JP4660922B2 - Thermistor and manufacturing method thereof - Google Patents

Description

【００３６】
表１から明らかなように、サーミスタ層７，８を構成するサーミスタペーストを異ならせることにより、同じサーミスタ素体２を用いた場合でも、最終的に得られた完成品としてのサーミスタ１における抵抗値及びＢ定数を大幅に変更し得ることがわかる。
【００３７】
すなわち、焼成によりサーミスタ素体２を得た後に本実施例によればＮＴＣサーミスタ１の抵抗値やＢ定数などの電気的特性を大幅に調整することができる。
従って、用途に応じた特性のＮＴＣサーミスタ１を容易にかつ速やかに提供し得ることがわかる。
【００３８】
なお、サーミスタ層７，８の厚みについては特に限定されるわけではないが、内部電極３〜６と外部電極９，１０との導通を確実なものとするためには、さほど厚くないことが望ましく、１０μｍ以下とすることが望ましい。
【００３９】
上記実施例では、外部電極９，１０の外表面にメッキ膜１１ａ，１１ｂ，１２ａ，１２ｂを形成したが、メッキ膜１１ａ，１１ｂ，１２ａ，１２ｂは必ずしも形成されずともよい。
【００４０】
また、上記実施例では、内部電極３〜６を有する積層型のＮＴＣサーミスタ１を説明したが、本発明は、内部電極を有しないサーミスタにも適用することができる。また、サーミスタ素体についても、円板状や角板状のサーミスタ素体を用いてもよく、円板状や角板状のサーミスタ素体の両主面にサーミスタ層及び外部電極を形成したものであってもよい。
【００４１】
さらに、ＮＴＣサーミスタだけでなく、ＰＴＣサーミスタにも本発明を適用することができる。
【００４２】
【発明の効果】
本発明に係るサーミスタによれば、セラミック焼結体の対向し合う第１，第２の端面にサーミスタペーストの焼付けにより第１，第２のサーミスタ層が形成されており、第１，第２のサーミスタ層上に第１，第２の外部電極が形成されている。従って、セラミック焼結体からなるサーミスタ素体を得た後に、様々な特性のサーミスタペーストから目的とする特性に応じたサーミスタペーストを選択して第１，第２のサーミスタ層を形成することにより、同じサーミスタ素体を用いた場合であっても、最終的に得られるサーミスタの抵抗値やＢ定数などの電気的特性を大幅にかつ容易に調整することができる。よって、必要とされる特性に応じたサーミスタを容易にかつ速やかに提供することができる。
【００４３】
サーミスタ素体内に複数の内部電極が形成されており、複数の内部電極が第１の端面または第２の端面に引き出されている構造を有する場合には、積層型のサーミスタを本発明に従って得ることができるので、様々な抵抗値のサーミスタを容易に設計することができる。
【００４４】
外部電極が導電ペーストの焼付けにより形成された導電膜により形成されており、かつ外部電極の外表面に積層されたメッキ膜をさらに備える場合には、導電ペーストの焼付けにより形成された外部電極により電気的接続の信頼性が高められ、かつ積層されたメッキ膜の材料を選択することにより半田付け性等を高めることができる。
【００４５】
セラミック焼結体が負の抵抗温度特性を有する半導体セラミックスからなる場合には、本発明に従って、抵抗値等の電気的特性を大幅に調整し得るＮＴＣ素子を容易に提供することができる。
【００４６】
本発明に係るサーミスタの製造方法では、サーミスタ素体を用意した後に、サーミスタ素体の第１，第２の端面上にサーミスタペーストを付与し、該サーミスタペーストを焼成することにより、第１，第２のサーミスタ層が形成されるので、サーミスタペーストを選択することにより、最終的に得られるサーミスタの電気的特性を大幅にかつ容易に調整することができる。
【００４７】
サーミスタ素体の第１，第２の端面にサーミスタペーストを付与するに先立ち、サーミスタ素体をバレル研磨し、サーミスタ素体の第１，第２の端面の外周縁の稜線を研磨した場合には、第１，第２のサーミスタ層を稜線部分においても十分な厚みに形成することができる。従って、第１，第２のサーミスタ層による電気的特性の調整を安定に行うことができる。
【００４８】
サーミスタ素体内に複数の内部電極が形成されており、複数の内部電極が第１，第２の端面に引き出されている場合には、本発明に従って、電気的特性を大幅にかつ速やかに調整し得る積層型のサーミスタを容易に提供することができる。
【００４９】
本発明に係る製造方法において、外部電極形成後に、外部電極表面にメッキ膜を形成する場合には、メッキ膜の材料を選択することにより、半田付け性などを容易に高めることができる。
【図面の簡単な説明】
【図１】本発明の一実施例のサーミスタを示す縦断面図。
【図２】図１に示したサーミスタを得るにあたって、サーミスタ素体の外表面に第１，第２のサーミスタ層を形成した状態を示す縦断面図。
【図３】図２に示したサーミスタ素体の第１，第２のサーミスタ層上に外部電極を形成した状態を示す縦断面図。
【図４】従来のサーミスタの一例を示す縦断面図。
【符号の説明】
１…サーミスタ
２…サーミスタ素体
２ａ，２ｂ…第１，第２の端面
３〜６…内部電極
７，８…第１，第２のサーミスタ層
９，１０…第１，第２の外部電極
１１ａ，１１ｂ，１２ａ，１２ｂ…メッキ膜[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermistor used for, for example, temperature detection or temperature compensation of a circuit component and a manufacturing method thereof, and more particularly to a chip type thermistor that can be surface-mounted on a printed circuit board and the like and a manufacturing method thereof.
