Flexible and Ultra-Thin Glass Substrates for RF Applications
Sridhar Sivapurapu, Rui Chen, Mutee ur Rehman, Kimiyuki Kanno, Takenori Kakutani, Martin Letz, Fuhan Liu, Suresh K. Sitaraman, Madhavan Swaminathan
Abstract
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 μm in total thickness with a core glass substrate (Schott AF32) of 30 μm thickness. One stack-up uses 15 μm JSR GT-N01 as a buildup dielectric and the other uses 15 μm 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.