JP2009129801A - Metal base circuit board - Google Patents

Abstract

A metal base circuit board having a light reflection function is provided.
A metal having a metal substrate, an insulating layer laminated on one surface of the metal substrate, a circuit formed on the exposed surface of the insulating layer, and a white film laminated on the exposed surface of the insulating layer and the circuit. An inorganic hollow powder is contained in the composition constituting the white film, which is a base circuit board, and the hollow ratio of the inorganic hollow powder is 30 volume% or more and 90 volume% or less, and the average particle of the inorganic hollow powder The metal base circuit board has a diameter of 0.1 μm or more and 30 μm or less.
[Selection] Figure 1

Description

The present invention relates to a metal base circuit board for a liquid crystal backlight using an LED (Light Emitting Diode) as a light source.

Conventionally, liquid crystal display devices have been used in various fields, and in particular, have been used in many fields in the electronic industry such as personal computers and televisions. Among these liquid crystal display devices, those that employ a direct-type backlight system have a backlight disposed on the back of the liquid crystal panel. In the edge light type, light emitted from the light source is guided to the light guide plate. And the propagated light is emitted from the surface side of the light guide plate through a prism sheet or the like, so that the entire back surface of the liquid crystal panel is irradiated. CCFL (Cold Cathode Fluorescent Lamp) was mainly used as the light source of the backlight, but the use of LEDs is increasing due to consideration of environmental aspects such as higher brightness and mercury-free. .

In particular, with the increase in the area of home televisions, the demand for higher brightness has increased for backlights, and various methods for effectively using reflected light as well as light emitted from LEDs have been proposed.

Conventionally, in order to make effective use of reflected light, it is common to use a light reflecting sheet, and even in a backlight mounted with an LED, an LED package is mounted on the printed circuit board, and further on the printed circuit board. A light reflecting sheet was pasted and used (Patent Document 1).

On the other hand, proposals have been made to whiten the substrate itself, but these are inferior in the diffusibility of the heat generated by the LED, and not only a stable luminance cannot be obtained, but also the life of the LED itself is shortened. In addition, there was a defect such as the above, and it did not have sufficient reflectivity (Patent Document 2).

JP 2006-310014 A JP 2006-317173 A

Conventionally, a printed circuit board for mounting an LED package for a backlight does not have a light reflecting function. Therefore, when used as a printed circuit board for a backlight, it has been necessary to attach a light reflecting sheet after mounting the LED package. . For this reason, there has been a problem that the number of man-hours and necessary members at the time of manufacture are complicated and handling is complicated in the manufacturing process, which is inconvenient.

An object of the present invention is to provide a completely new metal-based circuit board that solves the above problems.

That is, the present invention includes a metal substrate, an insulating layer laminated on one surface of the metal substrate, a circuit formed on the exposed surface of the insulating layer, and a white film laminated on the exposed surface of the insulating layer and the circuit. An inorganic hollow powder is contained in the composition constituting the white film, the hollow ratio of the inorganic hollow powder being 30% by volume to 90% by volume, and the average of the inorganic hollow powder The particle diameter is 0.1 μm or more and 30 μm or less, thereby effectively increasing the reflectivity due to the difference in refractive index between inorganic and medium spaces, and the reflectivity of the metal base circuit board for the visible light (wavelength range: 400 to 800 nm). The average is 70% or more.

According to the present invention, it is possible to effectively use reflected light only with a metal base circuit board without attaching a light reflecting sheet after LED mounting, and also effectively diffuses heat generated from the LED to increase the brightness of the LED. It can be expected to increase the service life as well as to stabilize.

Hereinafter, the present invention will be described with reference to the drawings.

<Embodiment 1 and one layer>
FIG. 1 is an example of a metal base circuit board according to the present invention. In the metal base circuit board of the present invention, a white film 14 having a high reflectance is formed on a metal base circuit board comprising a metal substrate, an insulating layer, and a circuit. As shown in FIG. 1, the metal base circuit board of the present invention is used by mounting and mounting a plurality of LED packages 115 by solder joints 16 or the like.

