High Temperature Storage Conditions Research Articles

Novel Electroformed Ni-Au Alloy for High Temperature Semiconductor Test Structures

The ongoing reduction in semiconductor and package pitch leads to challenges for engineering suitable miniaturized test and measurement contact vehicles. Traditional probe card approaches for miniaturization may reach fundamental limits for reduction in scale and pitch. Direct electroforming of conductive electrical contacts at pitch using LIGA technology can allow for direct registration to the test points, the simultaneous formation of all contacts and an opportunity to extend the roadmap for miniaturization. We report here on a new and novel nickel-gold alloy (one to three percent gold by weight) that can be produced by electroforming. This new material was computationally designed to optimize the thermodynamics of the two alloy components such that the alloy has a temperature stable nanocrystalline grain structure which produces highly desirable mechanical and physical properties. Specifically, the alloy is highly electrically and thermally conductive with a resistivity of 10 micro-ohm-cm, while also having a yield strength in excess of 1.5 GPa and an elastic modulus of 130 GPa. This combination of high strength and moderate elastic modulus creates and optimum for mechanical elastic stored energy in a formed contact beam. That is to say, contacts engineered from this material are flexible and strong enough to remain in the elastic regime and have sufficient normal force to maintain low and stable contact resistance, which boosts their long term service life. Further, the alloy shows a fixed cantilever beam bending fatigue limit of more than 1 GPa, further enhancing its viability for long term service. For applications requiring even more strength a 2 GPa yield strength version has also been produced, however this version leads to minor trade-offs in terms of ductility and electrical resistivity and cost. Since these contacts will be used at elevated temperature, the alloy has been designed to be nearly as electrically conductive as plated unalloyed nickel and thermodynamically stable under long term high temperature storage conditions of 400 C. Characterization of the microstructure shows that it is a supersaturated solid solution of Au in a Ni host matrix with evidence of preferential Au segregation to the Ni grain boundaries. Xray diffraction analysis confirms a nanocrystalline grain structure whose size varies as a function of the alloying content. By segregating the Au to the grain boundaries, we extend the electron mean free path and boost electrical conductivity. We also reduce the grain size of the metal leading to improvements in mechanical properties such as yield and fatigue. The electroplating solution is environmentally friendly with no significantly hazardous materials and is REACH compliant. We have shown chemical compatibility with a limited test set of standard photo-resists and masks used for the LIGA process. The plating process is reasonably fast and has shown the ability to plate layers as thick as 400 um without cracks, defects or voids. For some applications it may be desirable to add more plated layers to engineer the contact surface. Gold and other precious metals can be plated on top of the Ni-Au layer with good adhesion and lead to improvements in long term low level contact resistance.

Research Progress on Bonding Wire for Microelectronic Packaging

Wire bonding is still the most popular chip interconnect technology in microelectronic packaging and will not be replaced by other interconnect methods for a long time in the future. Au bonding wire has been a mainstream semiconductor packaging material for many decades due to its unique chemical stability, reliable manufacturing, and operation properties. However, the drastic increasing price of Au bonding wire has motivated the industry to search for alternate bonding materials for use in microelectronic packaging such as Cu and Ag bonding wires. The main benefits of using Cu bonding wire over Au bonding wire are lower material cost, higher electrical and thermal conductivity that enables smaller diameter Cu bonding wire to carry identical current as an Au bonding wire without overheating, and lower reaction rates between Cu and Al that serve to improve the reliability performance in long periods of high temperature storage conditions. However, the high hardness, easy oxidation, and complex bonding process of Cu bonding wire make it not the best alternative for Au bonding wire. Therefore, Ag bonding wire as a new alternative with potential application comes to the packaging market; it has higher thermal conductivity and lower electric resistivity in comparison with Cu bonding wire, which makes it a good candidate for power electronics, and higher elastic modulus and hardness than Au bonding wire, but lower than Cu bonding wire, which makes it easier to bond. This paper begins with a brief introduction about the developing history of bonding wires. Next, manufacturability and reliability of Au, Cu, and Ag bonding wires are introduced. Furthermore, general comparisons on basic performance and applications between the three types of bonding wires are discussed. In the end, developing trends of bonding wire are provided. Hopefully, this review can be regarded as a useful complement to other reviews on wire bonding technology and applications.

