhesives used for bonding a semiconductor chip and a semiconductor chip mounting substrate in a semiconductor package are required to have high thermal conductivity, sufficient insulating property, and adhesion reliability. Such a thermally conductive adhesive means an adhesive paste which is applied between a heat source such as a semiconductor chip and a heat radiation component such as a heat sink to perform adhesion and thermal conduction between components. The thermally conductive adhesive has the following characteristics: 1) it can be applied to sophisticated parts without complicated process (improvement of productivity), 2) it has excellent heat dissipation effect even in small amount, and maintains friction and impact protection between elements Modulus), 3) No void formation and insulation and heat resistance (~ 230 ℃), 4) No corrosion due to out gas, and rework is required .

As the thermally conductive adhesive so far, a UV curing type acrylic, a thermosetting type epoxy or urethane type resin is used as a matrix, and SiO ₂ alone; BN, AlN, Al ₂ O ₃ , TiO ₂ , ZnO, SiC, and Si ₃ N ₄ ; Metal powders such as Sn, Cu, and Ag; Or carbon-based materials such as CNT, carbon fiber, and graphite are used as conductive fillers. However, this type of thermally conductive adhesive has the following disadvantages: 1) it has excellent thermal conductivity, but has a high filling amount of filler (about 80 wt% or 60 vol%), 2) Surface cracking / chipping occurs and brittle causes degradation of the stability of the cured product after processing (coating, spreading, etc.), and (4) mechanical properties such as tensile strength, adhesive strength and hardness are inferior Lt; / RTI >

1. Japanese Laid-Open Patent Application No. 2010-123935 2. US Patent Application Publication No. 2007-810707 3. Japanese Patent Application Laid-Open No. 2007-055171 4. Korean Patent Publication No. 2009-0093649

Accordingly, it is an object of the present invention to provide a thermally conductive adhesive excellent in thermal conductivity even with a small filling amount, and excellent in mechanical properties (hardness, adhesive strength, tensile strength, etc.) of a cured product after processability and processing (coating, spreading, etc.).

In order to achieve the above object, one aspect of the present invention provides a thermally conductive adhesive composition comprising a polysiloxane resin matrix, and a metal nanorod filler.

The polysiloxane resin may be represented by the following chemical formula 1:

≪ Formula 1 >

R may include at least one aromatic ring compound containing a phenyl group.

Wherein the polysiloxane resin has a number average molecular weight of 1,000 to 3,000, a viscosity of 8,000 to 14,000 cps, a transparency of 90 or more with respect to light having a wavelength of 450 nm, a heat resistance of 300 DEG C or more, a refractive index (RI) 1.60.

In addition, the polysiloxane resin has a three-dimensional net structure through crosslinking, and is excellent in mechanical properties such as hardness and tensile strength, and has a thermal conductivity of 0.2 to 0.3 W / mK, which is superior to conventional epoxy, urethane, acrylic resin W / mk).

The metal nano-rods used as the filler of the thermally conductive adhesive composition of the present invention are nano-rods made of at least one metal material selected from silver (Ag), copper (Cu), tin (Sn), aluminum (Al) Lt; / RTI >

The metal nano-rods are preferably silver nano-rods having an average diameter of 30 to 100 nm and a length of 1 to 5 m.

It is preferable that the metal nano-rods are contained in the range of 3 to 20 wt% based on the total weight of the thermally conductive adhesive composition.

The thermally conductive adhesive composition of the present invention may further comprise spherical silica in the range of 1 to 15 wt% based on the total weight of the composition.

According to the present invention, it is possible to obtain a thermally conductive adhesive excellent in thermal conductivity even with a small filling amount, and excellent in mechanical properties (hardness, adhesive strength, tensile strength, etc.) of the cured product after processability and processing (coating, spreading, etc.).

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view schematically showing components of a thermally conductive adhesive composition according to the present invention. FIG.
2 is a schematic view showing a process for producing a thermally conductive adhesive according to the present invention.
3 is a SEM photograph of the silver (Ag) nanowire of the embodiment.
4 is a SEM photograph of the silver (Ag) nanorod of the embodiment.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

Fig. 1 shows a schematic view of the constitution of the thermally conductive adhesive composition of the present invention. Referring to Figure 1, the thermally conductive adhesive composition of the present invention may comprise the following components:

a) a polysiloxane resin matrix, and

b) Metal nanorod filler.

