Diamond film composite heat-conducting sheet and preparation method thereof

Abstract

The invention discloses a diamond film composite heat-conducting fin and a preparation method thereof, and the preparation method comprises the steps: selecting a diamond film with a predetermined thickness; carrying out surface flattening treatment on the diamond film; plating a layer of metal or coating a layer of solder containing metal active components on the surface of the diamond film, pasting a metal sheet on the upper surface of the metal coating or the solder, and bonding the metal sheet with the metal coating of the diamond film, or heating and welding the metal sheet with the diamond film by using the solder; and stripping the diamond film from the heterogeneous substrate by using a metal material sheet combined with the diamond film to form the diamond film composite heat-conducting sheet. According to the method, the diamond film is kept complete and free of cracks, the diamond film can be completely peeled off from the substrate at a time, the face, with high smoothness, of the diamond film is exposed, and the method is compatible with industrial application such as a next-step attaching process.

Description

Technical Field

[0001] The invention relates to the technical field of diamond film materials, and in particular to a diamond film composite heat conductive sheet and a preparation method thereof. Background Art

[0002] Diamond film has high thermal conductivity. The thermal conductivity of bulk diamond film material is as high as 2200W·m -1 ·K -1 In the prior art, the transfer and application of diamond films face many challenges.

[0003] Generally speaking, the diamond film has a strong adhesion to the substrate, which makes it difficult to peel it from the substrate, and the film is easily damaged during the peeling process, such as cracks, which affects its performance and subsequent applications, and thus cannot meet the growing industrial needs.

[0004] Therefore, it is necessary to improve the existing technology.

[0005] The above information is presented as background information only to assist with understanding the present disclosure and no determination or admission is made as to whether any of the above may be used as prior art with respect to the present disclosure. Summary of the invention

[0006] The invention provides a diamond film composite heat conductive sheet and a preparation method thereof, so as to solve the problems existing in the prior art.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A method for preparing a diamond film composite thermal conductive sheet, comprising:

[0009] Selecting a diamond film grown on a smooth foreign substrate, wherein the diamond film has a predetermined low adhesion to the foreign substrate and the diamond film has a predetermined thickness;

[0010] Smooth the surface of the diamond film and remove the uneven thickness.

[0011] A layer of metal is plated on the surface of the diamond film or a layer of solder containing metal active components is coated, a metal sheet is attached to the metal plated layer or the solder, the metal sheet is bonded to the metal plated layer of the diamond film, or the metal sheet and the diamond film are heated and welded together by solder;

[0012] The diamond film is peeled off from the foreign substrate by using a metal material sheet combined with the diamond film to form a diamond film composite heat conductive sheet, wherein the diamond film layer has predetermined longitudinal thermal conductivity and transverse thermal conductivity.

[0013] Optionally, the predetermined low adhesion force is less than 2 N / cm, and the predetermined thickness is less than 0.2 mm.

[0014] Optionally, the leveling process includes:

[0015] The uneven thickness skirt portion of the diamond film grown around the foreign substrate is cut off by laser.

[0016] Optionally, the metal active component is titanium metal.

[0017] Optionally, the solder is silver-copper-titanium nano-solder.

[0018] Optionally, the metal material sheet is one or an alloy of copper, aluminum, titanium, iron, tin, lead, silver, gold and nickel.

[0019] Optionally, the longitudinal thermal conductivity of the diamond film is greater than 1100 W·m -1 ・K -1 , transverse thermal conductivity greater than 800W・m -1 ・K -1 .

[0020] Optionally, the foreign substrate is a single crystal silicon wafer; and the metal material wafer is a copper wafer.

[0021] Optionally, the stripping method is to gradually cool down the diamond film bonded with the metal sheet together with the heterogeneous substrate, and rely on the difference in thermal expansion coefficients between the metal sheet and the diamond film to curl outward together with the metal sheet during the cooling process to achieve stripping from the heterogeneous substrate. After the diamond film is completely stripped from the heterogeneous substrate, it is heated back to room temperature to obtain a composite thermal conductive sheet of the diamond film and the metal sheet that automatically recovers to be flat.

[0022] The present invention also provides a diamond film composite thermally conductive sheet, which is made according to the preparation method of the diamond film composite thermally conductive sheet as described in any one of the above items.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention provides a diamond film composite thermal conductive sheet and a preparation method thereof. By combining a metal sheet and a diamond film together, the flexibility of the metal sheet and the difference in thermal expansion coefficient between the metal sheet and the diamond film are utilized to achieve complete peeling of the diamond film from a substrate, and directly form a composite thermal conductive sheet of the diamond film and the metal sheet. The diamond film is kept intact and free of cracks, and the diamond film can be completely peeled off from the substrate at one time, and the smoother side of the diamond film is exposed, which is compatible with industrial applications such as the next step of bonding process.

