JP2000091745A - Method for manufacturing rigid reflex multilayer printed-wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a plated through hole with improved connection reliability by eliminating a part corresponding to the through hole of a coverlay film before laminating a rigid substrate. SOLUTION: First, a circuit 2 is formed on both surfaces of a flexible substrate 1. Then, a coverlay film 3 including an adhesive layer 3a is laminated to both surfaces of the flexible substrate 1 with the circuit 2 on both the surfaces. Then, for example, a laser beam 4 is applied to a part corresponding to the through hole of the coverlay film 3 and an elimination part 5 is provided. After that, a rigid substrate 6 where a circuit is formed on one surface in advance is laminated on both the surfaces of the flexible substrate 1 where the coverlay film 3 is laminated via a prepreg 7. Then, a through hole 8 is punched at a specific site. After that, a smear on the inner wall surface of the through hole 8 is subjected to desmearing treatment and then the entire surface of the lamination substrate is subjected to the treatment of copper plating 9. After that, an outer-layer circuit 10 is formed on both the surfaces of the lamination substrate, thus obtaining a rigid flex multilayer printed-wiring board.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a rigid-flex multilayer printed wiring board.

[0002]

2. Description of the Related Art In recent years, electronic devices have been reduced in size and weight and have been operated at higher speeds, and it has been desired that thinner and lighter multilayer printed wiring boards for printed wiring boards constituting the electronic devices be used. In order to reduce the number of connectors and cables used for connection between printed wiring boards as multilayered printed wiring boards progress, some layers of each of multiple rigid multilayer printed wiring boards are shared by one flexible printed wiring board. A so-called rigid-flex multilayer printed wiring board has been attracting attention.

Conventionally, as a method for manufacturing such a rigid-flex multilayer printed wiring board, for example, a rigid board is laminated on a conductor circuit of a flexible board by interposing a coverlay film including an adhesive layer, and then a through hole is formed. As a pretreatment for copper plating, a method of removing smear in a through hole by a chemical or plasma (physical) treatment is known.

[0004] However, in such a conventional method, when a chemical desmearing treatment is generally performed by immersion in a sodium permanganate solution or the like, there is a problem that the adhesive layer of the cover lay film easily swells. was there. In addition, as a condition for desmearing, the rigid flex has a problem that, unlike ordinary desmearing treatment on a rigid substrate, the control range of the liquid concentration, temperature, immersion time, and the like is narrow.

[0005] In the case of plasma treatment, the adhesive layer of the coverlay film is attacked and etched back, or the surface of the substrate is coated with fluorine due to the use of Freon gas (water repellency). And there is a problem that it is difficult to attach copper plating to the through holes.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and eliminates the adverse effect of the adhesive layer of the coverlay film, and reduces the smear on the inner wall of the through-hole by a conventional rigid substrate. An object of the present invention is to provide a method of manufacturing a rigid-flex multilayer printed wiring board that can form a plated through hole with high connection reliability even if the same processing is performed.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method for manufacturing a rigid-flex multilayer printed wiring board having a rigid portion and a flexible portion, wherein a coverlay film including an adhesive layer is interposed on a conductor circuit of a flexible substrate. The above object has been achieved by removing a portion corresponding to a through hole of a coverlay film before laminating the rigid substrate when laminating the rigid substrate.

According to such a configuration, the rigid substrate is laminated in a state in which holes corresponding to the through holes are formed in the cover lay film in advance, so that after forming the through holes, the inner wall surface of the through holes is formed. Even if the smear is removed in the same manner as the desmear treatment on a normal rigid substrate, the adhesive layer of the coverlay film is peeled off by swelling, or the adhesive layer of the coverlay film is attacked by the plasma treatment and etched back. Therefore, a highly reliable plated through hole can be formed.

In the present invention, the portion corresponding to the through hole of the cover lay film may be removed after the cover lay film is laminated on the conductor circuit of the flexible substrate or before the lamination.

The means for removing the portion corresponding to the through-hole of the cover lay film is not particularly limited, and examples thereof include a laser, a drill, and a mold.

The present invention also relates to a method for manufacturing a rigid-flex multilayer printed wiring board having a rigid portion and a flexible portion, wherein the rigid substrate is laminated on a conductor circuit of the flexible substrate. The above-mentioned object is achieved by laminating a rigid substrate without interposing a coverlay film including an adhesive layer on the conductor circuit portion of the flexible circuit board and laminating the coverlay film only on the conductor circuit portion of the flexible substrate without laminating the rigid substrate. It has been achieved.

According to such a configuration, since the coverlay film including the adhesive layer does not exist in the portion where the through hole is formed after the rigid substrate is laminated, after the through hole is formed, the smear on the inner wall surface of the through hole is reduced. Even if the removal is performed in the same manner as the desmear treatment on the ordinary rigid substrate, there is no adverse effect from the adhesive layer of the coverlay film, so that a highly reliable plated through hole can be formed.

