Highly thermally conductive composite sheet of multi-stage diamondized filler and method of making

Abstract

The present application relates to the technical field of heat conduction, in particular to a high-thermal-conductivity composite heat-conduction sheet with multi-stage diamondized filler and a preparation method thereof, and provides a preparation method of the high-thermal-conductivity composite heat-conduction sheet with multi-stage diamondized filler, which comprises the following steps: mixing a heat-conduction filler and a polymer matrix to obtain mixed slurry; wherein the heat-conduction filler comprises micron-level diamond microspheres, boron nitride microsheets, nano-diamond particles and heat-conduction spheres with a particle size smaller than the diamond microspheres; placing a reinforcing fiber mesh in a mold, injecting the mixed slurry into the mold, and performing a pressurized curing treatment on the mold; and obtaining a composite heat-conduction sheet after curing. The present application provides a high-thermal-conductivity composite heat-conduction sheet with multi-stage diamondized filler and a preparation method thereof, and can provide a composite heat-conduction sheet with excellent heat conduction performance.

Description

Technical Field

[0001] This invention relates to the field of thermal conductivity technology, and in particular to a high thermal conductivity composite thermal conductive sheet with multi-stage diamondized filler and its preparation method. Background Technology

[0002] Flexible thermal pads are another crucial thermal interface material (TIM). Compared to thermal grease, they offer advantages such as non-flowing, non-curing, ease of installation, and rework, making them widely used in applications with high reliability requirements.

[0003] Currently, high-performance thermal conductive sheets mostly use silicone rubber as the matrix and are filled with ceramic fillers such as alumina, boron nitride, and aluminum nitride. However, due to the intrinsic thermal conductivity of the fillers themselves and the upper limit of the filler content, their thermal conductivity is usually difficult to exceed 10 W / (m·K). Summary of the Invention

[0004] This invention provides a high thermal conductivity composite thermal conductive sheet with multi-stage diamondized filler and its preparation method, which can provide a composite thermal conductive sheet with excellent thermal conductivity.

[0005] In a first aspect, embodiments of the present invention provide a method for preparing a high thermal conductivity composite thermally conductive sheet with multi-stage diamondized filler, comprising:

[0006] A thermally conductive filler and a polymer matrix are mixed to obtain a mixed slurry; wherein the thermally conductive filler includes micron-sized diamond microspheres, boron nitride microplates, nanodiamond particles, and thermally conductive spheres with a particle size smaller than the diamond microspheres;

[0007] The reinforcing fiber mesh is placed in a mold, the mixed slurry is injected into the mold, and the mold is subjected to pressure curing.

[0008] After curing, a composite thermal conductive sheet is obtained.

[0009] In one possible design, prior to mixing the thermally conductive filler and the polymer matrix to obtain the mixed slurry, the following is also included:

[0010] A 100-300 nm metal layer is deposited on the surface of the diamond microspheres.

[0011] In one possible design, prior to mixing the thermally conductive filler and the polymer matrix to obtain the mixed slurry, the following is also included:

[0012] The boron nitride microplates, diamond nanoparticles, and the reinforcing fiber web are treated with a silane coupling agent.

[0013] In one possible design, the mixed slurry also includes 1-2% by total mass of crosslinking agent and inhibitor.

[0014] In one possible design, the mixed slurry comprises 15-25% by mass of the polymer matrix, 73-84% by mass of the thermally conductive filler, and 1-3% by mass of the reinforcing fiber web;

[0015] In the thermally conductive filler, the mass percentage of the diamond microspheres is 50-65%, the mass percentage of the boron nitride microplates is 10-15%, the mass percentage of the nanodiamond particles is 10-15%, and the mass percentage of the thermally conductive spheres is 10-20%.

[0016] In one possible design, the thermally conductive sphere comprises an alumina sphere;

[0017] The reinforcing fiber web is made of materials including glass fiber or polymer fiber.

[0018] In one possible design, the diamond microspheres have a particle size of 20-50 μm, the boron nitride microsheets have a planar size of 1-5 μm and a thickness of 50-200 nm, the nanodiamond particles have a particle size of 5-100 nm, the thermally conductive spheres have a particle size of 1-5 μm, and the reinforcing fiber mesh has a pore size of 100 μm.

