Vacuum encapsulation for surface acoustic wave (SAW) devices
First Claim
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1. A vacuum encapsulated surface acoustic wave (SAW) structure, comprising:
- a SAW device including a substrate of desired material having a major surface on which electro-acoustic transducers and associated electrical conductors are disposed along an acoustic wave propagation path on said substrate, said transducers and propagation path defining an active signal region on said major surface, said electrical conductors providing electrical connections for external signals presented to and received from the active signal region; and
a cover, formed of material having substantially the same thermal characteristics and the same crystallographic orientation as the material comprising said substrate, said cover being bonded through a vacuum tight seal to said major surface of said substrate to enclose said active signal region in a vacuum environment.
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Abstract
A surface acoustic wave (SAW) device having a substrate of desired material is vacuum encapsulated in a structure fabricated from the same material as that comprising the substrate.
47 Citations
17 Claims
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1. A vacuum encapsulated surface acoustic wave (SAW) structure, comprising:
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a SAW device including a substrate of desired material having a major surface on which electro-acoustic transducers and associated electrical conductors are disposed along an acoustic wave propagation path on said substrate, said transducers and propagation path defining an active signal region on said major surface, said electrical conductors providing electrical connections for external signals presented to and received from the active signal region; and a cover, formed of material having substantially the same thermal characteristics and the same crystallographic orientation as the material comprising said substrate, said cover being bonded through a vacuum tight seal to said major surface of said substrate to enclose said active signal region in a vacuum environment. - View Dependent Claims (2, 3, 4, 5)
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6. A vacuum encapsulated surface acoustic wave (SAW) structure comprising:
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a SAW device including a substrate of desired material having a major surface on which electro-acoustic transducers and associated electrical conductors are disposed along an acoustic wave propagation path on said substrate, said transducers and propagation path defining the surface area of an active signal region on said major surface, said electrical conductors providing electrical connections for external signals presented to and received from the active signal region; and a cover, including a spacer assembly portion and a cap assembly portion each formed of material having substantially the same thermal characteristics and crystallographic orientation as the material comprising said substrate material, said spacer portion having a central aperture extending between an upper surface and a bottom surface thereof, said aperture having a minimum cross section area equal to the surface area of said active signal region, said spacer portion being positioned on said major surface to enclose said active signal region within said central aperture, and being bonded along its bottom surface to said major surface with a vacuum tight glass seal, said cap portion being bonded in position to said upper surface of said spacer with a vacuum tight metal seal to enclose said active signal region in a vacuum environment within said central aperture. - View Dependent Claims (7, 8, 9)
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10. In the vacuum encapsulation of a surface acoustic wave (SAW) device having a substrate of desired material, the method of minimizing strain produced in the substrate material by thermal expansion and contraction of a vacuum encapsulating structure, comprising the steps of:
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forming the vacuum encapsulating structure from material having substantially the same thermal characteristics and substantially the same crystallographic orientation as that of the substrate material; positioning the encapsulating structure on the substrate to provide alignment of the crystallographic axes of each; and bonding the encapsulating structure to the substrate in a vacuum environment. - View Dependent Claims (11)
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12. The method of vacuum encapsulating a SAW device of the type which includes a substrate material having a major surface on which electro-acoustic transducers are disposed within an active signal region thereof, and which further includes electrical conductors disposed on said major surface to provide electrical connections for external signals presented to and received from the transducers within the active signal region, comprising the steps of:
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forming a cover assembly which includes a spacer portion and a cap portion each fabricated with material having substantially the same thermal characteristics and substantially the same crystallographic orientation as that material comprising the substrate, the spacer being shaped to provide a central aperture extending between an upper surface and a bottom surface thereof and having a minimum cross sectional area equal to that of the active signal region; orientating the spacer portion over the active signal region on the major surface, and aligning the crystallographic axes of the spacer material with that of the substrate material; bonding the bottom surface of the spacer portion to the major surface with a vacuum tight glass seal; and sealing the cap portion to the upper surface of the spacer with a metal seal in a vacuum environment following alignment of the crystallographic axes of the cap with that of the spacer and substrate. - View Dependent Claims (13, 14, 15, 16, 17)
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Specification