JP2014231533A - Porous resin molded body, porous body substrate and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous resin molded body having excellent thermostability and very fine cell structure with low dielectric constant, and a production method thereof, and also to provide a porous body substrate having a metal foil on one side, and quite useful for such as a circuit board of electronic equipment.SOLUTION: A porous resin molded body includes cells of which the average cell diameter is 5 μm or less, the porosity is 40% or more, and relative dielectric constant at the frequency of 1 GHz is 2.00 or less.

Description

  The present invention relates to a heat-resistant porous resin molding having fine bubbles and a low dielectric constant, a porous substrate using the same, and a method for producing the same. The porous resin molded body and the porous body substrate are extremely useful as, for example, a circuit board of an electronic device.

  Conventionally, since a plastic film has high insulation, it is used for components and members that require reliability, for example, electronic / electrical devices such as circuit boards and printed wiring boards, and electronic parts. Recently, as electronic and electrical devices become more sophisticated and functional, a large amount of information is stored and processed and transmitted at high speed. For example, in high frequency circuit boards and antenna boards, transmission loss is reduced. Is required. Therefore, high performance is also required for the plastic materials used for these. In particular, a low dielectric constant and a low dielectric loss tangent are required as electrical characteristics corresponding to a high frequency from the MHz band to the GHz band. In addition, heat resistance that can withstand solder (for example, that it does not change even when soldering at 260 ° C.) is also required.

  However, since the dielectric constant of a plastic material is generally determined by its molecular skeleton, a method of modifying the molecular skeleton can be considered as an attempt to lower the dielectric constant, but there is a limit to lowering the dielectric constant by modifying the molecular skeleton. .

  As other attempts to lower the dielectric constant, various methods have been proposed in which the dielectric constant (1.00) of air is used to make a plastic material porous, and the dielectric constant is controlled by the porosity. Yes.

  Conventional methods for producing a porous body include a dry method and a wet method, and the dry method includes a physical method and a chemical method. A general physical method is to form a bubble by dispersing a low boiling point liquid (foaming agent) such as chlorofluorocarbons and hydrocarbons in a polymer and then volatilizing the foaming agent by heating. . Moreover, a chemical method forms a cell with the gas produced by adding a foaming agent to resin and thermally decomposing this, and obtains a foam by this.

  For example, it has been proposed to obtain a foamed polyetherimide using methylene chloride, chloroform, trichloroethane, or the like as a foaming agent (see, for example, Patent Document 1).

  In recent years, as a foam with a small cell diameter and high cell density, a gas such as nitrogen or carbon dioxide is dissolved in the polymer at a high pressure, and then the pressure is released to near the glass transition temperature or softening point of the polymer. There has been proposed a method of forming bubbles by heating up to. This foaming method forms nuclei from a thermodynamically unstable state, and expands and grows the nuclei to form bubbles, which has the advantage that an unprecedented microporous foam can be obtained. is there.

  For example, it has been proposed to obtain a foam having heat resistance by applying this method to a polyetherimide resin (see Patent Document 2). In addition, for example, it has been proposed that this method is applied to a styrene resin having a syndiotactic structure to obtain a foam having a pore size of 0.1 to 20 μm and used as an electric circuit member. (See Patent Document 3). Further, for example, a low dielectric constant containing a porous plastic foamed with carbon dioxide or the like and having a porosity of 10 Vol% or more, a heat resistance temperature of 100 ° C. or more, and a relative dielectric constant of 2.5 or less. Rate plastic insulation film has been proposed (see Patent Document 4).

  However, in the method of obtaining such a porous resin, in the physical method, the harmfulness of a substance used as a foaming agent and the influence on the environment such as ozone layer destruction caused by the substance are pointed out. . Moreover, although it is a suitable method for obtaining the foam which has a bubble diameter of several tens of micrometers or more, it is difficult to form a fine and uniform bubble diameter.

  In chemical methods, the residue of the foaming agent that generates gas after foaming may remain in the foam. For applications where low contamination is strongly required, such as electronic and electrical equipment and electronic parts. It is unsuitable.

  Further, in a method of generating bubbles by dissolving a gas in a resin at a high pressure and then releasing the pressure and heating the resin to near the glass transition point and softening point, for example, it is described in Patent Document 2. In this method, when the high pressure gas is impregnated in the pressure vessel, the pressure vessel is heated to or near the Vicat softening point of the resin, so that when the pressure is reduced, the high pressure gas tends to expand while the resin is in a molten state. The bubble diameter of the obtained foam is not so small. For example, when it is used as a circuit board, the thickness of the foam is increased, or the miniaturization is limited in patterning.

  Moreover, after forming a polyimide porous layer on base materials other than metal foil, the manufacturing method of the metal foil laminated body which laminated | stacked the metal layer on the one or both surfaces through the heat resistant adhesive layer is proposed ( (See Patent Document 5). However, although this method can avoid the problem of corrosion due to the penetration of the etching solution, it requires steps such as forming a porous layer using another substrate, peeling the substrate, laminating and curing the metal foil and adhesive. This is disadvantageous in the manufacturing process. In addition, in order to obtain sufficient adhesive strength between the adhesive layer and the porous layer, it is necessary to increase the thickness of the adhesive layer to some extent, and the adhesive may penetrate into the pores of the porous layer during bonding. In any case, there is a problem that the effect of reducing the dielectric constant of the obtained insulating layer is reduced.

