JP5834367B2 - Method for manufacturing metal-based circuit board - Google Patents

Description

  The present invention relates to a method of manufacturing a metal base circuit board by a simple process.

In recent years, along with miniaturization, high performance, and high power of electric and electronic equipment, circuit boards have sufficient heat resistance, adhesion strength between circuit conductors and insulating layers, and heat generated by the elements. Excellent heat dissipation to dissipate the water efficiently is required.
As a circuit board that realizes sufficient heat dissipation, a metal base circuit board in which an insulating layer and a conductor circuit are provided in this order on a metal base is used. In the metal base circuit board, the insulating layer not only electrically insulates the conductor circuit from the metal base, but also serves to bond them together. Therefore, resin is usually used for the insulating layer.
However, the resin has a low thermal conductivity. Therefore, research is being conducted on metal base circuit boards to increase the thermal conductivity of the insulating layer.

  For example, Patent Document 1 discloses a metal base substrate in which a metal foil and a metal substrate are integrated via an insulating layer containing 65 to 80% by volume of an inorganic filler and a dispersant. In this metal base substrate, a coating liquid composed of a thermosetting resin containing an inorganic filler and a dispersant is applied onto a metal foil, and the coating film is heated until the thermosetting resin reaches the B stage, thereby It is manufactured by superposing a metal base on the obtained insulating layer and heating them while applying pressure. However, this metal base substrate has a problem that heat dissipation is insufficient because the thermal conductivity of the thermosetting resin itself constituting the insulating layer is low.

  On the other hand, Patent Document 2 discloses a metal base circuit board using liquid crystal polyester having extremely high thermal conductivity among resins as a resin constituting an insulating layer. This metal base circuit board is said to have a high thermal conductivity of the insulating layer and high thermal stability and electrical reliability.

JP-A-8-83963 International Publication No. 10/117033

  However, when an insulating layer is formed using a coating liquid containing liquid crystal polyester, in the conventional method for manufacturing a metal base circuit board including the one disclosed in Patent Document 2, liquid crystal polyester is used at the time of forming the insulating layer. Heat treatment in an inert gas atmosphere is required to increase the molecular weight. For this reason, there is a problem that the number of steps and labor are increased, and the steps are complicated and economically disadvantageous.

  The present invention has been made in view of the above circumstances, and includes a metal base circuit that includes a liquid crystal polyester formed as an insulating layer and is excellent in heat resistance, adhesion strength between a conductor circuit and an insulating layer, and heat dissipation. It is an object of the present invention to provide a method for producing a metal base circuit board, which can be produced without forming a high molecular weight liquid crystal polyester in an inert gas atmosphere when forming an insulating layer.

To solve the above problem,
The present invention is a method for producing a metal base circuit board in which a conductor circuit is provided on a metal base via an insulating layer, and the liquid crystal polyester liquid composition containing a solvent and a liquid crystal polyester is used as a conductor circuit. Coating on the conductive foil, forming the insulating layer by removing the solvent, and stacking the metal base on the insulating layer, and heating the resulting laminate in a vacuum or in an inert gas atmosphere by the the step of insulating layer and the metal base of the thermocompression bonding, has the Ri flow initiation temperature of 300 to 340 ° C. der of the liquid crystalline polyester, in the heated press, the laminate is the maximum temperature Provided is a method for manufacturing a metal base circuit board, wherein pressing is started at the start of cooling .
In the manufacturing method of the metal base circuit board of this invention, it is preferable to cool the said laminated body using a cooling medium in the said heating press.
In the method for producing a metal base circuit board according to the present invention, it is preferable that, in the heating press, the maximum temperature of the laminate is maintained for a predetermined time before the cooling of the laminate is started.
In the manufacturing method of the metal base circuit board of this invention, the said liquid crystalline polyester has a repeating unit represented by the following general formula (1), (2) and (3), and the following general formula (1), ( The repeating unit represented by the following general formula (1) is 30 to 80 mol% and the repeating unit represented by the following general formula (2) with respect to the total amount of the repeating units represented by 2) and (3). It is preferable to have 10 to 35 mol% of repeating units represented by the following general formula (3).
(1) —O—Ar ¹ —CO—
(2) —CO—Ar ² —CO—
(3) ^-X-Ar 3 -Y-
(In the formula, Ar ¹ is a phenylene group, a naphthylene group or a biphenylylene group; Ar ² and Ar ³ are each independently a phenylene group, a naphthylene group, a biphenylylene group or a group represented by the following general formula (4): Yes; X and Y are each independently an oxygen atom or imino group; one or more hydrogen atoms in Ar ¹ , Ar ² and Ar ³ are each independently substituted with a halogen atom, an alkyl group or an aryl group May be.)
(4) -Ar ⁴ -Z-Ar ^5-
(In the formula, Ar ⁴ and Ar ⁵ are each independently a phenylene group or a naphthylene group; Z is an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or an alkylidene group.)
In the metal base circuit board manufacturing method of the present invention, it is preferable that the liquid crystal polyester liquid composition further includes an inorganic filler having a thermal conductivity of 10 W / (m · K) or more.
In the manufacturing method of the metal base circuit board of this invention, it is preferable to remove the said solvent at 100-210 degreeC .

  According to the present invention, a metal base circuit board having an insulating layer formed using a liquid crystal polyester and having excellent heat resistance, adhesion strength between a conductor circuit and an insulating layer, and heat dissipation is inactivated at the time of forming the insulating layer. It is possible to provide a method for producing a metal base circuit board that can be produced without increasing the molecular weight of liquid crystal polyester in a gas atmosphere.

It is a figure which illustrates the metal base substrate obtained with the manufacturing method which concerns on this invention, (a) is a schematic perspective view, (b) is a schematic sectional drawing in the BB line of (a). 1 is a schematic cross-sectional view illustrating a metal base circuit board according to the present invention.

