阅读说明：本技术 用于电子封装热界面材料的双面绒毛导热毯 (Double-sided plush heat conduction blanket for electronic packaging thermal interface material ) 是由 李雷 于 2020-06-18 设计创作，主要内容包括：本申请公开用于电子封装热界面材料的双面绒毛导热毯,其中所述用于电子封装热界面材料的双面绒毛导热毯包括一层基布和耸立的金属绒毛,其中所述基布由金属纤维构成,其中所述基布横截面金属纤维根数为5根以上,其中所述基布的厚度为0.05～1.6mm,其中所述金属绒毛分别被设置于所述基布的上下两面,所述金属绒毛的截面覆盖率大于20%,其中所述金属绒毛相对于所述基布的单侧高度为0.1～1.0mm,且所述金属绒毛直径为0.005～0.1mm,本发明的双面绒毛导热毯具有热量沿金属绒毛定向传热、吸能减震的特点。(The application discloses a double-sided plush heat conduction blanket for an electronic packaging thermal interface material, wherein the double-sided plush heat conduction blanket for the electronic packaging thermal interface material comprises a layer of base cloth and upright metal fluffs, wherein the base cloth is composed of metal fibers, the number of the metal fibers on the cross section of the base cloth is more than 5, the thickness of the base cloth is 0.05-1.6 mm, the metal fluffs are respectively arranged on the upper surface and the lower surface of the base cloth, the section coverage rate of the metal fluffs is more than 20%, the height of the metal fluffs relative to one side of the base cloth is 0.1-1.0 mm, the diameter of the metal fluffs is 0.005-0.1 mm, and the double-sided plush heat conduction blanket has the characteristics of directional heat transfer and shock absorption of heat along the metal fluffs.)

1. A double-sided pile heat-conductive blanket for an electronic packaging thermal interface material, wherein the double-sided pile heat-conductive blanket for an electronic packaging thermal interface material comprises:

a layer of base cloth, wherein the base cloth is made of metal fibers, and the thickness of the base cloth is 0.05-1.6 mm; and

the shrunken metal fluff is arranged on the upper surface and the lower surface of the base fabric respectively, wherein the height of the metal fluff relative to one side of the base fabric is 0.1-1.0 mm, the diameter of the metal fluff is 0.005-0.1 mm, and the yield strength of the metal fluff is more than half of the theoretical critical destabilizing stress.

2. The double-sided pile heat conductive blanket for an electronic packaging thermal interface material of claim 1, wherein the base fabric cross-section metal fibers number more than 5.

3. The double-sided plush heat conduction blanket for the electronic packaging thermal interface material as claimed in claim 1, wherein the base fabric is a woven metal fabric formed by weaving using metal yarns, and the thickness of the woven metal fabric is 0.2-1.2 mm.

4. The double-sided pile thermal blanket for an electronic packaging thermal interface material of claim 1, wherein said base fabric is a non-woven metal fabric formed by non-weaving with metal fibers.

5. The double-sided pile thermal blanket for an electronic package thermal interface material of claim 1, wherein the cross-sectional coverage of the metal pile is greater than 20%.

6. The double-sided pile heat conductive blanket for an electronic packaging thermal interface material of claim 1, wherein the material of the metal base fabric and the metal pile is selected from one or a combination of two or more of pure copper, pure aluminum, pure magnesium, pure iron, copper alloy, aluminum alloy, magnesium alloy, and steel alloy.

7. A double sided pile heat blanket for an electronic packaging thermal interface material, wherein the double sided pile heat blanket for an electronic packaging thermal interface material comprises:

a layer of base cloth, wherein the base cloth is made of metal foil, wherein the thickness of the metal foil is 0.01-0.08 mm, and the metal foil is provided with a plurality of flocking through holes; and

the shrunken metal fluff is arranged on the upper surface and the lower surface of the base fabric respectively, the height of the metal fluff relative to one side of the base fabric is 0.1-1.0 mm, the diameter of the metal fluff is 0.005-0.1 mm, the metal fluff penetrates through the flocking through holes to form the metal fluff on the upper surface and the lower surface of the base fabric, and the yield strength of the metal fluff is more than half of the theoretical critical destabilizing pressure stress.

8. The double-sided pile heat conductive blanket for an electronic packaging thermal interface material of claim 7, wherein the hole diameter of the flocked through holes is 0.5-2 mm, and the distance between the centers of two adjacent flocked through holes is 1.5-2 times the hole diameter.

9. The double-sided pile heat conductive blanket for electronic packaging thermal interface material of claim 7 or 8, wherein the material of the metal base fabric and the metal pile is selected from one or a combination of two or more of pure copper, pure aluminum, pure magnesium, pure iron, copper alloy, aluminum alloy, magnesium alloy and steel alloy.

10. The double-sided pile thermal blanket for an electronic package thermal interface material of claim 7, wherein the cross-sectional coverage of the metal pile is greater than 20%.

Technical Field

The present invention relates to an electronic packaging thermal interface material, and more particularly, to a double-sided plush thermal blanket for an electronic packaging thermal interface material.

Background

Thermal Interface Materials (TIM) are Interface connection Materials filled between a chip and a heat dissipation substrate or between a heat dissipation substrate and a heat sink, and mainly function to reduce Interface thermal resistance and improve heat transfer efficiency. The chip, the heat dissipation substrate and the heat sink are all rigid bodies, if the chip is directly contacted with the heat dissipation substrate or the heat dissipation substrate is directly contacted with the heat sink, due to the problems of surface flatness, roughness and the like of rigid body components, the contact part is only contacted with a small number of protruding positions, gaps exist among most surfaces, the gaps are filled with air, the heat conductivity coefficient of the air is extremely low and is only about 0.02W/(m.K), and the air gaps enable heat to be difficult to timely dissipate, so that the chip is overheated.

