High-thermal-conductivity low-thermal-resistance ceramic sheet material, preparation method and application thereof

Abstract

The application discloses a kind of high heat-conducting low thermal resistance ceramic sheet materials, preparation method and application thereof, the material includes ceramic substrate and functional coating on the upper surface of ceramic substrate and / or functional coating on the lower surface of ceramic substrate;Ceramic substrate is selected from any one of alumina ceramic sheet, aluminum nitride ceramic sheet, silicon nitride ceramic sheet;Upper functional coating, lower functional coating are PMC phase change material coating and heat-conducting gel coating any combination.The application is coated with functional coating on the surface of ceramic sheet, effectively fills ceramic surface micro gap, significantly reduces interface contact thermal resistance (reduces 50%-89%);PMC coating also has phase change temperature control capacity (phase change enthalpy 50-200J / g), can buffer device transient thermal shock;Coating and substrate are firmly combined, and the thermal resistance change rate is less than 13% after 500 times thermal cycle.The application has the advantages of wide substrate adaptability, high heat-conducting efficiency, excellent insulation performance, simple process and the like.

Description

Technical Field

[0001] This invention belongs to the field of electronic heat dissipation materials technology, specifically relating to a high thermal conductivity and low thermal resistance ceramic sheet material, its preparation method, and its application. Background Technology

[0002] As electronic components evolve towards miniaturization, high power density, and high frequency, the heat generated during operation is increasing dramatically. Taking the main drive inverter of a new energy vehicle as an example, the operating temperature of IGBT modules can reach 175℃, with a heat flux density exceeding 20W / cm²; the power consumption of 5G base station AAU equipment reaches hundreds of watts; and the heat flux density of AI computing chips has exceeded 100W / cm². Heat dissipation has become a key bottleneck restricting the performance and reliability of electronic systems.

[0003] Alumina, aluminum nitride, and silicon nitride ceramics have become core substrate materials in the field of electronic heat dissipation due to their excellent insulation properties, high-temperature resistance, mechanical strength, and chemical stability. Among them, alumina ceramic (Al2O3) has a thermal conductivity of approximately 20-30 W / m·K, is inexpensive, and readily mass-producible, making it the most widely used heat dissipation substrate. Aluminum nitride ceramic (AlN) has an intrinsic thermal conductivity as high as 170-230 W / m·K, and its coefficient of thermal expansion (4.5-5.0 ppm / ℃) is highly compatible with silicon chips, making it particularly suitable for high-power semiconductor packaging. Silicon nitride ceramic (Si3N4) has a thermal conductivity of approximately 80-130 W / m·K, a bending strength >800 MPa, and excellent fracture toughness, making it suitable for harsh mechanical conditions. Each of these three ceramic substrates has its own advantages, covering application needs at different cost and performance levels.

[0004] However, pure ceramic sheet materials have inherent technical drawbacks: ceramic materials have high surface hardness (Mohs hardness 7-9) and limited surface flatness (roughness Ra is typically 0.2-1.0 μm). When bonded to heat-generating / heat-dissipating devices, numerous microscopic voids are generated at the interface. The presence of air (with a thermal conductivity of only about 0.026 W / m·K) results in extremely high interfacial thermal resistance. Studies have shown that the contact thermal resistance between untreated ceramic sheets and metal heat sinks can reach 0.5-1.5 K·cm² / W, accounting for 40%-60% of the overall thermal resistance, significantly reducing overall heat dissipation efficiency. Furthermore, pure ceramic materials lack flexible bonding and dynamic heat regulation capabilities, making them unsuitable for the transient heating and complex heat dissipation requirements of high-power devices.

[0005] To address the above problems, existing technologies mainly employ the following solutions:

[0006] (1) Surface metallization method: A metal layer is formed on the ceramic surface through DBC (direct copper plating) or AMB (active metal brazing) processes. This method is complex, requires large equipment investment, has high production costs, and the metallized layer may reduce insulation performance, posing electrical safety hazards.

[0007] (2) Ceramic bulk doping modification: High thermal conductivity fillers are added during the ceramic sintering process. However, the types and contents of dopants are limited. Excessive addition will reduce the mechanical and insulation properties of the ceramic, and the increase in thermal conductivity is limited (usually only 20%-30%).

[0008] (3) Thermal grease application: Apply thermal grease to the surface of the ceramic sheet. Although it can improve contact thermal resistance in the short term, thermal grease has problems such as easy drying, poor reliability, complicated construction operation, and easy contamination of surrounding devices. In the long term, its reliability cannot meet the requirements of high reliability applications.

[0009] (4) Some coating technologies use only a single coating material and are adapted to a single ceramic substrate. They lack the concept of substrate-coating synergistic design, either lacking phase change temperature control capability or having poor flexible bonding effect, and cannot simultaneously achieve high thermal conductivity, low thermal resistance, high adaptability and high stability.

[0010] Therefore, there is an urgent need to develop a ceramic heat dissipation material and its preparation method that can be adapted to three mainstream ceramic substrates: alumina, aluminum nitride, and silicon nitride, and achieve high thermal conductivity, low interfacial thermal resistance, high insulation stability, and phase change temperature control capability through surface coating functional modification. Summary of the Invention

[0011] To address the shortcomings of existing technologies, this invention provides a high thermal conductivity, low thermal resistance ceramic sheet material, its preparation method, and its applications.

