JP2014096272A - Circuit protection element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit protection element capable of being blown by a low current.SOLUTION: The circuit protection element includes: an insulation substrate 11 containing alumina as main component; a pair of upper electrodes 12 formed at both ends of the insulation substrate 11; an element part 13 which is formed to bridge the pair of upper electrodes 12 and is electrically connected to the pair of upper electrodes 12; a base layer 14 formed between the element part 13 and the insulation substrate 11; and a fusion part 15 which is formed in the element part 13 positioned on the upper face of the base layer 14. The base layer 14 is formed of a mixture of glass and plural kinds of fillers containing amorphous silica or alumina as main component which are hollow or coarse inside.

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. 4, this type of conventional circuit protection element bridges the insulating substrate 1, a pair of upper surface electrodes 2 provided at both ends of the insulating substrate 1, and the pair of upper surface electrodes 2. Element part 3, base layer 4 made of resin formed between element part 3 and insulating substrate 1, and end face formed on both ends of insulating substrate 1 and connected to the upper surface of element part 3 The electrode 5 and the insulating layer 6 that protects the element portion 3 were provided.

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

JP 2004-319168 A

  In recent years, low consumption current is demanded from the market for electronic devices. Therefore, what is required for a circuit protection element is one that melts at a low current. And in order to make it fuse with a low electric current, it was necessary to make the thickness of an element part thin.

  However, in the above conventional configuration, when the thickness of the element portion 3 is reduced, if the pressure more than necessary is applied from above during mounting or the like, the base layer 4 is made of a soft resin. It becomes easy to deform | transform, and, thereby, the element part 3 located in the upper surface of the base layer 4 will become easy to deform | transform or damage. As a result, there was a problem that the thickness of the element portion 3 could not be reduced and could not be blown with a low current.

  The present invention solves the above-described problems, and an object of the present invention is to provide a circuit protection element that can be fused at a low current.

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

  According to the first aspect of the present invention, an insulating substrate mainly composed of alumina, a pair of upper surface electrodes provided at both ends of the insulating substrate, and the pair of upper surface electrodes are formed so as to bridge. And an element portion electrically connected to the pair of upper surface electrodes, an underlayer provided between the element portion and the insulating substrate, and an element portion located on the upper surface of the underlayer. The underlayer is composed of a mixture of glass and a plurality of fillers mainly composed of silica or alumina that is hollow or rough and amorphous inside. Since the base layer is made of glass harder than resin, the base layer is resistant to stress, and even if pressure is applied from above, the base layer is hardly deformed. This also deforms the element part on the top surface of the base layer. Damage or damage Because hardly or, it is possible to reduce the thickness of the element portion, as a result, it is possible to blow at a low current. In addition, since air is contained inside the filler, the thermal conductivity of the underlayer can be lowered, thereby obtaining the effect of improving the inrush resistance and quick disconnection. It is.

  According to a second aspect of the present invention, the underlayer covers at least a part of the pair of upper surface electrodes. According to this configuration, the pair of upper surface electrodes are insulated from each other with good adhesion to each other. Since the thermal expansion coefficient of both is close, even if the element part generates heat when a current is applied, the pair of top electrodes can be firmly held between the insulating substrate and the base layer. The effect of improving the adhesion between the pair of upper surface electrodes and the base layer is obtained.

  In the invention according to claim 3 of the present invention, the base layer is formed on substantially the entire upper surface of the insulating substrate, and according to this configuration, heat can be prevented from directly escaping from the upper electrode to the insulating substrate. Fast insulation can be improved, and furthermore, since the insulating substrate and the underlayer having close thermal expansion coefficients are in close contact with each other, cracks are generated between the insulating substrate and the underlayer even if the element portion generates heat during current application. The effect that it can prevent generating is obtained.

  As described above, the circuit protection element of the present invention comprises an underlayer composed of a mixture of glass harder than a resin and a plurality of fillers mainly composed of silica or alumina that is hollow or rough inside and is amorphous. Therefore, the underlying layer becomes strong against stress, and even if pressure is applied from above, the underlying layer is hardly deformed, which makes it difficult to deform or damage the element portion on the upper surface of the underlying layer. As a result, there is an effect that it can be melted at a low current.

