JP2003201363A - Porous polyimide film, its wiring board, its manufacturing method and its use - Google Patents

Abstract

(57) Abstract: An object of the present invention is to provide a porous polyimide film having a small dielectric constant and a small dielectric loss tangent, a wiring board thereof, a method of manufacturing the same, and various uses using the same. The present invention has a porous layer and skin layers formed on both sides of the porous layer and denser than the porous layer, and the porous layer has a length of at least 10 μm or more. Having a hole, a dielectric constant of 2.0 or less, a porous polyimide film characterized by a dielectric loss tangent of 0.003 or less, a wiring board using the same, a method of manufacturing the same, and an electronic component using the same, a mobile phone, and the like. It is in a high-frequency transceiver.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel porous polyimide film, a wiring board for the same, a method for manufacturing the same, an electronic component using the same, a mobile phone, and a high-frequency transceiver.

[0002]

2. Description of the Related Art In recent years, frequencies used in electronics and communication equipment have shifted to the GHz band.
In such a high frequency band, the transmission loss becomes large, so
The material used for the substrate material is required to have a low dielectric constant and a low dielectric loss tangent. As a low dielectric material for high frequency circuit boards,
Polytetrafluoroethylene, polyethylene and the like are used, but the coefficient of thermal expansion does not match that of copper used for wiring, and there is a problem such as cutting of wiring.

The dielectric properties of a material such as polyimide whose thermal expansion coefficient closely matches that of the wiring material are determined by the molecular structure of the material, and thus have a value unique to each material and there is a limit to control. Therefore, many porous materials have been reported in which air having a low dielectric constant of 1 is included in the material to make it porous and the dielectric properties of the material are controlled. Porous materials are classified by their structure. For example, there are a sponge structure in which small pores are uniformly dispersed, and a void structure in which the space surrounded by the upper and lower film layers and the internal structure is a pore. As a sponge structure,
Japanese Patent Laid-Open No. 2000-154273 discloses a nanopore using a supercritical carbon dioxide gas with a sponge structure having a pore size of nanosize.
It has been reported that a low dielectric property is obtained by using a porous material having a high surface area of 400 μm2 / g or more.

Further, as a porous polyimide material, Japanese Unexamined Patent Publication No.
293834, JP 2001-151929, JP 2001-2249
Many are known, such as JP-A-34-34, JP-A-2001-294704 and the like.

[0005]

There are some drawbacks to the above technique. When it is made porous and the porous layer has continuous pores, the etching solution penetrates into the porous layer when etching and creating wiring, and the wiring is also etched from the film side, making it difficult to form wiring Becomes

It is an object of the present invention to provide a porous polyimide film having a low dielectric constant and a low dielectric loss tangent, a wiring board for the same, a method for producing the same, and various applications using the same.

[0007]

The present invention has been found to be achieved by making the pore diameter and the shape of the pores of the porous material to be a specific shape and size.

The present invention has a porous layer and skin layers formed on both sides of the porous layer and denser than the porous layer, and most of the porous layer has pores having a length of 10 μm or more. And has a dielectric constant of 2.0 or less and a dielectric loss tangent of 0.003 or less.

The present invention also has a porous layer and skin layers formed on both sides of the porous layer and denser than the porous layer.
Most of the porous layer has rod-shaped pores, and the pores are inclined with respect to the thickness direction, or the porous layer has elliptical pores and diameters with respect to the thickness direction. The porous polyimide film is characterized in that it has large pores, or that the skin layer has pores in one side and the other side has a denser layer than one layer.

Further, according to the present invention, a film of a polyamic acid solution is formed on a conductor foil, which is then immersed in a coagulating solution together with the conductor foil to coagulate the polyamic acid solution, followed by drying and then heat treatment. Imidization treatment by, or to form a film of a polyamic acid solution having an aromatic diamine and an aromatic tetracarboxylic acid dianhydride on a copper foil, then immersed in water together with the copper foil to the polyamic acid The method for producing a porous polyimide wiring substrate is characterized in that the solution is solidified, dried, and then imidized by heat treatment.

In the porous polyimide film of the present invention, sponge-like structures are bonded to the upper and lower skin layers, and the skin layer has holes of 0.01 to 0.5 μm so that the inner pores and the outer pores are connected to each other. In addition, the space surrounded by the skin layer and the sponge-like structure has an elliptical shape, a finger void type, an ink bottle type, or a shape in which these are mixed, and the long axis of the hole has a large diameter of 10 μm or more. And its dielectric properties are
It is preferable that the dielectric constant is 2.0 or less and the dielectric loss tangent is 0.003 or less.

