JP2004342658A - Method for manufacturing positive temperature coefficient thermistor element - Google Patents
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Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は電流制御用スイッチング素子や定温発熱体素子として利用される正特性サーミスタ素子の製造方法に関するものである。
【０００２】
【従来の技術】
Ｎ型半導体である正特性サーミスタ磁器に電極を形成する際、磁器本来の抵抗値が現れるようにし、電圧依存性をなくするため、オーミック接触が得られる金属が用いられるが、オーミック接触が得られる金属としては、一般的にＮｉまたはＮｉ合金が用いられている。また、その他のオーミック接触が得られる電極としては、Ａｌが用いられている。
【０００３】
これらの金属のオーミック接触が良好な理由は、正特性サーミスタ磁器よりも仕事関数が小さいためであり、正特性サーミスタ磁器よりも仕事関数の大きい金属は良好なオーミック接触を得ることができない。
【０００４】
正特性サーミスタ磁器と良好なオーミック接触をすることのできない、Ａｇ、Ｐｔ、Ｐｄ、Ｃｕを正特性サーミスタの電極として使用する場合、磁器と電極の間にパルス電圧を（＋），（−）方向に印加する方法を用いれば、正特性サーミスタとして良好なオーミック接触が得られるとされている（例えば特許文献１参照）。
【０００５】
【特許文献１】
特開平６−１３２０３号公報（第２−３頁）
【０００６】
【発明が解決しようとする課題】
ところが、Ａｇを電極として用いた場合、長時間の通電によりＡｇによるマイグレーションが発生し、短絡や抵抗値の変動などの問題が発生するため、車載用ヒータや消磁用回路など、長時間通電される用途に使用することは困難であった。
また、Ｐｔ、Ｐｄは非常に高価な金属であるので、電極として用いるには一般にＡｇと混合させて使用する。その際、上述したＡｇのマイグレーションの問題が発生する。
さらに、Ｃｕを用いた場合は非常に安価であり、マイグレーションも生じにくいが、焼成する際、酸化されやすく、酸化防止のため還元性雰囲気が必要となる。しかし、正特性サーミスタは、還元性雰囲気下では、本来の特性であるキュリー点以上の温度での急激な抵抗値上昇を起こさなくなってしまう。
【０００７】
そこで、正特性サーミスタの電極には、一般的に安価で量産性に優れ、かつマイグレーションが起こらないＮｉまたはＮｉ合金が用いられているが、ＮｉまたはＮｉ合金は、はんだ付け性が非常に悪く、電流容量も小さいことから、Ｎｉ電極の上に、第２電極としてはんだ付け性改善と電流容量拡大を目的としてＡｇおよび／またはＰｄ電極を形成している。
しかし、上記構成の電極構造ではＡｇおよび／またはＰｄ電極ペーストを印刷／塗布した後、熱処理にて電極とする必要があるが、その熱処理によりある種の障壁層が発生し、オーミック接触が得られないという問題が生じていた。
磁器と電極との界面のオーミック接触していない界面層は電圧を印加することにより破壊できるが、正特性サーミスタ素子に上記した障壁層を破壊できるような電圧を印加した場合、正特性サーミスタ素子が瞬時に発熱し、サーマルショックにより正特性サーミスタ素子にクラックが発生し、素子が破壊する場合がある。
サーマルショックによるクラックを防ぐため、電圧を徐々に昇圧していく方法も考えられるが、この場合、正特性サーミスタ素子の抵抗値が昇圧と共に上昇し、正特性サーミスタ素子の抵抗値が障壁層抵抗に比べ著しく大きくなるため、障壁層に電圧がかからず障壁層が破壊されないという問題がある。
【０００８】
また、直流電源を用いて一方向から障壁層の破壊を試みた場合、磁器の両主面に形成された各々一対の第１電極と第２電極との界面に生成された障壁層のうち、電位の高い側に生成された障壁層と低い側に生成された障壁層との破壊の大きさに差が生じてしまい、その結果若干の整流作用が残存するという問題を生じていた。
整流作用を残存させることなく障壁層を破壊する対策として、（＋），（−）電圧を交互に印加する方法も考えられるが、（＋），（−）各々の電圧を交互に印加するだけでは、上記の正特性サーミスタ素子の破壊や整流作用の残存という問題を解決できなかった。
【０００９】
【課題を解決するための手段】
