Package Lifetime Research Articles

Comparison of energy efficiency and costs related to conventional and LED road lighting installations

Comparison of conventional (usually high-pressure sodium (HPS)) and LED luminaires in street/road lighting is not often based on photometrically equivalent lighting solutions and/or correct economic analysis, which may lead to either overestimation or underestimation of savings of any kind. Therefore, this paper presents a correct methodology for the determination of actual energy efficiency and cost indicators in street/road lighting. Both neutral white (NW) and warm white (WW) LEDs, all relevant street/road lighting classes and pole layouts were considered. Analyzing optimal lighting solutions, characterized by the lowest installed power, it was shown that when considering mesopic effects the average energy savings achieved comparing LED (NW and WW) with HPS lighting solutions amounted to 41–62% and 29–59%, respectively, while the ratio between the total costs of the comparable LED (NW and WW) and HPS lighting solutions belonged to the ranges 0.59–1.26 and 0.61–1.14, respectively. An expanded sensitivity analysis of the costs, carried out considering not only the usually taken discount and electricity cost rates, but also the LED package lifetime, showed that the last only slightly influences the total costs. The effects of the use of more efficient LED packages expected in the near future were also analyzed.

Degradation of silicone in white LEDs during device operation: a finite element approach to product reliability prediction

Silicone, which is a very common material for Light Emitting Diode (LED) packaging components like lens, casting and housing, undergoes degradation during high temperature and current operation. Indeed, electrical and optical losses cause material shrinkage and hardening, inducing mechanical stress within the LED assembly, which can end up into crack formation in silicone. In order to evaluate the reliability of LED package regarding the silicone crack, a degradation material model is developed, which is based on the experimental investigation of the mechanical properties of silicone during degradation. A thermo-optical model is used for the calculation of the temperature distribution in the device during steady-state operation. The crack reliability model, which is build combining the stress simulation results based on finite element approach and the visual inspection of the corresponding LED package during steady-state operation, is used to estimate the package lifetime depending on the operation conditions.

Packaging commercial CMOS chips for lab on a chip integration

Combining integrated circuitry with microfluidics enables lab-on-a-chip (LOC) devices to perform sensing, freeing them from benchtop equipment. However, this integration is challenging with small chips, as is briefly reviewed with reference to key metrics for package comparison. In this paper we present a simple packaging method for including mm-sized, foundry-fabricated dies containing complementary metal oxide semiconductor (CMOS) circuits within LOCs. The chip is embedded in an epoxy handle wafer to yield a level, large-area surface, allowing subsequent photolithographic post-processing and microfluidic integration. Electrical connection off-chip is provided by thin film metal traces passivated with parylene-C. The parylene is patterned to selectively expose the active sensing area of the chip, allowing direct interaction with a fluidic environment. The method accommodates any die size and automatically levels the die and handle wafer surfaces. Functionality was demonstrated by packaging two different types of CMOS sensor ICs, a bioamplifier chip with an array of surface electrodes connected to internal amplifiers for recording extracellular electrical signals and a capacitance sensor chip for monitoring cell adhesion and viability. Cells were cultured on the surface of both types of chips, and data were acquired using a PC. Long term culture (weeks) showed the packaging materials to be biocompatible. Package lifetime was demonstrated by exposure to fluids over a longer duration (months), and the package was robust enough to allow repeated sterilization and re-use. The ease of fabrication and good performance of this packaging method should allow wide adoption, thereby spurring advances in miniaturized sensing systems.

