JPH06296068A - Method of forming circuit pattern - Google Patents

Abstract

PURPOSE:To protect a conductor region against a short circuit caused by a plating layer formed after etching by a method wherein a plating metal foil layer formed on a resist is removed by etching. CONSTITUTION:A first plating metal foil layer 8 unnecessarily formed on a third region or a resist 5 is removed by etching with etchant. An etching operation is carried out so far as to remove plating metal from the surface of the third region 5 or till the surface of a first region metal adjacent to the third region 5 is lower than the surface of the third region resist 5, and it is preferable that the depth of the recessed surface is smaller than the thickness of the resist film 5 located there. By this setup, the conductor region 4 can be protected against a short circuit caused by a plating layer formed after etching.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern plating method applied to a precision printed circuit board or the like.

[0002]

2. Description of the Related Art Conventionally, photolithography has been often used for producing a precise printed circuit board, but it is said that a high density wiring circuit board can be formed by using the additive method, which is a considerably advantageous manufacturing method. It was The manufacturing method will be described below with reference to the drawings. (A) A fine pattern of the resist layer 5 is formed on the conductive substrate 7 by photolithography (FIG. 4). (B) Further, plating is performed on this fine pattern. After this plating is performed (FIG. 5), the plated surface is placed on the inside of the insulating substrate. (C) Next, the substrate is dissolved and removed, and further plating is performed to form plating layers above and below the resist layer (FIG. 6).

[0003]

However, if there is a portion where the substrate and the resist are not in close contact with each other, the plating wraps between the resist substrates during the first plating, and metal deposition occurs. Further, generally, a process of depositing a metal other than copper is performed before growing copper by plating, but this process also erodes the pretreatment liquid between the resist and the substrate, forming a metal layer between the resist layer and the substrate. It Therefore, copper is similarly deposited on the metal layer by the first plating thereafter.

In either case, the deposited portion 8 shown in FIG.
Therefore, there was a problem that the second plating started after the substrate was melted and the fine pattern to be formed was short-circuited on the resist (FIG. 6).

[0005]

In order to solve the above problems, in a substrate on which a conductor circuit pattern is formed, a first region which is a metal formed on the surface of the substrate and a second region which is formed of a non-conductor portion And a metal foil layer is formed on the surface, and there is a third region below which the same non-conductive portion as the second region exists, and plating is performed after removing the metal foil layer on at least the third region by etching. And a circuit pattern forming method characterized by the above.

First, the substrate on which the resist pattern is formed preferably has a dissolution rate different from that of the metal formed by plating in a dissolution solution, and the substrate is preferably an amphoteric metal. Copper is often used as the plating metal. For the substrate on which the resist pattern is formed,
Generally, a process of depositing a metal other than copper is performed before the copper is grown by plating. Particularly when the substrate is aluminum, it is preferable to form the zinc layer by so-called zincate treatment in order to enhance the adhesion of the copper plating layer to the substrate. After that, the first plating is performed, and the plated surface is placed on the inside to adhere to both sides of the insulating substrate, or the plated surface is coated with an insulating paint and then adhered with an adhesive. Next, the substrate is dissolved with a solution that does not dissolve the plating metal but the substrate. When the substrate is aluminum and the conductor layer is copper, the substrate may be removed using hydrochloric acid or the like.

Here, according to the invention of the present application, the third region, that is, the first plating metal foil layer 8 formed on the resist is removed by etching with a liquid capable of etching the metal. The amount of etching may be performed until the plating metal is removed from the surface of the third region (FIG. 1), and until the metal surface adjacent to the third region of the first region becomes concave due to the resist surface of the third region. Moreover, it is better that the thickness is not deeper than the resist film thickness in that portion (FIG. 2).

Because if the second plating start surface of the first region is concave from the resist surface of the third region, the formation of the conductor by the second plating is limited by the resist end face and the short circuit in the lateral direction of the pattern can be prevented. However, if the recess is formed by etching to a depth deeper than the resist film thickness, the overhanging resist layer collapses and plating grows from there.
On the contrary, a short circuit in the lateral direction of the pattern is likely to occur.

Here, in the central portion further away from the boundary between the first area and the third area, the height is higher than the height of the boundary portion, and the difference in height between the end portion and the central portion in the first area is 1 μm, It is preferably 2 μm or more. If the center of the first region is higher than the boundary of the third region, that is, the boundary of the first region in contact with the resist edge, even if the second plating thickness is increased, the first region moves toward the third and second regions. Lateral plating growth is reduced, and short circuit in the lateral direction of the pattern can be prevented more effectively. The prevention effect is stronger as the film thickness difference between the central portion and the end portion (boundary between the third region) of the first region is larger. On the other hand, this film thickness difference usually does not exceed 20 μm.

In this etching treatment, any liquid can be used as long as it can etch the plating metal, but when the plating metal is copper, ammonium persulfate (APS) having a concentration of 10 to 200 g / 1 is used, and the first region described above is used. It is more preferable that the central part has a higher shape than the boundary part of the third region, that is, the first region in contact with the resist end. Further, the erosion depth from the aluminum surface in the depth direction by the zincate treatment is 1 μm, preferably 2 μm or more.

FIG. 7 shows a preferred state in which the processing of the present application has been performed and the second plating has been completed.

