JP2007088056A - Wiring circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring circuit board provided with a noise preventing measures having sufficient reliability while assuring the realization of high packing density and high processing rate. <P>SOLUTION: A suspension substrate 1 with circuit is formed by sequentially laminating a metal supporting substrate 2, a base insulating layer 3, a conductor pattern 4, and a cover insulating layer 5. In this suspension substrate 1, a ground layer 6 which is in contact with the metal supporting substrate 2 is provided with an interval S1 kept in the widthwise direction opposing in the thickness direction to a signal wire 10 of the conductor pattern 4 within the base insulating layer 3, and a ground wire 9 is formed as the conductor pattern 4 together with a signal wire 8. Moreover, a connector 11 filling a connecting hole 7 formed on the base insulating layer 3, both ground layers 6 arranged adjacently with an interval S1 kept in the widthwise direction formed on the base insulating layer 3, and a part 12 opposing to the ground layer provided in opposition to the thickness direction are formed as the ground wire 9 with the lower end surface in direct contact with the metal supporting substrate 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a printed circuit board, and more particularly to a printed circuit board that supports high density and high speed.

A suspension board with circuit mounted on a hard disk drive is usually composed of 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 base insulating layer. And an insulating cover layer formed so as to cover the conductor pattern.
In such a suspension board with circuit, since the potential difference between the metal support board and the conductor pattern causes noise generation, as a countermeasure against the noise, the metal support board as well as the signal wiring for transmitting an electrical signal as a conductor pattern. The magnetic head is connected to the ground by forming a ground wiring that is electrically connected to the magnetic head and connecting the ground wiring to the magnetic head.

In addition, in such a suspension board with circuit, in order to reduce the transmission loss of the conductor pattern in response to the recent increase in density and speed, an insulating layer is sandwiched between the lower layers of the conductors and electrically grounded. Proposing a lower conductor to be a potential has been proposed (see, for example, Patent Document 1).
JP 2005-11387 A

However, if the ground wiring is provided and the lower conductor is provided, it is possible to take measures against noise while dealing with higher density and higher speed. Further, when the conductor patterns are arranged at high density, the ground wiring and the lower conductor face each other in the thickness direction. Therefore, if the ground wiring is connected to the lower conductor, the ground wiring can be easily connected to the ground.
However, when the ground wiring is connected to the lower conductor, there is a problem in that the adhesion failure occurs at the connection portion (interface) between the ground wiring and the lower conductor, and the reliability of the printed circuit board is lowered.

  An object of the present invention is to provide a printed circuit board in which noise countermeasures are taken with sufficient reliability while accommodating high density and high speed.

  In order to achieve the above object, a wired circuit board of the present invention is formed on a metal supporting board, a base insulating layer formed on the metal supporting board, and the base insulating layer, and transmits an electrical signal. A conductor pattern including a signal wiring portion to be connected and a ground wiring portion for ground connection, a cover insulating layer formed on the base insulating layer so as to cover the conductor pattern, and at least one of the signal wiring portions A ground layer embedded in the base insulating layer so as to be opposed to the portion in the thickness direction and to be connected to the metal support substrate, and the ground wiring portion is at least one of the ground layers. And a ground layer facing portion facing the portion in the thickness direction, and a connection portion connected to the metal support substrate.

  In the wired circuit board of the present invention, the ground layer is provided with a gap in a direction orthogonal to the direction in which the signal wiring portion extends, and the ground layer facing portion has the gap. Arranged so as to oppose at least one of the ground layers arranged in the thickness direction, and the connecting portion is arranged between the ground layers arranged with the gap therebetween. Is preferred.

In the wired circuit board of the present invention, a metal thin film for forming the conductor pattern by an additive method may be interposed between the ground wiring portion and the metal support substrate.
In the wired circuit board of the present invention, the metal support board may be formed with an opening that faces at least a part of the signal wiring part in the thickness direction.

  In addition, when the opening is formed, the insulating protection that covers the ground layer from the opening in order to prevent the ground layer embedded in the insulating base layer from being exposed from the opening. It is preferred to have a layer.

  According to the wired circuit board of the present invention, the conductor pattern can be formed at a high density so that the ground layer facing portion of the ground wiring portion faces at least a part of the ground layer in the thickness direction. Since the connection part of the part is not connected to the ground layer, but is connected to the metal support substrate, it is possible to improve the adhesion at the connection part between the connection part of the ground wiring part and the ground layer. The ground wiring portion can be securely connected to the ground. Therefore, in the printed circuit board according to the present invention, it is possible to reduce the generation of noise with sufficient reliability while accommodating high density and high speed.

