JPH06338663A - Rigid-flex printed wiring board and its manufacture - Google Patents

Abstract

PURPOSE:To enable uniform and stable through hole plating, by forming a protective layer of a flexible printed wiring board by using an organic insulating layer which is cured by light and/or heat and has flexibility after curing. CONSTITUTION:A flexible part 3 wherein a flexible printed wiring board is covered with a protective layer 6A, and rigid parts 1, 2 composed of rigid printed wiring boards 8 are made in a unified body, to constitute a rigid-flex printed wiring board. A base film 4 composed of polyimide resin or polyester resin or the like is formed as an insulating layer. The protective layer 6A covering a flexible copper clad laminate wherein copper foils are stuck on both surfaces of the film 4 is formed by using an organic insulating layer which is cured by light and/or heat and maintains flexibility, also after curing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rigid flex printed wiring board in which a flexible printed wiring board and a rigid printed wiring board are integrated and a method for manufacturing the same.

[0002]

2. Description of the Related Art A foldable flexible print in which a circuit is formed by adhering a metal conductor such as copper foil to a base film made of polyimide resin or polyester resin, and a cover film made of polyimide or polyester is adhered to this as a protective layer. Wiring boards are known. Also known is a rigid printed wiring board in which a circuit is formed on a laminate obtained by stacking a prepreg, which is a sheet impregnated with a resin, on a base material such as glass cloth or paper and subjecting it to heat and pressure. Further, a rigid flex printed wiring board in which these are integrated to form a flexible portion and a rigid portion is also known.

FIG. 2 is a sectional view of a conventional rigid flex printed wiring board. As shown here, rigid portions 1 and 2 and a flexible portion 3 connecting them are continuously formed. It is an integrated one. As shown in FIG. 2, the flexible portion 3 includes a base film 4 of a flexible printed wiring board, a metal conductor 5 such as a copper foil having excellent flexibility attached to both sides of the base film 4, and insulation for covering the metal conductor 5. The cover film 6B as a material is sequentially laminated, and the adhesive layer 6C is interposed between the cover film 6B and the metal conductor 5. The base film 4 is usually made of a resin such as a polyimide film or a polyester film. A circuit pattern is formed on the metal conductor 5, and a conductive through hole may be formed through the base film 4. The cover film 6B is usually a base film 4 such as polyimide or polyester.
An insulating film made of the same material as above is used, and this is adhered by an adhesive layer 6C coated with an acrylic adhesive or the like.

The rigid portions 1 and 2 are formed by laminating a rigid printed wiring board 8 on a portion having the same structure as the flexible portion 3 with a prepreg 7 interposed. That is, the cross-sectional structure of the flexible portion 3 extends not only to the flexible portion 3 but also to the rigid portions 1 and 2 as shown in FIG. 2, and the prepreg 7 and the rigid printed wiring board 8 are laminated on the cover film 6B in these rigid portions 1 and 2. It was done. Here, the prepreg 7 is a semi-cured state obtained by impregnating a base material such as glass cloth or paper with a resin such as epoxy or polyimide and drying it. Reference numeral 9 in FIG. 2 denotes a circuit pattern formed on the rigid printed wiring board 8.

In the conventional rigid flex printed wiring board having such a structure, when forming the through hole 10, there is a problem that the throwing around of the through hole plating is not stable and the product yield is deteriorated. That is, the formation of the through hole 10 is performed with the rigid portions 1, 2
A through hole is formed by drilling in the through hole, the through hole is subjected to chemical copper plating, and then electrolytic copper plating is performed. The adhesive layer 6C of the cover film 6B is usually made of an acrylic material or the like. Adhesives are used, but this is caused by the chemical desmear treatment such as permanganate or the like, which is deteriorated by the plating treatment liquid, and the phenomenon that the end face recedes from the through-hole holes or elutes into the through-hole holes. Inhibits throwing power. As described above, in the conventional rigid flex printed wiring board, the throwing power of the plating is reduced due to the influence of the adhesive layer used in the cover film, the thickness of the through-hole plating becomes uneven, and the circuit connection reliability is reduced. However, there is a problem that the product yield is deteriorated. Further, as a means for solving such a problem, when an epoxy resin-based adhesive having resistance to a treatment liquid such as permanganate is used, a usual epoxy resin-based adhesive is poor in flexibility in its cured state. When the flexible portion is bent, there is a problem that the bending of the base film 4 cannot be followed and the adhesive layer 6C is cracked.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made as a result of studies in view of the above problems, and enables uniform and stable through-hole plating. An object of the present invention is to provide a rigid flex printed wiring board having improved reliability and improved product yield, and a manufacturing method thereof.