[0012] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0013] The first objective of this invention is to provide a high thermal conductivity and low thermal resistance ceramic sheet material, comprising a ceramic substrate and an upper functional coating coated on the upper surface of the ceramic substrate and / or a lower functional coating coated on the lower surface of the ceramic substrate;

[0014] The ceramic substrate is selected from any one of alumina ceramic sheets, aluminum nitride ceramic sheets, and silicon nitride ceramic sheets;

[0015] The upper and lower functional coatings are any combination of PMC phase change material coatings and thermally conductive gel coatings.

[0016] Preferably, the PMC phase change material coating comprises a matrix resin, a phase change component, a thermally conductive filler, and functional additives;

[0017] The matrix resin is selected from at least one of acrylate copolymers, silicone polymers, polyurethanes, and epoxy resins;

[0018] The phase change component is selected from at least one of paraffin, fatty acids, polyols, polyethylene glycol, and n-alkanes;

[0019] The thermally conductive filler is selected from at least one of alumina, aluminum nitride, boron nitride, silicon carbide, graphene, expanded graphite, and carbon nanotubes.

[0020] Preferably, the thermally conductive gel coating comprises an organosilicon polymer matrix and a thermally conductive filler;

[0021] The organosilicon polymer matrix is ​​selected from at least one of vinyl silicone oil and hydrogen-containing silicone oil;

[0022] The thermally conductive filler is selected from at least one of alumina, aluminum nitride, boron nitride, zinc oxide, and silicon carbide.

[0023] Preferably, the ceramic substrate has a thickness of 0.2-2.0 mm, and the functional coating has a thickness of 10-500 μm.

[0024] Preferably, when the functional coating is a PMC phase change material coating, the coating thickness is 60-200 μm; when the functional coating is a thermally conductive gel coating, the coating thickness is 20-150 μm.

[0025] Preferably, the surface of the ceramic substrate undergoes surface pretreatment before coating, and the surface pretreatment includes at least one of plasma treatment, silane coupling agent treatment, and acid-base etching treatment.

[0026] The functional coating is applied to one side of the ceramic substrate, or simultaneously to both sides of the ceramic substrate.

[0027] Preferably, in the PMC phase change material coating, the matrix resin has a mass fraction of 100 parts, the phase change component has a mass fraction of 40-100 parts, and the thermally conductive filler has a mass fraction of 50-200 parts.

[0028] In the thermally conductive gel coating, the organosilicon polymer matrix is ​​100 parts by weight, and the thermally conductive filler is 200-500 parts by weight.

[0029] The second objective of this invention is to provide a method for preparing a high thermal conductivity and low thermal resistance ceramic sheet material, comprising the following steps:

[0030] Step S1: Ceramic substrate surface pretreatment - The ceramic substrate surface is cleaned and then subjected to at least one of the following treatments: plasma treatment, silane coupling agent treatment, and acid-base etching treatment.

[0031] Step S2: Preparation of functional coating slurry—Weigh out 100 parts by weight of matrix resin, 40-100 parts by weight of phase change component, and 50-200 parts by weight of thermally conductive filler for a PMC phase change material coating, or 100 parts by weight of organosilicon polymer matrix and 200-500 parts by weight of thermally conductive filler for a thermally conductive gel coating according to the formula; after mixing, dispersing, and vacuum degassing, the functional coating slurry is obtained;

[0032] Step S3: Coating - The slurry obtained in step S2 is coated onto the ceramic substrate surface after the pretreatment in step S1 by at least one of the following methods: scraping, screen printing, spraying, dipping or dispensing.

[0033] Step S4: Curing – The coated ceramic substrate is placed under heating conditions to cure, forming a functional coating.

[0034] Preferably, in step S1, the plasma treatment uses atmospheric pressure plasma or low pressure plasma, the treatment time is 10-300s, and the treatment power is 50-500W; the coupling agent used in the silane coupling agent treatment is selected from at least one of KH550, KH560, KH570, and A-174.

[0035] In step S4, the curing temperature is 80-150℃ and the curing time is 10-120min.

[0036] The third objective of this invention is to provide an application of a high thermal conductivity and low thermal resistance ceramic sheet material in heat dissipation of high-power electronic devices, semiconductor packaging, integrated circuit thermal management, new energy vehicle electronic heat dissipation, 5G communication equipment, IGBT modules, LED packaging, or power converters.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] (1) Significantly reduce interfacial thermal resistance: By coating the ceramic sheet with PMC phase change material or thermal conductive gel coating, the coating can effectively fill the micro-pores on the ceramic surface and reduce the interfacial contact thermal resistance by 50%-80%.

[0039] (2) Wide substrate compatibility: The technical solution of the present invention can be adapted to three mainstream ceramic substrates: alumina, aluminum nitride and silicon nitride. By adjusting the coating formula and coating process parameters, excellent interface bonding and heat dissipation performance can be achieved on different substrates, and the substrate compatibility range is wide.

[0040] (3) Phase change dynamic temperature control capability: When PMC phase change material coating is used, the coating can absorb a large amount of latent heat (phase change enthalpy 50-200J / g) near the phase change temperature (40-80℃), effectively buffering the transient thermal shock of the device and extending the working time of the device within the safe temperature range.

[0041] (4) Synergistic effect of high thermal conductivity and low thermal resistance: The ceramic substrate provides a high thermal conductivity path, and the functional coating provides interface filling and flexible bonding. The two work together to achieve efficient heat conduction from heat source to heat sink.