A method of manufacturing a metal base circuit board according to the present invention is a method of manufacturing a metal base circuit board in which a conductor circuit is provided on a metal base via an insulating layer, and the liquid crystal polyester liquid containing a solvent and a liquid crystal polyester A step of applying a composition (hereinafter sometimes referred to as “liquid composition”) onto a conductive foil for forming a conductor circuit and removing the solvent to form an insulating layer (hereinafter referred to as “insulating layer”). Forming a metal base on the insulating layer, and heat-pressing the obtained laminate in a vacuum or in an inert gas atmosphere to heat the insulating layer and the metal base. The liquid crystal polyester has a flow starting temperature of 300 to 340 ° C.
According to this production method, the liquid crystal polyester liquid composition can be applied onto the conductive foil while the liquid crystal polyester is sufficiently dissolved, and the liquid crystal polyester is heated by heat treatment in an inert gas atmosphere when forming the insulating layer. Even if molecular weight is not performed, a metal base circuit board excellent in heat resistance, adhesion strength between the conductor circuit and the insulating layer, and heat dissipation can be obtained.

(Insulating layer forming process)
In the insulating layer forming step, first, the liquid composition is applied onto a conductive foil for forming a conductor circuit.
The liquid composition contains a liquid crystal polyester and a solvent, and the liquid crystal polyester is more preferable as the dissolution ratio in the solvent is higher.

  The liquid crystalline polyester is a liquid crystalline polyester that exhibits liquid crystallinity in a molten state, and is preferably melted at a temperature of 450 ° C. or lower. The liquid crystal polyester may be a liquid crystal polyester amide, a liquid crystal polyester ether, a liquid crystal polyester carbonate, or a liquid crystal polyester imide. The liquid crystal polyester is preferably a wholly aromatic liquid crystal polyester using only an aromatic compound as a raw material monomer.

As a typical example of liquid crystal polyester,
(I) An aromatic hydroxycarboxylic acid, an aromatic dicarboxylic acid, and at least one compound selected from the group consisting of an aromatic diol, an aromatic hydroxyamine, and an aromatic diamine are polymerized (polycondensed). thing,
(II) a polymer obtained by polymerizing plural kinds of aromatic hydroxycarboxylic acids,
(III) A polymer obtained by polymerizing an aromatic dicarboxylic acid and at least one compound selected from the group consisting of an aromatic diol, an aromatic hydroxyamine and an aromatic diamine,
(IV) What polymerizes polyester, such as a polyethylene terephthalate, and aromatic hydroxycarboxylic acid is mentioned. Here, the aromatic hydroxycarboxylic acid, the aromatic dicarboxylic acid, the aromatic diol, the aromatic hydroxyamine, and the aromatic diamine are each independently replaced with a part or all of the polymerizable derivative. Also good.

Examples of polymerizable derivatives of a compound having a carboxyl group such as aromatic hydroxycarboxylic acid and aromatic dicarboxylic acid include those obtained by converting a carboxyl group into an alkoxycarbonyl group or an aryloxycarbonyl group (ester), carboxyl Examples include those obtained by converting a group into a haloformyl group (acid halide), and those obtained by converting a carboxyl group into an acyloxycarbonyl group (acid anhydride).
Examples of polymerizable derivatives of hydroxyl group-containing compounds such as aromatic hydroxycarboxylic acids, aromatic diols and aromatic hydroxyamines include those obtained by acylating hydroxyl groups and converting them to acyloxyl groups (acylated products) ).
Examples of polymerizable derivatives of amino group-containing compounds such as aromatic hydroxyamines and aromatic diamines include those obtained by acylating an amino group and converting it to an acylamino group (acylated product).

  The liquid crystalline polyester preferably has a repeating unit represented by the following general formula (1) (hereinafter sometimes referred to as “repeating unit (1)”). The repeating unit (1) and the following general formula (2) ) (Hereinafter sometimes referred to as “repeat unit (2)”) and a repeat unit represented by the following general formula (3) (hereinafter referred to as “repeat unit (3)”). More preferably).

(1) —O—Ar ¹ —CO—
(2) —CO—Ar ² —CO—
(3) ^-X-Ar 3 -Y-
(In the formula, Ar ¹ is a phenylene group, a naphthylene group or a biphenylylene group; Ar ² and Ar ³ are each independently a phenylene group, a naphthylene group, a biphenylylene group or a group represented by the following general formula (4): Yes; X and Y are each independently an oxygen atom or imino group; one or more hydrogen atoms in Ar ¹ , Ar ² and Ar ³ are each independently substituted with a halogen atom, an alkyl group or an aryl group May be.)
(4) -Ar ⁴ -Z-Ar ^5-
(In the formula, Ar ⁴ and Ar ⁵ are each independently a phenylene group or a naphthylene group; Z is an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or an alkylidene group.)

As said halogen atom, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom are mentioned.
Examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, n-hexyl group, An n-heptyl group, a 2-ethylhexyl group, an n-octyl group, an n-nonyl group, and an n-decyl group may be mentioned, and the number of carbon atoms is preferably 1-10.
Examples of the aryl group include a phenyl group, an o-tolyl group, an m-tolyl group, a p-tolyl group, a 1-naphthyl group, and a 2-naphthyl group, and the carbon number thereof is 6 to 20. Is preferred.
When the hydrogen atom is substituted with these groups, the number is preferably 2 or less independently for each of the groups represented by Ar ¹ , Ar ² or Ar ^3. More preferably.

  Examples of the alkylidene group include a methylene group, an ethylidene group, an isopropylidene group, an n-butylidene group, and a 2-ethylhexylidene group, and preferably have 1 to 10 carbon atoms.

