1. Nikhef/Bonn LepCol meeting
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)
Coca temperature up to 105 °C
Stump follows coca
ΔT = 10 °C
Thermistor list
White => Coca
Red => Coca
Green => Stump
Blue => Cold plate

5. 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

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 g Boron Nitride: 760 K/W.mm