JP2003129260A - Etchant for spray method and production method for suitable electronic circuit board using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an etchant which, when used in a spray method, i.e., an etching method suitable for mass-production, can strongly form a circuit wiring on an insulation board with good adhesion and can form a highly accurate, fine circuit wiring; and a production method for a suitable electronic circuit board using the same. SOLUTION: The etchant is based on a mixture mainly comprising sulfuric acid, nitric acid, and acetic acid. The wt. ratio (in terms of EL class) of sulfuric acid/nitric acid/acetic acid/water/copper nitrate is 5/1.5/10/8/0.1. In the production method for an electronic circuit board, a thin film substrate conductive layer 2 and a thin film substrate conductive layer 3 formed on an insulation board 1 are selectively etched with the etchant by spraying so as to form a circuit wiring 6A having a stable shape without causing side etch.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spray method etching solution suitable for forming circuit wiring on an electrically insulating substrate, and a method for manufacturing an electronic circuit board suitable for using the same. It is about Seki.

[0002]

2. Description of the Related Art A conventional method for manufacturing an electronic circuit board is designed so that predetermined wiring circuits, electrodes and / or wirings of connection terminals (hereinafter collectively referred to as "circuit wiring") are electrically insulated. When forming on a "substrate"), form a metal layer such as copper on the entire surface of the substrate by plating etc., apply photoresist to the entire surface, and form a circuit wiring pattern on the surface of the photoresist. After exposure, this was developed and the metal of the unnecessary part which a photoresist does not exist was removed by etching, and the electronic circuit board with which the predetermined circuit wiring was formed was obtained.

[0003]

However, in this method of manufacturing an electronic circuit board according to the prior art, the thickness of the metal layer formed on the board is usually 10 to 20 .mu.m, and unnecessary metal is added from the surface side. Since the layer portion is removed by etching,
Depending on the etching speed, the shape of the circuit wiring becomes a cross-sectional shape with a taper, and the accuracy variation is ± 40.
The width of the circuit wiring is 100 μm, and the distance between adjacent circuit wirings is 100 μm (hereinafter, L / S (Line &
Space) = 100}} was the limit.

Therefore, it has been impossible to accurately make the circuit wiring fine, to form an inductor or the like directly on an electronic circuit board, or to form a circuit which can cope with high frequency characteristics in the GHz band.

Therefore, in order to solve such a problem,
Through the manufacturing process shown in FIG. 4, a method of manufacturing an electronic circuit board has been developed, in which circuit wiring can be firmly adhered to the substrate and highly precise and fine circuit wiring can be formed.

That is, as shown in FIG. 4A, first, the substrate 1 is prepared, and the thin film underlying conductive layers 2 and 3 to be the seed metal are formed on the surface by sputtering. The thin film underlying conductive layer 2 is made of a metal that is easily adhered to the surface of the substrate 1, and the thin film underlying conductive layer 3 is made of a metal having a high plating property. In this embodiment, the thin film underlying conductive layer is shown as two layers, but it is not limited to two layers.

Next, as shown in FIG. 4B, a plating resist layer 4 is formed on the surface of the thin film underlying conductive layer 3, and a desired circuit wiring pattern 4A is formed on the plating resist layer 4.
To form.

Next, as shown in FIG. 4C, a metal conductor is plated in the pattern 4A of the plating resist layer 4 to form a conductive layer 5. The plating at this time may be either electrolytic plating or electroless plating, and is not limited to either one.

Next, as shown in FIG. 4D, the plating resist layer 4 is removed after the plating is completed.

Then, as shown in FIG. 4E, the thin film underlying conductive layers 2 and 3 exposed by removing the plating resist layer 4 are removed by etching.

In this manner, the thin film underlying conductive layers 2 and 3 and the circuit wiring 6 having a three-layer structure in which the conductive layer 5 is formed thereon.
It is possible to obtain a fine electronic circuit board 10 that is firmly adhered to the substrate 1 and is firmly formed.