Thermal Aging Effects on the Thermal Cycling Reliability of Lead-Free Fine Pitch Packages

The microstructure, mechanical response, and failure behavior of lead-free solder joints in electronic assemblies are constantly evolving when exposed to isothermal aging and/or thermal cycling environments. A direct and deleterious effect on packaging reliability has been observed during elevated temperature isothermal aging for fine-pitch ball grid array (BGA) packages with Sn-1.0Ag-0.5Cu (SAC105), Sn-3.0Ag-0.5Cu (SAC305), and Sn-37Pb solder ball interconnects. Package sizes range from 19 mm with 0.8-mm pitch BGAs to 5 mm with 0.4-mm pitch BGAs with three different board finishes (ImSn, ImAg, and SnPb) previously studied. This paper presents the latest results from an on-going investigation on the aging temperatures were 25 °C, 55 °C, 85 °C, and 125 °C, applied for a period of 12 months. Subsequently, the specimens were thermally cycled from -40°C to 125 °C with 15 min dwell times at the high temperature. Weibull analysis of failures versus cycle number show a ~ 57% reduction in package lifetimes when aged at 125 °C compared to no aging for 19 mm BGAs, for MLFs the degradation is even worse, more than 58% reduction in experiment result. In contrast, the reliability performance of Sn-37Pb is much more stable over long time up to 12 months and temperature. We also study the evolution during isothermal aging, which is one of the major failure modes of solder joints due to its high homologous temperature. The degradation is observed for both SAC alloys on all tested package sizes and board finishes. For the 19 mm SAC105 case, e.g., there was a 53% (57%) reduction of characteristic lifetime at 125 °C for 6 months (12 months) compared to room temperature aging. The trends are in the expected directions; namely, the reliability is reduced when using higher aging temperatures, smaller solder balls, and SAC105. The dominant failure mode can be associated with the growth of Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> intermetallic compounds during the aging, particularly on the pad side.

Impact of Isothermal Aging on the Long-Term Reliability of Fine-Pitch Ball Grid Array Packages With Different Sn-Ag-Cu Solder Joints

A direct and deleterious effect on packaging reliability has been observed during elevated temperature isothermal aging for fine-pitch ball grid array (BGA) packages with Sn-1.0Ag-0.5Cu (SAC105), Sn-3.0Ag-0.5Cu (SAC305), and Sn-37Pb solder ball interconnects. Package sizes ranging from 19 mm with 0.8-mm-pitch BGAs to 5 mm with 0.4-mm-pitch μ BGAs with three different board finishes (ImSn, ImAg, and SnPb) were evaluated. The aging temperatures were 25°C, 55°C, 85°C, and 125°C, applied for a period of 6 mo. Subsequently, the specimens were thermally cycled from -40°C to 125°C with 15-min dwell times at the high temperature. Weibull analysis of failures versus cycle number show a ~ 50% reduction in package lifetimes when aged at 125 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C compared to the same at room temperature, with less dramatic but measurable reductions in lifetime at 85°C and even 55°C. In contrast, the reliability performance of Sn-37Pb is much more stable over time and temperature. The degradation was observed for both SAC alloys on all tested package sizes and board finishes. For the 19-mm SAC105 case, for example, there was a 53% (32%) reduction of characteristic lifetime at 125°C (85°C) compared to room temperature aging. The trends were in the expected directions; namely, the reliability was reduced when using higher aging temperatures, smaller solder balls, and SAC105. The dominant failure mode can be associated with the growth of Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> intermetallic compounds during the aging, particularly on the pad side.

Getters and Design to Reliability: A Tool For Lifetime Assurance

The key to reaching multi-decade package lifetimes and device reliability is to not just take a snap shot with a RGA and declaring a part passed per MIL-STD-883. It requires a deep understanding of the sources of unwanted gases in a package, characterizing their true flow rates within, without and through the package system, and carefully choosing processes and materials, including getters, to manage the unwanted gases. This is true whether the package is hermetic or non-hermetic. A multi-step process is discussed to include identifying the gas sources, the species present and their quantities, modeling the true quantities of gas generated over the lifetime of the package, and removing it, either through process or materials. When package service lifetimes reach decades, traditional understandings start to fall apart and careful quantitative analysis is rewarded. Getters play a key role in attaining multi-decade lifetimes. Getter selection and sizing is discussed. Included in the discussion will be a brief synopsis of the current state of the art of gettering technology.

