JP2011060931A - Light reflectivity circuit substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit substrate formed from a thermoplastic liquid crystal polymer film which forms a melt phase of an optical anisotropy, and which has an excellent light reflectivity. <P>SOLUTION: A circuit substrate at least includes a thermoplastic liquid crystal polymer film 11 which forms a melt phase of an optical anisotropy, a circuit layer 12 formed on one side of the thermoplastic liquid crystal polymer film 11, and a light reflective layer 13 thermally compressed and bonded onto the other side of the thermoplastic liquid crystal polymer film 11. The average light reflectance in a wavelength region of 400-500 nm is 50% or more. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention is composed of a thermoplastic liquid crystal polymer film, a circuit layer disposed on one surface of the film, and a light reflection layer thermocompression bonded to the other surface of the film, and is excellent in light reflectivity. More particularly, the present invention relates to a circuit board that is excellent in both light reflectivity and heat dissipation.

  Light emitting elements such as LEDs are used in many electronic devices because of their low power consumption, long life, and small size. However, in recent years, in order to meet the needs for improving luminance and the increase in size of light emitting devices, it is necessary to form a path for effectively dissipating heat generated in the light emitting elements in the wiring board on which the light emitting elements are mounted. ing.

  From the viewpoint of forming such a path, Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2008-169513) discloses a light-reflective heat-conductive resin composition containing a specific light-reflective heat-conductive filler and a binder resin. An electronic mounting board is disclosed in which the light-reflective thermally conductive resin layer formed in (1) is laminated on the wiring pattern of the electronic mounting board via an electric insulating layer and / or an electric insulating adhesive layer.

  In this electronic mounting board, by stacking on the metal wiring pattern on the device mounting surface via an electrical insulation layer, a heat dissipation path (heat diffusion, heat transport) that efficiently dissipates the heat generated by the device in the device mounting surface is provided. At the same time, it can also function as a heat sink (heat release mechanism to the gas phase). Furthermore, since the light reflectivity of the surface of the mounting substrate can be improved, the light emitted from the light emitting element can be extracted to the external space more efficiently.

JP 2008-169513 A (claims, paragraph number [0077])

  However, since the electronic mounting substrate of Patent Document 1 uses a light-reflective thermally conductive filler, the light reflectivity is not sufficient due to scattering reflection. Moreover, since part of the light emitted from the light emitting element stays inside the substrate due to such scattering reflection, deterioration of the binder resin constituting the electronic mounting substrate derived from light energy cannot be sufficiently suppressed. .

Accordingly, an object of the present invention is to provide a circuit board that can reflect light incident on the circuit board mainly by regular reflection and has excellent light reflectivity.
Another object of the present invention is excellent in light reflectivity and heat dissipation, not only reducing the amount of light incident on the circuit board and suppressing the ingress of light energy, but also derived from the light incident on the circuit board. An object of the present invention is to provide a circuit board capable of quickly releasing generated heat to the outside.

  Still another object of the present invention is to provide a circuit board that is excellent in dielectric characteristics in a wide range of frequencies including high frequencies and has a low dielectric constant and a low dielectric loss tangent.

  Another object of the present invention is to provide a circuit board that has excellent integrity and can suppress the occurrence of warpage.

  As a result of intensive studies to solve the above-described problems of the prior art, the present inventors have paid attention to HEV (High Energy Visible Light) among the wavelengths of light, and in the thermoplastic liquid crystal polymer sheet, the circuit layer When the light reflecting layer is thermocompression bonded to the surface opposite to the surface provided with (i), the reflectance to the light of this wavelength increases, and the light to the thermoplastic liquid crystal polymer film constituting the circuit board Not only can the deterioration due to energy be effectively prevented, but also (ii) the efficiency of using light generated from the light emitter attached to the circuit board can be improved, and (iii) the light reflecting layer can be heated without going through the adhesive layer. Since the plastic liquid crystal polymer sheet is fused, it is found that a circuit board excellent in integrity between the light reflection layer and the thermoplastic liquid crystal polymer film can be obtained without inhibiting heat conduction. completed.

