Skip to main content
SpringerLink
Log in

Vertical Pattern of Interconnects to Bypass High Strain Near a Hard Die on a Flexible Substrate Under Mechanical Bending

  • Original Article - Electronics, Magnetics and Photonics
  • Published:
Electronic Materials Letters Aims and scope Submit manuscript

Abstract

The distinguishing feature of a flexible electronic device is that it maintains its function even when the shape changes repeatedly. As the degree of integration of flexible devices increases, revealing failure mechanisms and extending the lifetime of the flexible devices are getting more difficult. One of the potential damage zones is the interface of heterogeneous material components, where strain can be localized due to the mismatch of mechanical properties. In this study, we investigate the mechanically reliable interconnect design of the flexible printed circuit board (FPCB) system in which the packaging chip is integrated. When the FPCB was bent, folding occurred at the edge of the packaging chip due to the high bending rigidity compared with the plastic substrate and resulted in high strain concentration. By introducing interconnect architecture that bypassed the strain concentration area around the packaging chip, mechanical damage of the interconnects was successfully reduced. Through finite element simulation, the strain applied to the interconnect crossing the strain-concentrated region was predicted to be 2 times larger than that bypassing the strain-concentrated region, from 8.32 to 4.64%. In addition, the strain gap of these two interconnects could be increased as the Young’s modulus mismatch between the packaging chip and the substrate increased. This study is expected to improve the design guidelines to mechanically reliable interconnects in highly integrated flexible electronics.

Graphical Abstract

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5

Similar content being viewed by others

References

  1. Wang, B., Facchetti, A.: Mechanically flexible conductors for stretchable and wearable E-skin and E‐textile devices. Adv. Mater. 31, 1901408 (2019)

    Article  Google Scholar 

  2. Zhou, L., Wanga, A., Wu, S.-C., Sun, J., Park, S., Jackson, T.N.: All-organic active matrix flexible display. Appl. Phys. Lett. 88, 083502 (2006)

    Article  ADS  Google Scholar 

  3. Xu, S., Zhang, Y., Cho, J., Lee, J., Huang, X., Jia, L., Fan, J.A., Su, Y., Su, J., Zhang, H., Cheng, H., Lu, B., Yu, C., Chuang, C., Kim, T., Song, T., Shigeta, K., Kang, S., Dagdeviren, C., Petrov, I., Braun, P.V., Huang, Y., Paik, U., Rogers, J.A.: Stretchable batteries with self-similar serpentine interconnects and integrated wireless recharging systems. Nat. Commun. 4, 1543 (2013)

    Article  ADS  PubMed  Google Scholar 

  4. Kim, K., Lee, Y., Costa, A., Lee, Y., Jang, T., Lee, M., Joo, Y., Oh, K.H., Song, J., Choi, I.: Extremely versatile deformability beyond materiality: a new material platform through simple cutting for rugged batteries. Adv. Eng. Mater. 21, 1900206 (2019)

    Article  Google Scholar 

  5. Lee, Y.-J., Lim, S.-M., Yi, S.-M., Lee, J.-H., Kang, S., Choi, G.-M., Han, H.N., Sun, J.-Y., Choi, I.-S., Joo, Y.-C.: Auxetic elastomers: mechanically programmable meta-elastomers with an unusual Poisson’s ratio overcome the Gauge limit of a capacitive type strain sensor. Extreme Mech. Lett. 31, 100516 (2019)

    Article  Google Scholar 

  6. Choi, C., Choi, M.K., Liu, S., Kim, M.S., Park, O.K., Im, C., Kim, J., Qin, X., Lee, G.J., Cho, K.W., Kim, M., Joh, E., Lee, J., Son, D., Kwon, S.-H., Jeon, N.L., Song, Y.M., Lu, N., Kim, D.-H.: Human eye-inspired soft optoelectronic device using high-density MoS2-graphene curved image sensor array. Nat. Commun. 8, 1664 (2017)

    Article  ADS  PubMed  PubMed Central  Google Scholar 

  7. Byun, J., Oh, E., Lee, B., Kim, S., Lee, S., Hong, Y.: A single droplet-printed double‐side universal soft electronic platform for highly integrated stretchable hybrid electronics. Adv. Funct. Mater. 27, 1701912 (2017)