In the porous polyimide wiring board of the present invention, the porous layer is laminated on the copper foil, and a dense layer may be formed between the copper foil and the porous layer. Further, the porous layer has a structure in which upper and lower skin layers are bonded to a sponge-like structure, and the skin layer has pores of 0.01 to 0.5 μm, and a porous polyimide in which internal pores are connected to the outside. It is a wiring board. Furthermore, the space surrounded by the dense layer and the sponge-like structure has an elliptical shape, a finger void type, an ink bottle type, or a mixed shape thereof, and the long axis of the pores has a large pore diameter of 10 μm or more. Polyimide wiring board. Regarding the dielectric characteristics of the wiring board of the present invention, the dielectric constant is 2.0 or less and the dielectric loss tangent is 0.003 or less. Moreover, when a transmission line such as a coplanar line or a microstrip line is formed, the transmission loss at 10 GHz is 12 dB / m or less.

The present invention applies the porous polyimide wiring substrate to various electronic components, antenna plates for mobile phones, and antenna plates for millimeter-wave radar.

In the porous polyimide of the present invention, the polyimide is synthesized from an aromatic diamine and an aromatic tetracarboxylic dianhydride via a polyamic acid and imidized. There are numerous combinations of aromatic diamines and aromatic tetracarboxylic dianhydrides used. Although not particularly limited, PPD (paraphenylenediamine) and DDE (4,4-diaminodiphenyl ether) or a mixture thereof for the aromatic diamine, and sBPDA (3,3'-4) for the aromatic tetracarboxylic dianhydride. 4,4'-biphenyltetracarboxylic acid anhydride) is preferred. The mixing ratio of these is preferably such that the aromatic diamine and the aromatic tetracarboxylic dianhydride are equimolar, and the molar ratio of PPD and DDE is in the range of 70/30 to 100/0. With such a composition, a low thermal expansion polyimide can be obtained, a thermal expansion coefficient of which is the same as that of Cu which is a wiring material, and a reliable circuit board can be obtained.

The solvent is not particularly limited as long as it can dissolve the aromatic diamine and the aromatic tetracarboxylic dianhydride, and examples thereof include aromatic hydrocarbons such as toluene and xylene, and N-methylpyrrolidone. The organic solvent of.

The porous layer can be formed by various film forming methods such as a wet coagulation method, a dry coagulation method and a stretching method. The wet coagulation method is preferable because an open cell porous film can be obtained. In the wet coagulation method, generally, a film-forming stock solution (dope) is prepared by dissolving a resin, an additive, etc. in a solvent, which is applied (cast) to a substrate and immersed in a coagulating solution to replace the solvent. As a result, the resin is coagulated (gelled), and then the coagulation liquid or the like is dried and removed to obtain a porous layer.

At this time, the polymer solution was applied onto the copper foil,
It is also possible to directly form a non-porous film layer or porous layer on the copper foil.

The dope of the polymer solution in the wet coagulation method is preferably applied in the temperature range of -20 to 40 ° C. The coagulating liquid is not limited as long as it does not dissolve the resin used and is compatible with the above-mentioned solvent, but water, methanol, ethanol, alcohols such as isopropyl alcohol, and mixed liquids thereof are used. ,
Water is particularly preferably used. The temperature of the coagulating liquid during immersion is not particularly limited, but is preferably 0 to 50 ° C.

The polymer concentration of the film-forming stock solution is from 5% by weight to 2
The range of 5% by weight is preferable, and in particular, in order to obtain a porous molded body having more excellent strength, it is 7% by weight or more, and in order to obtain a porous molded body having a high porosity, 20% by weight is preferable. The following is more preferable. This is because if the concentration is too high, the viscosity becomes too high and handling becomes difficult, and if the concentration is too low, the porous film cannot be formed.

Inorganic substances such as lithium nitrate and organic substances such as polyvinylpyrrolidone can be added to control the shape and size of the pores. The concentration of the additive is preferably 1 wt% to 10 wt% in the solution.
When lithium nitrate is added, the substitution speed of the solvent and the coagulating liquid is high, and a finger void structure (a structure having finger-like voids) can be formed in the sponge structure. By adding an additive such as polyvinylpyrrolidone that slows the coagulation speed, a porous layer having a sponge structure uniformly spread can be obtained.

