JPH043084B2

JPH043084B2 -

Info

Publication number: JPH043084B2
Application number: JP1218398A
Authority: JP
Priority date: 1989-08-24
Filing date: 1989-08-24
Publication date: 1992-01-22
Also published as: JPH0284701A

Description

[Detailed description of the invention]

本発明は正特性磁器半導体の電極の形成方法に
関するものである。従来オーミツク接触が可能なこの種の電極形成
方法としては、無電解メツキ法により行なわれて
いるが、メツキの付着をよくするために正特性磁
器半導体の表面を研摩後、更に微細な凹凸状にす
るなどの感応化、活性化処理が必要であり、従つ
てこのいわゆる前処理が非常に面倒である。また、従来においては、メツキ不要な部分の処
理方法としては、不要な部分をマスキングした
り、あるいはメツキ後に不要な部分をエツチング
して取除くようにしており、これまた甚だ面倒な
処理である。そこで、本発明は上述の点に鑑み、チタン酸バ
リウム系を主成分とする材料よりなる正特性磁器
半導体に対するオーミツク接触が可能な電極の形
成を従来に比べて簡単に行う正特性磁器半導体の
電極の形成方法を提供するものである。そこで、本発明者の鋭意研究の結果、チタン酸
バリウム系を主成分とする材料よりなる正特性磁
器半導体の表面に、パラジウムの塩化物よりなる
ペースト状の活性化剤を塗布して焼付け、その後
この正特性磁器半導体を無電解メツキ浴に浸漬し
て活性化剤の焼付面上に電極を形成し、その後前
記正特性磁器半導体を前記メツキ浴より取出して
乾燥後、前記電極を焼付けることにより、上述の
諸問題を解決しようとするものである。本発明によれば、上記のパラジウムの塩化物よ
りなるペースト状の活性化剤を塗布焼付けするこ
とによつて予め金属の薄膜をチタン酸バリウム系
を主成分とする材料よりなる正特性磁器半導体に
形成し、その後メツキすることで上記金属膜を核
としてその表面上に集中的に金属粒子が付着して
電極が形成される。従つて、本発明はパラジウムの塩化物よりなる
ペースト状の活性化剤の塗布、焼付けにより電極
が形成される下地を予め設けており、前述したよ
うに、チタン酸バリウム系を主成分とする材料よ
りなる正特性磁器半導体の表面に凹凸を形成する
などの前処理を必要とせず、さらには簡単な方法
にて、正特性磁器半導体に必要なオーミツク接触
が可能な電極を形成することができるのである。また、本発明では、上記活性化剤の塗布、焼付
面上に集中して電極となる金属粒子が付着するの
で、この塗布、焼付面以外の部分はほとんどある
いは全く金属粒子が付着しない。このため、電極
の形成パターンを所望の形状にするには、上記活
性化剤の塗布パターンをそれと同じくするだけで
よく、特別のマスキング処理、エツチングによる
電極削除処理が不要となるのである。更に、メツ
キ時間も短縮される。以上のように、本発明においては、正特性磁器
半導体に対する電極の形成を従来に比べて簡単に
行なうことができ、従つて工数低減、電極材料の
削減において実用上多大なる有効な効果を奏す
る。以下本発明を具体的な実施例により詳細に説明
する。まず、第１図および第２図において、円板状の
正特性磁器半導体１はチタン酸バリウム
（BaTiO₃）系の公知材料より成る。この半導体
１の両面にはニツケル（Ni）電極２が形成され、
更にこの電極２の上には銀（Ag）のカバー電極
３が形成されている。次に、上記各電極の形成方法について説明す
る。まず、半導体の両面を研摩するとともに、そ
の両面を洗浄して乾燥させ、パラジウム（Pd）
の塩化物を含むペースト状の活性化剤（日本カニ
ゼン株式会社製造のK146）を所望パターンにし
て150メツシユ乃至300メツシユにてスクリーン印
刷をする。その後、乾燥して半導体を300℃乃至
750℃の高温度下に配置し、上記活性化剤を焼付
ける。次に、Ni−Ｐ系の無電解メツキ浴（浴温90℃
〜95℃）に半導体を浸漬し、Ni−メツキを行な
う。その後、メツキ浴より半導体を取出して乾燥
後、200℃乃至450℃の温度下で10分乃至５時間焼
付けてNi電極を得る。その後、このNi電極上に
Agペーストを塗布して450℃乃至800℃にて15分
間焼付け、カバー電極とする。このカバー電極は
Ni電極の保護を目的としている。上述の本発明方法によつて得たNi電極付半導
体と従来方法によるNi電極をもつた半導体との
比抵抗を確認したところ、ほぼ同等の特性が得ら
れ、品質的問題がないことがわかつた。その結果
を表１に示す。なお、表１において、「メツシユ」とは活性化
剤のスクリーン印刷メツシユ、「その他」は電源
電圧12Vを印加し、電圧ONを１分間、電圧OFF
を９分間とし、これを１サイクルを1000時間行な
つた耐久後の抵抗変化率であり、試料の半導体は
直径20mm、厚さ3.0mmで約2.4Ωの抵抗をもつ。ま
た、「抵抗変化率」とはキユリー点を境にした最
小抵抗と最大抵抗との比率である。 The present invention relates to a method of forming an electrode of a PTC ceramic semiconductor. Conventionally, this type of electrode formation method that allows ohmic contact has been carried out by electroless plating, but in order to improve the adhesion of the plating, the surface of the PTC ceramic semiconductor is polished and then made into finer irregularities. This so-called pre-treatment is very troublesome. Furthermore, in the past, methods for removing unnecessary portions that do not require plating include masking the unnecessary portions or removing the unnecessary portions by etching after plating, which is also a very troublesome process. Therefore, in view of the above-mentioned points, the present invention provides an electrode for a PTC ceramic semiconductor, which makes it easier to form an electrode capable of making ohmic contact with a PTC ceramic semiconductor made of a material containing barium titanate as a main component. The present invention provides a method for forming. Therefore, as a result of intensive research by the present inventor, a paste-like activator made of palladium chloride was coated on the surface of a positive characteristic ceramic semiconductor made of a material containing barium titanate as a main component, and then baked. This positive characteristic ceramic semiconductor is immersed in an electroless plating bath to form an electrode on the baking surface of the activator, and then the positive characteristic ceramic semiconductor is taken out from the plating bath, and after drying, the electrode is baked. , which attempts to solve the above-mentioned problems. According to the present invention, a thin metal film is