Through-Glass-Via Based Microstrip Band-Pass Filters Fabricated with Wafer-Level Low-Melting-Point Alloy Micro-Casting
Weibo Zhang, Jiebin Gu, Lingyun Li, Xinxin Li
Abstract
Through-glass-via based X-band microstrip band-pass filters are wafer-level fabricated by casting molten zinc-aluminum alloy into micromachined glass substrate. Instead of using time-consuming electroplating to form a via based GHz microstrip filter, where seed-layer deposition, plating and seed-layer removal process cycle should be repeated for several times, herein the metal parts of filter, including the resonators, the large-area ground and the metal plug in through-glass-via are all formed in one-step liquid-alloy filling in the pre-micromachined mold within only 5min for a whole wafer. This process is much quicker and simpler compared to those electroplating based approaches for microstrip filters. The micro-casting fabricated filter has a center frequency of 8.6GHz with 800MHz bandwidth. The measured insertion loss is -2.1dB, and the return loss is lower than -10dB within the passband. Good agreement is achieved between the measured results and the simulated ones. This technique can also be widely used for fabricating various RF devices.