The dope is applied to a certain thickness and immersed in a coagulating liquid such as water to coagulate, or left to stand in a steam atmosphere to coagulate and then immersed in water to be dissolved. It becomes a porous layer. After forming the porous layer, the porous layer is taken out from the coagulating liquid and then dried. The drying temperature is not particularly limited, but is 200 ° C.
The following drying is desirable.

The formed porous layer and film layer are finally heat-treated at 200 to 500 ° C. to heat-ring-close the precursor (polyamic acid) to form a polyimide.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION (Example 1) In a glove box capable of nitrogen flow, aromatic diamines PPD and DDE mixed at a molar ratio of 85:15 were added to N-methylpyrrolidone and stirred at room temperature. . Next, 1 mol of sBPDA, which is an acid anhydride, was added to 1 mol of aromatic diamine, and the mixture was stirred for 1 hour in a nitrogen flow to obtain a 10 wt% polyamic acid solution. The obtained polyamic acid solution was applied to a copper foil 1 having a thickness of 18 μm,
It was immersed in a coagulation tank containing water and brought into contact with water to cause gelation (coagulation). This was taken out, sufficiently dried at 120 ° C., further treated at 400 ° C. for 30 minutes and imidized to form a porous polyimide film 2 on the copper foil 1, and a porous polyimide film 3 with a copper foil was prepared. FIG. 1 is a cross-sectional view of a porous laminated plate 3 with a copper foil obtained in this example.

After the polyamic acid solution is applied to the copper foil 1 in this embodiment, the coagulation by immersing it in the coagulation tank is performed by continuously feeding the copper foil 1 by a plurality of rotating rolls. You can

Example 2 Using the polyamic acid solution prepared in Example 1, the polyamic acid solution was added to a copper foil 1 having a thickness of 18 μm.
Was applied to, and immersed in water to bring into contact with water to cause gelation. At this time, the water temperature in the coagulation tank was set higher than in Example 1. The obtained gel was processed in the same manner as in Example 1 to prepare a porous laminate 3 with a copper foil. The structure of the porous laminate is shown in FIG.
Is the same as.

(Example 3) KJOlioier, J. Polymer Sci., A-1,3,137 in a glove box capable of nitrogen flow.
3 (1965), PPD and DDE in a molar ratio of 8
The mixture was added in an amount of 5:15, and then sBPDA, which is an acid anhydride, was added to the aromatic diamine in an amount of 1 mol, and the mixture was stirred in a nitrogen flow for about 1 hour to obtain a 10 wt% polyamic acid solution. This was applied to a copper foil 1 having a thickness of 18 μm to form a film layer 4 (not imidized at this stage). Then, by the same operation as in Example 1, a porous polyimide film 2 is obtained on the film layer 4 (heat treatment is performed when forming the porous layer,
Both the film layer and the porous layer are imidized. ), And a copper foil-attached film layer-laminated porous laminate 5 in which a porous layer and a film layer were laminated. FIG. 2 is a cross-sectional view of the film layer-laminated porous laminate 5 with a copper foil obtained in this example.

Example 4 KJOlioier, J. Polymer Sci., A-1,3,137 in a glove box capable of nitrogen flow.
3 (1965), PPD and DDE in a molar ratio of 8
The mixture was added in an amount of 5:15, and then sBPDA, which is an acid anhydride, was added to the aromatic diamine in an amount of 1 mol, and the mixture was stirred in a nitrogen flow for about 1 hour to obtain a 10 wt% polyamic acid solution. This was applied to a copper foil 1 having a thickness of 18 μm to form a film layer 4 (not imidized at this stage). Then, by the same operation as in Example 2, a porous polyimide film 2 was obtained on the film layer 4 (heat treatment was performed when forming the porous layer,
Both the film layer and the porous layer are imidized. ), A copper foil-attached film layer-laminated porous polyimide film 5 in which a porous layer and a film layer were laminated. The structure of the film layer laminated porous polyimide film with copper foil is shown in FIG.
Is the same as.

(Example 5) The porous polyimide film of the present invention prepared in Examples 1 to 4 was etched out of a copper foil using an FeCl ₃ / HCl etching solution (manufactured by Wako Pure Chemical Industries, Ltd.) to form a porous film. It was created.

