Temperature issues

Despite rather low thermal dissipation (approx. 7.5 W), the cards are getting quite hot in installations. This page summarizes the Fine Delay heating problems and proposes solutions to mitigate them:
  • fit a heatsink
  • fit a fan
  • increase air flow in the crate/PC (fan speed) to improve heat transfer
  • replace LVPECL delay lines with low-power LVDS equivalents

Solutions

For those who don't want to read the rest of this page:
  • Elma 3U crates: increase fan speed to maximum, avoid slot 6.
  • Elma 1U and 6U crates: increase fan speed to maximum.
  • Wiener crates: increase fan speed to medium/maximum.
  • PCs (SPEC + FMC Delay): install a fan. Example fan design can be found here: here

Detailed temperature measurements on different platforms

Note: All temperatures in degrees Celsius. All thermal tests made with PCB version EDA-02267-V5-0.

Test environment

- VME: Wiener and Elma crates, with up to 7 SVECs (14 Fine Delays) installed in subsequent slots. Whenever possible, different combinations
of VME slots and fan speeds were used. All crates used a MEN A20 controller. Ambient temp 26-28.
- PCI Express: Kontron industrial PC, with 5 SPECs and 5 Fine Delays. Ambient temp 19-20.
- Temperatures were logged over time to make sure they have settled up before taking measurements. The first stable sample (with less than 1 degree temperature change over 1 minute) was used for the statistics.
- Unused slots were covered to ensure maximum airflow through the FMCs.
- PXI Express: National Instruments crates with the SPEXI and a Fine Delay: 4-slot (PXIe-1071) at ambient temp 25C and 8-slot (PXIe-1062Q) at ambient temp 29C with one Fine Delay in different slots.

Data (cards without heatsinks):

Wiener 21-slot VME64x crate, slots 4-10:

Fans Slot/FMC 4/1 4/2 5/1 5/2 6/1 6/2 7/1 7/2 8/1 8/2 9/1 9/2 10/1 10/2
Min (1200 rpm) Temp 65.69 71.38 56.88 66.25 50.69 63.88 51.19 63.62 58.62 73.25 61.44 71.00 50.12 59.62
Max (3600 rpm) 52.75 57.06 45.31 51.56 39.31 48.31 40.38 48.31 47.38 58.81 49.94 55.00 40.75 46.12
Wiener 21-slot VME64x crate, slots 9-15:
Fans Slot/FMC 9/1 9/2 10/1 10/2 11/1 11/2 12/1 12/2 13/1 13/2 14/1 14/2 15/1 15/2
Min (1200 rpm) Temp 62.00 71.12 60.19 74.31 61.25 73.75 51.94 65.12 48.75 60.88 51.31 62.75 52.12 64.06
Max (3600 rpm) 49.44 55.00 48.81 56.50 49.88 55.00 41.44 50.88 40.69 50.12 41.31 48.12 42.75 49.00

Elma 18-slot VME64x crate, default fan configuration:

Slots 4-10:

Slot/FMC 4/1 4/2 5/1 5/2 6/1 6/2 7/1 7/2 8/1 8/2 9/1 9/2 10/1 10/2
Temp 57.44 62.56 49.75 59.06 44.50 53.88 46.00 56.38 62.00 70.94 66.44 73.69 46.69 56.31

Slots 9-15:

Slot/FMC 9/1 9/2 10/1 10/2 11/1 11/2 12/1 12/2 13/1 13/2 14/1 14/2 15/2
Temp 66.00 72.06 66.88 73.56 57.38 65.44 46.94 59.88 45.31 56.31 50.56 60.06 59.31

Elma 6-slot VME64x crate, default fan configuration:

Fans Slot/FMC 2/1 2/2 3/1 3/2 4/1 4/2 5/1 5/2 6/1 6/2
Auto Temp 77.69 72.38 77.31 69.75 66.88 60.12 82.06 74.31 90.00 83.19
Max (3600 rpm) 67.38 62.81 66.50 62.62 58.25 52.06 70.56 64.06 80.94 73.44

Note: slot 6 has a much higher temperature than the other slots. One may need to recommend to not use slot 6.

Elma 2-slot VME64x crate

Fans Slot/FMC 2/1 2/2
Auto Temp 69.50 73.31
Max (3600 rpm) 63.50 67.50

Kontron KISS 6U industrial PC

Slot 1 2 3 7 8
Temp 89.25 92.56 98.75 88.56 79.50
National Instruments 4-slot PXIe crate PXIe-1071
Fans Slot/FMC 2 3 4
Auto Temp 57.2 55.5 55.2
Max 48.7 47.9 46.82
National Instruments 8-slot PXIe crate PXIe-1062Q
Fans Slot/FMC 2 3 4 5 6 7 8
Auto Temp x 76.0 74.8 77.5 x x x
Max x 63.3 63.5 64 x x x

Note: slot 2, 6, 7 and 8 cannot be tested, because they do not accept PXIe cards, only PXI. The SPEXI only exists in PXI Express.

