Thermal interface material

Abstract

A thermal interface material includes a hot melt material and an inner filler. The hot melt material comprises an olefin-acrylate copolymer having a melt flow index higher than 110 g / 10 min. And the inner filler comprises a plurality of heat-conducting fillers and high-dispersity fillers. Based on the volume of the thermal interface material being 100%, the volume percentage of the olefin-acrylate copolymer is 25%-35%, and the volume percentage of the heat-conducting filler and the high-dispersity filler is 65%-75%.

Description

Technical Field

[0001] This invention relates to a thermal interface material, and more specifically, to a thermal interface material with good durability and thermal conductivity. Background Technology

[0002] Electronic components (such as light-emitting diodes or other semiconductor components) generate heat during use, and when this heat accumulates to a certain level, it significantly impairs their performance. Therefore, heat sinks (such as heat sink fins) are often installed on the surface of electronic components to reduce heat buildup. To further reduce the contact thermal resistance between the electronic component and the heat sink, a thermal interface material can be added between them.

[0003] Traditionally, thermal interface materials include thermally conductive grease, thermally conductive gel, thermally conductive pads, and phase change materials. However, these materials often use silicone resin as their base material, which can lead to oil seepage during use. When phase change materials are used, the issue of lifespan arises. Lifespan refers to the number of high-temperature shocks the thermal interface material can withstand without damage or leakage. Phase change materials typically have melting points below 70°C. When the ambient temperature exceeds their melting point, they turn into a liquid, causing leakage from between electronic components and the heat sink. Alternatively, when the ambient temperature approaches their melting point, phase change materials can easily soften and deform, causing structural damage. Even with increased melting points, the high fluidity issue at or above the melting point persists. More importantly, while addressing all these issues, good thermal conductivity of the thermal interface material must still be maintained.

[0004] For example, to maintain good thermal conductivity, conventional thermal interface materials add two thermally conductive fillers with different average or median particle sizes (hereinafter referred to as the first thermally conductive filler and the second thermally conductive filler) to increase the filling rate of the thermally conductive filler. However, at the microscopic level, the first thermally conductive filler (or the second thermally conductive filler) is actually and inevitably still composed of many particles of different sizes. This results in a less than expected filling effect and also affects the overall structure and thermal conductivity of the thermal interface material. Therefore, thermal interface materials must contain a variety of additional additives (such as organic solvents, crosslinking agents, or other compounds) to improve the overall performance of the thermal interface material. It can be seen that traditional thermal interface materials not only cannot accurately control the composition of the thermally conductive filler, but also have a high degree of complexity in formulation design. Summary of the Invention

[0005] According to one embodiment of the present invention, a thermal interface material comprises a hot-melt material and an internal filler. The hot-melt material comprises an olefin-acrylate copolymer. The melt flow index of the olefin-acrylate copolymer is higher than 110 g / 10 min. The olefin-acrylate copolymer accounts for 25% to 35% of the volume of the thermal interface material, which is 100% of the total volume. The internal filler comprises various thermally conductive fillers and highly dispersible fillers. These thermally conductive fillers and highly dispersible fillers account for 65% to 75% of the volume of the thermal interface material, which is 100% of the total volume of the total volume.

[0006] According to some embodiments, the olefin-acrylate copolymer has a melting point below 70°C and a melt flow index between 110 g / 10 min and 500 g / 10 min. The olefin-acrylate copolymer is represented by the following formula (I): R can be selected freely from COOCH3, COOC2H5, COOC4H9, and COOC6H. 13 The groups formed by these groups. m is between 500 and 3000, and n is between 300 and 2000. m is greater than n.

[0007] According to some embodiments, the volume percentage of highly dispersible filler is 1% to 15% of the internal filler volume, which is 100%. The maximum particle size of the highly dispersible filler is less than 1.5 μm.

[0008] According to some embodiments, the highly dispersible filler comprises titanium oxide. The titanium oxide is selected from the group consisting of rutile titanium dioxide and unavoidable impurities. The rutile titanium dioxide accounts for more than 90% by weight, based on 100% of the titanium oxide.

[0009] According to some embodiments, these thermally conductive fillers include a first thermally conductive filler and a second thermally conductive filler. The maximum particle size of the first thermally conductive filler is less than 10 μm. The maximum particle size of the second thermally conductive filler is less than 50 μm.

[0010] According to some embodiments, the maximum particle size of the first thermally conductive filler is between 8 μm and 10 μm. Based on the volume of the inner filler being 100%, the first thermally conductive filler occupies 31% to 42% of the volume. The maximum particle size of the second thermally conductive filler is between 40 μm and 50 μm. Based on the volume of the inner filler being 100%, the second thermally conductive filler occupies 54% to 62% of the volume.

[0011] According to some embodiments, the first thermally conductive filler and the second thermally conductive filler are selected from the group consisting of aluminum nitride, aluminum oxide, boron nitride, silicon carbide and magnesium oxide.

[0012] According to some embodiments, the maximum particle size of these thermally conductive fillers is less than 50 μm, while the maximum particle size of the highly dispersible fillers is less than 1.5 μm. When the thickness of the thermal interface material is between 0.05 mm and 0.21 mm, the thermal resistance of the thermal interface material is 0.07 cm. 2 ·℃ / W to 0.5cm 2 ·℃ / W, while the thermal conductivity ranges from 3W / m·K to 81W / m·K.

[0013] According to some embodiments, when the thickness of the thermal interface material is between 0.06 mm and 0.15 mm, the thermal resistance of the thermal interface material is 0.08 cm. 2 ·℃ / W to 0.24cm 2 The temperature is ℃ / W, while the thermal conductivity ranges from 11.24 W / m·K to 80.08 W / m·K.

