A batch-fabricated high-density flexible coil enabled by low-temperature bonding technique

In this work, a high-density flexible coil (HFC) is designed and fabricated by stacking and bonding multiple layers of thin flexible coils. A batch fabrication process of the HFC is developed based on a low-temperature gold compression bonding technique. A Cu-Ni-Au electrode-dummy structure is implemented to realize simultaneous electrical connection and mechanical bonding between the flexible coil layers. A proof-of-concept HFC demonstrator is batch-fabricated by bonding process with temperature of 200℃ and pressure of 8 MPa. The fabricated HFC includes 500 turns of coil within a volume of 10 mm×10 mm×0.72 mm, enabling high-coil density with miniaturized footprint. The structural, electrical, and mechanical properties of the HFC are systematically characterized and discussed.