Data (with heatsinks)

All FMCs were fitted with a custom CNC-machined heatsink

NOTE that the heatsink is not recommended to mitigate the temperature issues. Its design is provided just for information purposes

Wiener 21-slot VME64x crate, slots 4-9:

Fans Slot/FMC 4/1 4/2 5/1 5/2 6/1 6/2 7/1 7/2 8/1 8/2 9/1 9/2
Min (1200 rpm) Temp 50.56 64.00 48.94 63.81 43.69 57.81 48.50 61.50 51.88 64.75 49.19 59.62
Max (3600 rpm) 41.19 52.38 39.25 49.69 36.12 45.00 39.69 48.81 42.56 52.50 47.42 46.62

Wiener 21-slot VME64x crate, slots 10-15:

Fans Slot/FMC 10/1 10/2 11/1 11/2 12/1 12/2 13/1 13/2 14/1 14/2 15/1 15/2
Min (1200 rpm) Temp 52.38 65.31 47.38 63.69 45.94 61.50 43.38 57.62 51.25 65.00 49.75 59.56
Max (3600 rpm) 43.06 53.88 39.94 50.56 38.06 47.44 35.62 43.81 40.31 50.12 41.31 45.62

Elma 18-slot VME64x crate:

Slots 4-9:
Fans Slot/FMC 4/1 4/2 5/1 5/2 6/1 6/2 7/1 7/2 8/1 8/2 9/1 9/2
Auto Temp 47.81 62.56 39.88 53.50 40.50 50.31 42.06 55.12 52.38 67.50 47.06 54.50
Max (3600 rpm) 43.94 55.94 36.88 47.00 36.56 43.56 38.38 49.19 48.69 59.25 41.75 47.69
Slots 10-15:
Fans Slot/FMC 10/1 10/2 11/1 11/2 12/1 12/2 13/1 13/2 14/1 14/2 15/1 15/2
Auto Temp 56.56 64.75 50.81 67.62 41.69 57.38 42.38 54.00 47.88 60.19 46.38 56.25
Max (3600 rpm) 51.31 56.06 45.81 58.12 37.44 48.00 37.94 45.94 42.62 52.12 40.75 48.50
Elma 6-slot VME64x crate
Fans Slot/FMC 2/1 2/2 3/1 3/2 4/1 4/2 5/1 5/2 6/1 6/2
Auto Temp 69.06 65.12 70.69 61.75 62.25 53.44 75.25 65.62 81.88 70.50
Max (3600 rpm) 62.12 58.75 62.06 55.12 53.06 47.12 66.12 58.56 74.62 63.69
Elma 2-slot VME64x crate
Fans Slot/FMC 2/1 2/2
Auto Temp 61.06 64.62
Max (3600 rpm) 56.38 60.62
Kontron KISS 6U industrial PC
Slot 1 2 3 7 8
Temp 88.19 81.94 89.12 83.0 71.75

Summary

Crate Airflow Heatsink Min Max Span Mean Median
Wiener (slots 4-10) Min (1200 rpm) no 50.12 73.25 23.13 61.69 62.53
Wiener (slots 4-10) Min (3600 rpm) no 39.31 58.81 19.50 48.64 48.31
Wiener (slots 9-15) Min (1200 rpm) no 48.75 74.31 25.56 61.40 61.62
Wiener (slots 9-15) Min (3600 rpm) no 40.69 56.50 15.81 48.50 49.22
Elma 6U (slots 4-10) Auto no 44.50 73.69 29.19 57.55 56.91
Elma 6U (slots 9-15) Auto no 45.31 73.56 28.25 59.98 59.88
Elma 3U (slots 2-6) Auto no 60.12 90.00 29.88 75.37 75.81
Elma 3U (slots 2-6) Max (3600 rpm) no 52.06 80.94 28.88 65.86 65.28
Elma 3U (slots 2-5) Auto no 60.12 82.06 21.94 72.56 73.34
Elma 3U (slots 2-5) Max (3600 rpm) no 52.06 70.56 18.50 63.03 63.44
Elma 1U Auto no 69.50 73.31 3.81 71.41 71.41
Elma 1U Max (3600 rpm) no 63.50 67.50 4.00 65.50 65.50
Kontron None no 79.50 98.75 19.25 89.72 89.25
Wiener (slots 4-9) Min (1200 rpm) yes 43.69 64.75 21.06 55.35 54.84
Wiener (slots 4-9) Max (3600 rpm) yes 36.12 52.50 16.38 45.10 45.81
Wiener (slots 10-14) Min (1200 rpm) yes 43.38 65.31 21.93 55.23 55.00
Wiener (slots 10-14) Max (3600 rpm) yes 35.62 53.88 18.26 44.14 43.44
Elma 6U (slots 4-9) Auto yes 39.88 67.50 27.62 51.10 51.34
Elma 6U (slots 4-9) Max (3600 rpm) yes 36.56 59.25 22.69 45.74 45.47
Elma 6U (slots 10-14) Auto yes 41.69 67.62 25.93 53.82 55.12
Elma 6U (slots 10-14) Max (3600 rpm) yes 37.44 58.12 20.68 47.05 46.97
Elma 3U (slots 2-6) Auto yes 53.44 81.88 28.44 67.56 67.34
Elma 3U (slots 2-6) Auto yes 47.12 74.62 27.50 60.12 60.41
Elma 1U Auto yes 61.06 64.62 3.56 62.84 62.84
Elma 1U Auto yes 56.38 60.62 4.24 58.50 58.50
Kontron None yes 71.75 89.12 17.37 82.80 83.00
NI 3U 4-slot Auto yes 55.19 57.19 0 0 0
NI 3U 4-slot Max yes 46.75 48.69 0 0 0
NI 3U 8-slot Auto yes 74.75 77.50 0 0 0
NI 3U 8-slot Max yes 63.31 64.00 0 0 0

