JP2007027077A - Chip type fuse device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the resistance of a fuse element and to facilitate the control of a resistance value of the fuse element, in a chip type fuse device with a fuse element formed by using a low-cost printing method. <P>SOLUTION: This chip type fuse device is provided, on a board, with the fuse element formed by a printing method. The fuse element includes a metal area and a metal oxide area and the metal area and the metal oxide area are formed of the same kind of metal. A surface part of a metal layer is oxidized and a metal oxide layer is formed on the surface thereof. An extraction electrode is connected to the metal layer. The metal included in the fuse element is preferably easily oxidized as compared with the metal included in the extraction electrode. The metal included in the fuse element is at least one kind selected from, for instance, Cu and Ni. The metal included in the extraction electrode is at least one kind selected from, for instance, Ag, Au, Pt, Pd, Rh, Ru and Ir. After the metal oxide layer is formed as the metal oxide area by sintering the metal oxide, the metal area may be formed by reducing a part thereof. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a chip-type fuse element having a fusible body formed by a printing method and a method for manufacturing the same.

  As a chip-type fuse element, one having a structure in which a narrow fusible body made of a metal film or the like is formed on an insulating substrate and terminal electrodes are connected to both ends of the fusible body is known. As a method for forming such a soluble material, there is a method using a thin film method such as vapor deposition or sputtering (see, for example, Patent Document 1, Patent Document 2, etc.). In this method, after forming a thin soluble body by a thin film method, thinning can be achieved by a lithography technique, and there is an advantage that the resistance of the soluble body can be easily increased. However, a thin film method such as vapor deposition or sputtering requires a vacuum technique and requires a large-scale manufacturing facility, which causes a problem that the cost of the chip-type fuse element is significantly increased.

In recent years, therefore, printing methods have attracted much attention. For example, Patent Document 3 describes that a soluble material is formed using a thick film technique based on screen printing of an Ag-based paste. Since the printing method does not require a large-scale production facility required for vapor deposition or sputtering, it is expected as a method that can greatly reduce the manufacturing cost of the chip-type fuse element.
JP-A-6-176680 JP 2003-173728 A JP 2002-140975 A

  However, a chip-type fuse element in which a fusible body is formed by a printing method has limitations in thinning and thinning the fusible body, so that it can be used in comparison with the fusible body formed by the thin film method (evaporation, sputtering). The cross-sectional area of the solution tends to increase. Therefore, the resistance value of the fusible body formed by the printing method is low, and as a result, there is a problem that Joule heat necessary for fusing the fusible body cannot be ensured and good fusing characteristics cannot be obtained.

  In addition, a manufacturer of chip-type fuse elements needs to prepare chip-type fuse elements having different current values (rated currents) that are fused in accordance with the user's application. Since the rated current is generally determined by the resistance value of the fusible body, a method of easily controlling the resistance value of the fusible body is important when manufacturing a chip-type fuse element having various resistance values.

  Therefore, the present invention has been proposed in view of such a conventional situation, and in the chip-type fuse element in which a fusible body is formed using a low-cost printing method, while increasing the resistance of the fusible body, It is an object of the present invention to provide a chip-type fuse element that can easily control the resistance value of a fusible body and a manufacturing method thereof.

  In order to achieve the above object, a chip-type fuse element according to the present invention is a chip-type fuse element including a fusible body formed on a substrate by a printing method, and the fusible body includes a metal region and a metal oxide. And the metal region and the metal oxide region are made of the same kind of metal.

  In the chip type fuse element as described above, by allowing the metal region and the metal oxide region containing the metal oxide to exist in the fusible body, the fusible body is possible compared to the case where the fusible body is made of only metal. The cross-sectional area of the region (metal region) functioning as a solution is made smaller than the actual cross-sectional area of the soluble body. For this reason, even if it is a case where the printing method in which thinning and thinning of a soluble body are difficult is utilized, the soluble body which shows a high resistance value will be obtained. Moreover, in the above-described chip-type fuse element, the resistance value of the fusible body can be arbitrarily controlled by controlling the ratio of the metal region to the metal oxide region in the fusible body. ) Is realized.

  The method for manufacturing a chip-type fuse element according to the present invention is characterized in that a fusible paste is printed on a substrate and baked to form a metal layer, and then a part thereof is oxidized to form a metal oxide. And

  The method for manufacturing a chip-type fuse element as described above is applied to a chip-type fuse element having a metal layer on the substrate side of the fusible body. After the metal layer is formed by the printing method, a part of the metal layer is oxidized and changed into an oxide, thereby reducing the abundance (thickness) of the metal region functioning as a soluble material. As a result, the cross-sectional area of the portion functioning as a soluble body is reduced as compared with a soluble body formed by a normal printing method, leading to an increase in the resistance value of the soluble body. The chip-type fuse element can have a desired resistance value by controlling the oxidation conditions when forming the metal oxide and controlling the ratio of the metal region to the metal oxide region in the fusible body. A solution is obtained.

  Furthermore, the invention described in claim 26 and claim 28 defines a manufacturing method applied to a chip-type fuse element having a metal oxide layer on the substrate side of the fusible body. That is, in the method for manufacturing a chip-type fuse element according to the present invention, a soluble paste containing a metal oxide is printed on a substrate, the metal oxide is sintered, and then reduced to be a part of the metal oxide. It is characterized by metallizing. Further, in the method for manufacturing a chip-type fuse element according to the present invention, a fusible paste containing a metal is printed on a substrate, a binder removal process is performed to convert the metal into a metal oxide, and the metal oxide is sintered. Thereafter, the metal oxide is partially metallized by reduction.

