JP2007129087A - Hybrid multilayer circuit board and method of manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To further enhance a bending property of a cable when a conductive layer is formed in an outside of a hybrid multilayer circuit board which extends at least one cable from a multilayer mounting part obtained by laminating an outer layer material on a circuit board serving as an inner layer and a shield layer is formed for electromagnetic wave disturbance. <P>SOLUTION: In the hybrid multilayer circuit board, at least one cable (b) extends from a layer except an outermost layer in a multilayer mounting part (a). The hybrid multilayer circuit board contains a shield layer for electromagnetic interference in an outside, and the shield layer 4 is arranged to have an opening gap between the shield layer 4 and the cable at a location corresponding to the cable in the outermost layer. The hybrid multilayer circuit board has a base film 11 shared with a circuit layer of the outermost layer in the part mounting part (1), a conductive layer 12 formed on the base film (2), and a cover layer 13 for insulating and protecting the conductive layer (3). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a circuit board used for an electronic device and a method for manufacturing the same, and in particular, a multilayer circuit board for mounting an outer layer material made of a film-based metal foil laminate or an insulating film on an inner circuit board. A hybrid multilayer circuit board having a conductive layer formed on an outer portion of a hybrid multilayer circuit board in which at least one cable portion extends from the section and forming a shield layer against electromagnetic interference (hereinafter referred to as EMI), and a method of manufacturing the same About.

  As a measure against EMI in a circuit board, it is known to form a conductive layer on the surface of the board (Patent Document 1).

  On the other hand, as a circuit board, there is a hybrid multilayer circuit board that has been conventionally used for a part having a hinge structure such as a notebook personal computer and a foldable mobile phone and that frequently repeats opening and closing (Patent Document 2). This is a structure in which an outer layer material is laminated on an inner layer flexible circuit board via an adhesive member, and the flexible circuit board extended from the inner layer part is used as a cable part to connect between component mounting parts. The structure is such that connection with other electronic components is made via a connection terminal at the tip of the cable portion.

  Conventionally, in such a hybrid multilayer circuit board, a shield layer that also serves as a ground pattern is formed on the outer layer of the component mounting part, and the flexible circuit board that becomes the cable part has a circuit copper foil on both sides. A shield pattern was formed on one side of the circuit board.

  In the case of using this flexible circuit board, in recent years, a flexible circuit board, which is a cable part, is spirally wound and stored in a hinge part (Patent Document 3). Furthermore, the hinge part structure corresponding to a complicated motion is also shown (patent document 4). For this reason, the flexible circuit board used as a cable part is calculated | required by the thing with better flexibility.

  In general, it is known that a flexible circuit board serving as a cable portion has better flexibility when a circuit copper foil is provided on one side than a circuit board foil provided on both sides (Patent Document 5). For this reason, Patent Document 6 discloses a cable portion structure using two flexible circuit boards each having a circuit copper foil on one side instead of a flexible circuit board having a circuit copper foil on both sides. . This method is effective for improving the flexibility, but the shield pattern cannot be formed on the cable portion because the circuit copper foil is provided only on one side.

  In forming the shield layer in this case, for example, a conductive shield film as shown in Patent Document 7 is bonded so as to straddle the cable portion and the component mounting portion. However, a softer material is required in order to obtain the flexibility corresponding to the complicated movement as shown in Patent Document 3.

  If a conductive paint is printed instead of the conductive shield film to form the shield layer, the flexibility is generally improved. Screen printing is often used for printing conductive paints, and this printing method is useful because it has no complicated steps and is versatile.

  However, a problem arises when the conductive coating is printed by screen printing on the part mounting part and the part mounting part extended from the inner layer part between the part mounting part and the step part of the cable part. For example, as shown in FIG. 6, in a multilayer circuit board in which an outer layer circuit board 3 is laminated on an inner layer circuit board 1 via an adhesive member 2, two cable parts b extend from the component mounting part a and the inner layer part. At the level difference A generated in the above structure, the conductive paint 4 is faintly printed or the paint film thickness becomes thin. This is because the screen printing plate cannot follow the step A, and generally occurs when the step A is 100 μm or more.

