| 摘要 |
A method of using acoustic signals in the form of waves or pulses to non- destructively measure the thickness of a bonding layer sandwiched between and bonding together overlying and underlying materials different from the bonding layer especially when th e thickness of the bonding layer is so small that the features (maxima, minima, time position)o f the echo from the interface of the bonding layer and the overlying material is indistinguishable, i.e., not independently observable from the features (maxima, minima, time position) o f echo from the interface of the bonding layer and the underlying material, is achieved by applying an acoustic wave to the layered body that will cause a primary echo to be reflected from the interface between the bonding material and the top or overlying material and cause a secondary echo to be reflected from the interface of the bonding material and the underlying material; detecting and digitizing the echoes to generate a digital time series containing both echoes, processing the digital time series to remove any noise there from; digitally filtering the time series using a filter matched to the primary echo; locating the time position and amplitude of the maximum of the filtered time series; time-translating and scaling the primary echo using th e time position and amplitude obtained from said localization; subtracting said transformed mode l of said primary echo from said time series to obtain a cleaned time series without the prima ry echo; digitally filtering said cleaned time series using a filter matched to the secondary echo; locating the time position of the maximum of said secondary echo filtered time series; determining the flight time, i.e., the time used by the acoustic wave or pulse to travel back and forth i n the bonding layer from the difference between the time locations of the primary and secondary echoes from the time positions of the maxima of the two filtered time series; and determinin g the thickness of the bonding layer of said body which is equal to one half of the measured flight time multiplied by the velocity of the acoustic wave or pulse in the bonding layer.
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