The repeating unit (1) is a repeating unit derived from a predetermined aromatic hydroxycarboxylic acid. As repeating unit (1), Ar ¹ is a 1,4-phenylene group (repeating unit derived from p-hydroxybenzoic acid), and Ar ¹ is a 2,6-naphthylene group (6-hydroxy). Preferred is a repeating unit derived from 2-naphthoic acid.

The repeating unit (2) is a repeating unit derived from a predetermined aromatic dicarboxylic acid. As the repeating unit (2), Ar ² is a 1,4-phenylene group (repeating unit derived from terephthalic acid), Ar ² is a 1,3-phenylene group (repeating unit derived from isophthalic acid) ), Ar ² is a 2,6-naphthylene group (repeating unit derived from 2,6-naphthalenedicarboxylic acid), and Ar ² is a diphenyl ether-4,4′-diyl group (diphenyl) Preferred is a repeating unit derived from ether-4,4′-dicarboxylic acid).

The repeating unit (3) is a repeating unit derived from a predetermined aromatic diol, aromatic hydroxylamine or aromatic diamine. As the repeating unit (3), Ar ³ is a 1,4-phenylene group (a repeating unit derived from hydroquinone, p-aminophenol or p-phenylenediamine), and Ar ³ is a 4,4′-biphenylylene group. (Repeating unit derived from 4,4′-dihydroxybiphenyl, 4-amino-4′-hydroxybiphenyl or 4,4′-diaminobiphenyl) is preferred.

The content of the repeating unit (1) is the total amount of all repeating units constituting the liquid crystal polyester (the substance of each repeating unit is obtained by dividing the mass of each repeating unit constituting the liquid crystal polyester by the formula weight of each repeating unit). The equivalent amount (mole) is obtained, and the sum of these is preferably 30 mol% or more, more preferably 30 to 80 mol%, still more preferably 30 to 60 mol%, and particularly preferably 30 to 40 mol%. Mol%.
As the content of the repeating unit (1) increases, the liquid crystalline polyester tends to improve the liquid crystallinity and to improve heat resistance, strength and rigidity. As the content of the repeating unit (1) decreases, the solvent of the liquid crystalline polyester increases. There is a tendency for the solubility to be improved.

The content of the repeating unit (2) is preferably 35 mol% or less, more preferably 10 to 35 mol%, still more preferably 20 to 35 mol%, based on the total amount of all repeating units constituting the liquid crystal polyester. Most preferably, it is 30-35 mol%.
As the content of the repeating unit (2) is larger, the solubility of the liquid crystalline polyester in the solvent tends to be improved, and as the content of the repeating unit (2) is smaller, the liquid crystalline property of the liquid crystalline polyester tends to be improved.

The content of the repeating unit (3) is preferably 35 mol% or less, more preferably 10 to 35 mol%, still more preferably 20 to 35 mol%, based on the total amount of all repeating units constituting the liquid crystal polyester. Most preferably, it is 30-35 mol%.
As the content of the repeating unit (3) is larger, the solubility of the liquid crystal polyester in the solvent tends to be improved, and as the content of the repeating unit (3) is smaller, the liquid crystal property of the liquid crystal polyester is likely to be improved.

  The ratio between the content of the repeating unit (2) and the content of the repeating unit (3) is expressed as [content of repeating unit (2)] / [content of repeating unit (3)] (mol / mol). The ratio is preferably 0.9 / 1 to 1 / 0.9, more preferably 0.95 / 1 to 1 / 0.95, and still more preferably 0.98 / 1 to 1 / 0.98. By setting it as such a range, the liquid crystal property of liquid crystal polyester improves more.

In addition, liquid crystalline polyester may have 2 or more types of repeating units (1)-(3) each independently. The liquid crystal polyester may have a repeating unit other than the repeating units (1) to (3), and the content thereof is preferably 10 with respect to the total amount of all repeating units constituting the liquid crystal polyester. The mol% or less, more preferably 5 mol% or less.
And it is preferable that liquid crystalline polyester has only repeating unit (1)-(3) as a repeating unit.

  The liquid crystalline polyester has a repeating unit (3) in which X and / or Y is an imino group (—NH—), that is, a repeating unit derived from a predetermined aromatic hydroxylamine and / or an aromatic diamine. It is preferable that the repeating unit (3) has only those in which X and / or Y is an imino group. By doing in this way, liquid crystalline polyester becomes the thing which was more excellent in the solubility with respect to a solvent.

  The liquid crystal polyester is preferably produced by melt polymerization of raw material monomers corresponding to the repeating units constituting the liquid crystal polyester and solid-phase polymerization of the obtained polymer (prepolymer). Thereby, high molecular weight liquid crystal polyester having high heat resistance, strength and rigidity can be produced with good operability. Melt polymerization may be carried out in the presence of a catalyst. Examples of the catalyst in this case include metals such as magnesium acetate, stannous acetate, tetrabutyl titanate, lead acetate, sodium acetate, potassium acetate, and antimony trioxide. Compounds, nitrogen-containing heterocyclic compounds such as 4- (dimethylamino) pyridine, 1-methylimidazole and the like can be mentioned, and nitrogen-containing heterocyclic compounds are preferably used.

  The liquid crystal polyester has a flow start temperature of 300 to 340. When the flow start temperature is lower than 300 ° C., the molecular weight of the liquid crystal polyester is too small, and gas is generated or the liquid composition flows due to polymerization (high molecular weight) progressing in an insulating layer forming process described later. There is a problem of doing. After applying the liquid composition, these problems can be solved by increasing the molecular weight of the liquid crystalline polyester by performing a heat treatment under an inert gas atmosphere. It is complicated and economically disadvantageous. On the other hand, as the flow start temperature is higher, the heat resistance and strength of the liquid crystal polyester tend to be improved. If the flow start temperature is 300 ° C. or higher, the flow of the liquid composition is reduced when the liquid composition is applied and the solvent is removed. An insulating layer can be formed while suppressing the above. On the other hand, when the flow start temperature is too high, the handleability deteriorates due to a decrease in the solubility of the liquid crystalline polyester in the solvent and an increase in the viscosity of the liquid composition.

