JP4020816B2 - Chip-shaped electronic component and manufacturing method thereof - Google Patents

Description

【００７０】
表１に示すように、Ｌｉ未処理の素子は、リフロー後における絶縁抵抗値の平均が１ＭΩ未満と低く、リフロー後の絶縁不良率も１００％以上と高かった（試料１，１１，２１，３１，４１）。
【００７１】
端子間ギャップが２０μｍの素子は、Ｌｉ処理していても、リフロー後における絶縁抵抗値の平均が１ＭΩ未満と低く、リフロー後の絶縁不良率も９８％以上と高かった（試料２〜９）。絶縁不良率の改善に至らなかったのは、ギャップ間の高抵抗化に寄与しているＺｎＯ結晶粒界の数が数個しか存在しないため、抵抗が低下する経路が発生する確率が増大したためと考えられる。
【００７２】
イオン強度比が０．０００１以下の素子は、Ｌｉ処理していても、リフロー後における絶縁抵抗値の平均が１ＭΩ未満と低く、リフロー後の絶縁不良率も６５％以上と高かった（試料１２，２２，３２，４２）。
【００７３】
端子間ギャップが５０μｍ以上で、かつイオン強度比が０．００１以上、５００以下の素子は、絶縁抵抗値の平均が３．８ＭΩ以上で、１ＭΩ未満を示す素子は一つもなく、しかも不良率は全て０であった（試料１３〜１９，２３〜２９，３３〜３９，４３〜４９）。特に、０．０１以上５００以下の素子は、絶縁抵抗値の平均が１０ＭΩ以上で、より好ましいことが確認できた。
本実施例では、Ｌｉ拡散による高抵抗化の影響がバリスタ試料の電気特性に影響を与えないことが確認できた。これにより、高信頼性を確保できる。
【００７４】
なお、イオン強度比が１０００以上のサンプルは、作製できなかった（試料１０，２０，３０，４０，５０）。また、試料番号２〜９，１２〜１９，２２〜２９，３２〜３９，４２〜４９については、Ｌｉ拡散処理の前後において、バリスタ特性（電圧非直線性）は変化しないことが、別の実験により確認された。
【００７５】
実施例２
Ｌｉ_２ ＣＯ_３ の代わりに、Ｎａ_２ ＣＯ_３ を用いる以外は、実施例１と同様の条件で、素子を作製した。この結果を表２にまとめた。
【表２】

【００７６】
表２に示すように、Ｎａ未処理の素子は、リフロー後における絶縁抵抗値の平均が１ＭΩ未満と低く、リフロー後の絶縁不良率も１００％以上と高かった（試料５１，６１，７１，８１，９１）。
【００７７】
端子間ギャップが２０μｍの素子は、Ｎａ処理していても、リフロー後における絶縁抵抗値の平均が１ＭΩ未満と低く、リフロー後の絶縁不良率も１００％と高かった（試料５２〜５８）。絶縁不良率の改善に至らなかったのは、上記実施例１と同様の理由と考えられる。
【００７８】
イオン強度比が０．０００１以下の素子は、Ｎａ処理していても、リフロー後における絶縁抵抗値の平均が１ＭΩ未満と低く、リフロー後の絶縁不良率も１００％と高かった（試料６２，７２，８２，９２）。
【００７９】
端子間ギャップが５０μｍ以上で、かつイオン強度比が０．００１以上、１００以下の素子は、絶縁抵抗値の平均が３．３ＭΩ以上で、１ＭΩ未満を示す素子は一つもなく、しかも不良率は４％以下であった（試料６３〜６８，７３〜７８，８３〜８８，９３〜９８）。特に、０．０１以上１００以下の素子は、絶縁抵抗値の平均が１０ＭΩ以上で、より好ましいことが確認できた。
本実施例では、Ｎａ拡散による高抵抗化の影響がバリスタ試料の電気特性に影響を与えないことが確認できた。これにより、高信頼性を確保できる。
【００８０】
なお、イオン強度比が５００以上のサンプルは、作製できなかった（試料５９，６０，６９，７０，７９，８０，８９，９０，９９，１００）。また、試料番号５２〜５８，６２〜６８，７２〜７８，８２〜８８，９２〜９８については、Ｎａ拡散処理の前後において、バリスタ特性（電圧非直線性）は変化しないことが、別の実験により確認された。
【００８１】
実施例３
Ｌｉ_２ ＣＯ_３ の代わりに、Ｋ_２ ＣＯ_３ を用いる以外は、実施例１と同様の条件で、素子を作製した。この結果を表３にまとめた。
【表３】

【００８２】
表３に示すように、Ｋ未処理の素子は、リフロー後における絶縁抵抗値の平均が１ＭΩ未満と低く、リフロー後の絶縁不良率も１００％以上と高かった（試料１０１，１１１，１２１，１３１，１４１）。
【００８３】
端子間ギャップが２０μｍの素子は、Ｋ処理していても、リフロー後における絶縁抵抗値の平均が１ＭΩ未満と低く、リフロー後の絶縁不良率も１００％と高かった（試料１０２〜１０８）。絶縁不良率の改善に至らなかったのは、上記実施例１と同様の理由と考えられる。
【００８４】
イオン強度比が０．０００１以下の素子は、Ｋ処理していても、リフロー後における絶縁抵抗値の平均が１ＭΩ未満と低く、リフロー後の絶縁不良率も１００％と高かった（試料１１２，１２２，１３２，１４２）。
【００８５】
端子間ギャップが５０μｍ以上で、かつイオン強度比が０．００１以上、１００以下の素子は、絶縁抵抗値の平均が４．１ＭΩ以上で、１ＭΩ未満を示す素子は一つもなく、しかも不良率は２％以下であった（試料１１３〜１１８，１２３〜１２８，１３３〜１３８，１４３〜１４８）。特に、０．０１以上１００以下の素子は、絶縁抵抗値の平均が８．５ＭΩ以上で、より好ましいことが確認できた。
本実施例では、Ｋ拡散による高抵抗化の影響がバリスタ試料の電気特性に影響を与えないことが確認できた。これにより、高信頼性を確保できる。
【００８６】
なお、イオン強度比が５００以上のサンプルは、作製できなかった（試料１０９，１１０，１１９，１２０，１２９，１３０，１３９，１４０，１４９，１５０）。また、試料番号１０２〜１０８，１１２〜１１８，１２２〜１２８，１３２〜１３８，１４２〜１４８については、Ｋ拡散処理の前後において、バリスタ特性（電圧非直線性）は変化しないことが、別の実験により確認された。
【００８７】
実施例４
Ｌｉ_２ ＣＯ_３ の代わりに、Ｒｂ_２ ＣＯ_３ を用いる以外は、実施例１と同様の条件で、素子を作製した。この結果を表４にまとめた。
【表４】

【００８８】
表４に示すように、Ｒｂ未処理の素子は、リフロー後における絶縁抵抗値の平均が１ＭΩ未満と低く、リフロー後の絶縁不良率も１００％以上と高かった（試料１５１，１６１，１７１，１８１，１９１）。
【００８９】
端子間ギャップが２０μｍの素子は、Ｒｂ処理していても、リフロー後における絶縁抵抗値の平均が１ＭΩ未満と低く、リフロー後の絶縁不良率も１００％と高かった（試料１５２〜１５８）。絶縁不良率の改善に至らなかったのは、上記実施例１と同様の理由と考えられる。
【００９０】
イオン強度比が０．０００１以下の素子は、Ｒｂ処理していても、リフロー後における絶縁抵抗値の平均が１ＭΩ未満と低く、リフロー後の絶縁不良率も１００％と高かった（試料１６２，１７２，１８２，１９２）。
【００９１】
端子間ギャップが５０μｍ以上で、かつイオン強度比が０．００１以上、１００以下の素子は、試料１６３を除き、絶縁抵抗値の平均が１．１ＭΩ以上で、１ＭΩ未満を示す素子はなく、しかも不良率は３８％以下であった（試料１６４〜１６８，１７３〜１７８，１８３〜１８８，１９３〜１９８）。特に、０．０１以上１００以下の素子は、絶縁抵抗値の平均が４．５ＭΩ以上で、より好ましいことが確認できた。
本実施例では、Ｒｂ拡散による高抵抗化の影響がバリスタ試料の電気特性に影響を与えないことが確認できた。これにより、高信頼性を確保できる。
【００９２】
なお、イオン強度比が５００以上のサンプルは、作製できなかった（試料１５９，１６０，１６９，１７０，１７９，１８０，１８９，１９０，１９９，２００）。また、試料番号１５２〜１５８，１６２〜１６８，１７２〜１７８，１８２〜１８８，１９２〜１９８については、Ｒｂ拡散処理の前後において、バリスタ特性（電圧非直線性）は変化しないことが、別の実験により確認された。
【００９３】
実施例５
Ｌｉ_２ ＣＯ_３ の代わりに、Ｃｓ_２ ＣＯ_３ を用いる以外は、実施例１と同様の条件で、素子を作製した。この結果を表５にまとめた。
【表５】

【００９４】
表５に示すように、Ｃｓ未処理の素子は、リフロー後における絶縁抵抗値の平均が１ＭΩ未満と低く、リフロー後の絶縁不良率も１００％以上と高かった（試料２０１，２１１，２２１，２３１，２４１）。
【００９５】
端子間ギャップが２０μｍの素子は、Ｃｓ処理していても、リフロー後における絶縁抵抗値の平均が１ＭΩ未満と低く、リフロー後の絶縁不良率も１００％と高かった（試料２０２〜２０８）。絶縁不良率の改善に至らなかったのは、上記実施例１と同様の理由と考えられる。
【００９６】
イオン強度比が０．０００１以下の素子は、Ｃｓ処理していても、リフロー後における絶縁抵抗値の平均が１ＭΩ未満と低く、リフロー後の絶縁不良率も１００％と高かった（試料２１２，２２２，２３２，２４２）。
【００９７】
端子間ギャップが５０μｍ以上で、かつイオン強度比が０．００１以上、１００以下の素子は、試料２１３，２２３を除き、絶縁抵抗値の平均が１．１ＭΩ以上で、１ＭΩ未満を示す素子はなく、しかも不良率は４８％以下であった（試料２１４〜２１８，２２４〜２２８，２３３〜２３８，２４３〜２４８）。特に、０．１以上１００以下の素子は、絶縁抵抗値の平均が７．２ＭΩ以上で、より好ましいことが確認できた。
