The transition from prototype to large-scale quantum computers requires a new class of microwave interconnect solutions capable of operating reliably at ultra-low temperatures. This paper presents a modular cryogenic interconnect framework designed for compatibility with superconducting quantum processors, addressing critical requirements for signal fidelity, thermal anchoring, and system scalability. The proposed architecture integrates cryogenic attenuators, filters, and switches optimized for operation in dilution refrigerators down to 10 millikelvin. Multiphysics modeling, including electro-thermal co-simulation and mesoscopic heat transport analysis, guides component design. Measurement validation combines calibrated RF methods with qubit-based performance metrics to assess thermal noise impact and signal integrity. Standardized calibration and benchmarking protocols ensure reproducibility across platforms. This work supports ongoing standardization efforts within CEN/CENELEC and paves the way toward scalable, low-noise quantum infrastructures.