<Embodiment 2 / Multilayer>
FIG. 2 is another example of the metal base circuit board of the present invention. In the metal base circuit board of the present invention, a white film 27 having a high reflectivity is formed on the outermost layer opposite to the metal substrate on the metal base circuit board in which a plurality of insulating layers and circuits are alternately formed on the metal substrate. Is. As shown in FIG. 2, the metal base circuit board of the present invention is used by mounting and mounting a plurality of LED packages 29 by solder joints 28 or the like. FIG. 2 shows a two-layer structure as an example, but the basic structure is the same when there are three or more layers.

<Reflectance>
In the present invention, the white film is characterized by having a high reflectance, and the average reflectance of light having a wavelength of 400 to 800 nm is 70% or more, preferably 450 to 470 nm or 520 to 250 nm. In the respective wavelength ranges of 570 nm and 620 to 660 nm, the maximum value of the reflectance is 80% or more, more preferably 85% or more.

<Reflectance, definition / measurement method>
The reflectance used in the present invention is obtained by removing light absorbed and transmitted through the substrate layer from incident light on the substrate surface. As the measuring device, a spectrophotometer equipped with an integrating sphere, which is capable of measuring in the wavelength range of 400 to 800 nm is desirable. In the present invention, Shimadzu spectrophotometer UV-2550 and integrating sphere ISR2200 satisfying the above specifications were used. This measuring apparatus can measure in the wavelength range from 220 nm to 850 nm.
Hereinafter, a method for measuring the reflectance will be described with reference to FIG. A measurement sample 34 can be attached to the bottom of the integrating sphere 31, and a window 33 for incident light is provided above the integrating sphere. When the incident light 35 is reflected on the surface of the measurement sample, it is further reflected on the surface of the integrating sphere and detected by the detector 32 provided on the side surface.

<Insulation layer thermal conductivity>
The metal base circuit board of the present invention has the above-described configuration, and the thermal conductivity of the insulating layer is 1 W / mK or more, preferably 1.5 W / mK or more. The higher the thermal conductivity, the better. In addition, it has high heat dissipation and withstand voltage characteristics such that the withstand voltage between the conductor circuit and the metal foil is 1.5 kV or more, preferably 2 kV or more, and the metal base circuit board efficiently generates heat generated from the LED light source. Radiating heat to the back side and further radiating to the outside reduces the heat storage of the LED package mounting circuit board, reduces the temperature rise of the LED, and equalizes the temperature in the backlight surface, thereby emitting light from the LED. The reduction in efficiency can be suppressed and the luminance can be made uniform. For this reason, it is possible to provide a bright and long-life backlight together with the effect of the high reflectance white film having a light reflection function.

<Insulating layer>
As a material constituting the insulating layer, a resin used as a circuit board such as a phenol resin, an imide resin, a silicone resin, or an epoxy resin can be appropriately selected. To achieve the above-described thermal conductivity and withstand voltage characteristics, an epoxy is used. A resin is preferable, and more preferably, the epoxy resin contains an inorganic filler and a curing agent for the epoxy resin.

<Epoxy resin>
Examples of the epoxy resin include known epoxy resins such as naphthalene type, phenylmethane type, tetrakisphenolmethane type, biphenyl type, and bisphenol A alkylene oxide adduct type epoxy resins, among which the reason for stress relaxation Thus, an epoxy resin in which the main chain has a polyether skeleton and is linear is preferable.
The epoxy resin whose main chain has a polyether skeleton is a bisphenol A type, bisphenol F type epoxy resin, bisphenol A type hydrogenated epoxy resin, polypropylene glycol type epoxy resin, polytetramethylene glycol type epoxy. There are aliphatic epoxy resins typified by resins, polysulfide-modified epoxy resins, and the like, and a plurality of these may be combined.
Among these epoxy resins, when high heat resistance is required for the metal base circuit board, use a bisphenol A type epoxy resin that has both high electrical insulation and thermal conductivity, and can provide a cured resin with high heat resistance. Is preferred. Moreover, as long as the effect of this bisphenol A type epoxy resin is exhibited, another epoxy resin may be used in combination with the bisphenol A type epoxy resin.

<Bisphenol A type epoxy resin>
When using a bisphenol A type epoxy resin, it is more preferable that the epoxy equivalent is 300 or less. This is because if the epoxy equivalent is 300 or less, it is possible to prevent a decrease in Tg (glass transition temperature) due to a decrease in crosslink density, which is observed when a polymer type is obtained, and hence a decrease in heat resistance. Further, when the molecular weight is increased, the liquid state becomes a solid state, and it becomes difficult to blend the inorganic filler into the curable resin, and the problem that a uniform resin composition cannot be obtained can be avoided.