That is, the present invention comprises a thermoplastic liquid crystal polymer film that forms an optically anisotropic melt phase;
A circuit layer formed on one side of the thermoplastic liquid crystal polymer film;
A light reflecting layer thermocompression bonded to the other surface of the thermoplastic liquid crystal polymer film;
And a circuit board having an average light reflectance of 50% or more in a wavelength region of 400 to 500 nm.

  The circuit board of the present invention may be further excellent in light reflectance in the visible light region. For example, the circuit board has an average light reflectance of 50% or more in a wavelength range of 380 to 770 nm. May be.

  The circuit board is excellent in heat dissipation, and for example, the thermal conductivity in the planar direction may be 3.0 W / mK or more.

  The circuit board is also excellent in dielectric characteristics in a high frequency region, for example, the relative permittivity at 1 GHz may be less than 4.0, and / or the dielectric loss tangent at 1 GHz is less than 0.005. Also good.

  In the circuit board, the light reflecting layer may be made of at least one metal selected from metals having specular reflectivity, for example, silver, aluminum, gold, nickel, and stainless steel.

  Furthermore, in the circuit board, the ratio (CTEp / CTEm) of the thermal expansion coefficient (CTEp) of the thermoplastic liquid crystal polymer film and the thermal expansion coefficient (CTEm) of the light reflection layer and / or the metal constituting the circuit layer. However, it may be within the range of 0.5-2.

  Since the circuit board is excellent in light reflectivity and heat dissipation, it can be usefully used for light emitting elements such as LEDs that are easily affected by heat. For example, the circuit board includes a light emitting element. You may use as a board | substrate for mounting.

  The circuit board of the present invention is particularly excellent in light reflectivity with respect to HEV, which is a high-energy visible ray. Therefore, the circuit board not only reflects this light to enhance the light utilization efficiency but also originates from this light. Photodegradation of the substrate can be suppressed.

  In the circuit board of the present invention, since the light reflecting layer is integrated with the thermoplastic liquid crystal polymer film by thermocompression bonding without using the adhesive layer, the circuit board has excellent integration as a circuit board, and the adhesive layer The resulting heat conduction inhibition does not occur.

  Furthermore, the circuit board of the present invention not only effectively suppresses the generation of heat to the board derived from light energy, but also dissipates the generated heat by having a high thermal conductivity with a high light reflectance. Thus, the influence of heat on the electronic component mounted on the circuit board can be reduced.

  In particular, the circuit board of the present invention is excellent in dielectric characteristics in a wide frequency band (especially, a high frequency band of 1 GHz or more), so that not only the signal transmission speed in an electronic device can be increased, but also the amount of heat generated itself is suppressed. can do.

1 is a schematic cross-sectional view showing a circuit board according to an embodiment of the present invention. It is the schematic for demonstrating the manufacturing method of the circuit board which concerns on one Embodiment of this invention.

  As shown in FIG. 1, the circuit board of the present invention includes a thermoplastic liquid crystal polymer film 11, a circuit layer 12 formed on one surface of the film 11, and light formed on the other surface of the film 11. A circuit board including the reflective layer 13.

  Although not shown, the circuit board of the present invention has one or more thermoplastic liquid crystal polymer films, one or more circuit layers, and one or more light reflecting layers as long as they have predetermined light reflectivity. A circuit board including the thermoplastic liquid crystal polymer film 11, a circuit layer 12 formed on one surface of the film 11, and a light reflecting layer 13 formed on the other surface of the film 11 is a basic structural unit. The multilayer circuit board may be laminated as follows.

(Thermoplastic liquid crystal polymer film)
The thermoplastic liquid crystal polymer film is formed from a liquid crystalline polymer that can be melt-molded. The thermoplastic liquid crystal polymer is not particularly limited as long as it has a chemical structure as long as it is a liquid crystalline polymer that can be melt-molded. , Thermoplastic liquid crystal polyester, or thermoplastic liquid crystal polyester amide having an amide bond introduced therein.