The structures of the surface and cross section of Examples 1 to 4 and Comparative Example 1 were observed by SEM. FIG. 3 is a cross-sectional photograph (a) of the film prepared in Example 1 and its surface (b), and FIG.
3A shows a cross-sectional photograph (a) of the film prepared in Example 2 and its surface (b). In FIG. 3, the finger void holes 8 of rod-like holes are formed to be inclined with respect to the thickness direction, and the skin layer 6 is denser on the copper foil side (below the paper surface) than on the surface side (above the paper surface). On the front side, surface hole 11 has a diameter of about
It has pores of 1 μm or less. The finger void holes 8 are inclined on the copper foil side with respect to the thickness direction more than on the copper foil side, and have a large diameter on the copper foil side. The surface is uneven and has a wavy pattern. The hole of FIG. 4 has a mixed type of an ink bottle hole 9 and an elliptical hole 10, and the diameter of the ink bottle hole 9 is larger on the copper foil side (below the paper surface) than on the surface side (above the paper surface).
Further, the surface side has a surface hole 11 having a diameter of about 1 μm or less.
In any of the shapes, there is a large hole having a major axis a of 10 μm or more, and the upper and lower skin layers 6 and a sponge-like structure 7 composed of continuous holes having a diameter of 0.01 to 0.5 μm.

The above-mentioned finger void type cross section has a finger-like shape, and the major axis a may be straight, curved or bent. The cross section of the ink bottle type is such that the entrance has a small hole diameter and the inside has a large hole diameter with respect to the direction perpendicular to the major axis a.

The surface, that is, the skin layer, has a surface void 11 of 0.01 to 0.5 μm in both the finger void type and the ink bottle type. The surface holes are continuous with large holes (ink bottle holes 9, finger void holes 8, elliptical holes 10) inside.

The films of Examples 3 and 4 are obtained by laminating a dense layer on the films of Examples 1 and 2, respectively.
The porous structure was the same as in Examples 1 and 2.

Next, various physical properties of Examples 1 to 4 were evaluated. In addition, the physical property evaluation method was performed as follows. [Porosity]; non-porous sample (NP) and porous body (p)
From the area S (cm ² ) on one side, the thickness d (cm) and the weight m (g), and the specific gravity D (g / cm ³ ) of the forming material thereof, the following formula can be used. Total porosity (%) = [1- (Dp / DNP)] * 100 = {1- [mp / (Sp * dp)] / [mNP / (SNP * dNP)]) x 100 [pore diameter]; It was measured from a scanning electron micrograph of a cross section of the body. [Thickness]: Measured with a caliper having an accuracy of 5/100 mm. [Dielectric property]: A network analyzer manufactured by Agilent Technologies was connected to a resonator manufactured by Kanto Electronics Co., Ltd., and the dielectric constant and the dielectric property at 10 GHz were measured.

Table 1 shows the evaluation results of various physical properties. The dielectric constant of each of the samples of Examples 1 to 4 is
A film having a low dielectric constant of less than 2 and a dielectric loss tangent of 0.003 or less could be obtained.

[0035]

[Table 1]

(Embodiment 6) FIG. 5 is a process diagram of forming wiring by etching the copper foil by photolithography using the copper foil-clad laminates prepared in Examples 3 and 4. Porous polyimide film 2, film layer 4,
On the copper foil surface of the wiring board using the porous polyimide film made of copper foil 1, the film resist (HR-130) manufactured by Tokyo Ohka Kogyo Co., Ltd. is laminated at 100 ° C. and 3 kg / cm _{2 as} in Step 1, A resist film 12 was laminated on the foil 1. Then, attach a mask with wiring drawn at 40 μm lines / spaces, expose with a super-high pressure mercury lamp at 30 mJ / cm ₂ , and apply 0.5% Na ₂ CO ₃
It was developed by spraying with an aqueous solution, and as in step 2, the resist film 12 was processed on the copper foil 8 to form a mask.

Next, using a spray on the mask surface, the FeCl ₃ / HCl etching liquid manufactured by Wako Pure Chemical Industries, Ltd. is wiped, and step 3
The copper foil was etched as shown in FIG. After the etching, the wiring board was washed with running water for 1 minute, immersed in diluted HCl for 2 minutes, and further washed with running water for 1 minute. Then, the resist film was peeled off by immersing in a 2% NaOH aqueous solution. After removing the resist, it was washed with running water for 2 minutes and dried at 120 ° C. for 60 minutes to obtain a circuit board 15 in which copper wirings 13 and spaces 14 were formed on the film layer 4 as in step 4.

