Silver nanoparticle paste is a promising interconnect material for high-temperature power electronics, but its direct bonding with silicon is hindered by the high chemical stability of silicon surfaces. This paper proposes a femtosecond laser method to induce micro-nanostructures on silicon surfaces for low-temperature, high-strength bonding with nano-silver paste. By adjusting the laser fluence, multi-level micro-nano structures comprising micrometer cones, nanoparticles, and periodic patterns are fabricated on silicon, with the optimal average microstructure depth reaching 7.65 μm at 3.11 J/cm2. Shear strength tests demonstrate that untreated flat silicon achieves only 3.1 MPa, while structured silicon reaches a peak strength of 30.5 MPa at 3.11 J/cm2, representing a tenfold increase. The transition in failure mode from interfacial adhesion to substrate internal failure confirms mechanical anchoring, and cross-sectional analysis reveals complete filling of the microstructures by the silver paste, forming three-dimensional interlocking. Thermal cycling and high-temperature aging yield average shear strengths of 15.1 MPa and 10.5 MPa, respectively. Finite element simulations further reveal that 150 °C serves as a critical transition temperature for stress relaxation in the Ag layer during cooling. This work provides an effective approach for reliable power device packaging.

The high-strength joining of glass and aluminum ensures the reliability of the components under extreme conditions. To solve the problem of poor joining strength of direct bonding between glass/aluminum alloy and metal solder, microstructure arrays are fabricated on the substrate by femtosecond laser to form mechanical interlocks to enhance the joining strength of the interface. The impact of microstructure arrays with different morphologies on the shear strength of the joints is investigated. By increasing the depth of the microstructures, it is possible to increase the strength of the glass/aluminum alloy joint up to 17.9 MPa, approximate to 23 times higher than direct joining of flat substrates (0.76 MPa). Meanwhile, a shear strength of up to 16.25 MPa is obtained at a low sintering temperature of 180 degrees C. The highest shear strength is 23.02 MPa when the sintering temperature is 200 degrees C, which contributes to the protection of the glass substrate against cracks caused by mismatch of the coefficient of thermal expansion. This method used to improve the strength of the glass-aluminum alloy joint by fabricating microstructure arrays promotes the application of glass in industry.

Dual-band antireflection (DBAR) windows based on surface microstructures offer a promising solution for mid-wave infrared (MWIR) and long-wave infrared (LWIR) co-aperture composite imaging. However, micro-nano manufacturing technology faces significant challenges in efficiently producing highly uniform microstructures with characteristic dimensions of ∼1 μm across hundreds of millimeters. Here, we report a laser optical field modulation (LOFM) technology for the rapid manufacture of ultra-large-scale arrays of antireflection microholes (ARMHs) on large-aperture and non-perfectly planar windows. LOFM technology, which modulates laser pulses in both temporal and spatial domains, enhances ARMH aspect ratios from 0.1 to 0.8 without reducing manufacturing time, and maintains processing accuracy even with laser focus shifts, thereby addressing inconsistencies in large-area processing. As a proof of concept, approximately 7 billion ARMHs are fabricated on a 100-mm-diameter zinc sulfide (ZnS) window at a rate of 20 000 holes per second using LOFM technology assisted by machine learning. The fabricated DBAR ZnS window exhibits ultra-broadband (3.5–14 μm), high transmittance (91.1%), wide-angle transmission, wear-resistant, and self-cleaning, making it suitable for environments with multiple interference factors. Dual-band imaging applications demonstrate the significant advantages of DBAR windows in target recognition, multi-scenario robustness, and information acquisition.

ABSTRACT Flexible pressure sensors are pivotal for wearable electronics and intelligent robotics, yet conventional single‐layer uniform microstructures suffer from a critical tradeoff between sensitivity and sensing range. Inspired by the dome‐shaped pressure receptors of varying sizes found in crocodile skin, this paper proposes and fabricates an asymmetric, bilayer microstructure array flexible piezoresistive pressure sensor based on one‐step femtosecond laser fabrication technology. The sensor uses polydimethylsiloxane (PDMS) as a flexible substrate, with micro‐dome arrays of different sizes fabricated on both surfaces using a femtosecond laser. This ensures high fidelity and consistency in the microstructure morphology. Benefiting from the asymmetric bilayer structural design, the sensor achieves high sensitivity (64.1 kPa − 1 ) and excellent linearity (R 2 = 0.985) across an extremely wide operating range of 0.5–2000 kPa, while also demonstrating fast response and recovery times (104 ms/38 ms), excellent cyclic stability (>10 000 cycles), and resistance to vibration interference. The microstructure remained stable even after 10 000 fatigue load cycles. It enables reliable geological identification for detector vehicles and precise object‐size classification for mechanical claws, demonstrating great promise for high‐performance robotic perception applications.