[0014] According to some embodiments, after the first weathering treatment, the thermal interface material has a thickness of 0.08 cm. 2 ·℃ / W to 0.24cm 2 Thermal resistance of ·℃ / W and thermal conductivity ranging from 11.24W / m·K to 80.08W / m·K. The first weathering treatment involves placing the thermal interface material at 85℃ and 85% humidity for 500 hours.

[0015] According to some embodiments, after the second weathering treatment, the thermal interface material has a thickness of 0.1 cm. 2 ·℃ / W to 0.31cm 2 Thermal resistance of ·℃ / W and thermal conductivity ranging from 5.62W / m·K to 66.4W / m·K. The second weathering treatment involves placing the thermal interface material at 125℃ for 500 hours.

[0016] According to some embodiments, the thickness of the thermal interface material is greater than 0.1 mm, and the operability of the thermal interface material is at least 2 times. The operability of the thermal interface material is defined as the number of times the thermal interface material can be verified according to ASTM D5470 without breakage.

[0017] According to some embodiments, the thickness of the thermal interface material is greater than 0.15 mm, and the thermal interface material is operable at least 5 times.

[0018] According to one embodiment of the present invention, an electronic device includes a heat sink, an electronic component, and the aforementioned thermal interface material. The heat sink has a front side and a back side opposite to the front side. The electronic component has a front side and a back side opposite to the front side. The back side of the electronic component faces the back side of the heat sink. The thermal interface material is disposed between the heat sink and the electronic component, simultaneously adhering to the back side of both the heat sink and the back side of the electronic component.

[0019] According to some embodiments, in the thermal interface materials of electronic devices, the olefin-acrylate copolymer has a melting point below 70°C and a melt flow index between 110 g / 10 min and 500 g / 10 min. The olefin-acrylate copolymer is represented by the following formula (I): R can be selected freely from COOCH3, COOC2H5, COOC4H9, and COOC6H. 13 The groups formed by these groups. m is between 500 and 3000, and n is between 300 and 2000. m is greater than n.

[0020] According to some embodiments, in the thermal interface material of an electronic device: the highly dispersible filler comprises a titanium oxide, selected from the group consisting of rutile titanium dioxide and unavoidable impurities; the rutile titanium dioxide accounts for more than 90% by weight of 100% of the titanium oxide; the highly dispersible filler accounts for 1% to 15% by volume of 100% of the internal filler; and the maximum particle size of the highly dispersible filler is less than 1.5 μm.

[0021] According to some embodiments, in electronic devices, the thermal interface material contains thermally conductive fillers comprising a first thermally conductive filler and a second thermally conductive filler. The maximum particle size of the first thermally conductive filler is between 8 μm and 10 μm. The first thermally conductive filler occupies 31% to 42% of the volume of the internal filler, which is 100% of the total volume. The maximum particle size of the second thermally conductive filler is between 40 μm and 50 μm. The second thermally conductive filler occupies 54% to 62% of the volume of the internal filler, which is 100% of the total volume.

[0022] According to some embodiments, in electronic devices, the first and second thermally conductive fillers of the thermal interface material are selected from the group consisting of aluminum nitride, aluminum oxide, boron nitride, silicon carbide and magnesium oxide.

[0023] According to some embodiments, in the thermal interface material of electronic devices, the maximum particle size of these thermally conductive fillers is less than 50 μm, while the maximum particle size of the highly dispersible fillers is less than 1.5 μm. When the thickness of the thermal interface material is between 0.05 mm and 0.21 mm, the thermal resistance of the thermal interface material is 0.07 cm. 2 ·℃ / W to 0.5cm 2 ·℃ / W, while the thermal conductivity ranges from 3W / m·K to 81W / m·K.

[0024] According to some embodiments, in electronic devices, the thickness of the thermal interface material is greater than 0.1 mm, and the thermal interface material is operable for at least two cycles. The operability of the thermal interface material is defined as the number of times the thermal interface material can be verified according to ASTM D5470 without breakage. Attached Figure Description

[0025] Figure 1 This shows a cross-sectional schematic diagram of a thermal interface material;

[0026] Figure 2 A cross-sectional view showing the thermal interface material of the present invention; and

[0027] Figure 3 A cross-sectional view of the electronic device of the present invention is shown. Detailed Implementation

[0028] To make the above and other technical contents, features and advantages of the present invention more apparent and understandable, relevant embodiments are provided below, and detailed descriptions are given in conjunction with the accompanying drawings.

[0029] This invention introduces a polymer melting material (PMM), also known as a thermally molten material, into the thermal interface material. Even in environments exceeding its melting point, the thermally molten material maintains low fluidity, thus preserving the stability of the overall structure. In other words, the thermally molten material can be rapidly cooled through changes in its physical state without compromising its durability (such as the aforementioned number of uses). Furthermore, the thermally molten material's low fluidity does not make it difficult to adhere to uneven surfaces. Additionally, to maintain good thermal conductivity in the thermal interface material, this invention incorporates various fillers. The thermally molten material already possesses stable physicochemical properties, and these fillers exhibit excellent compatibility with it, thus eliminating the need for additional additives in the thermal interface material.

[0030] For information on the various packing materials mentioned above, please refer to [link / reference]. Figure 1 and Figure 2 .

