TWI667338B - Composition for high thermal conductive materials - Google Patents

Abstract

The present invention discloses a composition comprising: (A) a resin, (B) a thermally conductive, electrically insulating filler, and (C) a thermally conductive, electrically conductive filler, wherein the content of (C) is from 0.2% by volume to 1.0% by volume. The molded article formed from the composition has an unexpectedly high thermal conductivity and good electrical insulation and processability suitable for the thermal management component.

Description

Composition for highly thermally conductive materials

The present invention relates to a composition for an insulating polymer material having a high thermal conductivity suitable for a thermal management element of an electronic device; a molded article; and a device containing the article.

Thermal management is critical in every aspect of the microelectronics space, such as integrated circuits (ICs), light-emitting diodes (LEDs), power electronics, displays, and photovoltaic devices. . The performance of their devices can be directly affected by the operating temperature. Reducing the operating temperatures of such devices can increase lifetime and improve performance compared to operating at higher temperatures.

In the solid state lighting industry, there is a strong need to improve thermal management. Proper heat dissipation in LED devices is critical to their reliable long term operation. Failure to adequately manage heat can have a negative impact on LED performance. Prolonged exposure to excessive operating temperatures can cause irreversible damage to the semiconductor components within the LED die, resulting in reduced light output, color rendering index changes, and significant reduction in LED lifetime. Therefore, materials having higher thermal conductivity properties are required for thermal management of LED devices.

A heat sink in an electronic system is a passive component that cools the device by dissipating heat into the surrounding air. The heat sink is used to cool electronic components or semiconductor components, such as high power semiconductor devices, and optoelectronic devices, such as higher power lasers and light emitting diodes (LEDs). Traditional The heat sink uses aluminum fins and several copper heat pipes to cool the high heat dissipation processor. The heat sink is designed to increase the surface area in contact with its surrounding cooling medium, such as air. However, metals are heavy and difficult to handle complex forms. Therefore, there has been a need to develop materials having higher thermal conductivity and lower weight and lower processing costs as a substitute for metals.

Although the polymer material is light and easy to handle, its low thermal conductivity hinders its application to heat sinks. In order to increase the thermal conductivity of the polymer material, a large amount of a thermally conductive filler, such as boron nitride, is added to the polymer material. See, for example, EP2094772B, WO2013012685A, US20090069483A, WO2012114309A, WO2009043850A, WO2011106252A, WO2012114310A, US20080265202A, and US20120229981 A. However, since the thermally conductive polymer material requires a relatively large amount of filler, it makes processing difficult because high pressure is required to mold the polymer.

Carbon-based fillers, such as graphite, have much higher thermal conductivity than boron nitride. Some of the above references disclose that the amount of graphite used is 5% by volume or more. However, the electrical conductivity of their fillers is high and therefore the electrical insulation of the polymeric material comprising the filler is poor.

Therefore, there is a need for an electrically insulating polymer material having a processability and a high thermal conductivity suitable for thermal management elements of electronic devices.

The inventors of the present invention have now found that a molded article is formed of a composition comprising at least two fillers: a thermally conductive, electrically insulating filler (filler-1) and a thermally conductive, electrically conductive filler (filler-2), and when filler-2 When the amount is small, the molded article achieves an unexpectedly high thermal conductivity and good electrical insulation suitable for the thermal management component.

Thus, one aspect of the invention relates to a composition comprising: (a) Resin, (b) thermally conductive, electrically insulating filler, and (c) thermally conductive, electrically conductive filler, and (c) is present in an amount of from 0.2% by volume to 1.0% by volume based on the total volume of the composition.

Another aspect of the invention relates to a molded article formed from the above composition.

Other aspects of the invention pertain to a device comprising a molded article.

As used throughout this specification, the abbreviations given below have the following meanings unless the context clearly indicates otherwise: g = grams; mg = milligrams; m = meters; mm = millimeters; cm = centimeters; min. = minutes; = sec; hr. = hour; °C = degrees Celsius; K = gram; W = watt; Ω = ohm; wt% = weight percent; vol% = volume percent. Throughout this specification, the words "resin" and "polymer" are used interchangeably.

