JP5586370B2 - Ceramic fuse and ceramic fuse package - Google Patents

Description

  The present invention relates to a ceramic fuse and a ceramic fuse package that cause an electronic device to be urgently stopped based on an abnormality in current or temperature of the electronic device.

  The ceramic fuse is built into the external device, and the thermal fuse element is melted by setting the heating resistor to a high temperature based on the signal from the outside, so that the electrical connection with the external device is eliminated and the external device is urgently stopped. Let Such a ceramic fuse has been proposed as a technique for preventing malfunction of an external device (for example, see Patent Document 1).

  In recent years, in the development of ceramic fuses, a technique for improving functionality capable of detecting a plurality of abnormalities in an external device has been demanded.

JP-A-11-96871

  The present invention has been made in view of the above, and an object thereof is to provide a multifunctional ceramic fuse and a ceramic fuse package.

A ceramic fuse according to an embodiment of the present invention includes a laminated ceramic substrate having a first mounting surface, a second mounting surface, and a third mounting surface , and a thermal fuse element provided on the first mounting surface of the ceramic substrate . A heating resistor provided in the ceramic substrate and disposed in a region overlapping with the thermal fuse element when seen through, and a current value of a flowing current provided on the second mounting surface of the ceramic substrate is not less than a predetermined value. A current fuse element that blows when the current value is reached, and a low melting point alloy that is provided on the third mounting surface of the ceramic substrate and that blows when the temperature reaches a predetermined temperature or higher.

  According to the present invention, a multifunctional ceramic fuse and a ceramic fuse package can be provided.

It is a perspective view which shows the external appearance of the ceramic fuse which concerns on this embodiment. It is a perspective view which shows the state except the low melting-point alloy of the ceramic fuse which concerns on this embodiment. It is sectional drawing of the ceramic fuse along X-X 'of FIG. FIG. 2 is a cross-sectional view of the ceramic fuse taken along Y-Y ′ in FIG. 1. It is a permeation | transmission perspective view which shows a current fuse element and a heating resistor. It is a permeation | transmission perspective view which shows a thermal fuse element.

  Embodiments of a ceramic fuse according to the present invention will be described below with reference to the accompanying drawings. In addition, this invention shall not be limited to the following embodiment.

<Schematic configuration of ceramic fuse>
FIG. 1 is a schematic perspective view of a ceramic fuse according to the present embodiment. FIG. 2 is a schematic perspective view of the ceramic fuse in a state where the low melting point alloy is removed. FIG. 3 is a cross-sectional view of the ceramic fuse taken along the line XX ′ in FIG. 4 is a cross-sectional view of the ceramic fuse taken along YY ′ of FIG. FIG. 5 is a transparent perspective view of one layer of the ceramic substrate showing the current fuse element and the heating resistor of the ceramic fuse. FIG. 6 is a transparent perspective view of one layer of the ceramic substrate showing the thermal fuse element of the ceramic fuse.

  The ceramic fuse of this embodiment is used as a circuit protection element of an external device, and is incorporated in a specific circuit together with an abnormality detector, and has a plurality of functions. The first function is that when an abnormality is detected in an external device with the ceramic fuse installed in the external device, the abnormality detector energizes the heating resistor and blows the thermal fuse element, thereby operating the circuit. It includes a function for emergency stop.

  The second function is that the current fuse element of the ceramic fuse is electrically connected to the external device, and if a current value exceeding a predetermined value flows to the external device, the current fuse element in the ceramic fuse A current value greater than a predetermined value flows. As a result, the ceramic fuse includes a function of urgently stopping the operation of the circuit when the current fuse element is blown.

  Furthermore, as a third function, the low melting point alloy of the ceramic fuse incorporated in the external device detects abnormal heat generation in the external device, and the low melting point alloy is melted to stop the operation of the circuit urgently. Includes functionality.

  The ceramic fuse 1 according to this embodiment includes a ceramic fuse package 2 and a thermal fuse element 3 mounted on the ceramic fuse package 2.

