Deep waterproof thermoelectric refrigerating unit and preparation method thereof

Abstract

The invention belongs to the technical field of semiconductor packaging, and particularly relates to a deep waterproof thermoelectric refrigerating unit and a preparation method thereof.The deep waterproof thermoelectric refrigerating unit comprises an upper ceramic substrate, a lower ceramic substrate, a semiconductor refrigerating column located between the upper ceramic substrate and the lower ceramic substrate and metal electrode layers arranged at the two ends of the refrigerating column; a closed hole type elastic sealing medium is filled in a circumferential gap of the semiconductor refrigeration column and is foamed to form a continuous sealing layer; trapezoidal extrusion arms, peripheral extrusion arms and peripheral sealing steps are processed on the edges of the upper ceramic substrate and the lower ceramic substrate, multiple waterproof pressing structures are formed on the edges after assembly, and a pressure self-adaptive coating shell formed through a mold is coated outside, so that the waterproof performance is remarkably improved while the thermoelectric refrigeration efficiency is ensured; the device can stably operate in extreme environments such as deep water, high humidity and strong condensation, and is suitable for outdoor refrigeration, temperature control of diving equipment and heat management of special electronic devices.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor packaging, and in particular relates to a deeply waterproof thermoelectric cooler and a preparation method thereof. Background Art

[0002] As solid-state cooling elements, thermoelectric coolers are widely used in electronic equipment cooling, precision instrument temperature control, and portable cooling devices due to their compact structure, lack of moving parts, and bidirectional cooling capability. They achieve temperature differential transfer between hot and cold ends through the Seebeck effect. However, in practice, thermoelectric coolers often need to operate in harsh environments such as high humidity, rain, and even liquid immersion. Their waterproof sealing performance directly affects the device's lifespan and stability.

[0003] Existing technologies often use epoxy resin, silicone rubber, or hot-melt adhesive as encapsulating materials, achieving waterproofing through edge coating or filling. However, these single-layer sealing structures are susceptible to interfacial delamination, microcracks, or sealant hardening failure under long-term thermal cycling and water vapor. This allows water vapor to penetrate the semiconductor components through the gap between the ceramic substrate and the encapsulating adhesive, corroding the solder layer and degrading thermoelectric performance. The outer protective structure is typically made of hard plastic or a single layer of elastic material, which lacks the ability to automatically adjust to changes in external pressure. This can easily lead to localized stress concentration, further weakening the sealing effect.

[0004] Therefore, existing thermoelectric coolers still have significant deficiencies in structural design, waterproof medium material selection and sealing methods. There is an urgent need for a comprehensive protection solution that can achieve compression sealing and combine an outer pressure-adaptive coating structure to improve the long-term waterproof capability and overall reliability of thermoelectric coolers in high humidity and underwater environments. Summary of the Invention

[0005] In response to the above problems, the purpose of the present invention is to propose: a deeply waterproof thermoelectric cooler, comprising an upper ceramic substrate, a lower ceramic substrate, multiple pairs of P-type semiconductor columns and N-type semiconductor columns located between the upper and lower ceramic substrates, metal electrode welding layers arranged at the upper and lower ends of the semiconductor columns, and a packaging sealing structure.

[0006] The upper ceramic substrate and the lower ceramic substrate have trapezoidal extrusion arms, peripheral extrusion arms, and peripheral sealing steps; The packaging sealing structure includes: a closed-cell elastic sealing medium and an outer pressure-adaptive covering shell; The closed-cell elastic sealing medium is arranged between the trapezoidal extrusion arm, the P-type semiconductor column and the N-type semiconductor column, and between the peripheral extrusion arm and the outer pressure-adaptive covering shell; When the upper and lower ceramic substrates are subjected to relative longitudinal pressure, the following occurs: T1: The trapezoidal extrusion arm applies oblique extrusion to the closed-cell elastic sealing medium, causing elastic deformation with increased pressure between the P-type semiconductor column and the N-type semiconductor column; T2: The peripheral extrusion arm applies longitudinal extrusion to the closed-cell elastic sealing medium, causing elastic deformation with increased pressure between the upper ceramic substrate, the lower ceramic substrate and the outer pressure-adaptive covering shell.