FIG. 1 is a cross-sectional view of an essential part of a suspension board with circuit showing an embodiment of a wired circuit board of the present invention.
In FIG. 1, a suspension board with circuit 1 is a suspension board with circuit mounted on a hard disk drive, and includes a metal supporting board 2, a base insulating layer 3 formed on the metal supporting board 2, and a base insulating board. A conductor pattern 4 formed on the layer 3 and a cover insulating layer 5 formed on the base insulating layer 3 so as to cover the conductor pattern 4 are provided. The suspension board with circuit 1 includes a ground layer 6 formed on the metal support board 2 and embedded in the insulating base layer 3.

The metal support substrate 2 is a flat plate extending in the longitudinal direction (paper thickness direction in FIG. 1), and is formed from a metal foil or a metal thin plate. As the metal forming the metal support substrate 2, for example, stainless steel, 42 alloy, or the like is used, and stainless steel is preferably used. Moreover, the thickness is 15-30 micrometers, for example, Preferably, it is 20-25 micrometers.
A plurality of (two) ground layers 6 are formed on the metal support substrate 2 at intervals S1 in the width direction (direction perpendicular to the longitudinal direction) so as to be in contact with the metal support substrate 2. As the metal forming the ground layer 6, for example, chromium, copper, gold, silver, platinum, nickel, titanium, silicon, manganese, zirconium, and alloys thereof, or oxides thereof are used. Of these, copper or a copper alloy is preferably used. Moreover, the thickness of the ground layer 6 is 2-10 micrometers, for example, Preferably, it is 2-4 micrometers. The interval S1 between the ground layers 6 adjacent in the width direction is, for example, 80 to 500 μm, or preferably 120 to 300 μm.

  The base insulating layer 3 is formed on the metal support substrate 2 so as to cover (embed) the ground layer 6. In the base insulating layer 3, the connection holes 7 pass through the thickness direction of the base insulating layer 3 between the ground layers 6 adjacent to each other with an interval S <b> 1 in the width direction to expose the metal support substrate 2. It is formed to let you. As the insulator forming the base insulating layer 3, for example, a synthetic resin such as polyimide, polyether nitrile, polyether sulfone, polyethylene terephthalate, polyethylene naphthalate, or polyvinyl chloride is used. Of these, polyimide is preferably used, and photosensitive polyimide is more preferably used. Moreover, the thickness is 5-15 micrometers, for example, Preferably, it is 8-10 micrometers. Moreover, the opening length S2 in the width direction of the connection hole 7 is, for example, 40 to 300 μm, or preferably 60 to 200 μm.

The conductor pattern 4 includes a signal wiring portion 8 for transmitting an electrical signal and a ground wiring portion 9 for grounding the magnetic head.
The signal wiring portion 8 is provided on the base insulating layer 3 covering one ground layer 6 so as to face the one ground layer 6 in the thickness direction (vertical direction). The signal wiring portion 8 is arranged at intervals in the width direction, and extends in the longitudinal direction. The signal wiring portion 8 extends in the longitudinal direction, and a plurality of terminals are connected to both ends in the longitudinal direction of each signal wiring 10. (Not shown). A terminal of the magnetic head is connected to a terminal at one end in the longitudinal direction, and a terminal of an external control circuit is connected to a terminal at the other end in the longitudinal direction.

In addition, the width | variety of each signal wiring 10 is 10-100 micrometers, for example, Preferably, it is 15-50 micrometers, and the space | interval between each signal wiring 10 is 10-100 micrometers, for example, Preferably it is 15-50 micrometers.
The ground wiring portion 9 is integrally provided with a connection portion 11, a ground layer facing portion 12, and a ground terminal portion 13.

The connection portion 11 is filled in the connection hole 7 formed in the base insulating layer 3 so that the lower end surface thereof is in direct contact with the metal support substrate 2.
The ground layer facing portion 12 is formed on the base insulating layer 3, extends from the connecting portion 11 to both outer sides in the width direction, and is adjacent to each of the ground layers 6 disposed adjacent to each other with an interval S1 in the width direction. They are provided so as to face each other with the base insulating layer 3 interposed therebetween (in the vertical direction).

  The ground terminal portion 13 is provided to connect to the ground terminal of the magnetic head, and is provided as a portion exposed from a ground terminal opening 14 of the cover insulating layer 5 described later. In FIG. 1, the ground terminal portion 13 is formed so that the ground terminal opening portion 14 of the insulating cover layer 5 is exposed so that the ground layer facing portion 12 facing the one ground layer 6 is exposed. For example, when the ground terminal opening 14 of the insulating cover layer 5 is formed so that the connection portion 11 is exposed, the connection is made. Provided in the section 11.

