JP2002144476A - Polyimide film good in laser processability, substrate and processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide film excellent in laser processability excellent in a through-hole surface state and capable of forming a through-hole reduced in taper and almost vertical to the front and rear surfaces of the film by applying laser processing to the polyimide film of a flexible metal layer laminate, a substrate and a processing method. SOLUTION: A polyimide film excellent in laser processability comprises a highly heat-resistant aromatic polyimide, which contains a biphenyltetracarboxylic acid component as an aromatic tetracarboxylic acid component and has a glass transition temperature of 300 deg.C or higher, as a principal constituent material. A metal layer is laminated on at least the single surface of the polyimide film through a polyimide resin layer having a low glass transition temperature of 200-375 deg.C and having thermal contact bonding properties and/or flexibility to form a laminate and the polyimide film of the laminate is subjected to laser processing to form a through-hole almost vertical to the upper and rear surfaces of the film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyimide film, a substrate and a processing method having good laser processability, and more particularly to a polyimide film containing a high heat-resistant aromatic polyimide as a main component. Then, a polyimide film of a laminate in which a metal layer is laminated on at least one surface of the polyimide film via a polyimide resin layer having thermocompression bonding property and / or flexibility is used as a laser.
A polyimide film with good laser processability that can be processed to form a through hole (sul-hole) that is substantially perpendicular to the cross section of the film. The present invention relates to a substrate having a through-hole formed therein, a substrate formed by subjecting a laser-processed portion to desmear treatment and then metal plating the inner surface of the through-hole, and a method of forming a through-hole in a polyimide film.

According to the present invention, a through hole having a good surface condition can be formed in a polyimide film of a laminate. Further, according to the present invention, it is possible to obtain a substrate with good conductivity by plating the through holes with metal. In this specification, a substantially perpendicular through-hole means that the through-hole is perpendicular or substantially perpendicular to the front and back of the cross section of the film, and the diameter ratio of the front and back of the film is about 1: 1 to 1: 1.5. Say.

[0003]

2. Description of the Related Art Aromatic polyimide films are widely used for electronic devices such as cameras, personal computers, and liquid crystal displays. BACKGROUND ART When an aromatic polyimide film is used as a substrate material of a flexible printed circuit board (FPC), a punching process of a flexible substrate in which a copper foil is bonded using an adhesive such as an epoxy resin is conventionally employed. Then, a step of plating the through holes of the perforated substrate to electrically connect the front and back surfaces is adopted.

It has been pointed out that an aromatic polyimide film is excellent in heat resistance, mechanical strength, electrical properties and the like, but deteriorates the original properties of polyimide due to poor heat resistance and the like of an adhesive. To solve such a problem,
A flexible copper foil laminate of all-polyimide by a casting method in which a polyimide precursor solution is applied to a copper foil, dried, and imidized has been developed. For the polyimide formed by this casting method, a special polyimide that can be imidized at a relatively low temperature is used because heating in the presence of a copper foil is required.

On the other hand, as a method for boring a flexible substrate, a conventional punching process has a hole diameter of up to 500 μmφ, and it is impossible to perform fine processing of 300 μmφ or less. For this reason, attempts have been made to form a fine pattern by laser processing with a CO ₂ gas laser or the like.

[0006] However, the above-mentioned casting method is not effective.
When a fine pattern is formed by applying laser processing to a flexible copper foil laminate of polyimide, a crack is formed inside the cross section of the laser-processed through hole as shown in FIG. Occurs and desmearing causes further scouring. Further, when a metal layer-polyimide film laminate using an adhesive having low heat resistance such as epoxy resin is laser-processed, the through hole becomes a slivery shape having a large amount of taper, and a fine pattern is formed. It was impossible. For this reason, it has not been possible to obtain a flexible metal layer laminate in which laser processing can be performed to form a substantially vertical through hole on the front and back of the cross section of the film.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to process a polyimide film of a flexible metal layer laminate by laser processing so that the surface condition of the through hole is good. It is an object of the present invention to provide a polyimide film, a substrate, and a processing method which are small in size and can form a substantially vertical through hole and have good laser processability.

[0008]

That is, the present invention provides:
A polyimide film containing a high heat-resistant aromatic polyimide as a main constituent material containing a biphenyltetracarboxylic acid component as an aromatic tetracarboxylic acid component and having a glass transition temperature of 300 ° C. or higher or a glass transition temperature that cannot be measured, At least one surface of the polyimide film has a thermocompression bonding property and / or flexibility of a polyimide film having a low glass transition temperature polyimide resin layer having a glass transition temperature of 200 to 375 ° C and a low glass transition temperature having flexibility. Laser processing a laminated polyimide film in which a metal layer is laminated via a polyimide resin layer in which the glass transition temperature of the polyimide resin having a low glass transition temperature is equal to or lower than the glass transition temperature of the highly heat-resistant aromatic polyimide, Laser capable of forming substantially vertical through holes on the front and back of the cross section of the film
It relates to a polyimide film having good processability.