U.S. Pat. No. 4,532,263 JP-A-6-322168 JP 10-45936 A Japanese Patent Application Laid-Open No. 9-130033 JP 2000-319442 A

  An object of the present invention is to provide a porous resin molded article having excellent heat resistance, a fine cell structure and a low dielectric constant, and a method for producing the same. A further object of the present invention is to provide a porous substrate having a metal foil on one side and being extremely useful as a circuit board for electronic equipment.

  As a result of research to solve the above problems, a porous resin molded body having bubbles with an average bubble diameter of 5 μm or less, a porosity of 40% or more, and a relative dielectric constant at a frequency of 1 GHz of 2.00 or less. It has been found that a porous substrate using a material exhibits good transmission characteristics when used as a high-frequency circuit substrate. In addition, such a porous resin molded body is formed by adding an additive to a resin component to form a specific microphase separation structure, and utilizing the difference in solubility of the two components in a solvent to extract the additive by solvent extraction. It was found that a porous resin molding having extremely fine bubbles and a low dielectric constant can be obtained by removing. The present invention is based on these findings.

  That is, the present invention provides a porous resin molded article having bubbles having an average cell diameter of 5 μm or less, a porosity of 40% or more, and a relative dielectric constant at a frequency of 1 GHz of 2.00 or less. I will provide a.

  The resin constituting the porous resin molded body of the present invention is preferably made of a resin selected from thermosetting resin, engineering plastic, or super engineering plastic, and particularly preferably made of polyimide resin or polyetherimide resin. .

  The present invention also provides a porous substrate in which a metal foil is provided on at least one surface of the porous resin molded body.

The present invention is also a method for producing the porous resin molded body,
A step of applying a resin composition containing a resin component and a phase separation agent that phase-separates with a cured product of the resin component on a substrate and curing it to produce a resin sheet having a microphase separation structure, a phase from the resin sheet Provided is a method for producing a porous resin molded body comprising a step of removing a separating agent to produce a porous body.

  The present invention also includes the step of converting the polyamic acid to polyimide after using the polyamic acid as a resin component and removing the phase separating agent from the resin sheet to make it porous. A method for manufacturing a body is provided.

  In particular, the present invention provides a method for producing the porous resin molded article, wherein a metal foil is used as a substrate on which the resin composition is applied.

  Further, the present invention is a method for producing a porous resin molded body in which the phase separation agent is removed by solvent extraction, and in particular, the solvent is a kind selected from liquefied carbon dioxide, subcritical carbon dioxide or supercritical carbon dioxide. A method for producing a porous resin molded body is provided.

  The porous resin molded body and porous substrate of the present invention are low dielectric constant materials used for high frequency circuits such as circuit boards for electronic devices and antennas for mobile phones, taking advantage of their excellent heat resistance and low dielectric constant. They can be used as electromagnetic wave control materials such as electromagnetic wave shields and electromagnetic wave absorbers, and heat insulating materials.

FIG. 1 is a schematic top view of a microstrip line for evaluating transmission loss in a transmission line, (a) is an overall top view of the line pattern, and (b) is an enlarged top view of a terminal portion. 2 is a cross-sectional view taken along line AA in FIG.

  Embodiments of the present invention will be described below. The porous resin molded article of the present invention has bubbles having an average cell diameter of 5 μm or less, a porosity of 40% or more, and a relative dielectric constant at a frequency of 1 GHz of 2.00 or less. .

  The porous resin molded body of the present invention has, for example, a resin composition containing a resin component and a phase separation agent that phase-separates with a cured body of the resin component on a substrate and is cured to form a microphase separation structure. It can be produced by a step of producing a resin sheet having a porous body by removing the phase separation agent from the resin sheet.

  The resin component used in the porous molded body of the present invention is not particularly limited, but is preferably a resin selected from thermosetting resins having heat resistance, engineering plastics, or super engineering plastics. Such a resin is not particularly limited as long as it has a 5% weight loss temperature of 250 ° C. or higher, preferably 280 ° C. or higher. Moreover, when using a thermoplastic resin, if a glass transition temperature is 150 degreeC or more, it can be used conveniently. Examples of such resin components include, but are not limited to, general-purpose plastics such as polystyrene, (meth) acrylic resins, ABS resins, and AS resins; polyamides, polycarbonates, polybutylene terephthalates, polyethylene terephthalates, and cyclic polyolefins. Engineering plastics; Super engineering plastics such as polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyamideimide, polyimide, and polyetherimide; epoxy resin, phenol resin, melamine resin, urea resin (urea resin), alkyd resin Thermosetting resins such as unsaturated polyester resin, polyurethane, thermosetting polyimide, silicone resin, and diallyl phthalate resin. It is. These resin components may be used alone or in combination of two or more.