[0042] (5) Excellent insulation performance and stability: The functional coating uses an organic polymer matrix combined with ceramic thermally conductive filler, without any metal conductive filler, to ensure the overall insulation performance of the material (breakdown voltage > 5kV / mm); the coating is firmly bonded to the ceramic substrate, and the performance degradation rate is < 10% after long-term thermal cycling and damp heat aging.

[0043] (6) Simple process and controllable cost: Compared with complex processes such as surface metallization (DBC / AMB), the coating process of the present invention is simple to operate, requires less equipment investment, and is suitable for large-scale production. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the structure of the high thermal conductivity and low thermal resistance ceramic sheet material of the present invention (single-sided coating).

[0045] Figure 2 This is a schematic diagram of the structure of the high thermal conductivity and low thermal resistance ceramic sheet material of the present invention (double-sided coating).

[0046] Figure 3 The graph shows a comparison of the thermal resistance test results of Examples 1-12 and Comparative Examples 1-6.

[0047] Figure 4 The graph shows a comparison of the heating and cooling curves for Examples 1, 5, and 9 (PMC phase change coating scheme).

[0048] Figure 5 The graph shows a comparison of the thermal conductivity of Examples 3, 7, and 11 (thermal conductive gel coating schemes). Detailed Implementation

[0049] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0050] Example 1: Alumina ceramic + PMC phase change material coating (single-sided).

[0051] (1) Ceramic substrate: 96% alumina ceramic sheet with dimensions of 50mm×50mm×0.5mm, thermal conductivity of 25W / m·K, and surface roughness Ra=0.3μm.

[0052] (2) Surface pretreatment: The ceramic sheet was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 10 min each, dried and then placed in an atmospheric pressure plasma treatment device with a treatment power of 200W and a treatment time of 60s.

[0053] (3) Preparation of PMC slurry: By mass, take 100 parts of acrylate copolymer (solid content 45%), 60 parts of paraffin (phase change temperature 52℃, phase change enthalpy 180J / g), 80 parts of aluminum nitride powder (average particle size 5μm), 10 parts of expanded graphite (average particle size 10μm), 2 parts of silane coupling agent KH570, and 1 part of defoamer. Disperse the mixture in a high-speed disperser at 3000rpm for 30min and degas it in a vacuum for 15min to obtain PMC phase change material slurry.

[0054] (4) Coating: The PMC slurry is uniformly coated on one side of the ceramic substrate by adjusting the gap between the scrapers to control the wet film thickness of the coating to about 120 μm.

[0055] (5) Curing: Place the coated ceramic sheet in an oven and cure at 120℃ for 60 min to obtain a high thermal conductivity, low thermal resistance ceramic sheet material with a coating thickness of approximately 80 μm. Figure 1 As shown, it includes a ceramic substrate 3 and an upper functional coating 2.

[0056] Example 2: Alumina ceramic + PMC phase change material coating (double-sided).

[0057] The preparation process is the same as in Example 1, except that PMC slurry is coated on both sides of the ceramic substrate to obtain a double-sided coated ceramic sheet material. Figure 2 As shown, it includes a ceramic substrate 3, an upper functional coating 2, and a lower functional coating 4.

[0058] Example 3: Alumina ceramic + thermally conductive gel coating (single-sided).

[0059] (1) Ceramic substrate: 96% alumina ceramic sheet with dimensions of 50mm×50mm×0.5mm, thermal conductivity of 25W / m·K, and surface roughness Ra=0.3μm.

[0060] (2) Surface pretreatment: Silane coupling agent was used for treatment. The cleaned ceramic sheet was immersed in 1wt% KH560 ethanol solution for 30 min, then removed and dried at 120℃ for 30 min.

[0061] (3) Preparation of thermally conductive gel slurry: By mass, take 100 parts of double-ended vinyl silicone oil (viscosity 500 Pa·s, 25℃), 5 parts of hydrogen-containing silicone oil (hydrogen content 0.3%), 300 parts of alumina filler (three-stage particle size compound: large particle size 40μm 50 parts, medium particle size 10μm 25 parts, small particle size 2μm 25 parts), 0.2 parts of platinum catalyst, and 0.05 parts of inhibitor. Mix them evenly with a planetary mixer and degas under vacuum to obtain thermally conductive gel slurry.

[0062] (4) Coating: The coating thickness is controlled to be about 100μm by screen printing process.

[0063] (5) Curing: Curing at 120℃ for 30 minutes yields a high thermal conductivity and low thermal resistance ceramic sheet material with a coating thickness of approximately 70μm.

[0064] Example 4: Alumina ceramic + thermally conductive gel coating (double-sided).

[0065] The preparation process is the same as in Example 3, except that thermally conductive gel slurry is coated on both sides of the ceramic substrate.

[0066] Example 5: Aluminum nitride ceramic + PMC phase change material coating (single-sided).

[0067] (1) Ceramic substrate: Aluminum nitride ceramic sheet with dimensions of 50mm×50mm×0.5mm, thermal conductivity of 180W / m·K, and surface roughness Ra=0.4μm is selected.

[0068] (2) Surface pretreatment: The ceramic sheet was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 10 min each, dried and then placed in an atmospheric pressure plasma treatment device with a treatment power of 200W and a treatment time of 60s.

[0069] (3) Preparation of PMC slurry: By mass, take 100 parts of organosilicon polymer (PDMS, viscosity 1000cSt), 70 parts of polyethylene glycol (PEG-4000, phase change temperature 58℃, phase change enthalpy 170J / g), 100 parts of boron nitride powder (average particle size 8μm), 30 parts of silicon carbide powder (average particle size 5μm), 2.5 parts of silane coupling agent KH550, and 1.5 parts of dispersant. After high-speed dispersion and mixing, vacuum degassing is performed.

[0070] (4) Coating: Scraping, wet film thickness is about 150μm.

[0071] (5) Curing: Curing at 100℃ for 90 minutes yields a high thermal conductivity and low thermal resistance ceramic sheet material with a coating thickness of approximately 100μm.

[0072] Example 6: Aluminum nitride ceramic + PMC phase change material coating (double-sided).

[0073] The preparation process is the same as in Example 5, except that it involves double-sided coating.

[0074] Example 7: Aluminum nitride ceramic + thermally conductive gel coating (single-sided).

[0075] (1) Ceramic substrate: Aluminum nitride ceramic sheet with dimensions of 50mm×50mm×0.5mm, thermal conductivity of 180W / m·K, and surface roughness Ra=0.4μm is selected.

[0076] (2) Surface pretreatment: Silane coupling agent treatment, same as in Example 3.

[0077] (3) Preparation of thermally conductive gel slurry: By mass, take 100 parts of vinyl silicone oil, 6 parts of hydrogen-containing silicone oil, 350 parts of aluminum nitride filler (three-level particle size compound), 50 parts of zinc oxide filler (average particle size 3μm), 0.25 parts of platinum catalyst, and 0.06 parts of inhibitor, mix evenly and then degas under vacuum.

[0078] (4) Coating: screen printing, controlling the coating thickness to about 80μm.

[0079] (5) Curing: Curing at 120℃ for 40 minutes yields ceramic sheet material with a coating thickness of approximately 55μm.

[0080] Example 8: Aluminum nitride ceramic + thermally conductive gel coating (double-sided).

[0081] The preparation process is the same as in Example 7, except that it is coated on both sides.

[0082] Example 9: Silicon nitride ceramic + PMC phase change material coating (single-sided).

[0083] (1) Ceramic substrate: Silicon nitride ceramic sheet with dimensions of 50mm×50mm×0.5mm, thermal conductivity of 85W / m·K, and surface roughness Ra=0.5μm is selected.

[0084] (2) Surface pretreatment: The ceramic sheet was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 10 min each, dried and then placed in an atmospheric pressure plasma treatment device with a treatment power of 200W and a treatment time of 60s.

[0085] (3) Preparation of PMC slurry: By mass, take 100 parts of epoxy resin (E-51), 80 parts of curing agent (methyl hexahydrophthalic anhydride), 50 parts of fatty acid (lauric acid, phase change temperature 44℃, phase change enthalpy 160J / g), 15 parts of expanded graphite (average particle size 15μm), 5 parts of carbon nanotubes, and 3 parts of silane coupling agent A-174. Mix them thoroughly with a three-roll mill and degas under vacuum.

[0086] (4) Coating: Scraping, wet film thickness is about 100μm.

[0087] (5) Curing: Segmented curing - curing at 80℃ for 30 min, then heating to 150℃ for 60 min to obtain ceramic sheet material with a coating thickness of about 65 μm.

[0088] Example 10: Silicon nitride ceramic + PMC phase change material coating (double-sided).

[0089] The preparation process is the same as in Example 9, except that it involves double-sided coating.

[0090] Example 11: Silicon nitride ceramic + thermally conductive gel coating (single-sided).

[0091] (1) Ceramic substrate: Silicon nitride ceramic sheet with dimensions of 50mm×50mm×0.5mm, thermal conductivity of 85W / m·K, and surface roughness Ra=0.5μm is selected.

[0092] (2) Surface pretreatment: Silane coupling agent was used for treatment. The cleaned ceramic sheet was immersed in 1wt% KH560 ethanol solution for 30 min, then removed and dried at 120℃ for 30 min.

[0093] (3) Preparation of thermally conductive gel slurry: By mass, take 100 parts of vinyl silicone oil, 5 parts of hydrogen-containing silicone oil, 200 parts of silicon carbide filler (average particle size 10μm), 100 parts of boron nitride filler (average particle size 6μm), 50 parts of alumina filler (average particle size 2μm), 0.2 parts of platinum catalyst, and 0.05 parts of inhibitor. Mix them evenly and then degas under vacuum.

[0094] (4) Coating: Spraying process, controlling the coating thickness to about 60μm.

[0095] (5) Curing: Curing at 120℃ for 35 minutes yields ceramic sheet material with a coating thickness of approximately 40μm.

[0096] Example 12: Silicon nitride ceramic + thermally conductive gel coating (double-sided).

[0097] The preparation process is the same as in Example 11, except that it is coated on both sides.

[0098] Example 13: Alumina ceramic + PMC phase change material coating (variable thickness scheme).

[0099] The preparation process was the same as in Example 1, except that the scraping gap was adjusted to control the coating thickness after curing to 30μm, 50μm, 80μm, 120μm and 200μm, respectively, and the effect of coating thickness on performance was investigated.

[0100] Example 14: Aluminum nitride ceramic + thermally conductive gel coating (variable filler ratio scheme).

[0101] The preparation process is the same as in Example 7, except that the total amount of thermally conductive filler added is adjusted to 200 parts, 300 parts, 400 parts and 500 parts respectively, and the effect of filler content on thermal conductivity and thermal resistance is investigated.

[0102] Comparative Example 1: Pure alumina ceramic sheet (uncoated).

[0103] Uncoated alumina ceramic sheets, 50mm×50mm×0.5mm in size, were used directly, with the surface only cleaned.

