Search Results (201)

High-power laser diodes (HPLDs) are increasingly used in space applications, yet solder layer (SL) reliability critically limits their performance and lifespan. This study employs finite element analysis to evaluate SL failure mechanisms in microchannel-cooled HPLDs with two packaging configurations under thermal cycling and vibration. Based on the Anand constitutive model, contour plot analysis revealed that the critical stress–strain regions in both SLs were located at their edges. The stress–strain values along the X-axis of the SLs exceeded those in other axial directions, and SL failure would preferentially initiate from the edges along the cavity length direction. During random vibration analysis with excitation applied along the Z-axis, the equivalent stresses in both SLs exceeded X-/Y-axis levels. However, these values remained far below their yield strengths, indicating that only elastic strain and high-cycle fatigue occurred in the SLs. The calculated thermal fatigue lives of the two SLs were 2851 cycles and 5730 cycles, respectively. Their random vibration fatigue lives were determined as 5.75 × 10⁷ h and 8.31 × 10⁷ h. Using damage superposition under combined thermal-vibration loading, the total fatigue lives were predicted as 14,821 h and 29,786 h, respectively, with thermal cycling-induced damage dominating the failure mechanism. Full article

This study presents the optimization of a laser ablation process designed to achieve the precise removal of polyamide coatings from ultra-thin platinum wires. Removing polymer coatings is a critical challenge in high-reliability manufacturing processes such as aerospace thermocouple fabrication. The ablation process must not only ensure the complete removal of the polyamide insulation but also maintain the tensile strength of the wire to withstand mechanical handling in subsequent manufacturing stages. Additionally, the exposed platinum surface must exhibit low surface roughness to enable effective soldering and be free of thermal damage or residual debris to pass strict visual inspections. The wires have a total diameter of 65 µm, consisting of a 50 µm platinum core encased in a 15 µm polyamide coating. By utilizing a UV laser with a wavelength of 355 nm, average power of 3 W, a repetition rate range of 20 to 200 kHz, and a high-speed marking system, the process parameters were systematically refined. Initial attempts to perform the ablation in an air medium were unsuccessful due to inadequate thermal control and incomplete removal of the polyamide coating. Hence, a water-assisted ablation technique was explored to address these limitations. Experimental results demonstrated that a scanning speed of 1200 mm/s, coupled with a line spacing of 1 µm and a single ablation pass, resulted in complete coating removal while ensuring the integrity of the platinum substrate. The incorporation of a water layer above the ablation region was considered crucial for effective heat dissipation, preventing substrate overheating and ensuring uniform ablation. The laser’s spot diameter of 20 µm in air and a focal length of 130 mm introduced challenges related to overlap control between successive passes, requiring precise calibration to maintain consistency in coating removal. This research demonstrates the feasibility and reliability of water-assisted laser ablation as a method for a high-precision, non-contact coating material. Full article

Advancements in semiconductor packaging toward higher integration and interconnect density have increased the risk of structural defects—such as missing solder balls, pad delamination, and bridging—that can disrupt thermal conduction paths, leading to localized overheating and potential chip failure. To address the limitations of traditional non-destructive testing methods in detecting micron-scale defects, this study introduces a multimodal detection approach combining finite-element thermal simulation, infrared thermography, and the YOLO11 deep learning network. A comprehensive 3D finite-element model of a ball grid array (BGA) package was developed to analyze the impact of typical defects on both steady-state and transient thermal distributions, providing a solid physical foundation for modeling defect-induced thermal characteristics. An infrared thermal imaging platform was established to capture real thermal images, which were then compared with simulation results to verify physical consistency. An integrated dataset of simulated and infrared images was constructed to enhance the robustness of the detection model. Leveraging the YOLO11 network’s capabilities in end-to-end training, dataset small-object detection, and rapid inference, the system achieved accurate and rapid localization of defect regions. Experimental results show a mean average precision (mAP) of 99.5% at an intersection over union (IoU) threshold of 0.5 and an inference speed of 556 frames per second on the simulation dataset. Training with the hybrid dataset improved detection accuracy on real images from 41.7% to 91.7%, significantly outperforming models trained on a single data source. Furthermore, the maximum temperature discrepancy between simulation and experimental measurements was less than 5%, validating the reliability of the proposed method. This research offers a high-precision, real-time solution for semiconductor packaging defect detection, with substantial potential for industrial application. Full article

