JP2000101216A - Manufacture of film substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a film substrate with double-sided wiring of fine pitch in which through-holes are formed by applying a plating resist anti-corro sive to an etching liquid over the through-holes. SOLUTION: First a film substrate is drilled to make through-holes, and Cu plating is formed on the wall surface of the through-holes. Next, electroless plating and substituent gold plating are applied to the through-holes to be protected from an etching liquid. Then a plating resist is removed, and the substrate is coated with a photoresist and is dried thereafter. Both surfaces thereof are exposed while a patterning mask is placed thereon, so as to remove unnecessary photoresists. Further, Cu is etched and patterned, and then the photoresists are removed and a solder resist is formed, and the pattern terminal is covered with electroless Sn plating. Finally, the substrate is punched into the shape of products to complete film substrates.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a double-sided wiring film substrate on which a fine pattern circuit (pattern having a pitch of 100 .mu.m or less) is formed, and a liquid crystal display used for a portable device or an electronic organizer. The present invention relates to an electronic circuit device having a device or an IC mounted on a bare chip.

[0002]

2. Description of the Related Art A liquid crystal display device has a driver IC package and C,
COF (Chip On FP) in which chip parts such as R and electronic parts such as package ICs are mixedly mounted on a film substrate.
A product in which C) is mounted on a liquid crystal panel has begun to be mass-produced. Conventionally, a film substrate has been formed by applying a film-like adhesive to a polyimide film, pasting a Cu foil formed by a method such as rolling or electrolysis and patterning, and performing resist coating, electrolytic plating, or electroless plating.

The film substrate having such a three-layer structure is not suitable for a fine pattern of 100 μm or less in terms of dimensional stability because the adhesive is deformed by heat and humidity. Therefore, a film substrate from which the adhesive has been removed has been developed. There are two manufacturing methods for a two-layer film substrate without an adhesive layer. One is a casting method in which a polyamic acid varnish is applied to a Cu film and the solvent is removed and then cured, and the adhesion of a polyimide film to, for example, nichrome alloy, molybdenum, titanium, nickel, cobalt, chromium, palladium, zirconium, molybdenum, and tungsten is improved. To form a metal thin film for Cu
After forming a Cu thin film by sputtering or vapor deposition, there is a vapor deposition method in which Cu is laminated by electrolytic plating.

[0004] The difference between the film substrates of these manufacturing methods is that
Is the thickness. The thickness of Cu used in the casting method is generally 35 μm or 18 μm, and recently 12 μm has been mass-produced. Also, 9 microns is under development. In the vapor deposition method, the thickness of Cu can be from 2 to 18 microns. In order to form a fine pattern, there is a casting method in which an electrolytic Cu foil is half-etched and then patterned, but it is not easy to obtain a stable yield. It is easy in terms of the manufacturing method that the thickness of Cu is thin and uniform, and when the pattern is 100 micron pitch or less, a film substrate of a vapor deposition method that can uniformly reduce the thickness of Cu is more suitable.

[0005] In the case of IC bare chip mounting, when connection is performed by using an adhesive, an IC pad is formed on a circuit board by using a plated bump formed by plating a bump made of Au or a stud bump using wire bonding. It has been press-bonded with an isotropic conductive film or transferred to a substrate by transferring a silver paste to a bump, and an underfill has been filled and connected between them.

In the case of using metal diffusion connection, a method of using solder for the bump of the IC, soldering it to the electrode of the substrate and filling the underfill, and using Au for the bump of the IC and plating the electrode on the substrate side with Sn plating. Then, Au-Sn diffusion connection was performed to fill the underfill. The bump pitch of the external connection electrodes of the IC is, for example, mass-produced at a pitch of 80 μm in a liquid crystal driving IC, but the process development of the IC is progressing and the miniaturization is progressing. For this reason, the bump pitch of the external connection electrode of the IC has been started to be developed at a pitch of 50 μm or 40 μm.

On the other hand, a liquid crystal display device is manufactured by connecting a COF (Chlp On Fpc) in which an IC is connected to a film substrate to a liquid crystal panel. Since the COF can package packages such as a liquid crystal driving IC, C and R chip components, a power supply IC, and an operational amplifier at a high density, the liquid crystal display device can be reduced in size and thickness. This liquid crystal display device is widely used in portable devices, among which mobile phones and PDAs
In recent years, demands for portable information terminals, such as the portable information terminals, have greatly increased.

[0008]

In order to use a liquid crystal driving IC having a pitch of 40 microns, the width of the pattern of the film substrate to be connected is 10 to 15 microns. Therefore, a film substrate formed by an evaporation method is used. However, a liquid crystal display device used in a portable information terminal has, for example, 320 pixels × 240 dots, and a liquid crystal driving IC has a multi-chip configuration.

