【発明の詳細な説明】[Detailed description of the invention]
本発明は銀−パラジウム合金を内部電極とする
積層型磁器コンデンサに関するものである。
市販の積層型磁器コンデンサは薄層の磁器誘電
体の表面に内部電極を形成したものを複数枚積層
して一体焼成し、この側面に形成する外部接続用
電極に内部電極を交互に並列に接続するような構
造としている。
近時、この様な磁器コンデンサは内部電極とし
て一般に使われる貴金属であるパラジウム（pd）
単体のものに代り、銀−パラジウム合金（Ag−
pd）を使用するものがあり、内部電極材料コス
トの低減を図つている。
しかしながら、銀−パラジウム合金（Ag−pd）
は銀（Ag）の含有率が少ないと比抵抗値が高い
こと、また焼成中銀（Ag）が蒸発することによ
り電極を形成する金属の絶対量が低下して電極膜
が網目状となり面積抵抗が増大することによりコ
ンデンサ−の等価直列抵抗（ESR）が大きくな
るため、高周波回路では使用できない。
そこで、銀−パラジウム合金（Ag−pd）中の
銀（Ag）の含有量を多くして比抵抗値を低くす
ることが考えられるが、銀（Ag）の含有量を増
加させると金属の融点が低下して安定した積層型
磁器コンデンサが得られない。また電極間のマイ
グレーシヨン（電界による原子移動）による短絡
防止のため銀（Ag）の割合を増やすのには限界
がある。一方、焼成中の銀（Ag）の蒸発を見込
んで、予じめ誘電体グリーンシート上に付与する
銀（Ag）の量を増加させておくことは積層型磁
器コンデンサの構造的欠陥（クラツク又はデラミ
ネーシヨン）を招き実用に供さない。
本発明者等は上記の現状に鑑み鋭意研究の結果
積層型磁器コンデンサの誘電体中に銀（Ag）を
予じめ一定量含有させておくことによつて、又は
焼成中に銀が拡散により誘電体中へ浸入させる雰
囲気を強制的に利用した焼成方法（例えば埋め焼
き）によつて、電極及びコンデンサ全体の構造に
欠陥を生じることなく等価直列抵抗（ESR）を
低減させると共に静電容量が向上していることを
知見した。
したがつて、本発明においては銀−パラジウム
合金（Ag−Pd）を内部電極とする積層型磁器コ
ンデンサにおいて、その等価直列抵抗（ESR）
を低下させて、静電容量を向上させることにより
高周波回路においても使用できる安価な積層型磁
器コンデンサであり、温度補償用CG特性（JIS規
格において静電容量温度係数が±30ppm／℃の範
囲内であることが必要とされている）を有する積
層型磁器コンデンサを提供することを目的とす
る。
本発明によれば、銀−パラジウム合金（Ag−
Pd）を内部電極とする積層型磁器コンデンサに
おいて、この誘電体中に銀（Ag）が0.05〜0.70重
量％含有していることを特徴とする積層型磁器コ
ンデンサが提供される。
誘電体中に銀（Ag）を含有させると、内部電
極である銀−パラジウム合金（Ag−Pd）中の銀
（Ag）の蒸発作用を抑制することができる。誘電
体中の銀（Ag）の含有量が0.05重量％未満であ
ると銀（Ag）の蒸発を抑制する効果がないので
等価直列抵抗（ESR）を低減させることができ
ず、0.70重量％を超えると静電容量温度係数が−
30ppm／℃を大きく超えるため積層型磁器コンデ
ンサの一定の温度特性（CG特性と称し、VIS規
格において±30ppm／℃の範囲内であることが必
要とされている）に合致しない。
実施例 １
予じめBaCO3とTiO2の等モルから固相合成法
に依つて1200℃で作成した純度98.5％以上の
BaTiO3と純度98％以上のNd2O3と純度97.5％以
上の二酸化チタン（アナターゼ）、純度95％以上
のBi2O3及び純度95％以上のPb3O4をそれぞれ重
量で22.6％，31.6％，35.5％，4.71％及び5.59％を
加えたものに対して、B2O3，SiO2及びZrOをそ
れぞれ重量で0.50％，2.50％及び2.50％添加した
ものを基本組成とした。この基本組成に対して第
１表の銀（Ag）添加量欄に記載した量になるよ
うに試薬Ag2O粉末を秤量し添加して内容積1.6l
の磁製ポツト中に、カサ容積0.8l（1.5Kg）のアル
ミナボール（17mmφ）とともに入れ、さらに分散
剤，消泡剤とともに有機バインダー、可塑剤並び
に分散媒トルエンを加えて回転数72rpmで24時間
回転した。得られた原料スリツプをドクターブレ
ード法に依つて肉厚25μmのグリーンシートを成
形した。グリーンシートを25枚重ねてホツトプレ
スし、グリーン成形板を作成し約10mm角、厚さ約
0.50mmのグリーン角板に切断した。グリーン角板
をAAl2O3の製連鉢の中に入れ1050℃にて２時間
焼成した。得られた約８mm角、厚さ約0.4mmの角
板の上下面全面に銀電極を焼付けて、先ず角板の
誘電体自体としての評価試料１−１〜１−６を作
成した。こうして得られた１〜６の試料を周波数
1MHz、入力レベル1Vrmsにて静電容量（PF）及
び品質係数（Ｑ）（JIS規格によりＱ値は1000以上
必要とされている）並びに−55℃〜＋125℃の温
度範囲に於ける静電容量温度係数を測定した。静
電容量の測定結果から誘電体磁器の比誘電率
（εr）を計算し、品質係数（Ｑ）及び静電容量温
度係数の測定結果とともに第１表に示した。第１
表に示す誘電体中の銀（Ag）の含有率は原子吸
光分析法による定量結果である。
The present invention relates to a multilayer ceramic capacitor having internal electrodes made of a silver-palladium alloy. Commercially available multilayer ceramic capacitors have internal electrodes formed on the surface of thin ceramic dielectrics, which are laminated and fired together, and the internal electrodes are alternately connected in parallel to external connection electrodes formed on the side surfaces of the layers. The structure is such that These days, such ceramic capacitors are made of palladium (PD), a noble metal commonly used as the internal electrode.