[0031] Figure 1 This shows a cross-sectional view of a thermal interface material 100. The thermal interface material 100 comprises a polymer 1 and a thermally conductive filler 2. The thermal interface material 100 is a composite material, with the polymer 1 as the base material and the thermally conductive filler 2 as a reinforcing material. Figure 1 As shown, the thermally conductive filler 2 is composed of multiple particles. Ideally, to maintain structural consistency and facilitate adjustment of the composition ratio, it would be desirable for all particles of the thermally conductive filler 2 to have the same size. If gaps G still exist between the particles, smaller thermally conductive fillers matching the size of gap G can be added at most. However, in reality, it is impossible for the particles of the thermally conductive filler 2 to be completely uniform in size during production. In other words, the gaps G formed by the particles are of different sizes, which makes it difficult to control the contact thermal resistance between particles, thereby affecting the overall thermal conductivity of the thermal interface material 100.

[0032] In view of this, the present invention additionally incorporates a highly dispersible filler to solve the aforementioned problem regarding the contact thermal resistance between fillers, while also simplifying the formulation. The thermal interface material of the present invention does not require a wet process for production, therefore it does not contain organic solvents used to dissolve the polymer and will not pollute the environment. Furthermore, the present invention does not contain crosslinking agents or other silicon-containing compounds. Please continue to refer to... Figure 2 .

[0033] Figure 2 This diagram shows a cross-sectional view of the thermal interface material 200 of the present invention. The thermal interface material 200 includes a hot-melt material 10 and an inner filler. The inner filler includes a first thermally conductive filler 20, a second thermally conductive filler 30, and a highly dispersible filler 40. As mentioned above, each filler is composed of multiple particles of varying sizes. For example, the first thermally conductive filler 20 has small particles 20a with smaller particle sizes and large particles 20b with larger particle sizes. Thus, the first thermally conductive filler 20 creates many gaps of varying sizes. Of course, the second thermally conductive filler 30 and the highly dispersible filler 40 are also composed of multiple particles, and therefore exhibit the same particle size distribution. To avoid excessive visual clutter, only similar or approximate sizes are shown here. Through testing, the present invention has observed that the contact thermal resistance between particles mainly depends on the largest particle. If the composition ratio of the filler is adjusted using the average particle size or median particle size as an indicator, too many particles with the largest particle size will be unable to fill the gaps, resulting in unpredictable performance of the thermal interface material 200. Accordingly, all fillers in this invention use maximum particle size as an indicator, thereby adjusting the composition ratio of the fillers. In the thermal interface material 200, this invention uses a first thermally conductive filler 20 and a second thermally conductive filler 30 with different maximum particle sizes dispersed in the hot-melt material 10, and then fills most of the remaining small gaps with a highly dispersible filler 40 with an extremely small maximum particle size. For specific details regarding the hot-melt material 10 and the internal fillers, please refer to the following text.

[0034] The hot melt material 10 comprises an olefin-acrylate copolymer. The melt flow index of the olefin-acrylate copolymer is between 110 g / 10 min and 500 g / 10 min, while its melting point is below 70°C. The hot melt material 10 of the present invention will not leak due to high temperatures and can also tightly fill the gaps between interfaces. For example, when the melt flow index is below 110 g / 10 min, the fluidity of the hot melt material 10 will be too low. As a result, the structure of the hot melt material 10 will be too rigid, causing the thermal interface material 200 to be unable to reliably fill the gaps between the contact surfaces of the two components, resulting in excessively high contact thermal resistance between the two components. When the melt flow index is above 500 g / 10 min, the aforementioned problems of overflow and breakage will occur. In one embodiment, the aforementioned melt flow index is between 110 g / 10 min and 500 g / 10 min, and may be, for example, 110 g / 10 min, 150 g / 10 min, 170 g / 10 min, 200 g / 10 min, 290 g / 10 min, 320 g / 10 min, 350 g / 10 min, 400 g / 10 min, 450 g / 10 min, or 500 g / 10 min. Preferably, the melt flow index is between 110 g / 10 min and 150 g / 10 min. If the melt flow index is below 150 g / 10 min, the thermal interface material 200, even in ultra-thin cases (e.g., with a thickness of 0.06 mm), is less prone to excessive deformation or breakage due to high temperatures.

[0035] In addition, olefin-acrylate copolymers are represented by the following formula (I): R can be selected freely from COOCH3, COOC2H5, COOC4H9, and COOC6H. 13 The groups consist of m, which is 500 to 3000, and n, which is 300 to 2000. m is greater than n. Furthermore, based on the volume of the thermal interface material as 100%, the volume percentage of the olefin-acrylate copolymer is 25% to 35%, for example, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, or 35%. In the olefin-acrylate copolymer, the -OR groups in the repeating acrylate units can chemically bond to the surface of the inorganic material. That is, the olefin-acrylate copolymer can improve the adhesion between the thermal interface material 200 and the metal surface. Furthermore, the repeating acrylate units make the thermal interface material 200 easier to mold than general silane compounds.

[0036] As for the internal filler, it includes various thermally conductive fillers (such as the first thermally conductive filler 20 and the second thermally conductive filler 30) and a highly dispersible filler 40. The first thermally conductive filler 20 and the second thermally conductive filler 30 are selected from the group consisting of aluminum nitride, aluminum oxide, boron nitride, silicon carbide, and magnesium oxide, while the highly dispersible filler 40 contains titanium oxide, such as high-purity titanium dioxide with a specific crystal form. The thermal conductivity of the titanium oxide is lower than that of the first thermally conductive filler 20 and the second thermally conductive filler 30, so it should not be used excessively to avoid increasing the overall thermal resistance of the thermal interface material 200. More specifically, the titanium oxide is selected from the group consisting of rutile titanium dioxide and unavoidable impurities. The aforementioned unavoidable impurities include trace elements and / or other crystal structures of titanium dioxide, such as anatase titanium dioxide and brookite titanium dioxide. Furthermore, based on the weight of titanium oxide as 100%, the weight percentage of rutile titanium dioxide is 90% or more. Preferably, the weight percentage of rutile titanium dioxide is 98% or more. Most preferably, the weight percentage of rutile titanium dioxide is 99%. The highly dispersible filler 40 not only reduces the contact thermal resistance between filler particles, but also allows for smooth mixing and molding of various materials. Without the addition of the highly dispersible filler 40, the hot-melt material 10 is difficult to mix and mold with the first thermally conductive filler 20 and the second thermally conductive filler 30. Based on the volume of the thermal interface material 200 as 100%, the total volume percentage of the first thermally conductive filler 20, the second thermally conductive filler 30, and the highly dispersible filler is 65% to 75%, for example, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, or 75%.