本実施例では、Ｃｓ拡散による高抵抗化の影響がバリスタ試料の電気特性に影響を与えないことが確認できた。これにより、高信頼性を確保できる。
【００９８】
なお、イオン強度比が５００以上のサンプルは、作製できなかった（試料２０９，２１０，２１９，２２０，２２９，２３０，２３９，２４０，２４９，２５０）。また、試料番号２０２〜２０８，２１２〜２１８，２２２〜２２８，２３２〜２３８，２４２〜２４８については、Ｃｓ拡散処理の前後において、バリスタ特性（電圧非直線性）は変化しないことが、別の実験により確認された。
【００９９】
比較例１
Ｌｉ_２ ＣＯ_３ を付着させて熱処理する工程を除いた以外は、実施例１と同様の条件で、端子間ギャップが５００μｍの素子を作製した。
【０１００】
得られた素子は、リフロー前の絶縁抵抗が１００ＭΩ以上であったが、リフロー後は、０．１ＭΩになり、リフロー後の絶縁不良率は１００％であった。
【０１０１】
【発明の効果】
以上説明してきたように、本発明によれば、極小サイズ（たとえば、その寸法が縦０．６ｍｍ以下×横０．３ｍｍ以下×厚み０．３ｍｍ以下）のチップ状電子部品において、ガラスコートなどの絶縁保護層が不要であり、温度変化に強く、しかも半田リフローによっても素子表面の高抵抗を維持可能であり、高信頼性で、製造が容易な積層チップバリスタなどのチップ状電子部品およびその製造方法を提供することができる。
【図面の簡単な説明】
【図１】図１は本発明の一実施形態に係る積層チップバリスタの概略断面図である。
【図２】図２は本発明の一実施形態に係る積層チップバリスタの製造工程を示すフローチャート図である。
【図３】図３は本発明の他の実施形態に係る積層チップバリスタの製造工程を示すフローチャート図である。
【符号の説明】
１… 電圧非直線性抵抗体層
２… 内部電極層
３… 端子電極
４… 高抵抗層
５… 端子間ギャップ
１０… 積層チップバリスタ
１２… 素子本体[0001]
BACKGROUND OF THE INVENTION
The present invention eliminates the need for an insulating protective layer such as a glass coat in a chip-shaped electronic component whose dimensions are smaller than 0.6 mm in length, 0.3 mm in width, and 0.3 mm in thickness, is resistant to temperature changes, and is solder reflowed. The present invention also relates to a chip-shaped electronic component such as a multilayer chip varistor that can maintain a high resistance on the element surface, is highly reliable, and can be easily manufactured, and a manufacturing method thereof.
[0002]
[Prior art]
In recent years, chip-shaped electronic components have become indispensable as electronic devices become smaller and have higher performance. Chip-shaped electronic components are usually placed on a circuit board and heat-treated with printed solder to form a circuit. This heat treatment is called solder reflow treatment. At this time, the solder contains a flux having a strong reducing power, which may damage the surface of the chip component and lower the insulation resistance.
[0003]
A multilayer chip varistor as a chip-like electronic component is no exception, and the element surface of the multilayer chip varistor is reduced by solder reflow, resulting in a problem that the insulation resistance is lowered and the reliability is inferior.
[0004]
In order to solve this problem, it has been attempted to improve the reliability by coating glass on the element surface of the multilayer chip varistor (for example, see Patent Document 1).
[0005]
However, it takes much time and effort to uniformly coat and cover the element surface with glass. Further, since the thermal expansion coefficients of the ceramic material and the glass material are different, the interface is easily damaged by a temperature cycle or the like. Therefore, the glass layer may be cracked, and the ceramic insulation constituting the element may be destroyed.
[0006]
A method for increasing the resistance of the element surface by diffusing Li or Na on the element surface has been proposed (see Patent Document 2). In the invention described in this patent document, the ratio (M1 / M2) between the SIMS ionic strength M1 of Li or Na on the surface of the element and the SIMS ionic strength M2 of Li or Na at a depth of 10 μm from the surface, It is assumed that 10 ≦ (M1 / M2) <50000.
[0007]
However, this method has been found to be insufficient for reduction from the flux in solder reflow, although it can improve the appearance defect during electroplating. That is, the reducing power of the flux activated at the time of solder reflow is much larger than the reducing power of electroplating. Therefore, when the thickness in the range where Li or Na is diffused is about 10 μm, there is no resistance to solder reflow. It was enough.
[0008]
In recent years, there has been a demand for further downsizing of electronic devices. For example, the size of a chip-shaped electronic component of an extremely small size (length 0.6 mm or less × width 0.3 mm or less × thickness 0.3 mm or less) is required. Development is also progressing.