Since the circuit board thus prepared uses the porous polyimide film of the present invention, a circuit board having a large propagation speed, an improved information processing speed, a low loss and a small power consumption is obtained. be able to.

(Embodiment 7) In order to evaluate the transmission characteristics of the wiring board, the wiring board prepared in Example 2 was etched with a copper foil by photolithography according to the process of Example 5 to form a coplanar and a microstrip line. Created. The transmission characteristic was evaluated by measuring the transmission loss at 10 GHz by using the cutback method.

(Embodiment 8) In order to evaluate the transmission characteristics of a wiring board, a coplanar and a microstrip line are formed in the same manner as in Embodiment 6 using the wiring board prepared in Embodiment 4, and a cutback method is used. Transmission loss at 10 GHz was measured.

(Comparative Example 1) In order to evaluate the transmission characteristics of the wiring board, a sample was prepared by pasting a film resist on the skin layer surface of the wiring board prepared in Example 2 on the side opposite to the copper foil. Unlike in Example 6, this is a sample simulating a film in which the holes present in the skin layer on the surface are eliminated.
The film resist attached to the skin layer surface is the final step.
It was peeled off by immersion in a NaOH aqueous solution. Otherwise, the copper foil was etched by photolithography according to the process of Example 5 to form a coplanar and a microstrip line. The transmission characteristics were evaluated by using the cutback method as in Example 6 and measuring the transmission loss at 10 GHz.

(Comparative Example 2) In order to evaluate the transmission characteristics of the wiring board, the wiring board prepared in Example 4 was used to close the holes in the surface skin layer on the side opposite to the copper foil in the same manner as in Comparative Example 2. In this state, coplanar and microstrip lines were formed, and the transmission loss at 10 GHz was measured using the cutback method.

Table 2 shows the results of evaluating the transmission characteristics of Examples 6 and 7 and Comparative Examples 1 and 2. In Examples 6 and 7, the transmission loss was smaller than that of Comparative Examples 1 and 2 in which a film resist was attached to the skin layer surface to close the holes on the surface. Since the surface of the skin layer has a hole continuous with the inner hole, the etching solution can be prevented from remaining.

When the porous layer has continuous pores, the etching solution permeates into the porous layer when the wiring is formed by etching, and the etching solution tends to remain in the pores, which requires sufficient cleaning. The porous polyimide of the present invention has a skin layer which is a surface layer and a void structure formed of an internal sponge-like structure. The skin layer has a hole of 0.01 to 0.5 μm, and the presence of this hole facilitates the discharge of the etching solution that has penetrated into the skin layer, which facilitates cleaning. Also, a small value of transmission loss of 12 dB / μm or less can be obtained, and a substrate having a transmission line with high-speed information processing and low power consumption can be obtained.

[0045]

[Table 2]

(Embodiment 9) In this embodiment, Embodiments 1 and 2 are used.
2 shows an example in which the porous polyimide wiring board having a low dielectric property produced by the method is applied to a built-in antenna for a mobile communication device. A porous polyimide wiring board having a low dielectric property can reduce transmission loss in a circuit using high frequency, and can be applied to an antenna board of a mobile communication device to reduce power consumption.

FIG. 6 is a side view of the essential part showing the built-in antenna structure of the mobile phone according to the embodiment of the present invention. A mobile phone (portable communication device) includes a receiver, a liquid crystal display, various function keys, numeric keys, a transmitter, an extendable rod antenna for transmission, and the like in a main body case. Although not shown, a well-known control circuit board,
A battery, an interface board, a receiving circuit board, a transmitting circuit board, an RF circuit board, and the like are housed, and the RF circuit board is housed in the RF pack casing.

The RF pack casing 16 is constructed by joining plate members made of a conductive material such as an iron plate into a rectangular parallelepiped shape. Although not shown, the RF pack casing 16 has a plated power feeding portion, and the power feeding portion is connected to the control circuit board described above by a coaxial cable or the like.

The antenna plate 17 comprises a porous polyimide film 18 and an antenna pattern 19, and is an RF package casing.
It is attached to 16 using epoxy resin. The antenna plate 17 has a coaxial cable connected to the power feeding unit 20 by thermocompression bonding or the like, and secures a capacitance between itself and the surface of the RF pack casing 16 to form a built-in antenna for reception. The coaxial cable is connected to the control circuit board to connect the antenna plate 17 to the control circuit board.