本発明は、第１電極であるＮｉと第２電極であるＡｇとの界面に存在する障壁層を略同時に極短時間印加できる装置にて、通電を行うことにより、正特性サーミスタ素子の破壊や整流作用の残存という問題を発生させずに第１電極と第２電極の界面の障壁層を破壊してオーミック接触を得ようとするものである。
すなわち、正特性サーミスタ素子の両主面上に、ＮｉまたはＮｉ合金からなる第１電極を形成する工程と、
第１電極上に、Ａｇおよび／またはＰｄからなる第２電極を形成する工程と、
第２電極間に交番電源を用いて短時間の通電を行う工程とからなることを特徴とする正特性サーミスタ素子の製造方法である。
【００１０】
また、交番電源により通電する正特性サーミスタ素子１個当たりの電流値が２５Ａ以上であり、通電時間が１００ｍｓ以下であることを特徴とする正特性サーミスタ素子の製造方法である。
【００１１】
【発明の実施の形態】
本発明は次の３工程、すなわち、
（１）正特性サーミスタ素子の両主面上に、ＮｉまたはＮｉ合金からなる第１電極を形成する工程、
（２）第１電極上に、はんだ付け性に優れ、かつ導電率の高いＡｇおよび／またはＰｄからなる第２電極を形成する工程、
（３）一対の第２電極間に交番電源を用い、通電する電流値を実効値として２５Ａ／個以上、通電時間を１００ｍｓ以下で、通電を行う工程を行うことにより、正特性サーミスタ素子の破壊、整流作用の残存という問題を発生させずに、第１電極のＮｉまたはＮｉ合金と、第２電極のＡｇおよび／またはＰｄとの界面に存在する障壁層を破壊して、良好なオーミック接触を得ることができる。
【００１２】
【実施例】
以下、本発明の実施例について図面を参照しながら説明する。
所定の特性が得られるよう、公知の粉末冶金法にてＢａ２ＣＯ３、ＴｉＯ２、ＳｒＣＯ３、ＰｂＯ、Ｙ２Ｏ３等を配合し、ボールミルにて混合を行い、脱水乾燥の後、仮焼を行い、再度ボールミルにて粉砕を行い、造粒の後、長辺３０ｍｍ×短辺２０ｍｍ×厚さ２．６ｍｍの寸法に成形を行った後、１３００℃で焼成し、正特性サーミスタ磁器を得た。
焼成後の磁器の両主面に、抵抗測定用のＩｎ−Ｇａ合金を塗布して電極とし、抵抗を測定したところ、磁器の抵抗値は１Ωであった。
【００１３】
上記焼成後の正特性サーミスタ磁器（抵抗測定用のＩｎ−Ｇａ合金を塗布せず。）の両主面に第１電極であるＮｉ電極を化学メッキにより形成し、熱処理した。
熱処理後の磁器の両主面に、Ｉｎ−Ｇａ合金を塗布して電極とし、抵抗測定を行ったところ、磁器の抵抗値は１Ωであった。
【００１４】
上記熱処理後の正特性サーミスタ磁器（抵抗測定用のＩｎ−Ｇａ合金を塗布せず。）のＮｉ電極の上にＡｇ電極を印刷塗布後、熱処理して第２電極とし正特性サーミスタ素子を得た。該素子の第２電極間の抵抗値を測定すると、５．５Ωであった。このことから、第１電極であるＮｉ電極と第２電極であるＡｇとの界面に障壁層が存在することが分かる。図１は、本状態の模式断面図である。正特性サーミスタ素子３の両主面にＮｉまたはＮｉ合金からなる一対の第１電極１ａ、１ｂが形成されており、その上に一対のＡｇおよび／またはＰｄからなる第２電極２ａ、２ｂが形成されている。第１電極１ａ、１ｂと第２電極２ａ、２ｂ間の界面に障壁層３ａ、３ｂが形成されている。
【００１５】
上記の障壁層を破壊するため、ＤＣ電圧１６Ｖを８秒間電圧印加したところ、正特性サーミスタ素子の急激な発熱によるサーマルショックで素子が破壊された。
【００１６】
上記のようなサーマルショックによる素子の破壊を発生させないようにするため、電圧を０Ｖから２Ｖ間隔で徐々に昇圧し、最終的にＤＣ電圧１６Ｖで８秒間通電を行った結果、正特性サーミスタ素子の抵抗値は４Ωまでしか下がらなかった。これは、正特性サーミスタ素子の抵抗値が電圧の昇圧と共に上昇し、正特性サーミスタ素子の障壁層間の抵抗が徐々に増大したため、障壁層が十分に破壊できなかったためと考えられる。
【００１７】
次に、上記のサーマルショックによる素子の破壊を防ぎ、かつ障壁層が破壊するに十分な電圧を調査した。
ＤＣ電圧１６Ｖで、３０ｍｓ通電したところ、電流は１８Ａ流れたが、短時間であるため、正特性サーミスタ素子は発熱せず、サーマルショックによる破壊は発生しなかった。この時の正特性サーミスタ素子の抵抗値は１．７Ωまで下がった。
また、ＤＣ電圧３０Ｖで、３０ｍｓ（１回）通電すると、正特性サーミスタ素子の抵抗値は１．２Ωまで下がった（表１、比較例３）。
【００１８】