[0037] Furthermore, as mentioned above, the present invention uses the maximum particle size of each filler as an indicator to adjust the proportion of each filler, as specifically described below. Regarding the first thermally conductive filler 20, it is composed of multiple particles, and the maximum particle size of these particles can be from 8 micrometers (μm) to 10 μm, for example, 8 μm, 8.2 μm, 8.4 μm, 8.7 μm, 9.1 μm, 9.5 μm, or 10 μm. Regarding the second thermally conductive filler 30, it is composed of multiple particles, and the maximum particle size of these particles can be from 40 μm to 50 μm, for example, 40 μm, 41.5 μm, 43.6 μm, 45.7 μm, 47.5 μm, 49.6 μm, or 50 μm. Regarding the highly dispersible filler 40, it is composed of multiple particles, the maximum particle size of which must be at least less than 1.5 μm, and may be, for example, 0.8 μm to 1.5 μm. In one embodiment, the maximum particle size of the highly dispersible filler 40 may be 0.8 μm, 0.95 μm, 1.1 μm, 1.26 μm, 1.32 μm, 1.45 μm, or 1.5 μm. The proportion of each filler is explained below. Based on the volume of the inner filler being 100%, the volume percentage of the first thermally conductive filler 20 is 31% to 42%, for example 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, or 42%. With the volume of the inner filler being 100%, the volume percentage of the second thermally conductive filler 30 is 54% to 62%, for example, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, or 62%. With the volume of the inner filler being 100%, the volume percentage of the highly dispersible filler 40 is 1% to 15%, for example, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%. Thus, the present invention fills the thermal interface material 200 with the aforementioned first thermally conductive filler 20 of the largest size, and then the gaps between the first thermally conductive fillers 20 are substantially filled by the second thermally conductive filler 30. Finally, the highly dispersible filler 40 reduces the contact thermal resistance between the first thermally conductive filler 20 and the second thermally conductive filler 30, while also helping the materials (the first thermally conductive filler 20, the second thermally conductive filler 30 and the hot-melt material 10) to be smoothly mixed and molded.

[0038] The thickness T of the thermal interface material 200 can be adjusted appropriately while maintaining good thermal conductivity. When the thickness T of the thermal interface material 200 is between 0.05 mm and 0.21 mm, the thermal resistance of the thermal interface material 200 is 0.07 cm. 2 ·℃ / W to 0.5cm 2The thermal conductivity ranges from 3 W / m·K to 81 W / m·K. When the thickness T of the thermal interface material 200 is between 0.06 mm and 0.15 mm, the thermal resistance of the thermal interface material 200 is 0.08 cm. 2 ·℃ / W to 0.24cm 2 The thermal conductivity ranges from 11.24 W / m·K to 80.08 W / m·K. Furthermore, the present invention further tests the anti-aging ability of the thermal interface material 200 under two conditions (hereinafter referred to as the first weathering treatment and the second weathering treatment). The first weathering treatment involves placing the thermal interface material 200 at 85°C and 85% humidity for 500 hours. After the first weathering treatment, the thermal interface material 200 exhibits a 0.08 cm² temperature gradient. 2 ·℃ / W to 0.24cm 2 The thermal resistance is ·℃ / W and the thermal conductivity ranges from 11.24 W / m·K to 80.08 W / m·K. The second weathering treatment involves placing the thermal interface material 200 at 125℃ for 500 hours. After the second weathering treatment, the thermal interface material 200 has a thermal resistance of 0.1 cm⁻¹. 2 ·℃ / W to 0.31cm 2 Thermal resistance at ℃ / W and thermal conductivity ranging from 5.62 W / m·K to 66.4 W / m·K.

[0039] Furthermore, as mentioned above, the thermal interface material 200 of the present invention exhibits excellent durability, capable of withstanding repeated temperature and high-pressure impacts without damage. For example, the present invention repeatedly validates the same thermal interface material 200 according to the ASTM D5470 standard. Each validation is performed at a pressure of 10 psi and a temperature of 70°C. The number of validations can be referred to as the operability of this material. That is, the operability of the thermal interface material 200 is defined as the number of times the thermal interface material 200 can be validated according to ASTM D5470 without damage. When the thickness of the thermal interface material 200 is greater than 0.1 mm, the operability is at least 2 times. When the thickness of the thermal interface material 200 is greater than 0.15 mm, the operability is at least 5 times.

[0040] Please continue to refer to Figure 3 . Figure 3This shows a cross-sectional view of the thermal interface material 200 of the present invention applied in an electronic device 300. In simple terms, the thermal interface material 200 can be attached to the surface of a heat sink and then disposed on a heat-generating component. Details are as follows. An electronic device 300 includes a heat sink 220, an electronic component 210, and the thermal interface material 200. The heat sink 220 has a front side and a back side opposite to the front side. The heat sink 220 may be a heat dissipation fin, thus the heat sink 220 extends multiple fin-like structures on its front side, while the back side is a generally flat surface. The electronic component 210 has a front side and a back side opposite to the front side. The back side of the electronic component 210 faces the back side of the heat sink 220. It should be understood that although the back side of the heat sink 220 is flat, it still has many uneven undulations under a microscopic level, and the back side of the electronic component 210 also has the same situation. If the back side of the heat sink 220 is directly attached to the back side of the electronic component 210, many gaps will be formed at the contact surface between the two, resulting in high contact thermal resistance. Therefore, by providing the thermal interface material 200, the aforementioned gap can be filled, thereby reducing the contact thermal resistance between the interfaces. That is, the thermal interface material 200 is disposed between the heat sink 220 and the electronic component 210, and is attached to the back of both the heat sink 220 and the electronic component 210.

