The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 27, 2007
Filed:
May. 26, 2004
Masamichi Yamada, Hitachinaka, JP;
Izumi Watanabe, Hitachinaka, JP;
Keiichi Nakada, Hitachinaka, JP;
Junichi Horie, Hitachinaka, JP;
Masamichi Yamada, Hitachinaka, JP;
Izumi Watanabe, Hitachinaka, JP;
Keiichi Nakada, Hitachinaka, JP;
Junichi Horie, Hitachinaka, JP;
Hitachi, Ltd., Tokyo, JP;
Abstract
A thermal flow sensor which is fabricated at a low cost and has improved reliability. Over a cavity () formed in a semiconductor substrate (), at least a heating resistance () is formed near the center of the cavity with an electrical insulation film interposed between the heating resistance and the cavity. The temperature (Th) of the heating resistance () is controlled to be higher than the medium temperature (Ta) by a constant temperature (ΔTh=Th−Ta). A distance (Ws) in the direction of airflow from an upstream end of the heating resistance () to an upstream end of the electrical insulation film lying over the cavity and the constant temperature (ΔTh) satisfy the following relationship:Δ≦800 (° C./mm)Thus, a thermal flow sensor is provided which can prevent deposition of floating fine particles, such as carbon particles, caused by the thermophoretic effect, can be fabricated at a low cost, and has high reliability.