As a method of etching the thin film underlying conductive layers 2 and 3, methods such as a spray method and a dip method are adopted.

Usually, a high-purity (EL-class) chemical solution is mixed to prepare a mixed acid. However, in the dip method, the etching rate changes depending on the number of times etching is repeated, so it is necessary to insert dummy etching. . On the other hand, in the spray method, etching is always performed with a new solution,
It was necessary to set a high etching rate.

Copper (Cu) is often used as the circuit wiring from the viewpoint of resistance and price, but the etching speed is faster than that of other metals, and any etching method is used. Until the completion of the step, a difference in etching rate occurs due to a difference in metal of the thin film underlying conductive layers 2, 3 and the conductive layer 5, and side etching easily occurs in the thin film underlying conductive layers 2, 3 and / or the conductive layer 5. There is a problem that the accuracy of circuit wiring is difficult to obtain.

The present invention is intended to solve such a problem of the prior art, and a circuit wiring can be firmly adhered and firmly formed on a substrate by using a spray method which is an etching method suitable for mass production. It is an object of the present invention to obtain an etching solution for a spray method capable of forming fine circuit wiring with high accuracy and a suitable method for manufacturing an electronic circuit board using the etching solution.

[0016]

Therefore, the etching solution for a spray method of the present invention is based on a mixed acid solution containing nitric acid, sulfuric acid and acetic acid as main components, and is added in the form of a salt such as copper sulfate and copper nitrate. The thing which added the thing. The amount of the additive added is preferably 1% by weight or less based on the total weight.

A method of manufacturing an electronic circuit board according to the present invention,
In a method of manufacturing an electronic circuit board in which circuit wiring is formed on the surface of a substrate by plating, a step of forming an underlying conductive layer on the surface of the substrate by sputtering, and a predetermined circuit using a plating resist on the thin film underlying conductive layer The step of forming a wiring pattern, the step of plating a conductive material on the circuit wiring pattern, the step of removing the plating resist, and the portion of the thin film underlying conductive layer exposed by removing the plating resist are treated with nitric acid. , Sulfuric acid, based on a mixed acid solution containing acetic acid as a main component, copper sulfate, copper nitrate, and the like through a manufacturing process including a step of etching by a spray method using an etching solution to which an additive in a salt state is added. The method of forming circuit wiring is adopted.

It is preferable that the thin film underlying conductive layer is composed of a plurality of layers of different metals, and it is desirable that the respective layers are sequentially etched from above by a spray method.

It is preferable that the thin film underlying conductive layer is composed of two layers, the lower metal layer is nickel and the upper metal layer is copper.

Therefore, according to the etching solution for the spray method of the present invention, it is possible to carry out etching even in the state of a new solution or even when the concentration of nitric acid or sulfuric acid is lowered, and the etching rate is stabilized and its control is controlled. It's easy.

Further, according to the method of manufacturing an electronic circuit board of the present invention, the etching speed of the thin film underlying conductive layer can be easily controlled by using the above-mentioned spray etching solution, and therefore, there is no side etching. A circuit wiring having a stable shape can be obtained.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION An etching solution for a spray method according to the present invention and a method for producing an electronic circuit board suitable using the same will be described below with reference to the drawings.

FIG. 1 is a partial cross-sectional view of an electronic circuit board for explaining an etching method by a spray method in a method for manufacturing an electronic circuit board of the present invention, and FIG. 2 is an etching method for the electronic circuit board in the state shown in FIG. FIG. 3 is a partial cross-sectional view of the electronic circuit board of the present invention in which the circuit wiring is formed by applying the etching solution, and FIG. 3 is a graph showing the stability of the graph of the etching time.

FIG. 1 is a reprint of a part of the electronic circuit board in the manufacturing process shown in FIG. 4D. Since the manufacturing steps of FIGS. 4A to 4C up to this manufacturing step are the same in the present invention, the same structural parts are denoted by the same reference numerals, and the description of the manufacturing steps will be omitted.