formed in advance into a positive characteristic ceramic semiconductor made of a material containing barium titanate as a main component by applying and baking a paste-like activator made of palladium chloride. By forming and then plating, metal particles are concentratedly attached to the surface of the metal film with the metal film serving as a nucleus, thereby forming an electrode. Therefore, in the present invention, a base on which electrodes are formed is provided in advance by coating and baking a paste-like activator made of palladium chloride, and as described above, a material whose main component is barium titanate is used. There is no need for pre-treatment such as forming irregularities on the surface of a PTC ceramic semiconductor, and furthermore, it is possible to form an electrode that can make the ohmic contact required for a PTC ceramic semiconductor using a simple method. be. Furthermore, in the present invention, since the metal particles that will become the electrodes are concentrated on the surface where the activator is applied and baked, little or no metal particles adhere to the area other than the surface where the activator is applied and baked. Therefore, in order to form the electrode formation pattern into a desired shape, it is sufficient to apply the activator in the same pattern as the pattern, and no special masking process or electrode removal process by etching is required. Furthermore, plating time is also shortened. As described above, in the present invention, it is possible to form an electrode on a PTC ceramic semiconductor more easily than in the past, and therefore it has a great practical effect in reducing the number of man-hours and electrode materials. The present invention will be explained in detail below using specific examples. First, in FIGS. 1 and 2, a disk-shaped positive characteristic ceramic semiconductor 1 is made of a known material based on barium titanate (BaTiO ₃ ). Nickel (Ni) electrodes 2 are formed on both sides of this semiconductor 1,
Furthermore, a cover electrode 3 made of silver (Ag) is formed on this electrode 2. Next, a method for forming each of the above electrodes will be explained. First, both sides of the semiconductor are polished, both sides are cleaned and dried, and palladium (Pd) is removed.
A paste-like activator (K146 manufactured by Nippon Kanigen Co., Ltd.) containing chloride is screen-printed in the desired pattern with 150 to 300 meshes. After that, the semiconductor is dried at 300℃ or
The activator is baked by placing it under a high temperature of 750°C. Next, a Ni-P based electroless plating bath (bath temperature 90℃
The semiconductor is immersed in a temperature of ~95°C) and Ni-plated. Thereafter, the semiconductor is taken out from the plating bath, dried, and then baked at a temperature of 200° C. to 450° C. for 10 minutes to 5 hours to obtain a Ni electrode. Then, on this Ni electrode
Apply Ag paste and bake at 450°C to 800°C for 15 minutes to form a cover electrode. This cover electrode
The purpose is to protect the Ni electrode. When we checked the specific resistance of the semiconductor with Ni electrodes obtained by the method of the present invention described above and the semiconductor with Ni electrodes obtained by the conventional method, it was found that almost the same characteristics were obtained and there were no quality problems. . The results are shown in Table 1. In Table 1, "mesh" means a screen-printed mesh with an activator, and "others" means applying a power supply voltage of 12V, turning the voltage ON for 1 minute, and turning the voltage OFF.
This is the resistance change rate after 1000 hours of one cycle, with 9 minutes, and the sample semiconductor has a diameter of 20 mm, a thickness of 3.0 mm, and a resistance of approximately 2.4 Ω. Furthermore, the "resistance change rate" is the ratio between the minimum resistance and the maximum resistance with the Curie point as a border.

