JP2004296481A - Multilayer wiring circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring circuit board capable of sufficiently achieving high density mounting on an external conductive layer by electrically conducting between each of conductors without forming through holes, even in a multilayer wiring circuit board having four-layers of conductive layers. <P>SOLUTION: In the four-layered wiring circuit board 14, two second conductor layers 3 are provided on both sides of a thermosetting adhesive layers 8, and two first conductor layers 2 are provided outside each of the layers 3 with an insulating layer 1 sandwiched. In this circuit board 4, the layer 3 of each double-sided substrate 4 is electrically connected to the layer 2 thereof by a blind hole plating layer 6 closed on the layer 2, and the respective layers 2 are electrically connected by a conducting layer 13 formed in the layer 8. In this way, the respective conductor layers can be electrically conducted without forming through holes, and connection pads are formed on arbitrary positions on a second surface of each of the layers 2 and electrical components can be mounted with high density. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a multilayer printed circuit board, and more particularly, to a multilayer printed circuit board having four conductor layers.
[0002]
[Prior art]
Conventionally, in a multilayer wiring circuit board having a plurality of conductor layers, in order to electrically connect between the conductor layers, a through hole is formed through the multilayer wiring circuit board in a thickness direction, and then the through hole is formed. Then, through-hole plating is formed by copper plating or the like.
[0003]
However, when a through hole is formed in a multilayer wiring circuit board, electronic parts cannot be mounted on a portion of the surface of the multilayer wiring circuit board where the through hole is formed, responding to recent demands for high-density mounting. Has limitations.
[0004]
On the other hand, for example, it has been proposed that a via hole is formed on a SUS plate surface by a build-up method, and a circuit-forming surface is faced and laminated to form a smooth mounting pad on the surface via hole (for example, See Patent Document 1.).
[0005]
When the printed circuit board is manufactured by this method, as shown in FIG. 4, the outer conductor layer 31 and the inner conductor layer 32 adjacent to the outer conductor layer 31 with the insulating layer 33 interposed therebetween are formed on the upper surface thereof. Are electrically conducted by the inner plating layer 35 formed on the photo via 34 closed by the outer conductor layer 31, and the mounting pad 36 is formed on the outer conductor layer 31 facing the photo via 34. And high-density mounting can be achieved.
[0006]
[Patent Document 1]
JP-A-9-186454
[Problems to be solved by the invention]
However, when four conductor layers are provided by the method described in Patent Document 1, a through hole 37 is also formed, and the conductor layers 31 and 32 are electrically connected by the through hole plating 38. In this case, electronic parts cannot be mounted on the portion where the through hole 37 is formed, which is insufficient for meeting recent demands for high-density mounting.
[0007]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a multi-layer wiring circuit board having four conductor layers without forming through holes. An object of the present invention is to provide a printed circuit board that is electrically conductive and can sufficiently achieve high-density mounting in an outer conductor layer.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a multilayer wiring circuit board of the present invention is a multilayer wiring circuit board having four conductor layers, wherein two inner conductor layers provided on both sides of an inner insulating layer, and each inner conductor layer Outside, and two outer conductor layers provided with an outer insulation layer interposed therebetween. The outer insulation layer penetrates the inner conductor layer and the outer insulation layer adjacent to the inner conductor layer in the thickness direction. A blind hole closed in the outer conductor layer adjacent to a layer, an outer conduction path formed in the blind hole for electrically connecting the outer conductor layer and the inner conductor layer, and the inner insulating layer. And an inner conduction path for electrically connecting the inner conductor layers to each other.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
1 to 3 are manufacturing process diagrams showing one embodiment of a manufacturing method for manufacturing a multilayer wiring circuit board of the present invention. Hereinafter, an embodiment of a method for manufacturing a multilayer wiring circuit board of the present invention will be described with reference to FIGS.
[0010]
In this method, first, as shown in FIG. 1A, a first conductor layer 2 serving as an outer conductor layer and a second conductor layer 3 serving as an inner conductor layer are provided on both sides of an insulating layer 1 serving as an outer insulating layer. A laminated double-sided substrate 4 is prepared.