The present invention also relates to a substrate in which the above-mentioned polyimide film is laser-processed to form substantially vertical through holes on the front and back of the cross section of the film. In addition, the present invention
The present invention relates to a substrate obtained by subjecting the polyimide film to laser processing, subjecting the laser-processed portion of the obtained substrate to desmear treatment, and then plating the inner surface of the through hole with metal. Further, the present invention provides a method of forming a through hole in a polyimide film for laser processing the polyimide film.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be listed below. 1) The above-mentioned polyimide film having good laser processability, wherein the metal layer is an electrolytic copper foil, a rolled copper foil, an aluminum foil or a stainless steel foil. 2) The above-mentioned polyimide film having good laser processability, wherein the metal layer is a metal film formed by vapor deposition and / or plating.

3) A polyimide film having a low glass transition temperature having a thermocompression bonding property and / or flexibility having a glass transition temperature of 200 to 375 ° C. on at least one surface, preferably both surfaces, of a highly heat-resistant aromatic polyimide precursor layer. The polyimide film having good laser processability, which has a multilayer structure obtained by laminating and integrating a polyimide precursor layer preferably by a coextrusion-cast film forming method. 4) The polyimide film having good laser processability, wherein the polyimide film has a thickness ratio of the highly heat-resistant aromatic polyimide layer of 55 to 99.9%. 5) The above-mentioned laser, wherein the metal layer has a thickness of 1 to 12 μm.
A polyimide film with good workability.

6) A laminate is formed by bonding a metal foil and a thermocompression-bondable multilayer polyimide film in which a thermocompression-bondable polyimide layer is laminated and integrated on at least one surface of a highly heat-resistant aromatic polyimide layer by a continuous laminating apparatus. The above-mentioned polyimide film having good laser processability, which is obtained by laminating by thermocompression bonding. 7) The above-mentioned polyimide film having good laser processability, wherein the laminate is obtained by using a double belt press as a continuous laminating apparatus, applying thermocompression bonding under pressure, cooling, and laminating.

The polyimide film according to the present invention comprises:
It is a polyimide film containing a high heat-resistant aromatic polyimide containing a biphenyltetracarboxylic acid component as an aromatic tetracarboxylic acid component as a main component. This polyimide film has, for example, a heat-resistant and thermocompression-bonding property and / or flexibility on one or both sides of a high heat-resistant aromatic polyimide precursor solution dried film containing a biphenyltetracarboxylic acid component as an aromatic tetracarboxylic acid component. After laminating the polyimide precursor solution having, or more preferably, co-extrusion-cast film forming method, heat-bonding property and / or flexibility with heat resistance on one or both sides of a high heat-resistant aromatic polyimide precursor solution. After laminating a polyimide precursor solution having properties, it can be obtained by drying and imidizing to obtain a multilayer polyimide film.

The aromatic polyimide having high heat resistance is preferably composed of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (hereinafter sometimes abbreviated simply as s-BPDA) and para. -Phenylenediamine (hereinafter sometimes abbreviated simply as PPD) and optionally 4,4'-
It is produced from diaminodiphenyl ether (hereinafter sometimes abbreviated simply as DADE) and / or pyromellitic dianhydride (hereinafter sometimes simply abbreviated as PMDA). In this case, the PPD / DADE (molar ratio) is 100/0 to 10/90, especially 100/0 to 85/15.
It is preferable that Also, s-BPDA / PMDA
Is 100: 0 to 15/85, especially 100: 0 to 50/5
It is preferably 0. As long as the physical properties of the high heat-resistant aromatic polyimide are not impaired, other types of aromatic tetracarboxylic dianhydrides and aromatic diamines, for example, 4,
4′-diaminodiphenylmethane or the like may be used.

As the high heat-resistant polyimide, a single-layer polyimide film has a glass transition temperature of 30.
It is preferably at least 0 ° C, more preferably at a temperature of less than 350 ° C, and particularly preferably at a temperature below 350 ° C, and particularly has a coefficient of linear expansion (50 to 200 ° C) (MD, TD and their average) of 5x. 10 ^{-6 to} 25 × 10 ^-6 cm / cm /
C. is preferred. In the synthesis of this highly heat-resistant polyimide, if the ratio of each component is finally within the above range, random polymerization, block polymerization, blending or synthesis of two or more kinds of polyimide precursor solutions in advance and preparing each polyimide precursor This is achieved by any method in which the solution is mixed and the copolymer is obtained by recombination of the respective polyimide precursors.

