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Electroluminescence measurement of microscale light-emitting diode wafers using a three-dimensional flexible probe head

Nature Electronics volume 8, pages 496–509 (2025)Cite this article

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Abstract

Microscale light-emitting diodes (LEDs) could be used as the backlights of next-generation displays. However, high-density, large-area displays have stringent requirements in terms of manufacturing yields and the lack of effective tools—capable of high-throughput electroluminescence detection, which can facilitate known-good-die transfer printing—limits mass production of microscale LEDs. Here we show that a three-dimensional flexible probe head (analogous to the rigid probe cards used to conduct wafer-level tests of chips in semiconducting testing) and a corresponding electroluminescence detection system can measure the electrical and optical properties of microscale LEDs without introducing surface defects. Elastic microposts in the probe head can deform adaptively to match the surface morphology of the microscale LEDs and can tolerate height differences between the LED pads. The probe head has 32 × 32 pairs of probes that can simultaneously measure 1,024 microscale LEDs using a passive-matrix driving approach in 0.5 s. The contact stress applied from the probe head to the microscale LEDs is 0.91 MPa, which is at least two orders of magnitude lower than the yield stress that will typically create surface defects. We show that the system can perform more than 1 million repeated contact measurements with negligible probe wear.

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Fig. 1: Principles and schematics of the 3D-FPH.
Fig. 2: Mechanical characterization of the 3D-FPH.
Fig. 3: Wafer detection results by the 3D-FPH and studies of influence factors of the measurement results.
Fig. 4: EL detection of different colours of microscale LEDs.
Fig. 5: Durability and effectiveness of the 3D-FPH.

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Data availability

Data that support the findings of this study are available from the corresponding author upon reasonable request. Source data are provided with this paper.

Code availability

The codes used in this study are available at https://github.com/imcort/3D-FPH.

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Acknowledgements

This work is supported by the National Natural Science Foundation of China under grant nos. 52121002 (X.H.) and 62371335 (X.H.). This work is also partially supported by the Tiankai Higher Education Sci-Tech Innovation Park Enterprise R&D Special Program under grant no. 23YFZXYC00031 (X.H.).

Author information

Author notes

  1. These authors contributed equally: Ziyue Wu, Xiangyu Zhang.

Authors and Affiliations

  1. State Key Laboratory of Precision Measurement Technology and Instruments, Tianjin University, Tianjin, China

    Ziyue Wu, Xiangyu Zhang, Chengjie Jiang, Jingyi Wang, Yuqing Zhang, Rongrong Zhong, Jiaxuan Xing, Wenxing Huo, Chenxi Li & Xian Huang

  2. School of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin, China

    Ziyue Wu, Xiangyu Zhang, Chengjie Jiang, Jingyi Wang, Yuqing Zhang, Rongrong Zhong, Jiaxuan Xing, Wenxing Huo, Chenxi Li & Xian Huang

  3. Center of Flexible Wearable Technology, Institute of Flexible Electronic Technology of Tsinghua, Jiaxing, China

    Qing Yang & Xian Huang

  4. Tianjin Onerole Technology Inc., Tianjin Science and Technology Plaza, Tianjin, China

    Xian Huang

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Contributions

Z.W. and X.Z. contributed equally to this work. Z.W. and X.H. designed the 3D-FPH. Z.W., X.Z., C.J., J.W., Y.Z., R.Z., J.X., W.H., Q.Y. and X.H. fabricated the 3D-FPH. Z.W., C.L. and X.H. designed and developed the measurement system. Z.W. designed and tested the interfacing circuit. Z.W. and X.Z. performed the experiments and simulations. All photographic and diagrammatic content in the figures was created and composed by Z.W. and X.H. X.H. conceived, designed and directed the project. All authors analysed the data, discussed the results and commented on the paper. X.H. and Z.W. wrote the paper with input from all authors.

Corresponding author

Correspondence to Xian Huang.

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Nature Electronics thanks Ziquan Guo and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Notes 1 and 2, Tables 1–3 and Figs. 1–34.

Supplementary Video 1

A microscale LED wafer measurement process using the 3D-FPH and the associated system.

Source data

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Statistical source data.

Source Data Fig. 2

Statistical source data.

Source Data Fig. 3

Statistical source data.

Source Data Fig. 4

Statistical source data.

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Wu, Z., Zhang, X., Jiang, C. et al. Electroluminescence measurement of microscale light-emitting diode wafers using a three-dimensional flexible probe head. Nat Electron 8, 496–509 (2025). https://doi.org/10.1038/s41928-025-01396-0

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