[0011]
The insulating layer 1 is not particularly limited as long as it is generally used as an insulating layer of a printed circuit board. For example, polyimide resin, acrylic resin, polyether nitrile resin, polyether sulfone resin, polyester resin, polyethylene naphthalate It is formed in a sheet shape from resin, polyvinyl chloride resin, or the like. The thickness of the insulating layer 1 is usually 9 μm or more and 100 μm or less, preferably 9 μm or more and 35 μm or less.
[0012]
The first conductor layer 2 and the second conductor layer 3 are not particularly limited as long as they are commonly used as the conductor layer of the printed circuit board. For example, copper, nickel, gold, solder, or these It is formed from a thin metal such as an alloy. Preferably, it is formed from a copper foil. The thickness is usually 9 μm or more and 50 μm or less, preferably 9 μm or more and 25 μm or less.
[0013]
For example, such a double-sided base material 4 is configured such that the first conductor layer 2 and the second conductor layer 3 are adhered to both surfaces of the insulating layer 1 via an adhesive layer, or are formed on both surfaces of the insulating layer 1. The first conductor layer 2 and the second conductor layer 3 can be formed by directly laminating them.
[0014]
There is no particular limitation on directly laminating the first conductor layer 2 and the second conductor layer 3 on the insulating layer 1. For example, first, a solution of a synthetic resin is applied to the surface of the first conductor layer 2 made of a metal foil. Is uniformly applied, dried and heated if necessary, to form an insulating layer 1. Then, a metal foil is formed on the surface of the insulating layer 1 (the opposite surface on which the first conductor layer 2 is laminated). May be laminated, or the second conductor layer 3 may be plated.
[0015]
More specifically, for example, first, a solution of a polyamic acid resin is uniformly applied to the surface of the first conductor layer 2 made of copper foil, and then dried, and then the second conductor layer 3 made of copper foil is formed. After lamination, the applied polyamic acid resin is cured (imidized), for example, by finally heating it to 300 ° C. or higher, thereby forming the insulating layer 1 made of a polyimide resin.
[0016]
Also, for example, first, a solution of a polyamic acid resin is uniformly applied to the surface of the first conductive layer 2 made of a copper foil, and then dried and cured (imidized) to form an insulating layer 1 made of a polyimide resin. Then, the second conductor layer 3 may be formed on the surface of the insulating layer 1 by copper plating.
[0017]
The double-sided substrate 4 in which the first conductor layer 2 and the second conductor layer 3 are directly laminated on both surfaces of the insulating layer 1 is commercially available, and such a commercially available product may be used. .
[0018]
Next, in this method, as shown in FIG. 1B, in a predetermined portion of the double-sided base material 4, the second conductor layer 3 and the insulating layer 1 penetrate in the thickness direction, and the first conductor layer 2 is exposed. After forming the blind hole 5, as shown in FIG. 1C, a blind hole plating layer 6 serving as an outer conduction path is formed in the blind hole 5.
[0019]
The formation of the blind hole 5 is not particularly limited. For example, using a known method such as laser drilling or etching, the second conductive layer 3 is formed from the surface of the second conductive layer 3 to the surface of the first conductive layer 2. The first conductor layer 2 is formed so as to penetrate the insulating layer 1 in the thickness direction and expose the first conductor layer 2. In the case of a circular shape, the size of the blind hole 5 is usually 50 μmφ to 300 μmφ, preferably 50 μmφ to 200 μmφ.
[0020]
In addition, the blind hole plating layer 6 is formed by plating a metal such as copper, nickel, gold, solder, or an alloy thereof around the blind hole 5 to thereby form the second conductor layer 3 and the first conductor layer. It is formed so as to be continuous with 2. Thereby, the second conductor layer 3 and the first conductor layer 2 are electrically connected via the blind hole plating layer 6.