The simultaneous improvement in sensitivity, response speed, and operating range of flexible pressure sensors is crucial for their applications in human-computer interaction, health monitoring, and robotic perception. Inspired by the microgroove structure of scorpion slit sensilla, a biomimetic pressure sensor based on a rigid-flexible hybrid design strategy is proposed in this study. This sensor is composed of a flexible layer of polydimethylsiloxane (PDMS) and a rigid layer of spring steel. A microgroove array template is fabricated on a zirconia ceramic substrate using a femtosecond laser, and a biomimetic microgroove array is formed on the PDMS surface via the template replication method. Silver nanoparticles are sputtered onto the surface as the conductive layer. Experimental results show that the sensor has a high sensitivity of 1.50 ± 0.04 kPa-1, a wide operating range of 0.2 kPa to 140 kPa, an average linearity (R2) as high as 0.995 within the 0.2 kPa to 20 kPa range, a response time of 45 ± 4 ms, and a recovery time of 40 ± 3 ms. By integrating the sensor into the sole of a quadruped robot and combining it with a Bluetooth wireless transmission module and machine learning algorithms, the system achieves high-precision identification of four types of geological environments.

Flexible pressure sensors with a wide working range and high sensitivity are crucial for intelligent robot perception. However, simultaneously enhancing these performance metrics remains challenging, and traditional microstructure fabrication methods often involve complex processes. Herein, a flexible piezoresistive pressure sensor is proposed, featuring corrugated structures fabricated on polydimethylsiloxane (PDMS) surfaces using femtosecond laser ablation. These corrugations dynamically adjust the contact area under pressure, enabling a broad operating range from 0.5 kPa to 500 kPa and high sensitivity of 3.8 kPa⁻¹. Notably, the sensor exhibits excellent linearity (R² = 0.994) across the 6.3-230 kPa pressure range and maintains stable performance through over 7000 loading-unloading cycles. Finite element analysis of stress distribution elucidates the sensing mechanism. Furthermore, integrating the sensor onto a mechanical claw and combining it with machine learning algorithms enabled intelligent recognition of objects with varying diameters, achieving a classification accuracy of up to 97.33%. This work provides a simple and efficient strategy for fabricating high-performance flexible pressure sensors and demonstrates their significant application potential in intelligent robotic perception systems.

Bionic anti-reflection windows are critical for enhancing the performance of aerospace infrared detection systems. The manufacturing of anti-reflective microstructures (ARMs), however, faces a significant challenge that the transmittance spectrum is difficult to predict both accurately and swiftly, leading to long-term reliance on blind and inefficient trial-and-error for process optimization. Here, we report a method that integrates machine learning (ML) with femtosecond laser for the rapid customization of high-performance anti-reflection windows. Embedding of the material's absorption characteristics as a physical constraint into the ML model enables highly accurate prediction across an ultra-broad transmittance spectrum, overcoming the failure of conventional simulations in these intrinsic absorption bands. The trained ML model serves as an intelligent agent to guide the precise control over multiple femtosecond laser parameters, thus converting the costly process of physical trial-and-error into one of efficient virtual screening and iteration. As a proof of concept, an anti-reflective sapphire window was produced that demonstrates broadband (3.3-6.0 mu m) and high transmittance (similar to 96.8% peak at 4.2 mu m), along with excellent wide-angle characteristics, mechanical wear resistance, and high-quality imaging capability. This work provides a novel paradigm for rapidly manufacturing high-performance anti-reflective windows, laying the foundation for next-generation optical components.

