KR20200089238A - Method for manufacturing RF heat dissipation sheet - Google Patents

Abstract

Provided is a method for manufacturing an RF heat dissipation sheet. The RF heat dissipation sheet according to an embodiment of the present invention is manufactured by including the steps of: manufacturing a preliminary sheet by filming a matrix-forming component containing ultra-high molecular weight polyolefin (UHMWPO); and stretching the preliminary sheet in at least one axial direction. Accordingly, the manufactured RF heat dissipation sheet includes the step of stretching at a specific ratio, and as a material having a specific crystallinity is used, the thermal conductivity is remarkably excellent and the heat dissipation characteristic is remarkably excellent. In addition, as the matrix is formed of a specific material, even though the RF heat dissipation sheet is designed to have excellent thermal conductivity, cracking, shrinkage, and generation of pores of the sheet are minimized or prevented, and excellent flexibility can be obtained.

Description

Method for manufacturing RF heat dissipation sheet

The present invention relates to a method for manufacturing an RF heat radiation sheet.

Although it is not intended to generate heat, heat generated in a device or device having parts that generate heat during operation not only decreases the function of the corresponding parts, but also produces various problems such as deterioration of functions, malfunction, and loss of function due to deterioration. Accordingly, research on the heat dissipation structure to solve the heat problem has been continued for a long time in various industries. As a result of these studies, various heat dissipation devices such as heat dissipation fans, heat dissipation fins, and heat pipes have been developed. Recently, heat dissipation materials such as heat dissipation pads, heat dissipation sheets, heat dissipation paints have been developed to assist or replace conventional heat dissipation devices. Doing.

Among them, the heat dissipation sheet has better heat dissipation characteristics than the heat dissipation paint, and is thinner, so it can be easily applied to the apparatus or device without any structural design change of the device or device, or even with a slight structural design change. In recent years, developments have been actively made in various fields such as the automotive field and the medical field.

However, in the case of the conventional heat dissipation mechanism, excellent heat dissipation properties could not be exhibited due to poor heat conductivity, and problems such as cracking, shrinkage, deterioration of flexibility, and generation of pores are inevitable in order to improve heat conductivity.

Registered Patent Publication No. 10-1817746

The present invention has been made in view of the above points, and an object of the present invention is to provide a method for manufacturing an RF heat dissipation sheet having excellent heat dissipation characteristics as heat conductivity is excellent.

In addition, the present invention has a different purpose to provide a method for manufacturing an RF heat dissipation sheet having excellent flexibility, while preventing or minimizing or preventing breakage, shrinkage, and porosity of the sheet even though it is designed to significantly improve thermal conductivity.

In order to solve the above-described problems, the present invention comprises the steps of preparing a preliminary sheet by film forming a matrix forming component including ultra high molecular weight poly olefin (UHMWPO); And stretching the preliminary sheet in at least a uniaxial direction.

According to an embodiment of the present invention, the step of manufacturing the preliminary sheet may be performed by mixing the matrix forming component and the heat dissipation filler.

In addition, the heat dissipation filler has an average particle diameter of 2 to 40㎛, and may be provided in an amount of 60% by weight or less based on the total weight of the RF heat dissipation sheet.

In addition, the ultra high molecular weight polyolefin may include ultra high molecular weight polyethylene (UHMWPE).

In addition, the ultra-high molecular weight polyolefin may have a crystallinity of 50% or more.

In addition, the filming may be performed by melt extruding the matrix forming component.

In addition, the stretching may be performed by stretching the pre-sheet at least 5 times in at least one axial direction.

The RF heat dissipation sheet manufactured by the present invention is stretched at a specific ratio, and as a material having a specific crystallinity is used, thermal conductivity is excellent and heat dissipation characteristics are excellent. In addition, even though the thermal conductivity is designed to be significantly excellent as the matrix is formed of a specific material, breakage, shrinkage, and porosity of the sheet are minimized or prevented, and excellent flexibility can be obtained.

1 is a photograph showing a film-formed pre-sheet according to an embodiment of the present invention, and
Figure 2 is a photograph showing a stretched pre-sheet according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art to which the present invention pertains can easily practice. The present invention can be implemented in many different forms and is not limited to the embodiments described herein.