  The ceramic fuse package 2 includes a first mounting surface R1 on which a thermal fuse element is mounted, and a second mounting surface R4 on which a current fuse element that melts when a current value of a flowing current reaches a predetermined current value or more, A ceramic substrate 4 having a third mounting surface R3 on which a low-melting-point alloy that melts when the temperature exceeds a predetermined temperature is mounted, and a first mounting that is provided on the ceramic substrate 4 and is mounted with a thermal fuse element as seen through the plane. And a heating resistor 5 provided in a region overlapping the surface R1.

  The ceramic substrate 4 is an insulating substrate and has a structure in which a plurality of substrates are stacked. For example, the ceramic substrate 4 is made of a ceramic material such as alumina, mullite, or aluminum nitride, or a glass ceramic material. Or it consists of a composite material which mixed several materials among these materials. In addition, the thickness of the ceramic substrate 4 is set to 0.5 mm or more and 3 mm or less, for example. Further, the thermal conductivity of the ceramic substrate 4 is set to, for example, 14 W / m · K or more and 200 W / m · K or less. The ceramic substrate 4 is a laminate of five ceramic plates.

  A recess P <b> 1 is provided on the upper surface of the ceramic substrate 4 positioned at the uppermost layer of the ceramic substrate 4. The low melting point alloy 7 is disposed in the recess P1. In addition, a recess P <b> 2 is provided on the lower surface of the ceramic substrate 4 positioned at the lowermost layer of the ceramic substrate 4. The thermal fuse element 3 is disposed in the recess P2.

  A conductive layer 8 that is electrically connected to the low melting point alloy 7 when the low melting point alloy 7 is mounted is formed in the recess P <b> 1 of the ceramic substrate 4. A part of the conductive layer 8 is connected to the heating resistor 5 and the current fuse element 6 formed inside the ceramic substrate 4. In the present embodiment, the conductive layer 8 is electrically opened when the low melting point alloy 7 is blown, when the temperature fuse element 3 is blown, or when the current fuse element 6 is blown. Is formed. The conductive layer 8 is electrically connected to the low melting point alloy 7, the temperature fuse element 3, and the current fuse element 6, and is formed in an arbitrary pattern. The width of the conductive layer 8 is set to 0.05 mm or more and 3 mm or less, for example. Here, the width of the conductive layer 8 refers to the width in the direction orthogonal to the direction of the current flowing through the conductive layer 8.

  The conductive layer 8 is made of, for example, a metal material such as tungsten, molybdenum, nickel, copper, silver, gold, or aluminum, or an alloy thereof, or a composite material obtained by mixing a plurality of these materials, or of those materials. It consists of a composite layer.

  The heating resistor 5 is formed in a closed space P3 provided in the ceramic substrate 4. The heating resistor 5 transmits the temperature of heat generated to the thermal fuse element 3 and melts the thermal fuse element 3. The heating resistor 5 is a region that overlaps the thermal fuse element 3 in a plan view, and is provided via the thermal fuse element 3 and the ceramic substrate 4.

  The heating resistor 5 is energized to the heating resistor 5 through the conductive layer 8 by detecting the abnormality of the circuit by the abnormality detector incorporated in the circuit together with the ceramic fuse. And the temperature of the heating resistor 5 rises. Furthermore, the temperature is transmitted to the thermal fuse element 3 through the ceramic substrate 4, and the thermal fuse element 3 can be blown when the thermal fuse element 3 reaches a predetermined temperature or higher.

  The heating resistor 5 has one end connected to the conductive layer 8 and the other end connected to the conductive layer 8. The heating resistor 5 has a resistance value for securing a required amount of heat generation. As an example of the resistance value securing method, the pattern shape is formed by being bent many times inside the ceramic substrate 4. ing. The width of the heating resistor 5 is set to 0.05 mm or more and 0.3 mm or less, for example. Here, the width of the heating resistor 5 refers to the width in the direction orthogonal to the direction of the current flowing through the heating resistor 5. The heating resistor 5 is made of a metallized material containing, for example, tungsten or molybdenum.