  The thermoplastic liquid crystal polymer may be a polymer in which an isocyanate-derived bond such as an imide bond, a carbonate bond, a carbodiimide bond, or an isocyanurate bond is further introduced into an aromatic polyester or an aromatic polyester amide.

  Specific examples of the thermoplastic liquid crystal polymer used in the present invention include known thermoplastic liquid crystal polyesters and thermoplastic liquid crystal polyester amides derived from the compounds (1) to (4) listed below and derivatives thereof. Can be mentioned. However, it goes without saying that there are suitable ranges for combinations of various raw material compounds in order to form a polymer liquid crystal.

(1) Aromatic or aliphatic dihydroxy compounds (see Table 1 for typical examples)

(2) Aromatic or aliphatic dicarboxylic acids (see Table 2 for typical examples)

(3) Aromatic or aliphatic hydroxycarboxylic acids (see Table 3 for typical examples)

(4) Aromatic diamine, aromatic hydroxyamine or aromatic aminocarboxylic acid (see Table 4 for typical examples)

  Representative examples of the liquid crystal polymer obtained from these raw material compounds include copolymers having the structural units shown in Tables 5 and 6.

  Of these copolymers, a polymer containing at least p-hydroxybenzoic acid and / or 6-hydroxy-2-naphthoic acid as a repeating unit is preferable, and in particular, (i) p-hydroxybenzoic acid and 6-hydroxyoxy- A polymer containing a repeating unit with 2-naphthoic acid, (ii) 6-hydroxy-2-naphthoic acid, at least one aromatic diol selected from the group consisting of 4,4′-dihydroxybiphenyl and hydroquinone, and terephthalate A polymer containing a repeating unit with at least one aromatic dicarboxylic acid selected from the group consisting of acid, isophthalic acid and 2,6-naphthalenedicarboxylic acid is the most preferred embodiment.

  For example, when the thermoplastic liquid crystal polymer contains at least a repeating unit of p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid, the repeating unit (A) of p-hydroxybenzoic acid and the repeating unit (B) of The molar ratio (A) / (B) with 6-hydroxy-2-naphthoic acid is desirably about (A) / (B) = 10/90 to 90/10 in the liquid crystal polymer, more preferably , (A) / (B) = about 50/50 to 85/15, and more preferably (A) / (B) = about 60/40 to 80/20.

  Further, the thermoplastic liquid crystal polymer is at least one aromatic diol selected from the group consisting of 6-hydroxy-2-naphthoic acid, 4,4′-dihydroxybiphenyl and hydroquinone, terephthalic acid, isophthalic acid and 2,6 -When including a repeating unit with at least one aromatic dicarboxylic acid selected from the group consisting of naphthalenedicarboxylic acid, the molar ratio of each repeating unit in the liquid crystal polymer is the repeating unit (C) of 6-hydroxy-2-naphthoic acid. : The aromatic diol (D): The aromatic dicarboxylic acid (E) = 30-80: 35-10: 35-10, more preferably (C) :( D) :( E ) = 35 to 75: 32.5 to 12.5: 32.5 to 12.5, more preferably (C) :( D) (E) = 40~70: 30~15: may be about 30 to 15.

  Moreover, it is preferable that the molar ratio of the repeating structural unit derived from aromatic dicarboxylic acid and the repeating structural unit derived from aromatic diol is (D) / (E) = 95 / 100-100 / 95. Outside this range, the degree of polymerization does not increase and the mechanical strength tends to decrease.

  The optical anisotropy at the time of melting referred to in the present invention can be recognized by, for example, placing a sample on a hot stage, heating and heating in a nitrogen atmosphere, and observing the transmitted light of the sample.

  The thermoplastic liquid crystal polymer preferably has a melting point (hereinafter referred to as Mp) in the range of 260 to 360 ° C, more preferably Mp of 270 to 350 ° C. Mp is determined by measuring the temperature at which the main endothermic peak appears with a differential scanning calorimeter (Shimadzu Corporation DSC).

  The thermoplastic liquid crystal polymer may contain a thermoplastic polymer such as polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyarylate, polyamide, polyphenylene sulfide, polyester ether ketone, and fluororesin within a range not impairing the effects of the present invention. It may be added.

