JPH05175636A - Manufacture of flexible printed wiring board - Google Patents

Abstract

PURPOSE:To make it possible to prevent a drop in flexibility and to deal with a high density pattern by forming plating only in a throughhole portion and a land portion. CONSTITUTION:A throughhole 4 is bored on a copper-clad film where copper foils 10 and 11 are bonded on both sides of a polyimide film 9. Then, a dry film is laminated thereon, thereby forming a negative type plating resist 12. The dry film is removed and an etching resist 13 is formed. Then, electroless copper plating and electrolytic plating 5 are carried out so as to take electric conduction for the copper foils 10 and 11. Then, the dry film is laminated, thereby forming a negative type resist 12. Then, there is formed an etching resist 14 for the throughhole and land portions by solder plating. Useless electroless plating, electrolytic plating and copper foils are etched so as to eliminate the solder plating and forming a specified circuit pattern.

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.

[0002]

2. Description of the Related Art A conventional method for manufacturing a flexible printed wiring board having a through-hole conductive structure is shown in FIG. Figure 2
As shown in (1), on a flexible printed wiring board base material in which conductive materials 2 and 3 are adhered on both surfaces of an insulating base material 1,
The required through-hole through-hole 4 is provided, and then, as shown in FIG. 2B, electroless plating is applied to the conductive materials 2 and 3 and the through-hole through-hole 4 is plated 5 to form the conductive material 2. Electrical connection between 3 is taken. Next, thickening is performed by electrolytic plating, an etching resist 7 is formed on a required circuit pattern portion as shown in FIG. 2C, an unnecessary conductive material is removed by etching, and the etching resist is removed. A circuit pattern as shown in (4) is formed. In this way,
Electrolytic plating having a hard structure may adhere to the through-hole portion and the circuit pattern portion, flexibility may be deteriorated in the bending portion, and the bending portion circuit pattern may be broken by the bending operation. As a means of eliminating the disconnection of the bent portion, a peelable mask material is applied to the bent portion circuit pattern, the mask is peeled off after plating, and a circuit is formed to prevent the adhesion of plating to the bent portion, and the flexed portion of the bent portion is prevented. Those which ensure the ability, for example, Japanese Patent Laid-Open Nos. 59-181094 and 5
There is a technique described in JP-A-7-79697. However, after removing the mask material, a step is generated on the plating boundary surface, which causes problems such as disconnection and cracking when forming a pattern. Also, after forming the circuit pattern and laminating the covering material, a masking film is attached to both covering material surfaces, a through hole is formed through the both masking films at the portion where the through hole should be taken, and then electroless plating is applied. Finally, there is a technique in which electroless plating is applied only to the through-hole portion by removing the masking film, for example, a technique described in JP-A-55-124295. However, after forming the circuit pattern, the through holes for the through holes must be processed in consideration of the dimensional change of the base material, which is a very difficult work for improving the hole position accuracy.

[0003]

The conventional manufacturing method as described above can be applied not only to a flexible printed wiring board but also to a general rigid wiring board. After plating on, the circuit is formed. Generally, the plating is thickened on the copper foil.
Therefore, the cross-sectional shape after etching is not limited to vertical etching, but copper foil protected by an etching resist is also etched horizontally, resulting in a larger undercut amount compared to etching copper foil alone. Accuracy becomes poor and it becomes difficult to form a high-density pattern. In order to deal with a high-density pattern, it is necessary to form a pattern in a state where electrolytic plating is not applied to the pattern forming portion. Further, since the plating is attached, the flexibility is lowered, and there is a problem that the bending operation causes disconnection at the bending portion. In order to prevent such a problem, it is necessary to attach a mask material to the bent portion and remove it after plating, but the step of attaching and removing the mask material requires a large number of steps and complicates the process. There is a problem.

