JP4347143B2 - Circuit board and manufacturing method thereof - Google Patents

Description

  The present invention relates to a structure of a circuit board and a manufacturing method thereof, and more particularly to a multilayer circuit board that performs interlayer connection using conductive protrusions and a manufacturing method thereof.

  In recent years, downsizing and higher functionality of electronic devices have been increasingly promoted, and for this reason, there is an increasing demand for higher density of circuit boards. In view of this, the circuit board is made to be a multi-layer circuit board from one side to both sides or three or more layers to increase the density of the circuit board.

  Conventionally, in these circuit boards, for interlayer connection, a technique of performing plating treatment after opening by laser, NC drill, plasma etching, chemical etching or the like has been adopted. However, the poor yield of the plating process itself and the complexity of the process of conducting the insulating resin layer are problems.

  Therefore, a method has been developed in which the interlayer connection of the circuit board is replaced with a conductive protrusion such as a printed bump by a conductive paste, plating, or a metal bump by etching instead of via hole connection by plating.

  FIG. 3 is a process diagram showing a method for manufacturing a double-sided flexible circuit board by connection using conductive protrusions according to a conventional method described in Patent Documents 1 and 2. First, as shown in FIG. 3 (1), a metal substrate 24 having a three-layer structure of a copper foil 21, a nickel foil 22, and a copper foil 23 (see Patent Document 2) is prepared. Next, as shown in FIG. 3 (2), the copper foil 21 is etched to form conductive protrusions 25 (Patent Document 3). Then, as shown in FIG. 3 (3), a polyimide film 26 having thermoplastic polyimide on both sides is attached to the surface on which the conductive protrusions 25 are provided. Subsequently, as shown in FIG. 3 (4), the top portion 27 of the conductive protrusion 25 is exposed from the polyimide film 26 to form a circuit substrate 28.

Thereafter, as shown in FIG. 3 (5), the conductive protrusions 25 are laminated on the copper foil 29 with the circuit substrate 28. And as shown in FIG.3 (6), the circuit pattern 30 is formed in the copper foil of both surfaces in a laminated body, and the double-sided flexible circuit board 31 is formed.
JP 2002-141629 A JP 2003-129259 A JP-A-6-350258 JP2003-327697

  Here, it is difficult for the conductive protrusion to directly penetrate the polyimide film, and the polyimide film may remain on the top of the conductive protrusion even though the conductive protrusion can penetrate.

  For this reason, it is necessary to remove the polyimide film at the top of the conductive protrusions by a mechanical or chemical method, which also has a problem that further post-treatment is required.

  The present invention has been made in consideration of the above-described points, and an object thereof is to provide a circuit board having a structure capable of stably manufacturing a circuit board for performing interlayer connection with conductive protrusions in fewer steps, and a method for manufacturing the circuit board. And

In order to achieve the above object, in the present invention,
A metal foil having conductive protrusions formed on at least one surface, and a circuit substrate having an insulating resin layer laminated with the conductive protrusions penetrating on one surface of the metal foil is another circuit member. Alternatively, in a circuit board that is laminated with a metal foil to form a plurality of circuit layers and that connects between the circuit layers by the conductive protrusions,
The insulating resin layer is
A core resin layer composed of a polyimide resin having low resistance to a resin etchant;
An adhesive layer made of a material having a higher resistance to a resin etching solution than the core resin layer;
I have a,
The core resin layer side of the insulating resin layer was laminated so as to face the surface of the metal foil on which the conductive protrusions were formed.
And a metal foil having conductive protrusions formed on at least one surface, and two or more insulating resin layers having different resistance to a resin etchant are provided on the one surface of the metal foil. A method of manufacturing a circuit board in which a layer having a low resistance to a resin etching solution is laminated so as to be in contact with the metal foil, and a top portion of the conductive protrusion is exposed by performing selective etching by a resin etching method,
Is to provide.

  In the present invention, as described above, the resin is removed by the resin etching method to expose the tops of the conductive protrusions, and two or more insulating resin layers having different resin etching resistance are made of a metal foil having low resin etching resistance. Since the substrate is laminated so as to be in contact with the resin, and the resin etching is performed, the circuit board can be manufactured with few steps.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

  1 (1) to 1 (6) show a process for manufacturing a circuit board according to the present invention.

First, as shown in FIG. 1 (1), a metal substrate 4 comprising a copper foil 1 having a thickness of 100 μm, a nickel foil 2 having a thickness of 2 μm, and a copper foil 3 having a thickness of 18 μm is prepared.

  Subsequently, as shown in FIG. 1 (2), the copper foil 1 is etched to form conductive protrusions 5. As an etching solution at this time, for example, cupric chloride is used.

  Thereafter, as shown in FIG. 1 (3), an insulating resin layer 6 composed of two or more layers having different resistance to the resin etching solution is formed on the surface of the metal base 4 where the conductive protrusions 5 are provided.