  After forming a sintered body of metal oxide by the printing method, a part of the metal that functions as a soluble body is reduced compared to a soluble body formed by a normal printing method by reducing a part of it to a metal. The existence ratio (thickness) is reduced. That is, a soluble body having a smaller cross-sectional area of a portion functioning as a soluble body is obtained as compared with a soluble body formed by a normal printing method, leading to an increase in the resistance value of the soluble body. Further, in the chip-type fuse element, the fusible body having a desired resistance value is controlled by controlling the reduction condition when forming the metal region and controlling the ratio of the metal region and the metal oxide region in the fusible body. Is obtained.

In the method for manufacturing a chip-type fuse element according to the present invention, a fusible paste containing a metal powder and an oxide powder of the metal is printed and fired to mix the metal region and the metal oxide region. It forms a soluble body in a state.
By the above method, formation of a soluble body in a state where the metal region and the metal oxide region are mixed is realized, leading to an increase in the resistance value of the soluble body. Further, in the chip-type fuse element, the fusible body having a desired resistance value is controlled by controlling the reduction condition when forming the metal region and controlling the ratio of the metal region and the metal oxide region in the fusible body. Is obtained.

  According to the present invention, it is possible to provide a chip-type fuse element that achieves high resistance of a fusible body while using a printing method in which thinning and thinning are difficult, enables low current fusing, and has excellent fusing characteristics. Is possible. Further, according to the present invention, the resistance value of the fusible body can be easily designed, and a chip-type fuse element having various rated currents can be provided. Furthermore, according to the present invention, since a printing method is used, a large-scale device such as a vacuum device is unnecessary, and an inexpensive chip-type fuse element can be provided.

  Hereinafter, a chip-type fuse element to which the present invention is applied and a manufacturing method thereof will be described in detail with reference to the drawings. A chip-type fuse element to which the present invention is applied basically includes a metal region containing a metal and a metal oxide region containing the same kind of element as the constituent element in the fusible body. And the chip-type fuse element to which the present invention is applied is described in the first embodiment to the following in accordance with the specific structure of the fusible body, that is, the existence form of each of the metal region and the metal oxide region. It can be roughly classified into the third embodiment.

(First embodiment)
As shown in FIG. 1, the chip-type fuse element according to the present embodiment is formed on, for example, a rectangular chip-shaped substrate 1, a fusible body 2 formed in a thick film on the substrate 1, and a fusible body 2. And a protective layer 3. The fusible body 2 includes two layers, and specifically includes a metal layer 4 formed on the substrate 1 and a metal oxide layer 5 formed on the metal layer 4. In addition, a pair of lead electrodes 6 are provided on the substrate 1 of the chip-type fuse element of the present embodiment. One end of the extraction electrode 6 is connected to the metal layer 4, and the other end is connected to a terminal electrode 7 formed on the end surface of the substrate 1. In FIG. 1A, the protective layer 3 is omitted.

  A pair of terminal electrodes 7 are formed on the end face of the substrate 1 so as to be connected to the extraction electrode 6. Although it does not specifically limit as a material which comprises the terminal electrode 7, For example, it forms with resin containing Ag etc.

  The fusible body 2 in the present embodiment is formed by first forming the metal layer 4 and then oxidizing a part (surface) of the metal layer 4 to form the metal oxide layer 5. Since the metal oxide layer 5 normally exhibits insulating properties, in the fusible body 2, only the metal layer 4 formed on the substrate 1 side functions as a substantially soluble body.

  In the present invention, the “metal oxide layer” means that the metal oxide region does not lead to the formation of a clear layer structure, for example, the metal oxide region partially exists on the surface of the metal layer. Also included.

  The fusible body 2 is made of metal, and is intended to protect an electric circuit or the like in which a chip-type fuse element is incorporated by fusing when an excessive current exceeding twice the rated current flows, for example. . From such a viewpoint, the metal constituting the fusible body 2 (metal layer 4) needs to be a metal having an appropriate melting point and specific resistance as the fusible body of the chip-type fuse element. At the same time, in the present embodiment, the surface of the metal layer 4 is oxidized to form the metal oxide layer 5. Therefore, the metal contained in the fusible body 2 is preferably a metal that is relatively easily oxidized. Examples of such a metal include Cu and Ni, and Cu is particularly preferable. On the other hand, the metal oxide layer 5 is composed of a metal oxide constituting the metal layer 4.

As a material constituting the protective layer 3, for example, glass such as ZnO-based glass, CaO-based glass, Bi ₂ O _3- based glass, SrO-based glass, silicone resin, or the like can be used.

  A pair of extraction electrodes 6 are connected to both ends of the fusible body 2 formed in a band shape. The metal contained in the extraction electrode 6 is preferably a metal that is less susceptible to oxidation than the metal contained in the soluble body 2. As will be described later, in the step of forming the metal oxide layer 5, the surface of the metal layer 4 needs to be oxidized, while the extraction electrode 6 is preferably not oxidized. Such relative ease of oxidation can be determined based on, for example, an Ellingham diagram as shown in FIG. 2, for example, at least one selected from Ag, Au, Pt, Pd, Rh, Ru, Ir, and the like. The species is suitable.

The board | substrate 1 becomes a support body of the soluble body 2, for example, is formed in square shape. The material constituting the substrate 1 is not limited, and any material used for this type of chip-type fuse element can be used. For example, an insulating material exhibiting low thermal conductivity can be used, and more specifically, an insulating material such as Al ₂ O ₃ or glass ceramic can be used.

  In the chip-type fuse element, a heat storage layer may be disposed between the substrate 1 and the fusible body 2 as necessary. Although it does not specifically limit as a material which comprises a thermal storage layer, It is preferable to use the material which shows low heat conductivity, For example, resin, glass, etc. can be mentioned. The heat storage layer may have a porous structure.