  The thermoplastic liquid crystal polymer film used in the present invention is obtained by extrusion molding of a thermoplastic liquid crystal polymer. Any extrusion molding method can be applied, but the known T-die method, laminate stretching method, inflation method and the like are industrially advantageous. In particular, in the inflation method and the laminate stretching method, stress is applied not only in the mechanical axis direction of the film (hereinafter abbreviated as MD direction) but also in the direction orthogonal thereto (hereinafter abbreviated as TD direction). And a film having a balance of mechanical and thermal properties in the TD direction.

  In extrusion molding, it may be accompanied by stretching treatment. For example, in extrusion molding by the T-die method, the melt sheet extruded from the T-die is not only in the mechanical axis direction of the film (hereinafter abbreviated as MD direction), You may extend | stretch simultaneously with respect to both the direction (henceforth TD direction) orthogonal to this, or the melt sheet | seat extruded from T-die is once extended | stretched to MD direction, and then extended to TD direction. Also good.

  In addition, in the extrusion molding by the inflation method, a predetermined draw ratio (corresponding to a stretching ratio in the MD direction) and a blow ratio (corresponding to a stretching ratio in the TD direction) with respect to a cylindrical sheet melt-extruded from a ring die. May be stretched.

  The stretch ratio of such extrusion molding may be, for example, about 1.0 to 10, preferably about 1.2 to 7, more preferably about 1. as the stretch ratio (or draw ratio) in the MD direction. About 3-5 may be sufficient. Further, the draw ratio (or blow ratio) in the TD direction may be, for example, about 1.5 to 20, preferably about 2 to 15, and more preferably about 2.5 to 10.

  Further, if necessary, the extruded raw sheet is subjected to a known or conventional heat treatment (for example, a melting point (Mp) or higher of the liquid crystal polymer (for example, about Mp to Mp + 30 ° C., preferably about Mp + 10 to Mp + 20 ° C.). ) To adjust the melting point and thermal expansion coefficient of the thermoplastic liquid crystal polymer film.

  The thermoplastic liquid crystal polymer film may be stretched as necessary after extrusion. The stretching method itself is known, and either biaxial stretching or uniaxial stretching may be adopted, but biaxial stretching is preferred because it is easier to control the degree of molecular orientation. For stretching, a known uniaxial stretching machine, simultaneous biaxial stretching machine, sequential biaxial stretching machine or the like can be used.

  From the viewpoint of improving heat dissipation, the thermoplastic liquid crystal polymer film has a thermal conductivity in the plane direction of 1.0 W / mK or more (for example, about 1 to 30 W / mK), preferably 1.2 W / mK or more. May be.

  Furthermore, from the viewpoint of enhancing the dielectric properties, for example, the relative dielectric constant at 1 GHz of the thermoplastic liquid crystal polymer film is 4.0 or less (for example, about 1.8 to 3.6), preferably 2.5 to 3.4. It may be a degree. By having such a relative dielectric constant, it is possible to reduce a transmission loss of an electric signal.

  Furthermore, the dielectric loss tangent at 1 GHz of the thermoplastic liquid crystal polymer film may be 0.005 or less (for example, about 0.0001 to 0.004), preferably about 0.001 to 0.003. By having such a dielectric loss tangent, it is possible to reduce power and noise, and to reduce the amount of generated heat.

  The thickness of the thermoplastic liquid crystal polymer film may be, for example, about 10 to 200 μm, more preferably 20 to 150 μm, and particularly preferably 25 to 100 μm.

  The thermoplastic liquid crystal polymer film has, for example, a coefficient of thermal expansion (CTEp) of the thermoplastic liquid crystal polymer film and a metal constituting the circuit layer, from the viewpoint of increasing the integrity of the circuit board and suppressing deformation such as warpage. The ratio (CTEp / CTEm1) to the thermal expansion coefficient (CTEm1) may be about 0.5 to 2, more preferably about 0.8 to 1.8.