[Patent Document 1]
JP-A-6-96907
[Patent Document 2]
Japanese Patent Laid-Open No. 9-246017
[0009]
[Problems to be solved by the invention]
An object of the present invention is that an insulating protective layer such as a glass coat is not required in a chip-shaped electronic component having a very small size (for example, a dimension of 0.6 mm or less × width 0.3 mm or less × thickness 0.3 mm or less). It is to provide a chip-like electronic component such as a multilayer chip varistor that is resistant to temperature changes and that can maintain a high resistance on the surface of the element even by solder reflow, and that is easy to manufacture, and a method for manufacturing the same. .
[0010]
[Means for Solving the Problems]
  In order to achieve the above object, a chip-shaped electronic component according to the first aspect of the present invention provides:
  A device body having a zinc oxide-based material layer containing a rare earth element and an internal electrode layer, and having dimensions (length 0.6 mm or less × width 0.3 mm or less × thickness 0.3 mm or less);
  A chip-shaped electronic component having a pair of terminal electrodes formed on the outer surface of the element body and having a distance between terminals facing each other on the same plane (inter-terminal gap) of 50 μm or more,
  The range from the surface of the element body to the depth (0.9 × l), where l is the shortest distance from the outermost side of the internal electrode layer in the stacking direction to the surface of the element bodyAnd at least 10 μm or more from the surface of the element bodyWhen the ion intensity ratio (Li / Zn) between Li and Zn is measured by secondary ion mass spectrometry (SIMS), 0.001 ≦ (Li / Zn) ≦ 500.
[0011]
Preferably, the ionic strength ratio is 0.01 ≦ (Li / Zn) ≦ 500.
[0012]
  The chip-shaped electronic component according to the second aspect of the present invention is
  A device body having a zinc oxide-based material layer containing a rare earth element and an internal electrode layer, and having dimensions (length 0.6 mm or less × width 0.3 mm or less × thickness 0.3 mm or less);
  A chip-shaped electronic component having a pair of terminal electrodes formed on the outer surface of the element body and having a distance between opposite ends on the same plane of 50 μm or more,
  The range from the surface of the element body to the depth (0.9 × l), where l is the shortest distance from the outermost side of the internal electrode layer in the stacking direction to the surface of the element bodyAnd at least 10 μm or more from the surface of the element bodyWhen the ion intensity ratio (Na / Zn) between Na and Zn is measured by secondary ion mass spectrometry, 0.001 ≦ (Na / Zn) ≦ 100.
[0013]
  The chip-shaped electronic component according to the third aspect of the present invention is
  A device body having a zinc oxide-based material layer containing a rare earth element and an internal electrode layer, and having dimensions (length 0.6 mm or less × width 0.3 mm or less × thickness 0.3 mm or less);
  A chip-shaped electronic component having a pair of terminal electrodes formed on the outer surface of the element body and having a distance between opposite ends on the same plane of 50 μm or more,
  The range from the surface of the element body to the depth (0.9 × l), where l is the shortest distance from the outermost side of the internal electrode layer in the stacking direction to the surface of the element bodyAnd at least 10 μm or more from the surface of the element bodyWhen the ionic strength ratio (K / Zn) between K and Zn is measured by secondary ion mass spectrometry, 0.001 ≦ (K / Zn) ≦ 100.
[0014]
  The chip-shaped electronic component according to the fourth aspect of the present invention is
  A device body having a zinc oxide-based material layer containing a rare earth element and an internal electrode layer, and having dimensions (length 0.6 mm or less × width 0.3 mm or less × thickness 0.3 mm or less);
  A chip-shaped electronic component having a pair of terminal electrodes formed on the outer surface of the element body and having a distance between opposite ends on the same plane of 50 μm or more,
  The range from the surface of the element body to the depth (0.9 × l), where l is the shortest distance from the outermost side of the internal electrode layer in the stacking direction to the surface of the element bodyAnd at least 10 μm or more from the surface of the element bodyWhen the ionic strength ratio (Rb / Zn) of Rb and Zn is measured by secondary ion mass spectrometry, 0.001 ≦ (Rb / Zn) ≦ 100.
[0015]
  The chip-shaped electronic component according to the fifth aspect of the present invention is
  A device body having a zinc oxide-based material layer containing a rare earth element and an internal electrode layer, and having dimensions (length 0.6 mm or less × width 0.3 mm or less × thickness 0.3 mm or less);
  A chip-shaped electronic component having a pair of terminal electrodes formed on the outer surface of the element body and having a distance between opposite ends on the same plane of 50 μm or more,
  The range from the surface of the element body to the depth (0.9 × l), where l is the shortest distance from the outermost side of the internal electrode layer in the stacking direction to the surface of the element bodyAnd at least 10 μm or more from the surface of the element bodyWhen the ion intensity ratio (Cs / Zn) of Cs and Zn is measured by secondary ion mass spectrometry, 0.001 ≦ (Cs / Zn) ≦ 100.
[0016]
  The chip-shaped electronic component according to the sixth aspect of the present invention is
  A device body having a zinc oxide-based material layer containing a rare earth element and an internal electrode layer, and having dimensions (length 0.6 mm or less × width 0.3 mm or less × thickness 0.3 mm or less);
  A chip-shaped electronic component having a pair of terminal electrodes formed on the outer surface of the element body and having a distance between opposite ends on the same plane of 50 μm or more,
  The range from the surface of the element body to the depth (0.9 × l), where l is the shortest distance from the outermost side of the internal electrode layer in the stacking direction to the surface of the element bodyAnd at least 10 μm or more from the surface of the element bodyWhen the ionic strength ratio (A / Zn) of alkali metal (A) and zinc (Zn) is measured by secondary ion mass spectrometry, 0.001 ≦ (A / Zn) ≦ 500. And
[0017]
  A method for manufacturing a chip-shaped electronic component according to the first aspect of the present invention includes:
  A device body having a zinc oxide-based material layer containing a rare earth element and an internal electrode layer, and having dimensions (length 0.6 mm or less × width 0.3 mm or less × thickness 0.3 mm or less);
  A manufacturing method of a chip-shaped electronic component having a pair of terminal electrodes formed on the outer surface of the element body and having a distance between end portions facing each other on the same plane of 50 μm or more,
  Forming the element body;
  Diffusing alkali metal (A) from the surface of the element body toward the inside of the element body;
  Then, forming the pair of terminal electrodes connected to the internal electrode layer on the outer surface of the element body,
  When diffusing the alkali metal, when the shortest distance from the outermost side in the stacking direction of the internal electrode layer to the surface of the element body is l, from the surface of the element body to a depth (0.9 × l) RangeAnd at least 10 μm or more from the surface of the element bodyWhen the ionic strength ratio (A / Zn) of alkali metal (A) and zinc (Zn) is measured by secondary ion mass spectrometry, the condition is 0.001 ≦ (A / Zn) ≦ 500, It is characterized by diffusing an alkali metal.
[0018]
  A method for manufacturing a chip-shaped electronic component according to the second aspect of the present invention includes:
  A device body having a zinc oxide-based material layer containing a rare earth element and an internal electrode layer, and having dimensions (length 0.6 mm or less × width 0.3 mm or less × thickness 0.3 mm or less);
  A method for manufacturing a chip-shaped electronic component having a pair of terminal electrodes formed on the outer surface of the element body and facing each other on the same plane and having a distance of 50 μm or more, the step of forming the element body When,
  Forming a terminal electrode connected to the internal electrode layer on the outer surface of the element body;
  Thereafter, a step of diffusing alkali metal (A) from the surface of the element body toward the inside of the element body,
  When diffusing the alkali metal, when the shortest distance from the outermost side in the stacking direction of the internal electrode layer to the surface of the element body is l, from the surface of the element body to a depth (0.9 × l) RangeAnd at least 10 μm or more from the surface of the element bodyWhen the ionic strength ratio (A / Zn) of alkali metal (A) and zinc (Zn) is measured by secondary ion mass spectrometry, the condition is 0.001 ≦ (A / Zn) ≦ 500, It is characterized by diffusing an alkali metal.
