JP2011096933A - Method of manufacturing wiring circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a wiring circuit board by which an additional insulating layer can be formed thin and prevented from peeling from a metal support substrate. <P>SOLUTION: A base insulating layer 3 is partially formed on the metal support substrate 2, a chrome thin film 20 and a copper thin film 21 are formed in order on the base insulating layer 3 and the metal support substrate 2 exposed from the base insulating layer 3, and a conductor pattern 4 is formed on the copper thin film 21. The copper thin film 21 exposed from the conductor pattern 4 is removed, a palladium catalyst 22 is stuck on surfaces of the conductor pattern 4 and chrome thin film 20, and the chrome thin film 20 exposed from the conductor pattern 4 is removed together with the palladium catalyst 22 stuck on a surface of the chrome thin film 20. A nickel plating layer is formed on a surface of the conductor pattern where the palladium catalyst is stuck, a cover insulating layer 5 is formed on the base insulating layer 3 so as to cover the conductor pattern 4, and a pedestal 13 is formed on the metal support substrate 2 exposed from the base insulating layer 3. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a wired circuit board, and more particularly to a method for manufacturing a wired circuit board such as a suspension board with circuit.

  The suspension board with circuit covers a metal supporting board, a base insulating layer formed on the metal supporting board, a conductor pattern formed on the base insulating layer, and a conductor pattern on the base insulating layer. A cover insulating layer formed as described above. Such a suspension board with circuit is mounted on, for example, a hard disk drive by mounting a head slider.

As a method for manufacturing a suspension board with circuit, for example, the following methods are known.
That is, first, an insulating base layer is formed in a predetermined pattern on a supporting substrate, and a chromium thin film and a copper thin film are sequentially formed on the surface of the supporting substrate exposed from the insulating base layer and the entire surface of the insulating base layer. . Next, the conductor layer is formed with a wiring circuit pattern on the surface of the copper thin film formed on the base insulating layer, and the copper thin film other than the portion where the wiring circuit pattern of the conductor layer is formed is removed. Next, the conductor layer is activated with a palladium chloride catalyst solution to form an electroless nickel plating layer that covers the conductor layer. Thereafter, after removing the chromium thin film other than the portion covered with the electroless nickel plating layer, a cover insulating layer for covering the conductor layer is formed in a predetermined pattern (see, for example, Patent Document 1).

In such a suspension board with circuit, the head slider is usually mounted on a pedestal formed on a metal support board.
Such a pedestal is formed as a pedestal base insulating layer together with the insulating base layer from the insulating layer similar to the insulating base layer at the head slider mounting position (see, for example, Patent Document 2).

JP 2005-135981 A JP 2009-104712 A

However, in the suspension board with circuit as described in Patent Document 1, the base insulating layer is formed to have a predetermined thickness or more in order to insulate the support substrate and the conductor layer.
Therefore, when a pedestal base insulating layer is formed together with the base insulating layer on such a suspension board with circuit by the method described in Patent Document 2, the pedestal base insulating layer is also formed thicker with the thickness of the base insulating layer. The

On the other hand, in recent years, it has been required to make the pedestal on which the head slider is mounted thin to achieve a thinner suspension board with circuit.
In order to meet such a demand, for example, it is considered to form a pedestal on which the head slider is mounted together with the cover insulating layer from the same insulating layer as the cover insulating layer.
Since the insulating cover layer can be formed thinner than the insulating base layer, according to such a method, the pedestal can be formed thin and the suspension board with circuit can be thinned.

And when forming a pedestal by the manufacturing method of the board | substrate with a circuit described in patent document 1, since the chromium thin film on a support substrate is activated with a palladium chloride catalyst liquid with a conductor layer, it is electroless nickel. A plating layer is also formed on the chromium thin film.
In this method, only the chromium thin film other than the portion covered with the electroless nickel plating layer is removed, so the chromium thin film and the electroless nickel plating layer formed on the support substrate are not removed. Remains.

