Research Papers

Analysis of Using Ferrofluid as an Interface Material in a Field Reversible Thermal Connector

[+] Author and Article Information
Ahmed S. Yousif

University of Technology,
Baghdad 00964, Iraq
University of Missouri,
Columbia, MO 65211
e-mail: AhmedYousif86@gmail.com

Gary L. Solbrekken

University of Missouri,
Columbia, MO 65211
e-mail: SolbrekkenG@missouri.edu

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received May 20, 2014; final manuscript received October 22, 2014; published online November 17, 2014. Assoc. Editor: Madhusudan Iyengar.

J. Electron. Packag 137(2), 021003 (Jun 01, 2015) (9 pages) Paper No: EP-14-1056; doi: 10.1115/1.4028958 History: Received May 20, 2014; Revised October 22, 2014; Online November 17, 2014

The electrical functionality of an avionics chassis is limited due to heat dissipation limits. The limits arise due to the fact that components in an avionic computer boxes are packed very compactly, with the components mounted onto plug-in cards, and the harsh environment experienced by the chassis limits how heat can be dissipated from the cards. Convective and radiative heat transfer to the ambient are generally not possible. Therefore, it is necessary to have heat transferred from the components conducted to the edge of the plug-in cards. The heat then needs to conduct from the card edge to a cold block that not only holds the card in place but also removes the generated heat by some heat transfer fluid that is circulated through the cold block. The interface between the plug-in card and the cold block typically has a high thermal resistance since it is necessary for the card to have the capability to be reworkable, meaning that the card can be removed and then returned to the chassis. Reducing the thermal resistance of the interface is the objective of the current study and the topic of this thesis. The current design uses a pressure interface between the card and cold block. The contact pressure is increased through the addition of a wedgelock, which is a field-reversible mechanical connector. To use a wedgelock, the cold block has channels milled on the surface with widths that are larger than the thickness of the plug-in card and the unexpanded wedgelock. The card edge is placed in the channel and placed against one of the channel walls. A wedgelock is then placed between the card and the other channel wall. The wedgelock is then expanded by using either a screw or a lever. As the wedgelock expands, it fills in the remaining channel gap and bears against the other face of the plug-in card. The majority of heat generated by the components on the plug-in card is forced to conduct from the card into the wall of the cold block, effectively a single sided, dry conduction heat transfer path. Having started as a student design competition named RevCon Challenge, work was performed to evaluate the use of new field-reversible thermal connectors. The new design proposed by the University of Missouri utilized oil based iron nanoparticles, commonly known as a ferrofluid, as a thermal interface material. By using a liquid type of interface material, the channel gap can be reduced to a few micrometers, within machining tolerances, and heat can be dissipated off both sides of the card. The addition of nanoparticles improves the effective thermal conductivity of base fluid. The use of iron nanoparticles allows magnets to be used to hold the fluid in place, so the electronic cards may be easily inserted and removed while keeping the ferrofluid in the cold block channel. The ferrofluid-based design which was investigated has shown lower thermal resistance than the current wedgelock design. These results open the door for further development of electronic cards by using higher heat emitting components without compromising the simplicity of attaching/detaching cards from cooling plates.

Copyright © 2014 by ASME
Your Session has timed out. Please sign back in to continue.


