JP2002299802A - Flexible printed wiring board and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible printed wiring board which hardly has a dielectric breakdown even if it operates on a high voltage under the conditions of high temperatures and high humidity. SOLUTION: A one-sided or double-sided flexible printed wiring board comprises a base material 1 having a pair of opposed surfaces, wiring pattern layers 2a and 2b formed on either or both of the surfaces of the base material 1, and coverlays 4a and 4b formed above the wiring pattern layers respectively. Oxide films 5a and 5b of silicon oxide or aluminum oxide are formed on at least one of the surfaces of the flexible printed wiring board.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible printed wiring board (hereinafter simply referred to as "F") used for electronic equipment and the like.
PC ") and a method for producing the same.

[0002]

2. Description of the Related Art In general, a flexible printed wiring board uses a three-layer type flexible copper-clad laminate in which an adhesive layer and a copper foil are provided on one or both sides of a base material having flexibility and electrical insulation. It is known to be manufactured. In general, a coverlay is provided on the flexible printed wiring board so as to cover the wiring pattern using an adhesive in order to protect the wiring pattern formed from the copper foil of the flexible copper-clad laminate. Generally, a polyimide film having high flexibility, electrical insulation and heat resistance is used for the base material and the coverlay.

[0003] In recent years, instead of a three-layer type flexible copper-clad laminate, a two-layer type flexible copper-clad laminate in which copper foil is directly provided on one or both sides of a base material without using an adhesive has been developed. Used. Since the two-layer type flexible copper-clad laminate does not have an adhesive layer, it generally has higher heat resistance, flame retardancy, electric characteristics (dielectric constant, Excellent dielectric loss tangent and volume resistivity), dimensional stability, chemical resistance, and adhesion at high temperatures.

A three-layer flexible copper-clad laminate is
It can be produced by laminating a copper foil on one or both sides of a base material such as a polyimide film using an adhesive such as an epoxy resin or an acrylic resin. On the other hand, a flexible copper-clad laminate of the two-layer type is a layer made of copper on one or both sides of a base material such as a polyimide film by a sputtering method or a plating method (this layer is also generally called “copper foil”). Can be made by forming Alternatively, a two-layer type flexible copper-clad laminate is prepared by applying a precursor of a base material, for example, a polyamic acid varnish, which is a precursor of a polyimide, to one surface of a copper foil, and further applying copper on the applied precursor in some cases. It can also be produced by a casting method in which foils are stacked, the precursor is sandwiched between copper foils, and this is heated and dried and cured.

[0005] Such an FPC is generally a two-layer FPC depending on the type of layer of the flexible copper-clad laminate used.
And a three-layer FPC, and a single-sided FPC and a double-sided FPC depending on whether the copper foil of the flexible copper-clad laminate exists on one or both sides of the base material.

Hereinafter, as one example, a conventional double-sided two-layer F
The structure of the PC and its manufacturing method will be described in more detail.

As shown in FIG. 3, a conventional double-sided double-layer FPC is used.
Reference numeral 60 designates wiring patterns 62a and 62b formed on both surfaces of a base material 61.
To cover 2b, coverlays 64a and 64b
Each is adhered to the base material 61 via the adhesive layers 63a and 63b. The base material 61 has a thickness of about 25
A polyimide film of 50 μm is used. The wiring patterns 62a and 62b are made of copper and have a thickness of about 8 to 36 μm.
m thickness. The adhesive layers 63a and 63b are formed using an adhesive such as an epoxy resin or an acrylic resin, and have a thickness of about 10 to 40 μm. For the coverlays 64a and 64b, a polyimide film having a thickness of about 5 to 25 μm is used.

[0008] Such a double-sided two-layer FPC 60 is manufactured as follows. First, both sides of a polyimide film serving as the base material 61 formed with copper foil on both sides by a plating method, a sputtering method, a casting method, or the like.
A layer type flexible copper-clad laminate is prepared, and the copper foil is etched to form copper wiring patterns 62 a and 62 b on the base material (polyimide film) 61. Thereafter, an adhesive such as an epoxy resin or an acrylic resin is applied in advance to apply the adhesive layers 63a and 63b.
The cover lays 64a and 64b made of another polyimide film on which the wiring patterns 62a and
The coverlays 64a and 64b are thermocompression-bonded to the base material 61 so as to cover the adhesive layers 63a and 3b so as to cover 2b. Thereby, the double-sided two-layer FPC 60 is manufactured.

[0009]

The use of FPCs has been expanding in recent years because of their flexibility and light weight. The FPC is required to operate at a voltage of several tens of volts in a mobile phone, a digital video camera, and the like. Further, the FPC is in a range of 100 to 500 volts in a document-related device such as a copy or a printer and a PDP (plasma display panel). Operating under a relatively high voltage. On the other hand, miniaturization and high integration of electronic circuit boards are desired. In FPCs, narrower pitches between terminals and wirings of electronic components, so-called narrower pitches, are being promoted.

However, in a severe environment, for example, at a temperature of 85 ° C.
And 10% for narrow pitch FPC under the environment of 85% humidity
If a voltage of 0 to 500 V is continuously applied, there is a problem that dielectric breakdown (or short circuit) occurs. It is known that such dielectric breakdown occurs due to the occurrence of so-called ion migration. It is believed that the occurrence of ion migration is closely related to the presence of water in the FPC.