With the advancement of 3D integration technology, the integration density and operational speed of circuits continue to increase. Consequently, there is a corresponding rise in the demand for interconnection reliability. However, traditional interconnection processes and materials are no longer able to meet the requirements for interconnection reliability. This study optimized the interconnection material by utilizing different ratios of organic compounds in nano-copper coating materials. Micro/nanostructures were processed using femtosecond laser and secondary thermal coating to enhance the interconnection process. Firstly, to ensure processing efficiency, we utilized femtosecond laser to create micro/nanostructures with increased surface contact area. Subsequently, varying molar ratios of ascorbic acid and benzimidazole were utilized in the preparation of copper (Cu) pastes to analyze their impact on the dispersion and sphericity of the copper nanoparticles and the shear strength of the interconnections. The ideal combination resulted in well-dispersed spherical copper nanoparticles, copper nano paste with an average shear strength of about 38 MPa was obtained. In addition, optimization was achieved through the femtosecond laser copper interconnection sintering process using a secondary heat coating, which reduced the unfilled rate of surface microstructures from 35.31 % to 11.25 % and increased the copper interconnection strength from 31.42 MPa to 43.65 MPa. Finally, finite element simulation analysis was employed to study the temperature and stress distribution of the copper interconnect during operation and to predict its service life under thermal cycling conditions (-50 degrees C-300 degrees C). The results demonstrated that the reliability of the sintered structure meets operational requirements.

Femtosecond laser processing of large-area micro- and nanostructures exhibits significant potential for applications in materials science, optical engineering, and biomedicine. However, existing methods for fabricating high-performance micro- and nanostructures heavily rely on empirical trial-and-error approaches, leading to cumbersome processes, high resource consumption, and low efficiency. To achieve the efficient manufacturing of anti-reflective microstructures with nearly perfect performance, we propose a strategy that utilizes machine learning (ML) to assist femtosecond lasers in real-time prediction and process optimization. A multilayer perceptron model was trained on simulation data derived from the finite-difference time-domain method, establishing a nonlinear mapping between microstructural morphology parameters and transmittance. By deploying the trained model in the fabrication system, transmittance spectra can be predicted within 0.004 s upon input of structural parameters, significantly enhancing process optimization efficiency. Ultimately, using ML-optimized processing parameters combined with a burst pulse and bow-tie scanning technique, large-area anti-reflective microhole arrays (12 × 12 mm2) with a periodicity of 2 μm were fabricated on the surface of magnesium fluoride (MgF2) windows at a rate of 10,000 holes per second. The anti-reflective MgF2 window achieved an average transmittance of 99.03% in the 3 to 5 μm range, maintaining stable transmittance across a broad angle range (0-50°) and demonstrating excellent infrared image capturing capabilities. This study facilitates the practical deployment of anti-reflective windows in extreme-environment imaging applications.

As three-dimensional integration technology evolves, the integration density and operating speed of circuits continue to increase, raising the demands for interconnect reliability. It is urgent to explore novel interconnect materials to meet reliability requirements. Given its excellent mechanical, physical, and electrical properties, graphene-nanocopper has emerged as a promising new interconnect material. However, graphene's low affinity with copper requires an exploration of its sintering mechanism to guide the sintering process. In this study, we initially utilized molecular dynamics calculations to compare the sintering processes of Cu NPs and G@Cu NPs. Graphene limits the sintering progress of G@Cu NPs, with shear strengths of Cu NPs (8.38 MPa) < G@Cu NPs (12.78 MPa) < benzimidazole@Cu NPs (13.28 MPa), and porosity rates of Cu NPs (38.19 %) > G@Cu NPs (14.28 %) > benzimidazole@Cu NPs (10.36 %). Post-sintering service reliability verifies that graphene limits the sintering process of G@Cu NPs. The sintering process of graphene with copper was subsequently simulated for different core-shell diameters, within a specific range, revealing that increasing the copper core diameter and graphene shell thickness decreases the sintering progression. However, the increase in graphene may concurrently alter defects, thus accelerating the sintering process. Finally, simulations conducted at sintering temperatures of 473 K, 573 K, and 673 K for G@Cu NPs show that increasing the temperature accelerates the sintering process, reducing the porosity rate from 19.48 % to 12.64 % and increasing the shear strength from 10.14 MPa to 13.92 MPa. It was verified that the temperature increase promoted the G@Cu sintering process. Our research reveals atomistic changes in G@Cu NPs under low-temperature conditions and provides a deeper understanding of low-temperature sintering for G@Cu NPs.

