Embedded Dielectric As A Barrier In An Acoustic Device And Method Of Manufacture

Abstract

A base assembly for an acoustic transducer includes a first substrate with an acoustic port and a dielectric layer having a substantially uniform initial density. One surface of the dielectric layer contacts the first substrate. An opposite surface of the dielectric layer contacts a second substrate having an acoustic port. The respective acoustic ports of the first and second substrates are aligned with each other. The first substrate, the dielectric layer, and the second substrate are laminated together. A substantial portion of the dielectric layer laminated to the first and second substrates has a higher final density due to compaction than does a portion of the dielectric layer disposed in the respective acoustic ports of the first and second substrates.

What is claimed is: 
     
         1 . A base assembly for an acoustic transducer, the base comprising:
 a first substrate with an acoustic port;   a dielectric layer having a substantially uniform initial density, wherein one surface of the dielectric layer contacts the first substrate; and   a second substrate with an acoustic port, wherein an opposite surface of the dielectric layer contacts the second substrate;   wherein the respective acoustic ports of the first and second substrates are aligned with each other, and   the first substrate, the dielectric layer, and the second substrate are laminated together, wherein a substantial portion of the dielectric layer laminated to the first and second substrates has a higher final density due to compaction than does a portion of the dielectric layer disposed in the respective acoustic ports of the first and second substrates.   
     
     
         2 . The base assembly of  claim 1 , wherein the dielectric layer is an expanded polymeric membrane. 
     
     
         3 . The base assembly of  claim 2 , wherein the density of the expanded polymeric membrane has an air volume of at least 70 percent. 
     
     
         4 . The base assembly of  claim 2 , wherein the expanded polymeric membrane is a polytetrafluoroethylene (ePTFE) membrane. 
     
     
         5 . The base assembly of  claim 2 , wherein the expanded polymeric membrane is a fluoropolymer-based membrane. 
     
     
         6 . The base assembly of  claim 1 ,
 wherein the first substrate further comprises a metal layer in contact with one surface of the compacted portion of the dielectric layer;   wherein the second substrate further comprises a metal layer in contact with an opposite surface of the compacted portion of the dielectric layer; and   wherein the compacted portion of the dielectric layer has a dielectric constant sufficient for the compacted portion of the dielectric layer and the contacting metal layers to operate as a capacitor.   
     
     
         7 . The base assembly of  claim 6 , wherein the first and second substrates each comprise additional metal layers and vias to allow electrical access to the capacitor embedded between the first and second substrates. 
     
     
         8 . The base assembly of  claim 1 , wherein a substantial portion of the non-compacted dielectric layer disposed in the respective acoustic ports of the first and second substrates is acoustically transparent. 
     
     
         9 . The base assembly of  claim 1 , wherein the diameter of the acoustic ports in the first and second substrates is at least 1.0 mm. 
     
     
         10 . The base assembly of  claim 1 , wherein the non-compacted dielectric layer disposed in the respective acoustic ports of the first and second substrates limits contaminants from passing through the acoustic ports. 
     
     
         11 . The base assembly of  claim 1 , wherein the first and second substrates comprise glass reinforced laminate material.