[0011] The base material and coverlay of the FPC include:
Generally, polyimide is used. This polyimide is hygroscopic, and usually has a water absorption of about 1 to 3% (for example,
(A water absorption rate in a state where the temperature has almost reached an equilibrium under an environment of a temperature of 20 ° C. and a humidity of 50%). Moisture existing in the atmosphere around the FPC penetrates into the vicinity of the wiring pattern through the hygroscopic polyimide of the base material and the coverlay. When a voltage is applied to the wiring pattern in this state, electrolysis of water occurs, and the following reactions progress at the anode and the cathode of the wiring pattern, respectively.

Embedded image

Due to the water electrolysis reaction, H at the anode
⁺ Is generated and the pH becomes 3 or less, and OH ⁻ is generated on the cathode and the pH becomes 10 or more. In such an environment, it is considered that metal ions constituting the wiring pattern are eluted and diffused, and the metal is deposited so as to grow from the wiring pattern, thereby causing ion migration.

Furthermore, for example, Cl ^- or impurity ions are introduced to adhere to the wiring pattern as a residue of the etching solution and washing water at the time of forming a wiring pattern such as, also,
It may be mixed with the adhesive and introduced into the vicinity of the wiring pattern, and it has been found that the presence of such impurity ions promotes the occurrence of ion migration.

In particular, under high temperature and high humidity conditions, a large amount of moisture penetrates into the polyimide generally used for the base material and the coverlay, so that a dielectric breakdown easily occurs when the device is operated under a high voltage. it is conceivable that. Further, such dielectric breakdown is more likely to occur as the interval between the wiring patterns is smaller.

An object of the present invention is to provide a flexible printed wiring board (FPC) which is less likely to cause dielectric breakdown even when operated by applying a high voltage under a high temperature and high humidity condition, and a method of manufacturing the same.

[0016]

According to one aspect of the present invention, a base material having a pair of opposing surfaces, a wiring pattern layer located on one surface of the base material, and A single-sided FPC including a coverlay located on the wiring pattern layer, wherein an oxide film made of silicon oxide or aluminum oxide is provided on the other surface of the base material and the upper surface with respect to the base material of the coverlay. A single-sided FPC provided on at least one is provided. Alternatively, a double-sided FPC including a base material having a pair of opposing surfaces, a wiring pattern layer positioned on both surfaces of the base material, and two coverlays respectively positioned on the wiring pattern layer with respect to the base material. An oxide film made of silicon oxide or aluminum oxide is provided on at least one of the upper surfaces of the two coverlay base materials.
A PC is provided.

In this specification, "upper" with respect to the base material refers to a position vertically away from a pair of opposing surfaces with respect to the base material, and is one of the base materials. It exists for both opposing surfaces of the pair.

According to the present invention, the oxide film as described above is provided on at least one surface, preferably both surfaces, of the FPC. More specifically, in the case of the single-sided FPC, an oxide film is provided on one or preferably both of the surface side of the base material and the surface side of the coverlay. In the case of a double-sided FPC, an oxide film is provided on one of the surfaces of the two coverlays, preferably on both surfaces. Generally, an oxide film made of silicon oxide or aluminum oxide has sufficiently low hygroscopicity and thus functions as a moisture-proof film. Such an oxide film acts as a barrier,
Moisture (or water vapor) that may be present in the surrounding atmosphere can be effectively reduced from penetrating into the base material and / or coverlay, which is generally made of a material having hygroscopicity such as polyimide, It is possible to effectively reduce the occurrence of dielectric breakdown due to the intrusion of moisture around the wiring pattern. This realizes an FPC that hardly causes dielectric breakdown even when operated by applying a high voltage under a high-temperature and high-humidity condition.

As the base material, for example, a film made of polyimide, polyethylene naphthalate or polyethylene terephthalate, preferably a film made of polyimide is used. A film made of, for example, polyimide, polyethylene naphthalate, polyethylene terephthalate, or the like, preferably a film made of polyimide, is used for the cover lay, similarly to the base material. The wiring pattern layer (also simply referred to as “wiring pattern” in this specification) is made of, for example, copper, silver, aluminum, or the like, preferably copper.

In such an FPC of the present invention, oxidation
A base material having an object film and / or an oxide film
Coverlay is 5.0g / m²・ Water vapor for 24 hours or less
Having a permeability (ie, 1 m in 24 hours)²Hit
Should have a water vapor transmission rate of 5.0 g or less).
No. A base with an oxide film having such a water vapor permeability.
By providing base material and / or coverlay,
For example, temperature 85 ° C. and humidity 85%, applied voltage 500
Conducted reliability test of 1000 hours of voltage and voltage application
However, good results can be obtained. Also, this oxidation
The material film is, for example, 2.5 cc / m²・ Oxygen for 24 hours or less
Can have a permeability (ie 1 m in 24 hours) ²Hit
2.5cc (2.5cm)³) Can be
).

The oxide film in such an FPC preferably has a thickness of 500 to 1500 °, more preferably 6 to 1500 ° C.
It has a thickness of 00-1200 °. The thickness of the oxide film in such a range is measured by, for example, a fluorescent X-ray measurement method. When the oxide film thickness is smaller than 500 °, the barrier property against the water vapor is remarkably reduced, and more water vapor is transmitted, thereby effectively preventing dielectric breakdown which may occur when a high voltage is applied under high temperature and high humidity conditions. It is not preferable because it cannot be done. On the other hand, if the oxide film thickness is larger than 1500 °, sufficient barrier properties against water vapor can be secured, but productivity is undesirably reduced. Therefore, when the oxide film thickness is 50
The angle is preferably from 0 to 1500 °, more preferably from 600 to 1200 °.