【表】この表１において、活性化剤のスクリーン印刷
メツシユは200メツシユが、その焼付温度は400℃
が、比抵抗、耐久後の変化率の点で特に望まし
い。なお、本発明は前述の実施例に限定されず、以
下のごとく種々の変形が可能である。 (1) 正特性磁器半導体の形状は円板状に限らず、
角板状、ハニカム状など種々の形状でもよいこ
とは勿論である。 (2) 電極の材料は特にNiに限定されず、他の金
属でも勿論よいが、半導体との接触抵抗の非常
に良好なNiが最適である。 (3) カバー電極の材料もAgの他に種々考えられ
る。なお、本発明の用途としては、一般の電流遮断
用抵抗器、あるいは加熱機器用発熱体など広範囲
な用途が考えられる。[Table] In Table 1, the screen printing mesh of the activator is 200 mesh, and its baking temperature is 400℃.
However, it is particularly desirable in terms of resistivity and rate of change after durability. Note that the present invention is not limited to the above-described embodiments, and various modifications can be made as described below. (1) The shape of PTC porcelain semiconductors is not limited to a disk shape.
Of course, various shapes such as a square plate shape and a honeycomb shape may be used. (2) The material of the electrode is not particularly limited to Ni, and of course other metals may be used, but Ni is optimal because of its very good contact resistance with the semiconductor. (3) Various materials other than Ag can be considered for the cover electrode. Note that the present invention can be used in a wide range of applications, such as a general current interrupting resistor or a heating element for a heating device.

[Brief explanation of drawings]

第１図は本発明の説明に供する正特性磁器半導
体を示す斜視図、第２図は第１図のＡ−Ａ断面図
である。１……正特性磁器半導体、２……Ni電極、３
……Agカバー電極。 FIG. 1 is a perspective view showing a PTC ceramic semiconductor used for explaining the present invention, and FIG. 2 is a sectional view taken along the line AA in FIG. 1...Positive characteristic ceramic semiconductor, 2...Ni electrode, 3
...Ag cover electrode.

Claims

[Scope of Claims] 1. A paste-like activator made of palladium chloride is applied to the surface of a positive characteristic porcelain semiconductor made of a material containing barium titanate as a main component, and then baked, and then this positive characteristic porcelain is The semiconductor is immersed in an electroless plating bath to form an electrode on the baked surface of the activator, and then the positive characteristic ceramic semiconductor is taken out from the plating bath, dried, and then the electrode is baked. A method for forming electrodes of positive characteristic ceramic semiconductors. 2. The method of forming an electrode of a PTC ceramic semiconductor according to claim 1, wherein the electrode is made of nickel. 3 The baking temperature and baking time of the above activator is 300℃
Any one of claims 1 to 2, characterized in that the baking temperature and baking time of the electrode after plating are 10 minutes to 5 hours at 200 degrees Celsius to 450 degrees Celsius. 1. A method for forming an electrode of a positive characteristic ceramic semiconductor according to 1. 4 A paste-like activator made of palladium chloride is applied and baked on the surface of a positive temperature ceramic semiconductor made of a material whose main component is barium titanate, and then this positive temperature ceramic semiconductor is subjected to an electroless plating bath. to form an electrode on the baked surface of the activator, then take out the positive characteristic ceramic semiconductor from the plating bath, dry it, bake the electrode, and form a cover electrode on the electrode surface. A method for forming an electrode of a positive characteristic ceramic semiconductor, characterized in that: 5. The method of forming an electrode of a PTC ceramic semiconductor according to claim 4, wherein the electrode is made of nickel. 6 The baking temperature and baking time of the activator are 300℃
Any one of claims 4 to 5, characterized in that the baking temperature and baking time of the electrode after plating are 10 minutes to 5 hours at 200 degrees Celsius to 450 degrees Celsius. 1. A method for forming an electrode of a positive characteristic ceramic semiconductor according to 1.