Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

High-efficiency cooling via the monolithic integration of copper on electronic devices


Electrification is critical to decarbonizing society, but managing increasing power densification in electrical systems will require the development of new thermal management technologies. One approach is to use monolithic-metal-based heat spreaders that reduce thermal resistance and temperature fluctuation in electronic devices. However, their electrical conductivity makes them challenging to implement. Here we report co-designed electronic systems that monolithically integrate copper directly on electronic devices for heat spreading and temperature stabilization. The approach first coats the devices with an electrical insulating layer of poly(2-chloro-p-xylylene) (parylene C) and then a conformal coating of copper. This allows the copper to be in close proximity to the heat-generating elements, eliminating the need for thermal interface materials and providing improved cooling performance compared with existing technologies. We test the approach with gallium nitride power transistors, and show that it can be used in systems operating at up to 600 V and provides a low junction-to-ambient specific thermal resistance of 2.3 cm2 K W–1 in quiescent air and 0.7 cm2 K W–1 in quiescent water.

Your institute does not have access to this article

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: Cu-coated heat spreader fabrication.
Fig. 2: Photographs of the tested configurations.
Fig. 3: Thermal performance of EPC2034 monolithically integrated with copper.
Fig. 4: Heat-spreading analysis.
Fig. 5: Coating effect on thermomechanical reliability.

Data availability

Data supporting the findings of this study are available at All other data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

Code availability

MATLAB, Ansys Static Structural and Ansys Icepak input files generated for this work are available at All other files that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.


  1. Masanet, E. et al. Recalibrating global data center energy-use estimates. Science 367, 984–986 (2020).

    Article  Google Scholar 

  2. Nadjahi, C., Louahlia, H. & Lemasson, S. A review of thermal management and innovative cooling strategies for data center. Sustain. Comput.: Inform. Syst. 19, 14–28 (2018).

    Google Scholar 

  3. Kim, J., Oh, J. & Lee, H. Review on battery thermal management system for electric vehicles. Appl. Therm. Eng. 149, 192–212 (2019).

    Article  Google Scholar 

  4. Modeer, T. et al. Design of a GaN-based interleaved nine-level flying capacitor multilevel inverter for electric aircraft applications. IEEE Trans. Power Electron. 35, 12153–12165 (2020).

    Article  Google Scholar 

  5. Lei, Y. et al. A 2-kW single-phase seven-level flying capacitor multilevel inverter with an active energy buffer. IEEE Trans. Power Electron. 32, 8570–8581 (2017).

    Article  Google Scholar 

  6. Kadam, S. T. & Kumar, R. Twenty first century cooling solution: microchannel heat sinks. Int. J. Therm. Sci. 85, 73–92 (2014).

    Article  Google Scholar 

  7. Ellsworth, M. J. et al. An overview of the IBM power 775 supercomputer water cooling system. J. Electron. Packag. 134, 020906 (2012).

  8. Kandlikar, S. G. & Hayner, C. N. Liquid cooled cold plates for industrial high-power electronic devices—thermal design and manufacturing considerations. Heat Transf. Eng. 30, 918–930 (2009).

    Article  Google Scholar 

  9. Baker, E. Liquid immersion cooling of small electronic devices. Microelectron. Reliab. 12, 163–173 (1973).

    Article  Google Scholar 

  10. Bergles, A. E. and Bar-Cohen, A. Immersion cooling of digital computers. in Cooling of Electronic Systems 539–621 (Springer, 1994).

  11. Birbarah, P. et al. Water immersion cooling of high power density electronics. Int. J. Heat. Mass Transf. 147, 118918 (2020).

    Article  Google Scholar 

  12. Agonafer, D., Spector, M. S. and Miljkovic, N. Materials and interface challenges in high vapor quality two-phase flow boiling research. IEEE Trans. Compon. Packag. Manuf. Technol. 11, 1583–1591 (2021).

  13. Tong, X. C. Thermal management fundamentals and design guides in electronic packaging. in Advanced Materials for Thermal Management of Electronic Packaging 30, 1–58 (Springer, 2011).