On the other hand, the thickness of the coverlay and / or the base material provided with the oxide film is balanced with the thickness of the oxide film in consideration of these materials, so that the thickness of the coverlay and / or the base material can be reduced. There is no particular limitation as long as a sufficient water vapor permeability is obtained together with the oxide film. Also, the coverlay and / or base material without the oxide film may have any suitable thickness. From the viewpoint of plasticity, thermal properties, mechanical properties, and the like, the thickness of the coverlay and / or the base material is, for example, about 10 to 100 μm.
m, preferably about 12.5-75 μm.

According to another aspect of the present invention, a base material having a pair of opposing surfaces, a wiring pattern layer located on one surface of the base material, and a wiring pattern layer above the base material. And an oxide film made of silicon oxide or aluminum oxide and a plastic film located thereunder, the upper surface of which is located on the other side of the base material and the base material of the coverlay. A single-sided FPC provided with an oxide film on the base material above the plastic film on at least one of the surfaces. Alternatively, a double-sided FPC including a base material having a pair of opposing surfaces, a wiring pattern layer positioned on both surfaces of the base material, and two coverlays respectively positioned on the wiring pattern layer with respect to the base material. An oxide film made of silicon oxide or aluminum oxide and a plastic film located thereunder are provided on at least one of the upper surfaces with respect to the base materials of the two coverlays, respectively, so that the oxide film is made of a material different from the plastic film. Double-sided FPC mounted on base material
Is provided.

According to the present invention, an oxide film and a base plastic film are provided on at least one surface, preferably both surfaces, of the FPC, with the oxide film above the base material. More specifically, one-sided FP
In the case of C, an oxide film and a plastic film are provided on one of the surface side of the base material and the surface side of the cover lay, preferably both, with the oxide film on the base material. In the case of a double-sided FPC, an oxide film and a plastic film are provided on one or preferably both surfaces of the two coverlays, with the oxide film on the base material. The oxide film and the plastic film, in particular, the oxide film serves as a barrier, and the moisture that may be present in the surrounding atmosphere becomes a base material composed of a generally hygroscopic material such as polyimide and / or
Alternatively, it is possible to effectively reduce the penetration into the coverlay, so that the FP which causes almost no dielectric breakdown even when operated by applying a high voltage under a high temperature and high humidity condition
C is realized.

In this type of FPC of the present invention,
Base material, coverlay, similar to FPC of the type described above
The material of the wiring pattern layer is used. Examples of the plastic film include films made of, for example, polyimide, polyester, polypropylene, polyethylene, polycarbonate, polyamide, polyacetal, polyvinylidene chloride, polyethersulfone, polyacrylate, polymethacrylate, polyvinyl alcohol, and polystyrene. Preferably, a film made of polyethylene is used.

In the FPC of the present invention, the base material and / or the cover lay provided with the oxide film and the plastic film preferably have a water vapor permeability of 5.0 g / m ² · 24 hours or less. By providing a base material and / or a coverlay with an oxide film and a plastic film having such a water vapor permeability, for example, a reliability test at a temperature of 85 ° C. and a humidity of 85%, an applied voltage of 500 V, and a voltage applied time of 1000 hours. , Good results can be obtained. The base material and / or the coverlay with the oxide film and the plastic film are, for example, 2.5 cc.
/ ^M 2 · 24 hours may have the following oxygen permeability.

The oxide film in this type of FPC preferably has a thickness of 100 to 500.degree.
It has a thickness of 0-400 °. The thickness of the oxide film in such a range is also measured by, for example, a fluorescent X-ray measurement method. In an FPC of the type including such an oxide film and a base plastic film, unlike the above-described type of FPC of the present invention including the oxide film alone,
A plastic film is disposed between the oxide film and the base material and / or the coverlay, and although the plastic film is inferior to the oxide film but has some water vapor barrier properties, the present invention of the type described above FPC
The thickness can be made thinner than the oxide film provided on the substrate.

In the case of this type of FPC of the present invention,
When the oxide film thickness is smaller than 100 °, the barrier property against the water vapor is remarkably reduced, so that more water vapor is permeated, and short circuit and dielectric breakdown are effectively prevented when a high voltage is applied under a high temperature and high humidity condition. It is not preferable because it cannot be done. On the other hand, when the oxide film thickness is larger than 500 °, a sufficient barrier property against water vapor can be ensured, but productivity is lowered, which is not preferable. Therefore, the oxide film thickness should be 100 to
Preferably, it is 500 °, more preferably 200 °.
Å400 °.

On the other hand, the thickness of the plastic film serving as the base of the oxide film and the coverlay and / or base material provided with the oxide film and the plastic film are balanced with the oxide film thickness in consideration of these materials. There is no particular limitation as long as a sufficient water vapor permeability is obtained by combining the coverlay and / or the base material, the plastic film and the oxide film. Also, the coverlay and / or base material without the oxide film may have any suitable thickness. From the viewpoints of plasticity, thermal properties, mechanical properties, and the like, the thickness of the plastic film is, for example, about 2 to 100 μm, preferably about 5 to 50 μm.
μm, and the thickness of the coverlay and / or the base material is, for example, about 10 to 100 μm, preferably about 12.5 μm.
７５75 μm.

According to another aspect of the present invention, a base material having a pair of opposing surfaces, a wiring pattern layer located on one surface of the base material, and A method of manufacturing a single-sided FPC including a coverlay located on at least one of the other surface of the base material and the upper surface of the coverlay with respect to the base material, comprising an oxide film made of silicon oxide or aluminum oxide. A manufacturing method is provided that includes forming by a vapor deposition method. Alternatively, a double-sided FPC including a base material having a pair of opposing surfaces, a wiring pattern layer positioned on both surfaces of the base material, and two coverlays respectively positioned on the wiring pattern layer with respect to the base material. A manufacturing method is provided, which comprises forming an oxide film made of silicon oxide or aluminum oxide on at least one of the upper surfaces of two base materials of the two coverlays by a vapor deposition method. .