    Article  Google Scholar 

  8. Lee, Y.-J., Lee, U., Yeon, Y., Shin, H.-W., Evans, H.-A.-S., Joo, L.A.: Influences of semiconductor morphology on the mechanical fatigue behavior of flexible organic electronics. Appl. Phys. Lett. 103, 241904 (2013)

    Article  ADS  Google Scholar 

  9. Lee, Y.-Y., Lee, J.-H., Cho, J.-Y., Kim, N.-R., Nam, D.-H., Choi, I.-S., Nam, K.T., Joo, Y.-C.: Stretching-induced growth of PEDOT-rich cores: a new mechanism for strain-dependent resistivity change in PEDOT: PSS films. Adv. Funct. Mater. 23, 4020–4027 (2013)

    Article  CAS  Google Scholar 

  10. Lee, Y.-Y., Kang, H.-Y., Gwon, S.H., Choi, G.M., Lim, S.-M., Sun, J.-Y., Joo, Y.-C.: A strain-insensitive stretchable electronic conductor: PEDOT:PSS/acrylamide organogels. Adv. Mater. 28, 1636–1643 (2016)

    Article  CAS  PubMed  Google Scholar 

  11. Yoon, S.G., Koo, H.-J., Chang, S.T.: Highly stretchable and transparent microfluidic strain sensors for monitoring human body motions. ACS Appl. Mater. Interfaces 7, 27562–27570 (2015)

    Article  CAS  PubMed  Google Scholar 

  12. Zhou, R., Guo, W., Yu, R., Pan, C.: Highly flexible, conductive and catalytic Pt networks as transparent counter electrodes for wearable dye-sensitized solar cells. J. Mater. Chem. A 3, 23028–23034 (2015)

    Article  CAS  Google Scholar 

  13. Hwang, B., Shin, H.-A.-S., Kim, T., Joo, Y.-C., Han, S.M.: Highly reliable Ag nanowire flexible transparent electrode with mechanically welded junctions. Small 10, 3397–3404 (2014)

    Article  CAS  PubMed  Google Scholar 

  14. Kim, D.-H., Ahn, J.-H., Choi, W.M., Kim, H.-S., Kim, T.-H., Song, J., Huang, Y.Y., Liu, Z., Lu, C., Rogers, J.A.: Stretchable and foldable silicon integrated circuits. Science 320, 507–511 (2008)

    Article  ADS  CAS  PubMed  Google Scholar 

  15. Hsu, Y.-Y., Gonzalez, M., Bossuyt, F., Vanfleteren, J., De Wolf, I.: Polyimide-enhanced stretchable interconnects: design, fabrication, and characterization. IEEE Trans. Electron. Devices 58, 2680–2688 (2011)

    Article  ADS  CAS  Google Scholar 

  16. Kim, B.-J., Cho, Y., Jung, M.-S., Shin, H.-A.-S., Moon, M.-W., Han, H.N., Nam, K.T., Joo, Y.-C., Choi, I.-S.: Fatigue-free, electrically reliable copper electrode with nanohole array. Small 8, 3300–3306 (2012)

    Article  CAS  PubMed  Google Scholar 

  17. Naserifar, N., LeDuc, P.R., Fedder, G.K.: Material gradients in stretchable substrates toward integrated electronic functionality. Adv. Mater. 28, 3584–3591 (2016)

    Article  CAS  PubMed  Google Scholar 

  18. Yi, S.-M., Choi, I.-S., Kim, B.-J., Joo, Y.-C.: Reliability issues and solutions in flexible electronics under mechanical fatigue. Electron. Mater. Lett. 14, 387–404 (2018)

    Article  ADS  CAS  Google Scholar 

  19. Gan, L., Ben-Nissan, B., Ben-David, A.: Modelling and finite element analysis of ultra-microhardness indentation of thin films. Thin Solid Films 290–291, 362–366 (1996)

    Article  ADS  Google Scholar 

  20. Yu, D.Y.W., Spaepen, F.: The yield strength of thin copper films on kapton. J. Appl. Phys. 95, 2991–2997 (2004)

    Article  ADS  CAS  Google Scholar 

  21. Kim, J.-H., Lee, T.-I., Kim, T.-S., Paik, K.-W.: Effects of ACFs adhesion on the bending reliability of chip-in-flex packages for wearable electronics applications. In: 2016 IEEE 66th Electronic Components and Technology Conference (ECTC), IEEE: Las Vegas, NV, USA, pp. 2461–2467 (2016)