Moreover, as a conductor which forms the conductor pattern 4, metals, such as copper, nickel, gold | metal | money, solder, or those alloys, are used, for example. Of these, copper is preferably used. Moreover, the thickness is 5-20 micrometers, for example, Preferably, it is 7-15 micrometers.
The insulating cover layer 5 is formed on the insulating base layer 3 so as to cover the conductive pattern 5. A terminal opening (not shown) is formed in the insulating cover layer 5 so as to face the terminals of the signal wiring portion 8 described above, and a ground terminal opening 14 is formed in a portion where the ground terminal portion 13 is formed. Is formed.

Further, as the insulator for forming the insulating cover layer 4, the same insulator as the above-described insulating base layer 3 is used. Moreover, the thickness is 3-10 micrometers, for example, Preferably, it is 4-5 micrometers.
2-6 is a manufacturing process figure which shows one Embodiment of the manufacturing method of this suspension board | substrate 1 with a circuit. Next, a method of manufacturing the suspension board with circuit 1 will be described with reference to FIGS.

In this method, first, a metal support substrate 2 is prepared as shown in FIG. 2A, and then a ground layer 6 is formed on the metal support substrate 2 as shown in FIG. 2B. To do.
In order to form the ground layer 6 on the metal support substrate 2, as shown in FIG. 3A, the metal thin film 21 is formed on the entire surface of the metal support substrate 2 by sputtering or electrolytic plating.

  As the metal forming the metal thin film 21, for example, the same metal as that of the ground layer 6 described above is used, and copper or chromium is preferably used. Moreover, the thickness is 0.01-1 micrometer, for example, Preferably, it is 0.1-1 micrometer. The metal thin film 21 has high adhesion to the ground layer 6 so that the metal having high adhesion to the metal support substrate 2 and the surface of the ground layer 6 are in contact with the surface of the metal support substrate 2. It can also be formed in multiple layers by laminating metal.

Next, as shown in FIG. 3B, the plating resist 22 is formed on the metal thin film 21 with the reverse pattern of the ground layer 6 described above. For the formation of the plating resist 22, for example, a known method of exposing and developing a dry film resist is used.
Thereafter, as shown in FIG. 3C, the ground layer 6 is spaced apart in the width direction on the surface of the metal thin film 21 exposed from the plating resist 22 by electrolytic plating, preferably electrolytic copper plating, as described above. It forms as a pattern which separated S1.

Next, as shown in FIG. 3D, after removing the plating resist 22 by, for example, etching (wet etching) or peeling, the plating resist 22 was formed as shown in FIG. The part of the metal thin film 21 is removed by etching (wet etching), for example.
As a result, a ground layer 6 is formed on the metal support substrate 2 as shown in FIG. In FIG. 2, the metal thin film 21 is omitted.

Next, in this method, as shown in FIG. 2C, the base insulating layer 3 is formed on the metal support substrate 2 so as to cover the ground layer 6.
In order to form the base insulating layer 3 on the metal supporting substrate 2 so as to cover the ground layer 6, the base insulating layer 3 is patterned on the metal supporting substrate 2 using, for example, photosensitive polyimide. 4A, first, as shown in FIG. 4A, a photosensitive polyimide precursor varnish (photosensitive polyamic acid resin solution) is coated on the metal support substrate 2 so as to cover the ground layer 6. It is applied to the entire surface and dried to form a film 23. Next, as shown in FIG. 4B, the film 23 is exposed through a photomask 24. The photomask 24 has a light transmitting portion 24a and a light shielding portion 24b formed as a pattern, and the light shielding portion 24b is disposed so as to face, for example, the peripheral portion of the film 23 and the portion where the connection hole 7 is formed.

  Thereafter, the film 23 is heated after exposure if necessary, and then developed by a dipping method, a spray method, or the like using a developer such as an alkali developer as shown in FIG. As a result, the portion of the film 23 that opposes the light-shielding portion 24b is melted and then heated to 250 ° C. or higher and cured as shown in FIG. The base insulating layer 3 made of polyimide is formed in a pattern in which the connection holes 7 are formed so as to cover the layer 6. In FIG. 4, the insulating base layer 3 is formed as a negative image, but it can also be formed as a positive image.