In order to mount these liquid crystal driving ICs on a single film substrate and supply signals, bus lines cannot be crossed over if the film substrate is a single-sided wiring plate, and wiring cannot be performed. For that purpose, a film substrate with double-sided wiring is required. However, a double-sided wiring film substrate requires through holes. A fine-pitch double-sided wiring film substrate with through holes formed has not been put to practical use. It depends on the manufacturing process of the film substrate.

In the process of manufacturing a film substrate, a photosensitive resist is applied to the entire surface of a polyimide film on which Cu is deposited, for example, in the case of single-sided wiring, by about 5 to 8 microns, and is cured by applying heat. At this time, the photoresist of the dry film is not suitable for forming a fine pattern and cannot be used. Next, the pattern portion is exposed to UV with a photomask, unnecessary portions of the photoresist are removed with a 5% aqueous solution of sodium hydroxide or the like, and the pattern is formed by etching with ferric chloride. There is no problem in this case.

However, in the case of a film substrate having a double-sided wiring, for example, an adhesion improving thin film is formed on the entire surface of a polyimide film, Cu is formed in a film formed by vapor deposition of 4 microns, and Cu plating is further performed to 4 microns. Thus, the hole portion is covered with Cu to complete the through hole. Alternatively, a through-hole is formed in a polyimide film to form an adhesion-improving thin film, Cu is vapor-deposited, Cu is simultaneously formed on the wall of the through-hole, and Cu is further plated by a total of 8
Form to the micron.

Next, when a photoresist is applied to a thickness of about 5 to 8 microns and cured by applying heat, the photoresist cannot completely cover the through holes. Therefore, there is a problem that when the photoresist is exposed using a photomask, the photoresist is removed with a 5% aqueous solution of sodium hydroxide, and etching is performed with ferric chloride, Cu in a through-hole portion is etched and conduction failure occurs. The thickness of the photoresist cannot be increased to cut the fine pattern. Also, through-hole plating cannot be made thick to cut fine patterns.

There is also a method of pouring a filling resin into a through-hole portion with a needle, a dispenser, printing, or the like before applying a photoresist. In the case of FPC, since the total thickness of a film is thin, a portion into which a filling material is poured and protruded is used. There was a problem that the filling material was removed in the step of polishing the surface. In particular, there will be a limit to the resin used to fill the holes in future substrates, which will be formed with fine holes through holes for high-density mounting.

For this reason, it has been difficult to commercialize a film substrate in which through holes are formed in a fine-patterned double-sided wiring board. In other words, the present invention is to provide a manufacturing method capable of easily forming a through hole and fine patterning in manufacturing a film substrate having a fine pattern double-sided wiring.

It is another object of the present invention to realize a thin and small liquid crystal display device using the fine-patterned double-sided wiring film substrate.

[0016]

[Means for Solving the Problems] To solve the problems,
In a method for producing a double-sided wiring film substrate having a through hole by directly forming a metal foil on both surfaces of an insulating film, at least Cu
Forming a hole for a through hole on a substrate on which one layer of metal foil such as a metal foil is formed, and forming a Cu plating on the entire surface including the wall surface of the hole, and a step of applying a plating resist having corrosion resistance to an etchant on the through hole portion. Then, by applying a liquid photoresist on both sides, curing and patterning, the through holes were protected from the etching solution. The plating having corrosion resistance is preferably plating formed in the order of Ni and Au.

Further, as another manufacturing method, a step of applying, curing and patterning a liquid photoresist on both sides using a substrate having at least one layer of metal foil formed on at least both sides of a film substrate, and a step of forming through-hole holes are provided. By conducting the resist coating on the portions other than the through-hole portions and plating the through-hole portions with Cu, the conduction failure due to the etching of the through-holes was solved.

Also, a step of forming a through-hole hole using a substrate having at least one layer of metal foil formed on at least both sides of a film substrate, a step of applying, curing and patterning a liquid photoresist on both sides, and a step of resisting a portion other than the through-hole portion The same effect as described above was obtained by performing the step of coating and plating the through-hole portion with Cu. Alternatively, using a substrate having at least one layer of metal foil formed on at least both sides of a film substrate, forming a hole for a through-hole and performing Cu plating on the entire surface including the wall surface, and forming an electrodeposition resist on the through-hole portion In addition, by applying a liquid photoresist on both surfaces, curing and patterning, the same effect as protection by plating was obtained.

With the film substrate processed by any of the above-mentioned manufacturing methods, a film substrate having through holes with double-sided wiring can be obtained together with a fine pattern. And a small electronic circuit device was realized. Further, by connecting the liquid crystal panel to the film substrate of high density mounting, a thin and small liquid crystal display device can be realized.

