Study on the Termination Electrode of Multi-Layer Ceramic Capacitor using Sputtering Copper Thin Film

[[abstract]]本實驗針對積層陶瓷電容器(MLCC)端電極利用DC磁控濺鍍法沈積銅膜，基材為鈦酸鋇(BaTiO3)具有MLCC介電材料Class II-X7R的特性。以實驗設計法做實驗規劃，進行薄膜濺鍍參數實驗及薄膜退火處理實驗，量測其附著力、膜厚、電阻率，評價銅膜與基材的可靠性，由兩實驗結果選擇適合的製程條件，製造積層陶瓷電容器之端電極使用濺鍍與浸鍍的比較。實驗之目的是利用濺鍍沈積的技術，來改善浸鍍技術的缺陷，使MLCC的端電極薄膜化且具有較佳的平坦尺度、良好的電鍍層及可焊性，應用於積層陶瓷電容器端電極的薄膜化。 由實驗結果得之銅薄膜退火處理後會使電阻率下降，在長時間與溫度的退火處理氣氛下導致鈦酸鋇(BaTiO3)的分解，在BaTiO3的表面上導致TiO2的形成，且當在氣氛條件退火時，會導致部份的銅膜氧化導致Cu2O的形成，TiO2與Cu2O形成鬆散結構，使銅電極與介電質的鈦酸鋇附著力下降。使用濺鍍法沈積銅膜能和MLCC之內電極接合；電鍍後的Ni層與Sn層具有良好的鍍層；電性方面具有較小的散逸因子(D.F)，其平均值為1.41E-02或Tanδ之損失角δ= 0.8078；而浸鍍Cu厚膜的平均值為1.79E-02，損失角δ= 1.025。焊性附著力及端電極拉力試驗皆附合MLCC標準規格；具有較佳的平坦尺度與薄膜化。實驗證明積層陶瓷電容器(MLCC)之端電極應用濺鍍沈積銅膜的可行性。[[abstract]]This research investigates the copper thin film termination electrode of multi-layer ceramic capacitor (MLCC) prepared by using DC magnetron sputtering. The substrates are barium titanates (BaTiO3) MLCC, which possess the Class II-X7R specification. The experimental design adopts the central composite design (CCD) to carry out the sputtering and annealing parameters. The adhesion, thickness and resistivity of Cu termination are measured to evaluate the reliability between Cu thin film and substrate. The comparison of the termination electrodes of MLCC prepared by either sputtering or dipping is also made. The purpose of the experiment is to improve the defects, produced by dipping technique through the sputtering technology. The improvement of Cu termination electrodes results in better surface smoothness, excellent plating layer and solderability, making Cu thin film applicable to MLCC termination electrode. The experimental results show that the resistivity of Cu termination electrode decreases after annealing. The long-term annealing at high temperature in air atmosphere may leads to the partial decomposition of barium titanates, resulting in the occurrence of TiO2 on the surface of BaTiO3. Moreover, the formation of Cu2O is due to partial oxidation of Cu when annealing in air conditions. The loose structure between Cu2O and TiO2 reduces the adhesion of Cu electrode and barium titanates (BaTiO3) dielectric. The Cu thin film termination electrode well attaches to the inner electrode. After electroplating, the excellent Ni and Sn plating layers are obtained due to the better smoothness of Cu termination. The MLCC with Cu thin film termination electrode has a lower dissipation factor(D.F), Its average value is 1.41E-02 or Tanδof loss angle is 0.8078, but dissipation factor of average value is 1.79E-02 or Tanδof loss angle is 1.025 using dipping Cu thick film. The soldering adhesion and pull strength can meet the MLCC standard specification. The experiment proves the feasibility of copper thin film termination electrode of MLCC by using sputtering technique