Methods and systems for multi-frequency transducer array fabrication

Abstract

An example of a method for a multi-frequency transducer array can include forming a first comb structure with a first sub-element having a first resonance frequency, forming a second comb structure, complementary in geometry to the first comb structure with a second sub-element having a second resonance frequency, combining the first and second comb structures to form an interdigitated structure, forming a third acoustic stack by coupling the interdigitated structure to a base package, and coupling the third acoustic stack to a matching layer block and a backing layer block to form a plurality of multi-frequency transducers.

1 . A method, comprising:
 forming a first comb structure with a first sub-element having a first resonance frequency;   forming a second comb structure, complementary in geometry to the first comb structure with a second sub-element having a second resonance frequency;   combining the first and second comb structures to form an interdigitated structure;   forming a third acoustic stack by coupling the interdigitated structure to a base package; and   coupling the third acoustic stack to a matching layer block and a backing layer block to form a plurality of multi-frequency transducers.   
     
     
         2 . The method of  claim 1 , further comprising forming the first comb structure from a first acoustic stack, the first acoustic stack having a first matching layer, the first sub-element, and a first backing layer and forming the second comb structure from a second acoustic stack, the second acoustic stack having a second matching layer, the second sub-element, and a second backing layer and wherein the first and second matching layers include one or more layers configured to be electrically conductive along a vertical axis of the first and second acoustic stacks. 
     
     
         3 . The method of  claim 2 , wherein forming the first comb structure includes dicing a first set of kerfs into the first acoustic stack to form a first set of fins, the first set of kerfs extending downwards from a top surface of the first acoustic stack and wherein forming the second comb structure includes dicing a second set of kerfs into the second acoustic stack to form a second set of fins, the second set of kerfs extending upwards from a bottom surface of the first acoustic stack. 
     
     
         4 . The method of  claim 3 , wherein forming the first and second comb structures further includes forming the first set of fins of the first comb structure with dimensions to allow the first set of fins to be inserted into the second set of kerfs of the second comb structure and forming the second set of fins of the second comb structure with dimensions to allow the second set of fins to be inserted into the first set of kerfs of the first comb structure. 
     
     
         5 . The method of  claim 3 , wherein dicing the first set of kerfs into the first acoustic stack and dicing the second set of kerfs into the second acoustic stack includes configuring the first and second sets of kerfs with a non-uniform dimension along at least one of an azimuth and an elevation direction. 
     
     
         6 . The method of  claim 3 , wherein forming the first and second acoustic stacks includes dicing the acoustic stacks so that at least one of the first set of kerfs and the second set of kerfs are non-uniformly spaced apart along at least one of an azimuth and an elevation direction. 
     
     
         7 . The method of  claim 1 , further comprising dicing the interdigitated structure prior to coupling the interdigitated structure to the base package and coupling the diced interdigitated structure to a third comb structure, and further comprising dicing the interdigitated structure a number times equal to a number of additional sub-elements to be incorporated into the interdigitated structure. 
     
     
         8 . The method of  claim 7 , wherein coupling the diced interdigitated structure to the third comb structure incorporates at least one additional sub-element with a different resonance frequency from either of the first and second sub-elements into the interdigitated structure. 
     
     
         9 . The method of  claim 7 , wherein dicing the interdigitated structure includes cutting kerfs into the interdigitated structure that are uniformly spaced apart. 
     
     
         10 . The method of  claim 9 , wherein the third comb structure also has uniformly spaced apart kerfs and a geometry complementary to a geometry of the diced interdigitated structure. 
     
     
         11 . The method of  claim 7 , wherein dicing the interdigitated structure includes cutting kerfs into the interdigitated structure that are non-uniformly spaced apart. 
     
     
         12 . The method of  claim 11 , wherein the third comb structure also has non-uniformly spaced apart kerfs and a geometry complementary to a geometry of the diced interdigitated structure. 
     
     
         13 . The method of  claim 1 , wherein the base package is formed from a conductive material including one selected from the group consisting of: graphite, porous graphite filled with resin, stainless steel, and aluminum. 
     
     
         14 . A method for fabricating a multi-frequency transducer, comprising:
 combining two or more comb structures into a single acoustic stack to incorporate two or more sub-elements with different resonance frequencies;   separating the single acoustic stack into transducer arrays, each of the transducer arrays including at least one transducer; and   varying a distribution of the two or more sub-elements along at least one of an azimuth and an elevation direction to have frequency apodization and frequency agility.   
     
     
         15 . The method of  claim 14 , wherein separating the single acoustic stack into transducer arrays includes singularizing the single acoustic stack to divide the single stack into the transducer arrays. 
     
     
         16 . The method of  claim 15 , wherein separating the single acoustic stack into transducer arrays includes forming transducer arrays with any of a linear, a curved linear, and a matrix-like arrangement. 
     
     
         17 . The method of  claim 14 , further comprising providing a common ground for the transducer arrays by coupling the acoustic stack to a base package electrically coupled to each of the transducers and wherein each of the transducers includes a piezoelectric element formed from the two or more sub-elements. 
     
     
         18 . The method of  claim 17 , further comprising forming an individual integrated circuit with each piezoelectric element. 
     
     
         19 . The method of  claim 14 , wherein varying the distribution of the two or more sub-elements includes incorporating at least one of the two or more sub-elements into each transducer. 
     
     
         20 . The method of  claim 19 , wherein varying the distribution of the two or more sub-elements includes varying relative proportions of the two or more sub-elements in each transducer.