[0007] As an optimal technical solution, the outer pressure-adaptive covering shell comprises an outer peripheral shell and a locking arm; the locking arm cooperates with the outer peripheral sealing step; and a closed-cell elastic sealing medium is provided between the outer peripheral shell and the outer peripheral extrusion arm.

[0008] As a preferred technical solution, a closed-cell elastic sealing medium is provided between the locking arm and the peripheral sealing step.

[0009] As an optimal technical solution, the outer pressure-adaptive covering shell is formed by laminating an inner fluororubber layer and an outer polyether block amide layer. The Shore A hardness of the inner fluororubber layer is 50-60, and the Shore A hardness of the outer polyether block amide layer is 90-100.

[0010] As an optimal technical solution, the closed-cell elastic sealing medium is a fluorine-containing elastomer foam sealing material with a closed-cell rate of 95% to 98%; the fluorine-containing elastomer foam sealing material is a composite of fluorine-containing liquid silicone rubber and hollow glass microspheres, the particle size of the glass microspheres is 5 to 20 μm, and the volume fraction is 20% to 35%.

[0011] As a preferred technical solution, the exposed surfaces of the upper ceramic substrate 1, the lower ceramic substrate 2, the P-type semiconductor column, the N-type semiconductor column and the metal electrode welding layer are covered with an oxide-fluoride composite hydrophobic barrier layer containing a rare earth fluoride crystal phase, and the surface water contact angle is 160°±5°.

[0012] As a preferred technical solution, the oxide-fluoride composite hydrophobic barrier layer is an aluminum oxide matrix with a thickness of 200 to 500 nm, and the rare earth fluoride crystal phase is lanthanum fluoride or cerium fluoride.

[0013] As a preferred technical solution, the total thickness of the outer pressure-adaptive covering shell is 0.6 to 1.2 mm.

[0014] As a preferred technical solution, the upper ceramic substrate and the lower ceramic substrate are aluminum nitride ceramics with a thickness of 0.3 to 0.6 mm and a thermal conductivity of 150 to 180 W / (m·K).

[0015] The present invention provides a method for preparing a deeply waterproof thermoelectric cooler, comprising the following steps: S1, welding multiple pairs of P-type semiconductor columns and N-type semiconductor columns to the upper and lower ends of the metal electrode welding layer respectively to form a semiconductor component; S2. Fix the semiconductor assembly in a molding die, and pour a closed-cell elastic sealing medium raw material into the space between the corresponding P-type semiconductor column, the N-type semiconductor column, the metal electrode welding layer, and the peripheral sealing space. The raw material is formed by mixing fluorine-containing liquid silicone rubber and hollow glass microspheres in a mass ratio of 100: (20-35), the hollow glass microspheres having a particle size of 5-20 μm and a volume fraction of 20%-35%, and a peroxide curing agent having a mass fraction of 0.5%-1.5%; S3. Heat and foam the closed-cell elastic sealing medium raw material at 80-120° C. and 0.05-0.1 MPa and cure for 2-5 hours to achieve a closed-cell ratio of 95%-98% and a Shore A hardness of 70-80. S4, machining the edges of the upper ceramic substrate and the lower ceramic substrate respectively to form a trapezoidal extrusion arm, a peripheral extrusion arm and a peripheral sealing step; S5. Assembling the processed upper and lower ceramic substrates to both sides of the semiconductor assembly, so that the trapezoidal extrusion arms and the peripheral extrusion arms cooperate with the closed-cell elastic sealing medium, and the peripheral sealing steps correspond to the engaging arms; S6. Form an outer pressure-adaptive covering shell in a mold, wherein the covering shell includes an inner fluororubber layer and an outer polyether block amide layer, the inner fluororubber layer has a Shore A hardness of 50 to 60, the outer polyether block amide layer has a Shore A hardness of 90 to 100, and the total thickness is 0.6 to 1.2 mm.

[0016] As a preferred technical solution, the closed-cell elastic sealing medium raw material in step S2 is stirred at a low speed of 25 to 35°C for 8 to 12 minutes before pouring to uniformly disperse the hollow glass microspheres, and is further stirred for 5 to 8 minutes after adding the curing agent to form a uniform reaction material.