[0021]
The thickness of the blind hole plating layer 6 is usually 5 μm or more and 25 μm or less, preferably 5 μm or more and 15 μm or less. The plating layer formed by the blind hole plating layer 6 is usually formed continuously from the blind hole plating layer 6 to the surfaces of the second conductor layer 3 and the first conductor layer 2. The plating layers formed on the surfaces of the layer 3 and the first conductor layer 2 are integrated with the already formed second conductor layer 3 and the first conductor layer 2, respectively, to form the second conductor layer 3 and the first conductor layer 2. The conductor layer 2 is formed.
[0022]
Next, in this method, the second conductor layer 3 and the first conductor layer 2 are each formed in a predetermined wiring circuit pattern. In order to form the second conductor layer 3 and the first conductor layer 2 in a predetermined wiring circuit pattern, respectively, first, as shown in FIG. 1D, the second conductor layer 3 and the first conductor layer 2 are formed by a subtractive method. After a plating resist 7 is laminated on the surface of the conductor layer 2 to form a resist pattern corresponding to the wiring circuit pattern, as shown in FIG. 1E, the plating resist 7 is used as a resist to form a second conductor. The layer 3 and the first conductor layer 2 may be etched.
[0023]
The plating resist 7 may be laminated, for example, by laminating a dry film resist by a known method, and the resist pattern may be formed, for example, by exposing the dry film resist through a photomask and then developing. Good.
[0024]
The etching using the plating resist 7 as a resist may be performed by wet etching using an etching solution. Examples of the etching solution include sulfuric acid, sulfuric acid-based solution, cupric chloride solution, ferric chloride solution, and ammonium persulfate. A solution, an ammonia-based alkali solution, or the like is used.
[0025]
Thereafter, as shown in FIG. 2 (f), the plating resist 7 is removed by a known method, so that the second conductor layer 3 and the first conductor formed as a predetermined wiring circuit pattern are formed on both surfaces of the insulating layer 1. A double-sided substrate 4 on which the layer 2 is laminated is obtained.
[0026]
In order to form the second conductor layer 3 and the first conductor layer 2 on both surfaces of the insulating layer 1 as predetermined wiring circuit patterns, respectively, the present invention is not limited to the above-described method. A known patterning method such as a method may be used.
[0027]
Next, in this method, as shown in FIG. 2 (g), a thermosetting adhesive layer 8 serving as an inner insulating layer is placed on the second conductor layer 3 including the opening portion of the blind hole 5 in a B-stage state. After the formation, an opening 9 is formed in the thermosetting adhesive layer 8 as shown in FIG.
[0028]
The thermosetting adhesive is usually used as an adhesive layer of a printed circuit board, and can be in a B-stage state (a state in which the thermosetting adhesive has been cured to an extent that it can maintain a predetermined shape). It is not particularly limited as long as it is, for example, an acrylic adhesive, an epoxy adhesive, an amide adhesive, an amide imide adhesive, an imide adhesive, and a blend of these thermosetting adhesives Are used. Further, such a thermosetting adhesive having a curing temperature of 100 ° C. or higher, preferably 125 ° C. or higher and 200 ° C. or lower is used.
[0029]
Further, such a thermosetting adhesive layer 8 has a thickness of usually 25 μm or more and 100 μm or less, preferably 40 μm or more and 60 μm or less.
[0030]
In order to form the thermosetting adhesive layer 8 on the second conductor layer 3 in the B-stage state, for example, after applying a solution containing a thermosetting adhesive on the second conductor layer 3, By heating, it is dried and brought into the B-stage state at the same time, or an adhesive sheet made of a thermosetting adhesive previously brought into the B-stage state is heated and / or pressed on the second conductor layer 3. In this way, the layers may be laminated (temporarily bonded).
[0031]
In this step, a separator 9 used as a mask is stacked on the surface of the thermosetting adhesive layer 8 opposite to the surface in contact with the second conductor layer 3 in a later-described solder paste 11 filling step. I do.