[0019] In one possible design, the mixing of the thermally conductive filler and the polymer matrix to obtain a mixed slurry includes:

[0020] The diamond microspheres, polymer matrix and boron nitride microsheets are mixed to obtain a first slurry;

[0021] The thermally conductive spheres, polymer matrix, and diamond nanoparticles are mixed to obtain a second slurry.

[0022] The first slurry and the second slurry are mixed to obtain a mixed slurry.

[0023] In one possible design, the pressure for the pressure curing process is 0.1~1MPa, the direction is perpendicular to the sheet-like mold, the processing temperature is 125℃, and the time is 30min.

[0024] Secondly, embodiments of the present invention also provide a high thermal conductivity composite thermally conductive sheet with multi-stage diamondized filler, prepared according to any of the methods described above.

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] Diamond microspheres, as the main component of the thermally conductive filler, bear the primary function of heat conduction and dissipation. Two-dimensional, sheet-like boron nitride microplates act as bridges between the diamond microspheres, forming a thermally conductive network. This increases the contact between different thermally conductive fillers and the heat dissipation rate. Diamond nanospheres are distributed within this network, contacting both the boron nitride microplates and the diamond microspheres, further increasing the thermally conductive area. The thermally conductive spheres fill the tiny gaps in the network, adjusting rheology and cost.

[0027] Diamond microspheres are spherical particles with a relatively large particle size, exhibiting high fluidity and mobility in slurries. During pressure curing, a force is applied along the thickness direction of the mold. Under pressure, the diamond microspheres easily roll and rearrange, forming a chain-like structure along the pressure direction (i.e., thickness-direction orientation). This orientation directly constructs efficient thickness-direction heat conduction pathways, increasing the heat conduction efficiency on both sides of the heat-conducting sheet. Under pressure, the two-dimensional sheet-like structure easily distributes parallel to the surface of the heat-conducting sheet, vertically connecting different diamond microspheres to form a bridge. Simultaneously, this also increases the flexibility and bending resistance of the heat-conducting sheet. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a flowchart illustrating a method for preparing a high thermal conductivity composite thermally conductive sheet with multi-stage diamondized filler, as provided in an embodiment of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0031] Please refer to Figure 1 This invention provides a method for preparing a high thermal conductivity composite thermally conductive sheet with multi-stage diamondized filler, comprising:

[0032] A thermally conductive filler and a polymer matrix (preferably addition-type liquid silicone rubber or thermally conductive silicone gel) are mixed to obtain a mixed slurry; wherein the thermally conductive filler includes micron-sized diamond microspheres, boron nitride microplates, nanodiamond particles, and thermally conductive spheres with a particle size smaller than the diamond microspheres;

[0033] The reinforcing fiber mesh is placed in a mold, the mixed slurry is injected into the mold, and the mold is subjected to pressure curing.

[0034] After curing, a composite thermal conductive sheet is obtained.

[0035] Diamond microspheres, as the main component of the thermally conductive filler, bear the primary function of heat conduction and dissipation. Two-dimensional, sheet-like boron nitride microplates act as bridges between the diamond microspheres, forming a thermally conductive network. This increases the contact between different thermally conductive fillers and the heat dissipation rate. Diamond nanospheres are distributed within this network, contacting both the boron nitride microplates and the diamond microspheres, further increasing the thermally conductive area. The thermally conductive spheres fill the tiny gaps in the network, adjusting rheology and cost.

[0036] Diamond microspheres are spherical particles with a relatively large particle size, exhibiting high fluidity and mobility in slurries. During pressure curing, a force is applied along the thickness direction of the mold. Under pressure, the diamond microspheres easily roll and rearrange, forming a chain-like structure along the pressure direction (i.e., thickness-direction orientation). This orientation directly constructs efficient thickness-direction heat conduction pathways, increasing the heat conduction efficiency on both sides of the heat-conducting sheet. Under pressure, the two-dimensional sheet-like structure easily distributes parallel to the surface of the heat-conducting sheet, vertically connecting different diamond microspheres to form a bridge. Simultaneously, this also increases the flexibility and bending resistance of the heat-conducting sheet.