さらに、正特性サーミスタ素子（第１電極：Ｎｉ化学メッキ、第２電極：Ａｇ印刷塗布）の性能評価を行うため、図２で示すように正特性サーミスタ素子に対し、Ａ、Ｂの２方向からＤＣ電圧１２Ｖを交互に印加し、正特性サーミスタ素子に流れる最大電流を測定したところ、Ａ方向から印加した場合は１３．３Ａであり、Ｂ方向から印加した場合は１１．９Ａであった。すなわち、印加する方向によって若干の整流作用が残存することが分かった。
【００１９】
上記の正特性サーミスタ素子の第１、第２電極間の障壁層を、整流作用が残存することなく破壊するため、ＤＣ電圧３０Ｖで、３０ｍｓ通電した試料をひっくり返し、逆方向から再度、ＤＣ電圧３０Ｖで、３０ｍｓ通電すると、正特性サーミスタ素子の抵抗値は１．１Ωとなり、焼成後の正特性サーミスタ磁器の両主面に第１電極（Ｎｉ電極）を化学メッキにより形成した時の抵抗値１Ωと略同じレベルとなった。
【００２０】
上記の正特性サーミスタ素子を用い、上記と同様にＤＣ電圧１２Ｖの性能評価試験を行ったところ、正特性サーミスタ素子に流れる最大電流をＡ方向から印加した場合は１４．５Ａであり、Ｂ方向から印加した場合は１３．９Ａであり、上記と比べて改善はされているが、まだ若干の整流作用が残存していることが分かった。
すなわち、最初の１方向目の通電で障壁層の大部分が破壊されてしまい、障壁層の抵抗値が磁器の抵抗値に比べ小さくなるが、不均等に障壁が残るので、２方向目の通電のときは磁器と、残存する障壁層とで分圧が生じ、障壁層に十分な電圧を印加することができず、障壁層がわずかに残り、若干の整流作用が残存してしまう。
【００２１】
上記正特性サーミスタ素子の障壁層を、整流作用が残存することなく確実に破壊するため、表１に示す電圧電流印加条件で、交番電源として周波数６０Ｈｚの交流電源を用い、略同時に両方向から印加し通電したところ、表１に示すように、正特性サーミスタ素子の抵抗値は１Ωまで下がり、焼成後の正特性サーミスタ磁器の両主面に第１電極（Ｎｉ電極）を化学メッキにより形成した時の抵抗値１Ωと略同じレベルとなった。なお、サーマルショックによる素子の破壊は皆無であった。
【００２２】
この正特性サーミスタ素子を用い、上記した性能評価試験を行ったところ、図２のようにＡ方向、Ｂ方向共に正特性サーミスタ素子に流れた最大電流は１６Ａであり印加方向による整流作用は見られなかった。すなわち、交番電源を用いて電圧を略同時に交互に印加すると磁器抵抗と障壁層抵抗との分圧が起こる前に障壁層を完全に破壊することができ、整流作用の残存という問題の発生を防ぐことができる。
交流電源による、電圧印加条件による処理の結果を実施例１〜４として、表１に示す。
【００２３】
上記と同様、直流の電圧印加条件による通電前後の抵抗値変化と整流作用の有無も比較例１〜４として表１に示す。
【００２４】
【表１】
正特性サーミスタ素子への印加時間を変えて印加した結果を表２に示す。印加時間以外は実施例３と同じである。
【００２６】
【表２】
上記したとおり、交番電源を用いて通電する電流値が実効値として２５Ａ以上の場合、第１電極と第２電極の界面に生成された障壁層は完全に破壊され、良好なオーミック接触が得ることができるが（実施例２〜４）、２５Ａ未満の場合、障壁層が完全に破壊されず、良好なオーミック接触を得ることができない（実施例１）。
【００２８】
また、交番電源による通電時間が１００ｍｓ以下の場合、正特性サーミスタ素子が発熱に至らず、サーマルショックによる正特性サーミスタ素子が破壊することなく、第１電極と第２電極との界面に生成された障壁層を破壊させることができるが（実施例５〜７）、１００ｍｓを超える場合は正特性サーミスタ素子が発熱し、サーマルショックにより正特性サーミスタ素子が破壊する場合がある（実施例８、９）。
【００２９】
【発明の効果】
上記したとおり本発明によれば、ＮｉまたはＮｉ合金からなる第１電極と、Ａｇおよび／またはＰｄからなる第２電極との界面に存在する一対の障壁層に対し、交番電源を用い、電流値を実効値として２５Ａ以上で、時間を１００ｍｓ以下で通電することにより、サーマルショックによる素子の破壊や整流作用の残存という問題を発生させることなく障壁層を破壊することができ、第１電極と、第２電極との界面に良好なオーミック接触が得られ、磁器本来の抵抗値が現われ、電圧依存性のない正特性サーミスタ素子を製造することができる。
【図面の簡単な説明】
【図１】従来の正特性サーミスタ素子の断面模式図である。
