CN112040743A - Heat conducting fin with coating layer structure - Google Patents

Abstract

The invention provides a heat conducting strip with a coating layer structure, wherein an inorganic layer, an organic layer and an inorganic layer are sequentially deposited on the surface of the heat conducting strip, and the inorganic layer is deposited by utilizing a plasma enhanced chemical vapor deposition method and has heat conductivity and gas barrier property; the organic layer is a polymer layer deposited by conventional chemical vapor deposition, and the toughness of the inorganic layer and the binding force between the inorganic layers are improved by hot melting treatment. The heat conducting fin with the coating layer structure has the characteristics of excellent heat conducting performance and good structural stability, and is suitable for heat conducting and radiating of high-power-consumption electronic and electric equipment.

Description

A thermally conductive sheet with a cladding structure

technical field

The invention relates to the technical field of thermally conductive materials, in particular to a thermally conductive sheet with a cladding layer structure.

Background technique

Graphite has a unique grain orientation, so it has the characteristics of anisotropic high thermal conductivity. Commercial products using graphite as thermal conductors are currently widely used in heat conduction and heat dissipation of heat sources such as mobile phones, notebook computers, medical equipment, and LED screens. Graphite thermally conductive sheets have the characteristics of poor toughness, easy to break, and good electrical conductivity. During die-cutting and use, graphite will be broken and powder will fall off, so there is a risk of short circuit in electronic equipment, so it often needs to be coated.

In order to prevent the graphite-based thermally conductive sheet from falling off powder, adhesives are currently used for surface coating, but the coating thickness is relatively thick, usually 2-10 μm, which affects the thermal conductivity of the graphite-based thermally conductive sheet. In order to reduce the thickness of the protective layer, the patent CN102321867B uses a vapor deposition method to coat the surface of the graphite sheet with a polymer layer. However, the thermal conductivity of the polymer itself is low. For example, the thermal conductivity of parylene used in this patent is only 0.1 W/ About m·k, which limits the thermal conductivity of graphite to a certain extent. In addition, the polymer is composed of polymer chains. There are gaps between the chains, and water vapor can easily penetrate into the interior. Long-term work will cause the coating layer and the graphite sheet to bubble off, destroying the structural integrity of the thermal conductive sheet, making the The cooling rate is slowed down.

Therefore, how to coat the thermally conductive sheet to make it excellent in thermal conductivity, low in water vapor permeability and good in structural stability is a problem that needs to be solved.

SUMMARY OF THE INVENTION

In view of the problems existing in the prior art, the purpose of the present invention is to provide a thermally conductive sheet with a coating layer structure, the coating layer replaces the coating of pure organic matter, and realizes that the coating layer itself has a high thermal conductivity, good thermal conductivity. The gas barrier property has a stable bonding force with the thermal conductive sheet, and the coating layer itself has a certain toughness, so that the thermal conductive sheet can stably exert thermal conductivity.

In order to achieve the above purpose, the present invention provides a thermally conductive sheet with a cladding structure, wherein an inorganic layer, an organic layer, and an inorganic layer are sequentially deposited on the surface of the thermally conductive sheet, and the inorganic layer is made of plasma-enhanced chemical vapor. It is deposited by deposition method and has thermal conductivity and gas barrier properties; the organic layer is a conventional chemical vapor deposited polymer layer, which is treated by hot melt to improve the toughness of the inorganic layer and the bonding force between the inorganic layers. The thermally conductive sheet has excellent thermal conductivity and good structural stability.

further,

The thermally conductive sheet is a graphite sheet, a graphene film, a foamed graphite film, and a graphite/resin thermal interface material.

According to actual requirements, the surface of the thermally conductive sheet may be subjected to plasma surface activation treatment to enhance the bonding force between the thermally conductive sheet and the inorganic layer.

The components of the inorganic layer are silicon dioxide and silicon nitride.

The inner and outer inorganic layers may be of the same or different compositions.

The plasma-enhanced chemical vapor deposition rate is 5-80 nm/min. When the deposition rate is less than 5nm/min, the deposition efficiency is low; when the deposition rate is greater than 80nm/min, the excessively fast deposition rate will cause large internal stress in the inorganic layer, resulting in high brittleness of the inorganic layer.

The thickness of the inorganic layer is not more than 3 μm. When the thickness is greater than 3 μm, the adhesion of the inorganic layer on the surface of the thermal conductive sheet is poor.

The thermal conductivity of the inorganic layer is not less than 1 W/m·k. When the thermal conductivity of the inorganic layer is lower than 1W/m·k, it will affect the overall thermal conductivity of the thermally conductive sheet.

The polymers of the intermediate layer are N-type parylene, C-type parylene, D-type parylene, F-type parylene, and HT-type parylene.