[0007]

According to the present invention, an object of the present invention is to provide a rigid flex printed wiring in which a flexible portion in which a flexible printed wiring board is covered with a protective layer and a rigid portion made of a rigid printed wiring board are integrated. In the board, the protective layer of the flexible printed wiring board,
A rigid flex printed wiring board, characterized by being cured by light and / or heat, and formed by an organic insulating layer having flexibility even after curing, and
In a method for manufacturing a rigid flex printed wiring board, which is a flexible printed wiring board covered with a protective layer and a rigid portion made of a rigid printed wiring board, a circuit is formed on a flexible copper clad laminate to form a flexible print. A step of processing a wiring board, and an organic resin that is cured by light and / or heat and has flexibility even after curing is applied to both surfaces of the flexible printed wiring board, and then the organic resin is exposed by light and / or heat. A step of manufacturing a flexible part by curing an organic insulating layer having flexibility on both sides of a flexible printed wiring board, and forming a circuit on a rigid copper clad laminate to process the rigid wiring board into a rigid part The process and the flexible part and the rigid part are integrated by using a prepreg. It is achieved by a process for preparing rigid-flex printed circuit board comprising the steps of.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of an embodiment of a rigid flex printed wiring board according to the present invention, FIG. 2 is a sectional view of a conventional rigid flex printed wiring board, and FIGS.
FIG. 8 shows a processing state in each step included in the manufacturing method of the present invention, (A) is a plan view and (B) is a sectional view. 1, 2 is a rigid part, 3 is a flexible part, 4 is a flexible core material obtained by curing a prepreg obtained by impregnating a base film or a base material such as glass cloth or paper with a resin, 5 is a metal conductor, 6A is a protective layer made of an organic insulating material having flexibility, 6B is a cover film, and 6C.
Is an adhesive layer, 7 is a prepreg, 8 is a rigid printed wiring board, 9 is a circuit pattern, 10 is a through hole, 11 is a light source such as an ultraviolet lamp or a heat source such as a heater, and 12 is a metal foil before circuit formation.

The flexible copper clad laminate used in the present invention has a base film such as a polyimide resin or a polyester resin as an insulating layer, and a copper foil adhered on both sides thereof, or a base material such as glass cloth or paper. A prepreg impregnated with a resin is used as an insulating layer, copper foil is applied to both surfaces of the prepreg, and heat and pressure molding is performed. As a specific example of a flexible copper clad laminate using a polyimide resin as a base film, MT-Neoflex (manufactured by Mitsui Toatsu Chemicals),
There are Chisso flex (made by Chisso), Espanex (made by Nippon Steel Chemical), Etcher flex (made by Southwall), etc. An example of a flexible copper-clad laminate using a polyester resin as a base film is Nikaflex (manufactured by Nikkan Kogyo). Further, as the prepreg type flexible copper clad laminate, there are Turnflex (manufactured by Matsushita Electric Works) and Greenflex (manufactured by Shin-Kobe Electric Machinery) based on epoxy resin. The thickness of the insulating layer of the flexible copper-clad laminate used in the present invention is 10 to 10
In general, the thickness of the copper foil is 0 μ, the upper limit is 70 μ, and the lower limit is not specified. As the type of copper foil, there are rolled copper foil, electrolytic copper foil, copper thin film by sputtering method, etc. There is also a method of pattern plating directly on the base film by an additive method, and therefore there is no particular lower limit to the copper foil thickness. Polyimide resin-based flexible copper-clad laminates are excellent in solder heat resistance but expensive, and polyester resin-based copper-clad laminates are low in price but poor in solder heat resistance. On the other hand, the prepreg type flexible copper clad laminate has solder heat resistance and is cheaper than the polyimide resin base, and is preferably used.

The flexible copper clad laminate used in the present invention has the structure shown in FIGS. 3A and 3B. In the present invention, the flexible printed wiring board is formed through the flexible copper clad laminate by a drilling process, a through-hole plating process, a dry film, an etching resist forming process using a liquid resist, and an etching process. The example is shown in FIGS. 4 (A) and 4 (B). For flexible printed wiring boards, a method of forming an ultra-thin copper foil film on an insulating layer by a sputtering method, forming a plating resist on a laminated board, performing pattern plating, peeling the resist, and removing unnecessary copper foil. There is also a method of forming a plating resist for plating on the insulating layer and forming a pattern by electroless plating.

