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:
Jan. 19, 2010
Filed:
Mar. 17, 2008
Kenjirou Mihara, Higashiomi, JP;
Atsushi Kishimoto, Kusatsu, JP;
Hideaki Niimi, Hikone, JP;
Murata Manufacturing Co., Ltd., Kyoto-fu, JP;
Abstract
A multilayer positive temperature coefficient thermistor that has a BaTiO-based ceramic material contained as a primary component in semiconductor ceramic layers, the ratio of the Ba site to the Ti site is in the range of 0.998 to 1.006, and at least one element selected from the group consisting of La, Ce, Pr, Nd, and Pm is contained as a semiconductor dopant. In this multilayer positive temperature coefficient thermistor, a thickness d of internal electrodes layer and a thickness D of the semiconductor ceramic layers satisfy d≧0.6 μm and d/D<0.2. Accordingly, even when the semiconductor ceramic layers have a low sintered density such that an actual-measured sintered density is 65% to 90% of a theoretical sintered density, a multilayer positive temperature coefficient thermistor having a low rate of temporal change in room-temperature resistance can be obtained without performing any complicated processes, such as a heat treatment. When the content of the semiconductor dopant is 0.1 to 0.5 molar parts with respect to 100 molar parts of Ti, a low-temperature firing at 1,150° C. can be realized, and a low room-temperature resistance and a sufficiently high rate of resistance change can be obtained.