JP3991198B2 - Multilayer printed circuit board and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multilayer printed circuit board and a method for manufacturing the same, and more particularly to a wiring formation technique when circuit wiring is formed in multiple layers via an insulating resin layer having a laser via hole.
[0002]
[Prior art]
One method for producing a multilayer printed circuit board is a build-up type. In the build-up type, a printed circuit board made of, for example, a copper-clad laminate is used as a core material, and an insulating resin layer is sequentially laminated on the substrate, and a circuit wiring is formed for each insulating resin layer.
[0003]
An example thereof will be described with reference to FIG. 3. First, circuit wirings 1 a and 1 b are formed in a predetermined pattern on both surfaces of the printed circuit board 1. If one of the circuit wirings 1a is the wiring of the inner layer circuit, the inner layer circuit wiring forming surface side is roughened by blackening or the like, and then the insulating resin layer (build-up resin layer) 2 is formed into a circuit. It is formed thicker than the wiring 1a.
[0004]
Next, a via hole 2a having a depth reaching the circuit wiring 1a is formed in the insulating resin layer 2. This drilling is selected according to the material of the insulating resin. For example, in the case of an epoxy resin, a laser drilling method is adopted, and in the case of a photovia development type insulating resin, the insulating resin is exposed by applying a predetermined mask, developed, and removed. Done.
[0005]
After drilling, the plating layer 3 is formed on the insulating resin layer 2 including the inside of the via hole 2a, and the plating layer 3 is etched to form the circuit wiring 3a that is electrically connected to the circuit wiring 1a on the insulating resin layer 2. To do. In this way, circuit wiring for the required number of layers is formed.
[0006]
FIG. 4 schematically shows an enlarged perspective view of the via hole 2a. Since the copper plating of the circuit wiring 3a exists in and around the via hole 2a, the circuit wiring 3a is not formed on the insulating resin layer 2. When another conductive wiring 4 is formed, wiring must be performed avoiding the via hole 2a.
[0007]
Normally, the diameter of the via hole 2a is about 0.1 to 0.2 mm. For example, when high-density wiring is performed on a large number of wires having a line width of about 30 to 100 μm, the presence of the via hole 2a is considered in wiring design. It is a big hindrance.
[0008]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to allow another wiring that is non-conductive to the circuit wiring to pass through the via hole connecting the circuit wiring in the build-up type multilayer printed circuit board. is there.
[0009]
[Means for Solving the Problems]
In order to solve the above-described problems, the first invention of the present application is, as described in claim 1, a printed circuit board as a core material having a first circuit wiring serving as an inner layer circuit on the surface, and the above-described printed circuit board. Including at least two insulating resin layers formed on the first circuit wiring, the insulating resin layer having a laser via hole having a depth reaching the first circuit wiring; In the multilayer printed circuit board in which the second circuit wiring that conducts to the first circuit wiring through the laser via hole is formed, the connection terminal portion of the second circuit wiring passes through a part of the inner surface of the laser via hole. In addition to being connected to the circuit wiring, the laser via hole is filled with an electrically insulating permanent filling material so as to be substantially flush with the insulating resin layer. 2 The road line is characterized by another wire of non-conduction is formed.
[0010]
According to the first invention, since the via hole is blocked by a permanent filling material, as possible out to form another wiring nonconductive and the second circuit interconnection to the via on the hole. Incidentally, as described in claim 2, it is preferable Les Zabia hole is conical hole.
