KR102618866B1 - Thermal conductive gap filler unit - Google Patents

Abstract

A heat transfer unit is disclosed that allows users to conveniently use a liquid heat transfer material in a gel or grease state. A sealing material having flexibility and elasticity is formed along the edges of the opposing surfaces of the first and second solid contact members that face each other and have respective thermal conductivity, and a portion of the internal space is filled with a heat transfer material having flowability or spreadability. When the force provided by the object presses the sealing material and the heat transfer material, the heat transfer material flows or spreads in the internal space due to flowability or spreading, thereby thinning the thickness of the heat transfer unit.

Description

Heat transfer unit {Thermal conductive gap filler unit}

The present invention relates to a heat transfer unit that is interposed between a heating source and a cooling body, which are opposing objects, and is used to transfer heat from the heating source to the cooling body. In particular, it relates to a gel or grease having flowability or spreadability. It is related to a heat transfer unit that allows users to conveniently use heat transfer materials in a (grease) state.

The thermally conductive gap filler, which is interposed between a heating source and a cooling body, which are opposing objects, and is used to transfer heat from the heating source to the cooling body, is a solid pad in the shape of a sheet that is pressed to a certain thickness by the object. pad, liquid gel with high viscosity, and liquid grease with medium viscosity.

Like thermally conductive silicone rubber pads, the pad is solid, so it is easy to come in a certain size, and because it usually has self-adhesiveness, it is easy to attach to a heat source or cooling body. However, because it has relatively high hardness, it takes a lot of force to press it a lot, so it can be easily damaged. The disadvantage is that it is difficult to apply when the tolerance between them is large. In addition, pads with high thermal conductivity and weak pressing force have a disadvantage in that they are difficult to manufacture and handle due to their low mechanical strength, making it difficult to provide them in thinner thicknesses than a certain level.

Since thermally conductive gels and greases are liquid, they are placed in a container such as a syringe and then formed directly on the heat source or coolant by printing or dispensing. Therefore, they can be printed or dispensed directly at the location where the heat transfer unit is applied. It has the disadvantage of having to be provided as .

In addition, even if a certain amount of gel and grease is provided to the object, the gel and grease have the ability to spread or flow, so when pressed between objects, they may escape in an undesired direction or be insufficient in some areas due to tolerances between objects. There is. For example, there is a disadvantage that it is difficult to provide a uniform amount and uniform shape between objects due to tolerances or pressing methods between objects.

In addition, gel and grease have the ability to spread or flow, so when applied to devices subject to a lot of vibration or impact, such as automobiles, the gel and grease interposed between objects may escape to unwanted places due to repeated vibration or impact. there is.

In addition, gel and grease have self-adhesive properties and low mechanical strength, so there is a disadvantage in that it is inconvenient to remove the gel and grease from the object when separating the object for repair or replacement after interposing the gel and grease between objects.

According to the applicant's Korean Patent No. 2139232 to overcome these shortcomings, there is a body composed of a ring-shaped elastic frame with a uniform thickness and a fixed width and a thermally conductive sheet adhered to the lower surface of the frame, and an accommodating space formed therein; and a thermoelectric element that has viscosity and is accommodated in the receiving space and adhered to the thermally conductive sheet, wherein the thermoelectric element spreads due to the viscosity of the thermoelectric element and is applied in a vertical direction to the thermoelectric element. Disclosed is a heat-conducting member characterized in that it spreads horizontally over the heat-conductive sheet in the receiving space.

According to this invention, a mechanical cover covering the thermoelectric element is not formed on the top of the thermoelectric element, and as a result, the thermoelectric element of the heat conduction member is exposed to the outside, making handling such as vacuum pickup in this area inconvenient, and the exposed thermoelectric element The disadvantage is that it is inconvenient to remove it when it comes into contact with an object.

In addition, when the thermoelectric element has a medium viscosity like grease, there is a disadvantage that the grease tends to flow out of the receiving space or be biased when vibration or rotation is provided after being mounted on the final product.

In addition, the elastic frame has the disadvantage of being cumbersome and difficult to provide economically because the corresponding solid sheet is punched out with a blade mold and adhered.

In addition, the frame and the thermally conductive sheet are adhered with an adhesive, so there is a disadvantage in that it is difficult to maintain reliable adhesion when the frame is narrow and high, has a complicated shape, or the temperature of the device used is high. .