In order to fill the gaps between the components in the electronic product, the thermal interface material is required to be flexible and compressible, and the size of the gap can be self-adapted. At present, the thermal interface material with the largest dosage is heat-conducting silicone grease which is a viscous liquid with strong viscosity, and in order to improve the heat conductivity coefficient, AlN, ZnO and Al are filled in the thermal interface material₂O₃SiC, aluminum powder, silver powder, graphite powder, diamond powder and the like, and has the advantages of capability of fully filling air gaps, low price and convenience in use. However, the method also has certain defects, such as low thermal conductivity which is only 1-4W/(m.k), and a serious "extrusion effect", which is called as "extrusion effect", because the thermal grease is a viscous liquid, and in the process of temperature change, due to the expansion and contraction effect, tiny reciprocating deformation is generated between the chip and the heat dissipation substrate, and between the heat dissipation substrate and the heat sink, and the tiny reciprocating deformation can cause the thermal grease to be extruded, so that the contact between the chip and the heat dissipation substrate is insufficient, the heat dissipation capability is reduced, and the thermal resistance is increased.

In addition, the heat-conducting silicone grease is easy to age after being used at high temperature for a long time, cannot be reused after being removed, and cannot be recycled. The common thermal interface material also comprises a heat conducting pad, wherein a high-heat-conducting filler is added into an elastic polymer to form a solid heat conducting pad with certain flexibility, the heat conductivity coefficient of the solid heat conducting pad is generally 0.8-3W/(m.K), and the thickness after installation is generally 0.2-1 mm.

In electronic packaging, the packaging pressure is small, and excessive packaging pressure may damage the chip. The thermal interface material plays a role in heat transfer medium, for example, when the heat dissipation substrate and the heat sink are packaged together, the thermal interface material receives heat transferred from the heat dissipation substrate and transfers the heat to the heat sink, the heat dissipation substrate and the heat sink are rigid bodies, when the heat dissipation substrate and the heat sink are packaged, gaps between the heat dissipation substrate and the heat sink are not uniform, the gap between the heat dissipation substrate and the heat sink is large, the gap between the heat dissipation substrate and the heat sink is small, the surfaces of the heat dissipation substrate and the heat sink are not completely smooth, the heat dissipation substrate and the heat. Therefore, as an excellent thermal interface material, it is necessary to have a certain flexibility, a certain compressibility in the thickness direction, and be able to adapt to package gaps of different sizes under a slight package pressure, fill in the uneven pits, and be closely attached to the surface of the heat sink and the heat spreader.

Metallic materials have much greater thermal conductivity than polymeric materials, but conventional metallic materials are rigid, inflexible, and nearly incompressible under slight packaging pressures. Even if a relatively flexible copper foil or aluminum foil with the thickness of 0.02mm is adopted, the copper foil or aluminum foil has no compressibility in the thickness direction under slight packaging pressure, can not adapt to packaging gaps with different sizes, and can not fill uneven surface pits, so that no metal-based thermal interface material is put into industrial application except for liquid metal and brazing solder at present, and if metal is used as the thermal interface material, the metal material has flexibility and compressibility.

Therefore, the present invention needs to solve the problem of conventional metals being rigid and incompressible under slight packaging pressure, and to make the metal material soft and compressible.

An Insulated Gate Bipolar Transistor (IGBT) is a fully-controlled voltage-driven power semiconductor device, and has the advantages of small driving power, fast switching speed, and low saturation voltage drop, and an IGBT module is a modular semiconductor product formed by bridging and packaging IGBTs and FWDs (Free Wheeling Diode chips) through a specific circuit, is a core device for energy conversion and transmission, and is widely applied in the fields of rail transit, smart grid, aerospace, electric vehicles, new energy equipment, and the like. For example, in an electric vehicle charging pile, an IGBT chip performs ac-dc conversion, during charging, ac power is converted into dc power required by a battery, and when the electric vehicle is in a driving state, the dc power output by the battery is converted into ac power to be supplied to an ac motor, and the IGBT chip also needs to regulate and control the voltage of the whole vehicle in real time. The IGBT is also a core component of a rail transit electric transmission control system, a traction electric transmission system is a key for controlling a high-speed rail and a heavy-load train, two important power modules, namely a main traction converter and an auxiliary converter, are formed inside an electric locomotive, the main traction converter provides power for the traction locomotive, the power is highest, the voltage is maximum, the working condition is severe, the auxiliary converter supplies power for other non-power currents, such as an air conditioner, a lamp, a backup power supply and the like, the voltage and the power are relatively low, and the current, the voltage and the frequency are controlled by the main traction converter and the auxiliary converter through the IGBT modules. Taking the IGBT module for the 7200 kilowatt high-power alternating-current electric locomotive as an example, 36 chips are packaged in one IGBT module, and the rapid conversion of current can be realized within one millionth of a second. Different from a common electronic product chip, the IGBT is a power chip and is used for converting and controlling current and voltage, the output power is different from several KW to thousands KW, the current reaches hundreds of amperes, so that the heat productivity is huge, the working temperature can reach 175 ℃ at most, the working temperature of the IGBT packaging module is higher than that of the common chip, and experiments show that the failure rate caused by the temperature is doubled when the working temperature of the chip rises by 10 ℃.

The IGBT module comprises four layers of components and three layers of connections, a lamination packaging technology is adopted, the four layers of structures sequentially comprise an IGBT chip, a DBC (direct Bonding coater) board, a heat dissipation substrate and a heat sink from top to bottom, and the DBC board is a mainboard with copper coated on two sides of a ceramic substrate. The three layers are connected, wherein the IGBT chip is connected with the copper layer of the DBC board through a bonding wire and brazing, the DBC board is connected with the heat dissipation substrate through brazing, the heat dissipation substrate is connected with the heat sink through heat-conducting silicone grease made of thermal interface materials, and the substrate and the heat sink are clamped through fasteners. The IGBT chip improves the packaging density through a welding technology, is compact in packaging, shortens the interconnection length of wires between the chips, and improves the operation speed of devices.

