Murata Manufacturing Co., Ltd.

Toshiharu Hirota

Yasuhiro Nabika

Tetsukazu Okamoto

Yoshitaka Nagao

Noriyuki Yamamoto

Yoshiaki Abe

Hiroki Tanaka

Masahiko Kawase

Yutaka Ikeda

Yoshiharu Kato

Osamu Kano

Takeo Haga

Takahiko Kawahara

Satoshi Kakihara

Hiroshi Kuwahara

A surface-mount positive temperature coefficient thermistor includes a disk-shaped positive temperature coefficient thermistor element having electrodes provided on opposing main surfaces thereof, an insulating case having an inner space with the thermistor element inserted therein, and a pair of metal terminals arranged to make electrical contact with the respective main surface electrodes of the thermistor element, and to sandwich therebetween the thermistor element. The insulating case includes a pair of main surfaces that are substantially parallel to the main surfaces of the thermistor element, a pair of opening side surfaces each having an opening, and a pair of end surfaces each having a terminal insertion hole provided therein. One end of each of the pair of metal terminals is inserted from the respective terminal insertion holes into the inner space, and the metal terminals press-hold the thermistor element so as to sandwich the thermistor element therebetween.

Surface-mount positive temperature coefficient thermistor and manufacturing method therefor

A starting circuit for a single-phase induction motor includes a motor starting positive characteristic thermistor and a triac arranged in a series connection, and a triac control positive characteristic thermistor connected in parallel with the motor starting positive characteristic thermistor, and including one terminal thereof connected to a gate of the triac. The triac control positive characteristic thermistor has a volume in the range of about 4.5 mmto about 30 mm. The relationship of (&#x221a;2&#xd7;V&#xd7;sin 45&#xb0;)/R&#x2267;I is maintained with the triac control positive characteristic thermistor within an operating temperature range, where V represents a root-mean-square value of a power source voltage, R represents a resistance of the triac control positive characteristic thermistor, and I represents a gate turn-on current of the triac. The gate turn-on current I at an operating temperature of about 25&#xb0; C. is about 20 mA or less.

Starting circuit for single-phase induction motor

A semiconductor ceramic contains erbium as a semiconducting agent in primary components of barium titanate, strontium titanate, lead titanate and calcium titanate, with the average grain diameter of the semiconductor ceramic exceeding about 5 &mgr;m but not exceeding about 14 &mgr;m. Further, the semiconductor ceramic contains as additives a compound containing Er with the Er being more than about 0.10 mol but no more than about 0.33 mol, a compound containing Mn with the Mn being about 0.01 mol or more but no more than about 0.03 mol, and a compound containing Si with the Si being about 1.0 mol or more but no more than about 5.0 mol, per 100 mol of the primary component. Thus, a semiconductor ceramic and positive-temperature-coefficient thermistor can be provided with high-flash-breakdown capability, excellent results in ON-OFF application tests and few irregularities in resistance values.

Semiconductor ceramic and positive-temperature-coefficient thermistor

Provided is a semiconductor ceramic and a semiconductor ceramic element each having a room temperature specific resistance of 3 &OHgr;&middot;cm or lower and a resistance temperature characteristic of 9%/&deg; C. or more. The semiconductor ceramic is characterized in that the ratio R /(R &plus;R ), in which R is the transgranular resistance value of the crystal particles and R is the intergranular resistance value of the crystal particles and R &plus;R is the overall resistance value representing the sum of R and R , is about 0.35 to 0.85.

Semiconductor ceramic, semiconductor ceramic element and circuit protection element

A semiconductor ceramic device comprises a body composed of a semiconductor ceramic having a positive resistance-temperature coefficient primarily composed of barium titanate and electrodes provided on the body, in which the resistance-temperature coefficient is 9%/&deg; C. or more, resistivity is 3.5 &cap;&middot;cm or less, and withstand voltage is 50 V/mm or more. As the semiconductor ceramic forming the body provided in a thermistor having positive resistance-temperature characteristics, a semiconductor ceramic having a positive resistance-temperature coefficient is used, in which the semiconductor ceramic has an average particle diameter of about 7 to 12 &mgr;m and comprises barium titanate as a major component and sodium in an amount of about 70 ppm or less on a weight basis.

Semiconductor ceramic and semiconductor ceramic device

A semiconductor ceramic composed of barium titanate, lead titanate, strontium titanate, and calcium titanate as primary components, includes samarium oxide as a semiconductor-forming agent in the primary components, and the average diameter of crystalline particles of the semiconductor ceramic is about 7 to 12 &mgr;m. The semiconductor ceramic has a resistivity at room temperature not greater than 3.5 &OHgr;cm, a withstand voltage not less than 50 V/mm, a resistance-temperature coefficient &agr; not less than 9%/&deg;C. and also has less variability of resistance.