[0012]

[Embodiment 1] An example of an embodiment of the present application will be described step by step. A negative photoresist “OMR83” manufactured by Tokyo Ohka Kogyo Co., Ltd. was applied onto an aluminum substrate having a thickness of 80 μm and prebaked. At this time, the resist film thickness is 10 on average.
became μm. Next, a photomask made of PET film was placed on the circuit pattern to expose it. Further, it was developed with a developing solution, rinsed with rinse, and finally afterbaked to obtain a conductive substrate on which a resist circuit pattern was formed. After cleaning the conductive substrate with the circuit pattern formed with acid,
Okuno Chemical Industries Co., Ltd. zincate treatment liquid "Substar Z
N-2 "was used for zincate treatment. By this treatment, the zincate treatment depth of the aluminum substrate was about 2 μm.

Washing with water was carried out in all the treatments. Using a copper pyrophosphate plating solution manufactured by Murata Co., Ltd., copper was electrolytically plated to a thickness of 1 μm using the substrate as a cathode. _{CuSO 4 · 5H 2 O 110g /} 1, H 2 SO 4 1
Electrolytic plating was performed to a thickness of 60 μm using a copper sulfate plating solution in which a brightening agent was added at 80 g / 1 and chlorine ion of 50 ppm. Hitachi Chemical Insulation Varnish "WI-"
640 ”is overcoated and made by Cemedine's“ SG-
EPO EP-007 "epoxy resin adhesive was used to bond with the plated surface inside. The aluminum substrate was dissolved and removed with a 14% hydrochloric acid aqueous solution. 25 with 100 g / 1 ammonium persulfate aqueous solution
Etched at 30 ° C. for 30 seconds. The second electrolytic copper plating was performed under the same conditions as the process. By the above processing, the substrate 30 of 400 mm × 400 mm
Although 30 substrates were manufactured, there was no short-circuited portion between the patterns on any of the 30 substrates.

After etching with an aqueous solution of ammonium persulfate in the step, a 10 × 10 mm sample was cut out from a part of one substrate, embedded in resin, and observed by observing a cross section. The average height from 10 points was 1.5 μm, and the difference in height between the center and the boundary of the conductor pattern was 0.5 μm. The lateral pattern growth was 43 μm while the second plating was grown to a thickness of 60 μm.

[0015]

Example 2 The same process as in Example 1 was performed except that the zincate treatment time in the step was increased and the etching time with ammonium persulfate in the step was extended. As a result, as shown in Table 1, there was no short circuit, and the lateral growth of the plating pattern was 35 μm.

[0016]

Example 3 The same process as in Example 1 was carried out except that the zincate treatment time in the step was increased and the etching time with ammonium persulfate in the step was extended. As a result, as shown in Table 1, there was no short circuit, and the lateral growth of the plating pattern was 30 μm.

[0017]

[Comparative Example] 30 steps of 400 mm × 400 mm substrates were manufactured by performing the steps from the step to the step of the example without performing steps, and a short-circuited portion between patterns was found on 20 of the boards. . Moreover, in 5 of them, short circuits were found on almost the entire surface of the substrate.

Before the above step, a 10 × 10 mm sample was cut out from a part of one substrate, embedded in resin, and a cross section was observed. As a result, a conductor was found to have been deposited on the resist pattern. Both the central portion and the boundary portion of the above were higher than the resist surface by 3 μm on average.

[0019]

[Table 1]

[0020]

EFFECT OF THE INVENTION The present invention comprises a first region, which is a metal formed on the surface of a substrate on which a conductor circuit pattern is formed, and a second region, which is formed of a non-conductor portion, and By the circuit pattern forming method characterized by performing plating after etching, it is possible to prevent a short circuit of a conductor region due to plating formed after etching and to form a fine circuit pattern without a short circuit.

[Brief description of drawings]

FIG. 1 is an example of a state in the middle of carrying out the present application.

FIG. 2 is an example of a more preferable mode in the middle of carrying out the present application.

FIG. 3 is a state immediately after removing the substrate, and shows a third region 3
In, the same metal foil layer 8 as the first region 1 remains on the surface.

FIG. 4 shows a state where a resist pattern is formed on a substrate.

[FIG. 5] Immediately after the first plating, the metal foil layer 8 is formed under the resist (second region).

[FIG. 6] Immediately after the second plating is performed by the conventional technique, a short circuit occurs between the patterns in the second plating due to the metal foil layer 8.

FIG. 7 is an example of implementing the present application, in which a short circuit between patterns does not occur.

[Explanation of symbols]

1 first area metal part 2 second area non-conductor part 3 third area part where the same metal foil layer as 1 remains on the surface 4 metal part formed by the first plating 4'by the second plating Formed metal part 5 Resist 6 Insulator to which conductor circuit pattern is attached 7 Substrate 8 Metal foil layer part on the third region

Claims (1)

[Claims] 1. A substrate on which a conductor circuit pattern is formed, wherein a metal first region formed on the substrate surface, a second region formed of a non-conductor portion, and a metal foil layer are formed on the surface. A circuit pattern forming method, characterized in that there is a third region below which the same non-conductor portion as the second region exists, and plating is performed after removing at least the metal foil layer on the third region by etching.