TWI383038B - Thermal interface material, electronic device with the same, and preparation method thereof - Google Patents

Description

Thermal interface material, electronic device with the same, and preparation method thereof

The invention relates to a thermal interface material, an electronic device with the thermal interface material and a preparation method of the electronic device.

In recent years, with the rapid development of semiconductor device integration processes, the integration of semiconductor devices has become higher and higher, and the device size has become smaller and smaller. However, the reduction in the size of semiconductor devices has also increased their requirements for heat dissipation. In order to meet the heat dissipation requirements of the semiconductor device, various heat dissipation methods such as fan heat dissipation, water cooling auxiliary heat dissipation and heat pipe heat dissipation are widely used, and a certain heat dissipation effect is obtained. However, because the contact interface between the heat sink and the heat source (semiconductor integrated device, such as the CPU) is not flat, the actual contact area is generally less than 2% of the total area, thus fundamentally affecting the effect of the heat source transferring heat to the heat sink. In order to increase the contact area between the heat source and the heat sink, a thermal interface material (Thermal Interface Materials) with a high thermal conductivity is usually added between the heat source and the heat sink to fill the heat source and the heat sink. The micro-voids and the uneven holes on the surface increase the contact area between the heat source and the heat sink, reduce the impedance of heat transfer, and improve the heat transfer between the heat source and the heat sink.

Conventional thermal interface materials are formed by adding some thermally conductive particles such as yttria, silver or other metals having excellent thermal conductivity to a flexible substrate such as silicone or rubber. The carbon nanotubes have a very high thermal conductivity along their axial direction, making them one of the most promising thermal interface materials. Applied on September 16, 2004 and published on June 2, 2005 US Patent Application Publication No. 2005/0116336 A1 discloses a thermal interface material that uniformly disperses a plurality of carbon nanotubes in a flexible matrix that overlaps each other between a heat source and a heat sink A plurality of heat conduction channels are formed.

The thermal conductivity of the carbon nanotube in the axial direction is relatively high, but the thermal conductivity in the radial direction is extremely low. Therefore, in the heat conduction channel formed by the plurality of carbon nanotubes, the length of the heat transfer path depends on the mutual overlap. The sum of the axial lengths of all the carbon nanotubes of the heat conduction channel. The direction of the plurality of carbon nanotubes in the flexible substrate is difficult to control, and the probability that the axial direction of the carbon nanotubes coincides with the heat transfer direction is small. Therefore, more carbon nanotubes are required to form a heat conduction. Channel, which causes the heat transfer path of the thermal interface material to be long; and, because of the small size of the carbon nanotubes, the thermal resistance between the two carbon nanotubes overlapping each other is large, and the nanometer cannot be effectively utilized. The thermal conductivity of carbon tubes. Therefore, the thermal conductivity of the thermal interface material needs to be further improved.

In view of the above, a thermal interface material having better thermal conductivity is provided, and an electronic device having the thermal interface material and a preparation method of the electronic device are necessary.

A thermal interface material comprising a flexible substrate and a plurality of composite thermally conductive particles distributed in the flexible substrate. The composite thermally conductive particles comprise a metal particle and at least one carbon nanotube is composited in the metal particle.

A thermal interface material comprising a flexible substrate and a plurality of metal particles distributed in the flexible substrate. Each of the at least a portion of the metal particles further includes at least one carbon nanotube composited to the first metal A plurality of composite thermally conductive particles are formed in the granules.

An electronic device includes a heat source and a thermal interface material disposed on a surface of the heat source. The thermal interface material includes a flexible substrate and a plurality of first metal particles distributed in the flexible substrate. At least a portion of each of the first metal particles further includes at least one carbon nanotube composited in the first metal particles to form a plurality of composite thermally conductive particles.

A method of fabricating an electronic device, comprising the steps of: providing a thermal interface material preform and a heat source having a protection temperature that prevents the heat source from being damaged by overheating, the thermal interface material preform comprising a flexible substrate, filling a plurality of second metal particles and a plurality of carbon nanotubes in the flexible substrate, the second metal particles having a particle size of less than 100 nanometers, and a melting temperature of the second metal particles at the particle diameter is less than the protective temperature; The thermal interface material preform is disposed on the heat source surface; the thermal interface material preform is heated to melt agglomerate the second metal particles; and the thermal interface material preform is cooled to form a thermal interface material on the heat source surface.

