JP3823484B2 - Thermistor - Google Patents

Description

【００４４】
表１から明らかなように、第１，第２の実施例のチップ型サーミスタでは、メッキ前後の抵抗値の変化率が、比較のために用意したチップ型サーミスタに比べて大幅に小さくなっていることがわかる。
【００４５】
また、信頼性評価においても、比較のために用意したチップ型サーミスタに比べて、第１，第２の実施例のチップ型サーミスタ１，１１は、高温放置試験、湿中放置試験、低温放置試験、ヒートサイクル試験及び湿中通電試験の何れにおいても良好な結果を示すことがわかる。
【００４６】
ＮｉＳｎメッキでは、メッキ液として硫酸溶液が用いられ、他方、Ａｇペーストの塗布・焼き付けにより形成された電極膜がポーラスであるため、メッキ液が浸透し易い。従って、従来のチップ型サーミスタ６１では、このメッキ液のサーミスタ素体６２内への侵入により特性のばらつきや、信頼性評価における特性の劣化が生じているものと思われる。
【００４７】
これに対して、第１，第２の実施例のチップ型サーミスタでは、距離Ｅ₂ が距離Ｅ₁ 以上とされているため、すなわち内部電極の長さが比較的小さいため、そのメッキ液の侵入による特性の劣化が抑制され、抵抗値のばらつき及び信頼性評価における特性の劣化が抑制されているものと思われる。
【００４８】
また、サーミスタ１を得るにあたって、距離Ｅ₁ ，距離Ｅ₂ を種々変化させ、その他の点は第１の実施例のチップ型サーミスタ１と同様にして種々のサーミスタを作製し、評価した。結果を下記の表２に示す。表２においては、初期値ばらつきＲ_3CV は、メッキ前のサーミスタの２５℃における抵抗値のばらつきを示し、メッキによる加工変化ΔＲは、メッキ前後の２５℃における抵抗値の変化を示し、信頼性評価は、上述した第１，第２の実施例のサーミスタにおいて行った信頼性評価における高温放置試験及び湿中通電試験と同様にして行ったものである。
【００４９】
【表２】

【００５０】
また、表２の結果から、Ｅ₂ −Ｅ₁ とサーミスタの抵抗値の初期値のばらつきとの関係を求めた。結果を表３に示す。
【００５１】
【表３】

【００５２】
さらに、上述した距離Ｅ₃ を第１の実施例において変化させた場合の抵抗値の初期値Ｒ₂₅、そのばらつきＲ_3CV 及び信頼性評価結果を表４に示す。
【００５３】
【表４】

【００５４】
表２及び表３から明らかなように、Ｅ₂ −Ｅ₁ を０以上、すなわち、Ｅ₁ ≦Ｅ₂ とすることにより、抵抗値の初期値のばらつきを５．３％以下と小さくすることができ、かつ信頼性評価においても良好な結果の得られることがわかる。
【００５５】
さらに、表４から明らかなように、中間電極部間の距離Ｅ₃ を変化させると、抵抗値のばらつきや信頼性評価における特性の変動をもたらすことなく、抵抗値の初期値Ｒ₂₅を調整し得ることがわかる。すなわち、第１，第２の実施例のチップ型サーミスタ１，１１では、中間電極部７ａ，７ｂ間の距離を調整することにより、抵抗値のばらつきの低減及び信頼性の向上を図りつつ所望の抵抗値のサーミスタを提供し得ることがわかる。
【００５６】
（変形例）
本発明のサーミスタは、図４〜図９に示すように、種々変形し得る。
図４に示すサーミスタ２１では、サーミスタ素体２内に第１，第２の内部電極及び中間電極が、それぞれ、複数形成されている。すなわち、第１の実施例における第１，第２の内部電極５，６が、それぞれ、３枚配置されており、かつ中間電極部７ａ，７ｂからなる中間電極７についても、２層にわたり形成されている。
【００５７】
また、図５は、第２の実施例のチップ型サーミスタ１１の変形例に相当し、ここでは、中間電極部７ａ，７ｂを有する中間電極７が３層にわたり形成されている。
【００５８】
また、図１に示したチップ型サーミスタ１では、中間電極７が、端面２ａ，２ｂを結ぶ方向に分割されて中間電極部７ａ，７ｂが形成されていたが、図６に示すように、端面２ａ，２ｂを結ぶ方向と直交する方法、すなわち側面２ｃ，２ｄを結ぶ方向に中間電極７を分割し、中間電極部７ｃ，７ｄを形成してもよい。この場合には、中間電極部７ｃ，７ｄ間の距離Ｅ₃ は、図６に示されているように、側面２ｃ，２ｄに沿う方向における中間電極部７ｃ，７ｄ間の距離をいうものとする。
【００５９】
また、図１〜図６に示した例では、中間電極部７ａ，７ｂは、サーミスタ素体２内において同一平面内に構成されていたが、図７に示すように、中間電極部７ａ，７ｂはサーミスタ素体２内において異なる高さ位置に形成されていてもよい。この場合、中間電極部７ａ，７ｂ間の対向距離Ｅ₃ は、図７に示すように水平方向に沿った中間電極部７ａ，７ｂ間の距離をいうものとする。
【００６０】
また、図１〜図７に示した例では、中間電極が、２つの中間電極部７ａ，７ｂに分割されていたが、中間電極は、３以上の中間電極部を有するように分割されていてもよい。また、図８に示すように、第１，第２の内部電極５，６にサーミスタ素体層を介して部分的に重なり合う中間電極として、複数の中間電極部に分割されていない中間電極８を形成してもよい。図８に示すチップ型サーミスタ３１においても、第１，第２の外部電極間の距離をＥ₁ 、第１，第２の内部電極５，６の先端間の対向距離をＥ₂ としたときに、Ｅ₁ ≦Ｅ₂ とされているので、第１の実施例のチップ型サーミスタ１と同様に、抵抗値のばらつきを抑制することができ、かつメッキ液の侵入や湿気の侵入に起因する特性の劣化を防止することが可能とされている。
【００６１】
また、図９に示すように、複数の中間電極８，８をサーミスタ素体２内に配置してもよい。なお、図９に示す変形例では、第１，第２の内部電極５，６Ａは、異なる高さ位置に形成されている。
【００６２】
（好ましい変形例）
好ましくは、第１の外部電極３の先端と、第２の外部電極４に接続されている第２の内部電極６，６Ａの先端との間の距離をＥ₄ 、第２の外部電極４の先端と、第１の外部電極３に電気的に接続されている第１の内部電極５の先端との間の距離をＥ₅ としたとき、Ｅ₁ ＜Ｅ₄ かつＥ₁ ＜Ｅ₅ とされる。このように、Ｅ₁ ＜Ｅ₄ 及びＥ₁ ＜Ｅ₅ の条件を満たすことにより、第１，第２の内部電極５，６の長さが相対的に短くなり、第１の内部電極５及び第２の外部電極４間並びに第２の内部電極６及び第１の外部電極３間の抵抗値に起因する抵抗値のばらつきを効果的に抑制することができる。