The formation of the insulating base layer 3 is not particularly limited to the above-described method. For example, a synthetic resin film in which the connection holes 7 are previously drilled is prepared, and the ground layer 6 is covered with the film. Moreover, it can also stick on the metal support substrate 2 through an adhesive bond layer.
Next, in this method, a conductor pattern 4 is formed on the base insulating layer 3 as shown in FIG. The conductor pattern 4 is formed as a pattern including the signal wiring portion 8 and the ground wiring portion 9 by a known patterning method such as an additive method or a subtractive method. From the viewpoint of forming a fine pattern, an additive method is preferably used.

In order to form the conductor pattern 4 on the base insulating layer 3 by the additive method, first, as shown in FIG. 5A, the surface of the base insulating layer 3 and the metal supporting substrate 2 exposed from the base insulating layer 3 are used. A metal thin film 25 is formed on the surface by sputtering.
As a metal for forming the metal thin film 25, for example, the same metal as that of the ground layer 6 described above is used, and copper or chromium is preferably used. Moreover, the thickness is 0.01-1 micrometer, for example, Preferably, it is 0.1-1 micrometer. Preferably, a metal having high adhesion to the metal support substrate 2 and the base insulating layer 3, for example, chromium, and the surface of the conductor pattern 4 are brought into contact with the surfaces of the metal support substrate 2 and the base insulating layer 3. As described above, a metal having high adhesion to the conductor pattern 4, for example, copper is sequentially laminated to form a multilayer.

Next, as shown in FIG. 5B, the plating resist 26 is formed on the metal thin film 25 in the reverse pattern of the conductor pattern 4 described above. For forming the plating resist 26, for example, a known method of exposing and developing a dry film resist is used.
Thereafter, as shown in FIG. 5C, the conductor pattern 4 is placed on the surface of the metal thin film 25 exposed from the plating resist 26 by electrolytic plating, preferably electrolytic copper plating, and the signal wiring portion 8 and the ground wiring described above. It forms as a pattern provided with the part 9. FIG.

The signal wiring part 8 is formed on the base insulating layer 3 by electrolytic plating, and at the same time, the ground wiring part 9 is first formed so that the connection part 11 is filled in the connection hole 7, and then The ground layer facing portion 12 is formed on the insulating base layer 3 surrounding the connection hole 7.
Next, as shown in FIG. 5D, after the plating resist 26 is removed by, for example, etching (wet etching) or peeling, the plating resist 26 is formed as shown in FIG. 6E. The portion of the metal thin film 25 is removed by etching (wet etching), for example.

As a result, a conductor pattern 4 is formed on the insulating base layer 3 as shown in FIG. In FIG. 2, the metal thin film 25 is omitted.
In this method, as shown in FIG. 2 (e), the insulating cover layer 5 is formed on the insulating base layer 3 so as to cover the conductive pattern 4.
In order to form the insulating cover layer 5 on the insulating base layer 3 so as to cover the conductive pattern 4, the insulating cover layer 5 is patterned on the insulating base layer 3 using, for example, photosensitive polyimide. 6A, first, as shown in FIG. 6A, a photosensitive polyimide precursor varnish (photosensitive polyamic acid resin solution) is coated on the base insulating layer 3 so as to cover the conductor pattern 4. The film 27 is applied to the surface and the surface of the metal support substrate 2 exposed from the base insulating layer 3 and dried to form a film 27. Next, as shown in FIG. 6B, the coating 27 is exposed through a photomask 28. In the photomask 28, a light transmitting portion 28a and a light shielding portion 28b are formed as a pattern. The light shielding portion 28b includes, for example, a peripheral portion of the film 27, a formation portion of a terminal opening of the signal wiring portion 8, and a ground terminal. It arrange | positions so that the formation part of the opening part 14 may be opposed.

  Thereafter, the film 27 is heated after exposure if necessary, and then developed by a dipping method, a spray method, or the like using a developer such as an alkali developer as shown in FIG. As a result, the portion of the film 27 that opposes the light shielding portion 28b is dissolved and then heated to 250 ° C. or higher and cured as shown in FIG. A cover insulating layer 5 made of polyimide is formed so as to cover the pattern 4 in a pattern in which the terminal opening of the signal wiring portion 8 and the ground terminal opening 14 are formed. In FIG. 6, the cover insulating layer 5 is formed as a negative image, but it can also be formed as a positive image.