Therefore, the purpose of the present invention is to provide a heat transfer unit that is convenient for users to handle and use while being equipped with a heat transfer material that has flowability and spreadability.

Another object of the present invention is to provide a heat transfer unit that can easily and reliably form a sealant into a desired size and shape.

Another object of the present invention is to provide a heat transfer unit in which a sealant is easily and reliably bonded to opposing first and second contact members.

Another object of the present invention is to provide a heat transfer unit with mechanical stability.

Another object of the present invention is to provide a heat transfer unit that can be easily applied between objects having various shapes and structures.

Another object of the present invention is to provide a heat transfer unit that is easy and convenient to repair or replace.

According to one aspect of the present invention, it is a heat transfer unit that is interposed between a heat source and a cooling body, which are opposing objects, and is used to transfer heat from the heat source to the cooling body, and is a heat transfer unit that is used to transfer heat from the heat source to the cooling body. first and second contact members; a sealing material having elasticity and flexibility that seals the first and second contact members by adhering them to each other along edges of opposing surfaces of the first and second contact members; an internal space formed by the sealing material between the first and second contact members; and a heat transfer material that fills a portion of the internal space and has flowability or spreadability, and when a force provided by the object presses the sealing material and the heat transfer material, the heat transfer material is transferred to the heat transfer material by the flowability or spreadability. A heat transfer unit is provided, wherein the heat transfer unit flows or spreads in the internal space, thereby reducing the thickness of the heat transfer unit.

In another aspect of the present invention, it is a heat transfer unit that is interposed between a heat source and a cooling body, which are opposing objects, and is used to transfer heat from the heat source to the cooling body. It is composed of a single piece and is bent on one side to face each other. A solid contact member having thermal conductivity and having first and second contact portions formed thereon; a thermally conductive sealant formed along opposing edges of the first and second contact portions and having elasticity and flexibility to seal the contact member; an internal space formed by the sealing material between the first and second contact portions; and a heat transfer material that fills a portion of the internal space and has flowability or spreadability, and when a force provided by the object presses the sealing material and the heat transfer material, the heat transfer material is transferred to the heat transfer material by the flowability or spreadability. A heat transfer unit is provided, wherein the heat transfer unit flows or spreads in the internal space, thereby reducing the thickness of the heat transfer unit.

According to another aspect of the present invention, it is a heat transfer unit that is interposed between a heat source and a cooling body, which are opposing objects, and is used to transfer heat from the heat source to the cooling body. It is composed of a single piece and has an opening on one side, and A rubber housing having heat conductivity, elasticity, and flexibility, in which first and second contact portions are formed opposing each other; a thermally conductive sealant formed by sealing the opening and having elasticity and flexibility to which the first and second contact parts are bonded; It includes a heat transfer material that fills a portion of the internal space of the housing and has flowability or spreadability, and when the housing is pressed by a force provided by the object, the heat transfer material flows into the interior by the flowability or spreadability. A heat transfer unit is provided, wherein the heat transfer unit flows or spreads in space to reduce the thickness of the heat transfer unit.

According to the present invention, the heat transfer unit has mechanical safety by sealing the heat transfer material with flowability or spreadability by the first and second contact members and the sealing material.

In addition, a soft heat transfer material with flowability and spreadability is built in, making it easy to apply between objects with various shapes and structures, and the heat transfer material does not escape to the outside, making it easy to repair and replace.

In addition, the sealant formed by adhering along the edges of the first and second contact members is formed by printing or dispensing the corresponding liquid silicone rubber adhesive and then hardening, so it is easy to adjust the width and dimensions and adheres even at high temperatures. It is reliable and can adhere to opposing objects.

In addition, since the sealant is made of an elastic and flexible material, it can maintain the seal to prevent cracks from occurring even when the heat transfer unit is bent or folded, and heat transfer is effective through elastic contact with the opposing object.

In addition, when an opposing object presses the heat transfer unit, the air formed in the internal space escapes to the outside through the through hole, making it easy for the heat transfer material to spread into the empty space.

In addition, when a graphite layer is formed on the first or second contact member existing in the internal space, the thermal conductivity in the plane direction improves, and when the first and second contact parts are bent on one side and face each other, more diverse characteristics or A heat transfer unit having a purpose can be provided.

