Cooling issues

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

2. 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

3. 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

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

5. Module on cold plate • Thermistor list • White => Coca • Red => Coca • Green => Stump • Blue => Cold plate • Coca temperature reduced • 105 => ~56 °C • Stump well cooled • ΔT = 5 °C • Biggest thermal resistance in joint Coca – Stump • ΔT = 27 °C

6. 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

7. 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

8. 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?

9. 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

10. SPARE

11. 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