Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1998-02-17
2000-12-12
Mayes, Curtis
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
156252, 1562755, 427 96, 4271262, 427269, 428210, 428901, B32B 3100, B32B 1800, B05D 512, H05K 100
Patent
active
061593222
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a new photosensitive ceramic green sheet, a method for forming through holes in a ceramic green sheet, a method for forming a circuit wiring pattern on a ceramic green sheet, and a ceramic package. The photosensitive ceramic green sheet of the present invention can be suitably used for a fired ceramic substrate on which is to be mounted semiconductor devices at a high density, particularly a multi-layer fired ceramic board, and is effective for forming a fine circuit pattern of electrodes for the surface layer and inner layer of a board.
BACKGROUND ART
In recent years, such systems as computers and communication apparatuses are being downsized and destined to have improved properties, and in this connection, it is desired to improve the technique for forming via holes and through holes (hereinafter simply called through holes) in a ceramic board on which is to be mounted semiconductor devices.
Especially the ceramic green sheet used for CPU, etc. of computer is desired to be higher in accuracy and to be made of a material which allows through holes with a high aspect ratio to be formed.
Multi-layer ceramic boards are generally produced by either the thick film printing lamination method or the green sheet method. The green sheet method can be further classified into the lamination method and the printing method. In the green sheet printing method, a conductive paste and an insulating paste are printed on a green sheet repetitively alternately for lamination, to form a multi-layer board, and after repeated printing and drying, firing is effected only once for completion. The green sheet lamination method is almost similar to the green sheet printing method, but when a multi-layer board is made, each time a conductor is printed is followed by thermocompression bonding and firing. The green sheet lamination method has such disadvantages in that fine through holes cannot be formed at the same time and that many jigs and pieces of equipment must be used. Semiconductor packaging requires techniques for precisely processing ceramic boards, and in the present situation where through holes are formed by mechanical methods such as mold pressing and NC punching and where patterns are formed by screen printing, any new technique to meet the demand for higher precision patterning suitable for smaller circuit materials is required.
As methods to improve these problems, Japanese Patent Laid-Open (Kokai) Nos. 1-183456 and 6-202323 propose the formation of through holes by photolithography using a photosensitive ceramic green sheet. However, since the photosensitive ceramic green sheet is low in sensitivity and resolution, the method has a disadvantage in that through holes with a high aspect ratio, for example, 100 .mu.m or less through holes cannot be formed accurately or uniformly on a thick sheet with a thickness of more than 50 .mu.m.
Furthermore, as a method for forming a circuit wiring pattern on a substrate, screen printing using a paste consisting of a metallic powder and an organic binder has been often used. However, screen printing has a disadvantage in that a highly accurate pattern cannot be formed.
Japanese Patent Laid-Open (Kokai) Nos. 5-204151 and 5-342992 propose methods for forming a pattern by lithography using a photosensitive paste. However, since the photosensitive paste is low in sensitivity and resolution, high accuracy cannot be achieved, and for example, the limit of lines and spaces is 80/80 .mu.m. Japanese Patent Laid-Open (Kokai) No. 4-139733 describes a method for forming a pattern on a film using an ultraviolet light setting resin. In this method, a pasty mixture consisting of a conductive powder mainly composed of one or more high melting point metals selected from W and Mo and a binder mainly composed of an ultraviolet light setting resin is formed as a layer on a film substrate of a flexible resin, etc. using a doctor blade, etc., and the mixture layer is irradiated with ultraviolet light through a photo mask, to harden the binder, for
REFERENCES:
patent: 6004705 (1999-12-01), Masaki et al.
Database WPI Section CH, Week 9212 Derwent Publications Ltd., London, GB; Class A14, AN 92-091972 XP 002114340.
JP 04 034808 A (NGK Insulators LTD), Feb. 5, 1992 (Feb. 5, 1992) *Abstract*.
Patent Abstracts Of Japan vol. 015, No. 434 (E-1129), Nov. 6, 1991 (Nov. 6, 1991).
JP 03 180092 A (Hitachi LTD; Others: 01), Aug. 6, 1991 (Aug. 6, 1991) *Abstract*.
Iguchi Yuichiro
Iwanaga Keiji
Masaki Takaki
Ogata Tomohiko
Tanaka Tuyosi
Mayes Curtis
Toray Industries Inc.
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