KR20190124653A - Method for manufacturing composite sheet for preventing heat and shielding electromagnetic interference - Google Patents

Abstract

The present invention relates to a method for manufacturing composite sheet for preventing heat and shielding electromagnetic interference. The method includes a step (a) of crushing graphite powder to refine powder particles; a step (b) of mixing the refined graphite powder with metal particles, mechanically alloying them and preparing mechanically alloyed composite powder; and a step (c) of coating the mechanically alloyed composite powder of the step (b) on a carbon fiber. According to the present invention, a composite sheet for preventing heat and shielding electromagnetic interference is manufactured by using graphite-metal composite powder in a prepreg method. So, it is possible to prevent heat and improve electric wave shielding rate.

Description

Manufacturing method of composite sheet for heat radiation electromagnetic wave shielding {METHOD FOR MANUFACTURING COMPOSITE SHEET FOR PREVENTING HEAT AND SHIELDING ELECTROMAGNETIC INTERFERENCE}

The present invention relates to a method for manufacturing a composite sheet for heat dissipation electromagnetic wave shielding, and more particularly, to a composite sheet for improving heat dissipation and electric wave shielding properties for improving durability and lifespan of electronic products.

In the display set maker industry, heat dissipation costs are rapidly increasing to solve the heat problem associated with the introduction of new technologies. Next-generation electronic devices are becoming highly integrated with light weight, short size, and multifunctionality. Therefore, measures to solve heat emission problems are required due to an increase in heat density.As various types of electronic devices are released, not only simple sheet-type heat dissipating materials but also electronic devices The development of heat dissipating materials that conform to the shape of the urgent reality is urgent. Graphite materials can be divided into natural graphite and artificial graphite according to the characteristics of the material and the manufacturing method. The natural graphite sheet is produced through expanded graphite, and expanded graphite is applied to the graphite interlayer compound obtained by acid treatment and alkali metal treatment of natural graphite. It is expanded by applying energy and can be molded without slipping. It is generally commercialized through pressing or rolling process, but it is known that there is a limit in improving characteristics due to low material density. The artificial graphite sheet currently on the market is a carbon material obtained by thermally decomposing a polymer film such as polyimide at a high temperature of about 3,000 degrees, and has a structure close to a single crystal, and thus exhibits high thermal conductivity that is difficult to take by natural materials.

Currently, metal foils such as aluminum and copper and polymer resins such as PE, PU, PET, and PI, mesh or foam type sheets are laminated and rolled into products for heat-shielding materials, or silver, copper, graphite, Although conductive fine particle powders such as carbon nanotubes (CNT) and silicon rubber are mixed and sold in the form of pads, they are sold in the form of pads, but their utility is still insufficient in terms of price and performance.

Korean Patent No. 10-2017-0003891 relates to a composite sheet integrated with electromagnetic shielding and heat dissipation, and a method for manufacturing the same. The second electric wave shielding layer having an appropriate composition and composition ratio while introducing a graphite sheet having a through hole is provided. And introducing a heat-dissipating adhesive, an electromagnetic wave shielding and heat-dissipating integrated composite sheet having high thermal diffusivity, electromagnetic wave shielding, and thermal shock resistance while having excellent adhesiveness without an additional adhesive layer between the second electromagnetic shielding layer and the graphite sheet, and manufacturing the same. Although it reported about the method, it has a lack of originality because the graphite sheet is purchased and manufactured. Meanwhile, in Korean Patent No. 10-2008-0052731, powder having a particle diameter of 1 mm or less of a metal or nonmetallic material is formed in a space inside a box made of a metal material having a predetermined shape and thickness and having a space therein regardless of the shape. Particles of carbide, clay, glass, cement, ceramics, vermiculite, metal oxides, polymers, minerals, or mixtures thereof are charged to 90% or less of the inner space of the metal box, and the charging slot of the metal box After welding and sealing the metal box as an anode and electrically surface treatment is characterized in that the electromagnetic shielding material having an electromagnetic shielding function and a method for producing the metal oxide layer characterized in that it is reported. However, the material itself is expensive and the manufacturing method is difficult for industrial applications.

Accordingly, the present invention provides a method of manufacturing a composite sheet for shielding electromagnetic radiation using a prepreg method of the graphite-metal composite powder using a solid phase reaction method that is easy to apply industrially and mass production.

An object of the present invention is to improve the heat dissipation and electric wave shielding rate by producing a heat dissipation and an electric vehicle shielding composite sheet using a graphite-metal composite powder using a prepreg method.

In order to achieve the above object, the present invention provides a method for producing a composite sheet for radiation shielding electromagnetic wave, comprising the steps of: (a) crushing the graphite powder to refine the powder particles; (b) preparing a mechanically alloyed composite powder by mixing the micronized graphite powder with metal particles and then mechanically alloying them; And (c) coating the mechanically alloyed composite powder of step (b) on the carbon fiber.