In the three-layer connection of the package, the interfaces between the first layer of IGBT chip and the DBC board and between the second layer of DBC board and the heat dissipation substrate are in brazing connection, the welding material is Sn-Pb series or Sn-Ag series metal welding flux, the heat conductivity coefficient is high and generally ranges from 20W/(m.K), the heat dissipation performance is good, the thermal interface material between the third layer of heat dissipation substrate and the heat sink is heat-conducting silicone grease, the heat conductivity coefficient is only 0.4W/(m.K), and a serious extrusion effect exists. The heat is conducted to the DBC board, the heat dissipation substrate and the heat sink from the IGBT chip in sequence, the heat can be smoothly transmitted between the IGBT chip and the DBC board and between the DBC board and the heat dissipation substrate through the metal brazing material, the heat dissipation substrate and the heat sink are connected through the heat conduction grease, the heat conduction coefficient is low, heat transmission is seriously restricted, a heat dissipation bottleneck is formed, the heat generated by the IGBT chip can not be smoothly transmitted to the heat sink, the temperature of the chip is increased, and the reliability is reduced.

The IGBT is mainly used to realize fast switching of current, which generates large power loss, and therefore heat dissipation is an important factor affecting reliability. In the seven-layer structure of the IGBT, due to mismatch of thermal expansion coefficients, very large thermal stress is brought to each layer, and under the condition of temperature difference, deformation of materials of each layer is different, and different parts of materials of the same layer are different in deformation degree due to difference of temperature distribution, so that the problem of excessive local stress exists, and cracking of the materials may be caused. On the other hand, because the automobile and the train have high speed and large jolt in the running process, the IGBT module for the new energy automobile and the rail transit bears the random impact load generated by the vibration of the automobile for a long time, and under the combined action of the thermal stress and the vibration stress, the chip and the DBC plate, the DBC plate and the heat dissipation substrate, and the heat dissipation substrate and the heat sink may crack and be dislocated, so that the IGBT module fails.

As a thermal interface material for packaging an IGBT, particularly an IGBT module which works under the working conditions of jolt and vibration in new energy automobiles, high-speed rails and aerospace, the thermal interface material bears larger thermal stress and certain random impact stress, a packaging gap may have certain fluctuation under the action of the thermal stress and the random impact stress, the thickness of the thermal interface material is required to fluctuate along with the fluctuation of the gap size, the thermal interface material is expected to have certain energy absorption and shock absorption performance so as to reduce the thermal stress and the random impact stress and improve the reliability of the IGBT module, so that higher requirements are provided for the packaging material, and the requirement on better flexibility, compressibility and rebound resilience is further provided.

Therefore, for the thermal interface material for packaging the IGBT module, in addition to high thermal conductivity, heat is smoothly transferred from the heat dissipation substrate to the heat sink, and a certain energy absorption and vibration reduction property is required to reduce thermal stress and vibration stress, thereby greatly improving the reliability of the IGBT module.

Patent application No. 201310659254.X discloses a thermally conductive fabric for use as a flexible heat sink, wherein the thermally conductive fabric comprises three layers: surface layer, basic unit and inlayer. The surface layer is a pure copper wire woven layer, the base layer is a 1:1 blended fabric of copper wires and heat conducting fibers, and the inner layer is a pure copper wire woven layer. The base layer is provided with heat conduction velvet vertical to the surface of the base layer, and the heat conduction velvet penetrates through the surface layer and the inner layer. The surface layer, the base layer and the inner layer are bonded together through silicon-based glue, the three-layer copper fabric is bonded through two layers of silicon-based glue, and the heat conductivity of the silicon-based glue is low and lower than 5W/m.K, so that the heat conductivity of the copper fabric is high, the two layers of silicon-based glue become heat dissipation blocking layers, a heat dissipation bottleneck is formed, and the heat conductivity of the copper fabric can be seriously reduced. The heat-conducting fabric comprises heat-conducting velvet made of carbon fibers penetrating through the surface layer and the inner layer. The carbon fiber has high strength, but poor plasticity, low elongation which is generally lower than 2%, transverse mechanical property of the carbon fiber is only about one percent of longitudinal mechanical property, and the heat-conducting velvet made of the carbon fiber is brittle and easy to break after being bent. When the thermal interface material is installed in gaps among components in an electronic product, the width of the gaps may be smaller than the overall thickness of the heat-conducting fabric, and the carbon fiber heat-conducting velvet is easy to break after bending and cannot be tightly attached to the surfaces of the electronic components under the action of resilience force, so that the heat-conducting fabric disclosed by 201310659254.X cannot be applied to the gaps with the gaps smaller than the thickness of the heat-conducting fabric because the heat-conducting fabric has no compressible and resilient performance, and in fact, the invention of 201310659254.X aims to be used as a flexible radiator and is not a thermal interface material for connecting a chip and the radiator, so the problems of compressibility and resilience are not solved.

Furthermore, US20040071870a1 discloses a thermal interface material whose inspiration comes from the gecko foot, which contains a structure that enables the gecko to run on a glass ceiling or crawl on a slippery glass wall, the gecko toe structure being mainly characterized by: there are pads consisting of thousands of bristles of about 5 microns, each bristle having a tip comprising hundreds of fibers of about 100 nanometers in diameter, each bristle capable of generating a 200 μ N adhesion force known as van der waals forces. The main purpose of the bonding material disclosed in US20040071870a1 is to create surface adhesion, and the key to the technique of creating surface adhesion is the necessity to use nano-sized fluff, such as carbon nanotubes.

Disclosure of Invention

One object of the present invention is to provide a double-sided plush heat conduction blanket for an electronic packaging thermal interface material, wherein the double-sided plush heat conduction blanket for an electronic packaging thermal interface material can be compressed and rebound, especially can rebound to an initial state after stress is removed, has energy absorption and shock absorption properties, and is especially suitable for packaging IGBT modules.

Another object of the present invention is to provide a thermal blanket for use as an electronic packaging thermal interface material, wherein the thermal blanket has directional heat transfer properties.

Another object of the present invention is to provide a heat conductive blanket used as an electronic packaging thermal interface material, wherein the heat conductive blanket can adapt to the gap between a chip and a heat dissipation substrate or between a heat dissipation substrate and a heat sink, and has a thermal conductivity greater than that of a thermal silicone grease thermal interface material in the prior art, and has better heat transfer and heat dissipation functions.

