JP3823876B2 - Voltage-dependent nonlinear resistor - Google Patents

Description

【００５７】
Ａサイト成分のモル比は、バリスタの電気的特性、特にバリスタ電圧Ｅ_１０の温度特性に大きな影響を与える。バリスタ電圧Ｅ_１０が１０Ｖ程度の試料１〜７においては、Ｅ_１０温度特性がゼロかわずかに負であるため、良好な特性であると判断される。しかしながら、再酸化時の温度を高くしてバリスタ電圧Ｅ_１０を２０〜３０Ｖとした試料８〜２１においては、Ｅ_１０温度特性が負の方向へ大きく外れる傾向がある。このＥ_１０温度特性が負の大きな値となると、動作中の温度上昇に伴なってバリスタ電圧が低下し、バリスタに過大電流が流れたり熱暴走を起こす恐れがあるので採用できない。
【００５８】
実施例１
この実施例１は、バリスタ電圧Ｅ_１０を大きくした場合にもＥ_１０温度特性がゼロ付近の値となるように、付加添加物としてＭｎＯを添加した試料による比較である。
【００５９】
Ａサイトモル比を比較例の場合と同様に変え、半導体化剤のモル％及び種類、トータルＡ／Ｂ、ＳｉＯ_２並びにＣｏＯ_４／３のモル％等のその他のパラメータを一定にし、さらに、付加添加物としてＭｎＯを一定量添加している。即ち、ＭｎＯを一定量添加したこと以外は比較例の場合と同様にして試料を作製し、これら各試料について比較例の場合と同様な測定を行った。結果を表２に示す。
【００６０】
【表２】

【００６１】
付加添加物としてＭｎを加えると、バリスタ電圧Ｅ_１０を大きくした場合にもＥ_１０温度特性がゼロ付近の良好な値となる。
【００６２】
従って添加物としてＭｎを添加した（主成分に対してＭｎＯを０．１モル％添加した）試料２２〜４２は、全て本発明の好ましい範囲である。これは、請求項１に規定した第５成分を含有することに対応している。
【００６３】
実施例２
この実施例２は、バリスタ電圧Ｅ_１０を大きくした場合にもＥ_１０温度特性がゼロ付近の値となるように、付加添加物としてのＭｎＯの添加量を変えた試料による比較である。
【００６４】
Ａサイトモル比、半導体化剤のモル％及び種類、トータルＡ／Ｂ、ＳｉＯ_２並びにＣｏＯ_４／３のモル％等の他のパラメータを一定にし、付加添加物としてのＭｎＯの量を表３に示されるものとしたこと以外は比較例の場合と同様にして試料を作製し、これらについても比較例の場合と同様な測定を行った。結果を表３に示す。なお、後述するように、試料４３、４９、５０、５６、５７及び６３は、実施例ではないが、比較のためにそのデータが記載されている。
【００６５】
【表３】

【００６６】
実施例１で述べたように、付加添加物としてＭｎを加えると、バリスタ電圧Ｅ_１０を大きくした場合にもＥ_１０温度特性がゼロ付近の値となる。ただし、Ｍｎ添加量が少ないと、バリスタ電圧Ｅ_１０の高い試料５０及び５７に見られるように、Ｅ_１０温度特性の改善効果がほとんど現れていない。また、Ｍｎ添加量が多すぎると、試料４９、５６及び６３に見られるように、Ｅ_１０温度特性が正に大きくなりすぎて好ましくない。
【００６７】
従って、主成分に対するＭｎＯのモル％が０．０３以上かつ３．００以下である試料４４〜４８及び５１〜５５が本発明の範囲である。これは、請求項１に規定した付加添加物の種類及びモル％に含まれている。さらに、主成分に対するＭｎＯのモル％が０．０３以上かつ１．００以下であれば、バリスタ電圧Ｅ_１０を３０Ｖと大きくした試料５８〜６１であっても、Ｅ_１０温度特性がゼロ付近の値となるので好ましい。これは、請求項６に規定した付加添加物の種類及びモル％に含まれている。
【００６８】
実施例３
この実施例３は、バリスタ電圧Ｅ_１０を大きくした場合にもＥ_１０温度特性がゼロ付近の値となるように、付加添加物としてＬｉ、Ｎａ、Ｃｕ、Ｚｎ、Ｓｃ及びＩｎをそれぞれ添加した試料による比較である。
【００６９】
Ａサイトモル比、半導体化剤のモル％及び種類、トータルＡ／Ｂ、ＳｉＯ_２並びにＣｏＯ_４／３のモル％等の他のパラメータを一定にし、付加添加物として表４に示されるものを一定量付加したこと以外は比較例の場合と同様にして試料を作製し、これらについても比較例の場合と同様な測定を行った。結果を表４に示す。
【００７０】
【表４】

【００７１】
バリスタ電圧Ｅ_１０を１０Ｖと低くした試料６４〜６９においてはもちろんのこと、再酸化時の温度を高くしてバリスタ電圧Ｅ_１０を２０Ｖ、３０Ｖと高くした試料７０〜８１のいずれにおいても、Ｅ_１０温度特性は−０．０２〜＋０．０５％／℃という良好な範囲に収まっている。従って、付加添加物として、ＭｎＯ以外に、ＬｉＯ_１／２、ＮａＯ_１／２、ＣｕＯ、ＺｎＯ、ＳｃＯ_３／２及びＩｎＯ_３／２を用いることは本発明の範囲である。これは、請求項１に規定した付加添加物の種類に含まれている。
【００７２】
実施例４
この実施例４は、半導体化剤の量を変えた試料による比較である。
【００７３】
Ａサイトモル比、半導体化剤の種類、トータルＡ／Ｂ、ＳｉＯ_２並びにＣｏＯ_４／３のモル％等の他のパラメータを一定にし、付加添加物としてＭｎＯを０．０３モル％添加し、半導体化剤のモル％を表４に示されるものとしたこと以外は比較例の場合と同様にして試料を作製し、これらについても比較例の場合と同様な測定を行った。サーマルクラック試験は、半田コテの温度として、３６０℃、４００℃及び４５０℃の３つの温度を用いた。結果を表５に示す。ただし、再酸化時の温度を調整してバリスタ電圧Ｅ_１０を２０Ｖとしている。この場合のＥ_１０温度特性は、全て、−０．０２〜＋０．０５％／℃という良好な範囲に収まっている。なお、後述するように、試料８２及び８７は、実施例ではないが、比較のためにそのデータが記載されている。
【００７４】
【表５】

