JP3241504B2 - Rigid flex printed wiring board and method of manufacturing the same - Google Patents

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 circuit board obtained by integrally forming a flexible board and a rigid board with a prepreg and a spacer interposed and processing the outer layer, and a method of manufacturing the same.

[0002]

BACKGROUND OF THE INVENTION A circuit is formed on a base film such as a polyimide resin or a polyester resin to which a metal conductor such as a copper foil is adhered, and a protective layer such as a cover film such as a polyimide or a polyester is adhered to the flexible film. Substrates are known. Also known is a rigid substrate in which a prepreg, which is a sheet in which a resin is impregnated on a base material such as glass cloth or paper, is stacked with a copper foil on the outside thereof, and a circuit board is formed by heating and pressing to form a laminate. . Further, a rigid flex printed circuit board including a rigid board and a flexible portion obtained by integrally forming a flexible board and a rigid board and processing an outer layer is also known.

In a conventional rigid-flex printed wiring board, it is common practice to form a prepreg at a portion corresponding to a flexible portion in the integral molding of a rigid substrate and a flexible substrate, and to integrally mold the cavity without forming a cavity. is there. According to this method, a dent is formed in a portion corresponding to a flexible portion on the outer layer surface after integrated formation, which affects the adhesion of the dry film at the stage of forming the outer layer pattern.
In addition, a method has been proposed to maintain uniformity of pressure by forming a spacer having no adhesive property in the removed portion, but in a rigid flex printed wiring board configured in this manner, the material cost of the spacer is reduced. However, it also requires processing work, which is a major factor in increasing the manufacturing cost.

[0004]

SUMMARY OF THE INVENTION The present invention has been made as a result of examining the above problems, and it is not necessary to prepare a new spacer in the integrated molding of a flexible substrate and a rigid substrate, so that the manufacturing cost is low and the integration is low. It is an object of the present invention to provide a rigid-flex printed wiring board having a smooth surface of a laminated board after molding and a method for manufacturing the same.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rigid-flex printed wiring board comprising a rigid portion and a flexible portion obtained by integrally forming a flexible substrate and a rigid substrate with a prepreg and a spacer interposed therebetween and processing the outer layer. In the prepreg for bonding the rigid substrate and the flexible substrate, a portion corresponding to the flexible portion is punched out, and the prepreg corresponding to the punched-out flexible portion is cured, and this is used for forming the rigid substrate and the flexible substrate. Rigid flex printed wiring board characterized by being used as a spacer of a flexible equivalent part, and a rigid flex printed wiring board comprising a rigid part and a flexible part obtained by integrally forming a flexible substrate and a rigid substrate and processing an outer layer. The method of manufacturing a flexible copper-clad laminate A step of forming a circuit, a step of covering the flexible substrate with a protective layer such as a cover film or a cover coat to form a protective layer, a step of forming a circuit on the rigid copper-clad laminate to form a rigid substrate, The process of punching out the part corresponding to the flexible part of the prepreg used, the step of hardening the prepreg corresponding to the punched flexible part, and the step of punching out the rigid substrate and corresponding to the hardened prepreg A method of manufacturing a rigid-flex printed wiring board including a step of aligning a prepreg with a flexible substrate together with a pin and a stopper such as an eyelet together with a flexible board, and a step of integrally forming the same using a lamination press, preferably a stamped flexible Wherein the prepreg corresponding to the part is cured and subjected to a release treatment. Method for producing a printed wiring board and the rigid flex printed circuit board is achieved by.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing a rigid flex printed wiring board manufactured according to one embodiment of the present invention. In FIG. 1, 1 is a flexible substrate, 2 is a cover film, a protective layer such as a cover coat (ink), 3 is a prepreg, 4 is a rigid substrate, 5 is a metal conductor, and 6 is a through hole. In FIG. 1, a prepreg is used for integrally forming the rigid substrate and the flexible substrate, and it is more preferable to use a prepreg having a resin flow of 8 to 16%. FIG. 2 is a cross-sectional structure before removing an unnecessary rigid board on a flexible portion in a process of manufacturing a rigid flex printed wiring board by the method of the present invention. FIG.
FIG. 4 is a cross-sectional structure before removing an unnecessary rigid board on a flexible portion in a process of manufacturing a rigid flex printed wiring board by a conventional method.