Study on high temperature storage reliability of crystal Oscillator

As the most accurate and stable oscillator, the crystal oscillator can provide a stable frequency signal source for the circuit. It has an extremely wide range of applications in various digital circuits and precision instruments, and is an important type of frequency control device. In the field of military and aerospace, crystal oscillators not only require good frequency accuracy and stability under long-term working conditions, but also require high storage reliability, which can meet the storage life requirements of products. In this paper, a high-temperature storage reliability study was conducted for a certain model of crystal oscillator. The high-temperature storage reliability test was designed and carried out. Through the degradation analysis and failure analysis of the test samples, the degradation trend of this model of crystal oscillator under high-temperature storage conditions and the failure mechanism of the leakage failure caused by the galvanic corrosion at the internal solder joints were found. The study in this paper has certain reference significance for the reliability research of crystal oscillator.

QTL analysis for soybean (Glycine max L. Merr.) seed storability in high-temperature storage conditions

Soybean (Glycine max L. Merr.) seeds are highly sensitive to the environmental conditions experienced in STORAGE. The objectives of this study were to identify QTLs for soybean seed storability by evaluating seed viability and seed vigor and investigating candidate genes for these traits in detected QTL regions. These objectives will aid in developing soybean cultivars with a high capacity for storability. The seeds of 109 and 90 recombinant inbred lines (RILs) derived from a cross between Misuzudaizu and Moshidou Gong 503 in 2010 and 2019, respectively, were used to evaluate seed viability by a germination test and seed vigor by an accelerated aging test, after storage under two temperature conditions (25 °C and 35 °C) for six months. Seed viability and seed vigor of Moshidou Gong 503 were higher than those of Misuzudaizu in both temperature conditions. The average seed viability and seed vigor of RILs decreased when stored at the higher temperature. A total of five QTLs were found for the two traits, seed viability and seed vigor, located in chromosomes 2, 6 and 8. The Misuzudaizu alleles decreased seed viability and seed vigor at all detected QTLs. Most QTLs in this study were found near loci controlling seed viability, maturity, germination, seed hardness, and seed surface micromorphology, indicating that seed storability is related to these traits. In addition, two new QTLs were found that are associated with seed storability.

Effects of Storage Temperature on Indica-Japonica Hybrid Rice Metabolites, Analyzed Using Liquid Chromatography and Mass Spectrometry.

The Yongyou series of indica-japonica hybrid rice has excellent production potential and storage performance. However, little is known about the underlying mechanism of its storage resistance. In this study, Yongyou 1540 rice (Oryza sativa cv. yongyou 1540) was stored at different temperatures, and the storability was validated though measuring nutritional components and apparent change. In addition, a broad-targeted metabolomic approach coupled with liquid chromatography-mass spectrometry was applied to analyze the metabolite changes. The study found that under high temperature storage conditions (35 °C), Yongyou 1540 was not significantly worse in terms of fatty acid value, whiteness value, and changes in electron microscope profile. A total of 19 key differential metabolites were screened, and lipid metabolites related to palmitoleic acid were found to affect the aging of rice. At the same time, two substances, guanosine 3′,5′-cyclophosphate and pipecolic acid, were beneficial to enhance the resistance of rice under harsh storage conditions, thereby delaying the deterioration of its quality and maintaining its quality. Significant regulation of galactose metabolism, alanine, aspartate and glutamate metabolism, butyrate metabolism, and arginine and proline metabolism pathways were probably responsible for the good storage capacity of Yongyou 1540.

