A new design of stripline transition structures and flip-chip interconnects for high-speed digital communication systems implemented in low-temperature cofired ceramic (LTCC) substrates is presented. Simplified fabrication, suitability for LTCC machining, suitability for integration with other components, and connection to integrated stripline or microstrip interconnects for LTCC multichip modules and system on package make this approach well suited for miniaturized, advanced broadband, and highly integrated multichip ceramic modules. The transition provides excellent signal integrity at high-speed digital data rates up to 28 Gbits/s. Full-wave simulations and experimental results demonstrate a cost-effective solution for a wide frequency range from dc to 30 GHz and beyond. Signal integrity and high-speed digital data rate performances are verified through eye diagram and time-domain reflectometry and time-domain transmissometry measurements over a 10-cm long stripline.Index Terms-Full tape thickness feature, low-temperature cofired ceramic (LTCC) interconnect, multichip module (MCM), quasi-coaxial vertical transition, signal integrity, system on package.

Characterisation results of the complex permittivity of select dielectric cooling fluids at room temperature and over a broad frequency range found using a low-loss printed circuit board microstrip ring resonator technique are presented. ANSYS HFSS, a finite-element full-wave electromagnetic simulation environment, was used to fit the simulated insertion loss to the calibrated measurements of the microstrip ring resonator in air and submerged in different dielectric fluids. The resulting frequency-dependent relative permittivity and loss tangent are provided up to 50 GHz for three dielectric cooling fluids: 3M™ Novec™ 649, 3M™ Novec™ HFE-7100 and 3M™ Fluorinert™ FC-72.

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