FIGS. 5 to 14 are a plan view (A) and a cross-sectional view (B) of a material at each stage of a manufacturing process of a rigid flex printed wiring board according to the present invention. In addition, this (A)
And (B) do not strictly correspond to each other, but merely serve to show the concept. 5 shows a flexible copper-clad laminate, FIG. 6 shows a flexible substrate obtained by processing a circuit of the flexible copper-clad laminate, FIG. 7 shows a cover film, and FIG. 8 shows a protective layer formed on the flexible substrate of FIG. 6 using the cover film of FIG. FIG. 9 shows a rigid substrate obtained by processing a circuit of a rigid copper-clad laminate, and FIG. 10 shows a prepreg punched out. It is necessary to harden the extracted prepreg using an oven or the like. FIG. 1 shows a state in which a cured prepreg is arranged in a punched portion.
It is shown in FIG. In addition, this punching processing is generally performed using a big die or an NC router. FIG. 12 shows the flexible substrate of FIG. 8 and the rigid substrate of FIG. 9 integrally formed using the prepreg of FIG. 11 and the cured prepreg. FIG. 13 shows the laminate of FIG. Plating, circuit formation, solder resist application,
This is a rigid flex printed wiring board created by performing exposed copper surface treatment, outer shape processing, and the like.

[0008] The flexible copper-clad laminate used in the present invention is not particularly limited, but those in which the insulating layers are all made of polyimide, such as MT-Neofrex (manufactured by Mitsui Toatsu Chemicals), Chissoflex ( Chisso), ESPANEX (Nippon Steel Chemical), Etcherflex (South Wall), etc., with a polyimide film and an acrylic or epoxy adhesive layer on both sides of the polyimide film, for example, Pyralux ( DuPont) and Nicaflex (Nikkan Industries).
The thickness of the insulating layer of the flexible copper-clad laminate used in the present invention is generally 10 μm to 100 μm, and the upper limit of the thickness of the copper foil is generally 70 μm, and there is no particular lower limit.
Examples of the type of the copper foil include a rolled copper foil, an electrolytic copper foil, a copper ultra-thin film formed by a sputtering method, and the like, which is properly used depending on the use and the like. There is also a method of directly pattern-plating polyimide by an additive method. Therefore, there is no particular lower limit of the copper foil thickness.

As the flexible copper-clad laminate used in the present invention, a thin copper-clad laminate containing glass fiber can be used, and the thickness of the insulating layer is 50 μm to 200 μm.
μm is common, for example, Turnflex (manufactured by Matsushita Electric Works), R-1766 (manufactured by Matsushita Electric Works), EM-145
(Made by Allied Signal), Semiflex (DIELE)
KTRE).

The flexible copper-clad laminate used in the present invention has the structure shown in FIGS. 5A and 5B.

The flexible substrate used in the present invention is formed on a flexible copper-clad laminate through a drilling step, a through-hole plating step, an etching resist forming step using a dry film, a liquid resist and the like, an etching step, and the like. There is an example, as shown in FIGS. 6A and 6B. In addition, a flexible substrate, a method of forming a plating resist on a laminate having an ultra-thin copper foil film formed on polyimide or the like by a sputtering method or the like, peeling the resist after pattern plating, removing unnecessary copper foil,
There is also a method of forming a plating resist on a film of polyimide or the like and forming a pattern by electroless plating.