According to another aspect of the present invention, a base material having a pair of opposing surfaces, a wiring pattern layer located on one surface of the base material, and a wiring pattern layer above the base material. A single-sided FPC including a coverlay and a plastic film having an oxide film made of silicon oxide or aluminum oxide formed on one surface by a vapor deposition method. A manufacturing method is provided that includes providing an oxide film on at least one of the upper surfaces of the ray with respect to the base material such that the oxide film is located above the base material with respect to the plastic film. Alternatively, a double-sided FPC including a base material having a pair of opposing surfaces, a wiring pattern layer positioned on both surfaces of the base material, and two coverlays respectively positioned on the wiring pattern layer with respect to the base material. In a manufacturing method, a plastic film in which an oxide film made of silicon oxide or aluminum oxide is formed on one surface by a vapor deposition method is provided on at least one of the upper surfaces with respect to the base material of the two coverlays, A manufacturing method is provided that includes providing an oxide film on a base material above a plastic film.

According to the manufacturing method of the present invention, single-sided and double-sided FPCs of the type having the oxide film of the present invention alone and the type having the oxide film and the underlying plastic film can be manufactured. .
Examples of the evaporation method that can be used to form an oxide film in the manufacturing method of the present invention include a vacuum evaporation method, a chemical evaporation method (CVD), a sputter evaporation method, and an ion beam evaporation method.

The oxide film may be formed at any stage of the FPC manufacturing process, but is preferably formed before bonding the base material on which the wiring pattern is formed and the coverlay. More specifically, F
Preferably, a PC is manufactured.

Single-sided FP of a type provided solely with an oxide film
In the case of manufacturing C, an oxide film is formed on one surface of the coverlay by a vapor deposition method, and a coverlay having the oxide film formed on one surface and a base having a wiring pattern layer formed on one surface. The cover lay is placed such that one surface of the cover lay is higher than the other surface with respect to the base material (or the other surface of the cover lay and one surface of the base material face each other, and (So that the wiring pattern layer is located between the substrate and the base material). Alternatively, an oxide film is formed by evaporation on the other surface of the base material on which the wiring pattern layer is formed on one surface, and the coverlay and the wiring pattern layer are formed on one surface, and the oxide film is formed on the other surface. Is bonded so that the wiring pattern layer is located between the coverlay and the base material. Of course, an oxide film is formed on one surface of the coverlay by an evaporation method, and an oxide film is formed on the other surface of the base material on which the wiring pattern layer is formed on one surface by an evaporation method. A coverlay in which an object film is formed on one surface and a base material in which a wiring pattern layer is formed on one surface and an oxide film is formed on the other surface are formed on one side of the coverlay with respect to the base material. (Or the other surface of the coverlay faces one surface of the base material, and the wiring pattern layer is located between the coverlay and the base material). And so on).

A double-sided FP having a single oxide film
When manufacturing C, an oxide film is formed on at least one side of at least one of the two coverlays by a vapor deposition method, and the two coverlays and the base material having the wiring pattern layer formed on both sides are formed into two coverlays. The wiring pattern layers are located between the lay and the base material, respectively, so that one surface of the at least one cover lay on which the oxide film is formed is positioned higher than the opposite surface with respect to the base material. Glue.

In the case of manufacturing a single-sided FPC having an oxide film and a base plastic film, an oxide film is formed on one surface of the plastic film by a vapor deposition method, and the oxide film is formed on one surface. Pressed the other side of the plastic film to one side of the coverlay,
The coverlay in which the plastic film is pressed on one surface and the base material in which the wiring pattern layer is formed on one surface are positioned such that one surface of the coverlay is higher than the other surface with respect to the base material. (Or so that the other surface of the coverlay and one surface of the base material face each other and the wiring pattern layer is located between the coverlay and the base material)
Glue. Alternatively, an oxide film is formed on one surface of a plastic film by an evaporation method, and the other surface of the plastic film having the oxide film formed on one surface is connected to a base on which a wiring pattern layer is formed on one surface. The coverlay and the base material with the wiring pattern layer formed on one surface and the plastic film pressed on the other surface are pressed between the coverlay and the base material. Glue so that the layers are in place. Of course, an oxide film is formed on one surface of each of the two plastic films by a vapor deposition method, and the other surface of the one plastic film is replaced with the other surface of the base material on which the wiring pattern layer is formed on one surface. And the other surface of the other plastic film is pressed against the other surface of the base material on which the wiring pattern layer is formed on one surface, and the plastic film is pressed against one surface. And a base material in which a wiring pattern layer is formed on one surface and a plastic film is pressed against the other surface, such that one surface of the coverlay is positioned above the base material with respect to the other surface. (Or the other side of the coverlay and the one side of the base material face each other, and the wiring pattern layer may be positioned between the coverlay and the base material).

In the case of manufacturing a double-sided FPC of a type including an oxide film and a base plastic film, an oxide film is formed on one surface of the plastic film by a vapor deposition method, and the oxide film is formed on one surface. The other surface of the applied plastic film is pressed on at least one surface of at least one of the two coverlays, and the two coverlays on which the plastic film is pressed on at least one surface and a wiring pattern layer are formed on one surface. A base material, a wiring pattern layer is positioned between each of the two coverlays and the base material, and at least one of the coverlays, on which one surface on which the oxide film and the plastic film are arranged, is smaller than the surface on the opposite side; Glue so as to be located on the upper side with respect to the base material.