【００６３】
また、好ましくは、第１，第２の内部電極５，６と中間電極７，８との間のサーミスタ素体層の厚みがＥ₆ であり、中間電極７，８のサーミスタ素体２の端面２ａもしくは２ｂ側の端縁と該端縁に近いサーミスタ素体の端面２ａもしくは２ｂとの間の距離をＥ₇ としたときに、Ｅ₆ ＜Ｅ₇ とされる。このように、Ｅ₆ ＜Ｅ₇ とすることにより、中間電極７，８と外部電極３，４との間の抵抗値に起因する抵抗値のばらつきを抑制することができる。
【００６４】
また、中間電極７が複数に分割されて複数の中間電極部７ａ，７ｂが形成されている場合、好ましくは、分割されている中間電極部間の間隔Ｅ₃ の合計をＥ_3'としたとき、Ｅ₃ ＜Ｅ₁ ≦Ｅ₂ とされ、それによって電位集中が防止でき、許容電流量を大きくすることができる。
【００６５】
【発明の効果】
請求項１に記載の発明によれば、サーミスタ素体の両端に第１，第２の外部電極が形成されており、サーミスタ素体内に第１，第２の外部電極とそれぞれ電気的に接続されており、かつ先端間が所定距離を隔てて対向された第１，第２の内部電極と、第１，第２の外部電極の何れにも電気的に接続されていない中間電極とを備えるサーミスタにおいて、第１，第２の内部電極の先端間の対向距離Ｅ₂ が第１，第２の外部電極間の距離Ｅ₁ 以上とされているので、第１，第２の内部電極の長さが相対的に短く、従って、メッキ液の侵入や湿気の侵入に起因する特性の変動を抑制することができ、かつ抵抗値のばらつきを低減することが可能となる。従って、請求項１に記載の発明によれば、第１，第２の外部電極の少なくとも１つの層をメッキ法により形成した場合であっても、初期抵抗値のばらつきが少ないだけでなく、周囲の環境や経時による特性の劣化の生じ難いサーミスタを提供することが可能となる。
【００６６】
請求項２に記載の発明では、第１の外部電極の先端と第２の外部電極に接続されている第２の内部電極の先端との間の距離をＥ₄ 、第２の外部電極の先端と、第１の内部電極の先端との間の距離をＥ₅ としたときに、Ｅ₁ ＜Ｅ₄ かつＥ₁ ＜Ｅ₅ とされているので、第１，第２の内部電極と、相手側の電位に接続される外部電極との間の抵抗に起因する抵抗値のばらつきを抑制することができ、より一層抵抗値のばらつきの少ないサーミスタを提供し得る。
【００６７】
請求項３に記載の発明では、第１，第２の内部電極と中間電極との間のサーミスタ素体層の厚みをＥ₆ 、中間電極のサーミスタ素体の端部側の端縁と、該端縁に近いサーミスタ素体の端部との間の距離をＥ₇ としたときに、Ｅ₆ ＜Ｅ₇ とされているので、中間電極と外部電極との間の抵抗に起因する抵抗値のばらつきを抑制することができ、より一層抵抗値のばらつきの少ないサーミスタを提供することができる。
【００６８】
請求項４に記載の発明では、複数の中間電極部を有する構成において、中間電極部間の対向距離の合計をＥ₃ としたときに、Ｅ₃ ＜Ｅ₁ とされているので、信頼性が向上し、抵抗ばらつきを小さくすることができる。
【図面の簡単な説明】
【図１】本発明の第１の実施例に係るチップ型サーミスタを示す縦断面図。
【図２】図１に示したチップ型サーミスタの平面断面図。
【図３】第２の実施例に係るチップ型サーミスタを示す縦断面図。
【図４】第１の実施例のチップ型サーミスタの変形例を示す縦断面図。
【図５】第２の実施例のチップ型サーミスタの変形例を示す縦断面図。
【図６】第１の実施例のチップ型サーミスタの変形例を説明するための平面断面図。
【図７】第２の実施例のチップ型サーミスタの変形例を示す縦断面図。
【図８】第１の実施例のチップ型サーミスタのさらに他の変形例を示す縦断面図。
【図９】第２の実施例のチップ型サーミスタのさらに他の変形例を示す縦断面図。
【図１０】従来の積層サーミスタを示す断面図。
【図１１】従来のチップ型サーミスタの一例を示す縦断面図。
【図１２】従来のチップ型サーミスタの他の例を示す縦断面図。
【符号の説明】
１…チップ型サーミスタ
２…サーミスタ素体
２ａ，２ｂ…端面
３，４…第１，第２の外部電極
５，６…第１，第２の内部電極
６Ａ…第２の内部電極
７ａ，７ｂ…中間電極部
７ｃ，７ｄ…中間電極部
８…中間電極
１１…チップ型サーミスタ
２１…チップ型サーミスタ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermistor used to detect temperature or compensate for changes in the characteristics of circuits and electronic components due to temperature. More specifically, the thermistor body has an internal electrode so that it can be surface mounted. The present invention relates to an improvement of a thermistor in which external electrodes are formed at both ends of a thermistor body.
[0002]
[Prior art]
Japanese Patent Laid-Open No. 4-130702 discloses a chip thermistor that can reduce variations in resistance value. This chip thermistor is shown in FIG. The chip thermistor 51 has a structure in which internal electrodes 53 and 54 are arranged in a thermistor body 52. The internal electrodes 53 and 54 have a distance D between their tips. ₁ Are spaced apart from each other. The internal electrodes 53 and 54 are electrically connected to external electrodes 55 and 56 formed at both ends of the thermistor body 52, respectively. Here, the distance D between the internal electrodes 53 and 54 ₁ It is said that the variation in resistance value can be reduced without considering the accuracy of the external electrodes 55 and 56.