[0041] To gain a clearer understanding of the thermal interface material 200 of the present invention, the following verification was performed.

[0042] Table 1. Polymers

[0043] type Melting point (°C) Melt flow index (g / 10min) Acrylate content (wt%) EEA-1 49 400 33 EBA 69 150 33 EEA-2 67 400 28 EEA-3 61 400 33

[0044] Table 2. Internal Packing

[0045] type d(0.1) d(0.5) d(0.9) d(max) AlN-1 0.60μm 1.40μm 3.20μm 8.70μm AlN-2 1.79μm 3.70μm 7.01μm 11.42μm AlN-3 0.54μm 2.10μm 5.90μm 15.13μm AlN-4 2.05μm 14.75μm 30.83μm 45.70μm AlN-5 31.21μm 48.88μm 75.83μm 104.80μm <![CDATA[Al2O3]]> 1.29μm 5.14μm 11.44μm 18.38μm <![CDATA[TiO2]]> 0.38μm 0.55μm 0.84μm 1.26μm

[0046] Table 3. Ratio of Polymer to Internal Filler

[0047]

[0048]

[0049] In this experiment, the thermal interface material 200 is composed of a polymer and internal fillers.

[0050] Table 1 lists the polymers (i.e., the aforementioned hot-melt materials) available for use in this invention, namely three ethylene-ethyl acrylate copolymers, namely EEA-1, EEA-2, and EEA-3; and one ethylene-butyl acrylate copolymer, namely EBA. These four polymers are olefin-acrylate copolymers with melting points ranging from 49°C to 69°C and melt flow indices ranging from 150 g / 10 min to 400 g / 10 min, and can all be applied to the thermal interface material 200 of this invention. The melt flow index can be adjusted appropriately depending on the polymerization method. For example, the melt flow index can be from 110 g / 10 min to 500 g / 10 min, and has the same or similar technical effects. Other applicable melt flow index values ​​have been described above and will not be elaborated upon here.

[0051] Table 2 lists the fillers available for use in this invention, namely five types of aluminum nitride (AlN-1, AlN-2, AlN-3, AlN-4, and AlN-5), alumina (Al2O3), and titanium dioxide (TiO2). Each filler consists of multiple particles with different particle size distributions. Particle size was measured using a Malvern Mastersizer 2000 particle size analyzer. 'd' represents the particle size distribution, and the number in square brackets after 'd' represents the proportion of the number of particles. For example, 0.1, 0.5, and 0.9 represent 10%, 50%, and 90%, respectively. For instance, d(0.1) represents that, in terms of the total number of particles, 10% of the particles are smaller than this value, and the same applies to d(0.5) and d(0.9). 'max' refers to the largest particle size that can be presented among all particles. Additionally, d(0.5) is the median value of the particle size distribution, also known as the median particle size. As mentioned above, the present invention uses the maximum particle size as an indicator to determine the proportion of filler. Considering the influence of error and the allowable range of variation, the maximum particle size can be moderately adjusted within a certain range, while still achieving the same or similar technical effects. For example, the d(max) of aluminum nitride (AlN-1) can be 8 μm to 10 μm; the d(max) of aluminum nitride (AlN-2) can be 9 μm to 13 μm; the d(max) of aluminum nitride (AlN-3) can be 14 μm to 17 μm; the d(max) of aluminum nitride (AlN-4) can be 40 μm to 50 μm; the d(max) of aluminum nitride (AlN-5) can be 90 μm to 110 μm; the d(max) of alumina can be 17 μm to 19 μm; and the d(max) of titanium dioxide can be 0.8 μm to 1.5 μm. Other moderately adjustable values ​​have been described above and will not be elaborated upon here. Aluminum nitride (AlN-1), aluminum nitride (AlN-2), aluminum nitride (AlN-3), aluminum nitride (AlN-4), aluminum nitride (AlN-5), and alumina are commonly used thermally conductive fillers. Titanium dioxide is the highly dispersible filler 40 mentioned earlier. Furthermore, the titanium dioxide used in this experiment is rutile titanium dioxide with a purity of 99 wt%.

[0052] Table 3 shows the composition ratios of Examples E1 to E8 and Comparative Examples C1 to C3. In practical applications, the polymer can be composed of one or more olefin-acrylate copolymers, and the internal filler can also be composed of one or more fillers. In Examples E1 to E8 and Comparative Examples C1 to C3, the ratio of polymer to internal filler is approximately equal. With the volume of the thermal interface material 200 as 100%, the volume percentage of the polymer is approximately 28% to 35%, while the volume percentage of the internal filler is approximately 65% ​​to 72%. In this experiment, to verify the effect of maximum particle size and dispersant (i.e., highly dispersible filler) on performance, the main difference between the examples and the comparative examples is the presence or absence of titanium dioxide (see Table 4 below). Accordingly, the polymers of Examples E1 to E8 and Comparative Examples C1 to C3 are all composed of ethylene-butyl acrylate copolymer (i.e., EBA in Table 1), while the internal fillers of each example and each comparative example are composed of different types of fillers.

