Search Results (7)

In this paper, a novel through-silicon via (TSV) fabrication strategy based on through-hole structures is proposed for low-cost and low-complexity manufacturing. Compared to conventional TSV fabrication processes, this method significantly simplifies the process flow by employing double-sided liner deposition, double-sided barrier layer/seed layer formation, and double-sided Cu electroplating. This method enhances the TSV stability by eliminating Cu contamination issues during chemical–mechanical polishing (CMP), which are a common challenge in traditional blind via fabrication processes. Additionally, the liner and barrier layer/seed layer achieve a high step coverage exceeding 80%, ensuring excellent conformality and structural integrity. For electroplating, a multi-stage bi-directional electroplating technique is introduced to enable void-free Cu filling in TSVs. The fabricated TSVs exhibit an ultra-low leakage current of 135 fA at 20 V, demonstrating their potential for advancing 3D integration technologies in heterogeneous integration. Full article

Effective thermal management is essential in welding processes to maintain structural integrity and material quality, especially in high-precision industrial applications. This study examines the thermal behavior of an AISI 1080 steel plate containing 100 blind holes filled using robotic electric arc welding. Temperature measurements, recorded with eight strategically positioned thermocouples, monitored the thermal evolution throughout the robotic welding process. The experimental results validated a computational heat transfer model developed with ANSYS Fluent software to simulate and predict temperature distribution achieving a mean absolute percentage error (MAPE) below 4.53%. A feedforward neural network was trained with simulation-generated data to optimize welding sequences. The optimization focuses on minimizing the area under the thermal history curves, reducing temperature gradients, and mitigating overheating risks. Integrating CFD simulations and neural networks introduces a hybrid methodology combining precise numerical modeling with advanced predictive capabilities. The hybrid CFD-FNN results reached a determination coefficient ($R^2$) of 0.93 and an MAPE of 3.5% highlighting the potential of this approach to predict the thermal behavior in multipoint welding processes. This model generated optimized welding trajectories improving the uniformity of the temperature field, reducing thermal gradients and minimizing temperature peaks, thus aiding in preventing overheating. This framework represents a significant advancement in welding technologies, demonstrating the effective application of deep learning techniques in optimizing complex industrial processes. Full article

When carbon-fiber-reinforced plastic (CFRP) and steel are joined using blind riveting and bolting, fastener inclination occurs due to the clearance between the fastener and hole. To this end, this study investigated the unavoidable occurrence of clearance when joining metal and composite materials using mechanical fastening. The effect of inclination on the lap shear strength (LSS) was quantitatively investigated under various conditions. In riveting, breakage occurred mainly in the rivet; the LSS between the CFRP and steel improved by approximately 33% when the clearance was filled with structural adhesive compared to that in the unfilled state. In bolting, a washer was essential since it not only reduced the force exerted on the bolt but also reduced the bending deformation of the steel plate where breakage occurred. The clearance-filling effect showed the same effect as using a washer even without using it. In addition, the LSS was improved by approximately 10% by filling the clearance with a structural adhesive in the case of bolting with washers. Additionally, the force distribution for the fastening segment was calculated under the application of an external force, and the results demonstrated that hybrid-bonded fastening using a clearance-filling during mechanical bonding is essential for strong fastening. Full article