[0002]
[Prior art]
Conventionally, thermistors have been widely used for temperature detection and temperature compensation of electronic circuits. The thermistor has a structure in which a pair of external electrodes are formed on the outer surface of a thermistor body made of semiconductor ceramics. In manufacturing, after obtaining a ceramic sintered body made of semiconductor ceramics, an external electrode is formed by applying and baking a conductive paste.
[0003]
As the thermistor, those having various structures are conventionally known. For example, Japanese Patent Laid-Open No. 9-186002 discloses a thermistor 51 shown in FIG. In the thermistor 51, external electrodes 53 and 54 are formed on both ends of the thermistor body 52. The external electrodes 53 and 54 have element electrodes 53a and 54a serving as bases, and cover electrodes 53b and 54b formed on the element electrodes 53a and 54a, respectively. The element electrodes 53a and 54a are made of an oxide having a low resistance value such as RuO _2, and the cover electrodes 53b and 54b are formed by applying and baking a conductive paste mainly containing Ag or the like. Here, by forming the device electrodes 53a and 54a made of low resistance oxide, even if part of the cover electrodes 53b and 54b disappears due to solder erosion during soldering, the device electrodes 53a and 54a remain. Therefore, it is said that the electrical characteristics of the thermistor 51, for example, a decrease in specific resistance and B constant can be prevented.
[0004]
[Problems to be solved by the invention]
As the thermistor, a thermistor having an electrical characteristic corresponding to its application, that is, a specific resistance or a B constant is used. On the other hand, in the conventional thermistor, it is difficult to easily correct the resistance value and the like. That is, after obtaining a thermistor body made of semiconductor ceramics, the resistance value could be adjusted only by changing the distance between a pair of external electrodes formed on the outer surface. For this reason, the adjustment range of the resistance value is narrow, and it is difficult to quickly provide a thermistor having the desired electrical characteristics.
[0005]
In the thermistor 51 disclosed in Japanese Patent Laid-Open No. 9-186002, the electrical characteristics can be prevented from being deteriorated, and although suitable for wiring processing with high-temperature solder, There is no mention of adjusting the electrical characteristics after obtaining the thermistor body.
[0006]
An object of the present invention is to provide a thermistor capable of greatly and easily adjusting electrical characteristics such as a resistance value after obtaining a thermistor body made of semiconductor ceramics, and a method for manufacturing the thermistor.
[0007]
[Means for Solving the Problems]
According to a wide aspect of the present invention, a thermistor body made of a ceramic sintered body and having opposing first and second end faces and formed by baking the thermistor paste on the first and second end faces. A thermistor is provided that includes the first and second thermistor layers formed, and the first and second external electrodes formed on the first and second thermistor layers.
[0008]
In a particular aspect of the present invention, prior SL has a plurality of internal electrodes formed on the thermistor element body, internal electrodes of the plurality of being drawn to the first end face and the second end surface.
[0009]
In another specific aspect of the present invention, the external electrode is made of a conductive film formed by baking a conductive paste, and further includes a plating film laminated on the outer surface of the external electrode.
[0010]
In still another specific aspect of the present invention, the ceramic sintered body is made of a semiconductor ceramic having negative resistance temperature characteristics.
According to another broad aspect of the present invention, a step of preparing a thermistor body made of a ceramic sintered body and having opposing first and second end faces, and first and second of the thermistor body. A step of applying a thermistor paste on the end face; a step of firing the thermistor paste to form first and second thermistor layers; and applying and baking a conductive paste on the first and second thermistor layers. Accordingly, there is provided a thermistor manufacturing method including the steps of forming the first and second external electrodes.
[0011]
In another specific aspect of the thermistor manufacturing method according to the present invention, prior to applying the thermistor paste to the first and second end faces of the thermistor body, the thermistor body is barrel-polished, The process of grind | polishing the ridgeline which exists in the outer periphery of 1 and 2nd end surface is further provided.
[0012]
In still another specific aspect of the method for manufacturing the thermistor of the present invention, as a pre-Symbol thermistor body, a plurality of which the internal electrode is formed and a plurality of internal electrodes inside is drawn to the first, second end face Thermistor element is used.
[0013]
According to still another specific aspect of the thermistor manufacturing method according to the present invention, the method further includes the step of forming a plating film on the surface of the external electrode after the external electrode is formed.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be clarified by giving specific examples of the present invention with reference to the drawings.
[0015]
FIG. 1 is a cross-sectional view showing an NTC thermistor according to an embodiment of the present invention. The NTC thermistor 1 has a rectangular parallelepiped thermistor body 2. The thermistor body 2 is configured using a ceramic sintered body made of semiconductor ceramics having negative resistance temperature characteristics.
[0016]
In the thermistor element body 2, a plurality of internal electrodes 3 to 6 are arranged so as to overlap with each other via the thermistor element layer. The internal electrodes 3 to 6 are formed by baking a conductive paste such as an Ag paste.
[0017]
The internal electrodes 3 and 5 are drawn out to the first end face 2 a of the thermistor body 2. The internal electrodes 4 and 6 are drawn out to the second end face 2b facing the first end face.
[0018]
First and second thermistor layers 7 and 8 are formed so as to cover the end faces 2a and 2b, respectively. The thermistor layers 7 and 8 are formed by baking the thermistor paste. That is, after the thermistor body 2 is obtained, the thermistor layers 7 and 8 are formed by applying and baking the thermistor paste so as to cover the end faces 2a and 2b.
[0019]
As the thermistor paste, a paste mainly composed of semiconductor ceramic powder having negative resistance temperature characteristics is used. In this case, the semiconductor ceramic powder constituting the thermistor layers 7 and 8 may be the same material as the semiconductor ceramic constituting the thermistor body 2 or may be a different material.
[0020]
The thermistor layers 7 and 8 are formed to reach not only the end faces 2a and 2b but also the upper surface 2c and the lower surface 2d of the thermistor element body 2 and a pair of side surfaces not shown. The portions where the thermistor layers 7 and 8 and external electrodes to be described later reach the upper surfaces 2c and 2d and the pair of side surfaces of the thermistor body 2 are hereinafter referred to as covered portions.
[0021]
On the outer surfaces of the thermistor layers 7 and 8, there are first and second external electrodes 9 and 10 formed by applying and baking a conductive paste. The external electrodes 9 and 10 are formed so as to cover the outer surfaces of the thermistor layers 7 and 8. Therefore, the external electrodes 9 and 10 are also configured to have the above-described cover portions.
[0022]
As the conductive paste constituting the external electrodes 9 and 10, an appropriate conductive paste conventionally used as an electrode material such as an Ag paste can be used.
[0023]
As is apparent from FIG. 1, the thermistor layers 7 and 8 are interposed between the external electrodes 9 and 10 and the end faces 2a and 2b, so that the internal electrodes 3 to 6 are directly electrically connected to the external electrodes 9 and 10. Not connected to.
[0024]
Plating films 11a, 11b, 12a, and 12b are laminated on the outer surfaces of the external electrodes 9 and 10. The plating films 11a and 12a are directly formed on the outer surfaces of the external electrodes 9 and 10, and are made of a metal such as Ni that hardly erodes solder. On the other hand, the second plating films 11b and 12b formed on the plating films 11a and 12a are made of a metal material having excellent solderability such as Sn and solder.
[0025]
The NTC thermistor 1 is characterized in that the thermistor layers 7 and 8 are interposed between the external electrodes 9 and 10 and the end faces 2a and 2b.
That is, in the NTC thermistor 1 of the present embodiment, the thermistor layers 7 and 8 and the external electrodes 9 and 10 are formed after the thermistor body 2 is obtained. Therefore, the materials and thermistor layers constituting the thermistor layers 7 and 8 are formed. By adjusting the thicknesses 7 and 8, the electrical characteristics such as the resistance value can be significantly adjusted. This will be described based on a specific experimental example.
[0026]
A ceramic slurry was obtained by adding and kneading a semiconductor ceramic powder having negative resistance temperature characteristics made of an oxide such as Mn, Ni, and Co, an organic binder, and water. Using this ceramic slurry, a ceramic green sheet having a thickness of 50 μm was produced and punched into a rectangular shape.