  Moreover, the ratio (CTEp / CTEm2) of the thermal expansion coefficient (CTEp) of the thermoplastic liquid crystal polymer film and the thermal expansion coefficient (CTEm2) of the metal constituting the light reflection layer is also about 0.5 to 2. More preferably, it may be about 0.8 to 1.8.

  Either CTEm1 or CTEm2 preferably satisfies the above relationship with CTEp, and more preferably both CTEm1 and CTEm2 satisfy the above relationship with CTEp.

  Such thermoplastic liquid crystal polymer films are marketed by Kuraray Co., Ltd. as “Vexa FA”, “Vexa OC”, “Vexa CT”, “Vexa CTV” and the like.

(Circuit layer)
The circuit layer is formed on one surface of the thermoplastic liquid crystal polymer film, and constitutes a wiring circuit having a predetermined pattern. The circuit layer is formed by a known or conventional method, and a sputtering method, a plating method, or the like may be used. In addition, for example, a circuit conductor sheet is attached to the thermoplastic liquid crystal polymer film by a known or conventional method such as thermocompression bonding, and then subjected to a photosensitive resist treatment, exposure, and etching process, and then a predetermined pattern. The wiring circuit may be formed on one surface of the thermoplastic liquid crystal polymer film.

  The metal forming the circuit layer is not particularly limited as long as a conductor circuit can be formed, and examples thereof include gold, silver, copper, nickel, aluminum, and alloy metals thereof. Of these metals, copper is preferably used.

  The thickness of the circuit layer may be, for example, about 5 to 50 μm, and preferably about 8 to 40 μm.

(Light reflecting layer)
The light reflecting layer is formed on the other surface of the thermoplastic liquid crystal polymer film on which the circuit layer is formed, and reflects light irradiated from the circuit layer side to the circuit layer side by the light reflecting layer. The absorption of light energy to the plastic liquid crystal polymer film is suppressed.

  In the present invention, in a circuit board provided with such a light reflection layer, the average light reflectance to HEV that is a wavelength region of 400 nm to 500 nm needs to be 50% or more. As long as the rate can be achieved, the material of the light reflecting layer is not particularly limited.

  For example, as the light reflection layer, a specular metal sheet formed from a metal having a specular reflectivity having a light reflectivity of 70% or more in a wavelength region of 400 nm to 500 nm can be mentioned. , Metal sheets such as aluminum, gold, nickel, and stainless steel. In the circuit board, a protective layer or the like may be formed on the outside of the light reflection layer as necessary.

  For example, the conductor sheet that forms the circuit layer and the specular metal sheet that forms the light reflecting layer may be formed of the same type of metal, or may be formed of different types of metals. In the combination, the metal constituting the conductor sheet is copper or aluminum, the metal constituting the metal sheet is aluminum or stainless steel, and particularly preferably, the metal constituting the conductor sheet is copper and constitutes the specular metal sheet. The metal to be used is aluminum.

  The thickness of the light reflecting layer (or specular metal sheet) may be, for example, about 5 to 100 μm, and preferably about 8 to 80 μm. Further, the thickness of the light reflecting layer may be twice or more (for example, 2 to 5 times), preferably 3 or more times (for example, 3 to 4 times) the thickness of the circuit layer.

  The light reflecting layer is attached to the surface opposite to the circuit layer by thermocompression bonding to the thermoplastic liquid crystal polymer film before the circuit layer is formed or the thermoplastic liquid crystal polymer film on which the circuit layer is formed. Alternatively, both the conductor sheet for forming the circuit layer and the specular metal sheet for forming the light reflecting layer may be simultaneously bonded to the thermoplastic liquid crystal polymer film by thermocompression bonding.