[0037] It should be noted that boron nitride microplates, nanodiamond particles, and thermally conductive spheres are used to reduce phonon scattering and interfacial thermal resistance, thereby optimizing the thermal conductivity network. However, they themselves do not constitute the dominant thermal path in the thickness direction.

[0038] In some embodiments of the present invention, before mixing the thermally conductive filler and the polymer matrix to obtain the mixed slurry, the method further includes:

[0039] A metal layer of 100~300nm (e.g., 100nm, 120nm, 140nm, 160nm, 180nm, 200nm, 220nm, 240nm, 260nm, 280nm or 300nm) is deposited on the surface of the diamond microspheres.

[0040] The metal layer can be obtained by plating with silver or copper. The metal layer enhances the electrical and thermal conductivity of the thermally conductive filler. At the same time, the metal layer has good interfacial compatibility with the polymer matrix. Most importantly, under pressure, the metallized surface is more likely to form a tight contact, reducing the contact thermal resistance.

[0041] It is important to emphasize that when vertical pressure is applied to the slurry in the mold, the slurry is squeezed and flows laterally in all directions. During this flow, larger, rigid particles (such as metallized diamond microspheres) are more easily "squeezed" to the end of the flow path, i.e., at the upper and lower interfaces of the mold, due to their greater inertia. This process is similar to the "particle segregation" phenomenon seen in some processes. The purpose of this design is very clear: to form an interface with low contact thermal resistance. When the heatsink is sandwiched between the chip and the heat sink, these two diamond-rich surface layers are in direct contact with the metal surface, achieving an approximate "metal-to-metal" contact and significantly reducing interfacial thermal resistance.

[0042] In some embodiments of the present invention, before mixing the thermally conductive filler and the polymer matrix to obtain the mixed slurry, the method further includes:

[0043] The boron nitride microplates, diamond nanoparticles, and the reinforcing fiber web are treated with a silane coupling agent.

[0044] In this embodiment, the silane coupling agent may be KH-550.

[0045] In some embodiments of the present invention, the mixed slurry further includes 1-2% by total mass of crosslinking agent and inhibitor.

[0046] In some embodiments of the present invention, the mixed slurry comprises 15-25% by mass of the polymer matrix (e.g., 15%, 18%, 20%, 22%, 24%, or 25%), 73-84% by mass of the thermally conductive filler (e.g., 74%, 76%, 78%, 80%, 82%, or 84%), and 1-3% by mass of the reinforcing fiber web (e.g., 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2.0%, 2.2%, 2.4%, 2.6%, 2.8%, or 3%).

[0047] In the thermally conductive filler, the mass percentage of the diamond microspheres is 50-65% (e.g., it can be 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, or 65%), the mass percentage of the boron nitride microsheets is 10-15%, the mass percentage of the nanodiamond particles is 10-15% (e.g., it can be 10%, 12%, 14%, or 15%), and the mass percentage of the thermally conductive spheres is 10-20% (e.g., it can be 10%, 12%, 14%, 16%, 18%, or 20%).

[0048] In some embodiments of the present invention, the thermally conductive sphere comprises an alumina sphere;

[0049] The reinforcing fiber web is made of materials including glass fiber or polymer fiber.

[0050] In some embodiments of the present invention, the diamond microspheres have a particle size of 20-50 μm (e.g., 20 μm, 24 μm, 26 μm, 28 μm, 30 μm, 32 μm, 34 μm, 36 μm, 38 μm, 40 μm, 42 μm, 44 μm, 46 μm, 48 μm, or 50 μm), the boron nitride microplates have a planar dimension of 1-5 μm (e.g., 1 μm, 2 μm, 3 μm, 4 μm, or 5 μm), and a thickness of 50-200 nm (e.g., 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 180 nm, or 200 nm), and the nanodiamond particles have a particle size of 5-100 nm (e.g., 5 nm, 10 nm, 20 nm, or 50 μm). The particle size of the thermally conductive spheres is 1~5μm (e.g., 1μm, 2μm, 3μm, 4μm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm), and the pore size of the reinforcing fiber mesh is 100μm.

[0051] In some embodiments of the present invention, the mixing of thermally conductive filler and polymer matrix to obtain a mixed slurry includes:

[0052] The diamond microspheres, polymer matrix and boron nitride microsheets are mixed to obtain a first slurry;

[0053] The thermally conductive spheres, polymer matrix, and diamond nanoparticles are mixed to obtain a second slurry.