[0019]
Preferably, the alkali metal is at least one of Li, Na, K, Rb, and Cs.
[0020]
Preferably, when the alkali metal is diffused, the element body is heat-treated at a temperature of 700 to 1000 ° C. with the powder of the alkali metal compound adhered to the surface of the element body, and the element At least one of the adhesion amount of the powder to the surface of the main body, the heat treatment temperature, and the heat treatment time is controlled.
[0021]
In the present invention, the chip-shaped electronic component is not particularly limited, but preferably, the element body has a structure in which zinc oxide-based voltage nonlinear resistor layers and internal electrode layers are alternately stacked, The chip-shaped electronic component is a multilayer chip varistor.
[0022]
[Effects of the Invention]
The present applicant has previously proposed a technique in which a large amount of alkali metals such as Li, Na, K, Rb, and Cs are contained in a single or plural alkali metal in a range of 100 μm in depth including the surface of the chip varistor body ( Japanese Patent Application No. 2002-313722). For example, in the case of Li, when the ionic strength ratio is measured for Li and Zn by secondary ion mass spectrometry (SIMS), the ionic strength measurement result is the ionic strength ratio of Li and Zn (Li / Zn), and is 0.1. By forming a multilayer chip varistor where 001 ≦ (Li / Zn) ≦ 500, a stable chip varistor can be obtained even with an activated flux during solder reflow.
[0023]
However, when this technology is applied to a very small chip as it is (dimension 0.6 mm or less x width 0.3 mm or less x thickness 0.3 mm or less), for example, the following inconvenience occurs. There was found. In general, a multilayer chip varistor exhibits varistor characteristics between two internal electrode layers adjacent in the stacking direction in the element body. In the case of the above-mentioned extremely small chip, the distance between the internal electrode layer arranged on the outermost side in the stacking direction among the internal electrode layers and the surface of the element body may be less than 100 μm. In this case, when the insulating layer is formed to a depth of 100 μm including the surface of the chip varistor element body as previously proposed, the inside of the chip inside the outermost layer in the stacking direction of the internal electrode layer (varistor characteristics are expressed). The alkali metal may diffuse to the inner electrode layer), and the electrical characteristics may fluctuate due to this influence.
[0024]
In a chip-shaped electronic component such as a multilayer chip varistor, the present invention provides the element body when the shortest distance from the outermost side in the stacking direction of the internal electrode layer in the element body to the surface of the element body is l. When the ionic strength ratio (A / Zn) of alkali metal (A) and zinc (Zn) is measured by secondary ion mass spectrometry in the range from the surface to the depth (0.9 × l), a predetermined value is obtained. By setting the ionic strength ratio within the range, even if the size is extremely small (for example, the dimension is 0.6 mm or less x 0.3 mm or less x 0.3 mm or less in thickness), the insulation resistance value is reduced by flux in solder reflow. It was found that the insulation failure rate after solder reflow can be greatly reduced.
[0025]
The state in the range from the surface of the element body where the alkali metal is diffused to the depth (0.9 × l) is not necessarily clear, but the oxidation contained in the zinc oxide-based material layer located outside the element body It is considered that the alkali metal is dissolved in the zinc particles.
[0026]
In the present invention, by setting the ionic strength ratio within a predetermined range, the range from the surface of the element body to the depth (0.9 × l) becomes a high resistance layer compared to other portions, and the solder It prevents current leakage from the element surface due to the flux reducing action by reflow. Therefore, it is possible to prevent the insulation resistance value from being lowered after the solder reflow, and to reduce the insulation failure rate. In addition, since a material having a different coefficient of thermal expansion such as a glass coat is not used, it is resistant to heat cycles. Even if it is not insulated by glass coating, etc. (in extremely small chip-like electronic parts, glass coating is not only difficult to apply, but even if it is applied temporarily, the chip becomes a ball-like shape due to glass. Insulation between terminals can be ensured with a chip having a very small size with a narrower gap between terminals (corresponding to reference numeral 5 in FIG. 1). For this reason, the high reliability of an electronic component can be maintained.
[0027]
Further, in the present invention, an alkali metal supply source is attached to the surface of the element body, and a high resistance layer is formed by diffusing the alkali metal from the surface of the element body toward the inside by heat treatment. Since it is not necessary to coat the glass layer, complicated equipment and processes are unnecessary, and a highly reliable chip-shaped electronic component can be manufactured easily and inexpensively.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described based on embodiments shown in the drawings. put it here,
FIG. 1 is a schematic cross-sectional view of a multilayer chip varistor according to an embodiment of the present invention.
FIG. 2 is a flowchart showing a manufacturing process of a multilayer chip varistor according to an embodiment of the present invention.
FIG. 3 is a flowchart showing a manufacturing process of a multilayer chip varistor according to another embodiment of the present invention.
[0029]
Multilayer chip varistor
As shown in FIG. 1, a multilayer chip varistor 10 as an example of a chip-shaped electronic component has an element body 12 having a structure in which a voltage nonlinear resistor layer 1 and internal electrode layers 2 are alternately stacked. A pair of external terminal electrodes 3 is formed on the outer surface of the element body 12. The pair of external terminal electrodes 3 has a distance between end portions facing each other on the same plane (inter-terminal gap, corresponding to reference numeral 5 in FIG. 1) of 50 μm or more. The internal electrode layers 2 are alternately exposed from opposite end surfaces of the element body 12 and are connected to the external terminal electrodes 3 to form a varistor circuit.
[0030]
The outermost layer 1a is laminated on the outer side of the internal electrode layer 2 in the laminating direction, and the internal electrode layer 2 is protected. The outermost layer 1 a is usually made of the same material as the resistor layer 1. The material of the resistor layer 1 will be described later. The high resistance layer 4 formed around the element body 12 will also be described later.
[0031]
The shape of the element body 12 is not particularly limited, and is usually a rectangular parallelepiped shape. In the present invention, the dimension of the element body 12 is vertical (0.6 mm or less, preferably 0.4 mm or less) × horizontal (0.3 mm or less, preferably 0.2 mm or less) × thickness (0.3 mm or less, preferably The target is a minimum size of 0.2 mm or less.
Because of this extremely small size, in the present invention, the thickness of the outermost layer 1a is usually less than 100 μm, preferably 90 μm or less. Depending on the interlayer thickness of the resistor layer 1 sandwiched between the pair of internal electrode layers 2, the thickness of the outermost layer 1a may exceed 100 μm.
[0032]
Voltage nonlinear resistor layer 1
The voltage nonlinear resistor layer 1 (the same applies to the outermost layer 1a) is composed of a zinc oxide varistor material layer. This zinc oxide-based varistor material layer has, for example, ZnO as a main component and rare earth elements, Co, IIIb group elements (B, Al, Ga and In), Si, Cr, alkali metal elements (K, Rb and Cs) as subcomponents. ) And alkaline earth metal elements (Mg, Ca, Sr and Ba) and the like. Alternatively, it may be made of a material containing ZnO as a main component and Bi, Co, Mn, Sb, Al, etc. as subcomponents.
