A thermal resistor includes a substrate, a thermistor, a front electrode, a passivation protection layer, and an external protection layer. The thermistor does not include an oxide and is made of a base metal. Therefore, it can reduce the production cost. The passivation protection layer is formed by sputtering, physical vapor deposition, or chemical vapor deposition, in which the passivation protection layer conformally covers a surface of the thermistor and can protect the underlying thermistor.

A copper foil having a matte side with nickel plated thereon in an amount of nickel in the range of 100,000-300,000 s/dm.sup.2. The plated copper foils have particular utility in Positive Temperature Coefficient (PTC) devices. The plated copper foils have a surface hardness of from 50 to 200, a tensile strength greater than 45 kg/mm.sup.2 and a shiny side surface roughness (Rz) not exceeding 2.0 m. The surface roughness of the matte side of the copper foil is in the range of 6 to 10 m. Copper nodules are present on the matte side of the copper foil between the copper foil and the nickel plating. Methods of producing the copper foil and PTC devices incorporating the copper foil are described.

A copper foil having a matte side with nickel plated thereon in an amount of nickel in the range of 100,000-300,000 s/dm.sup.2. The plated copper foils have particular utility in Positive Temperature Coefficient (PTC) devices. The plated copper foils have a surface hardness of from 50 to 200, a tensile strength greater than 45 kg/mm.sup.2 and a shiny side surface roughness (Rz) not exceeding 2.0 m. The surface roughness of the matte side of the copper foil is in the range of 6 to 10 m. Copper nodules are present on the matte side of the copper foil between the copper foil and the nickel plating. Methods of producing the copper foil and PTC devices incorporating the copper foil are described.

The present invention relates to a new PTC device having a configuration with which protrusion of solder paste and/or an excess portion of epoxy resin do not adversely affect a jig. Such PTC device 30 comprises a PTC member 32 and leads 34 and 36 electrically connected to both sides of the PTC member the PTC member comprises a PTC element 38 and metal electrodes 40 and 42 placed on both sides of the PTC element respectively, each lead is electrically connected to the metal electrode respectively via an electrically conductive connection portion 50, and at least one 36 of the leads has a concave portion which is defined with a bottom portion 44 located adjacently to the metal electrode of the PTC member and a wall portion 46 surrounding the electrically conductive connection portion which connects the leads to the metal electrode.

Surface-mountable conductive polymer devices include a conductive polymer layer between first and second electrodes, on which are disposed first and second insulation layers, respectively. First and second planar conductive terminals are on the second insulation layer. A first cross-conductor connects the second electrode to the first terminal, and is separated from the first electrode by a portion of the first insulation layer. A second cross-conductor connects the first electrode to the second terminal, and is separated from the second electrode by a portion of the second insulation layer. In some embodiments, at least one cross-conductor includes a beveled portion through the first insulation layer to provide enhanced adhesion between the cross-conductor and the first insulation layer, while allowing greater thermal expansion without undue stress. In other embodiments, these advantages are achieved by having at least one cross-conductor in physical contact with a metallized anchor pad on the first insulation layer.

A barium titanate based PTC thermistor ceramic composition without using Pb. Its Curie temperature is shifted to a temperature higher than 120 C. The PTC thermistor can readily turn semiconductive even if it is sintered in air. The resistivity at 25 C. is low and the variation rate of the resistivity at 25 C. with time is little. The PTC thermistor ceramic composition includes a sintered body having a barium titanate based compound represented by formula (1) as the main component, (Ba.sub.1-x-y-wBi.sub.xA.sub.yRE.sub.w).sub.(Ti.sub.1-zTM.sub.z)O.sub.3 (1), wherein, 1.02yx1.5y (2), 0.007y0.125 (3), 0(w+z)0.01 (4), 0.971.06 (5), and the sintered body contains Ca in a ratio of 0.01 mol or more and less than 0.05 mol relative to 1 mol of Ti site in terms of element.

An over-current protection device comprises a PTC device and a first external lead. The PTC device comprises first and second conductive layers and a PTC material layer laminated therebetween. The first conductive layer forms an upper surface of the PTC device. The first external lead has a lower surface soldered to the first conductive layer. The lower surface is provided with a plurality of protrusions of which tops are in direct contact with the first conductive layer to form a gap between the first external lead and the first conductive layer. Solder paste fills the gap to form an electrically conductive connecting layer. The over-current protection device may further comprise a second external lead with protrusions soldered to the second conductive layer to form an axial-lead or a radial-lead type device.

An electrical device having first and second electrodes and a layer of a conductive composite electrically in contact with the first and second electrodes. The conductive composite is a mixture of a semi-crystalline polymer and a conductive filler, the conductive filler including a plurality of particles containing an inner material including a first metal; and an outer material surrounding the inner material, the outer material including a second metal; and an intermetallic compound formed between the inner material and the outer material. The intermetallic compound has features from the inner material and the outer material. The device can be a circuit protection device. Also provided is a method of making a conductive composite by dry mixing the components.

A method of manufacturing a surface mount device includes forming a plaque from a material, forming a plurality of conductive protrusions on a top surface and a bottom surface of the plaque, and applying a liquid encapsulant over at least a portion of the top surface and at least a portion of the bottom surface of the plaque. The liquid encapsulant is cured and when cured encapsulant has an oxygen permeability of less than about 0.4 cm3.Math.mm/m2.Math.atm.Math.day. The assembly is cut to provide a plurality of components. After cutting, the top surface of each component includes at least one conductive protrusion, the bottom surface of each component includes at least one conductive protrusion, the top surface and the bottom surface of each component include the cured encapsulant, and a core of each component includes the material.

Surface-mountable conductive polymer devices include a conductive polymer layer between first and second electrodes, on which are disposed first and second insulation layers, respectively. First and second planar conductive terminals are on the second insulation layer. A first cross-conductor connects the second electrode to the first terminal, and is separated from the first electrode by a portion of the first insulation layer. A second cross-conductor connects the first electrode to the second terminal, and is separated from the second electrode by a portion of the second insulation layer. In some embodiments, at least one cross-conductor includes a beveled portion through the first insulation layer to provide enhanced adhesion between the cross-conductor and the first insulation layer, while allowing greater thermal expansion without undue stress. In other embodiments, these advantages are achieved by having at least one cross-conductor in physical contact with a metallized anchor pad on the first insulation layer.