Electrical Behavior of Thin Die Assembly on Flexible Substrate Under Vibration Testing

With the introduction of new technologies from the laboratory to the market, new reliability models must be developed to predict production, supply chain, and customer needs. Flexible electronics have already made their debut in the public world, but assumptions about their reliability in certain key stress cases remain stuck in the performance of traditional, rigid circuits. In particular, traditional manufacturing methods such as soldering require substrates to sustain high temperatures for long times, restricting substrate material choices to high temperature plastics such as polyimide [1]. Substrates with low manufacturing temperature, such as PET, require alternative techniques, such as conductive epoxy, that have not been fully explored in the field of vibrational reliability. In this study, thin die assemblies were created with 50 and 100 micron Si dies metalized with aerosol jet printing and attached through isotropic conductive epoxy to screen printed circuitry on PET substrates. The flexible assemblies were subjected to extensive vibrational testing surpassing JECETS military standard (MIL-STD) 810 requirements without signs of damage, thereby demonstrating the robustness of this technology when undergoing vibration. Computer simulations using ANSYS Mechanical were performed to understand the physics of the up close system. A "worst case scenario" was constructed to maximize the possible stresses that could be induced solely through vibration, and the samples still showed no signs of damage.