Foil-to-foil interconnection of capacitive humidity sensors using electrically conductive adhesives

The present study presents the development and comparison of two foil-to-foil lamination and interconnection methods of foil-based capacitive humidity sensors. The first method uses confined anisotropic conductive adhesive (ICA) in laser ablated vias through foil (TFV). The second method uses anisotropic conductive adhesive (ACA). Both integration methods were characterized during accelerated humidity (85°C / 85 R.H.),shock temperature (-40°C / 125°C) and bending forces. While the ACA method requires less processing steps and the TFV method was shown to be more robust to bending forces, the interconnection of both methods withstood more than 900 hours of environmental ageing. Finally, the correct functionality of two types of foil-based capacitive humidity sensors was successfully demonstrated by exposing them to different R.H. levels and comparing their readings to a commercial sensor.