The RF heat dissipation sheet manufactured according to an embodiment of the present invention is a step of preparing a preliminary sheet by filming a matrix forming component including an ultra high molecular weight poly olefin (UHMWPO), and at least one axis of the preliminary sheet. It is prepared, including the step of stretching.

First, a step of manufacturing the preliminary sheet will be described.

In the method of manufacturing the RF heat dissipation sheet of the present invention, by performing the steps of manufacturing the preliminary sheet, a filmed preliminary sheet as shown in FIG. 1 can be manufactured.

The filming can be used without limitation as long as it can be used to film the thermoplastic resin in the art, and can be preferably performed through a melt extrusion method.

In addition, the ultra-high molecular weight polyolefin included in the matrix forming component is not limited as long as it is a resin shape that can be applied to film a thermoplastic resin in the art, and preferably a powdered ultra high molecular weight polyolefin can be used. At this time, the ultra-high molecular weight polyolefin in the form of powder may be produced by pulverizing the ultra-high molecular weight polyolefin in a fibrous, film, or the like, but is not limited thereto.

The matrix forming component is a component that forms a matrix to perform a function of a carrier containing a heat dissipation filler, which will be described later, and maintains the shape of the implemented RF heat dissipation sheet.

The matrix forming component includes ultra high molecular weight poly olefin (UHMWPO) as described above, and preferably, ultra high molecular weight poly olefin (UHMWPO) is ultra high molecular weight polyolefin (Ultra high molecular weight). weight poly ethylene, UHMWPE).

At this time, the ultra-high molecular weight polyolefin may have a crystallinity of 50% or more, preferably 60% or more, more preferably 65% or more, and even more preferably a crystallinity of 70% or more. If the crystallinity of the ultra-high molecular weight polyolefin is less than 50%, heat dissipation characteristics may be deteriorated as the desired level of thermal conductivity cannot be expressed.

In addition, the ultra high molecular weight polyolefin may have a weight average molecular weight of 3,000,000 or more, preferably 3,300,000 or more. If the weight average molecular weight of the ultra-high molecular weight polyolefin is less than 3,000,000, heat dissipation characteristics may be deteriorated as the desired level of thermal conductivity cannot be expressed.

Meanwhile, the heating element to which the heat dissipation sheet is applied may not have only a flat surface, but may have a step. Accordingly, if the heat dissipation sheet is deteriorated in flexibility, the adhesion may not be good on the surface where the step is formed, and if it is pressed and pressed in order to increase the adhesion, the heat dissipation sheet may be broken or damaged, thereby significantly reducing the heat dissipation characteristics. I have a concern. In addition, in the case of some matrix forming components such as polyurethane, flexibility characteristics may be good, but there may be a fear that shrinkage occurs after being manufactured into a sheet or pores in the manufactured sheet are generated. Accordingly, the RF heat dissipation sheet according to an embodiment of the present invention uses the ultra-high molecular weight polyolefin described above in the matrix.

Meanwhile, the RF heat dissipation sheet manufactured according to another embodiment of the present invention may further include other resins in addition to the ultra-high molecular weight polyolefin described above in the matrix according to changes in purpose and use. In this case, the resin that may be further included may be used without limitation as long as it is a thermoplastic resin that can be used to form a matrix through melt extrusion, which is conventionally described in the art, but specific types of the thermoplastic resin may vary depending on changes in purpose and use However, in the present invention, this is not particularly limited.

The step of manufacturing the preliminary sheet may be performed by mixing the matrix forming component and the heat dissipation filler.

The heat dissipation filler is a component that imparts thermal conductivity to the RF heat dissipation sheet. The heat dissipation filler may be used without limitation in the case of a known heat dissipation filler having thermal conductivity, and may be, for example, a metal, ceramic, or carbon-based heat dissipation filler. In the case of the metal, aluminum, magnesium, copper, nickel, silver, gold, or the like, or a mixture thereof or an alloy thereof may be used. In addition, in the case of the ceramic, for example, alumina, silicon carbide, magnesium oxide, titanium dioxide, silicon dioxide, yttria, zirconia, aluminum nitride, silicon nitride, boron nitride, silica, zinc oxide, barium titanate, strontium titanate, beryllium oxide, It may include one or more of monocrystalline silicon and manganese oxide. In addition, in the case of the carbon-based may include one or more of graphite, graphene, carbon nanotubes, fullerene, carbon black. In addition, the heat dissipation filler may be a graphite composite having metal or ceramic nanoparticles on the graphite surface, or a polydopamine layer further provided on the nanoparticles. Meanwhile, the heat dissipation filler may be appropriately selected in consideration of the desired heat dissipation performance or additional insulating performance.

