Advanced transmission lines replacement for TSVs

By Debra Vogler, senior technical editor

February 18, 2011 — Jamal Izadian, co-founder & president of RFCONNEXT, made the case for shaped membrane transmission lines (SMTL) for use in high-speed 3D packaging applications, as guest speaker at a recent MEPTEC lunch forum (2/9/11, Santa Clara, CA). Observing that wire bonding is limiting high-speed performance and die stacking, and that high-speed digital signals are limited by traditional plastic packaging, he calls for SMTL use, in conjunction with two other solutions, called periodic micro transmission lines (PMTL) and via micro transmission lines (VMTL), as a total high-speed packaging interconnect solution.

Listen to Izadian speak: Download (iPhone/iPod users) or Play Now

Each of these technologies is described in a podcast interview with Izadian. He also explains how SMTL supports and improves flip-chip, micro-bumping, wafer thinning, system-in-package (SiP), package-on-package (PoP), and other packaging processes by extending the bandwidth and high-speed limits of these technologies.

An intriguing topic covered in the interview is Izadian’s contention that SMTL is an inexpensive PCB alternative solution to TSVs. Wire bonds are not transmission lines, so high-speed connectivity is not possible, observed Izadian. “With the advent of advanced transmission lines, which are almost as good as a coaxial line at the microscopic level, we have removed the requirement for the connections to be next to each other or on top of each other,” said Izadian. “You can have them dispersed around like a SiP and be able to connect them at high speed.” SMTL technology also allows plastic packaging to be used for high-speed applications, essentially obtaining the performance achieved with ceramic packages, but at a lower cost.  

Some of the advantages of SMTL include: controlled impedance, no parasitic inductance, no significant length limit, no cross-talk, noise immunity, 90% less metal in the process, and scalability.
SMTL for packaging applications is currently under evaluation by end users and RFCONNEXT intends to adapt the technology to existing manufacturing processes. Izadian said he expects advanced transmission lines to be ready within the next 6-12 months. Learn more at

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