- 學位論文
運用類鑽碳膜改善揚聲器頻率響應之研究
Improvement in the Frequency Response of Loudspeakers by using Diamond-Like Carbon Film Coatings
摘要
科技發展至今，鑽石作為揚聲器振膜是極佳的材料，但天然的鑽石價格昂貴、加工不易，而以人工方式的製程製造鑽石膜設備複雜、成本高昂、工藝繁瑣，而且對基材的要求比較嚴苛，如熔點要高、熱膨脹係數要小、與工作氣體中的碳和氫不能起反應等等；類鑽碳(Diamond-Like Carbon，簡稱DLC)膜具有高硬度與楊氏模數是眾所周知的事，其中之一的優異性質就是濺鍍在揚聲器振膜上可以提高傳聲速度，本研究裏類鑽碳膜在低溫以物理氣相沈積(physical vapor deposition，PVD)的射頻磁控濺鍍法鍍在聚亞醯胺(polyetherimide，PEI)當基材的振膜上；非晶質類鑽碳膜以150與175瓦特功率濺鍍3與1.5小時具有高的ID / IG比與低粗糙度，其ID / IG比與粗糙度分別是2.27與2.09 和l.21 nm與0.86 nm (Ra)，濺鍍在振膜後作頻率響應分析，平均提升0.1~5.1 dB，最值得一提的是在超過一般人耳聽覺20 kHz以上者，頻率響應衰減的趨勢比未濺鍍者緩和，因為此頻域關係著音樂鑑賞者所重視的順性(compliance)，非常有利於高檔音響產品，透過本研究也更確信類鑽碳膜與聚亞醯胺(或聚合物)基材擁有優秀的附著力，而經由不同的鍍膜形式，研究在微型揚聲器的頻率響應性能，並與未鍍膜之振動膜相比，得到相當不錯的結果，這對日後頗具潛力的電聲裝置應用提供了很好的方向。
並列摘要
Though there has been a tremendous progress in science and technology up to date, diamond is still recognized as the prior material for loudspeaker diaphragms. However, natural diamond is expensive and hard to manage. In addition to that, the equipment needed to produce diamond film by manual process is expensive and complicated. Moreover, the requirement for material is strict, for instance, the melting point must be high, thermal expansion should be small, and the carbon and hydrogen cannot be reacted in the working environment, etc. It is well known that a diamond-like carbon (DLC) film has a high mechanical hardness and Young’s modulus. One of the beneficial properties of a DLC film is its ability to change the sound velocity in loudspeakers through its application as a hard coating. In the present study, DLC films were coated onto polyetherimide (PEI) diaphragm substrates at low temperature with radio-frequency (RF) magnetron sputtering. Amorphous DLC films deposited at RF power of 150,175 Wand with deposition time of 3 and 1.5 h have a high ID/IG ratio and a low surface roughness. The ID/IG ratio and surface roughness were 2.27, 2.09 and l.21 nm, 0.86 nm (Ra), respectively. From frequency response analysis of the DLC film on the diaphragm, we found that the frequency response increased by 0.1~5.1 dB on average. There is one thing that is worth to be mentioned, that is beyond human hearing (20 kHz), the decreasing tendency of the frequency respond, compared with sputtering and non-sputtering, the sputtering decreases alleviative. This frequency domain considers the compliance of a music connoisseur, which benefits on high level loudspeakers products. This confirmed the excellent adhesion of DLC films onto PEI (or polymer) substrates. By sputtering differently, we do a research on micro loudspeakers with their performances of frequency respond. There was a good result compared with non-sputtering diaphragm. The result gives us a direction and could be the potential applications of electro-acoustic devices.