[0017] As a preferred technical solution, the machining in step S4 adopts CNC precision cutting, and the inclination angle of the trapezoidal extrusion arm 6 is 10° to 15°.

[0018] As a preferred technical solution, step S6 includes the following sub-steps: S61. Material preparation: Prepare a fluororubber mixture from a fluororubber raw material. Add 0.5% to 1.5% by mass of a peroxide curing agent to the mixture and stir at 25 to 35°C for 5 to 10 minutes. Prepare a polyether block amide mixture from a polyether block amide raw material. S62, surface treatment: performing plasma treatment or sandblasting on the outer surfaces of the upper ceramic substrate 1 and the lower ceramic substrate 2 and the peripheral sealing step 8 area, and depositing a titanium transition layer with a thickness of 50 to 150 nm on the treated surfaces; S63, inner fluororubber layer molding: Place the treated component into the first-stage mold cavity, inject the fluororubber mixture into the cavity and pressurize until it fits the outer surface of the peripheral extrusion arm. Heat and vulcanize at 150-170°C for 8-12 minutes to obtain the inner fluororubber layer. S64, outer polyether block amide layer molding: Place the assembly with the inner fluororubber layer into the second-stage mold cavity, inject the polyether block amide mixture into the cavity and melt-bond it with the outer surface of the inner fluororubber layer, and keep the temperature at 180-200°C for 5-8 minutes; S65, curing and cooling: maintain a pressure of 0.05-0.1 MPa in the mold for secondary vulcanization of the double-layer coating structure for 1-2 hours, and cool at room temperature for 15-25 minutes; S66. Demolding and inspection: Demold the molded outer pressure adaptive covering shell as a whole, and check that its total thickness is 0.6 to 1.2 mm, and the thickness ratio of the inner fluororubber layer to the outer polyether block amide layer is 1:1 to 1:1.5.

[0019] As a preferred technical solution, the fluororubber raw material in step S61 is a ternary copolymer fluororubber with a fluorine content of 65% to 70%, which is made by copolymerization of hexafluoropropylene, tetrafluoroethylene and perfluoroalkyl vinyl ether, and has a Mooney viscosity of 60 to 80 ML (1+10) @ 100 °C.

[0020] As a preferred technical solution, the polyether block amide raw material in step S61 is a thermoplastic elastomer formed by alternating copolymerization of polyamide hard segments and polyether soft segments, the relative viscosity of the polyamide hard segments is 1.6 to 1.9, the number average molecular weight of the polyether soft segments is 600 to 2000, and the total density is 1.01 to 1.03 g / cm 3 .

[0021] Beneficial effects: The present invention achieves high-density filling of the sealing medium under longitudinal and oblique bidirectional pressure conditions by in-situ pouring and foaming a closed-cell elastic sealing medium between the P-type semiconductor column, the N-type semiconductor column and the metal electrode welding layer, combined with the trapezoidal extrusion arms and peripheral extrusion arms formed by processing the edges of the upper and lower ceramic substrates, thereby significantly improving the sealing stability and anti-seepage performance.

[0022] The outer pressure-adaptive sheath is formed by laminating an inner fluororubber layer with an outer polyether block amide layer. The difference in material hardness results in synergistic compression under external pressure, further enhancing the package seal. An oxide-fluoride composite hydrophobic barrier layer covers the exposed surfaces of the upper and lower ceramic substrates and semiconductor components, forming a nanoscale hydrophobic interface that effectively prevents moisture infiltration. The multi-layered sealing design, combined with an in-situ molding process, ensures long-term stable operation in complex, hot and humid environments, while maintaining both structural strength and thermal conductivity, making it suitable for thermoelectric cooling applications in conditions of long-term high humidity or liquid immersion. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the structure of the thermoelectric cooler of the present invention; Figure 2 This is a schematic structural diagram of the upper ceramic substrate of the thermoelectric cooler of the present invention; Figure 3 Schematic diagram of the structure of the lower ceramic substrate of the thermoelectric cooler of the present invention; Figure 4 It is a schematic structural diagram of the outer pressure-adaptive covering shell of the thermoelectric cooler of the present invention. DETAILED DESCRIPTION

[0024] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to the examples. The examples are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0025] Example 1 This embodiment provides a deeply waterproof thermoelectric cooler, whose overall structure and sealing protection design are intended to maintain long-term stable thermoelectric cooling performance in high humidity and strong water pressure environments, and significantly extend the service life of the device.