  Among the above resin components, polyimide and polyetherimide are particularly preferably used. Polyimide and polyetherimide have the advantage of excellent dimensional stability at high temperatures. Polyimide can be obtained by a known or conventional method. For example, a polyimide can be obtained by reacting an organic tetracarboxylic dianhydride and a diamino compound (diamine) to synthesize a polyimide precursor (polyamic acid) and dehydrating and ring-closing the polyimide precursor.

  Examples of the organic tetracarboxylic dianhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, and 2,2-bis (2,3-dicarboxyl). Phenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexa Fluoropropane dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone A dianhydride etc. are mentioned. One of these organic tetracarboxylic dianhydrides may be used alone, or two or more thereof may be mixed and used.

  Examples of the diamino compound include m-phenylenediamine, p-phenylenediamine, 3,4-diaminodiphenyl ether, 4,4′-diaminophenyl ether, 4,4′-diaminodiphenyl sulfone, and 3,3′-diaminodiphenyl. Sulfone, 2,2-bis (4-aminophenoxyphenyl) propane, 2,2-bis (4-aminophenoxyphenyl) hexafluoropropane, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 2,4-diaminotoluene, 2,6-diaminotoluene, diaminodiphenylmethane, 4,4'-diamino-2,2-dimethylbiphenyl, 2,2-bis (trifluoromethyl)- 4,4'-diaminobiphenyl and the like. These diamino compounds may be used alone or in combination of two or more.

  As the polyimide used in the present invention, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride is used as the organic tetracarboxylic dianhydride, p-phenylenediamine is used as the diamino compound, 4,4. It is preferable to use '-diaminodiphenyl ether.

  The said polyimide precursor is obtained by making substantially equimolar organic tetracarboxylic dianhydride and a diamino compound (diamine) react normally at 0-90 degreeC for about 1 to 24 hours in an organic solvent. Examples of the organic solvent include polar solvents such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, and dimethyl sulfoxide.

  The dehydration cyclization reaction of the polyimide precursor is performed, for example, by heating to about 300 to 400 ° C. or by allowing a dehydration cyclization agent such as a mixture of acetic anhydride and pyridine to act. In general, polyimide is a polymer that is insoluble in organic solvents and difficult to mold. Therefore, when a porous body made of polyimide is produced, the above polyimide precursor is generally used as a polymer for the preparation of the polymer composition having the microphase separation structure.

  In addition to the above method, the polyimide can be obtained by a method in which a polyamic acid silyl ester obtained by reacting an organic tetracarboxylic dianhydride and an N-silylated diamine is heated to cyclize.

  The polyetherimide can be obtained by a dehydration cyclization reaction between the diamino compound and an aromatic bisether anhydride such as 2,2,3,3-tetracarboxydiphenylene ether dianhydride. For example, Ultem resin (manufactured by SABIC), Superior resin (manufactured by Mitsubishi Plastics) or the like may be used.

  In the present invention, the component constituting the discontinuous phase of the microphase separation structure (hereinafter sometimes simply referred to as “phase separation agent”) is compatible when mixed with the above heat-resistant resin component. And a compound that is phase-separated from the cured product of the resin component. However, even if it is a compound which phase-separates with a resin component, what becomes a uniform state (uniform solution) can be used by adding a suitable medium (for example, organic solvent). By making the phase separation agent uniform in the resin component, it is possible to obtain a porous resin molded article having a fine average cell diameter (specifically, 5 μm or less).

  Examples of such a phase separation agent include polyalkylene glycols such as polyethylene glycol, tripropylene glycol, and polypropylene glycol; one end or both end methyl-blocked polyalkylene glycol, or one end or both ends (meth) Acrylic blockade; urethane prepolymer; phenoxypolyethylene glycol (meth) acrylate, ε-caprolactone (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, urethane (meth) acrylate, epoxy ( Examples include (meth) acrylate compounds such as (meth) acrylate and oligoester (meth) acrylate. One of these phase separation agents may be used alone, or two or more thereof may be mixed and used.

  In the present invention, a fine microphase separation structure can be obtained by using the phase separation agent. For this reason, in the porous resin molding, the average cell diameter can be 5 μm or less.

  The molecular weight of the phase separation agent is not particularly limited, but is preferably 10000 or less, for example, about 100 to 10000, more preferably 100 to 2000, as the weight average molecular weight because the subsequent removal operation becomes easy. is there. When the weight average molecular weight is less than 100, it becomes difficult to phase separate from the cured resin component, whereas when the weight average molecular weight exceeds 10,000, the microphase separation structure becomes too large or removed from the resin molding. It may be difficult. When the weight average molecular weight of the phase separation agent is within the above range, a porous resin molded product having an average cell diameter of 5 μm or less can be obtained.

  The addition amount of the phase separation agent can be appropriately selected according to the combination of the phase separation agent and the resin component. In order to increase the porosity of the porous resin molded body to 40% or more, the resin component 100 is usually used. It is preferable to use 25 to 300 parts by weight, more preferably 50 to 200 parts by weight of the phase separation agent with respect to parts by weight.

