JP2008060535A - Radiating substrate for electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiating substrate having a mechanical structure which has an excellent radiation, a high voltage resistance, a dielectric insulation, and a flexibility. <P>SOLUTION: The radiating substrate 20 for an electronic device includes a first metal layer 21, a second metal layer 22, and a heat-conductive polymer dielectric insulating layer 23. An LED is mounted on the surface of the first metal layer 21. The heat-conductive polymer dielectric insulating layer 23 is laminated between the first metal layer 21 and second metal layer 22 so as to contact with the first metal layer 21 and second metal layer 22 directly, and there is at least one fine rough surface having a surface roughness (Rz) larger than 7.0 between them. There are many nodular protrusions on the fine rough surface, and the particle diameter of the nodular protrusion mainly is 0.1 to 100 μm. The heat conductivity of the radiating substrate 20 is more than 1 W/m×K, and its thickness is thinner than 0.5 mm, and the substrate contains (1) a polymer which has a melting point higher than 150°C and contains fluorine of 30 to 60 vol% and (2) a heat conductive filler, of 40 to 70 vol%, dispersed in the polymer containing fluorine. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat dissipation substrate, and more particularly to a heat dissipation substrate for an electronic device.

  In recent years, white LEDs have become a very popular new product that has gained widespread attention all over the world. The white LED is small in size, has low power consumption, long-term durability, and excellent response speed, so that the problems of conventional incandescent lamps may be solved. Therefore, the use of LEDs in backlight sources for displays, mini projectors, lighting, and light sources for vehicle lamps is becoming increasingly important in the market.

  Currently, Europe, the United States, Japan and other countries have agreements on energy saving and environmental protection, and white LEDs are being actively developed as new light sources for lighting in this century. Currently, many countries are importing energy, and the development of white LEDs in the lighting industry is valuable. According to expert evaluation, if all white light luminaires in Japan are replaced with white LEDs, it can save electricity equivalent to two power plants every year, and indirectly reduce fuel Consumption will be as much as 1 billion liters. Furthermore, carbon dioxide emitted by power generation is also reduced, thereby reducing greenhouse gases. Therefore, many European countries, the United States, and Japan have invested many people in developing white LEDs. Within 10 years, the possibility of replacing conventional lighting devices with white LEDs is expected.

  However, for high power LEDs for illumination, only 15-20% of the input power of the LED is converted to light, and the remainder of the input power is converted to heat. If heat cannot be dissipated to the surroundings at that time, the temperature of the LED device will be very high, which will adversely affect the light intensity and the service life. Therefore, thermal management of LED devices has attracted a great deal of attention.

  In general, for a conventional single LED, the operating current of the conventional single LED is about 20-40 mA, and the heat generated thereby is small, so the problem of heat dissipation is not a serious problem. Therefore, even a general FR4 printed circuit board (PCB) having a heat dissipation coefficient of about 0.3 W / m · K is sufficient to dissipate heat. However, when used for a backlight display or bright illumination, many LED devices are mounted on a circuit board. The need for higher current (> 1A) results in very large heat generation from the LED device, and the circuit board serves not only as a carrier for the LED device but also as a heat sink for heat dissipation. You have to bear A general FR4PCB cannot satisfy the heat dissipation requirement.

  The present invention has better heat dissipation, high voltage resistance, and dielectric insulation, and further, the metal layer is made of a thermally conductive polymer dielectric insulation layer so that it can be applied to high power LEDs, for example, mobile phones. The main purpose is to provide a heat dissipation board with a flexible mechanical structure that is well bonded.

  According to the present invention, the heat dissipation substrate for an electronic device includes a first metal layer, a second metal layer, and a thermally conductive polymer dielectric insulating layer. An electronic device such as an LED device is mounted on the surface of the first metal layer. The thermally conductive polymer dielectric insulation layer is in direct contact with and laminated between the first metal layer and the second metal layer. The bonding surface between the thermally conductive polymer dielectric insulating layer and the first and second metal layers has at least one minute unevenness (surface roughness (Rz) greater than 7.0 according to JIS B0601 1994). micro-round) surface. The micro uneven surface has many nodular protrusions having a particle size mainly in the range of 0.1 to 100 μm. The thermally conductive polymer dielectric insulating layer has a thermal conductivity greater than 1 W / m · K and a thickness of less than 0.5 mm. The thermally conductive polymer dielectric insulating layer comprises (1) 30-60% by volume fluorine-containing polymer having a melting point higher than 150 ° C., and (2) 40-70% by volume dispersed in the fluorine-containing polymer. A thermally conductive filler.

