Design of Flip-Chip Interconnect Using Epoxy-Based Underfill Up to $V$-Band Frequencies With Excellent Reliability

Connecting Chips With More Than 100 GHz Bandwidth

“…Also, on a liquid crystal polymer substrate (see [30]), 170 GHz bandwidth have been achieved [36]. Having a more detailed look at the results one finds in many cases relatively flat frequency characteristics without a cut-off at the higher frequency band so that one could expect even wider bandwidths than reported (e.g., for [32]- [34]).…”

“…An overview of the work on flip-chip at mm-wave frequencies until the early 2000 years can be found in [27], demonstrating bandwidths up to 100 GHz (e.g., [28]). Further examples for flip-chip realizations in the mm-wave range present W-band modules for point-to-point communications [29] and on organic substrate [30], solutions for 0 …67 GHz [31], [32] and those for the full band up to 110 GHz [33], [34]. In [35], a transceiver module for imaging applications with 220 GHz bandwidth is presented.…”

“…In [35], a transceiver module for imaging applications with 220 GHz bandwidth is presented. The publications include work on lead-free bumps [33] and underfiller [29], [32]. Also, on a liquid crystal polymer substrate (see [30]), 170 GHz bandwidth have been achieved [36].…”

Micromachined Millimeter- and Submillimeter-wave Circuits for Test and Integration

“…[21] demonstrates a twelve times mechanical strength improvement by applying underfill. However, the underfill will introduce extra loss [22] and detune RF circuits.…”

“…The SU-8 structures protect the gold microbumps from excessive deformation during the bonding process. Epoxy-based underfill has been used to improve the reliability of flip-chip interconnects [21]. However, this strategy requires taking the underfill effect into account in advance for both interconnect and chip designs.…”