[0104] Comparative Example 2: Pure aluminum nitride ceramic sheet (uncoated).

[0105] Uncoated aluminum nitride ceramic sheets, measuring 50mm × 50mm × 0.5mm, were used directly, with the surface only cleaned.

[0106] Comparative Example 3: Pure silicon nitride ceramic sheet (uncoated).

[0107] Uncoated silicon nitride ceramic sheets, measuring 50mm × 50mm × 0.5mm, were used directly, with the surface only cleaned.

[0108] Comparative Example 4: Alumina ceramic + commercially available thermal grease.

[0109] Apply a layer of commercially available thermal grease (nominal thermal conductivity 3.5 W / m·K) evenly to the surface of the alumina ceramic sheet. The grease layer thickness is approximately 50 μm.

[0110] Comparative Example 5: Aluminum nitride ceramic + commercially available thermal grease.

[0111] A layer of commercially available thermal grease (same as Comparative Example 4) was uniformly applied to the surface of the aluminum nitride ceramic sheet, with a grease layer thickness of approximately 50 μm.

[0112] Comparative Example 6: Silicon nitride ceramic + commercially available thermal grease.

[0113] A layer of commercially available thermal grease (same as Comparative Example 4) was uniformly applied to the surface of the silicon nitride ceramic sheet, with a grease layer thickness of approximately 50 μm.

[0114] Comparative Example 7: Alumina ceramic + PMC coating (without surface pretreatment).

[0115] The preparation process is the same as in Example 1, except that the ceramic substrate is not pretreated with plasma, but is directly coated with PMC slurry after cleaning.

[0116] Comparative Example 8: Alumina ceramic + thermally conductive gel coating (without surface pretreatment).

[0117] The preparation process is the same as in Example 3, except that the ceramic substrate is not treated with silane coupling agent, but is directly coated with thermally conductive gel slurry after cleaning.

[0118] Comparative Example 9: Alumina ceramic + PMC coating (without thermally conductive filler).

[0119] The preparation process is the same as in Example 1, except that the PMC slurry does not contain thermally conductive fillers such as aluminum nitride powder and expanded graphite, but only contains matrix resin and phase change components.

[0120] Comparative Example 10: Alumina ceramic + thermally conductive gel coating (no thermally conductive filler).

[0121] The preparation process is the same as in Example 3, except that no alumina filler is added to the thermally conductive gel slurry, which only contains an organosilicon polymer matrix.

[0122] Comparative Example 11: Component decomposition of thermal resistance for different coating thicknesses.

[0123] The preparation process was the same as in Example 3, except that the coating thickness was 15μm, 20μm, 50μm, 100μm, 150μm, and 200μm. The results are shown in Table 8.

[0124] The total interfacial thermal resistance consists of three parts:

[0125] R_Contact 1: Thermal resistance of heat source-coating contact;

[0126] R_coating body: thermal resistance of the coating material (proportional to thickness, R_body = d / λ);

[0127] R_Contact 2: Coating-ceramic contact thermal resistance;

[0128] While thicker coatings (200 μm) offer greater ability to fill macroscopic irregularities, they also significantly increase the bulk density (R_). Thinner coatings (20-150 μm), on the other hand, minimize the heat conduction path while still meeting interfacial filling requirements.

[0129] Therefore, there is an optimal range for coating thickness. Below 20 μm, the coating cannot effectively fill the microscopic voids on the ceramic surface, the porosity increases sharply, and contact thermal resistance dominates the total thermal resistance. Above 150 μm, the bulk thermal resistance increases linearly, and the total thermal resistance begins to rise again. The 20-150 μm range of this application falls within this critical equilibrium range, exhibiting a significant reduction in thermal resistance.

[0130] Meanwhile, the thermal conductivity time constant τ∝d² / α (where d is the thickness and α is the thermal diffusivity) of thinner coatings (e.g., 20-150 μm) is significantly smaller than that of thicker coatings (200 μm). When dealing with chip power pulses, thinner coatings can transfer heat from the heat source to the ceramic substrate more quickly, reducing the peak junction temperature. This quantitative comparison demonstrates the advantage of this application in terms of "transient thermal shock response speed."

[0131] Comparative Example 12: Optimal range of coating thickness for MC phase change materials.

[0132] The preparation process is the same as in Example 1, except that the thickness of the PMC phase change material coating is shown in Table 9.

[0133] When the PMC phase change material coating thickness is less than 60 μm, the phase change enthalpy per unit area is too low, and the buffer time for the device to rise from normal operating temperature to critical temperature does not meet practical requirements (such as the thermal buffer requirement corresponding to a short-circuit withstand time of ≥5 μs for IGBT modules). The content of the phase change component is insufficient to provide effective thermal buffering capability. This application selects a coating thickness of ≥60 μm (or >60 μm) as a comprehensive optimization result under the premise of satisfying "effective thermal buffering". Therefore, the PMC phase change material coating thickness is limited to 60-200 μm.

[0134] The following are performance tests of all embodiments and comparative examples.

[0135] First, the testing method.

[0136] (1) Thermal resistance test: The total thermal resistance of the sample under 40 psi pressure was measured using the ASTM D5470 standard method and a thermal resistance tester. Figure 1 or Figure 2 As shown, the sample is placed between the hot end (simulated heating device 4) and the cold end (simulated heat sink 5), and the temperature difference and heat flux density between the hot end and the cold end are measured under steady state. The thermal resistance value is calculated (unit: K·cm² / W or ℃·in² / W).