The polymer of the intermediate layer is preferably N-type parylene and C-type parylene. These two kinds of parylene have lower melting points, and the hot-melt treatment temperature is 100-160 °C, which can realize the bonding of inorganic layers without destroying the components contained in the thermal conductor (such as the resin in the graphite/resin thermal conductive sheet). .

The thickness of the organic layer is 50-500 nm. When the thickness is less than 50nm, the adhesion after hot-melting is poor, and when the thickness is greater than 500nm, the overall thermal conductivity of the thermally conductive sheet will be affected.

Compared with the prior art, the present invention has the following beneficial effects:

The coating layer of the present invention is an inorganic/organic/inorganic composite coating layer that replaces pure organic coating, and the coating layer has the following effects:

1. The thickness of the coating layer is thin and has good thermal conductivity, which minimizes the influence of the protective layer on the thermal conductivity of the thermal conductive sheet;

2. The coating layer has good gas barrier properties, which can prevent water vapor from entering the interior of the thermal conductive sheet and prevent the coating layer from separating from the thermal conductive sheet;

3. After the organic layer is hot-melted, the toughness of the inorganic layer and the bonding force between the inorganic layers are improved, which can keep the overall structure of the thermal conductive sheet stable.

Description of drawings

FIG. 1 is a schematic structural diagram of a thermally conductive sheet with a coating layer prepared in an embodiment of the present invention.

specific embodiment

The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementations obtained by those skilled in the art without creative efforts fall within the protection scope of the present invention.

Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art.

Referring to FIG. 1 , a preferred embodiment of the present invention provides a thermally conductive sheet 100 with a coating layer, and an inorganic layer 201 , an organic layer 202 , and an inorganic layer 203 are sequentially deposited on the surface of the thermally conductive sheet 100 , that is, chemical vapor deposition is used for the thermally conductive sheet. Coating inorganic/organic/inorganic composite layers.

The present invention will be described in detail below through specific embodiments.

Example 1:

A thermally conductive sheet with an inorganic/organic/inorganic composite layer was prepared, and a synthetic graphite sheet was selected as the thermally conductive sheet with a thickness of 25 μm, and then the following coating process was carried out:

Step S1, plasma enhanced chemical vapor deposition: the graphite sheet is placed in the deposition chamber, the surface of the graphite sheet is pretreated with oxygen-plasma, and ammonia gas with a flow rate of 20 sccm and a flow rate of 130 sccm of monosilane account for 5% by mass fraction. The monosilane/argon gas mixture, the glow discharge frequency is 13.56MHz, the power is 180W, the silicon nitride is deposited on the surface of the graphite sheet at a speed of 35nm/min, and the thickness of the silicon nitride layer is 300nm.

Step S2, conventional chemical vapor deposition: place the silicon nitride-coated graphite sheet of step S1 in a deposition chamber, evaporate the dichloro-paraxylene dimer at 130° C., decompose at 650° C. C-type parylene was deposited on the surface with a thickness of 100 nm.

In step S3, which is consistent with step S1, the thickness of the silicon nitride layer is also 300 nm.

Step S4, the silicon nitride/C-type parylene/silicon nitride-coated graphite sheet is heated at a pressure of 1 MPa and a temperature of 120° C. for 10 minutes, and the C-type parylene is hot-melted to make the bonding force of the coating layer. strengthen.

Example 2:

To prepare a thermally conductive sheet with a composite layer coated with inorganic/organic/inorganic, graphite fiber/silica gel thermal interface material is selected as the thermally conductive sheet. , oxygen, heat resistance, etc.), to coat it, the steps are:

Step S1, the plasma-enhanced chemical vapor deposition step: place the graphite fiber/silica gel sheet in the deposition chamber, pass hexamethyldisiloxane with a flow rate of 10 sccm and oxygen with a flow rate of 30 sccm, a glow discharge frequency of 13.56 MHz, and a power of 13.56 MHz. For 50W, silica is deposited on the surface of the graphite fiber/silica sheet at a speed of 40 nm/min, and the thickness of the silica layer is 200 nm.

Step S2, conventional chemical vapor deposition step: place the silica-coated graphite fiber/silica gel sheet of step S1 in a deposition chamber, evaporate the p-xylene dimer at 120 °C, decompose at 650 °C, N-type parylene was deposited on the surface of silicon oxide with a thickness of 150 nm.

In step S3, which is consistent with step S1, the thickness of the silicon dioxide layer is 200 nm.

In step S4, the silica/N-type parylene/silica-coated graphite fiber/silica gel sheet is placed at a temperature of 120° C. for 5 minutes, and the N-type parylene is hot-melted to bond the coating layer. strengthen.