In addition, if the first and second contact parts of the heat transfer unit are metal sheets, heat transfer is good, and if they are polymer sheets containing rubber, elasticity, flexibility and elasticity are good.

Figure 1(a) is an exploded perspective view showing a heat transfer unit according to an embodiment of the present invention, and 1(b) is a cross-sectional view.
Figure 2 shows the operation of the heat transfer unit.
Figure 3 shows a heat transfer unit according to another embodiment of the present invention.
Figure 4 shows a heat transfer unit according to another embodiment of the present invention.
Figure 5 shows a heat transfer unit according to another embodiment of the present invention.

It should be noted that the technical terms used in the present invention are only used to describe specific embodiments and are not intended to limit the present invention. In addition, the technical terms used in the present invention, unless specifically defined in a different sense in the present invention, should be interpreted as meanings generally understood by those skilled in the art in the technical field to which the present invention pertains, and are not overly comprehensive. It should not be construed in a literal or excessively reduced sense. Additionally, if the technical term used in the present invention is an incorrect technical term that does not accurately express the idea of the present invention, it should be replaced with a technical term that can be correctly understood by a person skilled in the art. In addition, general terms used in the present invention should be interpreted according to the definition in the dictionary or according to the context, and should not be interpreted in an excessively reduced sense.

Figure 1(a) is an exploded perspective view showing a heat transfer unit according to an embodiment of the present invention, and 1(b) is a cross-sectional view.

The heat transfer unit 100 may be interposed between a heat source and a cooling body (heat sink, case, etc.) and may be used to transfer heat from the heat source to the cooling body.

The heat transfer unit 100 has first and second thermally conductive contact members 110 and 120 facing each other, and is elastically bonded along the edges between the first and second contact members to seal the internal space 102. It is made of a sealing material 130 having high flexibility and a heat transfer material 140 that fills a portion of the internal space 102.

Here, the opposing inner surfaces of the first and second contact members 110 and 120 to which the sealing material 130 is bonded may be flat or may have protrusions or irregularities formed to improve adhesion to the sealing material 130, and the opposing inner surfaces may be flat. The externally exposed surfaces of the first and second contact members 110 and 120 in contact with the object form a flat surface.

In this embodiment, the first and second contact members 110 and 120 may be a thermally conductive polymer sheet including a thermally conductive rubber sheet, or a metal sheet including copper, copper alloy, aluminum, or aluminum alloy, or a combination thereof. You can.

When the first and second contact members 110 and 120 are metal sheets, they have higher thermal conductivity than polymer sheets, but have the disadvantage of having less surface contact with the object, and when they are polymer sheets, they have characteristics opposite to those of metal sheets.

The first and second contact members 110 and 120 have mechanical properties that prevent them from being destroyed while making a lot of contact with the object when the heat transfer unit 100 is pressed against the object.

Here, in the case of a polymer sheet, it may have self-adhesiveness and preferably has elasticity.

The first and second contact members 110 and 120 may be two independently separated contact members or a single contact member connected on one side, as will be described later.

In order for the heat transfer unit 100 to have flexibility, elasticity, and elasticity as a whole, the first and second contact members 110, 120 are made of silicone rubber sheets, and the internal heat transfer material 140 is formed by the force provided by the object. Ensure that it has enough mechanical strength to prevent leakage to the outside.

Since the first and second contact members 110 and 120 of the heat transfer unit 100 are in good contact with the opposing object by pressing, they are interposed between a cooling body such as a heat sink and a heat source such as a CPU chip, respectively. Even if there is no separate interface that can be easily pressed when making contact, a large area can be touched.

When the first and second contact members 110 and 120 are two independently separated contact members, the materials and sizes of the first and second contact members 110 and 120 may be the same or different from each other. In different cases, they can be effectively selected and applied according to the heat transfer effect and the situation of the object facing. For example, a contact member made of a material with high thermal conductivity can be selected to be used in the part that contacts the heat source, and a contact member made of a material with a large size and high mechanical strength can be selected to be used in the part that is in contact with the cooling body. Depending on the structure and capacity of the source and cooling body, a thermally conductive polymer sheet can be selected for the area in contact with the heating source, and a metal sheet can be selected for the area in contact with the cooling body.

Here, the first and second contact members 110 and 120 preferably have a thickness of about 0.01 mm to 0.3 mm and a flat shape.