[0137] (2) Thermal conductivity test: The out-of-plane thermal conductivity of the ceramic substrate was measured by laser flare method (LFA); the thermal conductivity of the coating material was measured by steady-state heat flow method.

[0138] (3) Phase change performance test: The phase change temperature and phase change enthalpy of the PMC coating were measured by differential scanning calorimetry (DSC) at a heating and cooling rate of 5℃ / min under nitrogen atmosphere.

[0139] (4) Interface bonding strength test: The peel strength between the coating and the ceramic substrate is measured by tensile method, in accordance with GB / T7122 standard.

[0140] (5) Insulation performance test: The breakdown voltage of the sample is measured using a withstand voltage tester with a boost rate of 500V / s and AC current.

[0141] (6) Reliability testing: Thermal cycling test (-40℃) 125℃, 500 cycles; high temperature and high humidity aging test (85℃ / 85%RH, 1000h). After the test, the thermal resistance and breakdown voltage were remeasured, and the performance degradation rate was calculated.

[0142] Second, the test results (see Tables 1 to 7).

[0143] Table 1: Test results of thermal resistance and thermal conductivity of each embodiment and comparative example

[0144]

[0145] Table 2: Phase change performance test results of Examples 1, 5, and 9 (PMC coating)

[0146]

[0147] Table 3: Reliability Test Results (After 500 Thermal Cycles)

[0148]

[0149] Table 4: Effect of coating thickness on performance (Example 13: Variable thickness test)

[0150]

[0151] Table 5: Effect of filler content on the properties of thermally conductive gel (Example 14: Variable filler ratio test)

[0152]

[0153] Table 6: Comparative test results without surface pretreatment

[0154]

[0155] Table 7: Comparative Test Results of No Thermally Conductive Filler

[0156]

[0157] Table 8: Component decomposition of thermal resistance

[0158]

[0159] Table 9: Optimal range of coating thickness for MC phase change materials

[0160]

[0161] Third, results analysis.

[0162] (I) Analysis of the effect of reducing thermal resistance.

[0163] From Table 1, Figure 3 As can be seen, the total interfacial thermal resistance of each embodiment of the present invention is significantly lower than that of the pure ceramic sheet and thermal grease solutions in the comparative examples:

[0164] Alumina system: The thermal resistance (0.14-0.28 K·cm² / W) of Examples 1-4 was reduced by 77%-89% compared to pure alumina ceramic sheets (Comparative Example 1, 1.25 K·cm² / W), and by 46%-73% compared to thermal grease solutions (Comparative Example 4, 0.52 K·cm² / W). Among them, the double-sided coating solutions (Examples 2 and 4) had the lowest thermal resistance.

[0165] Aluminum nitride system: The thermal resistance (0.09-0.19 K·cm² / W) of Examples 5-8 was reduced by 78%-89% compared to pure aluminum nitride ceramic sheet (Comparative Example 2, 0.85 K·cm² / W), and by 50%-76% compared to thermal grease solution (Comparative Example 5, 0.38 K·cm² / W).

[0166] Silicon nitride system: The thermal resistance (0.12-0.24 K·cm² / W) of Examples 9-12 was reduced by 76%-88% compared to pure silicon nitride ceramic sheets (Comparative Example 3, 0.98 K·cm² / W), and by 47%-73% compared to thermal grease solutions (Comparative Example 6, 0.45 K·cm² / W).

[0167] The main mechanism for reducing thermal resistance is that the organic polymer matrix in the functional coating can undergo micro-flow and deformation under assembly pressure, filling the micro-unevenness and voids on the ceramic surface, expelling the air medium between the interfaces, and forming a continuous solid-solid contact heat conduction path; at the same time, the high thermal conductivity filler in the coating constructs an efficient thermal conduction network, further reducing the thermal resistance of the coating body.

[0168] (II) Analysis of the phase change temperature control effect.

[0169] From Table 2, Figure 4 As can be seen, the PMC coatings of Examples 1, 5, and 9 all exhibit well-defined phase transition temperatures and high phase transition enthalpies (58-72 J / g), indicating that the coatings possess excellent phase transition energy storage capabilities. Taking Example 1 as an example, its coating phase transition temperature is 51.8℃, and its phase transition enthalpy is 68.5 J / g. During device operation, when the interface temperature rises to near the phase transition temperature, the phase transition components in the coating undergo a solid-liquid phase transition, absorbing a large amount of latent heat, thereby slowing down the temperature rise rate and providing thermal buffer protection for the device. This characteristic has unique advantages in dealing with transient thermal shocks to power devices (such as pulsed loads and startup moments).

[0170] (III) Reliability Comparison Analysis.

[0171] As shown in Table 3, the embodiments of the present invention, after undergoing 500 thermal cycles (-40℃), After reaching 125℃, the thermal resistance change rate was only 6.3%-12.5%, and the breakdown voltage change rate was within 5%. In contrast, the solutions using commercially available thermal grease in Comparative Examples 4-5 showed a thermal resistance change rate as high as 50%-60%, and a breakdown voltage decrease of 18%-22%. Furthermore, as shown in Table 6, the thermal resistance of Comparative Examples 7-8 without surface pretreatment increased significantly by 82%-89% after thermal cycling, while the change rate of Examples 1 and 3, which underwent plasma or silane coupling agent pretreatment, was only about 11%. This clearly demonstrates that surface pretreatment plays a crucial role in improving the bonding strength between the coating and the ceramic substrate and ensuring long-term reliability.

[0172] (iv) Analysis of the influence of coating thickness: the “non-monotonic optimal range” effect between coating thickness and thermal resistance.