Chemometrics optimized microencapsulation of ergocalciferol using emulsification technique and its physico-chemical characterization

The study reports the microencapsulation of ergocalciferol (vitamin D2) by emulsification technique, the experimental process parameters being chemometrically optimized by d-optimal mixture design approach followed by physico-chemical characterization of the resultant emulsion. Basing on desirability ramp function graph and lab experimentation results, the percentages of Ca stearate (0.124), Ca carbonate (0.385), Ethanol (5.0), Tween 80 (4.16), Span 80 (0.25) showed a maximum of 94.1% encapsulation efficiency. The optimized ergocalciferol emulsion showed particle size in the range of 469–493 nm, polydispersity index 0.23–0.24, zeta potential (ζ) value ranging from -15.27 to -15.35 mv; viscosity and interfacial tension was determined to be 1.401±0.02 mPaS and 23.1 mNm−1 respectively. The resultant emulsion showed no visual change in physical appearance, consistency, and color on keeping undisturbed for 7 days. Results of accelerated stability studies have shown that the initial ergocalciferol or (vitamin D2) content (83.75±0.03%) in the emulsion after storage at (55 °C, 75% RH) was found to be 83.05±0.01% and after storage at (75 °C, 80% RH) is 82.91±0.05%. From the results of accelerated stability studies it can be concluded that vitamin D2 emulsion is comparatively stable at high temperature storage conditions (75 °C, 80% RH). The devised optimized procedure of microencapsulation by emulsification of ergocalciferol was found to be effective with high encapsulation efficiency and significant stability of the emulsion system.

Investigating the influence of carbon nanotube on the performance of asphalt binder

The purpose of this study aims at investigating the impact of multi-walled carbon nanotubes (MWCNT’s) on the properties of low viscosity grade asphalt binder. Asphalt binder with viscosity grade-10 is selected as the control binder and later it is modified with different percentages of MWCNT’s (0.5–2.5%). Penetration, softening point, ductility and rotational viscosity test were employed for evaluating the effect of MWCNT’s on basic physical properties of modified asphalt binder. Dynamic Shear Rheometer (DSR) is used for evaluating the rheological properties of the base and modified bitumen, for both aged and unaged bitumen. Based on the conventional and basic rheological tests, it was seen that the addition of MWCNT’s improved the high-temperature performance of modified bitumen. Multiple Stress Creep and Recovery (MSCR) test results revealed that the addition of MWCNT’s improved the creep and recovery of modified binders for both stress intensities (0.1 kPa and 3.2 kPa) which confirms that the modified binder is more rut resistant. Moreover, it was observed that there was a significant improvement in the aging resistance of the asphalt binder due to addition of MWCNTs. However low temperature performance of MWCNTs was not encouraging. Also, MWCNTs addition to asphalt binder was found to be stable under high-temperature storage condition. Overall, there is a significant amount of improvement using MWCNTs in the base asphalt binder.

Study on understanding functional characteristics of multi-wall CNT modified asphalt binder

ABSTRACT This study evaluates important functional characteristics such as dispersion, aging resistivity potential, temperature susceptibility, and high temperature storage stability of Carbon Nano Tube (CNT) modified asphalt binders. CNT content was varied as 0%, 0.4%, 0.75%, 1.5% and 2.25% by weight of control binder (AC-10). Scanning Electron Microscopic (SEM) images was captured to get direct observation of CNT dispersion. Viscosity was further measured to understand the workability and dispersion characteristics. Further, viscosity temperature susceptibility parameters (A and VTS), activation energy and Penetration Index (PI) values were estimated to evaluate temperature susceptibility. SEM images and viscosity data showed that CNT content up to 1.5% may be recommended without potential problem of entanglement/clustering. Similarly, analysis of softening point, complex modulus and phase angle data showed positive effect of CNT on aging resistivity potential. Such improvement in functional characteristics can be attributed to high specific surface area (190 m2/gm), higher aspect ratio (length/diameter = 645) and excellent mechanical properties of CNT. Likewise, high temperature storage stability was evaluated using softening point and Multiple Stress Creep Recovery (MSCR) tests. Though softening point test method showed sufficiently stable nature of CNT under high temperature storage condition, settling of CNT (unstable nature) was observed from MSCR testing approach.

