The LHCb VELO Upgrade Module Construction

The LHCb detector has undergone a major upgrade for LHC Run 3. This Upgrade Idetector facilitates operation at higher luminosity and utilises full-detectorinformation at the LHC collision rate, critically including the use of vertexinformation. A new vertex locator system, the VELO Upgrade, has beenconstructed. The core element of the new VELO are the double-sided pixelatedhybrid silicon detector modules which operate in vacuum close to the LHC beamin a high radiation environment. The construction and quality assurance testsof these modules are described in this paper. The modules incorporate 200 \mumthick, n-on-p silicon sensors bump-bonded to 130 \nm technology ASICs. Theseare attached with high precision to a silicon microchannel substrate that usesevaporative CO$_2$ cooling. The ASICs are controlled and read out with flexibleprinted circuits that are glued to the substrate and wire-bonded to the chips.The mechanical support of the module is given by a carbon fibre plate, twocarbon fibre rods and an aluminium plate. The sensor attachment was achievedwith an average precision of 21 $\mathrm{\mu m}$, more than 99.5\% of allpixels are fully functional, and a thermal figure of merit of 3\mathrm{Kcm^{2}W^{-1}}$ was achieved. The production of the modules wassuccessfully completed in 2021, with the final assembly and installationcompleted in time for data taking in 2022.