As a method of desmearing the inner wall surface of the through-hole, the chemical method of swelling, dissolving and removing epoxy smear by, for example, immersing in concentrated sulfuric acid and / or chromic acid or a sodium or potassium permanganate solution. Liquid honing method for removing mild epoxy smear by the impact breaking force of abrasive grains; applying high frequency while flowing a mixed gas of O ₂ and CF ₄ into a vacuum chamber, and causing epoxy smear by free radicals in a highly excited state And a plasma method for removing carbon.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic cross-sectional manufacturing process explanatory view showing a first embodiment of the present invention. Referring to FIG. 1A, first, as shown in FIG. Then, the circuit 2 is formed by, for example, a photographic method. Next, as shown in (B), coverlay films 3 each including an adhesive layer 3a are laminated on both the front and back surfaces of the flexible substrate 1 on which the circuit 2 is provided on both surfaces. Next, as shown in (C), a portion corresponding to the through hole of the cover lay film 3 is irradiated with, for example, a laser beam 4 to provide a removing portion 5.
Next, as shown in (D), a rigid substrate 6 having a circuit formed on one side in advance by a photographic method or the like is laminated via a prepreg 7 on both front and back surfaces of the flexible substrate 1 on which the coverlay film 3 is laminated. I do. Then
As shown in (E), a through hole 8 is formed in a predetermined portion by, for example, drilling. Next, as shown in (F), after the smear on the inner wall surface of the through hole 8 is desmeared by, for example, a chemical treatment method, copper plating 9 is applied to the entire surface of the laminated substrate. Next, by forming the outer layer circuit 10 on the front and back of the laminated substrate by, for example, a photographic method, a rigid-flex multilayer printed wiring board as shown in (G) is obtained.

FIG. 2 is a schematic cross-sectional manufacturing process explanatory view showing a second embodiment of the present invention. Referring to FIG. 2A, first, as shown in FIG. The circuit 12 is formed by, for example, a photographic method. On the other hand, as shown in (B), in the cover lay film 13 including the adhesive layer 13a, a through hole 15 is previously formed in a portion corresponding to the through hole when laminated, for example, by a drill or a mold. Next, as shown in (C), the through-holes 15 are formed on both front and back surfaces of the flexible substrate 11 having the circuit 12 formed on both surfaces obtained in (A).
The coverlay film 13 including the adhesive layer 13a obtained in the above is laminated. Hereinafter, a rigid-flex multilayer printed wiring board is obtained by the same steps as those shown in FIGS. 1 (D) to 1 (G).

FIG. 3 is a schematic cross-sectional manufacturing process explanatory view showing a third embodiment of the present invention. First, as shown in FIG. 3A, as shown in FIG. Then, the circuit 22 is formed by, for example, a photographic method. Next, as shown in (B), the adhesive layers 23 are respectively applied only to the conductor circuit portions on which the rigid substrate is not laminated, of the front and back surfaces of the flexible substrate 21 on which the circuits 22 are provided on both surfaces.
The coverlay film 23 containing a is laminated. Then
As shown in FIG. 4C, a rigid body in which a circuit is formed on one side in advance by a photographic method or the like in a portion where the coverlay film 23 is not laminated among the front and back surfaces of the flexible substrate 21 having the circuit 22 formed on both sides. The substrates 26 are laminated via prepregs 27, respectively. Next, as shown in (D), a through hole 28 is formed in the rigid flex portion by drilling or the like. Then, as shown in (E),
After the smear on the inner wall surface of the through hole 28 is desmeared by, for example, a plasma method, copper plating 29 is applied to the entire surface of the rigid flex portion. Then, by forming the outer layer circuit 30 on the front and back of the laminated substrate by, for example, a photographic method,
A rigid-flex multilayer printed wiring board as shown in FIG.

[0018]

According to the method for manufacturing a rigid-flex multilayer printed wiring board of the present invention, since there is no adverse effect due to the adhesive layer of the cover lay film, the desmear treatment of the through holes is performed in the same manner as in a normal rigid substrate. , A plated through hole with high connection reliability can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional manufacturing process explanatory view showing a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional manufacturing process explanatory view showing a second embodiment of the present invention.

FIG. 3 is a schematic cross-sectional manufacturing process explanatory view showing a third embodiment of the present invention.

[Explanation of symbols]

 1,11,21: Flexible substrate 2,12,22: Conductor circuit 3,13,23: Coverlay film 3a, 13a, 23a: Adhesive layer 4: Laser light 5: Coverlay film removal part 15: Coverlay film penetration Hole 6, 26: rigid board 7, 27: prepreg 8, 28: through hole 9, 29: copper plating 10, 30: outer layer circuit

Claims (5)

[Claims] In a method of manufacturing a rigid-flex multilayer printed wiring board having a rigid portion and a flexible portion, a rigid board is laminated with a coverlay film including an adhesive layer interposed on a conductive circuit of a flexible substrate. A method for manufacturing a rigid-flex multilayer printed wiring board, wherein a portion corresponding to a through hole of a coverlay film is removed in advance before laminating the rigid substrate. 2. The rigid-flex multilayer printed wiring board according to claim 1, wherein the portion corresponding to the through hole of the coverlay film is removed after the coverlay film is laminated on the conductor circuit of the flexible substrate. Manufacturing method. 3. The rigid-flex multilayer printed wiring according to claim 1, wherein the portion corresponding to the through hole of the coverlay film is removed before the coverlay film is laminated on the conductor circuit of the flexible substrate. Plate manufacturing method. 4. The rigid-flex multilayer printed wiring board according to claim 1, wherein the portion corresponding to the through-hole of the coverlay film is removed by a laser, a drill, or a mold. Manufacturing method. 5. A method of manufacturing a rigid / flexible multilayer printed wiring board having a rigid portion and a flexible portion, wherein a rigid circuit board is laminated on the conductor circuit of the flexible substrate when the rigid substrate is laminated on the conductor circuit of the flexible substrate. Rigid-flex multilayer printing characterized by laminating a rigid substrate without interposing a coverlay film including an adhesive layer, and laminating the coverlay film only on the conductor circuit portion of a flexible substrate without laminating the rigid substrate Manufacturing method of wiring board.