If printing of the conductive paint 4 forming the shield layer is faded in the middle, a conduction failure with the ground pattern will occur, and the electromagnetic wave shield will not function. Also, when the paint film thickness becomes thin, when it is used in a part having the above-mentioned hinge structure and frequently opened and closed, it extends from the component mounting part a and the inner layer part where the paint film thickness is thin. Stress is applied to the step A with respect to the cable part b that has come out, a crack occurs in the conductive paint 4 and a conduction failure occurs, and the electromagnetic wave shield also fails.
Japanese Utility Model Publication No.55-29276 JP-A-64-7697 JP-A-6-311216 Japanese Patent Laid-Open No. 2003-133764 Japanese Utility Model Publication No. 1-93770 Japanese Unexamined Patent Publication No. 7-312469 JP 2000-269632 A Japanese Unexamined Patent Publication No. 5-145205

  As a measure for stress relaxation at the boundary portion between the component mounting portion and the cable portion, Patent Document 8 discloses that a shield layer made of a metal foil and a resin layer is laminated on the outside of a flexible circuit board, and a bent portion is flexibly formed. In this example, the shield layer and the circuit are connected by through-hole plating. However, since the shield layer overlaps with the metal foil and the plating layer and becomes thicker, the flexibility is limited.

  For this reason, when the conductive layer is formed on the outer side of the hybrid multilayer circuit board where at least one cable portion extends from the multilayer component mounting portion, and the shield layer against electromagnetic interference is formed, the flexibility of the cable portion is good. There is a need for a hybrid multilayer circuit board.

  The present invention has been made in consideration of the above-described points, and is a hybrid multilayer circuit board in which an outer layer material is laminated on a circuit board serving as an inner layer, and at least one cable part extends from a multilayer component mounting part. It is an object of the present invention to provide a hybrid multilayer circuit board and a method for manufacturing the same, in which the flexibility of the cable portion is further improved when a conductive layer is formed on the outer side of the substrate to form a shield layer against electromagnetic interference.

To achieve the above object, the present invention provides:
In a hybrid multilayer circuit board in which at least one cable part extends from a layer other than the outermost layer in the multilayer component mounting part, and the cable part is provided with a shield layer against electromagnetic interference, the shield layer is 1) a base film shared with an outermost circuit layer in the component mounting portion, 2) a conductive layer formed on the base film, and 3 (2) Provided is a hybrid multilayer circuit board having a cover layer for insulating and protecting the conductive layer and having a gap between the cable part and a method for manufacturing the same. .

  According to the present invention, the shield layer is provided along the cable portion extending from the multilayer component mounting portion, and this shield layer is formed by forming a conductive layer having good flexibility on the base film. Thus, it is possible to provide a hybrid multilayer circuit board with improved flexibility.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

Embodiment 1

  FIG. 1 shows a longitudinal sectional structure of Embodiment 1 of the present invention. This embodiment 1 is a four-layer board in which a single-sided flexible circuit board 1 constituting an inner layer and a cable part is laminated on two layers, and an outer layer circuit board 3 made of a film-based metal foil laminate is laminated on the outside. 2 shows a structure in which a cable part b is connected between the component mounting parts a. This is formed by the process shown in FIG.

  As shown in FIG. 1, if the insulating base 31 made of an outer layer material having no metal foil is extended from the component mounting portion a to connect the component mounting portions a, there is almost no step. . Therefore, when the conductive paint is printed by the screen printing method, the paint film as the shield layer can be formed with a more uniform thickness, and the problem of the step A in the conventional one shown in FIG. 6 is solved. .

  Here, in practice, an overcoat layer is formed of an insulating material on the outer side of the conductive paint 4, but is not shown in FIGS. 1, 3, and 6.