  When producing the porous resin molding of the present invention, the resin component and the phase separation agent described above can be used in appropriate combination, but the porous resin molding has bubbles having an average cell diameter of 5 μm or less, In order to have a porosity of 40% or more and a relative dielectric constant at a body frequency of 1 GHz of 2.00 or less, a polyimide resin is used as a resin component and polyalkylene glycol is used as a phase separation agent. Is preferred.

  In the present invention, the porous resin molded body may contain an additive as required in addition to the resin component. The type of the additive is not particularly limited, and various additives that are usually used for circuit boards and the like can be used.

  Examples of the additive include a plasticizer, a lubricant, a colorant, an ultraviolet absorber, an antioxidant, a filler, a reinforcing agent, a flame retardant, and an antistatic agent. The kind and addition amount are not particularly limited, and can be used within a range that does not impair the characteristics of the porous resin molding of the present invention.

  Hereinafter, the manufacturing method of the porous resin molding of this invention is demonstrated in detail.

  First, a resin composition containing the resin component and a phase separation agent is applied on a substrate.

  In order to prepare a uniform resin composition, aromatic hydrocarbons such as toluene and xylene; alcohols such as methanol, ethanol and isopropyl alcohol; ketones such as methyl ethyl ketone and acetone; N-methyl-2-pyrrolidone Organic solvents such as amides such as dimethylacetamide and dimethylformamide may be used. The usage-amount of an organic solvent is 100-500 weight part normally with respect to 100 weight part of resin components, Preferably it is 300-500 weight part.

  The substrate is not particularly limited as long as it has a smooth surface, and examples thereof include plastic films such as PET, PE, and PP; glass plates; metal foils such as stainless steel, copper, and aluminum. In order to manufacture a resin sheet continuously, you may use a belt-shaped base material.

  The method for applying the resin composition onto the substrate is not particularly limited, and examples of the method for continuous application include wire bar, kiss coat, and gravure. Examples of the method for applying in batch include: Applicators, wire bars, knife coaters and the like can be mentioned.

  Next, the resin composition applied on the substrate is cured to produce a resin sheet in which the phase separation agent is microphase-separated. The microphase separation structure usually has a sea-island structure in which the resin component is the sea and the phase separation agent is the island.

  When the resin composition does not contain a solvent, the coating film is subjected to a curing process such as a thermosetting process to cure the resin component in the coating film and insolubilize the phase separation agent.

  When the resin composition contains a solvent, the resin component may be cured after the solvent in the coating film is evaporated (dried) to form a microphase separation structure, or the solvent is evaporated after the resin component is cured. It may be (dried) to form a microphase separation structure. The temperature at which the solvent is evaporated (dried) is not particularly limited and may be appropriately adjusted depending on the type of the solvent used, but is usually 10 to 250 ° C, preferably 60 to 200 ° C.

  Next, the phase separation agent that has undergone microphase separation is removed from the resin sheet to produce a porous resin sheet. In addition, you may peel the resin sheet from a base material before removing a phase-separation agent.

  The method for removing the phase separation agent from the resin sheet is not particularly limited, but a method of extracting with a solvent is preferable. It is necessary to use a solvent that is a good solvent for the phase separation agent and does not dissolve the cured product of the resin component. For example, organic solvents such as toluene, ethanol, ethyl acetate, and heptane, liquefied carbon dioxide , Subcritical carbon dioxide, supercritical carbon dioxide and the like. Since liquefied carbon dioxide, subcritical carbon dioxide and supercritical carbon dioxide easily penetrate into the resin sheet, the phase separation agent can be efficiently removed.

  When liquefied carbon dioxide, subcritical carbon dioxide or supercritical carbon dioxide is used as a solvent, a pressure vessel is usually used. As the pressure vessel, for example, a batch type pressure vessel, a pressure vessel having a pressure-resistant sheet feeding and winding device, or the like can be used. The pressure vessel is usually provided with carbon dioxide supply means composed of a pump, piping, valves and the like.

  The temperature and pressure at the time of extracting the phase separation agent with liquefied carbon dioxide, subcritical carbon dioxide or supercritical carbon dioxide need only be higher than the critical point of carbon dioxide, and usually 32 to 230 ° C., 7.3 to 7.3 100 MPa, preferably 40 to 200 ° C. and 10 to 50 MPa.

  Extraction may be carried out by continuously supplying and discharging liquefied carbon dioxide, subcritical carbon dioxide or supercritical carbon dioxide into a pressure vessel containing a resin sheet. , Liquefied carbon dioxide, subcritical carbon dioxide or supercritical carbon dioxide may not be moved out of the container). When supercritical carbon dioxide and subcritical carbon dioxide are used, swelling of the resin sheet is promoted, and the phase separation agent is efficiently removed from the resin sheet by improving the diffusion coefficient of the insolubilized phase separation agent. The When liquefied carbon dioxide is used, the diffusion coefficient is reduced, but the permeability into the resin sheet is improved, so that the phase separation agent is efficiently removed from the resin sheet.