In the present invention, it is necessary to use a heat-resistant resin layer having thermocompression bonding and / or flexibility. If the resin layer in contact with the metal layer is not heat-resistant, the processed hole in the laser becomes sliver-like with a large amount of taper, making it difficult to form a fine pattern, which is not preferable. As the resin layer having heat resistance and thermocompression bonding and / or flexibility in the present invention, any resin layer having both heat resistance after lamination and thermocompression bonding and / or flexibility may be used, and preferably 300 to 400. ° C
Thermocompression-bondable polyimide which can be thermocompression bonded at a temperature of about (or Tg: glass transition temperature is 200 to 375 ° C, particularly 200 to 300 ° C). In particular,
1,3-bis (4-aminophenoxybenzene) (hereinafter sometimes abbreviated as TPER) and 2,3
A thermocompression-bondable polyimide produced from 3 ′, 4′-biphenyltetracarboxylic dianhydride (hereinafter sometimes abbreviated as a-BPDA) is preferably used. Also,
As the thermocompression bonding polyimide, 1,3-bis (4
-Aminophenoxy) -2,2-dimethylpropane (D
ANPG) and 4,4'-oxydiphthalic dianhydride (O
DPA).

Alternatively, a thermocompression-bondable polyimide produced from 4,4'-oxydiphthalic dianhydride (ODPA) and pyromellitic dianhydride and 1,3-bis (4-aminophenoxybenzene) may be used. . further,
1,3-bis (3-aminophenoxy) benzene and 3,
3 ', 4,4'-benzophenonetetracarboxylic dianhydride or from 3,3'-diaminobenzophenone and 1,3-bis (3-aminophenoxy) benzene and 3,3', 4,4'- Thermocompression-bondable polyimide produced from benzophenonetetracarboxylic dianhydride.

Further, as the resin having the above heat resistance and thermocompression bonding property and / or flexibility, 3,3 ′, 4,4
4'-biphenyltetracarboxylic dianhydride and 4,4 '
Flexible (and thus high elongation) polyimides made from diaminodiphenyl ether. In particular, as a resin having heat resistance and thermocompression bonding property and / or flexibility, a polyimide containing a biphenyltetracarboxylic acid component as an essential component, like the highly heat-resistant polyimide, is preferable.

A polyimide precursor solution having heat resistance and thermocompression bonding property and / or flexibility is applied to one or both sides of the above-mentioned solution-dried film of the aromatic polyimide precursor having high heat resistance and laminated. Later, or by a co-extrusion-cast film forming method, a polyimide precursor solution having thermocompression bonding and / or flexibility as well as heat resistance was laminated on one or both sides of a highly heat-resistant aromatic polyimide precursor solution. Thereafter, the multilayer polyimide film obtained by drying and imidization is preferably subjected to a surface treatment such as a plasma discharge treatment, and then a metal layer is directly formed to obtain a laminate.

Other tetracarboxylic dianhydrides, for example, 3,3 ', 4, as long as the physical properties of the polyimide having heat resistance and thermocompression bonding property and / or flexibility are not impaired.
4'-biphenyltetracarboxylic dianhydride, 2,2-
It may be replaced by bis (3,4-dicarboxyphenyl) propane dianhydride or the like. Further, other diamines such as 4,4′-diaminobenzophenone, 4,4′-diaminodiphenylmethane, and the like, as long as the physical properties are not impaired.
2,2-bis (4-aminophenyl) propane, 1,4
-Bis (4-aminophenoxy) benzene, 4,4'-
Bis (4-aminophenyl) diphenyl ether, 4,
4'-bis (4-aminophenyl) diphenylmethane,
A plurality of compounds such as 4,4'-bis (4-aminophenoxy) diphenyl ether, 4,4'-bis (4-aminophenoxy) diphenylmethane, and 2,2-bis [4- (aminophenoxy) phenyl] propane; It may be replaced by a flexible aromatic diamine having a benzene ring. To block the amine end of the polyimide, dicarboxylic acids, for example, phthalic acid and its substitution, hexahydrophthalic acid and its substitution, succinic acid and its substitution and derivatives thereof, especially phthalic acid May be used.

The polyimide having the above-mentioned heat resistance and thermocompression bonding property and / or flexibility can be prepared by mixing the above-mentioned components and, if necessary, other tetracarboxylic dianhydrides and other diamines in an organic solvent for about 100%. ℃ or less, especially 20
The solution is reacted at a temperature of ６０60 ° C. to form a polyamic acid solution, and this polyamic acid solution can be used as a dope solution. And, in the above-mentioned organic solvent, the total number of moles of the acid (as the total mole of tetracarboxylic dianhydride and dicarboxylic acid)
Is preferably 0.92 to 1.1, especially 0.98 to 1.
1, especially 0.99 to 1.1, and the amount of dicarboxylic acid used is preferably 0.00 to 0.1, particularly 0.02 to 0.1, as a ratio to the molar amount of tetracarboxylic dianhydride. A ratio such as 0.06 is preferred.

In order to limit the gelling of the polyimide precursor, a phosphorus-based stabilizer such as triphenyl phosphite,
Triphenyl phosphate or the like can be added in the range of 0.01 to 1% based on the solid content (polymer) concentration at the time of polyamic acid polymerization. Further, for the purpose of accelerating imidization,
A basic organic compound-based catalyst can be added to the solution. For example, imidazole, 2-imidazole, 1,2
-Dimethylimidazole, 2-phenylimidazole, etc., in an amount of 0.01 to 20 with respect to the polyamic acid (solid content).
%, In particular from 0.5 to 10% by weight. Since these form a polyimide film at a relatively low temperature, they are used to avoid insufficient imidization. For the purpose of stabilizing the adhesive strength, an organic aluminum compound, an inorganic aluminum compound or an organic tin compound may be added to the aromatic polyimide raw material dope. For example, aluminum hydroxide, aluminum triacetylacetonate, or the like is 1 ppm or more as aluminum or tin metal with respect to polyamic acid (solid content),
Particularly, it can be added at a ratio of 1 to 1000 ppm.