FIGS. 2A to 2C show the manufacturing method of the embodiment shown in FIG. 1 and will be described.
[1] First, as shown in FIG. 2 (a), the outer layer material 3 is laminated on at least one surface of the flexible circuit board 1 in which the circuit is formed in advance and the circuit 12 is covered with the cover lay 13 via the adhesive member 2. To do.
[2] Next, as shown in FIG. 2 (b), a through hole and an outer layer circuit 32 are formed. At the time of this circuit formation, the metal foil of the cable part b of the film base metal foil laminate 3 laminated via the adhesive member 2 is also removed, and the outer layer material of only the insulating base 31 not having this metal foil is extended. A structure for connecting the component mounting parts a to each other is formed.
[3] Subsequently, as shown in FIG. 2C, a solder resist 33 is formed on the surface of the component mounting portion a. FIG. 2 (c) shows this state. A surface of the outer layer circuit 32a to be connected to the conductive layer later is exposed without forming a solder resist.
[4] Hereinafter, a conductive paint is printed by a screen printing method on the structure in which the outer layer material of only the insulating base 31 not having the above circuit is extended to connect the component mounting portions a to each other. Get the structure.

  In the structure shown in FIG. 1, the insulating base 31 made of an outer layer material that does not have a metal foil extending from the component mounting portion a and the single-sided flexible circuit board 1 constituting the cable portion exist independently through a space. Therefore, it does not become a factor that hinders flexibility. However, it is preferable that the bending characteristic is equal to or better than that of the single-sided flexible circuit board 1 constituting the cable portion.

  In this case, since the metal foil is once removed from the film base metal foil laminate and the conductive layer is formed by the conductive paint 4, the metal foil of the film base metal foil laminate is left as a conductive layer. Flexibility can be improved.

  In addition, even when the conductive paint is printed by the screen printing method, the structure does not cause a step, so that the paint film as the shield layer can be formed with a more uniform thickness. Therefore, it is possible to prevent the coating film from fading or cracking to cause poor conduction and the electromagnetic wave shield from functioning.

  In the structure of FIG. 1, the connection to the conductive paint 4 as the shield layer is made at the portion 32a. However, as shown in FIG. 3, a non-through hole 32b is formed to connect to the lower layer. It is good also as a structure which takes.

  In the structure of FIG. 1, the solder resist 33 is separately provided on the component mounting portion. If there is no particular problem, the solder resist 33 is omitted, and the entire surface is insulated with this overcoat layer. Also good.

Embodiment 2

  4 (a) to 4 (c) show the manufacturing process of the second embodiment of the present invention. The second embodiment is manufactured by a semi-additive method. First, a conductive process is performed on the surface of the insulating substrate, then a mask pattern is formed with a plating resist, a circuit is formed by electrolytic plating, and then the unnecessary conductive process part is removed.

  In this conductive treatment portion, an extremely thin conductive layer is formed by leaving a portion of the outer layer material that exists independently via a space immediately above the cable portion. Flexibility can be improved by using a thinner conductive layer.

  As the conductive treatment that can be used in the present invention, it is necessary to remove the unnecessary conductive portion and to be resistant to the electrolytic plating bath. Preferably, it is made of the same material as that of the circuit, and is generally made of copper metal used in the circuit. For example, copper sputtering or electroless copper plating can be recommended.

The circuit is formed by the semi-additive method according to the following steps. This process will be described with reference to FIGS. 4 (a) to (c).
[1] First, as shown in FIG. 4 (a), a flexible circuit board 1 in which a circuit is formed in advance and the circuit 12 is covered with a cover lay 13 is formed from an insulating film via an adhesive member 2 on at least one side. The outer layer material 31 is laminated.
[2] Next, as shown in FIG. 4B, a thin metal layer 34 of about 0.1 to 1.0 μm is formed on the entire surface of the substrate formed in [1] by sputtering or electroless plating. A mask pattern is formed with the photoresist 35 for use.
[3] Next, as shown in FIG. 4C, a circuit pattern 32 is formed by electrolytic plating, and the photoresist 35 is peeled off.
[4] Thereafter, unnecessary portions of the metal layer 34 are removed by flash etching. At this time, the metal layer 34 at a portion connecting the component mounting portions a of the outer layer material 13 made of only the insulating layer laminated via the adhesive member 2 is also removed at the same time, and the outer layer material 31 having no circuit is extended. Thus, a structure for connecting the component mounting parts a to each other is formed.