Femtosecond laser micromachining, a remarkable technology for fabricating various micro/nanostructures, struggles to balance processing efficiency and quality. Here, a method is proposed that combines femtosecond laser optical field modulation technology with the wet chemical etching process to efficiently fabricate high-quality microhole arrays on zinc sulfide (ZnS). Utilizing Bessel beams and subpulse sequences for fabrication, a machining error of less than 0.3 μm (defocus amount of 1 to 16 μm) and a significant improvement in the aspect ratio are achieved. Inspired by the antireflective properties of stink bug compound eyes, approximately 25 million biomimetic microholes with an aspect ratio of 0.75 are fabricated on the ZnS surface in under 42 min. Biomimetic ZnS demonstrates broadband transmission (average of 81.3% from 8 to 12 μm) and excellent transmittance (83.2% at 9.2 μm). The utilization of the biomimetic window for monitoring an outdoor electric vehicle charging station demonstrates an improvement of 6.7% to 12.4% in target discrimination, detail capture, texture rendering, and edge resolution in the captured infrared images, thereby highlighting the potential application advantages of high-quality biomimetic microholes.

With the continuous advancement of integrated circuit technology, semiconductor chips are increasingly moving towards miniaturization and high-density integration. Consequently, achieving reliability standards in the copper interconnection modules used in semiconductor packaging has become challenging. This study employs sintering experiments to analyze the impact of graphene on copper interconnection modules. Integrating established molecular dynamics theories, we found that graphene tends to concentrate at the interface between nano copper and copper. Subsequently, femtosecond laser processing was used to create micro- and nanoscale structures on the substrate, reducing atomic spacing without altering the affinity between the substrate and the graphene-based paste. Furthermore, the results indicate that the laser-induced micro- and nanoscale structures facilitate a more uniform distribution of graphene, leading to a 35.3% increase in the shear strength of the copper interconnection module and a 31.25% reduction in unfilled areas.

The joint strength of ceramic/metal interfaces has become one of the major technical difficulties in the development of solid oxide fuel cells. Hence, a method to fabricate 3D cone structure arrays on the surface of yttriastabilized zirconia (YSZ) and stainless steel (Crofer 22 APU) by femtosecond laser machining technique is proposed to improve its shear strength. Compared to the shear strength of flat substrate (5 MPa), the optimized strength (23.4 MPa) is 4.7 times that of the original strength. Increasing the sintering temperature from 200 degrees C to 350 degrees C enhances the mobility and sintering of Ag nanoparticles, leading to a denser Ag layer and consequently improving the interfacial connection strength. Cross-sectional analysis of the sintered joint reveals that the 3D cone structure forms a mechanical interlock with the Ag layer, enhancing the interfacial shear strength. A finite element analysis model is also established for revealing the shear stress distribution in the Ag layer with microstructure.

The reliability of the sapphire-metal joint technology in electronic devices determines its performance for industrial applications. Hence, we propose a method to enhance the connection strength between sapphire and metal based on micro-nanostructures on the substrate surface fabricated by femtosecond laser technology. The micro-nano modification of the substrate surface effectively improves the wettability of the silver paste, contributing to the spreading of the solder. The influence of different substrate surface morphologies on the joint strength is also investigated. It is found that the Cu/ sapphire substrate with cone microstructure arrays has the highest joint strength, reaching 27.2 MPa at a sintering temperature of 300 degrees C, which is about 4 times increase compared to the flat substrate (7.3 MPa). Further, the effect of different sintering parameters on the joint strength of the cone-structured array substrate is studied. The morphology of the cross-section and shear damage surfaces for connecting structures is analyzed, revealing that the mechanism of interface strength enhancement is mechanical interlocking. This fabrication of micro-nanostructures on substrate surfaces by femtosecond lasers provides a simple and efficient approach for the high-performance joining of ceramics and metals.

Frequency selective surfaces (FSSs), also known as spatial filters, are special two-dimensional periodic structures with unique electromagnetic wave transmission and reflection characteristics. With the launch of 6G communication technology research, the terahertz band is an important topic of 6G technology, and miniaturization and compactness are major features of terahertz devices. A double-layer ultra-wideband terahertz FSS is designed, which has a compact FSS cell structure consisting of two layers of square ring-gap cascades and can be used to enhance the transmission of terahertz waves. The passband width of this FSS is 0.354 THz (0.407–0.761 THz), and the transmission coefficient decreases rapidly on both sides of the passband. Meanwhile, this FSS maintains the ultra-wideband characteristics with polarization stability at terahertz wave incidence angles less than 60°. The simulation results show that the multilayer cascaded FSS not only has a large operating bandwidth but also has good steepest degradation performance. In this paper, we explore the laser machining process of the designed terahertz FSS and analyze the effects of several factors, namely scanning speed, laser power, and number of scans, on the surface morphology of the terahertz FSS, respectively, and select the process parameters that can guarantee both the machining accuracy and the machining efficiency. In order to verify the actual working performance of the processed double-layer square ring FSS, the transmission coefficients of the processed FSS samples are tested, and the test results are basically consistent with the simulation results.