  The current fuse element 6 is blown when a current value exceeding a predetermined value flows. The current fuse element 6 is provided in a gap P <b> 2 provided in the ceramic substrate 4, and is arranged in parallel with the heating resistor 5. In P2, the current fuse element 6 and the heating resistor 5 may be provided side by side or in a separate gap. The current fuse element 6 has a larger resistance value per unit length at the center F1 than at both ends F2. The current fuse element 6 is provided on the surface in the gap P2 in the ceramic substrate 4 by a metallization technique. Alternatively, the current fuse element 6 may be mounted on a mounting portion for mounting the current fuse element 6 provided in advance in a gap provided separately on the upper and lower surfaces of the ceramic substrate 4.

The current fuse element 6 is energized through the conductive layer 8. At this time, when the current value becomes an overcurrent due to some abnormality, and the current value becomes a predetermined current value or more, the current fuse element 6 is blown.

  If the resistance value per unit length of the central portion of the current fuse element 6 is larger than the resistance value per unit length of the both end portions F2, the width of the central portion F1 of the current fuse element 6 is increased. You may set so that a width | variety may become narrow gradually toward the center of the center part F1. Further, the center of the current fuse element 6 at the center F1 is selected from a material having a larger resistance temperature coefficient than the material constituting the both ends F2 of the current fuse element 6 around it. As a result, the resistance value per unit length of the central portion F1 of the current fuse element 6 can be made larger than the resistance value per unit length of both ends F2 of the current fuse element 6, and further, the current fuse element The temperature rise of the center part F1 of 6 can be improved effectively. As a result, the center portion F1 of the current fuse element 6 can be quickly melted. Note that the current fuse element 6 is designed to be blown when, for example, a current value of 0.3 A or more is reached.

  As another example of a method for effectively improving the temperature rise in the central portion F1, it is also effective to provide a difference in resistance temperature coefficient between the central portion and both end portions. For example, the central portion F1 of the current fuse element 6 is made of, for example, a metallized material containing tungsten or molybdenum, the resistance temperature coefficient is, for example, 4000 ppm or more, and both ends F2 of the current fuse element 6 are, for example, tungsten. The temperature coefficient of resistance made of a metallized material containing molybdenum, nickel, rhenium, or the like is set to 3000 ppm or less, for example.

  The resistance temperature coefficient of the heating resistor 5 is a positive characteristic resistance temperature coefficient. When a current flows through the central portion F1 of the heating resistor 5 and both ends F2 of the heating resistor 5 to generate heat, the temperature rises depending on the amount of generated heat, and the resistance value increases. At this time, the temperature rise of the central portion F1 and both end portions F2 of the heating resistor 5 is affected by the heat radiation of both portions, and the temperature rise of the central portion F1 of the heating resistor 5 becomes large. The increasing range of the resistance value is larger than the increasing range of both end portions F2. Then, the partial pressure applied to the central portion F1 becomes larger than the partial pressure applied to both end portions F2, and the amount of heat generated in the central portion F1 increases, so that the central portion F1 of the heating resistor 5 is effective. The temperature rises. As a result, the central portion F1 of the heating resistor 5 can be heated to a high temperature in a short time, and the thermal fuse element 3 can be quickly blown due to the heat generated in the heating resistor 5.

  A low melting point alloy 7 is provided in the concave portion P1 of the uppermost layer of the ceramic substrate 4. The low melting point alloy 7 has a function of fusing when the temperature of the low melting point alloy 7 rises to a predetermined value or higher. When the low melting point alloy 7 is melted, the conductive layer 8 is electrically opened. One end of the low melting point alloy 7 is electrically connected to the conductive layer 8 extended from the inside of the ceramic substrate 4 to the lower surface of the ceramic substrate 4 through one of the current fuse element and the thermal fuse element. Further, the other end of the low melting point alloy 7 is electrically connected to the conductive layer 8 extended to the lower surface of the ceramic substrate 4 through either the temperature fuse element or the current fuse element. The order of forming the current fuse element, the low melting point alloy, and the thermal fuse element may be any order.