In this embodiment, the RF pack casing 16 and the antenna plate 17 constitute a built-in antenna for reception, and this built-in antenna for reception is a porous body having a low dielectric property as shown in FIG. Since high quality polyimide is used as the dielectric layer, an antenna plate with low loss can be produced. The antenna plate prepared in this manner can obtain an antenna plate having a large propagation speed, a high information processing speed, and a low loss and a small power consumption by using the above-described porous polyimide film of the present invention. it can.

(Embodiment 10) This embodiment is an example of a high frequency transmitter / receiver in which the porous polyimide wiring board having low dielectric properties similarly prepared in Embodiments 1 and 2 is applied to an antenna of an in-vehicle radar for an automobile or the like. Is shown. It is important to reduce transmission loss in a circuit using high frequencies, especially millimeter waves, in a porous polyimide wiring board with low dielectric properties, and by applying it to an antenna plate of a vehicle-mounted radar, low power consumption and high reliability can be achieved. It will be possible.

FIG. 7 is a sectional view of the high frequency transmitting / receiving apparatus of this embodiment. Antenna substrate 22 made of porous polyimide that forms an antenna on the upper surface of metallic base plate 21.
A semiconductor substrate (MMIC) 24 and a circuit board 23 made of a dielectric material that constitutes a transmission / reception circuit are bonded to the lower surface. Circuit board 23
Circuit pattern conductor 30 and antenna board 22 provided on the surface of
An antenna pattern conductor 27 provided on the surface of is connected by a central conductor 26 of the coaxial line. Since the MMIC is not packaged, the transceiver circuit is hermetically sealed by the transceiver circuit cover 25 made of metal. External terminals 32 for power supply and IF signals are provided in a part of the transmission / reception circuit cover 25, and these are electrically insulated from the conductor plate (base plate) and the cover by insulators 28 and 29, respectively. The external terminal 32, the transmission / reception circuit, the circuit pattern conductor, and the semiconductor chip are connected by a bonding wire wire 31. The semiconductor chip 24 may have a so-called flip-chip mounted structure that is directly connected to the circuit board 23. Further, the base plate 21 and the transmission / reception circuit cover 25 may be formed of non-metal such as plastic and the surfaces thereof may be covered by metal plating, vapor deposition or the like.

FIG. 8 is a view of the high-frequency transmitting / receiving apparatus as viewed from the back side. The dotted line shows the antenna substrate 22 adhered to the surface. In this embodiment, since the antenna substrate of this high-frequency transmitting / receiving device uses porous polyimide having low dielectric properties and high reliability as shown in FIG. 6 as the dielectric layer, the propagation speed is large. A millimeter-wave antenna plate with improved processing speed, low loss, and low power consumption can be produced.

[0054]

According to the present invention, it is possible to provide a porous polyimide film having high porosity and high strength, a wiring board for the same, an electronic component using the same, a mobile phone, and a high-frequency transceiver. In particular, the substrate can be used as a high-frequency circuit substrate for printed wiring boards for electronic devices, satellite communications, mobile radio and millimeter wave radar.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a porous polyimide film of the present invention.

FIG. 2 is a sectional view of a porous polyimide film having a film layer of the present invention.

FIG. 3 is a cross-sectional photograph of a finger-type void-containing porous polyimide film of the present invention.

FIG. 4 is a cross-sectional photograph of a porous polyimide film having an ink bottle type void of the present invention.

FIG. 5 is a cross-sectional view showing a manufacturing process of the porous polyimide wiring board of the present invention.

FIG. 6 is a side view of a mobile phone having a built-in antenna using the porous polyimide film of the present invention.

FIG. 7 is a cross-sectional view of a high frequency transmitter / receiver having an antenna plate using the porous polyimide film of the present invention.

8 is a top view of the back surface of the high frequency transmitting / receiving device of FIG. 7. FIG.

