Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/9938
標題: A Study of Low Temperature Cofiring of Microwave Multilayer Dielectric Ceramics
低溫共燒微波積層介電陶瓷之研究
作者: Lee, Ying-Chieh
李英杰
關鍵字: 微波陶瓷;Microwave ceramics;介電常數;溫度係數;積層陶瓷電容器;介電損失;Q value;temperature coefficient;MLCC;Dielectric constant;Dielectric loss;ZnMgTiO3;Ba2Ti9O20
出版社: 材料工程學研究所
摘要: 
Ba2Ti9O20微波介電陶瓷因具有優良的介電特性,包括低共振頻率溫度係數,高介 電常數高品質因子;但其缺點是在製程中不易以固態法反應獲得純Ba2Ti9O20相。本文 以 添加不同 比例的氧化鋅硼 (ZnBO) 和氧化硼 (B2O3) 之燒結助劑到 Ba2Ti9O20 陶瓷,研究此材料系統之微波介電性質,緻密性,顯微組織,及相結構的影響,而且燒結溫度是控制在900°到960°C。 對於ZnBO的添加, 最佳介電性質為添加 1 wt% ZnBO 的 Ba2Ti9O20 陶瓷在空氣中燒結且燒結溫度是940°C/2 小時:其Q值= 1137 、 er值 = 27.3 、 tf = 2.5 ppm/°C。另外對於B2O3的添加,最佳介電性質為添加3wt%B2O3的Ba2Ti9O20 陶瓷 在空氣中燒結且燒結溫度是 940°C/2小時: 其Q值 = 1477 、er值 = 28.3、tf = -8.2 ppm / °C。
在Ba2Ti9O20陶瓷添加 ZnBO 或 B2O3的實驗過程中,我們發現 BaZr(BO3)2相是隨 著燒結助劑的量之增加而增加。我們利用固態法將個別BaO、ZrO2和B2O3原材料依莫耳 比混合後,經鍛燒製備成BaZr(BO3)2相。從電子顯微鏡分析此材料之微結構,可以得知 BaZr(BO3)2晶粒成長是形成樹枝狀結構。在介電性質方面,介電損失對燒結溫度之關係 似乎是呈線性關係。如在溫度1080°C時,介電損失為8500。而在溫度1250°C時,介電 損失降低到801左右。但是介電常數 對燒結溫度之關係是 保持 非常小變動。
在另外的材料主題是探討添加 ZnBO 對於 Zn0.95Mg0.05TiO3 + 0.25TiO2 (ZMT’) 陶瓷材料之微結構及微波介電性質的變化,而且燒結溫度是控制在860°到940°C。研究結果發現只添加1wt% ZnBO 就可明顯改善此材料的緻密性和微波介電性質,且在 900°C 燒結其燒結緻密性可達理論密度的 95%。在 900°C 及2小時的燒結,對1wt% ZnBO 的 ZMT’ 陶瓷,其介電性質εr值為23.6、Q× f 值為 30990 (at 7.75 GHz) 和 t f 值為 —8 ppm/°C。
本文亦針對 Bi2O3 的添加到ZnBO-ZMT’陶瓷, 變化 Bi2O3 的添加量及控制燒結 溫度從 860 到 920°C來探討其燒結緻密性、介電特性、相變化及微結構。對於 5 wt% Bi2O3 添加 ZnBO-ZMT’ 陶瓷,有著較佳的介電性質:Q = 517、er值 =24.5、和tf = -14ppm / °C。此外,從 XRD 分析的結果顯示 ZnBO-ZMT’ 陶瓷 添加5wt% Bi2O3 時,Zn2TiO4 相沒有被形成從860°到960°C的溫度範圍,甚至燒結溫度 在960°C 亦沒有 發現Zn2TiO4的存在。比較到之前的實驗,在沒有添加Bi2O3時、 Zn2TiO4、相是被發現 在 燒結 溫度 920°C的試片。 所以 吾人相信 Bi2O3的添加可以抑制Zn2TiO4 相的形成。
(3) 內電極與端電極
在積層陶瓷電容內電極的研究,們選用不同銀鈀比例的金屬當內電極,例如Ag80- Pd20、Ag90Pd10、Ag95Pd05和純銀等。搭配B2O3-Ba2Ti9O20和ZnBO-ZMT’陶瓷材料 系統,製備成積層陶瓷電容器。探討不同銀鈀比例之內電極及不同材料對電的性質和高頻特性的相關性。從掃描式電子顯微鏡的線掃描(line-scan)分析在B2O3-Ba2Ti9O20 積層 陶瓷電容器的內電極之間的介電層,並沒有觀察到明顯Ag信號出現。這些內電極包括 Ag80Pd20、Ag90Pd10、Ag95Pd05 和 Ag,他們是被燒結在940°C/2小時。
在積層陶瓷電容與端電極共燒的研究,我們改變傳統MLCC製程方式,先預燒 積層陶瓷電容器 (MLCC) 生胚後再與端電極一起共燒。選用的端電極材料分別為銀金 屬加上不同的陶瓷粉末(20%、30%和40%)。因是900°C低溫共燒,所以材料系統是選用ZnBO-ZMT’陶瓷來搭配製備成積層陶瓷電容器。探討不同比例陶瓷粉末的添加之端電 極對電的性質和機械性質的影響。
在薄膜端電極的研究,將MLCC之熱處理製程方式改變,由薄膜端電極取代傳統的燒銀端電極。沉積薄膜端電極方式是使用真空濺鍍設備,其靶材是銀,鈦和鉻金屬。 實 驗發現鈦或鉻金屬當陶瓷體與薄膜Ag之中間層,可大大的提昇薄膜端電極附著在陶瓷體上的機械強度,而且附著強度與傳統端銀電極添加玻璃材料助燒的結果是一樣。此 外。 吾人亦探討薄膜 端電極對MLCC電的性質和高頻特性的影響。

Boron oxide and zinc oxide (ZnBO) added in dielectric materials have drawn great attention recently due to the capability of lowing the firing temperature. Microwave dielectric properties of the Ba2Ti9O20-based ceramics with ZnBO addition up to 3 wt% and B2O3 addition up to 5 wt% were investigated at sintering temperatures ranging from 900 to 960°C. Effects of the ZnBO additions on the bulk density, microstructure, and dielectric properties of the Ba2Ti9O20-based ceramics at microwave frequency are elucidated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and various dielectric measurements. Optimum dielectric properties were obtained for the Ba2Ti9O20-based ceramic with 1 wt% ZnBO and B2O3 addition sintered in air at 940°C for 2 h, with the dielectric properties: Q = 1137, er = 27.3, and tf = 2.5ppm / °C for ZnBO addition. Q = 1477, er = 28.3, and tf = -8.2 ppm / °C for BO3 addition.
