The Challenge
The demanding environment necessitated specialist assemblies to ensure dependable and accurate data transmission throughout the lifetime of the instrument. A small footprint within the inner barrel would rely on a compact solution, whilst achieving a 1mm cut back to the shield on the 34AWG wire would involve the development of bespoke tooling.
The Solution
To address the space constraints, ribbon cables were selected for their compact, lightweight, and flexible format, allowing the assembly to be installed in the raceways. The first step was to strip the insulation from the ribbon cables which involved collaboration between teams in the UK and US to design specialised tooling for Tekdata Interconnections’ latest innovative laser stripping machine. This created a robust and repeatable process enabling a 1mm cut back to the 34AWG.
This enabled our technicians to terminate the wires within the constraints of the 1mm pad on the PCB under high-power microscopes using precise soldering techniques. We also developed a piece of equipment to mirror the condition within the ATLAS instrument to allow us to test the assemblies in situ whilst the cables remained within the jig to protect them from potential handling damage.
Every harness was then encapsulated to safeguard the delicate joints during transportation and final installation.
The Result
The completed ribbon cable solution directly supports the upgrade of the ATLAS instrument within the Large Hadron Collider. The 34 AWG Molex Temp-Flex Twinax High-Temp/Low-Loss Twin-Axial Cable, with fluoropolymer insulation, was custom-designed radiation-hard wire used in the completed cable harnesses. Originally, CERN planned to use a thicker 30 AWG copper-clad aluminium wire bundled together to achieve 5.1 Gb/s. By moving to a woven ribbon approach, they could switch to thinner 34 AWG pure copper wires.
This change incorporated improved foil shielding and a Nomex woven exterior for better routing and density, operating at a passive data transmission rate of 1.28 Gb/s per pair. Switching to the thinner wire further improved the harness by reducing the solder to a microscopic dot, and naturally matched the high-speed PCB traces, keeping the electrical pathway uniform and smooth. Additionally, the thinner 34 AWG wires were placed exceptionally close to one another on the PCB, ensuring the cable’s internal balance was maintained to the millimetre.
The switch to the thinner wire in the woven ribbon assembly allowed the final bundled ribbon to carry a massive, steady stream of total data without lagging or dropping frames. Thanks to the protective qualities of Polyimide and Nomex, the final harnesses will safely operate for decades.
How can we support your scientific project?
For more information on our services, please visit our webpage or contact our sales team:
Phone: +44 (0)1782 254778
Email: sales@tekdatainterconnections.co.uk