In the present invention, the protective layer that covers the flexible printed wiring board corresponds to, but is not particularly limited to, a dry cover film or a liquid cover coat. As a specific example of the cover film, MT
-Neoflex (manufactured by Mitsui Toatsu Chemicals), Pyralux (manufactured by DuPont), Nicaflex (manufactured by Nickan Industries),
TFA-577 (manufactured by Toshiba Chemical) and the like, and examples of cover coats include SPI-150, SPI-200 (manufactured by Nippon Steel Chemical) and image masks (Nippon Polytech). The cover film is generally attached to the entire surface of the flexible printed wiring board using a press, a laminator, or the like. The cover coat is applied to the entire or a part of the flexible printed wiring board by printing such as screen printing or by a roll coater.

In the present invention, the cover film of the protective layer covering the flexible substrate is, for example, as shown in FIGS. 7A and 7B. The cover coat is in a liquid state before covering the flexible substrate, and a state before the covering is not shown.

In the present invention, the flexible substrate covered with the protective layer is, for example, as shown in FIGS. 8A and 8B. In the present invention, there are various methods of coating with a protective layer, and in addition to FIG. 8, there is also a method of forming only a finally exposed flexible portion as shown in FIG.

The big mold used in the present invention is a Victoria mold, which means a base made of wood or the like with a groove cut out and a metal blade inserted.

In the present invention, the rigid board is formed by subjecting the rigid copper-clad laminate to a drilling step, a through-hole plating step, an etching resist forming step using a dry film, a liquid resist, and the like, and an etching step. An example is as shown in FIGS. 9A and 9B.

In the present invention, the prepreg is a sheet-like material obtained by impregnating a base material such as glass cloth, paper, glass nonwoven fabric, or a composite thereof with a resin.

In the present invention, the prepreg used for bonding the flexible substrate and the rigid substrate has a resin flow of 8%.
It is preferably about 16% by weight. 16 resin flow
If the weight percent is exceeded, the resin in the prepreg will flow too much during hot pressing, which may contaminate the surface of the flexible part or hinder the removal of unnecessary rigid parts. It tends to decrease. When the resin flow is less than 8% by weight, the embedding property at the time of lamination tends to be insufficient, and there is a concern that voids are generated and solder heat resistance is reduced. The resin flow is defined by JIS
6. C 6487 (prepreg for multilayer printed circuit) It can be measured by the method described in 7.6 Resin Flow of Test Method. However, this JIS C 64
87 relates to a glass cloth base epoxy resin,
Although the press temperature is specified at 170 ° C. ± 3 ° C., when another resin prepreg is used, the temperature is changed to a press temperature suitable for curing the resin, and the same method is used.

The resin constituting the prepreg used in the present invention is not particularly limited. Epoxy, polyimide, BT resin, phenol, etc., a compound of two or more thereof, a reaction product, and the like may be used. JIS C performance when fully cured by press
6487 (prepreg for multilayer printed circuit) Those satisfying the items of 6.6 flame resistance and 6.7 electrical performance are desirable.

In the present invention, the type of glass cloth constituting the prepreg to be used is not particularly limited, and examples thereof include E-glass, C-glass, and S-glass. The thickness is not particularly limited,
0.03 mm to 0.3 mm is generally used.
5 mm to 0.2 mm is preferred.

The resin content of the prepreg used in the present invention is generally 40 to 75% by weight.

In the present invention, one or two or more prepregs are used for a bonding portion between a rigid portion and a flexible portion.

In the present invention, the prepreg to be used needs to be punched out of a portion corresponding to the flexible portion after completion using a big mold or the like, as shown in FIGS. 10 (A) and 10 (B). Things.

In the present invention, it is necessary to remove the adhesiveness by curing the prepreg at a portion corresponding to the extracted flexible portion. For example, there is a method of performing a heat treatment necessary for completely curing the prepreg using an oven or the like. For example, a glass epoxy prepreg (FR
In the case of -4), the temperature is generally about 40 minutes at 170 ° C.
By using the prepreg corresponding to the flexible portion in the cured state as a spacer when integrally forming the rigid substrate and the flexible substrate, the smoothness of the outer layer surface after lamination can be maintained. FIGS. 2 and 11 show a state in which the cured prepreg is arranged as a spacer.