Silver-palladium alloy (Ag-
PD) is used to reduce the cost of internal electrode materials. However, silver-palladium alloy (Ag-pd)
The specific resistance value is high when the silver (Ag) content is low, and the absolute amount of metal forming the electrode decreases due to the evaporation of silver (Ag) during firing, resulting in a mesh-like electrode film and a low sheet resistance. This increases the capacitor's equivalent series resistance (ESR), making it unusable in high-frequency circuits. Therefore, it may be possible to increase the silver (Ag) content in the silver-palladium alloy (Ag-pd) to lower the specific resistance value, but increasing the silver (Ag) content increases the melting point of the metal. As a result, a stable multilayer ceramic capacitor cannot be obtained. Furthermore, there is a limit to increasing the proportion of silver (Ag) in order to prevent short circuits due to migration (atom movement due to electric field) between electrodes. On the other hand, increasing the amount of silver (Ag) applied to the dielectric green sheet in advance in anticipation of evaporation of silver (Ag) during firing is recommended to prevent structural defects (cracks or delamination), making it unusable. In view of the above-mentioned current situation, the inventors of the present invention have conducted intensive research and found that by pre-containing a certain amount of silver (Ag) in the dielectric of a multilayer ceramic capacitor, or by causing silver to diffuse during firing. A firing method that forcibly utilizes an atmosphere that penetrates into the dielectric (for example, fill firing) reduces the equivalent series resistance (ESR) and increases the capacitance without causing defects in the electrodes or the overall structure of the capacitor. I found that it was improving. Therefore, in the present invention, in a multilayer ceramic capacitor having an internal electrode of silver-palladium alloy (Ag-Pd), its equivalent series resistance (ESR)
It is an inexpensive multilayer ceramic capacitor that can be used in high-frequency circuits by lowering the capacitance and improving the capacitance. An object of the present invention is to provide a multilayer ceramic capacitor having the following characteristics. According to the present invention, silver-palladium alloy (Ag-
A multilayer ceramic capacitor having Pd) as an internal electrode is provided, which is characterized in that the dielectric contains 0.05 to 0.70% by weight of silver (Ag). When silver (Ag) is contained in the dielectric, the evaporation effect of silver (Ag) in the silver-palladium alloy (Ag-Pd) that is the internal electrode can be suppressed. If the content of silver (Ag) in the dielectric is less than 0.05% by weight, there is no effect of suppressing the evaporation of silver (Ag), so the equivalent series resistance (ESR) cannot be reduced. If it exceeds, the capacitance temperature coefficient becomes −
