Flexible and Ultra-Thin Glass Substrates for RF Applications

Glass has been shown to be a capable core substrate material for high frequency applications. In this paper we examine the capabilities of ultra-thin glass as a flexible material that can be used for high frequency flexible applications. The two stack-ups discussed in this paper are $60\ \mu\mathrm{m}$ in total thickness with a core glass substrate (Schott AF32) of $30\ \mu\mathrm{m}$ thickness. One stack-up uses $15\ \mu\mathrm{m}$ JSR GT-N01 as a buildup dielectric and the other uses $15\ \mu\mathrm{m}$ Taiyo Photo Imageable Dielectric. Since neither of these stack-ups have previously been electrically characterized, this paper characterizes both stack-ups up to 110 GHz using microstrip ring resonators (MRRs) and conductor backed coplanar waveguides (CBCPWs). Based on the characterization results, these stack-ups compare favorably against other stack-ups used for applications in this frequency range. After completing the electrical characterization, the Taiyo PID stack-up is also mechanically characterized for its flexibility using Free Arc Bending. The Free Arc Bending test shows that the ultra-thin glass stack-up is suitable for high frequency bending applications as the tested samples are capable of bending up to a separation of 33% of the sample's total length, displaying the capabilities of this ultra-thin glass substrate as a good candidate for a flexible substrate.