[0025] The present invention has other features and advantages, which will be apparent from or will be described in detail in the accompanying drawings and the following detailed description incorporated herein, which together serve to explain the specific principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 The present invention provides a flow chart of a method for preparing a diamond film composite thermal conductive sheet. DETAILED DESCRIPTION

[0028] In order to explain in detail the possible application scenarios, technical principles, specific schemes that can be implemented, and the purposes and effects that can be achieved, the following is a detailed description of the specific embodiments listed in conjunction with the accompanying drawings. The embodiments described herein are only used to more clearly illustrate the technical solutions of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0029] Reference to "embodiment" herein means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The term "embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or association with other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, the various technical features mentioned in the embodiments can be combined in any way to form a corresponding implementable technical solution.

[0030] Unless otherwise defined, the technical terms used in this document have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms in this document is only for describing specific embodiments and is not intended to limit this application.

[0031] In the description of this application, the term "and / or" is an expression used to describe the logical relationship between objects, indicating that three relationships may exist, for example, A and / or B, which means: A exists, B exists, and A and B exist at the same time. In addition, the character " / " in this article generally indicates that the objects before and after are in an "or" logical relationship.

[0032] In the present application, terms such as “first” and “second” are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship of quantity, priority or sequence between these entities or operations.

[0033] Without further limitations, in this application, the words "include", "comprises", "has" or other similar expressions used in the sentences are intended to cover non-exclusive inclusion. These expressions do not exclude the presence of additional elements in the process, method or product including the elements, so that the process, method or product including a series of elements may include not only those limited elements, but also other elements not explicitly listed, or also include elements inherent to such process, method or product.

[0034] Similar to the understanding in the Examination Guidelines, in this application, expressions such as "greater than", "less than", "exceed" and the like are understood to exclude the number itself; expressions such as "above", "below", "within" and the like are understood to include the number itself. In addition, in the description of the embodiments of this application, "multiple" means more than two (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups", "multiple times", etc., unless otherwise clearly and specifically limited.

[0035] In the description of the embodiments of the present application, space-related expressions used, such as "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "vertical", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicate the orientation or position relationship based on the orientation or position relationship shown in the specific embodiments or drawings, and are only for the convenience of describing the specific embodiments of the present application or facilitating the reader's understanding, and do not indicate or imply that the referred device or component must have a specific position, a specific orientation, or be constructed or operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0036] Unless otherwise expressly specified or limited, in the description of the embodiments of the present application, the terms such as "install", "connect", "connect", "fix", "set", etc. used should be understood in a broad sense. For example, the "connection" can be a fixed connection, a detachable connection, or an integrated setting; it can be a mechanical connection, an electrical connection, or a communication connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium; it can be the internal connection of two elements or the interaction relationship between two elements. For technicians in the technical field to which the present application belongs, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0037] Please refer to Figure 1 The present invention provides a method for preparing a diamond film composite thermal conductive sheet, comprising:

[0038] S1. Select a diamond film grown on a smooth foreign substrate.

[0039] There is a predetermined low adhesion between the diamond film and the foreign substrate, and the diamond film has a predetermined thickness.

[0040] S2. Smooth the surface of the diamond film and remove the uneven thickness portion.

[0041] S3. Plate a layer of metal on the surface of the diamond film or apply a layer of solder containing metal active components, place a metal sheet on the metal coating or solder, bond the metal sheet to the metal coating of the diamond film, or heat and weld the metal sheet to the diamond film by soldering.

[0042] S4. The diamond film is peeled off from the foreign substrate by using a metal material sheet combined with the diamond film to form a diamond film composite thermal conductive sheet.

[0043] The diamond film layer has predetermined longitudinal thermal conductivity and transverse thermal conductivity.

[0044] In the present invention, by combining the metal sheet and the diamond film together, the flexibility of the metal sheet and the difference in thermal expansion coefficient between the metal sheet and the diamond film are utilized to realize complete peeling of the diamond film from the substrate, and a composite thermal conductive sheet of the diamond film and the metal sheet is directly formed, so that the peeling surface of the diamond film has high smoothness and flatness consistent with the growth substrate, and can be free of cracks, which greatly facilitates the next step of bonding and other industrial applications, and improves the quality and performance of the product.

[0045] Furthermore, the stripping method in the present invention is to gradually cool down the diamond film bonded with the metal sheet together with the heterogeneous substrate. Relying on the difference in thermal expansion coefficients between the metal sheet and the diamond film, the diamond film curls outward together with the metal sheet during the cooling process to achieve stripping from the heterogeneous substrate. After the diamond film is completely stripped from the heterogeneous substrate, it is heated back to room temperature to obtain a composite thermal conductive sheet of the diamond film and the metal sheet that automatically recovers to be flat.