<Epoxy resin / hydrolyzed chlorine concentration>
When employing an epoxy resin, the hydrolyzable chlorine concentration is preferably 600 ppm or less. When the hydrolyzable chlorine concentration is 600 ppm or less, sufficient moisture resistance as a metal base circuit board can be exhibited.

<Curing agent>
It is preferable to add a curing agent to the epoxy resin. As the curing agent, one or more selected from the group consisting of aromatic amine resins, acid anhydride resins, phenol resins and dicyanamide can be used.

<Addition amount of curing agent>
The addition amount of the curing agent is preferably 5 parts by mass or more and 50 parts by mass or less, and more preferably 10 parts by mass or more and 35 parts by mass or less with respect to 100 parts by mass of the epoxy resin.

<Curing catalyst>
A curing catalyst can also be used for the epoxy resin. As the curing catalyst, an imidazole compound, an organic phosphate compound, a tertiary amine, a quaternary ammonium, or the like is used, and any one or more types can be selected. The addition amount of the curing catalyst is not particularly limited because it varies depending on the curing temperature, but if the addition amount of the curing catalyst is small, the effect of adding the curing catalyst tends not to be exhibited, and if the addition amount is large, the degree of curing can be controlled. Since it tends to be difficult, for example, it is preferably 0.01 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the epoxy resin.

<Filler type>
As the inorganic filler contained in the epoxy resin, any inorganic filler may be used as long as it is electrically insulating and excellent in thermal conductivity. Examples of such an inorganic filler include silicon oxide, aluminum oxide, aluminum nitride, boron nitride, magnesium oxide, silicon nitride, and the like alone or in combination thereof. Of these inorganic fillers, aluminum nitride and boron nitride are preferred because of their high thermal conductivity. In addition, the use of crystalline silicon dioxide and boron nitride makes it possible to keep the dielectric constant of the cured body low, and it is easy to ensure electrical insulation when used as a heat dissipation material for electrical and electronic parts used at high frequencies. preferable.
Furthermore, in order to improve handling properties and fluidity, the inorganic filler preferably has a particle shape with an aspect ratio close to 1. When coarse particles and fine particles are mixed together, it is possible to achieve a higher packing than when crushed particles or spherical particles are used alone, which is more preferable.

<Filler, coarse powder / fine powder>
In the case of using a mixture of coarse particles and fine particles as the inorganic filler, (a) 50% by volume or more having a maximum particle size of 100 μm or less and a particle size of 1 μm to 12 μm and an average particle size of 5 μm to 50 μm It is preferable to use a mixed powder composed of certain coarse particles and (b) fine particles containing 70% by volume or more of particles having a particle size of 2.0 μm or less and having an average particle size of 0.2 μm or more and 1.5 μm or less. As a ratio of the coarse particles to the fine particles, the coarse particles are preferably 34% by volume or more and 70% by volume or less, and the fine particles are preferably 3% by volume or more and 24% by volume or less. In the case where coarse particles and fine particles are used in combination, at least one of them is more preferably spherical.

<Filler addition amount>
The blending ratio of the inorganic filler is preferably 70 parts by mass or more and 95 parts by mass or less with respect to 100 parts by mass of the total amount of the epoxy resin and the curing agent, a more preferable value as the lower limit is 80 parts by mass, and a more preferable value as the upper limit is 90 Part by mass.

<White pigment in insulating layer>
At least one or more kinds of white pigments selected from zinc oxide, calcium carbonate, titanium dioxide, alumina, and smectite can be added to the insulating layer of the present invention. In particular, the inclusion of a white pigment in the outermost insulating layer has the effect of improving the reflectance when a white film is provided on the metal base circuit board.

<Titania in insulating layer>
Of the white pigments, titanium dioxide has the highest refractive index and is more preferable when used for increasing the reflectance of the substrate. In the case of increasing the light scattering efficiency in the filler, it is preferable that the average particle diameter is 0.30 μm or less, and it is more effective to use the mixture with a filler having an average particle diameter of 0.3 μm or more. In addition, the reflectance can be improved.