Impact of Isothermal Aging on Long-Term Reliability of Fine-Pitch Ball Grid Array Packages with Sn-Ag-Cu Solder Interconnects: Surface Finish Effects

The interaction between isothermal aging and the long-term reliability of fine-pitch ball grid array (BGA) packages with Sn-3.0Ag-0.5Cu (wt.%) solder ball interconnects was investigated. In this study, 0.4-mm fine-pitch packages with 300-μm-diameter Sn-Ag-Cu solder balls were used. Two different package substrate surface finishes were selected to compare their effects on the final solder composition, especially the effect of Ni, during thermal cycling. To study the impact on thermal performance and long-term reliability, samples were isothermally aged and thermally cycled from 0°C to 100°C with 10 min dwell time. Based on Weibull plots for each aging condition, package lifetime was reduced by approximately 44% by aging at 150°C. Aging at 100°C showed a smaller impact but similar trend. The microstructure evolution was observed during thermal aging and thermal cycling with different phase microstructure transformations between electrolytic Ni/Au and organic solderability preservative (OSP) surface finishes, focusing on the microstructure evolution near the package-side interface. Different mechanisms after aging at various conditions were observed, and their impacts on the fatigue lifetime of solder joints are discussed.

Analytic implementation of the GRAAL model: Application to a R7T7-type glass package in a geological disposal environment

The Glass Reactivity with Allowance for the Alteration Layer Model (GRAAL) was proposed in 2008 to describe borosilicate nuclear glass alteration based on coupling an affinity law with the formation and dissolution of a passivating reactive interface. It is examined here in a simplified form in which only the affinity with respect to silicon is taken into account with a concentration at saturation C sat, and the precipitation of neoformed phases is described by an affine relation for silicon above a precipitation threshold C sat ′ . This simplified “analytical GRAAL” model is capable of predicting the quantities of altered glass and the silicon and boron concentration variations in analytical or semi-analytical form, and thereby identify the main characteristic quantities of the system. The model was tested against a series of laboratory experiments lasting from a few days to a few years; its sensitivity to the parameter values was examined, and the model was validated with respect to SON68 glass alteration in initially pure water. It was then applied to the alteration of a glass package in a repository over periods of up to a million years, by means of exploratory calculations comprising a sensitivity study of the internal model parameters and extrapolation to the temperatures expected in a geological repository in order to identify the parameters and mechanisms having the greatest impact on the residual alteration rate. Alteration is controlled by the precipitation of neoformed phases in every case. The transient conditions are of very limited duration with respect to either silicon or boron (no more than a 100 years, with less than 0.01% alteration of the package). In the precipitation law used in the model, the residual alteration rate and total package lifetime are determined primarily by two parameters: k′ (the precipitation kinetics) and σ′ (the precipitate surface area per unit volume in the geological barrier). The package lifetime is about 3 × 10 5 years at 30 °C assuming a reasonable value for σ′ (10 6 m −1), and would be increased by a factor 3–6 if precipitation in the barrier were disregarded. This cursory description of precipitation will be validated and refined through specific laboratory tests at 50 °C and lower temperatures, coordinated with the development of the “geochemical GRAAL” model and with integral tests in contact with clay and canister corrosion products.

Experimental study of WL-CSP reliability subjected to a four-point bend-test

This article deals with the reliability of WL-CSP subjected to a four-point bend-test according to the JEDEC standard and the repeatability of this test. The evaluation of the test repeatability shows a 5% variation on the characteristic Weibull parameter η. Two dedicated failure detection methods are used: with an event detector and with data acquisition and no difference are observed. Parameters considered are pre-load magnitude and loading frequency. PCB strain due to pre-load is measured and its effect on the product reliability is evaluated. Based on these measurements a pre-load value is defined. It is also shown that a frequency of 3 Hz modifies the studied package lifetime.