In the step (a), the powder particles may be micronized using a mechanical alloying method, and in the step (b), the weight ratio of the micronized graphite powder and the metal particles may be 30:70 to 60:40. In addition, the method of manufacturing the heat dissipating electromagnetic shielding composite sheet may further include drying the mechanically alloyed composite powder coated carbon fiber after the step (c), and the drying may be performed at 150 to 200 ° C. at 6 to 20 ° C. It may be to dry for minutes.

According to the present invention as described above it is possible to improve the heat radiation and electric wave shielding rate by manufacturing the heat radiation and electric vehicle shielding composite sheet using the graphite-metal composite powder using a prepreg method.

The heat dissipation electromagnetic wave sheet provided by the present invention has excellent electromagnetic shielding effect while minimizing thermal conductivity, and is manufactured by mixing and pressing a carbon composite prepreg with a binder to reduce the thickness, and to provide a high-strength peel strength and impact resistance, but have an integrated heat dissipation. An electromagnetic wave shielding sheet can be provided.

Figure 1 shows the electromagnetic shielding rate of the metal-graphite-carbon fiber prepreg heat radiation electromagnetic shielding sheet according to an embodiment of the present invention.
Figure 2 is an electron micrograph of a metal-graphite-carbon fiber prepreg heat radiation electromagnetic shielding sheet according to an embodiment of the present invention.

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

According to an embodiment of the present invention, a method for manufacturing a heat shielding electromagnetic wave shielding composite sheet includes: (a) crushing graphite powder to refine the powder particles; (b) preparing a mechanically alloyed composite powder by mixing the micronized graphite powder with metal particles and then mechanically alloying them; And (c) coating the mechanically alloyed composite powder of step (b) on the carbon fiber.

In the step (a), the graphite powder (50 ~ 100um, BTR energy, China) is refined through mechanical alloying. In this case, mechanical alloying may use a combination of one or more of a jet mill, planetary, attritor, and specs. The rotational speed is 100 to 500 rpm, preferably 250 to 350 rpm for 1 hour and a half to 5 hours, and more preferably 250 to 350 rpm for 2 to 3 hours. If the rotational speed is less than 100rpm, less than 1 hour and a half, particle refinement does not occur, so it is not compounded with the metal, so heat radiation and electromagnetic shielding effects cannot be obtained. The yield is lowered and complexation is not easy.

In the step (b), the micronized graphite powder is mixed with the metal particles to mechanically dry the alloy. At this time, reactive ball milling can be performed to suppress oxidation of the metal particles. In reactive ball milling, the reaction gas may be injected using one or more combinations of nitrogen, hydrogen, and argon, and the media may use one or more combinations of 5 to 50 mm zirconia and alumina balls. The ratio of balls to powder is 5: 1 to 10: 1, preferably 7: 1 to 9: 1. The ball milling rotation speed is 200 to 500 rpm, preferably 300 to 400 rpm, 2 hours to 5 hours, more preferably 2.5 hours to 3.5 hours. When the ball milling rotation speed is less than 200rpm and less than 2 hours, the finely divided graphite powder and the metal powder are not mixed so that the compounding is not achieved.If the milling exceeds 500rpm and more than 5 hours, the finer particles are intensified and the powders aggregate and dissipate. And electromagnetic shielding efficiency may be lowered.

The weight ratio of the graphite powder and metal particles micronized in step (b) may be 30:70 to 60:40, preferably 40:60 to 50:50. When the weight ratio is less than 30:70, carbon prepreg formation is not easy, and when the weight ratio exceeds 60:40, dispersion of metal particles may be lowered, thereby lowering electromagnetic shielding efficiency. On the other hand, the metal particles used at this time may be made of one or more combinations of Au, Cu, Ni, Al, Fe, Zn, Mn, preferably using Fe powder.

Step (c) is a step of coating the mechanical alloyed composite powder of step (b), wherein the mechanical alloyed composite powder is water or ethyl alcohol, methyl alcohol, isopropyl alcohol, acetone, methyl ethyl ketone, Gel using one or two or more solutions selected from ethyl isoketone, ethylene glycol, aniline, toluene, chloroform sodium dodecyl sulphate, polyvinyl alcohol, triton-x, hydropropyl cellulose and hydroxypropyl methylcellulose It is dispersed in a dispersant solution prepared as a solution in the state. . Then, a binder solution is prepared by mixing polyester and urethane, or by mixing silane (adhesive enhancer) and epoxy. The prepared binder solution is mixed with carbon fiber to prepare a prepreg sheet. At this time, the carbon fiber is spread in one direction (spread MC) is coated with a mechanical alloy alloy powder by spraying method, impregnated in epoxy resin, and the resin on the fabric surface is removed with a steel knife.