[0011]
The second invention of the present application relates to the manufacturing method of the first invention, and as described in claim 3, the printed circuit board as the core material having the first circuit wiring which becomes the inner layer circuit on the surface. A first step of forming an insulating resin layer on one circuit wiring forming surface; a second step of forming a laser via hole having a depth reaching the first circuit wiring in the insulating resin layer by laser light; A third step of forming a first plating layer on the insulating resin layer including the inner surface of the laser via hole, and connecting the first plating layer to the first circuit wiring through a part of the inner surface of the laser via hole; As described above, a fourth step of forming an etching resist on the first plating layer, and unnecessary plating portions exposed on the remaining inner surface of the laser via hole are removed by etching, so that the inner surface of the laser via hole is removed. of A fifth step of forming a connection terminal portion to be connected to the first circuit wiring in the portion, and an electrically insulating permanent filling material in the laser via hole so as to be substantially flush with the insulating resin layer. A sixth step of filling, a sixth step of forming a second plating layer over the first plating layer and the permanent hole filling material, and etching after forming an etching resist with a predetermined pattern on the second plating layer A second circuit wiring connected to the first circuit wiring via the connection terminal portion, and a seventh step of forming the second circuit wiring and another non-conductive wiring on the permanent hole filling material. It is characterized by at least implementation.
[0012]
Also in the second invention, as described in claim 4, it is preferable that the laser via hole is formed in a mortar shape in the second step .
[0013]
DETAILED DESCRIPTION OF THE INVENTION
First, explaining the referential embodiment of the present invention by FIG. 1, it will be described implementation form of the present invention with reference to FIG 2 the next. 1A to 1D are explanatory diagrams of the manufacturing process of the reference embodiment, and FIGS. 2A to 2D are explanatory diagrams of the manufacturing process of the embodiment of the present invention .
[0014]
First, in the reference embodiment, as shown in FIG. 1 (a), circuit wirings 11 and 12 are formed on both surfaces of a printed circuit board 10 as a core material made of a copper-clad laminated substrate, and then a build is performed on one surface thereof. The insulating resin layer 20 is laminated as the up resin layer.
[0015]
In this case, since the circuit wiring (first circuit wiring) 11 is an inner layer circuit, the insulating resin layer 20 is laminated on the formation surface side of the first circuit wiring 11. The method for forming the insulating resin layer 20 may be a curtain coating method, a roll coating method, a printing method, or the like. Prior to lamination, the surface of the printed circuit board 10 is preferably roughened by, for example, blackening. In some cases, a prepreg may be used for the insulating resin layer 20.
[0016]
In this reference embodiment, an epoxy resin is used for the insulating resin layer 20. A via hole 21 having a depth reaching the first circuit wiring 11 is formed in the insulating resin layer 20. In this reference embodiment, the drilling is performed by laser irradiation.
[0017]
Therefore, the via hole 21 is a laser via hole and has a mortar shape. The mortar shape includes all the shapes in which the upper surface side opening diameter is larger than the bottom surface side opening diameter and the inner surface is a smooth inclined surface.
[0018]
The inclined surface may be a straight line or a curved line when viewed in cross section. The reason for using the via hole 21 as a laser via hole is that it is easy to form in a mortar shape according to a laser. In actual size, the opening diameter on the upper surface side is preferably about 0.10 to 0.20 mm, and the opening diameter on the bottom surface side is preferably about 0.07 to 0.17 mm.
[0019]
Next, as shown in FIG. 1B, a plating layer 30 is formed on the insulating resin layer 20 including the inside of the via hole 21. The plating method is not particularly limited, and for example, a combination of electroless plating and electroplating or only electroless plating may be used.
[0020]
After forming the plating layer 30, as shown in the cross-sectional view of FIG. 1 (c1) and the enlarged perspective view of FIG. 1 (c2), etching for forming the circuit wiring of the insulating resin layer 20 on the plating layer 30 A resist 40 is formed.
[0021]
In this example, two etching resists 41 and 42 are included as the etching resist 40. Refer to the sectional view of FIG. 1 (d1) and the enlarged perspective view of FIG. The etching resist 41 is for forming a specific circuit wiring (second circuit wiring) 31 connected to the first circuit wiring 11 of the printed circuit board 10, and the other etching resist 42 is the second circuit wiring 31. This is for forming another non-conductive circuit wiring 32.