In the present invention, the protective layer covering the flexible copper clad laminate is formed of an organic insulating layer which is cured by light and / or heat and has flexibility even after curing. Considering the resistance to the permanganate treatment liquid, the solder heat resistance, etc., the epoxy resin is most preferable as the base resin constituting the organic insulating layer. This epoxy resin has a photosensitive group that can be crosslinked by reacting with light energy, such as acryloyl group, vinyl group, cinnamoyl group, diazo group, azide group, etc. The protective layer is formed by coating the surface of the printed wiring board and irradiating it with a predetermined amount of light such as ultraviolet rays to cure it. Alternatively, a resin composition in which an amino compound, an acid anhydride, a phenol compound or the like is mixed with an epoxy resin as a curing agent is applied to the surface of a flexible printed wiring board and cured by heating to form a protective layer. It is also possible to use light curing and heat curing together. The insulating material forming these protective layers is in a liquid state before coating and is applied to the surface of the flexible printed wiring board by a screen printing method, a roll coater method, a curtain coater method or the like. Further, these cured protective layers need to have flexibility in order to follow the flexibility of the flexible portion. The term "flexibility" as used herein means that the number of reciprocal bends before breaking is 10 with the MIT tester specified in JIS P8115.
It is more than once, preferably more than 30 times. Examples of such an insulating material include a photo-curing type USR-11 (manufactured by Tamura Corporation), a Pana Sealer CV7000 (manufactured by Matsushita Electric Works), an NPR-80 (manufactured by Nippon Polytec) as an ultraviolet curable type, and an SR as a thermosetting type. -29G
(Manufactured by Tamura Corporation), Pana Sealer CV5303 (manufactured by Matsushita Electric Works, Ltd.), NPR-5 (manufactured by Nippon Polytec), and the like, but are not particularly limited thereto.

In the present invention, an example in which the protective layer is formed on a flexible printed wiring board is shown in FIGS. 5 (A) and 5 (B). The thickness of the protective layer depends on the thickness of the circuit copper foil of the flexible printed wiring board, but it is 20 to 100 μm.
Is common. However, although it is not particularly limited because it depends on the method of applying a liquid insulating material, the method of drying / curing, and the thickness of the copper foil, it is generally necessary to secure 5 μ in the thinnest portion. In the present invention, a rigid printed wiring board is a glass cloth base epoxy resin. Using a dry film, liquid resist, etc. for a copper clad laminate made of glass cloth base material polyimide resin, paper base phenol resin, glass cloth / glass non-woven composite base material epoxy resin, glass cloth / paper composite base material epoxy resin, etc. It is formed by a step of forming an etching resist, a step of forming a circuit by etching, and the like. The thickness of the insulating layer of the copper clad laminate is 0.04 ~
The thickness of the copper foil is generally 1.6 mm, and the thickness of the copper foil is generally 9 to 70 μm. An example of the rigid printed wiring board processed in this way is as shown in FIGS. 6 (A) and 6 (B).

The prepreg used in the present invention is a glass cloth impregnated with an epoxy resin, a polyimide resin or the like, and the glass cloth generally has a thickness of 0.03 to 0.3 mm. 40 to 75% by weight is common, and the thickness of the prepreg after resin impregnation is 0.04.
~ 0.4 mm is typical. One or two or more prepregs are used between layers. In the present invention, the outer shape of the prepreg is processed using a mold, an NC router, or the like. The portion removed by the outer shape processing corresponds to the portion where the flexible portion is exposed in the final rigid flex printed wiring board. In the present invention, an example in which the outer shape of the prepreg is processed is as shown in FIGS. 7 (A) and 7 (B).

In the present invention, the flexible portion and the rigid portion are
When using a prepreg for integration, a pin, an eyelet, or the like is used to accurately maintain the positional relationship between the materials, and a hydropress, an autoclave press, or the like is used for thermocompression molding.
If necessary, use paper and synthetic resin cushion material,
Since the molding conditions depend on the type of prepreg used, the cushion structure, the number of layers in one step, the pressing method, etc., it cannot be said in any way, but the pressure is generally 6 to 60 kg / cm ² , and the temperature is generally 160 to 260 ° C. is there. In the present invention, an example in which the rigid portion and the flexible portion are integrated by using a prepreg is shown in FIGS. 8 (A) and 8 (B).