Ball Grid Array (BGA) failures are often dominated by stress concentrations at the outer solder joints, particularly under thermomechanical loading. To mitigate this issue, this study investigates the mechanical and reliability implications of optimizing the BGA solder joint array by removing the outermost rows and columns, positioning all connections directly beneath the silicon die. Two commonly used solder alloys—SAC305 and Sn37Pb—were selected to evaluate the effects of this optimized array design. A combined experimental and numerical approach was employed, including accelerated thermal cycling (–40 °C to 125 °C), in situ resistance monitoring, cross-sectional failure analysis, and finite element modeling (FEM) to assess fatigue behavior under the altered layout. The optimized array significantly improved performance for SAC305, yielding a 1.67× increase in mean cycles-to-failure and a 29% reduction in peak von Mises stress, with failure locations shifting from the corners to more evenly distributed areas beneath the die. Sn37Pb assemblies showed only a 1.01× improvement despite an 11% stress reduction, attributed to persistent shear-dominated failures at second-row joints. These results highlight the critical influence of joint array architecture and solder alloy selection on reliability, offering design-level guidance for applications prioritizing thermomechanical robustness with reduced I/O counts. Full article

Under the dual impetus of environmental regulations and reliability requirements, the Pb–free/Pb hybrid assembly process in aerospace-grade ball grid array (BGA) components has become an unavoidable industrial imperative. However, constrained process compatibility during single or multiple reflow protocols amplifies structural heterogeneity in solder joints and accelerates dynamic microstructural evolution, thereby elevating interfacial reliability risks at solder joint interfaces. This paper systematically investigated phase composition, grain dimensions, thickness evolution, and crystallographic orientation patterns of interfacial intermetallic compounds (IMCs) in hybrid micro-solder joints under multiple reflows, employing electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The result shows that the first reflow induces prismatic Cu₆Sn₅ grain formation driven by Pb aggregation zones and elevated Cu concentration gradients. Surface-protruding fine grains significantly increase kernel average misorientation (KAMave) of 0.68° while minimizing crystallographic orientation preference density (PF_max) of 15.5. Higher aspect ratios correlate with elongated grain morphology, consequently elevating grain size of 5.3 μm and IMC thickness of 5.0 μm. Subsequent reflows fundamentally alter material dynamics: Pb redistribution transitions from clustered to randomized spatial configurations, while grains develop pronounced in-plane orientation preferences that reciprocally influence Sn crystal alignment. The second reflow produces scallop-type grains with minimized dimensions of 4.0 μm and a thickness of 2.1 μm, with a KAMave of 0.37° and PF_max of 20.5. The third reflow initiates uniform growth of scalloped grains of 7.0 μm with a stable population density, whereas the fifth reflow triggers a semicircular grain transformation of 9.1 μm through conspicuous coalescence mechanisms. This work elucidates multiple reflow IMC growth mechanisms in Pb–free/Pb hybrid solder joints, providing critical theoretical and practical insights for optimizing hybrid technologies and reliability management strategies in high-reliability aerospace electronics. Full article

With the enhancement of environmental protection awareness and the implementation of related regulations, lead-free soldering materials are gradually replacing the traditional leaded soldering materials in the field of electronics manufacturing. Sn–Ag soldering materials have become a research hotspot because of their good mechanical properties, solderability, and thermal fatigue reliability, but their high cost limits their large-scale application. The low silver content of the Sn–Ag solder reduces the cost while maintaining an excellent performance. However, as the size of electronic components shrinks and the package density increases, the solder joint spacing decreases, the potential gradient increases, and electrochemical migration (ECM) becomes a key factor affecting the reliability of solder joints. In this study, the ECM failure process was simulated by the water droplet method, and the SEM and XPS analyses were utilized to investigate the ECM mechanism of Sn1.0Ag solder alloys, and the effects of different concentrations of NaCl solutions on their ECM were investigated. The results showed that the ECM of the Sn1.0Ag solder occurred in a 0.01 M NaCl solution, the dendritic composition was pure Sn, and the white precipitate was a mixture of Sn(OH)₂ and Sn(OH)₄. With the increase in the NaCl concentration, the corrosion resistance of the Sn1.0Ag solder alloy decreases and the ECM reaction intensifies, but with a high concentration of the NaCl solution, a large amount of precipitation hinders the migration of Sn ions, resulting in the generation of no dendrites. The present study provides new insights into the ECM behavior of a low-silver-content Sn–Ag solder system. Full article