Sectional drawing of the circuit protection element in one embodiment of this invention Sectional drawing of the other example of the circuit protection element Sectional drawing of the other example of the circuit protection element 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, a base layer 14 provided between the element part 13 and the insulating substrate 11, and a fusing part 15 formed in the element part 13 located on the upper surface of the base layer 14, The underlayer 14 is made of a mixture of glass and a plurality of fillers mainly composed of amorphous silica that is hollow or rough inside.

  Further, 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 a plating film is formed on the surface of the end face electrode layer 16. (Not shown) is formed. Further, an insulating layer 17 made of silicon resin is provided so as to cover the element portion 13.

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 formed by sputtering so as to cover substantially the entire surface of the insulating substrate 11, and is provided on the upper surface of the base layer 14 and the pair of upper surface electrodes 12. The element portion 13 is formed by sputtering Ti, Cu, and then sputtering Al, Zn, and Sn. Thus, since the element part 13 is comprised only by sputtering, the thickness of the element part 13 can be made thin. In addition, the element part 13 may use another material, and also may form it by thinly plating.

  Further, two trimming grooves 18 are formed in the central portion of the element portion 13 by a laser from the side surface of the element portion 13 facing each other toward the center direction of the element portion 13. A region surrounded by the trimming groove 18 is a fusing portion 15 that melts and breaks when an overcurrent is applied. The fusing part 15 may be formed by patterning the element part 13.

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 glass made of SiO ₂ or the like and a filler mainly composed of silica or alumina whose inside is hollow or whose inside density is rough. Further, 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 a filler mixing ratio of 50 to 60% by volume is particularly preferable. Here, if the mixing ratio of the filler is smaller than 10% by volume, the air inside the underlayer 14 is reduced, so that the heat generated in the element portion 13 may easily escape to the insulating substrate 11, thereby In some cases, quick disconnection may deteriorate (decrease). In addition, if the mixing ratio of the filler is larger than 90% by volume, the surface layer of the base layer 14 becomes uneven, so that there is a possibility that the element portion 13 cannot be formed.

  Further, this filler is mainly composed of silica or alumina, and since this silica or alumina is chemically stable and excellent in heat resistance and fire resistance, an overcurrent flows and the element portion 13 is heated to a high temperature. Even in this case, the fusing characteristics and the insulation resistance after fusing can be stabilized.

  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. The pair of upper surface electrodes 12 are formed by baking at about 850 ° C.

  Next, in the central part of the insulating substrate 11, glass and a filler mainly composed of silica or alumina having a hollow inside or a coarse inside density are mixed at a filler mixing ratio of 10 to 90% by volume. The mixture thus mixed is printed. Thereafter, the base layer 14 is formed by baking at about 850 ° C.

  At this time, since the base layer 14 is mainly composed of glass, the pair of upper surface electrodes 12 and the base layer 14 can be fired at the same time, thereby improving productivity.

  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 formed by first sputtering Ti or Cu, and then sputtering Al, Zn, and Sn in this order.

  Next, two trimming grooves 18 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 direction of the element portion 13. A fusing part 15 that melts and breaks when an overcurrent is applied is provided in a region surrounded by the groove 18.

  Next, a resin such as silicon is formed on the element portion 13 so as to cover at least the fusing portion 15, and the insulating layer 17 is provided.

  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, a plurality of fillers mainly composed of glass that is harder than a resin, that is, not easily deformed even when stress is applied, and silica or alumina that is hollow or rough and amorphous inside. Since the underlayer 14 is composed of a mixture of the underlayer 14 and the underlayer 14 is resistant to stress, the underlayer 14 is hardly deformed even when pressure is applied from above, so that the underlayer 14 is positioned on the upper surface of the underlayer 14. Even if the thickness of the element portion 13 to be reduced is reduced, the element portion 13 is difficult to be deformed or damaged, so that an effect that the element portion 13 can be blown even with a low current, for example, in the order of mA is obtained.

