KR101321814B1 - Variable resistor element and fabrication methods thereof - Google Patents

Abstract

PURPOSE: A resistance variable element and manufacturing method thereof has a plurality of pores on at least part of a ceramic sheet to obtain low nonresistance and high jump properties. CONSTITUTION: A main body (100) comprises a plurality of ceramic sheets (110) and an inner electrode (120) formed between ceramic sheets. At least part among the ceramic sheets has multiple pores. At least part of the ceramic sheets has a thermistor property. An outer electrode (200) is formed on the external side of the main body. The outer electrode comprises a first outer electrode (200a) and a second outer electrode (200b) connected to an inner electrode of each main body.

Description

Resistance variable element and manufacturing method thereof {Variable Resistor Element And Fabrication Methods Thereof}

The present invention relates to a resistance variable element and a method for manufacturing the same, and more particularly, to a resistance variable element manufactured by laminating a semiconducting ceramic sheet, and a method of manufacturing the same.

In recent years, the demand for surface mounting of electronic components has increased, and the PTC (Positive Temperature Coefficient) thermistor, which is a kind of stacked resistive variable elements, has also been required to be miniaturized and low in resistance. The PTC thermistor, which is a semiconducting ceramic element containing barium titanate (BaTiO ₃ ) as its main component, has three basic properties: resistance-temperature characteristics, current-voltage characteristics, and dynamic-time characteristics.

PTC thermistors have a relatively small resistance at low temperatures, but when a certain temperature is reached, the resistance suddenly increases from this temperature and increases significantly. At this time, even if a current is applied, the current hardly flows above this temperature. The temperature at which the resistance changes rapidly is called the Curie temperature or the Curie point, and beyond this temperature, the temperature rises into the positive resistance increase region. To use PTC thermistors for overcurrent protection, the resistance must be increased sensitive to changes in temperature, and the overcurrent must be cut off by increasing the resistance. That is, the overcurrent cut-off characteristic of generating heat when Joule heat is generated by overcurrent and rapidly increasing the resistance at a temperature exceeding the Curie temperature and suppressing the flow of current is important.

Conventionally, a fuse is used for overcurrent blocking, but the fuse cannot be repeatedly used because of a one-time characteristic, and there is a problem that the fuse must be replaced after the overcurrent blocking is made. Thus, PTC thermistors are recently used for overcurrent protection of electronic products and internal circuits. Unlike fuses, a PTC thermistor is used as a self-healing circuit protection device that is blocked when the overcurrent is cut off and the cause of the overcurrent is removed. Therefore, it has a feature that can be used semi-permanently repeated without replacing the device.

In the PTC thermistor, a characteristic in which the resistance of the device rapidly increases, that is, the resistance jumps, is called a jump characteristic. The jump characteristics are greatly influenced by the formation of dislocation barriers at grain boundaries, and it is generally known that a small amount of additives are added to the PTC thermistor composition so that the additive acts as an acceptor at the grain boundaries to obtain high jump characteristics. have. In addition, by increasing the grain size without adding additives

A high jump characteristic effect can be obtained by a number of grain boundaries.

On the other hand, the internal electrode used in the PTC thermistor element needs to use a metal having a melting point higher than the firing temperature for the ohmic connectivity and simultaneous firing with the ceramic layer. Such a metal is effective because pure Ni or Ni-based alloys are much cheaper than other metals. However, since Ni-based metals are easily oxidized at high temperatures, it is necessary to form a reducing atmosphere to prevent them. For this reason, when Ni-based metal material is used as the internal electrode, it is sintered simultaneously in the semiconductor ceramic layer and the reducing atmosphere, and thereafter, heat treatment is performed at a temperature lower than the firing temperature in the air or in an oxidizing atmosphere in order to exhibit the characteristics of the PTC thermistor. An external electrode was formed.

However, the conventional resistance variable device has a problem that the desired jump characteristics cannot be obtained even after oxidation treatment after firing.

In addition, even if the device is manufactured by containing an additive to improve the jump characteristics, it is difficult to control the jump characteristics and obtain the desired performance.

JP 10-2009-0007283 A1

The present invention provides a resistance variable element having excellent jump characteristics and a method of manufacturing the same.

In addition, the present invention provides a manufacturing method for manufacturing a resistance variable element having pores formed in a simple process.

A resistance variable element according to an exemplary embodiment of the present invention includes a main body having a plurality of ceramic sheets and an internal electrode formed between the ceramic sheets and having a plurality of pores, and connected to the internal electrodes and formed on an outer surface of the main body. An external electrode.

In addition, at least some of the ceramic sheets include those having a plurality of pores.

In addition, at least some of the ceramic sheets include those having thermistor characteristics.

In addition, the density of the body includes a range of 4.64 to 5.24g / cm 3.

In addition, an embodiment of the present invention, the process of providing a plurality of ceramic molded sheet, the process of manufacturing an internal electrode paste containing a blowing agent, the process of forming an internal electrode on at least a portion of the molding sheet, and the ceramic molding Laminating sheets to form a molded body, degreasing the molded body, sintering the molded body to prepare a sintered body, and oxidizing the sintered body.

In addition, the ceramic molded sheet includes manufacturing to contain a blowing agent.

The method may further include preparing the ceramic molded sheet to contain the blowing agent contained in the molded sheet in a range of 0.5 to 3 wt% based on the ceramic content of the ceramic molded sheet.

The method may further include preparing the internal electrode paste to contain the foaming agent contained in the internal electrode paste in a range of 2.5 to 10 wt% based on the metal powder content of the internal electrode.