[0003]
Japanese Patent Application Laid-Open No. 5-243007 discloses a laminated thermistor that hardly causes variations in the overlapping area between internal electrodes. This laminated thermistor is shown in FIG. In the laminated thermistor 61, external electrodes 63 and 64 are formed on both ends of the thermistor body 62. Internal electrodes 65 and 66 are formed in the thermistor body 62, and the internal electrodes 65 and 66 are electrically connected to the external electrodes 63 and 64, respectively. An intermediate electrode 67 is formed so as to overlap the internal electrodes 65 and 66 via the thermistor element layer. The intermediate electrode 67 is not connected to the external electrodes 63 and 64.
[0004]
Japanese Patent Laid-Open No. 4-261001 discloses a thermistor shown in FIG. 12 as a structure capable of reducing the resistance value of the thermistor. In this thermistor 71, an internal electrode 73 is embedded in a thermistor element body 72, and external electrodes 74 and 75 are formed at both ends of the thermistor element body 72. The internal electrode 73 is not electrically connected to the external electrodes 74 and 75.
[0005]
[Problems to be solved by the invention]
In the chip type thermistor 51 described in Japanese Patent Application Laid-Open No. 4-130702, although variation in resistance value can be reduced, the internal electrodes 53 and 54 are drawn out to the end faces 52a and 52b of the thermistor element body 52 to provide external electrodes 55 and 56. And are electrically connected. Therefore, when the external electrodes 55 and 56 are to be formed by plating, for example, the plating solution enters the thermistor body 52 from the portion where the plating solution is drawn to the end faces 52a and 52b of the internal electrodes 53 and 54, thereby deteriorating the characteristics. There was a problem.
[0006]
Further, the solder flux when the chip-type thermistor 51 is mounted on a printed circuit board or the like enters the inside of the thermistor body 52 from the portions that are similarly drawn out to the end faces 52a and 52b of the internal electrodes 53 and 54, and the reliability It may deteriorate. Further, the moisture resistance was not sufficient, and the characteristics tended to change with time.
[0007]
Also in the laminated thermistor 61 shown in FIG. 11, the internal electrodes 65 and 66 are drawn out to the end faces 62 a and 62 b of the thermistor body 62, so that there is a problem similar to that of the chip type thermistor 51.
