Nikhef/Bonn LepCol meeting Cooling issues Fred Hartjes NIKHEF Nikhef/Bonn LepCol meeting May 8, 2017

Thermal properties Coca glued on intended way to stump 1.3 ml Araldite 2020 (low viscosity) + 1 g Boron-Nitride => paste like substance Sufficient glue to fill all holes Dummy flexes included

Re-measurement using thermal glue Stump thermally coupled to cold plate Water cooled 4 heaters on coca 2.5 W each 1 heater on stump (2.5 W) Simulating LV regulation

Module isolated (on Styrofoam) Coca temperature up to 105 °C Stump follows coca ΔT = 10 °C Thermistor list White => Coca Red => Coca Green => Stump Blue => Cold plate

Module on cold plate Coca temperature reduced Stump well cooled ΔT = 5 °C Biggest thermal resistance in joint Coca – Stump ΔT = 27 °C Thermistor list White => Coca Red => Coca Green => Stump Blue => Cold plate

Thermal resistance of glued TPX3 chip Assume thermal resistivity of glue of 2500 K/W.mm (Araldite 2011) Glue parameters Surface: 200 mm2 Thickness 0.1 mm => thermal resistance 1.25 K/W 2.5 W => ΔT ~ 4 °C We may use Gloptop UV curing => only the edges Thickness << 0.1 mm => ΔT << 4 °C Hopefully the thermal resistance of chip to coca is not really an issue

Conclusions thermal issues Stump well cooled by cold plate We may not need a cooling line in the Stump Weakest point: joint Coca to Stump Presently ~ 60 °C chip temperature Improvements expected by Filling holes Coca – Stump Enlarging Stump Soon to be verified Still for the present design we have to live with 50 °C chip temperature Not constant, greatly depending on RO rate Significant improvement only expected by major changes in mechanical design

Quad assembly All PCBs / flexes due to arrive any moment Bonding board + flexes + LV regulator HV board Guard plate concentrator Modified alignment block produced, tested and black anodized Final drawings coca and stump completed In production Includes filled hole between coca and stump Finished May 12?

Pickup blocks Pickup blocks (for chips with InGrid) still bit problematic Big contact area to grid Surface structure bit rough Modified design (aluminium) just fabricated Contact surface to grid greatly reduced Just been fabricated Assembly jig for gluing coca onto stump still to be designed Waiting for PCBs

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Thermal conductivity glues Two aluminum plates 20 x 20 mm Equipped with NTCs and one heater 1 mm wide gap filled with glue Heater power adjusted getting 15 C temperature difference between the plates Measurements Araldite 2011: 2500 K/W.mm Araldite 2020: 2900 K/W.mm 1.3 ml Araldite 2020+ 0.69 g Boron Nitride: 760 K/W.mm