In addition, the blowing agent includes an organic material.

In addition, the blowing agent includes a decomposition temperature range of 155 to 250 degrees.

In addition, the blowing agent includes a decomposition gas amount of 100 to 200ml / g range.

In addition, the higher the decomposition temperature of the blowing agent includes reducing the content of the blowing agent.

The larger the amount of decomposition gas of the blowing agent, the lower the content of the blowing agent.

According to the embodiment of the present invention, a resistance variable element having a plurality of pores formed uniformly without residual carbide can be obtained.

As such, the resistance variable element having pores may increase oxygen adsorbed at grain boundaries because oxygen is introduced through the pores during the oxidation treatment.

In addition, the resistance variable element may obtain a low specific resistance and a high jump characteristic by forming a plurality of pores in at least a portion of the internal electrode and the semiconductive sheet. Improved overcurrent blocking characteristics can be obtained through a resistive variable element with low resistivity and high jump characteristics.

In addition, it is possible to manufacture a resistance variable element in which pores are formed in a simple process.

1 is a cross-sectional view illustrating a coupling of a resistance variable element according to a first exemplary embodiment of the present invention.
2 is an exploded perspective view of a resistance variable element according to a first exemplary embodiment of the present invention.
3 is a cross-sectional view illustrating a coupling of a resistance variable device according to a second exemplary embodiment of the present invention.
4 is a perspective view showing an infiltration path of oxygen gas in the oxidation process of the resistance variable device according to an embodiment of the present invention.
5 is a process flowchart illustrating a manufacturing process of a resistance variable device according to an exemplary embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms, and only the embodiments are intended to complete the disclosure of the present invention, and to those skilled in the art to fully understand the scope of the invention. It is provided to inform you. In the drawings, the thickness of layers, films, panels, regions, etc., may be exaggerated for clarity.

First, the resistance variable element according to the embodiment of the present invention includes a main body having a plurality of ceramic sheets and an inner electrode having a plurality of pores formed therebetween, and an outer electrode connected to the inner electrode and formed on an outer surface of the main body. do.

A plurality of pores may be provided in the internal electrode to improve jump characteristics. That is, the PTC thermistor, which is a kind of resistance variable element, performs firing in a reducing atmosphere to prevent oxidation of an internal electrode, which causes oxygen vacancies in the main body. In this case, since the jump characteristic in which the resistance increases rapidly at the Curie temperature is lost, an oxidation treatment process is performed to implement the jump characteristic. Oxygen gas is adsorbed to the grain boundary through the oxidation treatment process to increase the grain boundary resistance. Here, as the temperature increases, the grain resistance does not change significantly, but the grain boundary resistance rapidly increases, and the PTC thermistor realizes a jump characteristic in which the resistance value increases with increasing temperature.

In addition, the organic foaming agent may provide low specific resistance by uniformly forming pores without impurities in the resistance variable element internal electrode. That is, in the degreasing process of the resistance variable element, carbon is not retained by using an organic blowing agent that is completely burned without residual carbide. That is, it is possible to manufacture a resistance variable element having pores without residual carbide. Accordingly, the resistance variable element can maintain a low resistivity characteristic.

In the following, various embodiments of the present invention will be described in more detail.

≪ Embodiment 1 >

1 is a cross-sectional view illustrating a resistance variable device according to a first embodiment of the present invention, and FIG. 2 is an exploded perspective view of the resistance variable device according to a first embodiment of the present invention.

1 and 2, the resistance variable element 10 according to an exemplary embodiment includes a main body 100 exhibiting thermistor characteristics and external electrodes 200 (200a and 200b) formed on both sides of the main body. .

The main body 100 includes a plurality of ceramic sheets 110, 130, and 140 and internal electrodes 120 (120a and 120b) formed between the sheets. That is, the inner central region of the main body 100 includes a plurality of semiconducting ceramic sheets 110 and a plurality of first and second internal electrodes 120 (120a and 120b) formed on one of upper or lower surfaces of some of them. do.

The external electrode 200 includes a first external electrode 200a and a second external electrode 200b connected to internal electrodes of the main body on both sides of the surface of the main body 100 where the internal electrodes are exposed.

The ceramic sheets 110, 130 and 140 include a semiconducting ceramic sheet 110 having internal electrodes 120 (120a and 120b) having a plurality of pores on one surface of the ceramic sheet 110. In addition, the ceramic sheets 110, 130, and 140 may include ceramic sheets 130 positioned on the uppermost and lowermost sides of the semiconductive ceramic sheet 110 on which the internal electrodes 120 (120a and 120b) are formed. In addition, the cover sheet 140 may be disposed on the uppermost and lowermost sides of the main body 100. Here, the sheet 110 on which the internal electrodes 120: 120a and 120b are formed is a semiconducting ceramic sheet exhibiting thermistor characteristics. The cover sheet 140 and the ceramic sheet 130 may use the same semiconducting ceramic sheet as the sheet on which the internal electrodes are formed, or may use an insulating ceramic sheet regardless of the thermistor characteristics. When using a sheet different from the sheet on which the internal electrodes 120: 120a and 120b are formed, it is preferable to include the same main component so that the main body is less affected when the main body is fired.

The semiconductive ceramic sheet 110 includes a main component and a semiconducting additive and exhibits thermistor characteristics. For example, the semiconductive ceramic sheet (110) includes as a main component barium titanate (BaTiO _3), 3 tribe, La ^{3 +,} Y ^{3 +,} Ce ^{3 +,} Gd ^{3 +,} Sm ^{3 +,} Dy ^{3 +} etc. or 5 tribe, Nb ^{+ 5,} may be added to the semiconductive additives or additive containing a donor Ta ^{+ 5} and so on.