The organic solvent used for producing the above-mentioned polyimide precursor is N-methyl-organic for both high heat-resistant aromatic polyimide and thermocompression-bondable and / or flexible aromatic polyimide. 2-pyrrolidone, N,
N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, dimethylsulfoxide, hexamethylphosphoramide, N-methylcaprolactam, cresols, and the like. These organic solvents can be used alone. Or two or more of them may be used in combination.

In the production of the above-mentioned multilayer polyimide film, a coating-casting film forming method, for example, a thermocompression-bonding and / or flexible aromatic film is applied to one or both surfaces of a solution-dried film of a highly heat-resistant aromatic polyimide precursor. A solution coating of an aromatic polyimide precursor or co-extrusion-cast film forming method, for example, a thermocompression-bonding and / or flexible aromatic polyimide on one or both sides of the above-mentioned aromatic polyimide precursor solution having high heat resistance. The precursor solution is co-extruded and cast on a support surface such as a stainless steel mirror surface or a belt surface.
A method in which a semi-cured state at 00 ° C. or a dried state before that can be employed. Treating a cast film at a high temperature exceeding 200 ° C. tends to cause defects such as a decrease in adhesiveness in the production of a multilayer polyimide film. The semi-cured state or a state before that means that it is in a self-supporting state by heating and / or chemical imidization.

The co-extrusion of the high heat-resistant aromatic polyimide precursor solution and the thermocompression-bondable aromatic polyimide precursor solution is described, for example, in Japanese Patent Application Laid-Open No. 3-180343 (Japanese Patent Publication No. Hei 7-102661). Can be supplied to a two-layer or three-layer extrusion die and cast on a support by the coextrusion method described in (1). On one or both surfaces of an extruded material layer that provides a highly heat-resistant aromatic polyimide, a thermocompression-bondable and / or flexible aromatic polyimide precursor solution is applied and laminated to form a multilayer film, and then dried. Heat to a temperature below the glass transition temperature (Tg) of the thermocompression bondable and / or flexible aromatic polyimide and below the temperature at which degradation occurs, preferably 300 to 500 ° C (surface temperature measured by a surface thermometer). (Preferably by heating at this temperature for 1 to 60 minutes), and dried and imidized to form a thermocompression-bonding and / or flexible aromatic polyimide on one or both sides of a highly heat-resistant (substrate layer) aromatic polyimide. A multilayer polyimide film having polyimide can be manufactured.

The thermocompression-bonding and / or flexible aromatic polyimide of the present invention has a glass transition temperature of about 200 to 375 ° C., and particularly 200 to 300 ° C., by using the above-mentioned acid component and diamine component. In particular, in the range of from 200 to 275 ° C., preferably from the glass transition temperature to 300 ° C., which is obtained by drying and imidizing under the above-mentioned conditions to substantially prevent gelation of the thermocompression-bondable polyimide. Temperature is not liquefied at a temperature within the range, and the modulus of elasticity is usually 275 ° C.
(0 ° C.) is preferably about 0.0002 to 0.2 times the elastic modulus at 0 ° C.).

In the present invention, high heat resistance (substrate layer)
The thickness of the polyimide layer is 5 to 50 μm, especially about 5 to about 40.
μm, and particularly preferably about 5 to about 25 μm. If the thickness is less than 5 μm, problems arise in mechanical strength and dimensional stability of the formed multilayer polyimide film. 50 μm
If it is thicker, it is disadvantageous for fine patterning. In the present invention, the thickness of the thermocompression bonding and / or flexibility aromatic polyimide layer is preferably about 0.03 to 10 μm. The multilayer polyimide film has a thickness of about 7 to about 50 μm, particularly about 7 to 40 μm, and preferably about 7 to 25 μm. When the thickness is less than 7 μm, it is difficult to handle the produced film, and as the thickness increases, it is disadvantageous to obtain a fine pattern.

According to the coextrusion-casting film forming method and the coating and laminating method on the extruded product, the high heat-resistant polyimide layer is compared with one or both sides of thermocompression-bonding and / or flexible polyimide. It is possible to obtain a multilayer polyimide film in which the imidization and drying of the self-supporting film are completed without curing at a very low temperature without deteriorating the thermocompression bonding and / or flexibility polyimide. In particular, as a multi-layer polyimide film, thermocompression bonding and / or
Or it has a flexible polyimide layer and the total thickness is about 7
Those having a tensile modulus of elasticity (at 25 ° C.) of about 400 to 1000 kgf / mm ² are preferred from the viewpoint of high density.