[0173] As shown in Table 4, the thermal resistance continuously decreases with increasing thickness. Differentiating the coating thickness with the marginal benefit of reduced thermal resistance:

[0174] 30→50μm: ΔR=0.07, drag reduction per unit thickness=0.35 K·cm² / W / 100μm

[0175] 50→80μm: ΔR=0.07, drag reduction per unit thickness=0.23 K·cm² / W / 100μm

[0176] 80→120μm: ΔR=0.05, drag reduction per unit thickness=0.125 K·cm² / W / 100μm

[0177] 120→200μm: ΔR=0.04, drag reduction per unit thickness=0.05 K·cm² / W / 100μm

[0178] As the coating thickness increases from 30 μm to 200 μm, the total thermal resistance gradually decreases (from 0.42 to 0.19 K·cm² / W), while the phase change enthalpy significantly increases (from 25.3 to 158.4 J / g). However, excessive coating thickness increases the overall material thickness and the length of the heat conduction path, potentially negatively impacting the thermal conductivity response speed. Considering both thermal resistance and phase change capability, the optimal PMC coating thickness is 60-200 μm, and the optimal thermally conductive gel coating thickness is 20-150 μm. This provides sufficient phase change heat storage capacity while avoiding the diminishing marginal returns and encapsulation integration difficulties associated with excessively thick coatings.

[0179] This shows that the improvement in thermal resistance by coating thickness has a significant diminishing marginal effect. When the thickness exceeds 80 μm (corresponding to 120 μm data), the improvement in thermal resistance from further increasing the thickness decreases sharply, indicating the existence of a boundary between a "highly efficient improvement range" and a "lowly efficient improvement range".

[0180] (v) Analysis of the influence of filler content.

[0181] As shown in Table 5, as the amount of thermally conductive filler increased from 200 parts to 500 parts, the thermal conductivity of the coating increased from 3.2 W / m·K to 5.8 W / m·K, and the total thermal resistance decreased accordingly. However, when the filler content exceeded 400 parts, the slurry viscosity increased sharply (from 450 Pa·s to 1250 Pa·s), and the operability of the coating process decreased significantly. Therefore, the filler content is preferably 300-400 parts, balancing thermal conductivity and process operability.

[0182] (vi) Necessity analysis of surface pretreatment.

[0183] As shown in Table 6, the initial thermal resistance of the samples (Comparative Examples 7-8) that were not pretreated with plasma or silane coupling agent was significantly higher than that of the pretreated examples (0.45 vs 0.28, 0.36 vs 0.18), and the thermal resistance deteriorated severely after thermal cycling. The role of surface pretreatment is to: (1) clean organic contaminants on the ceramic surface and expose active hydroxyl groups; (2) plasma treatment can introduce polar functional groups on the ceramic surface, increase surface energy, and enhance coating wettability and adhesion; (3) silane coupling agent forms a chemical bridge between the ceramic surface and the coating polymer, which greatly improves the interfacial bonding strength.

[0184] This demonstrates that surface pretreatment not only reduces the initial thermal resistance but, more importantly, "locks in" the interfacial thermal resistance, ensuring its stability under harsh thermal cycling conditions. The thermal resistance degradation rate of the untreated sample after thermal cycling is over 80%, while that of the pretreated sample is only around 10%.

[0185] (vii) Necessity analysis of thermally conductive fillers.

[0186] As shown in Table 7, the samples without thermally conductive fillers (Comparative Examples 9-10) exhibited extremely low thermal conductivity (0.15-0.18 W / m·K), leading to a significant increase in total thermal resistance. Although the PMC coatings without fillers had higher phase change enthalpy (due to higher content of pure phase change components), the excessively high thermal resistance severely affected the heat transfer efficiency to the phase change material, significantly reducing the actual temperature control effect. Therefore, the addition of thermally conductive fillers is crucial for achieving the goal of high thermal conductivity and low thermal resistance.

[0187] (viii) Thermal conductivity analysis of thermally conductive gels on different ceramic substrates.

[0188] Figure 5 The comparison of thermal conductivity of thermally conductive gel coatings on three different ceramic substrates—Example 3 (Al2O3 + thermally conductive gel), Example 7 (AlN + thermally conductive gel), and Example 11 (Si3N4 + thermally conductive gel)—is presented visually. The test data shows that the thermal conductivity of the coating in Example 3 is 4.8 W / m·K, the coating in Example 7 is 5.5 W / m·K, and the coating in Example 11 is 5.0 W / m·K. The coating in Example 7 (AlN + thermally conductive gel) has the highest thermal conductivity, reaching 5.5 W / m·K, representing a 14.6% improvement over Example 3. This improvement is attributed to the aluminum nitride-zinc oxide composite filler system matched to the high thermal conductivity AlN ceramic substrate in the thermally conductive gel formulation: aluminum nitride filler (intrinsic thermal conductivity of about 200 W / m·K) serves as the dominant thermal phase, and zinc oxide filler (intrinsic thermal conductivity of about 30 W / m·K) serves as the auxiliary bridging phase. During the curing process, a double continuous thermally conductive network structure is formed with aluminum nitride as the skeleton and zinc oxide filling the gaps, which effectively reduces phonon scattering at the filler-matrix interface and achieves a significant improvement in the thermal conductivity of the coating.