The internal electrodes 120: 120a and 120b extend in the long side direction of the semiconducting ceramic sheet 110, one end of which is positioned to be exposed to the outside from the short side of the semiconducting ceramic sheet 110, and the other end of the semiconducting ceramic sheet ( It is formed not to be exposed to the outside spaced in the inward direction at the short side of 110). In addition, the internal electrodes may include first and second internal electrodes 120a and 120b that are alternately disposed, and a plurality of internal electrodes may be alternately exposed in opposite and opposite side surfaces of the plurality of semiconductive ceramic sheets 110. do.

Silver (Ag), palladium (Pd), platinum (Pt), Ag-Pd alloy (Ag-Pd), etc. may be used as the internal electrodes 120 (120a and 120b). ), Copper (Cu), and the like. In forming the internal electrodes 120: 120a and 120b, a screen printing method is generally applied. In order to form the internal electrodes 120: 120a and 120b by the screen printing method, the internal electrodes 120: 120a and 120b are pastes. The form of paste applies. In addition, when a metal powder such as nickel (Ni) is used for the internal electrode 120 (120a, 120b) paste, since the metal powder and the semiconductive ceramic sheet are essentially different materials, they show a large difference in sintering shrinkage. The greater the difference in shrinkage between the semiconducting ceramic sheet 110 and the internal electrodes 120 (120a, 120b) according to the firing temperature, the greater the incidence of internal defects such as deformation such as bending, peeling of the electrode, and cracking. As it becomes larger, it is necessary to minimize the shrinkage difference. Therefore, in order to reduce the difference in shrinkage rate during firing between the semiconductive ceramic sheet 110 and the internal electrodes 120 (120a, 120b), the paste of the internal electrodes 120: 120a, 120b is composed of a main component metal powder and a semiconducting ceramic sheet ( It is preferable that the ceramic shrinkage powder having the same or similar shrinkage and thermal contraction rate of 100) is included. At this time, the ceramic deducted powder may be added in the same composition as the semiconducting ceramic sheet or as the main component of the semiconducting ceramic sheet so that the deducting component does not act as an impurity. For example, when the main component of the semiconducting ceramic sheet is barium titanate (BaTiO ₃ ), the internal electrodes 120 (120a and 120b) may preferably include barium titanate (BaTiO ₃ ) as a deduction powder. Since the semiconductive ceramic sheet 110 and the internal electrodes 120 (120a and 120b) are combined therewith, firing may be performed simultaneously without occurrence of defects such as cracks. In addition, the difference in thermal shrinkage between the stacked semiconducting ceramic sheets 110 and the internal electrodes 120 (120a and 120b) is not great, and thus, between the semiconducting ceramic sheets 110 and the internal electrodes 120 (120a and 120b). The internal stress due to the shrinkage difference can be reduced to reduce the internal structural defects.

Firing may be performed at the same time after the semiconductor ceramic sheet 220 and the internal electrodes 120 (120a and 120b) are combined. In addition, the difference in thermal contraction rate between the main body 100 on which the semiconductive ceramic sheet 110 is stacked and the internal electrodes 120 (120a and 120b) is not large, so that the semiconductive ceramic sheet 110 and the internal electrodes 120: 120a, Internal stress due to the difference in shrinkage between 120b) can be reduced to reduce internal structural defects. At this time, in order to form a plurality of pores on at least some of the internal electrode may contain a foaming agent in the production of a conductive paste to be described later.

On the other hand, the internal electrode having a plurality of pores improves the jump characteristics. Referring to FIG. 4, the conventional multilayer ceramic PTC thermistor a has a compact internal electrode. In contrast, the multilayer ceramic PTC thermistor (b) according to the present invention has an internal electrode having a structure having a plurality of pores. Conventionally, due to the structure of the dense internal electrode, oxygen gas is hardly adsorbed to the grain boundary through the oxidation process, but the resistive variable element according to the present invention is efficiently adsorbed to the grain boundary through the pores formed in the internal electrode during the oxidation process. Proceeds to. In other words, as the temperature of the device increases, the jump characteristic of the PTC thermistor whose resistance increases rapidly near the Curie temperature is realized. This is because a plurality of pores uniformly formed in the internal electrode act as a passage to effectively penetrate the oxygen gas from the surface to the inside during the oxidation treatment process, thereby increasing the adsorption oxygen at the grain boundary, thereby realizing improved jump characteristics. The overcurrent blocking function can be improved.

In order to form a porous structure of the internal electrodes 120: 120a and 120b, a foaming agent may be included in the paste composition of the internal electrodes. For example, the internal electrode 120 may include Ni metal powder, BaTiO 3 powder, organic vehicle, and blowing agent as a paste component. In the case of containing the blowing agent, a device having a porous structure having increased jump characteristics by controlling the blowing agent content ratio to the metal powder is manufactured. At this time, by controlling the ratio of the blowing agent to the metal powder in the range of 2.5 to 10wt% can obtain a device having a desired porous structure. At this time, if the content of the blowing agent is less than 2.5wt%, the pore formation of the internal electrode is insufficient, and if the content of the blowing agent exceeds 10wt%, there is a problem that the room temperature resistivity of the resistance variable element increases. Therefore, it is preferable to prepare the internal electrode paste so as to contain the blowing agent in the range of 2.5 to 10wt% relative to the metal powder of the internal electrode. In order to control the jump characteristics as described above, when the internal electrode 120 (120: 120a, 120b) paste manufacturing, the foaming agent is controlled to be contained in comparison with the Ni metal powder. That is, the blowing agent content is increased to increase the jump characteristic. For example, organic blowing agents can be used. This will be described later in detail.