[0054] The first slurry and the second slurry are mixed to obtain a mixed slurry.

[0055] Different types of packing materials, due to their significant differences in size, shape, surface energy, and density, require different mixing processes and media environments to achieve optimal dispersion. Mixing all components at once may result in some components being neglected, making it impossible to construct the ideal "multi-stage packing network" designed in the patent. Therefore, mixing is carried out in a distributed manner.

[0056] Adding all polymers, fillers, and additives at once and mixing them intensively (such as through a three-roll mill) may have the following adverse effects:

[0057] Uneven dispersion: Boron nitride microplates (h-BN) may not be fully opened, and nanodiamonds and spherical alumina may be squeezed into the gaps of large fillers, forming "dead zones" and failing to effectively play their bridging and filling roles.

[0058] Filler damage: Under the powerful three-roll grinding force, the hard spherical alumina will act like an "abrasive" and severely scratch the metal coating on the surface of the primary diamond microspheres, greatly increasing the interfacial thermal resistance.

[0059] Process failure: Adding all fillers simultaneously will result in excessively high slurry viscosity, which may prevent effective mixing or grinding, and could even damage the equipment. Additives will also be difficult to distribute evenly, affecting curing.

[0060] Poor network structure: It is impossible to form an ideal hierarchical structure that first enriches around the fiber web and then orients under pressure, resulting in a significant decrease in the thermal conductivity and mechanical properties of the final product.

[0061] In some embodiments of the present invention, the pressure of the pressure curing process is 0.1~1MPa, the direction is perpendicular to the sheet-like mold, the processing temperature is 125℃, and the time is 30min.

[0062] This invention also provides a high thermal conductivity composite thermally conductive sheet with multi-stage diamondized filler, prepared according to any of the methods described above.

[0063] To more clearly illustrate the technical solution and advantages of the present invention, several embodiments are described in detail below.

[0064] Example 1

[0065] Formula (by weight):

[0066] Addition-cured liquid silicone rubber (16%)

[0067] Thermally conductive filler (81%):

[0068] Silver-coated diamond microspheres (40μm): accounting for 60% (48.6%) of the total filler weight.

[0069] KH-550 treated nanodiamond (20nm) + h-BN microflakes (5μm diameter, 0.1μm thickness) (1:1 weight ratio): accounting for 25% (i.e. 20.25%) of the total filler weight.

[0070] Spherical alumina (3μm): accounts for 15% (12.15%) of the total filler weight.

[0071] Crosslinking agent, inhibitor: 1%

[0072] KH-550 treated fiberglass mesh (100μm mesh size): 2%

[0073] Preparation method:

[0074] Preparation of the first slurry: Half of the silicone rubber is mixed with crosslinking agent, inhibitor, spherical alumina and nano diamond, and degassed by planetary stirring.

[0075] Preparation of the second slurry: Mix the other half of the silicone rubber with primary silver diamond microparticles and h-BN micro flakes, and grind three times with a three-roll mill.

[0076] Mix the first and second slurries and stir at low speed to obtain the final mixed slurry.

[0077] The fiber web is fixed in a 1mm thick mold, and the mixed slurry is injected.

[0078] Apply a pressure of 0.5 MPa and heat at 125°C for 30 minutes to cure.

[0079] Demolding yields a 1.0mm thick heat-conducting sheet.

[0080] Test results: According to the Hot Disk method, the thermal conductivity of the heat-conducting sheet in this embodiment is 38.5 W / (m·K) in the thickness direction, the hardness (Shore 00) is 60, and the compression ratio is >15%, which shows excellent performance.

[0081] Example 2

[0082] Formula (by weight):

[0083] Organosilicon gel (25%)

[0084] Thermally conductive filler (73%):

[0085] Silver-coated diamond microspheres (20μm): accounting for 50% (36.5%) of the total weight of the filler.

[0086] KH-550 treated nanodiamond (5nm) + h-BN microflakes (2.5μm diameter, 0.05μm thickness) (1:1 weight ratio): accounting for 20% (14.6%) of the total filler weight.

[0087] Spherical alumina (5μm): accounts for 20% (14.6%) of the total filler weight.