[0026] like Figure 1 As shown, the refrigerator includes an upper ceramic substrate 1, a lower ceramic substrate 2, multiple pairs of P-type semiconductor columns 3 and N-type semiconductor columns 4 located between the upper and lower ceramic substrates, metal electrode welding layers 5 arranged at the upper and lower ends of the semiconductor columns, and a packaging sealing structure.

[0027] In this embodiment, both the upper ceramic substrate 1 and the lower ceramic substrate 2 are made of aluminum nitride ceramic with a thickness of 0.3 to 0.6 mm and a thermal conductivity of 150 to 180 W / (m·K) to ensure excellent thermal conductivity during the temperature difference transfer between the two sides of the refrigerator while maintaining sufficient mechanical strength to withstand external pressure shocks.

[0028] Between the two ceramic substrates, multiple pairs of P-type semiconductor pillars 3 and N-type semiconductor pillars 4 are evenly spaced and arranged alternately to form a Seebeck circuit. The height, cross-sectional shape, and distribution density of the P-type and N-type semiconductor pillars are optimized based on actual cooling power requirements. This embodiment uses a height of 1.0-1.5 mm and a square cross-sectional side length of 0.8-1.0 mm. A rectangular array structure is used to minimize thermal resistance and electrical resistance unevenness.

[0029] The upper and lower ends of each semiconductor column are connected to the conductive circuit of the ceramic substrate through the metal electrode welding layer 5. The welding layer material is nickel-plated copper foil covered with tin-lead alloy solder. The thickness of the solder layer is controlled at 30-50 μm to reduce contact resistance and enhance mechanical bonding strength.

[0030] like Figure 2 、 Figure 3 As shown, the outer edge structure of the upper and lower ceramic substrates 1 and 2 is machined into three parts: a trapezoidal extrusion arm 6, a peripheral extrusion arm 7, and a peripheral sealing step 8. The trapezoidal extrusion arm 6 has an inclination angle of 10° to 15°, forming an oblique compression surface that closes inward when longitudinal force is applied, enhancing the extrusion force on the internal sealing medium. The peripheral extrusion arm 7 has a width of 0.8 to 1.2 mm, providing axial compression space in the direction of the outer sealing ring. The peripheral sealing step 8 has a height of 0.5 to 0.8 mm, ensuring stable cooperation with the locking arm of the outer covering shell, forming a secondary waterproof barrier.

[0031] The encapsulated sealing structure includes a closed-cell elastic sealing medium 9 and an outer pressure-adaptive covering shell 10, wherein the closed-cell elastic sealing medium 9 is distributed in two positions: (1) Fill the sealing gap between the trapezoidal extrusion arm 6 and the semiconductor column to prevent longitudinal water seepage; (2) The peripheral extrusion arm 7 and the outer pressure-adaptive covering shell 10 block the infiltration of external moisture and liquid water.

[0032] When longitudinal pressure is applied from the outside, the sealing action is divided into two parts: Part T1: The trapezoidal extrusion arm 6 compresses the internal closed-cell elastic sealing medium 9 with an oblique force, causing elastic deformation between the semiconductor pillars, increasing the local pressure and effectively filling the tiny gaps; Part T2: The peripheral extrusion arm 7 applies longitudinal extrusion to the peripheral sealing medium, forcing it to generate a high-pressure sealing ring between the ceramic substrate and the outer covering shell, forming a second waterproof barrier.

[0033] like Figure 4As shown, the outer pressure-adaptive covering shell 10 is composed of an outer peripheral shell 11 and a locking arm 12. The locking arm 12 and the outer peripheral sealing step 8 are locked with each other to form a stable mechanical connection, and a second layer of closed-cell elastic sealing medium 9 is arranged at the locking position to form a sealing area with local stress concentration.