Since it greatly exceeds 30ppm/°C, it does not meet the certain temperature characteristics (referred to as CG characteristics, which are required to be within ±30ppm/°C according to the VIS standard) of multilayer ceramic capacitors. Example 1 A sample with a purity of 98.5% or more was prepared in advance at 1200°C from equimolar amounts of BaCO 3 and TiO 2 by solid phase synthesis.
BaTiO 3 , Nd 2 O 3 with a purity of 98% or more, titanium dioxide (anatase) with a purity of 97.5% or more, Bi 2 O 3 with a purity of 95% or more, and Pb 3 O 4 with a purity of 95% or more, each 22.6% by weight, The basic composition was obtained by adding 31.6%, 35.5%, 4.71% and 5.59%, and 0.50%, 2.50% and 2.50% by weight of B 2 O 3 , SiO 2 and ZrO, respectively. To this basic composition, we weighed and added the reagent Ag 2 O powder to the amount listed in the silver (Ag) addition amount column in Table 1 to make an internal volume of 1.6 liters.
Alumina balls (17mmφ) with a bulk volume of 0.8L (1.5Kg) were placed in a porcelain pot, and an organic binder, plasticizer, and toluene dispersion medium were added together with a dispersant and antifoaming agent, and the mixture was heated at a rotation speed of 72 rpm for 24 hours. It rotated. The obtained raw material slip was formed into a green sheet with a wall thickness of 25 μm using a doctor blade method. Stack 25 green sheets and hot press to create a green molded board approximately 10mm square and approximately thick.
It was cut into 0.50mm green square plates. The green square plate was placed in a series of AAl 2 O 3 pots and fired at 1050°C for 2 hours. First, evaluation samples 1-1 to 1-6 were prepared as dielectrics of the rectangular plates themselves by baking silver electrodes on the entire upper and lower surfaces of the resulting rectangular plates of approximately 8 mm square and approximately 0.4 mm thick. Samples 1 to 6 obtained in this way are
Capacitance (PF) and quality factor (Q) at 1MHz, input level 1Vrms (Q value is required to be 1000 or more according to JIS standards) and capacitance in the temperature range of -55℃ to +125℃ The temperature coefficient was measured. The relative permittivity (εr) of the dielectric ceramic was calculated from the capacitance measurement results and is shown in Table 1 along with the quality factor (Q) and capacitance temperature coefficient measurement results. 1st
The silver (Ag) content in the dielectric shown in the table is a quantitative result by atomic absorption spectrometry.