【００７５】
半導体化剤の量は、バリスタ磁器の耐サーマルクラック性に影響を与える。試料８２及び８７は、半導体化剤がそれぞれ少なすぎる及び多すぎるため、半田コテ温度が３６０℃の試験でサーマルクラックが発生するため、好ましくない。従って、半田コテ温度が３６０℃の試験でサーマルクラックが発生しない試料８３〜８６が本発明の範囲である。これは、請求項１に規定した半導体化剤のモル％に対応する。
【００７６】
さらに、試料８６は半田コテ温度が４００℃及び４５０℃の試験においてサーマルクラックが発生するため、この４００℃及び４５０℃のサーマルクラック試験でクラックが発生しない試料８３〜８５が本発明の好ましい範囲となる。これは、請求項３に規定した半導体化剤のモル％に対応する。
【００７７】
実施例５
この実施例５は、半導体化剤の種類を変えた試料による比較である。
【００７８】
Ａサイトモル比、半導体化剤のモル％、トータルＡ／Ｂ、ＳｉＯ_２並びにＣｏＯ_４／３のモル％等の他のパラメータを一定にし、付加添加物としてＭｎＯを０．０３モル％添加し、半導体化剤の種類を表６に示されるものとしたこと以外は比較例の場合と同様にして試料を作製し、これらについても比較例の場合と同様な測定を行った。サーマルクラック試験は、半田コテの温度として、４００℃を用いた。結果を表６に示す。ただし、再酸化時の温度を調整してバリスタ電圧Ｅ_１０を２０Ｖとしている。この場合のＥ_１０温度特性は、全て、−０．０２〜＋０．０５％／℃という良好な範囲に収まっている。
【００７９】
【表６】

【００８０】
試料８８〜１０４のいずれも半田コテ温度が４００℃の試験においてサーマルクラックが発生しないため、半導体化剤としてＮｂＯ_５／２、ＴａＯ_５／２、ＹＯ_３／２、ＬａＯ_３／２、ＣｅＯ_２、ＰｒＯ_１１／６、ＮｄＯ_３／２、ＳｍＯ_３／２、ＥｕＯ_３／２、ＧｄＯ_３／２、ＴｂＯ_７／４、ＤｙＯ_３／２、ＨｏＯ_３／２、ＥｒＯ_３／２、ＴｍＯ_３／２、ＹｂＯ_３／２、ＬｕＯ_３／２又はＮｂＯ_５／２＋ＹＯ_３／２（等モル数）を用いることは本発明の範囲である。
【００８１】
実施例６
この実施例６は、トータルＡ／Ｂを変えた試料による比較である。
【００８２】
Ａサイトモル比、半導体化剤のモル％及び種類、ＳｉＯ_２並びにＣｏＯ_４／３のモル％等の他のパラメータを一定にし、付加添加物としてＭｎＯを０．０３モル％添加し、トータルＡ／Ｂを表７に示されるものとしたこと以外は比較例の場合と同様にして試料を作製し、これらについても比較例の場合と同様な測定を行った。サーマルクラック試験は、半田コテの温度として、３６０℃、４００℃及び４５０℃の３つの温度を用いた。結果を表７に示す。ただし、再酸化時の温度を調整してバリスタ電圧Ｅ_１０を２０Ｖとしている。この場合のＥ_１０温度特性は、全て、−０．０２〜＋０．０５％／℃という良好な範囲に収まっている。なお、後述するように、試料１０５及び１１０は、実施例ではないが、比較のためにそのデータが記載されている。
【００８３】
【表７】

【００８４】
トータルＡ／Ｂの値は、磁器の焼結性に影響を与える。試料１０５及び１１０は、トータルＡ／Ｂがそれぞれ小さすぎる及び大きすぎるため、緻密な磁器を焼結することができず、半田コテ温度３６０℃でサーマルクラックが発生している。表７から分かるように、ＳｉＯ_２の量が少なくかつ半導体化剤が多く添加される領域においては、耐サーマルクラック性を維持するために、トータルＡ／Ｂを制御することが不可欠となる。トータルＡ／Ｂが０．８４より小さいか、１．０２を越えると、半田コテ温度３６０℃でもサーマルクラックが発生するようになる。
【００８５】
即ち、試料１０６〜１０９は、半田コテ温度が３６０℃の試験においてサーマルクラックが発生しないため、本発明の範囲である。これは、請求項１に規定したトータルＡ／Ｂの範囲に対応する。
【００８６】
さらに、試料１０７〜１０９は、半田コテ温度が４００℃及び４５０℃の試験においてもサーマルクラックが発生しないため、本発明の好ましい範囲となる。これは、請求項２に規定したトータルＡ／Ｂの範囲に対応する。
【００８７】
実施例７
この実施例７は、ＳｉＯ_２のモル％を変えた試料による比較である。
【００８８】
Ａサイトモル比、半導体化剤のモル％及び種類並びにトータルＡ／Ｂ並びにＣｏＯ_４／３等の他のパラメータを一定にし、付加添加物としてＭｎＯを０．０３モル％添加し、ＳｉＯ_２のモル％を表８に示されるものとしたこと以外は比較例の場合と同様にして試料を作製し、これらについて、サーマルクラック試験の温度以外は比較例の場合と同様な測定を行った。サーマルクラック試験は、半田コテの温度として、３６０℃、４００℃及び４５０℃の３つの温度を用いた。結果を表８に示す。ただし、再酸化時の温度を調整してバリスタ電圧Ｅ_１０を２０Ｖとしている。この場合のＥ_１０温度特性は、全て、−０．０２〜＋０．０５％／℃という良好な範囲に収まっている。なお、後述するように、試料１１５は、実施例ではないが、比較のためにそのデータが記載されている。
【００８９】
【表８】

【００９０】
ＳｉＯ_２は焼結助剤として添加され、これが含まれると組成が変動しても安定に焼成することができるが、その量が増えると、サーマルクラックが発生し易くなる。
【００９１】
試料１１５は、ＳｉＯ_２が多すぎるため、半田コテ温度が３６０℃の試験でもサーマルクラックが発生するため、好ましくない。従って、半田コテ温度が３６０℃及び４００℃の試験においてもサーマルクラックが発生しない試料１１１〜１１４が本発明の範囲である。これは、請求項１に規定したＳｉＯ_２のモル％に対応する。なお、試料１１１は、ＳｉＯ_２の添加量が０の場合であるが、実際には、各原料に不純物としてＳｉＯ_２が含まれているため、この試料１１１のＳｉＯ_２含有量は０とはならない。
【００９２】
さらに、試料１１４は半田コテ温度が４５０℃の試験においてサーマルクラックが発生するため、半田コテ温度が４５０℃の試験においてもサーマルクラックが発生しない試料１１１〜１１３が本発明の好ましい範囲となる。これは、請求項４に規定したＳｉＯ_２のモル％に対応する。
【００９３】
実施例８
この実施例８は、ＣｏＯ_４／３のモル％を変えた試料による比較である。
【００９４】
Ａサイトモル比、半導体化剤のモル％及び種類並びにトータルＡ／Ｂ並びにＳｉＯ_２等の他のパラメータを一定にし、付加添加物としてＭｎＯを０．０３モル％添加し、ＣｏＯ_４／３のモル％を表９に示されるものとしたこと以外は比較例の場合と同様にして試料を作製し、これらについて、サーマルクラック試験の温度以外は比較例の場合と同様な測定を行った。サーマルクラック試験は、半田コテの温度として、３６０℃、４００℃及び４５０℃の３つの温度を用いた。結果を表９に示す。ただし、再酸化時の温度を調整してバリスタ電圧Ｅ_１０を試料１１６については１０Ｖ、その他の試料１１７〜１２３については２０Ｖとしている。この場合のＥ_１０温度特性は、全て、−０．０２〜＋０．０５％／℃という良好な範囲に収まっている。なお、後述するように、試料１１６、１１７及び１２３は、実施例ではないが、比較のためにそのデータが記載されている。
【００９５】
【表９】