[0027]
An Ag / Pd paste for forming internal electrodes was printed on a rectangular ceramic green sheet. Thereafter, a plurality of ceramic green sheets on which the internal electrode forming Ag / Pd paste is printed are laminated, and a plurality of plain rectangular ceramic green sheets are laminated on the top and bottom, and applied in the thickness direction. To obtain a mother laminate. The mother laminate was cut into individual thermistor laminates and fired at 1300 ° C. to obtain a thermistor body 2 made of a ceramic sintered body.
[0028]
The thermistor body 2 was barrel-polished. By the barrel polishing, the ridgeline portion formed by the upper surface 2c and the lower surface 2d and the end surfaces 2a and 2b was rounded as indicated by an arrow X in FIG. Further, although not shown in FIG. 1, the ridge line portion formed by the pair of side surfaces and the end surfaces 2a and 2b is similarly rounded.
[0029]
After the barrel polishing, the thermistor layers 7 and 8 were formed on the end faces 2 a and 2 b of the thermistor body 2. When the thermistor layers 7 and 8 are formed, the thermistor body 2 is immersed in the thermistor paste layer from the end face 2a side and pulled up. Thermistor paste was applied so as to cover 2b.
[0030]
Thereafter, the thermistor body 2 provided with the thermistor paste was baked at a temperature of 1000 to 1300 ° C. to form thermistor layers 7 and 8 having a thickness of 5 to 10 μm shown in FIG.
[0031]
Next, as shown in FIG. 3, Ag / Pd paste was applied to the outer surfaces of the thermistor layers 7 and 8 and baked to form external electrodes 9 and 10 having a thickness of 40 μm. Further, Ni films and Sn films were sequentially plated on the outer surfaces of the external electrodes 9 and 10 to form plated films 11a, 11b, 12a, and 12b.
[0032]
As described above, the NTC thermistor 1 was manufactured. At the time of manufacturing, the following three types of thermistor layers 7 and 8 had specific resistances ρ of 26 Ω · cm, 880 Ω · cm, and 4735 Ω · cm. The thermistors of Examples 1 to 3 were obtained using the thermistor paste.
[0033]
Thermistor paste 1 ... Mn-Ni-Co-Cu-O
Thermistor paste 2 ... Mn-Ni-Co-Al-O
Thermistor paste 3 ... Mn-Ni-Al-O
A conventional thermistor was produced in the same manner as in the above example except that the thermistor layers 7 and 8 were not formed.
[0034]
The characteristics of the thermistors of the conventional example and Examples 1 to 3 obtained as described above are shown in Table 1 below.
[0035]
[Table 1]

[0036]
As is clear from Table 1, the thermistor paste constituting the thermistor layers 7 and 8 is made different so that the resistance value in the thermistor 1 as a final product finally obtained even when the same thermistor body 2 is used. And it can be seen that the B constant can be changed significantly.
[0037]
That is, after obtaining the thermistor body 2 by firing, according to the present embodiment, the electrical characteristics such as the resistance value and the B constant of the NTC thermistor 1 can be significantly adjusted.
Therefore, it can be seen that the NTC thermistor 1 having characteristics according to the application can be provided easily and quickly.
[0038]
The thickness of the thermistor layers 7 and 8 is not particularly limited, but it is desirable that the thermistor layers 7 and 8 are not so thick in order to ensure conduction between the internal electrodes 3 to 6 and the external electrodes 9 and 10. It is desirable that the thickness be 10 μm or less.
[0039]
In the above embodiment, the plating films 11a, 11b, 12a, and 12b are formed on the outer surfaces of the external electrodes 9 and 10, but the plating films 11a, 11b, 12a, and 12b are not necessarily formed.
[0040]
Moreover, in the said Example, although the laminated type NTC thermistor 1 which has the internal electrodes 3-6 was demonstrated, this invention is applicable also to the thermistor which does not have an internal electrode. As for the thermistor body, a disc-like or square-plate thermistor element may be used, and a thermistor layer and external electrodes are formed on both main surfaces of the disc-like or square-plate thermistor body. It may be.
[0041]
Furthermore, the present invention can be applied not only to NTC thermistors but also to PTC thermistors.
[0042]
【The invention's effect】
According to the thermistor of the present invention, the first and second thermistor layers are formed by baking the thermistor paste on the opposing first and second end faces of the ceramic sintered body. First and second external electrodes are formed on the thermistor layer. Therefore, after obtaining a thermistor body made of a ceramic sintered body, by selecting a thermistor paste according to the desired characteristics from thermistor pastes of various characteristics, and forming the first and second thermistor layers, Even when the same thermistor body is used, the electrical characteristics such as the resistance value and B constant of the thermistor finally obtained can be adjusted greatly and easily. Therefore, the thermistor according to the required characteristic can be provided easily and promptly.