Optionally, a graphite layer may be formed on one of the surfaces where the first and second contact members 110 and 120 face each other. In this case, the heat transfer unit 100 has the advantage of better heat transfer in the horizontal direction due to the graphite layer.

A through hole 112 may be formed in a portion adjacent to the edge of the first contact member 110.

The through hole 112 may be formed in the first contact member 110 in contact with the cooling body corresponding to the portion not filled with the heat transfer material 140 in the internal space 102. As described later, the heat transfer material ( When 140) is pressed, the air existing in the internal space 102 is used as a passage to escape to the outside.

The size of the through hole 112 is such that the heat transfer material 140 in the internal space 102 does not escape through the through hole 112 when the heat transfer unit 100 is pressed, and is formed at an appropriate location. You can.

The sealant 130 has elasticity and flexibility, so the sealant 130 is not broken or torn by the force provided by the object, so the heat transfer material 140 does not leak to the outside.

In addition, the sealing material 130 has elasticity and flexibility, so that the first and second contact members 110 and 120 are pressed by an external force, as will be described later.

Preferably, the sealing material 130 has elasticity, so that when the first and second contact members 110 and 120 are pressed by an external force, the heat transfer unit 100 faces the opposite side due to the elastic restoring force of the sealing material 130. Ensure good elastic contact with the object.

The sealant 130 can be formed by, for example, printing or dispensing liquid silicone rubber adhesive on the edge of any one of the first and second contact members 110 and 120, then placing another contact member on top and curing it. there is. That is, the liquid silicone rubber adhesive is a curable material with elasticity, flexibility, and elasticity that has adhesive force with an opposing object after curing, and reliably seals the interior of the heat transfer unit 100.

Therefore, it is desirable that the flowability or spreadability of the heat transfer material 140 be better than that of the sealing material 130.

As such, the sealing material 130 may be silicone rubber having elasticity, flexibility, and elasticity containing thermally conductive powder. The higher the thermal conductivity of the sealing material 130, the higher the mechanical hardness, so the thermal conductivity is 0.5 W/mK to 2 W/mK. It may be to some extent.

In addition, the thickness of the sealing material 130 is not limited, but may preferably be 0.1 mm to 1 mm in consideration of the curing speed, heat transfer effect, and degree of sealing, and is preferably formed continuously at a constant thickness to form a closed loop. achieves

Preferably, the thickness of the sealant 130 may be thick to accommodate as much of the heat transfer material 140 as possible or to achieve good elastic performance.

For good adhesion, the width of the sealing material 130 has a dimension greater than the height, and considering the distance that can be pressed, the height of the sealing material 130 may be greater than the thickness of any one of the first and second contact members 110 and 120. there is.

As the silicone rubber constituting the sealing material 130 has elasticity, flexibility, and elasticity, when the manufactured heat transfer unit 100 is bent or folded, the sealing material 130 is able to maintain a reliable seal without forming cracks. there is.

The heat transfer material 140 may be liquid silicone rubber or various rubbers in which thermally conductive powder with self-adhesiveness or thermally conductive fibers are uniformly mixed.

The heat transfer material 140 has viscosity and can easily spread or flow horizontally by an external force applied vertically due to flowability and spreadability according to viscosity.

In the present invention, the heat transfer material 140 may be in the form of a thermally conductive gel with high viscosity or a thermally conductive grease with a medium viscosity.

The thermal conductivity of the heat transfer material 140 may be approximately 1W to 10W. The lower the thermal conductivity, the more it is in a grease state, and the higher the thermal conductivity, the more it is a gel state.

Accordingly, the manufactured heat transfer unit 100 can have a flat or curved shape by the sealing material 130 having elasticity, flexibility, and elasticity, and when pressed by an opposing object, the heat transfer material 140 is formed. As it spreads laterally, the heat transfer unit 100 is pressed and becomes thinner.

Hereinafter, the process of making the heat transfer unit 100 of the present invention will be described.

A closed loop-shaped sealant 130 is formed by continuously printing or dispensing a liquid silicone rubber adhesive at a designated portion (hereinafter referred to as a 'sealing portion') along the edge of the second contact member 110.

Next, the heat transfer material 140 is discharged using a dispenser or the like into a space formed with the second contact member 110 as the bottom and the sealing material 130 as the side wall, without contacting the sealing material 130 as much as possible.