【００９６】
ＣｏＯ_４／３を添加することによってバリスタ電圧Ｅ_１０を小さくすることができる。添加量が多すぎると、焼結過剰となりサーマルクラックが発生し易くなる。
【００９７】
試料１２３はＣｏＯ_４／３が多すぎるため、半田コテ温度が３６０℃の試験でもサーマルクラックが発生するので、好ましくない。さらに、試料１１６及び１１７の組成はＣｏＯ_４／３を添加していないので、先願（特願２００１−１６０５２７）で開示した、耐熱衝撃性と低いバリスタ電圧とを同時に取得する効果が、再酸化条件を調整しても得られなかった。よって、試料１１８〜１２２が本発明の範囲である。これは、請求項１に規定したＣｏＯ_４／３のモル％に対応する。
【００９８】
さらに、試料１２２も半田コテ温度が４５０℃の試験においてサーマルクラックが発生するため、半田コテ温度が４５０℃の試験においてもサーマルクラックが発生しない試料１１８〜１２１が本発明の好ましい範囲となる。これは、請求項５に規定したＣｏＯ_４／３のモル％に対応する。
【００９９】
以上述べた実施形態及び実施例は全て本発明を例示的に示すものであって限定的に示すものではなく、本発明は他の種々の変形態様及び変更態様で実施することができる。従って本発明の範囲は特許請求の範囲及びその均等範囲によってのみ規定されるものである。
【０１００】
【発明の効果】
以上詳細に説明したように本発明によれば、付加的添加物として、Ｌｉ、Ｎａ、Ｍｎ、Ｃｕ、Ｚｎ、Ｓｃ及びＩｎの酸化物から選択される少なくとも１種からなる成分を添加することによって、組成と焼成条件とを一定とし、再酸化条件を変えて幅広いバリスタ電圧Ｅ_１０を有するバリスタを作製したときも、Ｅ_１０温度特性をゼロ近傍の小さな値に抑えることができる。
【０１０１】
また、焼結助剤として用いられるＳｉＯ_２の量をできるだけ小さくすることにより、バリスタの耐サーマルショック性を高め、過酷な半田付け条件による局所的なサーマルショックに基づくサーマルクラックの発生を抑制すると共に、ＳｉＯ_２量の減少によって生じる焼結性の低下をトータルＡ／Ｂを調整して補償している。さらに、これらとＡサイトモル比及び半導体化剤の量及び種類をバランスよく適切に選ぶことによって、バリスタの電気的特性の向上を図ることができる。
【図面の簡単な説明】
【図１】本発明の一実施形態として、リングバリスタの構造を示す平面図及びそのＡ−Ａ線断面図である。
【図２】電極材料にＣｕ及びＡｇをそれぞれ使用した場合の半田温度に対する残存電極面積の割合を示す特性図である。
【図３】Ｅ_１及びＥ_１０の測定回路を示す回路図である。
【符号の説明】
１０ バリスタ磁器
１０ａ 半導体部分
１０ｂ 絶縁層
１１ 電極
３０ 電流計
３１ バリスタ
３２ 直流定電流源
３３ 電圧計[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a voltage-dependent non-linear resistor (varistor), and in particular, (Sr, Ba, Ca) TiO.₃The present invention relates to a varistor including a composite perovskite ceramic having the following composition.
[0002]
[Prior art]
A varistor is a resistance element whose resistance value changes non-linearly in response to changes in the applied voltage. Specifically, it is a resistance element whose resistance value rapidly decreases when a voltage exceeding a certain voltage value is applied. is there.
[0003]
As the porcelain mainly constituting the varistor, there are various types of porcelain. (Sr, Ba, Ca) TiO₃The composite perovskite porcelain having the composition of the above has both the non-linearity of its resistance value and the capacitance function, so it absorbs surge voltage generated in electronic devices and eliminates noise. It is very suitable to do. For example, it is applied to a ring varistor for a DC micromotor.
[0004]
The varistor equipped with this composite perovskite-type porcelain has a varistor voltage E by selecting the molar ratio of Sr, Ba and Ca, that is, the A site ratio.₁₀The temperature dependence of can be controlled. That is, varistor voltage (voltage at which the resistance value suddenly decreases) decreases as the temperature rises during operation, and temperature dependence is near zero in order to prevent excessive current from flowing through the varistor and causing thermal runaway. Can be adjusted. In Japanese Patent Publication No. 8-28287 (Japanese Patent Laid-Open No. 2-146702), Japanese Patent Laid-Open No. 3-45559 and Japanese Patent No. 2944697 (Japanese Patent Laid-Open No. 3-237057), the temperature dependence of the varistor voltage is thus described. A varistor with adjusted properties is described.
[0005]
The present applicant has already proposed a composite perovskite-type porcelain and varistor in which the porcelain composition and the stress structure are devised so that the function is not impaired even when high-temperature soldering is performed, and a manufacturing method thereof (specialty). (Applications 2001-349934, 2001-349935, 2000-371324, 2000-378732, 2001-140076, 2001-160527).
[0006]
[Problems to be solved by the invention]
However, in such a composition according to the prior application, a varistor voltage E in a limited range to some extent.₁₀The varistor voltage E for a sample having₁₀Temperature dependence (hereinafter referred to as E₁₀(Referred to as temperature characteristics)₁₀The temperature characteristics were near zero.
[0007]
In general, from the viewpoint of manufacturing cost, a wide range of varistor voltage E with materials of the same composition₁₀It is desirable to be able to obtain a varistor having Therefore, the varistor voltage E is maintained by keeping the composition and firing conditions constant and changing the reoxidation conditions.₁₀A varistor voltage E was produced.₁₀For those with large (15V or more)₁₀There was a phenomenon in which the temperature characteristics became large, that is, a phenomenon of leaving from the vicinity of zero, and an attempt was made to suppress this only by adjusting the A-site ratio.
[0008]
The object of the present invention is therefore to provide a wide range of varistor voltages E₁₀E in range₁₀It is an object of the present invention to provide a composite perovskite varistor that has low temperature characteristics and does not impair its function even when high-temperature soldering is performed.
[0009]
[Means for Solving the Problems]
  According to the present invention, a first component composed of oxides of Sr, Ba, Ca and Ti, a second component composed of at least one selected from oxides of R (Y and lanthanoid), and M (Nb and Ta ) At least one of the third components selected from oxides of oxides, the fourth component of Si oxides, and the oxides of Li, Na, Mn, Cu, Zn, Sc and In A fifth component comprising at least one selected fromA sixth component made of an oxide of Co;And a composite perovskite-based semiconductor ceramic containing 0.30 ≦ a / (a + b + c) ≦ 0.40, 0.30 ≦ b / (a + b + c) ≦ 0.40, 0.25 ≦ c / (a + b + c) ≦ 0.35, 0.84 ≦ (a + b + c + e) / (d + f) ≦ 1.02, 1.0 ≦ (e + f) /d×100≦10.0, g / d × 100 ≦ 0 .60.01 ≦ h / d × 100 ≦ 1.50, 0.03 ≦ i / d × 100 ≦ 3.00(However, a is the number of moles converted from Sr of the first component to SrO, b is the number of moles converted from Ba of the first component to BaO, c is the number of moles converted from Ca of the first component to CaO, and d is Ti of the first component is changed to TiO₂The number of moles converted to, e is R of the second component YO_3/2, CeO₂, PrO_11/6, TbO_7/4, RO_3/2The total number of moles converted to (other lanthanoids), f is the third component M is NbO_5/2, TaO_5/2The total number of moles converted in terms of g, g is the fourth component Si to SiO₂Number of moles converted to, H represents the sixth component Co as CoO _4/3 The number of moles converted to, i is the fifth component of Li, Na, Mn, Cu, Zn, Sc, In and LiO. _1/2 , NaO _1/2 , MnO, CuO, ZnO, ScO _3/2 , InO _3/2 Total number of moles converted toA varistor is provided.
[0010]
As an additional additive, by adding a fifth component made of at least one selected from oxides of Li, Na, Mn, Cu, Zn, Sc and In, the composition and the firing conditions are made constant, Wide range of varistor voltage E by changing oxidation conditions₁₀When producing a varistor having₁₀The temperature characteristic can be suppressed to a small value near zero.
[0011]
SiO used as a sintering aid₂By reducing the amount of the varistor, the thermal shock resistance of the varistor is increased, and the occurrence of thermal cracks due to local thermal shock due to severe soldering conditions is suppressed, and SiO 2₂Total A / B represented by (a + b + c + e) / (d + f) as a decrease in sinterability caused by a decrease in the amount (A site component including other elements that can enter the lattice of the A site component from the relationship of the ion radius) And the ratio of the total number of moles of the B site component including other elements that can enter the lattice of the B site component). Furthermore, the electrical characteristics of the varistor can be improved by appropriately selecting the A site molar ratio and the amount and type of the semiconducting agent in a balanced manner.
[0012]
In the present invention, the perovskite structure is not a simple A / B which is the ratio of the number of moles of the A site component composed solely of Sr, Ba and Ca and the number of moles of the B site component composed solely of Ti, but also includes additives. A parameter of total A / B, which is the molar ratio of ions, is introduced. That is, it is considered that such a total A / B is not a simple A / B that really contributes to sinterability. In particular, the semiconducting agent among the additives is an important solid solution ion, and in the case of the present invention having a large amount of addition, the error increases when using a simple A / B, and the total A / B is used. For the first time, accurate control becomes possible, and a varistor without characteristic variations can be provided.
[0013]
The composition of the first component and at least one of the second component and the third component is preferably 0.96 ≦ (a + b + c + e) / (d + f) ≦ 1.02. Further, the composition of the first component and at least one of the second component and the third component is also preferably 1.0 ≦ (e + f) /d×100≦4.0. Furthermore, it is more preferable that the composition of the first component and the fourth component is g / d × 100 ≦ 0.3.
[0014]
  In the present invention,The composition of the first component and the sixth component isAs mentioned above,0.01 ≦ h / d × 100 ≦ 1.50TheBy adding this sixth component, the varistor voltage E₁₀Can be reduced. However, if the added amount of the sixth component is too large, the sintering becomes excessive and thermal cracks are likely to occur. The composition of the first component and the sixth component is 0.01 ≦ h / d × 100 ≦ 1.00.PreferGood.
[0015]
  In the present invention,The composition of the first component and the fifth component isAs mentioned above,0.03 ≦ i / d × 100 ≦ 3.00AhTheFurthermore, 0.03 ≦ i / d × 100 ≦ 1.00PreferGood. If the added amount of the fifth component is too large, E₁₀The temperature characteristics are too large. Too little, E₁₀The effect of improving temperature characteristics is reduced.
[0016]
It is also preferable that an electrode formed on the surface of the porcelain is provided, and this electrode is made of Cu or a material mainly containing Cu.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a plan view showing a structure of a ring varistor and a cross-sectional view taken along line AA, as an embodiment of the present invention.
[0018]
In the figure, 10 is a varistor porcelain formed in a ring shape, and 11 is an electrode formed on one surface thereof. In this embodiment, five electrodes 11 are provided at equal angles. As shown in FIG. 2B, the varistor ceramic 10 is composed of an internal semiconductor portion 10a and an insulating layer 10b formed near the entire surface thereof.
[0019]
Hereinafter, the composition of the varistor ceramic 10 will be described.
[0020]
The varistor porcelain 10 includes a first component of a composite perovskite composed of oxides of Sr, Ba, Ca and Ti, and R (Y and lanthanoids (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho , Er, Tm, Yb, and Lu)) at least one selected from oxides and at least one selected from M (Nb and Ta) oxides. A fourth component composed of an oxide of Si, and a fifth component composed of at least one selected from oxides of Li, Na, Mn, Cu, Zn, Sc and In. a is the number of moles converted from Sr of the first component to SrO, b is the number of moles converted from Ba of the first component to BaO, c is the number of moles converted from Ca of the first component to CaO, and d is the first component. Ti of TiO₂The number of moles converted to, e is R of the second component YO_3/2, CeO₂, PrO_11/6, TbO_7/4, RO_3/2The total number of moles converted to (other lanthanoids), f is the third component M is NbO_5/2, TaO_5/2The total number of moles converted in terms of g, g is the fourth component Si to SiO₂Assuming that the number of moles is converted to, the composition of this varistor porcelain is 0.30 ≦ a / (a + b + c) ≦ 0.40, 0.30 ≦ b / (a + b + c) ≦ 0.40, 0.25 ≦ c. /(A+b+c)≦0.35, 0.84 ≦ (a + b + c + e) / (d + f) ≦ 1.02, 1.0 ≦ (e + f) /d×100≦10.0, g / d × 100 ≦ 0.6 It is.
[0021]
This composition is more preferably 0.96 ≦ (a + b + c + e) / (d + f) ≦ 1.02, 1.0 ≦ (e + f) /d×100≦4.0, g / d × 100 ≦ 0.3 is there.
[0022]
The first component is the main component of the varistor porcelain 10. In the composite perovskite, the first component is composed of an A site component made of Sr, Ba and Ca and a B site component made of Ti. The second component and the third component are metal oxides that contribute to semiconductorization, the fourth component is added mainly for improving the sinterability, and the fifth component is E₁₀It is added to suppress the temperature characteristic to a small value near zero.
