Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Including contaminant removal or mitigation
Reexamination Certificate
1997-01-02
2002-07-02
Graybill, David E. (Department: 2827)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Including contaminant removal or mitigation
C438S121000, C438S125000
Reexamination Certificate
active
06413800
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to the manufacture of integrated circuits (IC's), hybrid systems, and more specifically, to the packaging thereof.
BACKGROUND OF THE INVENTION
A common practice in the packaging of IC's (integrated circuits) is to mount the IC die (chip) onto a header which electrically connects the pads of the chip to complete the electrical connection to the socket pins. This assembly is then encapsulated in a plastic potting compound such as epoxy. In some cases, epoxies are used to adhere the lid to the base of an IC body. However, moderately high temperatures may cause this epoxy to release gaseous products which may damage the IC. Moisture coupled with internal IC materials has been a cause of catastrophic failure in some IC and hybrid systems. In the industry, an epoxy seal is generally considered not to be hermetic, since epoxies may gradually leak gaseous products from the surrounding atmosphere into the IC.
An alternative to plastic packaging is hermetic packaging. Some IC's and hybrid systems do not permit plastic encapsulation because of the application environment; for example, military standards for hermetic packages typically dictate that the seal material be metal. One type of hermetic seal in the prior art comprises an alumina ceramic base with printed wiring connections to electrically connect the package pins to the pad connections of the IC chip. The chip is surrounded by a suitable metal ring body, such as “Kovar”, which is hermetically sealed to the ceramic base. A lid is then hermetically sealed to this metal body. The hermetic sealing operation requires high temperatures to seal the lid to the body while at the same time providing an internal inert gaseous atmosphere. Another type of package is ceramic with plated metal seal (e.g. W, Ni and Au) surfaces on the upper edge of the base and on the lower edge of the lid. Solders (e.g. SnPb, SnAu) are typically used to solder seal the lid to the base.
SUMMARY OF THE INVENTION
The present invention is a hermetically sealed system, comprising a base, a metal sealing member mounted on the top edge of the base, an organic sealant mounted on the top edge of the base adjacent the metal sealing member, a lid mounted on the metal sealing member and the organic sealant and a hermetically sealed cavity contained within the lid, metal sealing member and base.
The present invention also involves a method for hermetically sealing a device, comprising the steps of providing a base, applying a metal seal member along the top edge of the base, applying an organic sealant adjacent the metal seal member, covering the metal seal member and the organic sealant with a lid to create a cavity between the base, the lid and the metal seal member, compressing the metal seal member between the lid and the base to provide a hermetic seal within the cavity, and curing the organic sealant, wherein the seal is formed at room temperature.
Advantages of the present invention include providing a hermetically sealed package at economical material, labor and tool costs without the need for high sealing temperatures. The shrinkage of the organic sealant
26
during curing applies pressure to the metal seal member
28
, enhancing the effectiveness of the hermetic seal.
REFERENCES:
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patent: 4382327 (1983-05-01), Bardens et al.
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patent: 5041695 (1991-08-01), Olenick et al.
patent: 5293511 (1994-03-01), Poradish et al.
Hanson, et al “Uncooled Thermal Imaging”, Texas Instruments Technical Journal, vol. 11, No. 5. Sep.-Oct. 1994 p.2-10.
Neal, et al “Texas Instruments Uncooled Infrared Systems”; Texas Instruments Technical Journal, vol. 11, No. 5. Sep.-Oct. 1994 p. 11-18.
Witter, et al “Pyroelectric Materials for Uncooled IR Detectors”;Texas Instruments Technical Journal, vol. 11, No. 5. Sep.-Oct. 1994 p.19-26.
Belcher, et al “Uncooled Infrared Detector Processing”; Texas Instruments Technical Journal, vol. 11, No. 5. Sep.-Oct 1994 p.27-36.
“Technique for Obtaining an Environmentally Secure Adhesive Seal”, 700 IBM Technical Disclosure Bulletin 29 (1986) Dec., No. 7, New York, USA, pp. 3085-3087.
Brady III W. James
Garner Jacqueline J.
Graybill David E.
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
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