<Zinc oxide in insulating layer>
Among the white pigments, zinc oxide is a material having both a high refractive index and a high heat dissipation property, and is more preferable when used to increase the reflectance and the heat dissipation property of the substrate. In the case of increasing the light scattering efficiency in the filler, it is preferable that the average particle size is 0.35 μm or less, and it is more effective to use a mixture with an average particle size of 0.3 μm or more. In addition, the reflectance can be improved.

<White film and titania>
Among titanium dioxides, rutile type is excellent in stability and thus has a weak photocatalytic action, and can be suitably used because deterioration of the resin component is suppressed as compared with other structures. Further, titanium dioxide surface-treated and suppressed in photocatalytic action can be suitably used, and examples of the surface treatment include coating with silicon dioxide or aluminum hydroxide.

<Inorganic hollow powder in insulating layer>
An inorganic hollow powder can be added to the insulating layer of the present invention. In particular, the inclusion of the inorganic hollow powder pigment in the outermost insulating layer has the effect of improving the reflectance when a white film is provided on the metal base circuit board.

<Inorganic hollow powder>
The average hollowness of the inorganic hollow powder of the present invention is 30% by volume or more and 90% by volume or less, and the average particle diameter is 0.1 μm or more and 30 μm or less. A more preferable upper limit of the average hollowness when the average particle diameter is 0.1 μm or more and 5 μm or less is 70% by volume, and a further preferable upper limit is 60% by volume. Further, when the average particle size is 5 μm or more and 30 μm or less, the preferable lower limit is 50% by volume, more preferable lower limit is 70% by volume, preferable upper limit is 90% by volume, and more preferable upper limit is 85% by volume. . If the average hollowness is reduced, the effect of improving the reflectivity due to the refractive index is difficult to obtain. Conversely, if the average hollowness is increased, the shell thickness of the particles is reduced and the particle strength is reduced, so that the powder is handled and kneaded with rubber or resin. The particles tend to break inside.

The average hollowness is defined as the ratio of the measured particle density to the theoretical density of the particles. For example, when the measured value of the density of the silica hollow particles is 1.1 g / cm ³ , the average hollow ratio is calculated as 50% by volume divided by the theoretical density of amorphous silica 2.2 g / cm ³ . The density is measured with a pycnometer automatic powder particle true density measuring instrument (for example, trade name “Auto True Densor MAT-7000” manufactured by Seishin Enterprise Co., Ltd.).

The average particle diameter of the inorganic hollow powder of the present invention is more preferably 0.1 μm or more and 20 μm or less. When the average particle size of the inorganic hollow powder is increased, the smoothness of the surface tends to be impaired. When the average particle size is decreased, the shell thickness is decreased and the inorganic hollow powder tends to be destroyed in order to obtain a sufficient hollow ratio. Therefore, the above range is preferable.

<Average particle size measurement method>
The average particle size and the maximum particle size of the inorganic hollow powder are obtained by measuring the particle size distribution by the laser diffraction scattering method. The particle size distribution is measured by dividing the range of 0.04 μm or more and 2000 μm or less into 116 divisions with a width of log (μm) = 0.04. An example of the measuring machine is “Model LS-230” manufactured by Beckman Coulter. The measurement is performed after mixing water and a sample, and dispersing with an ultrasonic homogenizer for 1 minute at an output of 200 W. The concentration of PIDS (Polarization Intensity Differential Scattering) is adjusted to 45 mass% or more and 55 mass% or less. The refractive index of water is 1.33, and the refractive index of the sample is the refractive index of the material, for example, 1.50 for amorphous silica.

<Inorganic hollow powder material>
There are no particular limitations on the material of the inorganic hollow powder, and examples thereof include silica, alumina, zirconia, titania, and magnesia, or titania particles that have high visible light reflectivity.

<Surface treatment 1>
The inorganic hollow powder of the present invention is preferably treated with a surface treatment agent such as a silane coupling agent. Usually, since the surface of the inorganic powder is hydrophilic, the dispersibility in a hydrophobic dispersion medium such as a resin or an organic solvent is not good. Therefore, when the surface is treated with a surface treatment agent, the dispersibility is improved. Further, when titania is used as the material of the inorganic hollow powder, it is preferable to perform a surface treatment having a photocatalytic action suppressing effect.

