JPH05347468A - Manufacture of printed circuit board - Google Patents

Abstract

PURPOSE:To form a circuit of a fine pattern on a surface of a base which is stereoscopically formed. CONSTITUTION:A conductive thin film 2 is provided on a surface of a base 1 which is stereoscopically formed. The surface of the film 2 is covered with electrodeposited photoresist 3. The photoresist 3 is exposed and developed to remove the photoresist 3 by a circuit pattern. The surface of the film 2 of a part exposed by removing the photoresist 3 is electroplated to form a conductor layer 4. After the photoresist 3 is peeled, the film exposed by peeling the photoresist 3 is removed by etching. A part exposed without covering with the photoresist 3 of the film 2 is electroplated to provide a conductor layer 4 having a predetermined thickness thereby to form a circuit, and hence etching may be lightly processed to remove the film 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a printed wiring board having a three-dimensional surface.

[0002]

2. Description of the Related Art MCB (Molded Circuit)
Board) and MID (Molded Interc)
As a connection device, a printed wiring board in which a base (substrate) is made of a resin molded product has recently been receiving attention. Since the surface of such a MCB or MID substrate is three-dimensionally formed, the conventional circuit forming method, which is premised on the surface being a smooth surface, cannot be adopted as it is.

Therefore, various measures have been taken. For example, Japanese Patent Laid-Open No. 4-76985 provides a method for manufacturing a printed wiring board using an electrodeposited photoresist as a resist. That is, electroless plating is performed on the entire surface of the substrate, and then electroplating is performed to provide a metal layer having a thickness required for a circuit, and then an electrodeposition photoresist is deposited on this metal layer. Conventionally, photoresist has been applied by coating or printing, and it is possible to apply photoresist with a uniform thickness on the surface of a substrate with a smooth surface. In this case, the photoresist cannot be applied with a uniform thickness. On the other hand, electrodeposition photoresist is an application of the technique of electrodeposition coating to the application of photoresist, in which the substrate is immersed in the electrodeposition photoresist solution to form a direct current between the electrodeposition photoresist solution and the metal layer of the substrate. When an electric current is applied, the resin component of the electrodeposition photoresist solution is deposited on the surface of the metal layer by an electrode reaction on the same principle as electroplating, and the electrodeposition photoresist can be electrodeposited on the surface of the metal layer. Since the electrodeposited photoresist deposited on the surface of the metal layer is electrically insulating, if there is a difference in the deposition amount of the electrodeposited photoresist on the surface of the metal layer, the deposition amount will be small and Precipitation concentrates on the lower portion, and as a result, the electrodeposited photoresist can be applied with a uniform thickness even if the surface of the substrate is three-dimensional and has concave portions. Then, the exposed portion is decomposed by exposing the electrodeposited photoresist according to a predetermined circuit pattern, and then the exposed and decomposed portion of the electrodeposited photoresist is dissolved and removed by developing. The metal layer is exposed in a reverse pattern. Then, the exposed portion of the metal layer is dissolved and removed by treatment with an etching solution to form a circuit in the remaining portion of the metal layer, and then the electrodeposition photoresist is removed to form a printed wiring board. It is possible.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the method disclosed in Japanese Patent Publication No. 85, the metal layer formed on the surface of the substrate by electroless plating and electrolytic plating needs to be formed to have a thickness necessary for a circuit, for example, 10 to 50 μm. Then, a circuit is formed by etching an unnecessary portion of this metal layer.
When etching a metal layer having a thickness of about μm, it is necessary to lengthen the processing time, etc. As a result, the side surface of the metal layer that should be left as a circuit is eroded by the etching liquid and is easily side-etched. .. Therefore, there has been a problem that the pattern accuracy of the circuit deteriorates and it becomes difficult to form a circuit with a fine pattern.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a method for manufacturing a printed wiring board capable of forming a circuit in a fine pattern.

