3 Innovation 1

3M Thermosyphon Technology for Passive 2-Phase Cooling of Electronics

March 2007

Phil E. TumaAdvanced Application Development Specialist

3M Electronic Markets Materials Division651-737-9895

petuma@mmm.com

3 Innovation 2

Introduction• 3M has manufactured fluorinated heat

transfer fluids since the 1950s

• Historically, these fluids were used in high value military or specialty applications

• For the past few years, 3M has been researching passive 2-phase or “Thermosyphon” technology for use in mainstream electronics

– 3M has published papers and builds thermosyphon prototypes to showcase that technology and prove feasibility

– 3M hopes to sell working fluids and boiling surfaces for thermosyphon manufacturers

– 3M works with electronics OEMs to help pull through the technology

3 Innovation 3

Air Cooled Thermosyphon

3 Innovation 4

• Terminology

– Thermosyphon performance characterized by the sink-to-ambient thermal resistance, Rsa=Rsf+Rfa

– The Evaporator performance is characterized by the sink-to-fluid thermal resistance,

Rsf=(Ts-Tf)/Q

– The Condenser performance is characterized by the fluid-to-ambient thermal resistance,

Rfa=(Tf-Ta)/Q

3 Innovation 5

• Product/Technology Offerings– 3M Will Supply Materials and technologies to spur the adoption of

thermosyphon technology.

Working Fluid

Boiling Materials/Technology

3 Innovation 6

• 3M Novec™ Hydrofluoroether Working Fluids– Clear, colorless, nearly odorless– Excellent toxicological properties– Non-conductive Dielectrics– Environmentally favorable properties

• This is not true of HFC refrigerants which are discouraged by global environmental regulations

3 Innovation 7

Working Fluid

3 Innovation 8

Working Fluid

3 Innovation 9

0

2

4

6

8

10

12

0 20 40 60 80 100Q" [W/cm2]

H [W

/cm

2 -K]

Prior Art, Fluorinert ~1atmPrior Art, Water 4kPaPrior Art, Fluorinert ~1 atmSmooth Flat Surface, Novec ~1 atm3M Coating, Flat Surface, Novec ~1atm3M Coating, Fins, Novec~1atm

Performance of 3M Boiling Enhancement Coating under conditions of uniform heat flux

Q” = Q / AreaH = Q” / (Tw-Tsat)

3 Innovation 10

Typical Rsf Values for 3M boilers applied to various heat source sizes

Taken from: Tuma, P.E. , “Evaporator/Boiler Design for Thermosyphons Utilizing Segregated Hydrofluoroether Working Fluids,” Proc. Semitherm 2006

Typical ModernMicroprocessor

Values

3 Innovation 11

Specifications (cont)Condenser Design #7 in Figure Below

Note: 1m3/min=35CFM

3 Innovation 12

Example – Air Cooled Thermosyphon

SpecificationsCondenser Dimensions 115x120x19mmMass 380gCapacity 200W

Design Orientations 2 (90°apart)

Horizontal Mother Board Vertical Mother Board

3 Innovation 13

Specifications (cont)Condenser Design #7 in Figure Below

Taken from: Tuma, P.E., et al , “Condenser Design for Thermosyphons Utilizing Segregated Hydrofluoroether Working Fluids,” Proc. Semitherm2007

3 Innovation 14

• This thermosyphon was tested on a 25x25mm copper heater from 50-200W – “Chip” temperature, Tc, was measured 1mm from the

heater surface– “Ambient” temperature, Ta, was measured at fan inlet– Fan was Panasonic FBL12G12H

3 Innovation 15

1x1mm Thermocouple “Sink” Groove, Ts

66x112mm Mounting Plate120mm Thermosyphon

Thermocouple Well, Tsat

3 Innovation 16

3 Innovation 17

• 3M has built and tested a 120mm thermosyphon that will produce Rsa<0.08 C/W at over 200W with <2 m3/min airflow at ΔP~2mm H2O

• Rsa<0.068 C/W is possible with a deeper 120mm condenser like #8 and has been demonstrated

• Remote form factors are possible

• Clear evaporators can be employed for gaming applications

Conclusion/Summary

3 Innovation 18

3M Thermosyphon in ATX Chassis

3 Innovation 19

Clear glass evaporator with immersion-cooled high intensity LED to illuminate boiling process

3 Innovation 20

Evaporator Close up

3 Innovation 21

3 Innovation 22

3M Thermosyphon in Dell E520

3 Innovation 23

Install

3 Innovation 24

Evaporator Close up

3 Innovation 25

3M Thermosyphon in Xbox 360

CPU GPUStock Heat Sinks 43.4 31.2Thermosyphon 23.9 19.2

ΔTja

3 Innovation 26

3M Thermosyphon, 320gBrass Copper Const.92x92mm face area

690g XP90C4 heat pipe heat sinkAll Copper95x95mm face area

Case-to-ambient thermal resistance on 25mm heat source with same 92mm fan