Although the discharge amount of the heat transfer material 140 is not specified, it may be discharged to an extent that occupies 50% to 90% of the internal space 102 formed by covering the first contact member 110.

The heat transfer material 140 may be a liquid silicone rubber with self-adhesiveness in which thermally conductive powder or thermally conductive fibers are uniformly mixed, and may be in a gel state with high viscosity and spreadability, or with medium viscosity and flowability. It may be a Greek state with .

Thereafter, the sealing portion formed along the edge of the first contact member 110 is brought into contact with the upper surface of the sealing material 130, and then the sealing material 130 is cured so that the sealing material 130 is formed on the first and second contact members 110 and 120. ) to be adhered to the sealing part by curing.

Here, the curing conditions of the sealant 130 vary depending on the material of the liquid silicone rubber adhesive corresponding to the sealant 130, but are due to heat or moisture.

Therefore, the sealing material 130 formed of liquid silicone rubber is not completely cured at the beginning but is finally cured at the end and has final adhesive strength after the final curing, so the sealing material 130 is formed on the second contact member 120. After discharging the heat transfer material 140, it is necessary to adjust the working conditions so that the sealing material 130 is not finally hardened before covering the first contact member 110.

To this end, the order is changed and the heat transfer material 140 is first discharged on the second contact member 120 before forming the sealing material 130, and then the sealing material 130 is formed and the second contact member 110 is immediately applied to the sealing material ( 130) can be covered and then cured to ensure complete final adhesion between the sealant 130 and the first contact member 110.

Preferably, the heat transfer unit 100 is plate-shaped to make surface contact with the object in many areas, and has a thin thickness to facilitate heat transfer within a possible range.

Figure 2 shows the operation of the heat transfer unit.

In Figure 2, the portion indicated by the dotted line shows the position before being pressed by an external force.

In a state where the heat transfer material 140 is filled to occupy approximately 80% of the internal space, when an external force is applied to the upper surface of the first contact member 110 and pressed, the heat transfer material 140 in the internal space contacts the first contact member 110. As it is pressed by the member 110, it begins to fill the empty space inside.

At this time, the air existing in the empty space is discharged like an arrow through the through hole 112, and the heat transfer material 140 spreads or flows into the empty space.

In this process, the sealing material 130 may be deformed so that both sides bulge outward due to its elasticity, flexibility, and elasticity.

As a result, although it may vary depending on the degree to which the first contact member 110 is pressed, when the first contact member 110 is pressed to the maximum as shown in FIG. 2, the heat transfer material 140 is in a state where only a small portion of the internal space communicating with the through hole 112 is empty. It almost fills the interior space.

If there is no through hole 112 and there is no gap through which air existing in the empty space escapes due to pressing force, air with better flowability than the heat transfer material 140 will flow to the area where force is not applied, causing some of that area to loosen and rise. However, if the swollen area does not come into contact with the heat source, it may not have a significant effect on heat transfer.

Figure 3 shows a heat transfer unit according to another embodiment of the present invention.

The heat transfer unit 200 includes opposing thermally conductive first and second contact members 210 and 220, respectively bonded along the edges between the first and second contact members to provide flexibility and elasticity to seal the internal space. It consists of a sealing material 230, a heat transfer material filled with a portion of the internal space, and a heat conductive adhesive sheet 250 having self-adhesiveness that is adhered to the lower surface of the second contact member 220.

In this embodiment, the adhesive sheet 250 is adhered to the lower surface of the second contact member 220 as an example, but the adhesive sheet 250 may be adhered to the upper surface of the first contact member 210 or both. You can.

According to this structure, the heat transfer unit 200 can be attached to an object, for example, at least one of a cooling body and a heat source.

Figure 4 shows a heat transfer unit according to another embodiment of the present invention.

The heat transfer unit 300 includes a thermally conductive solid contact member 310 that is composed of a single body and is bent on one side to form opposing first and second contact portions 312 and 314, except for one side. The first and second contact portions 312 and 314 are bonded by a sealant 330.

In this case, it can have advantages such as increased mechanical strength of the heat transfer unit 300 provided by the bent portion.

Figure 5 shows a heat transfer unit according to another embodiment of the present invention.