  In this state, the structure is almost the same as that shown in FIG. Subsequently, as in the first embodiment, the solder resist 33 is formed, and the outer layer material 31 having no metal layer is extended to connect the component mounting portions a to each other. When the paint 4 is printed by a screen printing method, the same structure as that shown in FIG. 1 is obtained. As long as there is no particular problem, the solder resist 33 may be omitted and the entire surface may be insulated with this overcoat layer, as in the first embodiment.

Embodiment 3

  5 (a) and 5 (b) show a third embodiment of the present invention, which is a modification of the second embodiment. This is because the metal layer 34 at the part connecting the component mounting portions a of the outer layer material 13 in the second embodiment is not etched away, and a shield layer made of a thin metal layer of about 0.1 to 1.0 μm is formed. To do.

  That is, after the state of FIG. 4C is obtained in the process of the second embodiment, the portion B of FIG. 5A is covered with a coverlay or the like and flash etching is performed. The shield layer formed here can be formed so thin as to be incomparable with, for example, that disclosed in Patent Document 8, and a shield layer having good bending characteristics can be obtained.

  Subsequently, the solder resist 33 is formed in the same manner as in the first embodiment, and the overcoat layer 33a is formed in the portion B of FIG. 5A, thereby obtaining the structure shown in FIG. As long as there is no particular problem, the solder resist 33 may be omitted, and the entire surface may be covered with the overcoat layer 33a as in the first embodiment.

  The conductive paint that can be used in the present invention is not particularly limited as long as it has good flexibility. For example, paints such as silver paste, copper paste, and cream solder can be used.

  Further, if a magnetic shield paint in which magnetic shielding metal powder is dispersed is used instead of the conductive paint, the magnetic shield layer can be formed. Of course, both may be printed as electromagnetic and magnetic shields.

1 is a longitudinal sectional view showing Embodiment 1 of the present invention. 2 (a) to 2 (c) are explanatory views showing manufacturing steps of Embodiment 1 of the present invention. The longitudinal cross-sectional view which shows Embodiment 2 of this invention. 4 (a) to 4 (c) are explanatory views showing a manufacturing process according to the second embodiment of the present invention. 5 (a) and 5 (b) are explanatory views showing manufacturing steps of Embodiment 3 of the present invention. Explanatory drawing which shows the problem in the conventional method.

Explanation of symbols

a component mounting part b cable part 1 inner layer flexible circuit board 11 insulating base 12 inner layer circuit 13 coverlay 2 adhesive member 3 outer layer circuit board 31 insulating base 32 outer layer circuit 33 solder resist 34 thin metal layer 35 plating resist 4 shield layer

Claims (6)