In the present invention, the above-mentioned multilayer polyimide film is preferable as the polyimide film.
Glass transition temperature of 30 with high heat resistance and flexibility
It may be a single-layer polyimide film of polyimide having a temperature of about 0 to 375 ° C. Examples of such a polyimide include a copolymerized polyimide of a highly heat-resistant polyimide precursor and a flexible polyimide precursor and a blended polyimide of a highly heat-resistant polyimide and a flexible polyimide.

The metal layer to be laminated on the film in the present invention may be a metal foil or a metal film of copper, aluminum, iron, gold or the like, or an alloy foil or an alloy film of these metals. Examples include an electrolytic copper foil, a vapor-deposited and / or plated copper film, and the like. As the metal foil, the surface roughness is not too large and not too small, preferably, the Rz of the contact surface with the polyimide is 3 μm or less, especially 0.5 to 3
μm, and particularly preferably 1.5 to 3 μm. Such metal foil, for example, copper foil is VLP, LP
(Or HTE). The thickness of the metal foil is preferably about 3 μm to 12 μm, particularly preferably about 3 μm to 9 μm. The greater the thickness of the metal foil, the more disadvantageous it is in fine patterning. When Rz is small, a metal foil whose surface is treated may be used.

In the present invention, preferably, the thermocompression-bondable multilayer polyimide film and the metal foil are combined with a roll laminate or a continuous laminator such as a double belt press.
In the in-line immediately before introducing the thermocompression-bonding multilayer polyimide film alone or the thermocompression-bonding multilayer polyimide film and the metal foil, it is about 150 to 250 ° C., and particularly 2 to 120 at a temperature higher than 150 ° C. and 250 ° C. or less. By preheating using a preheater such as a hot air supply device or an infrared heater so that preheating can be performed for about 2 seconds, and bonding by heating and pressing, a laminate that is a flexible metal foil laminate can be obtained. The double belt press is capable of performing high-temperature heating-cooling under pressure, and is preferably a hydraulic type using a heat medium. The above-mentioned in-line refers to a device in which a preheating device is installed between a raw material feeding device and a pressing portion of a continuous laminating device, and the device can be pressed immediately thereafter.

In particular, it is preferable that the temperature of the heat-compression bonding zone of the roll laminate or double belt press is 20 ° C. higher than the glass transition temperature of the thermocompression-bondable polyimide.
The thermocompression bonding is performed under pressure at a temperature higher than 400 ° C., especially higher than 30 ° C. and lower than 400 ° C., especially in the case of a double belt press. Preferably, the temperature is at least 20 ° C. lower than the glass transition temperature of
It can be manufactured by cooling to a temperature lower than or equal to ° C. and laminating.

In the above method, when the product is a single-sided metal foil flexible metal foil laminate, a highly heat-resistant film easily peelable, for example, a high heat-resistant film or a metal foil having an Rz of less than 2 μm, preferably Protective material is made of highly heat-resistant resin film such as polyimide film (UPILEX S, manufactured by Ube Industries, Ltd.) or fluororesin film, rolled copper foil, etc., which has low surface roughness and good surface smoothness. Alternatively, it may be interposed between the thermocompression-bondable polyimide layer and another metal surface. After lamination, this protective material may be removed from the laminate and rolled up, or the protective material may be rolled up with the laminated layer and removed at the time of use. In the above method, in particular, thermocompression bonding under pressure using a double belt press-
By cooling and laminating, the resulting flexible metal foil laminate is long and has a wide width of about 400 mm or more, particularly about 500 mm or more, and a large adhesive strength (90 ° peel strength: 0.7 kg / cm or more, particularly 1 kg / cm or more), and a laminate having a good appearance can be obtained so that wrinkles are not substantially observed on the surface of the metal foil.

Further, the laminate of the present invention is obtained by subjecting a polyimide film in which flexible polyimide is laminated and integrated on both sides of a highly heat-resistant aromatic polyimide layer to discharge treatment such as plasma discharge and the like, by vapor deposition, plating or the like. In particular, it can be obtained by forming a base metal layer by an evaporation method, forming a copper plating layer on the base metal layer, and forming a metal film.

The lamination of the metal vapor-deposited layer can be particularly preferably performed by a physicochemical vapor deposition method such as a vacuum vapor deposition method, an electron beam vapor deposition method, and a sputtering method. As a vapor deposition method, the degree of vacuum is 10 ⁻⁷ to 10 ⁻² Torr.
And the deposition rate is about 50 to 5000 ° / sec, and the temperature of the deposition substrate (film) is 20 to 6
The temperature is preferably about 00 ° C. In the sputtering method, an RF magnet sputtering method is particularly preferable, and the degree of vacuum at that time is 1 Torr or less, particularly 10 ⁻³ to
About 10 ^-2 Torr and the substrate (film) temperature is 2
0-450 ° C., and the layer formation rate is 0.5
It is preferably about 500 ° / sec.