[0008]
Further, the distance between the external electrodes 63 and 64 is set to E ₁ The distance between the tip of the external electrode 63 and the tip of the internal electrode 66 connected to the other external electrode 64 is defined as E _Four Similarly, the distance between the tip of the external electrode 64 and the tip of the other internal electrode 65 is represented by E _Five Then, E ₁ > E _Four And E ₁ > E _Five If the dimensions of the external electrodes 63 and 64 vary, E _Four , E _Five There was a problem that the variation in resistance between the gaps increased.
[0009]
On the other hand, in the thermistor 71 described in JP-A-4-261001, the internal electrode 73 is not electrically connected to the external electrodes 74 and 75 but is embedded in the thermistor body 72. Therefore, the above problems are unlikely to occur. However, the position of the internal electrode 73 inevitably varies in the lateral direction due to dimensional variations when the thermistor element body 72 is cut out from the mother thermistor element body. For this reason, the obtained thermistor 71 has a problem that the resistance value varies greatly.
[0010]
The object of the present invention is to hardly cause deterioration of characteristics due to penetration of moisture, plating solution or flux into the thermistor body, and resistance value variation due to the influence of thermistor body dimensions, electrode dimensions, etc. To provide a thermistor.
[0011]
[Means for Solving the Problems]
The thermistor according to the first aspect of the present invention includes a thermistor element body, first and second external electrodes formed at both ends of the thermistor element body, and the thermistor element with a predetermined distance between the tips. First and second internal electrodes facing each other, and the first and second internal electrodes are electrically connected to the first and second external electrodes, respectively, and are embedded in the thermistor body. An intermediate electrode that is not electrically connected to any of the first and second external electrodes, The internal electrode is not disposed at the same height position as the intermediate electrode provided in the thermistor body, The distance between the first and second external electrodes is E ₁ , The opposing distance between the tips of the first and second internal electrodes is E ₂ When E ₁ ≦ E ₂ It is said that it is said.
[0012]
Moreover, in a specific aspect of the present invention, as described in claim 2, between the tip of the first external electrode and the tip of the second internal electrode connected to the second external electrode. The distance of E _Four A distance between the tip of the second external electrode and the tip of the first internal electrode electrically connected to the first external electrode is E _Five E ₁ <E _Four And E ₁ <E _Five It is said that.
[0013]
According to another specific aspect of the present invention, as described in claim 3, the thickness of the thermistor element layer between the first and second internal electrodes and the intermediate electrode is set to E. ₆ , The distance between the edge of the intermediate electrode on the end side of the thermistor body and the end of the thermistor body close to the edge is E ₇ When E ₆ <E ₇ It is said that.
[0014]
Furthermore, according to another specific aspect of the present invention, as described in claim 4, the intermediate electrode is divided into a plurality of intermediate electrode portions, and the opposing distance between the intermediate electrode portions is set to E. _Three When E _Three <E ₁ It is said that.
[0015]
In the present invention, a plurality of the first and second internal electrodes may be formed at different height positions in the thermistor body.
In the present invention, a plurality of intermediate electrodes may be formed. In this case, the plurality of intermediate electrodes may be formed at different height positions in the thermistor body.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be clarified by giving non-limiting examples of the present invention with reference to the drawings.
[0017]
(First embodiment)
FIG. 1 is a longitudinal sectional view showing a chip type thermistor according to a first embodiment of the present invention, and FIG. 2 is a plan sectional view thereof.
[0018]
The chip type thermistor 1 is a negative characteristic thermistor having a negative resistance temperature characteristic. This chip-type thermistor 1 is configured using a rectangular thermistor body 2.
[0019]
The thermistor body 2 is composed of a semiconductor thermistor material exhibiting negative resistance temperature characteristics. The first and second external electrodes 3, 4 are formed so as to cover both the end faces 2 a, 2 b of the thermistor body 2 and to reach the upper surface, the lower surface and both side faces of the thermistor body 2 connecting the end faces 2 a, 2 b. Each is formed.
[0020]
The distance between the first external electrode 3 and the second external electrode 4 is represented by E ₁ And This distance E ₁ Is the distance of the closest part between the first and second external electrodes. In FIG. 1, the distance between the portions of the external electrodes 3 and 4 reaching the upper surface of the thermistor body 2 is E ₁ It is said that.
[0021]
The external electrodes 3 and 4 can be formed by applying and baking a conductive paste on the outer surface of the thermistor body 2 or by an appropriate conductive film forming method such as vapor deposition, plating, or sputtering. Preferably, a metal film having excellent solderability, such as Sn or Pb, is formed on the conductive film formed by applying and baking a conductive paste to form the external electrodes 3 and 4.
[0022]
In the thermistor body 2, first and second internal electrodes 5 and 6 are formed. The first and second internal electrodes 5 and 6 are extended from the end faces 2 a and 2 b toward the inside of the thermistor body 2, respectively. In the present embodiment, the internal electrodes 5 and 6 are formed in a plane at the same height position in the thermistor body 2, and the tips of each other are distance E. ₂ Are opposed to each other.