【表】
試料１〜６は銀（Ag）の誘電体への添加量が
０〜2.0重量％範囲で選択されたもので、誘電体
中の銀（Ag）の含有率は0.006〜0.596重量％であ
る。これらの各試料の比誘電率（εr）は67.9以
上、品質係数（Ｑ）も2500以上、容量温度係数
（ppm／℃）も±30ppm／℃以内と夫々積層型磁
器コンデンサの誘電体として充分な特性を備えて
いることが理解される。尚、銀（Ag）の含有率
が0.050重量％以上の試料４〜６は比誘電率（εr）
が72.6以上と比誘電率が68.0の試料３と比べその
比誘電率（εr）が顕著に向上していることが分つ
た。この理由については明確でないが、Agの存
在が、チタン酸ネオジミウム（Nd2O3・2TiO2）
の結晶成長を選択的に抑制する為であると考えら
れる。
実施例 ２
次に実施例１で得た厚さ25μmのグリーンシー
ト材に有効面積約１mm2の角形パターンを用いて銀
（Ag）を70重量％、パラジウム（Pd）を30重量
％の合金に有機結合剤及びその溶剤を加えてなる
ペーストを印刷し、こうして得られた印刷膜を有
するグリーンシートを２枚重ね、さらに印刷膜を
有しないグリーンシートを上下に10枚ずつ重ね合
せて、ホツトプレスし、たて約2.5m／ｍよこ約
1.5m／ｍのグリーンチツプに切断する。こうし
て得られた一層の積層型磁器コンデンサを形成す
るグリーンチツプをアルミナ連鉢に入れて大気雰
囲気中で1050℃にて２時間焼成し、両端に銀−パ
ラジウム合金（Ag−Pd）による引き出し電極を
焼き付けて第２表の評価試料７〜12を得た。
静電容量及び静電容量温度係数は周波数1MHz
で、等価直列抵抗値は周波数900MHzで測定し、
測定器はLCRメータ及びインピーダンスアナラ
イザを用いた。誘電体中の銀（Ag）の含有率は
XMA法（Ｘ線マイクロアナライザ法）による定
量結果を示す。これらの特性を試料７〜12と共に
に第２表に示す。[Table] In samples 1 to 6, the amount of silver (Ag) added to the dielectric was selected in the range of 0 to 2.0% by weight, and the content of silver (Ag) in the dielectric was 0.006 to 0.596% by weight. It is. The relative dielectric constant (εr) of each of these samples is 67.9 or higher, the quality factor (Q) is 2500 or higher, and the capacitance temperature coefficient (ppm/℃) is within ±30ppm/℃, which are sufficient as dielectric materials for multilayer ceramic capacitors. It is understood that it has certain characteristics. In addition, samples 4 to 6 with a silver (Ag) content of 0.050% by weight or more have a relative dielectric constant (εr)
It was found that the relative permittivity (εr) was 72.6 or more, which was significantly improved compared to Sample 3, which had a relative permittivity of 68.0. The reason for this is not clear, but the presence of Ag may cause neodymium titanate (Nd 2 O 3 2TiO 2
It is thought that this is to selectively suppress the crystal growth of. Example 2 Next, using a square pattern with an effective area of about 1 mm 2 on the 25 μm thick green sheet material obtained in Example 1, an alloy containing 70% by weight of silver (Ag) and 30% by weight of palladium (Pd) was formed. A paste made by adding an organic binder and its solvent is printed, two green sheets with the thus obtained printed film are stacked, and ten green sheets without the printed film are stacked one above the other, and then hot pressed. , height approx. 2.5m/width approx.
Cut into 1.5m/m green chips. The green chips forming the single layered ceramic capacitor obtained in this way were placed in an alumina pot and fired at 1050°C for 2 hours in the air, and lead electrodes made of silver-palladium alloy (Ag-Pd) were attached to both ends. After baking, evaluation samples 7 to 12 in Table 2 were obtained. Capacitance and capacitance temperature coefficient at frequency 1MHz
The equivalent series resistance value is measured at a frequency of 900MHz,
The measuring instruments used were an LCR meter and an impedance analyzer. The content of silver (Ag) in the dielectric is
Quantitative results using the XMA method (X-ray microanalyzer method) are shown. These properties are shown in Table 2 along with samples 7-12.