[0006]

According to the method of manufacturing a printed wiring board of the present invention, a conductive thin film 2 is provided on the surface of a three-dimensionally formed substrate 1, and the surface of this conductive thin film 2 is subjected to electrodeposition photo. Resist 3 is deposited and electrodeposited photoresist 3
Is exposed and developed to remove the electrodeposited photoresist 3 with a circuit pattern, and the surface of the conductive thin film 2 is electroplated at the portion exposed by the removal of the electrodeposited photoresist 3 to form a conductor layer 4. After peeling off the electrodeposited photoresist 3,
Conductive thin film 2 exposed by peeling of electrodeposited photoresist 3
Is removed by etching.

[0007]

A circuit can be formed by electroplating the exposed portion of the electroconductive thin film 2 provided on the surface of the substrate 1 without being covered with the electrodeposition photoresist 3 and providing the conductor layer 4 of a predetermined thickness. In addition, the thickness of the conductive thin film 2 is sufficiently thin that it can be energized when the electrodeposition photoresist 3 is provided or the conductor layer 4 is electroplated, and the etching is a light treatment for removing the thin conductive thin film 2. It's done.

[0008]

EXAMPLES The present invention will be described in detail below with reference to examples. The base 1 is formed by resin molding such as injection molding, and its surface is formed in a three-dimensional shape having irregularities as shown in FIG. In FIG. 1A, reference numeral 10 denotes a concave portion on the surface of the substrate 1, and 11 denotes a through hole penetrating the substrate 1. Then, first, the surface of the substrate 1 is subjected to pretreatment such as roughening, and then electroless plating such as electroless copper plating is performed to include the recesses 10 and the through holes 11 of the substrate 1 as shown in FIG. 1B. A conductive thin film 2 such as a copper coating is deposited on the entire surface. Since the conductive thin film 2 is provided for energizing when the electrodeposition photoresist 3 and the conductor layer 4 which will be described later are provided, it should be thinly formed within a range that does not hinder energization. , For example, 0.5 to 10
A thin thickness of about μm (preferably 5 μm or less) is sufficient.

After the conductive thin film 2 is provided on the surface of the substrate 1 as described above, the electrodeposited photoresist 3 is deposited on the entire surface of the conductive thin film 2 as shown in FIG. 1 (c). Electrodeposited photoresists include cation type and anion type as reported in JP-A-63-23389, and any generally provided one can be used. Then, the substrate 1 is dipped in the electrodeposition photoresist solution and an electrode is inserted into the electrodeposition photoresist solution, and the conductive thin film 2 of the substrate 1 is used as a cathode in the case of a cation type electrodeposition photoresist solution and an anion type electrodeposition photoresist. In the case of liquid, it is connected to the anode respectively, and the electrode is connected to the anode in the case of cation type electrodeposition photoresist solution and to the cathode in the case of anion type electrodeposition photoresist solution, and a direct current is passed between them. As a result, a photoresist can be deposited on the surface of the conductive thin film 2 for electrodeposition coating, and the electrodeposition photoresist 3 can be deposited. As described above, the electrodeposition photoresist 3 has the recess 10
It can be applied to the inside as well as the through hole 11 with a uniform thickness.

After depositing the electrodeposition photoresist 3 in this manner, a photomask 12 is overlaid on the surface of the substrate 1 as shown in FIG. As the photomask 12, a mask portion 12a is provided at a place where a circuit is to be formed, and the electrodeposited photoresist 3 is exposed to light passing through a portion other than the mask portion 12a by irradiating a parallel light beam to the electrodeposition photoresist 3 The exposed portion of photoresist 3 is cured. Next, the film is treated with a developing solution to dissolve and remove the unexposed portion of the electrodeposited photoresist 3. By performing the development process in this way, the electrodeposited photoresist 3 is removed with a circuit pattern as shown in FIG. 1E, and the electrodeposited photoresist 3 is left in a pattern opposite to the circuit pattern.