Examples of the material of the metal film include copper or copper alloy, aluminum, and palladium. In particular, chromium, titanium, nickel, molybdenum, zinc, tin, palladium or the like may be used as a base layer of the metal deposition layer, and copper or a copper alloy (particularly a copper-nickel alloy) may be used as a surface layer thereon. . The thickness of the underlayer is usually 1μ
m or less. A metal plating layer may be formed on the metal layer thus obtained, and examples of the material of the metal plating layer include copper, copper alloy, and silver. As a method for forming the metal plating layer, either an electroless plating method or an electrolytic plating method may be used. The metal film in the present invention has a thickness of about 1 μm to 12 μm, preferably 3 μm to 12 μm.
It is preferably about μm, especially about 3 μm to 9 μm. The greater the thickness of the metal film, the more disadvantageous it is in fine patterning. Further, it is preferable to form the metal film by a continuous roll including the above-mentioned sputtering and vapor deposition method.

In the present invention, the laminated polyimide film formed as described above is laser-processed to form through holes (through holes) in the film. An apparatus for laser processing is disclosed in, for example, Japanese Patent Application Laid-Open No. 10-323786.
And a laser processing apparatus described in Japanese Unexamined Patent Publication (Kokai) No. H11-15095. As a drilling method using a laser, for example, a laser processing method described in JP-A-6-142961 can be exemplified. For example,
As a laser, a laser having an oscillation wavelength in the infrared region, such as a CO ₂ or YAG laser, can be used as it is, or by irradiating a nonlinear optical crystal and taking out the laser.
Lasers in the ultraviolet region in the range of about 400 nm
Can be used.

For example, in the case of a laminate in which a metal layer is laminated on one side of a polyimide film, the laser processing is performed by using a mask that gives the polyimide layer a predetermined cross-sectional shape. Irradiate for about 3 to 300 μmφ, preferably about 30 to 300 μmφ, among which 30 to 100 μm
A through hole of φ, especially about 50 to 100 μmφ is formed. Then, after the laser-processed portion is desmeared with an oxidizing agent such as an aqueous solution of potassium permanganate, a pattern is formed on the unprocessed metal layer to form a substrate.

For example, in the case of a laminate in which a metal layer is laminated on both sides of a polyimide film, a metal layer on one side is chemically etched to form a pattern of a predetermined shape, and the remaining metal layer is masked. Irradiate the polyimide layer with a laser to obtain a diameter of about 3 to 300 μm, preferably about 30 to 3 μm.
A through hole having a diameter of 00 μmφ, particularly about 50 to 100 μmφ is formed. Then, after the laser-processed portion is desmeared in the same manner as described above, a pattern is formed on the other metal layers to form a substrate.

According to the present invention, since a high heat-resistant aromatic polyimide containing a biphenyltetracarboxylic acid component as an aromatic tetracarboxylic acid component is used as a main component, cracks occur in the film portion, -It is possible to form a substantially vertical through hole on the front and back of the cross section of the film, even after the desmearing, without making the wall surface of the hole uneven. According to the invention,
It has a small taper, and preferably has a pore diameter ratio of 1.5 or less, particularly 1.3 or less (that is, 1: 1 to 1:
1.3) Through-holes (via holes) that are usually cylindrical or nearly cylindrical
) Can be obtained.
Further, according to the present invention, since the surface of the hole of the laser-treated laminated body is smooth, it is easy to control the thickness when plating the inside of the hole with metal, preferably copper. In addition, poor metal plating hardly occurs.

In the present invention, the method for forming the metal plating layer may be either electroless plating or electrolytic plating. And, as the metal plating conditions, for example,
The bath composition of the acidic bath is 50 to 200 g of a metal salt such as copper sulfate.
/ L (particularly 50-100 g / l), sulfuric acid 100-300
g / l, and, if necessary, a small amount of brightener.
Cathode current density 2 to 8 A / dm2, air stirring, cathode efficiency 9
It is preferable that the conditions are 5 to 100%, the anode / cathode area ratio is 1: 1, the cathode is roll copper, the filtration is constant, and the voltage is 6 V or less. Further, the thickness of the plated metal layer is preferably about 1 μm to 18 μm, and the thickness of all metal layers is 2 to 1 to 12 μm of the thickness of the metal layer before laser processing.
It is preferably about 30 μm.

The laminate and the plated substrate obtained by laser processing according to the present invention can be suitably used as a substrate for electronic parts. For example, it can be suitably used as an FPC for COF, a TAB for package, and a base substrate of a multilayer substrate.

[0043]

The present invention will be described in more detail with reference to the following examples. In each of the following examples, physical properties were measured according to the following methods. Tensile modulus: measured according to ASTM D882. Glass transition temperature (Tg): Measured from viscoelasticity.

Synthesis Example 1 of Dope for Production of Highly Heat-Resistant Aromatic Polyimide A reaction vessel equipped with a stirrer and a nitrogen inlet tube was charged with N-methyl-
2-Pyrrolidone was added, and paraphenylenediamine (PPD) and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (s-BPDA) were further added at 1000: 9.
At a molar ratio of 98, the monomer concentration was 18% (% by weight, the same applies hereinafter). After completion of the addition, the reaction was continued for 3 hours while maintaining the temperature at 50 ° C. The obtained polyimide precursor solution is a brown viscous liquid, and the solution viscosity at 25 ° C. is about 1
It was 500 poise. This solution was used as S-dop.