[0053] Table 4. Composition of Internal Filler and Properties of Thermal Dielectric Materials

[0054]

[0055] As mentioned above, the internal packing materials of Examples E1 to E8 all contained a highly dispersible packing material (i.e., TiO2), while those of Comparative Examples C1 to C3 did not. Specific details are as follows: In Examples E1 to E3, the internal packing material consisted of a thermally conductive packing material (i.e., AlN-3) and a highly dispersible packing material (i.e., TiO2). In Examples E4 to E8, the internal packing material consisted of two thermally conductive packing materials (i.e., AlN-1 / AlN-2, AlN-1 / AlN-3, AlN-1 / AlN-4, AlN-1 / AlN-5, and AlN-1 / Al2O3) and a highly dispersible packing material (i.e., TiO2). In other words, the internal packing materials of Examples E1 to E8 may contain one or more thermally conductive packing materials and a highly dispersible packing material, wherein the thermally conductive packing material accounts for 85% to 96%, and the highly dispersible packing material accounts for 4% to 15%. In contrast, the internal packing of Comparative Examples C1 to C3 consisted of two types of thermally conductive packings, none of which contained highly dispersible packings.

[0056] Based on the above proportions, the fabrication process of the thermal interface material is as follows. First, based on the formulas presented in Tables 3 and 4, the materials in the formulas were added to a twin-screw mixer manufactured by HAAKE Corporation for mixing. The mixing temperature was set at 160°C, the premixing time was 3 minutes, and the mixing time was 15 minutes. After mixing, a thermally conductive composite material was obtained, which was then pressed into a sheet with a thickness of 0.1 mm using a hot press at 160°C. The sheet was then cut into thermal interface materials of approximately 3 cm × 3 cm. Copper foil of the same size was then placed on the upper and lower surfaces of the thermal interface material to form a three-layer structure for subsequent testing. This three-layer structure is more consistent with the actual application situation, and the data measured in the subsequent tests are closer to the data in actual applications. It should also be mentioned that this experiment found that Comparative Examples C1 to C3, which did not contain titanium dioxide, were less likely to be formed during the mixing process. That is, the thermally conductive composite materials of Comparative Examples C1 to C3 were prone to dispersing and did not easily aggregate into stable clumps. The proportion of titanium dioxide in Examples E1 to E8 can be appropriately adjusted to 1% to 15%.

[0057] This experiment measured the thermal resistance and thermal conductivity of the thermal interface material according to the standard method of ASTM D5470. The pressure during each measurement was 10 psi, and the temperature was 70°C. In Examples E1 to E3, the thermal resistance was 0.4 cm. 2 ·℃ / W to 0.73cm 2 The thermal resistance is 0.12 cm·℃ / W, while the thermal conductivity ranges from 1.76 W / m·K to 3.1 W / m·K. In Examples E4 to E8, the thermal resistance is 0.12 cm·℃ / W. 2 ·℃ / W to 0.43cm 2 The thermal resistance is 3.07 W / m·K to 52 W / m·K, while the thermal conductivity is 3.07 W / m·K to 52 W / m·K. In Comparative Examples C1 to C3, the thermal resistance is 0.24 cm. 2 ·℃ / W to 0.53cm 2The thermal resistance is 2.46 W / m·K to 5.9 W / m·K. As shown in Examples E1 to E3, when a thermally conductive filler is combined with a highly dispersed filler, no significant improvement in thermal resistance and thermal conductivity is observed. Particularly in Example E1, when titanium dioxide content reaches 15%, the thermal resistance of the interface material increases significantly. Furthermore, when excessive amounts of low-thermal-conductivity titanium dioxide are added (i.e., exceeding 15%), too much heat is transferred along low-thermal-conductivity paths, resulting in excessively high overall thermal resistance (not shown in Table 4), which does not meet the application requirements. However, when two thermally conductive fillers are combined with a highly dispersed filler (i.e., Examples E4 to E8), the interface material can have a lower range of thermal resistance and a higher range of thermal conductivity. It is particularly noteworthy that, after at least three repeated verifications, Example E6 of the present invention exhibits the best thermal conductivity characteristics (i.e., the lowest thermal resistance and the highest thermal conductivity).

[0058] In addition, the tensile strength (hereinafter referred to as fracture strength) of Examples E1 to E8 and Comparative Examples C1 to C3 at fracture was measured using an ALGOL (model: JSV-500D) tensile testing machine. The fracture strengths of Examples E1 to E8 were 0.735 kg, 1.11 kg, 1.05 kg, 1.145 kg, 1.06 kg, 0.98 kg, 1.07 kg, and 1.15 kg, respectively. The fracture strengths of Comparative Examples C1 to C3 were 1.22 kg, 1.12 kg, and 0.802 kg, respectively. That is, the fracture strengths of Examples E1 to E8 were approximately 0.7 kg to 1.2 kg, while the fracture strengths of Comparative Examples C1 to C3 were approximately 0.8 kg to 1.2 kg. This shows that a specific maximum particle size and a specific proportion of titanium dioxide do not negatively affect the fracture strength, thus the thermal interface material still maintains good structural strength.

[0059] Table 5. Properties of thermal dielectric materials at different thicknesses (I)

[0060]

[0061] Since Example E6 exhibits significant improvements in thermal resistance and thermal conductivity, this experiment further validates its performance by fabricating thermal interface materials of varying thicknesses. By adjusting the pressure of the aforementioned hot press, the thermal interface material of Example E6 can be pressed into different thicknesses: 0.06 mm, 0.1 mm, 0.15 mm, and 0.2 mm, corresponding to Examples E6-1, E6-2, E6-3, and E6-4, respectively. Furthermore, in each measurement, the thermal interface material is subjected to a pressure of 10 psi and a temperature of 70°C; therefore, the same thermal interface material cannot be measured an unlimited number of times. Conversely, with increasing measurement frequency, the thermal interface material will deform or even break. The number of times the same thermal interface material can be measured without breakage is the operable number shown in Table 5.