The BaZr(BO3)2 phase was found in the Ba2Ti9O20-based ceramics with ZnBO or B2O3 additions as sintering aids. It was synthesized by conventional solid-state methods from BaO, ZrO2 and B2O3 powders. Scanning electron microscopy shows that the BaZr(BO3)2 grains prefer to develop an oriented dendritic microstructure. Dielectric loss of the ceramic decreases approximately linearly with the sintering temperatures from 8500 (1080°C) to 801 (1250°C).
The effect of ZnBO additions up to 2 wt% on the microstructure and microwave dielectric properties of zinc magnesium titanate Zn0.95Mg0.05TiO3 + TiO2 (ZMT') ceramics was investigated at the sintering temperatures ranging from 860° to 940°C. It was found that low level of ZnBO addition (1 wt%) can significantly increase the density and microwave dielectric properties of ZMT' ceramics. Doped ZMT' ceramics can be sintered to a theoretical density higher than 95% at 900°C. The dielectric properties of the ZMT' ceramics with 1 wt% ZnBO addition sintered at 900°C for 2 h were measured to be er = 23.6, Q » 4000 and tf = -8ppm/°C.
The effect of Bi2O3 additions up to 10 wt% on the sintering characteristics of the ZMT' ceramics with 1 wt% ZnBO addition was investigated at the sintering temperatures ranging from 860 to 920°C. The ZnBO-ZMT' ceramic with 5 wt% Bi2O3 addition exhibits the optimum dielectric properties: Q = 517, er = 24.5, and tf = -14ppm / °C. ZnBO-ZMT' ceramic with Bi2O3 additions show no Zn2TiO4 (spinel phase) existence at 960°C sintering. It is, therefore, believed that the addition of Bi2O3 can suppress the formation of Zn2TiO4 in the ZnBO-ZMT' ceramics.
For the inner electrodes study, different Ag/Pd ratios were prepared for MLCCs made of Ba2Ti9O20 and ZMT' ceramics. The electric properties and high frequency characteristics of the MLCCs with different Ag/Pd ratios of inner electrodes were investigated. The microstructure of the MLCCs with different inner electrodes was studied by scanning electron microscopy along with energy-dispersive spectroscopy (EDS).
For the co-firing study, the green chips with end terminations were sintered at 900°C. There is no extra curing process, so the production cost can be cut down and thermal shock of the MLCCs can be reduced. The termination paste with different amounts of ceramics, e.g. 20%, 30%, and 40%, was co-fired with the dielectric body. The mechanical and electric properties of the MLCCs were investigated subsequently.
For the thin film end terminations, the purpose is to replace the conventional Ag paste by thin film terminations prepared by sputtering deposition. In addition to pure Ag, Ti/Ag and Cr/Ag were deposited on MLCCs as the end terminations. It was found that the adhesion of the end termination to the ceramic body could be improved for the Ti/Ag and Cr/Ag systems, whereas the dielectric properties are slightly degraded.
URI: http://hdl.handle.net/11455/9938
Appears in Collections:材料科學與工程學系

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