【表】
＊印の試料は本発明の範囲外である。
試料７〜12は試料１〜６の誘電体を使用するも
ので、この誘電体を積層した結果、銀（Ag）の
含有率が0.01〜0.60重量％となる。これらの各試
料の容量温度係数は±30ppm／℃の範囲内である
が、銀（Ag）の含有量が0.05未満である試料７
〜９の等価直列抵抗値は1870±290mΩ以上であ
るのに対し、銀（Ag）の含有量が0.05以上であ
る試料10〜12の等価直列抵抗値は283±63mΩと
その特性が向上した。その結果静電容量も試料７
〜９が20.56PF以下であるのに対し、試料10〜12
は25.33以上と向上していることが理解される。
各試料７〜９と試料10〜12を切断して誘電体間の
内部電極を観察したところ、試料７〜９に比べ試
料10〜12の誘電体間の内部電極は厚みが充分確保
されており、焼成中に銀（Ag）の蒸発が抑制さ
れていることを確認した。
実施例 ３
次に、前記実施例中の試料６及び12以上の銀
（Ag）を含有率を有する誘電体を作成するために
は、銀（Ag）の添加量が銀の含有率と比例して
増大せず飽和する傾向があるので、Al2O3100重
量部に対してAg2O5.0重量部（Ag4.65重量部）の
両者を混合して成る混合粉をAl2O3製容器に入
れ、この混合粉中に実施例１における試料１を埋
め込んで1050℃にて２時間焼成した。実施例１と
同様に焼成した角板に銀（Ag）電極を焼付けて
角板型コンデンサを作成し、評価試料13を得た。
こうして得られた試料13を実施例１と同様に評
価した結果を第３表に示す。尚、誘電体中の銀
（Ag）の含有率については原子吸光分析法によつ
た。[Table] Samples marked with * are outside the scope of the present invention.
Samples 7 to 12 use the dielectrics of Samples 1 to 6, and as a result of laminating these dielectrics, the silver (Ag) content is 0.01 to 0.60% by weight. The capacitance temperature coefficient of each of these samples is within the range of ±30 ppm/℃, but sample 7 with a silver (Ag) content of less than 0.05
The equivalent series resistance value of Samples 1 to 9 was 1870±290 mΩ or more, whereas the equivalent series resistance value of Samples 10 to 12, in which the silver (Ag) content was 0.05 or more, was 283±63 mΩ, which showed improved characteristics. As a result, the capacitance of sample 7
~9 is less than 20.56PF, while samples 10~12
It is understood that this has improved to 25.33 or higher.
When we cut each of Samples 7 to 9 and Samples 10 to 12 and observed the internal electrodes between the dielectrics, we found that the internal electrodes between the dielectrics in Samples 10 to 12 had a sufficient thickness compared to Samples 7 to 9. It was confirmed that evaporation of silver (Ag) was suppressed during firing. Example 3 Next, in order to create a dielectric material having a silver (Ag) content of 12 or more as in Sample 6 in the above example, the amount of silver (Ag) added must be proportional to the silver content. Therefore, a mixed powder consisting of 100 parts by weight of Al 2 O 3 and 5.0 parts by weight of Ag 2 O (4.65 parts by weight of Ag) is used to make Al 2 O 3. The mixed powder was placed in a container, and Sample 1 in Example 1 was embedded in this mixed powder and baked at 1050°C for 2 hours. A square plate type capacitor was prepared by baking a silver (Ag) electrode on a fired square plate in the same manner as in Example 1, and evaluation sample 13 was obtained. Sample 13 thus obtained was evaluated in the same manner as in Example 1, and the results are shown in Table 3. The content of silver (Ag) in the dielectric was determined by atomic absorption spectrometry.