[0032]
As the separator 9, for example, a film of a synthetic resin such as a polyester resin, a polyethylene naphthalate resin, and a polyimide resin is used, and the thickness thereof is generally 7.5 μm or more and 50 μm or less. Further, such a separator 9 may be attached to the second conductor layer 3 via the thermosetting adhesive layer 8.
[0033]
Then, in order to form the opening 10 in the thermosetting adhesive layer 8, the thermosetting adhesive layer 8 is formed with the separator 9 by using, for example, a laser such as a YAG laser. The opening 10 thus formed penetrates through the separator 9 and the thermosetting adhesive layer 8 in the thickness direction from the surface of the thermosetting adhesive layer 8 to the surface of the second conductor layer 3. Thus, the second conductor layer 3 is formed so as to be exposed.
[0034]
Also, in this step, instead of forming the opening 10 after forming the thermosetting adhesive layer 8 and the separator 9 on the second conductor layer 3, an opening is previously formed on the second conductor layer 3. The thermosetting adhesive layer 8 having the portion 10 formed thereon and the separator 9 may be formed. In order to form the thermosetting adhesive layer 8 and the separator 9 in which the opening 10 is formed in advance on the second conductor layer 3, for example, the separator 9 is formed on the thermosetting adhesive layer 8 made of an adhesive sheet. It may be attached and then formed on the second conductor layer 3 after forming the opening 10 in advance using a drill or a punch.
[0035]
The opening 10 is formed in a portion other than the portion facing the blind hole 5 in the thermosetting adhesive layer 8, and has a size of, for example, a circle having a diameter of 50 μmφ or more when it is circular. , 300 μmφ or less, preferably 200 μmφ or less.
[0036]
Next, in this method, as shown in FIG. 2 (i), a solder paste 11 containing a conductor powder 12 made of a solder powder or a metal powder is applied to the opening 10 of the thermosetting adhesive layer 8 at 5 ° C. Fill and dry at not less than 50 ° C.
[0037]
The solder paste 11 can be prepared by mixing a conductor powder 12 made of a solder powder or a metal powder into a solvent.
[0038]
Although there is no particular limitation on the solder powder, for example, a binary composition composed of Sn / Ag, Sn / Cu, Sn / Sb, Sn / Zn, Sn / Ag / Cu, Sn / Ag / Cu / Bi Those having a multi-component composition consisting of, for example, are used. Further, the solder powder having an average particle diameter of 50 μm or less, and more preferably 20 μm or less is preferably used.
[0039]
As the metal powder, for example, Ni, Au, Ag, Cu, Fe, Al, Cr, Pd, Co, Rh, or an alloy thereof is used. The metal powder having an average particle diameter of 50 μm or less, and preferably 20 μm or less is preferably used.
[0040]
The mixing ratio of the metal powder to the solder powder is preferably 0.1 to 60 parts by weight based on 100 parts by weight of the total of the solder powder and the metal powder. If the amount is less than 0.1 part by weight, the dispersibility in the blind holes 5 cannot be ensured. On the other hand, if the amount exceeds 60 parts by weight, the metal powders may aggregate and cracks may occur in the blind holes 5.
[0041]
The solvent is not particularly limited, but it is preferable to select a solvent that can be dried and removed in the range of 75 ° C. or more and 200 ° C. or less, and more preferably 160 ° C. or less in the next drying step. If a solvent that can be dried at a temperature lower than 75 ° C. is selected, the storage stability and continuous printability of the solder paste 11 may be reduced. When a solvent that can be dried at a temperature higher than 200 ° C. is selected, the curing of the thermosetting adhesive layer 8 proceeds during drying, and the adhesive strength may be reduced.
[0042]
More specifically, as the solvent, for example, a solvent obtained by adding a cellulose-based resin to an aliphatic alcohol in order to impart a thickening effect is preferably used. The addition amount of the cellulose resin is, for example, about 0.005 to 5% by volume based on the solder powder. The solder paste 11 can be prepared, for example, by mixing a solder powder, a metal powder, and a solvent at a volume ratio of about 9: 1: 10.
