JP2011023213A - Circuit protection element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit protection element capable of making it melt even in case of flowing of low electric current. <P>SOLUTION: The circuit protection element includes a pair of upper surface electrodes 12 fitted at either end part of an insulation substrate 11, an element part 13 bridging the pair of upper surface electrodes 12, a base layer 14 between the element part 13 and the insulation substrate 11, and an end surface electrode 16a connected with the upper surface of the element part 13. The element part 13 is formed by sputtering, and is structured of three layers which are a first element part 17, a second element part 18 and a third element part 19 from the insulation substrate 11 side in this order. The first element part 17 is structured of a material with excellent adhesion with the insulation substrate 11, the second element part 18 is structured of aluminum or an alloy with aluminum and copper, and the third element part 19 is structured of nickel or an alloy with nickel and copper. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a circuit protection element that melts and protects various electronic devices when an overcurrent flows.

  As shown in FIG. 2, this type of conventional circuit protection element includes an insulating substrate 1, a pair of electrodes 2 provided on both ends of the upper surface of the insulating substrate 1, and the pair of electrodes on the upper surface of the insulating substrate 1. An element portion 3 electrically connected to the upper surface electrode 2, an insulating layer 4 provided so as to cover the element portion 3, and a pair of end surface electrode layers 5 formed on both end surfaces of the insulating substrate 1, It was set as the structure provided with. The element portion 3 is formed by plating Cu on the upper surface of the thin film layer.

  As prior art document information relating to the invention of this application, for example, Patent Document 1 is known.

JP 2000-331590 A

  In the above-described conventional circuit protection element, since the element portion 3 is formed by plating, the thickness of the element portion 3 is increased, and as a result, the resistance value of the element portion 3 cannot be increased. When a low current flows, it has a problem that it cannot be melted.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a circuit protection element that can be melted even when a low current flows.

  In order to achieve the above object, the present invention has the following configuration.

  According to a first aspect of the present invention, an insulating substrate, a pair of upper surface electrodes provided at both ends of the insulating substrate, and the pair of upper surface electrodes are bridged, and the pair of upper surface electrodes are formed. The main component is an element part electrically connected to the upper electrode, diatomaceous earth, or silica or alumina having a hollow inside or a coarse inside density provided between the element part and the insulating substrate. Comprising an underlayer containing a filler, an insulating layer provided so as to cover the element part, and an end face electrode formed by plating connected to the upper surface of the element part at both ends of the insulating substrate, The element portion is formed by sputtering, and the element portion is provided in order from the insulating substrate side, a first element portion, a second element portion, and a third element portion. The first element portion is composed of a material having good adhesion to the insulating substrate, the second element portion is composed of aluminum or an alloy of aluminum and copper, and the third element portion is composed of three layers. The element part is composed of nickel or an alloy of nickel and copper. According to this structure, the element part is formed by sputtering, so that the thickness of the element part can be reduced. Since the resistance value of the portion can be increased, it can be melted even when a low current flows. In addition, since the second element portion is composed of aluminum or an alloy of aluminum and copper, the melting point of the element portion can be lowered, so that the fusing characteristics are not deteriorated. Since the third element portion of the outermost layer is composed of an alloy of nickel and copper, the effect that the adhesion between the element portion and the end face electrode can be improved is obtained.

  As described above, in the circuit protection element of the present invention, the element part is formed by sputtering, and the element part is provided in order from the insulating substrate side, the first element part, the second element part, and the third element part. And the first element part is made of a material having good adhesion to the insulating substrate, the second element part is made of aluminum or an alloy of aluminum and copper, and Since the element part 3 is made of nickel or an alloy of nickel and copper, the thickness of the element part can be reduced, and thereby the resistance value of the element part can be increased. Even if it flows, it can be melted, and an excellent effect that the adhesion between the element portion and the end face electrode can also be improved.

Sectional drawing of the circuit protection element in one embodiment of this invention Cross-sectional view of a conventional circuit protection element

  Hereinafter, a circuit protection element according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view of a circuit protection element according to an embodiment of the present invention.

  As shown in FIG. 1, the circuit protection element according to one embodiment of the present invention includes an insulating substrate 11, a pair of upper surface electrodes 12 provided at both ends of the insulating substrate 11, and the pair of upper surface electrodes 12. An element portion 13 formed so as to be bridged and electrically connected to the pair of upper surface electrodes 12, a base layer 14 provided between the element portion 13 and the insulating substrate 11, and the element An insulating layer 15 provided so as to cover the portion 13, and end electrodes 16 a connected to the upper surface of the element portion 13 at both ends of the insulating substrate 11 and formed by plating.