The formation of the insulating cover layer 5 is not particularly limited to the above method. For example, a synthetic resin film in which the terminal opening of the signal wiring portion 8 and the ground terminal opening 14 are previously drilled is prepared. A film can also be stuck on the insulating base layer 3 via an adhesive layer so as to cover the conductor pattern 4.
In the suspension board with circuit 1 obtained in this way, the ground layer facing portion 12 of the ground wiring portion 9 is in the thickness direction (vertical direction) with both the ground layers 6 arranged adjacent to each other with a gap S1 in the width direction. ). Therefore, the conductor pattern 4 can be formed as a fine pattern in which the signal wiring portion 8 and the ground wiring portion 9 are arranged with high density. In addition, since the connection portion 11 of the ground wiring portion 9 is not connected to the ground layer 6 but directly to the metal supporting board 2 (not directly through the ground layer 6), the ground wiring portion 9 is connected. The adhesion at the connection portion (interface) between the connection portion 11 and the ground layer 6 can be improved, and the ground wiring portion 9 can be reliably grounded.

In particular, in the manufacturing method described above, when the conductive pattern 4 is formed by the additive method, a metal thin film 25 is interposed at the interface between the connection portion 11 of the ground wiring portion 9 and the metal support substrate 2 (FIG. 5E). reference).
On the other hand, when the conductor pattern 4 is formed by the additive method, when the connection portion 11 of the ground wiring portion 9 is connected to the ground layer 6, the metal thin film 25 is formed at the interface between the connection portion 11 of the ground wiring portion 9 and the ground layer 6. As a result of the presence of the metal thin film 25, poor adhesion at the interface between the connection portion 11 of the ground wiring portion 9 and the ground layer 6 may become conspicuous.

That is, when the ground layer 6 is formed of copper, the metal thin film 25 is formed of two layers of chromium (lower layer) / copper (upper layer), and the conductor pattern 4 (connection portion 11) is formed of copper, the ground layer 6 and the metal thin film 25 cause an adhesion failure, and as a result, an adhesion failure at the interface between the connection portion 11 of the ground wiring portion 9 and the ground layer 6 becomes remarkable.
However, if the connection portion 11 of the ground wiring portion 9 is directly connected to the metal support substrate 2 as in the suspension board with circuit 1, even if the connection portion 11 of the ground wiring portion 9 is connected to the metal support substrate 2. Even if the metal thin film 25 is interposed, the adhesion at the interface between the connection portion 11 of the ground wiring portion 9 and the metal support substrate 2 can be improved.

That is, when the metal support substrate 2 is formed of stainless steel, the metal thin film 25 is formed of two layers of chromium (lower layer) / copper (upper layer), and the conductor pattern 4 (connection portion 11) is formed of copper, The adhesion between the support substrate 2 and the metal thin film 25 is improved, and as a result, the adhesion at the interface between the connection portion 11 of the ground wiring portion 9 and the metal support substrate 2 can be improved.
As a result, the suspension board with circuit 1 can reduce the generation of noise with sufficient reliability while accommodating high density and high speed.

FIG. 7 is a cross-sectional view of an essential part of a suspension board with circuit showing another embodiment of the wired circuit board of the present invention.
As shown in FIG. 7, in the suspension board with circuit 1, an opening 15 is further formed on the metal supporting board 2 so as to face the signal wiring 10 of the signal wiring section 8 in the thickness direction (vertical direction). You can also. By forming the opening 15, the characteristic impedance of the conductor pattern 4 can be adjusted and the flexibility can be partially improved.

  Although the opening 15 is not particularly limited, in FIG. 7, for example, in the metal support substrate 2, a plurality (two) of signal wirings 10 are opposed to one ground layer 6 facing in the thickness direction (vertical direction). The opposing portion is formed so as to penetrate in the thickness direction. The opening 15 is also formed in a portion facing the other ground layer 6 so as to penetrate in the thickness direction.

Further, in the suspension board with circuit 1 shown in FIG. 7, an insulating protective layer 16 is provided so as to cover the ground layer 6 from the opening 15. The insulating protective layer 16 is provided corresponding to one ground layer 6 and the other ground layer 6.
One insulating protective layer 16 corresponding to one ground layer 6 extends from one end in the width direction to the other end in the width direction until it covers the opening 15, and at one end in the width direction, the metal support substrate 2. Between the metal support substrate 2 including the opening 15 and the ground layer 6 on the inner side in the width direction. The other end in the width direction of the one insulating protective layer 16 is disposed in the middle of the one ground layer 6 in the width direction, whereby the other end in the width direction of the one ground layer 6 and the metal support substrate 2 are arranged. Contact is ensured.