  Liquid crystalline polyester can raise the flow start temperature by carrying out solid phase polymerization under nitrogen gas atmosphere. The temperature of the solid phase polymerization is preferably 230 to 300 ° C, and more preferably 260 to 290 ° C. Further, the time for solid phase polymerization is preferably 5 minutes to 30 hours, and more preferably 1 to 10 hours.

The flow start temperature is also called flow temperature or flow temperature, and the temperature is raised at a rate of 4 ° C./min under a load of 9.8 MPa (100 kg / cm ² ) using a capillary rheometer while liquid crystal polyester is used. Is a temperature showing a viscosity of 4800 Pa · s (48000 poise) when extruded from a nozzle having an inner diameter of 1 mm and a length of 10 mm, and is a measure of the molecular weight of the liquid crystalline polyester (Naide Koide, “ “Liquid Crystal Polymer—Synthesis / Molding / Application—”, CMC Co., Ltd., June 5, 1987, p. 95).

  The solvent in the liquid composition is preferably a solvent in which the liquid crystal polyester to be used can be dissolved. As such a solvent, the liquid crystal polyester has a concentration of 1% by mass or more ([liquid crystal polyester] / [liquid crystal polyester + Solvent] × 100) can be exemplified.

  Examples of the solvent include halogenated hydrocarbons such as dichloromethane, chloroform, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, 1-chlorobutane, chlorobenzene, and o-dichlorobenzene. Halogenated phenols such as p-chlorophenol, pentachlorophenol and pentafluorophenol; ethers such as diethyl ether, tetrahydrofuran and 1,4-dioxane; ketones such as acetone and cyclohexanone; esters such as ethyl acetate and γ-butyrolactone; Carbonates such as ethylene carbonate and propylene carbonate; amines such as triethylamine; nitrogen-containing heterocyclic aromatic compounds such as pyridine; nitriles such as acetonitrile and succinonitrile; N, N-dimethylformamide; N-dimethylacetamide, N-methylpyrrolidone (N-methyl-2-pyrrolidone) and other amide compounds (compounds having an amide bond); tetramethylurea and other urea compounds; nitromethane and nitrobenzene and other nitro compounds; dimethyl sulfoxide And sulfur compounds such as sulfolane; and phosphorus compounds such as hexamethylphosphoric acid amide and tri-n-butylphosphoric acid, and two or more of these may be used.

As the solvent, since it is low in corrosivity and easy to handle, an aprotic compound, particularly a solvent mainly comprising an aprotic compound having no halogen atom, is preferred, and the proportion of the aprotic compound in the entire solvent is: Preferably it is 50-100 mass%, More preferably, it is 70-100 mass%, More preferably, it is 90-100 mass%.
The aprotic compound is preferably N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, tetramethylurea, or γ-butyrolactone, since it easily dissolves liquid crystal polyester. N-dimethylformamide, N, N-dimethylacetamide, and N-methylpyrrolidone are more preferable.

  Moreover, as a solvent, since it is easy to melt | dissolve liquid crystalline polyester, the solvent which has a compound whose dipole moment is 3-5 as a main component is preferable, and the compound whose dipole moment occupies the whole solvent is 3-5 The ratio is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and still more preferably 90 to 100% by mass, and a compound having a dipole moment of 3 to 5 is used as the aprotic compound. It is preferable.

  Moreover, as a solvent, since it is easy to remove, the solvent which has as a main component the compound whose boiling point in 1 atmosphere is 220 degrees C or less is preferable. The ratio is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and still more preferably 90 to 100% by mass. As the aprotic compound, a compound having a boiling point of 220 ° C. or less at 1 atm. It is preferable to use it.

  In the liquid composition, the content of the liquid crystal polyester is preferably 5 to 60% by mass, more preferably 10 to 50% by mass, and still more preferably 10 to 45% by mass with respect to the total content of the liquid crystal polyester and the solvent. It is. What is necessary is just to adjust suitably content of liquid crystalline polyester so that the liquid composition of desired viscosity may be obtained, and so that the insulating layer of desired thickness may be obtained.

In addition to the liquid crystal polyester and the solvent, the liquid composition may contain one or more other components such as a filler, an additive, and a resin other than the liquid crystal polyester.
As said other component, a filler is preferable and an inorganic filler and an organic filler are mentioned as the example.

The inorganic filler is appropriately selected so as to obtain an insulating layer having desired performance such as low linear expansion, high thermal conductivity, high rigidity, and high elasticity.
Specific examples of inorganic fillers include oxides such as beryllium oxide, magnesium oxide, aluminum oxide, silicon oxide, titanium oxide, and zinc oxide; nitrides such as boron nitride, aluminum nitride, and silicon nitride; silicon carbide and the like Carbides; oxo acid salts such as aluminum borate, magnesium sulfate, potassium titanate and the like can be used. One or more of these can be used, and oxides and nitrides are preferable.

Moreover, the shape of the inorganic filler may be any of granular, fibrous, and plate-like, and two or more shapes may be mixed.
For example, the granular filler preferably has an average particle size of 0.1 to 20 μm, and more preferably 0.5 to 10 μm. The plate-like filler preferably has an average particle size of 0.1 to 50 μm, more preferably 1 to 30 μm.

  In order to improve the adhesion to the liquid crystal polyester and the dispersibility in the liquid composition, the inorganic filler may be subjected to a surface treatment as at least a part thereof. Examples of surface treatment agents that can be used for this surface treatment include silane coupling agents; titanium coupling agents; aluminum and zirconium coupling agents; long-chain fatty acids; isocyanate compounds; epoxy groups, methoxysilane groups, and amino acids. Examples thereof include polar polymers or reactive polymers containing a group or a hydroxyl group.

  In the liquid composition, the content of the inorganic filler is preferably 5 to 85% by volume, more preferably 10 to 80% by volume with respect to the total content of the liquid crystal polyester and the inorganic filler at room temperature such as 23 ° C. Therefore, it may be adjusted as appropriate so that an insulating layer having desired characteristics can be obtained. By setting it as more than a lower limit, the heat conductivity of an insulating layer improves more, and the intensity | strength of an insulating layer improves more by setting it as an upper limit or less. And as mentioned later, in order for the liquid composition to have an appropriate viscosity, the content of the inorganic filler is more preferably 30 to 70% by volume. In the present invention, even if the content of the inorganic filler in the insulating layer is high, the adhesion strength between the conductor circuit and the insulating layer is excellent.

  Examples of the organic filler include an epoxy resin, a benzoguanamine resin, an acrylic resin, a melamine resin, a urea resin, a styrene resin, and the like, and one or more of these can be used.

The filler preferably has a thermal conductivity of 10 W / (m · K) or more. The thermal conductivity of the filler can be calculated, for example, by measuring the thermal diffusivity, specific heat and density by the following method and calculating by the following formula.
Thermal conductivity = thermal diffusivity × specific heat × density The thermal diffusivity can be measured by a laser flash method.
Specific heat can be measured by comparison with a sapphire standard substance using a differential scanning calorimeter (DSC).
The density can be measured by the Archimedes method.

  Examples of the additive include a coupling agent, an anti-settling agent, a heat stabilizer, a leveling agent, an antifoaming agent, an antioxidant, an ultraviolet absorber, a flame retardant, and a colorant (dye, pigment). These can be used alone or in combination of two or more. The content of the additive is preferably 0 to 5 parts by mass with respect to 100 parts by mass of the liquid crystal polyester.

  Examples of the resin other than the liquid crystal polyester include polypropylene, polyamide, polyester other than the liquid crystal polyester, polyphenylene sulfide, polyether ketone, polycarbonate, polyether sulfone, polyphenylene ether, modified polyphenylene ether, and thermoplastic resin such as polyetherimide. Resins; Thermosetting resins such as phenol resins, epoxy resins, polyimide resins, and cyanate resins; elastomers such as copolymers of glycidyl methacrylate and polyethylene can be used, and one or more of these can be used. The content of the resin other than the liquid crystal polyester is preferably 0 to 20 parts by mass with respect to 100 parts by mass of the liquid crystal polyester.

  The liquid composition can be prepared by mixing the liquid crystal polyester, the solvent, and other components used as necessary, all at once or in an appropriate order. Especially, when using a filler, it is preferable to prepare by dissolving liquid crystal polyester in a solvent, obtaining a liquid crystal polyester solution, and dispersing the filler in this liquid crystal polyester solution. When other components other than the filler are used, other components may be dissolved or dispersed before or after dissolution of the liquid crystal polyester in the solvent, or the filler is dispersed in the liquid crystal polyester solution. Sometimes other components may be dissolved or dispersed before or after dispersion.

  The liquid composition preferably has a viscosity of 1 to 10 Pa · s (10 to 100 poise). By setting it to the lower limit value or more, the effect of suppressing excessive flow of the liquid composition on the conductive foil at the time of coating becomes high, and the coating thickness per coating is improved. Moreover, the handleability of a liquid composition improves more by setting it as below an upper limit.

  The coating of the liquid composition on the conductive foil is preferably performed by casting. For example, a roller coating method, a dip coating method, a spray coating method, a spinner coating method, a curtain coating method, a slot coating method, a screen. Various methods such as a printing method can be adopted.

The conductive foil is preferably a metal foil, and the material thereof is preferably copper, aluminum, nickel, silver or an alloy of one or more metals selected from these, and more preferably copper or a copper alloy.
The thickness of the conductive foil (that is, the conductor circuit) is preferably 9 to 140 μm, more preferably 18 to 70 μm. By setting the lower limit value or more, the function as a conductor circuit is further improved. By setting the upper limit value or less, the conductor circuit can be easily bent and the metal base circuit board can be bent and the metal base circuit board is improved. It is easy to reduce the size and thickness of an electronic device on which a circuit board is mounted.

In the insulating layer forming step, the solvent is then removed from the liquid composition coated on the conductive foil to form an insulating layer.
The method for removing the solvent is not particularly limited, but is preferably a method for evaporating the solvent in terms of simple operation, and a method for evaporating any one of heating, decompression and ventilation alone or in combination of two or more. Can be illustrated. Among these, from the viewpoint of production efficiency and handleability, a method of evaporating by heating is preferable, and a method of evaporating while ventilating and heating is more preferable. The heating for evaporating the solvent is preferably performed at 100 to 210 ° C. for 10 to 120 minutes. Here, “removing the solvent” does not necessarily mean “removing the entire amount of the solvent”, but for example, the solvent is sufficiently removed to such an extent that no obvious weight change of the insulating layer occurs. It is preferable to remove.

(Thermo-compression process)
In the thermocompression bonding step that follows the insulating layer forming step, a metal base is stacked on the insulating layer, and the obtained laminate is heated and pressed in a vacuum or in an inert gas atmosphere to thereby form the insulating layer and the metal. The base is thermocompression bonded. By this step, a metal base substrate in which the conductive foil, the insulating layer, and the metal base are laminated in this order is obtained.

The metal base is preferably a metal plate or a metal foil, and examples of the material include single metals such as copper, aluminum, and iron; alloys of these metals; stainless steel and the like.
The thickness of the metal base is preferably 100 to 3000 μm, and more preferably 500 to 2000 μm.
The metal base preferably has a thermal conductivity of 60 W / (m · K) or more.
The metal base may be a single layer or a plurality of layers. In the case of a plurality of layers, the materials (metals) of these layers may be the same as or different from each other.