Modelling glass alteration in an altered argillaceous environment

The long term behaviour of materials such as glass, steel and clay has been investigated in the context of deep geological disposal of radioactive wastes. The interactions between vitrified wastes, canister corrosion products (CPs) and clay are studied using a modified version of the reaction-transport code Crunch, especially looking at pH changes and possible cementation at the interface with the clayey materials. These perturbations may indeed affect the lifetime of glass matrix in deep repositories, e.g., high pH enhances the rate of glass alteration. This work focuses on the argillite of Bure. The calculations were performed at 323K with a glass alteration rate switching from a high initial rate to a residual rate according to the sorption capacity of CPs. The time at which this sorption capacity is saturated is crucial to the system in terms of wastes package lifetime. The results show that the glass alteration imposes a high pH value at the interface with CPs and clay: up to a value of 9.2, compared to 7.3 which is the initial pH value in the argillite. Experimental data show that the rate of glass alteration is much higher in such pH conditions. For a R7T7-type glass, the rate is about five times higher at pH 9 than at pH 7. This pH perturbation migrates through the clayey domain as a result of the migration of mobile elements such as boron and sodium, and despite the existence of strong pH buffers in the argillite. The cementation of porosity at the interface between glass and clay is predicted by the model due to the massive precipitation of iron corrosion products and glass alteration products. At this point of the evolution of the system, the pH starts to decrease and the alteration rate of the glass could be significantly reduced. This porosity clogging effect is difficult to confirm by experiments especially since existing data on short term experiments tend to show a pervasive precipitation of silica in the domain instead of a localized precipitation at the interface.

Modeling Corrosion Processes for Alloy 22 Waste Packages

ABSTRACTThe proposed waste package design for the disposal of high-level radioactive waste at the potential repository at Yucca Mountain, Nevada, consists of an outer container made of Alloy 22, a corrosion resistant Ni-Cr-Mo-W alloy, surrounding an inner container made of Type 316 nuclear grade stainless steel. Models to assess the influence of waste package degradation modes on the overall system performanceconsider uniform and localized corrosion processes. Based on measurements of passive anodic current density, the uniform aqueous corrosion rate of Alloy 22 is estimated to be slow, and long waste package lifetimes are projected in the absence of conditions that promote accelerated degradation processes. The initiation of localized corrosion is possible in chloride-containing waters with low concentrations of inhibiting oxyanions such as nitrate. Although propagation rates for localized corrosion are typically orders of magnitude greater than the passive uniform corrosion rates, the maximum penetration depth of localized attack may be limited to depths significantly less than the container thickness as a result of stifling andarrest of localized corrosion.

Effect of Inhibiting Oxyanions on the Localized Corrosion Susceptibility of Waste Package Container Materials

AbstractThe DOE is currently preparing a license application for the permanent disposal of high level radioactive waste at Yucca Mountain, Nevada. The proposed design of waste packages for the disposal of high level radioactive waste consists of an outer container made of Alloy 22, a corrosionresistant Ni-Cr-Mo-W alloy, surrounding an inner container made of Type 316 nuclear grade stainless steel. Under conditions where passivity is maintained, the uniform corrosion rate of Alloy 22 is slow and long waste package lifetimes are projected. However, the initiation of localized corrosion such as pitting or crevice corrosion may decrease waste package lifetimes. In this study the crevice corrosion susceptibility of Alloy22 was determined in chloride solutions with additions of oxyanions that are present in the groundwater at the potential repository site. When present in sufficient concentrations relative to chloride, nitrate, carbonate, bicarbonate, and sulfate inhibited pitting and crevice corrosion of Alloy 22.

Evaluation of The Long-Term Stability of Passive Corrosion On The Drip Shield and Waste Package Under Yucca Mountain Conditions

ABSTRACTPossible long term corrosion scenarios for the engineered barriers proposed for the Yucca Mountain (Nevada, USA) repository are reviewed.Introduction:The materials proposed for the engineered barriers in the Yucca Mountain repository (Nevada, USA), Alloy-22 for the waste packages (WP) and titanium Grade-7 (Ti-7) for the drip shield (DS), appear unlikely to suffer localized corrosion (LC) and have very low passive corrosion (PC) rates (1–3). Since environmental conditions will become more benign as temperatures decline and aqueous environments become more dilute (4), this leads to the prediction of exceedingly long waste package lifetimes. In this review, possible corrosion scenarios are discussed in the context of the anticipated evolution in the repository environment.