Time-dependent phase separation of amorphous solid dispersions: Implications for accelerated stability studies

Freshly prepared amorphous solid dispersions (ASDs) may not be in an equilibrium mixed state, as high-temperatures and/or solvents are generally used during their preparation. In this study, tolbutamide (TLB) and acetaminophen (AAP) were transformed into ASDs using hydroxypropylmethylcellulose acetate succinate, Eudragit E100 (E100), Soluplus, and Kollidon VA64 using the melt-quench method to observe their phase stability at 5, 25, 40, and 60 °C. Time-dependent phase separation was observed for all the drug and excipient combinations under all investigated storage conditions. The phase separation of the E100/TLB and Soluplus/TLB ASDs was faster under high-temperature storage conditions, whereas the opposite trend was observed with the other ASDs. In the above-mentioned stability studies, phase separation kinetics of the E100/TLB and Soluplus/TLB ASDs appeared to be dominated by molecular mobility due to the low glass transition temperature (Tg) of both the drug and polymer, whereas departure from equilibrium was a dominating factor for the other ASDs. The Tg of the mixed phase just after preparation could be used as an indicator for predicting phase separation after long-term storage, as the mixing ratio calculated from the Tg was in agreement with that after storage for certain ASDs.

Blister Testing for Adhesion Strength Measurement of Polymer Films Subjected to Environmental Conditions

A blister testing procedure combined with a numerical procedure can be used effectively for characterizing the adhesion strength. A challenge arises when it is implemented after subjecting samples to various environmental conditions. The concept of pseudoproperty is introduced to cope with the problem associated with property changes during environmental testing. The pseudoproperty set is determined directly from a deflection versus pressure curve obtained from a typical blister test. A classical energy balance approach is followed to evaluate the energy release rate from the critical pressure and pseudoproperty set. The proposed approach is carried out for an epoxy/copper interface after subjecting samples to full moisture saturation and a high temperature storage condition. In spite of significant change in property, the energy release rates are calculated accurately without extra tests for property measurements.

Synthesis and in vitro biological evaluation of dihydroartemisinyl-chalcone esters.

A series of dihydroartemisinyl-chalcone esters were synthesized through esterification of chalcones with dihydroartemisinin (DHA). The hybrids were screened against chloroquine (CQ) sensitive (3D7) and CQ resistant (W2) strains of intraerythrocytic Plasmodium falciparum parasites, and were all found to be active, with IC50 values ranging between 1.5 and 11 nM against both strains, with SI values over 5800. The esters featuring oxygenated aryl rings (7, 10 and 11), were found to be equipotent to DHA, but were 2-3 times more active than artesunate against the 3D7 and W2 strains of the malaria parasites. They were also screened in vitro against a panel of three cancer cell lines consisting of TK-10, UACC-62 and MCF-7. Compound 7, bearing a furan ring, displayed the most potent overall antitumor activity against all three cancer cell lines. TGA revealed that the targeted hybrids were all thermally more stable than DHA, which may be beneficial to the high temperature storage conditions that prevail in malaria endemic countries. During this study, ester 7 was identified as the best candidate for further investigation as a potential drug in search for new, safe and effective antimalarial drugs.

여름철 고온 환경 조건에서 참외(Cucumis melo var. makuwa)의 저장 중 선도유지를 위한 아이스 팩 처리 포장 박스 적용 연구

The effects of the ice pack and aluminum coated board in the corrugated boxes for maintaining the quality of fresh oriental melons (Cucumis melo var. makuwa) were investigated. The harvested oriental melons were stored at a temperature of 30°C for 21 days after placing them in the corrugated boxes treated with control, including ice pack and aluminum coated board. The treatment with the ice pack and aluminum coated board was identified to have maintained the relative low temperature in the corrugated box against the high temperature from the environment. For the storage study of the oriental melon, the treatments with the ice pack and aluminum coated board reduced the respiration rate, the development of external color, and total weight loss. All treatments were also effective in maintaining the firmness and decreasing the decay ratio of the oriental melon as compared to those that were controlled. However, the value of total soluble solids regarding the fruit was insignificantly affected by the ice pack treatment. The results indicated that the application of the ice pack and aluminum coated board in the corrugated box played an important role in maintaining the quality of oriental melons during storage. The combination with the ice pack and aluminum coated board had more effective values on the storage qualities for oriental melons than that with the ice pack only. Based on the results of this study, the ice pack and aluminum coated board were the useful treatments for reducing the loss of quality of the fresh oriental melons in high temperature storage conditions.