<composition>

The composition of the present invention comprises (a) a resin, (b) a thermally conductive, electrically insulating filler, and (c) a thermally conductive, electrically conductive filler, and (c) is present in an amount of from 0.2% by volume to 1.0% by volume based on the total volume of the composition.

(a) resin

The resin used in the present invention may be selected from a wide variety of thermoplastic resins, thermosetting resins or mixtures thereof. The resin may also be a blend of polymers, copolymers, terpolymers, or a combination comprising at least one of the foregoing organic polymers. The resin may also be an oligomer, a homopolymer, a copolymer, a block copolymer, an alternating block copolymer, a random polymer, a random copolymer, a random block copolymer, a graft copolymer, a star a block copolymer, a dendrimer or the like, or at least A combination of the foregoing polymers.

Examples of the thermoplastic resin include polyamidene, polyphenylene sulfide (PPS), polyolefin, polyacetal, polycarbonate (PC), polyoxymethylene (POM), polystyrene (polystyrene; PS), polyester (such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT)), liquid crystal polyester (LCP), ethylene - vinyl acetate copolymer, acrylonitrile-butadiene-stylene (ABS); acrylic resin such as polymethyl methacrylate, polyvinyl chloride, polyacrylonitrile, polyphenylene ether, Polyfluorene, polyether oxime, polyetheretherketone, polyimine, fluororesin.

Examples of thermosetting resins include epoxy resins, thermosetting polyimine, phenol resins, urea resins, melamine resins, unsaturated polyester resins, diallyl phthalate resins, polyoxyxylene resins, and thermosetting ureidocarboxylic acids. Ester resin.

Preferably, the resin is selected from thermoplastic resins because of its ease of processing, such as heat dissipating elements that can be injection molded into various shapes in electronic devices.

The content of the resin is 15% by volume or more, preferably 20% by volume or more, more preferably 30% by volume or more by 30% by volume or more based on the total volume of the composition. The content of the resin is 55 vol% or 55% by volume, preferably 45% by volume or less, and more preferably 40% by volume based on the total volume of the composition.

(b) Thermally conductive, electrically insulating filler (filler-1)

The composition used in the present invention contains a thermally conductive, electrically insulating filler (filler-1). The filler has an intrinsic thermal conductivity of 20 W/mK or more and 20 W/mK or more. More preferably, the filler has an inherent thermal conductivity of 30 W/mK or more. The filler volume resistivity of 10 ¹² Ω.cm or more than 10 ¹² Ω.cm, preferably 10 ¹³ Ω.cm or more than 10 ¹³ Ω.cm. The volume resistivity of the filler can be measured by the method according to ASTM D257-07.

Examples of the filler-1 include boron nitride (BN), aluminum nitride (AlN), magnesium oxide (MgO), tantalum nitride (Si ₃ N ₄ ), and aluminum oxide (Al ₂ O ₃ ). Preferably, the filler-1 is selected from the group consisting of aluminum nitride, magnesium oxide, and tantalum nitride. Filler-1 can be used as a mixture.

The particle size of the filler-1 is 0.1 μm or more, preferably 5 μm or more. For good processability and mechanical properties, the particle size of the filler-1 is 400 micrometers or less, preferably 100 micrometers or less, more preferably 50 micrometers or less. Particle size means the median particle size (D50) and can be measured by laser diffraction particle size measurement techniques.

The content of the filler-1 is 45% by volume or more, preferably 55% by volume or more, more preferably 60% by volume or more by 60% by volume or more based on the total volume of the composition. Meanwhile, the content of the filler-1 is 84.8 vol% or 84.8 vol% or less, preferably 80 vol% or 80 vol% or less, more preferably 7 vol% or 75% by volume or less based on the total volume of the composition.

(c) Thermally conductive, conductive filler (filler-2)

The composition used in the present invention also contains a thermally conductive, electrically conductive filler (filler-2). The inherent thermal conductivity of the filler is 20 W/mK or more, preferably 30 W/mK or more. At the same time, the filler 10 ^-2 Ω.cm or a volume resistivity of 10 ^-2 Ω.cm or less, preferably 10 ^-4 Ω.cm 10 ^-4 Ω.cm or less. The volume resistivity of the filler can be measured in the same manner as described above.

