Systematic Investigation and Characterization of Ag Paste for LED Die Attach

AbstractAbiotic stresses including drought, salinity, extreme temperatures, chemical toxicity and oxidative are the natural status of the environment to exert serious threats to agriculture. Abiotic stress-related microRNAs (ASmiRNAs) are a group of microRNAs (miRNAs) regulating stress responses in plants. However, the systematic investigation of ASmiRNAs is limited in Rice (O. sativa), a typical abiotic stress-resistant crop species. In the present work, we systematically investigated ASmiRNAs in silico. First, we identified 177 putative ASmiRNAs in O.sativa. Second, we found most ASmiRNAs were driven by TATA-promoter and most stress-related miRNA promoter regions contained the stress-related elements. Third, we found many ASmiRNAs families were species/family specific and a set of miRNAs might derive from genomic repeat-sequences in O. sativa. Finally, we found the ASmiRNAs in O. sativa target 289 genes with 1050 predicted target sites in which 98% sites have cleavage activity and 2% sites have translation inhibition activity. In conclusion, our findings provide an insight into both the function and evolution of ASmiRNAs and improve our understanding on the mechanism of abiotic stress resistance in O. sativa.

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Application of Atom Probe Microanalysis for Understanding Microstructure Evolution in Nickel Base Superalloy Welds

Microscopy and Microanalysis ◽

10.1017/s1431927600034243 ◽

2000 ◽

Vol 6 (S2) ◽

pp. 350-351

Author(s):

S. S. Babu ◽

S. A. David ◽

M. K. Miller

Keyword(s):

Microstructure Evolution ◽

Predictive Models ◽

Strong Relationship ◽

Atom Probe ◽

Systematic Investigation ◽

Nickel Base Superalloy ◽

Cooling Conditions ◽

Nickel Base ◽

Base Superalloy

The characterization of the microstructure evolution during welding of nickel base superalloys is required for efficient reuse and reclamation of used and failed components. Previous atom probe analysis of electron-beam and laser-beam welds revealed complex alloying elemental partitioning between the γ and γ phases. Rapid cooling conditions in the weld leads to non-equilibrium partitioning and large amplitude Cr and Co levels in the γ phase. These results indicated that there is a strong relationship between weld cooling rate and the precipitation of γ′ precipitates from the γ phase. To understand and develop predictive models, a systematic investigation of the microstructure evolution in CM247DS alloy under controlled thermomechanical conditions are being performed. This paper describes some recent results on the elemental partitioning between γ and γ′ phases obtained with atom probe microanalysis.

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Microstructural Evolution and Thermal Stability Characterization of a High Temperature Die Attach Lead-Free System

Additional Conferences (Device Packaging HiTEC HiTEN & CICMT) ◽

10.4071/hitec-ta22 ◽

2012 ◽

Vol 2012 (HITEC) ◽

pp. 1-11 ◽

Cited By ~ 1

Author(s):

Rogie I. Rodriguez ◽

Dimeji Ibitayo ◽

Pedro Quintero

Keyword(s):

High Temperature ◽

Melting Point ◽

Microstructural Evolution ◽

Diffusion Mechanism ◽

Processing Temperature ◽

Mechanical And Thermal Properties ◽

Promising Alternative ◽

Free System ◽

Die Attach

There is a need for electromechanical devices capable of operating in high temperature environments (>200°C) for a wide variety of applications. Today's wide-bandgap (WBG) semiconductor based power electronics have demonstrated a potential of operating above 400°C, however they are still limited by packaging. Among the most promising alternative is the Au-Sn eutectic solder, which have been widely used due to its excellent mechanical and thermal properties. However, the operating temperature of this metallurgical system is still limited to ∼250°C owing to its melting temperature of 280°C. Therefore, a higher temperature resistant system is much needed, but without affecting the current processing temperature of ∼325°C typically exhibited in most high temperature Pb-Free solders. This paper presents the development and characterization of a fluxless die attach soldering process based on gold enriched solid liquid inter-diffusion (SLID). A low melting point material (eutectic Au-Sn) was deposited in the face of a substrate, whereas a high melting point material, gold in this instance, was deposited in its mating substrate. Deposition of all materials was performed using a jet vapor deposition (JVD) equipment where thicknesses were controlled to achieve specific compositions in the mixture. Sandwiched coupons where isothermally processed in a vacuum reflow furnace. SEM and EDS were employed to reveal the microstructural evolution of the samples in order to study the interfacial reactions of this fluxless bonding process. Mechanical characterization of the each individual intermetallic phase was achieved by nanoindentation. Differential scanning calorimetry demonstrated the progression of the SLID process by quantifying the remaining low melting point constituent as a function of time and temperature. Post-processed samples confirmed the inter-diffusion mechanism as evidenced by the formation of sound joints that proved to be thermally stable up to ∼490°C after the completion of the SLID process.

