Non-destructive Assessment of the Porosity in Silver (Ag) Sinter Joints Using Acoustic Waves

Caused by its superior performance regarding bandwidth, power loss and form factors compound semiconductors like GaN or SiC recently moved into the interest of the semiconductor industry, particularly for applications in the high power segment. These improved performance parameters go along with increased power densities and thus, require a specifically optimized thermal concept of the packaging. Ag-sintering as die-attach process has been widely accepted as a promising alternative to soldering techniques with respect to thermal conductance. However, the thermal and the mechanical behavior of the sinter layer is influenced by its composition on the micro -and the macroscopic scale with respect to the presence of voids, inclusions and delamination but also the fractional content of porosity. Scanning acoustic microscopy (SAM) uses acoustic waves that interact with the mechanical properties of the sample materials and is thus, widely established for the non-destructive detection of voids, inclusions and delamination in microelectronic components. The current paper investigates the potential of SAM as a method for the assessment and characterization of the porosity in sintered Ag layers targeting the die-attach technology for novel power semiconductor devices.