  The heat dissipation substrate according to the present invention includes a thermally conductive polymer dielectric insulating layer, a first metal layer, and a second metal layer. The thermally conductive polymer dielectric insulating layer comprises (1) 30-60% by volume fluorine-containing polymer having a melting point higher than 150 ° C., and (2) 40-70% by volume dispersed in the fluorine-containing polymer. A thermally conductive filler. The first metal layer is in direct contact with one of the surfaces of the thermally conductive polymer dielectric insulation layer and protrudes from the surface by a distance of 0.1-100 μm having a surface roughness (Rz) greater than 7.0. It has a micro uneven surface which consists essentially of small bumps. The second metal layer is in direct contact with the other side of the thermally conductive polymer dielectric insulation layer and has a surface roughness (Rz) greater than 7.0 from the surface by a distance of 0.1-100 μm. It has a micro uneven surface substantially consisting of protruding small bumps. The heat dissipation substrate has a thermal conductivity greater than 1.0 W / m · K, and the overall thickness of the substrate is less than 0.5 mm.

  The fluorine-containing polymer is preferably selected from polyvinylidene fluoride (PVDF) or polyethylene tetrafluoroethylene (PETFE), and the melting point is higher than 150 ° C. and preferably 220 ° C. or higher. The conductive filler is selected from thermally conductive ceramic materials such as nitrides and oxides. In order to strengthen the bond with the fluorine-containing polymer, the filler may be pretreated with a silane coupling agent.

  It is well known that fluorine-containing polymers are non-sticky and have non-stick properties. The most common method of adhering fluorine-containing polymers to metal surfaces is to apply a tie-layer between them. However, bond layers commonly used for fluorine-containing polymers are not good thermal conductive materials. Even a thin layer of bonding layer can significantly reduce the thermal conductivity of the system. Adhering a fluorine-containing polymer to a metal substrate while maintaining good thermal conductivity is a major challenge. The present invention achieves good flexibility, good thermal conductivity, and good performance to withstand voltage, so it is small for bonding with highly filled thermally conductive fluoropolymers without the use of a tie layer. Teaching the application of a metal foil with a bump.

  The heat dissipation substrate can crosslink and cure the thermally conductive polymer dielectric insulation layer by irradiating with 0-20 millirad, and has preferable thermal conductivity and insulation effect. Furthermore, if the thickness of the first metal layer and the second metal layer is designed to be less than 0.1 mm and 0.2 mm, respectively, the thickness of the thermally conductive polymer dielectric insulating layer is preferably 0.5 mm (preferably If it is designed to be thinner than 0.3 mm), the heat dissipation board passes a bending test in which a test board having a width of 1 cm is bent into a column having a diameter of 5 mm, and a crack or crack is formed on the surface. Will be applicable to folding products.

  Furthermore, the fluorine-containing polymer material usually has a high melting point (for example, PVDF has a melting point of 165 ° C. and PETFE has a melting point of 260 ° C.), and has an advantage of being flame retardant and resistant to high temperatures. Fluorine-containing polymers are therefore valuable for safety applications.

BEST MODE FOR CARRYING OUT THE INVENTION

  Referring to FIG. 1, the LED device 10 is mounted on the heat dissipation substrate 20. The heat dissipation substrate 20 includes a first metal layer 21, a second metal layer 22, and a thermally conductive polymer dielectric insulating layer 23 laminated between the first metal layer 21 and the second metal layer 22. The LED device 10 is disposed on the surface of the first metal layer 21, and the bonding surface between the first metal layer 21 and the second metal layer 22 and the thermally conductive polymer dielectric insulating layer 23 are in direct contact, where At least one of the bonding surfaces is a micro uneven surface. The micro uneven surface has many nodular protrusions having a particle size mainly in the range of 0.1 to 100 μm, thereby increasing the tensile strength between them.

  A method for manufacturing the heat dissipation substrate 20 will be described below. The supply temperature of the batch type blender (HAAKE-600P) is set to 20 ° C. higher than the melting point (Tm) of the raw material, the raw material of the thermally conductive polymer dielectric insulating layer 23 mixed in advance is added, and the raw material is put in a steel cup. Stir uniformly with a measuring spoon. Initially, the rotational speed of the batch blender is 40 rpm, and after 3 minutes, the rotational speed is increased to 70 rpm. The raw materials are mixed for 15 minutes and then removed, thereby producing a heat dissipation composite material.