In the present invention, the prepreg at the portion corresponding to the extracted flexible portion is subjected to a release treatment such as applying a release agent such as silicon or Teflon to the cured prepreg, thereby obtaining a rigid flex printed wiring board. After the unnecessary rigid plate is removed in the outer layer processing, the operation of removing the spacer becomes easy, which is more preferable. The same effect can be expected even if this release treatment is performed before the prepreg is cured.

In the present invention, the rigid printed wiring board is a glass cloth base epoxy resin, a glass cloth base polyimide resin, a paper base phenol resin, a glass cloth / glass nonwoven composite base resin, a glass cloth / paper composite. It is formed from a step of forming an etching resist using a dry film, a liquid resist or the like on a copper-clad laminate made of a base epoxy resin or the like, 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 mm to 1.6.
mm is common, and the thickness of the copper foil is generally 9 μm to 70 μm.

In the present invention, the outer shape processing of the prepreg before lamination is performed using a big die, an NC router and 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, the rigid substrate is obtained by subjecting the rigid copper-clad laminate to a treatment such as etching, and examples thereof are shown in FIGS. 9A and 9B.

In the present invention, in the outer shape processing of the rigid substrate before lamination, a half die may be cut from the side to be bonded to the flexible substrate using a big mold. As a result, it is possible to avoid the danger of the surface of the flexible substrate being contaminated by a liquid such as plating or etching from the surface, and it is possible to manufacture a rigid flex printed circuit board excellent in quality. As a method of forming a half cut on a rigid substrate, there are an NC router, a big mold, and the like.

In the present invention, when the flexible substrate and the rigid substrate are integrally formed using a prepreg formed by punching, the prepreg extracted and cured by the punching process before laminating the prepreg as described above is used as a spacer in a portion corresponding to the flex. Insert it as As a result, the pressure at the time of integral molding can be kept uniform, and the surface property of the laminated plate after molding can be kept smooth.

In the present invention, when the flexible portion and the rigid portion are integrated by using a prepreg, the positional relationship between the materials is accurately maintained by using a stopper such as a pin or an eyelet, and a hydropress or an autoclave press is used. Hot pressing. The press method can be carried out by a hydropress or an autoclave press.However, the autoclave press has a higher pressure from the side, a lower molding pressure, and is more advantageous with respect to misalignment. preferable. If necessary, use cushioning material such as paper, synthetic resin, etc., and the molding conditions depend on the type of prepreg used,
Although it cannot be said unconditionally because it depends on the cushion configuration, the number of sheets to be stacked on one step, the pressing method, etc., the pressure is 6 to 60 kg /
cm ² , and the temperature is generally from 160 to 260 ° C. An example after integrated molding is as shown in FIGS. 12 (A) and 12 (B).

Rigid flex-printed wiring boards are manufactured by drilling, desmearing, through-hole copper plating, circuit formation, solder resist application, exposed copper surface treatment, outer shape processing, etc. on the integrally molded product. An example is shown in FIGS. 13A and 13B.

[0033]

EXAMPLES Specific examples will be described below. Embodiment 1 FIG. 1 is a sectional view of an embodiment of the present invention. In FIG. 1, the cover film 6 is formed by applying an epoxy-based adhesive to a polyimide film, and specifically uses Nikka Flex (manufactured by Nickan Industries). The thickness of the polyimide film used for the cover film is 25μ.
m, the thickness of the adhesive is 35 μm. The base film 4 of the insulating layer of the flexible part is entirely made of polyimide, and specifically uses a double-sided copper-clad laminate of MT-Neofrex (manufactured by Mitsui Toatsu Chemicals). Is a rolled copper foil having a thickness of 25 μm and a copper foil of 18 μm.