  When a soluble material is formed by using a printing method, a decrease in the resistance value of the soluble material becomes a problem, but by oxidizing a part of the metal layer 4 as described above, the metal oxide layer 5 is obtained. The thickness of the metal region (metal layer 4) containing the metal can be reduced from the actual thickness of the soluble body 2 and the resistance value of the soluble body 2 can be increased. Therefore, sufficient Joule heat required for fusing is ensured, for example, fusing at a low current is possible, and a chip-type fuse element exhibiting excellent fusing characteristics can be realized. In addition, since the printing method is used, it is very advantageous in terms of cost reduction of the chip type fuse element.

  Further, for example, the resistance value of the fusible body 2 is relatively controlled by controlling the film thickness ratio of the metal layer 4 and the metal oxide layer 5 without the complexity of changing the length and width of the fusible body 2. It can be easily controlled, and a chip-type fuse element having a desired standard (rated current) can be realized.

  A method for manufacturing the chip-type fuse element having the configuration shown in FIG. 1 will be described below. The manufacturing method of the chip-type fuse element of this embodiment basically includes a lead electrode forming step, a metal layer forming step, a metal oxide forming step, a protective layer forming step, and a terminal electrode forming step.

  First, in the lead electrode forming step, as shown in FIG. 3A, the lead electrode 6 is formed by printing and baking a conductive paste on the substrate 1. The conductive paste is prepared by mixing a metal powder, a glass composition, an organic vehicle and the like. As the metal powder contained in the conductive paste, a metal that is difficult to oxidize compared to the metal contained in the soluble body 2 can be used, and is selected from, for example, Ag, Au, Pt, Pd, Rh, Ru, Ir, and the like. There is at least one kind.

As the glass composition for the conductive paste, for example, ZnO glass, CaO glass, Bi ₂ O ₃ glass, SrO glass, or the like can be used.

  The organic vehicle for the conductive paste is prepared by dissolving a binder or the like in an organic solvent. It does not specifically limit as a binder, For example, what is necessary is just to select suitably from various binders, such as an ethyl cellulose and polyvinyl butyral. The organic solvent is not limited, and may be appropriately selected from various organic solvents such as terpineol, butyl carbitol, acetone, and toluene. Furthermore, in order to adjust the physical properties of the paste, various additives such as a dispersant may be added.

  Next, the process proceeds to the metal layer forming step. In the metal layer forming step, first, a soluble paste containing metal powder is printed on the substrate 1 in a soluble form by screen printing or the like. At this time, the soluble paste is printed so as to partially overlap the conductive paste (extracting electrode 6) applied on the substrate 1. Thereafter, the soluble paste is fired in an oxidizing atmosphere such as air. Thereby, the metal layer 4 as shown in FIG. 3B is formed.

  The soluble body paste is prepared by mixing the metal powder forming the soluble body 2 and the organic vehicle. As the metal powder contained in the soluble paste, a metal that is more easily oxidized than the metal contained in the extraction electrode 6 can be used at the heat treatment temperature in the oxide layer forming step. For example, at least one selected from Cu, Ni and the like is preferable. As the organic vehicle for the soluble paste, the same one as the conductive paste can be used.

By the way, the metal powder for soluble paste is made of a metal that is relatively easy to oxidize. Therefore, simply baking the soluble paste in an oxidizing atmosphere for the purpose of removing the binder in the soluble paste can be used for the soluble paste. The entire metal powder may be oxidized. In such a case, for example, after removing the binder by firing at 400 ° C. in the air, it is preferable to perform a reduction treatment for reducing the metal powder for the soluble paste. Thereby, the oxide generated by the binder removal treatment can be reduced and returned to the metal. The reduction treatment may be performed by heat treatment, for example, at 380 ° C. in a reducing atmosphere containing N ₂ , H ₂ or the like. After the reduction treatment, it is preferable to further perform baking at 750 ° C. in a non-oxidizing atmosphere such as N ₂ . By performing firing in a non-oxidizing atmosphere after the reduction treatment, it is possible to form a soluble body (metal layer 4) at a stage before the metal oxide layer 5 is formed.

  Next, an oxide layer forming step is performed. In the oxide layer forming step, the surface of the metal layer 4 is oxidized by heat-treating the metal layer 4 in an oxidizing atmosphere to form the metal oxide layer 5 as shown in FIG. By the metal layer forming step and the oxide layer forming step, the soluble body 2 composed of the metal layer 4 and the metal oxide layer 5 is formed.

  In the oxide layer forming step, it is necessary to oxidize the surface of the metal layer 4, while it is necessary to control the heat treatment conditions so that the extraction electrode 6 is not oxidized as much as possible from the viewpoint of ensuring conductivity. The heat treatment conditions in the oxide layer forming step need to be appropriately adjusted according to the type of metal used for the fusible body 2 (metal layer 4) and the extraction electrode 6, the required resistance value, and the like. It may be performed at a temperature of ° C.

  The oxygen partial pressure in the oxidizing atmosphere in the oxide layer forming step is determined in consideration of the equilibrium oxygen partial pressure of the metal contained in the soluble body 2 and the equilibrium oxygen partial pressure contained in the extraction electrode 6. preferable. Specifically, the oxygen partial pressure in the oxidizing atmosphere may be set higher than the equilibrium oxygen partial pressure of the metal constituting the fusible body 2 and lower than the equilibrium oxygen partial pressure of the metal constituting the extraction electrode 6. preferable. By setting the oxygen partial pressure in the oxidizing atmosphere within the above range, the surface of the metal layer 4 can be reliably changed to the metal oxide layer 5 without impairing the conductivity of the extraction electrode 6.

