JP5381352B2 - Circuit protection element - Google Patents

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 at both ends of the upper surface of the insulating substrate 1, and a central portion of the upper surface of the insulating substrate 1. A base layer 3 made of epoxy resin, an element portion 4 provided on the top surface of the base layer 3 and electrically connected to the pair of top surface electrodes 2, and so as to cover the element portion 4 The insulating layer 5 provided and a pair of end surface electrode layers 6 formed on both end surfaces of the insulating substrate 1 were provided.

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

Japanese Patent Laid-Open No. 5-225892

  In the configuration of the above-described conventional circuit protection element, since the underlayer 3 is formed of an epoxy resin having low heat resistance, when the laser is used to form a trimming groove in the element portion 4, the underlayer 3 is heated by the laser. Since the shape becomes unstable and the shape of the element portion 4 may not be stable, there is a problem that the fusing characteristics vary.

  The present invention solves the above-described conventional problems, and an object of the present invention is to provide a circuit protection element that can stabilize the fusing characteristics.

  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. An element part electrically connected to the upper surface electrode; a base layer provided between the element part and the insulating substrate; and an insulating layer provided so as to cover the element part. Is made of a mixture of a silicon resin and a filler mainly composed of silica or alumina whose inside is hollow or whose inside density is rough , and the content of the filler constituting the base layer is 50 to 60% by volume obtained by a, according to this arrangement, since the structure of silicon resin and silica or alumina are excellent underlayer heat resistance, laser be formed trimming groove in the element portion in a laser Rather that the shape of the underlying layer becomes unstable in heat, which, since the shape of the element portion is stabilized, it is possible to stabilize the fusing characteristics, also when constructing the element portion by sputtering, It is possible to obtain an operational effect that it is possible to prevent cracks from being generated in the element portion and that the base layer is not sputtered .

  The invention according to claim 2 of the present invention is particularly one in which carbon dioxide gas is filled in the filler, and according to this configuration, the thermal conductivity of the carbon dioxide gas filled in the filler is lower than that of air. Therefore, the heat generated in the element part can be stored in the element part, and thereby, the effect of being able to quickly melt the element part when an overcurrent flows can be obtained.

  As described above, the circuit protection element of the present invention is a mixture of a silicon resin excellent in heat resistance as a base layer and a filler mainly composed of silica or alumina in which the inside is hollow or the inside density is rough. Therefore, even if a trimming groove is formed in the element part with a laser, the shape of the underlayer will not be unstable due to the heat of the laser, and this will stabilize the shape of the element part. There is an excellent effect that can be stabilized.

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 shows 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 an embodiment of the present invention includes an insulating substrate 11 and the circuit board. A pair of upper surface electrodes 12 provided at both ends of the upper surface of the insulating substrate 11 and an element portion formed so as to bridge the pair of upper surface electrodes 12 and electrically connected to the pair of upper surface electrodes 12 13, an underlayer 14 provided between the element portion 13 and the insulating substrate 11, and an insulating layer 15 provided so as to cover the element portion 13. It is composed of a mixture of a silicone resin and a filler mainly composed of silica or alumina whose inside is hollow or whose inside density is rough.

In the above configuration, the insulating substrate 11 has a square shape and is made of alumina containing 55% to 96% of Al ₂ O ₃ . The pair of upper surface electrodes 12 are provided at both ends of the upper surface of the insulating substrate 11 and are formed by printing Ag or the like. 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 constituted by a thin film layer 13a and a plating layer 13b. .

  Further, the thin film layer 13a is formed by sputtering Ti or Cu, and the plating layer 13b is provided on the upper surface of the thin film layer 13a, and the thin film layer 13a is used as a plating nucleus to form Ni, Cu, It is formed by electroless plating of Ag in order.

  Furthermore, an end face electrode layer 16 made of a silver-based material is formed on both ends of the insulating substrate 11 so as to overlap a part of the element portion 13, and the surface of the end face electrode layer 16 is plated. A film (not shown) is formed.

  Further, two trimming grooves 17 are formed in the central portion of the element portion 13 by a laser from the side surfaces of the element portion 13 facing each other toward the center direction of the element portion 13. A region surrounded by the trimming groove 17 is a fusing portion 18 that melts and breaks when an overcurrent is applied.

  The underlayer 14 is provided at the center of the upper surface of the insulating substrate 11, and the underlayer 14 is provided between the element portion 13 located between the pair of upper surface electrodes 12 and the insulating substrate 11. It has been. Further, the underlayer 14 is composed of a mixture of a silicone resin and a filler mainly composed of silica or alumina whose inside is hollow or whose inside density is rough. The filler has a particle size of about 10 μm, and the inside of silica or alumina is hollow or the inner density is coarser than the surface density. The underlayer 14 has a filler mixing ratio of 10 to 90% by volume, and the filler mixing ratio is particularly preferably 50 to 60% by volume.

  The filler is mainly composed of silica or alumina. Since the silica or alumina is scientifically stable and excellent in heat resistance and fire resistance, an overcurrent flows and the element portion 13 is heated to a high temperature. Even if it becomes, a fusing characteristic can be stabilized.

  The underlayer 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 upper surface of the underlayer 14. May be.

  The insulating layer 15 is provided so as to cover the element portion 13, and includes a first insulating layer 15 a made of a resin such as silicon that covers the fusing portion 18, and the first insulating layer 15 a. And a second insulating layer 15b made of a resin such as an epoxy provided on the upper surface.

  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 containing silver as a main component 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 baking.