The low melting point alloy 7 fills the concave portion P1 provided on the upper surface of the ceramic substrate 4 with a flux and covers the upper portion of the low melting point alloy 7 to prevent the low melting point alloy 7 from being oxidized, and to transfer heat to the molten alloy. It is possible to accelerate the melting and separation of the low melting point alloy. In a mounted state in which the pads provided on the lower surface of the ceramic substrate 4 are electrically connected to an external circuit, a temperature rise due to heat generated by an external device disposed above the ceramic substrate 4 is transmitted to the ceramic fuse 1. To do. At that time, the shorter the heat transfer distance between the low melting point alloy 7 and the external device, the more easily affected by the temperature change of the external device. Thus, the ceramic fuse 1 is designed to be easily transmitted to the low melting point alloy 7.

  The low melting point alloy 7 is used to prevent the external device from being destroyed, smoked, or burned due to the abnormal temperature when the external device has an abnormal temperature. When the external device reaches an abnormal temperature, the temperature is transmitted to the low melting point alloy 7 of the ceramic fuse 1 and the low melting point alloy 7 is melted. Then, the conductive layer 8 of the ceramic fuse 1 is electrically opened, and the external device can be urgently stopped. The low melting point alloy 7 is made of, for example, a material such as indium, bismuth, tin, or zinc, or a mixed material thereof. The low-melting-point alloy 7 is designed to be melted when, for example, 120 degrees or more.

  The thermal fuse element 3 is mounted in the recess P2 in the lowermost layer of the ceramic substrate 4. The thermal fuse element 3 is blown when the temperature exceeds a specific temperature. The thermal fuse element 3 is made of, for example, a material such as indium, bismuth, tin, or zinc, or a mixed material thereof. Further, the melting point at which the thermal fuse element 3 melts is set to, for example, 80 ° C. or higher and 180 ° C. or lower.

  The thermal fuse element 3 is provided in a region that overlaps the heating resistor 5 when seen in a plan view. Further, when the thermal fuse element 3 is provided so as not to protrude from the region where the heating resistor 5 exists when seen in a plan view, the temperature of the heating resistor 5 can be efficiently transmitted to the thermal fuse element 3. . When the temperature fuse element 3 is set in a rectangular shape, the thickness of the temperature fuse element 3 is, for example, 0.1 mm or more and 3.0 mm or less, and the vertical or horizontal length of one side when viewed from above. However, it is set to 0.1 mm or more and 10.0 mm or less, for example.

  As described above, in the present embodiment, the ceramic fuse 1 incorporated in an external circuit quickly rises in temperature when a current flows through the heating resistor 5, and the thermal fuse element 3 can be blown by the heat. Further, according to the present embodiment, the current fuse element 6 is blown when the current value becomes an overcurrent due to some abnormality and becomes a predetermined current value or more. Furthermore, according to this embodiment, when the external circuit becomes abnormally high in temperature, the low melting point alloy 7 is melted. As a result, the external circuit can be urgently stopped, and damage can be minimized. Thus, the ceramic fuse 1 according to the present embodiment can detect any of a plurality of abnormalities in the external circuit, and has multi-functionality. According to this embodiment, the multifunctional ceramic fuse 1 and the ceramic fuse package 2 can be provided.

  In addition, this invention is not limited to the above-mentioned form, A various change, improvement, etc. are possible in the range which does not deviate from the summary of this invention. In the above-described embodiment, the thermal fuse element and the low melting point alloy are provided separately. However, the ceramic fuse package includes a single element that functions as both the thermal fuse element and the low melting point alloy. There may be. In the above-described embodiment, the current fuse element is formed by patterning using the metallization method, but the present invention is not limited to this. For example, a separate current fuse element may be mounted separately. In addition, the closed space P3 is divided into two, the heating resistor 5 may be provided on one side, and the current fuse element 6 may be provided on the other side. By dividing the closed space P3 into two, it is possible to suppress the heat generated in the heating resistor 5 and the heat generated in the current fuse element 6 from being mixed, and the accuracy of the ceramic fuse 1 as a protective element can be reduced. Can be increased. The closed space P3 is hermetically sealed in a reducing or neutral gas atmosphere or a vacuum atmosphere. In the above-described embodiment, the current fuse element is provided in the closed space P3. However, the present invention is not limited to this. For example, a recess may be provided in the outermost layer of the ceramic substrate, and a current fuse element may be provided in the recess.

