Influence of Ring-Shaped Beam Profiles on Process Stability and Productivity in Laser-Based Powder Bed Fusion of AISI 316L

A major factor slowing down the establishment of additive manufacturing processes as production processes is insufficient reproducibility and productivity. Therefore, this work investigates the influence of ring-shaped beam profiles on process stability and productivity in laser-based powder bed fusion of AISI 316L. For this purpose, the weld track geometries of single tracks and multi-track segments with varying laser power, scan speed, hatch distance, and beam profile (Gaussian profile and three different ring-shaped profiles) are analyzed. To evaluate the process robustness, process windows are identified by classifying the generated single tracks into different process categories. The influence of the beam profiles on productivity is studied by analyzing the molten cross-sectional areas and volumes per time. When using ring-shaped beam profiles, the process windows are significantly larger (up to a laser power of 1050 W and a scanning speed of 1700 mm/s) than those of Gaussian beams (laser power up to 450 W and scanning speed up to 1100 mm/s), which suggests a higher process robustness and stability. With ring-shaped beam profiles, larger volumes can be stably melted per track and time. The weld tracks created with ring-shaped profiles are significantly wider than those generated with Gaussian profiles (up to factor 2 within the process window), allowing enlargement of the hatch distances. Due to the higher scanning speeds and the enlarged hatch distances for ring-shaped beam profiles, the process can be accelerated by a factor of approximately 2 in the parameter range investigated.

Glass Die Ink Marking Media Selection for a Robust Glass Attach Process

Glass material used on a semiconductor device for isolating currents are one of the new breakthroughs of the modern world. Challenges are inevitable due to its complex characteristics and unique appearance. The study focuses on the phenomenon of reject glass die unrecognized, picked and bonded by die attach machine on good units of the semiconductor quad-flat no-leads (QFN) device in focus. This QFN device utilizes glass die as interposer on two active dice that separates the dielectric current of each die. During die attach process, machine photo recognition system failed to recognize and detect the glass die reject marking due to its unique transparent design and will be attached on good units. Thus, resulting to gross rejection and low process yield. Practical solutions to prevent the said phenomenon are simulated and determined by performing selection of variables like the contrast of the reject mark related to the product structure and compatibility through statistical analysis. The improvement drives to promote process robustness and scrap reduction that will help the manufacturing to be competitive through innovative resolutions on problems.

A Potential Practical Process for Remdesivir

A four-step synthesis of Remdesivir (1) is presented. This work focuses on the yield improvement of step 1, flow chemistry development of step 2 and 3, process optimization of step 4. The literatures reported (https://dx.doi.org/10.1021/acs.oprd.0c00310 and https://dx.doi.org/10.1021/acs.oprd.0c00172: SI part) step 1 was repeated, but failed in the crystallization, eventually step 1 product was obtained by column chromatography with >98% HPLC purity and 40% IY. The flow chemistry development of step 2(IY: 84%) and 3 (IY: 63%) was achieved and the release of toxic HCN was avoided, the process robustness was improved by flow chemistry. Step 4 was simplified to apply primary alcohol 6 directly (without protection) to react with chiral SM 8. Lewis acid catalysts were screened by HTS and MgI2 gave 50% AY. Cheap and commercially available MgCl2 and NaI were used to replace MgI2, finally Remdesivir (1) was obtained in >99% purity with 40.3% IY.

A Potential Practical Process for Remdesivir

A four-step synthesis of Remdesivir (1) is presented. This work focuses on the yield improvement of step 1, flow chemistry development of step 2 and 3, process optimization of step 4. The literatures reported (https://dx.doi.org/10.1021/acs.oprd.0c00310 and https://dx.doi.org/10.1021/acs.oprd.0c00172: SI part) step 1 was repeated, but failed in the crystallization, eventually step 1 product was obtained by column chromatography with >98% HPLC purity and 40% IY. The flow chemistry development of step 2(IY: 84%) and 3 (IY: 63%) was achieved and the release of toxic HCN was avoided, the process robustness was improved by flow chemistry. Step 4 was simplified to apply primary alcohol 6 directly (without protection) to react with chiral SM 8. Lewis acid catalysts were screened by HTS and MgI2 gave 50% AY. Cheap and commercially available MgCl2 and NaI were used to replace MgI2, finally Remdesivir (1) was obtained in >99% purity with 40.3% IY.

Die Attach Process Robustness through Epoxy Pattern Optimization for DFN Device

As the modern world evolves through innovation and technology, manufacturing companies of semiconductor drive their people to dedicate themselves on continuous improvement and technical advancement. Products they produce becomes smaller and thinner, but applications are limitless and innovative. In manufacturing of quad flat no lead packages, challenges were encountered during the die attach process especially in small die size. Die attach material overflow on pad is one of these, and certain parameters and techniques are explored to have a quality and robust process. Defining appropriate epoxy pattern with respect to the die size is a big factor to make sure no epoxy material will flow outside the die pad perimeter that may cause unit rejection. This paper will discuss the related issues of the said package by performing experiments and applying certain techniques to address the problem.

Energy-efficient butanol production by Clostridium acetobutylicum with histidine kinase knockouts to improve strain tolerance and process robustness

Under stress, Clostridium acetobutylicum sporulates and halts its metabolism, which limits its use in industrial acetone-butanol-ethanol (ABE) fermentation. It is challenging to manipulate the highly regulated sporulation program used by...