To achieve at least one of the above objects, the present invention provides a double-sided pile heat conduction blanket for an electronic packaging thermal interface material, wherein the double-sided pile heat conduction blanket for an electronic packaging thermal interface material comprises:

a layer of base cloth, wherein the base cloth is made of metal fibers, and the thickness of the base cloth is 0.05-1.6 mm; and

the shrunken metal fluff is arranged on the upper surface and the lower surface of the base fabric respectively, wherein the height of the metal fluff relative to one side of the base fabric is 0.1-1.0 mm, the diameter of the metal fluff is 0.005-0.1 mm, and the yield strength of the metal fluff is more than half of the theoretical critical destabilizing stress.

According to the implementation of the invention, the number of the metal fibers on the cross section of the base fabric is more than 5.

According to the implementation of the invention, the base fabric is a woven metal fabric formed by weaving metal yarns, and the thickness of the woven metal fabric is 0.2-1.2 mm.

According to one embodiment of the present invention, the base fabric is a non-woven metal fabric formed by non-weaving metal fibers.

According to another aspect of the present invention, the present invention provides a double-sided pile heat conductive blanket for an electronic packaging thermal interface material, wherein the double-sided pile heat conductive blanket for an electronic packaging thermal interface material comprises:

a layer of base cloth, wherein the base cloth is made of metal foil, wherein the thickness of the metal foil is 0.01-0.08 mm, and the metal foil is provided with a plurality of flocking through holes; and

the shrunken metal fluff is arranged on the upper surface and the lower surface of the base fabric respectively, the height of the metal fluff relative to one side of the base fabric is 0.1-1.0 mm, the diameter of the metal fluff is 0.005-0.1 mm, the metal fluff penetrates through the flocking through holes to form the metal fluff on the upper surface and the lower surface of the base fabric, and the yield strength of the metal fluff is more than half of the theoretical critical destabilizing pressure stress.

According to the implementation of the invention, the hole diameter of the flocking through hole is 0.5-2 mm, and the distance between the centers of two adjacent flocking through holes is 1.5-2 times of the hole diameter.

According to one embodiment of the present invention, the material of the metal base fabric and the metal wool is selected from one or a combination of two or more of pure copper, pure aluminum, pure magnesium, pure iron, copper alloy, aluminum alloy, magnesium alloy and steel alloy.

According to one embodiment of the present invention, the cross-sectional coverage of the metal wool is greater than 20%.

Further objects and advantages of the invention will be fully apparent from the ensuing description and drawings.

These and other objects, features and advantages of the present invention will become more fully apparent from the following detailed description, the accompanying drawings and the claims.

Drawings

Fig. 1 shows a schematic diagram of a double-sided plush thermal blanket structure for an electronic package thermal interface material and its package between a chip and a heat dissipation substrate according to the present invention.

Fig. 2 shows a top view of the metal foil substrate with flocked through-holes in an embodiment of the double-sided pile thermal blanket for an electronic package thermal interface material of the present invention.

Detailed Description

The preferred embodiments in the following description are given by way of example only, and other obvious variations will occur to those skilled in the art. The basic principles of the invention, as defined in the following description, may be applied to other embodiments, variations, modifications, equivalents, and other technical solutions without departing from the spirit and scope of the invention.

It will be understood by those skilled in the art that in the present disclosure, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship indicated in the drawings for ease of description and simplicity of description, and do not indicate or imply that the referenced devices or components must be constructed and operated in a particular orientation and thus are not to be considered limiting.

A double-sided pile thermal blanket for an electronic package thermal interface material according to a preferred embodiment of the present invention will be described in detail below with reference to fig. 1 and 2 of the specification, wherein the double-sided pile thermal blanket for an electronic package thermal interface material can be used for connecting a chip and a heat dissipation substrate, and connecting the heat dissipation substrate and a heat sink.

It is worth mentioning that the double-sided plush heat conducting blanket for electronic packaging thermal interface material is particularly suitable for connecting the heat dissipation substrate and the heat sink in the IGBT module. The double-sided plush heat conduction blanket for the electronic packaging thermal interface material has no extrusion effect, has the performances of compressibility and rebound, and further has good non-uniform gap adaptability.

The invention mainly solves several problems, firstly, the rigid metal material becomes soft and can be compressed under the action of slight packaging pressure, secondly, the thickness of the thermal interface material can fluctuate along with the fluctuation of the size of the gap, the thermal interface material can absorb energy and damp, and the two ends of the thermal interface material are always tightly attached to the surfaces of the heat dissipation substrate and the heat sink, and provides a novel thermal interface material which is soft and compressible, can absorb energy and damp, can conduct heat directionally and can self-adapt to the packaging gap.

In order to achieve the above objects, the present invention provides a solution for processing metal piles on both sides of a base fabric, the overall structure of the double-sided pile heat conduction blanket for an electronic packaging thermal interface material of the present invention is shown in fig. 1, and is composed of a base fabric 10 and metal piles 20 standing on both sides, the middle base fabric is of several types, one is a woven fabric formed by weaving or knitting metal yarns, the second is a non-woven metal fabric formed by non-woven process using metal fibers, the third is a metal foil with screen-shaped flocking through holes, the metal piles 20 are processed by metal fibers, when the double-sided metal pile heat conduction blanket is used for packaging, the double-sided metal pile heat conduction blanket is installed between a heat dissipation substrate and a heat sink, the metal piles 20 are soft, bendable and resilient, and under the action of thermal stress and stress vibration, the metal piles 20 can bend or rebound with the magnitude of stress, thereby enabling the thickness of the thermal interface material to fluctuate with fluctuations in the gap size. The metal fluff 20 stands on the base fabric 10, so that the metal fluff is directionally arranged, and two ends of the metal fluff are respectively clung to the surfaces of the heat dissipation substrate and the heat sink, so that heat is transferred from one end of the metal fluff to the other end, thereby realizing directional heat transfer and solving the problem of directional heat conduction.