In the hybrid multilayer circuit board in which at least one cable portion extends from a layer other than the outermost layer in the multilayer component mounting portion,
The hybrid multilayer circuit board is provided with a shield layer against electromagnetic interference at an outer portion,
The shield layer is
Arranged to have a gap between the cable portion at a position corresponding to the cable portion in the outermost layer,
1) a base film shared with the outermost circuit layer in the component mounting portion;
2) a conductive layer formed on the base film; and 3) a cover layer for insulating and protecting the conductive layer. The hybrid multilayer circuit board according to claim 1,
The hybrid multilayer circuit board, wherein the conductive layer is formed of a conductive paint. The hybrid multilayer circuit board according to claim 1,
The conductive layer is formed of a thin film metal. A hybrid multilayer circuit board. A hybrid multilayer circuit board in which at least one cable portion extends from a layer other than the outermost layer in the multilayer component mounting portion, the hybrid multilayer circuit board having a shield layer against electromagnetic interference at an outer portion, and the shield The layer includes the following steps 1) to 5) in the method for manufacturing a hybrid multilayer circuit board in which a gap is provided between the cable portion and the cable portion at a position corresponding to the cable portion in the outermost layer. A method for manufacturing a hybrid multilayer circuit board.
1) At least one surface of an inner layer circuit board in which a circuit is formed in advance and covered with the circuit is covered with an adhesive member from which a portion in contact with the cable portion is removed from the film base metal foil laminate. Laminating outer layer material.
2) At least one of a through hole and a non-through hole is formed in the component mounting portion, a metal is deposited in the hole by plating, and the inner layer circuit board and the outer layer material are electrically connected.
3) A circuit is formed on the metal foil of the outer layer material by a subtractive method, and the metal foil of the outer layer material is removed at a position corresponding to the cable portion extending from the component mounting portion, so that the structure has only a film. Form.
4) A conductive paint is printed at a position of the film corresponding to the cable portion by a screen printing method.
5) An insulating film is formed to cover the conductive paint. A hybrid multilayer circuit board in which at least one cable portion extends from a layer other than the outermost layer in the multilayer component mounting part, wherein the hybrid multilayer circuit board has a shield layer against electromagnetic interference at an outer portion, and the shield The layer includes the following steps 1) to 8) in the method for manufacturing a hybrid multilayer circuit board in which a gap is provided between the cable portion and the cable portion at a position corresponding to the cable portion in the outermost layer. A method for manufacturing a hybrid multilayer circuit board.
1) A film is laminated on at least one surface of an inner layer circuit board, in which a circuit is formed in advance and covered with a cover lay, through an adhesive member from which a portion in contact with the cable portion is removed.
2) At least one of a through hole and a non-through hole is formed in the component mounting portion.
3) A thin metal layer is formed on the surface of the film by a thin film forming method.
4) A plating resist developed into a desired circuit pattern is formed on the thin metal layer, and the plating resist is left at a position corresponding to the cable portion.
5) Electrolytic plating is performed using the plating resist to form a circuit.
6) An etching resist is formed at a position corresponding to the cable portion of the thin film metal layer.
7) The thin film metal layer is etched using the etching resist to remove unnecessary portions and form an outer layer circuit pattern.
8) An insulating film is formed at a position corresponding to the cable portion of the thin film metal layer. A hybrid multilayer circuit board in which at least one cable portion extends from a layer other than the outermost layer in the multilayer component mounting portion, the hybrid multilayer circuit board having a shield layer against electromagnetic interference at an outer portion, and the shield The layer includes the following steps 1) to 9) in the method for manufacturing a hybrid multilayer circuit board in which a gap is provided between the cable portion and the cable portion at a position corresponding to the cable portion in the outermost layer. A method for manufacturing a hybrid multilayer circuit board.
1) A film is laminated on at least one surface of an inner layer circuit board, in which a circuit is formed in advance and covered with a coverlay, through an adhesive member from which a portion that comes into contact with the cable portion is removed.
2) At least one of a through hole and a non-through hole is formed in the component mounting portion.
3) A thin metal layer is formed on the surface of the film by a thin film forming method.
4) A plating resist developed into a desired circuit pattern is formed on the thin metal layer, and the plating resist is left at a position corresponding to the cable portion.
5) Electrolytic plating is performed using the plating resist to form a circuit.
6) An etching resist is formed at a position corresponding to the cable portion of the thin film metal layer.
7) The thin film metal layer is etched using the etching resist to form an outer layer circuit pattern.
8) A conductive paint is printed by a screen printing method at a position corresponding to the cable portion of the thin film metal layer.
9) An insulating film is formed to cover the conductive paint.

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