In the coming years, biomedical instrument manufacturers will have to inform the Notified Body of RoHS conformity assessment of the new medical instruments. In particular, in the case of lead-free solders, the Notified Body will require evidence that such solders are equally reliable as tin-lead, for the proposed use and lifetime of the product. So, biomedical instrument manufacturers are strongly interested in evaluating the performance of new soldering lead-free material used for the implementation of electronic parts. In order to support them and fill the technology knowledge gap, this paper presents a novel 128-channel phased-array probe for echocardiograph applications realized by new soldering technique where isotropic silver electrically conductive adhesive is used. In particular, the new soldering material is taken into consideration in the design phase of ultrasound array transducer, which is the core of a linear phased-array probe that is able to monitor the cardiac muscle. Being such material innovative in the application, a detailed study of the failure condition regarding the phased-array probe by means of accelerated qualification testing is proposed in order to assure its performances under stress and over time. A comparison of the electroacoustic measurement results with respect to the conventional probe, soldered with Sn-Pb, is also presented in this paper.