[0043]
Then, in order to fill the opening 10 of the thermosetting adhesive layer 8 with the solder paste 11 containing the conductor powder 12, for example, using the separator 9 as a mask, the printing method is used to print the paste at 5 ° C or more and 50 ° C or less. An appropriate amount (a considerable amount) of the solder paste 11 is printed on the opening 10 at a temperature of 10 ° C. or more and 30 ° C. or less, more specifically, at room temperature. Note that the normal temperature refers to an atmosphere at room temperature that is not particularly heated.
[0044]
Thereafter, the solvent is heated and dried at a temperature of 75 ° C. or more and 200 ° C. or less, and further, 160 ° C. or less for an appropriate time as described above. The drying time may be appropriately determined depending on the filling amount of the solder paste 11 into the opening 10 and the size of the double-sided base material 4. However, if the drying time is too short, the solvent remains and the generation of outgas by heating may occur. In some cases, causing poor conduction. If the drying time is too long, the curing of the thermosetting adhesive layer 8 proceeds, and the adhesive strength may be reduced. From such a viewpoint, the drying time is preferably, for example, about 1 to 5 minutes.
[0045]
In the step of filling the solder paste 11, except that the solvent is dried and removed, the solder paste is carried out at 5 ° C. or more and 50 ° C. or less, furthermore, 10 ° C. or more and 30 ° C. or less, more specifically, at room temperature. Is done.
[0046]
Thereafter, as shown in FIG. 2 (j), the separator 9 is peeled off and removed together with the excess conductor powder 12 on the opening 10. As a result, the conductive powder 12 is filled in the opening 10 in a considerable amount.
[0047]
Note that, in this method, the solder paste 11 may be printed using a metal mask or the like without using the separator 9, and if necessary, the dried conductor powder 12 may be pressed at room temperature to form an opening. The portion 10 may be densely filled.
[0048]
Next, in this method, as shown in FIG. 3 (k), the double-sided base material 4 (the second conductor layer 3 and the first conductor layer 2 are separately formed by a predetermined wiring circuit pattern) separately formed by the same method as described above. And a double-sided base material 4 having a blind hole 5 and a blind-hole plating layer 6, but the wiring circuit pattern is arbitrary.) As shown in FIG. 4 is laminated on the thermosetting adhesive layer 8. This lamination is performed by using a hot press device or a hot press roll in a state where the separately formed second conductive layer 3 of the double-sided base material 4 is positioned so as to face the opening 10 filled with the conductive powder 12. Pressurization and / or heating may be performed using such as.
[0049]
The conditions of pressurization and / or heating may be appropriately determined according to the size of each double-sided base material 4 and the like. For example, the pressurization condition is 1 MPa or more and 10 MPa or less, and further 3 MPa or more and 5 MPa or less. The heating conditions are preferably, for example, 160 ° C. or more and 225 ° C. or less, and more preferably 175 ° C. or more and 200 ° C. or less. Thereby, the thermosetting adhesive layer 8 in the B-stage state is cured, and the double-sided base materials 4 are bonded and laminated via the thermosetting adhesive layer 8.
[0050]
Thereafter, as shown in FIG. 3 (m), the inner conductive path for electrically connecting the second conductor layers 3 of the opposing double-sided base materials 4 by heating and melting the solder powder in the conductor powder 12. By forming the conductive layer 13 as a substrate, a four-layer wiring circuit board 14 is obtained.
[0051]
The heating and melting of the solder powder may be set at a temperature equal to or higher than the melting temperature of the solder powder to be used, and it is preferable that the pressure is applied at 1 MPa to 10 MPa, and more preferably 3 MPa to 5 MPa.
[0052]
Note that such curing of the thermosetting adhesive layer 8 and heating and melting of the solder powder may be sequentially performed as separate steps, respectively, or may be performed simultaneously in the same step by selecting appropriate conditions. May be. Further, these steps may be performed under reduced pressure.
