由主機板上受壓電效應影響之積層陶瓷電容所造成的高頻異音實驗探討

Abstract

積層陶瓷電容器具有體積小、價格低廉、頻率特性佳等特性，同時其為表面黏著元件，使其可以大量快速生產並大幅減少元件於印刷電路板上所占的空間，目前廣泛應用訴求輕薄短小的可攜式產品與筆記型電腦中。

隨著筆記型電腦的普及，使用者陸續發現所使用的產品會產生微小的高頻異音，由於其音量極為細微，必須很靠近電腦才可以聽見，大多數的使用者認為其雖然不影響操作，但心理上仍難以容忍此不期望出現的高頻異音。探究其原因，為大量使用於筆記型電腦中的積層陶瓷電容器所引起。

由於積層陶瓷電容器其介電材料主要為鈦酸鋇類陶瓷，具有壓電特性，因此在交流電場下將會產生結構體的震動。本論文透過實驗方式驗證減少電源路徑上的漣波雜訊將能有效降低積層陶瓷電容器所引起的高頻顫噪現象，其中漣波雜訊減少了26.5%，高頻異音的響度減低19.4%，在頻率4KHz與8KHz的突出率也得到抑制。

Multilayer ceramic capacitor (MLCC) is of small size, low price, excellent frequency response and other characteristics, while at the same time it is surface mount components, so that it can be in rapid production and substantially reduce the share of components on the printed circuit board space, which currently widely used for portable products and laptop computers.

As the popularity of laptop computers, users have found that the product may produce a tiny high pitched noise. Because it is extremely subtle, and can be heard only very close to the computer. Although the majority of users think that it does not affect its operation, but remains psychologically difficult to tolerate this unexpected high-pitched noise. The source of this noise is the multilayer ceramic capacitors which intensively used in laptop computers.

The dielectric material of multilayer ceramic capacitor is mainly barium-titanate (BaTiO3), which has ceramic piezoelectric properties, so the vibration of its structure will occur under the AC electric field. This thesis verified that through experiments reducing ripple noise in the power trace could effectively reduce the high pitched microphonics phenomenon caused by the multilayer ceramic capacitors. The experimentation results show that the ripple noise was reduces by 26.5%, the loudness of high pitched noise was reduced by 19.4%, and the prominence ratios at 4KHz and 8KHz were lower.