  14. Lasance, C. J. How to estimate heat spreading effects in practice. J. Electron. Packag. 132, 031004 (2010).

  15. Werner, T., Grillberger, M. and Feustel, F. 3-D integrated semiconductor device comprising intermediate heat spreading capabilities. US patent 8,080,866 (2011).

  16. Seelmann-Eggebert, M. et al. Heat-spreading diamond films for GaN-based high-power transistor devices. Diam. Relat. Mater. 10, 744–749 (2001).

    Article  Google Scholar 

  17. Chiriac, V. et al. A figure of merit for smart phone thermal management. Electron. Cooling 17, 18–23 (2015).

  18. Smalc, M. et al. Thermal performance of natural graphite heat spreaders. in International Electronic Packaging Technical Conference and Exhibition 79–89 (ASME, 2005).

  19. Han, Y. et al. Thermal management of hotspots using diamond heat spreader on Si microcooler for GaN devices. IEEE Trans. Compon. Packag. Manuf. Technol. 5, 1740–1746 (2015).

    Article  Google Scholar 

  20. Gao, Z. et al. Thermal chemical vapor deposition grown graphene heat spreader for thermal management of hot spots. Carbon 61, 342–348 (2013).

    Article  Google Scholar 

  21. Seymour, J. P. et al. The insulation performance of reactive parylene films in implantable electronic devices. Biomaterials 30, 6158–6167 (2009).

    Article  Google Scholar 

  22. Sarvar, F., Whalley, D. C. and Conway, P. P. Thermal interface materials—a review of the state of the art. in 2006 1st Electronic System Integration Technology Conference 1292–1302 (IEEE, 2006).

  23. Hansson, J. et al. Novel nanostructured thermal interface materials: a review. Int. Mater. Rev. 63, 22–45 (2018).

    Article  Google Scholar 

  24. Hwang, G. et al. Multi-artery heat-pipe spreader: lateral liquid supply. Int. J. Heat Mass Transf. 54, 2334–2340 (2011).

    Article  Google Scholar 

  25. Weibel, J. A. & Garimella, S. V. Recent advances in vapor chamber transport characterization for high-heat-flux applications. Adv. Heat Transf. 45, 209–301 (2013).

    Article  Google Scholar 

  26. Mattox, D. M. Handbook of Physical Vapor Deposition (PVD) Processing (William Andrew, 2010).

  27. Kim, B. J. & Meng, E. Micromachining of parylene C for bioMEMS. Polym. Adv. Technol. 27, 564–576 (2016).

    Article  Google Scholar 

  28. Shin, Y. S. et al. PDMS-based micro PCR chip with parylene coating. J. Micromech. Microeng. 13, 768 (2003).

    Article  Google Scholar 

  29. Heid, A. et al. Examination of dielectric strength of thin parylene C films under various conditions. Curr. Dir. Biomed. Eng. 2, 39–41 (2016).

    Article  Google Scholar 

  30. Chang, S.-C. et al. The effect of plating current densities on self-annealing behaviors of electroplated copper films. J. Electrochem. Soc. 149, G535 (2002).

    Article  Google Scholar 

  31. Darveaux, R. Effect of simulation methodology on solder joint crack growth correlation and fatigue life prediction. J. Electron. Packag. 124, 147–154 (2002).

    Article  Google Scholar 

  32. Milman, Y. V., Gridneva, I. & Golubenko, A. Construction of stess-strain curves for brittle materials by indentation in a wide temperature range. Sci. Sinter. 39, 67–75 (2007).

    Article  Google Scholar 

  33. Kim, S. et al. Stress behavior of electrodeposited copper films as mechanical supporters for light emitting diodes. Electrochim. Acta 52, 5258–5265 (2007).

    Article  Google Scholar 

  34. Chu, K.-H. et al. Hierarchically structured surfaces for boiling critical heat flux enhancement. Appl. Phys. Lett. 102, 151602 (2013).

    Article  Google Scholar 

  35. Rahman, M. M., Olceroglu, E. & McCarthy, M. Role of wickability on the critical heat flux of structured superhydrophilic surfaces. Langmuir 30, 11225–11234 (2014).

