This document discusses thermal modeling of high power processors using CFD tools. It provides sample cases studying heat pipe performance, transient heating curves, conduction cooling through multiple cold plates, and liquid cooling of modules. Details include modeling parameters, temperature predictions and profiles, and meshing of up to 1.36 million cells for detailed package studies. Liquid cooled module designs are shown with parallel channel cold plates and temperature contours.

1. TM
HIGH POWER BGA
PROCESSOR
THERMAL modeling
with N.h. cfd tools
A few Sample Cases
D. Blanchet
04/14/2005

2. TM
THERMAL modeling NEW TOOL EVALUATION
Air cooling
Conduction cooling
 Heat pipes
 TE coolers
 Transient
Liquid Flow through cold plates
Natural Convection
Detailed Package study

3. TMHEAT PIPE STUDY
High temperature primary heat path
Heat pipes ON
Heat sink
+ 55C
CAB
Cold plate

4. TMLow temperature primary heat paths
CAB
Heat pipes OFF (frozen)
- 40C wall
standoffs
Cold plate
startup heater

5. TM
results hot ambient
Heat pipes operating
Sink attached to chassis wall

6. TM
results hot ambient

7. TM
results cold ambient -40C
frozen

8. TM
results cold ambient -40C
frozen

9. TM
Typical Transient Heating curves heater power only
warm up time
•9
Cell @ 0C ~ 820 sec
Total heater power = 250W
Ambient - 40C

10. TM
Conduction
cooled
8 modules
6U CC
6 modules
Heat Rejection Unit
section
(optional)
Not
Considered
In this study
3 Cold plates
(series)
inlet
outlet

11. TM
Chassis walls - 3 cold plates in series – 2.2 KW
800 w
800 w
300 w
300 wn
out
8 – CC
Modules @
~200W each
6 – CC 6U
Modules @
~100W each
20C
water
@
1 gpm

12. TM
Coolant temperature rise ~ 7C @ 1 gpm

13. TM
Component Model parameters

14. TM
6U module Model
Air flow Copper heat sinks

15. TM
Model top view

16. TMModel mesh – 340,000 cells

17. TMResults –
Typical temperature profile cross section
Air velocity vectors

18. TM
Results -
Air velocity vectors
Through heat sinks

19. TMResults – temperature contours
section through heat sink bases

20. TM
junction temperature predictions @ sea level
AIRFLOW >> 12 CFM 15 CFM 18 CFM 25 CFM
Power per
processor
0.8” pitch 0.8” pitch 0.8” pitch
35W– 178W total
Inlet Tj / outlet Tj Inlet Tj / outlet Tj Inlet Tj / outlet Tj
Inlet air 20C 60 / 80 56 / 74 53 / 69
Inlet air 40C 80 / 100 76 / 94 73 / 89
Inlet air 55C 95 / 115 91 / 109 88 / 104
Power per
processor
1.0” pitch 1.0” pitch 1.0” pitch 1.0” pitch
35W– 178W total
Inlet Tj / outlet Tj Inlet Tj / outlet Tj Inlet Tj / outlet Tj Inlet Tj / outlet Tj
Inlet air 20C 58 / 73 54 / 66 51 / 61 47 / 54
Inlet air 40C 78 / 93 74 / 86 71 / 81 67 / 74
Inlet air 55C 93 / 108 89 / 101 86 / 96 82 / 89

21. TM
Liquid Cooled Module Studies

22. TM
Serpentine Liquid Flow Path & Temperature Contours
Commercial Processor Design ~260 Watts Total
Laminar flow Nr ~ = 1100 (viscous fluid)
35C
0.25 gpm
90C
At spec limit
100 W

23. TM
Parallel channel cold plate 6U
6 CPUs @ 90W ea
540 Watts one side
35C Water @ 0.33 gpm
Straight
manifolds
Milled
Parallel
channels

24. TM
Local mesh control – parallel channels
5 cells per channel
Coarser grid
In metal frame
390,000 grid cells

25. TM
Cold plate
Full 2 Resistor < j-b / j-c > component models
(detailed models available)

26. TM
Parallel flow results
Back
view

27. TM
Results - Tj
Tj = 58.2C

28. TM
Detailed model

29. TM
Detailed CPU BGA model

30. TM
Detailed model
1,360,000 grid cells

31. TM
Detailed model bga
1,360,000 grid cells

32. TM
Detailed model – wind tunnel

33. TM
Detailed model
pwb
Heat sink
BGA
Air flow