New soldering technology for transducers: Characterization of a medical ultrasound phase array probe

In the next few years, in accordance with the RoHS European Directive [1] the research will focus the attention to develop knowledge about alternative no-dangerous materials, voted to reduce or eliminate Lead (Pb) in electronics devices and, in particular, in solder joints. As known, the Sn-Pb solder joint has over 50 years of manufacturing, field experience and knowledge; the Pb-free solutions, instead, aren´t near as mature or as well understood [2]-[5]. The paper presents some results, in terms of both joint performances and electrical properties of new electronic devices realised with Pb-free solder joints. The use of new soldering materials, such as silver conductive adhesive, is taken into consideration in the design of ultrasound array transducers. In particular the paper shows the use of conductive adhesive for the implementation of a medical phased array probe where the soldering material is located among a platelet of piezoelectric and fingers. A comparison between electro-acoustic measures on elements soldered with Electrically Conductive Adhesive [ECA] and those ones with the classic technology Sn-Pb will be also shown.