<Surface treatment 2>
As the surface treatment agent, a silane coupling agent, a Zr chelate, a titanate coupling agent, an aluminum coupling, or the like can be used. Examples of silane coupling agents include epoxy silanes such as γ-glycidoxypropyltrimethoxysilane and β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, such as aminopropyltriethoxysilane and ureidopropyltriethoxy. Examples thereof include aminosilanes such as silane and N-phenylaminopropyltrimethoxysilane, hydrophobic silane compounds such as phenyltrimethoxysilane, methyltrimethoxysilane, and octadecyltrimethoxysilane, and mercaptosilane.
Further, as a surface treatment having a photocatalytic action suppressing effect, there is a coating with silicon dioxide or aluminum hydroxide.

<White pigment in insulating layer / amount of inorganic hollow powder>
The addition amount when adding at least one or both of the white pigment and the inorganic hollow powder to the insulating layer is preferably 5% by volume or more and 50% by volume or less as the total amount of the white pigment and the inorganic hollow powder with respect to the entire insulating layer. More preferably, it is 5 volume% or more and 30 volume% or less. This is because if the amount added is small, the effect of improving the reflectance sufficiently tends to be difficult to obtain, and if the amount added is large, sufficient dispersion cannot be achieved and aggregates and the like tend to be formed. There is no restriction | limiting in particular in the ratio of a white pigment and inorganic hollow powder.

<Double insulation layer>
When adjusting the reflectivity and insulation reliability of the insulating layer, the insulating layer structure can be a two-layer structure. In the case where the insulating layer has a two-layer structure, it is preferable that the first layer serving as an inner layer be a highly insulating insulating layer and the second layer serving as an outer layer be a function separating structure having a highly reflective insulating layer. In addition, it is more effective to change the thickness ratio of each insulating layer in order to obtain desired characteristics.

<Auxiliary>
If necessary, the insulating layer of the present invention may contain various known auxiliaries such as a dispersion aid such as a coupling agent and a viscosity adjusting aid such as a solvent.

<Metal substrate / circuit>
The metal used as the metal substrate and circuit of the present invention includes aluminum, iron, copper alone or an alloy of these metals, and aluminum or copper alone or an alloy is preferable in consideration of heat dissipation. Further, in order to improve the adhesion to the insulating layer, surface treatment such as sandblasting, etching, various plating treatments, coupling agent treatment, etc. can be appropriately selected on the adhesive surface side with the insulating layer.

<Metal substrate thickness>
The thickness of the metal substrate is preferably 0.013 mm or more and 4 mm or less, a more preferable lower limit is 0.05 mm, and a further preferable upper limit is 0.50 mm. If this thickness is thin, wrinkles tend to occur during handling, and there are few technical limitations even if it is thick, but if it is too thick, it will not be used as a metal base circuit board and is not practical.

<Circuit thickness>
If the thickness of the circuit is too thin, there is a tendency that a sufficient conduction circuit cannot be secured as a circuit board for a backlight, and if it is too thick, there is a tendency to cause a problem in the manufacturing process of circuit formation. The upper limit is 0.005 mm, the more preferable lower limit is 0.03 mm, the preferable upper limit is 0.400 mm, and the more preferable upper limit is 0.30 mm.

<Insulation layer thickness>
In the present invention, the thickness of the insulating layer is preferably 80 μm or more and 200 μm or less. This range is preferable because if it is too thin, it tends to be impossible to ensure electrical insulation, and if it is too thick, heat dissipation tends to decrease, and further, it tends not to contribute to downsizing and thinning. .

<White film reflectance>
In the metal base circuit board of the present invention, by providing a white film on the insulating layer and the circuit, the surface of the white film has a reflectance of 70% or more with respect to light having a wavelength of 400 nm to 800 nm. Preferably, the maximum reflectance is 80% or more, more preferably 85% or more in the respective wavelength ranges of 450 nm to 470 nm, 520 nm to 570 nm, and 620 nm to 660 nm on the surface of the white film. .