  Here, when a mixture obtained by mixing a filler such as silicon with a resin instead of glass is used for the underlayer 14, there is no problem with a normal current, but since the resin is softer than glass, the element portion 13 on the underlayer 14 is not affected. Is easily deformed or damaged, and in order to prevent this, the thickness of the element portion 13 must be increased, and it is difficult to melt the element portion 13 at a low current value. Furthermore, it is conceivable to increase the strength against the stress of the element portion 13 itself. However, in this case as well, it is necessary to increase the thickness of the element portion 13, so that it is difficult to melt at a low current value. Therefore, in order to cope with a low current, it is necessary to configure the element portion 13 only by sputtering as in the present invention and to reduce its thickness.

  Further, since the filler contains air inside, the thermal conductivity is very low, and the glass also has low thermal conductivity, so that the heat of the element portion 13 is prevented from diffusing into the insulating substrate 11. be able to. 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.

  Note that, as described above, in order to achieve both inrush resistance and quick disconnection, it is necessary to lower the thermal conductivity of the filler. Therefore, the main component is preferably silica.

  Furthermore, since the base layer 14 contains glass, the adhesion between the insulating substrate 11 made of alumina and the base layer 14 is improved.

  In the above-described embodiment of the present invention, the base layer 14 is positioned between the pair of upper surface electrodes 12, but the base layer 14 is at least part of the pair of upper surface electrodes 12, as shown in FIG. May be covered.

With this configuration, the thermal expansion coefficient of alumina constituting the insulating substrate 11 is 6 to 8 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of the glass constituting the base layer 14 is 5 to 6 × 10 ⁻⁶ / ° C. Since the thermal expansion coefficient is close and the pair of upper surface electrodes 12 are sandwiched between the insulating substrate 11 and the base layer 14 having good adhesion to each other, the pair of upper surface electrodes 12 are firmly formed by the insulating substrate 11 and the base layer 14. Thus, even if the element portion 13 generates heat when a current is applied, the adhesion between the pair of upper surface electrodes 12 and the base layer 14 does not deteriorate.

  At this time, when a mixture obtained by mixing a filler such as silicon instead of glass is used for the base layer 14, the adhesion with the insulating substrate 11 and the upper surface electrode 12 is poor, and thus such an effect can be obtained. Can not.

  Furthermore, when the length of the base layer 14 is made constant, the distance between the pair of upper surface electrodes 12 can be shortened, so that downsizing can be realized.

  As shown in FIG. 3, the base layer 14 is formed not only on the central portion of the insulating substrate 11 but also on substantially the entire top surface of the insulating substrate 11, and the element portion 13 is formed on the top surface of the base layer 14. A pair of upper surface electrodes 12 may be formed on both ends of the upper surface of the substrate so that the pair of upper surface electrodes 12 and the insulating substrate 11 do not contact each other.

  With this configuration, heat can be prevented from directly escaping from the upper surface electrode 12 to the insulating substrate 11, so that quick disconnection can be improved. In addition, since the insulating substrate 11 and the underlayer 14 having close thermal expansion coefficients are in close contact with each other, even if the element portion 13 generates heat when a current is applied, the adhesion between the insulating substrate 11 and the underlayer 14 is reduced. Can be prevented. Further, since the main component of the underlayer 14 is glass, the underlayer 14 and the top electrode 12 can be fired at the same time, so that the adhesion between the underlayer 14 and the top electrode 12 can be improved.

  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 it can be melted at a low current, and is particularly useful in a circuit protection element that melts and protects various electronic devices when an overcurrent flows. is there.

DESCRIPTION OF SYMBOLS 11 Insulating board 12 Upper surface electrode 13 Element part 14 Underlayer 15 Fusing part

Claims (3)

An insulating substrate mainly composed of alumina, a pair of upper surface electrodes provided at both ends of the insulating substrate, and formed to bridge the pair of upper surface electrodes, and electrically connected to the pair of upper surface electrodes. A connected element part; a base layer provided between the element part and the insulating substrate; and a fusing part formed in the element part located on the upper surface of the base layer; And a mixture of a plurality of fillers mainly composed of silica or alumina, which is hollow or rough and amorphous inside. The circuit protection element according to claim 1, wherein the underlayer covers at least a part of the pair of upper surface electrodes. The circuit protection element according to claim 1, wherein the base layer is formed on substantially the entire upper surface of the insulating substrate.

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