Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
2001-04-06
2003-03-18
Paladini, Albert W. (Department: 2827)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S258000, C174S261000, C174S262000, C361S782000, C361S792000, C361S794000, C257S737000, C257S778000
Reexamination Certificate
active
06534723
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a multilayer printed-circuit board in which wiring can advantageously be done with an ultra-high density, a multilayer-printed-wiring board obtained by forming a build-up printed-wiring layer on the multilayer printed-circuit board, and a semiconductor device including semiconductor components mounted on the multilayer printed-circuit board or multilayer printed-wiring board.
The present invention relates more particularly to a multilayer printed-circuit board formed by stacking a plurality of singe-sided circuit boards one on the other, each having a plurality of filled via-hole formed therein, with an adhesive applied between them, and heating and pressing them together or by laminating a single-sided circuit board on either side of a double-sided circuit board as a core with an adhesive applied between the single-side circuit boards and double-sided circuit board, and heating and pressing the circuit boards together, a multilayer printed-wiring board obtained by forming a build-up wiring layer on at least one side of the multilayer printed-circuit board, and a semiconductor device using the multilayer printed-circuit board or multilayer printed-wiring board.
BACKGROUND ART
Along with the recent innovation of the electronic technology, the electronic devices have been designed to have a reduced physical size and operate at a higher speed, and thus the package circuit board on which IC chips are mounted has been required to have a correspondingly higher packaging density due to a finer pattern and operate with a correspondingly higher reliability.
Such a package circuit board is known from the disclosure in the monthly journal “Surface Mount Technology”, January issue, 1997. This conventional package circuit board has a build-up multilayer wiring layer formed on either side of a multilayer core circuit board.
In the above conventional package circuit board, however, a conductor layer in a multilayer core circuit board and build-up multilayer wiring layer are connected to each other by providing on the surface of the core multilayer circuit board an inner pad wired from through-holes and connecting via-holes to the inner pad. Thus, the land of each through-hole takes the form of a dumbbell or the like, the inner pad hinders through-holes from being disposed with an improved higher density, and only a limited number of through-holes can be formed. Hence, if the core circuit board is formed multilayered to increase the wiring density, it is not possible to assure a sufficient electrical connection between outer build-up wiring layers and conductor layers in the multilayer core circuit board.
The Inventors of the present invention proposed a method for overcoming the above-mentioned drawbacks of the prior art in the Japanese Patent Application No. 10-15346 (Unexarnined Patent Publication No. 214846/'99).
The multilayer printed-wiring board disclosed by the Inventors of the present invention in the above Unexamined Patent Publication No. 214846/'99 includes a build-up wiring layer formed by stacking interlinear insulative resin layers and conductor layers alternately one on the other on a multilayer core circuit board having an inner conductor layer and connecting the conductor layers to each other by via-holes, the core multilayer circuit board having formed therein through-holes each filled with a filler, a conductor layer being formed to cover an exposed surface of the filler from the through-holes, the via-holes being connected to the conductor layer, whereby the through-holes are disposed with an improved density and the conductor layer can positively be connected to the conductor circuit in the core multilayer circuit board via the through-holes disposed with the high density.
However, the through-hole in the multilayer printed-wiring board is formed by forming holes through a core multilayer circuit board using a drill or the like and by electroless-plating the wall surface and board surface of the drilled hole. Thus, when the precision and cost of forming the through-hole are taken in consideration, the lower limit of the opening diameter of such a through-hole is on the order of 300 &mgr;m. To realize the ultrahigh density of wiring demanded from the present electronic industries, there should desirably developed techniques capable of attaining a smaller opening diameter of the through-hole ranging from 50 to 250 &mgr;m and a smaller through-hole land pitch.
To meet the above demand, the Inventors of the present invention formed a core multilayer circuit board by preparing a plurality of circuit boards having a conductor circuit formed on one or either side of a core substrate made of a hard material and a plurality of filled via-hole formed through the core substrate to extend from the one side thereof to the conductor circuit, by stacking the plurality of circuit boards one on the other with an adhesive applied between them, and then heating and pressing of the circuit boards together. With this core multilayer circuit board, it was found that even with the no through-hole provided in the core multilayer circuit board, sufficient electrical connections can be made between the conductor circuits in the core multilayer circuit board, and conductor circuits in the core multilayer circuit board and build-up wiring layers formed on the core multilayer circuit board, by a plurality of filled via-hole formed in the core multilayer circuit board and those formed in the build-up wiring layer right above the core multilayer circuit board.
The multilayer printed-circuit board has various electronic components including a semiconductor chip such as LSI and the other mounted on the outermost surface thereof. The methods of mounting the electronic components include a pin mounting technology in which part holes into which terminals of the electronic component are to be introduced are formed in place on the conductor circuit formed on the outermost surface while connection lands whose diameter is slightly larger than that of the part hole are formed around the part holes, and a group of leads of the electronic component is connected, by soldering, to the part holes and connection lands, and a surface mounting technology in which a cream solder is applied to a land formed in place on the conductor circuit in advance, terminals of an electronic component are placed in contact with the cream solder and then the cream solder is made to reflow in an atmosphere maintained at the melting temperature of the solder to connect the electronic component.
When any of such mounting methods is employed to connect an electronic component, however, it is indispensable to form on the conductor circuit a land having an appropriate diameter. Nevertheless, in case an increased number of electronic components is to be mounted on the multilayer printed-circuit board because of the reduced physical sizes and higher functions of the recent electronic devices, the total area of such lands has to be too large to neglect, which stands in the way of attaining a higher packaging density.
Also, when soldering for connection of an electronic component, it is indispensable to previously apply a solder resist to the electronic component in order to prevent a melted solder from flowing to an unintended position where such flow is not desirable and causing a short-circuit, break or the like. Thus, the multilayer printed-circuit board has to be designed for an extra gap between wires with consideration given to a possible misregistration in the solder resist printing, which also stands in the way of attaining the higher packing density.
SUMMARY OF THE INVENTION
Accordingly, the present invention has an object to overcome the above-mentioned drawbacks of the prior art by providing a multilayer printed-circuit board and multilayer printed-wiring board in which wiring can be done with a high density and on which electronic components can be mounted with a high density, and a semiconductor device using the multilayer printed-circuit board and wiring board.
The Inven
Asai Motoo
Kariya Takashi
Greenblum & Bernstein P.L.C.
Ibiden Co. Ltd.
Paladini Albert W.
Patel I B
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