The high input/output demands of memory packages require precise trace width and spacing, posing challenges for contemporary package design. Substrate copper trace cracks are a major reliability issue during temperature cycling tests (TCTs). This study offers a detailed analysis of copper trace crack mechanisms through experimental observations, material characterization, and numerical simulations. Common failure modes of trace cracks are identified from experimental data, pinpointing initiation sites and propagation paths. Young’s modulus of copper foil samples is assessed using four testing methods, revealing consistent trends across samples from different substrate suppliers. Sample A with higher E/H values tested via nanoindentation correlated with lower failure rates in the experiment. Stress–strain testing on copper foil was successfully performed at the lower TCT temperature limit of −65 °C, providing vital input for finite element (FE) models. The simulations show strong alignment with trace crack locations under different failure modes. The impact of copper trace width and material properties is illustrated in numerical models by comparing variations in plastic strain responses, which show differences of up to 40% and 30%, respectively. The simulation design of the experiments (DOE) indicates that high-strength solder resist (SR) can significantly enhance temperature cycling performance by reducing SR and copper trace stress and strain by up to 75%. The accumulation of plastic strain in copper traces is predicted to increase up to four times when SR breaks at the crack location, underscoring the importance of SR in copper trace reliability. Full article

With the rapid growth of data center demand driven by AI, high-speed optical modules (such as 800G and 1.6T) have become critical components. Traditional 800G modules face issues such as complex processes and large sizes due to the separate packaging of EML chips, AlN substrates, and capacitors. This study proposes a high-speed EML module based on silicon integration, where resistors, capacitors, and AuSn soldering areas are integrated onto the silicon substrate, enabling the bonding of the EML chip, reducing packaging costs, and enhancing scalability. Key achievements include: the development of a 100G EML chip; the fabrication of a high-speed silicon integrated carrier; successful Chip-on-Carrier (COC) packaging and testing, with a laser output power of 10 mW, extinction ratio of 10 dB, and bandwidth greater than 40 GHz; and reliability verified through 500 h of aging tests. This study provides an expandable solution for next-generation high-speed optical interconnects. Full article

Addressing the issue of lifespan prediction for electronic packages under thermal loading, this paper proposes a method for predicting the lifespan of electronic packages based on ultrasonic microimaging. Firstly, experimental samples equipped with flip-chip packages were designed and fabricated and subjected to aging through thermal cycle acceleration tests. Ultrasonic microscopy was utilized to periodically acquire ultrasonic image data for monitoring solder joint degradation. Secondly, the internal ultrasonic wave propagation mechanism within electronic packages was investigated, establishing a qualitative relationship between the intensity in the central region of the solder joint’s ultrasonic image and internal defects within the joint. Image processing techniques were applied to enhance the quality of the solder joint images, and the mean intensity in the central region of the solder joint image was extracted as a failure feature. Finally, based on the extracted failure feature, a data-driven failure model for solder joints was developed, which predicts the lifespan of the solder joints based on cumulative failure probability. The research results indicate that the proposed model accurately describes the failure process of solder joints and effectively differentiates the lifespan variations among solder joints at different locations on the chip. This provides theoretical support for the reliability assessment of electronic package solder joints and holds practical value for enhancing the overall reliability of electronic packaging components. Full article

As semiconductor packaging technologies face limitations, through-silicon via (TSV) technology has emerged as a key solution to extending Moore’s law by achieving high-density, high-performance microelectronics. TSV technology enables enhanced wiring density, signal speed, and power efficiency, and offers significant advantages over traditional wire-bonding techniques. However, achieving fine-pitch and high-density interconnects remains a challenge. Solder flip-chip microbumps have demonstrated their potential to improve interconnect reliability and performance. However, the environmental impact of lead-based solders necessitates a shift to lead-free alternatives. This review highlights the transition from Sn-Pb solders to lead-free options, such as Sn-Ag, Sn-Cu, Sn-Ag-Cu, Sn-Zn, and Bi- or In-based alloys, driven by regulatory and environmental considerations. Although lead-free solders address environmental concerns, their higher melting points pose challenges such as thermal stress and chip warping, which affect device reliability. To overcome these challenges, the development of low-melting-point solder alloys has gained momentum. This study examines advancements in low-temperature solder technologies and evaluates their potential for enhancing device reliability by mitigating thermal stress and ensuring long-term stability. Full article

In the context of the rapid development of modern science and technology, time synchronization technology has become a critical support in the fields of communication and scientific research. Especially in large-scale research projects such as the China Spallation Neutron Source, the accuracy of time synchronization directly affects the precision of experimental data and the reliability of experimental results. White Rabbit (WR) technology surpasses the sub-microsecond precision limitations of traditional PTPs by precisely controlling and calibrating the delays between master and slave clocks, achieving sub-nanosecond time synchronization that meets the stringent timing accuracy requirements of 5G networks and quantum communications. To meet the demands for high precision, high flexibility, and broad applicability, a switch with WR functionality has been designed based on the Zynq platform. This design not only reduces the number of required components and the complexity of the soldering process but also allows for simple AXI bus communication between the PS and PL ends, thereby decreasing the development time and cost of both software and hardware. The hardware design includes power circuits, clock circuits, and SFP interface circuits. The time synchronization module encompasses the design of the RTU, NIC, SoftPLL, and PPS modules, as well as the design of the AXI to Wishbone bridge. Testing has shown that this switch can achieve sub-nanosecond level time synchronization accuracy. Full article

