Method for evaluating the quality of the bond between two members utilizing thermoacoustic microscopy

A method for evaluating the quality of the bond achieved between a combination of a first and second member comprising the steps of:

• causing a periodic localized heating at a microscopic spot in said first member to produce thermal waves which in turn give rise to acoustic waves of a longer wavelength that propagate through said combination and with the frequency of said periodic heating being selected to cause said combination to resonate and exhibit a plate-mode signature;
• detecting the acoustic waves produced in said combination and generating signals therefrom;
• scanning said first member with said localized heating in a two-dimensional array of microscopic spots;
• processing said detected signals as a function of the position of said heated spot to generate a two-dimensional image of the plate-mode resonant signature of said combination;
• and
• comparing said generated image of said plate-mode resonant signature to a predetermined plate-mode resonant signature associated with a similar combination where the quality of the bond is known whereby the quality of the bond between said members can be evaluated.

A method for evaluating the quality of the bond achieved between a combination of a first and second member comprising the steps of:

• causing a periodic localized heating at a microscopic spot in said first member to produce thermal waves which in turn give rise to acoustic waves of a longer wavelength that propagate through said combination;
• detecting the acoustic waves produced in the combination and generating signals therefrom;
• varying the frequency of the periodic heating while maintaining said heating at a single point to generate a plurality of plate-mode resonances in said combination;
• and
• comparing the detected signals to a set of predetermined signals associated with a similar combination where the quality of the bond is known whereby the quality of the bond between said members can be evaluated.

A method for evaluating the quality of the bond achieved between a combination of an integrated circuit die and a substrate comprising the steps of:

• causing a periodic localized heating at a microscopic spot in said die to produce thermal waves which in turn give rise to acoustic waves of a longer wavelength that propagate through said combination;
• detecting the acoustic waves produced in said combination and generating signals therefrom;
• varying the frequency of said periodic heating while maintaining said heating at a single spot to generate a plurality of plate-mode resonances in said combination;
• and
• comparing the detected signals to a set of predetermined signals associated with a similar combination where the quality of the bond is known whereby the quality of the bond between said die and substrate can be evaluated.

An apparatus for evaluating the quality of the bond achieved between a combination of a first and second member comprising:

• means generating a periodic localized heating in at least one microscopic spot in said first member to produce thermal waves which in turn gives rise to acoustic waves of longer wavelength which propagate through said combination in a manner to cause said combination to resonate;
• means for detecting the acoustic waves generated in said combination;
• means for processing the detected acoustic waves to obtain a plate-mode resonant signature;
• and
• means for comparing the obtained plate-mode resonant signature to a predetermined plate-mode resonant signature associated with a similar combination where the quality of the bond is known, whereby the quality of the bond between the members can be evaluated.