The polysiloxane resin is characterized by containing at least one selected from among M units and D units, and at least one selected from T units and Q units, wherein M, D, T and Q units are as shown below.

The polysiloxane resin can be represented by formula (1)

≪ Formula 1 >

In Formula (1), R includes at least one aromatic ring compound containing a phenyl group.

The polysiloxane resin has a number average molecular weight of 1,000 to 3,000, a viscosity of 8,000 to 14,000 cps, a light transmittance of 90 or more for light of 450 nm wavelength, a heat resistance of 300 DEG C or more, a refractive index (RI: 1.60.

When the number average molecular weight of the polysiloxane resin is less than 1,000, the wetting and dispersing properties of the metal nano-rod deteriorate. When the number average molecular weight exceeds 3,000, the polysiloxane resin itself becomes solid powder, There is no problem.

The viscosity of the polysiloxane resin is preferably 8,000 to 14,000 cps, and the fairness and compatibility are the best in this range. If the viscosity is less than 8,000, tailing or tail biting occurs in the dispensing process. If the viscosity is higher than 14,000, the color becomes blurred and the compatibility becomes poor. Since the resin becomes solid powder, it can be used as an adhesive none.

The polysiloxane resin has a refractive index of 1.40 to 1.60, which is advantageous in that the adhesive is used in packages and devices because of its excellent optical efficiency. The refractive index can be controlled by introducing an aromatic ring compound such as benzene, naphthalene, or anthracene into the polysiloxane resin.

The polysiloxane resin can form a three-dimensional net structure through crosslinking. Due to such a three-dimensional net structure, mechanical properties such as hardness and tensile strength are excellent, and thermal conductivity (0.2 to 0.3 W / mK) Urethane, and acrylic resin (0.05 ~ 0.1 W / mk).

Since the polysiloxane resin can promote the reaction between the metal nanorod or the hydrophilic functional group present on the silica surface by activating the hydrophilic functional group (Si-OH) on the resin surface, the adhesion between the resin matrix and the metal nano-rod or silica is excellent .

The polysiloxane resin can be obtained, for example, through the following chemical reaction:

(2)

In this formula,

R represents a vinyl group or a hydrogen atom,

는 -CH₂CH₂- 를 나타낸다.Connecting R and R

Represents -CH ₂ CH ₂ -.

As can be seen from the above chemical reaction formula, the polysiloxane resin used in the thermally conductive adhesive of the present invention can be prepared by the following method.

1) An oligomer is prepared by a sol-gel condensation reaction of a silane having a functional group such as disilanol and an alkenyl group including vinyl. In the above reaction scheme, the -OH group of diphenyl disilanol and the methoxy group of trimethoxysilane are subjected to a sol-gel condensation reaction to form a siloxane bond, .

2) In the presence of a catalyst such as platinum (Pt), a cross-linking reaction such as thermosetting may be carried out to obtain a three-dimensional network structure polysiloxane resin. In the above reaction scheme, the unsaturated bond of the vinyl group (-R) is covalently bonded to the surrounding hydrogen (H) to form a three-dimensional net structure.

The metal nano rod used in the thermally conductive adhesive composition of the present invention is a nano rod made of at least one metal material selected from silver (Ag), copper (Cu), tin (Sn), aluminum (Al) .

As the metal nano-rods, silver nano-rods having an average diameter of 30 to 100 nm and a length of 1 to 5 m are preferable. If the average diameter is smaller than 30 nm, the filling rate is too high, so that the formability of the adhesive containing the same is lowered, and if it is larger than 100 nm, the dispersibility is lowered. When the length of the nano-rods is less than 1 탆, thermal conductivity can not be realized. When the length of the nano-rods is more than 5 탆, the aspect ratio is too large and apparent irregularities can be formed.