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PRESSURELESS SINTERING OF NANO- AG PASTE WITH LOW POROSITY FOR DIE ATTACH

International Symposium on Microelectronics ◽

10.4071/isom-ta35 ◽

2014 ◽

Vol 2014 (1) ◽

pp. 000092-000098 ◽

Cited By ~ 2

Author(s):

Sihai Chen ◽

Guangyu Fan ◽

Xue Yan ◽

Chris LaBarbera ◽

Lee Kresge ◽

...

Keyword(s):

Shear Strength ◽

Thermal Aging ◽

Migration Rate ◽

Dense Layer ◽

Pressureless Sintering ◽

Thermal Shock Test ◽

Sintering Process ◽

Shock Test ◽

Die Attach ◽

Ag Paste

A novel nano-Ag sintering paste C has been developed for a pressureless sintering process under air. Paste C was sintered at 250°C (C1) and 280°C (C2), respectively; C1 showed a slightly higher porosity but higher shear strength after aging at 250°C for 840 hours. Both C1 and C2 exhibited a microstructure much more stable than the control solder 92.5Pb/5Sn/2.5Ag, which suffered both IMC spalling after thermal aging and voiding. Ag migration toward the DBC to form a dense layer of AgCuNi(Au) was observed for all nano-Ag pastes that were studied, with C1 and C2 being more moderate in the migration rate. The Ag migration could be attributed to the tendency of Ag to form an alloy with Au, with abundant Ni and Cu at the DBC side, and appeared to be affected by the chemistry of nano-Ag paste. A liquid to liquid thermal shock test from −45°C to 240°C was attempted, and was considered too harsh for the die/DBC system employed in this study.

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On the Structure of Certain Nest Algebra Modules

Canadian Journal of Mathematics ◽

10.4153/cjm-1987-065-7 ◽

1987 ◽

Vol 39 (6) ◽

pp. 1405-1412

Author(s):

G. J. Knowles

Keyword(s):

Operator Algebras ◽

Adjoint Operator ◽

Systematic Investigation ◽

Unique Determination ◽

Nest Algebra ◽

Minimal Elements ◽

Open Questions ◽

Weakly Closed ◽

Order Homomorphisms

Let be a nest algebra of operators on some Hilbert space H. Weakly closed -modules were first studied by J. Erdos and S. Power in [4]. It became apparent that many interesting classes of non self-adjoint operator algebras arise as just such a module. This paper undertakes a systematic investigation of the correspondence which arises between such modules and order homomorphisms from Lat into itself. This perspective provides a basis to answer some open questions arising from [4]. In particular, the questions concerning unique “determination” and characterization of maximal and minimal elements under this correspondence, are resolved. This is then used to establish when the determining homomorphism is unique.

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Mechanical Characterization of Transient Liquid Phase Sintered (TLPS) Cu-Sn

ASME 2018 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems ◽

10.1115/ipack2018-8392 ◽

2018 ◽

Cited By ~ 1

Author(s):

Erick Gutierrez ◽

Subramani Manoharan ◽

Maxim Serebreni ◽

Patrick McCluskey

Keyword(s):

Liquid Phase ◽

Mechanical Load ◽

Transient Liquid Phase ◽

Electronic Systems ◽

Power Electronic ◽

Nano Indentation ◽

Lap Shear ◽

Die Attach ◽

Power Modules

The increasing thermal demands in power electronic systems require the application of high temperature die attach materials. Transient Liquid Phase Sintered (TLPS) paste-based solder alloys have been demonstrated to effectively manage the thermal and mechanical load requirements of power modules. The microstructural features of these alloys provide interconnects with the necessary strength required to sustain high loads at high temperatures. To properly understand the influence of microstructure on mechanical behavior of these alloys, single lap shear experiments were performed on a TLPS system consisting of Copper and Tin particles (Cu-Sn). Nano-indentation measurements were performed on intermetallic phases of the TLPS, and the results obtained from lap shear testing and nano-indentation measurements are presented.

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Synthesis and Characterization of Acridinium Dyes for Photoredox Catalysis

Synlett ◽

10.1055/s-0037-1611744 ◽

2019 ◽

Vol 30 (07) ◽

pp. 827-832 ◽

Cited By ~ 9

Author(s):

Alexander White ◽

Leifeng Wang ◽

David Nicewicz

Keyword(s):

Photophysical Properties ◽

Direct Conversion ◽

Systematic Investigation ◽

Synthetic Methods ◽

Synthesis And Characterization ◽

Substitution Effects ◽

Photoredox Catalysis ◽

Methods Development

Photoredox catalysis is a rapidly evolving platform for synthetic methods development. The prominent use of acridinium salts as a sustainable option for photoredox catalysts has driven the development of more robust and synthetically useful versions based on this scaffold. However, more complicated syntheses, increased cost, and limited commercial availability have hindered the adoption of these catalysts by the greater synthetic community. By utilizing the direct conversion of a xanthylium salt into the corresponding acridinium as the key transformation, we present an efficient and scalable preparation of the most synthetically useful acridinium reported to date. This divergent strategy also enabled the preparation of a suite of novel acridinium dyes, allowing for a systematic investigation of substitution effects on their photophysical properties.

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