JP2004288989A - Multilayer printed circuit board and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To directly and surely connect only specific inner layers IVH with each other. <P>SOLUTION: A method for producing a multilayer printed circuit board where a plurality of IVH boards are laminated inserting an insulator layer previously clogs the inner layer sites of via holes IVHa and IVHb connecting respective IVH boards 10A and 10B with each other, and arranges a conductive paste 33 through at the same coordinates as those of the via hole of the insulator layer 30. In the case of laminating, the method connects the inner layer lands of the respective via holes IVHa and IVHb with the conductive paste 33. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a multilayer printed wiring board and a method of manufacturing the same, and more particularly, to a multilayer printed wiring board in which a plurality of IVH (interstitial via hole) substrates are stacked with an insulator layer interposed therebetween and a method of manufacturing the same.
[0002]
In recent years, as the circuit density has increased, the degree of freedom of wiring has been increased, and a non-penetrating through hole (interstitial via hole) (hereinafter also referred to as IVH) has been proposed as a means for effectively utilizing the board space. Multilayer printed wiring boards having the same have become widespread.
[0003]
[Prior art]
Conventionally, when a plurality of double-sided through-hole substrates 5 are laminated in multiple layers by the prepreg insulating layer 6, the intermediate prepreg insulating layer 6 is melted and filled into each through-hole to form a blind via hole 11. In addition, there is known a device in which inner-layer circuits are connected to each other by a conductive paste 8 to form an inner via-hole conduction 12 (Patent Document 1).
[0004]
Conventionally, in an IVH board in which a plurality of printed wiring boards 11 are connected in a stacked state, conductive particles 16a are dispersed in an insulating sheet 16b between wiring patterns 14 on each printed wiring board. A sheet 16 or a sheet 16 connected by connecting means made of an anisotropic conductive adhesive is known (Patent Document 2).
[0005]
[Patent Document 1]
JP-A-5-90762 (abstract, figure).
[0006]
[Patent Document 2]
JP-A-11-298148 (abstract, figure).
[0007]
[Problems to be solved by the invention]
By the way, since the IVH is originally made by a technique for forming a through-plated through-hole, the center thereof is hollow, and it is necessary to close this gap when laminating. Therefore, in order to electrically connect the IVHs to each other, it is necessary to draw out a conductor pattern from each IVH to another place and connect them with a conductive paste 8 as shown in Patent Document 1. . Otherwise, during lamination, the conductive paste 8 permeates into the cavities, and there is no guarantee that the IVHs can be reliably connected.
[0008]
On the other hand, the anisotropic conductive sheet of Patent Document 2 is a sheet in which a conductor is mixed with an insulating agent, and the conductors are connected only in a direction in which a force is applied, so that conduction is obtained only in the direction of the plate thickness. However, it is necessary to apply a resist 15 in advance to a portion to be made non-conductive, so that the work of making the local conduction is complicated, and the reliability of interlayer insulation is low.
[0009]
As described above, in the conventional IVH multilayer printed wiring board technology, there is no technology for directly bonding only specific inner layers IVH to each other. Therefore, there is a limit in increasing the degree of freedom of the conductor wiring and effectively using the board space. Was.
[0010]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems of the related art, and an object of the present invention is to provide a multilayer printed wiring board capable of directly and reliably connecting only specific inner layers IVH and a method of manufacturing the same. is there.
[0011]
[Means for Solving the Problems]
The above problem is solved, for example, by the configuration of FIG. That is, the method for manufacturing a multilayer printed wiring board of the present invention (1) is a method for manufacturing a multilayer printed wiring board in which a plurality of IVH boards are laminated with an insulator layer interposed therebetween, and the method for manufacturing the multilayer printed wiring boards beforehand in each of the IVH boards 10A and 10B Inner layer portions of the via holes IVHa and IVHb connected to each other are closed with a resin 19, and a conductive paste 33 is disposed so as to penetrate the insulator layer 30 at the same coordinates as the via holes, so that the via holes IVHa and IVHb Are connected by a conductive paste 33.
