A DBC ceramic substrate with stress relaxation, a thermoelectric device and a preparation method thereof

Abstract

The present invention discloses a DBC ceramic substrate with stress relaxation, a thermoelectric device and a preparation method thereof, wherein the DBC ceramic substrate comprises a directly bonded copper substrate, a multi-walled carbon nanotube and a copper film, wherein the directly bonded copper substrate comprises a copper strip and a ceramic plate, wherein the copper strip is fixed on the ceramic plate, wherein a plurality of holes are provided on the surface of the copper strip, wherein the holes comprise submicron holes and / or nano holes, wherein the multi-walled carbon nanotube is printed on the surface of the copper strip to form a multi-walled carbon nanotube layer, and wherein the copper film is plated on the multi-walled carbon nanotube layer. The DBC ceramic substrate, the thermoelectric device and the preparation method thereof provided by the present invention can greatly relax the thermal stress generated by temperature change and distribution, thereby improving the power generation efficiency and temperature adaptability of the thermoelectric device and extending the service life of the thermoelectric device.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor thermoelectric materials, and in particular to a DBC ceramic substrate with stress relaxation, a thermoelectric device and a preparation method thereof. Background Art

[0002] The surge in demand for developing a new energy supply strategy has stimulated the interest of countries around the world in new renewable energy technologies. Thermoelectric technology can directly convert waste heat into electricity without maintenance, and this technology has become a rapidly developing hot spot in sustainable energy harvesting technology. In recent years, the continuous emission of industrial waste heat has caused global climate deterioration and fossil fuel waste. The use of TE conversion technology can successfully collect and convert waste gas and waste heat emitted in industrial production processes into electricity, revealing that it can be used as a way of energy collection and conversion for "energy saving and emission reduction" applications. Currently, widely used inorganic TE materials, such as Bi2Te3, PbTe, SnSe, etc., have shown the best TE performance in their respective operating temperature ranges. However, their application scenarios are still severely limited by the inherent bonding characteristics that determine their inherent rigidity and brittleness. In recent years, organic TE materials have developed rapidly due to their unique advantages such as flexibility, light weight, and easy processing. However, their practical applications are still greatly limited due to low efficiency, high contact resistance with metal electrodes, difficult processing of n-type electrodes, poor air / thermal stability, narrow operating temperature range, corrosion problems, etc. Therefore, the preparation of high-performance TEG device systems with thermal stress relaxation remains a huge challenge. Finding effective ways to improve the thermal stress relaxation ability of inorganic TE material devices has always been a research hotspot in various disciplines. One method is to prepare porous inorganic materials on flexible organic substrates using solution and drip methods. The porous structure can adjust the deformation, thus providing an important contribution to flexibility. For example, Sun et al. prepared a room temperature (RT) ZT value of 7×10 -3 Dun et al. prepared flexible self-assembled Te nanorods on polyvinylidene fluoride sheets with a power factor (PF) of 45.8 μW / m·K at room temperature. 2 Lu et al. synthesized a thin film TE device of Bi2Te3-based nanoparticles on polyimide, with a maximum PF of 180 μW / m·K at 523 K. 2 . In addition, it was found that the nanoporous structure can effectively disperse phonons, reduce thermal conductivity and improve Seebeck coefficient. However, their conductive properties are severely deteriorated compared with bulk materials, which may be caused by contamination, poor interconnects, severe carrier scattering, etc. Therefore, it is very important to develop a suitable DBC ceramic substrate with stress relaxation. Summary of the invention

[0003] In order to solve the problems of the prior art, the present invention provides a DBC ceramic substrate with stress relaxation, a thermoelectric device and a preparation method thereof, and the technical scheme is as follows:

[0004] On the one hand, the present invention provides a DBC ceramic substrate with stress relaxation, comprising a directly bonded copper substrate, multi-walled carbon nanotubes and a copper film, wherein the directly bonded copper substrate comprises a copper bar and a ceramic plate, wherein the copper bar is fixed on the ceramic plate, wherein a plurality of holes are provided on the surface of the copper bar, wherein the holes include submicron holes and / or nanoholes, wherein the multi-walled carbon nanotubes are printed on the surface of the copper bar to form a multi-walled carbon nanotube layer, and the copper film is plated on the multi-walled carbon nanotube layer.