  The extraction time needs to be appropriately adjusted depending on the temperature and pressure at the time of extraction, the blending amount of the phase separation agent, the thickness of the resin sheet, and the like, but is usually 1 to 10 hours, preferably 2 to 10 hours. is there.

  On the other hand, when extracting using an organic solvent as the solvent, the phase separation agent can be removed under atmospheric pressure, so the deformation of the porous resin sheet is less than when extracting using liquefied carbon dioxide or supercritical carbon dioxide. Can be suppressed. In addition, the extraction time can be shortened. Furthermore, by sequentially passing the resin sheet through the organic solvent, the phase separation agent can be extracted continuously.

  Examples of the extraction method using an organic solvent include a method of immersing a resin sheet in an organic solvent, a method of spraying an organic solvent on the resin sheet, and the like. The immersion method is preferable from the viewpoint of the removal efficiency of the phase separation agent. Further, the phase separation agent can be efficiently removed by exchanging the organic solvent several times or performing extraction while stirring.

  After removing the phase separation agent, the porous resin sheet may be dried.

  In the present invention, when polyamic acid (polyimide precursor) is used as the resin component, the porous resin sheet is heated at about 300 to 400 ° C., or a dehydrating cyclizing agent such as a mixture of acetic anhydride and pyridine is used. By making it, a polyamic acid can be converted into a polyimide.

  In the present invention, when a phase separation agent that can be evaporated or decomposed by heating is used, it may be combined with a method of removing the phase separation agent by heating to evaporate or decompose before the extraction. it can. The heating temperature in the case of evaporating or decomposing the phase separation agent from heating can be appropriately selected according to the boiling point and decomposition temperature of the phase separation agent, but is generally 100 ° C. or higher, for example, 100 to 500 ° C., preferably 250 to It is about 450 ° C. The evaporation and decomposition operations are preferably performed under reduced pressure (for example, 1 mmHg or less) in order to increase the removal efficiency of the phase separation agent. Since the evaporation or decomposition and extraction operation are performed in combination, the additive residue that cannot be removed by one operation can be completely removed by another operation, and a porous body having a very low dielectric constant can be obtained.

  The shape of the porous molded body may be any of a tape shape, a sheet shape, a film shape, or a block shape depending on the purpose, but when used in a sheet shape, the thickness is usually 1 to 500 μm, Preferably it is 10-150 micrometers, More preferably, it is 15-100 micrometers.

  The porous resin molding obtained by the production method of the present invention has bubbles having an average cell diameter of 5 μm or less, preferably 4 μm or less (usually 0.05 μm or more). If the average bubble diameter is 5 μm or less, the dielectric constant and dielectric loss tangent can be lowered without lowering the insulation and mechanical strength. When the average bubble diameter exceeds 5 μm, the insulation properties and mechanical strength decrease.

  The average cell diameter of the bubbles contained in the porous resin molding of the present invention is determined by observing the cut surface of the porous resin molding with a scanning electron microscope (SEM), and then processing the image with image processing software (for example, Mitani Corporation). Binarized with “WinROOF”, and separated into a bubble part and a resin part to measure the maximum vertical chord length of the bubbles, and take the average value for the 50 bubbles from the larger bubble diameter. The diameter.

  The bubbles contained in the porous resin molding of the present invention are closed cell structure, semi-continuous semi-closed cell structure (a bubble structure in which closed cell structure and open cell structure are mixed, the ratio is not particularly limited) In particular, a cell structure in which the closed cell structure part is 80% or more (in particular, 90% or more) in the foam is desirable. Because of the closed cells, for example, when the porous resin molding of the present invention is used for a printed wiring board, the etching solution does not penetrate and deteriorate due to the etching process. Whether or not the bubbles contained in the porous resin molded body are closed cells can be confirmed by observation with the scanning electron microscope.

  Moreover, the porous resin molding obtained by the production method of the present invention has a porosity of 40% or more, preferably 50% or more (usually 90% or less). When the porosity is 40% or more, there is an advantage that uniform pores exist in the porous resin molded body, and variation in dielectric characteristics is eliminated. Further, in order to make the dielectric constant 2.00 or less, it is necessary to adjust the porosity to be 40%. When the volume porosity is less than 40%, the vacancy formation state is biased and variations in dielectric characteristics are likely to occur.

The porosity of the porous resin molded body of the present invention was calculated from the following formula by measuring the specific gravity of the resin composition before porous formation and the porous resin molded body.
Porosity (%) = {1− (specific gravity of porous resin molding) / (specific gravity of resin composition before porosity)} × 100

  In addition, the porous resin molding obtained by the production method of the present invention has a relative dielectric constant at a frequency of 1 GHz of 2.00 or less, preferably 1.90 or less, more preferably 1.80 or less (usually 1.40 or more). ). If the relative permittivity is within the above range, the dielectric loss in the high frequency band can be reduced, and the transmission loss can be reduced.