The flexible double-sided copper-clad laminate was drilled, plated with copper of about 15 μm, formed an etching resist using a dry film, and formed a circuit by etching. The above cover film was laminated on the flexible substrate on which the circuit was formed by using an autoclave press (temperature: 160 ° C., pressure: 15 kg / cm ² , time: 40 hours).
Minutes). Insulation layer thickness 0.2 as rigid double-sided copper-clad laminate
mm, copper foil thickness of 18 μm on one side and 35 μm on the other side, a circuit is formed on the 35 μm side in the same way as a flexible substrate to form a rigid substrate, and a flexible mold is used at the boundary between the flexible part and the rigid part using a die After a half-cut was made from the side of the adhesive surface, blackening treatment was performed. As the prepreg, epoxy prepreg R-1661 (manufactured by Matsushita Electric Works,
The prepreg, which has a thickness of 0.08 mm after molding, a resin flow of 11% by weight, and a resin content of 65% by weight) is externally processed with a big mold, inserted one by one between layers, and extracted with a big mold is 165.
After curing in an oven at 60 ° C. for 60 minutes, the mixture was cooled to room temperature, inserted as a spacer, and a rigid portion and a flexible portion were laminated using an autoclave press (temperature: 170 ° C., pressure: 10 kg / cm ² , time: 100 minutes). After drilling, desmangania permanganate treatment, copper plating (plating thickness: about 25 μm), pattern formation, solder resist film formation, character printing, and solder coating on the laminated substrate,
The outer shape was processed using an NC router to obtain a rigid flex printed circuit board.

According to this method, no depression on the outer layer surface was observed after the laminating press, and the removal of the unnecessary rigid plate and the spacer at the outer layer processing stage could be performed without any problem. Also, JIS C 5012 9. After performing the treatment of the 9.5 moisture resistance (steady state) test specified in the item of the weather resistance test for 240 hours, the solder was floated at 260 ° C. for 20 seconds, but no abnormality was found.

Example 2 In this Example 2, the prepreg extracted from the dies in Example 1 was placed in an oven at 165 ° C. for 60 minutes, cured, cooled to room temperature, and sprayed with a silicone release agent by spraying. After coating and drying, processing was carried out under the same conditions as in Example 1 except that the film was inserted as a spacer to obtain a rigid flex-printed wiring board. The quality evaluation of the prepared substrate was performed for the same items as in Example 1, and the results are shown in Table 1 together with the results of Example 1.

Comparative Example 1 In this Comparative Example 1, a rigid flex-printed wiring board was obtained by processing under the same conditions as in Example 1 except that the cured prepreg was not inserted with a cured spacer. In this substrate, the outer layer corresponding to the flexible portion was concave after lamination, and it was difficult to perform dry film lamination when forming the outer layer circuit.

Comparative Example 2 In Comparative Example 2, a cushion material (trade name: Pacotan Plus) was used as a spacer instead of curing the prepreg extracted in Example 1 to form a spacer by using a cushion material (trade name: Pacotan Plus). Working under the same conditions as in Example 1, a rigid flex printed wiring board was obtained.
In this method, the outer layer surface after lamination was smooth, but the production cost was increased because a cushion material was newly prepared and processed in a big mold.

The quality evaluation of the substrates prepared in these comparative examples was performed on the same items as in the examples, and the results are shown in Table 1.

[0040]

[Table 1]

Table 1 summarizes the results of Examples and Comparative Examples. According to the method of the present invention, as shown in Examples 1 and 2, the outer layer surface after lamination was smooth and the workability was high. And the solder heat resistance after the moisture resistance test was high, showing no abnormality. On the other hand, in Comparative Example 1, a dent was generated on the outer layer surface after lamination, and a defect occurred in the outer layer processing, so that a good product could not be obtained. In Comparative Example 2, it is necessary to newly prepare a spacer,
The number of man-hours increased and the manufacturing cost increased.

[0042]

As described above, according to the present invention, the prepreg used for the integrated lamination of the rigid substrate and the flexible substrate is processed by punching out a portion corresponding to a flexible portion, and the extracted prepreg is cured and used as a spacer. And an inexpensive rigid-flex printed wiring board having a smooth outer layer surface after lamination and a method for manufacturing the same.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view before removing an unnecessary rigid plate having a flexible portion.