In the above configuration, the insulating substrate 11 has a square shape and is made of alumina containing 55 to 96% Al ₂ O ₃ . The pair of upper surface electrodes 12 are formed by printing Ag or the like on both ends of the upper surface of the insulating substrate 11.

  The element portion 13 is provided on the upper surface of the base layer 14 and the pair of upper surface electrodes 12 so as to cover the entire surface of the insulating substrate 11, and is provided in order from the insulating substrate 11 side. The element portion 17, the second element portion 18, and the third element portion 19 are composed of three layers. These first to third element portions 17 to 19 are all formed by sputtering.

  The first element portion 17 is formed directly on the insulating substrate 11, the upper surface electrode 12, and the base layer 14, and is made of a material having good adhesion to the insulating substrate 11, such as chromium or titanium. Thereby, the adhesiveness of the 2nd, 3rd element parts 18 and 19 and the insulated substrate 11 can be improved. Furthermore, since this chromium, titanium, etc. are also materials with low thermal conductivity, the influence which the 1st element part 17 has on a characteristic can be made small.

  The second element portion 18 is formed on the first element portion 17 and constitutes a main portion of the element portion 13. The second element portion 18 is made of aluminum or an alloy of aluminum and copper. In addition, since the hillock may be generated when the second element portion 18 is made of only aluminum, the generation of hillock can be prevented by adding about 0.5% by weight of copper to form an alloy of aluminum and copper. it can. Furthermore, zinc may be used instead of aluminum.

  The third element portion 19 is made of nickel or an alloy of nickel and copper. At this time, the second element portion 18 is easily oxidized, and has poor adhesion to the end face electrode 16a formed by plating silver or the like. Therefore, the third element portion has good adhesion to the end face electrode 16a. 19, the second element portion 18 is covered to improve the adhesion with the end face electrode 16a. In addition, it is possible to prevent (reduce) oxidation more effectively and to further improve the adhesion, when the alloy is made of copper rather than only nickel.

  Furthermore, two trimming grooves 20 are formed at the center of the element portion 13 by laser from the side surfaces of the element portion 13 facing each other toward the center of the element portion 13, and the two trimming grooves 20 are formed. A region surrounded by is a fusing part 21 that melts and breaks when an overcurrent is applied. Note that three or more trimming grooves 20 may be formed so that the current meanders or the resistance value may be adjusted.

  The underlayer 14 is provided in the central portion of the insulating substrate 11, and is provided between the element portion 13 located between the pair of upper surface electrodes 12 and the insulating substrate 11. Furthermore, this foundation layer 14 is composed of a mixture of a diatomaceous earth or a filler mainly composed of silica or alumina whose inside is hollow or whose density is rough, and a silicon resin, Since the thermal conductivity of the diatomaceous earth, filler, and silicon resin is 0.2 W / m · K or less, the base layer 14 prevents the heat of the element portion 13 from diffusing into the insulating substrate 11. Can do.

  The underlying layer 14 is formed not only on the central portion of the insulating substrate 11 but also on almost the entire upper surface of the insulating substrate 11, and a pair of upper surface electrodes 12 are formed on both ends of the underlying layer 14. May be.

  The insulating layer 15 is provided so as to cover the element portion 13, and a first insulating layer 15 a made of a resin such as silicon covering the fusing portion 21, and an upper surface of the first insulating layer 15 a And a second insulating layer 15b made of a resin such as epoxy.

  The end face electrode 16a is formed by plating a silver-based material on both ends of the insulating substrate 11 so as to overlap a part of the element portion 13, and the end face electrode 16a has a nickel surface on the surface thereof. A plating film 16b made of tin is formed. At this time, the uppermost third element portion 19 of the element portion 13 is covered with the end face electrode 16a.

  Next, the manufacturing method of the circuit protection element in one embodiment of the present invention is explained.

In FIG. 1, first, silver paste or a silver-palladium alloy conductor paste mainly composed of silver is printed on both ends of the upper surface of an insulating substrate 11 made of alumina containing 55 to 96% Al ₂ O _3. A pair of upper surface electrodes 12 is formed by firing.

  Next, a mixture of silicon resin and 40% to 90% by volume of a filler mainly composed of diatomaceous earth or silica or alumina whose inside is hollow or whose inside density is rough is formed at the center of the insulating substrate 11. The paste consisting of the mixture and the organic solvent is printed, and then cured at about 150 ° C. to 200 ° C. to evaporate the organic solvent, thereby forming the underlayer 14.