[0012]
According to the present invention (1), since the inner layer portions of the via holes IVHa and IVHb connected to each other in each of the IVH substrates 10A and 10B are previously closed with the resin 19, the conductive paste 33 is applied to each of the IVH substrates 10A and 10B at the time of lamination. A reliable connection between the conductive paste 33 and each inner layer land can be obtained without entering the cavities of the via holes IVHa and IVHb. Therefore, only the specific inner layers IVHa and IVHb can be directly and reliably connected, thereby increasing the degree of freedom of wiring and effectively utilizing the board space.
[0013]
In the present invention (2), in the above-mentioned present invention (1), for example, as shown in FIG. 3, a part of the resin 19 in the inner layer portion of the via holes IVHa and IVHb is removed in advance to form the concave portion 20, and then the laminate is formed. Is what you do. Therefore, at the time of lamination, a part of the conductive paste 33 enters each of the recesses 20 of IVHa and IVHb, so that a more reliable connection can be obtained between them.
[0014]
The above-mentioned problem is solved by, for example, the configuration shown in FIG. That is, the multilayer printed wiring board of the present invention (3) is a multilayer printed wiring board obtained by laminating a plurality of IVH boards with an insulator layer interposed therebetween, and is provided at the same coordinates in each of the IVH boards 10A and 10B. Via holes IVHa and IVHb whose inner layer portions are closed with resin 19 and conductive resin 33 penetrating through the insulator layer 30 at the same coordinates as the via holes IVHa and IVHb. Connecting between the inner layer lands.
[0015]
According to the present invention (4), in the present invention (3), for example, as shown in FIG. 3, the conductive resin 33 penetrates into the concave portion 20 provided in the inner layer portion of each of the connected via holes IVHa and IVHb. It is.
[0016]
In the present invention (5), in the above-mentioned present invention (3) or (4), as shown in FIG. 5, for example, the diameter of each prepared via hole before plating is φ1, and the outer diameter of the inner layer land of the via hole is φ2. In this case, the sectional diameter φ of the conductive resin 33 connected between the inner-layer lands is expressed by the following formula:
φ1 ≦ φ ≦ {φ1 + (φ2-φ1) / 2}
Are in the range of Therefore, even when there is a slight displacement between the insulator layer 30 and the IVH substrate 10 during the lamination, a reliable connection is established between each of the via holes IVHa and IVHb to be connected and the conductive paste 33. can get.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a plurality of embodiments suitable for the present invention will be described in detail with reference to the accompanying drawings. Note that the same reference numerals indicate the same or corresponding parts throughout the drawings.
[0018]
FIGS. 1 and 2 are views (1) and (2) showing a method for manufacturing a multilayer printed wiring board according to the first embodiment, and show at least a portion of an IVH inner layer cavity in which an inner via hole is formed. Is previously covered with resin. Here, the inner via hole (also referred to as a buried via hole) means a through hole for connecting between separate conductors in an inner layer.
[0019]
First, as shown in FIG. 1A, a double-sided copper-clad laminate 13 having copper foils 12a and 12b provided on both sides of a base material (glass epoxy resin or the like) 11 is used as a base, and as shown in FIG. , IVH are formed in the through holes 14. Next, as shown in FIG. 1C, copper plating 15 is applied to the entire surface of the copper-clad laminate 13 to form a double-sided through-hole substrate 17 having a plated through hole 16. Next, as shown in FIG. 1 (D), necessary etching is performed on the double-sided through-hole substrate 17 to form a conductor circuit pattern, and thus the printed wiring board 10A is formed. Here, 18 is a land. Note that the above etching may be performed on at least the inner layer surface to be laminated. Then, as shown in FIG. 1 (E), a thermosetting resin 19 such as an epoxy resin is buried in the cavity of the plating through hole 16 and heated and cured in advance. The resin 19 may be any resin as long as it covers at least the inner surface of the plating through hole 16. Further, the resin 19 may be conductive.