Such a range of oxygen partial pressure can be calculated based on an Ellingham diagram as shown in FIG. For example, consider a case where the firing temperature is 900 ° C., Ni is left as a metal, and oxygen partial pressure is obtained by oxidizing Al to form an oxide (Al ₂ O ₃ ). The equilibrium oxygen partial pressure of Al is indicated by a point P _O2 (Al) obtained by extrapolating the straight line connecting the point O located at the upper left and the point a at a temperature of 900 ° C. corresponding to the Al oxide to the P _O2 scale. It is. On the other hand, the equilibrium oxygen partial pressure of Ni has a point O located at the upper left, the straight line connecting the point b at a temperature 900 ° C. of the line B corresponding to the Ni oxide P _O2 point was extrapolated to scale P _{O2 (Ni} ). That is, at 900 ° C., as indicated by X, if the oxygen partial pressure is below the Ni line (ΔG ^o ) and corresponding to the lower side of the Al line (ΔG ^o ), Al is oxidized. Ni remains as a metal. Therefore, at 900 ° C., the oxygen partial pressure P _O2 in an atmosphere that satisfies the condition of remaining Ni as a metal and oxidizing Al is in the range indicated by the arrow Y in FIG. 3, and P _O2 (Al) <P _{It is O2} <P _O2 (Ni).

  Next, a protective layer forming step is performed to form the protective layer 3 as shown in FIG. The method for forming the protective layer 3 is not particularly limited, but it is preferable to form the protective layer 3 by applying a paste containing a resin such as a silicone resin and curing with heat.

  After forming the protective layer 3, a terminal electrode formation process is implemented. For example, a terminal electrode 7 as shown in FIG. 3E is formed by applying and curing a paste containing Ag. The chip-type fuse element shown in FIG. 1 is obtained through the above steps.

  In the method of manufacturing a chip-type fuse element as described above, a region (metal layer) that actually functions as the fusible body 2 is obtained by changing a part of the metal layer 4 to the metal oxide layer 5 after forming the metal layer 4 by a printing method. The thickness of 4) is reduced. Therefore, in the present invention, even when the printing method is used, the cross-sectional area of the metal layer 4 can be made extremely small to increase the resistance of the fusible body 2. Both excellent fusing characteristics can be achieved.

  Further, the film thickness of the metal oxide layer 5 can be controlled relatively easily by controlling the heat treatment conditions and the like in the oxide layer forming step. Therefore, for example, the resistance value of the fusible body 2 can be easily designed to a desired value without changing any of the outer dimensions of the chip-type fuse element, the shape of the fusible body, and the material of the fusible paste. A simple chip-type fuse element can be manufactured.

  In the above description, the method of performing the oxide layer forming step and the protective layer forming step in this order when manufacturing the chip-type fuse element shown in FIG. 1 is taken as an example, but the structure shown in FIG. The manufacturing method of the chip-type fuse element is not limited to this. For example, as described below, the protective layer forming step and the oxide layer forming step can be made common. Such a manufacturing method will be described with reference to FIG.

  First, an extraction electrode forming step is performed, and an extraction electrode 6 is formed on the substrate 1 as shown in FIG. Next, a metal layer forming step is performed to form the metal layer 4 as shown in FIG. Since the steps up to here are the same as those of the manufacturing method described with reference to FIG. 2, detailed description thereof is omitted.

  After the metal layer forming step, a protective layer forming step is performed. First, as shown in FIG. 4C, a protective layer forming paste 3 a for forming the protective layer 3 is printed and applied so as to cover the metal layer 4. The protective layer forming paste 3a is prepared by mixing a material for forming the protective layer 3, an organic vehicle, and the like. Here, the material for forming the protective layer 3 is preferably a material having heat resistance against heat treatment in an oxidizing atmosphere described later, and glass is particularly preferably used.

  After applying the protective layer forming paste 3a, heat treatment is performed in an oxidizing atmosphere. By this heat treatment, the protective layer 3 is formed as shown in FIG. At the same time, oxygen in the atmosphere comes into contact with the surface of the metal layer 4 through the protective layer forming 3a paste and oxidizes the surface of the metal layer 4, resulting in the metal oxide layer as shown in FIG. 5 is formed.

  Then, a terminal electrode formation process is implemented and the terminal electrode 7 is formed as shown in FIG.4 (e). Through the steps as described above, the chip-type fuse element shown in FIG. 1 is obtained.

  In the manufacturing method as described above, the heat treatment in the protective layer forming step also serves as the heat treatment in the oxide layer forming step. In chip-type fuse elements, it is common to form the protective layer 3 for the purpose of improving the environmental resistance, etc., so that the protective layer forming step also serves as the oxide layer forming step. The heat treatment process only for the purpose becomes unnecessary. Therefore, according to the manufacturing method described above, the manufacturing process can be simplified, and further cost reduction of the chip-type fuse element can be realized.

(Second Embodiment)
The chip-type fuse element of the first embodiment is that the fusible body 2 has a metal region (metal layer 4) and a metal oxide region (metal oxide layer 5) in the fusible body 2. However, the stacking order of the metal layer 4 and the metal oxide layer 5 in the fusible body 2 is reversed. Hereinafter, the chip-type fuse element of the present embodiment will be described with reference to FIG. Note that in the following description, detailed description of portions overlapping with the first embodiment is omitted.

  As shown in FIG. 5, the chip-type fuse element according to this embodiment is formed on, for example, a rectangular chip-shaped substrate 1, a soluble body 2 formed in a thick film on the substrate 1, and a soluble body 2. And a protective layer 3. In FIG. 5A, the protective layer 3 is omitted.

  The stacking order of the metal layer 4 and the metal oxide layer 5 in the fusible body 2 of the present embodiment is opposite to that of the first embodiment. That is, the fusible body 2 of the present embodiment includes a metal oxide layer 5 formed on the substrate 1 and a metal layer 4 formed on the metal oxide layer 5. Terminal electrodes 7 are respectively formed on a pair of opposed end faces of the substrate 1. In the first embodiment, the lead electrode 6 is interposed between the metal layer 4 and the terminal electrode 7, but in the present embodiment, the metal layer 4 and each terminal electrode 7 are directly connected.