Therefore, when a pedestal is formed together with the insulating cover layer on the suspension board with circuit obtained by the above method, an electroless nickel plating layer is interposed between the support substrate and the pedestal. There arises a problem that it is easy to peel off from the support substrate.
The present invention has been made in view of such problems, and the object of the present invention is to provide a wiring circuit capable of forming an additional insulating layer thinly and preventing the additional insulating layer from peeling from the metal support substrate. It is to provide a method for manufacturing a substrate.

  In order to achieve the above object, a method of manufacturing a wired circuit board according to the present invention includes a step of preparing a metal support substrate, a step of partially forming a base insulating layer on the metal support substrate, and the base Forming a chromium thin film on the insulating layer and on the metal supporting substrate exposed from the base insulating layer; forming a copper thin film on the chromium thin film; and A step of forming a conductor pattern, a step of removing the copper thin film exposed from the conductor pattern, a step of attaching a palladium catalyst to the surface of the conductor pattern and the surface of the chromium thin film, and the conductor The step of removing the chromium thin film exposed from the pattern together with the palladium catalyst adhering to the surface, and the surface of the conductor pattern to which the palladium catalyst adheres Forming a nickel plating layer by nickel plating; and forming an insulating cover layer on the insulating base layer so as to cover the conductive pattern, and on the metal supporting substrate exposed from the insulating base layer. And a step of forming an additional insulating layer.

According to the method for manufacturing a wired circuit board of the present invention, since the palladium catalyst is removed together with the chromium thin film from the surface of the metal supporting board before the nickel plating layer is formed, the nickel plating layer is formed on the metal supporting board. It is not formed on the surface, but only on the surface of the conductor pattern.
Therefore, according to such a method for manufacturing a wired circuit board, the nickel plating layer is prevented from intervening between the additional insulating layer and the metal supporting board, and as a result, the additional insulating layer is peeled off from the metal supporting board. This can be prevented.

  Further, according to the method for manufacturing a wired circuit board of the present invention, since the additional insulating layer is formed together with the cover insulating layer, the additional insulating layer can be formed thin, and the printed circuit board can be thinned. it can.

It is a top view of the suspension board with circuit which is one embodiment of the wired circuit board of the present invention. FIG. 2 is an enlarged plan view of a tip portion of the suspension board with circuit shown in FIG. 1. It is the sectional view on the AA line of FIG. FIGS. 2A and 2B are process diagrams showing a manufacturing method of the suspension board with circuit shown in FIG. 1, in which FIG. 1A is a process for preparing a metal support board, and FIG. 2B is a partial insulating base layer on the metal support board; (C) forming a chromium thin film on the base insulating layer and a metal supporting substrate exposed from the base insulating layer, and (d) forming a copper thin film on the chromium thin film. The step of forming a thin film, (e) shows the step of forming a conductor pattern on the copper thin film, and (f) shows the step of removing the copper thin film exposed from the conductor pattern. FIG. 4 is a process diagram showing a manufacturing method of the suspension board with circuit shown in FIG. 1 following FIG. 4, wherein (g) is a process of attaching a palladium catalyst to the surface of the conductor pattern and the surface of the chromium thin film; h) a step of removing the chromium thin film exposed from the conductor pattern together with the palladium catalyst adhering to the surface, and (i) a nickel plating layer by electroless nickel plating on the surface of the conductor pattern to which the palladium catalyst adheres. (J) is a step of forming a cover insulating layer on the insulating base layer so as to cover the conductor pattern and forming a pedestal on the metal supporting substrate exposed from the insulating base layer. Indicates.

  FIG. 1 is a plan view of a suspension board with circuit as an embodiment of the wired circuit board of the present invention, FIG. 2 is an enlarged plan view of a front end portion of the suspension board with circuit shown in FIG. 1, and FIG. FIG. 4 is a process diagram showing a method for manufacturing the suspension board with circuit shown in FIG. 1, and FIG. 5 shows a method for manufacturing the suspension board with circuit shown in FIG. It is process drawing. In FIGS. 1 and 2, the insulating base layer 3 (described later) and the insulating cover layer 5 (described later) are omitted in order to clearly show the relative arrangement of the conductor patterns 4.