  Next, the element portion 13 is formed on the upper surface of the base layer 14 and the pair of upper surface electrodes 12. The element portion 13 is configured so as to be electrically connected to the pair of upper surface electrodes 12 by bridging between the pair of upper surface electrodes 12.

  The element portion 13 is first sputtered with chromium, titanium or the like to form the first element portion 17, and then the upper surface of the first element portion 17 is sputtered with aluminum or an alloy of aluminum and copper. Then, the second element portion 18 is formed, and then the third element portion 19 is formed by sputtering nickel or an alloy of nickel and copper on the upper surface of the second element portion 18.

  Next, two trimming grooves 20 are formed by cutting two portions of the central portion of the element portion 13 with a laser from the side surfaces of the element portion 13 facing each other toward the central portion of the element portion 13. A fusing part 21 that melts and breaks when an overcurrent is applied is provided in a region surrounded by the groove 20.

  Next, a resin such as silicon is formed so as to cover at least the fusing part 21 and the first insulating layer 15a is provided. Thereafter, a resin such as epoxy is formed on the upper surface of the first insulating layer 15a to provide a second insulating layer 15b, thereby forming the insulating layer 15 having two layers.

  Next, the end surface electrode 16a is formed by plating silver so that it may overlap a part of element part 13 (upper surface of the 3rd element part 19) in the both ends of the insulating substrate 11. FIG.

  Finally, a plating film 16b having a two-layer structure of nickel and tin is formed on the end face electrode 16a to manufacture the circuit protection element according to one embodiment of the present invention.

  In the above-described embodiment of the present invention, since the element portion 13 is formed by sputtering, the thickness of the element portion 13 can be reduced, thereby increasing the resistance value of the element portion 13. Therefore, even if a specified low current flows, the effect that it can be melted can be obtained.

  Further, since the second element portion 18 is made of aluminum or an alloy of aluminum and copper, the melting point of the element portion 13 can be lowered, the fusing characteristics are not deteriorated, and nickel or nickel Since the third element portion 19 of the outermost layer is composed of an alloy of copper and copper, the adhesion with the end face electrode 16a and the plating film 16b can be improved.

  That is, in one embodiment of the present invention, not only the element portion 13 is formed by sputtering in order to reduce the thickness of the element portion 13, but also the number of layers, material, and order constituting the element portion 13 are specified. Thus, improvement of fusing characteristics, suppression of oxidation, and improvement of adhesion with the end face electrode 16a are also achieved.

  Here, in order to melt even a low current value, the resistance value of the element portion 13 must be increased. However, in one embodiment of the present invention, the element portion 13 is entirely formed by sputtering. This is realized by reducing the thickness of 13. However, in order to blow at a low current value, it is necessary to further lower the melting point of the element portion 13 and prevent heat diffusion.

  In this case, since the second element portion 18 is made of aluminum or an alloy of aluminum and copper, the melting point of the element portion 13 can be lowered. Furthermore, since the underlayer 14 is composed of diatomaceous earth, which is a material with low heat conduction, or a filler mainly composed of silica or alumina whose inside is hollow or whose density is rough, the heat of the element portion 13 is reduced. Diffusion into the insulating substrate 11 can be suppressed, so that even a low current value can be fused.

  The circuit protection element according to the present invention has an effect that it can be melted even when a low current flows, and is particularly useful in a circuit protection element that melts and protects various electronic devices when an overcurrent flows. It will be.

DESCRIPTION OF SYMBOLS 11 Insulating substrate 12 Upper surface electrode 13 Element part 14 Underlayer 15 Insulating layer 16a End surface electrode 17 1st element part 18 2nd element part 19 3rd element part

Claims (1)

An insulating substrate; a pair of upper surface electrodes provided at both ends of the insulating substrate; and an element portion formed to bridge the pair of upper surface electrodes and electrically connected to the pair of upper surface electrodes; An underlayer containing a filler composed mainly of diatomaceous earth, or silica or alumina having a hollow inside or a coarse inside, provided between the element portion and the insulating substrate; and the element An insulating layer provided so as to cover the part, and an end face electrode formed by plating connected to the upper surface of the element part at both ends of the insulating substrate, the element part is formed by sputtering, and the element The first element portion, the second element portion, and the third element portion, which are provided in order from the insulating substrate side, and the first element The second element portion is made of aluminum or an alloy of aluminum and copper, and the third element portion is made of nickel or nickel and copper. Circuit protection element made of alloy.

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