<White film / resin>
The white film contains a white pigment and an inorganic hollow powder in a resin composition containing at least one of an ultraviolet curable resin and a thermosetting resin usually used as a resist material. As these curable resins, epoxy resins, acrylic resins and mixtures thereof are preferably used, but are not limited thereto.

<White film / pigment>
As the white pigment / inorganic hollow powder contained in the white film, those similar to those used in the above-mentioned insulating layer can be used.

<White film and pigment content>
The total content of the white pigment and the inorganic hollow powder in the white film is 30% to 70% by volume, more preferably 30% to 60% by volume. If the amount is too small, a sufficient reflection effect cannot be obtained. If the amount is too large, the fluidity at the time of film formation tends to be lowered and a uniform film tends not to be formed. There is no restriction | limiting in particular in the ratio of a white pigment and inorganic hollow powder.

In the white film formed on the circuit, the LED mounting portion can be arbitrarily provided with an opening in the wiring portion.

Example 1
Add a phenol novolac (Dainippon Ink & Chemicals, "TD-2131") as a curing agent to bisphenol A type epoxy resin (Japan Epoxy Resin, "EP-828") on a 35 µm thick copper foil In addition, silicon oxide of crushed coarse particles having an average particle diameter of 1.2 μm (manufactured by Tatsumori Co., Ltd., “A-1”) and silicon oxide of crushed coarse particles having an average particle diameter of 10 μm (manufactured by Tatsumori Co., Ltd., “5X”) is combined so that the volume of the insulating layer is 56% by volume (spherical coarse particles and spherical fine particles have a mass ratio of 7: 3), and the insulating layer is formed so that the thickness after curing is 150 μm. did. Next, an aluminum foil having a thickness of 200 μm was bonded and heated to thermally cure the insulating layer, thereby obtaining a metal base substrate having a sodium ion concentration of 50 ppm or less in the entire inorganic filler in the insulating layer.
About the obtained metal base substrate, a predetermined position was masked with an etching resist and the copper foil was etched, and then the etching resist was removed to form a copper circuit to obtain a metal base circuit substrate. Further, in order to form a white film having a high reflectance on the metal base circuit board, a white solder resist layer was applied and cured with heat and ultraviolet rays. At this time, a white coating film is not formed on the LED package mounting portion on the copper circuit. As the white solder resist, 5% by volume of titanium oxide hollow powder having an average particle size of 0.4 μm and a hollow ratio of 35% was added to “SSR-6300S” manufactured by Yamaei Chemical Co., Ltd.
The reflectance of the obtained substrate is measured, and as shown in FIG. 4, blue, red, and green LEDs with an output of 3 W class are mounted, and the luminance is measured with a color luminance meter (Topcon Technohouse BM-7). went. The evaluation results are shown in Table 1.

(Example 2)
A metal base circuit board was obtained in the same manner as in Example 1 except that 5% by volume of titanium oxide hollow powder having an average particle size of 0.4 μm and a hollow rate of 35% was further added to the insulating layer.

(Example 3)
The addition amount of silicon oxide (“A-1” manufactured by Tatsumori Co., Ltd.) and silicon oxide (“5X” manufactured by Tatsumori Co., Ltd.) in the insulating material layer is 46% by volume (spherical coarse particles and spherical fine particles are A metal base circuit board was prepared in the same manner as in Example 1 except that titanium dioxide (Ishihara Sangyo Co., Ltd. PFC104) was added as a white pigment in an amount of 10% by volume in the insulating layer. Obtained.

Example 4
A metal base circuit board was obtained in the same manner as in Example 3 except that 5% by volume of titanium oxide hollow powder having an average particle size of 0.4 μm and a hollow ratio of 35% was added to the insulating layer.

The reflectance of the obtained substrate is measured, and as shown in FIG. 4, blue, red, and green LEDs with an output of 3 W class are mounted, and the luminance is measured with a color luminance meter (Topcon Technohouse BM-7). went. The evaluation results are shown in Table 1.

Since the metal base circuit board of the present invention has a white coating film with high reflectivity formed on the surface of the metal base board on which the LED package is mounted, the metal base circuit board has a light reflection function with a configuration similar to that of a normal printed circuit board. ing. For this reason, the reflected light of the LED light source can be supplied to the liquid crystal part without using an expensive light reflecting sheet. Moreover, the man-hour at the time of liquid-crystal backlight manufacture can also be reduced, it is efficient, and it is very useful industrially as a metal base circuit board for LED.

