Estimation of the FR4 Microwave Dielectric Properties at Cryogenic Temperature for Quantum-Chip-Interface PCBs Design

Estimation of the FR4 Microwave Dielectric Properties at Cryogenic Temperature for Quantum-Chip-Interface PCBs Design

Ad-hoc interface PCBs (Printed Circuit Boards) are today the standard connection between cryogenic cabling and quantum chips. Besides low-loss and low-temperature-dependent-dielectric-permittivity materials, Flame Resistance n.4 (FR4) provides a low-cost solution for fabrication of cryogenic PCBs. H...

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Bibliographic Details
Published in:IEEE transactions on instrumentation and measurement Vol. 73; p. 1
Main Authors: Paghi, Alessandro, Trupiano, Giacomo, Puglia, Claudio, Burgaud, Hannah, De Simoni, Giorgio, Greco, Angelo, Giazotto, Francesco
Format: Journal Article
Language:English
Published: New York IEEE 01-01-2024
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subjects:
Circuit boards
Circuit design
Complex permittivity
Coplanar waveguides
Cryoforming
cryogenic
Cryogenic temperature
Cryogenics
dielectric permittivity
Dielectric properties
dielectric resonator
Dielectrics
Fire resistance
FR4
Laminates
loss tangent
Low cost
Low temperature
Low temperature resistance
Microwave circuits
Peak frequency
Performance evaluation
Permittivity
Printed circuits
quantum
Resonance
Resonant frequency
resonator
Resonators
Sensitivity
Substrates
temperature
Temperature dependence
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Summary:Ad-hoc interface PCBs (Printed Circuit Boards) are today the standard connection between cryogenic cabling and quantum chips. Besides low-loss and low-temperature-dependent-dielectric-permittivity materials, Flame Resistance n.4 (FR4) provides a low-cost solution for fabrication of cryogenic PCBs. Here, we report on an effective way to evaluate the dielectric performance of a FR4 laminate used as substrate for cryogenic microwave PCBs. We designed a coplanar waveguide λ/2 open-circuit series resonator, and we fabricated the PCB using a low-cost manufacturing process, obtaining in-plane geometric features with maximum variations of 50-100 μm compared to the PCB design. Such a geometry allows to exploit the resonance peak of the resonator to measure the variation of the complex permittivity as a function of the temperature. The resonance peak frequency was used to estimate the real permittivity, achieving a sensitivity of -470 MHz and a resolution of 1.2×10 -2 . Similarly, the resonance peak magnitude was involved in the extrapolation of the loss tangent, reaching a sensitivity of ~-337 dB and a resolution of 1.6×10 -4 . For the FR4 laminate used, we estimated a 9 % reduction of the real permittivity and a 70 % reduction of the loss tangent in the temperature range from 300 to 4 K. The proposed approach can be immediately extended to the detection of cryogenic temperature-dependent dielectric performance of any kind of substrate.
ISSN:0018-9456
1557-9662
DOI:10.1109/TIM.2024.3372217