JP4693001B2 - Chip-type circuit protection element - Google Patents

Description

  The present invention relates to a chip-shaped circuit protection element.

  An example of a conventional chip-type fuse resistor described in Patent Document 1 will be described. An undercoat glass layer is formed on the upper surface of an insulating substrate such as alumina, and a pair of thick film electrodes is formed thereon. A fuse resistor is formed to connect the thick film electrodes. The fuse resistor is composed of a wide junction with the thick film electrode and a narrow and rectangular functional part having a predetermined pattern width therebetween, that is, a fusing part. An end face electrode connected to the thick film electrode and reaching the lower surface of the insulating substrate is formed on both end portions of the insulating substrate, and an overcoat glass layer is formed on the uppermost portion. The overcoat glass layer is formed so as to completely cover the fuse resistor as a protective exterior film. Since the fuse resistor is covered with the upper and lower glass layers, a heat storage effect is generated in which heat generated from the fuse resistor is difficult to dissipate, and the fuse resistor can be blown at high speed even with a small overcurrent.

As the upper and lower glass layers, as described in Patent Document 2, the overcoat glass layer (protective glass layer) is made of a glass having a softening point lower than the softening point of the glass of the undercoat glass layer (underlying glass layer). Once formed, when an overcurrent flows, the overcoat glass layer first melts while reducing the heat radiation of the fuse resistor, and reduces the wettability between the fuse resistor and the underglass layer, thereby reducing the fuse resistance. It can be blown by the cohesive force of the body, and even if an overcurrent flows, the quick-movability of the fusing characteristics can be improved without causing smoke and the like, and the fusing can be surely performed.
Japanese Patent Laid-Open No. 4-65046 Japanese Patent No. 26008031

  As described above, in the chip-type fuse resistor, the fuse resistor is formed on the base glass layer, and the surface is covered with the protective glass layer. This glass layer on both sides brings about a heat storage effect, and in order to improve the quick movement, it is formed by a glass having a softening point such that the protective glass layer melts when the protective glass layer is melted by overcurrent. It is good to do.

  However, in the conventional chip type circuit protection element in which the fuse resistor is sandwiched between the base glass layer and the protective glass layer, the protective glass layer is formed so as to completely cover the fuse resistor. When the heat capacity of the glass layer is large and an overcurrent flows, a large calorific value is required until the protective glass layer is dissolved, which is not preferable from the viewpoint of rapid movement. If the thickness of the protective glass layer is reduced, the heat storage characteristics are deteriorated and the fusing characteristics are deteriorated. Further, if the portion covering the fuse resistor is restricted, there is a problem that the protective effect is deteriorated.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a chip-type circuit protection element that can improve fast dynamics and has a sufficient protective effect.

  The present invention relates to a chip-type circuit protection element, comprising: an insulating substrate; a base glass layer laminated on the insulating substrate; and both ends on the base glass layer, and outer end portions of the base glass layer A pair of metal layers disposed so as to be located on the inner side of the end portion of the layer, a pair of wide electrode portions disposed so as to cover the metal layer, and a narrow width connecting the electrode portions A fuse element composed of a fusing part, a glass layer having a width smaller than the width of the electrode part covering a part of the fuse element including the fusing part, covering the glass layer, and both ends thereof on the metal layer A protective resin layer that is positioned and wider than the electrode portion, an end electrode that is not connected to the pair of metal layers and is at least partially stacked on the electrode portion, and the end electrode And a parent solder layer coated with

  According to the present invention, since the volume of the glass layer can be reduced, the speed of fusing against overcurrent can be improved, and the protective resin layer can enhance the protective effect and also improve the heat storage property, and further, the metal By providing the layer, generation of cracks in the underlying glass layer can be suppressed.

  First, in the development of the chip-type circuit protection element of the present invention, a prototype chip-type circuit protection element will be described with reference to FIG. 3A is a cross-sectional view, FIG. 3B is a plan view for explaining a glass layer, and FIG. 3C is a plan view for explaining a protective resin layer. In the figure, 1 is an insulating substrate, 2 is a base glass layer, 3 is a back electrode, 4 is a fuse element, 4a is a fusing part, 4b is an electrode part, 5 is a glass layer, 6 is a protective resin layer, and 7 is an end face electrode. , 8 is a parent solder layer. 3A is a cross-sectional view taken along line AA in FIG. 3B, and in FIG. 3B, the range in which the glass layer 5 is formed is hatched in broken lines. In FIG. 3C, the range in which the protective resin layer 6 is formed is indicated by dashed hatching.