  22. Ko, C.-T., Yang, H., Lau, J.H., Li, M., Lin, C., Chang, C.-L., Pan, J.-Y., Wu, H.-H., Xu, I., Chen, T., Li, Z., Tan, K.H., Lo, P., So, R., Chen, Y.H., Fan, N., Kuah, E., Lin, M., Cheung, Y.M., Ng, E., Xi, C., Beica, R., Lim, S.P., Lee, N.C., Tao, M., Lo, J., Lee, R.: Feasibility study of fan-out panel-level packaging for heterogeneous integrations. In :2019 IEEE 69th Electronic Components and Technology Conference (ECTC); IEEE: Las Vegas, NV, USA, pp. 14–20 (2019)

  23. Lu, N., Suo, Z., Vlassak, J.: The effect of film thickness on the failure strain of polymer-supported metal films. Acta Mater. 58, 1679–1687 (2010)

    Article  ADS  CAS  Google Scholar 

  24. Kraft, O., Schwaiger, R., Wellner, P.: Fatigue in thin films: lifetime and damage formation. Mater. Sci. Eng. A 319–321, 919–923 (2001)

    Article  Google Scholar 

  25. Sun, X.J., Wang, C.C., Zhang, J., Liu, G., Zhang, G.J., Ding, X.D., Zhang, G.P., Sun, J.: Thickness dependent fatigue life at microcrack nucleation for metal thin films on flexible substrates. J. Phys. D Appl. Phys. 41, 195404 (2008)

    Article  ADS  Google Scholar 

  26. Schwaiger, R., Dehm, G., Kraft, O.: Cyclic deformation of polycrystalline Cu films. Philos. Mag. 83, 693–710 (2003)

    Article  ADS  CAS  Google Scholar 

  27. Kim, B.-J., Shin, H.-A.-S., Jung, S.-Y., Cho, Y., Kraft, O., Choi, I.-S., Joo, Y.-C.: Crack nucleation during mechanical fatigue in thin metal films on flexible substrates. Acta Mater. 61, 3473–3481 (2013)

    Article  ADS  CAS  Google Scholar 

  28. Deng, G., Nakanishi, T.: Advances in Ceramics-Characterization, Raw Materials, Processing, Properties, Degradation and Healing. IntechOpen, London (2011)

    Google Scholar 

  29. Lacour, S.P., Wagner, S., Huang, Z., Suo, Z.: Stretchable gold conductors on elastomeric substrates. Appl. Phys. Lett. 82, 2404–2406 (2003)

    Article  ADS  CAS  Google Scholar 

Download references

Acknowledgements

This work was supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (No. 2022R1A5A7000765), MOTIE(Ministry of Trade, Industry & Energy (20019469) and KSRC(Korea Semiconductor Research Consortium) (852) support program for the development of the future semiconductor device, and Technology Innovation Program (20011119) funded by the Ministry of Trade, Industry & Energy (MOTIE, Korea).

Author information

Author notes

  1. Jong-Sung Lee and Young-Joo Lee are contributed equally.

Authors and Affiliations

  1. Department of Materials Science and Engineering, Seoul National University, Seoul, 08826, Republic of Korea

    Jong-Sung Lee, Young-Joo Lee & Young-Chang Joo

  2. Materials Research Centre for Energy and Clean Technology, School of Materials Science and Engineering, Andong National University, Andong, 36729, Republic of Korea

    Jaegeun Seol

  3. Research Institute of Advanced Materials (RIAM), Seoul National University, Seoul, 08826, Republic of Korea

    Young-Chang Joo

  4. Department of Advanced Materials Engineering, Tech University of Korea, Siheung, 15073, Republic of Korea

    Byoung-Joon Kim

Authors
  1. Jong-Sung Lee
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Young-Joo Lee
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Jaegeun Seol
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Young-Chang Joo
    View author publications

    You can also search for this author in PubMed Google Scholar

  5. Byoung-Joon Kim
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Byoung-Joon Kim.

Ethics declarations

Conflict of interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Publisher’s Note

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

Rights and permissions

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Lee, JS., Lee, YJ., Seol, J. et al. Vertical Pattern of Interconnects to Bypass High Strain Near a Hard Die on a Flexible Substrate Under Mechanical Bending. Electron. Mater. Lett. 20, 122–130 (2024). https://doi.org/10.1007/s13391-023-00444-1

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s13391-023-00444-1

Keywords

Search

Navigation