[0023]
The internal electrode 5 is drawn out to the end face 2 a and is electrically connected to the external electrode 3. The internal electrode 6 is drawn out to the end face 2 b and is electrically connected to the external electrode 4.
[0024]
A thickness E is provided below the internal electrodes 5 and 6. ₆ The intermediate electrode 7 is formed so as to partially overlap through the thermistor element layer. In the present embodiment, the intermediate electrode 7 is divided into two and has intermediate electrode portions 7a and 7b. The intermediate electrode portion 7a and the intermediate electrode portion 7b have a distance E _Three Are arranged apart from each other. The intermediate electrode portion 7a partially overlaps the first internal electrode 5 via the thermistor element layer, while the intermediate electrode portion 7b partially overlaps the second internal electrode 6 via the thermistor element layer. They are overlapping.
[0025]
The intermediate electrode 7 is embedded in the thermistor body 2 and is therefore not electrically connected to the external electrodes 3 and 4.
The first and second internal electrodes 5 and 6 and the intermediate electrode 7 can be made of an appropriate conductive material such as an Ag—Pd alloy.
[0026]
The thermistor body 2 having the first and second internal electrodes 5 and 6 and the intermediate electrode 7 can be obtained by using a known multilayer ceramic electronic component manufacturing technique.
[0027]
An example of this manufacturing method will be described. First, an organic binder, a dispersant, and a surface active agent are mixed with a semiconductor ceramic material exhibiting negative resistance temperature characteristics to obtain a ceramic slurry, and a ceramic green sheet is formed using the ceramic slurry. This ceramic green sheet is punched out so as to have a predetermined planar shape, and then the first green sheet is printed with an Ag-Pd paste to form the first and second internal electrodes 5 and 6 on the upper surface. And A second green sheet is obtained by printing the same Ag-Pd paste on the other ceramic green sheets obtained in the same manner as described above in order to form the intermediate electrode portions 7a and 7b.
[0028]
The first and second ceramic green sheets are laminated such that the first ceramic green sheet is positioned above, and an appropriate number of ceramic green sheets not printed with conductive paste are laminated on the top and bottom, and the thickness is increased in the thickness direction. Press to obtain a laminate. The laminated body is fired to obtain the thermistor body 2.
[0029]
An Ag paste is applied to both end faces 2a and 2b of the thermistor body 2 and baked to form an Ag film. Thereafter, Ni and Sn are sequentially electrolytically plated on the Ag film to form the external electrodes 3 and 4.
[0030]
The feature of the chip type thermistor 1 of this embodiment is that the distance E between the first and second external electrodes 3 and 4 is as follows. ₁ Is the facing distance E between the first and second internal electrodes 5, 6. ₂ Accordingly, variation in resistance value is reduced, and variation in characteristics due to penetration of the plating solution, penetration of moisture over time, and the like are suppressed. This point will be described later based on a specific experimental example.
[0031]
(Second embodiment)
FIG. 3 is a longitudinal sectional view showing the chip type thermistor 11 according to the second embodiment of the present invention, and corresponds to FIG. 1 showing the chip thermistor 1 according to the first embodiment. The chip type thermistor 11 of the second embodiment is configured in the same manner as the chip type thermistor 1 except that the second internal electrode 6A is formed at a height position different from that of the first internal electrode 5. Has been. Therefore, about the same part, the description about the chip | tip thermistor 1 shall be used by attaching | subjecting the same reference number.
[0032]
As shown in FIG. 3, the second internal electrode 6A has a thickness E below the intermediate electrode portion 7b. ₆ This is partially opposed to the intermediate electrode portion 7b through the thermistor element layer. In other words, the intermediate electrode portions 7a and 7b constituting the intermediate electrode 7 are arranged at the intermediate height position between the first and second internal electrodes 5 and 6A.
[0033]
In the chip thermistor 11 as well, the facing distance E between the first and second internal electrodes ₂ , The distance E between the external electrodes 3 and 4 ₁ By setting it as the above, like the chip | tip thermistor 1 of a 1st Example, the fluctuation | variation of the characteristic by penetration | invasion of plating solution, moisture, etc. can be suppressed, aiming at reduction of the dispersion | variation in resistance value.
[0034]
Note that the facing distance E between the first and second internal electrodes in the present invention. ₂ Means the facing distance between the tips of the internal electrodes, and therefore, for example, as shown in FIG. 3, the distance along the horizontal direction between the tip of the internal electrode 5 and the tip of the internal electrode 6A. .
[0035]
(Evaluation of the chip type thermistor of the first and second embodiments)
Evaluation of the chip-type thermistors 1 and 11 according to the first and second examples was performed as follows.
[0036]
As the thermistor body 2, a thermistor material made of a plurality of transition metal oxides such as Mn, Ni, Co, and Fe is used. The thermistor body 2 has dimensions of 1.6 mm × 0.8 mm × 0.8 mm, 1, distance E between second external electrodes 3 and 4 ₁ = 0.8 mm, facing distance E between the first and second internal electrodes ₂ = 1.0 mm, distance E between the intermediate electrode portions 7a and 7b _Three = 0.2 mm, and the width W of the internal electrode and the intermediate electrode were both 0.4 mm. Further, the thickness E of the thermistor element layer between the first and second internal electrodes 5, 6, 6 A and the intermediate electrode 7. ₆ Was 0.040 mm. The external electrode was formed by laminating a Ni layer and a Sn layer by electrolytic plating after applying and baking Ag paste.