【図２】本発明の実施例による正特性サーミスタ素子に交番電源を用いて通電するときの状態図である。
【符号の説明】
１ａ、１ｂ 第１電極（ＮｉまたはＮｉ合金）
２ａ、２ｂ 第２電極（Ａｇおよび／またはＰｄ）
３ 正特性サーミスタ磁器
３ａ、３ｂ 障壁層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a positive temperature coefficient thermistor element used as a current control switching element or a constant temperature heating element.
[0002]
[Prior art]
When an electrode is formed on a positive temperature coefficient thermistor porcelain, which is an N-type semiconductor, a metal capable of providing ohmic contact is used so that the original resistance value of the porcelain appears and voltage dependence is eliminated, but ohmic contact is obtained. Generally, Ni or a Ni alloy is used as the metal. In addition, Al is used as an electrode for obtaining another ohmic contact.
[0003]
The reason why the ohmic contact of these metals is good is that the work function is smaller than that of the positive temperature coefficient thermistor porcelain. Metals having a higher work function than the positive temperature coefficient thermistor porcelain cannot obtain good ohmic contact.
[0004]
When using Ag, Pt, Pd, and Cu as the electrodes of the PTC thermistor, which cannot make good ohmic contact with the PTC thermistor, the pulse voltage is applied between the porcelain and the electrodes in the (+) and (-) directions. It is said that a good ohmic contact can be obtained as a positive temperature coefficient thermistor by using the method of applying a voltage to the substrate (see
[0005]
[Patent Document 1]
JP-A-6-13203 (pages 2-3)
[0006]
[Problems to be solved by the invention]
However, when Ag is used as an electrode, migration due to Ag occurs due to prolonged energization, causing problems such as short-circuiting and fluctuations in resistance. It was difficult to use for the purpose.
Since Pt and Pd are very expensive metals, they are generally mixed with Ag for use as electrodes. At this time, the Ag migration problem described above occurs.