The base fabric 10 is of three types, woven metal cloth, non-woven metal cloth, and metal foil with flocked through holes. The weaving cloth is processed by adopting the yarn through a weaving or knitting process, the yarn is spun by a plurality of fibers or a plurality of strands of yarns, the yarn is soft, the processed fabric is as soft as common cloth and can be contracted in the thickness direction under the action of slight packaging pressure, the non-woven metal cloth is processed by adopting metal short fibers through the non-woven process, the non-woven metal cloth has the characteristics of softness and compressibility, the weaving cloth and the non-woven cloth are soft but not necessarily compressible, in order to ensure that the metal base cloth can be compressed, the number of the fibers on the cross section of the metal cloth is more than 5, and the metal fibers can slide and dislocate with each other under the action of slight packaging pressure, so the non-woven metal cloth has certain compressibility, and the problem that the conventional metal material is rigid is solved. The invention can also adopt the metal foil as the middle layer base cloth, in order to plant the metal fluff on the metal foil, the flocking through holes are needed to be processed on the metal foil, the numerous flocking through holes enable the metal foil to be in a sieve mesh shape, the rigidity of the metal foil is reduced by the sieve mesh, and the metal foil with the sieve-shaped flocking through holes has higher flexibility than the metal foil without holes.

For the double-sided pile heat-conducting blanket for electronic packaging thermal interface material of the present invention, the metal pile 20 is required to have a certain yield strength, and still be in an elastic state after being compressed and bent, and can return to the original state after the pressure is removed.

The two longitudinal ends of the metal fluff are respectively clung to the surfaces of the heat dissipation substrate and the heat sink, so that heat is directionally conducted along the longitudinal direction of the metal fluff, and meanwhile, the metal fluff is clung to the rugged pits to fill gaps and the pits, thereby solving the problem that the conventional metal foil is difficult to clung to the surface of the heat dissipation substrate.

The double-sided plush heat conducting blanket for the electronic packaging thermal interface material has the characteristics of softness, compressibility, resilience and directional heat conduction along the plush by adopting the method for processing the shrunken metal plush on the base cloth, and can absorb certain vibration energy through the compression and resilience of the metal plush of the double-sided plush heat conducting blanket for the electronic packaging thermal interface material. In addition, the self-adaptive packaging clearance fluctuation solves the defects that the conventional metal material is rigid, has no compressibility and can not be self-adaptive to the packaging clearance, solves the difficult problem that the directional heat transfer is needed, and is particularly suitable for packaging the IGBT chip working under the vibration working condition.

The weaving method refers to a method for weaving or knitting a fabric by using yarns (warps and wefts), and comprises a weaving and knitting process, which is a common process in the textile industry. The yarn is processed by a spinning process, and is a product processed into a certain fineness by various textile fibers. Fibers are materials that are very thin, typically less than 100 microns in diameter, and hundreds or thousands of times longer than the diameter, and have some flexibility. Continuous strips of fibers that are elongated, flexible and have certain physical and mechanical properties are collectively referred to as yarns. The yarn is a general name of yarn and thread, and the section of a single yarn comprises a plurality of fibers.

Since the metal piles 20 are disposed on both sides of the base fabric 10 in the double-sided pile heat conduction blanket for an electronic packaging thermal interface material of the present invention, the base fabric 10 may not be too thick, otherwise the heat conductivity may be reduced. When the metal base cloth is formed in a weaving mode, the thickness of the metal base cloth formed in a weaving mode is preferably 0.2-1.2 mm and is lower than 0.2mm, yarns are prone to breakage in the weaving process, the thickness is larger than 1.2mm, and the heat conductivity is reduced.

When the base fabric 10 is formed by a non-woven process, it is processed using short metal fibers. Nonwoven processes refer to the process of combining oriented or randomly arranged fibers by friction, cohesion or bonding to form a sheet, web or batt, the main processes including web formation and web consolidation.

The forming of the fiber web is to form loose fiber web by fibers, the forming method of the metal fiber web is mainly mechanical web forming and air flow web forming, the air flow web forming is to make the fibers move in a certain flow field and uniformly deposit and lay layers in a certain mode to form the fiber web, and the fiber web has the characteristic of isotropy. The mechanical reinforcing method mainly comprises a needle punching method and a water punching method. The needle punching method is to repeatedly punch fluffy fiber webs by adopting needles with edges provided with barbs, and the barbs on the needles drive some fibers in the fiber webs to penetrate through the fiber webs, so that the fibers are intertwined in the moving process, thereby playing a reinforcing effect. The hydroentangling method is that a plurality of high-pressure fine water flows are used for carrying out reciprocating continuous injection on a fiber web, and fibers are mutually intertwined and reinforced in the moving process under the action of water pressure. Because the water needling method needs a subsequent drying process and is easy to oxidize when the metal non-woven mat is processed, the invention adopts the needle punching method to reinforce the metal fiber net to obtain the metal non-woven fabric.

Compared with the metal base cloth formed by a weaving mode, the metal base cloth formed by a non-weaving mode is bulkier, softer and more compressible, so that the thickness of the non-weaving metal base cloth can be larger than that of the weaving cloth, but the thickness is too large, the heat conductivity is reduced, and the thickness of the metal base cloth formed by processing the non-weaving mode is not more than 1.6 mm. On the other hand, if the thickness is less than 0.05mm, the difficulty of the needling reinforcement process is increased, so the thickness is not less than 0.05 mm. The air-laid process needs short metal fibers with the diameter of less than 0.005mm, the fiber processing cost is high, the diameter is more than 0.05mm, the flexibility is low, the fibers are not easy to float during air-laid, the diameter is preferably 0.005-0.05 mm, if the length of the metal fibers is less than 30mm, the fibers are not easy to wind and clamp, the length is more than 80mm, the air-laid is difficult, and therefore, when the metal base fabric is formed in a non-woven mode, the metal fibers used during processing have the diameter of 0.005-0.05 mm and the length of 30-80 mm.