  In this prototype, the volume of the glass layer 5 formed on the fuse element 4 is reduced to reduce the heat capacity to be melted by overcurrent, and the glass layer 5 is covered with the protective resin layer 6 to store heat. It has an action and a protective action. Since the fuse element 4 is provided with the wide electrode portions 4b on both sides of the narrow fusing portion 4a and the end surface electrode 7 is laminated on a part of the electrode portion 4b, a so-called front electrode is not provided.

  A thermal shock test was performed on the prototype chip-type circuit protection element. The test method is to prepare a thermostatic bath of -55 ° C and a thermostatic bath of + 125 ° C. The prototype chip-type circuit protection element is mounted on a circuit board and fixed by soldering. The sample is taken out after 30 minutes, and immediately + 125 ° C. is also put in a thermostatic bath for 30 minutes. This is set as one cycle, and the resistance value is measured every 10 cycles, and the change rate R of the resistance value is measured. The result of calculating% is shown in FIG. The number of chip-type circuit protection elements tested was 20. The change range shown vertically is the range of the change rate of the chip-type circuit protection element in which the maximum value and the minimum value are shown, and the change rate of the chip-type circuit protection element in which the minimum value is shown is 0%. The circles are average values. In some cases, the resistance value began to change in the 10-cycle thermal shock test, and in other cases, the change rate was as high as 10% in the 50-cycle thermal shock test. 5 and 6 show cross-sectional electron micrographs of the chip-type circuit protection element having a large change rate, which was removed from the circuit board by melting the solder. FIG. 6 is an enlarged micrograph of the upper left end of FIG. In the photograph of FIG. 5, the white solder layer remains on both outer sides, the parent solder layer and the end face electrode are seen on the inside, and the substrate and the underlying glass layer are seen on the inner rectangular portion. The ratio of the thickness of the substrate and the underlying glass layer is approximately 2: 1, and the surface of the underlying glass layer is a fuse resistance layer (which can be clearly seen in the vicinity of both ends of the underlying glass layer, but appears thin white. ), And a protective resin layer can be seen on the glass layer on the glass layer, and on the glass layer with a gray color close to black. However, since the protective resin layer formed on the uppermost surface is a gray color close to the black background, it is difficult to recognize the protective resin layer when printing, but the drawing data attached to the patent application In the display, the protective resin layer can be clearly recognized. It turns out that the crack has generate | occur | produced in the base glass layer toward the diagonal left direction from the lower end part of the left end part of the protective resin layer. This crack can be clearly seen in the electron micrograph of FIG. 6 in which the magnification is higher than that in FIG.

  When countermeasures for cracks were examined, in the base glass layer, when the temperature decreased or increased in the region covered with the protective resin layer and the region covered with the end face electrode and the parent solder layer. As a result of different temperature conditions and different shrinkage or expansion, it was estimated that distortion occurred at the boundary portion of the region and cracks occurred. Based on this assumption, a prototype of a metal layer with better thermal conductivity than glass was provided between the underlying glass layer and the fuse element in the neighboring region including the boundary between the two regions. According to the thermal shock test under the same conditions as described above, the resistance value hardly changed, and this data is not shown in FIG. 4, but most of the maximum value, minimum value, and average value are Was 0%, and none showed a change rate of 1%. Even if the micrograph of the cross section of FIG. 7 and the micrograph of the boundary portion between the region covered with the protective resin layer and the region covered with the end face electrode and the parent solder layer in FIG. I understand. It has also been found that the heat capacity per unit area of the metal layer is greater than the heat capacity per unit area of the fuse element, and the metal layer is preferably formed of a thick film material.