Synthesis Example 2 of Dope for Production of Highly Heat-Resistant Aromatic Polyimide Pyromellitic dianhydride instead of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) Is replaced with paraphenylenediamine (PPD),
A polyimide precursor solution was obtained using 4'-diaminodiphenyl ether (DADE). This solution is
Used as a loop.

Synthesis of Dope for Production of Aromatic Polyimide Having Heat Resistance, Thermocompression Bonding Property and / or Flexibility-1 N-methyl-doped in a reaction vessel equipped with a stirrer and a nitrogen inlet tube.
2-Pyrrolidone was added, and 1,3-bis (4-aminophenoxy) benzene (TPE-R) and 2,3,3
3 ', 4'-biphenyltetracarboxylic dianhydride (a
-BPDA) in a molar ratio of 1000: 1000 to give a monomer concentration of 22%, and triphenyl phosphate was added in an amount of 0.1% by weight of the monomer. After completion of the addition, the reaction was continued for 1 hour while maintaining the temperature at 25 ° C. This polyamic acid solution has a solution viscosity of about 200 at 25 ° C.
It was 0 poise. This solution was used as A-dop.

Synthesis of Dope for Production of Aromatic Polyimide Having Heat Resistance, Thermocompression Bonding Property and / or Flexibility-2 Using DADE instead of TPE-R and s-BPDA instead of a-BPDA A polyimide precursor solution was obtained.
This solution was used as B-dope.

Examples 1 and 2 and Comparative Example 1 The above-mentioned dope for aromatic polyimide having high heat resistance and the dope for producing aromatic polyimide having heat resistance and thermocompression bonding and / or flexibility were used. Using a film forming apparatus provided with a layer extrusion die (multi-manifold die), the polyimide precursor solution was cast on a metal support at a temperature of 140 ° C. while changing the thickness of the three-layer extrusion die. It was dried continuously with hot air to form a solidified film. After the solidified film was peeled from the support, the temperature was gradually raised from 200 ° C. to 320 ° C. in a heating furnace to remove the solvent and imidize, and three types of long three-layer extruded polyimide films were wound up. Rolled up. The obtained three-layer extruded polyimide film has the following configuration.

Thermocompression-bondable multilayer polyimide film-1 (composition: ASA) Thickness composition: 4 μm / 17 μm / 4 μm (25 μm in total) Tg of thermocompression-bondable aromatic polyimide: 250 ° C. (the same applies hereinafter)

Flexible multilayer polyimide film-2 (Constitution: BSB) Thickness constitution: 1 μm / 23 μm / 1 μm (25 μm in total) Tg of flexible aromatic polyimide: 275 ° C. (the same applies hereinafter)

Thermocompression-bondable multilayer polyimide film-3 (Constitution: AKA) Thickness constitution: 4 μm / 17 μm / 4 μm (25 μm in total)

Example 3 A multilayer polyimide film-1 and a thickness 1 on both outer sides thereof
2 μm electrolytic copper foil (manufactured by Mitsui Mining & Smelting Co., Ltd.) is pre-heated by heating with 200 ° C. hot air for 30 seconds in-line immediately before the double belt press, and is continuously supplied to the double belt press to obtain a temperature of the heating zone. (Highest heating temperature) 381 ° C, cooling zone temperature (minimum cooling temperature 117 ° C), thermocompression-bonding and cooling under continuous pressure and laminating to form copper foil / polyimide film / copper foil Flexible copper foil laminate (width:
530 mm, the same applies hereinafter). After chemical etching the single-sided copper foil of the flexible foil laminate by conventional methods, Sumitomo Heavy Industries, Ltd. Les - The - processing machine (impact Les - The -GS500, TEA-CO ₂ Les - The -) using The polyimide layer was laser-processed. Laser processing conditions: Via hole Aiming at 50 μmφ, Aiming at 100 μmφ Number of shots each 6 shots Output 23.1 W, 150 Hz Energy 13.3 J / cm ² As a result, as shown in FIG. -The hole is almost perpendicular to the cross-section.
1.3 for mφ, 1.15 for 100 μmφ]
The hole surface was smooth. After desmearing with a permanganate solution, electrolytic copper plating is applied to a thickness of 10 μm by a conventional method to make the via hole conductive, and fine pattern is applied to the untreated copper foil on the other surface.
Formed.

Example 4 After vacuum plasma treatment on both sides of the multilayer polyimide film-2, vacuum deposition and then electroplating of copper were performed to obtain a flexible copper foil laminate having a double-sided copper layer having a copper layer thickness of 5 μm. In the same manner as in No. 3, the polyimide layer was laser-processed.
The obtained laser-processed via hole had almost the same cross section as the result of Example 3 and a vertical hole surface. After desmearing, electrolytic copper plating was performed by a conventional method to make the via hole conductive, thereby forming a fine pattern.