[0004]

According to the manufacturing method of the present invention, a conductive material is provided on both sides of an insulating material, and an etching resist image is formed on a required circuit pattern portion before or after opening a through hole for a through hole. To do. Next, electroless plating and electrolytic plating are performed. After electrolytic plating, an etching resist image is formed on a required portion on the plating, and the conductive material, electroless plating and electrolytic plating are removed by etching to form a circuit pattern. That is, as shown in FIG. 1, one embodiment of the present invention is to drill or punch into a base material having conductive materials 2, 3 such as copper foil or aluminum foil on both sides of an insulating base material 1, for example, a polyimide film or a polyester film. Before or after the step of forming through holes for through-holes, etc., an etching resist 6, for example, solder plating, tin plating, gold plating, liquid resist, resist ink, etc., is applied to a desired circuit pattern shape by a printing method or a baking method. Formed (see FIG. 1A). Next, electroless plating and electrolytic plating 5 are performed to establish electrical continuity between the conductive materials 2 and 3 (see FIG. 1 (2)), and etching resist 7 such as solder plating is applied to the through holes for through holes and lands. A tin plating, a gold plating, a liquid resist, and a resist ink are formed by using a printing method and a baking method (see FIG. 1 (3)). Next, after removing the unnecessary conductive material by etching, the etching resist is removed by a stripping solution to form a circuit (see FIG. 1 (4)).

[0005]

[Function] By forming the etching resist of the circuit pattern before the electroless plating, it also functions as the plating resist of the circuit pattern. For this reason, the electroless plating and the electrolytic plating are followed by etching to etch the electroless plating and the electrolytic plating on the circuit pattern, and the conductive material 2 and 3 on the insulating base material form the circuit pattern, improving the etching accuracy. In addition, it is possible to deal with high-density patterns. In addition, electroless plating and electrolytic plating are formed on the through-holes and lands, and the electroless plating and electrolytic plating on the bent portions are etched, so that flexibility is not lost and electrical conduction between the conductive materials 2 and 3 is maintained. Can be taken. It is also possible to partially increase the thickness of the conductive material by forming an etching resist after electroless plating or electrolytic plating on a required portion 8 other than the through hole.

[0006]

EXAMPLE FIG. 3 shows a cross-sectional view of a manufacturing process of an example. Rolled copper foil 35μ on both sides of polyimide 25μm film 9
The through holes 4 for the through holes are opened by drilling in the copper-clad film in which m10 and m11 are bonded with an epoxy adhesive (see FIG. 3 (1).) Next, a dry film is laminated, baked, and developed. A negative type plating resist 12 is formed on the circuit pattern (see FIG. 3 (2)). Next, solder plating is applied to a thickness of 5 to 10 μm, the dry film is removed with a stripping solution, and an etching resist 13 is formed by solder plating (see FIG. 3C). Next, 0.5 electroless copper plating
˜1 μm, electrolytic copper plating 5 is applied for 15 to 20 μm, and the rolled copper foils 10 and 11 are electrically connected. Next, a dry film is laminated, baked, and developed to form a negative plating resist 12 on the circuit pattern (FIG. 3).
See (4). ). Next, solder plating is applied to a thickness of 5 to 10 μm.
Then, the through holes for through holes and the etching resist 14 for the lands are formed by solder plating (see FIG. 3 (5)). Next, unnecessary electroless plating, electrolytic plating, and copper foil are etched by alkali etching, and the solder plating is removed with a stripping solution to form a required circuit pattern (FIG. 3).
See (6). ).

[0007]

EFFECTS OF THE INVENTION By forming electroless plating and electrolytic plating only on through holes and lands, it is possible to prevent deterioration of flexibility. By forming an etching resist on the copper foil, a high density pattern can be dealt with. Further, after the electrolytic plating, the etching resist 15 is formed on a desired pattern portion, and the copper foil can be partially thickened by etching.

[Brief description of drawings]

FIG. 1 is a cross-sectional view for explaining each step of one embodiment of the present invention.

FIG. 2 is a cross-sectional view for explaining each step of a conventional example.

FIG. 3 is a cross-sectional view for explaining each step of another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Insulating base material 2 Conductive material 3 Conductive material 4 Through-hole through hole 5 Plating (electroless plating and electrolytic plating) 6 Etching resist 7 Etching resist 8 Etching resist 9 Polyimide film 10 Rolled copper foil 11 Rolled copper foil 12
Plating resist 13 Etching resist 14
Etching resist 15 Etching resist

Claims (1)

[Claims] 1. An electrically conductive material is provided on both sides of an insulating material, and an etching resist image is formed on a required circuit pattern portion before or after forming a through hole for a through hole. Next, electroless plating and electrolytic plating are performed. A flexible printed wiring board characterized in that after electroplating, an etching resist image is formed on a required portion on the plating, and the conductive material, electroless plating, and electroplating are removed by etching to form a circuit pattern. Manufacturing method.