The external electrode 200 is an ohmic electrode 210 (210a, 210b), a cover electrode 220 (220a, 220b), a first plating electrode 230 (230a, 230b) from the internal electrode 120 (120a, 120b) to the outside and Second plating electrodes 240 include 240a and 240b. The ohmic electrodes 210 (210a and 210b) are directly connected to the internal electrodes 120 (120a and 120b) to electrically contact the internal electrodes and the external electrodes, and are mainly made of a material such as Ag-Zn. The cover electrodes 220 (220a and 220b) are made of a material such as Ag to apply ohmic electrodes 210 (210a and 210b) and to improve contact with the plating layer, that is, the plating electrodes. The first plating electrodes 230: 230a and 230b and the second plating electrodes 240: 240a and 240b are formed only on the cover electrodes 220: 220a and 220b by plating. Ni is mainly used as the first plating electrodes 230: 230a and 230b, and Sn is used as the second plating electrodes 240: 240a and 240b. The electroplating is sequentially performed to form a plating layer.

≪ Embodiment 2 >

3 is a cross-sectional view illustrating a coupling of a resistance variable device according to a second exemplary embodiment of the present invention.

Referring to FIG. 3, the structure of the resistance variable element according to the second embodiment of the present invention is a structure in which a plurality of pores are formed in at least a portion of the ceramic sheet as compared with the resistance variable element according to the first embodiment. Thus, descriptions overlapping with those of the first embodiment will be omitted and the description will be made mainly on a ceramic sheet having a plurality of pores.

In order to form a porous structure in the ceramic sheet 110, a blowing agent may be contained in the slurry composition for manufacturing the sheet. For example, by controlling the ratio of the blowing agent to the ceramic content of the semiconductive ceramic molded sheet in a range of 0.5 to 3 wt%, a device having a desired porous structure can be obtained. In this case, when the content of the blowing agent is 0.5wt% or less, the pore formation of the ceramic sheet is insufficient, and when the content of the blowing agent is 3wt% or more, there is a problem that the room temperature specific resistance of the resistance variable element is increased. Therefore, it is preferable to prepare the ceramic sheet so as to contain the blowing agent in the range of 0.5 to 3wt% relative to the ceramic content of the ceramic molded sheet. In order to control the jump characteristics as described above, the foaming agent is contained by controlling the content of the ceramic in the ceramic molded sheet in comparison with the ceramic content of the ceramic formed sheet.

As such, when the pores are formed not only in the internal electrode but also in the ceramic sheet, the oxygen gas input path is more efficiently formed during the oxidation process described above, thereby promoting the penetration of oxygen, thereby performing the oxidation process more effectively.

In the above, the resistance variable element having a structure having a plurality of pores has been described by illustrating some embodiments, but the embodiments may be implemented alone or in combination with each other in various ways.

Hereinafter, a manufacturing method of manufacturing a resistance variable device will be described in detail. In the above description, the structure of a single resistance variable element has been described, but the resistance variable element is manufactured in a manner of producing a plurality of chips together to improve process convenience and productivity.

5 is a process flowchart illustrating a manufacturing process of a resistance variable device according to an exemplary embodiment of the present invention. A manufacturing process will be described in detail with reference to FIG. 5.

First, various molded sheets are prepared (S100 in Fig. 5). Semi-conductive ceramic molding sheet

Add semiconducting additives to commercially available BaTiO ₃ powder for industrial use to adjust to the desired composition, mix and dry water or alcohol with a solvent for a predetermined time (24 hours), and then calcinate at 900 ~ 1200 ℃. Raw material powder is prepared. However, in some cases, the calcination step may be omitted or an additive may be further added after the calcination step. Curie temperature control additives such as Sr and semiconducting additives having a donor function are preferably calcined together with BaTiO ₃ powder to be used in the form of a substituted solid solution, and Mn and sintering aid functioning as an acceptor. Is preferably added after calcination with additives related to grain boundary properties. Therefore, in the case of a simple composition without the acceptor or the sintering aid, the calcination step may be omitted. Complex compositions, on the other hand, may be subjected to multiple calcination processes for homogeneous mixing and solid solution formation. Next, to prepare a molded sheet, the prepared raw powder was weighed and dissolved in a solvent (for example, toluene / alcohol solvent) in a suitable amount of binder such as PVB binder, and then milled and mixed for about 24 hours using a ball mill. Prepare a slurry. This slurry is prepared into a semiconducting ceramic molded sheet (Green sheet) having a desired thickness by a method such as a doctor blade.

The cover molding sheet may use a composition different from the case of using the same composition as the semiconductive ceramic molding sheet, for example, an insulator cover molding sheet may be used. The former is prepared in the same manner as the method for preparing the semiconductive ceramic molded sheet. However, the insulator cover molded sheet has the same main component as the main component of the semiconductor ceramic molded sheet, but differs in specific composition. That is, by controlling the component ratio of the composition of BaTiO ₃ or by using the raw material powder was not added to the semiconductive additives to produce an insulation cover-shaped sheet. In this case, in order to form a plurality of pores in at least some of the various molded sheets, the molded sheet may be prepared to contain a blowing agent in the range of 0.5 to 3wt% relative to the ceramic content of the various molded sheets.