In FIG. 1, a suspension board with circuit 1 includes a conductor pattern 4 for electrically connecting a magnetic head (not shown) and a read / write board (not shown) to a metal supporting board 2 extending in the longitudinal direction. Are integrally formed.
The conductor pattern 4 connects a magnetic head side connection terminal portion 6 (hereinafter sometimes simply referred to as “terminal portion 6”) for connection to a connection terminal (not shown) of the magnetic head, and a read / write substrate. An external connection terminal portion 7 for connecting to a terminal (not shown) and a wiring 8 for connecting the magnetic head side connection terminal portion 6 and the external connection terminal portion 7 are integrally provided.

A plurality (four) of the wirings 8 are provided along the longitudinal direction of the metal support substrate 2 and are arranged in parallel at intervals in the width direction (direction orthogonal to the longitudinal direction).
The magnetic head side connection terminal portion 6 is formed as a square land, and a plurality (four) are provided so that the tip ends of the respective wires 8 are connected to each other, and the tip portion (one longitudinal end) of the metal support substrate 2 is provided. Part) is arranged in parallel at intervals in the width direction.

The external connection terminal portion 7 is formed as a square land, and a plurality (four) of the external connection terminal portions 7 are provided so that the rear end portions of the respective wires 8 are connected to each other. In the other end portion), they are arranged in parallel at intervals in the width direction.
As shown in FIG. 3, the suspension board with circuit 1 includes a metal supporting board 2, a base insulating layer 3 formed on the metal supporting board 2, and a conductor pattern formed on the base insulating layer 3. 4 and a cover insulating layer 5 formed on the insulating base layer 3 and covering the wiring 8 of the conductor pattern 4.

The insulating base layer 3 is formed on the surface of the metal supporting board 2 corresponding to the conductor pattern 4.
As will be described in detail later, the conductor pattern 4 is formed by, for example, a known additive method, and a copper thin film 21 and a chromium thin film 20 are interposed between each wiring 8 and the base insulating layer 3.
The copper thin film 21 and the chromium thin film 20 are formed on the lower surface of the wiring 8 so that they are sequentially laminated, and more specifically, are formed in substantially the same pattern as the wiring 8.

A nickel plating layer 23 is formed on the surface (upper surface and side surface) of the conductor pattern 4.
The insulating cover layer 5 is formed on the surface of the insulating base layer 3 so as to cover the wiring 8 and expose the magnetic head side connection terminal portion 6 and the external side connection terminal portion 7.
Next, the tip of the suspension board with circuit 1 will be described in detail with reference to FIGS.

As shown in FIG. 2, a terminal surface 6, a U-shaped opening 11, a joint surface 12 to which a slider 9 (see FIG. 3 (broken line)) is joined, and a slider 9 (see FIG. 3 (broken line)) is provided as a base 13 as an additional insulating layer.
Each terminal part 6 is arrange | positioned at the front-end | tip edge part of the suspension board | substrate 1 with a circuit, and is arrange | positioned in parallel at intervals in the width direction. The rear end surfaces of the terminal portions 6 are arranged so as to be flush with each other in the width direction. A wiring 8 is connected to the tip of each terminal portion 6. That is, the wiring 8 includes a pair (two) of wirings 8A on one side in the width direction and a pair (two) of wirings 8B on the other side in the width direction. After passing through both ends in the width direction (both sides in the width direction of the U-shaped opening 11) and reaching the tip edge, it bends inward in the width direction, and further bends to the rear side. Has been routed to be connected.

  The width (length in the width direction) of each terminal portion 6 is, for example, 15 to 200 μm, preferably 50 to 100 μm. The interval between the terminal portions 6 (interval in the width direction) is, for example, 15 to 200 μm, Preferably, it is 20-100 micrometers. Thereby, the length between the terminal parts 6 arrange | positioned at the width direction both outermost sides is set to 400-1100 micrometers, for example, Preferably, it is set to 500-1000 micrometers.

