ultrasonic phased array sensor optimized for the welding of compliance control

An ultrasonic sensor comprising at least one upper part (2) connected to an electronic unit (E) providing an acquisition and data processing, and a lower part (1) comprising: - a plurality of elements sensitive (4) providing transmission and reception of ultrasound, - a deformable contact membrane (5) at a lower end of said lower portion, coming into contact with a solder to be tested, - a liquid (6) facilitating ultrasound transmission between said deformable contact membrane (5) and said sensing elements (4), characterized in that the upper portion of said sensor comprises a device responsive to the force applied (3, 7) on said portion at a measurement, and in that from a certain predetermined value of said force, the data acquisition is started.