In the above embodiment, the metal pile 20 is formed in a manner similar to the formation of the pile of a carpet and a flannelette in daily life. The textile industry has developed a variety of well-established double-sided pile processing methods, such as floating-filament cut pile, napping, flocking, needle punching, and sewing, which can be used to process the double-sided pile heat conductive blanket for an electronic packaging thermal interface material of the present invention. The float long thread cutting method is to cut the pile loops formed by pile weft or pile warp floating on the front and back sides of the fabric to form double-sided pile. The napping method is also called napping and napping, and the fibers on the front and back sides of the woven fabric or the non-woven fabric are hooked and cut off by the napping needles on the surface of the card cloth roller of the napping machine to form double-sided fluff. The flocking method includes two methods of an Axminster loom and a tufting loom, wherein the Axminster method is that firstly, villi are cut into a designated length, then the villi are planted between ground warp layers of ground tissues by a U-shaped or J-shaped consolidation method, then the villi are fixed by weft yarns, and the pile yarns are planted while weaving a base fabric. The tufting machine has a working principle similar to that of a sewing machine, and the tufting needle reciprocates up and down to implant the pile yarn penetrating through the needle eye into the prepared base cloth, so that pile loops are formed on the front and back surfaces of the base cloth, and then the pile loops are cut into piles. The needle punching method is to repeatedly punch a fluffy fiber net by using a needle with a hooked edge, and the hooked edge hooks fibers out of the surface of the fiber net to form fluff while reinforcing the fiber net. The sewing method is to sew the smooth surfaces of two pieces of single-sided fluff cloth together to form double-sided fluff. The base fabrics of the float-long thread cut pile method and the Axminster method belong to woven fabrics, the base fabrics of the needle punching method belong to non-woven fabrics, and the base fabrics of the napping method, the tufting machine method and the sewing method can be woven fabrics or non-woven fabrics. After the metal heat-conducting blanket with double-sided fluff is processed by the method, the fluff can be further arranged, erected and consistent through the procedures of shearing, brushing and the like.

The processing technology of the double-sided fluff is a relatively mature method in the textile industry, the invention is not described in detail, and only natural fibers and chemical fibers used in the textile industry need to be replaced by metal fibers used in the invention, and common yarns used in the textile industry need to be replaced by metal yarns.

In another embodiment of the present invention, the base fabric 10 is implemented to be made of a metal foil. The base cloth 10 is provided with flocking through holes 101 for implanting the metal piles 20. After the metal wool 20 is implanted into the flocking through hole 101 of the base fabric 10, one end of the metal wool 20 passes through the flocking through hole 101, thereby being held on the upper and lower surfaces of the base fabric 10.

When the base fabric 10 is implemented as a metal foil, a carpet weaving gun or a tufting machine may be used to implant the metal wool 20 into the flocking through-hole 101. Because the metal foil is small in thickness and the difficulty of the punching process is high, the invention adopts laser punching, the flocking through holes 101 are processed on the foil in advance through high-energy laser beams to obtain the mesh-shaped metal foil, pile yarns are implanted into the flocking through holes, and the metal piles are neat and erect through the processes of pile cutting, pile shearing, pile brushing and the like.

Preferably, when the base fabric 10 is made of metal foil, the flocked through holes 101 are through holes having a hole diameter d of 0.5 to 2mm, and the distance L between the centers of two adjacent flocked through holes 101 is 1.5 to 2 times the hole diameter d, that is, L = (1.5 to 2) d.

When the base fabric 10 is implemented to be made of a metal foil, the thickness of the metal foil is 0.01 to 0.08 mm.

If the thickness of the foil is less than 0.01mm, the foil is easy to tear in the subsequent processing process, and if the thickness of the foil is more than 0.08mm, the flexibility is low, so that the thickness of the metal foil is 0.01-0.08 mm. Because the copper foil is planted with the flocking yarns which are metal yarns spun by a plurality of metal fibers, the copper foil is required to be processed with the flocking through holes 101, the diameter of the flocking through holes 101 is small, the diameter of the implanted flocking yarns is small, the area of the formed metal fluff 20 is small, the cross section coverage rate of the metal fluff 20 on the metal foil surface is low, the diameter of the flocking through holes 101 is not smaller than 0.5mm, but the flocking through holes 101 are not more than 2mm if the diameter of the implanted flocking yarns is too large and are difficult to cut, the diameter of the flocking through holes 101 is not more than 2mm, the diameter d of the flocking through holes 101 is preferably 0.5-2 mm, and in order to ensure that a certain connecting strength exists between the adjacent flocking through holes 101, the distance between the central lines of the two adjacent flocking through holes 101 is not more than 1.5-2 times of the hole diameter.

In the present invention, the base fabric 10 has flexibility but low compressibility and elasticity, so the present invention processes the metal piles 20 on both sides of the base fabric 10, thereby providing the heat conductive blanket used as a thermal interface material with high compressibility and resilience.

In the invention, the height H of the metal fluff 20 on one side relative to the base fabric 10 is 0.1-1.0 mm, and if the height of the metal fluff 20 on one side relative to the base fabric 10 is lower than 0.1mm, the compressibility and resilience are low, and higher than 1mm, the thermal resistance is increased, and materials are wasted, so the height of the metal fluff is preferably 0.1-1 mm.

In the invention, the section coverage rate of the metal fluff is more than 20%, the section coverage rate of the fluff is the percentage of the total of the section areas of the fluff to the total area of the base fabric, and the section coverage rate of the fluff is high, so that when the metal fluff is used as a packaging material, the contact area between the fluff and a radiator and a chip is large, and the heat conduction effect is good. The covering rate of the fluff of the traditional flannelette or carpet is generally lower than 20%, in order to ensure high thermal conductivity, the covering rate of the metal fluff needs to be more than 20%, and if the covering rate of the section of the metal fluff is less than 20%, gaps among the fluff are large, air gaps are large, and the thermal conductivity is seriously reduced.

The metal fluff 20 is processed by metal fibers, and the smaller the diameter of the metal fibers is, the better the flexibility and the compressibility are, the easier the filling of tiny pits on the surfaces of a chip and a radiator is, the contact area is increased, and the thermal resistance is reduced.

The metal fiber has a diameter of 0.005 to 0.1mm, and if the diameter of the metal fiber is less than 0.005mm, the fiber processing cost is high, and if the metal fiber is too thin, the specific surface area is large, and the metal fiber is easily oxidized to lose its efficacy, so that the diameter of the metal fiber is not preferably less than 0.005mm, while if the diameter of the metal fiber is more than 0.1mm, the flexibility is low, and the diameter of the metal pile 20 is preferably 0.005 to 0.1. In order to ensure that the metal wool 20 is still in an elastic deformation state and has a certain resilience after being bent under the packaging pressure, the metal fibers forming the metal wool 20 have certain requirements on plastic yield strength.