  The chip-type circuit protection element of the present invention developed based on the above consideration will be described with reference to FIG. 1A is a sectional view, FIG. 1B is a plan view for explaining a glass layer, and FIG. 1C is a plan view for explaining a protective resin layer. In the figure, 1 is an insulating substrate, 2 is a base glass layer, 3 is a back electrode, 4 is a fuse element, 4a is a fusing part, 4b is an electrode part, 5 is a glass layer, 6 is a protective resin layer, and 7 is an end face electrode. , 8 is a parent solder layer, and 9 is a metal layer. 1A is a cross-sectional view taken along line AA in FIG. 1B, and in FIG. 1B, the range in which the glass layer 5 is formed is hatched in broken lines. In FIG. 1C, the range in which the protective resin layer 6 is formed is indicated by dashed hatching. In FIGS. 1B and 1C, the metal layer 9 is below the fuse element 4 and is shown by a broken line.

  The insulating substrate 1 is made of a heat-resistant material such as ceramics, and a base glass layer 2 is provided on the surface of one surface thereof. Although a pair of back surface electrodes 3 is provided at both ends of the other surface of the insulating substrate 1, the back surface electrodes 3 are not necessarily provided. A pair of metal layers 9 are provided on the end side of the surface of the underlying glass layer 2. The metal layer 9 is provided at a distance from the end surface of the insulating substrate 1 and also at a distance from the side surface (an end surface orthogonal to the end surface). The fuse element 4 includes a pair of wide portions provided so as to cover the metal layer 9 and a narrow portion provided so as to connect the wide portions. The wide portion functions as the electrode portion 4b, and the narrow portion functions as the fusing portion 4a. A glass layer 5 is provided so as to cover the fusing part 4a. Further, a protective resin layer 6 is provided over the entire width of the insulating substrate 1 so as to cover the glass layer 5 except for a region where the electrode portion 4 b of the fuse element 4 is connected to the end face electrode 7. The protective resin layer 6 is. It is not necessary to cover the entire width of the insulating substrate 1, and the fuse element 4 can be protected if the width is wider than the width of the electrode portion 4b. Further, an end face electrode 7 is provided from the electrode portion 4b where the protective resin layer 6 is not provided to the back face electrode 3 through the end face of the insulating substrate 1, and the parent solder layer 8 is provided thereon.

  The metal layer 9 is used for the purpose of disposing a material having a thermal conductivity higher than that of the base glass. For example, an Ag—Pd-based material or the like can be used. 5 is provided in order to prevent cracks occurring in 5. The arrangement region is at least a region extending from below the boundary between the protective resin layer 6 and the end face electrode 7 to both sides thereof, but the end of the outer side of the metal layer 9 (end side of the insulating substrate 1) is insulative. It does not reach the end surface of the substrate 1 but has an appropriate distance from the end surface, and the inner side of the metal layer 9 (opposite side of the end portion side) has a fusing portion 4a and an electrode portion 4b. It does not reach the boundary of, but is within the lower surface of the electrode portion 4b. Since the metal layer 9 is provided on the lower surface of the electrode portion 4b, there is an effect that the electrical resistance of the electrode portion 4b can be reduced.

  The glass layer 9 is not expected to have a function of protecting the fusing part 4a. When the fusing part 4a is fused by an overcurrent, it is sufficient to melt while reducing the heat radiation from the fusing part 4a. Even if air bubbles, pinholes, etc. are present, it is acceptable, and it is sufficient to cover at least the fusing part 4a. Therefore, the width of the glass layer 5 (the width in the same direction as the width direction of the fusing part 4a) is narrower than the width of the electrode part 4b. When the width of the glass layer 5 is minimized, the width of the glass layer 5 is sufficient to protrude from the end in the width direction of the fusing part 4a and cover the end of the fusing part 4a in the width direction. If the direction perpendicular to the width direction of the glass layer 5 (the direction of the current flowing through the fusing part 4a) is called the longitudinal direction, the end in the longitudinal direction of the glass layer 5 may be in the electrode part 4b. In this case, the glass layer 5 covers a part of the fuse element 4 including the fusing part 4a. When the glass layer 5 protrudes from the end in the width direction of the fusing part 4a and the end in the longitudinal direction of the glass layer 5 is set slightly inside the electrode part 4b from the end of the fusing part 4a, the glass layer 5 Only the connection region between the portion 4b and the fusing portion 4a is covered. When the glass layer 5 protrudes from the end in the width direction of the fusing part 4a, and the end in the longitudinal direction of the glass layer 5 is set as the boundary line between the fusing part 4a and the electrode part 4b, the glass layer 5 Only the portion 4a is covered. When making the heat capacity of the glass layer 5 the smallest, the glass layer 5 covers only the fusing part 4a. The planar shape of the glass layer 5 may be made to depend on the shape of the fusing part 4a. However, when the width of the fusing part 4a is constant as in the embodiment of FIG. Is preferably rectangular.