Examples of the filler-2 include graphite, carbon nanotubes, carbon fibers, carbon black, and metal particles. Filler-2 can be used as a mixture. Preferably, Filler-2 is graphite. Graphite may be produced synthetically or naturally, or may be expanded graphite. Naturally produced graphite includes three types of stones Ink, that is, crystalline flake graphite, amorphous graphite, and crystalline vein graphite. Expanded graphite is produced by immersing natural flake graphite in a chromic acid bath followed by concentrated sulfuric acid, forcing the lattice plane to separate, thereby expanding the graphite. After expansion, the functional acid and OH groups are introduced and thus the affinity of the expanded graphite for the organic compound and the polymer is promoted. In addition, expanded graphite is more thermally conductive when compared to conventional carbon materials such as standard graphite. Expanded graphite is the best filler-2.

The particle diameter of the filler-2 is preferably 1 μm or more, more preferably 5 μm or more. The particle diameter of the filler-2 is preferably 100 μm or less, more preferably 50 μm or less. The particle size means the median diameter (D50).

The content of the filler-2 is 1.0% by volume or less based on the total volume of the composition. If the amount of the filler is more than 2.0% by volume, the insulation of the resulting cured polymer material is low. If the amount of the filler is less than 1.0% by volume, the insulation of the resulting cured polymer material is relatively high. The content of the filler is 0.2% by volume or more, preferably 0.5% by volume or more, based on the total volume of the composition.

If the amounts of (a) resin, (b) filler-1, and (c) filler-2 of the present invention are disclosed as % by weight based on the total weight of the composition, based on the weight of the composition, (a) A preferred amount is from 5% by weight to 30% by weight, a preferred amount of (b) is from 70% by weight to 95% by weight, and a preferred amount of (c) is from 0.1% by weight to 1.0% by weight. More preferably, the amount of (a) is from 15% by weight to 25% by weight, the amount of (b) is from 75% by weight to 85% by weight, and the amount of (c) is from 0.5% by weight to 1.0% by weight.

The composition used in the present invention may contain other additives such as a flame retardant, an antioxidant, a plasticizer, a coupling agent, a mold release agent, a pigment, and a dye.

Examples of the flame retardant for the composition include cerium oxide, a halogenated hydrocarbon, a halogenated ester, a halogenated ether, a brominated flame retardant, and a halogen-free compound such as an organic phosphorus compound, an organic nitrogen compound, Intumescent flame retardant.

Examples of the antioxidant used in the composition include sodium sulfite, sodium metabisulfite, sodium hydrogen sulfite, sodium thiosulfate, and dibutyl phenol.

Examples of the plasticizer for the composition include a dicarboxylate/tricarboxylate plasticizer such as a phthalate; a trimellitic acid ester; an adipate; a sebacate; Butenediates; organic phosphates; benzoates and polymeric plasticizers (such as polybutene).

Examples of the coupling agent for the composition include a chromium complex, a decane coupling agent, a titanate coupling agent, a zirconium coupling agent, a magnesium coupling agent, and a tin coupling agent.

Examples of the release agent for the composition include inorganic release agents such as talc, mica powder, clay and clay; organic mold release agents such as aliphatic acid soap, fatty acid, paraffin, glycerin and petrolatum; Agents such as polyoxyphthalic acid, polyethylene glycol and polyethylene.

Examples of the pigment or dye used in the composition of the present invention include chromate, sulfate, citrate, borate, molybdate, phosphate, vanadate, cyanate, sulfide, azo pigment, Phthalocyanine pigment, hydrazine, indigo, quinacridone and dye.

<Molding products>

The molded article of the present invention can be formed from the composition disclosed above. The method comprises the steps of: mixing (blending) the composition; pouring the blended composition into or into the mold and curing the mixture.

The method for blending the composition may use any known method such as melt blending or solution blending. Melt blending is preferred. Melt blending can be carried out using a melt mixer (such as a HAAKE Rheomix mixer), a single screw or twin screw extruder, a kneader, a Banbury mixer until uniform. The melt blending is preferably carried out at a temperature in which the composition has a low viscosity, for example, at least 10 ° C higher than the melting point of the resin in the composition.