[0015]

【Example】

Embodiment 1 FIG. 1 is a sectional view of an embodiment of the present invention. In FIG. 1, as the flexible copper-clad laminate, MT-Neoflex (manufactured by Mitsui Toatsu Chemical) using a polyimide resin base film was used. As the protective layer, UV-curable photocoat USR-11 (manufactured by Tamura Corporation) was used. Specifically, a double-sided copper clad laminate of MT-Neoflex (insulating layer thickness: 25 μ, copper foil: 18 μ rolled copper foil) is drilled, and copper plating of approximately 15 μ is performed.
An etching resist was formed using a dry film, and a circuit was formed by etching. On the flexible printed wiring board on which this circuit is formed, the above-mentioned photo coat USR-11
Was coated with a roll coater to a thickness of 30 μm, and a high pressure mercury lamp (80 W / cm, 3 lamps) was used, and an irradiation distance of 10 cm,
A protective layer was formed under a curing condition of a conveyor speed of 5 m / min.

The thickness of the rigid double-sided copper clad laminate is 0.1
Using a copper foil having a thickness of 5 mm and a copper foil thickness of 18 μ on one side and 35 μ on one side, a circuit was formed on the 35 μ side in the same manner as the flexible printed wiring board and blackened. As the prepreg, polyimide prepreg GIA-67N (N) (Hitachi Chemical Co., Ltd .: thickness after molding 0.07 mm) is externally processed with a Victoria type and inserted one by one between layers, and the rigid part and the flexible part are used by using an autoclave press. Layered (temperature 180 ℃, pressure 15kg
/ Cm ² , time 100 minutes). Drilling, permanganate desmear treatment, copper plating (plating thickness: about 25μ), pattern formation, solder resist film formation, on the substrate after this lamination
After performing character printing and solder coating, external processing was performed using an NC router to obtain a rigid flex printed wiring board.

According to this method, since there is no adhesive layer even when the through hole is drilled, the finished work is smooth, and permanganate treatment is carried out as a desmear treatment which is an essential condition in the multilayer structure. However, the plating deposition state after electroless and electrolytic copper plating was also extremely uniform. After completion of the rigid flex printed wiring board, JIS C5012 9. The 9.3 thermal shock (high temperature immersion) test specified in the item of the weather resistance test was carried out for 100 cycles, but no abnormality was observed. Also J
IS C5012 9. After carrying out the treatment of the 9.5 moisture resistance (steady state) test for 240 hours specified in the item of the weather resistance test, the solder at 260 ° C. was float treated for 20 seconds, but no abnormality was observed. Furthermore, JIS P81
When a flexural strength test was performed on the flexible part using the MIT test machine specified in No. 15, the number of reciprocal bending was 1
The protective layer was not destroyed even when the number of times exceeded 00.

Example 2 In FIG. 1, as a flexible printed wiring board, glass-epoxy double-sided copper-clad laminate Turnflex R
A circuit was formed in the same manner as in Example 1 by using 1766RF (manufactured by Matsushita Electric Works: insulating layer thickness 40 μ, copper foil 18 μ rolled copper foil). NPR-5 (manufactured by Nippon Polytex Co., Ltd.) was applied to the circuit-formed flexible printed wiring board with a roll coater to a thickness of 30 .mu.
The protective layer was formed by curing for 0 minutes. Example 1 below
A rigid flex printed wiring board was obtained in the same manner as. Also by this method, the same appearance and performance as in Example 1 were recognized.

Comparative Example 1 FIG. 2 is a sectional view of a comparative example. In FIG. 2, the cover film 6B is provided with an adhesive layer 6C.
As a product having a structure in which B and 6C were combined, Pyralux product number LF-0210 (cover film thickness 25 μ, adhesive layer thickness 50 μ) manufactured by DuPont was used. A circuit was formed in the same manner as in Example 1 using a double-sided copper-clad laminate of MT-Neoflex. The Piralux LF-021 is attached to the flexible printed wiring board on which the circuit is formed.
0 as a stacking condition, temperature 180 ° C., pressure 45 kg / cm
² , laminated for 50 minutes to form a protective layer. Thereafter, a rigid flex printed wiring board was obtained in the same manner as in Example 1. According to this method, when the through hole is drilled, since the adhesive layer is present, the finished work state is rough and smearing is remarkable. Also, permanganic acid treatment was performed as desmear treatment to remove smear, and electroless and electrolytic copper plating were performed, but the adhesive layer was eluted in the through hole part or the adhesive layer was dug away. And the throwing power of the plating is extremely poor. A thermal shock (high temperature immersion) test similar to that in Example 1 was performed after the printed wiring board was completed, but disconnection occurred in the third cycle. After the moisture resistance (steady state) test treatment, the solder was subjected to a float treatment for 20 seconds at 260 ° C. However, peeling occurred between the cover film and the flexible printed wiring board in 3 pieces out of 10 pieces of the sample.

