Electricity: conductors and insulators – Anti-inductive structures – Conductor transposition
Reexamination Certificate
2003-11-07
2004-11-23
Ngo, Hung V. (Department: 2831)
Electricity: conductors and insulators
Anti-inductive structures
Conductor transposition
C257S698000, C257S728000, C257S704000
Reexamination Certificate
active
06822162
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
REFERENCE TO MICROFICHE APPENDIX
Not applicable.
FIELD OF THE INVENTION
The present invention relates generally to packaging for high-frequency microcircuits, and more particularly to gaskets providing an environmental and electromagnetic seal in a microcircuit package.
BACKGROUND OF THE INVENTION
FIG. 1A
shows a perspective view of a base
12
of a prior art microcircuit package used for housing microwave and millimeter-wave circuits, which will be referred to as “high-frequency microcircuits” for purposes of discussion. The base
12
is machined from a block of metal, such as aluminum alloy. Cavities
14
and channels
16
are machined into the base
12
to accept and interconnect various types of electronic components, such as thickfilm or thinfilm substrates, monolithic microwave integrated circuits (“MMICs”), and beam-lead devices (not shown). This type of microcircuit package is often referred to as a “canyon-style” package. Electrical components are typically secured to the floor of the base with epoxy and interconnected using wire-bond, mesh-bond, and ribbon-bond techniques.
Electrical signals are brought into the high-frequency microcircuit through feedthroughs
18
,
20
mounted on a bottom
22
or side
24
of the base. High-frequency feedthroughs, such as the feedthrough
20
on the side
24
of the base
12
, typically have a coaxial structure, with a center conductor lying along the central axis of the feed-through. The center conductor of the high-frequency feed-through is electrically coupled to the center conductor of a planar microcircuit or other electronic component in a coaxial-to-planar connection. The outer conductor of the high-frequency feedthrough is electrically coupled to the package housing, which serves as electrical ground.
At millimeter-wave frequencies, broadband coaxial-to-planar transitions perform best if the coaxial connector axis lies in the same plane as the planar microcircuit to avoid impedance mismatch and electromagnetic leakage. This is commonly known as an in-line launch. The base
12
is sufficiently thick to allow integrating coaxial high-frequency feedthroughs for in-line launch configurations. The base
12
has a planar surface
26
to accommodate a flat gasket (see
FIG. 1B
, ref. no.
28
) that is placed on the base
12
to seal the perimeter of the base when a lid is attached.
FIG. 1B
shows a cross section of a portion of a prior art microcircuit package
10
. A flat gasket
28
is held between a planar lid
30
and the base
12
. The flat gasket is typically made of a compliant material, such as silicon rubber loaded with carbon powder, that provides a degree of electromagnetic shielding to the electronic components within the microcircuit package, as well as an environmental seal. Screws (not shown) compress the flat gasket
28
between the planar lid
30
and the base
12
when the screws are tightened.
Unfortunately, it is difficult to assemble high-frequency microcircuits inside the channels and cavities of a canyon-style package.
BRIEF SUMMARY OF THE INVENTION
A base of a microcircuit housing (package) has a flat base portion transitioning into a sidewall connector feature. The lid of the microcircuit housing has a corresponding flat lid portion transitioning into a sloped lid portion. A contiguous gasket is compressed against the lid between both the flat portion of the base and the sidewall connector feature when the microcircuit housing is assembled. The gasket is formed from a conductive elastomer, such as by stamping, injection molding, or die cutting. Stops are optionally included on the base and/or lid to limit the proximity of the base to the lid to avoid overcompression of the gasket. The gasket provides an electromagnetic and environmental seal between the base and the lid. In a further embodiment, a high-frequency feedthrough extends through the sloped base portion and is coupled to an electronic component mounted on the flat base portion. In a particular embodiment, a face of the sidewall connector feature slopes at an angle between 30 degrees and 60 degrees, relative to a perpendicular of the flat base portion to avoid undesired distortion or damage to the gasket.
REFERENCES:
patent: 4167647 (1979-09-01), Salera
patent: 4590617 (1986-05-01), Kraemer
patent: 6028497 (2000-02-01), Allen et al.
patent: 6498551 (2002-12-01), Ammar et al.
patent: 6653916 (2003-11-01), Ammar et al.
patent: 10107475 (1998-04-01), None
Blume Anthony R.
Neumann Michael J.
Robertson Adam E.
Valentine Roger L.
Agilent Technologie,s Inc.
Ngo Hung V.
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