The blending composition can be formed into an article by methods known to those skilled in the art, such as injection molding or extrusion at temperatures at which the blended composition has low viscosity and good flow.

The molded article has high thermal conductivity as well as good insulating properties. The thermal conductivity of the molded article is preferably 5 W/mK or more, more preferably 6 W/mK or more. Further preferably, the thermal conductivity is 8 W/mK or more. The volume resistivity of the molded article is preferably 1 × 10 ⁸ Ω.cm or above 1 × 10 ⁸ Ω.cm, more preferably 1 × 10 ¹² Ω.cm or more 1 × 10 ¹² Ω.cm, and further preferably 1 ×10 ¹³ Ω·cm or 1×10 ¹³ Ω·cm or more.

<device>

The apparatus of the present invention includes a heat source and a thermal management component located adjacent to the heat source. The thermal management component comprises a molded article formed from the above composition. Since the molded article used in the present invention has high thermal conductivity, the heat generated by the heat source is sufficiently transferred and removed from the heat source.

Examples of such heat sources include integrated circuit (IC) wafers, light emitting diodes (LEDs), power electronics, displays, and photovoltaic devices.

The thermal management component of the present invention can be a heat sink or a joining material comprising a heat source and a heat sink. As disclosed above, the heat sink is used to cool electronic components or semiconductor components, such as high power semiconductor devices, and optoelectronic devices, such as higher power lasers and light emitting diodes (LEDs). Since the molded article of the present invention has high thermal conductivity, heat generated by the heat source is efficiently transferred and removed from the heat source.

Other examples of thermal management components are electronic encapsulants, sealants, adhesives, electrical switches, printed circuit boards, and wire coatings.

The device of the present invention may be an electronic device such as an IC chip or a power electronic device a substrate of a component or a semiconductor component (heat source) and a plastic substrate or plastic film (thermal management component) in contact with the heat source. IC chips or other electronic components are typically mounted on a laminated plastic substrate such as an epoxy or polyimide resin. Ceramic substrates, such as aluminum or aluminum nitrate, are also used as substrates for power electronics because of the thermal management that is required by power electronics. Since the ceramic substrate is difficult to laminate or process, a plastic substrate having a high thermal conductivity is required. The molded article of the present invention can be used for this purpose.

The apparatus of the present invention may be a system comprising an electronic device (heat source) and a device covering a thermosetting resin (thermal management component). In order to protect the electronic device from mechanical damage, the electronic device is covered by a material such as a thermosetting resin. Since the electronic device generates heat, thermal management of the material is required. The molded article having high thermal conductivity of the present invention can be used for this purpose. An example of such a device is an LED illumination system in which the LED lamps are encapsulated by a molded article.

The device of the present invention may be a solid state lighting system comprising an LED lamp (heat source) and a pedestal (thermal management component) on which the LED lamp is mounted. In solid state lighting systems, LED lights are mounted on a pedestal and surrounded by side walls. Since the LED lamps generate heat, thermal management of the solid state lighting system is required. The molded article having high thermal conductivity of the present invention can be used for this purpose.

Example

The raw materials shown in Table 1 were used.

Process

Samples were prepared using a laboratory scale HAAKE mixer. Filler-1 and Filler-2 were mixed by vigorous shaking. For PA 66, the mixer was initially set at 280 ° C, set at 290 ° C for PPS and the rotor speed was 50 revolutions per minute (rpm). The resin was loaded into the mixer and completely melted. The already mixed filler was then slowly added and thoroughly mixed for 15 min at 50 rpm. Depending on the type of filler and the loading content, the melting temperature is between 290 ° C and 294 ° C at the end of the mixing cycle. The composite material thus obtained was separately compression-molded (at 290-294 ° C and 16 MPa) into a 1 mm film for resistivity measurement, a 0.5 mm film for dielectric strength measurement, and a 2 mm thin plate for thermal conductivity measurement. The thermal conductivity and electrical properties of these samples were analyzed by the following methods.