【表】
銀（Ag）の含有率0.70重量％の誘電体は、比
誘電率（εr）80.8品質係数（Ｑ）が1000以上及び
容量温度係数（ppm／℃）は±30ppm／℃の範囲
内と充分である。
実施例 ４
前記実施例３で記載したAl2O3とAg2Oの混合
粉中に実施例２の試料７及び12の積層型磁器コン
デンサグリーンチツプを埋め込んで1050℃で２時
間焼成したのち実施例２と同様に引き出し用電極
として銀−パラジウム合金（Ag−Pd）をチツプ
の両端に焼付けた評価用試料14及び15を得た。実
施例２と同様の方法に依つて評価した結果を第４
表に記載する。尚、実施例２と同様にXMA法に
よつて各試料の誘電体における銀（Ag）の定量
を行つた。[Table] A dielectric material with a silver (Ag) content of 0.70% by weight has a relative dielectric constant (εr) of 80.8, a quality factor (Q) of 1000 or more, and a capacitance temperature coefficient (ppm/℃) within the range of ±30ppm/℃ That is sufficient. Example 4 The green chips of laminated porcelain capacitors of Samples 7 and 12 of Example 2 were embedded in the mixed powder of Al 2 O 3 and Ag 2 O described in Example 3 and fired at 1050°C for 2 hours. Similarly to Example 2, evaluation samples 14 and 15 were obtained in which silver-palladium alloy (Ag-Pd) was baked on both ends of the chip as extraction electrodes. The results evaluated using the same method as in Example 2 were evaluated in the fourth example.
Record in the table. Incidentally, as in Example 2, silver (Ag) in the dielectric of each sample was determined by the XMA method.
【表】
＊印の試料番号は本発明の範囲外である。
試料番号14は銀（Ag）の含有率が0.69重量％
で本発明の範囲内であり等価直列抵抗値（mΩ）
は158±6mΩで前記実施例中本発明の範囲外の試
料７〜９と比較して著じるしく低く、また静電容
量（PF）も27.96PFと充分であり、また容量温度
係数も−23ppm／℃と所定の温度特性（±
30ppm／℃）範囲を満たしている。
これに対し試料15は銀（Ag）の含有率が0.74
重量％で本発明の上限である銀（Ag）の含有率
0.70を超えており、等価直列抵抗値（mΩ）及び
静電容量（PF）は充分であるが容量温度係数が
−47ppm／℃と所定の温度特性（±30ppm）の範
囲内を維持できない。
叙上の如く本発明は銀−パラジウム合金（Ag
−Pd）を内部電極とする積層型磁器コンデンサ
において、この磁器誘電体中に銀（Ag）が0.05
〜0.70重量％含有させたものであり、誘電体の等
価直列抵抗（ESR）を低下させて、静電容量を
向上させることにより高周波回路においても使用
できる安価な積層型磁器コンデンサを提供するこ
とができる。[Table] Sample numbers marked with * are outside the scope of the present invention.
Sample number 14 has a silver (Ag) content of 0.69% by weight
is within the scope of the present invention and the equivalent series resistance value (mΩ)
is 158±6 mΩ, which is significantly lower than Samples 7 to 9 which are outside the scope of the present invention, and the capacitance (PF) is also sufficient at 27.96 PF, and the capacitance temperature coefficient is - 23ppm/℃ and specified temperature characteristics (±
30ppm/℃) range. On the other hand, sample 15 has a silver (Ag) content of 0.74.
Silver (Ag) content which is the upper limit of the present invention in weight%
It exceeds 0.70, and although the equivalent series resistance value (mΩ) and capacitance (PF) are sufficient, the capacitance temperature coefficient is -47 ppm/°C, which cannot be maintained within the specified temperature characteristic (±30 ppm) range. As mentioned above, the present invention utilizes a silver-palladium alloy (Ag
-Pd) as an internal electrode, silver (Ag) is present in the ceramic dielectric by 0.05%.
It contains ~0.70% by weight, and by lowering the equivalent series resistance (ESR) of the dielectric and improving capacitance, it is possible to provide an inexpensive multilayer ceramic capacitor that can be used even in high-frequency circuits. can.