Compared to the prior art, the carbon nanotubes in the thermal interface material are combined with the first metal particles to form composite thermally conductive particles. Since the heat transfer direction of the composite heat conductive particles is not directional, the heat conduction channel formed by the overlapping of the plurality of composite heat conductive particles has a short heat transfer path; and, since the composite heat conductive particles have a large particle diameter, The thermal resistance between the composite thermally conductive particles that overlap each other is small. Therefore, the thermal interface material effectively utilizes the excellent thermal conductivity of the carbon nanotubes and has better thermal conductivity.

The thermal interface material of the embodiment of the present invention, the electronic device having the thermal interface material, and the preparation method of the electronic device will be further described with reference to the accompanying drawings. Detailed description.

1 is an electronic device 100 according to an embodiment of the present invention. The electronic device 100 includes a heat source 10, a heat sink 20, and a thermal interface material 30. The thermal interface material 30 is disposed between the heat source 10 and the heat sink 20. The heat generated by the heat source 10 is transferred to the heat sink 20.

The heat source 10 can be a semiconductor integrated device or an IC circuit, a resistor or other heat generating component. The heat source 10 has a protection temperature T1 that prevents the heat source 10 from being damaged by overheating. It can be understood that when the temperature of the heat source 10 exceeds T1, the heat source 10 may be damaged due to overheating, that is, T1 is the maximum tolerated temperature at which the heat source 10 is not damaged. Preferably, the protection temperature T1 is less than 350 °C. In the present embodiment, the heat source 10 is a CPU having a protection temperature T1 of 120 °C.

The heat sink 20 is used to quickly derive the heat generated by the heat source 10 so that the heat source 10 does not generate heat accumulation.

The thermal interface material 30 is disposed between the heat source 10 and the heat sink 20 . Referring to FIG. 2 , the thermal interface material 30 includes a flexible substrate 31 and a plurality of composite thermally conductive particles 32 filled in the flexible substrate 31 .

The melting temperature of the flexible substrate 31 is greater than the protection temperature T1, so that the thermal interface material 30 can maintain a fixed shape during operation without overflowing from the electronic device 100. In the present embodiment, the flexible substrate 31 is a mixture of a thermoplastic resin and a thermosetting polymer. The thermoplastic resin may be any one of an epoxy resin series, a phenolic resin series, and a polyamidamide resin series; the thermosetting polymer material may be any one of a styrene-butadiene rubber series, a sol-gel series, and a silicone-based series. In this embodiment The flexible substrate 31 is a mixture of a phenolic resin series and a sol gel series.

The plurality of composite thermally conductive particles 32 are uniformly dispersed in the flexible substrate 31. The mass percentage of the plurality of composite thermally conductive particles 32 in the thermal interface material 30 is 15% to 95%, and the particle size of the composite thermally conductive particles 32 is greater than 100. The melting temperature of the nanoparticle at the particle size is greater than the protective temperature T1. The composite thermally conductive particles include a first metal particle 321 and at least one carbon nanotube 322 composited in the first metal particle 321 . The first metal particles 321 are 15% to 95% by mass in the thermal interface material 30, and the first metal particles 321 may be made of silver, copper, tin-lead alloy or aluminum. The carbon nanotube 322 has a mass percentage of 1% to 25% in the thermal interface material 30, and includes a single-walled carbon nanotube, a double-walled carbon nanotube or a multi-walled carbon nanotube, and further In order to enhance the affinity of the carbon nanotube 322 for the first metal particle 321 , the surface of the carbon nanotube 322 may be modified, such as by metal plating or the surface of the carbon nanotube 322 is plated with metal or alloy.

The composite thermally conductive particles 32 are formed by combining the first metal particles 321 with at least one carbon nanotube 322. Specifically, the carbon nanotubes 322 are dispersed in the first metal particles 321 . The composite thermally conductive particles 32 effectively utilize the excellent thermal conductivity of the carbon nanotubes 322 and greatly reduce the interface thermal resistance between the plurality of carbon nanotubes 322 dispersed in the same first metal particles 321 . Since the heat transfer direction of the composite heat conductive particles 32 is not directional, the heat conduction channel formed by the overlapping of the plurality of composite heat conductive particles 32 has a short heat transfer path; and, since the composite heat conductive particles 32 have a larger The particle size and the thermal resistance between the composite thermally conductive particles 32 overlapping each other are small. Therefore, the thermal interface material 100 effectively utilizes the excellent thermal conductivity of the carbon nanotube 322 Performance, with good thermal conductivity.

