Reliability evaluation of 3D-package with specific test structures

This paper reports the test structures used to evaluate and characterize the reliability of flip-chip joints by using soldering or adhesives. In addition, one multifunctional test die has been designed and fabricated using a 3M/2P CMOS process. The test die (size 4.87×4.87 mm²) can be used to characterize interconnections on rigid or flexible substrates. Structures in addition to daisy-chain include heaters, temperature sensors (diode-connected transistors), strain-gauges, moisture sensors, current driving structures and bump offset structures. Measurement structures are connected to the PWB via the most reliable FC-joints. Furthermore, some heaters, temperature sensors, and strain gauges connections can be done via wire-bonding. The test die can be used to characterize the reliability of a 3D system-on-package. In this approach, thicknesses for PWBs of around 160 μm and for test dies of 90 μm were selected. Heaters and temperature sensors are to play an important role checking thermal management properties of the 3D-module.