[0053]
In the four-layer printed circuit board 14 thus obtained, two second conductor layers 3 are provided on both sides of the thermosetting adhesive layer 8, and the insulating layer 1 is provided outside each second conductor layer 3. The first conductor layer 2 is provided between the first conductor layer 2 and the second conductor layer 3 and the first conductor layer of each double-sided base material 4 due to the blind hole plating layer 6 closed in the first conductor layer 2. 2 are electrically connected to each other, and each of the second conductor layers 3 is electrically connected to each other by the conductive layer 13 formed in the thermosetting adhesive layer 8.
[0054]
That is, since each blind hole plating layer 6 is not opened outward from each first conductor layer 2 and is formed inward on the back surface of each first conductor layer 2, each blind hole plating layer 6 The surface of each first conductor layer 2 facing the portion where is formed can be a mounting portion 15a for mounting an electronic component. Further, since each second conductor layer 3 is electrically connected by the conductive layer 13 penetratingly formed in the thermosetting adhesive layer 8, there is no need to form a through hole, and the conductive layer 13 is not required. The surface of each of the first conductor layers 2 facing the portion on which is formed can also be a mounting portion 15b for mounting an electronic component.
[0055]
Therefore, when an electronic component such as a semiconductor is mounted on the surface of each first conductor layer 2 by solder bumps or the like, connection pads can be provided at arbitrary positions and mounted at high density.
[0056]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples. However, the present invention is not limited to the Examples and Comparative Examples.
[0057]
Example 1
A double-sided copper-clad base material (Nippon Steel Chemical's ESPANEX) is prepared by laminating a first conductor layer and a second conductor layer made of a 9-μm-thick copper foil on both sides of an insulating layer made of a 13-μm-thick polyimide resin. (See FIG. 1A).
[0058]
In a predetermined portion of the second conductor layer of the double-sided copper-clad base material, a blind hole having a hole diameter of 100 μmφ through which the first conductor layer was exposed was formed by penetrating the second conductor layer and the insulating layer in the thickness direction by the YAG laser ( FIG. 1 (b). Then, after the blind holes are desmeared by a plasma device, electroless / electrolytic copper plating is performed to form a blind hole plating layer, and the second conductor layer and the first conductor layer are electrically connected via the blind hole plating layer. (See FIG. 1 (c)).
[0059]
Next, a plating resist is laminated on the surfaces of the second conductor layer and the first conductor layer, respectively, and then exposed through a photomask and developed, so that the plating resist becomes a resist pattern corresponding to the wiring circuit pattern. It was formed (see FIG. 1D). Thereafter, the second conductor layer and the first conductor layer were formed as a predetermined wiring circuit pattern by wet-etching the second conductor layer and the first conductor layer using the plating resist as a resist (FIG. 1 (e)). )reference).
[0060]
Then, after removing the plating resist (see FIG. 2F), the separator made of a polyethylene naphthalate film having a thickness of 12 μm and subjected to a mold release treatment is heated with an adhesive sheet made of an acrylic adhesive having a thickness of 50 μm. It was laminated on the second conductor layer including the opening portion of the blind hole via the curable adhesive layer, and temporarily bonded at 160 ° C. and 50 MPa for 1 minute using a press device (see FIG. 2 (g)). .
[0061]
Next, using a YAG laser, an opening having a hole diameter of 150 μmφ through which the second conductor layer is exposed, penetrating through the separator and the thermosetting adhesive layer, in addition to the portion facing the blind hole in the thermosetting adhesive layer. It was formed (see FIG. 2 (h)).
[0062]
Then, after the opening was desmeared by a plasma apparatus, the opening was filled with a solder paste at room temperature by a printing method using a separator as a mask (see FIG. 2 (i)). The solder paste used was a mixture of Sn / Ag powder, Ni powder, an alcohol-based solvent, and ethyl cellulose in a volume ratio of 45: 5: 49: 1. Thereafter, the solder paste was dried at 160 ° C. for 5 minutes, and then the separator was peeled off (see FIG. 2 (j)).
