Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
1998-06-22
2001-10-30
Budd, Mark O. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
Reexamination Certificate
active
06310420
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an electronic component, in particular an SAW component operating with surface acoustic waves with contacts suitable for SMD mounting. The component has electrically conductive structures on a piezoelectric substrate sealingly encapsulated against environmental influences by a cap cover. Through-plated holes are formed in the cover to connect the terminal pads of the electrically conductive structures to solderable metallized areas on the cover. The invention also pertains to a method of producing such an electronic component.
An earlier, commonly owned application No. 08/743,540 (see international published application WO 95/30276) describes an encapsulation for electronic components with a cap that seals component structures on a substrate. The cap is formed by a cover which is provided on the substrate and has cutouts accommodating the component structures in regions thereof. Such an encapsulation protects the component structures against environmental influences, with the result that electronic components encapsulated in such a way can be used directly in further applications, without the need for an additional housing.
U.S. Pat. No. 4,639,631 to Chason et al. describes am SMD type SAW component, in which the piezoelectric substrate is arranged by means of electrically conductive epoxy resin above a mounting plate. A cap is placed over the substrate and sealingly seated on the mounting plate. Electrical contact with the electrically active structures on the piezoelectric substrate is in this case made via the electrically conductive epoxy resin, a through-plated hole in the cap plate part and mounting plate part and metallized areas on the outside of the cap and mounting plate.
The three-piece configuration of the prior art component—mounting plate, piezoelectric substrate and cap—is quite complex. Furthermore, the component cannot be mass-produced at a reasonable cost.
With increasing miniaturization, there is an aim to produce components which occupy minimum casing volume and have a low physical height. Such requirements arise, for example, when electronic components are used in smartcards, such as telephone cards or credit cards. Components with encapsulation according to the above-noted commonly owned application No. 08/743,540 satisfy these requirements in an optimum manner.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide an electronic component—particularly a surface acoustic wave component—and a method of producing it, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which is suitable for SMD (surface mounted device) mounting and for economical mass production.
With the foregoing and other objects in view there is provided, in accordance with the invention, an electronic component, comprising:
a piezoelectric substrate, electrically conductive structures on the substrate and a cap cover sealingly encapsulating the substrate and the structures for protection against environmental influences;
the cap cover being seated directly on the piezoelectric substrate and having passages in the form of blind holes formed therein, the passages having bottom parts defined by pad metallizations applied directly on the substrate and electrically connected to the structures; and the cap cover carrying solderable metallizations and having through-plated holes formed therein electrically connecting the pad metallizations of the structures with the metallizations on the cap cover;
In accordance with an added feature of the invention, the electrically conductive structures are SAW structures such as electrode fingers of interdigital transducers, resonators and reflectors.
In accordance with another feature of the invention, the pad metallizations, the through-plated holes, and the metallized areas on the cap cover are made from one and the same material.
In accordance with an additional feature of the invention, the metallized areas on the cap cover are layers formed with a material layer sequence of TiW, Ni and Au. In a preferred embodiment, the layer of TiW has a thickness of <0.1 &mgr;m, a Ni layer has a thickness of about 1 &mgr;m, and an Au layer has a thickness of about 0.05 &mgr;m.
With the above and other objects in view there is also provided, in accordance with the invention, a method of producing an electronic component with contacts suitable for SMD assembly, the method which comprises:
providing a piezoelectric substrate, electrically conductive structures on the substrate and sealingly encapsulating the substrate and the structures with a cap cover for protection against environmental influences;
vapor-depositing a layer sequence of TiW, Cu or Ni and Au, and structuring the layer sequence by pulsed laser radiation, for forming solderable metallized areas on the cap cover; and non-electrically reinforcing the metallized areas with Cu.
In accordance with a further feature of the invention, the layer sequence is formed with an overall layer thickness of no more than 10 &mgr;m and, in particular, the layers have a thickness of substantially 0.1 &mgr;m per layer.
In accordance with again a further feature of the invention, a layer of gold is deposited with a thickness of substantially 0.05 &mgr;m on the layer sequence.
In accordance with again another feature of the invention, through-plated holes are formed together with the metallized areas. In a preferred mode of the invention, two through-plated holes are provided for each pad of tae electrically conductive structures.
With the above objects in view there is also provided a method of mass producing the above-noted electronic components. The method comprises:
providing a piezoelectric substrate wafer, forming a plurality of electrically conductive structures on the substrate wafer defining a plurality of component systems, and sealingly encapsulating individual component systems with a cap cover;
vapor-depositing a layer sequence of TiW, Cu or Ni and Au, and structuring the layer sequence by pulsed laser radiation, for forming solderable metallized areas on the cap covers, and currentlessly reinforcing the metallized areas with Cu; and
forming through-plated holes in the cap cover for electrically connecting the metallized areas on the cap covers with the electrically conductive structures on the substrate wafer and allocating each through-plated hole to two component systems.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an electronic component, in particular an SAW component operating with surface acoustic waves and a method for its production, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
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International Publication WO 95/30276 (Fübacher, B. et al.), dated Nov. 9. 1995.
Kruger Hans
Pahl Wolfgang
Stelzl Alois
Budd Mark O.
Greenberg Laurence A.
Lerner Herbert L.
Siemens Aktiengesellschaft
Stemer Werner H.
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