Dicing Development for low-k Copper Wafers using Nickel-Palladium-Gold Bond Pads for Automotive Application

New automotive requirements expect plastic packages to survive higher operating temperatures with extended thermal duration. Mission profiles for under-the-hood and transmission application historically specified minimal duration at maximum junction temperature, such as 50 total hours at 150C, while keeping most of the total operating duration at lower temperatures. Further module integration and more stringent environmental requirements push modules and thus plastic packages closer to the heat source. As such, new mission profiles include more than 3500 total hours at 150°C. To satisfy new automotive requirements, plastic packages must meet AEC Grade 0 or higher. One key limitation of the conventional plastic package is the use of gold bond wire on aluminum bond pad. Au-Al intermetallic degradation due to intermetallic transformation in high temperature storage condition remains the main reliability concern. More reliable intermetallic systems have been proposed that change the wire material and/or the bond pad metallization. An alternative wire material to gold, copper, has many benefits including low cost, high electrical and thermal conductivities and excellent reliability with aluminum pad metallization. Pad re-metallization using nickel/palladium, nickel/gold or nickel/palladium/gold over aluminum bond pad or copper bond pad offers a noble and reliable metal interconnect. This study focused on the development of dicing process for low-K-copper wafers having aluminum pad re-metallized with electroless nickel / electroless palladium / immersion gold Over Pad Metallization (OPM). Development wafers were pizza mask wafers on which multiple die designs and scribe grid production control (SGPC) modules were designed. SGPC modules are designed with aluminum probe pads that are used to monitor wafer-level process control. All aluminum features on the wafer were plated with nickel/palladium/gold OPM. With the hardness of nickel and palladium being more than 10 to 15 times the hardness of aluminum, OPM-plated SGPC's were much more difficult to dice than conventional SGPC's with aluminum pads. Cracking on silicon sidewall with crack propagating towards the die was found to cause back-end-of-line (BEOL) delamination and device failure. Extensive mechanical dicing studies were conducted to modulate the failures and resolve the dicing challenge. Specifically, dicing was observed to be not centered on SPGC pads on the pizza mask. Off-centered dicing produced drastic change in Ni loading at the center of the blade and on the edges of the blade. Packages underwent extensive reliability stress conditions. The associated process improvements described in this paper supported a successful integration of a 55nm die technology in Low Profile Quad Flat Package with Exposed Pad (LQFP-EP) meeting and exceeding AEC grade 0 requirements.

Thermal analysis and exergy evaluation of packed bed thermal storage systems

Thermal energy storage in a packed bed is analyzed for dynamic temperature response during cyclic storage and recovery. A robust system-scale heat transfer model for the packed bed is developed and accounts for wall heat transfer and intra-particle diffusion effects. Based upon the temperature field modeling, recovered and lost exergy are calculated. The analysis shows that, for packed beds, sensible heat storage systems can provide much higher exergy recovery as compared to phase change material (PCM) storage systems under similar high temperature storage conditions. The roles of axial dispersion and wall heat losses are considered.

Dicing Development for low-k Copper Wafers using Nickel-Palladium-Gold Bond Pads for Automotive Application