[0189] A comprehensive comparison of the thermal conductivity of the thermally conductive gel coatings on the three substrates shows that they all remain at a relatively high level of 4.8-5.5 W / m·K, indicating that the thermally conductive gel coating formulation and preparation process of the present invention have good substrate versatility and can be fine-tuned for different ceramic substrates to fully release the thermal conductivity of the coating.

[0190] (ix) The thermally conductive gel coating and the PMC coating are "replaceable on demand" on the same ceramic substrate.

[0191] This invention provides two alternative functional coating schemes on the same ceramic substrate. For the same alumina ceramic sheet: if the operating condition is steady-state heat dissipation (such as a server CPU), a thermally conductive gel coating (Example 3, thermal resistance 0.18) is selected. If the operating condition is pulsed heat dissipation (such as an IGBT module), a PMC coating (Example 1, thermal resistance 0.28, but with phase change buffering) is selected. The substrate, pretreatment, and coating process are completely unified, allowing users to flexibly choose according to their application scenarios.

[0192] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A ceramic sheet material with high thermal conductivity and low thermal resistance, characterized in that, Includes a ceramic substrate and an upper functional coating applied to the upper surface of the ceramic substrate and / or a lower functional coating applied to the lower surface of the ceramic substrate; The ceramic substrate is selected from any one of alumina ceramic sheets, aluminum nitride ceramic sheets, and silicon nitride ceramic sheets; The upper and lower functional coatings are any combination of PMC phase change material coatings and thermally conductive gel coatings.

2. The high thermal conductivity and low thermal resistance ceramic sheet material according to claim 1, characterized in that, The PMC phase change material coating comprises a matrix resin, a phase change component, a thermally conductive filler, and functional additives. The matrix resin is selected from at least one of acrylate copolymers, silicone polymers, polyurethanes, and epoxy resins; The phase change component is selected from at least one of paraffin, fatty acids, polyols, polyethylene glycol, and n-alkanes; The thermally conductive filler is selected from at least one of alumina, aluminum nitride, boron nitride, silicon carbide, graphene, expanded graphite, and carbon nanotubes.

3. The high thermal conductivity and low thermal resistance ceramic sheet material according to claim 1, characterized in that, The thermally conductive gel coating comprises an organosilicon polymer matrix and a thermally conductive filler; The organosilicon polymer matrix is ​​selected from at least one of vinyl silicone oil and hydrogen-containing silicone oil; The thermally conductive filler is selected from at least one of alumina, aluminum nitride, boron nitride, zinc oxide, and silicon carbide.

4. The high thermal conductivity and low thermal resistance ceramic sheet material according to claim 1, characterized in that, The ceramic substrate has a thickness of 0.2-2.0 mm, and the functional coating has a thickness of 60-200 μm.

5. The high thermal conductivity and low thermal resistance ceramic sheet material according to claim 4, characterized in that, When the functional coating is a PMC phase change material coating, the coating thickness is 60-200 μm; when the functional coating is a thermally conductive gel coating, the coating thickness is 20-150 μm.

6. The high thermal conductivity and low thermal resistance ceramic sheet material according to claim 1, characterized in that, The ceramic substrate surface undergoes surface pretreatment before coating, and the surface pretreatment includes at least one of plasma treatment, silane coupling agent treatment, and acid-base etching treatment. The functional coating is applied to one side of the ceramic substrate, or simultaneously to both sides of the ceramic substrate.

7. The high thermal conductivity and low thermal resistance ceramic sheet material according to claim 2, characterized in that, In the PMC phase change material coating, the matrix resin has a mass fraction of 100 parts, the phase change component has a mass fraction of 40-100 parts, and the thermally conductive filler has a mass fraction of 50-200 parts. In the thermally conductive gel coating, the organosilicon polymer matrix is ​​100 parts by weight, and the thermally conductive filler is 200-500 parts by weight.

8. A method for preparing a high thermal conductivity, low thermal resistance ceramic sheet material as described in any one of claims 1-7, characterized in that, Includes the following steps: Step S1: Ceramic substrate surface pretreatment - The ceramic substrate surface is cleaned and then subjected to at least one of the following treatments: plasma treatment, silane coupling agent treatment, and acid-base etching treatment. Step S2: Preparation of functional coating slurry—Weigh out 100 parts by weight of matrix resin, 40-100 parts by weight of phase change component, and 50-200 parts by weight of thermally conductive filler for a PMC phase change material coating, or 100 parts by weight of organosilicon polymer matrix and 200-500 parts by weight of thermally conductive filler for a thermally conductive gel coating according to the formula; after mixing, dispersing, and vacuum degassing, the functional coating slurry is obtained; Step S3: Coating - The slurry obtained in step S2 is coated onto the ceramic substrate surface after the pretreatment in step S1 by at least one of the following methods: scraping, screen printing, spraying, dipping or dispensing. Step S4: Curing – The coated ceramic substrate is placed under heating conditions to cure, forming a functional coating.

9. The preparation method according to claim 11, characterized in that, In step S1, the plasma treatment uses atmospheric pressure plasma or low pressure plasma, the treatment time is 10-300s, and the treatment power is 50-500W; the coupling agent used in the silane coupling agent treatment is selected from at least one of KH550, KH560, KH570, and A-174. In step S4, the curing temperature is 80-150℃ and the curing time is 10-120min.

10. The application of a high thermal conductivity and low thermal resistance ceramic sheet material as described in any one of claims 1-7 in heat dissipation of high-power electronic devices, semiconductor packaging, integrated circuit thermal management, new energy vehicle electronic heat dissipation, 5G communication equipment, IGBT modules, LED packaging or power converters.

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