  The fusible body 2 in the present embodiment is formed by first forming the metal oxide layer 5, and then reducing and metalizing a part (surface) of the metal oxide layer 5 to form the metal layer 4. is there. Since the metal oxide layer 5 normally exhibits insulating properties, in the soluble body 2, only the metal layer 4 formed on the surface functions as a substantially soluble body.

  In the present invention, the “metal layer” includes a case where the metal region does not lead to the formation of a clear layer structure, for example, the metal region partially exists on the surface of the metal oxide layer. . However, in this case, in order to function as the fusible body 2, the metal regions need to be in contact with each other to form a network.

  The material that can be used for the fusible body 2 (metal layer 4) of the present embodiment needs to be a metal having an appropriate melting point and specific resistance as the fusible body of the chip-type fuse element. At the same time, the metal layer 4 of the present embodiment preferably uses a metal that is easy to reduce and deposit the metal from the oxide. From such a viewpoint, the metal layer 4 is preferably composed of Cu.

  By reducing a part of the metal oxide layer 5 to the metal layer 4 as described above, the thickness of the metal region (metal layer 4) is reduced from the actual thickness of the soluble body 2 and the resistance value of the soluble body 2 is reduced. Can be increased. Therefore, it is possible to realize a chip-type fuse element that has sufficient Joule heat necessary for fusing and exhibits excellent fusing characteristics that can be fusing at a low current, for example. In addition, since the printing method is used, it is very advantageous in terms of cost reduction of the chip type fuse element.

  Further, the resistance value of the fusible body 2 can be controlled relatively easily by controlling the film thickness ratio between the metal oxide layer 5 and the metal layer 4, and the chip type fuse having a desired standard (rated current). An element can be realized. At this time, there is no complication such as changing the length and width of the fusible body 2.

  Hereinafter, an example of a manufacturing method of the chip-type fuse element shown in FIG. 5 will be described with reference to FIG. The manufacturing method of the chip type fuse element of this embodiment basically includes a metal oxide layer forming step, a metal layer forming step, a terminal electrode forming step, and a protective layer forming step.

  First, a soluble paste is prepared prior to the metal oxide layer forming step. The soluble paste used here is prepared by mixing a metal oxide powder with an organic vehicle or the like as a soluble material. For example, when the metal layer 4 of the soluble body 2 is made of Cu, the soluble body paste contains CuO powder.

  The fusible paste is printed on the substrate 1 in the form of a fusible body by screen printing or the like, and then, for example, held in the atmosphere at 900 ° C. for a predetermined time and baked. Thereby, the binder in the soluble paste is removed and the metal oxide powder is sintered to form the metal oxide layer 5 as shown in FIG.

Next, in the metal layer forming step, the surface (part) of the metal oxide layer made of a sintered metal oxide is reduced to metallize part of the metal oxide, as shown in FIG. The metal layer 4 is formed. Thereby, the soluble body 2 which consists of the metal oxide layer 5 and the metal layer 4 is formed. In order to make a part of the metal oxide layer 5 into the metal layer 4, the metal oxide layer 5 may be heat-treated in a reducing atmosphere such as N ₂ or H ₂ .

  Next, a terminal electrode forming step is performed. For example, a terminal electrode 7 as shown in FIG. 6C is formed by dipping a thermosetting resin containing Ag or the like and then curing it.

  Finally, a protective layer forming step is performed to form the protective layer 3 as shown in FIG. The chip-type fuse element shown in FIG. 5 is obtained through the above steps.

  In the method of manufacturing a chip-type fuse element as described above, after forming a sintered body of metal oxide (metal oxide layer 5), a part of the sintered body is reduced and changed to the metal layer 4, thereby forming the fusible body 2. The actually functioning region (metal layer 4) is thinly formed. Therefore, in the present invention, even when the printing method is used, the cross-sectional area of the metal layer 4 of the fusible body 2 can be made extremely small to increase the resistance of the fusible body 2, which is an advantage of the printing method. It is possible to achieve both low cost and excellent fusing characteristics.

  Further, the film thickness of the metal layer 4 can be controlled relatively easily by controlling the reducing conditions in the metal layer forming step. Therefore, for example, the resistance value of the fusible body 2 can be easily designed to a desired value without changing any of the external dimensions of the chip-type fuse element, the shape of the fusible body, and the material of the fusible body paste. A chip-type fuse element can be manufactured.

  In the above description, the case where the fusible paste containing the metal oxide powder is used when producing the chip-type fuse element shown in FIG. 5 is described as an example, but the metal powder is used instead of the metal oxide powder. A soluble paste may be used.

  Even when a fusible paste containing metal powder is used, a chip-type fuse element is basically manufactured through a metal oxide layer forming step, a metal layer forming step, a terminal electrode forming step, and a protective layer forming step. However, in the metal oxide layer forming step, after the fusible paste is printed on the substrate 1, a binder removal process for removing the binder in the fusible paste is essential. The binder removal process may be performed by heating and holding at a predetermined temperature in the atmosphere, for example. By performing the binder removal process prior to the sintering, the metal powder in the soluble paste is oxidized to become a metal oxide powder. By sintering this, the metal oxide layer 5 made of a sintered metal oxide can be formed.

(Third embodiment)
By the way, in the first embodiment and the second embodiment described above, the case where the fusible body 2 has a structure in which a metal and a metal oxide each form a layer is taken as an example, but the present invention is limited to this. It is not a thing. For example, in the fusible body 2, the metal region and the metal oxide region may exist in a mixed state.