FIG. 1 is a schematic view showing an example of a metal base circuit board according to the present invention. FIG. 2 is a schematic view showing an example of a metal base circuit board according to the present invention. FIG. 3 is a schematic diagram showing an example of metal base circuit board reflectivity measurement according to the present invention. FIG. 4 is a schematic diagram of LED mounting in the embodiment.

Explanation of symbols

11 Metal foil 12 Insulating layer 13 Circuit 14 White film
15 Solder joint 16 LED package 21 Metal foil 22 Insulating layer first layer 23 Insulating layer second layer 24 Circuit first layer
25 Metal Pillar 26 Circuit Second Layer 27 White Film 28 Solder Joint 29 LED Package 31 Integrating Sphere 32 Detector 33 Window for Incident Light 34 Measurement Sample 35 Incident Light 36 Reflected Light 41 Substrate 42 Green LED
43 Red LED
44 Blue LED

Claims (15)

Metal having a metal substrate, an insulating layer laminated on one or both surfaces of the metal substrate, a circuit formed on the exposed surface of the insulating layer, and a white film laminated on the exposed surface of the insulating layer and the circuit An inorganic hollow powder is contained in the composition constituting the white film, which is a base circuit board, and the hollow ratio of the inorganic hollow powder is 30 volume% or more and 90 volume% or less, and the average particle of the inorganic hollow powder A metal base circuit board having a diameter of 0.1 μm or more and 30 μm or less. The metal base circuit board according to claim 1, wherein a plurality of both the insulating layer and the circuit are laminated on one surface or both surfaces of the metal substrate. 3. The metal base circuit board according to claim 1, wherein a circuit is formed on one or both surfaces of the metal board. The metal base circuit board according to any one of claims 1 to 3, wherein an average reflectance of the white film with respect to light having a wavelength range of 400 nm to 800 nm is 70% or more. The insulating layer contains an epoxy resin, an inorganic filler, and a curing agent for the epoxy resin, and the thermal conductivity after curing is 1.0 W / mK or more and 18 W / mK or less. Metal base circuit board as described in any one. The metal base circuit according to any one of claims 1 to 5, wherein the inorganic filler is blended in an amount of 70 to 95 parts by mass with respect to 100 parts by mass of the total amount of the epoxy resin and the curing agent. substrate. The metal base circuit board according to claim 1, wherein the curing agent includes a substance having a hydroxyl group. Any one of the insulating layers in which at least a white film is laminated, some insulating layers including the white film laminated insulating layer, or all the insulating layers contains a white pigment, and the white pigment The metal base circuit board according to claim 1, which contains at least one white pigment selected from zinc oxide, calcium carbonate, titanium dioxide, alumina, and smectite. The white pigment in the insulating layer is either titanium dioxide alone or a mixture of titanium dioxide and at least one white pigment selected from the following materials: “zinc oxide, calcium carbonate, alumina, smectite”. A metal base circuit board according to any one of claims 1 to 7. The white pigment in the insulating layer is made of zinc oxide alone or a mixture of zinc oxide and at least one white pigment selected from the following materials "titanium dioxide, calcium carbonate, alumina, smectite". The metal base circuit board as described in any one of thru | or 7. The insulating layer contains an inorganic hollow powder, the hollow ratio of the inorganic hollow powder is 40 volume% or more and 90 volume% or less, and the average particle diameter of the inorganic hollow powder is 0.1 μm or more and 30 μm or less. The metal base circuit board according to any one of claims 1 to 10. The metal base circuit board according to claim 8, wherein the white pigment in the insulating layer contains zinc oxide. The insulating layer contains an inorganic hollow powder, the hollow ratio of the inorganic hollow powder is 40 volume% or more and 90 volume% or less, and the average particle diameter of the inorganic hollow powder is 0.1 μm or more and 30 μm or less. The metal base circuit board according to any one of claims 1 to 12. The metal base circuit board according to any one of claims 1 to 13, wherein the white film contains titanium dioxide as a white pigment. The metal base circuit board according to claim 8, wherein the titanium dioxide is of a rutile type and the surface thereof is coated with aluminum hydroxide or silicon dioxide.

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