  The protective resin layer 6 covers the glass layer 5 to provide a function as a protective layer for protecting the end face electrode 7 and the resistance layer not covered by the glass layer 5 and at the time of fusing by utilizing a heat insulating action. This improves the heat storage performance. However, as described above, since the metal layer 9 is disposed in order to avoid the generation of cracks due to the use of the protective resin layer 6, the positions in the longitudinal direction of both ends of the protective resin layer 6 are the metal layers 9 As described above, the arrangement of the protective resin layer 6 and the metal layer 9 is determined. In this embodiment, the position immediately below the longitudinal positions of both ends of the protective resin layer 6 is substantially at the center in the longitudinal direction of the metal layer 9.

  An embodiment of a method for manufacturing a chip-type circuit protection element of the present invention will be described with reference to FIG. In the figure, the same parts as those in FIG. Reference numeral 10 denotes a metal film. 2A to 2G, in each process, the newly added portion is hatched for easy understanding, and in each process, the reference numerals illustrated in the previous processes are shown. The illustration is omitted. A multi-piece substrate is used as the insulating substrate shown in FIG. 2, but only one element is illustrated in FIG. Moreover, in each figure, sectional drawing which passes along a centerline was illustrated under the top view.

  FIG. 2A illustrates an insulating substrate. As a multi-chip substrate, prepare a substrate in which dividing grooves (slits) for dividing each element one by one are prepared vertically, or by laser scribing on a received plain substrate A dividing groove is formed. A base glass layer 2 is formed on one surface of the insulating substrate 1 on which the dividing grooves are formed. The base glass layer 2 is formed by applying a glass paste and baking it. In one example, the firing temperature of the base glass layer 2 is 950 ° C.

  FIG. 2B is a process of forming the metal layer 9 and the back electrode 3. Both are formed of an Ag—Pd-based material, for example, a thick film material by screen printing of silver palladium paste. The material is not limited to the Ag—Pd-based material, and the metal layer 9 and the back electrode 3 may be formed of different materials. The back electrode 3 is formed up to the position of the end surface of the insulating substrate 1, but the metal layer 9 is formed inside the end surface of the insulating substrate 1. Therefore, it is not directly connected to the end face electrode 7 described later. By forming the metal layer 9 on the inner side of the end face of the insulating substrate 1, dicing described later becomes easy. The metal layer 9 is also formed inside the end surface orthogonal to the end surface of the insulating substrate 1, that is, the side surface of the insulating substrate 1, but the back electrode 3 is also formed inside the side surface. However, it may be formed so as to be connected to the back surface electrode of the adjacent element so as to be formed up to the end face. Of course, as described above, the back electrode may be omitted.

  2C and 2D show the process of forming the fuse element 4. FIG. 2C shows a process for forming the metal film 10 to be the fuse element 4. First, as shown in FIG. 2C, a metal film 10 is formed on the entire surface where the metal layer 9 is formed on the base glass layer 2. In this example, the metal film 10 is formed by sputtering of Cr and then Cu. Subsequently, the fuse element 4 is formed by removing the metal film in a region other than the portion where the fuse element is formed in a photolithography process. The fuse element 4 has a pattern in which wide electrode portions 4b are formed so as to cover the metal layer 9 on both end sides, and a narrow fusing portion 4a is formed so as to connect the electrode portions. The fuse element 4 is not limited to being formed as a thin film as in this example, but may be formed as a thick film.

  FIG. 2E shows a process for forming the glass layer 5. The glass layer 5 is formed by screen printing and baking of a glass paste so as to cover the fusing part 4a, but the glass softening point of the glass layer 5 is lower than the softening point of the glass of the underlying glass layer, and the fusing part is It is good to set it as the softening point which the glass of the glass layer 5 melt | dissolves when fusing by an overcurrent. In one example, the firing temperature of the glass layer 5 is 640 ° C.