  For example, as shown in FIG. 7, the chip-type fuse element of the present embodiment includes a substrate 1, a soluble body 2 formed in a thick film on the substrate 1, a protective layer 3 formed on the soluble body 2, and a soluble body 2. Terminal electrodes 7 connected to both ends.

  The fusible body 2 is formed by a printing method and exists in a state in which a metal region and a metal oxide region are mixed. The abundance ratio between the metal region and the metal oxide region is arbitrary. For example, the state in which the metal oxide region is dispersed in the metal layer, conversely, the state in which the metal region is dispersed in the metal oxide layer. Either is fine. In addition, when it is set as the state where the metal area | region disperse | distributed in the metal oxide layer in the soluble body 2, for example, the ratio of the metal area | region occupied in the soluble body 2 shall be 30 volume% or more, and metal areas are made to mutually contact. By forming a network, the fusible body 2 can function reliably.

  Since the effective cross-sectional area of the fusible body 2 is smaller than that of the conventional fusible body made of metal by the fusible body 2 having the above-described structure, the resistance of the fusible body 2 is increased. . Therefore, it is possible to realize a chip-type fuse element that has sufficient Joule heat necessary for fusing and exhibits excellent fusing characteristics that can be fusing at a low current, for example. In addition, since the printing method is used, it is very advantageous in terms of cost reduction of the chip type fuse element.

  In addition, by controlling the abundance ratio of the metal and the metal oxide in the soluble body 2, the resistance value of the soluble body 2 can be relatively easily reduced without the complexity of changing the length and width of the soluble body 2. Thus, a chip-type fuse element with a desired standard (rated current) can be realized.

  Hereinafter, an example of a method for manufacturing the chip-type fuse element of the present embodiment will be described. The manufacturing method of the chip-type fuse element of the present embodiment basically includes a fusible body forming step, a terminal electrode forming step, and a protective layer forming step.

  First, a soluble paste is prepared prior to the metal oxide layer forming step. The soluble paste used here contains a metal powder and an oxide powder of the metal, and is prepared by mixing these with an organic vehicle. It is particularly preferable to use Cu powder as the metal powder. When Cu powder is included in the soluble paste, Cu oxide powder is used as the metal oxide powder.

  Next, after the fusible paste is printed on the substrate 1 and subjected to binder removal treatment, the paste is held at an oxygen partial pressure atmosphere such that Cu and Cu oxide respectively remain at 900 ° C. for a predetermined time. Thereby, the soluble body 2 in which Cu and Cu oxide coexist is formed. The oxygen partial pressure at which Cu and Cu oxide each remain may be calculated from the Ellingham diagram as described above.

  Next, a terminal electrode forming step is performed. For example, after dipping a thermosetting resin containing Ag or the like, the terminal electrode 7 is formed by curing.

  Finally, a protective layer forming step is performed to form the protective layer 3. Through the above steps, a chip-type fuse element having a fusible body in which a metal region and a metal oxide region are mixed as shown in FIG. 7 is obtained.

  Hereinafter, specific examples to which the present invention is applied will be described based on experimental results. Needless to say, the present invention is not limited to the following examples.

(Experiment 1)
In Experiment 1, when producing a chip-type fuse element having a fusible body in which a metal layer and a metal oxide layer are laminated in this order, an oxide layer and a protective layer on the surface of the fusible body are formed in separate steps. investigated.

<Example 1>
First, a conductive paste was prepared. The conductive paste was prepared by weighing Ag powder and organic vehicle so as to have each composition, and kneading with a three-roll mill. The organic vehicle contains ethyl cellulose as a binder and butyl carbitol as an organic solvent.

  The conductive paste was printed in the shape of a pair of extraction electrodes on an alumina substrate and dried. Next, the extraction electrode was formed by baking at 850 ° C. in the atmosphere.

  On the other hand, a soluble paste was prepared. The soluble paste is prepared by weighing Cu powder and organic vehicle so as to have each composition and kneading them with a three-roll mill. The organic vehicle contains ethyl cellulose as a binder and butyl carbitol as an organic solvent. The blending ratio of the Cu powder and the organic vehicle was set so that the obtained soluble paste had a viscosity suitable for screen printing.

The fusible paste was screen-printed into a fusible body shape so as to be in contact between a pair of extraction electrodes and dried. Next, the binder in the soluble paste was removed by heat treatment at 400 ° C. in the atmosphere. After removing the binder, Cu reduction treatment was performed. The reduction treatment was performed in a N ₂ and H ₂ mixed gas atmosphere at 380 ° C. for 30 minutes. Then, _{N 2} atmosphere, 750 ° C., and calcined for 10 minutes condition. This formed the metal layer which consists of Cu. The film thickness of the Cu metal layer obtained here was 5 μm. The metal layer had a width of 200 μm and a length of 1.5 mm.

  Next, a part of the surface of the metal layer was made into an oxide layer by oxidizing the surface of the metal layer. The oxide layer was formed by heat treatment in air at 400 ° C. for 10 minutes. Thereby, the soluble body which consists of two layers of Cu layer and Cu oxide layer is formed. An unoxidized Cu layer becomes a substantially soluble material. Thereafter, a film made of a silicone resin was formed by screen printing so as to cover the soluble material, and this was used as a protective layer.

  Next, after dipping a resin containing Ag or the like on the side surface of the substrate, a terminal electrode was formed by thermosetting. Then, the small chip-type fuse element of Example 1 was obtained by performing a plating process.

<Example 2 to Example 4>
A small chip-type fuse element was obtained in the same manner as in Example 1 except that the heat treatment temperature for forming the oxide layer was changed as shown in Table 1.

<Comparative Example 1>
After forming the metal layer, a small chip type fuse element was obtained in the same manner as in Example 1 except that surface oxidation was not performed.