  In the present invention, the dielectric constant of the porous resin molded body was measured by a complex dielectric constant at a frequency of 1 GHz by a cavity resonator contact method, and the real part was defined as the dielectric constant. For example, a cylindrical cavity resonator (“Network Analyzer N5230C” manufactured by Agilent Technologies, “Cavity Resonator 1 GHz” manufactured by Kanto Electronics Application Development Co., Ltd.) is used as a measuring instrument, and a strip-shaped sample (sample size 2 mm × 70 mm length) is used. Can be measured.

  The porous resin molded body of the present invention can be used as it is as an internal insulator for electronic devices, buffer materials, circuit boards, etc., but the porous body is provided with a metal foil on at least one surface of the porous resin molded body. It can also be a substrate. The porous substrate is used as an electromagnetic wave control material such as an antenna for a mobile phone or an antenna substrate, a high-frequency circuit board, an electromagnetic wave shield, or an electromagnetic wave absorber.

  Although it does not specifically limit as metal foil, Usually, stainless steel foil, copper foil, aluminum foil, copper-beryllium foil, phosphor bronze foil, iron-nickel alloy foil, etc. are used.

  Although it does not specifically limit as a method of forming a metal foil layer, In the manufacturing method of an above described porous resin molding, it is suitable to use metal foil as a board | substrate which coats a resin composition. That is, a resin composition is coated on a metal foil, cured, a resin sheet in which a phase separation agent is microphase-separated, and a phase separation agent that has been microphase-separated is extracted. A porous resin molding can be formed.

  In addition, a method of adhering a metal foil to a preformed porous resin molded body, a method of metallizing a preformed porous resin molded body by a known method such as sputtering, electrolytic plating, electroless plating, and the like can be given. Also, two or more techniques can be used in combination.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

(Average bubble diameter)
The porous resin molding was cooled with liquid nitrogen and cut perpendicularly to the sheet surface using a blade to produce an evaluation sample. The cut surface of the sample was subjected to Au deposition treatment, and the cut surface was observed with a scanning electron microscope (SEM) (“S-3400N” manufactured by Hitachi, Ltd.). The image was binarized with image processing software (“WinROOF” manufactured by Mitani Corporation), separated into a bubble portion and a resin portion, and the maximum vertical chord length of the bubbles was measured. The average value of 50 bubbles from the larger bubble diameter was taken as the average bubble diameter.

(Porosity)
The specific gravity of the resin composition before foaming and the porous resin molding after foaming was measured with a hydrometer (“MD-300S” manufactured by Alpha Mirage), and the porosity was calculated according to the following formula.
Porosity (%) = {1− (specific gravity of porous resin molding) / (specific gravity of resin composition before porosity)} × 100

(Relative permittivity)
The relative dielectric constant at a frequency of 1 GHz was measured by the cavity resonator perturbation method. The measuring instrument uses a strip-shaped sample (sample size 2 mm × 70 mm length) by a cylindrical cavity resonator (“Network Analyzer N5230C” manufactured by Agilent Technologies, “Cavity Resonator 1 GHz” manufactured by Kanto Electronics Application Development Co., Ltd.). The complex dielectric constant at a frequency of 1 GHz was measured, and the real part was taken as the relative dielectric constant.

(Solder heat resistance)
The porous resin molding was floated for 30 seconds in a solder reflow heated to 260 ° C., and the presence or absence of a change was confirmed. Those with changes in appearance and external shape such as shrinkage and melting were designated as “no solder”, and those without any change were designated as “with” solder heat resistance.

Example 1
In a 1000 ml four-necked flask, 785.3 g of N-methyl-2-pyrrolidone (NMP), 44.1 g of p-phenylenediamine, and 20.4 g of 4,4′-diaminodiphenyl ether were charged and dissolved while stirring at room temperature. . Next, 150.2 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was added, reacted at a temperature of 25 ° C. for 1 hour, and then heated at 75 ° C. for 25 hours to be a B-type viscometer. A polyamic acid solution (solid content concentration 20 wt%) having a solution viscosity of 160 Pa · s was obtained.

  120 parts by weight of polypropylene glycol having a weight average molecular weight of 400 with respect to 100 parts by weight of the polyamic acid solution was added to the obtained polyamic acid solution and stirred to obtain a transparent uniform resin composition. This resin composition was applied onto a 12 μm copper foil using an applicator, and then dried at 110 ° C. for 3 minutes to evaporate and remove NMP, thereby producing a polyamic acid film. This polyamic acid film is placed in a 500 cc pressure vessel, pressurized to 25 MPa in an atmosphere at 25 ° C., and then the amount of gas is maintained while maintaining the pressure to inject and exhaust carbon dioxide at a flow rate of about 15 liters / minute. The operation of extracting polypropylene glycol was performed for 5 hours to obtain a porous material. Thereafter, the polyamic acid porous body is taken out from the pressure vessel, put in a vacuum oven, depressurized to 5 Torr or less, heated to 340 ° C. over 60 minutes, held in that state for 10 minutes and heated to convert the polyamic acid to polyimide. After conversion, a porous substrate in which a polyimide porous resin molded body having a thickness of 25 μm was provided on a copper foil was produced. The resulting polyimide porous resin molding had an average cell diameter of 4 μm, a porosity of 68%, a relative dielectric constant of 1.43 (1 GHz), and a solder heat resistance of “Yes”.