  The other insulating protective layer 16 corresponding to the other ground layer 6 extends from the other end in the width direction toward one end in the width direction until it covers the opening 15, and at the other end in the width direction, the metal support substrate 2 and the base insulating layer 3, and on the inner side in the width direction, it is interposed between the metal support substrate 2 including the opening 15 and the ground layer 6. In addition, one end portion in the width direction of the other insulating protective layer 16 is disposed in the middle of the other ground layer 6 in the width direction, whereby the one end portion in the width direction of the other ground layer 6 and the metal support substrate 2 are arranged. Contact is ensured.

Further, as the insulator for forming the insulating protective layer 16, the same insulator as that of the above-described base insulating layer 3 is used. Moreover, the thickness is 1-10 micrometers, for example, Preferably, it is 1-3 micrometers.
By forming such an insulating protective layer 16, it is possible to prevent the ground layer 6 embedded in the base insulating layer 3 from being exposed from the opening 15, and to prevent corrosion of the ground layer 6. Can do.

FIG. 8 is a manufacturing process diagram showing an embodiment of a manufacturing method of the suspension board with circuit 1 shown in FIG. Next, a method for manufacturing the suspension board with circuit 1 shown in FIG. 7 will be described with reference to FIG.
In this method, first, a metal support substrate 2 is prepared as shown in FIG. 8A, and then an insulating protective layer 16 is formed on the metal support substrate 2 as shown in FIG. 8B. Form.

  In order to form the insulating protective layer 16 on the metal support substrate 2, first, a varnish (photosensitive polyamic acid resin solution) of a photosensitive polyimide precursor is applied to the entire surface of the metal support substrate 2 and dried to form a film. Then, similarly to the formation of the insulating base layer 3, exposure and development are performed to form the insulating protective layer 16 made of polyimide as a pattern at the position where the insulating protective layer 16 is formed.

Next, as shown in FIG. 8C, the ground layer 6 is formed on the insulating protective layer 16 and the metal supporting board 2 by the same method as described above so that the outer end portion in the width direction of the insulating protective layer 16 is exposed. Form on top. As a result, the insulating protective layer 16 is partially covered by the ground layer 6 so that the outer end in the width direction is exposed.
Thereafter, as shown in FIG. 8D, the base insulating layer 3 is formed on the metal supporting substrate 2 and the insulating protective layer 16 so as to cover the ground layer 6 by the same method as described above. As shown in FIG. 8E, the conductor pattern 4 is formed as a pattern including the signal wiring portion 8 and the ground wiring portion 9 on the base insulating layer 3 by the same method as described above.

Next, as shown in FIG. 8 (f), the insulating cover layer 5 is formed on the insulating base layer 3 so as to cover the conductor pattern 4 by the same method as described above, and then, FIG. As shown in FIG. 3, the opening 15 is formed in the metal supporting board 2 to obtain the suspension board with circuit 1.
In order to form the opening 15 in the metal support substrate 2, for example, an etching resist is formed on a portion of the metal support substrate 2 excluding the portion where the opening 15 is formed, and then the metal support substrate 2 exposed from the etching resist is formed. For example, chemical etching (wet etching) is performed by an immersion method or a spray method using an etching solution such as an aqueous ferric chloride solution, and then the etching resist is removed.

  In the suspension board with circuit 1 obtained in this way shown in FIG. 7, in addition to the advantages of the suspension board with circuit 1 shown in FIG. 1, the characteristic impedance of the conductor pattern 4 is adjusted by forming the opening 15. In addition, since the insulating protection layer 16 is provided so that the flexibility can be partially improved and the ground layer 6 is covered from the opening 15, the ground layer embedded in the base insulating layer 3. 6 can be prevented from being exposed from the opening 15, and corrosion of the ground layer 6 can be prevented.

In the suspension board with circuit 1 described above, a protective film can be provided on the surface of the ground layer 6 and the surface of the conductor pattern 4. In the manufacturing method described above, the protective film can be formed as a nickel film, for example, by electroless nickel plating after the formation of the ground layer 6 or after the formation of the conductor pattern 4.
In the above description, the wired circuit board of the present invention has been described by exemplifying the suspension board with circuit. However, the wired circuit board of the present invention is not limited to the suspension board with circuit, for example, a reinforcing layer (metal support) A flexible wiring circuit board (corresponding to a substrate) (including a single-sided flexible wiring circuit board, a double-sided flexible wiring circuit board, and a multilayer flexible wiring circuit board).