The metal nano-rods are preferably included in the range of 10 to 20 wt% based on the total weight of the thermally conductive adhesive composition. When the content of the metal nano-rods is less than 10 wt%, the thermal conduction effect is almost zero. When the content of the metal nano-rods is more than 20 wt%, the metal nanorods may aggregate with each other.

The metal nano-rod can be, for example, a silver (Ag) nano-rod, and the silver (Ag) nano-rod can be produced by grinding the silver (Ag) nanowire. In the case of an adhesive using ceramic fillers such as BN, AlN, Al ₂ O ₃ , ZnO, TiO ₂ , Si ₃ N ₄ and SiC, ceramic fillers are used in an amount of about 80 wt% / mK, it is possible to obtain thermal conductivity equal to or higher than that of a small amount of nano rod of about 10 wt%.

When a metal nano-rod having a length of 1 to 5 占 퐉 is used as a filler, physical properties such as cracking / chipping or Brittleness can be improved.

The metal nanowires used in the production of the metal nano-rods used in the present invention can be prepared by a known method including the following steps:

1) A capping agent (for example, polyvinylpyrrolidone (PVP), a chloride ion (Cl ^- ) source (for example, TBAC, PtCl ₃ , NaCl, LaCl ₃ , Is dissolved in an organic solvent (for example, ethyleneglycol, propyleneglycol, etc.) and stirred while heating.

2) Add a metal precursor (for example, silver nitrate (AgNO ₃ )) solution slowly dropwise.

3) After allowing the solution to react for a certain period of time, the reaction is terminated.

4) The synthesized metal nanowires are separated, washed and purified to obtain metal nanowires.

The metal nano-rods used in the present invention can be obtained by pulverizing the metal nanowires obtained by a known method in a ball mill or by ultrasonication.

The thermally conductive adhesive composition of the present invention may further comprise spherical silica in the range of 0.1 to 15 wt% based on the total weight of the composition. When the spherical silica is added, the effect of increasing the hardness and durability of the thermally conductive adhesive can be obtained. In addition, when spherical silica is added, the silver nanorods are connected to each other by the spherical silica to increase the heat transfer contact point and convert the point conduction to line conduction, thereby improving the thermal conductivity 1). If the content of the spherical silica is less than 0.1 wt%, the effect of increasing the hardness and durability is insignificant. If the content of the spherical silica is more than 15 wt%, dispersion is difficult.

In general, the adhesive dispensing process uses an auto dispensing method, and the adhesive is discharged through a syringe needle, which is discharged through a fine needle. Therefore, even if the viscosity of the adhesive composition is high, It does not matter. By adding the spherical silica, such a plasticity can be ensured and the discharge viscosity can be easily controlled, so that the processability can be secured.

The thermally conductive adhesive composition of the present invention can be produced by the following method (see Fig. 2).

1) Polysiloxane resin can be mixed with, for example, spherical silica. In some cases, 0.1 to 0.5 ml of a wetting agent of volatile silanes such as hexamethyldisiloxane or tetramethylcyclosiloxane may be added. The wetting agent functions to improve the dispersion of the resin and the spherical silica. After the mixing, the wetting agent is volatilized and removed by self-heating at about 50 ° C.

2) A metal nano-rod, for example, a silver (Ag) nano-rod can be further added and then dispersed. The dispersion may be firstly dispersed through a mixer, and then secondarily dispersed using a three-roll mill. The primary dispersion is preferably carried out under a condition of 60 DEG C or less and a reduced pressure of 200 to 600 rpm.

3) Purification through filtration or the like to obtain the final product.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The embodiments are provided to aid those of ordinary skill in the art to understand the present invention and should not be construed as limiting the present invention in any way.

silver( Ag Manufacturing of nano-rods

A 100 ml round bottom flask equipped with a stirrer and a condenser was placed in a heating water bath, and 28 g of polyvinylpyrrolidone (PVP) as a capping agent and 22 g of tetrabutylammonium chloride (TBAC) Was dissolved in 100 ml of ethylene glycol as an organic solvent, and stirred while heating from 80 ° C to 140 ° C at a heating rate of 1 ° C per minute for 1 hour while maintaining at 140 ° C for 2 hours. At this time, reflux cooling was continuously carried out to prevent vaporization of ethyleneglycol.