Reference numeral 1 is an organic substrate serving as a base, reference numeral 2 is a thin film base conductive layer made of, for example, Ni formed by sputtering to increase the degree of adhesion with the substrate 1, and reference numeral 3 is a thin film base conductive layer 2. A thin-film underlying conductive layer of, for example, Cu, which is a seed metal formed by sputtering, and reference numeral 5 is a conductive layer of, for example, Cu, which is formed by plating. The metal of the thin film underlying conductive layers 2 and 3 and the conductive layer 5 is not limited, and the same applies to the substrate 1.

Examples of the present invention will be described below.

As shown in FIG. 1, a thin film base conductive layer 2 of Ni having a thickness of 250Å is formed on the surface of the substrate 1 by sputtering, and further, a thickness of 5000Å is formed on the thin film base conductive layer 2. Of Cu was formed by sputtering.

Next, the conductive layer 5 having a thickness of 1 is formed by plating.
Cu of 0 μm was formed.

Thereafter, the thin film underlying conductive layers 2 and 3 which are unnecessary for the circuit wiring 6A are removed by etch back using a spraying method, and the circuit wiring 6A having the structure shown in FIG. 2 is finished.

An example of the etching solution of the present invention used for the etch back will be described below.

An etching solution as a base is prepared from a mixed solution containing three kinds of acids, that is, sulfuric acid, nitric acid and acetic acid as main components. The ratio is an EL grade weight ratio of sulfuric acid / nitric acid / acetic acid / water: 5 / 1.5 / 10/8.

FIG. 3 is a graph showing the number of repeated etchings and the etching time of the electronic circuit board which was etched by the dipping method using this etching solution. From this graph, only the time of the first etching in the state of the new liquid is long, the etching time of the second and subsequent etchings is short, and is almost constant and stable.

In the case of etching by the spray method, since it is always in the state of a new solution, it is necessary to increase the acid concentration in order to shorten the etching time, and the rate changes during etching. It was found that the cause of this was greatly influenced by the impurity metal concentration in the etching solution.
Then, the metal concentration of the etching target is important, and in the case of this embodiment, the Cu concentration has a great influence. After the second time,
The etching time is stable because the etched Cu
This is because it is itself dissolved as an impurity.

Therefore, in the present invention, a trace amount of copper in the form of a salt such as copper sulfate or copper nitrate is added in advance to stabilize the etching rate even in the state of a new solution.

With the etching solution of the present invention, the same etching effect as the second and subsequent times could be obtained with the following composition ratios. That is, sulfuric acid / nitric acid / acetic acid / water / copper nitrate: 5 / 1.5 / 10/8
/0.1 (weight ratio) As a result, the etching solution of the present invention was able to reduce the acid concentration as a whole, and it was possible to obtain a circuit wiring 6A having a finer and straight cross-sectional shape. The accuracy of the circuit wirings 6 and 6A of the electronic circuit board manufactured by the conventional technique and the manufacturing method of the present invention was 100 ± 40 μm (the trapezoidal sectional shape) of the conventional method and 10 ± 2 μm (the rectangular sectional shape) of the present invention. .

In the conventional etching solution, due to the difference in etching rate between Ni of the thin film underlying conductive layer 2 and Cu of the thin film underlying conductive layer 3, side etching occurs in the Cu portion of the conductive layer 5, and conversely the thin film underlying conductive layer is etched. Although the etching residue of Ni of the layer 2 was likely to occur, the above-mentioned unfavorable phenomenon could be prevented by etching by the spray method using the etching solution of the present invention.