EXAMPLES The present invention will be described more specifically below with reference to examples and comparative examples, but the present invention is not limited to these examples and comparative examples.
Example 1
A stainless steel substrate having a thickness of 25 μm is prepared as a metal support substrate (see FIG. 2A), and a chromium thin film having a thickness of 0.03 μm and a copper thin film having a thickness of 0.07 μm are formed on the metal support substrate as metal thin films. Were sequentially formed by sputtering (see FIG. 3A). Next, a plating resist was formed using a dry film resist with a reverse pattern of the ground layer (see FIG. 3B). Thereafter, a copper foil having a thickness of 4.0 μm was formed on the surface of the metal thin film exposed from the plating resist by electrolytic copper plating using an aqueous copper sulfate solution (see FIG. 3C). Two copper foils were formed at an interval in the width direction.

Next, after removing the plating resist by peeling off using a sodium hydroxide aqueous solution (see FIG. 3 (d)), the metal thin film where the plating resist was formed is removed by etching (see FIG. 3 (e)). ) A nickel film having a thickness of 0.1 μm was formed on the surface of the ground layer by electroless nickel plating as a protective film.
Next, a varnish of a photosensitive polyamic acid resin is applied on the metal support substrate so as to cover the ground layer, and then dried to form a film (see FIG. 4A), and the film is exposed (see FIG. 4). 4 (b)) and development (see FIG. 4 (c)), followed by heat-curing (see FIG. 4 (d)), a base insulation made of polyimide having a thickness of 10 μm as a pattern for forming connection holes. A layer was formed (see FIG. 2C).

  Next, a chromium thin film having a thickness of 0.03 μm and a copper thin film having a thickness of 0.07 μm were sequentially formed by sputtering on the surface of the base insulating layer and the surface of the metal supporting substrate exposed from the connection holes (FIG. 5 ( a)). Next, a plating resist was formed using a dry film resist with a reverse pattern of the conductor pattern (see FIG. 5B). Thereafter, a copper foil having a thickness of 10 μm was formed as a conductive pattern on the surface of the metal thin film exposed from the plating resist by electrolytic copper plating using an aqueous copper sulfate solution (see FIG. 5C).

  Next, after removing the plating resist by peeling off using a sodium hydroxide aqueous solution (see FIG. 5D), the metal thin film in the portion where the plating resist was formed is removed by etching (see FIG. 5E). ) A nickel film having a thickness of 0.1 μm was formed on the surface of the conductor pattern by electroless nickel plating as a protective film. In addition, this conductor pattern was formed as a pattern provided with the above-mentioned signal wiring part and ground wiring part.

  Thereafter, a varnish of photosensitive polyamic acid resin is applied on the metal support substrate and the insulating cover layer so as to cover the conductor pattern, and then dried to form a film (see FIG. 6A). Is exposed (see FIG. 6 (b)) and developed (see FIG. 6 (c)), and further heat-cured (see FIG. 6 (d)), the terminal opening of the signal wiring portion 8 and the ground terminal A cover insulating layer made of polyimide having a thickness of 5 μm was formed as a pattern for forming the openings 14, thereby obtaining a suspension board with circuit (see FIG. 2E).

Example 2
As a metal support substrate, a stainless steel substrate having a thickness of 25 μm is prepared (see FIG. 8A), a varnish of photosensitive polyamic acid resin is applied on the metal support substrate, and then dried to form a film. The film was exposed and developed, and further heat-cured to form an insulating protective layer made of polyimide having a thickness of 2 μm as a pattern at the position where the insulating protective layer was formed (see FIG. 8B).

Next, a ground layer made of a copper foil having a thickness of 4.0 μm is formed on the insulating protective layer and the metal supporting substrate in the same manner as in Example 1 so that the outer ends in the width direction of each insulating protective layer are exposed. It formed (refer FIG.8 (c)).
Thereafter, a base insulating layer made of polyimide having a thickness of 10 μm is formed on the metal supporting substrate and the insulating protective layer so as to cover the ground layer by the same method as in Example 1 (see FIG. 8D). Then, a conductor pattern made of a copper foil having a thickness of 10 μm was formed on the insulating base layer as a pattern having a signal wiring portion and a ground wiring portion by the same method as in Example 1 (FIG. 8E). reference).

  Next, an insulating cover layer made of polyimide having a thickness of 5 μm was formed on the insulating base layer so as to cover the conductor pattern by the same method as in Example 1 (see FIG. 8F), and then supported by metal. The substrate was etched using a ferric chloride aqueous solution to form openings, and a suspension board with circuit was obtained (see FIG. 8G).