In addition, the heat dissipation filler may have a spherical shape or a plate-like shape, and may have a plate shape in terms of improving thermal conductivity in the horizontal direction. The heating element may generate heat in all parts constituting the heating element, but there may be a hot spot area in which heat is increased in a specific part, and in this case, the heat conduction in the horizontal direction may generate heat by dispersing heat concentrated in the hot spot to the surroundings. There is an advantage of preventing this from being concentrated.

In addition, the heat dissipation filler may have an average particle diameter of 1 ~ 200㎛. However, according to an embodiment of the present invention, the heat dissipation filler may have an average particle diameter of 50 μm or less, more preferably 40 μm or less, and even more preferably 2 to 40 μm, and the heat dissipation filler having such a particle size may be an RF heat dissipation sheet. It may be provided in 70% by weight or less, preferably 60% by weight or less. If the average particle diameter of the heat dissipation filler exceeds 40 μm, sheet formation may not be easy, and surface quality may be deteriorated. However, the heat dissipation filler may have an average particle diameter of 1 μm or more, which has the advantage of further improving the dispersibility and thermal conductivity in the matrix. In addition, if the heat dissipation filler is provided in excess of 60% by weight based on the total weight of the RF heat dissipation sheet, cracking of the sheet may occur or flexibility may be deteriorated.

On the other hand, in the present invention, the particle diameter of the heat dissipation filler is a diameter when the shape is spherical, and when the shape is polyhedral or irregular, it means the longest distance among the straight lines between two different points on the surface.

In addition, the heat dissipation filler may be designed with several particle diameter groups having different particle diameters in order to provide a heat dissipation filler with an improved content in the RF heat dissipation sheet. As an example, the heat dissipation filler may include a first heat dissipation filler having a particle diameter of 1 to 5 μm, a second heat dissipation filler having a particle diameter of 10 to 20 μm, and a third heat dissipation filler having a particle size of 25 to 40 μm 1: 1.5 to 3: 3.5 to 3.5 ~ It may be included in a weight ratio of 5, through which it is possible to significantly increase the content of the heat dissipation filler in the RF heat dissipation sheet, further improving the heat dissipation characteristics. If the particle size distribution of the heat dissipation filler is outside the above range, the content that can be provided in the RF heat dissipation sheet cannot be increased.

In addition, the heat dissipation filler is provided in the form of dispersed in the matrix in the RF heat dissipation sheet, the interface formed between the matrix and the heat dissipation filler can be reduced thermal conductivity at the interface due to low compatibility due to dissimilar materials, relatively The heat dissipation performance of the RF heat dissipation sheet may be low. In addition, there may be an excitation phenomenon at the interface, in this case, the heat dissipation performance may be further deteriorated, and the durability of the RF heat dissipation sheet may be deteriorated, such as cracks in the corresponding portion. Accordingly, the heat dissipation filler may be surface-treated or surface-modified to improve the interfacial properties of the matrix.

The surface treatment may be to remove heterogeneous inorganic substances or impurities on the surface of the heat dissipation filler, and through such a surface treatment, the heat conduction properties of the heat dissipation filler itself may be fully exhibited, and it may be advantageous to improve the interfacial properties with the matrix. .

In addition, the surface modification may be used without limitation in the case of a known modification that can increase the compatibility between the heat-radiating filler and the components forming the matrix. In one example, the surface modification may be a modification having one or more functional groups selected from the group consisting of an alkyl group, an alkane group, an amine group, and an aniline group on the surface of the heat dissipation filler, and in one example, the functional group is a group consisting of an amine group and an aniline group. It may be one or more selected.

The surface treatment or surface modification may be performed by employing a known method, for example, through acid treatment. The acid treatment may be performed by treating an acidic solution such as nitric acid, sulfuric acid, aluminum, and titanium based on a heat dissipation filler, and preferably, sulfuric acid or nitric acid is better for expressing improved thermal conductivity properties. Through the acid treatment, not only the removal of inorganic substances or contaminants on the surface of the heat dissipation filler, but also a hydroxy group functional group can be provided on the surface.