[0023]
The electrical characteristics of the varistor are mainly varistor voltage E₁₀Is expressed by the temperature characteristic and the nonlinear coefficient α. Varistor voltage E₁₀Represents an applied voltage value when a current of 10 mA flows through the varistor, and the nonlinear coefficient α is generally α = 1 / log (E₁₀/ E₁). However, E₁Is the applied voltage value when a current of 1 mA flows through the varistor.
[0024]
The molar ratio of Sr, Ba and Ca which are A site components is such that Sr is 0.30 or more and 0.40 or less, Ba is 0.30 or more and 0.40 or less, Ca is 0.25 or more and 0.35 or less. By setting so that the varistor voltage E₁₀Controllability, E₁₀Electrical characteristics such as temperature characteristics and nonlinear coefficient α can be improved, and the thermal shock resistance of the varistor can be improved. That is, if there is too much Sr, E₁₀If the temperature characteristic becomes negative and is too low, the varistor voltage E₁₀Becomes higher. Also, if there is too much Ba, the varistor voltage E₁₀Becomes higher or the non-linear coefficient α becomes smaller.₁₀The temperature characteristic becomes negative. Furthermore, the varistor voltage E can be used regardless of whether Ca is too much or too little.₁₀As a result, the non-linear coefficient α becomes smaller. In addition, if there is too much Ca, the varistor voltage E₁₀Becomes larger and control becomes difficult.₁₀The temperature characteristic becomes negative.
[0025]
This E₁₀The tendency of the temperature characteristics is observed when the composition, firing and reoxidation conditions are limited. Wide range of varistor voltage E by changing reoxidation conditions₁₀If you get E₁₀Temperature characteristics are varistor voltage E₁₀It turned out to depend greatly on.
[0026]
Main component (TiO₂) So that the mol% (calculated by the number of moles of metal ions) of the semiconducting agent (second and / or third component) is 1.0 or more and 10.0 or less, more preferably 1.0 or more and 4. By setting it to be 0 or less, the thermal shock resistance of the varistor can be enhanced. That is, thermal cracks are likely to occur if there is too much or too little semiconducting agent.
[0027]
By setting so that the total A / B is 0.84 or more and 1.02 or less, more preferably 0.96 or more and 1.02 or less, the fourth component ( SiO₂The sinterability can also be improved when the amount of) is reduced. That is, if the total A / B is too large or too small, sintering is inhibited, and the base is insulated by reoxidation. Further, if the total A / B is too large or too small, the strength is lowered and thermal cracks are likely to occur. SiO₂In a region where a small amount of the semiconducting agent is added as described above, it is necessary to control the total A / B in order to maintain the thermal crack resistance.
[0028]
Main component (TiO₂) The fourth component (SiO₂), The thermal shock resistance of the varistor can be greatly improved. That is, SiO₂Is added as a sintering aid, and if it is included, it can be fired stably even if the composition fluctuates. However, if the amount increases, thermal cracks are likely to occur. In addition, SiO₂The content (mol%) of 0.6 or less or 0.3 or less includes the case where the addition amount is 0.
[0029]
LiO as the fifth component_1/2, NaO_1/2, MnO, CuO, ZnO, ScO_3/2And InO_3/2Is added. In this case, the main component (TiO₂) Is set so that the mol% of the fifth component is 0.03 or more and 3.0 or less, the composition and the firing conditions are kept constant, and the re-oxidation conditions are changed to change the varistor voltage E.₁₀When producing a varistor having₁₀The temperature characteristic can be suppressed to a small value near zero. The mol% of the fifth component is more preferably 0.03 or more and 1.0 or less. If too much is added, E₁₀The temperature characteristics are too large. Too little E₁₀The effect of improving temperature characteristics is lost.
[0030]
  Varistor porcelain 10IsCoO, the sixth component_4/3Further containsTheMain component (TiO₂) Is set such that the mol% of the sixth component is 0.01 or more and 1.50 or less.₁₀Can be reduced. The mol% of the sixth component is 0.01 or more and 1.00 or less.PreferGood. If the amount is too large, sintering will be excessive and thermal cracks will easily occur.
[0031]
The varistor ceramic 10 may contain other elements such as P, S, K, Al, and Zr as inevitable impurities in addition to such additives. Such elements are usually present as oxides.
[0032]
As described above, the varistor porcelain 10 is a polycrystalline body composed of a perovskite crystal. Each component is partly dissolved in the crystal grains and enters the perovskite crystal, and part is present as an oxide or composite oxide at the crystal grain boundary. For example, Ba, Ca, Sr, Ti, Nb, Ta, Y, lanthanoids and the like are present in the crystal grains, and Si, Co, Li, Na, Mn, Cu, Zn, Sc, In and the like are crystal grains. There are many in the world.
[0033]
The average crystal grain size of the varistor ceramic 10 is usually about 0.5 to 10 μm, particularly about 1 to 6 μm.
[0034]
The electrode 11 is formed of Cu or a material mainly containing Cu. When the electrode is made of Ag, the Ag component of the electrode is eluted in the solder due to the high temperature of soldering, and at least a part of the electrode disappears. The electrode 11 is less susceptible to corrosion even at high temperatures and can withstand high temperature soldering operations.
[0035]
The material containing Cu as a main component is a Cu alloy such as Cr, Zr, Ag, Ti, Be, Zn, Sn, Ni, Al or Si, or Li, Na, K, Sr, Ba, Mn, Cu, Zn. Cu containing glass frit with oxides such as B, Si, Al, Bi or Pb.
[0036]
FIG. 2 is a characteristic diagram showing the ratio of the remaining electrode area to the solder temperature when Cu and Ag are used as electrode materials, respectively.
[0037]
After applying a flux to a sample ring varistor and preheating it, it is immersed in a solder bath of eutectic solder at each temperature for 5 seconds.
[0038]
As is clear from the figure, when the solder temperature is 400 ° C., the Ag electrode is eroded and the remaining electrode area is about 55.5%, whereas the Cu electrode is not eroded at all. The remaining electrode area is 100%.
[0039]
Next, a method for manufacturing the varistor ceramic 10 will be briefly described.
[0040]
The varistor porcelain 10 is obtained by processing the raw material powder in the order of mixing, calcination, pulverization, molding, binder removal, reduction firing, and reoxidation.
[0041]
As the raw material powder, a powder of a compound of each constituent element of porcelain is usually used. As the raw material powder, an oxide or a compound that becomes an oxide by firing, such as a carbonate or a hydroxide, can be used. For example, taking Ba as an example, the raw material is BaCO.₃, BaSiO₃, BaO, BaCl₂, Ba (OH)₂, Ba (NO₃)₂Alkoxides (eg (CH₃O)₂At least one barium compound such as Ba) can be used. The average particle diameter of the raw material powder is usually about 0.2 to 5 μm.
[0042]
First, the raw material powder is weighed so that the final composition becomes the composition described above, and usually wet mixed. Next, after dehydration, it is dried and pre-baked at about 1080 to 1250 ° C. for about 2 to 4 hours. Next, after pulverizing the temporarily fired product, an organic binder is added, and water, a pH adjuster, a moisturizing agent, and the like are further added and mixed. Next, the mixture is molded and treated to remove the binder, and then fired in a reducing atmosphere at about 1250 to 1400 ° C. for about 2 to 4 hours to obtain a semiconductor ceramic.
[0043]
In addition, you may add each raw material powder, such as Nb, Ta, Y, a lanthanoid, Si, Co, Li, Na, Mn, Cu, Zn, Sc, In, at the time of mixing after temporary baking.
[0044]
The thus obtained semiconductor ceramic is subjected to heat treatment (reoxidation treatment) at a temperature of, for example, about 800 to 1000 ° C. in an oxidizing atmosphere such as air so that an appropriate varistor voltage corresponding to the purpose can be obtained. Apply. By this heat treatment, the insulating layer 10b is formed in the surface layer portion. Varistor characteristics are manifested by the presence of this insulating layer. If this insulating layer is thick, the nonlinear coefficient α and the varistor voltage increase, and if it is thin, the nonlinear coefficient α and the varistor voltage decrease, so that the insulating layer has an appropriate thickness according to the characteristics required for the product. What is necessary is just to select the heat processing conditions suitably.
[0045]
After the re-oxidation treatment, an electrode is formed on one surface of the varistor porcelain with Cu or a material mainly containing Cu to form a varistor.
[0046]
【Example】
Hereinafter, the present invention will be described in more detail with reference to specific examples and comparative examples.
[0047]
Comparative example
This comparative example shows the mol% and type of semiconducting agent, total A / B, SiO₂And CoO_4/3This is a comparison using a sample in which other parameters such as mol% of A are constant and the molar ratio of the A site component is changed.
[0048]
First, SrCO as a raw material₃, BaCO₃, CaCO₃TiO₂, NbO_5/2, SiO₂CoO_4/3Each was converted and weighed so as to have the composition shown in Table 1 and blended, then mixed for 10 to 20 hours using a wet media mill, dehydrated and dried.
[0049]
The obtained mixture was calcined at 1150 ° C. using a tunnel furnace, coarsely pulverized, mixed again by a wet media mill for 10 to 20 hours, dehydrated and dried. Next, 1.0 to 1.5% by weight of polyvinyl alcohol is mixed as an organic binder and granulated, and the molding pressure is 2 t / cm.²To form a molded body having an outer diameter of 12 mm, an inner diameter of 9 mm, and a thickness of 1.0 mm.
[0050]
After removing the binder from the molded body in an air atmosphere at about 1000 ° C., N₂(95% by volume) + H₂In a reducing atmosphere of (5% by volume), firing was performed at about 1300 ° C. for 4 hours to obtain a semiconductor ceramic. Next, the varistor voltage E of the varistor sample for measurement₁₀Was appropriately re-oxidized so as to be 10 V, 20 V, and 30 V, and respective varistor porcelains were obtained.
[0051]
Next, as shown in FIG. 1, a Cu paste is applied to one surface of the varistor porcelain 10 and baked at 750 ° C. in a neutral atmosphere to form a 5-electrode Cu electrode 11 as shown in FIG. A varistor sample was prepared.
[0052]
Then, E of each sample at 20 ° C.₁And E₁₀And measured E₁And E₁₀Using α = 1 / log (E₁₀/ E₁) To determine the nonlinear coefficient α. Furthermore, the varistor voltage E₁₀The temperature characteristics (temperature coefficient) were also obtained. Furthermore, a thermal crack test of each sample was performed.
[0053]
E₁And E₁₀The measurement of was performed using the measurement circuit shown in FIG. In this measurement circuit, an ammeter 30 is connected in series between a varistor 31 and a DC constant current source 32, and a voltmeter 33 is connected in parallel to the varistor 31. E₁And E₁₀Measured the voltage value between the two terminals of the varistor 31 when currents of 1 mA and 10 mA flowed through the varistor 31 using the ammeter 30 and the voltmeter 33, respectively.
[0054]
Varistor voltage E₁₀Temperature characteristics (temperature coefficient) ΔE_10TFor each sample
ΔE_10T= {E₁₀(85) -E₁₀(20)} / {E₁₀(20) × (85-20)} × 100 [% / ° C.] E₁₀(20) and E₁₀(85) is the varistor voltage E at temperatures of 20 ° C. and 85 ° C., respectively.₁₀It is. These were measured using a thermostat.
[0055]
In the thermal crack test, a soldering iron whose temperature was set in advance was brought into contact with the electrode surface of the sample left at room temperature for 3 seconds while supplying eutectic solder. The temperature of the soldering iron was 400 ° C. The number of samples was 100, and the presence or absence of cracks was visually determined using alcohol. The results are shown in Table 1.
[0056]
[Table 1]