Example 2
120 parts by weight of polypropylene glycol having a weight average molecular weight of 400 with respect to 100 parts by weight of the polyamic acid solution was added to the polyamic acid solution obtained in Example 1 and stirred to obtain a transparent uniform resin composition. This resin composition was applied onto a 12 μm copper foil using an applicator, and then dried at 95 ° C. for 4 minutes to evaporate and remove NMP, thereby producing a polyamic acid film. Subsequent processing was performed in the same manner as in Example 1 to prepare a porous substrate in which a polyimide porous resin molded body having a thickness of 18 μm was provided on a copper foil. The obtained polyimide porous resin molding had an average cell diameter of 3.5 μm, a porosity of 47%, a relative dielectric constant of 1.64 (1 GHz), and a solder heat resistance of “Yes”.

Example 3
120 parts by weight of tripropylene glycol having a molecular weight of 192 with respect to 100 parts by weight of the polyamic acid solution was added to the polyamic acid solution obtained in Example 1, and stirred to obtain a transparent uniform resin composition. This resin composition was applied onto a 12 μm copper foil using an applicator, and then dried at 85 ° C. for 10 minutes to evaporate and remove NMP to produce a polyamic acid film. Subsequent processing was performed in the same manner as in Example 1 to prepare a porous substrate in which a polyimide porous resin molded body having a thickness of 18 μm was provided on a copper foil. The obtained polyimide porous resin molding had an average cell diameter of 3 μm, a porosity of 52%, a relative dielectric constant of 1.98 (1 GHz), and a solder heat resistance of “Yes”.

Comparative Example 1
The polyamic acid solution obtained in Example 1 was applied onto a 12 μm copper foil using an applicator and dried at 85 ° C. for 10 minutes to evaporate and remove NMP to produce a polyamic acid film. The subsequent treatment was carried out in the same manner as in Example 1, and a polyimide film having a thickness of 40 μm was produced on the copper foil. SEM observation of the cross section of the obtained polyimide film was performed, but no bubbles were observed. The relative dielectric constant was 3.22 (1 GHz).

Comparative Example 2
120 parts by weight of polyoxypropylene-glycerin ether having a weight average molecular weight of 330 to 100 parts by weight of the polyamic acid solution was added to the polyamic acid solution obtained in Example 1, and stirred to obtain a transparent uniform resin composition. Obtained. This resin composition was applied onto a 12 μm copper foil using an applicator, and then dried at 85 ° C. for 10 minutes to evaporate and remove NMP to produce a polyamic acid film. Subsequent processing was performed in the same manner as in Example 1, and a porous substrate in which a polyimide porous resin molded body having a thickness of 25 μm was provided on a copper foil was produced. The resulting polyimide porous resin molding had an average cell diameter of 2.0 μm, a porosity of 18%, a relative dielectric constant of 3.09 (1 GHz), and a solder heat resistance of “Yes”.

Comparative Example 3
100 parts by weight of a trade name “ARTON” (manufactured by JSR) which is a cycloolefin copolymer, 400 parts by weight of toluene as a solvent and 100 parts by weight of tripropylene glycol having a molecular weight of 192 are added and stirred to form a transparent uniform resin composition I got a thing. This resin composition was applied onto a PET film using an applicator, and then dried at 60 ° C. for 4 minutes to evaporate and remove toluene. This resin molded body is put into a 500 cc pressure vessel, pressurized to 25 MPa in an atmosphere of 25 ° C., and then the amount of gas is maintained while maintaining the pressure to inject and exhaust carbon dioxide at a flow rate of about 15 liters / minute. The operation of extracting tripropylene glycol was performed for 5 hours to obtain a porous body having a thickness of 100 μm. Thereafter, the porous body was bonded to a 12 μm copper foil using a 25 μm epoxy adhesive sheet to prepare a porous substrate in which a porous resin molded body of a cycloolefin copolymer was provided on the copper foil. The resulting cycloolefin copolymer porous resin molded article had an average cell diameter of 8 μm, a porosity of 60%, a relative dielectric constant of ε = 1.81 (1 GHz), and a solder heat resistance of “none”. .

(Evaluation of transmission loss)
When the porous substrate of the present invention was applied to a high frequency circuit substrate, the transmission loss in the transmission line was evaluated. A transmission loss evaluation method will be described with reference to FIGS. The numbers in parentheses below correspond to the symbols in FIGS.

