Integrated circuit header assembly

Details Integrated circuit header assembly Integrated circuit header assembly

1997-12-05

2001-08-28

Chaudhuri, Olik (Department: 2814)

Active solid-state devices (e.g., transistors, solid-state diode

Housing or package

With contact or lead

C257S698000

Reexamination Certificate

active

06281572

ABSTRACT:

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
Not Applicable
REFERENCE TO MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE INVENTION
This invention relates to integrated circuit header assemblies and, more particularly, to an assembly comprising an integrated circuit (IC) die mounted to a header assembly and method for making the same. The integrated circuit header assembly used in electron bombarded charged coupled devices (EBCCDs) provides improved control of the spacing between the die and the cathode and accommodates combinations of materials having different coefficients of thermal expansion.
Integrated circuit devices are typically fabricated from semiconductor or silicon dies that are mounted in modules that can include supporting carriers or substrates and headers. In applications where the IC die is fragile or subject to further processing, the IC die can be mounted to a substrate or carrier to provide further support or facilitate further processing. Typically, the IC die carrier (or substrate) assemblies are subsequently mounted to a header which includes pins or other leads which allow the device to be electrically and mechanically connected to the system in which is used. The header can facilitate mounting the IC module to a circuit board, a mating socket or module housing or enclosure. Typically, fine gold wires are bonded to conductive pads on the die or the carrier and the header to establish electrical connections between the pins or leads of the header and the integrated circuit on the die.
In EBCCDs, the spacing between the IC die and the cathode determines the acceleration voltage required. In prior art devices, the header includes an integral pedestal that fixed the amount of reentrance (the distance between the IC die and the cathode) at the time of the header was fabricated. This required a different header for each different type of EBCCD tube. In addition, because the header is constructed from materials which match the thermal expansion coefficient of the side walls of EBCCD tube, it is not a good thermal expansion match for the silicon IC die. The stresses caused by the thermal expansion mismatch can cause the EBCCD die to warp or crack.
Accordingly, it is an object of this invention to provide an improved integrated circuit device.
It is another object of the invention to provide an improved header subassembly device for supporting an IC die.
It is yet another object of the invention to provide an improved integrated circuit device that is suitable for processing and use in higher temperature environments.
It is a further object of the invention to provide an improved circuit device comprising an integrated circuit die mounted to a header wherein thermal coefficients of expansion of the components are selected to reduce the stress associated with thermal expansion of different materials having different expansion coefficients.
It is a further object of the invention to provide an improved method of mounting an integrated circuit device to a header.
It is a further object of the invention to provide an improved method of mounting a electron bombarded charged coupled device to a header.
SUMMARY OF THE INVENTION
The present invention is directed to integrated circuit devices or modules such as those composed of integrated circuit dies and header subassemblies. As used herein, the term IC die assembly is intended to include IC dies that can be directly mounted to a header as well as IC dies that are mounted to carriers or substrates wherein the IC die carrier assembly is mounted to the header. In accordance with the invention, the integrated circuit device includes an IC die assembly which has conductive pads for establishing connections with the integrated circuit contained therein and a header to which the IC die assembly is mounted. The header also includes conductive pads connected to pins or leads to facilitate electrical connections with the IC. In order to effect electrical connections between the conductive pads on the IC die assembly and conductive pads on the header, one or more conducting elements can be used. In order to effect mechanical attachment of the IC die assembly to the header, a spacer is provided between the die and carrier. Where the IC die assembly is an EBCCD die carrier assembly, the height or thickness of the spacer can be used to control or vary the reentrance characteristic (distance between the EBCCD die and the cathode) of the EBCCD tube. The spacer can be constructed of a material that is has a coefficient of thermal expansion between the coefficient of thermal expansion of the IC die assembly and the header to provide operation over a broader range of temperatures. In addition, the width and length of the spacer are substantially smaller than that of the IC die assembly such that IC die is substantially pedestal mounted thereby minimizing the length of the contacting surfaces between the spacer and the IC die assembly and minimizing the risk of warping or cracking due to differences in thermal expansion. This allows EBCCD tubes and other IC devices with much larger IC dies and pixel arrays to be fabricated.
The process of fabricating the IC device can include the steps of: A) attaching the spacer to the header via a metal or glass reflow material; B) applying a layer of mounting material, preferably glass frit, to the first side of the spacer; C) fixturing the IC die assembly in position on the spacer and D) under controlled temperature conditions, applying pressure to the join the IC die assembly and the spacer on the header.
In step A, the spacer can be attached to the header by applying a layer of metal reflow material on mating surfaces of the spacer and the header and under controlled temperature conditions applying pressure to join the spacer to the header. Alternatively, a layer of glass reflow material can be applied to either the header or the spacer and under controlled temperature conditions, applying pressure to join the IC die assembly to the header.


REFERENCES:
patent: 4400870 (1983-08-01), Islam
patent: 5264726 (1993-11-01), Yamaguchi et al.
patent: 5315155 (1994-05-01), O'Donnelly et al.
patent: 5717245 (1998-02-01), Pedder
patent: 5753974 (1998-05-01), Masukawa

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