New automotive requirements expect plastic packages to survive higher operating temperatures with extended thermal duration. Mission profiles for under-the-hood and transmission application historically specified minimal duration at maximum junction temperature, such as 50 total hours at 150C, while keeping most of the total operating duration at lower temperatures. Further module integration and more stringent environmental requirements push modules and thus plastic packages closer to the heat source. As such, new mission profiles include more than 3500 total hours at 150°C. To satisfy new automotive requirements, plastic packages must meet AEC Grade 0 or higher. One key limitation of the conventional plastic package is the use of gold bond wire on aluminum bond pad. Au-Al intermetallic degradation due to intermetallic transformation in high temperature storage condition remains the main reliability concern. More reliable intermetallic systems have been proposed that change the wire material and/or the bond pad metallization. An alternative wire material to gold, copper, has many benefits including low cost, high electrical and thermal conductivities and excellent reliability with aluminum pad metallization. Pad re-metallization using nickel/palladium, nickel/gold or nickel/palladium/gold over aluminum bond pad or copper bond pad offers a noble and reliable metal interconnect. This study focused on the development of dicing process for low-K-copper wafers having aluminum pad re-metallized with electroless nickel / electroless palladium / immersion gold Over Pad Metallization (OPM). Development wafers were pizza mask wafers on which multiple die designs and scribe grid production control (SGPC) modules were designed. SGPC modules are designed with aluminum probe pads that are used to monitor wafer-level process control. All aluminum features on the wafer were plated with nickel/palladium/gold OPM. With nickel about four times as hard as aluminum, OPM plated SGPC's were much more difficult to dice than conventional SGPC's with aluminum pads. Cracking on silicon sidewall with crack propagating towards the die was found to cause back-end-of-line (BEOL) delamination and device failure. Surface roughness and hardness measurements were taken on OPM variations. Extensive mechanical dicing studies were conducted to modulate the failures and resolve the dicing challenge. Laser grooving followed by mechanical dicing of OPM wafers was also performed. Packages underwent extensive reliability stress conditions. The associated process improvements described in this paper supported a successful integration of a 55nm die technology in Low Profile Quad Flat Package with Exposed Pad (LQFP-EP) meeting and exceeding AEC grade 0 requirements.

Comparison of Gold and Copper Wire Bonding on Aluminum and Nickel-Palladium-Gold Bond Pads for Automotive Application

New automotive requirements expect plastic packages to survive higher operating temperatures with extended thermal duration. Mission profiles for under-the-hood and transmission application historically specified minimal duration at maximum junction temperature, such as 50 total hours at 150C, while keeping most of the total operating duration at lower temperatures. Further module integration and more stringent environmental requirements push modules and thus plastic packages closer to the heat source. As such, new mission profiles include more than 3500 total hours at 150°C. To satisfy new automotive requirements, plastic packages must meet AEC Grade 0 or higher. One key limitation of the conventional plastic package is the use of gold bond wire on aluminum bond pad. Au-Al intermetallic degradation due to intermetallic transformation in high temperature storage condition remains the main reliability concern. More reliable intermetallic systems have been proposed that change the wire material and/or the bond pad metallization. An alternative wire material to gold, copper, has many benefits including low cost, high electrical and thermal conductivities and excellent reliability with aluminum pad metallization. Pad re-metallization using nickel/palladium, nickel/gold or nickel/palladium/gold over aluminum bond pad or copper bond pad offers a noble and reliable metal interconnect. This study focused on evaluating Au and Cu wire bonding on low-K-copper wafers having two types of bonding surfaces, the conventional aluminum pad and aluminum pad re-metallized with electroless nickel / electroless palladium / immersion gold. Ni thickness ranging from 1μm to 3μm was evaluated. Defects on as-plated Ni/Pd/Au bond pads such as color difference and surface roughness were determined to be due to nodule growth and plating non-uniformity. Wire bonded strip-level thermal aging was conducted to compare the high-temperature performance of the four interconnect types. Packages underwent extensive reliability stress conditions. Cross-sectioning through the ball bonds was also conducted to examine the welding region between the ball bond and bond pad. Defects in plating and wire bonding processes causing package reliability failures were identified. Recommendations for plating and wire bonding processes were derived to ensure high quality and reliable interconnect exceeding AEC grade 0 requirements.

Long-term evaluation of hermetically glass frit sealed silicon to Pyrex wafers with feedthroughs

The reliability of bonding silicon to Pyrex wafers using a reflowed glass frit seal is examined in this paper. The Pyrex wafers have metal feedthroughs, which are used to actuate and capacitively sense a single-crystal, silicon resonator. Long-term, high-temperature storage conditions for chips with and without getters are examined. The reflowed glass seal is demonstrated to be hermetic for years at high temperature using both diaphragm deflection and the Q and frequency of resonators as a vacuum indicator. The use of a thin film getter is found to eliminate Q hysteresis due to gas desorption and adsorption, observed in other resonators studies.