  Regarding the fusible bodies of the chip-type fuse elements of Examples 1 to 4 manufactured as described above, the film thickness of the metal layer made of Cu was measured. Moreover, the fusing time of the chip-type fuse elements of Examples 1 to 4 and Comparative Example 1 was measured. The fusing time was defined as the time from when the current of 4 A started to flow through the soluble material until the soluble material was cut. The results are shown in Table 1.

  As described above, from the results shown in Table 1, by forming the oxide layer, the film thickness of the metal layer (Cu) substantially functioning as a soluble material can be reduced, and the fusing time can be shortened. confirmed. In particular, by making the Cu film thickness smaller than 4.3 μm, the fusing time is less than 1 second, and even better fusing characteristics are obtained. In addition, since the fusing time is shortened as the Cu film thickness decreases, it can be seen that the fusing time can be controlled by controlling the film thickness of the oxide layer and the metal layer.

(Experiment 2)
In Experiment 2, an example in which glass was used as the protective layer and the protective layer forming step also served as the oxide layer forming step was examined.

<Example 5>
First, in the same manner as in Example 1, a lead electrode and a metal layer made of Cu were formed on an alumina substrate.
On the other hand, a glass paste for forming a protective layer was prepared. The glass paste was prepared by blending Bi ₂ O ₃ , B ₂ O ₃ and SiO _{2 so} that the softening point was 420 ° C. and kneading.

  Next, the said glass paste was apply | coated so that a metal layer might be coat | covered, and it baked on 500 degreeC and the conditions for 10 minutes in the air. As a result, a protective layer was formed, and the surface of the metal layer was oxidized to form a metal oxide layer, thereby forming a soluble material.

  Thereafter, terminal electrodes were formed in the same manner as in Example 1, and plating treatment was performed to obtain a small chip type fuse element of Example 5.

<Example 6, Example 7>
Glass having a softening point corresponding to each heat treatment temperature was used while changing the heat treatment temperature when forming the protective layer and the oxide layer as shown in Table 2. Other than that was carried out similarly to Example 5, and obtained the small chip-type fuse element.

  For the fusible bodies of the chip-type fuse elements of Examples 5 to 7 manufactured as described above, the film thickness of Cu was measured in the same manner as in Experiment 1. Further, in the same manner as in Experiment 1, the fusing time of the chip-type fuse elements of Examples 5 to 7 was measured. The results are shown in Table 2.

  As described above, even when the oxide layer is formed simultaneously with the formation of the glass protective layer, the film thickness of Cu functioning as a soluble material can be reduced by forming the oxide layer, and the fusing time can be reduced. It was confirmed that shortening of

(Experiment 3)
In Experiment 3, a chip-type fuse element including a fusible body in which a metal oxide layer and a metal layer were laminated in this order was examined.

<Example 8>
First, a soluble paste was prepared. The soluble paste is prepared by weighing cupric oxide CuO powder (average particle size 1 μm) and organic vehicle so as to have each composition and kneading them with a three-roll mill. The organic vehicle contains ethyl cellulose as a binder and butyl carbitol as an organic solvent. The mixing ratio of the CuO powder and the organic vehicle was set so that the obtained soluble paste had a viscosity suitable for screen printing.

  The soluble paste was screen printed on an alumina substrate. The width of the narrow part of the printed soluble paste was 100 μm, the film thickness was 20 μm, and the length was 2.5 mm.

Next, it was kept in the atmosphere at 900 ° C. for 5 minutes and fired. This obtained the sintered compact which consists of Cu oxides. Thereafter, reduction heat treatment was performed to deposit Cu on the surface of the Cu oxide layer to obtain a soluble material. The conditions for the reduction heat treatment were 400 ° C. for 1 minute in an N ₂ -4% H ₂ atmosphere.

  Next, after dipping a resin containing Ag or the like on the side surface of the substrate, a terminal electrode was formed by thermosetting, and the small chip type fuse element of Example 8 was obtained.

<Comparative example 2>
First, a soluble paste was prepared. The soluble paste is prepared by weighing a metal Cu powder (average particle size 1 μm) and an organic vehicle so as to have each composition and kneading them with a three-roll mill. The organic vehicle contains ethyl cellulose as a binder and butyl carbitol as an organic solvent. The blending ratio of the Cu powder and the organic vehicle was set so that the obtained soluble paste had a viscosity suitable for screen printing.

  Next, the soluble paste was screen printed on an alumina substrate. The printing shape is the same as that in the eighth embodiment.

  Next, a binder removal process was performed to remove the binder in the soluble paste. The binder removal treatment was performed in the atmosphere at 400 ° C. for 30 minutes.

Since the Cu powder in the soluble paste was oxidized by the binder removal treatment, it was reduced to Cu. The reducing conditions here were 400 ° C. and 30 minutes in an N ₂ -4% H ₂ atmosphere. Next, the reduced Cu was sintered. The sintering of Cu was performed in an N ₂ atmosphere at 900 ° C. for 5 minutes. Thereby, the soluble body which consists of Cu was formed.

  Next, after dipping a resin containing Ag or the like on the side surface of the substrate, a terminal electrode was formed by thermosetting. Thereby, the small chip type fuse element of Comparative Example 2 was obtained.

  About Example 8 and Comparative Example 2 produced as described above, the resistance value and the fusing time of the soluble material were measured. The results are shown in Table 3.

  As described above, from the results shown in Table 3, it is possible to obtain a fusible body having a high resistance value by precipitating metal Cu on the surface of a sintered body made of Cu oxide and to shorten the fusing time. confirmed.

