Radiant energy – Photocells; circuits and apparatus – Signal isolator
Reexamination Certificate
2000-08-07
2002-05-14
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Signal isolator
C250S239000
Reexamination Certificate
active
06388264
ABSTRACT:
FIELD OF THE INVENTION
This invention is related to optical isolators and optocouplers and compact ceramic packages for optocouplers.
BACKGROUND OF THE INVENTION
Optocouplers occupy an integral position in electronics by electrically isolating and separating non-common circuitry.
A common layout for optocoupler packages used on printed circuits and hybrid circuits is the side-by-side reflective construction. The light emitter and the light detector are on the same plane and covered with a transparent light piping material which is coated with a reflector to couple the light between the emitter and detector. The light piping or coupling materials are usually silicones or epoxies. Optocouplers having light piping or coupling materials are sensitive to thermal or mechanical shock, due to thermomechanical stress the light piping places on the light emitting and light detecting components and the wire bonds connected to them.
An alternate layout for optocoupler package is the over-under, direct coupling, where the light emitter is opposite the light detector. The side-by-side reflective coupler is more widely used than the over-under, direct coupled package because it has been easier to manufacture.
In plastic optocoupler packages, whether side-by-side or over-under, direct coupled optocouplers, the light emitting and light detecting devices are first mounted on lead frames and then encapsulated first in a light transparent light piping material and then an outer encapsulation of molded plastic.
Fully hermetically sealed optocoupler packages are formed by putting the light emitter and light detecting elements with the light piping in either a metal or dense ceramic package. Closure is a seal ring between the body and the cover utilizing either a low melting sealing glass or a metallic, solder or braze seal. Exclusion of moisture and other hostile gases is the object of these packages. Helium leakage rates should be less than 1×10
−8
cm
2
/s. MIL-STD-883B limits sealed-in moisture to 5,000 ppm of cavity volume. Hermetically sealed optocouplers are currently available only in standard packages sealed with a metal lid such as a T0-5 can, leaded-chip-carrier (LCC), flatpack, or duel-in-line-package (DIP). No smaller hermetically sealed packages are available.
SUMMARY OF THE INVENTION
This invention is an optical isolator comprising a photon emitter and a photon detector in the over-under direct coupling mode, i.e., opposing each other in a small, compact ceramic package. The top and bottom of the package are made from two ceramic, printed circuits which serve both as exterior walls and as functional parts of the optocoupler, making a completely self-contained package. The photon emitter and the photon detector of the optocoupler are mounted directly on the ceramic, printed circuits.
One embodiment of the invention is an optocoupler package comprising first and second inorganic, insulating substrates and an inorganic, ring frame joined to the first and second substrates forming a cell. The first substrate is a ceramic circuit having at least one photon emitter mounted on a conductive pattern of the substrate. The photon emitter is in direct over-under opposition to at least one photon detector mounted on a second, conductive pattern of a second inorganic, insulating substrate. An inorganic, ring frame surrounds the photon emitter and photon detector joining the first and second substrates together. The frame is bonded to the first and second substrates forming a hemetically sealed cell capable of containing an inert environment. The hermetically sealed cell is a completely self-contained optocoupler package.
In another embodiment the invention comprises multiple channel, photon couplers having multiple, photon emitters and photon detectors opposing each other in a small, compact package. The compact package contains multiple cells. Each cell contains at least one emitter opposing at least one detector. Each cell is optically isolated. The package is hermetically sealed, and capable of containing an inert environment. The package is capable of parallel transmission of multiple signals.
Further embodiments of the invention are simplified, low cost methods of manufacturing optocouplers wherein the package is the optocoupler.
The present invention provides a method of manufacturing hermetically sealed optocoupler packages using a minimum amount of material, labor and minimum number of manufacturing steps. In one embodiment the method comprises providing first and second, inorganic, insulating substrates, and forming conductive patterns on the substrates. A photon emitter is mounted on the conductive pattern of the first insulating substrate; and a photon detector is mounted on the conductive pattern of the second insulating substrate. The photon emitter and photon detector are surrounded by an inorganic frame, and the frame is hermetically sealed to the first and second substrates enclosing the photon emitter and photon detector spaced apart from and opposite each other. The first and second substrates and the frame form the exterior surfaces of the package.
The invention includes a method of manufacturing a hermetically sealed package containing a plurality of optocouplers comprising: printing a metallic, conductive pattern on a first, ceramic, insulating substrate; printing a metallic, conductive pattern on a second, ceramic, insulating substrate; mounting a plurality of photon emitters and photon detectors directly on the conductive patterns of the first and second substrates; hermetically sealing a ceramic frame having a plurality of cells between the first and second substrates so that a cell encloses at least one photon emitter opposite at least one photon detector.
Another embodiment of the invention is a method of manufacturing a hermetically sealed optocoupler package comprising: forming a metallic, conductive pattern on a first, planar, insulating, ceramic, substrate, the conductive pattern including conductors on the edge of the substrate; mounting a photon emitter directly on the conductive pattern of the first substrate; forming a metallic, conductive pattern on a second, planar, insulating, ceramic, substrate, the conductive pattern including conductors on the edge of the substrate; mounting a photon detector directly on the conductive pattern of the second substrate; providing a ceramic, ring frame having conductors on its outer edges; positioning the frame between the first and second substrates with the edge conductors of the frame, and first and second substrates aligned creating a cell containing a photon emitter opposite a photon detector; hermetically sealing the first and second substrates to the frame, and electrically connecting the edge conductors of the package.
Yet another embodiment of the invention is a method of manufacturing the optocoupler or optical isolator package comprising joining together three layers: the first and third layers having conductive patterns with at least one photon emitter and at least one photon detector. The second layer is a middle layer having at least one transparent window or opening surrounded by an opaque frame. The three layers are joined with emitters opposing detectors through the transparent windows of the second layer.
Objects of this invention are a hermetically sealed optocouplers having a shorter list of materials, lower packaging costs and simplified, unitary construction.
It is an object of this invention to provide an efficient method of manufacturing over-under, direct coupled, optocoupler packages.
Another object of this invention is to provide a very compact, optocoupler package.
An additional object of the invention is a robust, optical, coupler package that is resistant to thermal and mechanical shock.
Another object is an inorganic, optical, coupler package that is hermetically sealed and capable of operation at temperatures over 200° or 300° C., the operating temperature depending on the melting point of the sealing glass. These optocouplers are is thermally limited only by the temperature limitation
Le Que T.
McCormack John F
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