Sputtering with copper and electroplating were performed on the resin side of the porous substrate (1) obtained in Example 1 to form a copper foil layer having a thickness of 6 μm to produce a copper-clad laminate of double-sided copper foil. The obtained double-sided copper foil copper-clad laminate was subjected to φ75 μm through hole processing (3) and plating (not shown) to form a 12 μm thick copper foil layer. Thereafter, a film resist (HR-130) manufactured by Tokyo Ohka Kogyo Co., Ltd. was laminated at 100 ° C. and 3 kg / cm ² , a resist film was laminated on the copper foil, and a single-ended microstrip line (MSL) [line length (L) 5 cm , Line width (W) 100 μm], mask exposed at 30 mJ / cm ² with an ultra high pressure mercury lamp, developed by spraying with 0.5% Na ₂ CO ₃ aqueous solution, resist on one side copper foil The film was processed to form a mask.
Next, using a spray, an FeCl ₃ / HCl etching solution manufactured by Wako Pure Chemical Industries, Ltd. was sprayed onto the mask surface, and after etching the copper foil, the wiring board was washed with running water for 1 minute and immersed in dilute HCl for 2 minutes. Further, it was washed with running water for 1 minute.
Then, it is immersed in 2% NaOH aqueous solution, the resist film is peeled off, washed with running water for 2 minutes, dried at 120 ° C. for 60 minutes to produce MSL (2), and a transmission loss measurement sample (10) is obtained. It was.

  MSL (2) having different line lengths was produced in the same manner as described above except that a mask having a single-end microstrip line (MSL) [line length (L) 3 cm, line width (W) 100 μm] was used, A sample for transmission loss measurement (10) was obtained.

  For the porous substrate 1 obtained in Comparative Example 2, a mask having [line length (L) 5 cm, line width (W) 66 m] and [line length (L) 3 cm, line width (W) 66 μm] was used. In the same manner, two transmission loss measurement MSLs 2 having different line lengths were obtained.

  The sample 10 for measuring transmission loss based on the porous substrate of Example 1 and Comparative Example 2 is subjected to TDR evaluation using “Digital Sampling Oscilloscope DSA8200 made by Tektronix,“ TDR Module 80E04 ”made by Tektronix, and the characteristic impedance is 50. It was confirmed that it was within ± 0.5Ω.

  For evaluation of transmission loss, the probe tip was connected to the MSL terminal portion by “Probe ACP40-GSG125” manufactured by Cascade Microtech Co., Ltd. on a substrate via a 50Ω coaxial cable to “Vector Network Analyzer 8722D” manufactured by Agilent Technologies. As transmission loss, S parameters (S21) of MSL having different line lengths were measured. In order to calculate the loss amount (dB / cm) of the transmission line at 10 GHz and 40 GHz, the influence on the transmission loss of the terminal portion of the MSL is removed (measured value of the line length 5 cm−measured value of the line length 3 cm), and the rest The amount of loss per unit length (dB / cm) was calculated from the value of.

  For comparison, the same evaluation was performed for LCP (liquid crystal polymer) and PI (polyimide) used as conventional copper-clad laminates. The MSL line width (W) was adjusted to 65 μm for the LCP copper clad laminate and 60 μm for the polyimide copper clad laminate so that the characteristic impedance was 50 ± 0.5Ω by TDR measurement.

  The results are shown in Table 1.

  The MSL produced using the porous substrate of Example 1 was transmitted as the line width was widened by reducing the dielectric constant and the conductor loss was reduced compared to the MSL produced using the porous substrate of Comparative Example 2. It can be seen that the loss is improved. In addition, it can be seen that the transmission loss is equal to or smaller than that of the LCP used for the high-frequency substrate, and excellent transmission characteristics are exhibited. According to the present invention, it is possible to provide a circuit board in which a transmission loss is reduced by reducing a conductor loss by improving a line width by reducing a relative dielectric constant and reducing a dielectric loss.

1 Porous substrate 2 Single-ended microstrip line (MSL)
3 Through hole 10 Transmission loss measurement sample

Claims (9)

A porous resin molded article having bubbles having an average cell diameter of 5 μm or less, a porosity of 40% or more, and a relative dielectric constant at a frequency of 1 GHz of 2.00 or less. The porous resin molded article according to claim 1, comprising a resin selected from a thermosetting resin, an engineering plastic, and a super engineering plastic. The porous resin molded article according to claim 1 or 2, comprising a polyimide resin or a polyetherimide resin. The porous substrate which provided the metal foil in the at least one surface of the porous resin molding of any one of Claims 1-3. A method for producing a porous resin molded body according to any one of claims 1 to 3,
A step of applying a resin composition containing a resin component and a phase separation agent that phase-separates with a cured product of the resin component on a substrate and curing it to produce a resin sheet having a microphase separation structure, a phase from the resin sheet The manufacturing method of a porous resin molding including the process of removing a separating agent and producing a porous body. 6. The porous resin molding according to claim 5, comprising a step of using polyamic acid as a resin component and converting the polyamic acid to polyimide after removing the phase separating agent from the resin sheet to make it porous. Body manufacturing method. The method for producing a porous resin molded article according to claim 5 or 6, wherein a metal foil is used as a substrate to which the resin composition is applied. The method for producing a porous resin molding according to any one of claims 5 to 7, wherein the phase separation agent is removed by solvent extraction. The method for producing a porous resin molded article according to claim 8, wherein the solvent is one kind selected from liquefied carbon dioxide, subcritical carbon dioxide, or supercritical carbon dioxide.

Images