For the demand of low-temperature, high-strength joining between silicon and glass in semiconductor packaging, a composite joining method based on femtosecond laser micro/nano-fabrication and low-temperature sintering of silver nanoparticle paste is proposed. Conventional anodic bonding technology is prone to device performance degradation due to thermal stress introduced by high-temperature processes. This research employs femtosecond lasers to fabricate a multi-level structure composed of micron-scale cones and nanoparticles on the substrate surface. Combined with silver nanoparticle paste, a high-strength joint is achieved under 300 °C. The results indicate that surface micro–nano-structures provide abundant mechanical anchor points for silver particles, enhancing interfacial joining strength through mechanical interlocking. Meanwhile, the increased contact area enhances the thermal diffusion coefficient at the interface, facilitating heat dissipation from the chip. The influence of microstructure dimensions, sintering temperature, and pressure on joining strength is also analyzed. This method of enhancing interfacial bonding strength through micro–nano-structures provides a pathway for addressing thermal stress issues in semiconductor packaging.

The demand for flexible pressure sensors with high performance is increasing with the growing wearable technology market. According to the developing requirement for green electronics, paper-based sensors, which are more environmentally friendly, have received more and more attention. However, the intrinsic mechanical properties of paper materials limit the sensing performance of paper-based sensors, such as restricted working range and response bandwidth. Herein, a rigid-soft hybrid design strategy is proposed to improve the sensing performance of paper-based pressure sensors, and bioinspired microstructures are introduced into the architecture of sensors for further improvement. As a result, the prepared paper-based pressure sensor has a faster response/recovery speed (<50 ms), a wide sensing range (1 MPa) and frequency response bandwidth (0.05-1000 Hz) and excellent cycling stability (5000 cycles). In addition, the paper-based pressure sensor is superhydrophobic with a water contact angle of 152.62 degrees. Based on the excellent sensing performance and waterproofness, the paper-based pressure sensor can be used as a wearable device for detecting joint movements or gait of humans/robots in both air and underwater. In addition, it can be used to send communication signals, showing great potential for applications in future underwater rescue.

The reliability of Cu bonding technology in three-dimensional integration packaging is limited by high sintering temperatures and the growth of oxide at the joining interface. Hence, we propose a bionic adhesion interface of creeper sucker on the Cu substrate and covered with monolayer graphene, which increases the shear strength by 3 times compared to the conventional flat Cu substrate. The covered graphene layer effectively inhibits the generation of oxide at the joint interface and maintains a high shear strength after aging at 300 °C for 48 h. Nanoscale Cu particles could reduce the chemical potential energy of the substrate surface, and stable bonding was achieved at 200 °C under a pressure of 2 MPa. Molecular dynamics simulation models reveal crystal structure evolution and residual stresses during the sintering process. This work demonstrates that bionic microstructures applied to copper bonding play an important role in interface enhancement, resulting in reliable bonding of Cu substrate at low temperatures. The method proposed here can provide insight into diversified applications including high-power light-emitting diodes soldering, SiC electronic devices, and flexible electrode interconnects.

本文应用焓-多孔介质模型数值模拟研究电子设备热控系统性能.利用某航天电子设备作为研究对象,采用正二十四烷/泡沫铜复合相变材料作为热控组件.根据电路板芯片额定功率完成热源分布和热量加载,通过瞬态升温过程研究初始设计的相变装置热控性能.主要关注芯片的温度变化、温度均匀性、相变热控装置内固液相界面变化及温度分布情况,分析相变热控装置的可靠性、可行性.从而提供一种电路板应用泡沫铜复合相变材料热控装置的数值模拟方法.

针对传统射频电路板加工周期长、工艺流程复杂等问题,创新性地采用压电喷墨3D打印技术打印射频天线多层电路板,开展了打印材料、打印参数及打印工艺对成型效果的研究.经测试,打印的样件在外形尺寸、打印线路精度,以及驻波损耗等电性能方面均能达到设计指标要求.论证了压电喷墨3D打印技术可有效用于射频多层电路的快速制造和快速验证,为压电喷墨3D打印射频多层电路的制造提供了良好的基础,可加速实现射频多层电路的绿色制造、集成制造和快速制造,并缩短了研发周期.