[0034] The outer shell is constructed from a double-layer composite: the inner layer is fluororubber (50-60 Shore A hardness), offering excellent resistance to oil, acid, alkali, and high and low temperatures; the outer layer is polyether block amide (90-100 Shore A hardness), combining high strength and impact resistance. The total thickness is controlled between 0.6 and 1.2 mm to ensure adequate protection and flexibility.

[0035] The closed-cell elastic sealing medium 9 has a closed porosity of 95% to 98%. It is made of a composite of fluorinated liquid silicone rubber and hollow glass microspheres, with the glass microspheres having a particle size of 5 to 20 μm and a volume fraction of 20% to 35%. The closed-cell structure deforms uniformly and rebounds quickly under pressure, while the hollow glass microspheres impart excellent dimensional stability and resistance to water penetration.

[0036] To further prevent moisture from entering the semiconductor interface, the exposed surfaces of the upper and lower ceramic substrates (1), (2), (3) P-type and (4) N-type semiconductor pillars, and (5) the metal electrode solder layer are covered with a composite hydrophobic oxide-fluoride barrier layer. This coating, based on an aluminum oxide matrix (200-500 nm thick), contains a dispersed rare earth fluoride crystal phase (lanthanum fluoride or cerium fluoride). The surface water contact angle reaches 160°±5°, demonstrating superhydrophobic properties and effectively preventing liquid water from adhering.

[0037] Example 2 This embodiment provides a semiconductor power device package assembly having a closed-cell elastic sealing structure and an outer pressure-adaptive covering shell, the preparation method of which is as follows: S1. Preparation and connection of semiconductor column and metal electrode welding layer: P-type and N-type semiconductor pillars with a diameter of 2.5 mm and a length of 10 mm were selected. The materials were boron-doped silicon single crystal and phosphorus-doped silicon single crystal, respectively. Their resistivities were controlled between 0.01 and 0.05 Ω·cm to ensure low on-resistance characteristics of the power device at the operating current. The metal electrode soldering layer consisted of nickel-plated copper-based pads with a thickness of 0.2 mm to improve soldering strength and current-carrying capacity.

[0038] First, the end face of the semiconductor column was plasma cleaned to remove surface oxides and organic residues. Then, Sn-3.0Ag-0.5Cu (SAC305) lead-free solder was used to firmly weld the end face of the semiconductor column to the metal electrode welding layer through a vacuum reflow process. The peak of the welding temperature curve was set at 245°C, and the holding time was controlled at 60 s to ensure sufficient wetting of the solder and the formation of a dense intermetallic compound layer.

[0039] S2. Infusion and foaming of closed-cell elastic sealing medium: The gaps between the solder layer and adjacent semiconductor pillars are filled with a fluororubber-based closed-cell elastic sealing medium. The fluororubber raw material is fluorinated ethylene-propylene copolymer (FEPM), with a Mooney viscosity of 60-80 ml (1+10) @ 100°C. Two phr of an organic peroxide crosslinker, 10 phr of a microsphere foaming agent, and an appropriate amount of carbon black reinforcing filler are added, and the mixture is uniformly mixed in a planetary mixer.

[0040] The perfusion method is quantitative injection, evenly injecting the adhesive into the gap between the metal electrode layer and the semiconductor pillar. The material is then preheated at 120°C for 5 minutes to activate the foaming agent, and then held at 180°C for 15 minutes to fully crosslink the material and establish the closed-cell structure. The compression set of this closed-cell sealing medium is controlled within 25%, ensuring that the device maintains its sealing performance even under long-term pressure.

[0041] S3. Ceramic substrate edge structure processing: Both the upper and lower ceramic substrates are made of high-purity aluminum nitride ceramic. CNC grinding is used to form trapezoidal extrusion arms, peripheral extrusion arms, and peripheral sealing steps at their mating edges. The main planar area is 1 mm thick, with the trapezoidal extrusion arms having a base width of 1.5 mm, a top width of 0.8 mm, and a height of 0.6 mm. The peripheral extrusion arms are 0.5 mm thick and 0.8 mm high, and the peripheral sealing step is 1.2 mm wide and 0.4 mm high. This structure creates multi-directional compression on the closed-cell elastic sealing medium during subsequent component assembly, enhancing sealing reliability and dissipating external mechanical shock.