  For example, as shown in FIG. 2, a conductor sheet 4 fed from the circuit conductor sheet feed roll 1 is superposed on the upper surface of the thermoplastic liquid crystal polymer film 5 fed from the film feed roll 2, and is thermoplastic. On the lower surface of the liquid crystal polymer film 5, a specular metal sheet 6 fed from the metal sheet feed roll 3 for the light reflecting layer is overlaid. And the laminated body in which the conductor sheet 4, the thermoplastic liquid crystal polymer film 5, and the specular metal sheet 6 were laminated | stacked in order from the top passes between between a pair of heating rolls 7 and 7, and is crimped | bonded. The heating rolls 7 are dielectric heating type metal rolls. As a result, the conductor sheet 4 is thermally bonded to the upper surface of the thermoplastic liquid crystal polymer film 5 and the specular metal sheet 6 is thermally bonded to the lower surface to form a metal-clad laminate 9 which is wound around the laminate winding roll 10.

  Thereafter, the conductive sheet of the metal-clad laminate 9 is subjected to photosensitive resist treatment, exposure, and etching processing, and a circuit board of the present invention in which a wiring circuit having a predetermined pattern is applied can be manufactured.

(Circuit board)
Since the circuit board formed in this way forms a light reflection layer, the average light reflectance to HEV (High Energy Visible Light) which is a wavelength region of 400 to 500 nm is 50% or more. Further, the average light reflectance to HEV is preferably 60% or more, more preferably 70% or more. In addition, an average light reflectance shows the value measured by the method described in the Example mentioned later.

  More preferably, the circuit board of the present invention has an average light reflectance to visible light in the wavelength range of 380 to 770 nm of 50% or more, preferably 60% or more, more preferably 70% or more. Also good.

  From the viewpoint of improving heat dissipation, the circuit board has a thermal conductivity in the plane direction of 3.0 W / mK or more (for example, about 3.0 to 300 W / mK), preferably 10 W / mK or more, and more preferably 50 W. / MK or more.

  Furthermore, from the viewpoint of enhancing the dielectric characteristics, for example, the relative dielectric constant at 1 GHz of the circuit board is less than 4.0 (for example, about 1.8 to 3.8), preferably about 2.5 to 3.6. May be. By having such a relative dielectric constant, it is possible to reduce a transmission loss of an electric signal.

  Furthermore, the dielectric loss tangent at 1 GHz of the circuit board may be less than 0.005 (for example, about 0.0001 to 0.004), preferably about 0.001 to 0.003. By having such a dielectric loss tangent, it is possible to reduce power and noise, and to reduce the amount of generated heat.

  Since the circuit board of the present invention has such a high light reflectance, it is possible to suppress the light deterioration of the thermoplastic liquid crystal polymer film. Therefore, the circuit board of the present invention can be effectively used as a circuit board on which various electronic elements are mounted. In particular, when both high light reflectivity and heat dissipation are provided, the circuit board of the present invention can be particularly suitably used as a circuit board for mounting a light-emitting element such as an LED that is easily affected by heat.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited at all by this Example. In the following examples and comparative examples, various physical properties were measured by the following methods.

[Average light reflectance]
Using a spectrophotometer (manufactured by JASCO Corporation, “V-570”), the total reflectance (specular reflectance + diffuse reflectance) of the circuit board in the wavelength region of 380 nm to 770 nm is measured every 2 nm. The average total reflectance in a predetermined wavelength region was obtained by calculation.

[Coefficient of thermal expansion (ppm / ° C)]
The thermal expansion coefficient of the film is a coefficient obtained by dividing the expansion coefficient when heated at a constant temperature increase rate from room temperature to near the thermal deformation temperature of the film by the temperature difference, and is calculated as follows.

First, using a known thermomechanical analyzer, one end of a strip cut film is fixed, a tensile load is applied to the other end, and the amount of expansion when heated at a constant temperature increase rate is measured. For example, assuming that the length in the tensile load direction of the film is L0 (mm), the length of the film during heating is L1 (mm), the heating temperature is T2 (° C.), and the room temperature is T1 (° C.), the thermal expansion coefficient αL can be calculated by the following equation.
αL = [(L1-L0) / (T2-T1)] / L0 (× 10 ⁻⁶ cm / cm / ° C.)
In the present invention, L0 is 20 mm, T2 is 150 ° C., T1 is 25 ° C., and the tensile load is 1 g.