During the packaging process, the double-sided pile thermal blanket for the thermal interface material of the electronic package is compressed under the packaging pressure, and the metal piles 20, which are initially shrunken, are deflected under the pressure. During the deformation process, each of the metal piles 20 can be approximately considered as an elongated round rod with one fixed end and one free end, the free end is subjected to pressure P along the axial direction, and assuming that the height of one side of the metal pile 20 relative to the base fabric 10 is H, the diameter is D, and the cross-sectional area a = (pi D)²) (ii)/4, modulus of elasticity E, moment of inertia I =(πD⁴)/64. According to the Euler formula of the compression bar instability, the critical pressure P of the metal fluff 20 for deflection instability_c=(π²EI)/(4H²) Critical compressive stress of σ_c=P_c/A=π²/64(D/H)²E. In order to ensure that the metal wool 20 is still in an elastic state after compression instability, the plastic yield strength σ of the metal wool 20_sShould be greater than the critical compressive destabilizing stress sigma_cI.e. sigma_s>σ_c。

It is worth mentioning that the critical stress σ estimated here_cIn practical applications, this is a large value, mainly because during the bending of the metal wool 20, most of the metal wool is not perfectly vertical, but rather is inclined, so that the actual flexural stress is much smaller than the theoretical critical compressive stress σ_c. Considering the above practical factors, the actual yield strength of the metal wool 20 can be properly smaller than the theoretical critical compressive destabilizing compressive stress, and practice proves that the plastic yield strength of the metal wool 20 is greater than 0.5 sigma_cIt is ensured that most of the metal wool 20 is still in an elastic state after being flexed, and the yield strength of the metal wool 20 is not too high, which may result in an increase in the required packaging pressure.

The metal fluff 20 of the double-sided fluff heat conduction blanket for the electronic packaging thermal interface material is still in an elastic state after being bent under the action of slight packaging pressure, and under the action of resilience force, the metal fluff 20 can be tightly attached to electronic components forming a gap, such as the surfaces of a chip and a radiator in an IGBT module, so that the double-sided fluff heat conduction blanket for the electronic packaging thermal interface material is tightly attached to the chip and the radiator. The two-sided plush heat conduction blanket for the thermal interface material of the electronic package has the characteristic of directional heat conduction because the ends of the metal fluffs 20 on both sides of the base fabric 10 are respectively tightly attached to the heat dissipation substrate and the heat sink to play a role of directional heat conduction, and heat is guided from the heat dissipation substrate to the heat sink along the two-sided plush heat conduction blanket for the thermal interface material of the electronic package. Compared with the conventional heat-conducting silicone grease, the double-sided plush heat-conducting blanket for the electronic packaging thermal interface material has the advantages that the heat conductivity is far greater than that of the heat-conducting silicone grease in the prior art, the blanket has the characteristics of compressibility, resilience and directional heat conduction, vibration energy can be buffered, micro deformation of an IGBT assembly caused by circulating thermal stress can be naturally relaxed to a certain degree, fatigue thermal stress is released, and the blanket is not possessed by other thermal interface materials.

The double-sided plush heat-conducting blanket for the electronic packaging thermal interface material has a structure similar to that of the traditional carpets and flannelette, and is composed of the base cloth 10 and the metal plush 20, so that the method for processing the carpets and flannelette can be transplanted to process the double-sided plush heat-conducting blanket for the electronic packaging thermal interface material, and the processing process is simple.

For the IGBT module working under the severe vibration working condition, the double-sided plush heat conducting blanket for the electronic packaging thermal interface material can be stacked for use, so that the thickness of the thermal interface material is increased, the flexibility and the compressibility of the thermal interface material are further improved, the capacity of absorbing certain vibration energy is improved, and the stress born by a module component is reduced.

The double-sided plush heat conduction blanket for the electronic packaging thermal interface material has no caking property, and can be used together with the traditional heat conduction silicone grease, heat conduction glue and the like under the condition that the surface bonding force between the thermal interface material and the heat dissipation substrate is required to be large, the metal blanket thermal interface material of the invention is dripped into the metal plush 20 of the double-sided plush heat conduction blanket for the electronic packaging thermal interface material and then packaged, for example, the double-sided plush heat conduction blanket is packaged between the heat dissipation substrate and the heat sink of an IGBT module, so that the bonding force between the double-sided plush heat conduction blanket for the electronic packaging thermal interface material and a chip and a radiator can be improved.

The IGBT chip has high power which can reach thousands of kw, the working temperature is high and can reach 175 ℃, the working temperature fluctuates in a large range, a temperature gradient from high to low can be formed among the four layers of components of the IGBT chip, the DBC board, the radiating substrate and the heat sink, the materials of the four layers of components are different, the thermal expansion coefficients are different, fluctuating thermal stress exists among the components along with the fluctuation of the temperature, on the other hand, the IGBT module which works under the bumping and vibrating working conditions of new energy vehicles, high-speed rails and the like can bear random or regular vibration impact, vibration stress is generated among the components, the fatigue cracking of the structure can be caused under the combined action of two stresses of the long-term circulating thermal stress and the vibration stress, and the reliability of the IGBT module is reduced. The double-sided plush heat conduction blanket for the electronic packaging thermal interface material has high heat conductivity, softness, compressibility and rebound resilience, and can buffer partial thermal stress and vibration stress, thereby improving the reliability of the IGBT module. The end of the metal fluff 20 at one side of the base fabric 10 of the double-sided fluff heat conduction blanket for electronic packaging thermal interface material of the present invention is tightly attached to the surface of the heat dissipation substrate or heat sink, and the end of the metal fluff 20 at the other side of the base fabric 10 is tightly attached to the surface of the heat sink or heat dissipation substrate, so as to realize the directional conduction of heat along the double-sided fluff heat conduction blanket for electronic packaging thermal interface material.

It should be noted that the base fabric 10 and the metal wool 20 may be made of metal fibers, and the material of the metal fibers is generally copper and copper alloy, aluminum and aluminum alloy, magnesium and magnesium alloy, and steel alloy.