  The U-shaped opening 11 is formed in a substantially U shape that is open toward the front side in a plan view, and is formed so as to penetrate the metal support substrate 2 in the thickness direction. In the width direction, the U-shaped opening 11 is disposed between a pair of wirings 8A on one side in the width direction and a pair of wirings 8B on the other side in the width direction. Specifically, the U-shaped opening 11 is set with a margin between both ends in the width direction of the metal support substrate 2 so that a pair of wirings 8 can pass through both outer sides in the width direction. A margin with the front end edge of the metal supporting board 2 is set so that the terminal part 6 is disposed at the front edge part.

The joint surface 12 is partitioned on the surface of the metal support substrate 2 on the inner side in the width direction of the U-shaped opening 11, and is substantially rectangular in plan view so that the slider 9 (see FIG. 3 (broken line)) is opposed to the joint surface 12. Divided into shapes. The joint surface 12 is disposed adjacent to the terminal portion 6 with a gap in the longitudinal direction.
The pedestal 13 is formed in a substantially rectangular flat plate shape in plan view slightly smaller than the joint surface 12 on the inner side in the width direction of the U-shaped opening 11.

Although not shown, a metal plating layer is provided on the surfaces of the magnetic head side connection terminal portion 6 and the external side connection terminal portion 7 exposed from the insulating cover layer 5 as necessary.
Next, a method for manufacturing the suspension board with circuit 1 will be described with reference to FIGS.
A known roll-to-roll method is employed as a method for manufacturing the suspension board with circuit 1.

First, in this method, a metal support substrate 2 is prepared as shown in FIG.
As a metal material for forming the metal support substrate 2, for example, stainless steel, 42 alloy or the like is used, and stainless steel is preferably used.
The thickness of the metal supporting board 2 is, for example, 10 to 60 μm, preferably 15 to 25 μm, and the length in the width direction is, for example, 50 to 500 mm, preferably 100 to 300 mm.

Next, in this method, as shown in FIG. 4B, the base insulating layer 3 is partially formed on the metal support substrate 2. More specifically, the base insulating layer 3 is formed so as to correspond to the portion where the conductor pattern 4 is formed and to expose the surface of the metal support substrate 2 at the bonding surface 12 (see FIG. 2).
The insulating material forming the base insulating layer 3 is, for example, a synthetic resin such as polyimide resin, polyamideimide resin, acrylic resin, polyether nitrile resin, polyethersulfone resin, polyethylene terephthalate resin, polyethylene naphthalate resin, polyvinyl chloride resin, etc. Is used. Of these, a photosensitive synthetic resin is preferably used, and a photosensitive polyimide is more preferably used.

A known method is employed to form the base insulating layer 3. More specifically, for example, a photosensitive synthetic resin solution (varnish) is applied to the entire surface of the metal support substrate 2 and heated at, for example, 60 to 180 ° C., preferably 90 to 160 ° C. After obtaining the precursor film, a predetermined pattern is formed using an irradiation beam having a wavelength of, for example, 300 to 450 nm, preferably 350 to 420 nm, using a photomask. In addition, the integrated exposure amount in exposure is 100-2000 mJ / cm < ² >, for example, Preferably, it is 600-1300 mJ / cm < ² >. Next, for example, after heating at 150 to 200 ° C. to insolubilize the exposed portion, development is performed in a predetermined pattern with a known developer such as an alkali developer. Then, for example, it is heated at 250 ° C. or higher and cured.

The insulating base layer 3 is formed by uniformly applying the above-described synthetic resin solution (varnish) on the entire surface of the metal support substrate 2, then drying, and then curing by heating as necessary. Thereafter, the pattern can be formed by etching or the like.
Furthermore, the base insulating layer 3 is formed by, for example, previously forming a synthetic resin on a film having the above-described pattern, and sticking the film to the surface of the metal support substrate 2 via a known adhesive layer. You can also.

