Stock material or miscellaneous articles – Composite – Of metal
Patent
1998-01-09
1999-09-28
Jones, Deborah
Stock material or miscellaneous articles
Composite
Of metal
428209, 4284735, 428901, 174257, 174258, 174260, 174261, 528353, 430 14, 430 15, 430 16, 430 18, 430313, 430317, 430319, B32B 1508, H05K 109, G03C 300
Patent
active
059586001
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a circuit board and a method of manufacturing the circuit, and particularly to a structure of a thin film circuit formed on a wiring board made from a ceramic or the like and a method of manufacturing the structure.
BACKGROUND ART
With the recent trend toward higher integration and higher performance of ceramic wiring boards for mounting LSIs, it has been attempted to make finer geometries of wirings and to make narrower pitches of via-wirings. As a structure of a typical wiring circuit board of this type, there is known a structure in which a thin film circuit is laminated on a thick film circuit board. A technology to which the above structure pertains is disclosed, for example, in "Microelectronics Packaging Handbook (edited by Rao R. Tummala, Eugene J. Rymaszewski), p.14, published by Nikkei PB Co., Ltd. (March, 1991)".
The above-described prior art, however, has the following three disadvantages:
(1) Upon formation of a thin film circuit on a ceramic board containing wirings, it is necessary to connect conductors on the ceramic board side to the thin film circuit. The number of the connecting points therebetween becomes enormous for a large-sized board having high density wirings, and also, in the ceramic board, the above connecting points may be displaced with a variation at steps of printing wirings to green sheets, laminating the green sheets, and sintering the laminated green sheets. As a result, it is difficult to connect all of the connecting points between the conductors on the ceramic board side and the thin film circuit without any problem.
(2) If the above ceramic board contains defects such as short-circuit and/or disconnection of wirings, the defects must be corrected before connection of the conductors on the ceramic board side to the thin film circuit; however, it is not easy to correct the defects.
(3) In the case where a conducting material such as copper, chromium, or nickel is used in combination with an organic insulating material such as polyimide for forming a thin film circuit on a ceramic board, there occurs a problem that a film made from the organic insulating material such as polyimide may be cracked due to film stress of a film made from the conducting material.
The present inventors have undertaken studies to solve all of the above problems (1) to (3) and to realize a circuit board with a high density and a high reliability and a method of manufacturing the circuit board, and accomplished the present invention.
DISCLOSURE OF INVENTION
(1) The present invention solves the first problem regarding connection between conductors on a ceramic board side and a thin film circuit in accordance with the following method:
A ceramic board is manufactured in such a manner that a first conductor exposed from a front surface of the ceramic board has an area being as wide as possible insofar as the first conductor is not brought in contact with any conductor therearound. To ensure the broadest area of the first conductor, it is advantageous that a pattern of the first conductor may be formed into an approximately square shape.
A film made from an insulating material such as polyimide is then formed in such a manner as to have via-holes. Since the via-holes are formed by photolithography, it is possible to ensure a high dimensional accuracy of the via-holes. The first conductor exposed from the front surface of the ceramic board is electrically connected to the thin film circuit through the via-holes. In this way, the first conductor pattern on the ceramic board side is wide in area while the size of the via-hole can be made as small as possible depending on a processing limitation of photolithography. Consequently, each of displacement of the first conductor pattern of the ceramic board and a variation in displacement thereof is allowable to such an extent as to nearly correspond to the area of the first conductor pattern. A conductor material is then deposited over the entire surface by sputtering or vapor-deposition, followed by pat
REFERENCES:
patent: 5536584 (1996-07-01), Sotokawa et al.
patent: 5851681 (1998-12-01), Matsuyama et al.
patent: 5868949 (1999-02-01), Sotokawa et al.
Inoue Takashi
Matsuyama Haruhiko
Narizuka Yasunori
Ogihara Mamoru
Shigi Hidetaka
Hitachi , Ltd.
Jones Deborah
Lam Cathy
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