Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
1999-12-03
2003-02-11
Abrams, Neil (Department: 2839)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C361S748000
Reexamination Certificate
active
06518513
ABSTRACT:
CROSS REFERENCES TO RELATED APPLICATIONS
This application is based upon priority International Application PCT/JP98/02498 filed Jun. 5, 1998, International Publication No. WO 98/56220 published Dec. 10, 1998, which is based upon Japanese Application 9/165291 filed Jun. 6, 1997.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a single-sided circuit board and a manufacturing method therefor, and more particularly to a single-sided circuit board used for manufacture of a multilayer printed circuit board having an interstitial via hole (IVH) structure and a manufacturing method therefor.
2. Description of the Related Art
A conventional multilayer printed circuit board is constituted by a laminate obtained by alternately laminating copper-clad laminates and prepregs. The laminate has a surface on which a surface wiring pattern has been formed. Moreover, an internal wiring pattern is formed between interlayer insulating layers. Through holes are, by punching formed in the direction of the thickness of the laminate to establish the electric connections among internal wiring patterns or among internal wiring patterns and the surface wiring patterns.
The multilayer printed circuit board having the above-mentioned through hole structure must have regions for forming the through holes. Therefore, the density at which elements are mounted cannot be easily raised. As a result, there arises a problem in that the multilayer printed circuit board having the through hole structure cannot easily address needs for considerable reductions in the sizes of the portable electronic apparatuses, realizing narrow pitch packages and practical use of MCM.
As an alternative to the foregoing multilayer printed circuit board having the through hole structure, a multilayer printed circuit board has recently received attention which is formed into a full-thickness interstitial via-hole (IVH) structure which is able to easily address raising of the density.
The multilayer printed circuit board having the full-thickness IVH structure is a printed circuit board having a structure in which via holes for electrically connecting conductive layers to one another are formed in each of the interlayer insulating layers which constitute the laminate. That is, the foregoing printed circuit board has the via holes (buried via holes or blind via holes) which do not penetrate the substrate on which the circuit is formed and which electrically connect the internal wiring patterns to one another or the internal wiring patterns and the surface wiring patterns to one another. Therefore, the multilayer printed circuit board having the IVH structure is free from a necessity of specially forming regions for forming the through holes. Therefore, arbitrary layers can freely be connected to one another through small via holes. As a result, size reduction, high density and high-speed propagation of signals can be easily realized.
The multilayer printed circuit board having the IVH structure is manufactured by a process arranged, for example, as shown in FIG.
6
.
Initially, a material having a structure in which an aramide nonwoven fabric cloth is impregnated with epoxy resin is employed as prepreg
112
. Then, an operation for forming holes in the prepreg
112
is performed by using carbon dioxide gas laser. Then, conductive paste
114
is enclosed in obtained hole portions
112
a (see FIG.
6
(A)).
Then, copper foil
116
is laminated on each of the two sides of the prepreg
112
, and then heat and pressure are applied to the prepreg
112
having the copper foil
116
by heat pressing. Hence it follows that the epoxy resin and the conductive paste of the prepreg
112
are hardened so that the electrical connection between the two copper foil members
116
on the two sides of the prepreg
112
is established (see FIG.
6
(B)).
Then, the copper foil
116
on each side is patterned by an etching method so that a hard and double-sided substrate having via holes is obtained (see FIG.
6
(C)).
Then, the obtained double-sided substrates are used as core layers to form a multilayer structure. Specifically, the prepreg and copper foil are sequentially laminated on the two sides of the foregoing core layer while the prepreg and the copper foil are being aligned. Then, heat pressing is again performed, and then the uppermost copper foil
116
is etched. Thus, a four-layer substrate is obtained (see FIGS.
6
(D) and
6
(E)). When a structure having a large number of layers is formed, the foregoing process is repeated. Thus, a six-layer substrate or an eight-layer substrate can be obtained.
The foregoing conventional technique, however, must repeat the laminating process using heat pressing and the process for patterning the copper foil by performing the etching operation. Therefore, the manufacturing process becomes too complicated and considerable time is required to complete the manufacturing operation.
If the multilayer printed circuit board having the IVH structure which can be obtained by the above-mentioned manufacturing method encounters only one defective portion (only one defective process) in the patterning operation during the manufacturing process, the overall circuit board, which is the final product, becomes a defective product. Hence it follows that the manufacturing yield deteriorates excessively.
To overcome the above-mentioned problems, an object of the present invention is to provide a high-density multilayer printed circuit board having the IVH structure which can be efficiently manufactured and which permits a satisfactory high manufacturing yield.
BRIEF SUMMARY OF THE INVENTION
To achieve the above-mentioned object, a single-sided circuit board in the present invention is structured as follows. A single-sided circuit board according to the present invention is characterized in that an insulating base member on either side of which a conductive circuit is formed, wherein said insulating base member has non-penetrating holes which reach said conductive circuit, via holes are formed by enclosing electrolytic plating in said non-penetrating holes, projecting conductors made of conductive paste or metal having a low melting point are formed on the surfaces of said via holes formed on the surface of said insulating base member opposite to the surface on which said conductive circuit has been formed.
In accordance with the more preferred teaching of the present invention, said non-penetrating holes are characterized by being completely filled with electrolytic plating.
In accordance with the more preferred teaching of the present invention, said non-penetrating holes are characterized by being filled with the electrolytic plating to an average depth of 50% or higher of the depth of said non-penetrating holes and lower than 100% of the same.
In accordance with the more preferred teaching of the present invention, said insulating base member is characterized as an organic insulating member.
In accordance with the more preferred teaching of the present invention, said electrolytic plating is characterized as copper electrolytic plating.
In accordance with the more preferred teaching of the present invention, said insulating member is characterized as a single-sided copper-clad laminate.
A method of manufacturing a single-sided circuit board according to the present invention is characterized by at least comprising the steps (1) to (4):
(1) forming non-penetrating holes which reach a metal layer by a laser process in a insulating base member having said metal layer formed on either side thereof;
(2) enclosing electrolytic plating into said non-penetrating holes formed in step (1) to form via holes;
(3) forming a conductive circuit by etching said metal layer; and
(4) forming projecting conductors made of conductive paste or metal having a low melting point on the surfaces of said via holes formed on the surface of said insulating base member to the surface on which said conductive circuit has been formed so that a single-sided circuit board is obtained.
A method of manufacturing a single-sided
Enomoto Ryo
Hiramatsu Yasuji
Abrams Neil
Ibiden Co. Ltd.
Tolpin Thomas W.
Webb Brian S.
Welsh & Katz Ltd.
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