The film substrate processed by the above-described manufacturing method was able to easily manufacture a fine pattern and through holes stably on both-sided wiring. Also, by employing this film substrate, it was possible to obtain a high-density electronic circuit device and a thin and small liquid crystal display device using the same.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart of a process for manufacturing a film substrate of the present invention. First, a film made of polyimide was manufactured by Toray Dubon Kapton EN25μ.
A metal thin film for improving adhesion is vapor-deposited on the entire surface of the m-thick film, and Cu is vapor-deposited and plated to form a through-hole hole on a film substrate having a 4-micron-thick Cu formed on both surfaces by drilling. The diameter of the hole is φ0.4mm. When forming with a smaller diameter, etching or laser is used. In the case of a laser, it is necessary to remove smear.

Next, to form Cu on the wall surface of the through hole, Cu plating is formed to a thickness of 4 μm. In the portion where the pattern is formed, Cu has a thickness of 8 microns. Next, a plating resist is formed by printing on portions other than the through-hole portions. When the diameter of the through-hole is small, a plating method may be used for the plating resist. Next, in order to protect the through holes from the etching solution, the electroless Ni plating is replaced with 1 micron by gold plating. A method may be used in which the Cu plating on the wall surface of the through hole is thinned, and the replacement gold plating is followed by thick Au plating to increase the reliability of the through hole.

At this time, for example, if a film substrate that performs two-color plating of Sn and Au plating is required, that portion is also plated with Au. For example, the input terminal section, S
For example, a pad of a component to be mounted in the MT. The plating for protection is not limited to Ni and Au, but may be anything that does not corrode by the plating solution such as solder. However, since the solder is melted by reflow, the reliability is not higher than that of Ni and Au plating.

Next, the plating resist is removed with an alkaline solution or the like. Next, a photoresist is applied by dipping, dried and formed to a thickness of 5 to 8 microns. Exposure is performed on both sides simultaneously or sequentially with a patterning mask, and unnecessary photoresist is removed simultaneously with a 5% aqueous sodium hydroxide solution on both sides.

Next, Cu is etched on both surfaces simultaneously with ferric chloride and patterned. At this time, the through hole is Au
Since it is protected by plating, it is not eroded by the etching solution. Also, since Cu is 8 microns, fine patterns can be easily cut. Here, plating is performed, but the same effect is obtained by using an electrodeposition resist instead of plating.

Next, the photoresist is removed, a solder resist is formed by a photographic method, and electroless Sn plating is coated on the terminals of the pattern. Finally, the film substrate is completed by punching into the shape of the product. By adopting the above-described method for manufacturing a film substrate, a film substrate having a fine-patterned double-sided wiring in which a through-hole is formed can be easily obtained.

A liquid crystal driving IC is provided on the film substrate 2.
The Au-plated pattern No. 4 and the Sn-plated pattern connected to the bumps on the film substrate 2 are aligned, and bonded by thermocompression bonding. An underfill is caused to flow between the liquid crystal drive IC 4 and the film substrate 2 and is cured by heat or light and sealed. A chip part 3 such as a capacitor and a resistor and a semiconductor package 5 such as an operational amplifier are mounted by SMT to complete an electronic circuit device.
Further, the liquid crystal panel 1 and the anisotropic conductive film are thermocompression-bonded, and the exposed portions of the terminals of the liquid crystal panel are coated with a silicone adhesive to complete the liquid crystal display device shown in FIG.

Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a flowchart of the film substrate manufacturing process of the present invention. First, a film made of polyimide is formed by depositing a metal thin film for improving adhesion on the entire surface of a film having a thickness of 25 μm, manufactured by Kapton EN manufactured by Toray Dubon.
A film substrate on which u is formed on both sides of 4 microns by vapor deposition and plating is used.

A photoresist is applied to the film substrate by dipping, dried and formed to a thickness of 5 to 8 microns.
Exposure is performed on both sides simultaneously or sequentially with a patterning mask, and unnecessary photoresist is removed simultaneously with a 5% aqueous sodium hydroxide solution on both sides. Next, both surfaces are simultaneously etched and patterned with ferric chloride.

A through hole is formed by a drill. The diameter of the hole is φ0.4mm. When forming with a smaller diameter, etching or laser is used. In the case of a laser, it is necessary to remove smear. Next, a plating resist is formed by printing on portions other than the through-hole portions. When the diameter of the through-hole is small, a plating method may be used for the plating resist.

Next, in order to form Cu on the wall surfaces of the through holes, Cu plating is formed to a thickness of 8 to 10 μm. Since the Cu plating of the through holes is formed after the patterning, there is no problem of etching solution erosion. Next, the plating resist is removed with an alkaline solution or the like.

