- 學位論文
低介電常數CaO-B2O3-SiO2玻璃陶瓷 之特性研究
Formulation/Microstructure/Relations for CaO-B2O3-SiO2 Glass Ceramics
摘要
在多種低溫共燒陶瓷玻璃陶瓷系統中，鈣硼矽系統(CaO-SiO2-B2O3)常被用於微波電子元件及微電子封裝，因為其低材料成本、低燒成溫度和低介電常數等優點已成為具有潛力的玻璃陶瓷，然而，利用鈣硼矽玻璃陶瓷作為LTCC基板在應用上仍有許多尚待克服的問題，包括製程容許度太窄、組織對氧氣很敏感、與電極共燒不穩定及與其他內埋元件之匹配性差等。所以因應低溫共燒陶瓷實際應用之需要，必須對鈣硼矽玻璃陶瓷更深入了解，包括玻璃陶瓷的組成、燒成條件、微結構與其物理性質之關聯性，以便用來提昇製程上之穩定性。 本研究之目的除了探討CBS玻璃(CaO-SiO2-B2O3系統)之組成、製程及其物理性質之關聯性外，同時對於相同成分之玻璃。利用高低軟化點玻璃進行雙玻璃混合製程及單一玻璃製程燒結特性、物性及化性之影響。然後以高低軟化點玻璃 透過修飾劑及填充材的添加，探討其燒結行為及其物性及化性。最後從本研究中；擇一適當玻璃陶瓷實際作成晶片天線，驗證應用於微波天線之可行性。 研究結果顯示：CBS玻璃之組成配比與其熱性質及介電性質有關。大多數玻璃的軟化點是從672至723oC。高CaO之玻璃具有高介電常數之趨勢(7~8)，燒結後之主要結晶相為CaSiO3相。高SiO2之玻璃具有低介電常數之優點(4~5)但須提高B2O3之含量以降低燒結溫度，需添加填充劑或修飾劑預防燒結時方石英(Cristobalite)之生成。各玻璃配方中50.1CaO–7.3B2O3–42.6SiO2 (CBS-10)玻璃陶瓷是低溫燒結玻璃陶瓷基材，原因是其燒結緻密溫度低於850oC，在4.3 GHz其介電常數為6，介電損耗為0.0014，適用於用微波領域。CBS-9具有低的介電常數（3.8），低的介電損失（0.0017），其熱傳導係數為1.1 W/mK，電阻值為25.8×1011 Ω，熱膨脹係數為3.2 ppm/°C，但是因是其燒結緻密溫度為1035oC，適當的添加填充劑或修飾劑可以改變其功能特性，在微波應用領域有良好之特性。 高低軟化點CBS-950複合玻璃之設計，是利用高溫玻璃10.5CaO–22.2B2O3– 67.3SiO2 (CBS-9)作為基材，並使用低溫玻璃45CaO–31.7B2O3–23.3SiO2 (CBS-4)扮演燒結助溶劑，以低溫(800~900oC)燒結獲得高密度及高強度之基板。設計上選用同系列高低軟化點玻璃系統，可避免填充材料與玻璃產生複雜反應。同時將 27.8CaO–27B2O3–45.3SiO2 (CBS-950)複合玻璃及相同組成之單一玻璃27.8CaO–27B2O3–45.3SiO2 (CBS-11)在相同條件下燒結，CBS-11單一玻璃與CBS-950複合玻璃主要之差異為CBS-11由純非晶質玻璃呈現，隨著燒結溫度之升高結晶相逐步成長，於開始結晶初期階段達到燒結緻密點，其結晶相為CaB2O4及SiO2 (Tridymite)相，緻密燒結之溫度降低了25oC與商用LTCC玻璃基板材料之燒結溫度相近， CBS-950複合玻璃燒結過程中有CaSiO3及SiO2 (Cristobalite)相參與反應，其燒結停止收縮溫度範圍較為寬廣最終收縮率為18.8%有利於製程寬裕度之改善，相同之處是整體之介電特性顯示一致之結果，此外兩種玻璃燒結緻密後之主結晶相，同為CaB2O4及 SiO2（Tridymite）。 進一步探討添加填料、潤濕劑、及成核劑對複合玻璃CBS-950之影響，添加劑Li2CO3（1wt％）顯著將緻密化溫度由875 oC降至800oC，有促進石英及CaB2O4結晶成長之功能。填充劑Al2O3（大於30wt％）可以抑制Li4B2O5產生、阻止石英相及CaB2O4相結晶成長及調整製程寬裕度之作用，且有不參與化學反應之優點。添加TiO2（約0.3wt％）會抑制方石英相之生成，會穩定石英相及CaB2O4相。 利用CBS-10製成小型化曲折單極晶片天線，天線型態是由曲折狀之電極線所構成，是應用電容負載原理減短為1/4波長之設計，達到縮小天線尺寸之結果，天線設計之中心頻率為1.575 GHz，其頻寬約100MHz，實際晶片天線尺寸為10 mm×10mm × 2(mm)，使用在1.575 GHz 頻率時具有全方向的場型，天線駐波比(VSWR)為1.5，符合實際應用，駐波比應小於2之標準，並具有良好之指向性功能，其增益的變動量為2.058~3.154 dBi。實作天線之反射損耗小於-12dB，合乎商用天線小於-10dB之特性，適用於小型化通訊產品。
並列摘要
Among a variety of LTCC glass-ceramic systems available, calcium boron silicon system (CaO-SiO2-B2O3) is often used in microwave electronic components and microelectronic packaging, because of its low cost, low sintering temperature and low dielectric constant, etc. It has become a potential advantage of the glass-ceramic to use calcium with boron and silicon substrates in the application of LTCC. However, there are still many problems to be overcome, including the too narrow range of processing, the very sensitive organization of oxygen, and the electrodes being burned and buried within due to the instability and mismatch with other components. So in response to practical applications of LTCC, there is a need for in-depth understanding of calcium silicate boron glass-ceramic, including the composition of glass-ceramic, firing conditions, the micro-structure and the physical nature of the relevance that could be used to enhance the process stability. The purpose of this study is to understand the glass-ceramic CBS (CaO-SiO2-B2O3 system) in terms of its composition, processing etc. in addition to its physical nature of relevance with the same composition of the glass. The high and low softening points of glass were modified through the addition of filling materials and their sintering behavior and resistance were also explored. Finally, this study optimizes an appropriate making of the actual glass-ceramic chip antenna and verifies its feasibility of application in microwave antennas. The results showed that: CBS glass composition proportionally matches with its thermal properties and the dielectric nature. Most of the glass softening points are from 672 to 723oC. The high CaO glass with high dielectric constant trend (7-8), gets sintered after the main crystallization phase of CaSiO3. The high SiO2 glass has an advantage (4-5) of low dielectric constant but B2O3 content has to be raised in order to reduce the sintering temperature. The need to add a filler to modify or prevent