This document contains the demonstration of a new masterless mould process for the fabrication of piezoelectric pillar structures suitable for use as an ultrasound micro-transducer active matrix.
The standard manufacturing route for the mass production of piezoelectric composites is the dice-and-fill method where a square pillar pattern or ‘bristle block’ is produced by dicing a sintered ceramic block. The spaces between the piezoelectric ceramic pillars are then filled with a polymer and the resulting structure is lapped to final thickness. This is known as a 1-3 composite structure, and is the active component in many ultrasound imaging systems. However, the dice-and-fill manufacturing process becomes commercially unviable for high frequency devices (above 15MHz) due to the high aspect ratios and the small dimensions of the features required, which either limit the properties of the composite or make it impossible to manufacture at all (above 25 MHz). An alternative route is to micro-mould colloidal suspensions of the appropriate ceramic powders to form the final or net shape in the green or unsintered state. Using this route high aspect ratio features and irregular patterns can be produced and then sintered. However, from a commercial point of view, this is not yet possible due to the high costs associated with the production of the moulds required.
The FaBiMed project aims for simple and cost effective production routes, which balance mass production methods and flexibility to accomplish the needs of the medical device industry. An approach with a considerable reduction in the number of stages from concept to final product is pursued, in particular avoiding the use of master moulds or sacrificial moulds, in order to lower the manufacturing costs of the parts.