The base material and / or the above-mentioned single-sided or double-sided FPC manufacturing method of a type provided solely with an oxide film
Alternatively, the step of forming an oxide film on a coverlay and the step of forming an oxide film on a plastic film in the above-described single-sided or double-sided FPC manufacturing method of the type including an oxide film and a base plastic film are both performed. It can be performed in a substantially equivalent manner using a vapor deposition method.

According to these manufacturing methods, an oxide film provided in advance on a base material and / or a coverlay is used instead of a conventional base material and / or coverlay, or The FPC of the present invention can be manufactured simply by using a plastic film with a film provided in advance on a base material and / or a coverlay in place of a conventional base material and / or coverlay, thereby facilitating manufacture. There is an advantage.

However, the method of manufacturing an FPC of the present invention is not limited to this. For example, a conventional (single-sided or double-sided) is obtained by bonding a base material on which a wiring pattern is formed and a coverlay (one or two). After forming a structure having the same structure as that of the FPC, an oxide film is formed on at least one surface of the structure by an evaporation method, or an oxide film formed on a plastic film by an evaporation method is converted into an oxide film. Can be pressed to at least one surface of the structure to complete the FPC.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Two embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 below
And 2 each relate to the structure of a double-sided two-layer flexible printed wiring board (FPC) and a method of manufacturing the same, but the present invention is not limited thereto.

(Embodiment 1) F of the present embodiment shown in FIG.
The PC 10 includes a base material 1, wiring pattern layers 2 a and 2 b formed on both surfaces of the base material 1, and a cover lay 4 a arranged to cover the wiring pattern layers 2 a and 2 b via adhesive layers 3 a and 3 b. And 4b. Further, the FPC 10 includes the oxide film 5a on the surface outside the cover lay 4a with respect to the wiring pattern 2a, and includes the oxide film 5a on the surface outside the cover lay 4b with respect to the wiring pattern 2b. These oxide films 5a and 5b
Are located above the base material 1, and the FPC1
0 on a pair of surfaces.

The oxide films 5a and 5b are made of silicon oxide or aluminum oxide, and
It has a thickness of １1500 °, more preferably about 600-1200 °. The base material 1 and the coverlays 4a and 4b can be, for example, a polyimide film having a thickness of about 25 to 50 μm. The wiring pattern layers 2a and 2b are made of, for example, copper or the like, and may have a thickness of about 8-36 μm. The adhesive layers 3a and 3b are made of, for example, epoxy resin or acrylic resin, and
It may have a thickness of 0 μm. In FIG. 1, the thicknesses of the oxide films 5a and 5b are enlarged for easy viewing. Further, the wiring pattern layers 2a and 2b have any appropriate patterns, and may have different patterns from each other.

Next, a method of manufacturing the FPC 10 of the present embodiment will be described.

First, the coverlay 4a with the oxide film 5a
And, as the cover lay 4b with the oxide film 5b, the cover lays 6a and 6b with the oxide film are produced. For example, using a plastic film such as a roll-shaped polyimide film that becomes the coverlays 4a and 4b, the plastic film is unwound from the unwind roll in a vacuum chamber, and is wound on a take-up roll through a cooling drum. On the other hand, silica or aluminum is used as a vapor deposition source, and is melted and vapor-deposited by a vacuum vapor deposition method (or a chemical vapor deposition method) while supplying oxygen gas when the plastic film passes over a cooling drum. An oxide film made of silicon oxide or aluminum oxide can be formed on the plastic film. By cutting the obtained product to an appropriate size, a coverlay 6 with an oxide film can be formed.
a and 6b are produced. The resulting cover lays 6a and 6b with an oxide film (the cover lay 4a with an oxide film 5a and the cover lay 4b with an oxide film 5b)
5.0g ^{/ m} 2 · 24 hours or less of water vapor permeability of may have respectively.

At this time, the oxygen gas may be supplied onto the plastic film in a state where plasma is generated by discharging the oxygen gas by direct current, alternating current, high frequency, microwave or the like. In this case, the oxygen gas is more activated and the reaction efficiency between aluminum and oxygen is improved, so that
Evaporated films (oxide films) 5a and 5b made of denser and higher quality silicon oxide or aluminum oxide are easily formed, so that an oxide film having a smaller thickness and a lower water vapor permeability can be obtained. In this case, only oxygen gas may be supplied, or oxygen gas and argon gas may be mixed and supplied. When oxygen gas is supplied by mixing argon gas, stronger plasma is generated and oxygen gas is more activated than when only oxygen gas is supplied, so a more dense and high-quality deposited film made of silicon oxide or aluminum oxide. (Oxide film) 5a and 5b can be easily formed, and an oxide film having a smaller thickness and a lower water vapor permeability can be obtained. However, if the mixing ratio of the argon gas is too high, the aluminum oxide or the silicon oxide reaches the plastic film incompletely and reduces the degree of vacuum in the vacuum chamber. Is preferably adjusted appropriately.

On the other hand, using a general double-sided two-layer flexible copper-clad laminate having copper foil on both sides of a base material made of, for example, polyimide, the copper foil is etched or laser-processed to form copper on both surfaces of the base material 1. Wiring pattern layer 2
a and 2b are formed. The double-sided two-layer flexible copper-clad laminate may be produced by any method such as a sputtering method, a plating method, and a casting method.

The surfaces of the coverlays 6a and 6b with the oxide film formed as described above on the side where the coverlays are exposed (that is, the surface opposite to the surface on which the oxide films 5a and 5b are formed) An adhesive such as an epoxy resin or an acrylic resin is applied to the base material 1 and an oxide film is provided via the adhesive layers 3a and 3b so as to cover the wiring pattern layers 2a and 2b formed on both surfaces of the base material 1. The coverlays 6a and 6b are bonded by, for example, thermocompression bonding. Thus, the FPC 10 shown in FIG. 1 is manufactured.

