Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
2002-07-09
2004-07-27
Whitehead, Jr., Carl (Department: 2827)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S258000, C174S261000
Reexamination Certificate
active
06768064
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from prior Japanese Patent Application P2001-209595 filed on Jul. 10th, 2001, prior Japanese Patent Application P2002-188639 filed on Jun. 27th, 2002, prior Japanese Patent Application P2002-188660 filed on Jun. 27th, 2002, prior Japanese Patent Application P2002-188640 filed on Jun. 27th, 2002, prior Japanese Patent Application P2002-188664 filed on Jun. 27th, 2002; the entire contents of which are incorporated by reference herein.
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to a multilayer wiring board assembly composed of a plurality of printed circuit boards in a multilayered structure, a multilayer wiring board assembly component for use in laminating the same and the manufacturing method of the same. In particular, the present invention relates to a multilayer wiring board assembly, a multilayer wiring board assembly component for use in laminating the same and the manufacturing method of the same, wherein the multilayer wiring board assembly is flexible and implemented with a highly packing density by the Flip Chip Mounting technique and so forth.
2. Description of the Related Art
A flexible printed circuit board (which is simply referred to as an “FPC” in this description) is composed of a resin film having a small thickness for the purpose of maintaining the flexibility thereof. Because of this, in the case of such FPCs, it is essentially very difficult to assemble a plurality of FPCs in a multilayered structure (a multilayer wiring board assembly). However, along with the advent of the implementation of FPCs with a highly packing density, the need for multilayered structures of FPCs has increased in recent years, for example, in consideration of the arrangement of lead wirings as connected to flip chips mounted on FPCs. In this situation, a multilayer wiring board assembly has been manufactured by multilayering a plurality of FPCs with an intervening glass epoxy prepreg sheet and so forth between each adjacent boards while one or both surface of each FPC has been formed with a circuit pattern, forming holes through the entirety of all the layers by means of a drill and the like, and interlayer interconnecting the layers by the use of a through hall plating and the like.
However, in the case of such a conventional method of manufacturing multilayer wiring board assemblies by the use of is a through hall plating, it is impossible to form a via hole anew on another via hole and to mount a chip on a via hole, generally called as via-on-via since a hole remains in the center of a through hall even after plating. Because of this, when a multilayer wiring board assembly is implemented with a highly packing density, there are several impediments such that a lead can not be extended from the position just below the chip while interlayer interconnection tends to excessively occupy a substantial area.
On the other hand, for example, ALIVH (Any Layer Interstitial Via Hole: a registered trademark of Matsushita Electric Industrial Co., Ltd.) is a rigid multilayer wiring board assembly in which via-on-via is possible while a conductive paste is used for interlayer interconnection between each adjacent layers. An ALIVH board is formed by repeating the process sequence including opening a through hole in an uncured resin board, filling the through hole with a conductive paste, joining a copper foil to the uncured resin board, hardening the resin while compression bonding in order to form a multilayered structure and etching the copper foil in order to form a circuit pattern.
However, while via-on-via is possible in the case of the manufacturing method as described above to form ALIVH boards since the interlayer interconnection is made by means of a conductive paste, it is extremely difficult to manufacture FPCs in the form of a multilayer wiring board assembly by applying the manufacturing method to FPCs because it is necessary to open a hole through a resin film such as a polyimide film having a small thickness followed by filling up the hole with a conductive paste. This is because, when opening a hole in a resin film having a small thickness, the position and the size of the hole tend to change due to distortion of the resin film, the sucking force of a drill and the like so that the necessary accuracy of alignment is hardly achieved during the printing operation of the conductive paste and the positioning of the respective layers.
Also, while via-on-via is possible in the case of the manufacturing method making use of a conductive paste for the interlayer interconnection like ALIVH, it is difficult to make electric connection between a copper foil and a conductive paste without compromising the electric characteristics of the copper foil and the conductive paste so that the respective venders make use of proprietary methods respectively. Namely, generally speaking, when interlayer interconnection is made by via-on-via, a copper foil and a conductive paste are connected to each other by inserting the copper foil between adjacent conductive paste layers. In this case, the conductive paste is arranged to pierce the copper foil for the purpose of preserving electric connectivity between the copper foil and the conductive paste. For example, in the case of an ALIVH board, a conductive paste is printed in order to form a projection while the thickness of the board is reduced during thermocompression for bonding because of the use of an uncured resin board so that it becomes possible to make electric connection of a copper foil pierced by the projection of the conductive paste.
However, in the case of a board made of such a substance that the thickness of the board is not reduced during thermocompression for bonding, like a polyimide used for making a resin film in the case of FPCs, the projection of a conductive paste is less effective in piecing the copper foil. As a result, it is difficult to make electric connection between a copper foil and a conductive paste without compromising the electric characteristics.
Furthermore, in the case where a through hole is filled with a conductive paste, the conductive paste is printed in the condition that the surface of the conductive paste is slightly depressed since the conductive paste is pressed during printing. Because of this, there is a problem that, even if boards having through holes filled with a conductive paste are joined to each other, it is impossible to achieve sufficient electric connectivity between the fillers of the conductive paste.
Also, while the resin film having adhesivity is contracted or expanded during heating, the contraction or expansion can be cancelled out if there is a center line of symmetry in the cross section thereof. However, in the case of an adhesive layer having no center line of symmetry, there is observed curl in the cross section of the board during heating for lamination. Particularly, a polyimide film is a highly flexuous material and therefore tends to be significantly curled.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made in order to solve the shortcomings as described above. It is an object of the present invention to provide a multilayer wiring board assembly, a multilayer wiring board assembly component and a method of manufacture thereof in which it is possible to easily laminate together flexible FPCs having highly packing densities by via-on-via and chip-on-via.
It is another object of the present invention to provide a multilayer wiring board assembly which can be manufactured by joining multilayer wiring board assembly components to each other with a uniform pressure and therefore it is possible to fixedly laminate the multilayer wiring board assembly with a better electric connectivity.
It is a further object of the present invention to provide a multilayer wiring board assembly which is manufactured in order that the opening of a through hole near a copper foil is placed on a plane table having a hole of a diameter larger tha
Higuchi Reiji
Itou Shouji
Nakao Osamu
Dinh Tuan
Fujikura Ltd.
Jr. Carl Whitehead
LandOfFree
Multilayer wiring board assembly, multilayer wiring board... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Multilayer wiring board assembly, multilayer wiring board..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Multilayer wiring board assembly, multilayer wiring board... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3185979