As an example, to explain the method of performing the acid treatment, the heat dissipation filler is added to an acidic solution having a concentration of 60 to 70%, and then stirred for 1 to 10 hours at 20 to 40°C, and then the heat dissipation filler is added to the water. After neutralization, a process of washing with distilled water may be performed. At this time, in the step of stirring after being added to the acidic solution, ultrasonic waves may be additionally added during or after stirring.

Next, a step of stretching the preliminary sheet in at least one axis will be described.

In the RF heat dissipation sheet manufacturing method of the present invention, by performing the stretching step, it is possible to manufacture an RF heat dissipation sheet as shown in FIG.

The stretching step may be performed by stretching the pre-sheet in at least one axial direction. Accordingly, due to the long polymer chain of the ultra-high molecular weight polyolefin provided in the pre-sheet, the polymer chains are aligned to express more excellent thermal conductivity. , Due to this, the heat dissipation characteristics may be more excellent.

At this time, the stretching step may be performed by stretching the pre-sheet at least 5 times in at least one axial direction, preferably 8 times or more, and more preferably 10 times or more. , More preferably, it can be carried out by stretching 10 to 30 times. If the preliminary sheet is stretched at least less than 5 times in the uniaxial direction, or unstretched as shown in FIG. 1, since the polymer chains are not aligned, the desired level of thermal conductivity cannot be expressed. Relatively, the heat dissipation characteristics may be deteriorated.

Meanwhile, the RF heat dissipation sheet manufactured through the manufacturing method according to the present invention may have a thickness of 10 to 200 μm, and may be 50 μm, for example, but is not limited thereto, and may be appropriately changed in consideration of application, heat dissipation performance, etc. Can.

The present invention will be described in more detail through the following examples, but the following examples are not intended to limit the scope of the present invention, which should be interpreted to help understand the present invention.

<Example 1>

A preliminary sheet as shown in FIG. 1 was prepared by mixing 50% by weight of ultra-high molecular weight polyethylene with a weight average molecular weight of 5,000,000 and 80% of crystallinity in powder form and 50% by weight of graphite having an average particle diameter of 30 µm with a heat-radiating filler. Then, the prepared preliminary sheet was stretched 20 times in a uniaxial direction to prepare an RF heat dissipation sheet as shown in FIG. 2. At this time, the manufactured RF heat radiation sheet had a thickness of 50 μm.

<Examples 2 to 5 and Comparative Examples 1 to 2>

Prepared in the same manner as in Example 1, but by changing the crystallinity of the ultra-high molecular weight polyolefin, the preliminary sheet elongation and elongation, the content of the heat dissipating filler and the type of matrix forming components, RF heat dissipation sheets as shown in Tables 1 and 2 below. Was prepared.

<Experimental Example>

For the RF heat-radiating sheet prepared according to Examples and Comparative Examples, the following physical properties were evaluated and are shown in Tables 1 and 2 below.

1. Evaluation of heat dissipation characteristics

가 되도록 조절하였다.After placing the LEDs spaced apart at predetermined intervals on a circumference of a circle having a diameter of 25 mm, a thermometer is placed at the center of the circle, and a measurement device is prepared to apply a predetermined voltage to the LED, and then the The measuring equipment is placed inside an acrylic chamber that is 32 cm x 30 cm x 30 cm in width, length, and height, and the temperature inside the acrylic chamber is 25±0.2.

Was adjusted to be.

Subsequently, a predetermined input power was applied to the LED of the measurement equipment, and after a predetermined time elapsed, a thermal image was taken on the top of the LED to measure the average temperature.

가 되도록 조절하고, 측정장비의 LED 상에 RF 방열시트를 올려놓은 뒤, LED에 동일한 입력전력을 인가하고, 동일한 시간 경과 후, 상기 RF 방열시트 없이 측정한 동일 지점에 대해 열화상 촬영하여 평균온도를 측정하였다.And again, the temperature inside the acrylic chamber is 25±0.2

Control, and place the RF heat dissipation sheet on the LED of the measuring equipment, apply the same input power to the LED, and after the same time, take the thermal image taken at the same point measured without the RF heat dissipation sheet and average temperature Was measured.