[0057]
The molar ratio of the A site component depends on the electrical characteristics of the varistor, in particular,₁₀This greatly affects the temperature characteristics. Varistor voltage E₁₀In samples 1 to 7 having a voltage of about 10 V, E₁₀Since the temperature characteristic is zero or slightly negative, it is determined that the temperature characteristic is good. However, by increasing the temperature during reoxidation, the varistor voltage E₁₀In Samples 8 to 21 with 20 to 30 V, E₁₀There is a tendency for temperature characteristics to deviate greatly in the negative direction. This E₁₀If the temperature characteristic is a large negative value, the varistor voltage decreases as the temperature rises during operation, and an excessive current may flow through the varistor or thermal runaway may occur.
[0058]
Example 1
In this example 1, the varistor voltage E₁₀E is also increased when₁₀This is a comparison using a sample to which MnO is added as an additional additive so that the temperature characteristic becomes a value near zero.
[0059]
The A site molar ratio was changed in the same manner as in the comparative example, and the mol% and type of semiconducting agent, total A / B, SiO₂And CoO_4/3Other parameters such as mol% of the above are made constant, and a certain amount of MnO is added as an additive. That is, samples were prepared in the same manner as in the comparative example except that a certain amount of MnO was added, and the same measurement as in the comparative example was performed for each of these samples. The results are shown in Table 2.
[0060]
[Table 2]