    Article  Google Scholar 

  36. Li, J. et al. Ultrascalable three-tier hierarchical nanoengineered surfaces for optimized boiling. ACS Nano 13, 14080–14093 (2019).

    Article  Google Scholar 

  37. Zhang, C. et al. Enhanced capillary‐fed boiling in copper inverse opals via template sintering. Adv. Funct. Mater. 28, 1803689 (2018).

    Article  Google Scholar 

  38. Azizi, A., Daeumer, M. A. & Schiffres, S. N. Additive laser metal deposition onto silicon. Addit. Manuf. 25, 390–398 (2019).

    Google Scholar 

  39. Azizi, A. et al. Additive laser metal deposition onto silicon for enhanced microelectronics cooling. in 2019 IEEE 69th Electronic Components and Technology Conference (ECTC) 1970–1976 (IEEE, 2019).

  40. Matijevic, E., Poskanzer, A. & Zuman, P. Characterization of the stannous chloride/palladium chloride catalysts for electroless plating. Plat. Surf. Finish. 62, 958–965 (1975).

    Google Scholar 

  41. Taylor, R. & Welber, B. Laser-monitored deposition of parylene thin films. Thin Solid Films 26, 221–226 (1975).

    Article  Google Scholar 

  42. White, G. & Minges, M. Thermophysical properties of some key solids: an update. Int. J. Thermophys. 18, 1269–1327 (1997).

    Article  Google Scholar 

  43. Jiang, P., Huang, B. & Koh, Y. K. Accurate measurements of cross-plane thermal conductivity of thin films by dual-frequency time-domain thermoreflectance (TDTR). Rev. Sci. Instrum. 87, 075101 (2016).

    Article  Google Scholar 

  44. Pena, E. M. D. & Roy, S. Electrodeposited copper using direct and pulse currents from electrolytes containing low concentration of additives. Surf. Coat. Technol. 339, 101–110 (2018).

    Article  Google Scholar 

  45. Chiang, K.-N. & Yuan, C.-A. An overview of solder bump shape prediction algorithms with validations. IEEE Trans. Adv. Packag. 24, 158–162 (2001).

    Article  Google Scholar 

Download references


We gratefully acknowledge funding support from the Advanced Research Projects Agency-Energy (ARPA-E) with cooperative agreement no. DE-AR0000900. N.M. and T.G. gratefully acknowledge funding support from the Power Optimization of Electro-Thermal Systems (POETS) National Science Foundation Engineering Research Center with cooperative agreement no. EEC-1449548. T.G. gratefully acknowledges funding support from a PPG-MRL assistantship. N.M. gratefully acknowledges funding support from the International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), sponsored by the Japanese Ministry of Education, Culture, Sports, Science and Technology. We thank S. Robinson of the Microscopy Suite at the Beckman Institute for Advanced Science and Technology (part of the University of Illinois at Urbana-Champaign) for help with thermal evaporation. Laser scanning confocal microscopy, scanning electron microscopy, four-point probe and parylene C coating were carried out in part at the Materials Research Laboratory’s Central Research Facilities, University of Illinois.

Author information

Authors and Affiliations



T.G. and N.M. conceived the initial idea and designed the experiments. T.G., J.L. and J.M. fabricated the samples and carried out the material characterization. T.G., A.R.G., J.M., N.M., J.S., L.H. and R.P.-P. performed the experimental and theoretical analyses and wrote the manuscript. R.P.-P. and N.M. edited the manuscript and guided the work.

Corresponding author

Correspondence to Nenad Miljkovic.

Ethics declarations

Competing interests

The authors declare no competing interests.

Peer review

Peer review information

Nature Electronics thanks the anonymous reviewers for their contribution to the peer review of this work.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Sections 1–11, Tables 1–18, Figs. 1–11 and refs. 1–40.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Gebrael, T., Li, J., Gamboa, A.R. et al. High-efficiency cooling via the monolithic integration of copper on electronic devices. Nat Electron 5, 394–402 (2022).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing