High element count two dimensional transducer array

Preliminary work on a fully sampled (32/spl times/32 element) 2D array is presented. This forms a component of a planned system capable of C-Scans (and ultimately B-Scans) of shallow blood vessels as a guide for intravenous needle insertion. Amongst the challenges faced when fabricating such an array, the process by which to form 1024 electrical connections in a compact area is probably most burdensome. The approach used here employs a printed circuit board (PCB) with an eight layer substrate through which electrical signal connections to each element were routed. In an early prototype, in which only edge elements were electrically accessible, we have achieved a high yield (approximately 90%) of active elements without open or short circuits. In a later prototype, using a full scale PCB we achieved approximately 80%+ yield of working elements. A discussion of the design and fabrication challenges is presented. Finite element analysis (FEA) was used as part of the design and optimization. Strategies for future improvements to both the design and fabrication processes are presented.