To the solution, a solution prepared by previously dissolving 20 g of silver nitrate (AgNO ₃ ) in 30 ml of ethylene glycol was added dropwise for 20 minutes using a syringe pump.

The above solution was allowed to react for 4 hours, and then 100 ml of water was added thereto for quenching.

Thereafter, separation / washing / purification was performed by centrifugation to obtain silver (Ag) nanowires. SEM photographs of the obtained silver nanowires are shown in FIG.

The obtained silver (Ag) nanowires were ultrasonicated for 1 hour to obtain silver (Ag) nanorods. SEM photographs of the obtained silver nanorods are shown in FIG.

The physical properties of the obtained silver (Ag) nano-rod are as follows.

- Thermal conductivity: 720 W / mK

- average diameter: 50 nm

- Length: 2.8㎛

Polysiloxane  Synthesis of resin

200 mmol of diphenyldisilanol and 50 mmol of trimethoxysilane containing functional groups containing an alkenyl group or hydrogen containing vinyl are introduced into a round bottom flask reactor equipped with a reflux condenser, , 25 ml of isopropanol was added, and the sol-gel condensation reaction was carried out at room temperature for 30 minutes with stirring. At this time, the temperature of the contents of the reactor rose to 74 ° C due to the heat of own reaction. Thereafter, the mixture was heated to 150 DEG C over 60 minutes while stirring. Then, 0.5 g of Pt-Karstedt Catalyst, which is a platinum group metal catalyst, was added and crosslinking reaction proceeded to obtain a polysiloxane resin.

The physical properties of the obtained polysiloxane resin are as follows.

- Light Transmittance: 91% at 450 nm

- Thermal Stability: 300 ° C (temperature at which 5% mass reduction in TGA occurs)

Refractive index (RI) (n): 1.52

Number average molecular weight (Mn): 2,800

- Viscosity: 11,300 cP

Thermal conductivity  Preparation of adhesive composition

A thermally conductive adhesive composition was prepared according to the following procedure, with the above polysiloxane resin, silver (Ag) nanorod, spherical silica, other thermally conductive filler (filler), and additives as shown in Table 1 below.

1) The above polysiloxane resin and spherical silica were put into a cylindrical mixing vessel made of SUS604 and mixed with stirring. When an epoxy resin is used, an amine catalyst is added thereto. When a urethane resin is used, a cross linker is added thereto. Two kinds of resin were packed in one syringe and made into one liquid type. Karstedt's cat. (Pt) and the reaction retarder (Pt) were added to each resin to ensure curing, fairness and storage stability.

2) silver (Ag) nano-rods were added and dispersed for 60 minutes at 50 ° C, 0.7 atm, and 400 rpm using Planetary Mixer (YUYU MACHINE, PL-80M) (Dialectech, EXAKT) for 30 minutes.

3) Pressing with a sieve of 100 mesh to obtain a purified thermally conductive adhesive composition.

Thermal conductivity  Evaluation of properties of adhesive composition

The properties of each of the thermally conductive adhesives prepared in the above manner were evaluated in the following manner and are shown together in Table 1.

a) Thermal conductivity

The thermally conductive adhesive composition was measured by a thermal conductivity meter (Shinko, C-THERM, TCI) five times for 20 minutes at 25 DEG C and 50% RH, and then expressed as an average value.

b) Hardness

A thermally conductive adhesive composition was cured in a 150 캜 hot air convection oven for 1 hour to prepare a sheet having a thickness of 6 mm and a load of 50 gf and a relative humidity of 50 gf were measured with an ASKER hardness meter (KOBUNSHI KEIKI, SUPER EX-D, Shore D type) 50%, and then expressed as an average value.

c) Tensile strength and elongation

The thermally conductive adhesive composition was cured in a hot air convection oven at 150 캜 for 1 hour to prepare a sheet having a thickness of 2 mm. Five dumbbell specimens were prepared in accordance with the KSM-6518 standard and subjected to a universal tensile test at 25 캜 and a relative humidity of 50% Measured with a tester (Instron, UTM-4484) and expressed as an average value.

d) Adhesion

A copper (Cu) substrate coated with 20 ㅧ 20 ㅧ 2 mm of silver (Cu) and a substrate of 5 ㅧ 5 ㅧ 2 mm were bonded to each other with a thermally conductive adhesive composition and cured for 1 hour in a hot air convection oven at 150 캜, (Dage-4000, manufactured by Dako Korea) at 25 ° C and a relative humidity of 50%.

