Frontend and transducer technology for next generation cardiovascular ultrasound probes

The purpose of this project is unchanged and is still to save human lives by improving the ultrasound image quality used for heart disease diagnosis and interventional guidance. This shall be obtained by integration of new transducer technology into existing ultrasound imaging platforms. The successful implementation of the CFRON project will improve image quality for patients with cardiovascular disease. Furthermore, it will provide the project partners with cutting-edge technology and knowledge to maintain an international leading position in cardiovascular ultrasound. WP1: During the period, we have assembled and tested two prototypes of combined PZT-PVDF transducers. Electrical and mechanical measurements on these transducers show promising results, although we have identified challenges concerning the electrical impedance levels of PVDF. The PZT-PVDF transducers are now assembled into complete probes that can be integrated with the electronics developed in WP3 for testing in an ultrasound scanner. We have submitted one manuscript to a scientific journal, this manuscript describes fabrication of a dual frequency hybrid PZT-CMUT transducer. WP2: The assembly process of an ultra-thin MEMS-based 2D CMUT array to a driver electronics CMOS ASIC using anisotropic conductive film (ACF) has been successfully developed. The process demonstrated proper approach for handling and bonding of dummy CMUT sensor dies with extreme thicknesses of 50 µm, 35 µm and 20 µm and ASIC chips mimicking relevant devices. ACF bonding parameters providing satisfactory electrical connections and yield has been successfully established for CMUT sensor dies with different thicknesses down to 20 µm. Stray capacitance of individual ACF interconnects was identified, which is a crucial input for designing electronics. The following works include investigation of CMUT-ASIC assembly by means of soldering technologies, and thus compare the two assembly technologies (ACF and soldering). A new bonding technology, Cu-(Sn-Bi) solid-liquid interdiffusion (SLID), that provides low process temperatures (< 200 °C) has been studied. The technology has potential to enable assembly of CMUT-ASIC at wafer level with low stress induced as well as assembly temperature-sensitive materials, such as conventional PZT-based ultrasound transducers. A proper understanding of the Cu-(Sn-Bi) SLID has been established, providing a baseline for selection of parameters corresponding to desired bonds. Continuing work on characterization of mechanical, electrical and robustness of Cu-(Sn-Bi) SLID bonds are on-going. WP3: During the period, we have produced and tested two circuit boards. Additionally, a complete cable HLA has been finalized. This assembly is ready for integration with the ultrasound system, both on the console side and for assembly with the newly developed transducer stack. Tests indicate that both mechanical and electrical requirements are met. The main objective of the work package has been achieved, as we have created a functional and complete cable HLA. WP4: THe main purpose of this workpackage is to perform a console integration of the prototype probe developed in WP1-WP3. Imaging will bve done and a side-by-side comparison with an existing product will be done to asess a potential lift in image quality. This workpackage has just started, but will gain significant momentum in Q4/24 and 2025.

The vision for this project is to save human lives by improving the ultrasound image quality used for heart disease diagnosis and interventional guidance. Such improvements are obtained by integration of new transducer technology with existing ultrasound imaging platforms. In brief, the main approaches of the project will i) bridge a conventional ultrasound transducer based on piezoelectric material (e.g. SC) with a new technique for transducer production, known as Piezoelectric Polyvinylidene Fluoride (PVDF), into a hybrid solution; and ii) integrate pure PVDF directly to specially designed ASIC. This will improve bandwidth and sensitivity of the transducers. The image quality will therefore be increased , increasing diagnostic confidence. The high integration level in 3D ultrasound medical probes makes it necessary to develop the in-probe necessary electronics to transmit and receive ultrasound pulses suitable for cardiac imaging. To enhance real time imaging, compact and reliable integration of the acoustic and electronic elements is crucial. For high quality imaging and cost-effective production processes, the ultrasound array is traditionally made with conventional single crystal (SC) material. The new technique for transducer production known as PVDF is highly cost effective. Direct connections between the acoustic elements and the ASICs with low signal parasitic capacitance are required using the new PVDF technology. This means 3D stacking of ASICs and transducers. Therefore, assembly technology for electro acoustic modules (EAM) in which the PVDF array is attached directly to the active electronics for transmit and receive contained in an ASIC is an innovative approach that will be studied in this project.