The insulating base layer 3 thus formed has a thickness of, for example, 5 to 15 μm, or preferably 8 to 10 μm.
Next, in this method, as shown in FIG. 4C, the chromium thin film 20 is formed on the base insulating layer 3 and on the metal supporting substrate 2 exposed from the base insulating layer 3.
The chromium thin film 20 can be formed by a known method such as a sputtering method, a vacuum deposition method, or an ion plating method. Preferably, a sputtering method (chromium sputtering method) is used.

The thickness of the chromium thin film 20 is, for example, 10 to 60 nm, preferably 20 to 40 nm.
Next, in this method, as shown in FIG. 4D, a copper thin film 21 is formed on the chromium thin film 20.
The copper thin film 21 can be formed by a known method such as a sputtering method, a vacuum deposition method, or an ion plating method. Preferably, a sputtering method (copper sputtering method) is used.

The thickness of the copper thin film 21 is, for example, 50 to 200 nm, preferably 60 to 80 nm.
Next, in this method, the conductor pattern 4 is formed on the copper thin film 21 as shown in FIG.
As a conductive material for forming the conductive pattern 4, for example, a conductive material such as copper, nickel, gold, solder, or an alloy thereof is used, and preferably copper is used.

In order to form the conductor pattern 4, first, a plating resist made of, for example, a photosensitive dry film resist or the like is formed on the surface of the copper thin film 21 as an inverted pattern of the conductor pattern 4.
Thereafter, the conductor pattern 4 is formed by electrolytic plating on the surface of the copper thin film 21 exposed from the plating resist, and then the plating resist is removed by a known resist stripping solution such as an aqueous sodium hydroxide solution.

The thickness of the conductor pattern 4 thus formed is, for example, 3 to 50 μm, preferably 5 to 25 μm.
Next, in this method, as shown in FIG. 4F, the copper thin film 21 exposed from the conductor pattern 4 is removed.
The copper thin film 21 can be removed by etching using, for example, a nitrate hydrogen peroxide mixed solution as an etching solution.

Next, in this method, as shown in FIG. 5G, the palladium catalyst 22 is attached to the surface of the conductor pattern 4 and the surface of the chromium thin film 20.
For example, the palladium catalyst 22 can be attached to the surface of the conductive pattern 4 and the chromium thin film 20 by immersing them in an aqueous palladium chloride solution. The immersion time in such a case is, for example, 30 to 150 seconds, and preferably 60 to 120 seconds.

Next, in this method, as shown in FIG. 5H, the chromium thin film 20 exposed from the conductor pattern 4 is removed together with the palladium catalyst 22 adhering to the surface.
In this method, the chromium thin film 20 can be removed by etching using, for example, an etching solution having low solubility in copper and high solubility in chromium. More specific examples of such a solution include an aqueous potassium ferricyanide solution.

As a result, the chromium thin film 20 on the metal support substrate 2 is removed together with the palladium catalyst 22, and the palladium catalyst 22 adheres only to the surface (upper surface and side surfaces) of the conductor pattern 4.
Next, in this method, as shown in FIG. 5 (i), a nickel plating layer 23 is formed by electroless nickel plating on the surface of the conductor pattern 4 to which the palladium catalyst 22 adheres.

In this method, for example, the electroless nickel plating layer 23 is not formed on the surface of the metal support substrate 2 exposed from the base insulating layer 3, but the conductor pattern 4 (magnetic head side connection terminal portion 6) to which the palladium catalyst 22 is attached. And the external connection terminal portion 7).
The electroless nickel plating layer 23 is formed as a hard nickel thin film, and the thickness thereof is, for example, 0.05 to 0.2 μm.

Next, in this method, as shown in FIG. 5 (j), the insulating cover layer 5 is formed on the insulating base layer 3 so as to cover the conductive pattern 4, and the metal support exposed from the insulating insulating layer 3 is supported. A pedestal 13 is formed on the substrate 2.
More specifically, in this method, the insulating cover layer 5 is formed so as to cover the wiring 8 and expose the magnetic head side connection terminal portion 6 and the external side connection terminal portion 7, and the metal support substrate 2. A pedestal 13 is formed on the surface.