A conductive paste which is an internal electrode paste is prepared (S110 in Fig. 5). For example, a commercially available metal powder 35 to 55 wt%, a BaTiO ₃ subtractive powder 5 to 15 wt%, and an organic vehicle 40 to 60 wt% are mixed with a conductive paste component, and then filtered and bubbles are removed. Prepare the paste. At this time, nickel may be used as the metal powder. Commercially available conductive pastes can also be used. In this case, in order to form a plurality of pores in at least some of the internal electrode, the conductive paste may be prepared to contain a blowing agent in the range of 2.5 to 10 wt% with respect to the metal powder of the internal electrode.

The internal electrode pattern is printed on the manufactured semiconductive ceramic molded sheet by a screen printing method using the internal electrode pattern screen. At this time, the internal electrodes are alternately printed on the sheet using the above-mentioned conductive paste. In addition, a plurality of internal electrode patterns are formed on the semiconductive ceramic molding sheet, and are repeatedly formed in accordance with regions to be separated into respective elements (single elements) by a cutting process performed thereafter (S120 of FIG. 5).

A molded product is manufactured using various prepared molding sheets (S130 of FIG. 5). The molded article is produced by laminating and pressing a plurality of cover molded sheets and semiconducting molded sheets.

Thereafter, the molded body is cut. That is, the molded bodies are cut to form a molded unit in the form of a unit element (eg, a hexahedron) in order to make an individual unit element having a desired unit chip size.

Insulation treatment is performed on all surfaces of the molded body in the form of a plurality of cut units except the exposed surface of which the internal electrode is exposed. For example, in the case of the molded article using the insulator cover molding sheet, all surfaces except the exposed surface of the insulator cover molding sheet and the exposed surface of the internal electrode are subjected to insulation treatment. On the other hand, in the case of the molded article using the cover molding sheet having the same composition as the semiconducting ceramic molded sheet, all surfaces except the exposed surface to which the internal electrodes are exposed are subjected to insulation treatment. The insulation treatment can be performed by, for example, a method of covering the insulation layer.

The molded bodies coated with the insulator layer are degreased (S140 of FIG. 5). This is a process for burning organic matter in the molded article in the form of unit elements. Here, the degreasing process may be performed in the range of 300 to 400 degrees in the atmosphere or oxygen atmosphere. In this case, when the molded products are degreased to form a plurality of pores, the blowing agent may be completely removed without remaining carbides in the degreasing process using an organic material.

Thereafter, the molded bodies are fired or sintered (S150 of FIG. 5). That is, sintering which heat-processes at high temperature advances. Sintering can be carried out in a reducing atmosphere in the range of 1000 to 1300 degrees, for example at 1300 degrees.

In addition, when the sintering process is completed, the molded body becomes a sintered body, and becomes a sintered body in which the semiconductive ceramic sheet laminate and the insulator layer are firmly bonded on all surfaces except the exposed surfaces of the internal electrodes.

Thereafter, oxidation is performed through heat treatment for 1 hour or more at a temperature in a range of 500 to 700 degrees in an air or oxygen atmosphere to give a jump characteristic (S160 in FIG. 5). As the heat treatment temperature increases, it is advantageous to reoxidation, but it is better to perform it within the proper temperature range because the internal electrode causes deterioration of characteristics due to oxidation. In this case, in the case of the sintered body in which the plurality of pores are formed, the oxidation treatment may be efficiently performed by improving the jump characteristic of the resistance variable element as described above by the plurality of pores formed in the sintered body.

Thereafter, an external electrode is formed on the surface where the insulator is not formed (S160 of FIG. 5).

First and second external electrodes 200a and 200b are connected to both side surfaces of the internal electrode 120 of the sintered body. Ohmic electrodes 210 (210a and 210b) are formed in direct contact with the exposed surfaces of the internal electrodes 120 (120a and 120b). Subsequently, cover electrodes 220 (220a, 220b) are formed. Next, the first and second plating electrodes 230 and 240 are formed by electroplating on the cover electrodes 220 (220a and 220b).

Hereinafter, various conditions for forming pores will be described in detail.

First, Table 1 shows the specimens in which the blowing agent content of the Ni internal electrode paste component was adjusted to improve jump characteristics. The reference specimen is specimen No. 1 in Table 1, and the foaming agent content was adjusted in the Ni internal electrode paste component based on specimen No. 1 without adding a blowing agent.

First, the semiconductive ceramic sheet used in the sample is the main component is _{(Ba 0 .9 Sr 0 .1 Y} 0.004) TiO _3, and a ceramic powder, a binder, an organic catalyst, a dispersing agent was molded into a sheet tape casting method. The conductive paste is printed on the semiconductive ceramic sheet using Ni commercially available Ni paste, by screen printing method, and the prepared sheets are laminated, pressed, and sized to 1608 (L = 1.6mm, W = 0.8mm). It cut | disconnected and prepared the molded object.

Thereafter, the prepared molded body is degreased at 360 degrees of the atmosphere in the atmosphere, after which N ₂ Sintered specimens were prepared by firing in a reducing atmosphere at 1250 ° C. for 2 hours using a mixed gas having a ratio of 1% to H ₂ .

Thereafter, the prepared sintered piece was subjected to oxidation treatment for 1 hour at 600 degrees in the atmospheric atmosphere before the Ag-Zn terminal electrode was formed.

