Flexible and stretchable Micro-LED array devices with Optical-Thermal layered packaging
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摘要:
针对柔性可拉伸微型LED阵列器件在高电流密度下热积累严重，以及传统导热填料易导致有机硅基体固化抑制的难题，本文提出一种基于铂金催化改性的光热分层封装结构，构建了集基底层散热反射、中层蛇形导电互连LED阵列及顶层透光功能于一体的4×4柔性可拉伸LED阵列。基底层采用AlN颗粒作为导热填料，并引入铂金催化剂作为固化补偿剂，实现了填充量20 wt%、粒径60 μm的AlN在Ecoflex 00-30基体中均匀分散与完全固化。实验表明，AlN/Ecoflex 00-30复合基底材料具备良好的热学与力学性能，其热导率达0.222 W/(m·K)，较纯Ecoflex 00-30提升了35.4%，且在300%的拉伸应变下仍保持结构完整。通过将高柔韧性的基底层与高拉伸度蛇形导电互连结构结合，有效释放了机械形变过程中的应力，保障了器件在动态弯曲下的电学连接可靠性。瞬态热阻测试表明，采用光热分层封装的LED发光单元在20 mA恒定驱动电流下的稳态结温较纯Ecoflex 00-30封装降低2.95 °C。验证了该方案在协同实现热管理与力学顺应性的可行性。
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关键词:
- 柔性微型LED封装 /
- AlN/Ecoflex 00-30复合材料 /
- 蛇形导电互连 /
- 瞬态结温测试
Abstract:Flexible and stretchable micro-LED arrays suffer from severe heat accumulation at high current densities. Conventional thermally conductive fillers can also inhibit curing of silicone matrices. We propose a platinum-catalyst-modified optical-thermal layered packaging structure to address both problems. A 4 × 4 flexible and stretchable LED array was fabricated. It integrates a heat-dissipating and light-reflecting substrate layer. The middle layer contains an LED array with serpentine conductive interconnects. A light-transmitting functional layer forms the top layer. AlN particles were used as thermally conductive fillers in the substrate. Additional platinum catalyst was introduced as a curing compensator. Uniform dispersion and complete curing were achieved at 20 wt% loading and 60 μm particle size. The composite substrate showed favorable thermal and mechanical properties. Its thermal conductivity reached 0.222 W/(m·K), 35.4% higher than pristine Ecoflex 00-30. It remained structurally intact under 300% tensile strain. The flexible substrate and serpentine interconnects effectively released stress during mechanical deformation. They maintained reliable electrical connections under dynamic bending. Transient thermal resistance tests were conducted at a constant driving current of 20 mA. The steady-state junction temperature was 2.95 °C lower than that of pristine Ecoflex 00-30 packaging. These results demonstrate effective thermal management while maintaining mechanical compliance.
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图 1 光热分层柔性可拉伸微型LED阵列结构示意图。(a)4×4阵列正视图；(b)器件结构分解图
Figure 1. Schematic of the optical-thermal layered flexible and stretchable micro-LED array. (a) Front view of the 4 × 4 array; (b) three-dimensional structure of the device
图 2 AlN/Ecoflex 00-30复合材料光学显微图。(a)未添加固化补偿剂；(b)添加固化补偿剂
Figure 2. Optical micrographs of AlN/Ecoflex 00-30 composites. (a) Without curing compensator; (b) With curing compensator
图 3 李氏盘稳态热导率测试系统结构示意图
Figure 3. Schematic of the Lee's disk steady-state thermal conductivity measurement system
图 4 1 μm粒径AlN填料不同质量分数下 AlN/Ecoflex 00-30 复合基底热导率测试结果
Figure 4. Thermal conductivity of AlN/Ecoflex 00-30 composite substrates at different AlN mass fractions using 1 μm AlN fillers
图 5 固定20 wt%质量分数下不同AlN粒径AlN/Ecoflex 00-30复合基底热导率测试结果
Figure 5. Thermal conductivity of AlN/Ecoflex 00-30 composite substrates with different AlN particle sizes at a fixed mass fraction of 20 wt%
图 6 单轴拉伸。(a)试样几何尺寸参数(单位：mm)；(b)制备的实体试样
Figure 6. Uniaxial tensile test. (a) Geometric dimensions of the specimen (unit: mm); (b) photograph of the prepared specimen
图 7 多周期循环单轴拉伸测试结果。(a)-(d)分别对应第1次、第5次、第20次及第50次循环加载过程中的应力-应变迟滞曲线；(e)单轴拉伸初始状态；(f)单轴拉伸300%状态
Figure 7. Multi-cycle uniaxial tensile test results. (a)-(d) Stress-strain hysteresis curves for the 1st, 5th, 20th, and 50th cycles, respectively; (e) initial state of the specimen; (f) specimen at 300% tensile strain
图 8 柔性可拉伸微LED阵列的制备工艺流程
Figure 8. Fabrication process flow for the flexible and stretchable micro-LED array
图 9 柔性LED阵列器件与发光状态（a）柔性LED阵列器件图；（b）阵列点亮图；（c）单折叠发光图；（d）双折叠发光图；（e）锥状形变发光图
Figure 9. Flexible LED array device and its light-emitting states. (a) Flexible LED array device; (b) illuminated array; (c) light emission under single folding; (d) light emission under double folding; (e) light emission under conical deformation
图 10 基于“双面主动加热-热阻尼缓冲-中心均温”架构的柔性器件固态K因子标定系统原理图
Figure 10. Schematic of the solid-state K-factor calibration system for flexible devices based on "bilateral active heating, thermal damping buffering, and central temperature equalization"
图 11 LED的正向电压-结温（
$ {V}_{f}-{T}_{j} $ ）标定拟合曲线Figure 11. Calibration and fitted curves of LED forward voltage versus junction temperature (
$ {V}_{f}-{T}_{j} $ )
图 12 方波扫描热-电耦合瞬态测温原理与时序控制逻辑图
Figure 12. Schematic of the principle and timing control logic for square-wave scanning thermo-electric coupled transient temperature measurement
图 13 不同基底封装材料发光单元的热-电耦合测试结果对比
Figure 13. Comparison of thermo-electric coupled test results for LED devices with different substrate encapsulation materials
图 14 不同基底封装材料发光单元达到热学平衡后的稳态结温（
$ {T}_{j} $ ）与净温升（$ \text{Δ}T $ ）Figure 14. Steady-state junction temperature (
$ {T}_{j} $ ) and net temperature rise ($ \text{Δ}T $ ) of LED devices with different substrate encapsulation materials after reaching thermal equilibrium
图 15 不同基底封装材料LED发光单元连续工作过程中的平均峰值波长变化。阴影区域表示5次测试结果的标准差
Figure 15. Variation of average peak wavelength for LED units with different substrate packaging materials during continuous operation. The shaded area represents the standard deviation of five measurements.
表 1 LED阵列器件封装散热基底层和未封装5次光功率密度测试结果(单位：
$ \text{mW/}{\text{cm}}^{2} $ )Table 1. Five optical power density measurements of the LED array device with and without heat-dissipating substrate encapsulation (unit: mW/cm2)
1 2 3 4 5 平均值 封装 2.0406 2.0347 2.0312 2.0317 2.0339 2.03442 未封装 1.7641 1.7595 1.7583 1.7622 1.7548 1.75978 
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