[0088] Crosslinking agent, inhibitor: 1%

[0089] KH-550 treated fiberglass mesh (100μm mesh size): 1%

[0090] Preparation method:

[0091] Preparation of the first slurry: Half of the silicone rubber is mixed with crosslinking agent, inhibitor, spherical alumina and nano diamond, and degassed by planetary stirring.

[0092] Preparation of the second slurry: Mix the other half of the silicone rubber with primary silver diamond microparticles and h-BN micro flakes, and grind three times with a three-roll mill.

[0093] Mix the first and second slurries and stir at low speed to obtain the final mixed slurry.

[0094] The fiber web is fixed in a 1mm thick mold, and the mixed slurry is injected.

[0095] Apply a pressure of 0.1 MPa and heat at 125°C for 30 minutes to cure.

[0096] Demolding yields a 1.0mm thick heat-conducting sheet.

[0097] Test results: According to the Hot Disk method, the thermal conductivity of the heat-conducting sheet in this embodiment is 30.0 W / (m·K) in the thickness direction, the hardness (Shore 00) is 50, and the compression ratio is >20%, which shows excellent performance.

[0098] Example 3

[0099] Formula (by weight):

[0100] Organosilicon gel (25%)

[0101] Thermally conductive filler (70%):

[0102] Silver-coated diamond microspheres (20μm): accounting for 65% (45.5%) of the total weight of the filler.

[0103] KH-550 treated nanodiamond (100nm) + h-BN microflakes (5μm diameter, 0.1μm thickness) (1:1 weight ratio): accounting for 30% (21%) of the total filler weight.

[0104] Spherical alumina (5μm): accounts for 20% (14%) of the total filler weight.

[0105] Crosslinking agent, inhibitor: 2%

[0106] KH-550 treated fiberglass mesh (100μm mesh): 3%

[0107] Preparation method:

[0108] Preparation of the first slurry: Half of the silicone rubber is mixed with crosslinking agent, inhibitor, spherical alumina and nano diamond, and degassed by planetary stirring.

[0109] Preparation of the second slurry: Mix the other half of the silicone rubber with primary silver diamond microparticles and h-BN micro flakes, and grind three times with a three-roll mill.

[0110] Mix the first and second slurries and stir at low speed to obtain the final mixed slurry.

[0111] The fiber web is fixed in a 1mm thick mold, and the mixed slurry is injected.

[0112] Apply 1 MPa pressure and heat at 125°C for 30 minutes to cure.

[0113] Demolding yields a 1.0mm thick heat-conducting sheet.

[0114] Test results: According to the Hot Disk method, the thermal conductivity of the heat-conducting sheet in this embodiment is 40.0 W / (m·K) in the thickness direction, the hardness (Shore 00) is 65, and the compression ratio is >10%, which shows excellent performance.

[0115] Comparative Example 1

[0116] Formula (by weight):

[0117] Addition-cured liquid silicone rubber (16%)

[0118] Thermally conductive filler (81%):

[0119] Silver-coated diamond microspheres (40μm): accounting for 60% (48.6%) of the total filler weight.

[0120] KH-550 treated nanodiamond (20nm) + h-BN microflakes (5μm diameter, 0.1μm thickness) (1:1 weight ratio): accounting for 25% (i.e. 20.25%) of the total filler weight.

[0121] Spherical alumina (3μm): accounts for 15% (12.15%) of the total filler weight.

[0122] Crosslinking agent, inhibitor: 1%

[0123] KH-550 treated fiberglass mesh (100μm mesh size): 2%

[0124] Preparation method:

[0125] Preparation of the first slurry: Half of the silicone rubber is mixed with crosslinking agent, inhibitor, spherical alumina and nano diamond, and degassed by planetary stirring.

[0126] Preparation of the second slurry: Mix the other half of the silicone rubber with primary silver diamond microparticles and h-BN micro flakes, and grind three times with a three-roll mill.

[0127] Mix the first and second slurries and stir at low speed to obtain the final mixed slurry.

[0128] The fiber web is fixed in a 1mm thick mold, and the mixed slurry is injected.

[0129] Under normal pressure, heat at 125°C for 30 minutes to cure.

[0130] Demolding yields a 1.0mm thick heat-conducting sheet.

