Abstract: The invention relates to a method for checking an assembly comprising first (W1) and second (W2) joined substrates, comprising the following steps: a) transmitting an ultrasonic excitation signal towards the assembly by means of an ultrasonic transducer (301) located on the front face (A1) side of the first substrate (W1); b) measuring, using the transducer (301), an ultrasonic feedback signal including at least one echo (EF) of the excitation signal on the rear face (B2) of the second substrate (W2); c) calculating, using a processing circuit (303), a spectral signal representative of the change in frequency of an overall reflection coefficient of the assembly, defined as the ratio between the feedback signal measured in step b) and the excitation signal; and d) deriving, from said spectral signal, information relating to the quality of the bond between the first (W1) and second (W2) substrates.

Abstract: The invention relates to a method for checking an assembly comprising first (W1) and second (W2) joined substrates, comprising the following steps: a) transmitting an ultrasonic excitation signal towards the assembly by means of an ultrasonic transducer (301) located on the front face (A1) side of the first substrate (W1); b) measuring, using the transducer (301), an ultrasonic feedback signal including at least one echo (EF) of the excitation signal on the rear face (B2) of the second substrate (W2); c) calculating, using a processing circuit (303), a spectral signal representative of the change in frequency of an overall reflection coefficient of the assembly, defined as the ratio between the feedback signal measured in step b) and the excitation signal; and d) deriving, from said spectral signal, information relating to the quality of the bond between the first (W1) and second (W2) substrates.

Abstract: A device measures the propagation time for an acoustic wave in a continuous phase of a two-phase mix (28) comprising the continuous phase and a dispersed phase forming droplets (40) in the continuous phase. The device comprises an electro-acoustic transducer (12) capable of emitting acoustic waves (30) and outputting a reception signal of reflected acoustic waves, a signal pulse generator capable of determining a propagation time starting from signals output by the transducer, and an acoustic lens for focusing acoustic waves and the frequency of the acoustic waves being adjusted to cause reflection of the waves on the droplets of the dispersed phase, essentially located within a focusing area.