[0037]
For comparison, a conventional chip thermistor 61 shown in FIG. 11 was prepared. In this case, the thermistor body and the external electrode similar to the chip type thermistors 1 and 11 of the first and second embodiments are used, provided that the opposing distance E between the internal electrodes 65 and 66 is ₂ Was 0.2 mm.
[0038]
The evaluation method is as follows.
(1) Initial characteristics before and after plating: resistance value R before and after electrolytic plating of Ni and Sn when forming the external electrodes 3 and 4 _{twenty five} (Resistance value at 25 ° C.), variation R _3CV , B constant B _25/50 , B constant B _25/50 Variation B _3CV Was measured. The results are shown in Table 1 below together with the rate of change before and after plating.
[0039]
(2) Reliability evaluation: a) high temperature storage test, b) wet storage test, c) low temperature storage test, d) heat cycle test, and e) wet current test, respectively, the thermistor before and after plating. R before and after plating _{twenty five} Was measured. This R _{twenty five} The change rate before and after plating is shown in Table 1 below.
[0040]
a) High temperature standing test: The thermistor body was left at a temperature of 125 ° C. for 1000 hours.
b) In-humidity test: The thermistor was left in a thermostatic chamber at a relative humidity of 95% RH and a temperature of 60 ° C. for 1000 hours.
[0041]
c) Low temperature standing test: The thermistor body was left in a thermostatic chamber at -55 ° C for 1000 hours.
d) Heat cycle test: The thermistor body is maintained at a temperature of −55 ° C. for 30 minutes, then heated to a temperature of 125 ° C., left at a temperature of 125 ° C. for 30 minutes, then cooled, and again at −55 ° C. The process of cooling to a temperature of 1 was taken as one cycle, and this heat cycle was repeated 100 times.
[0042]
e) In-humidity energization test: A current of 1 mA was applied to the thermistor for 1000 hours at a relative humidity of 95% RH and a temperature of 40 ° C.
[0043]
[Table 1]

[0044]
As is apparent from Table 1, in the chip thermistors of the first and second embodiments, the rate of change in resistance value before and after plating is significantly smaller than that of the chip thermistors prepared for comparison. I understand that.
[0045]
Also, in the reliability evaluation, the chip thermistors 1 and 11 of the first and second embodiments are compared with the chip thermistors prepared for comparison in the high temperature storage test, the humidity storage test, and the low temperature storage test. It can be seen that both the heat cycle test and the wet energization test show good results.
[0046]
In NiSn plating, a sulfuric acid solution is used as the plating solution. On the other hand, the electrode film formed by applying and baking the Ag paste is porous, so that the plating solution is likely to penetrate. Therefore, in the conventional chip type thermistor 61, it is considered that the dispersion of the characteristics and the deterioration of the characteristics in the reliability evaluation are caused by the penetration of the plating solution into the thermistor body 62.
[0047]
On the other hand, in the chip type thermistor of the first and second embodiments, the distance E ₂ Is the distance E ₁ As described above, that is, because the length of the internal electrode is relatively small, deterioration of characteristics due to penetration of the plating solution is suppressed, and variation in resistance values and deterioration of characteristics in reliability evaluation are suppressed. I think that the.
[0048]
In obtaining the thermistor 1, the distance E ₁ , Distance E ₂ Various thermistors were prepared and evaluated in the same manner as the chip-type thermistor 1 of the first embodiment. The results are shown in Table 2 below. In Table 2, the initial value variation R _3CV Indicates the variation in resistance value of the thermistor before plating at 25 ° C., the processing change ΔR due to plating indicates the change in resistance value at 25 ° C. before and after plating, and the reliability evaluation is based on the first and second reliability evaluations described above. This was performed in the same manner as the high temperature storage test and the wet energization test in the reliability evaluation performed in the thermistor of the example.
[0049]
[Table 2]

[0050]
From the results in Table 2, E ₂ -E ₁ And the variation in the initial value of the resistance value of the thermistor was obtained. The results are shown in Table 3.
[0051]
[Table 3]

[0052]
Further, the distance E described above _Three The initial value R of the resistance value when V is changed in the first embodiment _{twenty five} , Its variation R _3CV Table 4 shows the reliability evaluation results.
[0053]
[Table 4]

[0054]
As is clear from Tables 2 and 3, E ₂ -E ₁ Is greater than or equal to 0, ie, E ₁ ≦ E ₂ By doing so, it can be seen that the variation of the initial value of the resistance value can be reduced to 5.3% or less, and good results can be obtained in the reliability evaluation.