[0042] S4. Assembly of upper and lower ceramic substrates and semiconductor welding components: The upper and lower ceramic substrates are placed on either side of the semiconductor pillars and aligned using a precision positioning jig to ensure that the vertical center deviation between the P-type and N-type semiconductor pillars does not exceed 0.05 mm. Moderate mechanical pressure is then applied to pre-compress the closed-cell elastic sealing medium with the trapezoidal extrusion arms and the peripheral extrusion arms. Simultaneously, the peripheral sealing step contacts the sealing medium to form an outer ring seal, improving overall airtightness and uniformity of the medium filling.

[0043] S5. Moulding of the outer pressure adaptive covering shell: Polyether block amide (PEBA) is used as the overmolding material, with a Shore hardness of 72D selected to balance elastic recovery and impact resistance. After vacuum drying, the PEBA material is overmolded using a temperature-controlled injection mold. The mold cavity reserves a 1.5 mm overmolding layer thickness based on the component's shape, with curved transition sections formed around the perimeter to prevent stress concentration. During the overmolding process, the mold temperature is controlled at 70°C, the injection temperature at 200°C, the injection pressure at 60 MPa, the holding time at 30 seconds, and the cooling time at 90 seconds. After removal, the overmolding is inspected for appearance and dimensions to ensure a tight fit between the overmolding shell, the ceramic substrate, and the sealing medium, forming a cohesive outer protective structure.

[0044] Through the above steps, this embodiment not only achieves a firm connection between the semiconductor column and the metal electrode, but also provides a long-term and stable sealing effect through the closed-cell elastic sealing medium and the multi-layer mechanical compression structure. At the same time, the outer pressure-adaptive coating shell further enhances the impact resistance and environmental adaptability of the device.

[0045] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A deeply waterproof thermoelectric cooler, comprising an upper ceramic substrate (1), a lower ceramic substrate (2), a plurality of pairs of P-type semiconductor columns (3) and N-type semiconductor columns (4) located between the upper and lower ceramic substrates, metal electrode welding layers (5) provided at the upper and lower ends of the semiconductor columns, and a packaging sealing structure, characterized in that: The upper ceramic substrate and the lower ceramic substrate have trapezoidal extrusion arms (6), peripheral extrusion arms (7), and peripheral sealing steps (8); The packaging sealing structure comprises: a closed-cell elastic sealing medium (9) and an outer pressure-adaptive covering shell (10); The closed-cell elastic sealing medium is arranged between the trapezoidal extrusion arm (6), the P-type semiconductor column (3) and the N-type semiconductor column (4), and between the peripheral extrusion arm (7) and the outer pressure-adaptive coating shell (10); When the upper ceramic substrate (1) and the lower ceramic substrate (2) are subjected to relative longitudinal pressure, the following occurs: T1: the trapezoidal extrusion arm (6) applies oblique extrusion to the closed-cell elastic sealing medium (9), causing elastic deformation with increased pressure between the P-type semiconductor column (3) and the N-type semiconductor column (4); T2: The peripheral extrusion arm (7) applies longitudinal extrusion to the closed-cell elastic sealing medium (9), causing elastic deformation with increased pressure between the upper ceramic substrate (1), the lower ceramic substrate (2) and the outer pressure-adaptive covering shell (10).

2. The deep waterproof thermoelectric cooler according to claim 1, characterized in that: The outer pressure-adaptive covering shell (10) comprises an outer peripheral shell (11) and a locking arm (12); the locking arm (12) cooperates with the outer peripheral sealing step (8); and a closed-cell elastic sealing medium (9) is provided between the outer peripheral shell (11) and the outer peripheral extrusion arm (7).

3. The deep waterproof thermoelectric cooler according to claim 1, characterized in that: A closed-cell elastic sealing medium (9) is provided between the locking arm (12) and the peripheral sealing step (8).

