Ge 31/10/03
First thermal measurements on modules on stave
M.Dameri, F.Vernocchi et al. (R. Cereseto, G.Gariano, C.Gemme, M. Parodi,
C. Pizzorno, L.Rossi, A.Rovani, E.Ruscino)
3 FEI1 modules:
20210020420058 in position 3, power: 3.3W (chip7 off, chip8
malfunctioning)
20210020420026 in position 4, power: 2.4W (chip14 off)
20210020420023 in position 11, power: 2.5W (chip 8&13 off)
have been mounted on a prototype stave with the production machine
and procedure.
Thermal images have been taken with the module fully configured and
with a power consumption as detailed above. Cooling was done
circulating fluid at ~10C in a room temperature environment.
chip7
chip0
Tntc=120C
20210020420023 no power
High digital current
on pigtail
20210020420023 power on
Tntc=17.50C
Tntc=130C
20210020420026 no power
Tntc=16.50C
20210020420026 power on
Tntc=12.60C
20210020420058 no power
Tntc=16.10C
20210020420058 power on
• Measurements were done switching on one module at the time.
• Comparison between power-off and power-on cancels most of the
systematic effects.
• There is good agreement between Tntc and thermal images
• The temperature over the modules is quite uniform with the
exception of chip8 of module 20210020420023 that has too much
digital consumption.
• It is not possible to see individual chips which are switched off
• The DTntc between the fluid temperature (assumed* to be the same
as the module when power is off) and the module with power on is:
1.67 (mod. 20210020420058), 1.46 (mod. 20210020420026) and
1.4 (mod. 20210020420023) degrees per W
• Assuming
DT=1.50C/W implies that the maximum allowed
temperature drop happens with 10W modules (i.e. we are very much
on the safe side).
(*)The NTC measurement should be redone at fluid temperature closer to room temperature to see if
the above assumption holds.
Glue thickness has then been measured with a microscope, looking at the module
cross section, as shown:
chip7
chip0
Glue thickness
Results are
Glue layer is not uniform and the temperature on NTC (on chip 14 toward the
module center) feels this. The glue layer thickness does not appear to be very
critical (~1 C per 10W), unless we go above 200mm.
We do not observe local hot spots indicating that the silicon and C-C heat
transmission coefficient smears out local effects.
Geometrical position has been checked, measuring the edge of the pads on the FE
chips (reference crosses are not visible in those modules) in positions A and B:
B
A
The lateral displacement relative to the stave reference system are:
20210020420058: A=-20mm, B= 0 mm
20210020420026 A= 0mm, B= 10 mm
20210020420023 A=-40mm, B=-100 mm
All measurements indicate a problem in the placement of module 20210020420023