  In the thermocompression bonding step, first, a metal base is stacked on the insulating layer in a vacuum or an inert gas atmosphere, and the stacked laminate is heated and pressed from at least one side of the conductive foil and the metal base.

When heat-pressing under vacuum, it is preferable to carry out under reduced pressure, such as 2 KPa or less.
When heat-pressing in an inert gas atmosphere, an inert gas such as nitrogen gas may be used.

The heating temperature at the time of hot pressing is preferably 250 to 400 ° C., and the pressing pressure is preferably 50 to 300 kg / cm ² .

  When performing hot pressing, it is preferable to start pressing at the start of cooling of the laminate at the maximum temperature. At this time, for example, there may be a time lag of preferably within 1 minute, more preferably within 30 seconds, between the start of cooling and the start of pressing. However, the smaller this time lag, the better. More preferably, the start and the press start are simultaneous. When the start of cooling and the start of pressing are not simultaneous, whichever may be first, it is preferable that the start of cooling is first. By doing so, the gas component remaining or generated in the insulating layer can be removed, and the insulating layer and the metal base are subjected to thermocompression bonding after the removal of the gas component, so that deterioration of the insulating layer is suppressed and heat resistance is improved. And a metal base circuit board with improved adhesion strength between the conductive foil and the insulating layer.

The maximum temperature of the laminate is preferably determined by the temperature of the insulating layer. That is, it is preferable to start cooling the laminated body when the insulating layer is at the highest temperature and start pressing at the start of the cooling.
Moreover, it is preferable to cool the said laminated body using cooling media, such as cooling water.

Furthermore, it is preferable to maintain the maximum temperature of the laminated body for a certain time before starting cooling. By doing in this way, as mentioned above, the more superior effect which can remove the gas ingredient which remained or generated in an insulating layer is acquired.
At this time, the maximum temperature holding time is preferably 5 to 60 minutes, and more preferably 10 to 40 minutes.

A metal base substrate obtained by the above manufacturing method is illustrated in FIG. FIG. 1A is a schematic perspective view of a metal base substrate, and FIG. 1B is a schematic cross-sectional view taken along line BB in FIG. In addition, in FIG.1 (b), the cross section is expanded and shown.
The metal base substrate 1 ′ shown here is obtained by laminating a conductive foil 4 ′, an insulating layer 3 and a metal base 2 in this order. However, in the present invention, the metal base substrate is not limited to the one shown here.
In FIG. 1, the X direction and the Y direction are parallel to the main surface of the metal base 2 (contact surface with the insulating layer 3) and are orthogonal to each other, and the Z direction is relative to the X direction and the Y direction. Vertical direction (thickness direction of the metal base substrate 1 ′).

  The metal base circuit board is obtained by patterning the conductive foil of the metal base board into a desired shape and performing processing such as cutting and drilling as necessary. The patterning of the conductive foil can be performed, for example, by forming a mask pattern having a corresponding pattern shape on the conductive foil and removing the exposed portion of the unmasked conductive foil by etching. The mask pattern may be removed after patterning the conductive foil.

  A metal base circuit board obtained by the above manufacturing method is illustrated in FIG. FIG. 2 is a schematic cross-sectional view of the metal base circuit board, and corresponds to the schematic cross-sectional view of the metal base board shown in FIG. The metal base circuit board 1 shown here has a conductor circuit 4 provided on a metal base 2 via an insulating layer 3. However, the metal base circuit board according to the present invention is not limited to the one shown here.

  The metal base circuit board according to the present invention has an excellent heat dissipation property because the insulating layer is formed using liquid crystal polyester. In addition, since the liquid crystal polyester having a flow start temperature of 300 to 340 ° C. is used, the liquid crystal polyester liquid composition can be coated on the conductive foil while the liquid crystal polyester is sufficiently dissolved, and additionally insulated. It is not necessary to increase the molecular weight of the liquid crystal polyester by heat treatment in an inert gas atmosphere when forming the layer. The formed insulating layer is excellent in heat resistance and adhesion strength between the conductor circuit and the insulating layer. Thus, even if the manufacturing process is simplified, the obtained metal base circuit board has excellent characteristics.

  Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to the following examples. In addition, the flow start temperature of liquid crystalline polyester was measured with the following method.

(Measurement of flow start temperature of liquid crystal polyester)
Using a flow tester (manufactured by Shimadzu Corp., CFT-500 type), about 2 g of liquid crystalline polyester was filled into a cylinder equipped with a die having a nozzle having an inner diameter of 1 mm and a length of 10 mm, and 9.8 MPa (100 kg / cm ^2). The liquid crystal polyester was melted while being heated at a rate of 4 ° C./min under a load of 4), extruded from a nozzle, and a temperature showing a viscosity of 4800 Pa · s (48000 poise) was measured.

<Manufacture of liquid crystal polyester>
[Production Example 1]
A reactor equipped with a stirrer, a torque meter, a nitrogen gas inlet tube, a thermometer and a reflux condenser was charged with 6-hydroxy-2-naphthoic acid (1976 g, 10.5 mol) and 4-hydroxyacetanilide (1474 g, 9. 75 mol), isophthalic acid (1620 g, 9.75 mol) and acetic anhydride (2374 g, 23.25 mol) were charged, and the gas in the reactor was sufficiently replaced with nitrogen gas, followed by stirring under a nitrogen gas stream. The temperature was raised from room temperature to 150 ° C. over 15 minutes, and this temperature (150 ° C.) was maintained and refluxed for 3 hours.
Then, while distilling off acetic acid as a by-product to be distilled and unreacted acetic anhydride, the temperature was raised to 300 ° C. over 2 hours and 50 minutes, and the contents were immediately taken out from the reactor. The contents were cooled to room temperature, and the resulting solid was pulverized by a pulverizer to obtain a low molecular weight liquid crystal polyester powder. The flow starting temperature of this liquid crystal polyester powder was 180 ° C.