The heat dissipation composite material is placed in a mold while being leveled in the vertical direction. In the mold, a steel plate is used for the outer layer, and the thickness is medium, for example, 0.15 mm. Place Teflon (registered trademark) release cloth on the upper and lower sides of the mold. First, the heat-dissipating composite material is preheated for 5 minutes, and then pressure is applied for 15 minutes under a pressure of 150 kg / cm ² and the same temperature as during mixing. Then, a heat dissipation sheet having a thickness of 0.15 mm is formed.

The first metal layer 21 and the second metal layer 22 are arranged on the upper and lower sides of the heat-dissipating sheet. Next, the pressure is applied again and heated in advance for 5 minutes, and then the pressure is 150 kg / cm ² and the same temperature as that during mixing When the pressure is applied for 15 minutes, the thermally conductive polymer dielectric insulating layer 23 exists in the middle, and the first metal layer 21 and the second metal layer 22 adhere to the upper and lower sides of the polymer dielectric insulating layer 23, respectively. The heat dissipation substrate 20 is formed.

Table 1 shows the experimental results of the tensile and withstand voltage tests according to the difference in the roughness of the metal layer. For the heat conductive polymer dielectric insulating layer 23, polyvinylidene fluoride (PVDF) having a melting point of 165 ° C. is used as a raw material, and heat conductive fillers Al ₂ O ₃ and AlN are dispersed in PVDF. Here, the volume% of these two kinds of fillers is 60% and 45%, respectively. In this embodiment, the thickness of the thermally conductive polymer dielectric insulation layer 23 is less than 0.3 mm. The adhesion test is performed based on JIS standard C6481 for the peel strength test of the adhesive surface.

  As shown in Table 1, the surface roughness (Rz) of the comparative example is in the range of 3.0 to 4.5 and is lower than those of Examples 1 to 7. The adhesion of the comparative example is 7.5 N / cm, much lower than Examples 1-7. It is clear that as the roughness increases, the peel strength between the thermally conductive polymer dielectric insulation layer and the first and second metal layers can increase. Furthermore, all of the implementations can pass a withstand voltage test higher than 5 kV or at least 3 kV, and the thermal conductivity is greater than 1.0 W / m · K.

Table 2 shows a comparative experiment table for different types of high molecular polymers.

Examples 1 and 2 use PVDF and PETFE (Tefzel (trademark)) as polymer raw materials, respectively, and the thermally conductive filler is Al ₂ O ₃ . Comparative Examples 1 and 2 are selected from HDPE and EPOXY (epoxy resin) that do not contain fluorine. In the examples and comparative examples, the volume percentages of the polymer and the thermally conductive filler are 40% and 60%, respectively, and a copper foil having the same roughness (Rz) of 7.0 to 9.0 is used as the first metal layer. And used as the second metal layer.

Comparative examples of epoxy resins include liquid epoxy resins, novolac resins, dicyandiamide, urea catalysts, and Al ₂ O ₃ . For the liquid epoxy resin, the DER331 model manufactured by Dow Chemical Company (Michigan, USA) is selected. For the novolak resin, the DEN438 model manufactured by Dow Chemical Company is selected. ) Dyhard UR300 manufactured by Degussa Fine Chemicals is selected as the urea catalyst. The particle diameter of Al ₂ O ₃ is 5 to 45 μm and is manufactured by Denki Kagaku Kogyo Co., Ltd.