It is principal part sectional drawing of the suspension board | substrate with a circuit which shows one Embodiment of the wired circuit board of this invention. FIGS. 2A and 2B are manufacturing process diagrams illustrating a manufacturing method of the suspension board with circuit shown in FIG. 1, in which FIG. 1A is a process for preparing a metal supporting board, and FIG. 1B is a process for forming a ground layer on the metal supporting board. Step (c) is a step of forming a base insulating layer on the metal supporting substrate so as to cover the ground layer. (D) is a step of forming a conductor pattern on the base insulating layer. e) shows a step of forming a cover insulating layer on the base insulating layer so as to cover the conductor pattern. It is the detail of the process of forming a ground layer on the metal support substrate shown in FIG. 2B, (a) is a process of forming a metal thin film on the entire surface of the metal support substrate, (b) A step of forming a plating resist on the metal thin film in a reverse pattern of the ground layer, (c) a step of forming a ground layer on the surface of the metal thin film exposed from the plating resist by electrolytic plating; FIG. 4 shows a step of removing the plating resist, and FIG. 3E shows a step of removing the portion of the metal thin film where the plating resist was formed. It is the detail of the process of forming a base insulating layer on a metal support substrate so that the ground layer shown in FIG.2 (c) may be coat | covered, Comprising: (a) is a photosensitive polyimide precursor varnish, a ground layer is shown. A step of coating the entire surface of the metal support substrate so as to coat and drying to form a film, (b) a step of exposing the film through a photomask, and (c) developing the film Step (d) shows a step of curing the film. FIG. 2D is a detail of a process of forming a conductor pattern on the base insulating layer shown in FIG. Forming a thin film; (b) forming a plating resist on the metal thin film in a reverse pattern of the conductor pattern; and (c) forming a thin film on the surface of the metal thin film exposed from the plating resist by electrolytic plating. The step of forming a conductor pattern, (d) shows the step of removing the plating resist, and (e) shows the step of removing the metal thin film in the portion where the plating resist was formed. It is the detail of the process of forming a cover insulating layer on a base insulating layer so that the conductor pattern shown in FIG.2 (b) may be coat | covered, Comprising: (a) is varnish of the photosensitive polyimide precursor, a base insulating layer (B) is a step of applying a film through a photomask, and (c) is a film. (D) shows the process of hardening | curing a film | membrane. It is principal part sectional drawing of the suspension board | substrate with a circuit which shows other embodiment of the wired circuit board of this invention. FIGS. 8A and 8B are manufacturing process diagrams illustrating a manufacturing method of the suspension board with circuit shown in FIG. 7, in which FIG. 7A is a process for preparing a metal supporting board, and FIG. 7B is an insulating protective layer formed on the metal supporting board. (C) forming a ground layer so as to partially cover the insulating protective layer on the metal supporting substrate; and (d) forming a metal supporting substrate so as to cover the ground layer. And (e) a step of forming a conductor pattern on the base insulating layer, and (f) a base insulation so as to cover the conductor pattern. (G) shows the process of forming an opening part in a metal support substrate, the process of forming a cover insulating layer on a layer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Suspension board with a circuit 2 Metal support board 3 Base insulating layer 4 Conductor pattern 5 Cover insulating layer 6 Ground layer 8 Signal wiring part 9 Ground wiring part 11 Connection part 12 Ground layer opposing part 14 Ground terminal opening part 15 Insulating protective layer 25 Metal Thin film

Claims (5)

A metal support substrate;
A base insulating layer formed on the metal support substrate;
A conductor pattern formed on the insulating base layer and including a signal wiring portion for transmitting an electrical signal and a ground wiring portion for ground connection;
An insulating cover layer formed on the insulating base layer so as to cover the conductive pattern;
A ground layer embedded in the insulating base layer so as to be opposed to at least a part of the signal wiring part in the thickness direction and to be connected to the metal supporting substrate at least a part of the signal wiring part;
The wired circuit board, wherein the ground wiring part includes a ground layer facing part facing at least a part of the ground layer in a thickness direction, and a connection part connected to the metal supporting board. The ground layer is provided at an interval in a direction orthogonal to the direction in which the signal wiring portion extends,
The ground layer facing portion is disposed so as to face at least one of the ground layers disposed at an interval in the thickness direction,
The wired circuit board according to claim 1, wherein the connection portion is disposed between the ground layers disposed at a distance from each other.   The wired circuit board according to claim 1, wherein a metal thin film for forming the conductive pattern by an additive method is interposed between the ground wiring portion and the metal supporting board. .   The wired circuit board according to any one of claims 1 to 3, wherein the metal supporting board is formed with an opening facing at least a part of the signal wiring part in a thickness direction.   The insulating layer for covering the ground layer from the opening is provided in order to prevent the ground layer embedded in the insulating base layer from being exposed from the opening. Item 5. The printed circuit board according to Item 4.

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