[0005] Furthermore, the bonding strength between the multi-walled carbon nanotube layer and the copper strip is greater than or equal to 30 MPa.

[0006] Furthermore, the thermal conductivity of the multi-walled carbon nanotube layer in a direction perpendicular to the surface of the ceramic plate is greater than or equal to 800 W / (m·K), and the electrical conductivity in a direction parallel to the surface of the ceramic plate is greater than or equal to 10 S / cm.

[0007] Furthermore, the overall thermal conductivity of the combination of the multi-walled carbon nanotube layer and the copper strip in a direction perpendicular to the surface of the ceramic plate is greater than or equal to 350 W / (m·K), and the electrical conductivity in a direction parallel to the surface of the ceramic plate is greater than or equal to 5.98×10 5 S / cm.

[0008] Furthermore, the copper film has a thickness ranging from 20 μm to 30 μm.

[0009] Furthermore, the bonding strength between the copper film and the multi-walled carbon nanotube layer is greater than or equal to 45 MPa.

[0010] Furthermore, the holes are of a honeycomb structure.

[0011] On the other hand, the present invention provides a thermoelectric device with stress relaxation, comprising the DBC ceramic substrate with stress relaxation.

[0012] In another aspect, the present invention provides a method for preparing a DBC ceramic substrate with stress relaxation, comprising the following steps:

[0013] S1, placing the directly bonded copper substrate in an organic acid solution for micro-etching to form submicron holes and / or nano-holes;

[0014] S2, cleaning and drying the directly bonded copper substrate and then performing a T treatment process, so that nano-holes are further formed on the copper bars of the directly bonded copper substrate;

[0015] S3, printing the multi-walled carbon nanotube sol onto the copper strip directly bonded to the copper substrate by screen printing, and curing by natural aging to form a multi-walled carbon nanotube layer on the copper strip;

[0016] S4, placing the directly bonded copper substrate containing the multi-walled carbon nanotube layer in S3 in a bonding furnace for bonding treatment to strengthen the bonding force between the multi-walled carbon nanotube layer and the copper strip;

[0017] S5, covering the direct-bonded copper substrate that has undergone bonding treatment in S4 with a metal mask plate accordingly, and placing it in an electron beam evaporation system for evaporation coating, so as to deposit a layer of copper film on the surface of the multi-walled carbon nanotube layer.

[0018] Furthermore, the multi-walled carbon nanotube sol is prepared by using conductive carbon glue, and the pH value of the organic acid solution is greater than or equal to 5.0.

[0019] Furthermore, the bonding process is performed in a vacuum isothermal and isobaric environment.

[0020] The beneficial effects brought by the technical solution provided by the present invention are as follows:

[0021] a. Able to work normally within a wider temperature range;

[0022] b. It has stress relaxation performance and can still work normally in millimeter wave working environment without cracks;

[0023] c. Improved the power generation efficiency and temperature adaptability of thermoelectric devices and extended the service life of thermoelectric devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. 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 creative work.

[0025] Figure 1 is a plan view of a DBC ceramic substrate with stress relaxation provided by an embodiment of the present invention;

[0026] Figure 2 is a schematic cross-sectional view in a direction perpendicular to the substrate of a DBC ceramic substrate with stress relaxation provided by an embodiment of the present invention;

[0027] Figure 3 It is a schematic flow chart of a method for preparing a DBC ceramic substrate with stress relaxation provided by an embodiment of the present invention.

[0028] The reference numerals include: 1-ceramic plate, 2-copper strip, 3-multi-walled carbon nanotube layer, 4-copper film. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0030] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, device, product or equipment that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or equipment.