For each specimen, the room temperature resistivity (ρ _{30 ° C} ) and jump (ρ _{150 ° C} / ρ _{30 ° C} ) characteristics were measured with Ag-Zn terminal electrodes, and the density was measured by mass and volume calculations. Since the measuring methods are general measuring methods, detailed descriptions thereof will be omitted.

The larger the jump characteristic is, the better the lower the resistivity is, the better the PTC thermistor is. If these two characteristics are good, one might be worse. Therefore, in the present invention, jump / resistance is indicated in order to control two characteristics and to compare that the numerical value of each characteristic is controlled. In other words, the larger the jump / resistance value, the better the PTC thermistor characteristic of the specimen.

Psalter
Blowing agent content compared to Ni metal powder (wt%)
Resistivity
(Ωcm)
jump
characteristic
Jump / resistance
density
(g / cm3) One 0 10.8 20.3 1.88 5.29 2 5 11.1 24.6 2.21 5.23 3 10 12.4 26.3 2.12 5.19 4 15 16.7 26.2 1.56 5.14

As can be seen from Table 1, the overall jump characteristics are increased as the blowing agent content is increased compared to the Ni metal powder. Specimens No. 2 and Specimens No. 3 showed 2.21 and 2.12 jump characteristics, respectively, which were 0.3 or higher than those of other specimens. Among them, specimen 2 was the highest with a jump characteristic value of 2.21.

On the other hand, specimen No. 4 having a foaming agent content of 15wt% showed a high jump characteristic value of 26.2, but shows a significantly higher resistivity value than other specimens. This indicates that as the blowing agent content increases, the jump value can be improved, but when the content exceeds the appropriate content, the specific resistance value is rather deteriorated.

On the other hand, unlike specimen No. 1, when the blowing agent is contained, it can be seen that pores are formed according to the blowing agent content, and thus the density decreases. It can be seen that the density of the specimen prepared is increased by increasing the content of the blowing agent compared to the Ni metal powder.

From this, the blowing agent content is preferably contained in less than 15wt% compared to the Ni metal powder, more preferably contained in the range of 2.5 to 10wt%. At this time, when contained in less than 2.5wt%, the pores were not sufficiently formed, and the jump characteristic improvement was also insignificant.

In addition, the blowing agent content is more preferably contained in the range of 5 to 10wt% compared to the Ni metal powder. This is because in this range, as shown in Table 1, both the specific resistance and the jump characteristic are excellent, and a high quality PTC thermistor can be obtained.

In Table 2 below, the blowing agent content of the Ni internal electrode paste component was the same, and the results of using the blowing agent under various conditions in the specimen were shown. Based on the second specimen having a blowing agent content of 5wt%, a specimen was prepared using a blowing agent having a different decomposition temperature and decomposition gas amount. In addition, the manufacturing conditions of all the specimens were the same as those of Table 1 above.

Psalter
Decomposition temperature
(℃)
Gas amount
(ml / g)
Resistivity
(Ωcm)
jump
Jump / resistance
density 2 155-165 100-120 11.1 24.6 2.21 5.23 5 150 to 160 120 to 130 11.8 25.2 2.13 5.21 6 240 to 250 180 to 200 13.3 25.3 1.90 5.17 7 175 to 185 210 to 255 22.4 27.3 1.22 5.12 8 270 to 300 160-170 117.5 21.0 0.18 5.18

As can be seen from Table 2, it can be seen that the density of the specimen produced using a blowing agent having a large amount of decomposition gas as a whole decreases. The difference in density between Specimen No. 2 and other specimens can be seen that the difference in the pore formation according to the amount of decomposition gas of the blowing agent appears as a difference in density. As can be seen from the results of Specimens 2, 5, and 6, when the amount of decomposition gas is increased, the pore formation is smooth and the jump characteristic is improved. However, if the amount of cracked gas is too large, exceeding 200 ml / g, the resistivity property is deteriorated and the ratio of jump / resistance is also reduced. For example, specimen No. 7 having a decomposition gas amount of 210 to 255 ml / g has a poor jump / resistance value of 1.22. Therefore, the decomposition gas amount is preferably in the range of 100 to 200 ml / g. If the amount of blowing agent decomposition gas is too small, the pore-forming effect of the blowing agent is reduced, on the contrary, if the amount of gas is too large, sudden gas generation may be accompanied by internal defects such as cracks in the sintered body.

The blowing agent decomposition temperature is preferably lower than the degreasing temperature (eg, 360 degrees) so that the blowing agent can be completely burned at a temperature below the degreasing process temperature. As can be seen from the results of Specimens 2, 5 and 6, an increase in decomposition temperature improves the jump characteristic. However, if the decomposition temperature becomes excessively higher than 250 degrees, the resistivity characteristic deteriorates rapidly and the jump characteristic also decreases. For example, when looking at Specimen No. 8 with decomposition temperature of 270 ~ 300 degrees, the specific resistance is 117.5. Therefore, the decomposition temperature of the blowing agent is preferably 250 degrees or less.

On the other hand, when it contains the same amount of blowing agent, as described above, it can be seen that as the amount of decomposition gas or decomposition temperature of the blowing agent increases, more pores are formed from the decrease in the density of the device. Accordingly, when the amount of decomposition gas of the blowing agent is increased or the decomposition temperature is increased, the content of the blowing agent may be reduced to form an appropriate amount of pores in the device.