[Thermal conductivity (W / mK)]
The measurement was performed at a measurement temperature of 20 ° C. using a laser flash method thermal constant measuring apparatus (manufactured by Rigaku Corporation, “LF / TCM FA8510B”).

[Sheet thickness (μm)]
The thickness of the circuit board was measured using a Digimatic indicator manufactured by Mitutoyo Corporation. In the measurement, a sample piece (length 50 cm × width 50 cm) was collected from the circuit board, 100 points were randomly measured for each sample, and the average value was used as the sheet thickness.

[Dielectric properties]
The dielectric constant was measured by a resonance perturbation method at a frequency of 1 GHz. Connect a 1 GHz cavity resonator (Kanto Electronics Co., Ltd.) to a network analyzer (Agilent Technology "E8362B"), and insert a minute material (width: 2 mm x length: 90 mm) into the cavity resonator. The dielectric constant and dielectric loss of the material were measured from the change in resonance frequency before and after insertion for 96 hours in an environment of temperature 20 ° C. and humidity 65% RH.

Example 1
With respect to a thermoplastic liquid crystal polymer film (thickness 25 μm, melting point 280 ° C., manufactured by Kuraray Co., Ltd., “BEXTER FA”), an electrolytic copper foil (thermal expansion coefficient 18 × 10 ⁻⁶ cm / cm) having a thickness of 18 μm on one surface. cm / ° C.) is superimposed on a 50 μm thick aluminum foil (coefficient of thermal expansion of 24 × 10 ⁻⁶ cm / cm / ° C.) on the other surface and supplied to the continuous hot roll press machine in a state where these are superposed. Then, it was pressure-bonded in a heated state at 300 ° C. to prepare a laminate having a structure of electrolytic copper foil / thermoplastic liquid crystal polymer film / aluminum foil.
Subsequently, it was introduced into an oven under a nitrogen atmosphere at 270 ° C. and heat-treated for 30 seconds. The resulting laminated copper foil is subjected to photosensitive resist treatment, exposure, and etching to print circuit wiring, and the circuit layer is reflected on one side of the thermoplastic liquid crystal polymer film and light reflected on the other side. A circuit board with layers was produced. Table 7 shows the physical properties of the obtained circuit board.

(Example 2)
With respect to a thermoplastic liquid crystal polymer film (thickness 25 μm, melting point 328 ° C., manufactured by Kuraray Co., Ltd., “Bexter CTV”), an electrolytic copper foil (thermal expansion coefficient 18 × 10 ⁻⁶ cm / cm) having a thickness of 18 μm on one surface. cm / ° C.) and 50 μm thick aluminum foil (coefficient of thermal expansion: 23 × 10 ⁻⁶ cm / cm / ° C.) on the other surface, and these are superposed and supplied to the continuous hot roll press device Then, it was pressure-bonded in a heated state at 300 ° C. to prepare a laminate having a structure of electrolytic copper foil / thermoplastic liquid crystal polymer film / aluminum foil. Subsequently, it was introduced into an oven under a nitrogen atmosphere at 280 ° C. and heat-treated for 30 seconds. The resulting laminated copper foil is subjected to photosensitive resist treatment, exposure, and etching to print circuit wiring, and the circuit layer is reflected on one side of the thermoplastic liquid crystal polymer film and light reflected on the other side. A circuit board with layers was produced. Table 7 shows the physical properties of the obtained circuit board.

(Example 3)
A circuit board was produced in the same manner as in Example 1 except that the thickness of the film of Example 1 was changed to 50 μm. Table 7 shows the physical properties of the obtained circuit board.

Example 4
A circuit board was produced in the same manner as in Example 2 except that the thickness of the film of Example 2 was changed to 50 μm. Table 7 shows the physical properties of the obtained circuit board.