Semiconductor ceramic and device using the same

A ceramic for the PTC thermistor having a resistivity at room temperature of 5 &OHgr;&middot;cm or less, static withstanding voltage of 60 V/mm or more and temperature resistance coefficient of 9.0 %/&deg; C., having small dispersion of the resistance, is composed of principal components of about 30 to 97 mol % of BaTiO , about 1 to 50 mol % of PbTiO , about 1 to 30 mol % of SrTiO and about 1 to 25 mol % of CaTiO (the total content of them being 100 mol %), as well as about 0.1 to 0.3 mole of Sm, about 0.01 to 0.03 mole of Mn and 0 to about 2.0 mole of Si relative to 100 moles of the principal components, the composite material being preferably heat-treated in an oxidative atmosphere after being fired in a reducing or neutral atmosphere for obtaining the ceramic.

Composite material for positive temperature coefficient thermistor, ceramic for positive temperature coefficient thermistor and method for manufacturing ceramics for positive temperature coefficient thermistor

Thermistor chips are produced by first obtaining elongated strips made of a sintered ceramic plate having a specified resistance-temperature characteristic and having thereon a plurality of mutually parallel grooves extending perpendicularly to its direction of elongation. On each of these strips, ohmic electrodes are formed, one extending continuously from one of its main surfaces to one of its side surfaces and another extending continuously from the other oppositely facing main surface to the opposite side surface. This may done by covering the strip completely with an electrically conductive film and separating it into two areal parts by forming a longitudinally extending slit on each of the main surfaces. These strips are then stacked one on top of another by aligning the grooves on each of these strips and adhesively attached together with a glass paste in between. The layered structure thus obtained is broken up along the aligned grooves to obtain individual units of which newly exposed surfaces may later be covered by an electrically insulating material.

Method of producing thermistor chips

A barium titanate-based semiconductive ceramic composition for facilitating miniaturization of thermistor devices by improving rush current resistance characteristics is provided. In the barium titanate-based semiconductive ceramic composition, a fraction of the Ba in BaTiO,as the major component is replaced with 1 to 25 mole percent of Ca, 1 to 30 mole percent of Sr, and 1 to 50 mole percent of Pb; and wherein to 100 mole percent of the major component, the semiconductivity-imparting agent is added in an amount of 0.2 to 1.0 mole percent as a converted element content, and the additive comprises manganese oxide in an amount of 0.01 to 0.10 mole percent as a converted Mn content, silica in an amount of 0.5 to 5 mole percent as a converted SiO,content, and magnesium oxide in an amount of 0.028 to 0.093 mole percent as a converted Mg content.

Barium titanate-based semiconductive ceramic composition

A chip thermistor is produced by providing a planar rectangular thermistor block with a pair of electrodes formed on its surfaces, each of the electrode being formed so as to be in part on a different one of the main surfaces and extending continuously at least onto one of the side surfaces. The thermistor block thus prepared is cut transversely to obtain a plurality of thermistor elements. A specified number of these thermistor elements are then aligned and stacked one on top of another with their main surfaces facing each other. A layer of an insulating material such as glass with thickness greater than 10 .mu.m is inserted between each mutually adjacently stacked pair of these thermistor elements. Outer electrodes are formed on the outer surfaces of the stacked structure so as to electrically connect to the electrodes on the stacked thermistor elements on their aligned end surfaces.

Chip thermistors and methods of making same

A thermistor element with positive temperature characteristic (PTC) has a planar ceramic member with a positive temperature characteristic of which the thickness is greater at its peripheral part than at the center part, decreasing either gradually or in a stepwise manner. Protrusions may be formed along its periphery. A PTC thermistor is formed with electrodes formed on both main surfaces of such a PTC thermistor, each electrode having a lower-layer electrode all over a main surface and an upper-layer electrode on the lower-layer electrode. The upper-layer electrode has a smaller surface area than the lower-layer electrode such that a portion of the lower-surface electrode is exposed at the periphery. The upper-layer electrodes may be formed at the center parts of the main surfaces, exclusive of the peripheral parts or where the protrusions are formed. The lower-layer electrodes may be mostly of Ni and the upper-layer electrodes mainly of Ag.

Positive temperature characteristic thermistor and thermistor element

A thermistor element in which in a thermistor body having first and second outer electrodes formed on a pair of its end surfaces, a first inner electrode connected to the first outer electrode and a second inner electrode connected to the second outer electrode are so disposed that their ends are opposed a predetermined distance away from each other.

Thermistor element

A ceramic dielectric composition for temperature compensating capacitors comprising 64-70.5% by weight of SrTiO.sub.3, 28-34% by weight of CaTiO.sub.3 and 1.5-4.5% by weight of Bi.sub.2 O.sub.3 or Bi.sub.2 O.sub.3.nTiO.sub.2 (where n=1 to 5). Not more than 10% by weight of MgTiO.sub.3 may be added, as necessary. The composition has high dielectric constant above 235 and Q above 2000 and low temperature coefficient of a dielectric constant up to -1000.times.10.sup.-6 /.degree.C. The ceramic element obtained by the composition has a large adhesion strength to electroless plating electrodes (nickel or copper).

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Hikone, Japan

Toshiharu Hirota