[0062] As shown in Table 5, the thermal resistance of Examples E6-1 to E6-4 is 0.08 cm. 2 ·℃ / W up to 0.47cm 2 The thermal resistance is 3.75 W / m·K to 80.08 W / m·K, while the thermal conductivity ranges from 3.75 W / m·K to 80.08 W / m·K. Compared to all the embodiments in Table 3, even though the thickness of Embodiment E6-4 is doubled, it still maintains low thermal resistance and high thermal conductivity. More importantly, Embodiment E6-4 has a workability of 6 times. In other words, in order to improve the durability (i.e., the number of workability) of the thermal interface material, Embodiment E6 can be made thicker without compromising thermal resistance and thermal conductivity. It should be understood that, considering the influence of error and the allowable range of variation, the thickness of the aforementioned Embodiments E6-1 to E6-4 can be moderately adjusted within the range of 0.05 mm to 0.21 mm, and have the same or similar technical effects.

[0063] Table 6. Properties of thermal dielectric materials at different thicknesses (Part 2)

[0064]

[0065] This experiment further selected Examples E6-1 to E6-3 to test the anti-aging ability of the thermal interface materials. "Thermal resistance" and "thermal conductivity" refer to the thermal resistance and thermal conductivity measured when the thermal interface material has not undergone any heat treatment or humidity treatment. "Thermal resistance-1" and "thermal conductivity-1" refer to the thermal resistance and thermal conductivity measured after the thermal interface material has been treated at 85°C and 85% humidity for 500 hours (i.e., the aforementioned first weathering treatment). "Thermal resistance-2" and "thermal conductivity-2" refer to the thermal resistance and thermal conductivity measured after the thermal interface material has been treated at 125°C for 500 hours (i.e., the aforementioned second weathering treatment). As shown in Table 5, even after exposure to different environments, Examples E6-1 to E6-3 can still maintain low thermal resistance and high thermal conductivity. After the first weathering treatment, the thermal resistance of Examples E6-1 to E6-3 remained at 0.08 cm. 2 ·℃ / W to 0.24cm 2 The thermal resistance was ·℃ / W, while the thermal conductivity ranged from 11.24 W / m·K to 80.08 W / m·K. After the second weathering treatment, the thermal resistance of Examples E6-1 to E6-3 remained at 0.1 cm. 2 ·℃ / W to 0.31cm 2 The thermal resistance is 5.62 W / m·K to 66.4 W / m·K, while the thermal conductivity ranges from 5.62 W / m·K to 66.4 W / m·K. As can be seen from the above, the thermal interface material of the present invention maintains the same performance at a temperature of 85°C and a humidity of 85%. Even at a high temperature of 125°C, the thermal resistance and thermal conductivity change only slightly. Furthermore, the AC insulation strength of Examples E6-1 to E6-3 is above 30 kV / mm, exhibiting good voltage withstand capability.

[0066] The technical content and features of this invention have been disclosed above. However, those skilled in the art may still make various substitutions and modifications that do not depart from the spirit of this invention based on the teachings and disclosures of this invention. Therefore, the scope of protection of this invention should not be limited to what is disclosed in the embodiments, but should include various substitutions and modifications that do not depart from this invention, and is covered by the following claims.

[0067] Symbol explanation:

[0068] 1 polymer

[0069] 2 Thermally conductive filler

[0070] 10 Hot melt materials

[0071] 20 First thermally conductive filler

[0072] 20a small particles

[0073] 20b large particles

[0074] 30 Second thermally conductive filler

[0075] 40 Highly Dispersible Filler

[0076] 100, 200 thermal interface materials

[0077] 210 Electronic Components

[0078] 220 radiator

[0079] 300 electronic devices

[0080] G gap

[0081] Thickness T

Claims

1. A thermal interface material, comprising: A hot-melt material comprising an olefin-acrylate copolymer, wherein: The melt flow index of this olefin-acrylate copolymer is higher than 110 g / 10 min; and Based on the volume of the thermal interface material being 100%, the olefin-acrylate copolymer accounts for 25% to 35% of the volume; and An internal filler comprising a variety of thermally conductive fillers and a highly dispersible filler, wherein the volume percentage of the thermally conductive fillers and the highly dispersible filler is 65% to 75% based on the volume of the thermal interface material as 100%.

2. The thermal interface material according to claim 1, wherein the olefin-acrylate copolymer has a melting point below 70°C and a melt flow index between 110 g / 10 min and 500 g / 10 min, and the olefin-acrylate copolymer is represented by the following formula (I): in: R can be selected freely from COOCH3, COOC2H5, COOC4H9, and COOC6H. 13 The groups formed; m is 500 to 3000, and n is 300 to 2000; and m is greater than n.

3. The thermal interface material according to claim 1, wherein: Based on the volume of the internal packing being 100%, the highly dispersible packing accounts for a volume percentage of 1% to 15%; and The maximum particle size of this highly dispersible filler is less than 1.5 μm.

4. The thermal interface material of claim 3, wherein the highly dispersible filler comprises a titanium oxide selected from the group consisting of rutile titanium dioxide and unavoidable impurities, wherein the rutile titanium dioxide accounts for more than 90% by weight, based on 100% of the weight of the titanium oxide.

5. The thermal interface material according to claim 1, wherein the thermally conductive fillers comprise a first thermally conductive filler and a second thermally conductive filler, wherein: The maximum particle size of the first thermally conductive filler is less than 10 μm; and The maximum particle size of the second thermally conductive filler is less than 50 μm.

