Fingerprint Sensor Interposer for Uniform Capacitive Coupling

The patent introduces an interposer structure as an intermediary element between the protective plate and the sensing elements. This interposer has a dielectric constant higher than the surrounding adhesive, creating a dielectric gradient that focuses electric field lines toward the sensing elements. The interposer acts as a mediator that allows the protective plate to maintain distance for protection while still enabling strong capacitive coupling through controlled field distribution.

The patent replaces the mechanical/conductive solution (conductive strands) with a dielectric-based solution. Instead of using conductive materials to enhance capacitive coupling, the invention uses an interposer with specific dielectric properties to achieve the same effect through electric field control, thereby eliminating the need for conductive elements that could pose ESD risks.

The patent employs composite material construction where the interposer is made from non-metallic dielectric materials with optimized electrical properties. This composite approach combines mechanical support functionality with enhanced capacitive coupling through dielectric gradient design, eliminating the oxidation and aesthetic problems associated with metallic materials while maintaining or improving sensing performance.

The patent applies local quality enhancement by positioning the interposer structure specifically above each sensing element or in strategic locations within the sensing array. This localized dielectric enhancement focuses the electric field precisely where needed, improving measurement uniformity across the array without requiring larger sensing elements, thereby maintaining device miniaturization while achieving consistent measurements.