FIG. 3 is a cross-sectional view before removing a rigid plate having an unnecessary flexible portion in the conventional method.

FIG. 4 is a cross-sectional view before removing a rigid plate having an unnecessary flexible portion in the conventional method.

FIG. 5 (A) of the flexible copper-clad laminate according to the present invention.
Plan view, (B) sectional view

FIG. 6A is a plan view and FIG. 6B is a cross-sectional view of a flexible substrate obtained by processing the circuit of the flexible copper-clad laminate.

7A is a plan view of a cover film according to the present invention, FIG.
(B) Sectional view

8A is a plan view and FIG. 8B is a cross-sectional view of a state in which a protective layer is formed on the flexible substrate of FIG. 6 using the cover film of FIG.

9A is a plan view and FIG. 9B is a cross-sectional view of a rigid substrate.

FIG. 10A is a plan view of a punched product of a prepreg,
(B) Sectional view

11A and 11B are a plan view and a cross-sectional view, respectively, showing a state in which a cured prepreg is disposed at a punched portion of a punched workpiece.

12A and 12B are a plan view and a cross-sectional view of a laminate in which a flexible substrate and a rigid substrate are integrated using a prepreg and a cured prepreg.

13A is a plan view and FIG. 13B is a cross-sectional view of a rigid flex printed wiring board obtained by processing a laminate into an outer layer.

14A and 14B are a plan view and a cross-sectional view, respectively, of a rigid flex printed wiring board formed only in a finally exposed flexible portion in an example of a coating method using a protective layer.

[Explanation of symbols]

1-flexible substrate 2-protective layer (cover film or cover coat) 3-prepreg 4-rigid substrate 5-metal conductor 6-through hole 7-cured prepreg 8-spacer (pacotan plus) 9-protective layer (flexible part) (Limited, cover film or cover coat) 10-flexible copper-clad laminate 13-rigid part 14-flexible part 15-half cut

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-13958 (JP, A) JP-A-3-55892 (JP, A) JP-A-56-96891 (JP, A) JP-A-2- 229492 (JP, A) JP-A-3-141694 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05K 1/02 H05K 3/46

Claims (4)

(57) [Claims] 1. A rigid-flex printed circuit board comprising a rigid portion and a flexible portion obtained by integrally forming a flexible substrate and a rigid substrate with a prepreg and a spacer interposed therebetween and processing an outer layer. The part corresponding to the flexible part is punched out of the prepreg for integral molding of the prepreg, and the prepreg of the part corresponding to the extracted flexible part is cured and used as a spacer when the rigid substrate and the flexible substrate are integrally molded. Rigid flex printed wiring board. 2. The rigid flex printed wiring board according to claim 1, wherein the prepreg corresponding to the extracted flexible portion is cured and subjected to a release treatment. 3. A method for manufacturing a rigid-flex printed circuit board comprising a rigid portion and a flexible portion obtained by integrally forming a flexible substrate and a rigid substrate with a prepreg and a spacer interposed therebetween and processing the outer layer. A step of forming a circuit on the laminate, a step of manufacturing a flexible substrate by covering with a protective layer such as a cover film or a cover coat, a step of forming a circuit on a rigid copper-clad laminate to form a rigid substrate, and a flexible portion of a prepreg. And a step of hardening a portion corresponding to the flexible portion of the extracted prepreg,
A process in which a prepreg obtained by punching a flexible substrate and a rigid substrate and a prepreg corresponding to a flexible portion that is extracted and hardened are positioned by using a stopper such as a pin or an eyelet, and are integrally formed. A method for manufacturing a rigid flex printed wiring board, comprising: 4. A method for manufacturing a rigid-flex printed wiring board according to claim 3, further comprising a step of curing and curing the prepreg in a portion corresponding to the extracted flexible portion.