Further, when Cu is used, it is very inexpensive and migration hardly occurs, but it is easily oxidized during firing, and a reducing atmosphere is required to prevent oxidation. However, the positive temperature coefficient thermistor does not cause a sudden increase in resistance at a temperature equal to or higher than the Curie point, which is the original characteristic, in a reducing atmosphere.
[0007]
Therefore, Ni or Ni alloy which is generally inexpensive, has excellent mass productivity, and does not cause migration is used for the electrode of the positive temperature coefficient thermistor. However, Ni or Ni alloy has very poor solderability. Since the current capacity is also small, an Ag and / or Pd electrode is formed as a second electrode on the Ni electrode for the purpose of improving the solderability and expanding the current capacity.
However, in the electrode structure having the above-described structure, it is necessary to print / apply the Ag and / or Pd electrode paste and then heat-treat the electrode. However, the heat treatment generates a certain kind of barrier layer, and an ohmic contact is obtained. There was a problem that there was no.
An interface layer that is not in ohmic contact with the interface between the porcelain and the electrode can be destroyed by applying a voltage.However, when a voltage that can destroy the barrier layer described above is applied to the PTC thermistor element, the PTC thermistor element cannot be used. Heat is generated instantaneously, and the thermal shock causes cracks in the positive temperature coefficient thermistor element, which may destroy the element.
In order to prevent cracks due to thermal shock, a method of gradually increasing the voltage is also conceivable. As a result, there is a problem that no voltage is applied to the barrier layer and the barrier layer is not broken.
[0008]
Further, when the barrier layer is destructed from one direction using a DC power supply, of the barrier layers generated at the interface between the pair of first and second electrodes formed on both main surfaces of the porcelain, There is a difference in the magnitude of destruction between the barrier layer generated on the higher potential side and the barrier layer generated on the lower potential side, resulting in a problem that some rectifying action remains.
As a countermeasure to destroy the barrier layer without leaving the rectifying action, a method of alternately applying (+) and (−) voltages can be considered, but only applying the (+) and (−) voltages alternately. Thus, the above-mentioned problems of destruction of the positive temperature coefficient thermistor element and remaining rectification cannot be solved.
[0009]
[Means for Solving the Problems]
The present invention provides a device that can apply a barrier layer existing at the interface between Ni as the first electrode and Ag as the second electrode almost simultaneously for a very short time, thereby performing destruction of the PTC thermistor element by conducting electricity. It is intended to obtain an ohmic contact by destroying the barrier layer at the interface between the first electrode and the second electrode without causing the problem of remaining rectifying action.
That is, a step of forming a first electrode made of Ni or a Ni alloy on both main surfaces of the positive temperature coefficient thermistor element;
Forming a second electrode made of Ag and / or Pd on the first electrode;
Performing a short-time energization using an alternating power supply between the second electrodes.
[0010]
A method of manufacturing a positive temperature coefficient thermistor element characterized in that a current value per positive temperature coefficient thermistor element energized by an alternating power supply is 25 A or more and an energization time is 100 ms or less.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention comprises the following three steps:
(1) forming a first electrode made of Ni or a Ni alloy on both main surfaces of the PTC thermistor element;
(2) a step of forming a second electrode made of Ag and / or Pd having excellent solderability and high conductivity on the first electrode;
(3) Destruction of the positive temperature coefficient thermistor element by performing an energizing step using an alternating power supply between a pair of second electrodes with an energizing current value of 25 A / unit or more and an energizing time of 100 ms or less as an effective value. The barrier layer existing at the interface between Ni or the Ni alloy of the first electrode and Ag and / or Pd of the second electrode is destroyed without causing the problem of the remaining rectifying action, and a good ohmic contact is achieved. Obtainable.
[0012]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
Ba 2 CO 3 , TiO 2 , SrCO 3 , PbO, Y 2 O 3 and the like are blended by a known powder metallurgy method to obtain predetermined characteristics, mixed by a ball mill, dehydrated and dried. After baking, pulverized again by a ball mill, and after granulation, formed into a size of 30 mm long side × 20 mm short side × 2.6 mm thick, and fired at 1300 ° C. to form a positive temperature coefficient thermistor porcelain. Obtained.