[0031] In one embodiment of the present invention, a DBC ceramic substrate with stress relaxation is provided. Figure 1 and Figure 2 , including a directly bonded copper substrate, multi-walled carbon nanotubes and a copper film 4, the directly bonded copper substrate including a copper strip 2 and a ceramic plate 1, the copper strip 2 being fixed on the ceramic plate 1, the surface of the copper strip 2 being provided with a plurality of holes, the holes including submicron holes and / or nano holes, the holes being a honeycomb structure, the multi-walled carbon nanotubes being printed on the surface of the copper strip 2 to form a multi-walled carbon nanotube layer 3, the copper film 4 being plated on the multi-walled carbon nanotube layer 3, the thickness of the copper film 4 being in the range of 20μm-30μm, preferably 25μm, the bonding strength of the copper film 4 and the multi-walled carbon nanotube layer 3 being greater than or equal to 45MPa. It should be noted that in this embodiment, the copper strip and the copper film can be replaced with other metals with similar functions, and the solution of using a simple metal replacement for the copper strip or the copper film to achieve the same function is still within the protection scope of this embodiment.

[0032] The bonding strength between the multi-walled carbon nanotube layer 3 and the copper strip 2 is greater than or equal to 30 MPa, the thermal conductivity of the multi-walled carbon nanotube layer 3 in a direction perpendicular to the surface of the ceramic plate 1 is greater than or equal to 800 W / (m·K), and the electrical conductivity in a direction parallel to the surface of the ceramic plate 1 is greater than or equal to 10 S / cm; the overall thermal conductivity of the combination of the multi-walled carbon nanotube layer 3 and the copper strip 2 in a direction perpendicular to the surface of the ceramic plate 1 is greater than or equal to 350 W / (m·K), and the electrical conductivity in a direction parallel to the surface of the ceramic plate 1 is greater than or equal to 5.98×10 5 S / cm. It should be noted that the surface of the ceramic plate 1 mentioned here refers to the plane where the copper strip 2 contacts the ceramic plate 1, and the plane is also parallel to the upper surface of the copper strip 2, and the upper surface of the copper strip 2 contacts the multi-walled carbon nanotubes, see Figure 2 The stress-relaxed DBC ceramic substrate comprises, from top to bottom, a copper film 4, a multi-walled carbon nanotube layer 3, a copper strip 2 and a ceramic plate 1.

[0033] In one embodiment of the present invention, a thermoelectric device with stress relaxation is also provided, including the DBC ceramic substrate with stress relaxation. The use of the DBC ceramic substrate with stress relaxation allows the thermoelectric device to greatly relax the thermal stress generated by temperature changes and distribution, thereby improving the power generation efficiency and temperature adaptability of the thermoelectric device, which can be used for high-temperature heat recovery power generation and prolongs the service life of the thermoelectric device.

[0034] In one embodiment of the present invention, a method for preparing a DBC ceramic substrate with stress relaxation is also provided. Figure 3 , including the following steps:

[0035] S1, placing the directly bonded copper substrate in an organic acid solution for micro-etching to form submicron holes and / or nano-holes, wherein the pH value of the organic acid solution used is greater than or equal to 5.0;

[0036] S2, cleaning and drying the directly bonded copper substrate and then performing a T treatment process, so that nano-holes are further formed on the copper bars of the directly bonded copper substrate;

[0037] S3, printing the multi-walled carbon nanotube sol prepared with the conductive carbon glue onto the copper strip directly bonded to the copper substrate by screen printing, and curing by natural aging to form a multi-walled carbon nanotube layer on the copper strip;

[0038] S4, placing the directly bonded copper substrate containing the multi-walled carbon nanotube layer in S3 in a bonding furnace for vacuum isothermal and isobaric bonding treatment to strengthen the bonding force between the multi-walled carbon nanotube layer and the copper strip, so that the bonding strength between the multi-walled carbon nanotube layer and the copper strip is greater than or equal to 30 MPa;

[0039] S5. Cover the direct-bonded copper substrate that has undergone bonding treatment in S4 with the metal mask plate accordingly, and place it in an electron beam evaporation system for evaporation coating to deposit a layer of copper film on the surface of the multi-walled carbon nanotube layer, wherein the thickness of the deposited copper film ranges from 20 μm to 30 μm, and the bonding strength between the copper film and the multi-walled carbon nanotube layer is greater than or equal to 45 MPa.