In addition, the method of manufacturing the heat dissipating electromagnetic wave shielding composite sheet may further include drying the carbon fiber coated with the mechanically alloyed composite powder after the step (c). In this step, the prepreg sheet is manufactured by drying at 150-200 ° C. for 6-20 minutes in a dryer. At this time, when the drying temperature is less than 150 ° C and 6 minutes, the prepreg sheet is not sufficiently dried, the flexibility is lowered, and when the drying is more than 200 ° C and 20 minutes, peeling may occur due to rapid heat.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are only for illustrating the present invention, and it will be apparent to those skilled in the art that the scope of the present invention is not to be construed as being limited by these examples.

Example

Graphite powder (50 ~ 100um, BTR energy, China) was refined by jet mill method for 2 hours and 30 minutes at a rotational speed of 300rpm. Thereafter, the micronized graphite powder is mixed with Fe powder, which is a metal particle (weight ratio of the micronized graphite powder and Fe powder is 45:55), and nitrogen gas is injected, so that the ratio of the ball and the powder is 8: 1 in zirconia media. Reactive ball milling was performed for 3 hours at a ball milling rotational speed of 350 rpm.

Thereafter, the obtained graphite-Fe fine powder was dispersed in ethyl alcohol as a dispersant to prepare a gel solution. A secondary gel solution was prepared by mixing a silane (adhesive enhancer) and an epoxy resin as a binder solvent. And spread the carbon fiber (GS Caltex, 5㎛ dia.) In one direction (spread MC) coated graphite-metal mixed powder dispersed in ethyl alcohol by spray method, impregnated in the secondary gel solution, the resin on the fabric surface The prepreg sheet was prepared by removing with a knife and drying for 13 minutes at 170 ℃ in a dryer.

Comparative example

As a comparative example, a NiZn ferrite-based heat dissipation electromagnetic shielding material, which was previously used, was compared with the embodiment.

Measurement example

The composite sheet for electric vehicle shielding prepared in each of Examples and Comparative Examples was cut into a size of 100 mm × 10 mm (horizontal and vertical), and a double-sided tape was attached to one surface of copper foil (Cu). Next, the prepared sample was attached onto a heating block and the temperature of the heating block was raised to 80 ° C. (Evaluation proceeded to 80 ℃, which is the temperature of AP chip heating temperature level in smart phone) Next, the heating block is sealed in a box, and then stabilized for 10 minutes, and then the temperature is measured using an IR camera to determine the hot spot and cold spot of the composite sheet. The thermal diffusivity of the composite sheet was measured by measuring the temperature difference. In this case, the smaller the difference ㅿ T between the two temperatures, the better the heat dissipation performance. In addition, the prepared composite sheets prepared in Examples and Comparative Examples were prepared in accordance with JIS C 6741 standard to measure the peel strength (Peel Strength) by 180 ° Peel Test (180 ° Peel Test) and the results are shown in the table below It was.

Meanwhile, the electromagnetic shielding rate (dB) was measured in a frequency range of 30 MHz to 1 GHz using a spectrum analyzer (Agilent N1996A spectrum analyzer from Agilent, USA) of 133 mm in diameter according to ASTM D4935 method. The results are shown in FIG.

Overall Peel Strength [gf / cm ² ] Hot spot [℃] Cold spot [℃] △ T (hot spot-cold spot) Example 668 79.59 55.27 24.32 Comparative example 449 75.29 59.15 16.14

As shown in Table 1, it can be confirmed that the heat dissipation performance of the Example is superior to the comparative example. This is due to the improved heat dissipation characteristics due to the interaction of the composite graphite powder and the metal particles.

Claims (5)

(a) crushing the graphite powder to refine the powder particles;
(b) preparing a mechanically alloyed composite powder by mixing the micronized graphite powder with metal particles and then mechanically alloying them; And
(c) coating the mechanically alloyed composite powder of the step (b) on the carbon fiber; manufacturing method of a heat shielding electromagnetic shielding composite sheet comprising a.
The method of claim 1,
The step (a) is a method for producing a heat dissipating electromagnetic shielding composite sheet, characterized in that the fine powder particles using a mechanical alloying method.
The method of claim 1,
In the step (b), the weight ratio of the finely divided graphite powder and the metal particles is 30:70 to 60:40.
The method of claim 1,
After the step (c) further comprising the step of drying the carbon fiber coated with the mechanical alloyed composite powder manufacturing method of a heat radiation electromagnetic shielding composite sheet.
The method of claim 4, wherein
The drying is a method for manufacturing a heat dissipating electromagnetic shielding composite sheet, characterized in that for 6 to 20 minutes to dry at 150 to 200 ℃.

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