Bakhshi, R., Kunche, S., and Pecht, M., 2014, “Intermittent Failures in Hardware and Software,” ASME J. Electron. Packag., 136(1), p. 011014. [CrossRef]
3M, 2001, Technical Bulletin: Characteristics of Thermal Interface Material, 3M, St. Paul, MN.
Stafford, J., Newport, D., and Grimes, R. A., 2013, “Compact Modeling Approach to Enhance Collaborative Design of Thermal-Fluid Systems,” ASME J. Electron. Packag., 136(1), p. 011004. [CrossRef]
David, T., Mendler, D., Mosyak, A., Bar-Cohen, A., and Hetsroni, G., 2014, “Thermal Management of Time-Varying High Heat Flux Electronic Devices,” ASME J. Electron. Packag., 136(2), p. 021003. [CrossRef]
Jolivet, J. P., Massart, R., and Fruchart, J. M., 1983,” Synthesis and Physiochemical Study on Nonsurfactant Magnetic Colloids in Aqueous Medium,” Nouv. J. Chim., 7, pp. 325–331.
Yiping, L., Tang, Z. X., Hadjipanayis, G. C., Sorensen, C. M., and Klabunde, K. J., 1993, “Co-Pt-B Particles Prepared by Chemical Reduction,” IEEE Trans. Magn., 29(6), pp. 2646–2648. [CrossRef]
Kobayashi, Y., Horie, M., Konno, M., Rodríguez-González, B., and Liz-Marzán, L. M., 2003, “Preparation and Properties of Silica-Coated Cobalt Nanoparticles,” J. Phys. Chem. B, 107(30), pp. 7420–7425. [CrossRef]
Pileni, M. P., 1997, “Nanosized Particles Made in Colloidal Assemblies,” Langmuir, 13(13), pp. 3266–3276. [CrossRef]
Petit, C., and Pileni, M. P., 1997, “Nanosize Cobalt Boride Particles: Control of the Size and Properties,” J. Magn. Magn. Mater., 166(1–2), pp. 82–90. [CrossRef]
Duxin, N., Brun, N., Bonville, P., Colliex, C., and Pileni, M. P., 1997, “Nanosized Fe−Cu−B Alloys and Composites Synthesized in Diphasic Systems,” J. Phys. Chem. B, 101(44), pp. 8907–8913. [CrossRef]
Lisiecki, I., and Pileni, M. P., 2003, “Synthesis of Well-Defined and Low Size Distribution Cobalt Nanocrystals: The Limited Influence of Reverse Micelles,” Langmuir, 19(22), pp. 9486–9499. [CrossRef]
Ely, T. O., Amiens, C., Chaudret, B., Snoeck, E., Verelst, M., Respaud, M., and Broto, J.-M., 1999, “Synthesis of Nickel Nanoparticles. Influence of Aggregation Induced by Modification of Poly(vinylpyrrolidone) Chain Length on Their Magnetic Properties,” Chem. Mater., 11(3), pp. 526–529. [CrossRef]
Zitoun, D., Respaud, M., Fromen, M. C., Casanove, M. J., Lecante, P., and Amiens, C., 2002, “Magnetic Enhancement in Nanoscale CoRh Particles,” Phys. Rev Lett., 89(3), p. 037203. [CrossRef] [PubMed]
Dumestre, F., Chaudret, B., Amiens, C., Renaud, P., and Fejes, P., 2004, “Superlattices of Iron Nanocubes Synthesized From Fe[N(SiMe3)2]2,” Science, 303(5659), pp. 821–823. [CrossRef] [PubMed]
Salgueiriño-Maceira, V., Liz-Marzán, L. M., and Farle, M., 2004, “Water-Based Ferrofluids From FexPt1-x Nanoparticles Synthesized in Organic Media,” Langmuir, 20(16), pp. 6946–6950. [CrossRef] [PubMed]
OmegaElectronics, 2011, Revised Thermocouple Reference Tables, Omega Engineering Inc., Stamford, CT, available at: http://www.omega.com/prodinfo/thermocouples.html
Ferrotec, 2009, “Material Safety Data Sheet,” EFH Series, Ferrotec Corp., Bedford, NH, available at: https://ferrofluid.ferrotec.com/downloads/efhmsds.pdf
Gieras, J. F., 2002, Permanent Magnet Motor Technology: Design and Applications, Marcel Dekker, New York.


Grahic Jump Location
Fig. 1

Wedgelock design setup. (a) Wedgelock in expanded mode and (b) wedgelock in loose mode.

Grahic Jump Location
Fig. 2

Wedgelock in action

Grahic Jump Location
Fig. 4

The final setup for the card

Grahic Jump Location
Fig. 5

(a) Thermocouple attached to card using solder paste. (b) Thermocouple attached to cooling block using same solder paste.

Grahic Jump Location
Fig. 6

(a) A single neodymium magnet. (b) Magnets installed in the cooling block.

Grahic Jump Location
Fig. 8

Card before and after being wiped

Grahic Jump Location
Fig. 9

Cooling block dimensions

Grahic Jump Location
Fig. 10

Lower half of the cooling block with copper pipes installed

Grahic Jump Location
Fig. 11

Cooling system setup

Grahic Jump Location
Fig. 12

Heater electric setup

Grahic Jump Location
Fig. 13

The device with the ferrofluid design card attached

Grahic Jump Location
Fig. 14

Stability check for the wedgelock design at 36.5 W

Grahic Jump Location
Fig. 15

Stability check for the ferrofluid design at 36.5 W

Grahic Jump Location
Fig. 16

Thermal resistance versus time for wedgelock design for aluminum card

Grahic Jump Location
Fig. 17

Thermal resistance versus power (wedgelock design)

Grahic Jump Location
Fig. 18

Thermal resistance versus time for ferrofluid design for aluminum card

Grahic Jump Location
Fig. 19

Thermal resistance versus power (oil based ferrofluid)

Grahic Jump Location
Fig. 20

Oil based ferrofluid design wedgelock design

Grahic Jump Location
Fig. 21

Model with boundary conditions

Grahic Jump Location
Fig. 22

Temperature distribution for ferrofluid design

Grahic Jump Location
Fig. 23

Heat flux distribution for ferrofluid design

Grahic Jump Location
Fig. 24

Temperature distribution for the wedgelock design

Grahic Jump Location
Fig. 25

Heat flux direction

Grahic Jump Location
Fig. 26

Heat flux distribution

Grahic Jump Location
Fig. 27

Thermal conductivity of wedgelock versus the thermal resistance



Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In