[0061]
When Mn is added as an additive, the varistor voltage E₁₀E is also increased when₁₀The temperature characteristic is a good value near zero.
[0062]
Therefore, samples 22 to 42 to which Mn is added as an additive (0.1 mol% of MnO is added to the main component) are all within the preferable range of the present invention. This corresponds to containing the fifth component as defined in claim 1.
[0063]
Example 2
In this example 2, the varistor voltage E₁₀E is also increased when₁₀This is a comparison using samples in which the amount of MnO added as an additive is changed so that the temperature characteristic becomes a value near zero.
[0064]
  A site molar ratio, mol% and type of semiconducting agent, total A / B, SiO₂And CoO_4/3Samples were prepared in the same manner as in the comparative example, except that other parameters such as mol% were constant and the amount of MnO as an additive was as shown in Table 3. Measurements similar to the above were performed. The results are shown in Table 3.As will be described later, samples 43, 49, 50, 56, 57, and 63 are not examples, but their data are described for comparison.
[0065]
[Table 3]

[0066]
As described in Example 1, when Mn was added as an additive, varistor voltage E₁₀E is also increased when₁₀The temperature characteristics are near zero. However, if the amount of Mn added is small, the varistor voltage E₁₀As seen in high samples 50 and 57, E₁₀There is almost no improvement in temperature characteristics. In addition, when the amount of Mn added is too large, as seen in Samples 49, 56 and 63, E₁₀The temperature characteristic becomes too large, which is not preferable.
[0067]
  Therefore, samples 44 to 48 and 51 to 55 in which the mol% of MnO with respect to the main component is 0.03 or more and 3.00 or less are used in the present invention.Range ofIt is a circle. This is the claim1Is included in the types and mol% of additive additives specified in 1. Further, if the molar percentage of MnO with respect to the main component is 0.03 or more and 1.00 or less, the varistor voltage E₁₀Even in the case of samples 58 to 61 having a large value of 30 V, E₁₀The temperature characteristics are near zero.GoodGood. This is the claim6Is included in the types and mol% of additive additives specified in 1.
[0068]
Example 3
In this example 3, the varistor voltage E₁₀E is also increased when₁₀This is a comparison using samples to which Li, Na, Cu, Zn, Sc, and In are added as additive additives so that the temperature characteristic becomes a value near zero.
[0069]
A site molar ratio, mol% and type of semiconducting agent, total A / B, SiO₂And CoO_4/3Samples were prepared in the same manner as in the comparative example, except that other parameters such as mol% were constant and a certain amount of the additive shown in Table 4 was added as an additive. The same measurement was performed. The results are shown in Table 4.
[0070]
[Table 4]