Examples of the insulating material for forming the insulating cover layer 5 and the pedestal 13 include the same insulating materials as those for the insulating base layer 3.
In order to form the insulating cover layer 5 and the base 13 simultaneously, for example, a photosensitive synthetic resin solution (varnish) is applied to the entire surface of the insulating base layer 3 and the metal supporting substrate 2 exposed from the insulating base layer 3. Then, after drying, exposure and development are performed by a method similar to the formation of the base insulating layer 3 described above, and curing is performed as necessary. In addition, the integrated exposure amount in exposure is 100-2000 mJ / cm < ² >, for example, Preferably, it is 300-1300 mJ / cm < ² >.

The insulating cover layer 5 and the pedestal 13 are formed by uniformly applying the above-described synthetic resin solution (varnish) to the entire upper surface of the insulating base layer 3, drying, and then heating as necessary. Then, it can be cured, and then formed into the above-described pattern by etching or the like.
Furthermore, the insulating cover layer 5 and the pedestal 13 are formed, for example, by previously forming a synthetic resin on a film having the above-described pattern, and attaching the film to the surface of the insulating base layer 3 via a known adhesive layer. You can also wear it.

The insulating cover layer 5 and the pedestal 13 thus formed have a thickness of, for example, 3 to 8 μm, preferably 4 to 5 μm.
Thereafter, although not shown, the nickel plating layer 23 formed on the surface (upper surface) of the magnetic head side connection terminal portion 6 and the external side connection terminal portion 7 exposed from the insulating cover layer 5 is removed, and then the magnetic head side A metal plating layer is formed on the surfaces (upper surfaces) of the connection terminal portion 6 and the external connection terminal portion 7 by, for example, electrolytic gold plating.

The nickel plating layer 23 can be removed by etching using, for example, a nitric acid-hydrogen peroxide mixture or the like as an etching solution.
Thereafter, if necessary, the metal support substrate 2 is processed into a desired shape.
The outer shape processing is not particularly limited. For example, a photosensitive dry film resist is laminated on the front surface (including the base insulating layer 3, the conductor pattern 4, the cover insulating layer 5, and the pedestal 13) and the back surface of the metal support substrate 2, for example. Then, after exposing and developing to a predetermined pattern, the metal supporting substrate 2 exposed from the dry film resist is treated with an acid such as ferric chloride, hydrogen peroxide / sulfuric acid mixture, ammonium persulfate, sodium persulfate, etc. Etching is performed using an etching solution such as a chemical solution.

Thereby, the suspension board with circuit 1 can be formed.
Although not shown, in order to control the impedance of the suspension board with circuit 1, for example, the metal supporting board 2 on the lower surface of the base insulating layer 3 can be partially removed to form an opening. .
The opening part in particular of the metal support substrate 2 is not restrict | limited, For example, it can form with the same method with the external shape process of the said metal support substrate 2. FIG.

Then, as shown in FIG. 3, a slider 9 (see the broken line) is mounted on the suspension board with circuit 1 thus obtained. Although not shown, the slider 9 is formed in a rectangular flat plate shape having a size slightly larger than the joining surface 12, and a magnetic head is mounted on the tip of the slider 9.
As a method for mounting the slider 9, a known method may be used. For example, after applying an adhesive to the upper surface of the pedestal 13, the slider 9 is placed on the pedestal so that the lower surface thereof is in contact with the upper surface of the pedestal 13. 13 is placed.

Thereafter, a solder ball (not shown) is disposed between the connection terminal (not shown) of the magnetic head and the terminal portion 6 (or a metal plating layer formed on the surface of the terminal portion 6), and the solder After the ball is melted and solidified, the connection terminal (not shown) of the magnetic head and the terminal portion 6 are electrically connected.
Thereby, the slider 9 can be mounted on the suspension board with circuit 1.

