Batch-Mode μUSM Process for Surrounding Air Cavity and TCV Holes of AlN Ceramic Substrate Application for Patch Antenna

Narrow bandwidth of miniaturization patch antenna caused by substrate material severely limits its applications, fabricating air cavity on AlN ceramic substrate for decreasing its dielectric constant is a potential method for increasing the bandwidth. But it's a critical challenge for simultaneous fabricating of surrounding air cavity and TCV holes on AlN ceramic substrate with high precision.This paper presents a patch antenna on AlN ceramic substrate with surrounding air cavity and TCV holes. And its key process of surrounding air cavity and TCV holes fabrication on AlN ceramic is developed by batch-mode μUSM. AlN ceramic simple with step depth of surrounding air cavity and TCV blind hole is machined simultaneously. Its machining feature resolution and surface roughness are below 1μm and Ra 200nm respectively, machining removal rate is higher than 4.5μm/min. The patch antenna property is simulated and analyzed, the results show the increment of bandwidth reach up to 68.42% because of the surrounding air cavity existing.