Abstract High reliability requirements are imposed on the quality of the soldered joints. Typical defects in the soldered joints of heat exchangers are non-soldered. The minimum size of the non-penetration area that must be detected is about 1 square millimeter. The existing assessment of the quality of soldering is reduced to destructive tests. These tests include hydraulic and pneumatic tests. There are control technologies that use non-destructive methods. For example, the applicability of the ultrasonic echo method based on thermo-optical (laser) excitation of ultrasonic waves has been proven. However, continuous inspection of the liquid-propellant engine chamber using the traditional echo method is not rational, since the inspection speed is limited by the size of detected defects (1 square millimeter) and amounts to a few millimeters per minute. In order to increase the scanning speed without losing the ability to reliably detect defects such as “non-soldered”, it is proposed to use phased array antennas (PA) as a means of implementing the ultrasonic echo method. The paper considers the issues related to the interpretation of the information obtained when scanning the soldered joint, as well as issues related to modeling the acoustic field in the model of the soldered joint of the heat exchanger.