Next, the photoresist is removed, a solder resist is formed by a photographic method, and the terminals of the pattern are covered with electroless Sn plating. Finally, the film substrate is completed by punching into the shape of the product. By adopting the above-described method of manufacturing a film substrate, Cu can be patterned while keeping Cu thin, so that the yield is good. Also, through holes can be reliably formed.

Thereafter, a liquid crystal driving IC and a liquid crystal panel are mounted in the same manner as in the first embodiment to complete an electronic circuit device and a liquid crystal display device. Hereinafter, a third embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a flowchart of the film substrate manufacturing process of the present invention. First, as a film made of polyimide, a film substrate in which a metal thin film for improving adhesion is vapor-deposited on the entire surface of a film having a thickness of 25 μm made by Kapton EN manufactured by Toray DuPont, and Cu is vapor-deposited and plated to form a 4-micron thick film on both sides is used.

A through hole is formed by a drill. The diameter of the hole is φ0.4mm. When forming with a smaller diameter, etching or laser is used. In the case of a laser, it is necessary to remove smear. A photoresist is applied to the film substrate by dipping, dried, and formed to a thickness of 5 to 8 microns.

Exposure is performed on both sides simultaneously or sequentially with a patterning mask, and unnecessary photoresist is removed simultaneously with a 5% aqueous sodium hydroxide solution on both sides. Next, both surfaces are simultaneously etched and patterned with ferric chloride. Next, a plating resist is formed by printing on portions other than the through-hole portions. When the diameter of the through-hole is small, a plating method may be used for the plating resist.

Next, Cu plating is formed to a thickness of 8 to 10 μm to form Cu on the wall surface of the through hole. Since the Cu plating of the through holes is formed after the patterning, there is no problem of etching solution erosion. Next, the plating resist is removed with an alkaline solution or the like.

Next, the photoresist is removed, a solder resist is formed by a photographic method, and the terminals of the pattern are covered with electroless Sn plating. Finally, the film substrate is completed by punching into the shape of the product. In the method of manufacturing a film substrate described above, the yield is good because Cu can be patterned while being thin as in the second embodiment. Also, through holes can be reliably formed.

Thereafter, a liquid crystal driving IC and a liquid crystal panel are mounted in the same manner as in the first embodiment to complete an electronic circuit device and a liquid crystal display device.

[0039]

As described above, according to the present invention, it is possible to easily manufacture a double-sided wiring film substrate having fine pattern through holes. Accordingly, the film, the electronic circuit device and the liquid crystal display device using the film can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a flowchart of Embodiment 1 of a method for manufacturing a film substrate of the present invention.

FIG. 2 is a top view of the liquid crystal display device of the present invention.

FIG. 3 is a flowchart of a method for manufacturing a film substrate according to a second embodiment of the present invention.

FIG. 4 is a flowchart of Embodiment 3 of the method for manufacturing a film substrate of the present invention.

FIG. 5 is a flowchart of a conventional method for manufacturing a film substrate.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 liquid crystal panel 2 flexible substrate with double-sided wiring with through holes 3 chip component 4 liquid crystal drive IC 5 semiconductor package

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[Procedure amendment]

[Submission date] November 12, 1999 (1999.11.
12)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

Patent application title: Method for manufacturing a film substrate

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

Claims (5)

[Claims] 1. A method for producing a double-sided wiring film substrate having through holes by directly forming a metal foil on both surfaces of an insulating film, wherein at least one metal layer is formed on at least both surfaces of the insulating film substrate. Forming a hole for a through-hole, forming a Cu plating on the entire surface including the wall surface of the hole, and applying a metal resist or an electrodeposition resist having corrosion resistance to an etchant on at least the through-hole portion, A method of manufacturing a film substrate, comprising a step of applying, curing and patterning a liquid photoresist on both sides. 2. The method for manufacturing a film substrate according to claim 1, wherein said metal resist having corrosion resistance is plating formed in the order of Ni and Au. 3. A method for producing a double-sided wiring film substrate having a through hole by directly forming a metal foil on both surfaces of an insulating film, wherein at least one metal layer is formed on both surfaces of the film substrate. A step of applying, curing and patterning a liquid photoresist on both sides of the film substrate, a step of forming holes for through holes before and after the step, and a step of resist coating at least portions other than the through holes to form the through holes. A method of manufacturing a film substrate, comprising a step of plating through holes. 4. An electronic circuit device wherein at least an IC is mounted face-down on a film substrate processed by the manufacturing method according to claim 1. 5. A liquid crystal display device comprising the electronic circuit device according to claim 4 connected to a liquid crystal panel.