Polyimide damper for surface acoustic wave device

Claim 1

A surface acoustic wave (SAW) device comprising: piezoelectric means having end and side edges; an input transducer in contact with the piezoelectric means for launching acoustic surface waves along a propagation path on the piezoelectric means in response to input electrical signals; an output transducer in contact with the piezoelectric means across the propagation path from the input transducer and responsive to surface waves generated by the input transducer for generating output electrical signals corresponding to the received surface waves; and an acoustic energy absorbing polyimide area formed on the surface of the piezoelectric means between the input transducer and an edge of the piezoelectric means adjacent the input transducer, the acoustic energy absorbing polyimide area having a sound attenuation constant greater than 30 dB per centimeter at 300 megahertz and stable and without gaseous discharge at temperatures about 180 degrees Centigrade.

Claim 10

A method of forming an area of acoustic wave absorber material on a surface acoustic wave (SAW) device, comprising the steps of: (a) introducing a polyimide precursor having a sound attenuation constant greater than 30 dB per centimeter at 300 megahertz and stable and without gaseous discharge at temperatures above 180 degrees Centigrade to the surface of the device; (b) patterning the polyimide precursor to a desired shape using photolithography; and (c) curing the patterned polyimide precursor.

Claim 11

A method of forming an area of acoustic wave absorber material on a surface acoustic wave (SAW) device, comprising the steps of: (a) introducing a polyimide precursor having a sound attenuation constant greater than 30 dB per centimeter at 300 megahertz and stable and without gaseous discharge at temperatures above 180 degrees Centigrade to the surface of the device; (b) patterning the polyimide precursor to a desired shape using photolithography; and (c) curing the patterned polyimide precursor.

Claim 12

A method of simultaneously forming acoustic wave absorbers on a plurality of surface acoustic wave (SAW) devices in wafer form, the SAW devices being of the type wherein an input transducer is formed on the surface of piezoelectric means for launching acoustic surface waves along a propagation path on the piezoelectric means in response to input electrical signals and an output transducer is formed on the surface of the piezoelectric means across the propagation path from the input transducer and is responsive to surface waves generated by the input transducer for generating output signals corresponding to the received surface waves, the method comprising the sequential steps of: (a) spinning an adhesion promoter on a surface of the wafer common to the transducers of the SAW devices comprising the wafer; (b) flooding the wafer surface with a polyimide precursor; (c) spinning the polyimide precursor on the surface of the wafer; (d) baking the polyimide precursor at between about 93-97° C.; (e) cooling the wafer to room temperature; (f) spinning a positive photoresist on the surface of the wafer; (g) baking the photoresist at between about 78-82° C.; (h) exposing selected portions of the baked photoresist to define the polyimide acoustic wave absorbers; (i) dissolving away the photoresist and polyimide except for the polyimide acoustic wave absorbers; and (j) curing the polyimide acoustic wave absorbers.

Claim 13

A method of simultaneously forming acoustic wave absorbers on a plurality of surface acoustic wave (SAW) devices in wafer form, the SAW devices being of the type wherein an input transducer is formed on the surface of piezoelectric means for launching acoustic surface waves along a propagation path on the piezoelectric means in response to input electrical signals and an output transducer is formed on the surface of the piezoelectric means across the propagation path from the input transducer and is responsive to surface waves generated by the input transducer for generating output signals corresponding to the received surface waves, the method comprising the sequential steps of: (a) spinning an adhesion promoter on a surface of the wafer common to the transducers of the SAW devices comprising the wafer; (b) flooding the wafer surface with a polyimide precursor; (c) spinning the polyimide precursor on the surface of the wafer; (d) baking the polyimide precursor at between about 93-97° C.; (e) cooling the wafer to room temperature; (f) spinning a positive photoresist on the surface of the wafer; (g) baking the photoresist at between about 78-82° C.; (h) exposing selected portions of the baked photoresist to define the polyimide acoustic wave absorbers; (i) dissolving away the photoresist and polyimide except for the polyimide acoustic wave absorbers; and (j) curing the polyimide acoustic wave absorbers.