In the thermal interface material 30, a plurality of first metal particles 321 which are not composited with the carbon nanotubes 322 may be further included, and the first metal particles 321 have a particle diameter greater than 100 nm. That is, the thermally conductive particles in the flexible substrate 31 include the composite thermally conductive particles 32 and the first metal particles 321 . At this time, the heat conduction channel is formed by overlapping the plurality of composite thermally conductive particles 32 and the plurality of first metal particles 321 . It can be understood that when the thermal interface material 30 further includes a plurality of first metal particles 321 that are not composited with the carbon nanotubes 322, the thermal interface material 30 can also be described as follows, the thermal interface material 30 includes a flexible substrate 31 and A plurality of first metal particles 321 dispersed in the flexible substrate 31. A portion of the first metal particles 321 are combined with the carbon nanotubes 322 to form a plurality of composite thermally conductive particles 32.

Referring to FIG. 3 and FIG. 4, the method for manufacturing the electronic device 100 includes the following steps.

In step S101, a thermal interface material preform and a heat source 10 are provided. The heat source 10 has a protection temperature T1 for preventing the heat source 10 from being damaged by overheating. The heat interface material preform includes a flexible substrate 31 and is filled with the flexible substrate. a plurality of second metal particles 3211 and a plurality of carbon nanotubes 322 having a particle diameter of less than 100 nm, and a melting temperature T2 of the second metal particles 3211 at the particle diameter is less than the protection Temperature T1. Preferably, the protection temperature T1 is 120 ° C, and the second metal particle 3211 has a particle diameter of less than 50 nm. In the present embodiment, the second metal particles 3211 are silver particles having a particle diameter of about 20 nm, and the melting temperature T2 of the particle diameter is about 100 °C. The second metal particles 3211 may also be tin-lead alloy particles having a particle size ranging from 10 nm to 20 nm, and the melting of the particle size The melting temperature T2 was 91 °C.

In step S102, the thermal interface material preform is disposed on the surface of the heat source 10. The thermal interface material preform may be disposed by directly disposing the thermal interface material preform on the surface of the heat source 10; or dissolving the hot interface material preform in a solvent to be applied to the surface of the heat source 10, and then volatilizing the solvent to set the thermal interface material preform On the surface of the heat source 10.

In step S103, the thermal interface material preform is heated to melt agglomerate the second metal particles 3211. Specifically, the heating temperature is between the melting temperature T2 of the second metal particles 3211 and the protective temperature T1. The second metal particles 3211 are combined with each other in a molten state to form first metal particles 321 having a larger particle diameter, and the first metal particles 321 have a particle diameter larger than 100 nm. Wherein, part of the first metal particles 321 may be combined with at least one carbon nanotube 322 to form composite thermally conductive particles 32. At this time, the composite thermally conductive particles 32 have a particle diameter of more than 100 nm. It can be understood that the first metal particles 321 are the same as the second metal particles 3211, and the particle diameters are different. The first metal particles 321 have a particle diameter larger than 100 nm, and the second metal particles 3211 have a particle diameter smaller than 100 nm. The first metal particles 321 and the second metal particles 3211 have different physical properties, because when the metal material has a particle diameter of less than 100 nanometers, especially when the particle diameter is less than 50 nanometers, the melting point of the metal particles The decrease is reduced, and when the metal material has a particle diameter of more than 100 nm, the melting point thereof remains stable and is greater than the melting point of the metal material at a particle diameter of less than 100 nm. The second metal particles 3211 can be converted into the first metal particles 321 under certain conditions, and the plurality of second metal particles 3211 are fused to each other in the molten state to be converted into the first metal particles 321 . In this embodiment, the heating temperature is less than 120 ° C, specifically, when the second metal particles 3211 When the silver particles are 20 nm, the heating temperature is 100 ° C to 120 ° C; when the second metal particles 3211 are tin-lead alloy particles having a particle diameter ranging from 10 nm to 20 nm, the heating temperature is It is from 91 ° C to 120 ° C.