[0046] Furthermore, in the present invention, the predetermined low adhesion between the diamond film and the foreign substrate is less than 2N / cm, and the predetermined thickness of the diamond film is less than 0.2mm.

[0047] Furthermore, in step S2, the flattening process includes: using a laser to cut off the uneven thickness skirt portion of the diamond film grown around the foreign substrate, thereby ensuring the flatness of the smooth surface exposed after the diamond film is peeled off from the foreign substrate. The diamond composite thermal conductive sheet with a smooth surface can fit more closely and evenly with the target device in subsequent applications, reduce the interface thermal resistance, and achieve excellent heat dissipation effect.

[0048] Furthermore, the metal active component is titanium metal, which has good chemical activity and can form a good bonding layer with both diamond and metal, and can give full play to the high thermal conductivity of diamond and metal materials.

[0049] Furthermore, the solder is silver-copper-titanium nano-solder, which has excellent fluidity and wettability, and can be evenly spread on the surface of the diamond film to achieve close contact with the diamond and metal material sheets.

[0050] Furthermore, the metal material sheet is one or an alloy of copper, aluminum, titanium, iron, tin, lead, silver, gold and nickel. These metals have good thermal conductivity, ductility and a higher thermal expansion coefficient than diamond, which makes it easy to strip the diamond film. Different materials can adapt to different application occasions.

[0051] Furthermore, the longitudinal thermal conductivity of the diamond film is greater than 1100 W·m -1 ・K -1 , transverse thermal conductivity greater than 800W・m -1 ・K -1 The higher longitudinal and lateral thermal conductivity can ensure that the diamond composite thermal conductive sheet can efficiently conduct heat in all directions.

[0052] Furthermore, the foreign substrate is a single crystal silicon wafer, and the polished single crystal silicon wafer has high surface flatness, good chemical stability, and a thermal expansion coefficient close to that of the silicon wafer, which can form a certain degree of interface matching during the growth process of the diamond film.

[0053] Furthermore, the metal sheet is a copper sheet, which has extremely high thermal conductivity, second only to silver, and can quickly diffuse the heat transferred from the diamond film, greatly improving the heat dissipation efficiency of the composite thermal conductive sheet.

[0054] The present invention also provides a diamond film composite thermally conductive sheet, which is made according to any of the above methods for preparing the diamond film composite thermally conductive sheet.

[0055] In summary, the present invention not only keeps the diamond film intact without cracks, but also can completely peel off the diamond film from the substrate at one time, and expose the smooth side of the diamond film. The diamond composite thermal conductive sheet has high thermal conductivity and is compatible with industrial applications such as the next step of bonding process. In addition, the solution provided by the present invention is simple in process, omitting the polishing process of the diamond material, and can directly combine a diamond film with a thickness as low as 1 micron or less with a metal sheet, greatly reducing the cost of large-area diamond composite sheets.

[0056] Some possible embodiments of the present application are as follows:

[0057] Embodiment 1:

[0058] A single crystal silicon wafer with a diameter of 8 inches and a thickness of 5 mm and a (100) crystal orientation was selected as the substrate material. The polishing surface roughness Rms of the silicon wafer in the 200x200 micron measurement area was <10 nm.

[0059] During the growth process, the growth process parameters are controlled to grow the diamond film in the microwave plasma chemical vapor deposition (MPCVD) equipment so that the adhesion between the diamond film and the silicon substrate is less than 1N / cm. When the diamond film grows to a predetermined thickness of 100μm, the growth of the diamond film is completed and the film is cooled and taken out.

[0060] After taking out the silicon substrate with the diamond film grown on it from the MPCVD device, the diamond film on the side of the silicon substrate is removed with a laser. Then, silver-copper-titanium nano-solder is applied on the surface of the diamond film, and a copper sheet with a length and width of 220mmx205mm and a thickness of 1mm is pasted on the silver-copper-titanium nano-solder, and then placed in a vacuum brazing furnace for welding. After welding, a suction cup with vacuum suction holes is used to suck the silicon substrate, and a roller with vacuum suction holes is used to peel the copper sheet and the polycrystalline diamond film off the silicon substrate, thus realizing an 8-inch composite thermal conductive sheet of polycrystalline diamond film and copper sheet.

[0061] Preferably, the copper sheet can be replaced by one of aluminum, titanium, gold, nickel or an alloy thereof.

[0062] Preferably, in the aforementioned silver-copper-titanium nano-solder, the weight ratio of silver:copper:titanium is 20:75:5.