An In-Ga alloy for resistance measurement was applied to both main surfaces of the fired porcelain to form electrodes, and the resistance was measured. The resistance value of the porcelain was 1Ω.
[0013]
A Ni electrode as a first electrode was formed by chemical plating on both main surfaces of the fired positive temperature coefficient thermistor porcelain (not coated with an In-Ga alloy for resistance measurement) and heat-treated.
The In-Ga alloy was applied to both main surfaces of the heat-treated porcelain to form electrodes, and the resistance was measured. The resistance value of the porcelain was 1Ω.
[0014]
An Ag electrode was printed and applied on the Ni electrode of the PTC thermistor porcelain (without applying an In-Ga alloy for resistance measurement) after the heat treatment, and then heat treated to obtain a PTC thermistor element. . When the resistance value between the second electrodes of the device was measured, it was 5.5Ω. This indicates that a barrier layer exists at the interface between the Ni electrode as the first electrode and Ag as the second electrode. FIG. 1 is a schematic sectional view of this state. A pair of
[0015]
When a DC voltage of 16 V was applied for 8 seconds to destroy the barrier layer, the element was destroyed by thermal shock due to rapid heat generation of the PTC thermistor element.
[0016]
In order to prevent the element from being destroyed due to the thermal shock as described above, the voltage was gradually increased from 0 V at intervals of 2 V, and finally the current was applied at a DC voltage of 16 V for 8 seconds. The resistance decreased only to 4Ω. This is presumably because the resistance value of the positive temperature coefficient thermistor element increased with increasing voltage, and the resistance between the barrier layers of the positive temperature coefficient thermistor element gradually increased, so that the barrier layer could not be sufficiently destroyed.
[0017]
Next, a voltage sufficient to prevent the element from being broken by the above thermal shock and to break the barrier layer was investigated.
When a DC voltage of 16 V was applied for 30 ms, a current of 18 A flowed. However, since the current was short, the positive temperature coefficient thermistor element did not generate heat and did not break down due to thermal shock. At this time, the resistance value of the positive temperature coefficient thermistor element dropped to 1.7Ω.
Further, when a current was applied for 30 ms (once) at a DC voltage of 30 V, the resistance value of the PTC thermistor element dropped to 1.2Ω (Table 1, Comparative Example 3).
[0018]
Further, in order to evaluate the performance of the positive temperature coefficient thermistor element (first electrode: Ni chemical plating, second electrode: Ag print coating), as shown in FIG. The maximum current flowing through the positive temperature coefficient thermistor element was measured by applying a DC voltage of 12 V alternately, and it was 13.3 A when applied from the A direction and 11.9 A when applied from the B direction. That is, it was found that a slight rectifying action remained depending on the direction of application.
[0019]
In order to destroy the barrier layer between the first and second electrodes of the above-mentioned positive temperature coefficient thermistor element without the rectifying action remaining, the sample which had been energized for 30 ms at a DC voltage of 30 V was turned over, and the DC voltage was again applied in the reverse direction. When a current is applied at 30 V for 30 ms, the resistance value of the positive temperature coefficient thermistor element becomes 1.1Ω, and the resistance value when the first electrode (Ni electrode) is formed on both main surfaces of the fired positive temperature coefficient thermistor ceramic by chemical plating is 1Ω. It was almost the same level.
[0020]
When a performance evaluation test was performed using the above-described positive-characteristic thermistor element at a DC voltage of 12 V in the same manner as described above, when the maximum current flowing through the positive-characteristic thermistor element was applied from the A direction, it was 14.5 A, and from the B direction. When the voltage was applied, it was 13.9 A, which was improved as compared with the above, but it was found that a slight rectifying action still remained.
That is, most of the barrier layer is destroyed by the first energization in the first direction, and the resistance value of the barrier layer becomes smaller than the resistance value of the porcelain. In this case, a partial pressure is generated between the porcelain and the remaining barrier layer, so that a sufficient voltage cannot be applied to the barrier layer, the barrier layer slightly remains, and a slight rectifying action remains.