[Production Example 2]
The liquid crystal polyester powder obtained in Production Example 1 was subjected to solid phase polymerization by heat treatment at 223 ° C. for 3 hours in a nitrogen gas atmosphere. The flow starting temperature of the liquid crystal polyester after solid phase polymerization was 270 ° C.

[Production Example 3]
The liquid crystal polyester powder obtained in Production Example 1 was subjected to solid phase polymerization by heat treatment at 270 ° C. for 3 hours in a nitrogen gas atmosphere. The flow starting temperature of the liquid crystal polyester after the solid phase polymerization was 300 ° C.

[Production Example 4]
The liquid crystalline polyester powder obtained in Production Example 1 was subjected to solid phase polymerization by heat treatment at 290 ° C. for 3 hours in a nitrogen gas atmosphere. The flow starting temperature of the liquid crystalline polyester after solid phase polymerization was 340 ° C.

[Production Example 5]
The liquid crystal polyester powder obtained in Production Example 1 was heat-treated at 320 ° C. for 3 hours in a nitrogen gas atmosphere to carry out solid phase polymerization. When the flow start temperature of the liquid crystalline polyester after solid phase polymerization was measured, the viscosity of 4800 Pa · s was not exhibited even when the temperature exceeded 360 ° C., and the flow start temperature was higher than 360 ° C.

<Production of liquid crystal polyester solution>
[Production Example 6]
The liquid crystal polyester (3000 g) obtained in Production Example 1 was added to N-methyl-2-pyrrolidone (hereinafter referred to as “NMP”) (7000 g) and heated at 100 ° C. for 2 hours to completely dissolve the liquid crystal polyester. After confirming that a clear solution was obtained, this solution was stirred and degassed to obtain a liquid crystal polyester solution (1).

[Production Example 7]
The liquid crystal polyester (2200 g) obtained in Production Example 2 was added to NMP (7800 g) and heated at 100 ° C. for 2 hours to confirm that a transparent solution in which the liquid crystal polyester was completely dissolved was obtained. The solution was stirred and degassed to obtain a liquid crystal polyester solution (2).

[Production Example 8]
The liquid crystal polyester (1800 g) obtained in Production Example 3 was added to NMP (8200 g) and heated at 100 ° C. for 2 hours to confirm that a transparent solution in which the liquid crystal polyester was completely dissolved was obtained. The solution was stirred and degassed to obtain a liquid crystal polyester solution (3).

[Production Example 9]
The liquid crystal polyester (1200 g) obtained in Production Example 4 was added to NMP (8800 g) and heated at 100 ° C. for 2 hours to confirm that a transparent solution in which the liquid crystal polyester was completely dissolved was obtained. The solution was stirred and degassed to obtain a liquid crystal polyester solution (4).

[Production Example 10]
When the liquid crystal polyester (1000 g) obtained in Production Example 5 was added to NMP (9000 g) and heated at 100 ° C. for 2 hours, the liquid crystal polyester was not completely dissolved, and a liquid containing a large amount of insoluble matter of the liquid crystal polyester was obtained. Obtained.

<Manufacture of metal base circuit board>
[Example 1]
(Manufacture of liquid crystal polyester liquid composition)
To the liquid crystal polyester solution (4) obtained in Production Example 9, aluminum oxide (manufactured by Sumitomo Chemical Co., Ltd., “AA-5”, thermal conductivity 38 W / (m · K), average particle size 5 μm), and boron nitride (Manufactured by Mizushima Alloy Iron Co., Ltd., “HP-40”, thermal conductivity 60 W / (m · K), average particle size 20 μm) was added to prepare a liquid crystal polyester liquid composition as a dispersion. Here, the addition amounts of aluminum oxide and boron nitride were adjusted so that the proportion of aluminum oxide accounted for 25% by volume and the rate of boron nitride accounted for 25% by volume in the insulating layer formed from this dispersion. .

(Manufacture of metal base circuit boards)
The liquid crystalline polyester liquid composition obtained above was stirred for 5 minutes with a centrifugal stirring and defoaming machine, and then applied onto a 70 μm thick copper foil, and dried at 100 ° C. for 20 minutes and further at 200 ° C. for 10 minutes. As a result, a 110 μm-thick liquid crystal polyester film was formed on the copper foil as the insulating layer.
Next, an aluminum alloy plate having a thermal conductivity of 140 W / (m · K) and a thickness of 1.5 mm is stacked on the liquid crystal polyester film, and the obtained laminate is heated at 340 ° C. under vacuum for 20 minutes. After the treatment, the copper foil, the liquid crystal polyester film and the aluminum alloy plate are laminated in this order by applying a pressure of 100 kg / cm ² simultaneously with the start of cooling by spraying water and thermocompression bonding the aluminum alloy plate and the liquid crystal polyester film. A metal base substrate was obtained.
Further, the obtained metal base substrate is cut into a predetermined dimension, the predetermined position is masked with an etching resist, the copper foil is partially etched, the etching resist is removed, and a circuit pattern having a width of 10 mm is obtained. A copper foil pattern was formed to obtain a metal base circuit board.

[Example 2]
A metal base circuit board was prepared in the same manner as in Example 1 except that the liquid crystal polyester solution (3) obtained in Production Example 8 was used instead of the liquid crystal polyester solution (4) obtained in Production Example 9. Obtained.

[Comparative Example 1]
Instead of the liquid crystal polyester solution (4) obtained in Production Example 9, the liquid crystal polyester solution (1) obtained in Production Example 6 was used in the same manner as in Example 1 except that the metal base circuit board was used. Although production was attempted, the liquid crystal polyester flowed and a liquid crystal polyester film could not be formed.

[Comparative Example 2]
A metal base circuit board was prepared in the same manner as in Example 1 except that the liquid crystal polyester solution (2) obtained in Production Example 7 was used instead of the liquid crystal polyester solution (4) obtained in Production Example 9. Obtained.