[0033]
The main component containing ZnO acts as a substance that exhibits excellent voltage nonlinearity in voltage-current characteristics and a large surge resistance. The voltage non-linearity is a phenomenon in which the current flowing through the element increases non-linearly when a gradually increasing voltage is applied between the terminal electrodes 3.
[0034]
The content of ZnO as the main component in the resistor layer 1 is not particularly limited. Usually, when the total material constituting the resistor layer 1 is 100% by mass, it is usually 99.8 to 69.0. % By mass.
[0035]
Internal electrode layer 2
The conductive material contained in the internal electrode layer 2 is not particularly limited, but is preferably made of Pd or an Ag—Pd alloy. The thickness of the internal electrode layer 2 may be appropriately determined according to the application, but is usually about 0.5 to 5 μm.
[0036]
External terminal electrode 3
The conductive material contained in the external terminal electrode 3 is not particularly limited, but usually Ag, Ag—Pd alloy, or the like is used. Further, if necessary, Ni and Sn / Pb films are formed on the surface of the underlayer such as Ag or Ag—Pd alloy by electroplating or the like. The thickness of the external terminal electrode 3 may be appropriately determined according to the application, but is usually about 10 to 50 μm.
[0037]
High resistance layer 4
The high resistance layer 4 is formed so as to cover the entire outer surface of the element body 12. The high resistance layer 4 diffuses alkali metal from the surface of the element body 12 toward the inside by performing heat treatment in a state where an alkali metal compound that is thermally decomposed to be an oxide is attached to the surface of the element body 12. Is formed.
[0038]
Note that the boundary between the high resistance layer 4 and the outermost layer 1a of the element body 12 is not necessarily clear, and the high resistance layer 4 is a range in which an alkali metal diffuses in the outermost layer 1a. The high resistance layer 4 serves to protect the voltage non-linear resistance layer 1 during solder reflow.
[0039]
The thickness of the high resistance layer 4 is not particularly limited, but is at least 10 μm or more and does not reach the internal electrode layer 2. If the thickness is too thin, the effect of the present invention is small, and if it is too thick, the electrical characteristics of the voltage nonlinear resistor layer 1 may be adversely affected.
[0040]
In the high resistance layer 4, when the shortest distance from the outermost side in the stacking direction of the internal electrode layer 2 to the surface of the element body 12 is 1, the depth (0.9 × l) from the surface of the element body 12 When the ion intensity ratio (A / Zn) between the alkali metal (A) and zinc (Zn) is measured by secondary ion mass spectrometry, the range up to is 0.001 ≦ (A / Zn) ≦ 500. .
[0041]
The ion intensity ratio can be obtained by secondary ion mass spectrometry (SIMS). SIMS is a method that can measure the ion concentration distribution in the depth direction with high sensitivity on the order of microns from the surface layer. When a solid surface is irradiated with a high energy (several keV to 20 keV) ion beam, the atoms constituting the sample are emitted as neutrons or ions by a sputtering phenomenon. In this way, SIMS is a method of performing elemental analysis and compound analysis of the sample surface by dividing the secondaryly released ions into a mass / charge ratio using a mass spectrometer.
[0042]
The alkali metal diffused in the high resistance layer 4 is not particularly limited, but is preferably at least one of Li, Na, K, Rb, and Cs, and more preferably Li.
[0043]
When the alkali metal is Li, the ionic strength ratio (Li / Zn) between Li and Zn is preferably 0.001 ≦ (Li / Zn) ≦ 500, more preferably 0.01 ≦ (Li / Zn). ) ≦ 500.
[0044]
When the alkali metal is Na, the ionic strength ratio (Na / Zn) between Na and Zn is preferably 0.001 ≦ (Na / Zn) ≦ 100, more preferably 0.01 ≦ (Na / Zn). ) ≦ 100.
[0045]
When the alkali metal is K, the ionic strength ratio (K / Zn) between K and Zn is preferably 0.001 ≦ (K / Zn) ≦ 100, more preferably 0.01 ≦ (K / Zn). ) ≦ 100.
[0046]
When the alkali metal is Rb, the ionic strength ratio (Rb / Zn) between Rb and Zn is preferably 0.001 ≦ (Rb / Zn) ≦ 100, more preferably 0.01 ≦ (Rb / Zn). ) ≦ 100.
[0047]
When the alkali metal is Cs, the ionic strength ratio (Cs / Zn) between Cs and Zn is preferably 0.001 ≦ (Cs / Zn) ≦ 100, more preferably 0.1 ≦ (Cs / Zn). ) ≦ 100.
[0048]
If the ionic strength ratio is too small, the insulation resistance value after solder reflow tends to be too low, and if the ionic strength ratio is too large, the electrical characteristics of the voltage nonlinear resistor layer 1 may be adversely affected. In addition, the increase in insulation resistance value after solder reflow tends to decrease.
[0049]
Manufacturing method of multilayer chip varistor 10
Next, a manufacturing process of the multilayer chip varistor 10 according to the present invention will be described with reference to FIG.
[0050]
First, the voltage nonlinear resistor layers 1 (varistor layers) and the internal electrode layers 2 are alternately laminated so that the internal electrode layers 2 are alternately exposed at both ends by a printing method or a sheet method. And the outermost layer 1a is laminated | stacked on the both ends of the lamination direction, and a laminated body is formed (process a of FIG. 2).
[0051]
Next, this laminate is cut to obtain a green chip (step b).
[0052]
Next, a binder removal process is performed as necessary, and the green chip is baked to obtain a chip body to be the chip body 12 (step c).
[0053]
The obtained chip body is adhered to the surface of the chip body by a sealed rotating pot (step d). Although it does not specifically limit as an alkali metal compound, It is a compound which an alkali metal can diffuse inside from the surface of the element main body 12 by heat processing, and an alkali metal oxide, hydroxide, chloride, nitrate, borate Carbonate and oxalate are used. The ionic strength ratio can be controlled by controlling the adhesion amount of the alkali metal compound.
[0054]
Next, the chip body to which the alkali metal compound is attached is heat-treated in an electric furnace at a predetermined temperature and time (step e). As a result, the alkali metal is diffused from the surface of the chip body toward the inside from the alkali metal compound, and the element body 12 in which the high resistance layer 4 is formed is obtained. The ionic strength ratio can be controlled by the heat treatment temperature and heat treatment time at this time, and the thickness of the high resistance layer 4 can be controlled. A preferable heat treatment temperature is 700 to 1000 ° C., and the heat treatment atmosphere is in the air. The heat treatment time is preferably 10 minutes to 4 hours.
[0055]
Next, a terminal electrode is applied and baked on both ends of the element body after the heat treatment to form an Ag base electrode (step f). Here, Ag is selected as the base electrode material. However, the element body 12 has good seizure, good connectivity with the material constituting the internal electrode layer 2, and is easily plated in the subsequent plating process. Any material can be used as long as it is a material.
[0056]
Finally, a Ni plating film and / or a Sn / Pb plating film is formed on the surface of the base electrode by electroplating (step g), and the multilayer chip varistor 10 is obtained.
[0057]
The means for diffusing the alkali metal from the surface of the element body 12 is not limited to the above means, and for example, the following means can be employed. That is, a method of heat-treating the element body 12 before forming the terminal electrode 3 in an alkali supply source, a method of heat-treating the alkali supply source that has been liquefied by spraying or the like uniformly over the outer periphery of the element body 12, Examples include a method in which air mixed with alkali metal source powder is uniformly sprinkled on the outer periphery of the element body 12 and then heat-treated.
