Capacitive sensing array device
First Claim
1. A capacitive sensing array device comprising an array of sensing electrodes deposited on a substrate and each comprising a capacitor electrode, said sensing electrodes being covered by a layer of electrically insulating material defining a sensing surface spaced from the sensing electrodes with the insulating material forming a capacitor dielectric, wherein the sensing electrodes comprise chromium and the electrically insulating covering layer comprises chromium oxide formed from an oxidized surface region of the chromium sensing electrode.
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Accused Products
Abstract
A capacitive sensing array device, such as a fingerprint sensing device, includes an array of individual sensing electrodes (14) covered by a layer of insulating material (40) defining a sensing surface on which a person'"'"'s finger is placed, each sensing electrode, its overlying fingerprint portion and intervening insulating layer providing a capacitance in operation. The sensing electrodes are of chromium and the covering insulating material includes a thin layer of chromium oxide which offers excellent scratch resistance and can be formed conveniently by oxidation of a surface region of the sensing electrodes. In a row and column array, address lines (18) extending between rows of electrodes (14) may also include chromium and be covered by chromium oxide. Preferably, the sensing electrodes and address lines are defined from a common deposited chromium layer.
24 Citations
6 Claims
- 1. A capacitive sensing array device comprising an array of sensing electrodes deposited on a substrate and each comprising a capacitor electrode, said sensing electrodes being covered by a layer of electrically insulating material defining a sensing surface spaced from the sensing electrodes with the insulating material forming a capacitor dielectric, wherein the sensing electrodes comprise chromium and the electrically insulating covering layer comprises chromium oxide formed from an oxidized surface region of the chromium sensing electrode.
Specification