Mechanical and electrical properties of ultra-thin chips and flexible electronics assemblies during bending

In this paper a modified four-point bending method is presented, which is capable of measuring chip stress at high curvatures. The strength of several types of ultra-thin chips is evaluated, including standalone ultra-thin test chips and back-thinned 20 μm thick microcontrollers, as well as assemblies containing integrated ultra-thin microcontroller chips. The effect of chip thickness, bending direction and backside finish on strength and minimum bending radius is investigated using the modified four point bending method. The effect of bonding ultra-thin chips to flexible foils on the assembly strength and minimum bending radius is evaluated as well as the effect of bending on electrical properties of the bonded microcontroller dies.