[0020]
On the other hand, as shown in FIG. 2A, a through hole 32 is formed in a portion of the prepreg insulating layer 31 where an inner via hole is required. The prepreg insulating layer (prepreg) 31 is an adhesive sheet in which a glass cloth reinforcing material is impregnated with an uncured thermosetting resin to be in a semi-cured B-stage state. Further, a conductive paste 33 is applied to the through holes 32 by printing or the like. The conductive paste 33 is a paste in which fine particles of carbon (C), silver (Ag), or copper (Cu) are mixed with a high-concentration viscous thermoplastic resin binder. Thus, the prepreg material 30 is formed.
[0021]
Next, as shown in FIG. 2 (B), two printed wiring boards 10A and 10B are arranged so as to sandwich the intermediate prepreg material 30. Further, as shown in FIG. The multilayer printed wiring board 10 is formed by applying pressure. At that time, the intermediate prepreg material 30 is melted and adheres to each inner layer surface of the printed wiring boards 10A and 10B. At the same time, the conductive paste 33 is connected to the copper plating land surface 18 of IVHa and IVHb to make conduction between IVHa and IVHb. At this time, since the inner layer surfaces of the IVHa and IVHb are previously closed with the resin 19, a reliable connection between the IVHa and IVHb can be obtained by an appropriate amount of the conductive paste 33.
[0022]
FIG. 3 is a diagram showing a method of manufacturing a multilayer printed wiring board according to the second embodiment. In each of the resin layers that cover the insides of the connected IVHa and IVHb, a concave portion is provided for the conductive paste 33 to enter by an appropriate amount. Shows the case. First, as shown in FIG. 3A, a concave portion 20 is provided in advance at a portion connected to the conductive paste 33 for at least the resin 19 that blocks the connected IVHa and IVHb. The recess 20 can be formed by a chemical or the like that dissolves the resin 19. Further, the two printed wiring boards 10A and 10B are arranged so as to sandwich the intermediate prepreg material 30, and the multilayer printed wiring board 10 is formed by applying heat and pressure in this state as shown in FIG. . At this time, since the concave portions 20 are formed in advance on the inner layer surfaces of the IVHa and IVHb, the conductive paste 33 penetrates and adheres to partially exposed portions of the inner walls of the IVHa and IVHb, and is cured. As a result, more reliable electrical connection characteristics can be obtained by bonding between IVHa and IVHb via a large area.
[0023]
FIG. 4 is a view showing a method of manufacturing a multilayer printed wiring board according to another embodiment, and shows a case where the number of board multilayers is increased by increasing the number of layers of the printed board 10 and the prepreg material 30. In the same manner as described above, the prepreg materials 30A, 30B are inserted between the printed boards 10A, 10B, 10C, and they are heated, pressed, and bonded. In this case, the conductive paste 33a connects between IVHa and IVHb, and the conductive paste 33b connects between IVHc and IVHd. Thus, there is no through-hole penetrating the whole, but the same effect can be obtained. The printed wiring board 10 is formed. Further, the connection between the IVHe and the conductor pattern 21 can be easily obtained, so that the degree of freedom in wiring design is improved and the board space can be effectively used. In addition, since it is not necessary to perform through-hole copper plating for a through hole on the outer layer copper foil, the outer layer copper foil can be thinner and the patterning accuracy can be improved.
[0024]
FIG. 5 is a view for explaining the diameter of the filling hole of the conductive paste. In FIG. 5A, when the diameter of a prepared hole (hole formed by drilling or laser processing) before copper plating of IVH is φ1 and the outer diameter of the IVH inner layer land 18 is φ2, connection to the land 18 is performed. The sectional diameter φ of the conductive paste 33 is given by the following formula:
φ1 ≦ φ ≦ {φ1 + (φ2-φ1) / 2}
Within the range. Therefore, even if there is some displacement between the IVHa, IVHb and the conductive paste 33 at the time of lamination, a reliable connection can be obtained between them.