The ambient temperature on the Kontron measurement is 20 degrees. It is 28 degrees on the other measurements.

Configurations marked green have maximum temperature less than 65 degC. Configurations marked in red exceed 80 degC.

Replacing the LVPECL delay lines with LVDS counterparts

We tried replacing the SY89295 chips (and their LVPECL terminations) with an LVDS version: ICS854S296I-33. Temperature test
(identical conditions) performed on a SVEC showed 5 degrees less on the modified card:
  • new delay line (LVDS) 51.31 Celsius
  • old delay line (PECL) 56.38 Celsius

Note that the EDA-02267-V6-0 PCB is not foreseen for the LVPECL termination resistors for the new delay line chip. In case we decide to use the new chip, for production purposes a new revision of the PCB should be made. Also, the new LVDS delay line is much harder to obtain than the PECL version.

Fitting a fan on SPEC/Kontron PCs

We tried fitting a small fan below the FMC in the cutout on the SPEC card. The fan is installed on a mechanical support made from FR4 and attached to the board using the FMC's mounting screws. The fan design is available here

Kontron with FMC fans
Fan direction Slot: 1 2 3
blowing Temp: 58.62 72.19 77.50
exhaust 65.62 63.69 64.62
no fan 98.75 88.56 79.50

Exhaust fan (pumping the air outside the FMC area) proved the most effective, keeping all FMC temperatures below 65 degrees C.

Capacitor temperature

Electrolytic capacitors lifetime is the most important failure factor caused by high operating temperature. We measured the temperatures of the capacitors:
  • using a thermal vision camera
  • by gluing the DS18B22 sensor directly over the hottest capacitors.

We found out that the worst capacitor temperature was around 75 degrees C, while the board's temperature was 89 degrees C, that is, 14 degrees C of difference. For the temperature (as measured by the normally placed onboard sensor) of 65 degrees C, it means the capacitors are never hotter
than approx. 51 degrees C.

The photo below shows the temperature distribution on the board (note the temperatures are much lower, because the card is placed outside a crate on an extender cable, thus getting better ventilation).

Conclusions

What to do:
  • Don't use heatsinks.
  • Elma crates. Set air flow to maximum level. Do not use slot 6 on Elma 3U crate.
  • Wiener crates. Set air flow to medium/maximum level.
  • Kontron PCs must be equipped with additional fan units.
Notes/observations:
  • Heatsink is not effective if the air flow is too slow. In such case, the heat is exchanged through radiation with the cards in immediate neighbourhood, causing collective heating of all mezzanines/carriers (the ones in the middle are the worst).
  • Forced airflow is absolutely necessary. Set the fans to the maximum level in all VME installations.
  • Using an LVDS delay line chip gives little thermal advantage.
  • Cards in the middle slots (8-10) are the worst (25 degC difference over slots 7 and 12). This suggests uneven air flow in the crate.
  • FMC1 is approximately 8-10 degrees cooler than FMC2 in 3U and 1U crates (opposite on Wiener/big Elma). FMC1 is closer to the fans and obstructs air flow to FMC2.
  • Large temperature spans in VME crates suggest uneven air flow between different slots.
  • On Elma 6U and Kontron PC platforms, the temperatures are unacceptable and exceed the components rating (-40 ... +85).
  • Not using slot 6 on Elma 6U, only on Kontron PC platforms, the temperatures are unacceptable and exceed the components rating (40 ... +85).
    --

29 August 2014

heatsink.jpg (155.2 kB) Tomasz Wlostowski, 2014-08-29 15:51

IR_0180.jpg (175.7 kB) Tomasz Wlostowski, 2014-08-29 16:02

fan.jpg (184.6 kB) Tomasz Wlostowski, 2014-08-29 17:09