In Table 3 below, the foaming agent content of the Ni internal electrode paste component was the same, and the result of adding the foaming agent to the semiconductive ceramic molding composition of the specimen was adjusted. Based on Specimen No. 2 with no blowing agent added to the semiconducting ceramic composition, the experimental results for Specimen Nos. 9 to 12 were prepared by adjusting the amount of the blowing agent relative to the semiconducting ceramic composition. Each specimen was prepared under the same conditions as the fabrication conditions of the specimens of Table 2 except that the foaming agent content was adjusted to the semiconducting ceramic composition.

Psalter
Semiconducting ceramic
Composition
Foaming agent content
(wt%)
Resistivity
(Ωcm)
jump
Jump / resistance
density
(g / cm3) 2 0 11.1 24.6 2.21 5.23 9 One 11.9 30.5 2.56 4.95 10 2 13.2 32.2 2.43 4.78 11 3 15.8 33.4 2.11 4.64 12 4 25.4 33.8 1.33 4.54

As can be seen from Table 3, it can be seen that the specimen prepared by increasing the blowing agent content relative to the semiconducting ceramic composition as a whole, the less the density. That is, the difference between the density of the sample 2 and the other specimens in which the foaming agent is not added to the semiconducting ceramic composition can be seen that the difference in the pore formation according to the content of the foaming agent compared to the semiconducting ceramic composition is the difference in density.

Compared to the case where the pores are formed only on the internal electrode (Sample 2), the jump characteristics are improved when the pores are also formed on the semiconductive ceramic composition (ie, the ceramic sheet) (Samples 9 to 12). In addition, as the blowing agent content in the semiconducting ceramic composition increases, the jump characteristic is improved. However, if the foaming agent content is excessively increased, the jump numerical value can be improved, but rather shows a deterioration in which the resistivity value is increased, and the ratio of jump / resistance is also lowered. For example, the resistivity of specimen No. 12 with a foaming agent content of 4 wt% increases rapidly to 25.4 kPa and the jump / resistance value is 1.33, which is low.

Therefore, the content of the blowing agent for the semiconductive ceramic composition is preferably contained in 3wt% or less, more preferably in the range of 0.5 to 3wt% or less. In this case, if the content is less than 0.5wt%, pores are not sufficiently formed, and the improvement of the jump characteristic is also insignificant. In addition, the blowing agent content is more preferably contained in the range of 1 to 3wt% or less compared to the semiconducting ceramic composition. This is because in this range, as shown in Table 3, both the specific resistance and the jump characteristic are excellent, and a high quality PTC thermistor can be obtained.

Table 4 shows the results of adjusting the sintering temperature of each specimen in which the same amount of blowing agent was added to the Ni internal electrode paste, or adjusting the sintering temperature of each specimen in which the same amount of blowing agent was added to the internal electrode paste and the ceramic composition. Indicated. Specimen No. 2 and Specimen No. 9 used in Table 4 used a Ni internal electrode using a blowing agent having a decomposition temperature in the range of 155 to 165 degrees and a decomposition gas amount of 100 to 120 ml / g, 5wt% of Ni metal powder. Burn is a specimen containing no blowing agent compared to the semiconducting ceramic composition, specimen 9 was prepared by containing 1wt% of the blowing agent compared to the semiconducting ceramic composition. Specimen Nos. 2 to 9-3 used in Table 4 below were prepared by adjusting the sintering temperature in the range of 1240 to 1280 degrees. The fabrication conditions of all other specimens were the same as those of Specimen No. 2 in Table 2.

Psalter

Sintering temperature
(℃) Semiconducting ceramic
Composition
Foaming agent content
(wt%)
Resistivity
(Ωcm)
jump
Jump / resistance
density
(g / cm3) 2 1240 0 11.1 24.6 2.21 5.23 2-2 1260 0 9.8 19.4 1.98 5.61 2-3 1280 0 9.2 12.5 1.36 5.84 9 1240 One 11.9 30.5 2.56 4.95 9-2 1260 One 11.2 28.4 2.54 5.06 9-3 1280 One 10.9 25.7 2.36 5.24

As can be seen from Table 4, it can be seen that by forming a foaming agent in at least a portion of the internal electrode and the semi-conductive sheet during the production of the molded body as a whole, it shows an improved jump characteristics as the porous structure of the molded body is maintained in a wide sintering temperature range .

 When only the internal electrode paste contains a blowing agent (Samples 2, 2-2, 2-3), the resistivity decreases as the sintering temperature increases, but the jump characteristic also tends to decrease. On the other hand, when the semiconducting ceramic composition also contains a blowing agent (Samples 2, 2-2, 2-3), even if the specific resistance decreases as the sintering temperature increases, the jump characteristics are maintained. That is, it is possible to manufacture a device having good characteristics over the entire temperature range.

From this, the molded article containing the foaming agent can be produced in a device having good characteristics in a wide sintering temperature range, thereby extending the process margin of the device manufacturing process.

In Table 5 below, the conditions of the foaming agent contained in the internal electrode paste were the same, and the measurement results of the specimens prepared by changing the conditions (decomposition temperature and decomposition gas amount) of the foaming agent added to the semiconductive ceramic composition were shown. As in Specimen # 9, all other specimens were fabricated using foaming agents with different decomposition temperatures and decomposition gas concentrations. In addition, the fabrication conditions of all specimen manufactures are the same as those of the specimens of Table 2 above.

