Raytheon Company

Thomas E Parker

James A Greer

Earl F Borchelt

Charles B Willingham

Clarence J Dunnrowicz

Gary K Montress

Frank H Spooner

Donald Andres

A pair of crystallographically matched piezoelectric substrates are sealed together to provide a package for a SAW device. A sealant material including a glass frit is deposited on a selected portion of a first one of the pair of substrates. The substrate having the sealant material is then heated to a temperature which is substantially below the glazing temperature of the sealant material to dry the sealant material. The substrate having the dried sealant material is heated a second time at a temperature just above the softening temperature of the glass frit to glaze the glass frit component with other components of the sealant material being driven from the glass frit during the heating cycles. The substrate having the glazed frit and the other remaining substrate are then mated together in a predetermined manner. While the substrates are held together by exerting a downward pressure on the two mated substrates, the mated substrates are heated in a vacuum to a temperature substantially above the softening temperature of the sealant material, but below the crystallographic transformation temperature of the material of the substrates. This last heating cycle is used to seal the mated pair of substrates and to provide the packaged SAW device.

Method for packaging a surface acoustic wave device

A SAW oscillator circuit including a housing having disposed therein a surface wave propagation supporting substrate with a pair of transducers coupled by surface waves propagating through the substrate and electronic circuitry connected to the pair of transducers and arranged to provide, with the connected resonator, the SAW oscillator circuit. A weight is attached to the resonator. The housing is susceptible of vibratory deflections which induce vibratory deflections in the substrate and the weight suppresses the vibratory deflections induced in the substrate of the resonator. With such arrangement, while sufficiently thick externally mounted stiffeners are not used because of space limitations, the effects of vibratory deflections induced in the substrate of the insufficiently thick, or un-stiffened housing are compensated by the weight attached to the resonator.

Saw device and method of manufacture

A low vibration sensitive SAW device includes a first quartz substrate having a pair of opposing surfaces, each surface which supports surface wave propagation. A pair of transducers are coupled to each of said surface wave propagation surfaces providing a pair of surface wave devices on opposing surfaces of the substrate. Each surface wave propagating surface is covered by a matching quartz cover and a glass-frit seal to provide a three piece all-quartz package. The pair of devices are connected together in parallel generally externally from the package, and when the dual device package undergoes vibration in a direction perpendicular to the surface wave propagation surfaces, one surface of the substrate will be subjected to a tensile strain field, whereas the opposite surface of the substrate will be subjected to identical but opposite direction strain field that is compressive. The pair of strain fields will induce equal but opposite shifts in resonant frequency of the device which will cancel each other out, providing a SAW device which is substantially invariant with vibration.

SAW device and method of manufacturing

A SAW oscillator package having low vibration sensitivity includes a stiffener layer disposed between a mounting surface for the oscillator and the oscillator circuit package. Preferably, the stiffening layer comprises a slab of a highly stiff material such as a ceramic and, in particular, aluminum oxide, as well as other material which preferably have suitable thermal expansion coefficients matched between the material of the package and the mounting surface. Moreover, the rigidly of the SAW device itself is also increased by either reducing the lateral dimensions of the SAW device or increasing the thickness of the SAW substrate and/or cover.

A surface acoustic wave device having interdigitated transducers comprised of an improved metalization system including copper and titanium doped aluminum transducers. A method of producing the interdigitated transducers includes deposition of the metals on a quartz substrate and subsequent heat treatment. The metalization system provides SAW devices having improved long-term frequency stability, particularly when operated at high power levels. The surface acoustic wave device may be incorporated in a feedback loop of an amplifier to form an oscillator circuit.

High power surface acoustic wave devices having copper and titanium

A surface acoustic wave (SAW) device is provided with short-term and long-term stability by recessing the electrode structure into the surface of the piezoelectric crystal of the device. In addition, the surface is passivated with the silicon polymer, and a cover of the same crystalline material is placed above the electrode structure to prevent absorption of impurities into the surface from the atmosphere. The passivation is believed to reduce the effect of thermal agitation of the bonds of the crystal lattice structure, and thereby prevent the making and breaking of chemical bonds with hydroxyl ions that may have been entrapped from the atmosphere. The SAW device is particularly useful in the construction of stable oscillator circuits wherein the passivation provides improved short-term frequency stability and the cover provides long-term frequency stability.

Stabilized surface wave device

A temperature compensated surface acoustic wave device having an SiO.sub.2 film layer upon a substrate of piezoelectric material. The positive temperature coefficient of delay of the piezoelectric substrate is counterbalanced by the negative temperature coefficient of the SiO.sub.2 layer. The thickness and shape of the SiO.sub.2 layer are chosen to give a zero first order temperature coefficient for the composite device. Lithium niobate and lithium tantalate are preferred piezoelectric materials for the substrate. A high degree of temperature stability is thereby obtained with coupling coefficients much greater than were previously obtained by prior temperature compensated surface acoustic wave devices.

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Framingham, MA, United States of America

Thomas E Parker