The insulating resin layer 6 may be selected from a cast method, a laminate method, and the like according to the properties of the resin.

  At this time, the insulating resin layer 6 is formed on the entire surface where the conductive protrusions 5 are provided, but is also formed on the top of the conductive protrusions 5 as shown in FIG. The insulating resin layer 6 is composed of two layers, that is, an insulating resin layer 8 having low resin etching solution resistance and an insulating resin layer 9 having high resin etching solution resistance and adhesiveness. The insulating resin layer 8 having a low resistance to resin etching solution is provided so as to be in contact with the copper foil 3, and the insulating resin layer 9 having a high resistance to resin etching solution is provided thereon.

  A polyimide resin is used as the insulating resin layer 8 having a low resistance to resin etching solution, and an adhesive resin such as acrylic, epoxy, or thermoplastic polyimide is used as the insulating resin layer 9 having a high resistance to resin etching solution. .

  Next, as shown in FIG. 1 (4), resin etching is performed to remove the insulating resin layers 8 and 9 formed on the top of the conductive protrusion 5 and expose the top of the conductive protrusion 5. As the resin etching solution, one containing oxyalkylamine and an alkali metal compound can be used.

  By this resin etching, the layer 8 having low resin etching resistance is selectively etched, and the insulating resin layer 6 formed on the top 7 of the conductive protrusion 5 is removed. At this time, since the insulating resin layer 8 in contact with the copper foil 3 and the insulating resin layer 9 thereabove are highly resistant to the resin etching solution of the insulating resin layer 9, it serves as a stopper layer against the resin etching and protects the lower layer. To do. And the circuit base material 10 which the electroconductive protrusion 5 penetrated the insulating resin layer 6, ie, the insulating resin layers 8 and 9, is obtained.

  Subsequently, as shown in FIG. 1 (5), the copper foil 11 is laminated on the surface of the circuit substrate 10 where the conductive protrusions 5 are exposed, and the two copper foils 3, 11 sandwiching the insulating resin layers 8, 9 are formed. A double-sided substrate connected by the conductive protrusions 5 is formed.

  Then, as shown in FIG. 1 (6), after forming a circuit pattern on the copper foils 3 and 11 on the double-sided substrate, a cover film, a solder resist layer, electroless nickel plating, gold plating, etc. A circuit board 13 is formed.

  2 (1) and 2 (2) show a process of forming a flexible multilayer circuit board having a cable portion by using the flexible double-sided circuit board 13 produced in the process shown in FIG. .

  As shown in FIG. 2 (1), a multilayer core substrate 14 separately formed on a flexible double-sided circuit board 13 is laminated and pressed, and then a circuit pattern 15 is formed on both sides of the outer layer as shown in FIG. 2 (2). Form. Thereby, the flexible multilayer circuit board 17 having the cable portion 16 can be formed.

1 (1) to (6) are process diagrams showing a manufacturing process according to an embodiment of the present invention. FIGS. 2A and 2B are process diagrams showing a process of creating a flexible multilayer circuit board having a cable using the flexible circuit board created in the process of FIG. The process figure which shows the creation process of the conventional flexible double-sided circuit board.

Explanation of symbols

1 copper foil, 2 nickel foil, 3 copper foil, 4 metal substrate, 5 conductive protrusion,
6 insulating resin layer, 7 top of conductive protrusion, 8, 9 insulating resin layer,
10 circuit base, 11 copper foil, 12 circuit pattern, 13 flexible circuit board,
14 multilayer core substrate, 15 circuit pattern, 16 cable part,
17 Flexible multilayer circuit board.

Claims (3)

A metal foil having conductive protrusions formed on at least one surface, and a circuit substrate having an insulating resin layer laminated with the conductive protrusions penetrating on one surface of the metal foil is another circuit member. Alternatively, in a circuit board that is laminated with a metal foil to form a plurality of circuit layers and that connects between the circuit layers by the conductive protrusions,
The insulating resin layer is
A core resin layer composed of a polyimide resin having low resistance to a resin etchant;
An adhesive layer made of a material having a higher resistance to a resin etching solution than the core resin layer;
I have a,
The core resin layer side of the insulating resin layer was laminated so as to face the surface of the metal foil on which the conductive protrusions were formed.
A circuit board characterized by that . In the circuit board according to claim 1,
The adhesive layer is a circuit board made of polyimide resin. Prepare a metal foil with conductive protrusions formed on at least one surface,
Laminating two or more insulating resin layers having different resin etchant resistance on the one surface of the metal foil such that a layer having low resin etchant resistance is in contact with the metal foil,
A method for manufacturing a circuit board, wherein selective etching is performed by a resin etching method to expose a top portion of the conductive protrusion.

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