Analog Devices, Inc.
Embedded capacitive sensor in metal case

Abstract:

Metal cases are increasingly in popularity in electronics such as smart phones, tablets, portable speakers, etc., since the look and feel of a metal case are appealing to the consumer. Unfortunately, the metal case is generally incompatible traditional capacitive sensing electrodes, which are usually provided on a printed circuit board or flex circuit and are only usable with plastic cases. To provide capacitive sensing with a metal case, a specialized material stack can be fabricated to embed capacitive sensors with the metal case. Specifically, a conductor (a conductive pad, or conductive layer) can be deposited over an oxide layer formed on the metal case (e.g., through anodization). An outer coating can be provided to protect the conductor. A further conductor and dielectric can be included in the material stack to form a double layer capacitive sensor.