At this time, the temperature difference between the case of including and not including the RF heat dissipation sheet was calculated, and the temperature difference for Examples 2 to 12 and Comparative Examples 1 to 2 was calculated based on the temperature difference of Example 1 as 100. The heat dissipation characteristics were evaluated.

2. Defect rate evaluation

After preparing 100 RF heat dissipation sheets according to the above Examples and Comparative Examples with the same specifications each, counting the number of cracks, sheet shrinkage, and pores generated among 100 specimens, and the proportion of defective specimens among 100 specimens The defective rate was evaluated through.

3. Flexibility Assessment

If a plurality of RF heat dissipation sheets according to the above Examples and Comparative Examples are manufactured with the same specifications, cracks and cracks occur when the RF heat dissipation sheets bent at a curvature of 20 mm for each of the 100 RF heat dissipation sheets in which defects did not occur in the evaluation of the defect rate. The number of sheets generated by observation was counted.

division Example 1 Example 2 Example 3 Example 4 Matrix-forming component Kinds Ultra high molecular weight polyethylene Ultra high molecular weight polyethylene Ultra high molecular weight polyethylene Ultra high molecular weight polyethylene Crystallinity (%) 80 40 80 80 Heat dissipation filler Content (% by weight) 50 50 50 75 Stretching stage Stretch magnification (times) 20 20 3 20 Evaluation of heat dissipation characteristics 100 86.2 88.4 106.6 Defective rate (%) 0 0 0 15 Flexibility (pcs) 0 0 0 19

division Example 5 Comparative Example 1 Comparative Example 2 Matrix-forming component Kinds Polyethylene ^{1 )} Ultra high molecular weight polyethylene Thermoplastic polyurethane Crystallinity (%) - 80 - Heat dissipation filler Content (% by weight) 50 50 50 Stretching stage Stretch magnification (times) - Undrawn 20 Evaluation of heat dissipation characteristics 78.3 85.8 71.2 Defective rate (%) 0 0 44 Flexibility (pcs) One 0 3 1) In Example 12, polyethylene having a weight average molecular weight of 200,000 was used as the matrix forming component.

As can be seen from Table 1 and Table 3, Example 1 satisfies all of the crystallinity of the ultra high molecular weight polyolefin according to the present invention, the preliminary sheet stretching ratio and stretching, the heat dissipation filler content, and the types of matrix forming components, etc. Compared to Examples 2 to 5 and Comparative Examples 1 to 2, which do not satisfy any one, the thermal conductivity and heat dissipation characteristics are excellent, and the defect rate is significantly low as the cracks, shrinkage, and pores in the sheet are minimized or prevented. It can be seen that the flexibility is excellent.

Although one embodiment of the present invention has been described above, the spirit of the present invention is not limited to the embodiments presented herein, and those skilled in the art to understand the spirit of the present invention may add elements within the scope of the same spirit. However, other embodiments may be easily proposed by changing, deleting, adding, or the like, but this will also be considered to be within the scope of the present invention.

Claims (7)

Preparing a preliminary sheet by filming a matrix forming component including ultra high molecular weight poly olefin (UHMWPO); And
Stretching the preliminary sheet in at least one axis direction; RF heat radiation sheet manufacturing method comprising a. According to claim 1,
The step of manufacturing the preliminary sheet,
RF heat radiation sheet manufacturing method performed by mixing the matrix forming component and the heat dissipation filler. According to claim 2,
The heat dissipation filler has an average particle diameter of 2 ~ 40㎛, RF heat dissipation sheet manufacturing method provided with less than 60% by weight based on the total weight of the heat dissipation sheet. According to claim 1,
The ultra high molecular weight polyolefin is ultra high molecular weight polyethylene (Ultra high molecular weight poly ethylene, UHMWPE) RF heat radiation sheet manufacturing method comprising. According to claim 1,
The ultra high molecular weight polyolefin has a crystallinity of 50% or more RF heat radiation sheet manufacturing method. According to claim 1,
The film forming is performed by melt-extruding the matrix-forming component to produce an RF heat dissipation sheet. According to claim 1,
The stretching step is performed by stretching the preliminary sheet at least 5 times in at least one axial direction.

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