Prediction of Waste Package Life for High-Level Radioactive Waste Disposal at Yucca Mountain

The U.S. Department of Energy (DOE) has released a Viability Assessment (VA) of the proposed high-level waste (HLW) repository at Yucca Mountain (YM), Nevada. The proposed standard for the repository requires the evaluation of the predicted —over 10,000 yr— performance of the system. In the VA, it is argued that long waste package (WP) lifetimes are responsible for significant containment and delay in release of the HLW. This paper examines the DOE WP lifetime prediction by combining the VA parameters modeling the corrosion behavior of the WP materials with the repository performance assessment code developed by the U.S. Nuclear Regulatory Commission (NRC) and the Center for Nuclear Waste Regulatory Analyses (CNWRA). The objective of the analysis is to exercise and strengthen the NRC review capabilities in preparation for receipt of the DOE license application for the proposed HLW repository. The results indicate that during the first 10,000 yr, radionuclide release depends almost entirely on the fraction of initially defective waste packages (IDWP). Radionuclide release resulting from corrosion of the WPs occurs only beyond 10,000 yr. The long WP lifetimes (>10,000 yr), reported in the VA and in this study, primarily depend on corrosion rates developed from an expert elicitation consensus. Given the importance in the estimation of the onset of radionuclide release and the lifetime of the WP materials, it is suggested the need for a stronger technical basis to assess the fraction of IDWP and to support the low corrosion rates of the WP materials.

The Effect f Waste Package and Engineered Barrier System Design:Options on Long-Term Waste Package Degradation Characteristics

AbstractSensitivity analyses were conducted to evaluate the impact of a number of waste package and engineered barrier system (EBS) design options on long-term waste package degradation in the potential repository at Yucca Mountain, Nevada. The evaluations were performed by analyzing the waste package degradation in terms of the first breach and first pit-breach profiles with time. Results for each design option were assessed by comparing to results for the reference-case design. An important finding from the analyses is that the waste package lifetime could be extended substantially by limiting and delaying the contact of dripping water with the Alloy 22 corrosion resistant material (CRM) barrier. In the current model, this would keep the CRM barrier outside the conditions that makes the alloy susceptible to localized corrosion. Uncertainty in waste package degradation analysis would be reduced by improved understanding and characterization of the processes that create the local exposure condition on waste package.

Performance Analysis of Conceptual Waste Package Designs in Salt Repositories

ABSTRACTA performance analysis of commercial high-level waste and spent fuel conceptual package designs in reference repositories in three salt formations was conducted with the WAPPA waste package code. Expected conditions for temperature, stress, brine composition, radiation level, and brine flow rate were used as boundary conditions to compute expected corrosion of a thick-walled overpack of 1025 wrought steel. In all salt formations corrosion by low Mg salt-dissolution brines typical of intrusion scenarios was too slow to cause the package to fail for thousands of years after burial. In high Mg brines judged typical of thermally migrating brines in bedded salt formations, corrosion rates which would otherwise have caused the packages to fail within a few hundred years were limited by brine availability. All of the brine reaching the package was consumed by reaction with the iron in the overpack, thus preventing further corrosion. Uniform brine distribution over the package surface was an important factor in predicting long package lifetimes for the high Mg brines.

The Composition and Stratigraphic Distribution of Materials in the Lower San Andres Salt Unit 4

ABSTRACTThe salt bed in depositional cycle 4 of the Permian Lower San Andres Formation, Palo Duro Basin, Deaf Smith County, Texas consists of massive salt interlayered with discrete bands and beds of anhydrite and claystone. The massive salt consists of about 90% halite, with 7% anhydrite and 3% clays disseminated in and among the halite crystals.The halite in this salt bed contains fluid inclusions filled with a (Na, K, Mg)Cl brine, with an average Mg concentration of about 50,000 mg/liter. The anhydrite in the salt will saturate the brines in CaSO4, which in turn may coat the waste package with anhydrite because of the retrograde solubility of CaSO4. This may increase waste package lifetime to failure by corrosion.