[0055]
Further, as apparent from Table 4, the distance E between the intermediate electrode portions _Three Changing the initial value R of the resistance value without causing variations in the resistance value or fluctuations in characteristics in the reliability evaluation. _{twenty five} It can be seen that can be adjusted. That is, in the chip type thermistors 1 and 11 of the first and second embodiments, the distance between the intermediate electrode portions 7a and 7b is adjusted to reduce the variation in resistance value and improve the reliability. It can be seen that a thermistor of resistance value can be provided.
[0056]
(Modification)
The thermistor of the present invention can be variously modified as shown in FIGS.
In the thermistor 21 shown in FIG. 4, a plurality of first and second internal electrodes and a plurality of intermediate electrodes are formed in the thermistor body 2. That is, the first and second internal electrodes 5 and 6 in the first embodiment are each arranged in three pieces, and the intermediate electrode 7 including the intermediate electrode portions 7a and 7b is also formed over two layers. ing.
[0057]
FIG. 5 corresponds to a modification of the chip type thermistor 11 of the second embodiment. Here, the intermediate electrode 7 having intermediate electrode portions 7a and 7b is formed over three layers.
[0058]
In the chip thermistor 1 shown in FIG. 1, the intermediate electrode 7 is divided in the direction connecting the end faces 2a and 2b to form the intermediate electrode portions 7a and 7b. However, as shown in FIG. The intermediate electrode 7 may be formed by dividing the intermediate electrode 7 in a method orthogonal to the direction connecting the 2a and 2b, that is, in the direction connecting the side surfaces 2c and 2d. In this case, the distance E between the intermediate electrode portions 7c and 7d _Three Is the distance between the intermediate electrode portions 7c and 7d in the direction along the side surfaces 2c and 2d, as shown in FIG.
[0059]
Moreover, in the example shown in FIGS. 1-6, although intermediate electrode part 7a, 7b was comprised in the same plane within the thermistor element body 2, as shown in FIG. 7, intermediate electrode part 7a, 7b May be formed at different height positions in the thermistor body 2. In this case, the facing distance E between the intermediate electrode portions 7a and 7b _Three Is the distance between the intermediate electrode portions 7a and 7b along the horizontal direction as shown in FIG.
[0060]
In the example shown in FIGS. 1 to 7, the intermediate electrode is divided into two intermediate electrode portions 7a and 7b. However, the intermediate electrode is divided so as to have three or more intermediate electrode portions. Also good. Further, as shown in FIG. 8, the intermediate electrode 8 that is not divided into a plurality of intermediate electrode portions is used as an intermediate electrode that partially overlaps the first and second internal electrodes 5 and 6 via the thermistor element layer. It may be formed. Also in the chip-type thermistor 31 shown in FIG. 8, the distance between the first and second external electrodes is set to E ₁ , The opposing distance between the tips of the first and second internal electrodes 5, 6 is E ₂ When E ₁ ≦ E ₂ Therefore, similar to the chip type thermistor 1 of the first embodiment, it is possible to suppress variation in resistance value and prevent deterioration of characteristics due to penetration of plating solution or moisture. Is possible.
[0061]
Further, as shown in FIG. 9, a plurality of intermediate electrodes 8, 8 may be arranged in the thermistor body 2. In the modification shown in FIG. 9, the first and second internal electrodes 5 and 6A are formed at different height positions.
[0062]
(Preferred modification)
Preferably, the distance between the tip of the first external electrode 3 and the tip of the second internal electrodes 6 and 6A connected to the second external electrode 4 is E _Four The distance between the tip of the second external electrode 4 and the tip of the first internal electrode 5 electrically connected to the first external electrode 3 is E _Five When E ₁ <E _Four And E ₁ <E _Five It is said. Thus, E ₁ <E _Four And E ₁ <E _Five By satisfying the above condition, the lengths of the first and second internal electrodes 5 and 6 are relatively shortened, and the first internal electrode 5 and the second external electrode 4 and the second internal electrode 6 and Variations in resistance value due to the resistance value between the first external electrodes 3 can be effectively suppressed.
[0063]
Preferably, the thickness of the thermistor body layer between the first and second inner electrodes 5, 6 and the intermediate electrodes 7, 8 is E ₆ The distance between the end face 2a or 2b side edge of the thermistor body 2 of the intermediate electrodes 7 and 8 and the end face 2a or 2b of the thermistor body close to the end edge is represented by E ₇ When E ₆ <E ₇ It is said. Thus, E ₆ <E ₇ By doing so, it is possible to suppress variations in resistance values caused by the resistance values between the intermediate electrodes 7 and 8 and the external electrodes 3 and 4.
[0064]
In addition, when the intermediate electrode 7 is divided into a plurality of parts to form a plurality of intermediate electrode parts 7a and 7b, preferably, an interval E between the divided intermediate electrode parts E _Three The total of E _{3 '} When E _Three <E ₁ ≦ E ₂ Thus, potential concentration can be prevented and the allowable current amount can be increased.