4. The deep waterproof thermoelectric cooler according to claim 1, characterized in that: The outer pressure-adaptive covering shell (10) is formed by laminating an inner fluororubber layer and an outer polyether block amide layer, wherein the inner fluororubber layer has a Shore A hardness of 50 to 60, and the outer polyether block amide layer has a Shore A hardness of 90 to 100.

5. The deep waterproof thermoelectric cooler according to claim 1, characterized in that: The closed-cell elastic sealing medium (9) is a fluorine-containing elastomer foam sealing material with a closed-cell rate of 95% to 98%. The fluorine-containing elastomer foam sealing material is a composite of fluorine-containing liquid silicone rubber and hollow glass microspheres, wherein the particle size of the glass microspheres is 5 to 20 μm and the volume fraction is 20% to 35%.

6. The deep waterproof thermoelectric cooler according to claim 1, characterized in that: The exposed surfaces of the upper ceramic substrate (1), the lower ceramic substrate (2), the P-type semiconductor column (3), the N-type semiconductor column (4) and the metal electrode welding layer (5) are covered with an oxide-fluoride composite hydrophobic barrier layer containing a rare earth fluoride crystal phase, and the surface water contact angle is 160°±5°.

7. The deep waterproof thermoelectric cooler according to claim 6, characterized in that: The oxide-fluoride composite hydrophobic barrier layer is an aluminum oxide matrix with a thickness of 200 to 500 nm, and the rare earth fluoride crystal phase is lanthanum fluoride or cerium fluoride.

8. The deep waterproof thermoelectric cooler according to claim 1, characterized in that: The upper ceramic substrate (1) and the lower ceramic substrate (2) are made of aluminum nitride ceramics, and have a thermal conductivity of 150 to 180 W / (m·K).

9. A method for preparing a deeply waterproof thermoelectric cooler, characterized in that: The following steps are involved: S1, welding a plurality of pairs of P-type semiconductor columns (3) and N-type semiconductor columns (4) to the upper and lower ends of the metal electrode welding layer (5) to form a semiconductor assembly; S2, fixing the semiconductor assembly in a forming mold, and pouring a closed-cell elastic sealing medium raw material into the space between the corresponding P-type semiconductor column (3), the N-type semiconductor column (4) and the metal electrode welding layer (5) and the peripheral sealing space, wherein the raw material is formed by mixing fluorine-containing liquid silicone rubber and hollow glass microspheres in a mass ratio of 100: (20-35), the hollow glass microspheres have a particle size of 5-20 μm and a volume fraction of 20%-35%, and a peroxide curing agent is added in a mass fraction of 0.5%-1.5%; S3. Heat and foam the closed-cell elastic sealing medium raw material at 80-120° C. and 0.05-0.1 MPa and cure for 2-5 hours to achieve a closed-cell ratio of 95%-98% and a Shore A hardness of 70-80. S4, machining the edges of the upper ceramic substrate (1) and the lower ceramic substrate (2) respectively to form a trapezoidal extrusion arm (6), a peripheral extrusion arm (7) and a peripheral sealing step (8); S5. Assembling the processed upper ceramic substrate (1) and the lower ceramic substrate (2) to both sides of the semiconductor assembly, so that the trapezoidal extrusion arm (6) and the peripheral extrusion arm (7) match the closed-cell elastic sealing medium (9), and the peripheral sealing step (8) corresponds to the locking arm (12); S6. Forming an outer pressure-adaptive covering shell (10) in a mold, wherein the covering shell comprises an inner fluororubber layer and an outer polyether block amide layer, wherein the inner fluororubber layer has a Shore A hardness of 50 to 60, and the outer polyether block amide layer has a Shore A hardness of 90 to 100, and the total thickness is 0.6 to 1.2 mm.

10. The preparation method according to claim 9, characterized in that: In step S2, the closed-cell elastic sealing medium raw material is stirred at a low speed of 25 to 35° C. for 8 to 12 minutes before pouring to uniformly disperse the hollow glass microspheres, and is further stirred for 5 to 8 minutes after adding the curing agent to form a uniform reaction material.

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