For this reason, there is a margin in the processing accuracy of the prepared hole, and the multilayer printed wiring board can be mass-produced.
[0025]
FIG. 5B shows examples of the outer diameter φ2 of various lands 18. Generally, the outer peripheral shape of the land 18 includes a circle, a square, an octagon and the like. In the case of a circle, the diameter is φ2, in the case of a square, one side is φ2, and in the case of a rectangle, the short side is φ2. Further, in the case of a polygon including an octagon, the diameter of the inscribed circle can be φ2.
[0026]
In the above-described embodiments, an example of the conductive paste 33 has been described. However, a wide range of other materials such as a paste which is metalized by heating can be applied.
[0027]
In place of the insulating resin 19, the conductive paste 33 may be filled in the copper plating through hole 16 in advance and cured.
[0028]
Although the preferred embodiments of the present invention have been described above, it is needless to say that various changes can be made in the configurations, processes, and combinations of the components without departing from the spirit of the present invention.
[0029]
【The invention's effect】
As described above, according to the present invention, only the specific inner layers IVH can be directly and reliably connected, so that the degree of freedom of the conductor wiring can be increased and the board space can be more effectively used, and thus the multilayer printed wiring can be used. It greatly contributes to the high density of the plate.
[Brief description of the drawings]
FIG. 1 is a diagram (1) illustrating a method for manufacturing a multilayer printed wiring board according to a first embodiment.
FIG. 2 is a diagram (2) illustrating a method for manufacturing a multilayer printed wiring board according to the first embodiment.
FIG. 3 is a diagram illustrating a method for manufacturing a multilayer printed wiring board according to a second embodiment.
FIG. 4 is a diagram showing a method for manufacturing a multilayer printed wiring board according to another embodiment.
FIG. 5 is a diagram illustrating the diameter of a filling hole of a conductive paste.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Multilayer printed wiring board 10A, 10B Printed wiring board 11 Base material 12a, 12b Copper foil 13 Double-sided copper-clad laminate 14 Through hole 15 Copper plating 16 Plating through hole 17 Double-sided through-hole board 18 Land (copper foil, copper plating)
19 thermosetting resin 20 recess 30 prepreg material 31 prepreg insulating layer 32 through hole 33 conductive paste IVH interstitial via hole

Claims (5)

What is claimed is: 1. A method for manufacturing a multilayer printed wiring board, comprising: laminating a plurality of IVH substrates with an insulator layer interposed therebetween, wherein the via hole inner layer portions connected to each other in each IVH substrate are closed with a resin in advance, and the via hole of the insulator layer is formed. A method for manufacturing a multilayer printed wiring board, characterized in that a conductive paste is penetrated at the same coordinates as in (1) and the inner lands of the via holes are connected by a conductive paste during lamination. 2. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein a concave portion is formed by removing a part of the resin in the via hole inner layer portion in advance, and then laminating. A multilayer printed wiring board formed by laminating a plurality of IVH substrates with an insulator layer interposed therebetween, wherein via holes provided at the same coordinates in each IVH substrate and the inner layer portions of which are closed with a resin. And a conductive resin penetrating through the insulator layer at the same coordinates and connecting between inner lands of each via hole. 4. The multilayer printed wiring board according to claim 3, wherein a conductive resin penetrates into a concave portion provided at an inner layer portion of each via hole to be connected. When the pilot hole diameter before plating of each via hole to be connected is φ1 and the outer diameter of the inner layer land of the via hole is φ2, the cross-sectional diameter φ of the conductive resin connected between the inner land is represented by the following formula:
φ1 ≦ φ ≦ {φ1 + (φ2-φ1) / 2}
The multilayer printed wiring board according to claim 3 or 4, wherein

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