[0131] Test results: According to the Hot Disk method, the thermal conductivity of the heat-conducting sheet in this embodiment is 20 W / (m·K) in the thickness direction, the hardness (Shore 00) is 55, and the compression ratio is >20%, which shows excellent performance.

[0132] Comparative Example 1 is essentially the same as Example 1, except that no pressure was applied.

[0133] Comparative Example 2

[0134] Formula (by weight):

[0135] Addition-cured liquid silicone rubber (16%)

[0136] Thermally conductive filler (81%):

[0137] Silver-coated diamond microspheres (40μm): accounting for 60% (48.6%) of the total filler weight.

[0138] Spherical alumina (3μm): accounts for 40% (32.4%) of the total filler weight.

[0139] Crosslinking agent, inhibitor: 1%

[0140] KH-550 treated fiberglass mesh (100μm mesh size): 2%

[0141] Preparation method:

[0142] Preparation of the first slurry: Mix half of the silicone rubber with crosslinking agent, inhibitor, and spherical alumina, and degas by planetary stirring.

[0143] Preparation of the second slurry: Mix the other half of the silicone rubber with the first-grade silver diamond microparticles and grind them three times with a three-roll mill.

[0144] Mix the first and second slurries and stir at low speed to obtain the final mixed slurry.

[0145] The fiber web is fixed in a 1mm thick mold, and the mixed slurry is injected.

[0146] Apply a pressure of 0.5 MPa and heat at 125°C for 30 minutes to cure.

[0147] Demolding yields a 1.0mm thick heat-conducting sheet.

[0148] Test results: According to the Hot Disk method, the thermal conductivity of the heat-conducting sheet in this embodiment is 25.0 W / (m·K) in the thickness direction, the hardness (Shore 00) is 60, and the compression ratio is >15%, which shows excellent performance.

[0149] Comparative Example 3 is basically the same as Example 1, except that the thermally conductive filler contains only diamond microspheres and spherical alumina.

[0150] Comparative Example 4

[0151] Formula (by weight):

[0152] Addition-cured liquid silicone rubber (16%)

[0153] Thermally conductive filler (81%):

[0154] Silver-coated diamond microspheres (40μm): accounting for 60% (48.6%) of the total filler weight.

[0155] KH-550 treated nanodiamonds (20nm) account for 25% (20.25%) of the total filler weight.

[0156] Spherical alumina (3μm): accounts for 15% (12.15%) of the total filler weight.

[0157] Crosslinking agent, inhibitor: 1%

[0158] KH-550 treated fiberglass mesh (100μm mesh size): 2%

[0159] Preparation method:

[0160] Preparation of the first slurry: Half of the silicone rubber is mixed with crosslinking agent, inhibitor, spherical alumina and nano diamond, and degassed by planetary stirring.

[0161] Preparation of the second slurry: Mix the other half of the silicone rubber with the first-grade silver diamond microparticles and grind them three times with a three-roll mill.

[0162] Mix the first and second slurries and stir at low speed to obtain the final mixed slurry.

[0163] The fiber web is fixed in a 1mm thick mold, and the mixed slurry is injected.

[0164] Apply a pressure of 0.5 MPa and heat at 125°C for 30 minutes to cure.

[0165] Demolding yields a 1.0mm thick heat-conducting sheet.

[0166] Test results: According to the Hot Disk method, the thermal conductivity of the heat-conducting sheet in this embodiment is 28.0 W / (m·K) in the thickness direction, the hardness (Shore 00) is 60, and the compression ratio is >15%, which shows excellent performance.

[0167] Comparative Example 4 is essentially the same as Example 1, except that it does not contain boron nitride microplates.

[0168] Comparative Example 5

[0169] Formula (by weight):

[0170] Addition-cured liquid silicone rubber (16%)

[0171] Thermally conductive filler (81%):

[0172] Silver-coated diamond microspheres (40μm): accounting for 60% (48.6%) of the total filler weight.

[0173] KH-550 treated h-BN microplates (5μm diameter, 0.1μm thickness): accounting for 25% (i.e. 20.25%) of the total filler weight.

[0174] Spherical alumina (3μm): accounts for 15% (12.15%) of the total filler weight.