[0020]

As described above, the present invention uses an organic insulating material having excellent heat resistance and flexibility as a protective layer of a flexible printed wiring board, and eliminates an adhesive layer having poor heat resistance. It is possible to provide a rigid flexprint wiring board having excellent through-hole hole workability and excellent plating throwing power and extremely high through-hole reliability.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a conventional rigid flex printed wiring board.

FIG. 3 is a diagram showing a flexible copper-clad laminate in the processing state of each of the steps included in the manufacturing method of the present invention. (A)
Is a plan view and (B) is a sectional view.

FIG. 4 is a diagram showing a flexible printed wiring board in a processing state in each step included in the manufacturing method of the present invention.
(A) is a plan view and (B) is a sectional view.

FIG. 5 is a view in which a protective layer is formed on the surface of a flexible printed wiring board in the processing state of each of the steps included in the manufacturing method of the present invention. (A) is a plan view and (B) is a sectional view.

FIG. 6 is a diagram showing a rigid printed wiring board in a processing state in each step included in the manufacturing method of the present invention. (A)
Is a plan view and (B) is a sectional view.

FIG. 7 is a view showing a prepreg that has been subjected to external shape processing in the processing state of each of the steps included in the manufacturing method of the present invention.
(A) is a plan view and (B) is a sectional view.

FIG. 8 is a view in which a rigid portion and a flexible portion are integrated by using a prepreg in a processing state in each step included in the manufacturing method of the present invention. (A) is a plan view and (B) is a sectional view.

[Explanation of symbols]

 1 Rigid part 2 Rigid part 3 Flexible part 4 Base film or core material 5 Metal conductor 6A Protective layer (organic insulating layer having flexibility) 6B Cover film 6C Adhesive layer 7 Prepreg 8 Rigid printed wiring board 9 Circuit pattern 10 Through hole 11 Light source or heat source 12 Metal foil before circuit formation

Claims (5)

[Claims] 1. A rigid flex printed wiring board in which a flexible portion obtained by covering a flexible printed wiring board with a protective layer and a rigid portion made of a rigid printed wiring board are integrated, wherein the protective layer of the flexible printed wiring board comprises: A rigid flex printed wiring board, which is formed by an organic insulating layer that is cured by light and / or heat and has flexibility even after curing. 2. A method for producing a rigid flex printed wiring board, which comprises a flexible portion obtained by covering a flexible printed wiring board with a protective layer and a rigid portion made of a rigid printed wiring board, wherein a flexible copper clad laminate is provided with a circuit. Forming and processing the flexible printed wiring board, and applying an organic resin which is cured by light and / or heat and has flexibility even after curing on both surfaces of the flexible printed wiring board, and then light and / or A process of manufacturing a flexible part by curing the organic resin by heat to form flexible organic insulating layers on both sides of the flexible printed wiring board, and forming a circuit on the rigid copper clad laminate to process the rigid wiring board A rigid portion, and a pre-preparation of the flexible portion and the rigid portion. Method for manufacturing a rigid-flex printed circuit board comprising the step of integrating using. 3. The rigid flex printed wiring board according to claim 1, and the rigid printed wiring board according to claim 2, wherein the flexible printed wiring board is formed by forming a circuit on a laminated board in which metal conductors are attached to both surfaces of a polyimide resin base film. Manufacturing method of flex printed wiring board. 4. The rigid flex printed wiring board according to claim 1 and the rigid printed wiring board according to claim 2, wherein the flexible printed wiring board is formed by forming a circuit on a laminated board in which metal conductors are attached to both surfaces of a polyester resin base film. Manufacturing method of flex printed wiring board. 5. The rigid flex printed wiring board according to claim 1, and the rigid printed wiring board according to claim 2, wherein the flexible printed wiring board is formed by forming a circuit on a laminated board having metal conductors on both surfaces of a glass cloth base epoxy resin. Manufacturing method of flex printed wiring board.