Four-Level Micro-Via Technology (4LµV) for ASIC Integration in Active Flexible Sensor Arrays

Area of Science:

• Materials Science
• Electrical Engineering
• Sensor Technology

Background:

• Flexible sensor systems often face scalability issues due to extensive wiring requirements.
• Integrating active circuits like ASICs is crucial for multiplexing and reducing data lines in sensor foils.

Purpose of the Study:

• To develop a new manufacturing process for multilayer wiring in polyimide-based sensor foils.
• To enable reliable integration and soldering of ASIC chips within flexible sensor systems.

Main Methods:

• A novel galvanic copper deposition process for creating micro-via connections and contact pads after polyimide layer curing.
• Demonstration using a six-strain-sensor-node array connected to a surface-mounted ASIC for detecting bending states.

Main Results:

• Significantly reduced processing time compared to layer-by-layer via technology.
• Elimination of copper oxidation risk during polyimide curing by performing copper plating as the final step.
• Successful demonstration of a flexible sensor foil capable of bending +/-120° without damage.

Conclusions:

• The developed manufacturing process enables robust, scalable flexible systems-in-foil with integrated ASICs.
• This technology is suitable for complex flexible systems, especially large sensor arrays.
• The process enhances reliability and reduces manufacturing complexity for advanced sensor applications.