[0040] It should be noted that the nanopores further generated on the copper strip under the T treatment process in step S2 are honeycomb structures and are smaller than the pores generated on the copper strip in step S1, so as to facilitate the printing and attachment of the multi-walled carbon nanotube sol.

[0041] The stress-relaxed DBC ceramic substrate and thermoelectric device provided by the present invention overcome the problems of traditional semiconductor thermoelectric devices in relatively high-temperature waste heat thermoelectric conversion. After limited experiments, the TEG thermoelectric device prepared using the DBC ceramic substrate can operate continuously at -20°C to +200°C, and its operating failure rate does not exceed 0.02%. The probability of cracks on the ceramic substrate in a millimeter wave working environment does not exceed 1%.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A DBC ceramic substrate with stress relaxation, characterized in that: The invention comprises a directly bonded copper substrate, multi-walled carbon nanotubes and a copper film (4), wherein the directly bonded copper substrate comprises a copper strip (2) and a ceramic plate (1), wherein the copper strip (2) is fixed on the ceramic plate (1), wherein a plurality of holes are provided on the surface of the copper strip (2), wherein the holes comprise submicron holes and / or nano holes, wherein the multi-walled carbon nanotubes are printed on the surface of the copper strip (2) to form a multi-walled carbon nanotube layer (3), wherein the bonding strength between the multi-walled carbon nanotube layer (3) and the copper strip (2) is greater than or equal to 30 Mpa; and wherein the copper film (4) is plated on the multi-walled carbon nanotube layer (3); The thermal conductivity of the multi-walled carbon nanotube layer (3) in a direction perpendicular to the surface of the ceramic plate (1) is greater than or equal to 800 W / (m·K), and the electrical conductivity in a direction parallel to the surface of the ceramic plate (1) is greater than or equal to 10 S / cm.

2. The DBC ceramic substrate with stress relaxation according to claim 1, characterized in that: The overall thermal conductivity of the combination of the multi-walled carbon nanotube layer (3) and the copper strip (2) in a direction perpendicular to the surface of the ceramic plate (1) is greater than or equal to 350 W / (m·K), and the electrical conductivity in a direction parallel to the surface of the ceramic plate (1) is greater than or equal to 5.98×10 5 S / cm.

3. The DBC ceramic substrate with stress relaxation according to claim 1, characterized in that: The thickness of the copper film (4) is in the range of 20 μm to 30 μm, and the bonding strength between the copper film (4) and the multi-walled carbon nanotube layer (3) is greater than or equal to 45 MPa.

4. The DBC ceramic substrate with stress relaxation according to claim 1, characterized in that: The holes are in a honeycomb structure.

5. A thermoelectric device with stress relaxation, characterized in that: It comprises a DBC ceramic substrate with stress relaxation as described in any one of claims 1 to 4.

6. A method for preparing a DBC ceramic substrate with stress relaxation, characterized in that: The following steps are involved: S1, placing the directly bonded copper substrate in an organic acid solution for micro-etching to form submicron holes and / or nano-holes; S2, cleaning and drying the directly bonded copper substrate and then performing a T treatment process, so that nano-holes are further formed on the copper bars of the directly bonded copper substrate; S3, printing the multi-walled carbon nanotube sol onto the copper strip directly bonded to the copper substrate by screen printing, and curing by natural aging to form a multi-walled carbon nanotube layer on the copper strip; S4, placing the directly bonded copper substrate containing the multi-walled carbon nanotube layer in S3 in a bonding furnace for bonding treatment to strengthen the bonding force between the multi-walled carbon nanotube layer and the copper strip; S5, covering the direct-bonded copper substrate that has undergone bonding treatment in S4 with a metal mask plate accordingly, and placing it in an electron beam evaporation system for evaporation coating, so as to deposit a layer of copper film on the surface of the multi-walled carbon nanotube layer.

7. The method for preparing a DBC ceramic substrate with stress relaxation according to claim 6, characterized in that: The multi-walled carbon nanotube sol is prepared by using conductive carbon glue, and the pH value of the organic acid solution is greater than or equal to 5.

0.

8. The method for preparing a DBC ceramic substrate with stress relaxation according to claim 6, characterized in that: The bonding process is performed in a vacuum, isothermal and isobaric environment.

Images