The epoxy resin is prepared according to the following steps. First, 50 parts (phr) of DER331 and 50 parts of DEN438 are put in a resin kettle and mixed at 80 ° C. until a uniform solution is obtained. Next, 10 parts of Dyhard 100S and 3 parts of Dyhard UR300 are added to the resin kettle as a percentage of outer shell and further mixed at 80 ° C. for 20 minutes. Subsequently, 570 parts of Al ₂ O ₃ filler in an outer percentage is added to the resin kettle and mixed until the filler is completely dispersed in the resin to form a resin suspension. The gas in the resin suspension is removed in vacuo for 30 minutes. Next, the resin suspension is placed on the surface of the copper foil, and the other copper foil is placed on the surface of the resin suspension, thereby forming a composite structure of copper foil / resin suspension / copper foil. The composite structure of copper foil / resin suspension / copper foil is placed on a metal frame having a thickness of 3 mm. Use a rubber roller to flatten the surface of the copper foil. The composite structure with the metal frame is placed in a heating furnace at a temperature of 130 ° C. and precured for 1 hour. Next, the composite structure with the metal frame is placed in a vacuum heating press with a vacuum of 1330 Pa (10 torr) and a pressure of 4.9 × 10 ⁶ Pa (50 kg / cm ² ), and further cured at 150 ° C. for 1 hour. The composite structure is cooled to 50 ° C. or lower at a pressure of 4.9 × 10 ⁶ Pa (50 kg / cm ² ) and taken out from the hot press.

  The following tests were conducted on test substrates using examples of PVDF and PETFE and comparative examples of HDPE and epoxy resin.

  1. Flexibility: A 1 cm wide test specimen is folded 180 ° along the outer circumference of a diameter metal rod. It is necessary that the surface of the test specimen does not crack or crack.

  2. Peel strength test: T-type peel strength measurement at 180 ° is performed on a test specimen (1.0 cm × 12 cm).

In this method, the upper and lower portions of the metal foil at one end of the specimen are fixed and the sample is tested with a tensile tester at a constant tensile speed of 3 cm / min.

  3. Dielectric strength (insulation withstand voltage) test: a withstand voltage test using a TOS5101 model withstand voltage test apparatus manufactured by Kikusui Electronics Corporation, 1 kV for 30 seconds on the upper and lower electrodes of a sample having a diameter of 2.54 cm (1 inch) A continuous test is performed in which the voltage is increased by 0.5 kV each time until the voltage exceeds the withstand voltage of the insulating layer of the sample.

  As shown in Table 2, Examples 1 and 2 using PVDF and PETFE, which are fluorine-containing polymers, have excellent flexibility, and these two examples can withstand voltages higher than 5 kV. The test is also passed. On the other hand, Comparative Example 1 using HDPE as the polymer passed the flexibility test, but the HDPE system can withstand only voltages lower than 2 kV, which is clearly lower than Examples 1 and 2. The withstand voltage test is rejected. In Comparative Example 2 in which an epoxy resin is used as the polymer, the dielectric strength test is acceptable, but it is unacceptable in terms of flexibility.

  Furthermore, fluorine-containing raw materials such as PVDF and PETFE do not ignite easily, do not promote combustion (conforms to the combustion test standard UL94V-0) and are much more suitable for safety applications than HDPE or epoxy resins. .

  The volume percentages of the fluorine-containing polymer and the thermally conductive filler are somewhat compliant and still retain similar properties. The volume percentage of the fluorine-containing polymer is preferably 30 to 60%, the volume percentage of the thermally conductive filler is 40 to 70%, and more preferably 45 to 65%.

  In addition to the previously mentioned materials, the thermally conductive polymer polymer, together with a cure site monomer terpolymer, poly (tetrafluoroethylene) (PTFE), tetrafluoroethylene-hexafluoropropylene (FEP). ), Ethylene-tetrafluoroethylene copolymer (ETFE), perfluoroalkoxy modified tetrafluoroethlenes (PFA), poly (chlorotri-fluorotetrafluoroethylene) (PCTFE), vinylidene fluoride-tetrafluoroethylene Copolymer (VF-2-TFE), poly (vinylidene fluoride), tetrafluoroethylene-perfluorodioxole copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, and Tetrafluoroethylene - can be selected from the group consisting of perfluoromethyl vinyl ether.

The thermally conductive filler may be a nitride and an oxide, where the nitride includes zirconium nitride (ZrN), boron nitride (BN), aluminum nitride (AlN) and silicon nitride (SiN); Oxides include aluminum oxide (Al ₂ O ₃ ), magnesium oxide (MgO), zinc oxide (ZnO), and titanium dioxide (TiO ₂ ).
Furthermore, for the purpose of using for a light emitting diode such as a high power LED, it is possible to use copper for the first metal layer 21 on which the LED device 10 is mounted and to assemble the circuit of the LED device 10 thereon. The lower second metal layer 22 can be made of copper, aluminum, or an alloy thereof.