  Next, a silicon resin and a filler mainly composed of silica or alumina in which the inside is hollow or the inside has a coarse density are mixed in the central portion of the insulating substrate 11 at a filler mixing ratio of 10 to 90% by volume. The paste obtained by adding an organic solvent to the mixture thus mixed is printed. Here, if the mixing ratio of the filler is smaller than 10% by volume, the difference in thermal shrinkage between the thin film layer 13a formed by sputtering and the underlayer 14 becomes large, so that the thin film layer 13a is generated by heat generation during sputtering. A crack occurs in the thin film layer 13a due to the difference in thermal shrinkage between the base layer 14 and the underlayer 14. On the other hand, when the mixing ratio of the filler is larger than 90% by volume, the unevenness of the surface of the underlayer 14 increases, so that there is a possibility that the thin film layer 13a cannot be formed or the viscosity of the underlayer 14 increases. 14 will cause a pinhole.

  Further, at this time, the interval and pressure of the three rolls are adjusted so that the air inside the filler does not escape.

  Thereafter, the base layer 14 is formed by curing at about 150 ° C. to 200 ° C. and evaporating the organic solvent.

  Next, the element portion 13 is formed on the upper surface of the base layer 14 and the pair of upper surface electrodes 12. In this case, the element portion 13 is configured to be electrically connected to the pair of upper surface electrodes 12 by bridging the pair of upper surface electrodes 12.

  The element portion 13 is first provided with a thin film layer 13a by sequentially sputtering Ti and Cu, and then Ni, Cu, and Ag are sequentially formed on the upper surface of the thin film layer 13a using the thin film layer 13a as a plating nucleus. It is formed by electroless plating and providing a plating layer 13b.

  Next, two trimming grooves 17 are formed by cutting two portions of the central portion of the element portion 13 with lasers from the side surfaces of the element portion 13 facing each other toward the central portion of the element portion 13. A fusing part 18 that melts and breaks when an overcurrent is applied is provided in a region surrounded by the groove 17.

  Next, a first insulating layer 15a is provided by forming a resin such as silicon so as to cover at least the fusing portion 18. 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 face electrode layer 16 is formed by applying and curing a resin silver paste so as to overlap a part of the element portion 13 at both ends of the insulating substrate 11. The end face electrode layer 16 may be formed by a thin film process such as sputtering.

  Finally, a plated film (not shown) having a two-layer structure of nickel and tin is formed on the end face electrode layer 16 to manufacture the circuit protection element according to one embodiment of the present invention.

  In one embodiment of the present invention described above, the base layer 14 is a mixture of a silicon resin excellent in heat resistance and a filler mainly composed of silica or alumina in which the inside is hollow or the inside density is rough. Therefore, even if the trimming groove 17 is formed in the element portion 13 with a laser, the shape of the base layer 14 is not unstable due to the heat of the laser. Since it stabilizes, the effect that a fusing characteristic can be stabilized is acquired.

  Further, since the filler contains air inside, the thermal conductivity is very low, and the silicon resin also has a low thermal conductivity, so that the heat of the element portion 13 is prevented from diffusing into the insulating substrate 11. can do. Accordingly, since the underlayer 14 can be used as a heat insulating layer, heat generated in the element portion 13 can be stored in the element portion 13 even if the cross-sectional area of the element portion 13 is increased in order to improve inrush resistance. As a result, when an overcurrent flows, the element portion 13 can be melted quickly, so that both inrush resistance and quick disconnection can be achieved.

  That is, since the filler is mainly composed of silica or alumina, the heat resistance of the underlayer 14 can be improved, thereby not only stabilizing the fusing characteristics but also containing air inside the filler. Therefore, the thermal conductivity of the underlayer 14 can be lowered, thereby making it possible to achieve both inrush resistance and quick disconnection.

  Furthermore, since the cross-sectional area of the element portion 13 can be increased, the DC resistance value of the circuit protection element can also be reduced.

  In addition, since it is necessary to make the thermal conductivity of a filler low in order to make inrush resistance and quick cut-off compatible as mentioned above, the main component is preferably silica.

  In addition, since the silicon resin can enter between the filler particles, the base layer 14 can be firmly fixed. Further, since the silicon resin has almost no water absorption, moisture and plating solution in the atmosphere are not in the base layer 14. Intrusion can be eliminated, thereby improving moisture resistance.

  Further, if carbon dioxide gas is filled in the filler, since the carbon dioxide has lower thermal conductivity than air, the heat generated in the element portion 13 can be stored in the element portion 13. When the current flows, the element portion 13 can be melted quickly. In addition to the carbon dioxide gas, helium, argon, nitrogen, oxygen, or the like can be used as the gas filled in the filler.

  In the above-described embodiment of the present invention, the circuit protection element has been described. However, the present invention can also be applied to other electronic components such as a fuse resistor that requires stabilization of the fusing characteristics.

  The circuit protection element according to the present invention has an effect that the fusing characteristics can be stabilized, and is particularly useful in a circuit protection element that melts and protects various electronic devices when an overcurrent flows. It is.

DESCRIPTION OF SYMBOLS 11 Insulating substrate 12 Upper surface electrode 13 Element part 14 Underlayer 15 Insulating layer

Claims (2)

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; A base layer provided between the element portion and the insulating substrate; and an insulating layer provided so as to cover the element portion. A circuit protection element comprising a mixture of coarse silica or alumina as a main component and a filler content of 50 to 60% by volume constituting the underlayer . The circuit protection element according to claim 1, wherein carbon dioxide gas is filled in the filler.

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