Example 3:

Prepare a thermally conductive sheet with an inorganic/organic/inorganic composite layer, select a foamed graphite film as the thermally conductive sheet, and the coating steps are:

Step S1, the plasma-enhanced chemical vapor deposition step: placing the foamed graphite film in the deposition chamber, pretreating the surface of the foamed graphite film with oxygen-plasma, and then introducing ammonia gas with a flow rate of 20 sccm and monosilane with a flow rate of 130 sccm Monosilane/argon gas mixture with a mass fraction of 5%, the glow discharge frequency is 13.56MHz, the power is 180W, silicon nitride is deposited on the surface of the foamed graphite film at a speed of 70nm/min, and the thickness of the silicon nitride layer is 600nm .

Step S2, a conventional chemical vapor deposition step: placing the silicon nitride-coated foamed graphite film of step S1 in a deposition chamber, evaporating the dichloro-paraxylene dimer at 130° C., decomposing at 650° C., C-type parylene was deposited on the surface of silicon nitride with a thickness of 300 nm.

S3, consistent with step S1 in Example 2, the thickness of the silicon dioxide layer is 200 nm.

S4, the silica/C-type parylene/silicon nitride-coated foamed graphite film is placed at a temperature of 120° C. for 5 minutes, and the C-type parylene is hot-melted to strengthen the bonding force of the coating layer.

Comparative ratio:

A synthetic graphite sheet with a thickness of 25 μm is selected as the thermal conductive sheet, and the coating steps are as follows:

The graphite sheet was placed in a deposition chamber, and the surface of the graphite sheet was pretreated with oxygen-plasma. The dichloro-paraxylene dimer was evaporated at 130 °C, and after decomposing at 650 °C, C-type polyparatyl was deposited on the surface of the graphite sheet. The thickness of xylene is 700 nm (the same as the total thickness of silicon nitride 300 nm, C-type parylene layer 100 nm, and silicon nitride 300 nm in Example 1).

The pure C-type parylene-coated graphite sheet was treated at a pressure of 1 MPa and a temperature of 120 °C for 10 min.

The thermal conductivity and gas barrier properties of the cladding layers in the thermal conductivity chapter were tested for the thermally conductive sheets with cladding layer structures prepared in Examples 1-3 and Comparative Examples. The test method for thermal conductivity is the 3ω transient planar heat source method (DOI: 10.1063/1.2714650). The test method of gas barrier property is the differential pressure gas permeability method, the test standard is ASTM D1653, and the instrument is W3/0120 water vapor transmission rate tester. The results are shown in Table 1.

Table 1 Performance test results

It can be seen from Table 1 that the thermal conductivity of the inorganic/organic/inorganic-coated composite layer is higher and the water vapor transmission rate is lower than that of the pure organic coating. That is to say, the inorganic/organic/inorganic coated composite layer has high thermal conductivity and good gas barrier properties.

The above descriptions are only preferred embodiments of the present application, and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims (10)

1. The heat conductor with the coating structure is characterized in that an inorganic layer, an organic layer and an inorganic layer are sequentially deposited on the surface of the heat conductor, the inorganic layer is deposited by utilizing a plasma enhanced chemical vapor deposition method, and the organic layer is a polymer layer deposited by utilizing a conventional chemical vapor deposition method and is subjected to hot melting treatment.

2. A thermally conductive sheet having a clad structure as claimed in claim 1, wherein the thermally conductive sheet is a graphite sheet, a graphene film, a foamed graphite film, or a graphite/resin thermal interface material.

3. A heat-conductive sheet having a clad structure as claimed in claim 1, wherein the inner and outer inorganic layers may be of the same or different composition.

4. A heat conductive sheet having a clad structure as claimed in claim 1 or 3, wherein the inorganic layer is preferably silicon dioxide and/or silicon nitride.

5. A thermally conductive sheet having a clad structure as claimed in claim 1, wherein the inorganic layer has a thickness of not more than 3 μm.

6. The heat conductive sheet with a clad structure as claimed in claim 1 or 5, wherein the PECVD deposition rate is 5-80 nm/min.

7. A thermally conductive sheet having a clad structure as claimed in claim 1, wherein the inorganic layer has a thermal conductivity of not less than 1W/m-k.

8. A heat conductive sheet having a clad structure as claimed in claim 1, wherein the polymer of the intermediate layer is parylene N, parylene C, parylene D, parylene F, parylene HT.

9. A heat conductive sheet having a clad structure as claimed in claim 1, wherein the organic layer has a thickness of 50 to 500 nm.

10. The heat conductive sheet with a covering layer structure as claimed in claim 1, wherein the hot-melt processing temperature is 100 to 160 ℃.

Images