  The heat dissipation board according to the present invention has excellent thermal conductivity, excellent voltage resistance, excellent tensile strength, and flexibility, and therefore can be used for LED modules for lighting to dissipate heat. Is possible. Furthermore, the heat dissipation board can be used for a small portable device such as a notebook or a mobile phone that requires efficient heat dissipation.

  The above-described embodiments of the present invention are intended to be examples only. Numerous alternative embodiments will be devised by those skilled in the art without departing from the scope of the appended claims.

FIG. 1 represents a heat dissipation substrate according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 LED apparatus 20 Heat dissipation board 21 1st metal layer 22 2nd metal layer 23 Thermally conductive polymer dielectric insulating layer

Claims (17)

(1) 30-60% by volume fluorine-containing polymer having a melting point higher than 150 ° C .;
(2) 40-70% by volume thermally conductive filler dispersed in the fluorine-containing polymer;
Thermally conductive polymer dielectric insulation layer, including
From a small bump that is in direct contact with one surface of the thermally conductive polymer dielectric insulation layer and protrudes from the surface by a distance of 0.1-100 μm with a surface roughness (Rz) greater than 7.0. A first metal layer having a micro asperity surface, and in direct contact with the other surface of the thermally conductive polymer dielectric insulation layer, having a surface roughness (Rz) greater than 7.0 A second metal layer having a micro uneven surface substantially consisting of small bumps protruding from the surface by a distance of 0.1 to 100 μm;
An electronic device heat dissipation board having a thermal conductivity greater than 1.0 W / m · K.   The heat dissipation substrate for an electronic device according to claim 1, wherein the thickness of the first metal layer is 0.1 mm or less.   The heat dissipation substrate for an electronic device according to claim 1, wherein the thickness of the second metal layer is 0.2 mm or less.   The heat dissipation substrate for an electronic device according to claim 1, wherein the melting point of the fluorine-containing polymer is higher than 220 ° C.   The heat dissipation substrate for an electronic device according to claim 1, wherein the heat conductive filler has a capacity percentage of 45 to 65%.   The heat dissipation substrate for an electronic device according to claim 1, wherein a tensile strength between the thermally conductive polymer dielectric insulating layer and the first and second metal layers is greater than 8 N / cm.   2. The heat dissipation board for an electronic device according to claim 1, wherein when the heat dissipation board having a width of 1 cm is bent by 180 ° along the outer periphery of a metal rod having a diameter of 5 mm, no tear or crack is formed on the surface.   2. The heat dissipation substrate for an electronic device according to claim 1, wherein the withstand voltage is larger than 3 kV.   2. The heat dissipation substrate for an electronic device according to claim 1, wherein the fluorine-containing polymer is selected from the group consisting of polyvinylidene fluoride and polyethylene tetrafluoroethylene.   The fluorine-containing polymer is a poly (tetrafluoroethylene), a tetrafluoroethylene-hexafluoro-propylene copolymer, an ethylene-tetrafluoroethylene copolymer, a perfluoroalkoxy-modified tetrafluoroethylene, together with a terpolymer of a curing site monomer. Poly (chlorotri-fluorotetrafluoroethylene), vinylidene fluoride-tetrafluoroethylene copolymer, poly (vinylidene fluoride), tetrafluoroethylene-perfluorodioxole copolymer, vinylidene fluoride-hexafluoropropylene copolymer Selected from the group consisting of a polymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer and tetrafluoroethylene-perfluoromethyl vinyl ether Electronic device for heat radiation substrate Motomeko 1 wherein.   The heat dissipation substrate for an electronic device according to claim 1, wherein the thermally conductive filler is a nitride or an oxide.   The heat dissipation substrate for an electronic device according to claim 11, wherein the nitride is selected from the group consisting of zirconium nitride, boron nitride, aluminum nitride, and silicon nitride.   The heat dissipation substrate for an electronic device according to claim 11, wherein the oxide is selected from the group consisting of aluminum oxide, magnesium oxide, zinc oxide, and titanium dioxide.   The heat dissipation substrate for an electronic device according to claim 1, wherein the heat dissipation substrate is irradiated with 0 to 20 millirads in order to crosslink and cure the thermally conductive polymer dielectric insulating layer.   The heat dissipation substrate for an electronic device according to claim 1, wherein the electronic device is a light emitting diode device.   The heat dissipation substrate for an electronic device according to claim 1, wherein the first metal layer contains copper.   The heat dissipation substrate for an electronic device according to claim 1, wherein the second metal layer contains aluminum.

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