  Further, in the above-described embodiment, the ceramic fuse package has a structure in which the temperature fuse element, the current fuse element, and the low melting point alloy are incorporated. However, the present invention is not limited to this. For example, the ceramic fuse package may have a structure in which functions of only the thermal fuse element and the low melting point alloy are incorporated without providing the current fuse element. In such a case, only one of the thermal fuse element and the low melting point alloy may be used, and the structure may be used for both functions.

<Manufacturing method of ceramic fuse>
Here, a method for manufacturing the ceramic fuse 1 and the ceramic fuse package 2 shown in FIG. 1 will be described.

  First, five ceramic plates constituting the ceramic substrate 4 are prepared. When the five ceramic plates constituting the ceramic substrate 4 are made of, for example, an aluminum oxide sintered body, an organic binder, a plasticizer, a solvent, and the like are added to raw powders such as aluminum oxide, silicon oxide, magnesium oxide, and calcium oxide. Addition and mixing to obtain a mixture. And the green sheet is shape | molded using the mixture.

  Moreover, a high melting point metal powder such as tungsten or molybdenum is prepared, and an organic binder, a plasticizer, a solvent, or the like is added to and mixed with the powder to obtain a metal paste.

  Then, through holes are provided at predetermined positions of the ceramic plate in the green sheet state, and the conductive layer 8 and the via conductor are formed by applying a metal paste using, for example, a screen printing method. Similarly, the heating resistor 5 and the current fuse element 6 are formed, and a metal paste as a castellation is applied to the side surface of the ceramic plate. Thereafter, five ceramic plates are laminated to produce the ceramic substrate 4.

  Next, firing is performed at a temperature of about 1600 degrees in a state where the prepared ceramic substrate 4 before sintering is connected. Then, the ceramic substrate 4 is integrally sintered. Necessary plating is performed on the surface of the thermal fuse element mounting portion of the integrally sintered member. Here, the manufacturing method of the individual product for the ceramic fuse has been described. However, the manufacturing with a multi-piece sheet shape is preferable from the viewpoint of mass productivity and cost. In this way, the ceramic fuse package 2 can be manufactured.

  Next, the thermal fuse element 3 is mounted at a predetermined position in the recess P2 in the lowermost layer of the ceramic substrate 4, and the low melting point alloy is mounted in the recess P1 in the uppermost layer. Then, the thermal fuse element 3 and the conductive layer 8 are electrically connected. As a result, the ceramic fuse 1 can be manufactured.

DESCRIPTION OF SYMBOLS 1 Ceramic fuse 2 Ceramic fuse package 3 Thermal fuse element 4 Ceramic substrate 5 Heating resistor 6 Current fuse element 7 Low melting point alloy 8 Conductive layer F1 Center part F2 End part

Claims (4)

A laminated ceramic substrate having a first mounting surface, a second mounting surface and a third mounting surface ;
A thermal fuse element provided on the first mounting surface of the ceramic substrate;
A heating resistor provided on the ceramic substrate and disposed in a region that overlaps the thermal fuse element as seen through a plane;
A current fuse element that is provided on the second mounting surface of the ceramic substrate and that blows when a current value of a flowing current reaches a predetermined current value;
A ceramic fuse, comprising: a low melting point alloy provided on a third mounting surface of the ceramic substrate , which melts when a temperature exceeds a predetermined temperature. The ceramic fuse of claim 1,
The ceramic fuse, wherein the low-melting-point alloy is disposed in a recess provided on an upper surface of the ceramic substrate. The ceramic fuse according to claim 1 or 2, wherein
The ceramic fuse, wherein the heating resistor and the current fuse element are arranged in a closed space provided in the ceramic substrate. 4. The ceramic fuse according to claim 1, wherein the thermal fuse element is disposed in a recess provided in a lower surface of the ceramic substrate. 5.

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