[0058]
In these methods, alkali metal diffuses somewhat to the exposed end surfaces of the internal electrode layer 2 exposed at both ends of the element body 12, but this affects the conductivity of the internal electrode layer 2. There is no.
[0059]
In order to reliably prevent alkali metal from diffusing with respect to the exposed end face of the internal electrode layer 2, for example, as shown in FIG. 3, the formation of the high resistance layer (steps d and e) and the formation of terminal electrodes (step f) You may go after. In that case, the high resistance layer 4 shown in FIG. 1 is not formed inside the terminal electrode 3. Therefore, the alkali metal does not diffuse from the exposed end surface of the internal electrode layer 2. Further, when the terminal electrode is applied and dried, an alkali metal is attached to the surface and baking is performed, and at the same time, diffusion of the alkali metal into the element body can be performed and the process can be simplified.
[0060]
The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.
[0061]
【Example】
Hereinafter, the present invention will be described based on further detailed examples, but the present invention is not limited to these examples.
[0062]
Example 1
In accordance with steps a to c and the normal method shown in FIG. 2, a chip body to be the element body 12 having a 0603 shape (outer dimensions: 0.6 mm × 0.3 mm × 0.3 mm) was formed. The non-linear resistor layer 1 and the outermost layer 1a of the chip body are made of a zinc oxide-based material, specifically, ZnO (99.725 mol%) with a purity of 99.9%, Pr 0.5 mol%, Co 1.5 mol%, Al 0.005 mol%, K 0.05 mol%, Cr 0.1 mol%, Ca 0.1 mol%, Si It comprised with what was added in the ratio of 0.02 mol%. The internal electrode layer 2 was made of Pd.
[0063]
The obtained chip body was placed on the surface of the chip body by a sealed rotating pot.₂CO₃Of powder was deposited. Li₂CO₃The average particle size of the powder was 3 μm.
[0064]
Li₂CO₃The input amount was set to a range of 0.01 μg to 10 mg per chip element body. By increasing or decreasing this input amount, samples having different ion intensity ratios described later can be obtained.
[0065]
Li₂CO₃The chip body to which the powder was adhered was heat-treated in air at a heat treatment temperature of 700 to 1000 ° C. for 10 minutes to 4 hours to diffuse Li from the surface of the chip body, and the high resistance layer 4 was in the vicinity of the surface. Formed. By changing the heat treatment temperature and the heat treatment time, samples having different ion intensity ratios described later can be obtained.
[0066]
Thereafter, an Ag base electrode is formed by a normal method, and a Ni plating film and a Sn / Pb plating film are formed on the surface of the base electrode by electroplating to form the terminal electrode 3, thereby obtaining the multilayer chip varistor 10. It was. The inter-terminal gap 5 was produced in five different modes (20 μm, 50 μm, 100 μm, 300 μm, 500 μm).
[0067]
For a plurality of multilayer chip varistor samples obtained in this way, the range from the surface of the element body to the depth (0.9 × l) was measured by secondary ion mass spectrometry using the ion intensity ratio (Li / Zn) was measured. Further, the insulation resistance values before and after solder reflow were measured to determine the insulation failure rate, and are summarized in Table 1.
[0068]
The solder reflow was performed by printing a cream solder containing flux on the substrate, mounting the element, and passing through a reflow furnace having a peak temperature of 230 ° C.
[0069]
The ion intensity ratio of Li / Zn is determined by the secondary ion mass spectrometry (SIMS), where the shortest distance from the outermost side in the stacking direction of the internal electrode layer 2 to the surface of the element body 12 is l. The value from the surface to the depth (0.9 × l) was averaged. Further, the insulation resistance value was measured at an applied voltage of 3 V and obtained from an average value of 100 pieces, and the insulation failure rate was calculated as an element having less than 1 MΩ as a failure. Note that the insulation resistance of each element before solder reflow was 100 MΩ or more.
[Table 1]

[0070]
As shown in Table 1, the Li-untreated element had a low average insulation resistance value after reflow of less than 1 MΩ, and a high insulation failure rate after reflow of 100% or more (Samples 1, 11, 21, 31). 41).
[0071]
An element having a terminal-to-terminal gap of 20 μm had an average insulation resistance value after reflow as low as less than 1 MΩ even after Li treatment, and an insulation failure rate after reflow was as high as 98% or more (Samples 2 to 9). The reason why the insulation failure rate was not improved is that there are only a few ZnO crystal grain boundaries that contribute to the increase in resistance between the gaps, and therefore the probability that a path in which the resistance decreases is increased. Conceivable.
[0072]
Even when the element having an ionic strength ratio of 0.0001 or less was subjected to Li treatment, the average insulation resistance value after reflow was as low as less than 1 MΩ, and the insulation failure rate after reflow was as high as 65% or more (Sample 12, 22, 32, 42).
[0073]
An element having a terminal gap of 50 μm or more and an ionic strength ratio of 0.001 or more and 500 or less has an average insulation resistance value of 3.8 MΩ or more and no element showing less than 1 MΩ, and the defect rate is All were 0 (samples 13-19, 23-29, 33-39, 43-49). In particular, it was confirmed that an element having an average insulation resistance value of 10 MΩ or more was more preferable for an element of 0.01 to 500.
In this example, it was confirmed that the effect of increasing the resistance due to Li diffusion does not affect the electrical characteristics of the varistor sample. Thereby, high reliability can be secured.
[0074]
Samples having an ionic strength ratio of 1000 or more could not be produced (Samples 10, 20, 30, 40, 50). In addition, it is another experiment that varistor characteristics (voltage nonlinearity) do not change before and after the Li diffusion treatment for sample numbers 2 to 9, 12 to 19, 22 to 29, 32 to 39, and 42 to 49. Confirmed by
[0075]
Example 2
Li₂CO₃Instead of Na₂CO₃A device was fabricated under the same conditions as in Example 1 except that was used. The results are summarized in Table 2.
[Table 2]

[0076]
As shown in Table 2, the Na-untreated element had an average insulation resistance value after reflow as low as less than 1 MΩ, and the insulation defect rate after reflow was as high as 100% or more (Samples 51, 61, 71, 81). 91).
[0077]
Even when the element having a terminal gap of 20 μm was treated with Na, the average insulation resistance value after reflowing was as low as less than 1 MΩ, and the insulation failure rate after reflowing was as high as 100% (Samples 52 to 58). The reason why the insulation failure rate was not improved is considered to be the same reason as in Example 1.
[0078]
Even when the element having an ionic strength ratio of 0.0001 or less was treated with Na, the average insulation resistance value after reflow was as low as less than 1 MΩ, and the insulation failure rate after reflow was as high as 100% (Samples 62 and 72). 82, 92).
[0079]
An element having a terminal gap of 50 μm or more and an ionic strength ratio of 0.001 or more and 100 or less has an average insulation resistance value of 3.3 MΩ or more and no element exhibiting less than 1 MΩ, and the defect rate is 4% or less (Samples 63 to 68, 73 to 78, 83 to 88, 93 to 98). In particular, it was confirmed that an element having an insulation resistance value of 0.01 to 100 was more preferable with an average insulation resistance value of 10 MΩ or more.
In this example, it was confirmed that the effect of increasing the resistance due to Na diffusion does not affect the electrical characteristics of the varistor sample. Thereby, high reliability can be secured.