  In the method of manufacturing the suspension board with circuit 1, for example, if the nickel plating layer 23 is interposed between the pedestal 13 and the metal support substrate 2, the pedestal 13 is removed when the nickel plating layer 23 is removed by etching. The lower nickel plating layer 23 is partially removed (that is, an undercut occurs in the pedestal 13), which may cause the pedestal 13 to peel from the metal support substrate 2.

On the other hand, according to the method for manufacturing the suspension board with circuit 1, the palladium catalyst 22 is removed from the surface of the metal supporting board 2 together with the chromium thin film 20 before the nickel plating layer 23 is formed. The plating layer 23 is not formed on the surface of the metal support substrate 2 but is formed only on the surface (upper surface and side surface) of the conductor pattern 4.
Therefore, according to the manufacturing method of the suspension board with circuit 1 as described above, the nickel plating layer 23 is prevented from intervening between the pedestal 13 and the metal support board 2, and as a result, the metal support board 2 to the pedestal 13. Can be prevented from peeling off.

  Further, according to the method of manufacturing the suspension board with circuit 1, since the pedestal 13 is formed together with the insulating cover layer 5, the pedestal 13 can be formed thin, and the suspension board with circuit 1 can be thinned. Can be planned.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the examples and comparative examples.
Example A suspension board with circuit was manufactured by the following method by a roll-to-roll method.

That is, first, a roll-shaped stainless steel foil having a width of 300 mm, a thickness of 18 μm, and a length of 140 m is prepared (see FIG. 4A), and a photosensitive polyamic acid solution (JR-3380P, manufactured by Nitto Denko Corporation) is prepared thereon. ) Was applied at a thickness of 25 μm and then heat-treated at 150 ° C. to obtain a polyimide precursor film. Next, the polyimide precursor film was exposed with a predetermined pattern on which a base insulating layer was formed using a photomask. At this time, the integrated exposure amount was set to 1000 mJ / cm ² . Thereafter, the polyimide precursor film is developed using an organic solvent developer to form a predetermined pattern, and then cured at 370 to 400 ° C. to partially form a base insulating layer having a thickness of 10 μm on the stainless steel foil. It formed (refer FIG.4 (b)).

Next, a chromium thin film having a thickness of 30 nm is formed by sputtering on the base insulating layer and on the stainless steel foil exposed from the base insulating layer (see FIG. 4C), and then on the chromium thin film. A copper thin film having a thickness of 70 nm was formed by sputtering (see FIG. 4D).
Then, a photosensitive dry film resist (UFG255, manufactured by Asahi Kasei E-Materials Co., Ltd.) was laminated, and exposed using a photomask in a pattern opposite to the pattern in which the conductor pattern was formed. At this time, the integrated exposure amount was 180 mJ / cm ² . Thereafter, at 25 ° C., the photosensitive dry film resist was developed with a 0.7 wt% sodium carbonate aqueous solution to form a plating resist having a pattern opposite to the pattern on which the conductor pattern was formed.

Next, a conductor pattern having a thickness of 12 μm was formed by electrolytic copper plating on the copper thin film exposed from the plating resist, and then the plating resist was removed (see FIG. 4E).
Next, the copper thin film exposed from the conductor pattern was removed by etching using a mixed solution of hydrogen nitrate and hydrogen peroxide (see FIG. 4F).
Subsequently, it was immersed in the palladium chloride aqueous solution, and the palladium catalyst was made to adhere to the surface of a conductor pattern, and the surface of a chromium thin film (refer FIG.5 (g)).

Next, the chromium thin film exposed from the conductor pattern was etched using an aqueous potassium ferricyanide solution and removed together with the palladium catalyst adhering to the surface (see FIG. 5 (h)).
Next, an electroless nickel plating process was performed, and a nickel plating layer was formed by electroless nickel plating on the upper and side surfaces of the conductor pattern to which the palladium catalyst was adhered (see FIG. 5 (i)).