In step S104, a heat dissipating device 20 is fastened to the surface of the thermal interface material preform so that the thermal interface material preform is located between the heat source 10 and the heat sink 20. When the heat interface material preform is in a molten state, the heat sink 20 is fastened to the surface of the heat interface material preform, and the distance between the heat sink 20 and the heat source 10 can be flexibly adjusted. It can be understood that the thermal interface material preform is more easily compressed in the molten state, so that the distance between the heat sink 20 and the heat source 10 can be further shortened, and the heat transfer path can be shortened.

In step S105, the thermal interface material preform is cooled to form a thermal interface material 30 on the surface of the heat source 10. After cooling the thermal interface material preform to form the thermal interface material 30, the first metal particles 321 have a particle size greater than 100 nm, and the melting temperature at the particle size is greater than the protection temperature T1. Specifically, when the first metal particles 321 are silver particles having a particle diameter of more than 100 nm, the melting temperature thereof is 962 ° C; when the first metal particles 321 are tin-lead alloy particles having a particle diameter of more than 100 nm, Its melting temperature was 183 °C. It can be understood that after the thermal interface material preform is cooled to form the thermal interface material 30, when the temperature is raised again to the melting temperature T2 of the first metal particle 321 at a smaller particle diameter, the composite carbon nanotube is composited. The first metal particles 321 or the composite thermally conductive particles 32 are also not melted, so that they can be kept in a solid state.

In this step S102, the method further includes the steps of: fastening a heat dissipating device 20 to the surface of the thermal interface material preform, and prefabricating the thermal interface material. The body is located between the heat source 10 and the heat sink 20. Moreover, at this time, the step S104 will no longer be necessary.

The preparation method utilizes the characteristic that the particle diameter of the metal material changes at a melting temperature of less than 100 nm, and the metal having a high thermal conductivity is combined with the carbon nanotube at a lower temperature to obtain a thermal interface having better thermal conductivity. material. During the formation of the thermal interface material, the metal material has a phase change process, and the molten metal material can effectively infiltrate into the gap between the contact surface of the thermal interface material and the heat source, thereby making the thermal interface material and the heat source And the heat dissipating device is in surface contact, reducing the thermal resistance between the thermal interface material and the heat source and the heat dissipating device, and the melting temperature does not cause damage to the heat source; secondly, the composite thermally conductive particle has a larger particle diameter and decreases The interface thermal resistance between the composite thermally conductive particles and the flexible substrate; again, the composite thermally conductive particles remain solid during operation of the heat source, maintaining excellent thermal conductivity of the metal material and the carbon nanotube.

The carbon nanotubes in the thermal interface material are composited in the first metal particles to form composite thermally conductive particles. Since the heat transfer direction of the composite heat conductive particles is not directional, the heat conduction channel formed by the overlapping of the plurality of composite heat conductive particles has a short heat transfer path; and, since the composite heat conductive particles have a large particle diameter, The thermal resistance between the composite thermally conductive particles formed by overlapping each other is small. Therefore, the thermal interface material effectively utilizes the excellent thermal conductivity of the carbon nanotubes and has better thermal conductivity.

In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above description is only a preferred embodiment of the present invention, and it is not possible to limit the scope of the patent application of the present invention. Any person skilled in the art will be able to make equivalent modifications or variations in accordance with the spirit of the invention. All should be covered by the following patent application.

100‧‧‧Electronic devices

10‧‧‧heat source

20‧‧‧heating device

30‧‧‧Hot interface materials

31‧‧‧Flexible substrate

32‧‧‧Composite thermal conductive particles

321‧‧‧First metal particles

3211‧‧‧Second metal particles

322‧‧‧Nano Carbon Tube

FIG. 1 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.

2 is a schematic view showing the microstructure of the thermal interface material in FIG.

3 is a schematic view showing the microstructure of a thermal interface material preform for preparing a thermal interface material according to the present invention.

4 is a schematic flow chart of a method for preparing an electronic device according to an embodiment of the present invention.

