Self-healing of Interconnect Cracks for Reliable and Defect-Free Smart Manufacturing of Flexible Packages

Metal-particle nanocomposite interconnects are widely utilized for chip-on-flex isotropic conductive adhesives (ICA) because of their low-temperature assembly and compatibility with additive manufacturing on flexible substrates. They are also emerging as an option for printed fan-out interconnections between chip pads and flexible substrate traces. However, cracks in interconnections during bending and thermal cycling remain as key concerns. Self-healing of interconnect cracks is being widely pursued with various actuation schemes such as shape-memory recovery forces, or irradiation with photonic, capacitive or magnetic fields. These fields specifically generate heat inside the interconnect materials through various resonance and relaxation mechanisms. Heating raises the temperature to above the melting point of the nanocomposite and causes the polymer liquid with conducting nanoparticles to flow into the cracks to cause crack closure and regain the conducting path. Synthesis and process design of such printed nanocomposite interconnect materials are demonstrated in this work. These materials are then applied as fan-out interconnects in embedded-chip packages. Self-healing is demonstrated through conduction recovery after heating. This work will eventually lead to the multiscale package interconnection material and process design from remote heating.