[0071]
  Varistor voltage E₁₀As a matter of course, in the samples 64 to 69 in which the voltage was reduced to 10 V, the varistor voltage E was increased by increasing the temperature during reoxidation.₁₀In any of the samples 70 to 81 having a high value of 20 V and 30 V, E₁₀The temperature characteristics are within a favorable range of -0.02 to + 0.05% / ° C. Therefore, as an additive, in addition to MnO, LiO_1/2, NaO_1/2, CuO, ZnO, ScO_3/2And InO_3/2Use of the present inventionRange ofIt is a circle. This is included in the type of additive as defined in claim 1.
[0072]
Example 4
Example 4 is a comparison using samples with different amounts of semiconducting agent.
[0073]
  A site molar ratio, type of semiconducting agent, total A / B, SiO₂And CoO_4/3The other parameters such as the mol% of the above were made constant, 0.03 mol% of MnO was added as an additive, and the mol% of the semiconducting agent was as shown in Table 4 as in the comparative example. Samples were prepared in the same manner, and the same measurement as in the comparative example was performed. In the thermal crack test, three temperatures of 360 ° C., 400 ° C. and 450 ° C. were used as the temperature of the soldering iron. The results are shown in Table 5. However, the varistor voltage E can be adjusted by adjusting the temperature during reoxidation.₁₀Is set to 20V. E in this case₁₀All the temperature characteristics are within a favorable range of -0.02 to + 0.05% / ° C.As will be described later, samples 82 and 87 are not examples, but their data are described for comparison.
[0074]
[Table 5]

[0075]
  The amount of semiconducting agent affects the thermal crack resistance of the varistor porcelain. Samples 82 and 87 are not preferable because the amount of the semiconducting agent is too small and too large, and thermal cracks occur in a test at a soldering iron temperature of 360 ° C. Therefore, samples 83 to 86 in which thermal cracks do not occur in a test where the soldering iron temperature is 360 ° C. are the present invention.Range ofIt is a circle. This corresponds to the mol% of the semiconducting agent as defined in claim 1.
[0076]
  Further, since the sample 86 has a thermal crack in the test with the soldering iron temperature of 400 ° C. and 450 ° C., the samples 83 to 85 in which no crack is generated in the 400 ° C. and 450 ° C. thermal crack test are the present invention.FavorIt is a good range. This corresponds to the mol% of the semiconducting agent as defined in claim 3.
[0077]
Example 5
This Example 5 is a comparison using samples with different types of semiconducting agents.
[0078]
A site molar ratio, mol% of semiconducting agent, total A / B, SiO₂And CoO_4/3Other parameters such as mol% of the above were made constant, 0.03 mol% of MnO was added as an additive, and the type of semiconducting agent was as shown in Table 6 in the same manner as in the comparative example. Samples were prepared, and these were also measured in the same manner as in the comparative example. In the thermal crack test, 400 ° C. was used as the temperature of the soldering iron. The results are shown in Table 6. However, the varistor voltage E can be adjusted by adjusting the temperature during reoxidation.₁₀Is set to 20V. E in this case₁₀All the temperature characteristics are within a good range of -0.02 to + 0.05% / ° C.
[0079]
[Table 6]

[0080]
  None of Samples 88 to 104 have NbO as a semiconducting agent because thermal cracks do not occur in a test where the soldering iron temperature is 400 ° C._5/2, TaO_5/2, YO_3/2, LaO_3/2, CeO₂, PrO_11/6, NdO_3/2, SmO_3/2, EuO_3/2, GdO_3/2, TbO_7/4, DyO_3/2, HoO_3/2, ErO_3/2, TmO_3/2, YbO_3/2, LuO_3/2Or NbO_5/2+ YO_3/2It is the present invention to use (equal moles).Range ofIt is a circle.
[0081]
Example 6
Example 6 is a comparison using samples with different total A / B.
[0082]
  A site molar ratio, mol% and type of semiconducting agent, SiO₂And CoO_4/3In the same manner as in the comparative example, except that other parameters such as mol% were constant, 0.03 mol% of MnO was added as an additive, and total A / B was as shown in Table 7. Samples were prepared, and these were also measured in the same manner as in the comparative example. In the thermal crack test, three temperatures of 360 ° C., 400 ° C. and 450 ° C. were used as the temperature of the soldering iron. The results are shown in Table 7. However, the varistor voltage E can be adjusted by adjusting the temperature during reoxidation.₁₀Is set to 20V. E in this case₁₀All the temperature characteristics are within a good range of -0.02 to + 0.05% / ° C.As will be described later, the samples 105 and 110 are not examples, but their data are described for comparison.
[0083]
[Table 7]

[0084]
The total A / B value affects the sinterability of the porcelain. In Samples 105 and 110, the total A / B is too small and too large, respectively, so that it is impossible to sinter dense porcelain and thermal cracks are generated at a soldering iron temperature of 360 ° C. As can be seen from Table 7, SiO₂In a region where a small amount of and a large amount of semiconducting agent are added, it is indispensable to control the total A / B in order to maintain the thermal crack resistance. If the total A / B is less than 0.84 or exceeds 1.02, thermal cracks occur even at a soldering iron temperature of 360 ° C.
[0085]
  That is, the samples 106 to 109 are free from thermal cracks in the test where the soldering iron temperature is 360 ° C.Range ofIt is a circle. This corresponds to the total A / B range defined in claim 1.
[0086]
  Furthermore, since the samples 107 to 109 are free from thermal cracks even in tests at a soldering iron temperature of 400 ° C. and 450 ° C., the present inventionFavorIt is a good range. This corresponds to the total A / B range defined in claim 2.
[0087]
Example 7
In Example 7, SiO 2₂It is the comparison by the sample which changed mol% of.
[0088]
  A site molar ratio, mol% and type of semiconducting agent, total A / B and CoO_4/3Other parameters such as MnO are added as 0.03 mol% as an additive, and SiO 2 is added.₂Samples were prepared in the same manner as in the comparative example except that the mol% of those shown in Table 8 was used, and the same measurements as in the comparative example were performed except for the temperature of the thermal crack test. In the thermal crack test, three temperatures of 360 ° C., 400 ° C. and 450 ° C. were used as the temperature of the soldering iron. The results are shown in Table 8. However, the varistor voltage E can be adjusted by adjusting the temperature during reoxidation.₁₀Is set to 20V. E in this case₁₀All the temperature characteristics are within a good range of -0.02 to + 0.05% / ° C.As will be described later, the sample 115 is not an example, but its data is described for comparison.
[0089]
[Table 8]