6. The thermal interface material according to claim 5, wherein: The maximum particle size of the first thermally conductive filler is between 8 μm and 10 μm, and the volume percentage of the first thermally conductive filler, based on the volume of the inner filler being 100%, is 31% to 42%; and The maximum particle size of the second thermally conductive filler is between 40 μm and 50 μm, and the volume percentage of the second thermally conductive filler is between 54% and 62% based on the volume of the inner filler being 100%.

7. The thermal interface material according to claim 6, wherein the first thermally conductive filler and the second thermally conductive filler are selected from the group consisting of aluminum nitride, aluminum oxide, boron nitride, silicon carbide and magnesium oxide.

8. The thermal interface material according to claim 1, wherein the maximum particle size of the thermally conductive fillers is less than 50 μm, and the maximum particle size of the highly dispersible filler is less than 1.5 μm, wherein the thermal resistance of the thermal interface material is 0.07 cm when the thickness of the thermal interface material is between 0.05 mm and 0.21 mm. 2 ·℃ / W to 0.5cm 2 ·℃ / W, while the thermal conductivity ranges from 3W / m·K to 81W / m·K.

9. The thermal interface material according to claim 8, wherein when the thickness of the thermal interface material is between 0.06 mm and 0.15 mm, the thermal resistance of the thermal interface material is 0.08 cm. 2 ·℃ / W to 0.24cm 2 The temperature is ℃ / W, while the thermal conductivity ranges from 11.24 W / m·K to 80.08 W / m·K.

10. The thermal interface material according to claim 1, wherein after a first weathering treatment, the thermal interface material has a thickness of 0.08 cm. 2 ·℃ / W to 0.24cm 2 The thermal resistance is ·℃ / W and the thermal conductivity is 11.24W / m·K to 80.08W / m·K, wherein the first weathering treatment is to place the thermal interface material at a temperature of 85℃ and a humidity of 85% for 500 hours.

11. The thermal interface material according to claim 1, wherein after a second weathering treatment, the thermal interface material has a thickness of 0.1 cm. 2 ·℃ / W to 0.31cm 2 The thermal resistance is ·℃ / W and the thermal conductivity is 5.62W / m·K to 66.4W / m·K, wherein the second weathering treatment is to place the thermal interface material at a temperature of 125℃ for 500 hours.

12. The thermal interface material of claim 1, wherein the thickness of the thermal interface material is greater than 0.1 mm, and the number of operable operations of the thermal interface material is at least 2, wherein the number of operable operations of the thermal interface material is defined as the number of times the thermal interface material can be verified according to ASTM D5470 without damage.

13. The thermal interface material according to claim 12, wherein the thickness of the thermal interface material is greater than 0.15 mm, and the thermal interface material is operable at least 5 times.

14. An electronic device comprising: A radiator having a front side and a back side disposed opposite to the front side; An electronic component has a front side and a back side disposed opposite to the front side, wherein the back side of the electronic component faces the back side of a heat sink; and The thermal interface material as described in claim 1 is disposed between the heat sink and the electronic component, wherein the thermal interface material is attached to the back side of the heat sink and the back side of the electronic component.

15. The electronic device of claim 14, wherein the olefin-acrylate copolymer in the thermal interface material has a melting point below 70°C and a melt flow index between 110 g / 10 min and 500 g / 10 min, and the olefin-acrylate copolymer is represented by the following formula (I): in: R can be selected freely from COOCH3, COOC2H5, COOC4H9, and COOC6H. 13 The groups formed; m is 500 to 3000, and n is 300 to 2000; and m is greater than n.

16. The electronic device of claim 14, wherein the thermal interface material comprises: The highly dispersible filler comprises a titanium oxide, selected from the group consisting of rutile titanium dioxide and unavoidable impurities, wherein the rutile titanium dioxide accounts for more than 90% by weight, based on 100% of the weight of the titanium oxide. Based on the volume of the internal packing being 100%, the highly dispersible packing accounts for a volume percentage of 1% to 15%; and The maximum particle size of this highly dispersible filler is less than 1.5 μm.

17. The electronic device of claim 14, wherein the thermally conductive fillers of the thermal interface material comprise a first thermally conductive filler and a second thermally conductive filler, wherein: The maximum particle size of the first thermally conductive filler is between 8 μm and 10 μm, and the volume percentage of the first thermally conductive filler, based on the volume of the inner filler being 100%, is 31% to 42%; and The maximum particle size of the second thermally conductive filler is between 40 μm and 50 μm, and the volume percentage of the second thermally conductive filler is between 54% and 62% based on the volume of the inner filler being 100%.

18. The electronic device of claim 17, wherein the first thermally conductive filler and the second thermally conductive filler are selected from the group consisting of aluminum nitride, aluminum oxide, boron nitride, silicon carbide and magnesium oxide.

19. The electronic device of claim 14, wherein the maximum particle size of the thermally conductive fillers in the thermal interface material is less than 50 μm, and the maximum particle size of the highly dispersible filler is less than 1.5 μm, wherein the thermal resistance of the thermal interface material is 0.07 cm when the thickness of the thermal interface material is between 0.05 mm and 0.21 mm. 2 ·℃ / W to 0.5cm 2 ·℃ / W, while the thermal conductivity ranges from 3W / m·K to 81W / m·K.

20. The electronic device of claim 14, wherein the thickness of the thermal interface material is greater than 0.1 mm, and the number of operable operations of the thermal interface material is at least 2, wherein the number of operable operations of the thermal interface material is defined as the number of times the thermal interface material can be verified according to ASTM D5470 without damage.

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