According to the present invention, the cover lay 4a with the oxide film 5a and the cover lay 4b with the oxide film 5b can each have a water vapor permeability of 5.0 g / m ² · 24 hours or less. For this reason, the flexible printed wiring board 1
It is possible to effectively prevent the moisture existing in the atmosphere around 0 from passing through the coverlays 4a and 4b and being located around the wiring patterns 2a and 2b. Therefore, the occurrence of dielectric breakdown due to the presence of moisture around the wiring pattern can be reduced. This realizes an FPC that hardly causes dielectric breakdown even when operated by applying a high voltage under a high-temperature and high-humidity condition. FP of the present embodiment
C is, for example, a temperature of 85 ° C. and a humidity of 85%, and an applied voltage of 5%.
Good results can be obtained even when a reliability test is performed with a voltage of 00 V and a voltage application time of 1000 hours.

Further, according to the present embodiment, a coverlay with an oxide film is prepared in advance and used instead of a conventional coverlay, without using a complicated process and utilizing existing equipment. Therefore, there is an advantage that the FPC can be easily manufactured.

In this embodiment, the double-sided two-layer FP
Although the one having the oxide film on both sides of C has been described,
F having an oxide film on only one surface of a double-sided two-layer FPC
You can also get a PC. Further, a double-sided three-layer FPC can also be obtained by using a double-sided three-layer flexible laminate instead of the double-sided two-layer flexible copper-clad laminate. Alternatively, by using a single-sided two-layer or three-layer flexible copper-clad laminate instead of the double-sided two-layer flexible copper-clad laminate, the surface on the coverlay side of the single-sided two-layer or three-layer FPC and / or the surface on the base material side Single-sided two-layer or three-layer F provided with an oxide film
You can also get a PC.

(Embodiment 2) F of this embodiment shown in FIG.
The PC 20 is different from the FPC 10 of the first embodiment shown in FIG. 1 in that the plastic films 14a and 14b and the oxide films 15a and 15b are used instead of the oxide films 5a and 5b.
b. In FIG. 2, the same members as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

In this embodiment, the oxide films 15a and 15b and the plastic films 14a and 14a
4b constitutes the plastic films 16a and 16b with an oxide film. Oxide films 15a and 15b are made of silicon oxide or aluminum oxide, preferably about 100-500 °, more preferably about 200-40 °.
It has a thickness of 0 °. As the plastic films 14a and 14b, for example, a polyimide film having a thickness of about 25 to 50 μm is used.

Plastic film 16a with oxide film
And 16b can be manufactured by the same method as the cover lays 6a and 6b with the oxide film of the first embodiment. Such a plastic film 16 with an oxide film
a and 16b are bonded to the coverlays 4a and 4b by, for example, thermocompression bonding. The resulting coverlays 6a and 6b on which the plastic films 16a and 16b with the oxide film (the plastic film 14a with the oxide film 15a and the plastic film 14b with the oxide film 15b) are respectively provided are 5.0 g / m ^2. Can each have a water vapor transmission rate of 24 hours or less.

The coverlays of the coverlays 4a and 4b provided with the plastic films 16a and 16b with the oxide films obtained in this manner have epoxy resin or acrylic resin or the like on the exposed side of the coverlays. An adhesive is applied, and the base material 1 is applied in the same manner as in the first embodiment.
Cover lays 6a and 6b with an oxide film are adhered by, for example, thermocompression bonding via adhesive layers 3a and 3b so as to cover wiring pattern layers 2a and 2b formed on both surfaces of the substrate. Thus, the FPC 20 shown in FIG. 2 is manufactured.

According to the present invention, the cover lay 4a provided with the plastic film 16a with the oxide film and the cover lay 4b provided with the plastic film 16b with the oxide film have a water vapor transmission of 5.0 g / m ² · 24 hours or less. Each may have a degree. For this reason, it is possible to effectively prevent moisture existing in the atmosphere around the FPC 10 from passing through the coverlays 4a and 4b and being located around the wiring patterns 2a and 2b. Therefore, it is possible to reduce the occurrence of short circuit and dielectric breakdown caused by the presence of moisture around the wiring pattern. This realizes an FPC that hardly causes dielectric breakdown even when operated by applying a high voltage under a high-temperature and high-humidity condition. The FPC of the present embodiment is:
For example, temperature 85 ° C. and humidity 85%, applied voltage 500
Good results can be obtained even when a reliability test is performed with a voltage and voltage application time of 1000 hours.

Further, according to this embodiment, a plastic film with an oxide film provided on a base material and / or a cover lay is prepared in advance, and is used instead of the conventional base material and / or cover lay. There is an advantage that an FPC can be easily manufactured using existing equipment without requiring a complicated process.

In this embodiment, the double-sided two-layer FP
C has been described in which a plastic film with an oxide film is provided on both surfaces, but an FP having a plastic film with an oxide film on only one surface of a double-sided two-layer FPC is described.
C can also be obtained. Further, a double-sided three-layer FPC can also be obtained by using a double-sided three-layer flexible laminate instead of the double-sided two-layer flexible copper-clad laminate. Alternatively, by using a single-sided two-layer or three-layer flexible copper-clad laminate instead of the double-sided two-layer flexible copper-clad laminate, the surface on the coverlay side of the single-sided two-layer or three-layer FPC and / or the surface on the base material side A single-sided two-layer or three-layer FPC including a plastic film with an oxide film can also be obtained.