Psalter

Decomposition temperature
(℃) decomposition
Gas amount
(ml / g)
Resistivity
(Ωcm)
jump
Jump / resistance
density
(g / cm3) 9 155-165 100-120 11.9 30.5 2.56 4.95 13 150 to 160 120 to 130 12.3 32.2 2.62 4.86 14 240 to 250 180 to 200 14.8 34.8 2.35 4.72 15 175 to 185 210 to 255 25.1 30.7 1.22 4.47 16 270 to 300 160-170 152.4 28.6 0.19 4.77

As can be seen from Table 5, it can be seen that the density of the specimen produced using a blowing agent having a large amount of decomposition gas as a whole decreases. The difference in density between Specimen No. 9 and other specimens can be seen that the difference in the pore formation according to the amount of decomposition gas of the blowing agent appears as a difference in density.

As can be seen from the results of specimens 9, 13 and 14, when the amount of decomposition gas is increased, the pore formation is smooth and the jump characteristic is improved. However, if the amount of cracked gas is too large, exceeding 200 ml / g, the resistivity property is deteriorated and the ratio of jump / resistance is also reduced. For example, specimen 15 having a decomposition gas amount of 210 to 255 ml / g has a poor jump / resistance value of 1.22. Therefore, the decomposition gas amount is preferably in the range of 100 to 200 ml / g. If the amount of blowing agent decomposition gas is too small, the pore formation of the blowing agent is reduced, on the contrary, if the amount of gas is too high, sudden gas generation may be accompanied by internal defects such as cracks in the sintered body.

The decomposition temperature of the blowing agent is preferably lower than the degreasing temperature (eg, 360 degrees) so that the decomposition temperature of the blowing agent can be completely burned at a temperature below the degreasing process temperature. As can be seen from the results of specimens 9, 13 and 14, the jump characteristic is improved as the decomposition temperature is increased. However, if the decomposition temperature becomes excessively higher than 250 degrees, the resistivity characteristic deteriorates rapidly and the jump characteristic also decreases. For example, when looking at Specimen 16 with a decomposition temperature of 270 to 300 degrees, the specific resistance is very large, 152.4. Therefore, the decomposition temperature of the blowing agent is preferably 250 degrees or less.

On the other hand, when it contains the same amount of blowing agent, as described above, it can be seen that as the amount of decomposition gas or decomposition temperature of the blowing agent increases, more pores are formed from decreasing the density of the device. Accordingly, when the amount of decomposition gas of the blowing agent is increased or the decomposition temperature is increased, the content of the blowing agent may be reduced to form an appropriate amount of pores in the device.

From the above experimental results, it can be seen that the specific resistance and the jumping characteristics can be controlled by forming pores in the resistance variable element, and the degree of pore formation can be known by measuring the density of the element. In the resistance variable device, the density can be controlled to an appropriate range to form pores having a desired amount (quantity), and a high quality device can be manufactured therefrom. The resistive variable element of the embodiment of the present invention has a lower density of the element body compared to the conventional one which does not contain a blowing agent, and the density range of the main body is preferably in the range of 4.64 to 5.24 g / cm 3. If the density is too low, the pores are excessively formed to increase the resistivity, and if the density is too high, the pore formation is insignificant.

Although the embodiments, modifications, embodiments, and modifications of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the embodiments, modifications, embodiments, and modifications, but various other forms. It is possible to manufacture a variety of combinations between embodiments and modifications, and those skilled in the art to which the present invention pertains may be carried out in other specific forms without changing the technical spirit or essential features of the present invention. I can understand that you can. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

10: resistance variable element 100: main body
110: semiconductive ceramic sheet 120: internal electrode
120a: first internal electrode 120b: second internal electrode
200: external electrode 200a: first external electrode
200b: second external electrode 210a: ohmic electrode
210b: ohmic electrode 220a: cover electrode
220b: cover electrode 230a: first plating electrode
230b: first plating electrode 240a: second plating electrode
240b: second plating electrode

Claims (13)

A main body having a plurality of ceramic sheets and internal electrodes formed between the ceramic sheets and having a plurality of pores;
And an external electrode connected to the internal electrode and formed on an outer surface of the main body. The method according to claim 1,
At least some of the ceramic sheet has a resistance variable element having a plurality of pores. The method according to claim 1 or 2,
At least some of the ceramic sheet has a resistance thermistor device. The method according to claim 1 or 2,
The resistive variable element of the main body has a density ranging from 4.64 to 5.24g / cm 3. Providing a plurality of ceramic molded sheets;
Preparing an internal electrode paste containing a blowing agent;
Forming internal electrodes on at least some of the ceramic molded sheets;
Stacking the ceramic molded sheets to prepare a molded body;
Degreasing the molded body;
Sintering the molded body to prepare a sintered body; And
A method of manufacturing a resistance variable device comprising the step of oxidizing the sintered body. The method according to claim 5,
The ceramic molded sheet is a method of manufacturing a resistance variable element to produce a foaming agent. The method of claim 6,
The method of manufacturing a resistance variable element for manufacturing the ceramic molded sheet to contain the blowing agent contained in the ceramic molded sheet in a range of 0.5 to 3wt% relative to the ceramic content of the ceramic molded sheet. The method according to any one of claims 5 to 7,
The method of manufacturing a resistance variable element for manufacturing the internal electrode paste to contain the blowing agent contained in the internal electrode paste in the range of 2.5 to 10wt% relative to the metal powder content of the internal electrode. The method according to claim 5 or 6,
The blowing agent is a method of manufacturing a resistance variable element of an organic material. The method according to claim 5 or 6,
The blowing agent is a method of manufacturing a resistance variable element having a decomposition temperature range of 155 to 250 degrees. The method according to claim 5 or 6,
The blowing agent is a method of producing a resistance variable element having a decomposition gas amount of 100 to 200ml / g range. delete delete

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