Soldering with Sn alloys has always been the essential assembly step of microelectronics. The conductive Sn whiskers, which can spontaneously grow from soldering surfaces, mean a considerable reliability risk for microelectronics due to possible short circuit formation between the leads of the components. Since their discovery in 1951, thousands of research studies have been conducted to unravel their growth mechanisms and find effective prevention methods against them. Till 2006, the Sn whisker problem was solved and partially forgotten due to the very effective whisker suppression effect of Pb alloying into the solder materials. The lead-free change gave new impetus to the problem, which was further enhanced by the application of new material systems, growing reliability requirements, and accelerating miniaturization in the 21st century. Our review would like to give an overview of the Sn whisker’s history from the beginning till the latest results, focusing on the suppression solutions by the modification of the solder alloy compositions. Recently, promising results have been reached by alloying Bi and In, which are metals that are the focus of low-temperature soldering, and by composite solders. Full article

This paper demonstrates the application of eutectic welding to Ce³⁺:YAG transparent ceramics for reliable detection and imaging of UV emission, particularly focusing on demanding conditions, such as high repetition rate, high energy, and high vacuum. A series of Ce³⁺:YAG transparent ceramics with different Ce³⁺ doping concentrations (0.1 at%, 0.3 at%, 0.5 at%, and 1.0 at%) were prepared via vacuum sintering. Their crystal microstructure, luminescence properties, transmittance, and fluorescence lifetime were studied. It was found that the optimal Ce³⁺ doping concentration is 0.3 at%. The measured ultraviolet-to-visible energy conversion efficiency of the 0.3 at% Ce³⁺:YAG transparent ceramics with a thickness of 1.0 mm is 3.9%. Compared with silicone encapsulated Ce³⁺:YAG transparent ceramic samples, the eutectic-soldered samples exhibited excellent resistance to temperature quenching of the luminescence, which indicates that eutectic welding can effectively improve the fluorescence performance of Ce³⁺:YAG transparent ceramics for the application of deep ultraviolet light detection. Full article

Converters play a critical role in wind power generation systems, with their reliability directly impacting system stability and operational efficiency. To address the challenges posed by increased thermal load fluctuations due to solder layer aging in insulated gate bipolar transistor (IGBT) modules in converters, this paper proposes an aging-aware multi-objective thermal management (AAMO-TM) strategy to enhance the performance of aging modules. An improved junction temperature estimation model is developed, incorporating coordinated control of switching frequency and gate drive resistance to account for the dynamic thermal behavior of IGBT modules during aging. Pareto and hierarchical optimization techniques are employed to resolve the multi-objective problem of excessive junction temperature suppression, junction temperature fluctuation smoothing, and power quality improvement. Experimental results demonstrate that our proposed AAMO-TM strategy outperforms a competing strategy at temperature fluctuation by a large margin (up to 59.4%). Our proposed strategy significantly enhances the thermal stability of aging IGBT modules while effectively suppressing grid-connected current harmonics. This study provides valuable theoretical insights and practical guidance for achieving the stable operation of wind turbines and delivering high-quality power output. Full article

This paper examined the reliability of complex PCB assemblies under random vibration and temperature cycling, which are two primary causes of assembly failure. A combination of finite element simulation and environmental testing was employed to investigate the effects of different reinforcement methods and solder joint morphology on assembly reliability. The linear accumulation of damage was utilized to predict assembly failure, and the predicted failure damage was compared with the damage extracted post-testing to validate the simulation analysis. The results indicate that SAC305 solder exhibits greater strength than Sn63Pb37 solder in withstanding temperature cycling fatigue, yet is weaker than Sn63Pb37 solder in withstanding random vibration fatigue. When the solder is Sn63Pb37, the temperature cycling life of the assembly with the bottom filled and the corners fixed is reduced by 92.3% and 99.3%, respectively, compared to the unreinforced method, while the random vibration life is enhanced by 84 times and 3.9 times, respectively. An increase in pad diameter is advantageous for improving the random vibration life of the assembly, but results in a decrease in the temperature cycling life. When the lower pad diameter ranges from 0.35 mm to 0.55 mm, the assembly temperature cycling life decreases by 28.83%, 82.03%, 90.66%, and 91.22% with the increase of the lower pad diameter, and the random vibration life improves by 4.8 times, 9.5 times, 20.4 times, and 33.6 times, respectively. The predicted locations of vulnerable solder joints for the assembly are consistent with the experimental results, and the failure prediction accuracy of the assembly is 88.89%. Full article