[0043]
Are formed a plurality of internal electrodes to thermistors element body, if having a structure in which a plurality of internal electrodes are led out to the first end face and the second end face, obtained in accordance with the present invention a laminated thermistor Therefore, thermistors having various resistance values can be easily designed.
[0044]
When the external electrode is formed of a conductive film formed by baking a conductive paste and further includes a plating film laminated on the outer surface of the external electrode, the external electrode formed by baking the conductive paste The reliability of the general connection can be improved, and the solderability and the like can be improved by selecting the material of the laminated plating film.
[0045]
When the ceramic sintered body is made of a semiconductor ceramic having negative resistance temperature characteristics, an NTC element capable of greatly adjusting electrical characteristics such as resistance can be easily provided according to the present invention.
[0046]
In the method for producing the thermistor according to the present invention, after the thermistor body is prepared, the thermistor paste is applied to the first and second end faces of the thermistor body, and the thermistor paste is fired to obtain the first, Since the second thermistor layer is formed, the electrical characteristics of the thermistor finally obtained can be greatly and easily adjusted by selecting the thermistor paste.
[0047]
Prior to applying the thermistor paste to the first and second end faces of the thermistor body, the thermistor body is barrel-polished, and the outer peripheral edge lines of the first and second end faces of the thermistor body are polished. In this case, the first and second thermistor layers can be formed to a sufficient thickness even in the ridge line portion. Therefore, the electrical characteristics can be stably adjusted by the first and second thermistor layers.
[0048]
Are formed a plurality of internal electrodes in the body thermistors containing a plurality of internal electrodes first, when being drawn on the second end face, in accordance with the present invention, significantly and quickly adjust the electrical characteristics Therefore, it is possible to easily provide a stacked thermistor.
[0049]
In the manufacturing method according to the present invention, when a plating film is formed on the surface of the external electrode after forming the external electrode, the solderability and the like can be easily improved by selecting the material of the plating film.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a thermistor according to an embodiment of the present invention.
FIG. 2 is a longitudinal sectional view showing a state in which first and second thermistor layers are formed on the outer surface of a thermistor body when the thermistor shown in FIG. 1 is obtained.
3 is a longitudinal sectional view showing a state in which external electrodes are formed on the first and second thermistor layers of the thermistor body shown in FIG.
FIG. 4 is a longitudinal sectional view showing an example of a conventional thermistor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Thermistor 2 ... Thermistor body 2a, 2b ... 1st, 2nd end surface 3-6 ... Internal electrode 7, 8 ... 1st, 2nd thermistor layer 9, 10 ... 1st, 2nd external electrode 11a , 11b, 12a, 12b ... plating film

Claims (8)

A thermistor body made of a ceramic sintered body and having first and second end faces facing each other;
First and second thermistor layers formed by baking the thermistor paste on the first and second end faces;
A thermistor comprising first and second external electrodes formed on the first and second thermistor layers. Before SL has a plurality of internal electrodes formed on the thermistor element body, internal electrodes of the plurality of being drawn to the first end face and the second end surface, a thermistor of claim 1.   3. The thermistor according to claim 1, wherein the external electrode is formed of a conductive film formed by baking a conductive paste, and further includes a plating film laminated on an outer surface of the external electrode.   The thermistor in any one of Claims 1-3 in which the said ceramic sintered compact consists of semiconductor ceramics which have a negative resistance temperature characteristic. A step of preparing a thermistor body made of a ceramic sintered body and having opposing first and second end faces;
Applying a thermistor paste on the first and second end faces of the thermistor body;
Firing the thermistor paste to form first and second thermistor layers;
Forming a first external electrode by applying a conductive paste on the first and second thermistor layers and baking the conductive paste, and a method for manufacturing the thermistor. Prior to applying the thermistor paste to the first and second end faces of the thermistor element body, the thermistor element body is barrel-polished, and the ridge lines of the outer peripheral edges of the first and second end faces of the thermistor element body are polished. The thermistor manufacturing method according to claim 5, further comprising a step. As before Symbol thermistor body, using a thermistor element in which a plurality of which internal electrodes are formed and a plurality of internal electrodes inside is drawn to the first and second end surfaces, according to claim 5 or 6 Thermistor manufacturing method.   The method of manufacturing a thermistor according to claim 5, further comprising a step of forming a plating film on a surface of the external electrode after forming the external electrode.

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