It is understood that metals have high thermal conductivity, much higher than polymeric materials and polymers, for example, silver has thermal conductivity 429W/(m.k), copper 401W/(m.k), gold 263W/(m.k), aluminum 237W/(m.k), tungsten 173W/(m.k), magnesium 148W/(m.k), molybdenum 138W/(m.k), zinc 116W/(m.k), chromium 97.3W/(m.k), nickel 90W/(m.k), pure iron 80W/(m.k), platinum 71W/(m.k), tin 67W/(m.k), lead 34.8W/(m.k), vanadium 30.7W/(m.k), zirconium 20W/(m.k), titanium 15W/(m.k), manganese 7.8W/(m.k) at room temperature.

For the alloy material, C17510 beryllium copper alloy 245W/(m.K), 1050 aluminum alloy 209W/(m.K), 6063 aluminum alloy 201W/(m.K), 6061 aluminum alloy with thermal conductivity of 155W/(m.K), 5052 aluminum alloy 138W/(m.K), 7075 aluminum alloy 130W/(m.K), 2024 aluminum alloy 121W/(m.K), Cu-35Zn brass alloy (containing 35wt% of zinc) 119W/(m.K), C17200 beryllium copper alloy 105W/(m.K), AZ31 magnesium alloy 96W/(m.K), C5210 phosphor bronze 63W/(m.K), C00 copper nickel zinc alloy 50W 727m.K), gallium (melting point 29.9 ℃) 40.6W/(m.K), stainless steel 10-30W/(m.K) (316L and 301 stainless steel 16W/(m.K)), nickel chromium alloy (containing 20wt% of chromium) 13.4W m.K), N0440W/(m.K), and Ti (13W) (13.044W/(m.K), and Ti (13-6W/(m.K).

The heat conducting silicone grease is the most commonly used heat interface material in the prior art, the heat conductivity of the heat conducting silicone grease is only about 1-5W/(m.K), generally 2W/(m.K), the heat conductivity of copper is 200 times that of the heat conducting silicone grease, even 316L stainless steel with low heat conductivity is 3 times that of silicone grease, so the heat conductivity of the heat conducting blanket for electronic packaging can be improved by adopting metal or/and alloy materials as the heat interface material.

For processing metal woven fabric, metal non-woven fabric or metal fluff, the raw material is metal fiber, and at present, various mature metal fiber processing methods such as monofilament drawing method, cluster drawing method, melt drawing method and cutting method have been developed in the industry, wherein the former two methods can process metal filament fiber with large length, and the cutting method can only produce short fiber. The monofilament drawing method adopts a plurality of dies for continuous drawing, each die can only draw one long fiber, the production efficiency is low, and the cost is high. The cluster drawing method is used for coating a plurality of metal wires and then intensively drawing the metal wires, so that a plurality of long-length metal fibers can be prepared at one time, the production efficiency is high, and the uniformity of the wire diameter and the surface smoothness are lower than those of a monofilament drawing method. The melting and drawing method uses a roller wheel rotating at high speed to dip a liquid thin layer from an alloy melt, and the liquid thin layer is rounded into filaments under the action of cooling, solidification and self surface tension, so that the metal fibers with medium length can be prepared. The cutting method only can produce short fibers by scraping metal fibers from solid metal by using a cutter, the fibers are bent and have rough surfaces, the wire diameters are not uniform and uniform, and the production efficiency is high. Long fibers or short fibers with different materials and different wire diameters ranging from 1 to 100 micrometers are commercially available at present, wherein the amount of the stainless steel fibers is the largest. The metal long fiber or short fiber can be spun into metal yarn, and can be used for weaving metal base cloth, and the weaving methods commonly used in the weaving process include weaving and knitting, which can be used for processing the metal base cloth used in the invention.

From the above description, it can be understood by those skilled in the art that the present invention has the following advantageous technical effects compared to the existing thermal interface material:

1. the thermal interface material has good energy absorption and shock absorption properties, metal fluff is arranged on two sides of the thermal interface material, the thermal interface material can rebound after compression, can deform in a self-adaptive manner, absorbs partial thermal stress and vibration stress, is particularly suitable for an IGBT chip working under a vibration working condition, and can improve the reliability of an IGBT module;

2. the thermal conductivity is high, the thermal conductivity can reach 100W/(m.K) under the condition of adopting the red copper material and is about 30 times of that of the heat-conducting silicone grease, and the thermal conductivity can reach 60W/(m.K) under the condition of adopting the 6063 aluminum alloy material and is about 20 times of that of the heat-conducting silicone grease.

3. The double-sided plush heat conduction blanket for the electronic packaging thermal interface material can be compressed, rebounded and has good fitting performance, the double-sided plush heat conduction blanket for the electronic packaging thermal interface material can be self-adaptively provided with gaps under packaging pressure, and metal plush can be tightly fitted to the surfaces of a chip and a radiator under the action of rebounding force, so that the fitting performance is good;

4. the heat is directionally conducted, two ends of the metal fluff are tightly attached to the surfaces of the heat dissipation substrate and the heat sink, and the heat is directionally conducted from the heat dissipation substrate to the heat sink along the metal fluff;

5. no pumping effect exists, and because the thermal interface material is solid, no liquid pumping effect exists;

6. the thermal interface material is processed by metal fibers, is made of copper and copper alloy, aluminum and aluminum alloy, steel alloy, magnesium and magnesium alloy, is durable, and does not have the aging problem of high polymer materials;

7. the thermal interface material can be cut into the shape of a chip or a radiator, can be placed on the surface of the chip or the radiator, is simple and easy to use, install, replace and clean, can be repeatedly used, and cannot flow to pollute the chip;

8. the thickness can be adjusted, and a plurality of layers of the heat conducting blankets can be stacked, so that the effects of further damping and reducing stress impact are achieved;

9. the processing technology is mature, the cost is low, the adopted weaving or non-weaving method is mature in the textile industry, the processing method is various, and the processing cost is low;

10. the user selection range is wide, can select metal fiber heat conduction blanket, and corrosion resistance, density are different, and the user can select according to actual need.

11. After the service life is over, the double-sided plush heat conduction blanket for the electronic packaging thermal interface material can be recycled, while the traditional heat conduction silicone grease can not be recycled.