30‧‧‧Hot interface materials

31‧‧‧Flexible substrate

32‧‧‧Composite thermal conductive particles

321‧‧‧First metal particles

322‧‧‧Nano Carbon Tube

Claims (19)

A thermal interface material comprising a flexible substrate, wherein the thermal interface material further comprises a plurality of composite thermally conductive particles distributed in the flexible substrate, the composite thermally conductive particles comprising a first metal particle and at least one carbon nanotube composite In the first metal particle, the at least one carbon nanotube is dispersed inside the first metal particle. The thermal interface material according to claim 1, wherein the plurality of composite thermally conductive particles are in contact with each other in the flexible substrate to form a plurality of heat conduction channels. The thermal interface material according to claim 1, wherein the composite thermally conductive particles have a particle diameter greater than 100 nm. The thermal interface material according to claim 1, wherein the first metal particles are in a mass percentage of 15% to 95% in the thermal interface material. The thermal interface material according to claim 1, wherein the material of the first metal particles comprises silver, copper, tin-lead alloy or aluminum. The thermal interface material according to claim 1, wherein the carbon nanotubes have a mass percentage of 15% to 95% in the thermal interface material. The thermal interface material according to claim 1, wherein the surface of the carbon nanotube is modified to have affinity for the metal. A thermal interface material comprising a flexible substrate, wherein the thermal interface material further comprises a plurality of first metal particles distributed in the flexible substrate, each of the at least a portion of the first metal particles further comprising at least one The carbon nanotubes are composited in the first metal particles to form a plurality of composite thermally conductive particles, and the at least one carbon nanotube is dispersed inside the first metal particles. The thermal interface material according to item 8 of the patent application, wherein the first The particle size of the metal particles is greater than 100 nm. An electronic device comprising a heat source and a thermal interface material disposed on the surface of the heat source, the thermal interface material comprising a flexible substrate, wherein the thermal interface material further comprises a plurality of first metal particles distributed in the flexible substrate Each at least a portion of the first metal particles further includes at least one carbon nanotube composited in the first metal particles to form a plurality of composite thermally conductive particles, the at least one carbon nanotube being dispersed in the first metal Inside the particle. The electronic device of claim 10, wherein the electronic device further comprises a heat dissipating device disposed on a surface of the thermal interface material opposite to the heat source. The electronic device of claim 11, wherein the heat source has a protection temperature that prevents the heat source from being damaged by overheating, and the heat interface material is located between the heat source and the heat sink, and the melting temperature of the first metal particle Greater than the protection temperature. A method of fabricating an electronic device, comprising the steps of: providing a thermal interface material preform and a heat source having a protection temperature that prevents the heat source from being damaged by overheating, the thermal interface material preform comprising a flexible substrate, filling a plurality of second metal particles and a plurality of carbon nanotubes in the flexible substrate, the second metal particles having a particle size of less than 100 nanometers, and a melting temperature of the second metal particles at the particle diameter is less than the protective temperature; The thermal interface material preform is disposed on the heat source surface; the thermal interface material preform is heated to melt agglomerate the second metal particles; and the thermal interface material preform is cooled to form a thermal interface material on the heat source surface. The method for preparing an electronic device according to claim 13, wherein the heat medium material preform is heated to melt the second metal particles. After the step of dispersing, before the step of cooling the thermal interface material preform to form the thermal interface material on the heat source surface, the method further comprises the steps of: fastening a heat dissipating device to the surface of the thermal interface material preform to make the thermal interface material preform Located between the heat source and the heat sink. The method of manufacturing the electronic device of claim 13, wherein the step of disposing the thermal interface material preform on the surface of the heat source further comprises the step of: fastening a heat dissipating device to the thermal interface material The surface of the preform is such that the thermal interface material preform is located between the heat source and the heat sink. The method for preparing an electronic device according to claim 13, wherein the thermal interface material preform heating temperature is between a melting temperature of the second metal particles at the particle diameter and the protection temperature. The method for producing an electronic device according to claim 16, wherein the second metal particles have a particle diameter of less than 50 nm, and the heating temperature is less than 120 °C. The method for preparing an electronic device according to claim 17, wherein the second metal particles are silver particles having a particle diameter ranging from 18 nm to 22 nm, and the heating temperature is 100 ° C to 120 ° C. . The method for preparing an electronic device according to claim 17, wherein the second metal particles are tin-lead alloy particles having a particle diameter ranging from 10 to 20 nm, and the heating temperature is from 91 ° C to 120 ° C.