[0022]
In this example, the first circuit wiring 11 of the printed circuit board 10 is divided by etching, one of the divided first circuit wirings 11 is connected to the second circuit wiring 31, and the first circuit wiring 11 of the divided first circuit wiring 11 is connected. In order to connect the other to another circuit wiring 32 that is non-conductive with the second circuit wiring 31, as shown in FIG. 1 (c1) and FIG. 1 (c2), the etching resist 41 and the etching resist 42 are connected to the via hole 21. Are opposed to each other at a predetermined interval.
[0023]
As described above, after the etching resist 40 including the etching resists 41 and 42 is formed on the plating layer 30, the first circuit wiring 11 of the printed circuit board 10 is divided by etching and connected to the divided one. Second circuit wiring 31 and circuit wiring 32 connected to the other divided part are formed.
[0024]
What is important here is that the connection terminal portion 31 a of the second circuit wiring 31 is formed not on the entire inner surface of the mortar-shaped via hole 21 but on a part thereof.
[0025]
Thereby, as shown in FIG. 1 (d1) and FIG. 1 (d2), another circuit wiring 32 that is non-conductive with the second circuit wiring 31 is passed through the remaining part of the inner surface of the via hole 21 as necessary. Thus, the wiring density can be further increased.
[0026]
Next, referring to FIG. 2 (a) ~ (d) , will be described implementation form of the present invention. Implementation form of this is to filling the via holes 21 of the referential embodiment, which has to be able to form another wire also thereon until diagram above referential embodiment 1 (a) ~ (b) Follow the same process.
[0027]
As described in FIG. 1B, the plating layer 30 in the reference embodiment is used as the first plating layer, and the first plating layer is formed on the insulating resin layer 20 including the inside of the via hole 21 of the insulating resin layer 20. after forming the 30, in the implementation form of this, cross-section and as shown in the enlarged perspective view of the FIG (a2), a portion of the inner surface of the first plating layer 30 via holes 21 in FIG. 2 (a1) An etching resist 40 is formed on the first plating layer 30 so as to be connected to the first circuit wiring 11 on the printed circuit board 10 side.
[0028]
That is, the first plating layer 30 on the insulating resin layer 20 is covered with the etching resist 40, and a part of the first plating layer 30 reaches the first circuit wiring 11 on the inner surface of the via hole 21, for example. Covering in the shape of a tongue, the remaining part of the inner surface of the via hole 21 and the first plating layer 30 on the periphery thereof are exposed.
[0029]
Then, after removing the unnecessary first plating layer 30 exposed on the inner surface of the via hole 21 by etching, the etching resist 40 is peeled off, and the sectional view of FIG. 2B1 and the enlarged view of FIG. As shown in the perspective view, a connection terminal portion 31 a of the first plating layer 30 connected to the first circuit wiring 11 is formed on a part of the inner surface of the via hole 21.
[0030]
Next, as shown in the cross-sectional view of FIG. 2C, the via hole 21 is filled with a permanent hole filling material 22, and the surface of the permanent hole filling material 22 is substantially flush with the first plating layer 30. So as to polish. For the permanent hole filling material 22, for example, an epoxy thermosetting resin can be used. The permanent hole filling material refers to a hole filling material that will not be removed from the insulating resin layer thereafter.
[0031]
Next, after the second plating layer 50 is formed on the first plating layer 30 and the permanent hole filling material 22 by, for example, electroplating, an etching resist 60 for forming a wiring required for the insulating resin layer 20 is formed. Form. The etching resist 60 may be formed by a printing method, but in this example, a photosensitive dry film is used.
[0032]
The implementation form of this, as shown in FIG. 2 (c), as the etching resist 60, connected to the first circuit interconnection 11 of the printed circuit board 10 through the connection terminal portions 31a that are left in the via hole 21 An etching resist 61 for obtaining a second circuit wiring to be used, and an etching resist 62 for obtaining a wiring passing through the permanent hole filling material 22 by another circuit wiring that is non-conductive with the second circuit wiring. Forming.
[0033]
After such etching resists 61 and 62 are formed, the exposed unnecessary second plating layer 50 and the first plating layer 30 thereunder are both removed by etching.