(A) is a schematic plan view which shows an example of the chip-type fuse element of 1st Embodiment, (b) is a schematic sectional drawing of (a). It is the schematic of an Ellingham figure. FIG. 2 is a schematic cross-sectional view for explaining an example of a manufacturing method of the chip-type fuse element shown in FIG. 1, (a) is a lead electrode forming step, (b) is a metal layer forming step, and (c) is an oxide layer forming. Step, (d) shows a protective layer forming step, and (e) shows a terminal electrode forming step. It is a schematic sectional drawing for demonstrating the other example of the manufacturing method of the chip-type fuse element shown in FIG. 1, (a) is an extraction electrode formation process, (b) is a metal layer formation process, (c) is a protective layer. A forming paste applying step, (d) shows a protective layer and oxide layer forming step, and (e) shows a terminal electrode forming step. (A) is a schematic plan view which shows an example of the chip-type fuse element of 2nd Embodiment, (b) is a schematic sectional drawing of (a). 6A and 6B are schematic cross-sectional views for explaining an example of a manufacturing method of the chip-type fuse element shown in FIG. 5, wherein FIG. 5A is a metal oxide layer forming step, FIG. 5B is a metal layer forming step, and FIG. A formation process and (d) show a protective layer formation process. It is a schematic sectional drawing which shows an example of the chip-type fuse element of 3rd Embodiment.

Explanation of symbols

  1 substrate, 2 fusible body, 3 protective layer, 4 metal layer, 5 metal oxide layer, 6 lead electrode, 7 terminal electrode

Claims (30)

A chip-type fuse element comprising a fusible body formed by a printing method on a substrate,
The fusible body includes a metal region and a metal oxide region, and the metal region and the metal oxide region are made of the same kind of metal.   2. The chip-type fuse element according to claim 1, wherein after the metal layer is formed as the metal region, a part of the metal layer is oxidized to form the metal oxide region.   3. The chip-type fuse element according to claim 2, wherein a surface portion of the metal layer is oxidized to form a metal oxide layer on the surface.   4. The chip type fuse element according to claim 2, wherein a lead electrode is connected to the metal layer.   5. The chip-type fuse element according to claim 4, wherein the metal contained in the fusible body is more easily oxidized than the metal contained in the extraction electrode.   6. The chip-type fuse element according to claim 5, wherein the metal contained in the fusible body is at least one selected from Cu and Ni.   The chip-type fuse according to any one of claims 4 to 6, wherein the metal contained in the lead electrode is at least one selected from Ag, Au, Pt, Pd, Rh, Ru, and Ir. element.   The chip-type fuse element according to claim 4, wherein a terminal electrode is connected to the lead electrode.   The chip-type fuse element according to claim 2, further comprising a protective layer on the fusible body.   2. The chip type according to claim 1, wherein a metal oxide layer is formed as the metal oxide region by sintering a metal oxide, and then a part of the metal oxide layer is reduced to form the metal region. Fuse element.   11. The chip-type fuse element according to claim 10, wherein a surface portion of the metal oxide layer is reduced and has a metal layer on the surface.   The chip-type fuse element according to claim 10 or 11, wherein the metal oxide is an oxide of Cu, and the metal is Cu.   The chip-type fuse element according to claim 1, wherein the metal region and the metal oxide region are mixed in the fusible body.   14. The chip type fuse element according to claim 13, wherein the metal oxide region is dispersed in the metal layer.   14. The chip-type fuse element according to claim 13, wherein the metal region is dispersed in the metal oxide layer.   A method of manufacturing a chip-type fuse element, wherein a fusible paste is printed on a substrate and fired to form a metal layer, and then a part thereof is oxidized to form a metal oxide.   17. The method for manufacturing a chip-type fuse element according to claim 16, wherein a metal oxide layer is formed on the surface of the metal layer as the region containing the metal oxide.   18. The method of manufacturing a chip-type fuse element according to claim 16, wherein a conductive paste is printed on the substrate and fired to form a lead electrode before forming the metal layer.   19. The method for manufacturing a chip-type fuse element according to claim 18, wherein a metal that is more easily oxidized than a metal contained in the conductive paste is used as the metal contained in the soluble paste.   20. The method for manufacturing a chip-type fuse element according to claim 19, wherein the metal contained in the fusible paste is at least one selected from Cu and Ni.   21. The chip fuse according to claim 18, wherein the metal contained in the conductive paste is at least one selected from Ag, Au, Pt, Pd, Rh, Ru, and Ir. Device manufacturing method.   The method for manufacturing a chip-type fuse element according to any one of claims 16 to 21, further comprising forming a protective layer on the surface of the soluble body after forming the metal oxide.   The method for manufacturing a chip-type fuse element according to claim 22, wherein the protective layer is a resin. After forming the metal layer, the method includes printing a protective layer forming paste on the surface of the metal layer and heat-treating in an oxidizing atmosphere to form the protective layer. The step of forming the protective layer includes the metal oxide. The method for manufacturing a chip-type fuse element according to any one of claims 16 to 21, which also serves as a step of forming a chip.   The method for manufacturing a chip-type fuse element according to claim 24, wherein the protective layer is made of glass.   A fusible paste containing a metal oxide is printed on a substrate, the metal oxide is sintered, and then reduced to metallize a part of the metal oxide. Method.   27. The method for manufacturing a chip-type fuse element according to claim 26, wherein an oxide of Cu is used as the metal oxide.   Print a fusible paste containing metal on the substrate, remove the binder, convert the metal into a metal oxide, sinter the metal oxide, and reduce to metallize part of the metal oxide A method for manufacturing a chip-type fuse element.   29. The method of manufacturing a chip-type fuse element according to claim 28, wherein Cu is used as the metal.   A chip characterized in that a fusible body in which a metal region and a metal oxide region are mixed is formed by printing a fusible paste including a metal powder and an oxide powder of the metal and firing the paste. Method for manufacturing a type fuse element.

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