Reliability Analysis of Flip-Chip Packaging GaN Chip with Nano-Silver Solder BUMP.

Gallium nitride (GaN) power devices have many benefits, including high power density, small footprint, high operating voltage, and excellent power gain capability. However, in contrast to silicon carbide (SiC), its performance and reliability can be negatively impacted by its low thermal conductivity, which can cause overheating. Hence, it is necessary to provide a reliable and workable thermal management model. In this paper, a model of a flip-chip packing (FCP) GaN chip was established, and it was assigned to the Ag sinter paste structure. The different solder bumps and under bump metallurgy (UBM) were considered. The results indicated that the FCP GaN chip with underfill was a promising method because it not only reduced the size of the package model but also reduced thermal stress. When the chip was in operation, the thermal stress was about 79 MPa, only 38.77% of the Ag sinter paste structure, lower than any of the GaN chip packaging methods currently in use. Moreover, the thermal condition of the module often has little to do with the material of the UBM. Additionally, nano-silver was found to be the most suitable bump material for FCP GaN chip. Temperature shock experiments were also conducted with different UBM materials when nano-silver was used as bump. It was found that Al as UBM is a more reliable option.

Tension-free hiatal hernia repair with biological mesh: A real-world experience.

Laparoscopic Nissen fundoplication and esophagoplasty are the standards for gastroesophageal reflux disease (GERD) and hiatal hernia (HH) repair. Biologically derived mesh is also associated with reduced recurrence. This study attempted to evaluate the effectiveness of a biological mesh in the 4K laparoscopic repair of HH. This retrospective study reviewed patients with a severe GERD complicated with HH from August 2019 to August 2020. All patients underwent the HH repair using a biological mesh under a 4K laparoscope accompanying Nissen fundoplication. Up to 16 months postoperatively, GERD-health-related quality-of-life (GERD-HRQL) scale, radiologic studies on HH recurrence, and symptoms were recorded. The mean surgical time and postoperative hospital stay were 70.9 ±â€…8.72 min, 4.8 ±â€…0.76 days, respectively. The postoperative symptom relief rate was 96.5%, and no recurrence exhibited during follow-up. Dysphagia occurred in 10 (9.43%) patients. There were no intraoperative vagus nerve injury or postoperative complications, mesh infection, and reoperation for mesh. The tension-free repair of HH with the biological mesh is an option for clinical use, with effectiveness and few short-term complications being reported.

Heat Dissipation Characteristics of IGBT Module Based on Flow-Solid Coupling.

With the increase of power level and integration in electric vehicle controllers, the heat flux of the key silicon-based IGBT (Insulated Gate Bipolar Transistor) device has reached its physical limit. At present, third-generation semiconductor devices including SiC MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistor) are gradually replacing the dominant IGBT module. The hybrid IGBT module consists of both and can improve the performance and reduce the cost of controllers. Limits due to the installation space, location, and other conditions in the car make it difficult to meet the requirements of controllers with an air-cooled heatsink due to their large size and limited heat dissipation capacity. A smaller and more powerful water-cooled heatsink case is required to ensure the heat dissipation of the IGBT in the controller. Based on previous experience in finite element numerical simulation, hydrodynamics calculation, and heat transfer calculation, ANSYS Workbench finite element software was used to analyze the thermal resistance of each structure inside the module and the heatsink structure. The fluid characteristics and heat transfer performance of three different flow channel structures were analyzed, and the design of the cooling flow fin was improved to provide a reference for the heat dissipation of the hybrid IGBT module.

Development of LED Package Heat Dissipation Research.

LEDs are widely used in medicine, navigation and landscape lighting. The development of high-power LED is a severe challenge to LED heat dissipation. In this review, packaging technology and packaging structure are reviewed in terms of the thermal performance of LED packaging, and related technologies that promote heat dissipation in LED packaging are introduced. The design of three components to enhance heat dissipation in LED packaging is described: substrate, lens and phosphor layer. By conducting a summary of the technology and structure of the package, the defects of LED package technology and structure are deeply investigated, and the package is prospected. This has reference value for the heat dissipation design of the LED package and helps to improve the design and manufacture of the LED package.

Research on Heat Dissipation of Multi-Chip LED Filament Package.

By studying the substrate material, structure, chip distribution, and array form of the multi-chip light-emitting diode (LED) package, the heat-dissipation capacity of the LED package is improved. Finite element analysis and steady-state thermal analysis are used to simulate and analyze LED packages with different materials and structures. Using the theory of LED illuminance and uniformity, the illuminance of some structures is computed. The results show that the change of substrate material and structure can greatly impact heat dissipation, while changing array forms has little effect on heat dissipation. By improving the spatial distribution of the chip, the temperature superposition problem of the substrate is solved, and the illuminance and uniformity are improved while dissipating heat. The LED filaments of the combined, equidistant, chip-distribution mode have improved heat dissipation. The S-type equal difference has the highest illumination and high illumination uniformity.