analysis

Thermal conductivity

The thermal diffusivity α (mm ² /s) of the sample was measured in the plane of the plate through the Netzsch Nanoflash LFA 447 instrument in accordance with ASTM D1461-01. The experimental parameters used to collect the data were: temperature 25 ° C, sample diameter 12.67 mm. A laser light absorbing spray was applied to the surface of the disc-shaped sample to dry the disc-shaped sample. Four flash shots were taken and then the alpha average and standard deviation were obtained. The density ρ (g/cm ³ ) of the sample at room temperature is measured by static flow weighing, which uses the water displacement due to immersion of the object to determine the density of the object. The heat capacity Cp (J/g C) of the sample at 25 ° C was determined by the DSC (DSC-Q2000) method (ASTM E1269-11 standard test method for determining the specific heat capacity by differential scanning calorimetry). The thermal conductivity (W/mK) is calculated according to the following equation: TC = α * ρ * Cp.

2. Electrical characteristics

The volume/surface resistivity of the cured sample was measured using the following: 6517B electrometer/high resistance meter, Keithley Instruments, Inc.; fixture: 8009 resistivity test fixture; according to ASTM D257-07; sample size: 1 mm x 10 cm x 10 cm

The dielectric strength was measured using a D149 AC dielectric breakdown test set according to ASTM D149-09 (2013). The voltage rise rate is 1 kV/sec.

Inventive embodiment 1

35 vol% PA66 (20.7 g), 64.5 vol% AlN-2 (109.7 g), and 0.5 vol% expanded graphite-2 (0.58 g) were used in Inventive Example 1. The cured sample was prepared by the process disclosed above. The results are shown in Table 2.

The cured samples of Inventive Example 2 to Inventive Example 3 and Comparative Example 1 to Comparative Example 10 were prepared in the same manner as in Inventive Example 1, except that the components and their amounts were changed as shown in Tables 2 to 5.

The thermal conductivity of Invention Example 1 and Invention Example 2 increased, and the thermal conductivity of Comparative Example 1 was about 20%. Further, the surface resistivity and the volume resistivity is maintained in the order of 10 ¹⁴ or 10 ¹⁴ or more orders of magnitude, thus showing good electrical insulating properties. A dielectric strength of 9 kV/mm or 10 kV/mm was obtained in Inventive Example 1 and Inventive Example 2, which allowed the application of a relatively high puncture resistance.

The results of Comparative Example 7 to Comparative Example 10 show that when the volume % of the filler-2 exceeds 2.5, the electrical insulation is poor. The results of Comparative Example 3 and Comparative Example 5 show that when the volume % of the filler-2 is 1.5, the volume resistivities of the cured samples are 2.38 × 10 ⁸ and 3.30 × 10 ^{10 , respectively} .

Claims (10)

A composition comprising: (A) a resin; (B) a filler having an intrinsic thermal conductivity greater than 20 W/mK, a volume resistivity of at least 10 ¹² Ω.cm, and a particle diameter of from 0.1 μm to 400 μm; and (C) a filler, a volume resistivity of 10 ^-2 Ω.cm or less and 10 ^-2 Ω.cm intrinsic thermal conductivity of greater than 20W / mK, and the total volume of the composition, (A) the content of 15 volume percent to 45 volume percent, (B) is 55 volume percent to 84.8 volume percent, and (C) is 0.2 volume percent to less than 1.0 volume percent. The composition of claim 1, wherein (B) is selected from the group consisting of magnesium oxide, aluminum nitride, and tantalum nitride. The composition of claim 1 wherein (C) is graphite. The composition of claim 3, wherein (C) is expanded graphite. A molded article formed of the composition according to any one of claims 1 to 4. The molded article of claim 5, wherein the article has a volume resistivity of 10 ¹² Ω·cm or more and 10 ¹² Ω·cm or more. The molded article of claim 5, wherein the product has a thermal conductivity of 5 W/mK or more. A device comprising a heat source and an electrically insulating thermal management component located adjacent to the heat source, wherein the thermal management component comprises a molded article according to any one of claims 5 to 7. The device of claim 8, wherein the heat source is an electrical component or a semiconductor component. The device of claim 8 or 9, wherein the electrical component or the semiconductor component is selected from the group consisting of a lighting component, a display component, a power component, and a photovoltaic cell.