[0065]
【The invention's effect】
According to the first aspect of the present invention, the first and second external electrodes are formed at both ends of the thermistor body, and are electrically connected to the first and second external electrodes, respectively, in the thermistor body. A thermistor including first and second internal electrodes whose tips are opposed to each other with a predetermined distance, and an intermediate electrode that is not electrically connected to any of the first and second external electrodes , The facing distance E between the tips of the first and second internal electrodes ₂ Is the distance E between the first and second external electrodes ₁ As described above, the lengths of the first and second internal electrodes are relatively short. Therefore, it is possible to suppress variation in characteristics due to penetration of plating solution and moisture, and resistance value. It is possible to reduce the variation of. Therefore, according to the first aspect of the invention, even when at least one layer of the first and second external electrodes is formed by plating, not only the initial resistance value is small, but also the surroundings Thus, it is possible to provide a thermistor in which the deterioration of characteristics due to the environment and the aging hardly occurs.
[0066]
According to the second aspect of the present invention, the distance between the tip of the first external electrode and the tip of the second internal electrode connected to the second external electrode is E _Four , The distance between the tip of the second external electrode and the tip of the first internal electrode is E _Five When E ₁ <E _Four And E ₁ <E _Five Therefore, variation in resistance value due to resistance between the first and second internal electrodes and the external electrode connected to the other-side potential can be suppressed, and the resistance value can be further reduced. A thermistor with little variation can be provided.
[0067]
In the invention according to claim 3, the thickness of the thermistor body layer between the first and second internal electrodes and the intermediate electrode is set to E. ₆ , The distance between the edge of the intermediate electrode on the end side of the thermistor body and the end of the thermistor body close to the edge is E ₇ When E ₆ <E ₇ Therefore, variation in resistance value due to resistance between the intermediate electrode and the external electrode can be suppressed, and a thermistor with less variation in resistance value can be provided.
[0068]
In the invention according to claim 4, in the configuration having a plurality of intermediate electrode portions, the total of the opposing distances between the intermediate electrode portions is E. _Three When E _Three <E ₁ Therefore, reliability is improved and resistance variation can be reduced.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a chip thermistor according to a first embodiment of the present invention.
2 is a plan sectional view of the chip thermistor shown in FIG. 1. FIG.
FIG. 3 is a longitudinal sectional view showing a chip type thermistor according to a second embodiment.
FIG. 4 is a longitudinal sectional view showing a modification of the chip thermistor according to the first embodiment.
FIG. 5 is a longitudinal sectional view showing a modification of the chip thermistor according to the second embodiment.
FIG. 6 is a plan sectional view for explaining a modification of the chip-type thermistor according to the first embodiment.
FIG. 7 is a longitudinal sectional view showing a modification of the chip thermistor according to the second embodiment.
FIG. 8 is a longitudinal sectional view showing still another modification of the chip thermistor according to the first embodiment.
FIG. 9 is a longitudinal sectional view showing still another modification of the chip thermistor according to the second embodiment.
FIG. 10 is a cross-sectional view showing a conventional laminated thermistor.
FIG. 11 is a longitudinal sectional view showing an example of a conventional chip type thermistor.
FIG. 12 is a longitudinal sectional view showing another example of a conventional chip type thermistor.
[Explanation of symbols]
1 ... Chip type thermistor
2 ... Thermistor body
2a, 2b ... end face
3, 4 ... first and second external electrodes
5, 6 ... first and second internal electrodes
6A ... second internal electrode
7a, 7b ... Intermediate electrode section
7c, 7d ... intermediate electrode part
8 ... Intermediate electrode
11 ... Chip type thermistor
21 ... Chip type thermistor

Claims (6)

The thermistor body,
First and second external electrodes formed at both ends of the thermistor body;
The thermistor body includes first and second internal electrodes facing each other with a predetermined distance between the tips, and the first and second internal electrodes are respectively connected to the first and second external electrodes. Electrically connected,
An intermediate electrode that is embedded in the thermistor body and is not electrically connected to any of the first and second external electrodes;
The internal electrode is not disposed at the same height position as the intermediate electrode provided in the thermistor body,
Said first, E ₁ the distance between the second external electrode, the first, when the opposing distance between the tips of the second internal electrode was E _2, that is the E ₁ ≦ E ₂ Characteristic, thermistor. The distance between the tip of the first external electrode and the tip of the second internal electrode connected to the second external electrode is E ₄ , the tip of the second external electrode, and the first E ₁ <E ₄ and E ₁ <E ₅ , where E ₅ is the distance from the tip of the first internal electrode electrically connected to the external electrode, The thermistor according to claim 1. The thickness of the thermistor body layer between the first and second internal electrodes and the intermediate electrode is E ₆ , the edge of the intermediate electrode on the end side of the thermistor body, and the thermistor body close to the edge thermistor of the distance between the end portion when the E _7, there is a E ₆ <E _7, according to claim 1 or 2. The intermediate electrode is divided into a plurality of intermediate electrode portions, and E ₃ <E ₁ when the facing distance between the intermediate electrode portions is E _{3. 5.} Thermistor.   The thermistor according to any one of claims 1 to 4, wherein a plurality of first and second internal electrodes are respectively formed at different height positions in the thermistor body.   The thermistor according to claim 1, comprising a plurality of intermediate electrodes, wherein the plurality of intermediate electrodes are formed at different height positions in the thermistor body.

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