As is clear from the above description, the thin film underlying conductive layer 2 is formed on the substrate 1 by sputtering according to the method for manufacturing an electronic circuit board of the present invention. Can be firmly adhered to the
Since the thin film underlying conductive layer 3 as a seed metal is formed on the surface of the thin film underlying conductive layer 2 by sputtering, and the conductive layer 5 is formed thereon by plating using a mask of a plating resist, the circuit wiring 6A is formed. It can be firmly formed on the substrate 1,
Then, by etching the thin film underlying conductive layers 2 and 3 by a spray method using the etching solution of the present invention, the fine and highly accurate circuit wiring 6A can be formed without the conductive layer 5 being side-etched. Is now possible.

It should be noted that in order to obtain higher-performance characteristics with less loss at high frequencies, it is desirable to use a substrate having high heat resistance as the material of the base substrate 1. For example, in addition to the above LCP (liquid crystal polymer), PI (polyimide), PPE (polyphenyl ether) and the like can be mentioned. Examples of the material of the insulating layer of the thin film wiring portion formed on the base substrate 1 include BCB (benzocyclobutene), PI, PNB (polynorporne).

[0039]

As described above, according to the present invention,
As a whole, the circuit wiring can be adhered firmly to the substrate made of an organic material or the like, and the circuit wiring can be formed with precise fine lines. Therefore, 1. 1. High-precision circuit wiring can be obtained, impedance matching can be easily achieved, and a circuit corresponding to high frequency characteristics in the GHz band can be formed. 2. Inductors, which were conventionally mounted as components, can be directly formed on the surface of the board. Many excellent effects can be obtained, such as being able to mount many parts and simultaneously downsizing the electronic circuit board itself.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of an electronic circuit board for explaining an etching method by a spray method in a method for manufacturing an electronic circuit board of the present invention.

FIG. 2 is a partial cross-sectional view of the electronic circuit board of the present invention in which circuit wiring is formed by etching the electronic circuit board in the state shown in FIG.

FIG. 3 is a graph showing the stability of a graph of the number of repeated etchings and the etching time when the electronic circuit board is etched by the dipping method using the etching solution of the present invention.

FIG. 4 is a process drawing for explaining a general method for manufacturing an electronic circuit board.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Insulating substrate, 2, 3 ... Thin film base conductive layer, 4 ... Plating resist, 5 ... Conductive layer, 6 ... Circuit wiring, 10 ... Electronic circuit board of one embodiment of the present invention

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 4K057 WA13 WB03 WB04 WC08 WE02                       WE03 WE12 WK07 WM04 WN01                 5E339 BC01 BC02 BE17 CE17                 5E343 BB24 BB44 CC33 CC34 CC50                       DD25 DD32 DD76 EE52 ER26                       GG06

Claims (5)

[Claims] 1. An etching solution for a spray method, wherein an additive in the form of a salt such as copper sulfate or copper nitrate is added to a mixed acid solution containing nitric acid, sulfuric acid or acetic acid as a main component as a base. 2. The amount of the additive added is 1% by weight based on the total weight.
The etching solution for a spray method according to claim 1, wherein: 3. A method of manufacturing an electronic circuit board, wherein circuit wiring is formed on a surface of an electrically insulating substrate by plating, a step of forming an underlayer conductive layer on the surface of the electrically insulating substrate by sputtering, and on the thin film underlayer conductive layer. To form a predetermined circuit wiring pattern using a plating resist, a step of plating a conductive material on the circuit wiring pattern, a step of removing the plating resist, and a portion exposed by removing the plating resist. The thin film underlying conductive layer is etched by a spray method using an etching solution containing a mixed acid solution containing nitric acid, sulfuric acid and acetic acid as a main component and an additive in a salt state such as copper sulfate and copper nitrate. A method for manufacturing an electronic circuit board, comprising forming the circuit wiring through a manufacturing process including a process. 4. The method for manufacturing an electronic circuit board according to claim 4, wherein the thin film underlying conductive layer is composed of a plurality of layers of different metals, and the respective layers are sequentially etched from above by a spray method. . 5. The method of manufacturing an electronic circuit board according to claim 3, wherein the thin film underlying conductive layer is composed of two layers, the lower layer metal is nickel, and the upper layer metal is copper. .