Comparative Example 2 The same procedure as in Example 3 was repeated except that a multilayer polyimide film-3 was used instead of the multilayer polyimide film-1.
A flexible copper foil laminate (width: about 530 mm, the same applies hereinafter) having a polyimide film / copper foil configuration was obtained, and then the polyimide layer was laser-processed. The resulting laser hole is
The smoothness of the hole surface was poor.

[0055]

According to the present invention, the following effects can be obtained because of the above configuration. According to the present invention, there is provided a polyimide film containing a high heat-resistant aromatic polyimide as a main constituent material, and a metal layer laminate in which a metal layer is laminated on at least one surface of the polyimide film directly or via a different resin layer. Which can be formed into a substantially vertical through-hole on the front and back of the cross section of the film by laser processing
A polyimide film having good workability and a substrate having good conductivity can be obtained by metal plating the through holes.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a through-hole obtained by applying laser processing to a double-sided copper-clad flexible copper foil laminate by a casting method, which is a competitor's product, after laser drilling and desmearing. FIG.

FIG. 2 is a view showing a through hole obtained by applying laser processing to the double-sided copper-clad flexible copper foil laminate obtained in Example 1;
FIG. 3 is a schematic sectional view after laser drilling and after desmearing.

[Explanation of symbols]

1, 10 Laser-drilled flexible copper foil laminate 2, 12 Polyimide film 3, 13 Copper foil 4, 14 Through hole

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Shuichi Hashiguchi 1-2-1 Shibaura, Minato-ku, Tokyo, N-Ban N Building Ube Industries, Ltd. Tokyo Head Office F-term (reference) 4F100 AB01A AB01E AB04A AB04E AB10A AB10E AB17A AB17E AB33A AB33E AK49B AK49C AK49D BA05 BA06 BA10A BA10E EH20 EH66A EH66E EH71A EH71E EH90 EJ18 EJ42 EJ88 GB43 JA05B JA05C JA05D JK17B JK17D JL00 YY00A YY00B YY00B YY00B YY00B YY00A

Claims (11)

[Claims] 1. A polyimide film containing a biphenyltetracarboxylic acid component as an aromatic tetracarboxylic acid component and having a glass transition temperature of 300 ° C. or higher or a high heat-resistant aromatic polyimide whose glass transition temperature cannot be measured as a main constituent material. A polyimide film having a low glass transition temperature polyimide resin layer having a thermocompression bonding property and / or flexibility having a glass transition temperature of 200 to 375 ° C. on at least one surface of the polyimide film. A polyimide film of a laminate in which a metal layer is laminated via a polyimide resin layer having a thermocompression bonding property and / or flexibility of a polyimide film having a glass transition temperature equal to or lower than the glass transition temperature of a highly heat-resistant aromatic polyimide. −
A polyimide film with good laser processability that can be processed to form substantially vertical through holes on the front and back of the cross section of the film. 2. The polyimide film having good laser processability according to claim 1, wherein the metal layer is an electrolytic copper foil, a rolled copper foil, an aluminum foil or a stainless steel foil. 3. The laser according to claim 1, wherein the metal layer is a metal film formed by vapor deposition and / or plating.
A polyimide film with good workability. 4. A polyimide film comprising a high heat-resistant aromatic polyimide precursor layer and a low glass transition temperature polyimide precursor layer having heat resistance and thermocompression bonding and / or flexibility on at least one surface, preferably both surfaces, The polyimide film having good laser processability according to any one of claims 1 to 3, which preferably has a multilayer structure obtained by laminating and integrating by a coextrusion-cast film forming method. 5. The polyimide film has a thickness of 55 to 99.9.
5. The polyimide film having good laser processability according to claim 1, having a thickness ratio of the high heat-resistant aromatic polyimide layer of 5%. 6. The polyimide film having good laser processability according to claim 1, wherein the metal layer has a thickness of 1 to 12 μm. 7. A laminate comprising a thermocompression-bondable multilayer polyimide film in which a thermocompression-bondable polyimide layer is laminated and integrated on at least one surface of a highly heat-resistant aromatic polyimide layer by a continuous laminating apparatus. The polyimide film having good laser processability according to any one of claims 1 to 6, which is obtained by laminating by thermocompression bonding. 8. The laminate according to claim 1, wherein the laminate is obtained by using a double belt press as a continuous laminating apparatus, thermocompression bonding under pressure, cooling and bonding. Polyimide film with good laser processability. 9. A substrate obtained by laser processing the polyimide film according to claim 1 and forming substantially vertical through holes on the front and back surfaces of the cross section of the film. 10. A substrate obtained by subjecting the polyimide film according to claim 1 to laser processing, subjecting the laser-processed portion of the obtained substrate to desmear treatment, and then metal plating the inner surface of the through hole. 11. A processing method for forming a through hole in a polyimide film for laser processing the polyimide film according to claim 1.