[0090]
SiO₂Is added as a sintering aid, and if it is included, it can be fired stably even if the composition fluctuates. However, if the amount increases, thermal cracks tend to occur.
[0091]
  Sample 115 is SiO₂Therefore, a thermal crack is generated even in a test where the soldering iron temperature is 360 ° C., which is not preferable. Therefore, the samples 111 to 114 in which thermal cracks do not occur even in tests where the soldering iron temperature is 360 ° C. and 400 ° C. are the present invention.Range ofIt is a circle. This is the SiO as defined in claim 1.₂Corresponds to the mole percent of Sample 111 is made of SiO.₂However, in practice, SiO2 as an impurity is included in each raw material.₂This sample 111 contains SiO.₂The content is not zero.
[0092]
  Furthermore, since thermal cracks occur in the sample 114 in the test where the soldering iron temperature is 450 ° C., the samples 111 to 113 in which thermal cracking does not occur in the test where the soldering iron temperature is 450 ° C. are the present invention.FavorIt is a good range. This is the SiO as defined in claim 4.₂Corresponds to the mole percent of
[0093]
Example 8
In Example 8, CoO_4/3It is the comparison by the sample which changed mol% of.
[0094]
  A site molar ratio, mol% and type of semiconducting agent, total A / B and SiO₂The other parameters such as MnO are added as 0.03 mol% as an additive, and CoO is added._4/3Samples were prepared in the same manner as in the comparative example except that the mol% of those shown in Table 9 was used, and the same measurements as in the comparative example were performed except for the temperature of the thermal crack test. In the thermal crack test, three temperatures of 360 ° C., 400 ° C. and 450 ° C. were used as the temperature of the soldering iron. The results are shown in Table 9. However, the varistor voltage E can be adjusted by adjusting the temperature during reoxidation.₁₀Is set to 10 V for the sample 116 and 20 V for the other samples 117 to 123. E in this case₁₀All the temperature characteristics are within a good range of -0.02 to + 0.05% / ° C.As will be described later, the samples 116, 117, and 123 are not examples, but their data are described for comparison.
[0095]
[Table 9]

[0096]
CoO_4/3Varistor voltage E by adding₁₀Can be reduced. If the amount is too large, sintering will be excessive and thermal cracks will easily occur.
[0097]
  Sample 123 is CoO_4/3Therefore, a thermal crack is generated even in a test at a soldering iron temperature of 360 ° C., which is not preferable.further,The composition of samples 116 and 117 is CoO._4/3Thus, the effect of simultaneously obtaining the thermal shock resistance and the low varistor voltage disclosed in the prior application (Japanese Patent Application No. 2001-160527) was not obtained even when the reoxidation conditions were adjusted. Therefore, the samples 118 to 122 are the present invention.Range ofIt is a circle. This is the claim1CoO specified in_4/3Corresponds to the mole percent of
[0098]
  Further, since the sample 122 also has a thermal crack in the test at a soldering iron temperature of 450 ° C., the samples 118 to 121 in which the thermal crack does not occur in the test at a soldering iron temperature of 450 ° C.FavorIt is a good range. This is the claim5CoO specified in_4/3Corresponds to the mole percent of
[0099]
The above-described embodiments and examples are all illustrative and do not limit the present invention, and the present invention can be implemented in various other modifications and changes. Therefore, the scope of the present invention is defined only by the claims and their equivalents.
[0100]
【The invention's effect】
As described above in detail, according to the present invention, as an additive, at least one component selected from oxides of Li, Na, Mn, Cu, Zn, Sc and In is added. A wide range of varistor voltage E with constant composition and firing conditions and varying reoxidation conditions₁₀When producing a varistor having₁₀The temperature characteristic can be suppressed to a small value near zero.
[0101]
SiO used as a sintering aid₂As much as possible, the varistor's resistance to thermal shock is increased, and the occurrence of thermal cracks due to local thermal shock due to severe soldering conditions is suppressed.₂The decrease in sinterability caused by the decrease in the amount is compensated by adjusting the total A / B. Furthermore, the electrical characteristics of the varistor can be improved by appropriately selecting the A site molar ratio and the amount and type of the semiconducting agent in a balanced manner.
[Brief description of the drawings]
FIG. 1 is a plan view showing a structure of a ring varistor and a cross-sectional view taken along line AA, as an embodiment of the present invention.
FIG. 2 is a characteristic diagram showing the ratio of the remaining electrode area to the solder temperature when Cu and Ag are used as electrode materials, respectively.
FIG. 3 E₁And E₁₀It is a circuit diagram which shows these measurement circuits.
[Explanation of symbols]
10 Varistor porcelain
10a Semiconductor part
10b Insulating layer
11 electrodes
30 Ammeter
31 Barista
32 DC constant current source
33 Voltmeter

Claims (7)

A first component composed of oxides of Sr, Ba, Ca and Ti, a second component composed of at least one selected from oxides of R (Y and lanthanoids), and an oxide of M (Nb and Ta) At least one selected from at least one third component consisting of at least one, a fourth component consisting of an oxide of Si, and at least one selected from oxides of Li, Na, Mn, Cu, Zn, Sc and In A composite perovskite semiconductor ceramic containing a fifth component made of seed and a sixth component made of an oxide of Co is provided, and the composition of the ceramic is 0.30 ≦ a / (a + b + c) ≦ 0.40. 0.30 ≦ b / (a + b + c) ≦ 0.40, 0.25 ≦ c / (a + b + c) ≦ 0.35, 0.84 ≦ (a + b + c + e) / (d + f) ≦ 1.02, 1.0 ≦ ( e + f) / d × 100 ≦ 10 0, g / d × 100 ≦ 0.6, 0.01 ≦ h / d × 100 ≦ 1.50,0.03 ≦ i / d × 100 ≦ 3.00 ( where, a is the Sr of the first component The number of moles converted to SrO, b is the number of moles converted from Ba of the first component to BaO, c is the number of moles converted from Ca of the first component to CaO, and d is converted from Ti of the first component to TiO ₂ . The number of moles, e is the total number of moles in which the second component R is converted to YO _3/2 , CeO ₂ , PrO _11/6 , _{TbO 7/4} , RO _3/2 (other lanthanoids), and f is the third number. The total number of moles in which component M is converted to NbO _5/2 and TaO _5/2 , g is the number of moles in which the fourth component Si is converted to SiO ₂ , and h is the sixth component Co to CoO _4/3 . Convert the number of moles, i LiO ₁ is Li fifth component, Na, Mn, Cu, Zn , Sc, and in _{2, NaO 1/2, MnO, CuO} , ZnO, ScO 3/2, the voltage-dependent nonlinear resistor which is a _{InO 3/2} the total number of moles of converted respectively).   The composition of at least one of the first component and the second component and the third component is 0.96 ≦ (a + b + c + e) / (d + f) ≦ 1.02. The voltage-dependent nonlinear resistor described.   The composition of at least one of the first component and the second component and the third component is 1.0 ≦ (e + f) /d×100≦4.0. 2. The voltage-dependent nonlinear resistor according to 2.   4. The voltage-dependent nonlinear resistor according to claim 1, wherein the composition of the first component and the fourth component is g / d × 100 ≦ 0.3. 5. The composition of the first component and the sixth component is 0.01 ≦ h / d × 100 ≦ 1.00, and the voltage-independent non-dependency according to claim 1, Linear resistor. The composition of the first component and the fifth component, the voltage dependency according to claims 1, characterized in that a 0.03 ≦ i / d × 100 ≦ 1.0 0 to any one of the 5 Non-linear resistor. The voltage-dependent non-dependency according to any one of claims 1 to 6 , further comprising an electrode formed on a surface of the porcelain, wherein the electrode is made of Cu or a material mainly containing Cu. Linear resistor.

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