[0059]

EXAMPLES In the following examples, silicon oxide films having different thicknesses were formed on a plastic film by vacuum deposition, and the water vapor permeability and oxygen permeability of each sample were examined. In addition, each physical property value was measured by the following measurement conditions (standard) and apparatus. 1. 1. Water vapor permeability Standard: JIS K 7129 (Method A) 40 ° C x 90% Equipment: WATER VAPOR PERMEATION TESTER L80-4000J (manufactured by Lissi, Switzerland) 2. Oxygen permeability Standard: JIS K 7126 (Method B) 23 ° C. × 70% Apparatus: MOCON OX-TRAN (made by Modern Controls, USA) Film thickness X-ray fluorescence analyzer: Model 3370 (manufactured by Rigaku Corporation)

(Example 1) First, two kinds of polyimide films (Kapton (trademark) and Apical (trademark)) each having a thickness of about 25 μm were formed on a silicon oxide film having different thicknesses using silica as a vapor deposition source. (Oxide film or vapor-deposited film) was formed by vacuum vapor deposition. The thickness (hereinafter, also simply referred to as the film thickness), the water vapor permeability and the oxygen permeability of the oxide film of the obtained sample were measured. For comparison, the water vapor transmission rate and the oxygen transmission rate were also measured for a sample without a silicon oxide film (ie, a sample containing only a polyimide film). Table 1 shows the results.

[0061]

[Table 1]

As shown in Table 1, samples A2 and B2 on which an oxide film (silicon oxide film) having a thickness of about 600 ° were formed, and oxide films (silicon oxide film) having a thickness of about 1200 ° were formed. 4. Samples A3 and B3 have significantly lower water vapor permeability and oxygen permeability than Samples A1 and B1 in which no oxide film was formed.
The 0g ^{/ m} 2 · 24 hours or less of water vapor permeability had.

Next, using these samples A2, A3, B2 and B3 as coverlays,
An FPC having a configuration similar to that of was manufactured. These FPCs
About 85 ° C. and 85% humidity, applied voltage 50
When a reliability test was performed at 0 V and a voltage application time of 1000 hours, no abnormality was observed, and no dielectric breakdown occurred.

(Example 2) As in Example 1, silica was used as a vapor deposition source, and a silicon oxide film (oxide film or vapor-deposited film) having a different thickness was formed on one side of polyethylene terephthalate (plastic film) having a thickness of about 12 μm. A film) was formed by vacuum evaporation, and two types of polyimide films having a thickness of about 25 μm were thermocompression-bonded (so-called dry lamination) on the side opposite to the silicon oxide film of polyethylene terephthalate. The thickness, water vapor permeability and oxygen permeability of the oxide film of the obtained sample were measured. Table 2 shows the results. For comparison, polyethylene terephthalate with a silicon oxide film was not subjected to thermocompression bonding (that is, a sample containing only a polyimide film,
Table 2 also shows the water vapor transmission rate and oxygen transmission rate of the same samples A1 and B1).

[0065]

[Table 2]

As shown in Table 2, samples A2 and B2 on which an oxide film (silicon oxide film) having a thickness of about 600 ° were formed, and oxide films (silicon oxide film) having a thickness of about 1200 ° were formed. 4. Samples A3 and B3 have significantly lower water vapor permeability and oxygen permeability than Samples A1 and B1 in which no oxide film was formed.
The 0g ^{/ m} 2 · 24 hours or less of water vapor permeability had.

Next, using these samples A4 and B4 as a coverlay, an FPC having a configuration similar to that of the second embodiment was manufactured. When a reliability test was performed on these FPCs at a temperature of 85 ° C. and a humidity of 85%, an applied voltage of 500 V, and a voltage application time of 1000 hours, no abnormality was observed and no dielectric breakdown occurred.

[0068]

According to the present invention, an oxide film or a plastic film with an oxide film is provided on a base material and / or a coverlay of a flexible printed wiring board to apply a high voltage under high temperature and high humidity conditions. Provided is a flexible printed wiring board that is less likely to cause dielectric breakdown even when operated in a non-operational manner, and a method for manufacturing the same.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a double-sided two-layer flexible printed wiring board according to one embodiment of the present invention.

FIG. 2 shows a double-sided surface 2 according to another embodiment of the present invention.
It is a schematic sectional drawing of a layer flexible printed wiring board.

FIG. 3 is a schematic sectional view of a conventional double-sided two-layer flexible printed wiring board.

[Explanation of symbols]

1, 61 base material 2a, 2b, 62a, 62b, wiring pattern layer 3a, 3b, 63a, 63b adhesive layer 4a, 4b, 64a, 64b coverlay 5a, 5b oxide film 6a, 6b coverlay with oxide film 14a, 14b Plastic film 15a, 15b Oxide film 16a, 16b Plastic film with oxide film 10, 20, 60 Flexible printed wiring board (FP
C)

Claims (18)