The heat transfer unit 400 of this embodiment is composed of a single body 410 made of a silicone rubber material having flexibility, elasticity, and elasticity, and is formed with first and second contact portions 412 and 414 that are open on one side and face each other. .

For example, it has the shape of a housing including first and second contact portions 412 and 414 that are formed flatly and having an internal space.

Although the size is not particularly limited, a sealing material 430 having flexibility, elasticity, and elasticity is formed in the opening formed on one side to seal the internal space by adhering the first and second contact portions 412 and 414 to each other.

According to this structure, all parts except the sealing material 430 formed in the open portion are composed of a monolith 410 made of silicone rubber, and when an external force is applied perpendicular to the contact area, the monolith 410 itself becomes elastic. As the internal space increases as it expands, the heat transfer material in the internal space spreads in the direction in which it is pressed, making the heat transfer unit 400 thinner.

Preferably, the monolith 410 is provided by impregnating a fixture corresponding to the shape of the monolith 410 with liquid silicone rubber, hardening it, and then removing it from the fixture.

When the monolith 400 is damaged by an external force, the internal heat transfer material is preferably in a gel state with a relatively high viscosity to prevent the internal heat transfer material from escaping to the outside.

In some cases, a mechanical auxiliary to protect the monolith 400 may be installed at a certain portion of the monolith 400.

The heat transfer unit 400 can be applied when the spacing between opposing objects is large, when multiple spacings exist, or when there is a large area.

Although the above description focuses on embodiments of the present invention, it goes without saying that various changes can be made at the level of those skilled in the art. Therefore, the scope of the present invention cannot be construed as limited to the above-described embodiments, and should be interpreted in accordance with the claims set forth below.

100: Heat transfer unit
102: Internal space
110: First contact member
112: Through hole
120: Second contact member
130: sealant
140: Heat transfer material

Claims (21)

A heat transfer unit that is interposed between a heating source and a cooling body, which are opposing objects, and is used to transfer heat from the heating source to the cooling body,
First and second solid contact members having thermal conductivity facing each other;
a sealing material having elasticity and flexibility adhered to the first and second contact members along edges of opposing surfaces of the first and second contact members;
an internal space formed by the sealing material between the first and second contact members; and
Filling a portion of the internal space and comprising a heat transfer material having flowability or spreadability,
A heat transfer unit, characterized in that a through hole is formed in a portion of the first contact member or a portion of the second contact member so that air in the internal space escapes through the through hole when the heat transfer unit is pressed. In claim 1,
A heat transfer unit, wherein the first and second contact members are two independently separated contact members or a single contact member connected at one side. ◈Claim 3 was abandoned upon payment of the setup registration fee.◈ In claim 2,
A heat transfer unit, wherein in the case of the two separated contact members, the sealing material forms a closed loop. ◈Claim 4 was abandoned upon payment of the setup registration fee.◈ In claim 2,
A heat transfer unit, wherein in the case of a single contact member connected to each other on one side, the sealing material is formed continuously except for the connected portion. delete ◈Claim 6 was abandoned upon payment of the setup registration fee.◈ In claim 1,
The first and second contact members are each a metal sheet containing copper, copper alloy, aluminum or an aluminum alloy, a heat conductive polymer sheet containing a heat conductive rubber sheet, or a combination thereof. ◈Claim 7 was abandoned upon payment of the setup registration fee.◈ In claim 6,
A heat transfer unit, characterized in that a thermally conductive adhesive sheet is adhered to at least one externally exposed surface of the metal sheet and the polymer sheet. ◈Claim 8 was abandoned upon payment of the setup registration fee.◈ In claim 6,
A heat transfer unit wherein the polymer sheet has self-adhesiveness. ◈Claim 9 was abandoned upon payment of the setup registration fee.◈ In claim 1,
A heat transfer unit, characterized in that a graphite layer is formed on a portion between the opposing surfaces of the first and second contact members. delete delete In claim 1,
A heat transfer unit, characterized in that the sealing material is thermally conductive silicone rubber with elasticity. delete delete delete delete In claim 1,
A heat transfer unit, characterized in that when the heat transfer unit is pressed, the heat transfer material in the internal space does not escape through the through hole. ◈Claim 18 was abandoned upon payment of the setup registration fee.◈ In claim 1,
The heat transfer material is a liquid thermally conductive silicone rubber mixed with thermally conductive powder, and is in a gel or grease state.
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