[0080]
A sample having an ionic strength ratio of 500 or more could not be prepared (Samples 59, 60, 69, 70, 79, 80, 89, 90, 99, 100). In addition, it is another experiment that sample numbers 52 to 58, 62 to 68, 72 to 78, 82 to 88, and 92 to 98 do not change the varistor characteristics (voltage nonlinearity) before and after the Na diffusion treatment. Confirmed by
[0081]
Example 3
Li₂CO₃Instead of K₂CO₃A device was fabricated under the same conditions as in Example 1 except that was used. The results are summarized in Table 3.
[Table 3]

[0082]
As shown in Table 3, the K-untreated element had an average insulation resistance value after reflow as low as less than 1 MΩ, and the insulation failure rate after reflow was as high as 100% or more (Samples 101, 111, 121, and 131). 141).
[0083]
An element having a terminal-to-terminal gap of 20 μm had an average insulation resistance value after reflowing as low as less than 1 MΩ even after K treatment, and an insulation failure rate after reflowing was as high as 100% (Samples 102 to 108). The reason why the insulation failure rate was not improved is considered to be the same reason as in Example 1.
[0084]
An element having an ionic strength ratio of 0.0001 or less had an average insulation resistance value after reflowing of less than 1 MΩ even after K treatment, and an insulation failure rate after reflowing was as high as 100% (Samples 112 and 122). 132, 142).
[0085]
An element having a terminal gap of 50 μm or more and an ionic strength ratio of 0.001 or more and 100 or less has an average insulation resistance value of 4.1 MΩ or more and no element showing less than 1 MΩ, and the defect rate is 2% or less (Samples 113 to 118, 123 to 128, 133 to 138, 143 to 148). In particular, it was confirmed that an element having an insulation resistance value of 0.01 to 100 was more preferable because the average insulation resistance value was 8.5 MΩ or more.
In this example, it was confirmed that the effect of increasing resistance by K diffusion does not affect the electrical characteristics of the varistor sample. Thereby, high reliability can be secured.
[0086]
Samples having an ionic strength ratio of 500 or more could not be produced (samples 109, 110, 119, 120, 129, 130, 139, 140, 149, 150). In addition, it is another experiment that varistor characteristics (voltage nonlinearity) do not change before and after the K diffusion process for sample numbers 102 to 108, 112 to 118, 122 to 128, 132 to 138, and 142 to 148. Confirmed by
[0087]
Example 4
Li₂CO₃Instead of Rb₂CO₃A device was fabricated under the same conditions as in Example 1 except that was used. The results are summarized in Table 4.
[Table 4]

[0088]
As shown in Table 4, in the Rb-untreated element, the average insulation resistance value after reflow was as low as less than 1 MΩ, and the insulation failure rate after reflow was as high as 100% or more (Samples 151, 161, 171, 181). , 191).
[0089]
An element having a terminal-to-terminal gap of 20 μm had an average insulation resistance value after reflow as low as less than 1 MΩ even after Rb treatment, and an insulation failure rate after reflow was as high as 100% (samples 152 to 158). The reason why the insulation failure rate was not improved is considered to be the same reason as in Example 1.
[0090]
An element having an ionic strength ratio of 0.0001 or less had an average insulation resistance value after reflow as low as less than 1 MΩ even after Rb treatment, and an insulation failure rate after reflow was as high as 100% (Samples 162 and 172). , 182, 192).
[0091]
For elements having a terminal gap of 50 μm or more and an ionic strength ratio of 0.001 or more and 100 or less, except for the sample 163, there is no element having an average insulation resistance value of 1.1 MΩ or more and less than 1 MΩ. The defective rate was 38% or less (samples 164 to 168, 173 to 178, 183 to 188, 193 to 198). In particular, it was confirmed that an element having an insulation resistance value of 4.5 MΩ or more was more preferable for an element of 0.01 to 100.
In this example, it was confirmed that the effect of increasing the resistance due to Rb diffusion does not affect the electrical characteristics of the varistor sample. Thereby, high reliability can be secured.
[0092]
A sample having an ionic strength ratio of 500 or more could not be produced (Samples 159, 160, 169, 170, 179, 180, 189, 190, 199, 200). In addition, it is another experiment that varistor characteristics (voltage non-linearity) do not change before and after the Rb diffusion process for sample numbers 152 to 158, 162 to 168, 172 to 178, 182 to 188, and 192 to 198. Confirmed by
[0093]
Example 5
Li₂CO₃Instead of Cs₂CO₃A device was fabricated under the same conditions as in Example 1 except that was used. The results are summarized in Table 5.
[Table 5]

[0094]
As shown in Table 5, the Cs-untreated element had an average insulation resistance value after reflowing as low as less than 1 MΩ, and a high insulation failure rate after reflowing of 100% or more (Samples 201, 2111, 221, 231). , 241).
[0095]
An element having a terminal-to-terminal gap of 20 μm had an average insulation resistance value after reflow as low as less than 1 MΩ even after Cs treatment, and an insulation failure rate after reflow was as high as 100% (samples 202 to 208). The reason why the insulation failure rate was not improved is considered to be the same reason as in Example 1.
[0096]
Even when the element having an ionic strength ratio of 0.0001 or less was subjected to Cs treatment, the average insulation resistance value after reflow was as low as less than 1 MΩ, and the insulation failure rate after reflow was as high as 100% (Samples 212 and 222). , 232, 242).
[0097]
There are no elements having an average insulation resistance value of 1.1 MΩ or more and less than 1 MΩ, except for Samples 213 and 223, for elements having a terminal gap of 50 μm or more and an ionic strength ratio of 0.001 or more and 100 or less. Moreover, the defect rate was 48% or less (samples 214 to 218, 224 to 228, 233 to 238, 243 to 248). In particular, it was confirmed that an element having an average insulation resistance value of 0.1 to 100 MΩ was more preferably 0.1 to 100 MΩ.
In this example, it was confirmed that the effect of increasing the resistance due to Cs diffusion does not affect the electrical characteristics of the varistor sample. Thereby, high reliability can be secured.
[0098]
A sample having an ionic strength ratio of 500 or more could not be produced (Samples 209, 210, 219, 220, 229, 230, 239, 240, 249, 250). In addition, it is another experiment that varistor characteristics (voltage non-linearity) do not change before and after the Cs diffusion process for sample numbers 202 to 208, 212 to 218, 222 to 228, 232 to 238, and 242 to 248. Confirmed by
[0099]
Comparative Example 1
Li₂CO₃A device having a gap between terminals of 500 μm was manufactured under the same conditions as in Example 1 except that the step of attaching and heat-treating was removed.
[0100]
The obtained element had an insulation resistance of 100 MΩ or more before reflow, but after reflow, it became 0.1 MΩ, and the insulation failure rate after reflow was 100%.
[0101]
【The invention's effect】
As described above, according to the present invention, in a chip-shaped electronic component having a very small size (for example, the dimension is 0.6 mm or less × width 0.3 mm or less × thickness 0.3 mm or less), Chip-like electronic components such as multilayer chip varistors that are highly reliable and easy to manufacture, and their manufacture that do not require an insulating protective layer, are resistant to temperature changes, and can maintain high resistance on the element surface even by solder reflow A method can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a multilayer chip varistor according to an embodiment of the present invention.
FIG. 2 is a flowchart showing a manufacturing process of a multilayer chip varistor according to an embodiment of the present invention.
FIG. 3 is a flowchart showing a manufacturing process of a multilayer chip varistor according to another embodiment of the present invention.
