A Chip-on-Board Packaging Scheme for Amorphous Wire GMI Magnetic Sensors

Amorphous wire giant magnetoimpedance (GMI) sensors exhibit advantages such as high sensitivity, fast response, and compact size. To achieve scalable manufacturing, microelectronic manufacturing has been adopted to ensure device consistency and enable mass production. However, challenges remain in the packaging stage. The research on the packaging approaches specifically for this type of sensor is insufficient. Traditional packaging approaches, such as ceramic packaging methods and lead-frame packaging methods, face issues including high cost and large dimensions. Compared to traditional packaging, the chip-on-board (COB) packaging provides the advantages of compact size and low cost. To address the problem in the sensor packaging stage, this paper proposes a COB packaging scheme for amorphous wire sensors and has achieved device fabrication. The sensor based on microelectronic manufacturing technology is attached to the printed circuit board (PCB). Electrical connection of the amorphous wire is achieved by wire bonding, and the gold wires are used to connect the pads at both ends of the amorphous wire to the corresponding pads on the PCB. Finally, the epoxy encapsulant is employed on the chip and bonding wire areas, fully covering both to complete the COB packaging of the device. The amorphous wire weak magnetic sensor after COB packaging exhibits excellent linearity within a magnetic field range of –0.75 Oe to +0.75 Oe, with a sensitivity of 5.19 V/Oe and a noise level of 94 pT/√Hz at 1 Hz (21 pT/√Hz at 1 kHz).