Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1999-07-28
2001-05-29
Arbes, Carl J. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S846000, C029S740000, C029S741000, C174S254000, C428S209000
Reexamination Certificate
active
06237218
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an apparatus and method for manufacturing multi-layered wiring boards, particularly relates to an apparatus and method for laminating plural base materials comprising wiring layers and insulating layers.
Further, the present invention relates to an apparatus and method for manufacturing a multi-layered wiring board, in particular, relates to an apparatus and method that perform inter-layer connection among plural wiring layers using conductive pillars.
Furthermore, the present invention relates to a multi-layered wiring board, in particular relates to a multi-layered wiring board which can be laminated accurately with high productivity.
BACKGROUND ART
As various kinds of electronic instrument become smaller in size and higher in performance, a demand for higher electronic component packaging density is increasing. As for wiring boards, multi-layered wiring boards in which insulating layers and wiring layers are stacked alternately are widely used reflecting the demand. The multi-layered wiring boards respond to the demand for higher density and higher performance due to the multi-layered wiring structure. In the multi-layered wiring boards, the connection among wiring pattern layers is performed through via-connection or the like.
FIG. 28
is a cross sectional view showing an example of a cross section structure of an existing ordinary multi-layered wiring board. In this figure, a multi-layered wiring board
901
, wiring circuits formed over five layers are connected by via-holes. Each of a first wiring circuit
901
, a second wiring circuit
902
, a third wiring circuit
903
, a fourth wiring circuit
904
and a fifth wiring circuit
905
is formed respectively by patterning a conductor layer. Each wiring circuit of the respective layers is insulated each other by an insulating layer
906
.
An existing ordinary method for manufacturing the multi-layered wiring boards as illustrated in
FIG. 28
will be described. First, in order to perform interlayer connection between a double-sided laminate board prepared by adhering conductor layers such as copper foils on both surfaces of an insulating layer, through-hole
907
will be formed at a portion where the double-sided laminate is electrically connected. An inner wall surface of the through-hole
907
is plated by chemical plating, further, plating by electrical plating is given to enhance reliability of the interlayer connection by thickening the conductor layer
907
b
of the inner wall surface of the through-hole.
Next, the conductor layers on both surfaces are patterned with prescribed circuits using, for example, photo-etching etching method or the like.
Then, the patterned conductor layers are laminated thereon by insulating layers such as, for example, prepreg cloth or the like, further by conductor layer such as copper foil. Thereafter, they are heated and pressed to integrate into one body. The processes from the formation of the through-hole to the patterning of the circuit are repeated to obtain multi-layered structure.
The multi-layered wiring boards in which interlayer connection between wiring layers is made by using via-hole, have a problem that the multi-layered wiring boards are difficult to cope with high density packaging.
For example, in an ordinary way, in a region where a through-hole is disposed, wiring cannot be formed, and an electronic component cannot be disposed. Accordingly, attaining higher wiring density and higher packaging density are restricted. Further, as the packaging density of the electronic component goes up, the wiring density of the wiring board becomes higher in recent years. If diameters of the through-holes are made small to meet with such finer wiring patterns, there occurs a problem that reliability of the interlayer connection becomes difficult to secure.
In addition, the formation of connection between wiring layers by a through-hole involves through-hole formation process, plating process or the like, accordingly the manufacturing processes are redundant and are unfavorable from the viewpoint of productivity.
For example, the through-hole formation process is carried out by boring the through-holes one by one with a drill or the like. Accordingly, it takes long time for boring operation. Further, after boring a through-hole, polishing step is necessary for removing burrs. In addition, the through-holes are required to be formed with high positioning accuracy, and compatibility with plating has to be considered for the inner wall surface of the through-hole. Therefore, the accuracy of through-hole formation and management of formation condition become troublesome.
In addition, the plating process for obtaining electrical connection among plural wiring layers by through-holes requires a sophisticated process control such as concentration and temperature control of chemicals, or the like. Further, both the through-hole forming process and the plating process require large scale apparatus.
Such interlayer connection of a multi-layered wiring board by through-holes lowers productivity of printed wiring boards (PWB), accordingly, it is difficult to meet with the demand for cost reduction or the like.
To simplify the electrical connection between wiring layers of a multi-layered wiring board, a method is proposed in which the connection between wiring layers are made by conductive bumps. In this method, conductive bumps are formed at via-lands placed on the wiring circuits and formed for interlayer connections. By putting the conductive bumps through an interlayer insulating layer in the thickness direction, connection between via-lands formed on the opposing wiring layer is established.
FIG.
29
A and
FIG. 29B
show an example of a method for manufacturing a multi-layered wiring board in which wiring layers are connected by conductive bumps described above.
First, a double-sided wiring board
913
in which wiring circuits
912
consisting of copper are formed on both surfaces of an insulating resin base material
911
consisting of, for example, paper-phenol system is prepared as an inner layer core. The wiring circuits
912
formed on both surfaces of the insulating resin base material
911
have via-lands
912
a
for interlayer connection. On these via-lands
912
a
, conductive bumps
914
formed by printing conductive paste, for example, are formed.
Next, an insulating resin sheet
915
of B stage (semi-cured state) and a copper foil
916
are laminated, and on both sides of the double-sided wiring board
913
, the wiring circuits
912
and copper foil
916
are disposed facing oppositely through the insulating resin sheet
915
(FIG.
29
A).
Thereafter, this laminate is pressed and heated. Thereby, the insulating resin sheets
915
of B stage are cured to form a board having all layers in one body. At this time, by pressing, the conductive bumps
914
is put through the insulating resin sheets
915
of B stage (semi-cured) and is connected with the copper foil
916
in a body while deforming plastically. Thus, connection between conductive layers by the conductive bump is formed.
Then, through-holes
917
are formed at prescribed positions, conductive material, for example, silver paste
918
is filled in this through-hole
917
, or the conductive material such as, for example, silver paste is coated on the inner wall of the through-holes
917
. Thereby, conductor layers on the external surfaces of the board are connected. The copper foils
916
of the external surfaces are patterned by, for example, a photo-etching method or the like to form prescribed wiring circuit
916
b
including via-lands
916
a
. Thereby, a multi-layered wiring board in which the conductive bumps and the through-holes are combined to form interlayer connection between the wiring circuits is formed (FIG.
29
B).
FIG.
30
A and
FIG. 30B
are diagrams showing another example of the method for manufacturing multi-layered wiring boards that are connected between the wiring layers by conductive bumps.
First, a double-sided wiring board
923
in which wiring circu
Fukuoka Yoshitaka
Ogawa Akira
Arbes Carl J.
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Kabushiki Kaisha Toshiba
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