[Explanation of symbols]
1 ... Voltage nonlinear resistor layer
2 ... Internal electrode layer
3 ... Terminal electrode
4 ... High resistance layer
5 ... Gap between terminals
10 ... Multilayer Chip Varistor
12 ... Element body

Claims (12)

A device body having a zinc oxide-based material layer containing a rare earth element and an internal electrode layer, and having dimensions (length 0.6 mm or less × width 0.3 mm or less × thickness 0.3 mm or less);
A chip-shaped electronic component having a pair of terminal electrodes formed on the outer surface of the element body and having a distance between terminals facing each other on the same plane (inter-terminal gap) of 50 μm or more,
When the shortest distance from the outermost layer in the stacking direction of the internal electrode layer to the surface of the element body is l , at least the surface of the element body in a range from the surface of the element body to the depth (0.9 × l). When the ionic strength ratio (Li / Zn) between Li and Zn is measured by secondary ion mass spectrometry (SIMS) in a range of 10 μm or more from 0.001 ≦ (Li / Zn) ≦ 500 A chip-like electronic component. 2. The chip-shaped electronic component according to claim 1, wherein the ionic strength ratio is 0.01 ≦ (Li / Zn) ≦ 500. A device body having a zinc oxide-based material layer containing a rare earth element and an internal electrode layer, and having dimensions (length 0.6 mm or less × width 0.3 mm or less × thickness 0.3 mm or less);
A chip-shaped electronic component having a pair of terminal electrodes formed on the outer surface of the element body and having a distance between opposite ends on the same plane of 50 μm or more,
When the shortest distance from the outermost layer in the stacking direction of the internal electrode layer to the surface of the element body is l , at least the surface of the element body in a range from the surface of the element body to the depth (0.9 × l). When the ionic strength ratio (Na / Zn) of Na and Zn is measured by secondary ion mass spectrometry in a range of 10 μm or more from 0.001 ≦ (Na / Zn) ≦ 100 Chip electronic components. A device body having a zinc oxide-based material layer containing a rare earth element and an internal electrode layer, and having dimensions (length 0.6 mm or less × width 0.3 mm or less × thickness 0.3 mm or less);
A chip-shaped electronic component having a pair of terminal electrodes formed on the outer surface of the element body and having a distance between opposite ends on the same plane of 50 μm or more,
When the shortest distance from the outermost layer in the stacking direction of the internal electrode layer to the surface of the element body is l , at least the surface of the element body in a range from the surface of the element body to the depth (0.9 × l). When the ion intensity ratio (K / Zn) between K and Zn is measured by secondary ion mass spectrometry in a range of 10 μm or more from 0.001 ≦ (K / Zn) ≦ 100 Chip electronic components. A device body having a zinc oxide-based material layer containing a rare earth element and an internal electrode layer, and having dimensions (length 0.6 mm or less × width 0.3 mm or less × thickness 0.3 mm or less);
A chip-shaped electronic component having a pair of terminal electrodes formed on the outer surface of the element body and having a distance between opposite ends on the same plane of 50 μm or more,
When the shortest distance from the outermost layer in the stacking direction of the internal electrode layer to the surface of the element body is l , at least the surface of the element body in a range from the surface of the element body to the depth (0.9 × l). When the ion intensity ratio (Rb / Zn) of Rb and Zn is measured by secondary ion mass spectrometry in a range of 10 μm or more from 0.001 ≦ (Rb / Zn) ≦ 100 Chip electronic components. A device body having a zinc oxide-based material layer containing a rare earth element and an internal electrode layer, and having dimensions (length 0.6 mm or less × width 0.3 mm or less × thickness 0.3 mm or less);
A chip-shaped electronic component having a pair of terminal electrodes formed on the outer surface of the element body and having a distance between opposite ends on the same plane of 50 μm or more,
When the shortest distance from the outermost layer in the stacking direction of the internal electrode layer to the surface of the element body is l , at least the surface of the element body in a range from the surface of the element body to the depth (0.9 × l). When the ionic strength ratio (Cs / Zn) of Cs and Zn is measured by secondary ion mass spectrometry in a range of 10 μm or more from 0.001 ≦ (Cs / Zn) ≦ 100 Chip electronic components. A device body having a zinc oxide-based material layer containing a rare earth element and an internal electrode layer, and having dimensions (length 0.6 mm or less × width 0.3 mm or less × thickness 0.3 mm or less);
A chip-shaped electronic component having a pair of terminal electrodes formed on the outer surface of the element body and having a distance between opposite ends on the same plane of 50 μm or more,
When the shortest distance from the outermost layer in the stacking direction of the internal electrode layer to the surface of the element body is l , at least the surface of the element body in a range from the surface of the element body to the depth (0.9 × l). When the ionic strength ratio (A / Zn) of alkali metal (A) and zinc (Zn) is measured by secondary ion mass spectrometry in the range of 10 μm or more from 0.001 ≦ (A / Zn) ≦ 500 A chip-like electronic component, characterized in that The element body has a structure in which zinc oxide-based voltage non-linear resistance layers and internal electrode layers are alternately stacked, and the chip-shaped electronic component is a multilayer chip varistor. The chip-shaped electronic component according to any one of the above. A device body having a zinc oxide-based material layer containing a rare earth element and an internal electrode layer, and having dimensions (length 0.6 mm or less × width 0.3 mm or less × thickness 0.3 mm or less);
A manufacturing method of a chip-shaped electronic component having a pair of terminal electrodes formed on the outer surface of the element body and having a distance between end portions facing each other on the same plane of 50 μm or more,
Forming the element body;
Diffusing alkali metal (A) from the surface of the element body toward the inside of the element body;
Then, forming the pair of terminal electrodes connected to the internal electrode layer on the outer surface of the element body,
When diffusing the alkali metal, when the shortest distance from the outermost side in the stacking direction of the internal electrode layer to the surface of the element body is l, from the surface of the element body to a depth (0.9 × l) When the ionic strength ratio (A / Zn) of alkali metal (A) and zinc (Zn) is measured by secondary ion mass spectrometry at least in the range of 10 μm or more from the surface of the element body in the range of 0. A manufacturing method of a chip-like electronic component, characterized by diffusing an alkali metal under a condition of 001 ≦ (A / Zn) ≦ 500. A device body having a zinc oxide-based material layer containing a rare earth element and an internal electrode layer, and having dimensions (length 0.6 mm or less × width 0.3 mm or less × thickness 0.3 mm or less);
A manufacturing method of a chip-shaped electronic component having a pair of terminal electrodes formed on the outer surface of the element body and having a distance between end portions facing each other on the same plane of 50 μm or more,
Forming the element body;
Forming a terminal electrode connected to the internal electrode layer on the outer surface of the element body;
Thereafter, a step of diffusing alkali metal (A) from the surface of the element body toward the inside of the element body,
When diffusing the alkali metal, when the shortest distance from the outermost side in the stacking direction of the internal electrode layer to the surface of the element body is l, from the surface of the element body to a depth (0.9 × l) When the ionic strength ratio (A / Zn) of alkali metal (A) and zinc (Zn) is measured by secondary ion mass spectrometry at least in the range of 10 μm or more from the surface of the element body in the range of 0. A manufacturing method of a chip-like electronic component, characterized by diffusing an alkali metal under a condition of 001 ≦ (A / Zn) ≦ 500. 11. The method for manufacturing a chip-shaped electronic component according to claim 9, wherein the alkali metal is at least one of Li, Na, K, Rb, and Cs. When the alkali metal is diffused, the element body is heat-treated at a temperature of 700 to 1000 ° C. with the alkali metal compound powder adhered to the surface of the element body. 12. The method for manufacturing a chip-shaped electronic component according to claim 9, wherein at least one of an adhesion amount of the powder to the heat treatment, a heat treatment temperature, and a heat treatment time is controlled.

Images