[0021]
In order to surely destroy the barrier layer of the positive temperature coefficient thermistor element without remaining rectifying action, an AC power supply having a frequency of 60 Hz was used as an alternating power supply under the voltage / current application conditions shown in Table 1, and voltage was applied from both directions substantially simultaneously. When current was applied, as shown in Table 1, the resistance value of the positive temperature coefficient thermistor element dropped to 1Ω, and the first electrode (Ni electrode) was formed on both main surfaces of the fired positive temperature coefficient thermistor ceramic by chemical plating. The level was substantially the same as the resistance value of 1Ω. In addition, there was no destruction of the element due to the thermal shock.
[0022]
When the above-described performance evaluation test was performed using this PTC thermistor element, the maximum current flowing through the PTC thermistor element in both the A and B directions was 16 A as shown in FIG. Did not. That is, when a voltage is applied alternately and substantially simultaneously using an alternating power supply, the barrier layer can be completely destroyed before the voltage division of the porcelain resistance and the barrier layer resistance occurs, thereby preventing the problem of remaining rectifying action from occurring. be able to.
Table 1 shows the results of the processing by the AC power supply under the voltage application conditions as Examples 1 to 4.
[0023]
Similarly to the above, Table 1 also shows the change in resistance value before and after energization and the presence or absence of a rectification effect depending on the DC voltage application condition as Comparative Examples 1 to 4.
[0024]
[Table 1]
Table 2 shows the results of applying the voltage to the PTC thermistor element while changing the application time. Except for the application time, it is the same as the third embodiment.
[0026]
[Table 2]
As described above, when the value of the current passed through the alternating power supply is 25 A or more as an effective value, the barrier layer generated at the interface between the first electrode and the second electrode is completely destroyed, and a good ohmic contact is obtained. However, if it is less than 25 A, the barrier layer is not completely destroyed, and good ohmic contact cannot be obtained (Example 1).
[0028]
In addition, when the energization time by the alternating power supply is 100 ms or less, the PTC thermistor element does not generate heat, and the PTC thermistor element is generated at the interface between the first electrode and the second electrode without being destroyed by the thermal shock. Although the barrier layer can be destroyed (Examples 5 to 7), if it exceeds 100 ms, the PTC thermistor element generates heat and the PTC thermistor element may be destroyed by thermal shock (Examples 8 and 9). .
[0029]
【The invention's effect】
As described above, according to the present invention, an alternating power supply is used for a pair of barrier layers existing at the interface between the first electrode made of Ni or a Ni alloy and the second electrode made of Ag and / or Pd. By applying a current of 25 A or more as an effective value and a time of 100 ms or less, the barrier layer can be destroyed without causing a problem of destruction of the element due to thermal shock or remaining rectification action, and the first electrode, Good ohmic contact is obtained at the interface with the second electrode, the original resistance value of the porcelain appears, and a positive temperature coefficient thermistor element having no voltage dependency can be manufactured.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a conventional PTC thermistor element.
FIG. 2 is a state diagram when power is supplied to a PTC thermistor element according to an embodiment of the present invention using an alternating power supply.
[Explanation of symbols]
1a, 1b First electrode (Ni or Ni alloy)
2a, 2b Second electrode (Ag and / or Pd)
3 Positive characteristic thermistor porcelain 3a, 3b Barrier layer
Claims (2)
第１電極上に、Ａｇおよび／またはＰｄからなる第２電極を形成する工程と、
第２電極間に交番電源を用いて短時間の通電を行う工程とからなることを特徴とする正特性サーミスタ素子の製造方法。Forming a first electrode made of Ni or a Ni alloy on both main surfaces of the positive temperature coefficient thermistor element;
Forming a second electrode made of Ag and / or Pd on the first electrode;
Performing a short-time energization using an alternating power supply between the second electrodes.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2011083843A1 (en) * | 2010-01-08 | 2011-07-14 | 株式会社村田製作所 | Thermistor and method for producing same |
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| JPS6048201U (en) * | 1983-09-09 | 1985-04-04 | ティーディーケイ株式会社 | Positive characteristic thermistor device |
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| JPS6048201U (en) * | 1983-09-09 | 1985-04-04 | ティーディーケイ株式会社 | Positive characteristic thermistor device |
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| JPH01106401A (en) * | 1987-10-19 | 1989-04-24 | Nitto Denko Corp | Adhesive sheet for forming electrode |
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