sintering, has led to quartz (Cristobalite) generation as well. The glass-ceramic with formula 50.1CaO-7.3B2O3-42.6SiO2 (CBS-10) is a low-temperature sinterable glass-ceramic substrate. The reasons for obtaining a dense ceramic with a sintering temperature below 850 oC, at 4.3 GHz are (i) its dielectric constant which was 6, (ii) dielectric loss that was 0.0014 and hence it is applicable to the use of microwave field. CBS-9 has a low dielectric constant (3.8), a low dielectric loss (0.0017), a thermal conductivity of 1.1W/mK, a resistance value of 25.8 × 1011 Ω, a coefficient of thermal expansion of 3.2 ppm /°C, but because of its dense sintering temperature of 1035oC, an appropriate filler should be added that can change or modify its features, and therefore will have good characteristics in microwave applications. High Low softening point CBS-950 composite glass is designed by using a high-temperature glass 10.5CaO-22.2B2O3-67.3SiO2 (CBS-9) as a substrate and a low-temperature glass 45CaO-31.7B2O3-23.3SiO2 (CBS-4) as a sintering aid to lower the temperature (800 ~ 900 oC) of sintering across the high-density and high strength of the substrate. Selection of the glass design makes use of high and low softening point, in the same series of glass systems, to avoid the filling material’s reaction with the glass. Under the same conditions of sintering, a glass-ceramic of composition 27.8 CaO-27B2O3-45.3SiO2 (CBS-950) and a single glass of same composition 27.8 CaO-27B2O3-45.3SiO2 (CBS-11) are examined. The main difference of the glass-ceramic CBS-950 with that of pure amorphous glass CBS-11 is that the CBS- 11 is a pure non-crystal glass and as the sintering temperature is gradually increased the crystallization increases resulting in densely sintered material with the formation of CaB2O4 and SiO2 (Tridymite) phases. There is a reduction of 25oC sintering temperature compared to the sintering temperature of commercial LTCC glass substrate materials. In the CBS-950 composite glass sintering process, the reaction between CaSiO3 and SiO2 (Cristobalite) is involved and their sintering has broad temperature range of contraction, with final contraction rate of 18.8 %. This is conducive to the improvement of the process window, similar to the overall dielectric properties which showed consistent results, in addition to sintering of dense glass after crystallization of the main phase from CaB2O4 and SiO2 (Tridymite). To explore further we added fillers, wetting agents, and nuclear agents into the composite glass CBS-950. The impact of additive Li2CO3 (1wt%) is that densification temperature has significantly reduced from 875 oC to 800 oC by promoting the growth and function of CaB2O4 and quartz crystals. Fillers like Al2O3 (greater than 30 wt%) can inhibit the Li4B2O5 formation and impede the crystallization of CaB2O4 phase and quartz crystal growth. However it regulates the process in the well-off role, and does not involve in the merit of chemical reactions. Addition of TiO2 (about 0.3 wt%) will inhibit the formation of cristobalite but keeps the quartz phase and CaB2O4 phase stable. CBS-10 was used to make miniatured unipolar chip antenna. It consists of a meander electrode wire and a capacitive loading principle is used in its design by applying 1/4 wavelength. To reduce the resulting antenna size, the central frequency of antenna design is kept at 1.575 GHz, with its bandwidth of about 100 MHz. The actual size of the chip antenna is 10 mm × 10mm × 2 mm and by using the frequency of 1.575 GHz, the Omni-direction of the field pattern makes the antenna standing wave ratio (VSWR) to be 1.5. For practical applications, the standing wave ratio should be less than 2 and have a good point of omni-direction, to gain the change of 2.058 ~ 3.154 dBi. In reality, the reflection loss of antennas is less than -12 dB, which conforms with the commercial antennas that are smaller than characteristic -10 dB, and therefore applicable to miniatured communications products.