Next, a photosensitive polyamic acid solution (JR-3380P, manufactured by Nitto Denko Corporation) was applied at a thickness of 9 μm, and then heat-treated at 150 ° C. to obtain a polyimide precursor film. Next, the polyimide precursor film was exposed with a predetermined pattern in which a cover insulating layer and a pedestal were formed using a photomask. At this time, the integrated exposure amount was set to 1000 mJ / cm ² . Thereafter, the polyimide precursor film is developed using an organic solvent developer to form a predetermined pattern, and then cured at 370 to 400 ° C. to cover the base insulating layer so as to cover the conductor pattern. A layer was formed, and a pedestal was formed on the stainless steel foil exposed from the base insulating layer (see FIG. 5J). The cover insulating layer and the pedestal had a thickness of 5 μm.

Next, the nickel plating layer formed on the conductor pattern exposed from the insulating cover layer (the upper surface of the magnetic head side connection terminal portion and the upper surface of the external connection terminal portion) is etched using a hydrogen peroxide nitrate mixed solution. Removed.
Next, the stainless steel foil was trimmed and an impedance control opening was formed in the stainless steel foil on the lower surface side of the base insulating layer. That is, a photosensitive dry film resist (AQ-4059, manufactured by Asahi Kasei E-Materials Co., Ltd.) was laminated and exposed with a predetermined pattern using a photomask. At this time, the integrated exposure amount was set to 105 mJ / cm ² . Thereafter, at 25 ° C., the photosensitive dry film resist was developed with a 0.7 wt% sodium carbonate aqueous solution to form an etching resist in a predetermined pattern.

Next, using a ferric chloride solution, the stainless steel foil exposed from the etching resist was removed by etching, the stainless steel foil was trimmed, and an opening was formed in the stainless steel foil, and then the etching resist was peeled off.
Thereafter, a metal plating layer was formed on the conductor pattern exposed from the insulating cover layer (the upper surface of the magnetic head side connection terminal portion and the upper surface of the external connection terminal portion) by electrolytic gold plating.

As a result, a suspension board with circuit was obtained.
In the obtained suspension board with circuit, the pedestal had excellent adhesion to the stainless steel foil, and did not peel from the stainless steel foil.
Comparative Example Before removing the chromium thin film, a nickel plating layer was formed by electroless nickel plating on the top and side surfaces of the conductor pattern to which the palladium catalyst adheres and the surface of the metal support substrate, and then exposed from the nickel plating layer. A suspension board with circuit was obtained by the same operation as in the example except that the chromium thin film to be removed was removed together with the palladium catalyst.

  In the obtained suspension board with circuit, the pedestal had poor adhesion to the stainless steel foil and was easy to peel from the stainless steel foil.

DESCRIPTION OF SYMBOLS 1 Suspension board with a circuit 2 Metal support board 3 Base insulating layer 4 Conductive pattern 5 Cover insulating layer 6 Magnetic head side connection terminal part 7 External side connection terminal part 8 Wiring 9 Slider 11 U-shaped opening part 12 Joint surface 13 Base 20 Chrome thin film 21 Copper thin film 22 Palladium catalyst 23 Nickel plating layer

Claims (1)

Preparing a metal support substrate;
Partially forming a base insulating layer on the metal support substrate;
Forming a chromium thin film on the base insulating layer and on the metal supporting substrate exposed from the base insulating layer;
Forming a copper thin film on the chromium thin film;
Forming a conductor pattern on the copper thin film;
Removing the copper thin film exposed from the conductor pattern;
Attaching a palladium catalyst to the surface of the conductor pattern and the surface of the chromium thin film;
Removing the chromium thin film exposed from the conductor pattern together with the palladium catalyst adhering to the surface thereof;
Forming a nickel plating layer by electroless nickel plating on the surface of the conductor pattern to which the palladium catalyst adheres;
Forming a cover insulating layer on the base insulating layer so as to cover the conductor pattern, and forming an additional insulating layer on the metal supporting substrate exposed from the base insulating layer. A method of manufacturing a printed circuit board.

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