Tilt- and warpage measurement of bonded dies as an inline quality assessment tool

Tilt of semiconductor dies is a common issue during assembly in power electronics as e.g., die bonding during silver sintering caused by inhomogeneous thicknesses of applied die-attach material, problems with a homogeneous force application, uneven substrates etc. This tilt usually leads to reliability problems later during testing or operation in the field. Unlike delamination and voids, excessive porosity and consequently resulting weakened bulk or interface regions can often be overlooked by SoA failure analytical techniques like scanning acoustic microscopy (SAM) or pulsed infrared thermography (PIRT), since acoustic impedance and thermal conductivity respectively are no adequate measure to resolve porosity changes in that interval. In this work, we present a scanning system, based on confocal polychromatic distance sensors, which can scan a fully loaded tray of bonded dies on substrate for industry grade inline integration. We demonstrate the novel system on different bonded power dies on AMB substrate under industrial production conditions. We achieve this in the required accuracy of about $2-3\ \mu {\mathrm {m}}$ in an environment with strong vibration influence. The in-line capability has been proven by using a setup, which is independent of mechanical vibrations and used only optical fibers to transfer measuring signals within future smart production environments.