Flip-chip STW filters and frequency trimming method

This paper describes 2.4 GHz and 3.5 GHz flip-chip narrow-band filters using surface transverse waves (STWs) on quartz for oscillator applications. A Q of about 1300 and insertion losses of 3 dB and 5 dB are achieved for 2.4 GHz and 3.5 GHz flip-chip STW filters, respectively. Also, oscillator characteristics using the flip-chip STW filters are presented. In addition, trimming methods for flip-chip STW filters are described. We have succeeded in frequency trimming using CF₄ chemistry, in situ monitoring the center frequency for flip-chip STW filters with 3.2 mm×2.5 mm ceramic packages.