JP4350922B2 - Manufacturing method of double-sided flexible circuit board - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a double-sided flexible circuit board, and more particularly, to a method for manufacturing a double-sided flexible circuit board that can suitably form a conduction hole for forming a via hole in an insulating base material by a wet etching technique.
[0002]
[Prior art and its problems]
In recent years, miniaturization and high functionality of electronic devices have been promoted more and more, and therefore, there is an increasing demand for narrowing circuit wiring patterns to accommodate high-density mounting on circuit boards.
[0003]
On the other hand, the conventional double-sided flexible circuit board uses the first conductor layer of the double-sided copper-clad laminate as a mask layer for opening the conduction holes on both sides with respect to the insulating base material, and laser processing It is necessary to perform hole processing using plasma etching and wet etching methods, conduct conductive treatment and plating to form via holes, and perform etching treatment on the conductive layers on both sides after ensuring conduction on both sides The wiring pattern was formed.
[0004]
That is, in order to manufacture a double-sided flexible circuit board from a double-sided copper-clad laminate in which conductor layers 21 and 22 are provided on both sides of an insulating base material 20 as shown in FIG. ), An opening 23 necessary for drilling the insulating base material 20 from one conductor layer 21 by laser machining, plasma etching, or wet etching is formed in the conductor layer 21. It functions as a mask layer.
[0005]
Next, as shown in FIG. 3 (3), the conductor layer 21 is used as a mask layer to form holes in the insulating base material 20 by laser processing, plasma etching, or wet etching, and both surfaces are formed at the position of the opening 23. A conduction hole 24 is formed.
[0006]
Further, as shown in FIG. 4 (4), conducting treatment and plating are performed, and via holes 25 are formed by plating after the conducting treatment. Thereafter, as shown in FIG. 5 (5), the double-sided wiring patterns 26, 27, 28 and 29 are processed to obtain a double-sided flexible circuit board.
[0007]
Since the double-sided flexible circuit board manufactured using this method is further thickened on one conductor layer, the conductor layer thickness increases and it is difficult to form a fine wiring pattern on both sides. Met.
[0008]
Therefore, the present invention provides a method for manufacturing a double-sided flexible circuit board that can suitably solve the above-mentioned conventional problems.
[0009]
[Means for Solving the Problems]
Therefore, in the method for manufacturing a double-sided flexible circuit board according to the present invention, a double-sided copper-clad laminate is used to form a required wiring pattern and a conductive hole on both sides using a wet etching technique. A conductive wiring pattern to be a mask layer when performing is formed in advance, and then a resist layer having an opening larger than the opening formed by the conductive wiring pattern is formed on the conductive wiring pattern and other wiring patterns. And removing the insulating base material located in the opening using a wet etching method to form a conduction hole, and conducting the conductive treatment while leaving the resist layer, and conducting the conductive on the resist layer surface. A method is employed in which, after selectively removing the formation layer, a current is passed from the other conductor layer and electroplating is performed to form a via hole.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be further described below with reference to the illustrated embodiments. FIG. 1 is a manufacturing process diagram of a double-sided flexible circuit board according to an embodiment of the present invention.
[0011]
First, as shown in FIG. 1A, a double-sided copper-clad laminate having conductor layers 2 and 3 on both sides of an insulating base material 1 is prepared. Therefore, as shown in FIG. 2 (2), the conductive wiring pattern 4 and the other wiring pattern 5 which are mask layers when the insulating base material 1 is drilled from one conductor layer 2 by the wet etching method are formed by a conventional method. Form.
[0012]
Next, a resist layer 6 having an opening 7 larger than the opening of the conductive wiring pattern 4 to be a mask layer is provided on the wiring patterns 4 and 5 as shown in FIG. Thereafter, as shown in FIG. 4 (4), a hole 8 is formed in the insulating base material 1 by a wet etching method using the resist layer 6 and the wiring pattern 4 to form the conduction hole 8, and the resist layer 6 is left. Conducting treatment is performed.
[0013]
Since a strong alkali solution containing 20 wt% or more of potassium hydroxide is used as the wet etching solution, it is considered that the resist layer 6 is required to have alkali resistance. However, negative dry film resists are stripped with an alkaline solution of about 3 wt% sodium hydroxide, but the wet etching solution has a significantly higher ph than the stripping solution, and the stripping rate in the wet etching solution is higher than that in the stripping solution. Remarkably slow.
[0014]
For this reason, when a dry film resist is used as the resist layer 6, the mask layer is laminated in a wet etching solution by laminating at a higher temperature than usual, post-exposure after development, post-baking, etc. to improve alkali resistance. Function as. However, when washed with water, the pH of the resist layer surface decreases and the dry film resist peels off, so that it is dried immediately after wet etching, and the alkali component on the resist surface is removed by techniques such as leveling and polishing. It is necessary to conduct a conductive treatment after a pretreatment such as washing with water. In the case where a positive resist is used for the resist layer, the conductive treatment can be performed by washing with water after wet etching.
[0015]
Next, as shown in FIG. 5 (5), in order to prevent the resist layer 6 from being plated, a current is passed from the other conductor layer 3, and electroplating is performed to form the via hole 9.
[0016]
At this time, in order to prevent the other conductor layer 3 from being plated, it is possible to open only the plating lead portion and provide a mask layer on the entire other surface. Alternatively, the resist layer 6 can be prevented from being plated by removing the conductive treatment layer on the resist by leveling and polishing the resist layer 6 after the conductive treatment.
[0017]
Thereafter, as shown in FIG. 6 (6), the required wiring patterns 10 and 11 are processed on the conductor layer 3 side, and the resist layer 6 is peeled off to obtain a double-sided flexible circuit board.
[0018]
【The invention's effect】
The method for manufacturing a double-sided flexible circuit board according to the present invention can form a via hole without thickening the plating on the wiring part, and simultaneously form a wiring pattern located on the same surface as the mask processing of the conduction hole on both sides. Since the area of the land portion of the via hole can be set smaller than before, it is preferable to reduce the pitch of the wiring patterns on both sides, which was difficult with the conventional method for manufacturing a double-sided flexible circuit board. Can be achieved.
[Brief description of the drawings]
FIG. 1 is a manufacturing process diagram of a double-sided flexible circuit board according to an embodiment of the present invention.
FIG. 2 is a manufacturing process diagram of a double-sided flexible circuit board according to a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Insulation base material 2 Conductor layer 3 Conductor layer 4 Conductive wiring pattern 5 Wiring pattern 6 Resist layer 7 Opening part 8 Conductive hole 9 Via hole 10 Wiring pattern 11 Wiring pattern

Claims (1)

Using a double-sided copper-clad laminate, preliminarily form a conductive wiring pattern that becomes a mask layer when drilling a required wiring pattern and a conductive hole on both sides in one conductor layer using a wet etching technique, A resist layer having an opening larger than the opening formed by the conductive wiring pattern is provided on the conductive wiring pattern and another wiring pattern, and an insulating board positioned in the opening using a wet etching technique. The conductive material is removed by removing the conductive material and conducting the conductive process while leaving the resist layer, and after selectively removing the conductive layer on the surface of the resist layer, a current is supplied from the other conductive layer. A method of manufacturing a double-sided flexible circuit board, including a step of forming a via hole by pouring and electroplating.

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