Design and Optimization of LTCC Broadband Interconnect Structures for Bare-Chip Integration

In bare-die integration based on low-temperature co-fired ceramic (LTCC) multilayer interconnects, broadband signal transmission is often limited by impedance mismatch, parasitic effects introduced by gold-wire bonding, and discontinuities in interlayer transitions. These issues collectively form major bottlenecks for achieving low-loss and wideband interconnections in high-frequency LTCC modules. To address these challenges, this paper proposes a multi-layer collaborative optimization framework for LTCC bare-die interconnects operating from 1 to 20 GHz. The proposed framework jointly considers impedance matching, bonding parameter optimization, and interlayer transition enhancement to achieve broadband and high-performance signal transmission. First, two T-type microstrip matching networks are designed based on the complex input impedance of the bare die, and their parameters are optimized using ADS (an integrated circuit design software, version 2020). Second, a microstrip–gold-wire bond–bare-die interconnect model is established to analyze bonding-induced parasitic effects, revealing that a bond center spacing of 0.12 mm provides optimal high-frequency performance. Third, for the stripline–via–microstrip transition, a coaxial-like via structure combined with a square defected ground structure (DGS) is introduced to improve impedance continuity and electromagnetic field confinement. Full-path cascaded simulations demonstrate that the proposed interconnect achieves a return loss better than −23.1 dB and an insertion loss below 0.45 dB across the 1–20 GHz frequency range. Compared with conventional LTCC interconnect structures, the proposed method improves return loss by more than 7 dB and reduces insertion loss by approximately 0.12 dB. The results confirm the effectiveness of the proposed collaborative optimization strategy and provide reusable design guidelines for broadband bare-die integration in high-frequency LTCC multilayer modules.