[0034]
As a result, as shown in the cross-sectional view of FIG. 2 (d1) and the enlarged perspective view of FIG. 2 (d2), the first circuit of the printed circuit board 10 via the connection terminal portion 31a remaining in the via hole 21. A second circuit wiring 51 connected to the wiring 11 and another circuit wiring 52 that is non-conductive with the second circuit wiring 51 and passes over the permanent hole filling material 22 are formed.
[0035]
The second circuit wiring 51 includes two layers of the first plating layer 30 and the second plating layer 50, but only one layer of the second plating layer 50 passes through the permanent hole filling material 22 of another circuit wiring 52. Consists of.
[0036]
Above you facilities embodiment, although the insulating resin layer 20 and the first layer, and further laminating the insulating resin layer as needed, to form a suitable laser via holes for connecting between the inner layer circuit wiring that Can do.
[0037]
【The invention's effect】
As described above, according to the present invention, in a build-up type multilayer printed circuit board, it is possible to pass another wiring that is non-conductive with the inner layer circuit, also in the via hole that connects the inner layer circuits. The wiring density can be further increased.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram for explaining a manufacturing process in a reference embodiment of the present invention.
Explanatory view for explaining a manufacturing step in the implementation form of the present invention; FIG.
FIG. 3 is a cross-sectional view showing a via hole portion of a conventional build-up type multilayer printed circuit board.
4 is an enlarged perspective view showing a via hole portion of FIG. 3;
[Explanation of symbols]
10 Printed circuit board (core material)
11 First circuit wiring (inner layer circuit)
20 Insulating resin layer 21 Via hole 30 Plating layer (first plating layer)
31, 51 Second circuit wiring 31a Connection terminal portion 32, 52 Another wiring 40, 60 Etching resist 50 Second plating layer

Claims (4)

A printed circuit board as a core material having a first circuit wiring serving as an inner layer circuit on the surface; and an insulating resin layer formed on the first circuit wiring of the printed circuit board, the insulating resin layer Is provided with a laser via hole having a depth reaching the first circuit wiring, and a second circuit wiring that is electrically connected to the first circuit wiring through the laser via hole is formed on the insulating resin layer. In the substrate,
The connection terminal portion of the second circuit wiring is connected to the first circuit wiring through a part of the inner surface of the laser via hole, and an electrically insulating permanent filling material is formed in the insulating resin layer in the laser via hole. A multilayer printed circuit board , wherein another wiring that is substantially non-conductive with the second circuit wiring is formed on the permanent hole-filling material so as to be substantially flush with each other . The multilayer printed circuit board according to claim 1, wherein the laser via hole is a mortar-shaped hole . A first step of forming an insulating resin layer on the first circuit wiring formation surface of the printed circuit board as a core material having a first circuit wiring serving as an inner layer circuit on the surface;
A second step of forming a laser via hole having a depth reaching the first circuit wiring in the insulating resin layer by laser light;
A third step of forming a first plating layer on the insulating resin layer including the inner surface of the laser via hole;
A fourth step of forming an etching resist on the first plating layer so as to connect the first plating layer to the first circuit wiring through a part of the inner surface of the laser via hole;
  A fifth step of forming a connection terminal portion connected to the first circuit wiring on a part of the inner surface of the laser via hole by removing unnecessary plating portions exposed on the remaining portion of the inner surface of the laser via hole by etching. When,
A sixth step of filling the laser via hole with an electrically insulating permanent hole filling material so as to be substantially flush with the insulating resin layer;
A sixth step of forming a second plating layer over the first plating layer and the permanent hole filling material;
An etching resist having a predetermined pattern is formed on the second plating layer, and then etched to connect the first circuit wiring to the first circuit wiring through the connection terminal portion, and the second hole on the permanent hole filling material. A method for manufacturing a multilayer printed board, comprising performing at least a seventh step of forming two-circuit wiring and another non-conductive wiring. The method for producing a multilayer printed board according to claim 3, wherein in the second step, the laser via hole is formed in a mortar shape.

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