積層式氧化鋅變阻器之製備與電性研究

Abstract

影響積層式氧化鋅變阻器電特性的因素有 (1)所添加陶瓷粉末性質 (2)薄 帶形成過程中所添加有機物比例以及 (3)在燒結過程中燒結曲線是否適 當. 特性好的添加玻璃之氧化鋅陶瓷粉末主要取決於尖晶石相(Spi- nel) 和矽鋅礦相(zinc-silicate)的含量, 前者代表了變阻器的穩定度,後者則 意味著變阻器的漏電流多寡. 經由調整煆燒流程以加強它們的含量. 實驗 證實煆燒在600C持溫10個小時可得最佳陶瓷粉末.所添加之有機物的比例 是否適當可將薄帶作有機燒盡處理以觀察陶缺陷密度和氧化鋅晶粒之分佈 是否均勻來作判斷. 一般不論酒精含量多寡陶瓷粉體均會產生結團現象. 陶瓷粉體將因結團而沉積在薄帶底部,因而造成薄帶的不均勻. 陶瓷粉體 佔整個添加物比重多寡影響了薄帶的緻密性. 這種緻密性的程度亦會影響 陶瓷粉體分佈的均勻性. 實驗測得 55Wt%的陶瓷粉體比例可得最佳均勻狀 態. 不均勻的薄帶是日後燒結完成後孔洞的主要來源. 同時實驗也證明了 不同的燒結曲線對於孔洞分佈,大小以及多寡亦有相當影響. 而這些孔洞 在電性量測上將使得原本三段式的電流-電壓曲線在前崩潰區和崩潰區間 多了一段線性區. 我們相信此線性區是來自於外在濕氣與元件內部孔洞結 和而成一串聯電阻所造成. 藉由改變濕度, 由相對濕度15%下停留4個小時 到相對濕度95%下停留1個小時, 來證實這個論點. 當然這實驗是在固定溫 度(25C)下進行. 由於分佈位置不同, 這些孔洞可歸納成類似開孔洞與類 似閉孔洞兩種. The electrical characteristics of multilayer chip ZnO varistor are widely influenced by the property of ceramic powder the amount of organic component additives and the firing schedule of the process of fabrication. The different combinations of calcined temperature and retained time were employed to obtain suitable ceramic powder for sintering process. Spinel phase is enhanced in the samples which are calcined at 600C for 10hrs and 700C for 2hrs, respectively. Zinc-silicate glass was crystallized in the sample calcined at 600C for 10hrs and the electrical characteristics of the samples are imploved at the same time. The microstructure of the green tape after binder burn-out treated are affected by unsuitable amount of orgranic components additives. It reveals that the unsuitable amount of alcohol additive would induce the aggregation of ceramic powder and destroy the uniformity of green tape. The content of ceramic powder in the slurry influences the density of green tape, and it also decides the level of uniformity of green tape. The non- uniformity green tape is the main reason of pores formed. However, the different sintering profiles would affect the distribution, the size and the density of pores in the samples. Through the distribution of these pores, they can be distinguished from two types, one is like-open pores the other is like-close pores. This phenomenon will lead to large leakage current of device on working condition and express a linear region on I-V characteristics. By way of the examination of varying environment, such as from a low relative humidity (r. h.) (15%) for 4hrs to high r.h. (95%) for 1hr at fixed temperature (25C), we can verify that the linear region attributes to the inside pores associated with outside moist.