[Comparative Example 3]
Instead of the liquid crystal polyester solution (4) obtained in Production Example 9, an attempt was made to produce a metal base circuit board in the same manner as in Example 1, using the liquid containing liquid crystal polyester obtained in Production Example 10. However, since the liquid crystal polyester (flow start temperature> 360 ° C.) was not sufficiently dissolved in NMP, a liquid crystal polyester film could not be formed by applying the liquid.

<Evaluation of metal base circuit board>
The following evaluation was performed about the metal base circuit board (metal base board | substrate) obtained by each said Example and comparative example.

(Peel strength test)
For the above metal base circuit board, hold one end of the copper foil pattern and apply a force so that the peeled portion of the copper foil pattern is perpendicular to the main surface of the metal base, It was peeled off from the metal base (insulating layer) at a rate of / min. The force applied to the copper foil pattern at this time was defined as peel strength (N / cm), which was used as an index of adhesion strength between the copper foil and the liquid crystal polyester film. The results are shown in Table 1.

(Solder heat resistance test)
The metal base substrate obtained above is cut so that the dimension of the metal base is 50 × 50 mm, and the copper foil is partially etched away by the same method as described above, so that a land having a size of 25 × 50 mm is obtained. Formed. Then, this is placed on a solder bath at 300 ° C. so that the land becomes a contact surface with the solder, and this state is maintained for 4 minutes, and then the metal base substrate is visually inspected for swelling and peeling. Then, the presence or absence of defects was confirmed and the heat resistance was evaluated. The results are shown in Table 1.

  Table 1 shows the result of visual observation of the state during the formation of the liquid crystal polyester film and the measurement result of the thickness (μm) of the liquid crystal polyester film. In Table 1, “LCP” means liquid crystal polyester, and “FT” means flow start temperature. In addition, “-” means not measured or not evaluated.

As is clear from the above results, in Examples 1 and 2 where the flow start temperatures of the liquid crystalline polyester are 340 ° C. and 300 ° C., respectively, the high molecular weight of the liquid crystalline polyester is not increased by heat treatment when forming the liquid crystalline polyester film. However, a metal base circuit board having a good liquid crystal polyester film formation state and excellent peel strength and solder heat resistance was obtained.
On the other hand, in Comparative Example 1, the flow start temperature of the liquid crystal polyester is too low, and when the liquid crystal polyester liquid composition is applied onto the copper foil, the liquid crystal polyester flows and the liquid crystal polyester film cannot be formed. It was.
In Comparative Example 2, when the liquid crystal polyester liquid composition was applied onto the copper foil, the liquid crystal polyester slightly flowed to form a liquid crystal polyester film, but both the peel strength and the solder heat resistance were poor. It was.
Moreover, in the comparative example 3, the flow start temperature of liquid crystalline polyester was too high, the liquid crystalline polyester solution was not obtained, and the liquid crystalline polyester film was not able to be formed.

  The present invention can be used for the manufacture of circuit boards for electrical and electronic equipment.

  DESCRIPTION OF SYMBOLS 1 ... Metal base circuit board, 1 '... Metal base board, 2 ... Metal base, 3 ... Insulating layer, 4 ... Conductor circuit, 4' ... Conductive foil

Claims (6)

A method of manufacturing a metal base circuit board, wherein a conductor circuit is provided on a metal base via an insulating layer,
Applying a liquid crystal polyester liquid composition containing a solvent and a liquid crystal polyester onto a conductive foil for forming a conductor circuit, and removing the solvent to form an insulating layer;
Stacking the metal base on the insulating layer, and heat-pressing the obtained laminate in a vacuum or in an inert gas atmosphere to thermally press-bond the insulating layer and the metal base, and
The flow temperature of the liquid crystal polyester Ri 300 to 340 ° C. der,
In the heating press, the metal base circuit board manufacturing method is characterized in that pressing is started at the start of cooling of the laminate at the highest temperature . The method for manufacturing a metal base circuit board according to claim 1, wherein in the heating press, the stacked body is cooled using a cooling medium. 3. The method of manufacturing a metal base circuit board according to claim 1, wherein in the heating press, the maximum temperature of the laminated body is maintained for a predetermined time before the cooling of the laminated body is started. The liquid crystalline polyester has repeating units represented by the following general formulas (1), (2) and (3), and the repeating units represented by the following general formulas (1), (2) and (3) 30 to 80 mol% of the repeating unit represented by the following general formula (1), 10 to 35 mol% of the repeating unit represented by the following general formula (2), and the following general formula (3) based on the total amount The method for producing a metal base circuit board according to any one of claims 1 to 3, comprising 10 to 35 mol% of a repeating unit represented by formula (1 ) .
(1) —O—Ar ¹ —CO—
(2) —CO—Ar ² —CO—
(3) ^-X-Ar 3 -Y-
(In the formula, Ar ¹ is a phenylene group, a naphthylene group or a biphenylylene group; Ar ² and Ar ³ are each independently a phenylene group, a naphthylene group, a biphenylylene group or a group represented by the following general formula (4): Yes; X and Y are each independently an oxygen atom or imino group; one or more hydrogen atoms in Ar ¹ , Ar ² and Ar ³ are each independently substituted with a halogen atom, an alkyl group or an aryl group May be.)
(4) -Ar ⁴ -Z-Ar ^5-
(In the formula, Ar ⁴ and Ar ⁵ are each independently a phenylene group or a naphthylene group; Z is an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or an alkylidene group.) The liquid crystal polyester liquid composition further metal base circuit board according to any one of claims 1-4 for thermal conductivity, characterized in that it comprises a 10W / (m · K) or more inorganic fillers Manufacturing method. The method for producing a metal base circuit board according to any one of claims 1 to 5 , wherein the solvent is removed at 100 to 210 ° C.

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