In order to obtain high-quality through-silicon via (TSV) arrays for high voltage applications, we optimized the fabrication processes of the Si holes, evaluated the dielectric layers, carried out hole filling by Cu plating, and detected the final structure and electric properties of the TSVs. The Si through-hole array was fabricated in an 8-inch Si substrate as follows: First, a blind Si hole array was formed by the Si deep reactive etching (DRIE) technique using the Bosch process, but with the largest width of the top scallops reduced to 540 nm and the largest notch elimidiameternated by backside grinding, which also opens the bottom ends of the Si blind holes and forms 500-μm-deep Si through holes. Then, the sidewalls of the Si holes were further smoothed by a combination of thermal oxidation and wet etching of the thermal oxide. The insulating capability of the dielectric layers was evaluated prior to metal filling by using a test kit. The metal filling of the through holes was carried out by bottom-up Cu electroplating and followed by annealing at 300 °C for 1 h to release the electroplating stress and to prevent possible large metal thermal expansion in subsequent high-temperature processes. The TSV arrays with different hole diameters and spacing were detected: no visible defects or structure peeling was found by scanning electron microscopy (SEM) observations, and no detectable interdiffusion between Cu and the dielectric layers was detected by energy dispersive X-ray (EDX) analyses. Electric tests indicated that the leakage currents between two adjacent TSVs were as low as 6.80 × 10⁻¹⁰ A when a DC voltage was ramped up from 0 to 350 V, and 2.86 × 10⁻⁹ A after a DC voltage was kept at 100 V for 200 s. Full article

Owing to the shortcomings of blindness and inaccuracy when backfilling in goafs and based on the key stratum theory, we propose the “multi-arch pier-column” backfilling method. This method involves drilling holes at specific locations on the surface to inject filling and slurry materials into the goaf and separation area under the key stratum. This allows the broken gangue to be cemented to form a stone body, to improve its overall strength. This process, along with filling in the separation area under the key stratum, ensures that the key stratum does not break, forming a joint medium of “separation area filling body + backfilled pier-columns + key stratum + coal column”, which prevents new subsidence on the surface layer. Using the Gaojialiang coal mine as an example, the effects of the proposed method on controlling surface subsidence were determined using a numerical simulation based on FLAC^3D simulation software. The results indicate that this method can effectively control the key stratum and ensure that the surface subsidence is within a safe range. The multi-arch pier-column backfilling method utilises the self-bearing capacity of the overburden structure and greatly reduces the backfilling workload and the cost of backfilling for controlling surface subsidence. At present, the multi-arch pier-column system of the new backfill method is an unexplored and new area of research. Full article

In this work, we developed an eco-friendly and facile microvia filling method by using printing and sintering of Cu-Ag core-shell nano-microparticles (Cu@Ag NMPs). Through a chemical reduction reaction in a modified silver ammonia solution with L-His complexing agent, Cu@Ag NMPs with compact and uniform Ag shells, excellent sphericity and oxidation resistance were synthesized. The as-synthesized Cu@Ag NMPs show superior microvia filling properties to Cu nanoparticles (NPs), Ag NPs, and Cu NMPs. By developing a dense refill method, the porosity of the sintered particles within the microvias was significantly reduced from ~30% to ~10%, and the electrical conductivity is increased about twenty-fold. Combing the Cu@Ag NMPs and the dense refill method, the microvias could obtain resistivities as low as 7.0 and 6.3 μΩ·cm under the sintering temperatures of 220 °C and 260 °C, respectively. The material and method in this study possess great potentials in advanced electronic applications. Full article

Here, in a certain high density interconnect (HDI) printed circuit board, the effect of copper sulfate and sulfuric acid on the filling effect of a blind hole with a certain diameter and depth was investigated by making a blind hole using a CO₂ laser drilling machine, filling the blind hole via electroplating by simulating the electroplating line in a Halin cell, and observing the cross-section of a micro blind hole after polishing using metallographic microscope, as well as the effect of hole filling, are evaluated. The results show that, under the conditions of a certain plating solution formula and electroplating parameters (current density and electroplating time), the sag degree decreases with the increase in the copper sulfate concentration. When the concentration of copper sulfate increases from 210 g/L to 225 g/L, the filling effect is good and the sag degree is about 0. However, with the increase in sulfuric acid concentration, the sag increases gradually. When the sulfuric acid concentration is 25–35 g/L, both the sag and copper coating thickness are in a small range. Under appropriate electroplating conditions, a better blind hole filling effect can be obtained. The volume of blind hole has a certain effect on the diffusion and exchange of copper sulfate and sulfuric acid, as well as on the concentration distribution of additives. Full article