(Comparative Example 1)
An electrolytic copper foil (thermal expansion coefficient 18 × 10 ⁻⁶ cm / cm / ° C.) having a thickness of 18 μm on one side against a polyimide film (thickness 50 μm, no melting point, “Kapton” manufactured by Toray DuPont Co., Ltd.) ) Are laminated on the other surface with an aluminum foil having a thickness of 50 μm (coefficient of thermal expansion 23 × 10 ⁻⁶ cm / cm / ° C.) through an adhesive layer of 12.5 μm inserted between them, In a state where these were superposed, they were supplied to a vacuum hot press apparatus and pressure-bonded in a heated state at 180 ° C. to prepare a laminate having a structure of electrolytic copper foil / polyimide film / aluminum foil. The electrolytic copper foil of the obtained laminate is subjected to photosensitive resist treatment, exposure and etching to print circuit wiring, and a circuit layer is provided on one side of the polyimide film and a light reflection layer is provided on the other side. A circuit board was produced. Table 7 shows the physical properties of the obtained circuit board.

  As shown in Table 7, the circuit boards of Examples 1 to 4 all have an average light reflectance of 50% or more in the wavelength region of 400 to 500 nm, and the average light reflectance in the wavelength region of 380 to 770 nm is also shown. 50% or more. Moreover, in the circuit boards of Examples 1 to 4, the thermal expansion coefficient of the polymer base material layer and the thermal expansion coefficients of the circuit layer and the light reflection layer are in specific ranges, respectively. , Less likely to warp. Furthermore, the circuit boards of Examples 1 to 4 have high thermal conductivity and excellent heat dissipation. Furthermore, the circuit boards of Examples 1 to 4 have excellent dielectric characteristics, and in particular, excellent dielectric performance in a high frequency region of 1 GHz.

On the other hand, in Comparative Example 1 using polyimide instead of the thermoplastic liquid crystal polymer, the average light reflectance is very low even when the same light reflection layer as in the example is used, and the average light reflectance in the wavelength region of 380 to 770 nm. Only 30% is shown. In particular, the average light reflectance in the wavelength region of 400 to 500 nm is extremely low and is only 10% or less.
Also, the dielectric constant and the dielectric loss tangent are large values as compared with Examples 1 to 4.

  The circuit board of the present invention can also be used as a circuit board material for electric / electronic products as described above, and is particularly effective as a printed wiring circuit board material for LEDs that are becoming thinner and smaller. Can be used.

  As described above, the preferred embodiments of the present invention have been described. However, various additions, modifications, or deletions are possible without departing from the spirit of the present invention, and such modifications are also included in the scope of the present invention. It is.

DESCRIPTION OF SYMBOLS 1 ... Circuit conductor sheet delivery roll 2 ... Film delivery roll 4 ... Conductor sheets 5, 11 ... Thermoplastic liquid crystal polymer film 6 ... Light reflection layer metal sheet 7 ... Heating roll 9 ... Metal-clad laminate 10 ... Laminate Winding roll 12 ... circuit layer 13 ... light reflecting layer

Claims (8)

A thermoplastic liquid crystal polymer film forming an optically anisotropic melt phase;
A circuit layer formed on one side of the thermoplastic liquid crystal polymer film;
A light reflecting layer thermocompression bonded to the other surface of the thermoplastic liquid crystal polymer film;
And a circuit board having an average light reflectance of 50% or more in a wavelength region of 400 to 500 nm.   The circuit board according to claim 1, wherein an average light reflectance is 50% or more in a wavelength range of 380 to 770 nm.   The circuit board according to claim 1, wherein the thermal conductivity in the planar direction is 3.0 W / mK or more.   The circuit board according to any one of claims 1 to 3, wherein a relative dielectric constant at 1 GHz is less than 4.0.   The circuit board according to any one of claims 1 to 4, wherein a dielectric loss tangent at 1 GHz is less than 0.005.   6. The circuit board according to claim 1, wherein the light reflecting layer is made of at least one metal selected from silver, aluminum, rhodium, and stainless steel.   The ratio of the coefficient of thermal expansion (CTEp) of the thermoplastic liquid crystal polymer film to the coefficient of thermal expansion (CTEm) of the metal constituting the light reflecting layer and / or the circuit layer according to any one of claims 1 to 6 ( CTEp / CTEm) is a circuit board in the range of 0.5-2. The circuit board for mounting a light emitting device according to claim 1.

Images