[Explanation of symbols]

1 ... Copper foil, 2 ... Porous polyimide film, 3 ... Copper foil-attached porous laminate, 4 ... Film layer, 5 ... Copper foil-attached film layer laminated porous laminate, 6 ... Skin layer, 7 ... Sponge-like Structure, 8 ... Finger void hole, 9 ... Ink bottle hole, 10 ...
Elliptical hole, 11 ... Surface hole, 12 ... Resist film, 13 ... Copper wiring, 14 ... Space, 15 ... Circuit board, 16 ... RF pack casing, 17 ... Antenna plate, 18 ... Porous polyimide film, 19 ... Antenna pattern , 20 ... Feed unit, 21 ... Base plate, 22 ... Antenna board, 23 ... Circuit board, 24 ... Semiconductor chip (MMIC), 25 ... Transceiver cover, 26 ... Center conductor, 27 ... Antenna pattern conductor, 28, 29 ... Insulation Things, 30 ...
Circuit pattern conductor, 31 ... Bonding wire Wire, 32 ...
External terminal for IF signal.

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) H05K 1/03 630 H05K 1/03 670A 670 3/00 R 3/00 C08L 79:08 // C08L 79:08 H01L 23 / 14 R (72) Shinji Yamada, Inventor Shinji Yamachome 1-1-1, Omika-cho, Hitachi City, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Toshiyuki Kawashima 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Electric Works Co., Ltd. (72) Inventor Shinji Tahara 1-2-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Electric Works Co., Ltd. (72) Kenichi Ikeda 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Shares In-house F-term (reference) 4F074 AA74 CB37 CB43 CB45 DA03 DA13 DA47 4F100 AB01B AB10 AB33B AK49A BA42A DJ00A EH462 GB43 JG01B JG05A YY00A

Claims (14)

[Claims] 1. A porous layer and a skin layer which is formed on both sides of the porous layer and is denser than the porous layer. Most of the porous layer has pores having a length of 10 μm or more. The dielectric constant
A porous polyimide film having a dielectric loss tangent of 2.0 or less and 0.003 or less. 2. A porous layer, and a skin layer formed on both sides of the porous layer and denser than the porous layer, the porous layer having mostly rod-shaped pores. A porous polyimide film characterized by being inclined with respect to the thickness direction. 3. A porous layer, and a skin layer formed on both sides of the porous layer and denser than the porous layer, wherein the porous layer has elliptical pores and a diameter in the thickness direction. A porous polyimide film having large pores. 4. A porous layer and a skin layer formed on both sides of the porous layer and denser than the porous layer, one of the skin layers having pores, and the other of the skin layers having the pores. A porous polyimide film having a dense layer. 5. A porous polyimide film according to any one of claims 1 to 4, which has a structure in which a hole of 0.01 to 0.5 μm is present at a portion in contact with one of the skin layers and is connected to the outside. 6. The porous polyimide film according to claim 1, wherein the holes have an elliptical shape, a finger void type, an ink bottle type, or a shape in which these are mixed. 7. A porous polyimide wiring board having a resin layer on a conductor foil, wherein the resin layer comprises the porous polyimide film according to any one of claims 1 to 7. substrate. 8. A porous polyimide substrate according to claim 1, which has a transmission line made of a resin film on one surface thereof and has a transmission loss of 12 dB / m or less at 10 GHz. 9. A film of a polyamic acid solution is formed on a conductor foil, which is then immersed in a coagulating solution together with the conductor foil to coagulate the polyamic acid solution, which is then dried and then imidized by heat treatment. A method of manufacturing a substrate for porous polyimide wiring, comprising: 10. A film of a polyamic acid solution containing an aromatic diamine and an aromatic tetracarboxylic acid dianhydride is formed on a copper foil, and then immersed in water together with the copper foil to coagulate the polyamic acid solution. A method for manufacturing a substrate for porous polyimide wiring, which comprises: drying, and then imidizing treatment by heat treatment. 11. The method for manufacturing a porous polyimide film according to claim 9, wherein the conductor foil or the copper foil is removed by etching after the imidization treatment. 12. A porous polyimide wiring board according to claim 7 or 8, or a porous polyimide wiring board formed by the method for manufacturing a substrate for porous polyimide wiring according to claim 9 or 10. Characteristic electronic parts. 13. A conductor is formed on the porous polyimide wiring board according to claim 7 or 8, or the porous polyimide wiring board formed by the method for manufacturing a porous polyimide wiring board according to claim 9 or 10. A mobile phone having a fixed antenna plate. 14. A high frequency transmitting / receiving device having an antenna plate on one surface of a substrate and a circuit board having a semiconductor element on the other surface thereof, wherein the antenna plate is according to any one of claims 1 to 6. A high frequency transmitting / receiving device, wherein a conductor is formed on the surface of the porous polyimide film or on the surface of the porous polyimide film formed by the method for producing a porous polyimide film according to claim 10.