Next, electrodes are connected to the conductive thin film 2, the substrate 1 is immersed in a plating liquid such as a copper plating liquid, and a direct current is applied to the conductive thin film 2 to perform electroplating such as electrolytic copper plating. .. When electroplating is performed in this manner, plating metal is deposited on the exposed surface of the conductive thin film 2 that is not covered with the electrodeposition photoresist 3,
The conductor layer 4 made of metallic copper can be formed as shown in FIG. The conductor layer 4 is provided in a portion where the electrodeposition photoresist 3 is removed in the circuit pattern, and is formed with a thickness of about 10 to 50 μm required for a circuit.
At this time, gold plating 13 can be applied to the surface of the conductor layer 4 if necessary. The gold plating 13 can be applied by performing electric gold plating for energizing the conductive thin film 2, and it is not necessary to draw a plating lead wire for gold plating.

After electroplating the conductor layer 4 as described above, the electrodeposition photoresist 3 is dissolved in a stripping solution to strip it as shown in FIG. 1 (g) and treated with an etching solution. As shown in FIG. 1 (h), unnecessary conductive thin film 2 exposed by peeling of electrodeposited photoresist 3 is removed by etching, and a circuit can be formed by conductor layer 4. Here, since the conductive thin film 2 is formed thin within a range in which current can be applied, it can be removed by a light etching process, and the side surface of the conductor layer 4 forming a circuit is eroded by an etching solution. Since the influence of the side etching is almost eliminated, the pattern accuracy of the circuit can be obtained with high accuracy, and the fine pattern circuit can be formed. By the way, in the construction method described in the conventional technique, the circuit width is 80 μm and the circuit interval is 80 μm.
m is the limit, but in the construction method of the present invention, the circuit width is 40 μm,
A circuit spacing of 40 μm is possible. Although the surface of the conductor layer 4 is also etched during the etching process,
There is no problem because only the same thickness as the conductive thin film 2 is removed. If the gold plating 13 is applied to the surface of the conductor layer 4 at this time, the conductor layer 4 can be protected by the gold plating 13 and protected from the etching solution, and there is no possibility that the conductor layer 4 becomes thin.

[0013]

As described above, according to the present invention, a conductive thin film is provided on the surface of a three-dimensionally formed substrate, and the surface of the conductive thin film is coated with an electrodeposition photoresist and the electrodeposition photoresist is formed. The electrodeposition photoresist is removed by a circuit pattern by exposure and development, and the surface of the conductive thin film is electroplated in the portion exposed by the removal of the electrodeposition photoresist to form a conductor layer. After peeling, the conductive thin film exposed by peeling of the electrodeposited photoresist was removed by etching.Therefore, the conductive thin film provided on the surface of the substrate was not covered with the electrodeposited photoresist and the exposed portion was electrically exposed. A circuit can be formed by plating and providing a conductor layer of a predetermined thickness.The thickness of the conductive thin film is the amount of electricity applied when an electrodeposition photoresist is provided or the conductor layer is electroplated. It is enough to have a thin thickness as much as possible, and etching can be done by a light treatment to remove this thin conductive thin film, so that side etching of the conductor layer forming the circuit during etching is reduced and the circuit is reduced. The precision of the pattern can be improved, and a circuit can be formed with a fine pattern.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, in which (a) to (h) are cross-sectional views in each step.

[Explanation of symbols] 1 substrate 2 conductive thin film 3 electrodeposited photoresist 4 conductor layer

Claims (1)

[Claims] 1. A conductive thin film is provided on the surface of a three-dimensionally formed substrate, and an electrodeposition photoresist is deposited on the surface of the conductive thin film, and the electrodeposition photoresist is exposed and developed to perform electrodeposition. After removing the photoresist with a circuit pattern and forming a conductor layer by electroplating on the surface of the conductive thin film in the portion exposed by the removal of the electrodeposition photoresist, the electrodeposition photoresist is peeled off, and then the electrodeposition photoresist is removed. A method for manufacturing a printed wiring board, which comprises removing the conductive thin film exposed by the peeling of the substrate by etching.