  FIG. 2F shows a process for forming the protective resin layer 6. In this example, the epoxy resin layer was formed by screen printing. The glass layer 5 is covered with the protective resin layer 6. After forming the protective resin layer 6, display printing of a product symbol etc. is performed on the surface as needed. The metal layer 9 is disposed below the end portion of the protective resin layer 6, and the metal layer 9 is viewed in the longitudinal direction of the insulating substrate 1 from directly below the end portion of the protective resin layer 6. It will be arrange | positioned so that it may extend on both sides.

  Until this step, a large number of elements are arranged vertically and horizontally on the insulating substrate 1. The primary division is performed after the step of FIG. In the primary division, a strip-shaped intermediate product is obtained in which the end faces are exposed and adjacent elements are connected by side faces. In this embodiment, in the embodiment, a dicing saw is used to make a cut from the surface side to the base glass layer, and the division is performed by cracking along the dividing groove.

  In FIG. 2G, the end face electrode 7 is formed on the strip-shaped intermediate product. The end face electrode 7 is formed by sputtering of NiCr in this embodiment, but is not limited to NiCr, and an appropriate electrode material can be used. As the forming method, an appropriate method such as an immersion method or a coating method can be adopted.

  FIG. 2H shows a process of forming the parent solder layer 8. A parent solder layer 8 is formed on the end face electrode 7 by plating four layers of Ni, Cu, Ni, and Sn in this order. The material of the parent solder layer is not limited to this example, and an appropriate material can be selected.

  After this step, the chip-type circuit protection element is manufactured by dividing into one element by cracking using the dividing groove along the side surface of each element.

BRIEF DESCRIPTION OF THE DRAWINGS It is for demonstrating one Example of the chip type circuit protection element of this invention, (A) is sectional drawing, (B) is a top view for demonstrating a glass layer, (C) demonstrates a protective resin layer It is a top view for doing. It is explanatory drawing because it is one Example of the manufacturing method of the chip-type circuit protection element of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is for demonstrating the prior art of the chip-type circuit protection element of this invention, (A) is sectional drawing, (B) is a top view for demonstrating a glass layer, (C) demonstrates a protective resin layer. FIG. It is explanatory drawing of the result of the thermal shock test of the prototype chip-type circuit protection element. It is a microscope picture which shows the crack which the chip-type circuit protection element made as an experiment produced by the thermal shock test. It is a microscope picture which shows the crack which the chip-type circuit protection element made as an experiment produced by the thermal shock test. It is a microscope picture of the result of having conducted the thermal shock test about the chip type circuit protection element of the present invention. It is a microscope picture of the result of having conducted the thermal shock test about the chip type circuit protection element of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Insulating substrate, 2 ... Base glass layer, 3 ... Back electrode, 4 ... Fuse element, 4a ... Fusing part, 4b ... Electrode part, 5 ... Glass layer, 6 ... Protective resin layer, 7 ... End surface electrode, 8 ... Parent solder layer, 9 ... metal layer, 10 ... metal film.

Claims (7)

  An insulating substrate, a base glass layer laminated on the insulating substrate, and disposed on both ends of the base glass layer so that an outer end is located on an inner side than an end of the base glass layer. A fuse element comprising a pair of metal layers disposed on a pair, a pair of wide electrode portions disposed so as to cover the metal layer, and a narrow fusing portion connecting between the electrode portions, and the fusing Covering a part of the fuse element including a portion, covering a glass layer having a width narrower than the width of the electrode portion, covering the glass layer, both ends thereof being located on the metal layer, and more than the width of the electrode portion A wide protective resin layer; an end electrode that is not connected to the pair of metal layers and is at least partially laminated on the electrode portion; and a parent solder layer that covers the end electrode. A chip-type circuit protection element.   The chip-type circuit protection element according to claim 1, wherein the planar shape of the glass layer is rectangular.   The chip-type circuit protection element according to claim 1, wherein the glass layer covers only the fusing part.   The chip-type circuit protection element according to claim 1, wherein the glass layer covers only the fusing part and a connection region between the electrode part and the fusing part.   5. The chip-type circuit protection element according to claim 1, wherein a heat capacity per unit area of the metal layer is larger than a heat capacity per unit area of the fuse element.   5. The chip-type circuit protection element according to claim 1, wherein the metal layer is formed of a thick film material, and the fuse element is formed of a thin film material. 6.   7. The chip according to claim 1, wherein the glass layer is formed of glass having a softening point that melts when an overcurrent flows through the fuse element. Type circuit protection element.

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