[0063]
Then, similarly to the above, a double-sided copper-clad base material in which a blind hole and a blind hole plating layer are formed and the second conductor layer and the first conductor layer are formed in a predetermined wiring circuit pattern is prepared (FIG. 3 (k)). )), And the second conductor layer of the separately prepared double-sided copper-clad base material is superposed in a state where the second conductor layer faces the opening filled with the solder powder and the metal powder (see FIG. 2 (l)). Under vacuum pressure (3 MPa), the temperature is raised to the melting point (250 ° C.) or more of the solder powder to cure the thermosetting adhesive layer in the B-stage state, and the double-sided copper-clad base material is cured by the thermosetting adhesive layer. And a conductive layer was formed by melting the solder to obtain a four-layer wiring circuit board in which the second conductive layer and the first conductive layer of each double-sided copper-clad base material were electrically connected (FIG. 3 (m Reference).
[0064]
【The invention's effect】
As described above, according to the wired circuit board of the present invention, each outer conductor layer and each inner conductor layer can be electrically connected by the outer conduction path, and each inner conductor layer can be electrically connected by the inner conduction path. Since the layers can be electrically connected, each outer conductor layer and each inner conductor layer can be electrically connected without forming a through hole. Therefore, more areas for mounting the electronic components can be secured on the surface of the outer conductor layer, and the electronic components can be mounted at a high density.
[Brief description of the drawings]
FIG. 1 is a manufacturing process diagram showing one embodiment of a manufacturing method for manufacturing a multilayer wiring circuit board of the present invention, wherein (a) shows a first conductor layer 2 and a second conductor layer 2 on both surfaces of an insulating layer 1; A step of preparing a double-sided base material 4 on which the conductor layer 3 is laminated; and (b) a step of forming a blind hole that penetrates the second conductor layer and the insulating layer in the thickness direction and exposes the first conductor layer. , (C) a step of forming a blind hole plating layer in the blind hole, (d) a step of forming a plating resist as a resist pattern on the surface of the second conductor layer and the first conductor layer, (e) Shows a step of etching the second conductor layer and the first conductor layer using a plating resist as a resist.
FIG. 2 is a manufacturing process diagram showing one embodiment of a manufacturing method for manufacturing a multilayer wiring circuit board of the present invention, following FIG. 1, wherein (f) shows a step of removing a plating resist; g) is a step of laminating a separator on the second conductor layer via a thermosetting adhesive layer, (h) is a step of forming an opening in the thermosetting adhesive layer, and (i) is a step of forming an opening in the thermosetting adhesive layer. (A) a step of filling the opening of the thermosetting adhesive layer with the solder paste, and (j) a step of peeling the separator.
FIG. 3 is a manufacturing process diagram showing one embodiment of a manufacturing method for manufacturing a multilayer wiring circuit board of the present invention, following FIG. 2, wherein (k) separately prepares a double-sided base material; Step (l) is a step of laminating a separately prepared double-sided base material on the double-sided base material via a thermosetting adhesive layer, and (m) is a step of forming a conductive layer.
FIG. 4 is a side sectional view showing a main part of a conventional multilayer wiring circuit board.
[Explanation of symbols]
1 insulating layer
2 First conductor layer
3 Second conductor layer
5 blind holes
6 blind hole plating layer
8 Thermosetting adhesive layer
13 Conductive layer
14 Four-layer wiring circuit board

Claims (1)

A multilayer wiring circuit board having four conductor layers,
Two inner conductor layers provided on both sides of the inner insulating layer,
Outside of each inner conductor layer, two outer conductor layers provided with an outer insulating layer interposed therebetween,
The inner conductor layer, penetrating the outer conductor layer adjacent to the inner conductor layer in the thickness direction, blind holes closed in the outer conductor layer adjacent to the outer insulation layer,
An outer conduction path formed in the blind hole and electrically connecting the outer conductor layer and the inner conductor layer,
A multilayer wiring circuit board, comprising: an inner conductive layer that is provided so as to penetrate the inner insulating layer in a thickness direction and electrically connects the inner conductor layers.

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