[0175] Crosslinking agent, inhibitor: 1%

[0176] KH-550 treated fiberglass mesh (100μm mesh size): 2%

[0177] Preparation method:

[0178] Preparation of the first slurry: Mix half of the silicone rubber with crosslinking agent, inhibitor, and spherical alumina, and degas by planetary stirring.

[0179] Preparation of the second slurry: Mix the other half of the silicone rubber with primary silver diamond microparticles and h-BN micro flakes, and grind three times with a three-roll mill.

[0180] Mix the first and second slurries and stir at low speed to obtain the final mixed slurry.

[0181] The fiber web is fixed in a 1mm thick mold, and the mixed slurry is injected.

[0182] Apply a pressure of 0.5 MPa and heat at 125°C for 30 minutes to cure.

[0183] Demolding yields a 1.0mm thick heat-conducting sheet.

[0184] Test results: According to the Hot Disk method, the thermal conductivity of the heat-conducting sheet in this embodiment is 30.0 W / (m·K) in the thickness direction, the hardness (Shore 00) is 60, and the compression ratio is >15%, which shows excellent performance.

[0185] Comparative Example 5 is basically the same as Example 1, except that no nanodiamond particles were added.

[0186] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high thermal conductivity composite thermally conductive sheet with multi-stage diamondized filler, characterized in that, include: A thermally conductive filler and a polymer matrix are mixed to obtain a mixed slurry. The thermally conductive filler comprises micron-sized diamond microspheres, boron nitride microplates, nanodiamond particles, and thermally conductive spheres with a particle size smaller than the diamond microspheres. The mixed slurry comprises 15-25% by mass of the polymer matrix and 73-84% by mass of the thermally conductive filler. Specifically, the thermally conductive filler comprises 50-65% by mass of the diamond microspheres, 10-15% by mass of the boron nitride microplates, 10-15% by mass of the nanodiamond particles, and 10-20% by mass of the thermally conductive spheres. The diamond microspheres have a particle size of 20-50 μm, the boron nitride microplates have a planar dimension of 1-5 μm and a thickness of 50-200 nm, the nanodiamond particles have a particle size of 5-100 nm, and the thermally conductive spheres have a particle size of 1-5 μm. The reinforcing fiber mesh is placed in a mold, the mixed slurry is injected into the mold, and the mold is subjected to pressure curing treatment. The pressure of the pressure curing treatment is 0.1~1MPa, and the direction is perpendicular to the sheet-like mold, so that the diamond microspheres form a chain-like structure along the pressure direction. After curing, a composite thermal conductive sheet is obtained.

2. The preparation method according to claim 1, characterized in that, Before mixing the thermally conductive filler and the polymer matrix to obtain the mixed slurry, the method further includes: A 100-300 nm metal layer is deposited on the surface of the diamond microspheres.

3. The preparation method according to claim 1, characterized in that, Before mixing the thermally conductive filler and the polymer matrix to obtain the mixed slurry, the method further includes: The boron nitride microplates, diamond nanoparticles, and the reinforcing fiber web are treated with a silane coupling agent.

4. The preparation method according to claim 1, characterized in that, The mixed slurry also includes 1-2% by total mass of crosslinking agent and inhibitor.

5. The preparation method according to claim 1 or 4, characterized in that, The mass percentage of the reinforcing fiber web is 1-3%.

6. The preparation method according to claim 1, characterized in that, The thermally conductive spheres include alumina spheres; The reinforcing fiber web is made of materials including glass fiber or polymer fiber.

7. The preparation method according to claim 1, characterized in that, The pore size of the reinforcing fiber web is 100 μm.

8. The preparation method according to claim 1, characterized in that, The process of mixing thermally conductive filler and polymer matrix to obtain a mixed slurry includes: The diamond microspheres, polymer matrix and boron nitride microsheets are mixed to obtain the first slurry; The thermally conductive spheres, polymer matrix, and diamond nanoparticles are mixed to obtain a second slurry. The first slurry and the second slurry are mixed to obtain a mixed slurry.

9. The preparation method according to claim 1, characterized in that, The pressure curing process is carried out at a temperature of 125°C for 30 minutes.

10. A high thermal conductivity composite thermal conductive sheet with multi-stage diamondized filler, characterized in that, Prepared according to any one of claims 1-9.

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