Ingredients Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Remarks Adhesive composition ^PVM Polysiloxane Resin ¹ 44 44 42 40 Resin Matrix ^PHM Polysiloxane Resin ² 40 40 42 44 Epoxy Resin ³ 27 27 Amine Cat ⁴ 3 3 Urethane Resin ⁵ 20 Cross-linker ⁶ 10 Ag nanorod ⁷ 15 10 7 4 Thermally conductive filler Spherical Silica ⁸ 5 8 11 h-BN ⁹ 70 50 Al ₂ O ₃ ¹⁰ 70 20 Karstedt's cat. (Pt) ¹¹ 0.5 0.5 0.5 0.5 additive Inhibitor ¹² 0.5 0.5 0.5 0.5 Properties Thermal conductivity (W / mk) 2.31 2.56 2.17 2.08 1.68 1.44 1.86 Hardness (Shore D) 53 50 48 48 13 16 22 Tensile strength (kg _f / ㎝2) 152 144 142 143 93 81 103 Adhesive strength (kg _f / ㎝) 22.3 21.8 21.6 20.6 13.3 11.4 10.6 Elongation (%) 83 76 86 84 43 47 31

The sources of the raw materials used in Examples and Comparative Examples are as follows.

ㆍ 1: Phenyl vinyl methyl resin directly manufactured in the present invention

ㆍ 2: Direct production in the present invention, Phenyl Hydrogen methyl resin

ㆍ 3: Kukdo Chemical, YD-128 (BPA system)

ㆍ 4: Aldrich, 3-propylenediamine

ㆍ 5: BASF, PP-400

ㆍ 6: KPX Chemical, KR-6350

ㆍ 7: Direct manufacture in the present invention

ㆍ 8: Tokuyama, Excelica ㄾ UF-320

ㆍ 9: National Nitride Tech, NW-04

ㆍ 10: Tokuyama

11: Aldrich, Pt-VMM

12: Aldrich, 1-Ethynylcyclohexanol

Referring to Table 1, according to the present invention, a thermally conductive adhesive containing a metal nano-rod and a spherical silica as a filler in the polysiloxane resin matrix has not only excellent thermal conductivity, but also tensile strength, hardness, It can be seen that the mechanical properties are also excellent.

When a semiconductor device, for example, a computer CPU is used as an adhesive for adhering to a heat sink, the heat of the CPU is efficiently dissipated to improve the performance of the CPU, and the CPU is deteriorated And the life span of the CPU is prolonged.

Claims (8)

a) a polysiloxane resin matrix, and
b) a thermally conductive adhesive composition comprising a metal nanorod filler.
The thermally conductive adhesive composition according to claim 1, wherein the polysiloxane resin is represented by a repeating unit structure represented by the following formula (1):
≪ Formula 1 >

In Formula (1), R includes at least one aromatic ring compound containing a phenyl group.
3. The thermally conductive adhesive composition of claim 2, wherein the polysiloxane resin has a refractive index of 1.4 to 1.6.
The thermally conductive adhesive composition according to claim 1, wherein the metal nanorod is at least one selected from the group consisting of silver, copper, tin and aluminum.
5. The thermally conductive adhesive composition according to claim 4, wherein the metal nanorods are silver nanorods having an average diameter of 30 to 100 nm and a length of 1 to 5 m.
The thermally conductive adhesive composition of claim 1, wherein the metal nanorods are included in the range of 10 to 20 wt% based on the total weight of the composition.
The thermally conductive adhesive composition of claim 1, further comprising a spherical silica.
8. The thermally conductive adhesive composition of claim 7, wherein the spherical silica is included in the range of 0.1 to 15 wt% based on the total weight of the composition.

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