[0063] In addition, the longitudinal thermal conductivity of the diamond film layer is greater than 1300 W·m -1 ·K -1 , transverse thermal conductivity greater than 900 W·m -1 ·K -1 .

[0064] Embodiment 2:

[0065] A single crystal silicon wafer with a diameter of 8 inches and a thickness of 5 mm was selected as the substrate material. The polishing surface roughness Rms of the silicon wafer in the 200x200 micron measurement area was <10 nm.

[0066] During the growth process, the growth process parameters are controlled to grow the diamond film in the microwave plasma chemical vapor deposition (MPCVD) equipment so that the adhesion between the diamond film and the silicon substrate is less than 2N / cm. When the diamond film grows to a predetermined thickness of 50μm, the growth of the diamond film is completed and the film is cooled and taken out.

[0067] After taking out the silicon substrate with the diamond film grown on it from the MPCVD device, the diamond film on the side of the silicon substrate was removed with a laser. Then, 200nm of titanium copper was evaporated on the surface of the diamond film, and the diamond film evaporated with titanium copper alloy was bonded to a copper sheet with a diameter of 8 inches and a thickness of 0.1mm. Then, it was placed in liquid nitrogen to achieve automatic peeling of the composite thermal conductive sheet of diamond and copper from the silicon substrate. The sample was taken out and restored to room temperature, and the sample automatically returned to flatness, completing the preparation of the composite thermal conductive sheet of 8-inch polycrystalline diamond film and copper sheet.

[0068] Finally, it should be noted that although the above embodiments have been described in the specification and drawings of this application, this does not limit the scope of patent protection of this application. All technical solutions generated by replacing or modifying equivalent structures or equivalent processes based on the essential concept of this application using the contents recorded in the specification and drawings of this application, as well as directly or indirectly implementing the technical solutions of the above embodiments in other related technical fields, are included in the scope of patent protection of this application.

Claims

1. A method for preparing a diamond film composite thermal conductive sheet, characterized in that: include: Selecting a diamond film grown on a smooth foreign substrate, wherein the diamond film has a predetermined low adhesion to the foreign substrate and the diamond film has a predetermined thickness; Smooth the surface of the diamond film and remove the uneven thickness. A layer of metal is plated on the surface of the diamond film or a layer of solder containing metal active components is coated, a metal sheet is attached to the metal plated layer or the solder, the metal sheet is bonded to the metal plated layer of the diamond film, or the metal sheet and the diamond film are heated and welded together by solder; The diamond film is peeled off from the foreign substrate by using a metal material sheet combined with the diamond film to form a diamond film composite thermal conductive sheet, wherein the diamond film layer has predetermined longitudinal thermal conductivity and transverse thermal conductivity.

2. The method for preparing the diamond film composite thermal conductive sheet according to claim 1, characterized in that: The predetermined low adhesion is less than 2 N / cm, and the predetermined thickness is less than 0.2 mm.

3. The method for preparing the diamond film composite thermal conductive sheet according to claim 1, characterized in that: The leveling process includes: The uneven thickness skirt portion of the diamond film grown around the foreign substrate is cut off by laser.

4. The method for preparing the diamond film composite thermal conductive sheet according to claim 1, characterized in that: The metal active component is titanium metal.

5. The method for preparing the diamond film composite thermal conductive sheet according to claim 1 or 4, characterized in that: The solder is silver-copper-titanium nano-solder.

6. The method for preparing the diamond film composite thermal conductive sheet according to claim 1, characterized in that: The metal material sheet is one of copper, aluminum, titanium, iron, tin, lead, silver, gold and nickel, or an alloy thereof.

7. The method for preparing the diamond film composite thermal conductive sheet according to claim 1, characterized in that: The longitudinal thermal conductivity of the diamond film is greater than 1100 W·m -1 ・K -1 , transverse thermal conductivity greater than 800W・m -1 ・K -1 .

8. The method for preparing the diamond film composite thermal conductive sheet according to claim 1, characterized in that: The foreign substrate is a single crystal silicon wafer; The metal material sheet is a copper sheet.

9. The method for preparing the diamond film composite thermal conductive sheet according to claim 1, characterized in that: The stripping method is to gradually cool down the diamond film bonded with the metal sheet together with the heterogeneous substrate, and rely on the difference in thermal expansion coefficients between the metal sheet and the diamond film to curl outwards together with the metal sheet during the cooling process to achieve stripping from the heterogeneous substrate, and after the diamond film is completely stripped from the heterogeneous substrate, heat it back to room temperature to obtain a composite heat conductive sheet of the diamond film and the metal sheet that automatically recovers to be flat.

10. A diamond film composite thermal conductive sheet, characterized in that: The diamond film composite thermal conductive sheet is made according to the preparation method of any one of claims 1 to 9.

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