[Claims] A base material having a pair of opposing surfaces;
A flexible printed wiring board including a wiring pattern layer located on one surface of a base material and a coverlay located on the wiring pattern layer with respect to the base material, wherein the oxide film is made of silicon oxide or aluminum oxide Is provided on at least one of the other surface of the base material and the upper surface of the coverlay with respect to the base material. 2. A base material having a pair of opposing surfaces;
A flexible printed wiring board including a wiring pattern layer located on both surfaces of a base material, and two coverlays respectively located on the wiring pattern layer with respect to the base material,
A flexible printed wiring board wherein an oxide film made of silicon oxide or aluminum oxide is provided on at least one of the upper surfaces of the two coverlay base materials. 3. The flexible printed wiring according to claim 1, wherein the base material provided with the oxide film or the coverlay provided with the oxide film has a water vapor permeability of 5.0 g / m ² · 24 hours or less. Board. 4. The flexible printed wiring board according to claim 1, wherein the oxide film has a thickness of 500 to 1500 °. 5. A base material having a pair of opposing surfaces;
A flexible printed wiring board including a wiring pattern layer located on one surface of a base material and a coverlay located on the wiring pattern layer with respect to the base material, wherein the oxide film is made of silicon oxide or aluminum oxide And a plastic film located thereunder has an oxide film on at least one of the other surface of the base material and the upper surface of the coverlay with respect to the base material, with the oxide film being higher than the plastic film with respect to the base material. Flexible printed wiring boards. 6. A base material having a pair of opposing surfaces;
A flexible printed wiring board including a wiring pattern layer located on both surfaces of a base material, and two coverlays respectively located on the wiring pattern layer with respect to the base material,
An oxide film made of silicon oxide or aluminum oxide and a plastic film thereunder are provided on at least one of the upper surfaces with respect to the base material of the two coverlays, and the oxide film is formed on the base material rather than the plastic film. A flexible printed wiring board that is provided on the top. 7. An oxide film and a plastic film
Base material, or oxide film and plastic foil
Coverlay with film is 5.0g / m ²・ 24:00
7. The method according to claim 5, which has a water vapor permeability of less than or equal to.
Flexible printed wiring board. 8. The flexible printed wiring board according to claim 5, wherein the oxide film has a thickness of 100 to 500 °. 9. A base material having a pair of opposing surfaces;
A method of manufacturing a flexible printed wiring board including a wiring pattern layer located on one surface of a base material and a coverlay located on the wiring pattern layer with respect to the base material, the other surface of the base material and A manufacturing method comprising forming an oxide film made of silicon oxide or aluminum oxide on at least one of the upper surfaces of a coverlay base material by a vapor deposition method. 10. An oxide film made of silicon oxide or aluminum oxide is formed on one surface of a coverlay by a vapor deposition method, and the coverlay having the oxide film formed on one surface and the wiring pattern layer are formed on one surface. The manufacturing method according to claim 9, further comprising: bonding the base material formed on the surface to the base material such that one surface of the coverlay is located above the other surface. 11. An oxide film made of silicon oxide or aluminum oxide is formed by vapor deposition on the other surface of a base material on which a wiring pattern layer is formed on one surface, and the coverlay and the wiring pattern layer are formed on one side. 11. The method according to claim 9, further comprising: bonding a base material formed on one surface and having an oxide film formed on the other surface such that a wiring pattern layer is located between the coverlay and the base material. The manufacturing method as described. 12. A base material having a pair of opposing surfaces, a wiring pattern layer located on both sides of the base material, and two coverlays respectively located on the wiring pattern layer with respect to the base material. A method for manufacturing a flexible printed wiring board, comprising forming an oxide film made of silicon oxide or aluminum oxide on at least one of upper surfaces of two base materials of two coverlays by a vapor deposition method. Method. 13. An oxide film made of silicon oxide or aluminum oxide is formed on at least one side of at least one of the two coverlays by a vapor deposition method.
A base material having a wiring pattern layer formed on both sides thereof, a wiring pattern layer being positioned between two coverlays and the base material, and at least one coverlay having an oxide film formed thereon is a base material. The method according to claim 12, further comprising: bonding to a position above the other surface. 14. A base material having a pair of opposing surfaces, a wiring pattern layer located on one surface of the base material,
A method of manufacturing a flexible printed wiring board including a coverlay positioned on a wiring pattern layer with respect to a base material, wherein an oxide film made of silicon oxide or aluminum oxide is formed on one surface by vapor deposition. The method includes providing a plastic film on at least one of the other surface of the base material and the upper surface of the cover lay with respect to the base material such that the oxide film is located above the plastic film with respect to the base material. Production method. 15. An oxide film made of silicon oxide or aluminum oxide is formed on one surface of a plastic film by a vapor deposition method, and the other surface of the plastic film having the oxide film formed on one surface is used as a coverlay. A coverlay that has been pressed to one side and a plastic film has been pressed to one side, and a base material that has a wiring pattern layer formed on one side. The method according to claim 14, further comprising bonding the material to an upper position. 16. An oxide film made of silicon oxide or aluminum oxide is formed on one surface of a plastic film by a vapor deposition method, and the other surface of the plastic film having the oxide film formed on one surface is connected to a wiring pattern. A cover lay and a base material in which a wiring pattern layer is formed on one surface and a plastic film is pressed on the other surface, and the cover material is pressed against the other surface of the base material having the layer formed on one surface. 15. The method according to claim 14, further comprising bonding the wiring pattern layer between the lay and the base material.
5. The production method according to 5. 17. A base material having a pair of opposing surfaces, a wiring pattern layer located on both sides of the base material, and two coverlays respectively located on the wiring pattern layer with respect to the base material. A method for manufacturing a flexible printed wiring board, wherein a plastic film having an oxide film made of silicon oxide or aluminum oxide formed on one surface by a vapor deposition method is provided on each of upper surfaces with respect to two coverlay base materials. A manufacturing method including providing an oxide film on at least one of the base material and the base material above the plastic film. 18. An oxide film made of silicon oxide or aluminum oxide is formed on one surface of a plastic film by a vapor deposition method, and the other surface of the plastic film having the oxide film formed on one surface is covered with two covers. Two cover lays in which a plastic film is pressed in at least one side of at least one side of the lay, and a base material in which a wiring pattern layer is formed on one side, and a cover lay and a base material. The method according to claim 17, further comprising bonding the wiring pattern layer so as to be positioned therebetween.