Evaluation of electronic packaging reliability using acoustic microscopy.

摘要

Reliability of integrated circuit packages depends in many respects on their mechanical integrity. The effect of structural weaknesses caused by poor bonding, voids, microcracks or delaminations may not be evident immediately in the electrical performance characteristics, but may cause premature failure. The C-mode scanning acoustic microscopy (C-SAM) is an excellent tool for non-destructive failure analysis of IC packages. To gain insights into the nature of images obtained from acoustic microscopy the acoustic wave parameters must be understood and used to interpret the data (images and waveforms) obtained via acoustic microscopy.;Basic material parameters pertinent to acoustic microscopy have been calculated in this thesis and they will assist researchers in the understanding and interpretation of acoustic images. The spot size, depth of focus, lateral and axial resolutions for different materials in electronic packaging and the pressure and intensity coefficients of reflection and transmission for typical material systems in electronic packaging are presented and analytical methods are developed to calculate these parameters. The basic resolution limitations of acoustic microscopy are tied to the limitations to the electronic packaging material systems.;Transmission and reflection scanning acoustic microscopy techniques for reliability evaluation of electronic packaging are presented and the limitations of each of these techniques are discussed.;This thesis also demonstrates the use of acoustic microscopy to systematically identify the package defects and determine the mechanisms for package failures. The application of the acoustic wave parameters and principles of C-SAM to the solution of three key problems in the physics of failure of electronic packages are presented. The examples selected ranged from plastic to ceramic packages, thus showing the application of C-SAM to packaging materials from low to high acoustic impedance.